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1

Activation and reactivity of epoxides on solid acid catalysts  

Microsoft Academic Search

The aminolysis of epoxides over novel solid catalysts (Brönsted-acidic SBA-15 functionalized with propylsulfonic acid and Lewis-acidic Ti-MCM-41) is reported. The acidic properties of these catalysts were determined by FTIR spectroscopy and temperature-programmed desorption of pyridine and NH3, respectively. The mesoporous solid acids of the present study are reusable and exhibit significantly higher catalytic activities than known catalysts for opening of

L. Saikia; J. K. Satyarthi; D. Srinivas; P. Ratnasamy

2007-01-01

2

Hydrolysis of disaccharides over solid acid catalysts under green conditions  

Microsoft Academic Search

The hydrolysis of the three most important disaccharides: sucrose, maltose and cellobiose, has been comparatively studied in mild conditions (50–80°C) in water over several solid acid catalysts. Strong acidic resins (Amberlite A120 and A200), mixed oxides (silica-alumina and silica-zirconia), and niobium-containing solids (niobic acid, silica-niobia, and niobium phosphate) have been chosen as acid catalysts. The hydrolysis activity was studied in

Matteo Marzo; Antonella Gervasini; Paolo Carniti

3

Phosphorylated Mesoporous Carbon as a Solid Acid Catalyst  

SciTech Connect

Mesoporous carbon catalyst supports are attractive due to their wide chemical stability while potentially increasing masstransport through and providing a path for larger molecules to access catalytic sites. Herein we report the synthesis of a 10 phosphorylated mesoporous carbon solid-acid catalyst characterized by NH3-TPD and isopropanol dehydration.

Dai, Sheng [ORNL; Mayes, Richard T [ORNL; Fulvio, Pasquale F [ORNL; Ma, Zhen [ORNL

2011-01-01

4

Hydrolysis of disaccharides over solid acid catalysts under green conditions.  

PubMed

The hydrolysis of the three most important disaccharides: sucrose, maltose and cellobiose, has been comparatively studied in mild conditions (50-80°C) in water over several solid acid catalysts. Strong acidic resins (Amberlite A120 and A200), mixed oxides (silica-alumina and silica-zirconia), and niobium-containing solids (niobic acid, silica-niobia, and niobium phosphate) have been chosen as acid catalysts. The hydrolysis activity was studied in a continuous reactor with fixed catalytic bed working in total recirculation mode. Rate constants and activation parameters of the hydrolysis reactions have been obtained and discussed comparing the reactivity of the ?-1,?-2-, ?-1,4-, and ?-1,4-glycosidic bonds of the employed disaccharides. The following order of reactivity was found: sucrose > maltose > cellobiose. The sulfonic acidic resins, as expected, gave complete sucrose conversion at 80°C and good conversions for cellobiose and maltose. Among the other catalysts, niobium phosphate provided the most interesting results toward the disaccharide hydrolysis, which are here presented for the first time. Relations between activity and surface acid properties are discussed. PMID:22127325

Marzo, Matteo; Gervasini, Antonella; Carniti, Paolo

2011-10-17

5

Xanthan Sulfuric Acid: An Efficient and Recyclable Solid Acid Catalyst for Pechmann Condensation  

Microsoft Academic Search

In this paper, substituted coumarins are reported via Pechmann condensation by using various substituted phenols and ethyl acetoacetates in presence of Xanthan sulfuric acid as a solid acid catalyst under solvent-free conditions. This method is very simple, cost effective, shorter reaction times and the catalyst could be reused.

B. Suresh Kuarm; J. Venu Madhav; B. Rajitha

2011-01-01

6

Xanthan Sulfuric Acid: An Efficient and Recyclable Solid Acid Catalyst for Pechmann Condensation  

Microsoft Academic Search

In this report, substituted coumarins are formed via Pechmann condensation using various substituted phenols and ethyl acetoacetates in the presence of xanthan sulfuric acid as a solid acid catalyst under solvent-free conditions. This method is very simple, cost-effective, and has shorter reaction times, and the catalyst could be reused.

B. Suresh Kuarm; J. Venu Madhav; B. Rajitha

2012-01-01

7

Modified zirconia solid acid catalysts for organic synthesis and transformations  

Microsoft Academic Search

A series of sulfate, molybdate and tungstate promoted ZrO2 catalysts were prepared by wet impregnation method. To incorporate these promoters to Zr(OH)4, sulfuric acid, ammonium heptamolybdate, and ammonium metatungstate were used as precursors, respectively. Further, a Pt promoted Mo-ZrO2 catalyst was also prepared separately by impregnating with hexachloroplatinic acid. The surface and bulk properties of various promoted ZrO2 catalysts were

Benjaram M. Reddy; Pavani M. Sreekanth; Vangala R. Reddy

2005-01-01

8

Esterification of acidic oils over a versatile amorphous solid catalyst.  

PubMed

An amorphous SiO(2)-ZrO(2) catalyst shows high activity in the esterification of free fatty acids contained in vegetable oils while at the same time promoting the transesterification of triglycerides. The catalyst is hence a good candidate for a low-waste deacidification pretreatment or for a one-pot biodiesel production process starting from oils with a high acid content. PMID:19479893

Zaccheria, Federica; Brini, Simona; Psaro, Rinaldo; Scotti, Nicola; Ravasio, Nicoletta

2009-01-01

9

Syntheses of 5-hydroxymethylfurfural and levoglucosan by selective dehydration of glucose using solid acid and base catalysts  

Microsoft Academic Search

Selective dehydration of glucose, the most abundant monosaccharide, was examined using a solid acid catalyst individually or a combination of solid acid and base catalysts to form anhydroglucose (levoglucosan) or 5-hydroxymethylfurfural (HMF), respectively. Glucose was dehydrated to anhydroglucose by acid catalysis in polar aprotic solvents including N,N-dimethylformamide. Amberlyst-15, a strongly acidic ion-exchange resin, functioned as an efficient solid acid catalyst

Mika Ohara; Atsushi Takagaki; Shun Nishimura; Kohki Ebitani

2010-01-01

10

Conversion of biomass into 5-hydroxymethylfurfural using solid acid catalyst  

Microsoft Academic Search

5-Hydroxymethylfurfural (HMF) was produced from monosaccharide (fructose and glucose), polysaccharide (inulin) and the Jerusalem artichoke juice by a simple one-pot reaction including hydrolysis and dehydration using solid acid under mild condition. Hydrated niobium pentoxide (Nb2O5·nH2O2NA, niobic acid; NA-p, Niobic acid treated with 1M phosphoric acid and calcinated at 573 K.2) after pretreatment showed high catalytic activities for dehydration of mono-

Fengli Yang; Qishun Liu; Xuefang Bai; Yuguang Du

2011-01-01

11

Shape Selective Solid Acid Catalysts Based on Tungstophosphoric Acid Supported on Mesoporous Silica  

SciTech Connect

Solid acid catalysts comprising up to 70wt% tungstophosphoric acid (PW) dispersed on three mesoporous silicas with uniform pore size distributions of 18 Angstrom, 30 Angstrom, and 100 Angstrom, as well as on amorphous silica were synthesized. The effects of support pore size and catalyst preparation procedures on the chemical and physical properties of the synthesized catalysts were characterized using 31P magic angle spinning NMR, in-situ X-ray diffraction, and N2 physisorption. It was observed that right pore size of catalyst supports is important for PW dispersion via solution impregnation method and PW is highly dispersed even at a 70wt% loading when the support pore size is greater or equal to 30 Angstrom. Acid neutralization of silica supports and utilization of non-hydrolyzing organic polar solvents such as methanol are required to retain the Keggin structure of PW during sample preparation. The thermal stability of PW is enhanced when it is supported on silica supports. In addition, mesoprous silica with 30 Angstrom uniform pores eexhibits improved PW stability to polar solvent leaching, probably as a result of steric hindrance of the silica support due to the compatible size between the pores of the silica support (30 Angstrom) and the cluster of PW (12 Angstrom).

Wang, Yong (BATTELLE (PACIFIC NW LAB)); Kim, Anthony Y. (BATTELLE (PACIFIC NW LAB)); Li, Xiaohong (BATTELLE (PACIFIC NW LAB)); Wang, Li-Qiong (BATTELLE (PACIFIC NW LAB)); Peden, Charles HF (BATTELLE (PACIFIC NW LAB)); Bunker, Bruce C. (BATTELLE (PACIFIC NW LAB)); Chunshan Song, Juan M. Garces and Yoshihiro Sugi

2000-02-01

12

Application of Supercritical Fluids to Solid Acid Catalyst Alkylation and Regeneration  

SciTech Connect

Supercritical fluid (SCF) regeneration is a promising alternative method for regenerating solid catalysts deactivated by carbonaceous deposits. The unique solvent and transport properties of SCFs such as solvent strength similar to liquids and transport properties similar to gases make them highly suitable for extraction of fouling materials from porous heterogeneous catalysts. A brief review of the research work performed at the Idaho National Laboratory (INL) on the application of supercritical fluids to both isobutane/butene alkylation reaction and solid acid catalyst regeneration is presented in this contribution.

Lucia M. Petkovic; Daniel M. Ginosar; David N. Thompson; Kyle C. Burch

2007-05-01

13

Deactivation of a solid acid hydrocarbon conversion catalyst  

SciTech Connect

The activity, selectivity and stability of catalyst are considered in designing and screening of a potential catalyst for chemical processes. Of these, stability (i.e., resistance to deactivation) is one of the most important aspects of the catalyst. Even though there are some chemical processes that utilize fast deactivating catalysts (such as FCC), catalysts with too short lifetimes do not usually become commercialized. The deactivated catalyst can sometimes be regenerated depending on the deactivation mechanism, but most often, is simply discarded. Even if regeneration of the catalyst is possible, the down time associated with removing and loading of the catalyst has such a large impact on the economics of the process that the use of fast deactivating but regenerable catalyst is often discouraged. Therefore, catalyst stability is important in determining whether a catalyst is used commercially or not. Lately, sulfated zirconia (SZ) has been attracting a lot of attention as a potential replacement for alkane isomerization and alkylation catalysts and as a part of a Fischer-Tropsch synthesis catalyst. One shortcoming of SZ catalysts for hydrocarbon conversion is the fast deactivation of the catalysts as usually seen during n-butane isomerization. Understanding the deactivation mechanism of SZ can aid in designing a more deactivation resistant SZ catalyst that can be utilized in other hydrocarbon processes. In this study, the authors report on the changes in the concentration of active sites on SZ with TOS during n-butane isomerization at 150 C.

Kim, S.Y.; Goodwin, J.G. Jr.

1999-07-01

14

Sulfated Zirconia-Based Strong Solid-Acid Catalysts: Recent Progress  

Microsoft Academic Search

This review article deals with recent progress in the preparation of sulfated zirconia (SZ)-bassed, strong solid-acid catalysts, the characterization of their physicochemical properties and the evaluation of their catalytic performance in various promising applications. Strong emphasis was put on discussion of controversial issues such as the strength of acid sites, the nature of active sites, the reaction mechanism, and the

XUEMIN SONG; ABDELHAMID SAYARI

1996-01-01

15

Esterification reaction using solid heterogeneous acid catalysts under solvent-less condition  

Microsoft Academic Search

The preparation of di-2-ethylhexylphthalate (DOP) via esterification reaction of phthalic anhydride by 2-ethylhexanol in the presence of solid acidic catalysts has been investigated. The used catalysts were natural zeolite, synthetic zeolites (ZEOKAR-2, ASHNCH-3), heteropolyacid H4Si(W3O10)4 and sulfated ZrO2. The reactions were carried out under solvent-less conditions. It was observed that sulfated ZrO2 has higher reactivity and efficiency among the investigated

Firdovsi Tataroglu Sejidov; Yagoub Mansoori; Nadereh Goodarzi

2005-01-01

16

Synthesis of biodiesel from cottonseed oil and methanol using a carbon-based solid acid catalyst  

Microsoft Academic Search

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt and used to catalyze the transesterification of methanol with cottonseed oil. This catalyst was characterized by scanning electron microscopy\\/energy dispersive spectroscopy, BET surface area and pore size measurement, thermogravimetry analysis and Fourier transform infrared spectroscopy. The sulfonated multi-walled carbon nanotubes (s-MWCNTs) was also prepared and

Qing Shu; Qiang Zhang; Guanghui Xu; Zeeshan Nawaz; Dezheng Wang; Jinfu Wang

2009-01-01

17

Preparation and characterization of biomass carbon-based solid acid catalyst for the esterification of oleic acid with methanol.  

PubMed

A solid acid catalyst, prepared by sulfonating carbonized corn straw, was proved to be an efficient and environmental benign catalyst for the esterification of oleic acid and methanol. Various synthetic parameters, such as carbonization temperature and time were systematically examined. It was found that the catalyst exhibited the highest acid density of 2.64 mmol/g by NaOH titration. A quantitative yield (98%) of ester was achieved, using the most active sulfonated catalyst at 333 K with a 7 wt.% catalyst/oleic acid ratio for 4h, at a 7:1 M ratio of methanol/oleic acid, while the commercial available Amberlyst-15 only gave 85% yield under the same reaction condition. PMID:23453798

Liu, Tiantian; Li, Zhilong; Li, Wei; Shi, Congjiao; Wang, Yun

2013-02-09

18

Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst  

ERIC Educational Resources Information Center

|An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

Seen, Andrew J.

2004-01-01

19

Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst  

ERIC Educational Resources Information Center

An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

Seen, Andrew J.

2004-01-01

20

A highly active bagasse-derived solid acid catalyst with properties suitable for production of biodiesel.  

PubMed

A novel bagasse-based solid acid catalyst was successfully prepared through sulfonation of incompletely carbonized bagasse. A range of conditions for producing the catalyst were investigated, and the optimized catalyst, produced under carbonization at 648 K for 0.5 h and sulfonation at 423 K for 15 h, showed excellent catalytic activity and resulted in around 95 % yield of methyl oleate. Its activity was not only substantially greater than that of niobic acid and Amberlyst-15, but also comparable to or superior to that of catalysts made from pure starch or glucose, respectively. Additionally, the bagasse-derived catalyst could be repeatedly employed for at least eight cycles and still retained around 90 % of its original activity, exhibiting excellent operational stability. Furthermore, the catalyst efficiently converted waste cooking oils with 38.6 wt % free fatty acids into biodiesel and afforded a high yield of about 93.8 % within 12 h. These results clearly show that the bagasse-derived catalyst is economic, eco-friendly, and promising for biodiesel production from low-cost feedstocks and may find wide applications. PMID:22693163

Lou, Wen-Yong; Guo, Qiang; Chen, Wen-Jing; Zong, Min-Hua; Wu, Hong; Smith, Thomas J

2012-06-12

21

Preparation of solid acid catalyst from glucose-starch mixture for biodiesel production.  

PubMed

The aim of this work is to study the catalyst prepared by glucose-starch mixture. Assessment experiments showed that solid acid behaved the highest esterification activity when glucose and corn powder were mixed at ratio of 1:1, carbonized at 400°C for 75 min and sulfonated with concentrated H(2)SO(4) (98%) at 150°C for 5 h. The catalyst was characterized by acid activity measurement, XPS, TEM and FT-IR. The results indicated that solid acid composed of CS(0.073)O(0.541) has both Lewis acid sites and Bronsted acid sites caused by SO(3)H and COOH. The conversions of oleic acid esterification and triolein transesterification are 96% and 60%, respectively. Catalyst for biodiesel production from waste cottonseed oil containing high free fatty acid (FFA 55.2 wt.%) afforded the methyl ester yield of about 90% after 12h. The catalyst deactivated gradually after recycles usage, but it could be regenerated by H(2)SO(4) treatment. PMID:21067915

Chen, Guo; Fang, Baishan

2010-10-25

22

Acidity and reactivity of trifluoromethanesulfonic acid in liquid and solid acid catalysts  

Microsoft Academic Search

The acidic properties of CF3SO3H\\/SiO2 acid catalysts have been investigated by the protonation of weak bases (B) (B+H+?BH+) and the proton-transfer process from (H+A?) to (BH+A?) has been analysed by a thermodynamic procedure used to account the variation of the activity coefficient terms of the species involved. Acid–base systems with different substituted pyridines as back-titrating agents of BH+ (i.e. BH+?B)

Nunziata Clara Marziano; Lucio Ronchin; Claudio Tortato; Armando Zingales; Abdiqafar A Sheikh-Osman

2001-01-01

23

Supercritical n-butane isomerization on solid acid catalysts  

Microsoft Academic Search

n-Butane isomerization was investigated at the supercritical state in a flow type reactor. Sulfated zirconia (SZ), heteropolyacids (HPA) of the Keggin type H3PW12O40 (HPWO), H4SiW12O40 (HSiWO) supported on titania, H-mordenite (HM) were studied as catalysts at 488, 533 and 573K and 6.1, 11.0 and 13.8MPa, respectively. Gas-phase isomerization was carried out on the same catalysts for comparison. Rapid deactivation of

V. I Bogdan; T. A Klimenko; L. M Kustov; V. B Kazansky

2004-01-01

24

Efficient and stable solid acid catalysts synthesized from sulfonation of swelling mesoporous polydivinylbenzenes  

Microsoft Academic Search

Efficient and stable solid acid catalysts, sulfonic groups functional swelling mesoporous polydivinylbenzenes (PDVB-x-SO3Hs), were synthesized from sulfonation of swelling mesoporous polydivinylbenzenes (PDVB-xs) by chlorosulfonic acid in CH2Cl2. Nitrogen adsorption–desorption isotherms showed that PDVB-x-SO3Hs have high surface area and abundant mesoporosity. Elemental analysis and acid–base titration techniques showed that PDVB-x-SO3Hs have high concentration of sulfonic groups. Esterifications of acetic acid with

Fujian Liu; Xiangju Meng; Yonglai Zhang; Limin Ren; Faisal Nawaz; Feng-Shou Xiao

2010-01-01

25

Synthesis of biodiesel from waste vegetable oil with large amounts of free fatty acids using a carbon-based solid acid catalyst  

Microsoft Academic Search

A carbon-based solid acid catalyst was prepared by the sulfonation of carbonized vegetable oil asphalt. This catalyst was employed to simultaneously catalyze esterification and transesterification to synthesis biodiesel when a waste vegetable oil with large amounts of free fatty acids (FFAs) was used as feedstock. The physical and chemical properties of this catalyst were characterized by a variety of techniques.

Qing Shu; Jixian Gao; Zeeshan Nawaz; Yuhui Liao; Dezheng Wang; Jinfu Wang

2010-01-01

26

Direct production of biodiesel from high-acid value Jatropha oil with solid acid catalyst derived from lignin  

PubMed Central

Background Solid acid catalyst was prepared from Kraft lignin by chemical activation with phosphoric acid, pyrolysis and sulfuric acid. This catalyst had high acid density as characterized by scanning electron microscope (SEM), energy-dispersive x-ray spectrometry (EDX) and Brunauer, Emmett, and Teller (BET) method analyses. It was further used to catalyze the esterification of oleic acid and one-step conversion of non-pretreated Jatropha oil to biodiesel. The effects of catalyst loading, reaction temperature and oil-to-methanol molar ratio, on the catalytic activity of the esterification were investigated. Results The highest catalytic activity was achieved with a 96.1% esterification rate, and the catalyst can be reused three times with little deactivation under optimized conditions. Biodiesel production from Jatropha oil was studied under such conditions. It was found that 96.3% biodiesel yield from non-pretreated Jatropha oil with high-acid value (12.7 mg KOH/g) could be achieved. Conclusions The catalyst can be easily separated for reuse. This single-step process could be a potential route for biodiesel production from high-acid value oil by simplifying the procedure and reducing costs.

2011-01-01

27

Butyric acid esterification kinetics over Amberlyst solid acid catalysts: the effect of alcohol carbon chain length.  

PubMed

The liquid phase esterification of butyric acid with a series of linear and branched alcohols is examined. Four strong cation exchange resins, Amberlyst™ 15, Amberlyst™ 36, Amberlyst™ BD 20, and Amberlyst™ 70, were used along with para-toluenesulfonic acid as a homogeneous catalyst. The effect of increasing alcohol carbon chain length and branching on esterification rate at 60°C is presented. For all catalysts, the decrease in turnover frequency (TOF) with increasing carbon chain length of the alcohol is described in terms of steric hindrance, alcohol polarity, and hydroxyl group concentration. The kinetics of butyric acid esterification with 2-ethylhexanol using Amberlyst™ 70 catalyst is described with an activity-based, pseudo-homogeneous kinetic model that includes autocatalysis by butyric acid. PMID:23380294

Pappu, Venkata K S; Kanyi, Victor; Santhanakrishnan, Arati; Lira, Carl T; Miller, Dennis J

2012-12-20

28

Supported zirconium sulfate on carbon nanotubes as water-tolerant solid acid catalyst  

SciTech Connect

A new solid acid of zirconium sulfate (CZ) was successfully supported on carbon nanotube (CNT) for esterification reaction. Preparation conditions of the supported CZ have been investigated, to obtain highest catalytic activity for esterification reaction. XRD, TEM, BET, X-ray photoelectron spectra (XPS) and in situ FTIR analysis has also been carried out to understand the characteristics of the catalyst. In the esterification of acrylic acid with n-octanol, the supported CZ exhibited high catalytic activity and stability. The catalytic activity was nearly unchanged during four times of reuse. XRD and TEM analysis indicated that CZ was finely dispersed on CNT. XPS analysis shows that the CZ species was preserved and the chemical environment of the CZ has changed after loaded on CNT. This finding show that CNT as CZ support is an efficient water-tolerant solid acid.

Juan, Joon Ching [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Advanced Catalysis Technology Laboratory, School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600 (Malaysia); Jiang Yajie [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Meng Xiujuan [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Cao Weiliang [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China); Yarmo, Mohd Ambar [Advanced Catalysis Technology Laboratory, School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Bangi 43600 (Malaysia); Zhang Jingchang [Institute of Modern Catalysis, Beijing University of Chemical Technology, State Key Laboratory of Chemical Resource Engineering, Ministry of Education, Beijing 100029 (China)]. E-mail: zhangjc1@mail.buct.edu.cn

2007-07-03

29

Synthesis of biodiesel from a model waste oil feedstock using a carbon-based solid acid catalyst: reaction and separation.  

PubMed

A solid acid catalyst that can keep high activity and stability is necessary when low cost feedstocks are utilized for biodiesel synthesis because the reaction medium contains a large amount of water. Three solid acid catalysts were prepared by the sulfonation of carbonized vegetable oil asphalt and petroleum asphalt. The structure of these catalysts was characterized by a variety of techniques. A new process that used the coupling of the reaction and separation was employed, which greatly improved the conversion of cottonseed oil (triglyceride) and free fatty acids (FFA) when a model waste oil feedstock was used. The vegetable oil asphalt-based catalyst showed the highest catalytic activity. This was due to the high density and stability of its acid sites, its loose irregular network, its hydrophobicity that prevented the hydration of -OH species, and large pores that provided more acid sites for the reactants. PMID:20219353

Shu, Qing; Nawaz, Zeeshan; Gao, Jixian; Liao, Yuhui; Zhang, Qiang; Wang, Dezheng; Wang, Jinfu

2010-03-09

30

New Method of Determining Acid Base Strength Distribution and a New Acidity-Basicity Scale for Solid Catalysts: The Strongest Point, H (sub O).  

National Technical Information Service (NTIS)

The use of the strongest H (sub 0) as an acid-base scale is illustrated. It is concluded that the catalytic activity arises from carbonium ions for solid catalysts whose strongest point values are less than 2, from carbanions for solid catalysts whose str...

T. Yamanaka K. Tanabe

1988-01-01

31

Sulfonated mesoporous silica-carbon composites and their use as solid acid catalysts  

NASA Astrophysics Data System (ADS)

The synthesis of highly functionalized porous silica-carbon composites made up of sulfonic groups attached to a carbon layer coating the pores of three types of mesostructured silica (i.e. SBA-15, KIT-6 and mesocellular silica) is presented. The synthesis procedure involves the following steps: (a) removal of the surfactant, (b) impregnation of the silica pores with a carbon precursor, (c) carbonization and (d) sulfonation. The resulting silica-carbon composites contain ˜30 wt % of carbonaceous matter with a high density of acidic groups attached to the deposited carbon (i.e.sbnd SO3H, sbnd COOH and sbnd OH). The structural characteristics of the parent silica are retained in the composite materials, which exhibit a high surface area, a large pore volume and a well-ordered porosity made up uniform mesopores. The high density of the sulfonic groups in combination with the mesoporous structure of the composites ensures that a large number of active sites are easily accessible to reactants. These sulfonated silica-carbon composites behave as eco-friendly, active, selective, water tolerant and recyclable solid acids. In this study we demonstrate the usefulness of these composites as solid acid catalysts for the esterification of maleic anhydride, succinic acid and oleic acid with ethanol. These composites exhibit a superior intrinsic catalytic activity to other commercial solid acids such as Amberlyst-15.

Valle-Vigón, Patricia; Sevilla, Marta; Fuertes, Antonio B.

2012-11-01

32

Influence of solid acid catalyst on DME production directly from synthesis gas over the admixed catalyst of Cu\\/ZnO\\/Al 2O 3 and various SAPO catalysts  

Microsoft Academic Search

This study focused on the effect of solid acid catalyst on the catalytic performance in direct DME synthesis. The various SAPO catalysts were prepared to perform methanol dehydration and direct DME synthesis. In methanol dehydration, SAPO-34 and -18 with strong acid sites and showed high initial activity, but deactivated rapidly. This is mainly attributed to the formation of coking materials

Kye Sang Yoo; Ji-Hyun Kim; Min-Jo Park; Sun-Jin Kim; Oh-Shim Joo; Kwang-Deog Jung

2007-01-01

33

Sulfamic acid: an efficient, cost-effective and recyclable solid acid catalyst for the three-component synthesis of ?-amino nitriles  

Microsoft Academic Search

?-Amino nitriles are synthesized by the three-component coupling reaction of aldehydes, amines and trimethylsilyl cyanide using sulfamic acid as a heterogeneous solid acid catalyst, under solvent-free conditions in excellent yields. The catalyst was recovered by simple filtration and was recycled in subsequent reactions.

Akbar Heydari; Samad Khaksar; Mehrdad Pourayoubi; Ali Reza Mahjoub

2007-01-01

34

The Origin of Regioselectivity in 2-butanol Dehydration on Solid Acid Catalysts  

SciTech Connect

The origin in the variations of trans-/cis-2-butene product selectivity ratios in 2-butanol dehydration over solid acid catalysts were investigated using a combined experimental-theory approach. Reactivity measurements over ?-Al2O3, AlOx/SBA-15, and H-form zeolites with widely varying Si/Al ratios and pore structures showed over two orders of magnitude change in the trans-/cis-2-butene product ratio. Activation energy barriers calculated for the concerted C-O and ?-C-H bond breakings of adsorbed butoxy intermediates by dispersion-corrected DFT calculations correctly predicted the trans-/cis-2-butene product ratio observed on ?-Al2O3. The very low trans-2-butene selectivity on ?-Al2O3 can now be understood by the formation of a late transition state with high energy barrier caused by the strong van der Waals interaction between the ?-H atoms and the flat catalyst surface. Decreasing the dispersive attractive force between the adsorbed butoxide and the surface (e.g., by moving it further away from the support surface in AlOx/SBA-15) leads to almost equimolar formation of the trans- and cis-2-butene isomers. Trans-/cis-2-butene selectivity ratios much higher than that dictated by thermodynamic equilibrium can be achieved by introducing additional geometric constraints around the active catalytic site (e.g., varying the 3D environment around the active center in zeolites). We propose a model to explain the widely varying trans-/cis-2-butene selectivity in 2-butanol dehydration over solid acid catalysts that is consistent with the experimental results in this study. A key outcome of the study is the realization that van der Waals interactions between the reactant and the active catalyst surface must be included in the theoretic models in order to be able to accurately predict product selectivities. This information, in turn, significantly advances our ability to develop catalyst materials with designed active centers in order to achieve desired regioselectivities.

Kwak, Ja Hun; Rousseau, Roger J.; Mei, Donghai; Peden, Charles HF; Szanyi, Janos

2011-10-17

35

Activity and Evolution of Vapor Deposited Pt-Pd Oxygen Reduction Catalysts for Solid Acid Fuel Cells  

SciTech Connect

The performance of hydrogen fuel cells based on the crystalline solid proton conductor CsH2PO4 is circumscribed by the mass activity of platinum oxygen reduction catalysts in the cathode. Here we report on the first application of an alloy catalyst in a solid acid fuel cell, and demonstrate an activity 4.5 times greater than Pt at 0.8 V. These activity enhancements were obtained with platinum-palladium alloys that were vapor-deposited directly on CsH2PO4 at 210 C. Catalyst mass activity peaks at a composition of 84 at% Pd, though smaller activity enhancements are observed for catalyst compositions exceeding 50 at% Pd. Prior to fuel cell testing, Pd-rich catalysts display lattice parameter expansions of up to 2% due to the presence of interstitial carbon. After fuel cell testing, a Pt-Pd solid solution absent of lattice dilatation and depleted in carbon is recovered. The structural evolution of the catalysts is correlated with catalyst de-activation.

Papandrew, Alexander B [ORNL; Chisholm, Calum R [ORNL; Zecevic, strahinja [LiOx, Inc., Pasadena, California 91106, United States; Veith, Gabriel M [ORNL; Zawodzinski, Thomas A [ORNL

2013-01-01

36

Efficient production of biodiesel from high free fatty acid-containing waste oils using various carbohydrate-derived solid acid catalysts.  

PubMed

In the present study, such carbohydrate-derived catalysts have been prepared from various carbohydrates such as d-glucose, sucrose, cellulose and starch. The catalytic and textural properties of the prepared catalysts have been investigated in detail and it was found that the starch-derived catalyst had the best catalytic performance. The carbohydrate-derived catalysts exhibited substantially higher catalytic activities for both esterification and transesterification compared to the two typical solid acid catalysts (sulphated zirconia and Niobic acid), and gave markedly enhanced yield of methyl esters in converting waste cooking oils containing 27.8wt% high free fatty acids (FFAs) to biodiesel. In addition, under the optimized reaction conditions, the starch-derived catalyst retained a remarkably high proportion (about 93%) of its original catalytic activity even after 50 cycles of successive re-use and thus displayed very excellent operational stability. Our results clearly indicate that the carbohydrate-derived catalysts, especially the starch-derived catalyst, are highly effective, recyclable, eco-friendly and promising solid acid catalysts that are highly suited to the production of biodiesel from waste oils containing high FFAs. PMID:18504123

Lou, Wen-Yong; Zong, Min-Hua; Duan, Zhang-Qun

2008-05-27

37

Degradation of polyethylene and polypropylene into fuel oil by using solid acid and non-acid catalysts  

Microsoft Academic Search

The thermal and catalytic degradation of plastic polymers, polyethylene (PE) at 430°C and polypropylene (PP) at 380°C into fuel oil were carried out by batch operation. The catalysts employed were acid-catalysts silica–alumina (SA-1, SA-2), zeolite ZSM-5 and non acidic mesoporous silica catalysts (silicalite, mesoporous silica gel and mesoporous folded silica (FSM). The yields of product gas, liquid and residues; recovery

Yusaku Sakata; Akinori Muto

1999-01-01

38

Conversion of furfuryl alcohol into ethyl levulinate using solid acid catalysts.  

PubMed

Furfural, a potential coproduct of levulinic acid, can be converted into levulinic acid via hydrogenation to furfuryl alcohol and subsequent ethanolysis to ethyl levulinate. The ethanolysis reaction is known to proceed in the presence of H(2)SO(4). We show here that several strongly acidic resins are comparably effective catalysts for this reaction. Optimal performance is achieved by balancing the number of acid sites with their accessibility in the resin. Acidic zeolites such as H-ZSM-5 also catalyze this reaction, although with a lower activity and a higher co-production of diethyl ether. PMID:19370740

Lange, Jean-Paul; van de Graaf, Wouter D; Haan, René J

2009-01-01

39

Expeditious Pechmann Condensation by Using Biodegradable Cellulose Sulfuric Acid as a Solid Acid Catalyst  

Microsoft Academic Search

A facile synthesis of coumarins was performed in excellent yields via Pechmann condensation by using different type of phenols and ethylacetoacetates under solvent–free media using both conventional method and microwave irradiation in short reaction times is described. The reaction workup is very simple, and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent

B. Suresh Kuarm; J. Venu Madhav; S. Vijaya Laxmi; B. Rajitha; Y. Thirupathi Reddy; P. Narsimha Reddy; Peter A. Crooks

2010-01-01

40

Selective reduction of nitrogen monoxide by catalysts based on composites between solid acid and perovskite in the presence of excess oxygen  

Microsoft Academic Search

The influence of the acid property of solid acids on the selective reduction of nitrogen monoxide by catalyst composites from perovskite and solid acid materials was examined for the case of excess of oxygen by using the perovskite YFeO3 and the solid acids TiO2 and ZrO2. For comparison cordierite was likewise employed as support material. It is shown that the

G. Knell; P. Kessler; E. Plies

1996-01-01

41

A highly efficient magnetic solid acid catalyst for synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation.  

PubMed

Fe(3)O(4) nanoparticles were prepared by chemical coprecipitation method and subsequently coated with 3-aminopropyltriethoxysilane (APTES) via silanization reaction. Grafting of chlorosulfuric acid on the amino-functionalized Fe(3)O(4) nanoparticles afforded sulfamic acid-functionalized magnetic nanoparticles (SA-MNPs). SA-MNPs was found to be a mild and effective solid acid catalyst for the efficient, one-pot, three-component synthesis of 2,4,5-trisubstituted imidazoles under ultrasound irradiation. This protocol afforded corresponding imidazoles in shorter reaction durations, and in high yields. This green procedure has many obvious advantages compared to those reported in the previous literatures, including avoiding the use of harmful catalysts, easy and quick isolation of the products, excellent yields, short routine, and simplicity of the methodology. PMID:23137656

Safari, Javad; Zarnegar, Zohre

2012-10-17

42

Synthesis and characterization of sulfonated single-walled carbon nanotubes and their performance as solid acid catalyst  

SciTech Connect

Single-walled carbon nanotubes (SWCNTs) were treated with sulfuric acid at 300 deg. C to synthesize sulfonated SWCNTs (s-SWCNTs), which were characterized by electron microscopy, infrared, Raman and X-ray photoelectron spectroscopy, and thermo analysis. Compared with activated carbon, more sulfonic acid groups can be introduced onto the surfaces of SWCNTs. The high degree ({approx}20 wt%) of surface sulfonation led to hydrophilic sidewalls that allows the SWCNTs to be uniformly dispersed in water and organic solvents. The high surface acidity of s-SWCNTs was demonstrated by NH{sub 3} temperature-programmed desorption technique and tested by an acetic acid esterification reaction catalyzed by s-SWCNTs. The results show that the water-dispersive s-SWCNTs are an excellent solid acid catalyst and demonstrate the potential of SWCNTs in catalysis applications. - Graphical abstract: Sulfonated SWCNTs with 20 wt% -SO{sub 2}OH groups were prepared by a high-temperature H{sub 2}SO{sub 4} process, which transformed the hydrophobic surface of pristine SWCNTs to a hydrophilic surface and provided an excellent performance as solid acid catalyst.

Yu Hao [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China)], E-mail: yuhao@scut.edu.cn; Jin Yuguang; Li Zhili [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China); Peng Feng [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China)], E-mail: cefpeng@scut.edu.cn; Wang Hongjuan [School of Chemical and Energy Engineering, South China University of Technology, Guangzhou 510641 (China)

2008-03-15

43

Activation Energies for Carbon Acid/D2 Exchange Over a Solid Base Catalyst. Correlation with Gas Phase Acidities.  

National Technical Information Service (NTIS)

Thermally activated Magnesium oxide has been employed as a highly basic solid catalyst for carrying out CH/D2 exchange in hydrocarbons. A series of benzylic, aromatic, and alkane C-H bonds were studied. Reaction rates at various temperatures yielded activ...

M. Fazlul K. J. Klabunde

1988-01-01

44

Nano sulfated titania as solid acid catalyst in direct synthesis of fatty acid amides.  

PubMed

Nanosized sulfated titania was prepared by a sol-gel hydrothermal process. X-ray diffraction (XRD), transmission electron, and scanning electron micrographs (TEM and SEM), FT-IR specific surface area, and BET N(2) adsorption were employed to characterize the properties of the synthesized sulfated TiO(2). The results indicate that both anatase and rutile TiO(2) are obtainable. This prepared sulfated titania showed high catalytic activity in direct amidation of fatty acids as well as benzoic acids with various amines under solvent-free conditions. PMID:21405011

Hosseini-Sarvari, Mona; Sodagar, Esmat; Doroodmand, Mohammad Mahdi

2011-03-23

45

Low-quality vegetable oils as feedstock for biodiesel production using K-pumice as solid catalyst. Tolerance of water and free fatty acids contents.  

PubMed

Waste oils are a promising alternative feedstock for biodiesel production due to the decrease of the industrial production costs. However, feedstock with high free fatty acids (FFA) content presents several drawbacks when alkaline-catalyzed transesterification reaction is employed in biodiesel production process. Nowadays, to develop suitable processes capable of treating oils with high free fatty acids content, a two-step process for biodiesel production is being investigated. The major problem that it presents is that two catalysts are needed to carry out the whole process: an acidic catalyst for free fatty acids esterification (first step) and a basic catalyst for pretreated product transesterification (second step). The use of a bifunctional catalyst, which allows both reactions to take place simultaneously, could minimize the production costs and time. In the present study, the behavior of pumice, a natural volcanic material used as a heterogeneous catalyst, was tested using oils with several FFA and water contents as feedstock in the transesterification reaction to produce biodiesel. Pumice as a bifunctional solid catalyst, which can catalyze simultaneously the esterification of FFA and the transesterification of fatty acid glycerides into biodiesel, was shown to be an efficient catalyst for the conversion of low-grade, nonedible oil feedstock into biodiesel product. Using this solid catalyst for the transesterification reaction, high FAME yields were achieved when feedstock oils presented a FFA content until approximately 2% wt/wt and a water content until 2% wt/wt. PMID:22799882

Díaz, L; Borges, M E

2012-08-01

46

Sulfamic acid: an efficient, cost-effective and recyclable solid acid catalyst for the Friedlander quinoline synthesis  

Microsoft Academic Search

o-Aminoaryl ketones undergo smooth condensation with ?-methylene ketones in the presence of sulfamic acid (NH2SO3H) (SA) under mild reaction conditions to afford the corresponding polysubstituted quinolines in excellent yields. The catalyst can be recovered by simple filtration and can be recycled in subsequent reactions. The method is simple, cost-effective and environmentally benign.

J. S. Yadav; P. Purushothama Rao; D. Sreenu; R. Srinivasa Rao; V. Naveen Kumar; K. Nagaiah; A. R. Prasad

2005-01-01

47

Solid acids as catalysts for the conversion of D-xylose, xylan and lignocellulosics into furfural in ionic liquid.  

PubMed

With the aim to develop an ecologically viable catalytic pathway for furfural production without the use of inorganic acids, H3PW12O40, Amberlyst-5 and NKC-9 (macroporous styrene-based sulfonic acid resin) were used as catalysts for producing furfural from xylose, xylan and lignocellulosic biomass in [BMIM]Cl under microwave irradiation at atmospheric pressure. A surprisingly high furfural yield of 93.7% from xylan was obtained by H3PW12O40 at 160 °C in 10 min. The degradation of furfural affected by single addition of [BMIM]Cl and solid acids was also investigated. The IL could be easily recycled and reused with stable solvent capacity for multiple runs (5×) after the product furfural was extracted with ethyl acetate. PMID:23567725

Zhang, Luxin; Yu, Hongbing; Wang, Pan

2013-03-18

48

Alkali metal salts and ammonium salts of Keggin-type heteropolyacids as solid acid catalysts for liquid-phase Friedel-Crafts reactions  

Microsoft Academic Search

The possibility of using a heteropolyacid salt as solid acid catalyst for liquid-phase Friedel-Crafts reactions was investigated through extensive examinations on various kinds of the salt prepared from different combinations of Keggin anions and their counter cations including ammonium ion. The catalytic behavior of the salt was discussed in relation to acidity, surface area, porosity, and thermal stability. Of the

Yusuke Izumi; Mayumi Ogawa; Kazuo Urabe

1995-01-01

49

Direct Alcohol Fuel Cells Using Solid Acid Electrolytes.  

National Technical Information Service (NTIS)

Direct alcohol fuel cells using solid acid electrolytes and internal reforming catalysts are disclosed. The fuel cell generally comprises an anode, a cathode, a solid acid electrolyte and an internal reforming catalyst. The internal reforming catalyst may...

S. M. Haile T. Uda

2005-01-01

50

Cellulose Sulfuric Acid: Novel and Efficient Biodegradable and Recyclable Acid Catalyst for the Solid-State Synthesis of Thiadiazolo Benzimidazoles  

Microsoft Academic Search

An efficient method for the synthesis of 2-substituted benzimidazoles has been developed. In this method, benzo[c][1,2,5]thiadiazole-4,5-diamine was condensed with different aldehydes in the presence of cellulose sulfuric acid under solvent-free conditions by simple physical grinding of reactants using a mortar and pestle at room temperature. The methodology is mild, high-yielding, and green, and the catalyst could be easily recycled.

B. Suresh Kuarm; J. Venu Madhav; B. Rajitha; Y. Thirupathi Reddy; P. Narsimha Reddy; Peter A. Crooks

2011-01-01

51

Novel efficient mesoporous solid acid catalyst UDCaT-4: dehydration of 2-propanol and alkylation of mesitylene.  

PubMed

A novel mesoporous solid acid catalyst named UDCaT-4 was synthesized by incorporating superacidic centers of persulfated alumina and zirconia into highly ordered and well-defined hexagonal mesoporous silica. The catalyst is well characterized, and its properties are compared with those of bulk persulfated alumina and zirconia (PAZ) by FTIR spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, pore size analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and ammonia temperature-programmed desorption. UDCaT-4 is more acidic than PAZ. The dehydration processes of 2-propanol, diisopropyl ether, and n-propanol were studied independently including a mixture of n-propanol and 2-propanol to throw light on kinetics and mechanism. For alkylation of mesitylene with 2-propanol, UDCaT-4 exhibits superior catalytic activity in comparison with PAZ and also it shows remarkable stability toward coke formation. Kinetic interpretations of the observed rate data are presented for all reactions, and mechanistic models are developed. The results are novel. PMID:15595790

Yadav, Ganapati D; Murkute, Ambareesh D

2004-12-21

52

Transesterification of triacetin with methanol on solid acid and base catalysts  

Microsoft Academic Search

Biodiesel is a particularly attractive renewable fuel as it can be used in existing engines, is environmentally friendly, and is readily synthesized from animal fats and vegetable oils. Heterogeneous catalysts offer exciting possibilities for improving the economics of biodiesel synthesis; however, few published investigations have addressed the use of such catalysts to date. The purpose of this research was to

Dora E. López; James G. Goodwin; David A. Bruce; Edgar Lotero

2005-01-01

53

Solid phosphorus fluoride catalysts  

SciTech Connect

Olefinic hydrocarbons which contain from three to about six carbon atoms may be subjected to oligomerization reactions as well as being used as alkylating agents in the alkylation of alkylatable hydrocarbons by treatment at reaction conditions in the presence of a catalyst comprising a phosphorus fluoride such as phosphorus trifluoride or phosphorus pentafluoride composited on a high surface area metal oxide such as gamma-alumina. The oligomers which are obtained in the oligomerization process will contain less branching than those which are obtained when utilizing other catalysts.

Imai, T.

1984-08-14

54

Vapor-phase nitration of benzene over solid acid catalysts (1): Nitration with nitric oxide (NO 2)  

Microsoft Academic Search

Vapor-phase nitration of benzene over acidic catalysts is expected to be a clean process with no sulfuric acid waste. We investigated this process over acidic catalysts utilizing nitric oxide (NO2) as a nitrating agent, and found that several mixed metal oxides, such as silica–alumina, zinc-oxide–titania, and tungsten-oxides–molybdenum-oxide, exhibited a fairly good activity. Among them, WO3–MoO3 is the most active, but

H. Sato; K. Hirose

1998-01-01

55

Production of middle distillate in a dual-bed reactor from synthesis gas through wax cracking: Effect of acid property of Pd-loaded solid acid catalysts on the wax conversion and middle distillate selectivity  

Microsoft Academic Search

Selective production of middle distillate (C10–C20) from synthesis gas (CO+H2) was carried out in a dual-bed reactor. Co-based catalysts were used in the first-bed reactor to produce wax (C21+) from synthesis gas, and Pd-loaded solid acid catalysts were used in the second-bed reactor to produce middle distillate from wax through hydrocracking. Co\\/TiO2 catalyst in the first-bed reactor produced more than

Kyung Min Cho; Sunyoung Park; Jeong Gil Seo; Min Hye Youn; Sung-Hyeon Baeck; Ki-Won Jun; Jin Suk Chung; In Kyu Song

2008-01-01

56

Comparison of mesoporous solid acid catalysts in the production of DABCO by cyclization of ethanolamine  

Microsoft Academic Search

DABCO have been synthesized under vapor phase reaction conditions using ethanolamine in the presence of water over synthesized and characterized Zn–Al–MCM-41 and Al–MCM-41 as catalysts. On increasing the Si\\/(Zn+Al) ratios of Zn–Al–MCM-41 and Si\\/Al ratios of Al–MCM-41 catalysts from 75 to 380 and 21 to 104 respectively, the yield and selectivity of DABCO decreased. This may be due to the

Manickam Selvaraj; Byoung Ryul Min; Yong Gun Shul; Tai Gyu Lee

2004-01-01

57

Sulfated zirconia as a solid acid catalyst for the dehydration of fructose to 5-hydroxymethylfurfural  

Microsoft Academic Search

Sulfated zirconia was prepared by impregnation with H2SO4, and was characterized using BET surface area, XRD, TG–DTA and FT-IR techniques. The sulfated zirconia was evaluated as a catalyst for the dehydration of fructose to 5-hydroxymethylfurfural (5-HMF) by microwave heating. With sulfated zirconia catalyst, high fructose conversion of 93.6% with 5-HMF yield of 72.8% could be attained at 180°C for 20min

Xinhua Qi; Masaru Watanabe; Taku M. Aida; Richard L. Smith Jr.

2009-01-01

58

A bifunctional palladium/acid solid catalyst performs the direct synthesis of cyclohexylanilines and dicyclohexylamines from nitrobenzenes.  

PubMed

Nitroderivatives are transformed to cyclohexylanilines at room temperature in good yields and selectivity via a hydrogenation-amine coupling cascade reaction using Pd nanoparticles on carbon as a catalyst and a Brönsted acid. PMID:23925659

Rubio-Marqués, Paula; Leyva-Pérez, Antonio; Corma, Avelino

2013-09-25

59

Surface characterization and catalytic activity of sulfate-, molybdate- and tungstate-promoted Al 2O 3–ZrO 2 solid acid catalysts  

Microsoft Academic Search

Alumina–zirconia mixed oxide-supported sulfate-, molybdate- and tungstate-promoted solid acid catalysts were synthesized and characterized by various techniques. The Al–Zr hydroxide gel was obtained by a co-precipitation method from their corresponding nitrate salts by hydrolysis with aqueous ammonia. To the Al–Zr-hydrous mixed oxide support, aqueous solutions of sulfuric acid, ammonium heptamolybdate and ammonium metatungstate were added and the mixtures were refluxed

Benjaram M. Reddy; Pavani M. Sreekanth; Yusuke Yamada; Tetsuhiko Kobayashi

2005-01-01

60

Surface characterization of sulfate, molybdate, and tungstate promoted TiO 2-ZrO 2 solid acid catalysts by XPS and other techniques  

Microsoft Academic Search

Titania–zirconia binary oxide supported sulfate, molybdate, and tungstate promoted solid acid catalysts were prepared by suspending the hydrous mixed oxide support in aqueous solutions of sulfuric acid, ammonium heptamolybdate, and ammonium metatungstate. The suspensions were refluxed at 383K followed by evaporation of the water, drying and calcination at 1073K. The resulting materials were characterized by means of X-ray powder diffraction,

Benjaram M Reddy; Pavani M Sreekanth; Yusuke Yamada; Qiang Xu; Tetsuhiko Kobayashi

2002-01-01

61

Synthesis of phenoxy ethers of methyl lesquerolate over solid acid catalysts  

Technology Transfer Automated Retrieval System (TEKTRAN)

Lesquerolic acid is the primary fatty acid found in Lesquerella. The seeds are 33% oil of which about 55% is the 20 carbon unsaturated hydroxyl fatty acid, lesquerolic acid. A simple derivatization of this fatty acid could expand its potential as an industrial oil. We have used a heterogeneous Le...

62

Efficient conversion of furfuryl alcohol into alkyl levulinates catalyzed by an organic-inorganic hybrid solid acid catalyst.  

PubMed

A clean, facile, and environment-friendly catalytic method has been developed for the conversion of furfuryl alcohol into alkyl levulinates making use of the novel solid catalyst methylimidazolebutylsulfate phosphotungstate ([MIMBS]?PW??O??). The solid catalyst is an organic-inorganic hybrid material, which consists of an organic cation and an inorganic anion. A study for optimizing the reaction conditions such as the reaction time, the temperature and the catalyst loading has been performed. Under optimal conditions, a high n-butyl levulinate yield of up to 93?% is obtained. Furthermore, the kinetics of the reaction pathways and the mechanism for the alcoholysis of furfuryl alcohol are discussed. This method is environmentally benign and economical for the conversion of biomass-based derivatives into fine chemicals. PMID:21226220

Zhang, Zehui; Dong, Kun; Zhao, Zongbao Kent

2011-01-17

63

SYNTHESIS AND CHARACTERIZATION OF A NOVEL SOLID ACID CATALYST FOR IMPROVED USE OF WASTE OIL FEEDSTOCK FOR BIODIESEL PRODUCTION  

EPA Science Inventory

Carbon Catalyst Synthesis - Sucrose was treated directly with excess sulfuric acid sulfuric acid (9:1 mol/mol, 25°C). A carbon foam (nearly 20 fold increase in bulk volume) was immediately formed. The foam was then washed until no sulfate was dete...

64

Hydrocracking of polyolefins to liquid fuels over strong solid acid catalysts  

Microsoft Academic Search

Post-consumer plastic makes up about 13 wt% of the 48 million tons of total packaging wastes generated annually. Plastics are non-biodegradable, constitute a increasingly large volume of solid wastes (20 vol. % in 1990), and are not being recycled to a significant extent. Pyrolysis, as an alternative for plastic waste recycling, usually results in unsaturated and unstable oils of low

K. R. Venkatesh; J. Hu; J. W. Tierney; I. Wender

1995-01-01

65

A Skeletal Rearrangement Study of Labeled Butanes on a Solid Superacid Catalyst : Sulfuric-Acid Treated Zirconium-Oxide  

Microsoft Academic Search

The reactions of n-butane and isobutane have been studied in a flow system in the presence of hydrogen at 250°C using sulfuric acid treated zirconia as catalyst. The conversion of the butanes occurs with high selectivity in isomerization. The branched isomer reacts much faster than the linear one. The use of 13C labelled starting material and analysis of the isotope

F. Garin; L. Seyfried; P. Girard; G. Maire; A. Abdulsamad; J. Sommer

1995-01-01

66

Al and Ga-promoted WO 3\\/ZrO 2 strong solid acid catalysts and their catalytic activities in n-butane isomerization  

Microsoft Academic Search

A series of Al- and Ga-promoted tungstated zirconia strong solid acid catalysts were prepared. The effect of Al2O3 and Ga2O3 on the structural, acidic and redox features of WO3\\/ZrO2 (WZ) has been characterized by means of X-ray powder diffraction (XRD), N2 adsorption (BET), UV–visible diffuse reflectance spectra (UV–vis), infrared spectra (IR), NH3 temperature-programmed desorption (NH3-TPD) and H2 temperature-programmed reduction (H2-TPR).

Xiao-Rong Chen; Chang-Lin Chen; Nan-Ping Xu; Chung-Yuan Mou

2004-01-01

67

Decomposition of oxalic acid on solid-phase catalysts in nitric acid solutions in the presence of hydrazine  

SciTech Connect

Decomposition of N{sub 2}H{sub 4} and H{sub 2}C{sub 2}O{sub 4} has been studied by titrimetric method in HNO{sub 3} solutions in the presence of Pt/SiO{sub 2} catalyst and BAU activated carbon. Under static conditions, the rate of N{sub 2}H{sub 4} decomposition in the presence of Pt/SiO{sub 2} increases monotonically with increasing temperature, Pt content, and amount of catalyst per unit volume of the solution. With increasing HNO{sub 3} concentration from 0.2 to 7 M, the N{sub 2}H{sub 4} decomposition rate peaks at 1-2 M. Decomposition of H{sub 2}C{sub 2}O{sub 4} begins only after N{sub 2}H{sub 4} is almost completely decomposed. When passing a mixture of H{sub 2}C{sub 2}O{sub 4} with N{sub 2}H{sub 4}through a column packed with catalyst, decomposition of H{sub 2}C{sub 2}O{sub 4} begins before complete disappearence of N{sub 2}H{sub 4}.

Krot, N.N.; Shilov, V.P.; Dzyubenko, V.I. [Institute of Physical Chemistry, Moscow (Russian Federation)] [and others

1995-01-01

68

A skeletal rearrangement study of labelled butanes on a solid superacid catalyst: Sulfuric acid treated zirconium oxide  

SciTech Connect

Under the pressure of the worldwide trend towards more severe environmental legislation the refining industry has started to produce cleaner fuels. The reactions of n-butane and isobutane have been studied in a flow system in the presence of hydrogen at 250{degrees}C using sulfuric acid treated zirconia as catalyst. The conversion of the butanes occurs with high selectivity in isomerization. The branched isomer reacts much faster than the linear one. The use of {sup 13}C labelled starting material and analysis of the isotopic distribution in the products show that the rearrangement is of intramolecular nature in accord with the superacidic properties of the catalyst. 26 refs., 3 figs., 4 tabs.

Garin, F.; Seyfried, L.; Girard, P.; Maire, G.; Abdulsamad, A.; Sommer, J. [Universite Louis Pasteur, Strasbourg (France)

1995-01-01

69

Sulfamic acid: An efficient and cost-effective solid acid catalyst for the synthesis of ?-aminophosphonates at ambient temperature  

Microsoft Academic Search

Sulfamic acid catalyzed solvent-free protocol has been developed for the synthesis of ?-aminophosphonates by three component condensation between aldehydes, amines and diethyl phosphite at ambient temperature.

S. D. Mitragotri; D. M. Pore; U. V. Desai; P. P. Wadgaonkar

2008-01-01

70

Acidic Cs +, NH 4 +, and K +Salts of 12-Tungstophosphoric Acid as Solid Catalysts for Isobutane\\/2-butene Alkylation  

Microsoft Academic Search

The caesium, ammonium, and potassium salts of 12-tungstophosphoric acid (HPW) have been prepared with different stoichiometries (1?x?3), and their catalytic behavior measured for the liquid phase alkylation of isobutane with 2-butene at 80°C. The salts with a cation content of 2.5?x?3, and that of Cs+withx=2, showed a much higher surface area than the parent acid, which is partially due to

A. Corma; A. Mart??nez; C. Mart??nez

1996-01-01

71

Characterizing Surface Acidic Sites in Mesoporous-Silica-Supported Tungsten Oxide Catalysts Using Solid State NMR and Quantum Chemistry Calculations  

SciTech Connect

The acidic sites in dispersed tungsten oxide supported on SBA-15 mesoporous silica were investigated using a combination of pyridine titration, both fast-, and slow-MAS {sup 15}N NMR, static {sup 2}H NMR, and quantum chemistry calculations. It is found that the bridged acidic -OH groups in surface adsorbed tungsten dimers (i.e., W-OH-W) are the Broensted acid sites. The unusually strong acidity of these Broensted acid sites is confirmed by quantum chemistry calculations. In contrast, terminal W-OH sites are very stable and only weakly acidic as are terminal Si-OH sites. Furthermore, molecular interactions between pyridine molecules and the dimer Broensted and terminal W-OH sites for dispersed tungsten oxide species is strong. This results in restricted molecular motion for the interacting pyridine molecules even at room temperature, i.e., a reorientation mainly about the molecular 2-fold axis. This restricted reorientation makes it possible to estimate the relative ratio of the Broensted (tungsten dimer) to the weakly acidic terminal W-OH sites in the catalyst using the slow-MAS {sup 1}H-{sup 15}N CP PASS method.

Hu, Jian Z.; Kwak, Ja Hun; Wang, Yong; Hu, Mary Y.; Turcu, Romulus VF; Peden, Charles HF

2011-10-18

72

A comparative study of solid carbon acid catalysts for the esterification of free fatty acids for biodiesel production. Evidence for the leaching of colloidal carbon.  

PubMed

The preparation of a variety of sulfonated carbons and their use in the esterification of oleic acid is reported. All sulfonated materials show some loss in activity associated with the leaching of active sites. Exhaustive leaching shows that a finite amount of activity is lost from the carbons in the form of colloids. Fully leached catalysts show no loss in activity upon recycling. The best catalysts; 1, 3, and 6; show initial TOFs of 0.07s(-1), 0.05s(-1), and 0.14s(-1), respectively. These compare favorably with literature values. Significantly, the leachate solutions obtained from catalysts 1, 3, and 6, also show excellent esterification activity. The results of TEM and catalyst poisoning experiments on the leachate solutions associate the catalytic activity of these solutions with carbon colloids. This mechanism for leaching active sites from sulfonated carbons is previously unrecognized. PMID:24021721

Deshmane, Chinmay A; Wright, Marcus W; Lachgar, Abdessadek; Rohlfing, Matthew; Liu, Zhening; Le, James; Hanson, Brian E

2013-08-20

73

Assessing the acid strength of solid acid catalysts with the use of linear free energy relationship: H\\/D exchange with substituted benzene derivatives  

Microsoft Academic Search

The acid strength of solid acid materials can be assessed using the linear free energy relationship, applying the Hammett–Brown equation (logkX\\/kH=??+) for the H\\/D exchange with substituted benzenes. The magnitude of the ? varies for different solid acid materials (Amberlyst-15, zeolite HUSY, K-10 montmorillonite, and niobic acid) and is associated with the degree of proton transfer in the transition state.

Valter L. C. Gonçalves; Rogério C. Rodrigues; Rodolfo Lorençato; Claudio J. A. Mota

2007-01-01

74

Silica Sulfuric Acid, an Efficient and Recyclable Solid Acid Catalyst for the Synthesis of 4,4?-(Arylmethylene)bis (1H-pyrazol-5-ols)  

Microsoft Academic Search

Silica sulfuric acid (SSA) is employed as a recyclable catalyst for the condensation reaction of aromatic aldehydes with 3-methyl-l-phenyl-5-pyrazolone. This condensation reaction is performed in a mixture (1:1 v\\/v) of water–ethanol at 70 °C, giving 4,4?-alkylmethylene-bis(3-methyl-5-pyrazolones) in 75–93% yields.

Khodabakhsh Niknam; Salimeh Mirzaee

2011-01-01

75

Sulfamic Acid: An Efficient, Cost-Effective, and Reusable Solid Acid Catalyst for the Synthesis of 1,8-Naphthyridines Under Solvent-Free Heating and Microwave Irradiation  

Microsoft Academic Search

An efficient and convenient method is described for the synthesis of 1,8-naphthyridines in excellent yields by condensation of 2-aminonicotinaldehyde with various active methylene compounds in the presence of sulfamic acid as the catalyst in a solvent-free media using both conventional heating and microwave irradiation.

Y. Thirupathi Reddy; P. Raghotham Reddy; M. Nikhil Reddy; B. Rajitha; Peter A. Crooks

2008-01-01

76

Superior performance of metal-organic frameworks over zeolites as solid acid catalysts in the Prins reaction: green synthesis of nopol.  

PubMed

The catalytic performance of a set of metal-organic frameworks [CuBTC, FeBTC, MIL-100(Fe), MIL-100(Cr), ZIF-8, MIL-53(Al)] was investigated in the Prins condensation of ?-pinene with formaldehyde and compared with the catalytic behavior of conventional aluminosilicate zeolites BEA and FAU and titanosilicate zeolite MFI (TS-1). The activity of the investigated metal-organic frameworks (MOFs) increased with the increasing concentration of accessible Lewis acid sites in the order ZIF-8acid sites of zeolites BEA and FAU, which showed significantly lower selectivity to the target nopol than the MOFs. Its high activity, the preservation of its structure and active sites, and the possibility to use it in at least three catalytic cycles without loss of activity make MIL-100 (Fe) the best performing catalyst of the series for the Prins condensation of ?-pinene and paraformaldehyde. Our report exemplifies the advantages of MOFs over zeolites as solid catalysts in liquid-phase reactions for the production of fine chemicals. PMID:23592600

Opanasenko, Maksym; Dhakshinamoorthy, Amarajothi; Hwang, Young Kyu; Chang, Jong-San; Garcia, Hermenegildo; ?ejka, Ji?í

2013-04-16

77

Sulfated Ce x Zr 1? x O 2 solid acid catalyst for solvent free synthesis of coumarins  

Microsoft Academic Search

A novel SO42?\\/CexZr1?xO2 catalyst has been employed for Pechmann condensation of phenols under solvent-free conditions. Catalyst loads as low as 10wt.% could be used leading to high yields with activated phenols at an oil bath temperature of 393K. To make the catalyst, Ce–Zr–hydroxide gel was prepared by a coprecipitation method and SO42? ions were deposited by treating the gel with

Benjaram M. Reddy; Meghshyam K. Patil; Pandian Lakshmanan

2006-01-01

78

A new selective route to 5-hydroxymethylfurfural from furfural and furfural derivatives over microporous solid acidic catalysts  

Microsoft Academic Search

Hydroxymethylation of furfural and its 1,3 dithiolane derivative with aqueous formaldehyde was performed in a batch mode in the presence of dealuminated mordenites as catalysts, at 363 K. Starting from furfural, the selectivity to 5-hydroxymethylfurfural is about 30% whatever the catalysts. However, the selectivity can rise up to 50% if an organic co-solvent is used for simultaneous extraction of 5-hydroxymethylfurfural

Jérôme Lecomte; Annie Finiels; Claude Moreau

1999-01-01

79

Brønsted acid sites in metal-containing solid acids: from quantification to molecular design of new catalysts/silver(I)-polyoxometalates.  

PubMed

Based on H/D isotope exchange studies devoted to the quantification of the number of Brønsted acid sites in solid acids, we report herein an innovative approach to determine the amount of silver cations present in Keggin-type polyoxometalates (POM). The molecular design of these bifunctional heteropolyacids can therefore be achieved by varying the Ag(+)versus H(+) exchange ratio in the starting mixture. Consequently, the stoichiometries of Ag(x)H(4-x)SiW??O?? POM were ascertained for 0 < x < 4 by the H/D exchange technique. PMID:21210069

Borghèse, Sophie; Blanc, Aurélien; Pale, Patrick; Louis, Benoît

2011-01-06

80

ZrO 2 –SiO 2 Mixed Oxides Xerogel and Aerogel as Solid Acid Catalysts for Solvent Free Isomerization of ?-Pinene and Dehydration of 4Methyl2Pentanol  

Microsoft Academic Search

\\u000a Abstract  Sulfated and non-sulfated ZrO2–SiO2 mixed oxide xerogel and aerogel samples having varied Zr\\/Si molar ratio were evaluated as solid acid catalysts for the isomerization\\u000a of ?-pinene and dehydration of 4-methyl-2-pentanol. Sulfation resulted into enhancement in the catalytic activity of both\\u000a xerogel and aerogel samples towards the studied reactions. For example, sulfated catalysts showed 86–98% conversion of ?-pinene\\u000a and 8–35% conversion

Kalpesh B. Sidhpuria; Beena Tyagi; Raksh V. Jasra

2011-01-01

81

Synthesis and structural study of N-acetyl-1,2,3,4-tetrahydroisoquinoline-2-sulfonamide obtained using H6P2W18O62 as acidic solid catalyst  

NASA Astrophysics Data System (ADS)

At room temperature and under acidic conditions, acylation of sulfamides derivatives in various solvents using diverse solid catalysts has been investigated. The best yields are obtained in acetonitrile with a Wells-Dawson type heteropolyacid H6P2W18O62 as acidic solid catalyst. Crystals of N-acetyl-1,2,3,4-tetrahydroisoquinoline-2-sulfonamide suitable for X-ray study have been obtained after recrystallization in toluene. The detailed analysis of molecular and crystal structure is presented in comparison with the structure of 1,2,3,4-tetrahydroisoquinoline-2-sulfonamide, before acylation, previously studied by our team. The role of both intra- and intermolecular weak interactions is discussed. The Hirshfeld surfaces analysis in form of dnorm representation and decomposed fingerprint plots were used to find out different weak but directional hydrogen bonds and ? interactions. Both structures present similar sandwich structures with alternation of primary layers involving strong hydrogen bonds with secondary layers involving mostly weaker interactions.

Bougheloum, Chafika; Barbey, Carole; Berredjem, Malika; Messalhi, Abdelrani; Dupont, Nathalie

2013-06-01

82

Influence of the acid–base properties of solid catalysts derived from hydrotalcite-like compounds on the condensation of formaldehyde and acetaldehyde  

Microsoft Academic Search

The vapor-phase aldol condensation of formaldehyde with acetaldehyde was studied using various oxide mixtures obtained in situ from hydrotalcite-like materials as catalysts. All samples exhibited catalytic activity, but the selectivity to both the aldol condensation and the acrolein formation is governed by the balance of acidic and basic properties. The oxides containing Mg and Al or Co and Al showed

Emil Dumitriu; Vasile Hulea; Carmen Chelaru; Cezar Catrinescu; Didier Tichit; Robert Durand

1999-01-01

83

Immobilized cell reactors in mineralization of dicarboxylic acid solid waste  

Microsoft Academic Search

Dicarboxylic acid solid waste containing phthalic acid, malic acid, quinone, saturated and unsaturated dicarboxylic esters etc., are discharged in huge quantities during the crackdown of benzene over the catalyst vanadium at temperatures greater than 500 C in a dicarboxylic acid manufacturing industry. Concern over the biological effects of these compounds underlines the necessity to treat this solid waste. The role of

Ganesh Kumar Arumugam; Swarnalatha Somasundaram; Victor Babu Kassey; Sekaran Ganesan

2006-01-01

84

Sulfuric acid on silica-gel: an inexpensive catalyst for aromatic nitration  

Microsoft Academic Search

Solid acidic catalysts made of sulfuric acid supported on silica-gel and their application to the nitration of aromatics with nitric acid and isopropyl nitrate are described. Substrates with very different levels of activation were investigated. Methods to overcome the poisoning produced by water and to tune the catalyst activity according to the reactivity of the substrate are outlined.

Juan M Riego; Zeno Sedin; JoséM Zaldívar; Nunziata C Marziano; Claudio Tortato

1996-01-01

85

Tri-potassium phosphate as a solid catalyst for biodiesel production from waste cooking oil  

Microsoft Academic Search

Transesterification of waste cooking oil with methanol, using tri-potassium phosphate as a solid catalyst, was investigated. Tri-potassium phosphate shows high catalytic properties for the transesterification reaction, compared to CaO and tri-sodium phosphate. Transesterification of waste cooking oil required approximately two times more solid catalyst than transesterification of sunflower oil. The fatty acid methyl ester (FAME) yield reached 97.3% when the

Guoqing Guan; Katsuki Kusakabe; Satoko Yamasaki

2009-01-01

86

Esterification of Fatty Acid by Zirconic Catalysts  

Microsoft Academic Search

Sulfated zirconia (SO4\\u000a 2?\\/ZrO2) was proved as an efficient catalyst for the esterification of fatty acids and alcohols, the alkyl esters of long chain fatty\\u000a acids are wildly used in industry and daily life. In this paper, the esterification of long chain fatty acid (both saturated\\u000a and unsaturated) with simple alcohol catalyzed by SZ catalyst was presented. It is found

Xiaoting Hu; Zheng Zhou; Defang Sun; Yuantao Wang; Zhibing Zhang

2009-01-01

87

Calcium-based Lewis acid catalysts.  

PubMed

Recently, Lewis acidic calcium salts bearing weakly coordinating anions such as Ca(NTf?)?, Ca(OTf)?, CaF? and Ca[OCH(CF?)?]? have been discovered as catalysts for the transformation of alcohols, olefins and carbonyl compounds. High stability towards air and moisture, selectivity and high reactivity under mild reaction conditions render these catalysts a sustainable and mild alternative to transition metals, rare-earth metals or strong Brønsted acids. PMID:23712417

Begouin, Jeanne-Marie; Niggemann, Meike

2013-05-24

88

Acidic Cs{sup +}, NHâ{sup +}, and K{sup +} salts of 12-tungstophosphoric acid as solid catalysts for isobutane\\/2-butene alkylation  

Microsoft Academic Search

The cesium, ammonium, and potassium salts of 12-tungstophosphoric acid (HPW) have been prepared with different stoichiometries (1â¤xâ¤3) and their catalytic behavior measured for the liquid phase alkylation of isobutane with 2-butene at 80°C. The salts with a cation content of 2.5 â¤xâ¤3, and that of Cs{sup +} with x=2, showed a much higher surface area than the parent acid, which

A. Corma; A. Martinez; C. Martinez

1996-01-01

89

The effect of acid–base pairing on catalysis: An efficient acid–base functionalized catalyst for aldol condensation  

Microsoft Academic Search

Acid–base bifunctionalized heterogeneous catalysts may be capable of exhibiting reactivity not achievable with homogeneous catalysts. We investigated the effect of pKa of the acid component of mesoporous solids containing acid–base bifunctionality on their catalytic ability toward aldol condensation between 4-nitrobenzaldehyde and acetone. We found that higher levels of aldol product conversion were obtained when weaker acid components (phosphoric, carboxylic vs

Ryan K. Zeidan; Mark E. Davis

2007-01-01

90

Sulfamic Acid as a Novel, Efficient, Cost?Effective, and Reusable Solid Acid Catalyst for the Synthesis of Pyrroles under Solvent?Free Conditions  

Microsoft Academic Search

Paal–Knorr condensation of 2,5?hexadione with primary amines in the presence of a catalytic amount of sulfamic acid under solvent?free conditions has been accomplished with an excellent yield. This is a very easy, rapid, and high?yielding reaction for the synthesis N?substituted pyrrole derivatives.

Surya K. De

2008-01-01

91

Method of distributing liquefaction catalysts in solid carbonaceous material  

DOEpatents

A method of dispersing a liquefaction catalyst within coal or other carbonaceous solids involves providing a suspension in oil of microcapsules containing the catalyst. An aqueous solution of a catalytic metal salt is emulsified in the water-immiscible oil and the resulting minute droplets microencapsulated in polymeric shells by interfacial polycondensation. The catalyst is subsequently blended and dispersed throughout the powdered carbonaceous material to be liquefied. At liquefaction temperatures the polymeric microcapsules are destroyed and the catalyst converted to minute crystallites in intimate contact with the carbonaceous material. 2 tables.

Weller, S.W.

1984-05-23

92

Method For Reactivating Solid Catalysts Used For Alklation Reactions  

DOEpatents

A method for reactivating a solid alkylation catalyst is provided which can be performed within a reactor that contains the alkylation catalyst or outside the reactor. Effective catalyst reactivation is achieved whether the catalyst is completely deactivated or partially deactivated. A fluid reactivating agent is employed to dissolve catalyst fouling agents and also to react with such agents and carry away the reaction products. The deactivated catalyst is contacted with the fluid reactivating agent under pressure and temperature conditions such that the fluid reactivating agent is dense enough to effectively dissolve the fouling agents and any reaction products of the fouling agents and the reactivating agent. Useful pressures and temperatures for reactivation include near-critical, critical, and supercritical pressures and temperatures for the reactivating agent. The fluid reactivating agent can include, for example, a branched paraffin containing at least one tertiary carbon atom, or a compound that can be isomerized to a molecule containing at least one tertiary carbon atom.

Ginosar, Daniel M. (Idaho Falls, ID); Thompson, David N. (Idaho Falls, ID); Coates, Kyle (Shelley, ID); Zalewski, David J. (Proctorville, OH); Fox, Robert V. (Idaho Falls, ID)

2005-05-03

93

Comparison of different heterogeneous catalysts and different alcohols for the esterification reaction of oleic acid  

Microsoft Academic Search

Oils with high amount of free fatty acid (FFA) are becoming one of the most promising alternatives to produced biodiesel; due, principally, to it low cost. However, because of the presence of FFA, the conventional basic homogenous catalyst should not be used with the aim to avoid the production of soaps.In this work, different catalysts, such as solid resins, zeolite

J. M. Marchetti; A. F. Errazu

2008-01-01

94

Role of dehydration catalyst acid properties on one-step DME synthesis over physical mixtures  

Microsoft Academic Search

The direct synthesis of dimethyl ether (DME) was studied in a continuous high-pressure unit composed basically of a Berty reactor and on-line gas chromatograph. A commercial methanol synthesis catalyst and some solid-acid catalysts (alumina, HZSM-5, tungsten–zirconia and sulfated-zirconia) were used as physical mixtures. The dehydration catalysts were characterised by pyridine adsorption followed by IR spectroscopy and tested in the methanol

F. S. Ramos; A. M. Duarte de Farias; L. E. P. Borges; J. L. Monteiro; M. A. Fraga; E. F. Sousa-Aguiar; L. G. Appel

2005-01-01

95

Application of solid ash based catalysts in heterogeneous catalysis  

SciTech Connect

Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the higher stability of its major component, aluminosilicates, fly ash could be employed as catalyst support by impregnation of other active components for various reactions. On the other hand, other chemical compounds in fly ash such as Fe{sub 2}O{sub 3} could also provide an active component making fly ash a catalyst for some reactions. In this paper, physicochemical properties of fly ash and its applications for heterogeneous catalysis as a catalyst support or catalyst in a variety of catalytic reactions were reviewed. Fly-ash-supported catalysts have shown good catalytic activities for H{sub 2} production, deSOx, deNOx, hydrocarbon oxidation, and hydrocracking, which are comparable to commercially used catalysts. As a catalyst itself, fly ash can also be effective for gas-phase oxidation of volatile organic compounds, aqueous-phase oxidation of organics, solid plastic pyrolysis, and solvent-free organic synthesis. 107 refs., 4 figs., 2 tabs.

Shaobin Wang [Curtin University of Technology, Perth, WA (Australia). Department of Chemical Engineering

2008-10-01

96

Calcined Mg–Al hydrotalcites as solid base catalysts for methanolysis of soybean oil  

Microsoft Academic Search

Methyl ester of fatty acids, derived from vegetable oils or animal fats and known as biodiesel, is a promising alternative diesel fuel regarding the limited resources of fossil fuel and the environmental concerns. In this work, an environmentally benign process for the methanolysis of soybean oil to methyl esters using calcined Mg–Al hydrotalcites as solid base catalysts in a heterogeneous

Wenlei Xie; Hong Peng; Ligong Chen

2006-01-01

97

One-step synthesis of a novel carbon-based strong acid catalyst through hydrothermal carbonization  

Microsoft Academic Search

\\u000a Abstract  A novel carbon-based strong acid catalyst was synthesized through the one-step hydrothermal carbonization of furaldehyde and\\u000a p-toluenesulfonic acid (PTSA) in aqueous solution at 180 °C for only 4 h. The novel carbon-based solid acid possessed high\\u000a acidity, and the catalytic activities were investigated by esterification and oxathioketalization. The results showed that\\u000a the novel catalyst demonstrated much greater activity than the traditional solid

Huiquan Xiao; Yingxue Guo; Xuezheng Liang; Chenze Qi

2010-01-01

98

Introduction of poly(4-vinylpyridinium) perchlorate as a new, efficient, and versatile solid acid catalyst for one-pot synthesis of substituted coumarins under ultrasonic irradiation.  

PubMed

Poly(4-vinylpyridinium) perchlorate, is a supported, recyclable, eco-benign catalyst for synthesis of substituted coumarins via Pechmann reaction using ultrasound irradiation at room temperature and neat condition in high yields with short reaction times. The catalyst was studied by FT-IR, X-ray diffraction, scanning electron microscope, thermo-gravimetric and energy dispersion X-ray analyses. All the products were extensively characterized by (1)H NMR, FT-IR, MS and melting point analyses. This methodology offers momentous improvements over various options for the synthesis of coumarins with regard to yield of products, simplicity in operation and green aspects by avoiding toxic catalysts and solvents. Further, the catalyst can be reused and recovered for several times without loss of activity. PMID:22922036

Khaligh, Nader Ghaffari; Shirini, Farhad

2012-08-02

99

Niobic acid — a new heterogeneous catalyst for processes in petrochemical and organic syntheses  

NASA Astrophysics Data System (ADS)

Questions associated with the application of niobium compounds in catalysis are considered. Niobic acid Nb2O5.nH2O contains an appreciable amount of water, but its surface exhibits a high acidity — equivalent to the acidity of 70% sulfuric acid. This unusual solid acid manifests not only a high activity and sensitivity but also an appreciable stability as a catalyst in reactions in which water is present or is evolved (condensation, hydration, dehydration, and esterification). It may be used also as a catalyst in other reactions. The structure and properties of the surface of niobic acid are examined. The bibliography includes 54 references.

Chernyshkova, F. A.

1993-08-01

100

Catalyst deactivation in gas-solid photocatalysis  

SciTech Connect

Photocatalyst lifetime is potentially important in process economics, as it sets maximum run times between catalyst regeneration or replacement. This note surveys the literature of photocatalytic air treatment and purification in order to identify the emerging photocatalyst deactivation issue. For each pertinent paper, the authors evaluate the total number of molecules converted by a photocatalyst over time and compare this cumulative photocatalytic molecular conversion to the estimated total number of illuminated surface sites. This comparison establishes that photocatalyst deactivation is virtually always found in single-pass fixed-bed photoreactors for cumulative contaminant conversion in excess of 1-10 equivalent monolayers. 28 refs., 1 fig., 1 tab.

Sauer, M.L.; Ollis, D.F. [North Carolina State Univ., Raleigh, NC (United States)

1996-09-15

101

Niobic acid — a new heterogeneous catalyst for processes in petrochemical and organic syntheses  

Microsoft Academic Search

Questions associated with the application of niobium compounds in catalysis are considered. Niobic acid Nb2O5.nH2O contains an appreciable amount of water, but its surface exhibits a high acidity — equivalent to the acidity of 70% sulfuric acid. This unusual solid acid manifests not only a high activity and sensitivity but also an appreciable stability as a catalyst in reactions in

F A Chernyshkova

1993-01-01

102

Niobic acid --- a new heterogeneous catalyst for processes in petrochemical and organic syntheses  

Microsoft Academic Search

Questions associated with the application of niobium compounds in catalysis are considered. Niobic acid Nb2O5.nH2O contains an appreciable amount of water, but its surface exhibits a high acidity --- equivalent to the acidity of 70% sulfuric acid. This unusual solid acid manifests not only a high activity and sensitivity but also an appreciable stability as a catalyst in reactions in

F. A. Chernyshkova

1993-01-01

103

Dehydration of glycerol over niobia-supported silicotungstic acid catalysts.  

PubMed

Liquid-phase dehydration of glycerol to acrolein over nanosized niobia-supported silicotungstic acid catalysts was performed to investigate the effect of the silicotungstic acid loading on the catalytic performance of the catalysts. The catalysts were prepared by following an impregnation method with different HSiW loadings in the range of 10-50 wt%. The prepared catalysts were characterized by N2 physisorption, XRD, FT-IR, TPD of ammonia, and TGA. Dehydration of glycerol was conducted in an autoclave reactor under the conditions of controlled reaction temperatures under corresponding pressure. Increasing HSiW loading rapidly increased the acidity of HSiW/Nb205 catalyst and rate of glycerol conversion, but acrolein selectivity decreased due to enhanced deactivation of the catalyst by carbon deposit. Consequently, it was confirmed that catalytic activity for the dehydration of glycerol to acrolein was dependant on the acidity of catalyst and can be controlled by HSiW loading. PMID:23646735

Lee, Young Yi; Ok, Hye Jeong; Moon, Dong Ju; Kim, Jong Ho; Park, Nam Cook; Kim, Young Chul

2013-01-01

104

Catalyst and electrode research for phosphoric acid fuel cells  

Microsoft Academic Search

An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst

A. C. Antoine; R. B. King

1987-01-01

105

Catalyst and electrode research for phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

An account is given of the development status of phosphoric acid fuel cells' high performance catalyst and electrode materials. Binary alloys have been identified which outperform the baseline platinum catalyst; it has also become apparent that pressurized operation is required to reach the desired efficiencies, calling in turn for the use of graphitized carbon blacks in the role of catalyst supports. Efforts to improve cell performance and reduce catalyst costs have led to the investigation of a class of organometallic cathode catalysts represented by the tetraazaannulenes, and a mixed catalyst which is a mixture of carbons catalyzed with an organometallic and a noble metal.

Antoine, A. C.; King, R. B.

106

Mechanism of neopentane cracking over solid acids  

SciTech Connect

Neopentane was used as a probe to test whether catalyst protons can attack the C-C and/or the C-H sigma-bonds in the cracking of alkanes. Over a variety of solid acids approximately one CH/sub 4/ molecule was formed for every neopentane reacted. Moreover, in most cases nearly as much isobutene was formed. With H-Y zeolite (H-Y) and particularly with H-mordenite (H-M), however, hydride transfer leading to paraffin formation became important or dominant. Generally, the results conformed to (CH/sub 3/)/sub 3/C-H/sup +/-CH/sub 3/ ..-->.. CH/sub 4/ + (CH/sub 3/)/sub 3/C/sup +/ with the t-butyl ion either decomposing to isobutene or else undergoing secondary reactions. The latter tended to increase with the intensive factor of the acidity, i.e., with the strength of the acid-base interaction. The fraction of neopentane converted to CH/sub 4/, when plotted in the Arrhenius fashion against T/sup -1/, produced straight lines from which apparent activation energies could be calculated. Values obtained fell between 30 kcal/mol for silica-alumina and 14 kcal/mol for H-M (the most acidic and active catalyst investigated). Controversial views found in current literature are discussed in light of the present results.

Lombardo, E.A.; Pierantozzi, R.; Hall, W.K.

1988-03-01

107

MoVO-based catalysts for the oxidation of ethane to ethylene and acetic acid  

Microsoft Academic Search

The influence of niobium and\\/or palladium in MoV0.4Ox on both solid state chemistry and catalytic properties in the oxidation of ethane to acetic acid and ethylene is examined. Catalysts without molybdenum (VNb0.31Pd3e-4Ox) are also studied for comparison. The structural properties of the precursors and of the catalysts obtained by calcination of precursors at 350 and 400°C are studied by X-ray

Martial Roussel; Michel Bouchard; Khalid Karim; Saleh Al-Sayari; Elisabeth Bordes-Richard

2006-01-01

108

Kinetics of alkane adsorption on a solid cracking catalyst  

Microsoft Academic Search

A microreactor technique is developed for a study of alkane chemisorption on solid cracking catalysts. Kinetics of adsorption–desorption processes can be observed at ca. 200°C; it manifests itself as extensive tailing of alkane peaks in gas chromatograms. A kinetic model of the adsorption process is developed. The model allows calculation of two kinetic parameters, those of alkane adsorption, ka[C*], and

Yury V Kissin

1998-01-01

109

Synthesis, characterization and activity study of SO 4 2?\\/Ce x Zr 1? x O 2 solid superacid catalyst  

Microsoft Academic Search

Sulfated CexZr1?xO2 catalyst was found to exhibit solid super-acidity and good catalytic activity for synthesis of ?-amino ketones by a three-component Mannich type reaction in the liquid phase under solvent free conditions at ambient temperature. To make the sulfated CexZr1?xO2 catalyst, Ce-Zr hydroxide gel was prepared by a coprecipitation method and SO42? ions were deposited by treating the gel with

Benjaram M. Reddy; Pavani M. Sreekanth; Pandian Lakshmanan; Ataullah Khan

2006-01-01

110

Solid heterogeneous catalysts for transesterification of triglycerides with methanol: A review  

Microsoft Academic Search

Increasing number of researches focusing on the use of solid heterogeneous catalysts for the production of biodiesel provides evidence that these catalysts continue to evolve as viable alternatives. While liquid alkaline metal alkoxides remain to be appealing in the industries, it is expected that solid base catalyst will soon become more attractive due to the economics and environmental concern. Limited

Z. Helwani; M. R. Othman; N. Aziz; J. Kim; W. J. N. Fernando

2009-01-01

111

Reactivity and Characterization of Solid State Hydrodesulfurization Catalysts.  

NASA Astrophysics Data System (ADS)

The identification of the phase responsible for hydrodesulfurization (HDS) activity has been the subject of extensive research. In this study, model solid state catalysts prepared from elemental starting materials were synthesized, characterized, and then used to desulfurize thiophene at temperatures ranging from 200-400 ^circC and a pressure of one atmosphere. The results of this work indicate that an increased HDS activity can be correlated with the presence of a poorly crystalline molybdenum sulfide-like phase detected by XRD, HREM, or AEM. The formation of this sulfur-deficient, non-stoichiometric phase could be accomplished by either removing sulfur directly from the catalyst synthesis mixture to yield a non-stoichiometric MoS_{ rm 2-x} moiety, or by introducing a transition metal promoter such as Fe, Co, Ni, or Cu into the system. The promoter atoms induced structural changes in the molybdenum sulfide edge planes by effectively scavenging sulfur during catalyst synthesis to form promoter sulfide species, which enhanced the formation of a non-stoichiometric, highly active molybdenum sulfide. This morphological effect was the primary function of the promoter in this system. All model catalysts displayed similar structure in the (0002) basal plane of MoS_2; however, only the catalytically active samples showed a high concentration of defects and disorder in the (1010), (1011), and (1012) edge planes. The HREM images obtained from these edge planes and their correlation with HDS activity dramatically illustrated the importance of the often-discussed edge plane structure of MoS_2 and its significance on HDS catalysis. Normalization of the HDS activities for the solid state models and a commercial catalyst with O_2 or CO chemisorption uptakes suggested that a similarity may exist between the catalytically active sites of these materials. In-situ XPS revealed that increasing promoter atom concentrations resulted in a more complete reduction of the promoter atom; but this shift to lower binding energies could not necessarily be correlated with activity. However, it was observed that the more active catalysts all exhibited the ability to dissociate H_2 and remove oxygen from their surface. This H_2 spillover or activation may also influence catalyst performance.

Lindner, James Henry

1990-01-01

112

Surface Diffusion on Solid Oxide Fuel Cell Catalysts  

SciTech Connect

This paper demonstrates how detailed surface science data bases can lead to improved results in practical applications. The case investigated concerns how surface diffusivities affect concentration polarization on metal electrocatalyst particles. The application is to solid oxide fuel cells (SOFCs). A common assumption for SOFCs is that the hydrogen-oxygen reaction that produces the electrical current is strictly localized at the triple phase boundary (TPB) between the metal catalyst particle, the zirconia support, and the gas atmosphere. Detailed treatment of oxygen spillover indicates that the reactive area simply spreads over the catalyst surface as needed to support the current, leading to TPB widths of several hundred Angstroms. Lower adspecies surface diffusivities (due to catalyst crystallography), lower reactant partial pressures (due to electrode design), higher temperatures, and higher current demands, generally shift the peak turnover number (TON) for H2O generation away from the TPB in practical SOFCs with cermet anodes. The diffusivity-coverage relationship (repulsive, neutral, or attractive adspecies interactions) affects the location of the TON peak on the catalyst surface in a non-monotonic manner, indicating that detailed surface science data are needed for decisive determination of the source of anodic concentration polarization in SOFCs. The most detailed surface diffusion model investigated in this work indicates that the catalytic process is limited by oxygen surface diffusion on the metal particle.

Williford, Rick E.

2005-10-01

113

Direct Green Iodination of Phenol over Solid Acids  

Microsoft Academic Search

\\u000a Abstract  Examination of several solid acid catalysts of different nature (acid resins, zeolites, mixed oxides, Nb-oxide, and Nb-phosphate)\\u000a was performed for the direct iodination reaction of phenol by using molecular iodine. The experiments were carried out in\\u000a mild and green conditions (50 °C at ambient pressure) in methanol in the presence of H2O2 as oxidant agent. Iodine was introduced in reduced amount,

Paolo Carniti; Stefano Colonna; Antonella Gervasini

2010-01-01

114

Parallel solid-phase synthesis, screening, and encoding strategies for olefin-polymerization catalysts  

Microsoft Academic Search

A solid-phase protocol has been developed that allows for the parallel synthesis, screening, and chemical encoding of nickel (II) and palladium (II) olefin-polymerization catalysts. These catalysts display activity profiles comparable to the analogous homogeneous catalyst systems prepared by traditional methods. A chemical encoding strategy has also been developed which enables the chemical history of pooled solid-phase catalysts to be evaluated.

Thomas R. Boussie; Vince Murphy; Keith A. Hall; Carla Coutard; Cameron Dales; Miroslav Petro; Eric Carlson; Howard W. Turner; Timothy S. Powers

1999-01-01

115

Catalytic conversion of glucose to 5-hydroxymethylfurfural over SO 4 2?\\/ZrO 2 and SO 4 2?\\/ZrO 2–Al 2O 3 solid acid catalysts  

Microsoft Academic Search

SO42?\\/ZrO2 and SO42?\\/ZrO2–Al2O3 catalysts were prepared by impregnation of Zr(OH)4 and Zr(OH)4–Al(OH)3 with ethylene dichloride solution of chlorosulfonic acid, and characterized by ICP-AES, BET, XRD, NH3-TPD, CO2-TPD and FTIR of adsorbed pyridine. The catalysts were used in the catalytic conversion of glucose to 5-hydroxymethylfurfural. An optimized 5-hydroxymethylfurfural yield of 47.6% was obtained within 4h at 403K over SO42?\\/ZrO2–Al2O3 with Zr–Al

Hongpeng Yan; Yu Yang; Dongmei Tong; Xi Xiang; Changwei Hu

2009-01-01

116

Acetone condensation reaction on acid catalysts  

SciTech Connect

The condensation reaction of acetone on alumina and acid zeolites has been followed by FTIR. Under identical conditions, the reaction rate is faster on alumina, and the condensation goes beyond the formation of mesityl oxide. Zeolites without nonframework aluminum are poor catalysts. On HZSM-5 the reaction is about two orders of magnitude slower than on USY at 105 C. From these data, it appears that Lewis sites, even if they bound acetone less energetically than Broensted sites, are responsible for the activation of the molecule. On alumina, the reaction would take place between gas phase acetone and acetone adsorbed on Lewis sites. On zeolites with nonframework aluminum and, thus, with Lewis sites, the reaction would involve acetone molecules adsorbed on Broensted and Lewis sites, the activation occurring on the Lewis site.

Panov, A.G.; Fripiat, J.J. [Univ. of Wisconsin, Milwaukee, WI (United States)

1998-08-15

117

Poly(4-vinylpyridine) supported acidic ionic liquid: A novel solid catalyst for the efficient synthesis of 2,3-dihydroquinazolin-4(1H)-ones under ultrasonic irradiation.  

PubMed

A novel poly(4-vinylpyridine) supported acidic ionic liquid catalyst was synthesized by the reaction of 4-vinylpyridine with 1,3-propanesultone, followed by the polymerization and the addition of the heteropolyacid. Due to the combination of polymer features and ionic liquid, it acted as a heterogeneous catalyst to effectively catalyze the cyclocondensation reaction of anthranilamide with aldehydes under ultrasonic irradiation and afforded the corresponding 2,3-dihydro-4(1H)-quinazolinones compounds in good to excellent yields. In addition, the catalyst could be easily recovered by the filtration and reused six times without significant loss of catalytic activity. More importantly, the use of ultrasonic irradiation can obviously accelerate the reaction. PMID:23751459

Wang, Junke; Zong, Yingxiao; Fu, Rugang; Niu, Yuying; Yue, Guoren; Quan, Zhengjun; Wang, Xicun; Pan, Yi

2013-05-29

118

[sup 13]C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO[sub 2] catalyst at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon-containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus cannot be observed as the reaction product. Ethylene oxide, however, has been observed after the saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. In conjunction with this project, the author has designed and constructed a multiport high vacuum glass apparatus which was used for sample preparation prior to the NMR experiments as well as chemisorption measurements and a single-coil double resonance probe.

Hosseini, S.

1992-01-01

119

sup 13 C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO{sub 2} catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus can not be observed as the reaction product. Ethylene oxide, however, has been observed after saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. A multiport high vacuum glass apparatus was developed along with a single-coil double resonance probe.

Hosseini, S.

1992-07-21

120

{sup 13}C solid-state NMR study of ethylene oxidation over supported silver catalysts  

SciTech Connect

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO{sub 2} catalysts at temperature ranging from 298 to 613 K. Standard cross-polarization with magic angle spinning (CP/MAS), CP/MAS with dipolar dephasing, and single-pulse experiments have been applied to identify carbon containing species that are formed on the surface of catalyst at various temperatures. Ethylene, acetic acid, carbon dioxide, ethane and an alkoxy species have been identified. Under the above experimental conditions, no ethylene oxide is detected by NMR. In pursuit of a better understanding of the chemistry taking place on the catalyst, silica-supported silver catalysts as well as pure silica were dosed with labeled ethylene, carbon dioxide and ethylene oxide. It was found that under conditions employed in this study, ethylene oxide reacts with both metal and silica support and thus can not be observed as the reaction product. Ethylene oxide, however, has been observed after saturation of silica surface with unlabeled ethylene oxide prior to ethylene oxidation. A multiport high vacuum glass apparatus was developed along with a single-coil double resonance probe.

Hosseini, S.

1992-07-21

121

Hydrogen from formic acid decomposition over Pd and Au catalysts  

Microsoft Academic Search

Vapour phase decomposition of formic acid has been studied systematically over a range of catalysts: 1.0 and 10wt.% Pd\\/C, 0.8wt.% Au\\/C and 1.0wt.% Au\\/TiO2. The mean metal particle size of these materials was estimated by HRTEM and turnover frequencies were calculated using these data. The Au\\/C catalyst was the least active and the Pd\\/C catalysts were the most active for

Dmitri A. Bulushev; Sergey Beloshapkin; Julian R. H. Ross

2010-01-01

122

Manganese Triazacyclononane Oxidation Catalysts Grafted under Reaction Conditions on Solid Co-Catalytic Supports  

SciTech Connect

Manganese complexes of 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) are highly active and selective alkene oxidation catalysts with aqueous H{sub 2}O{sub 2}. Here, carboxylic acid-functionalized SiO{sub 2} simultaneously immobilizes and activates these complexes under oxidation reaction conditions. H{sub 2}O{sub 2} and the functionalized support are both necessary to transform the inactive [(tmtacn)Mn{sup IV}({mu}-O)3Mn{sup IV}(tmtacn)]{sup 2+} into the active, dicarboxylate-bridged [(tmtacn)Mn{sup III}({mu}-O)({mu}-RCOO){sub 2}Mn{sup III}(tmtacn)]{sup 2+}. This transformation is assigned on the basis of comparison of diffuse reflectance UV-visible spectra to known soluble models, assignment of oxidation state by Mn K-edge X-ray absorption near-edge spectroscopy, the dependence of rates on the acid/Mn ratios, and comparison of the surface structures derived from density functional theory with extended X-ray absorption fine structure. Productivity in cis-cyclooctene oxidation to epoxide and cis-diol with 2-10 equiv of solid cocatalytic supports is superior to that obtained with analogous soluble valeric acid cocatalysts, which require 1000-fold excess to reach similar levels at comparable times. Cyclooctene oxidation rates are near first order in H{sub 2}O{sub 2} and near zero order in all other species, including H{sub 2}O. These observations are consistent with a mechanism of substrate oxidation following rate-limiting H{sub 2}O{sub 2} activation on the hydrated, supported complex. This general mechanism and the observed alkene oxidation activation energy of 38 {+-} 6 kJ/mol are comparable to H{sub 2}O{sub 2} activation by related soluble catalysts. Undesired decomposition of H{sub 2}O{sub 2} is not a limiting factor for these solid catalysts, and as such, productivity remains high up to 25 C and initial H{sub 2}O{sub 2} concentration of 0.5 M, increasing reactor throughput. These results show that immobilized carboxylic acids can be utilized and understood like traditional carboxylic acids to activate non-heme oxidation catalysts while enabling higher throughput and providing the separation and handling benefits of a solid catalyst.

Schoenfeldt, Nicholas J.; Ni, Zhenjuan; Korinda, Andrew W.; Meyer, Randall J.; Notestein, Justin M. (NWU); (UIC)

2012-01-23

123

Single event microkinetics of hydrocarbon cracking on acid catalysts  

Microsoft Academic Search

Zeolite catalysts are the workhorses of oil refining indust ry. Main applications, among many others, are fluid catalytic cr acking, hy- drocracking and aromatics transformations. The use of zeolites for hydro- carbon conversions is based on their acid properties and their framework topology. This work aims at investigating the influence of th ese catalyst properties on the rates of the

Rhona Van Borm

124

Organometallic catalysts for primary phosphoric acid fuel cells  

Microsoft Academic Search

A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and\\/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides

Fraser Walsh

1987-01-01

125

EPA'S CATALYST RESEARCH PROGRAM: ENVIRONMENTAL IMPACT OF SULFURIC ACID EMISSIONS  

EPA Science Inventory

A sulfuric acid review conference sponsored by EPA's automotive Catalyst Research Program was held recently at Hendersonville, NC, for researchers whose work is funded by EPA. Emissions characterization research indicated that in-use catalyst-equipped vehicles emit low levels of ...

126

Synthesis of dimethyl carbonate from urea and methanol over solid base catalysts  

Microsoft Academic Search

The synthesis of dimethyl carbonate (DMC) from urea and methanol was found to take place over solid base catalysts. In the first step, the intermediate MC was produced with high yield by urea monomethanolysis and then MC further converted to DMC by reacting with methanol, which was the key step. Solid bases were found to be effective catalysts for the

Mouhua Wang; Hui Wang; Ning Zhao; Wei Wei; Yuhan Sun

2006-01-01

127

Electrochemical catalyst recovery method  

DOEpatents

A method of recovering catalyst material from latent catalyst material solids includes: a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications.

Silva, Laura J. (Richland, WA); Bray, Lane A. (Richland, WA)

1995-01-01

128

Electrochemical catalyst recovery method  

DOEpatents

A method of recovering catalyst material from latent catalyst material solids includes: (a) combining latent catalyst material solids with a liquid acid anolyte solution and a redox material which is soluble in the acid anolyte solution to form a mixture; (b) electrochemically oxidizing the redox material within the mixture into a dissolved oxidant, the oxidant having a potential for oxidation which is effectively higher than that of the latent catalyst material; (c) reacting the oxidant with the latent catalyst material to oxidize the latent catalyst material into at least one oxidized catalyst species which is soluble within the mixture and to reduce the oxidant back into dissolved redox material; and (d) recovering catalyst material from the oxidized catalyst species of the mixture. The invention is expected to be particularly useful in recovering spent catalyst material from petroleum hydroprocessing reaction waste products having adhered sulfides, carbon, hydrocarbons, and undesired metals, and as well as in other industrial applications. 3 figs.

Silva, L.J.; Bray, L.A.

1995-05-30

129

Absence of expected side-reactions in the dehydration reaction of fructose to HMF in water over niobic acid catalyst  

Microsoft Academic Search

The catalytic dehydration of fructose (FRU) to 5-hydroxymethylfurfural (HMF) usually runs with the formation of several side products. Among these, levulinic acid (LA) is often reported as the product of a consecutive reaction of HMF re-hydration. In this work, side reactions of the dehydration of FRU performed in very green conditions (water as solvent and niobic acid as solid catalyst)

Paolo Carniti; Antonella Gervasini; Matteo Marzo

2011-01-01

130

Acetylation of glycerol to synthesize bioadditives over niobic acid supported tungstophosphoric acid catalysts  

Microsoft Academic Search

Acetylation of glycerol to yield mono, di and triacetin (acetylated glycerol) was carried over niobic acid supported tungstophosphoric acid (TPA) catalysts. The catalysts with varying TPA content were prepared and characterized by different techniques. The characterization results reveal the presence of well-dispersed Keggin ion on support. The results suggest that the glycerol conversion and selectivities depend on the acidity of

M. Balaraju; P. Nikhitha; K. Jagadeeswaraiah; K. Srilatha; P. S. Sai Prasad; N. Lingaiah

2010-01-01

131

Staining of fluid-catalytic-cracking catalysts: localising Brønsted acidity within a single catalyst particle.  

PubMed

A time-resolved in situ micro-spectroscopic approach has been used to investigate the Brønsted acidic properties of fluid-catalytic-cracking (FCC) catalysts at the single particle level by applying the acid-catalysed styrene oligomerisation probe reaction. The reactivity of individual FCC components (zeolite, clay, alumina and silica) was monitored by UV/Vis micro-spectroscopy and showed that only clay and zeolites (Y and ZSM-5) contain Brønsted acid sites that are strong enough to catalyse the conversion of 4-fluorostyrene into carbocationic species. By applying the same approach to complete FCC catalyst particles, it has been found that the fingerprint of the zeolitic UV/Vis spectra is clearly recognisable. This almost exclusive zeolitic activity is confirmed by the fact that hardly any reactivity is observed for FCC particles that contain no zeolite. Confocal fluorescence microscopy images of FCC catalyst particles reveal inhomogeneously distributed micron-sized zeolite domains with a highly fluorescent signal upon reaction. By examining laboratory deactivated FCC catalyst particles in a statistical approach, a clear trend of decreasing fluorescence intensity, and thus Brønsted acidity, of the zeolite domains is observed with increasing severity of the deactivation method. By comparing the average fluorescence intensities obtained with two styrenes that differ in reactivity, it has been found that the Brønsted acid site strength within FCC catalyst particles containing ZSM-5 is more uniform than within those containing zeolite Y, as confirmed with temperature-programmed desorption of ammonia. PMID:22161809

Buurmans, Inge L C; Ruiz-Martínez, Javier; van Leeuwen, Sanne L; van der Beek, David; Bergwerff, Jaap A; Knowles, William V; Vogt, Eelco T C; Weckhuysen, Bert M

2011-12-09

132

Removal of tar base from coal tar aromatics employing solid acid adsorbents  

Microsoft Academic Search

Aromatic compounds from coal tar generally contain a small amount of tar bases, such as quinoline and isoquinoline. These nitrogen-containing compounds can poison the acid-type catalysts and downgrade the aromatic products because of stinking odor. Four solid acid catalysts, silica-alumina, HY, NH4-mordenite, and ?-alumina are used to remove tar bases by adsorption. Wash oil (WO), refined naphthalene (RN), and an

Jeffrey Chi-Sheng Wu; Hsueh-Chang Sung; Yu-Fu Lin; Shi-Long Lin

2000-01-01

133

Effect of water on silica-supported phosphotungstic acid catalysts for 1-butene double bond shift and alkane skeletal isomerization  

Microsoft Academic Search

The thermal stability, acidity, catalytic activity and regenerability of silica-supported phosphotungstic acid were evaluated in reference to the bulk solid acid. Samples were prepared with 5, 10, and 25wt.% heteropolyacid (HPA) on fumed silica to examine the effect of loading on the properties of supported acid catalysts. X-ray absorption spectroscopy indicated that the supported heteropolyacids did not completely decompose when

Billy B Bardin; Robert J Davis

2000-01-01

134

Impacts of acid gases on mercury oxidation across SCR catalyst  

Microsoft Academic Search

A series of bench-scale experiments were completed to evaluate acid gases of HCl, SO2, and SO3 on mercury oxidation across a commercial selective catalytic reduction (SCR) catalyst. The SCR catalyst was placed in a simulated flue gas stream containing O2, CO2, H2O, NO, NO2, and NH3, and N2. HCl, SO2, and SO3 were added to the gas stream either separately

Ye Zhuang; Jason Laumb; Richard Liggett; Mike Holmes; John Pavlish

2007-01-01

135

Perfluorinated resinsulfonic acid--a catalyst for certain organic reactions  

SciTech Connect

The purpose of this work was to examine the possibility of using, as a catalyst in certain organic reactions, the perfluorinated resinsulfonic acid F-4SK in the H form, which is an analog of the perfluorinated resinsulfonic acid Nafion-H.

Etlis, V.S.; Beshenova, E.P.; Semenova, E.A.; Shomina, F.N.; Dreiman, N.A.; Balaev, G.A.

1986-09-10

136

Analysis of recycled poly (styrene-co-butadiene) sulfonation: a new approach in solid catalysts for biodiesel production.  

PubMed

The disposal of solid waste is a serious problem worldwide that is made worse in developing countries due to inadequate planning and unsustainable solid waste management. In Mexico, only 2% of total urban solid waste is recycled. One non-recyclable material is poly (styrene-co-butadiene), which is commonly used in consumer products (like components of appliances and toys), in the automotive industry (in instrument panels) and in food services (e.g. hot and cold drinking cups and glasses). In this paper, a lab-scale strategy is proposed for recycling poly (styrene-co-butadiene) waste by sulfonation with fuming sulfuric acid. Tests of the sulfonation strategy were carried out at various reaction conditions. The results show that 75°C and 2.5 h are the operating conditions that maximize the sulfonation level expressed as number of acid sites. The modified resin is tested as a heterogeneous catalyst in the first step (known as esterification) of biodiesel production from a mixture containing tallow fat and canola oil with 59% of free fatty acids. The preliminary results show that esterification can reach 91% conversion in the presence of the sulfonated polymeric catalyst compared with 67% conversion when the reaction is performed without catalyst. PMID:24098857

Aguilar-Garnica, Efrén; Paredes-Casillas, Mario; Herrera-Larrasilla, Tito E; Rodríguez-Palomera, Felicia; Ramírez-Arreola, Daniel E

2013-09-21

137

Heteropoly compounds as catalysts for hydrogenation of propanoic acid  

Microsoft Academic Search

Bulk Keggin heteropoly acids (HPAs) H3+n[PMo12?nVnO40] (n=0–2) and their Cs+ salts catalyse the vapour-phase hydrogenation of propanoic acid at 350?°C and 1 bar H2 pressure, yielding propanal together with 3-pentanone and propane as the main products. Catalyst acidity (controlled by Cs substitution) has crucial effect on the reaction selectivity. As the Cs content increases, the selectivity to propanal passes a

H. Benaissa; P. N. Davey; Y. Z. Khimyak; I. V. Kozhevnikov

2008-01-01

138

Organometallic catalysts for primary phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 hr. in full cell at 160 to 200 C in phosphoric acid H3PO4, and was shown to provide stable performance. The mixed catalyst contains an organometallic to catalyze electroreduction of oxygen to hydrogen peroxide and a metal to catalyze further electroreduction of the hydrogen peroxide to water. Cathodes containing an exemplar mixed catalyst (e.g., Co bisphenyl TAA/Mn) operate at approximately 650 mV vs DHE in 160 C, 85% H3PO4 with oxygen as reactant. In developing this mixed catalyst, a broad spectrum of TAAs were prepared, tested in half-cell and in a rotating ring-disk electrode system. TAAs found to facilitate the production of hydrogen peroxide in electroreduction were shown to be preferred TAAs for use in the mixed catalyst. Manganese (Mn) was identified as a preferred metal because it is capable of catalyzing hydrogen peroxide electroreduction, is lower in cost and is of less strategic importance than platinum, the cathode catalyst normally used in the fuel cell.

Walsh, Fraser

1987-03-01

139

Transition metal sulfide hydrogen evolution catalysts for hydrobromic acid electrolysis.  

PubMed

Mixed metal sulfides containing combinations of W, Fe, Mo, Ni, and Ru were synthesized and screened for activity and stability for the hydrogen evolution reaction (HER) in aqueous hydrobromic acid (HBr). Co- and Ni-substituted RuS(2) were identified as potentially active HER electrocatalysts by high-throughput screening (HTS), and the specific compositions Co(0.4)Ru(0.6)S(2) and Ni(0.6)Ru(0.4)S(2) were identified by optimization. Hydrogen evolution activity of Co(0.4)Ru(0.6)S(2) in HBr is greater than RuS(2) or CoS(2) and comparable to Pt and commercial Rh(x)S(y). Structural and morphological characterizations of the Co-substituted RuS(2) suggest that the nanoparticulate solids are a homogeneous solid solution with a pyrite crystal structure. No phase separation is detected for Co substitutions below 30% by X-ray diffraction. In 0.5 M HBr electrolyte, the Co-Ru electrode material synthesized with 30% Co rapidly lost approximately 34% of the initial loading of Co; thereafter, it was observed to exhibit stable activity for HER with no further loss of Co. Density functional theory calculations indicate that the S(2)(2-) sites are the most important for HER and the presence of Co influences the S(2)(2-) sites such that the hydrogen binding energy at sufficiently high hydrogen coverage is decreased compared to ruthenium sulfide. Although showing high HER activity in a flow cell, the reverse reaction of hydrogen oxidation is slow on the RuS(2) catalysts tested when compared to platinum and rhodium sulfide, leaving rhodium sulfide as the only suitable tested material for a regenerative HBr cell due its stability compared to platinum. PMID:23205859

Ivanovskaya, Anna; Singh, Nirala; Liu, Ru-Fen; Kreutzer, Haley; Baltrusaitis, Jonas; Nguyen, Trung Van; Metiu, Horia; McFarland, Eric

2012-12-18

140

On the nature of the deactivation of supported palladium nanoparticle catalysts in the decarboxylation of fatty acids.  

SciTech Connect

Supported palladium catalysts are effective catalysts for the hydrogen-free decarboxylation of fatty acids. However, the catalysts deactivate severely after one use. Here, the recyclability of a well-defined, mesoporous silica-supported palladium nanoparticle catalyst is evaluated in the batch decarboxylation of stearic acid at 300 C under inert atmosphere, producing n-heptadecane. The nature of the catalyst deactivation is examined in detail via an array of characterization techniques. X-ray photoelectron spectroscopy (XPS) demonstrates that little palladium surface oxidation occurs over the course of the reaction, and a combination of X-ray absorption spectroscopy and transmission electron microscopy (TEM) suggests negligible particle sintering or agglomeration. Physisorption and chemisorption measurements demonstrate substantial loss in total surface area and porosity as well as accessible palladium surface area with these losses attributed to significant organic deposition on the catalyst, as verified via thermogravimetric analysis. High temperature calcination is applied to combust and remove these residues, but resultant nanoparticle agglomeration is significant. Solid state nuclear magnetic resonance spectroscopy (NMR), Fourier transform infrared spectroscopy (FT-IR) and solid dissolution followed by organic extraction methodologies demonstrate that the carbonaceous deposits are not coke but rather strongly adsorbed reactants and products. Detrimental coke formation, as suggested by prior literature, is verified to be absent, as extraction of the surface-deposited organic species yields nearly complete recovery of the total surface area, pore volume, and active palladium surface area. Furthermore, the regenerated catalyst exhibits a corresponding significant recovery of decarboxylation activity.

Ping, E. W.; Pierson, J.; Wallace, R.; Miller, J. T.; Fuller, T. F.; Jones, C. W. (Chemical Sciences and Engineering Division); (Georgia Institute of Technology)

2011-04-15

141

Solid-phase extraction of acidic herbicides.  

PubMed

A discussion of solid-phase extraction method development for acidic herbicides is presented that reviews sample matrix modification, extraction sorbent selection, derivatization procedures for gas chromatographic analysis, and clean-up procedures for high-performance liquid chromatographic analysis. Acidic herbicides are families of compounds that include derivatives of phenol (dinoseb, dinoterb and pentachlorophenol), benzoic acid (acifluorfen, chloramben, dicamba, 3,5-dichlorobenzoic acid and dacthal--a dibenzoic acid derivative), acetic acid [2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T)], propanoic acid [dichlorprop, fluazifop, haloxyfop, 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP) and silvex], butanoic acid [4-(2,4-dichlorophenoxy)butanoic acid (2,4-DB) and 4-(4-chloro-2-methylphenoxy)butanoic acid (MCPB)], and other miscellaneous acids such as pyridinecarboxylic acid (picloram) and thiadiazine dioxide (bentazon). PMID:10941675

Wells, M J; Yu, L Z

2000-07-14

142

Characterization of the acid properties of tungsten/zirconia catalysts using adsorption microcalorimetry and n-pentane isomerization activity  

SciTech Connect

Ammonia adsorption microcalorimetry was conducted on various solid acid tungsten/zirconia catalysts prepared by different techniques. The calorimetric data were compared to catalytic test results using n-pentane isomerization as a measure of acid activity. The results show that (1) the co-precipitation method of making the tungsten/zirconia catalyst produces a greater number of acidic sites than impregnating tungsten on hydrous zirconia, resulting in a more active catalyst, and (2) the addition of small amounts of iron to the tungsten/zirconia catalyst increases the acid site strength as determined by ammonia adsorption and improves the paraffin isomerization activity. The calorimetry data indicate that the acid site strength of the tungsten/zirconia materials is similar to or slightly higher than that found in zeolites or sulfated zirconia and is comparable to sulfuric acid. However, the paraffin isomerization activity results suggest that the acid sites of the tungsten/zirconia catalyst should be about four orders of magnitude more active than that of zeolite {beta} on the basis of turnover frequency. Their experimental results indicate a lack of correlation between the heat of ammonia adsorption with catalytic activity. Comparisons of catalytic activity between materials based entirely on acid strength may not be valid, and kinetic probes would be more appropriate.

Vartuli, J.C.; Santiesteban, J.G.; Traverso, P.; Cardona-Martinez, N.; Chang, C.D.; Stevenson, S.A.

1999-10-01

143

Thermal decomposition of lignocellulosic biomass in the presence of acid catalysts.  

PubMed

Transformation of lignocellulosic biomass to biofuels involves multiple processes, in which thermal decomposition, hydrotreatment are the most central steps. Current work focuses on the impact of several solid acids and Keggin-type heteropolyacids on the decomposition temperature (Td) of pine wood and the characterization of the resulted products. It has been observed that a mechanical mixture of solid acids with pine wood has no influence on Td, while the use of heteropolyacids lower the Td by 100°C. Moreover, the treatment of biomass with a catalytic amount of H3PW12O40 leads to formation of three fractions: solid, liquid and gas, which have been investigated by elemental analysis, TGA, FTIR, GC-MS and NMR. The use of heteropolyacid leads, at 300°C, to a selective transformation of more than 50wt.% of the holocellulose part of the lignocellulosic biomass. Moreover, 60wt.% of the catalyst H3PW12O40 are recovered. PMID:24055967

Larabi, Cherif; Al Maksoud, Walid; Szeto, Kai C; Roubaud, Anne; Castelli, Pierre; Santini, Catherine C; Walter, Jean J

2013-08-23

144

Decomposition of methanol vapour over solid catalyst, measured by DSC  

Microsoft Academic Search

The activity of copper containing catalysts for the formation of methanol from CO and H2 is investigated by DSC measurement of the methanol decomposition. Calibration of the DSC signal can be performed by melting experiments with tin under reaction conditions. Comparison of catalysts is well possible by measurement of the standard activity at 240°, the apparent activation energy for the

G. Hakvoort; Xu Xiaoding

1991-01-01

145

Process for the generation of α,β-unsaturated carboxylic acids and esters using niobium catalyst  

Microsoft Academic Search

A process using a niobium catalyst includes the step of reacting an ester or carboxylic acid with oxygen and an alcohol in the presence a niobium catalyst to respectively produce an α,β-unsaturated ester or carboxylic acid. Methanol may be used as the alcohol, and the ester or carboxylic acid may be passed over the niobium catalyst in a vapor stream

M. R. Gogate; J. J. Spivey; J. R. Zoeller

1999-01-01

146

Process for the generation of .alpha., .beta.-unsaturated carboxylic acids and esters using niobium catalyst  

Microsoft Academic Search

A process using a niobium catalyst includes the step of reacting an ester or carboxylic acid with oxygen and an alcohol in the presence a niobium catalyst to respectively produce an .alpha.,.beta.-unsaturated ester or carboxylic acid. Methanol may be used as the alcohol, and the ester or carboxylic acid may be passed over the niobium catalyst in a vapor stream

Makarand Ratnakav Gogate; James Jerome Spivey; Joseph Robert Zoeller

1999-01-01

147

Cumene cracking on dodecatungstosilicic acid catalyst  

SciTech Connect

Cumene cracking on supported H{sub 4}SiW{sub 12}O{sub 40} was studied in the temperature range 150-244{degrees}C using a constant flow microreactor. In the initial periods of runs, besides the two predominant products benzene and propylene some less important amounts of C{sub 4}, C{sub 5}, and C{sub 6} hydrocarbons as well as toluene and ethylbenzene were obtained. Based on these results and separate experiments with propylene and benzene, a reaction pattern was proposed. The side products vanished after some 10-20 min of run time during which there was rapid deactivation of the catalyst and a decrease from an initially high conversion to 20-30% conversion depending on temperature. From the mass balance the amount of carbonaceous deposit was estimated and it was shown that the precursors for its formation are propylene and cumene. Arrhenius plots of the rate constants at a given coking degree indicate that below 170{degrees}C at low coking degree it is the surface reaction which is the rate controlling factor. Above this temperature the reaction is predominantly a diffusion controlled process. 23 refs., 11 figs., 1 tab.

Malecka, A. [Polish Academy of Sciences, Krakow (Poland)

1997-01-15

148

Optimising catalytic properties of supported sulfonic acid catalysts  

Microsoft Academic Search

Siliceous mesoporous molecular sieves (SBA-15) have been functionalised with propylsulfonic acid groups by both co-condensing 3-mercaptopropyltrimethoxysilane with the solid at the synthesis (sol–gel) stage and by grafting the same compound to pre-prepared SBA-15, followed, in both cases, by oxidation to sulfonic acid. The acidic and catalytic properties of the supported sulfonic acids prepared in the two ways have been compared,

P. F. Siril; N. R. Shiju; D. R. Brown; K. Wilson

2009-01-01

149

Hydrogen production by electrochemical decomposition of formic acid via solid polymer electrolyte  

Microsoft Academic Search

The aim of this work is to investigate the feasibility of simultaneous hydrogen production by electrochemical decomposition of formic acid via solid polymer electrolyte (SPE) in an electrochemical reactor. Titanium oxide coated with iridium oxide as anode and carbon fibre with Pt catalyst as cathode were used in the experiments.Effects of applied current density, flow rates and temperature of formic

Ebru Önder Kiliç; Ali Sava? Koparal; Ülker Bakir Ö?ütveren

2009-01-01

150

Efficient Dehydrogenation of Formic Acid Using an Iron Catalyst  

Microsoft Academic Search

Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO2H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H2 from FA. Applying 0.005

Albert Boddien; Dörthe Mellmann; Felix Gärtner; Ralf Jackstell; Henrik Junge; Paul J. Dyson; Gábor Laurenczy; Ralf Ludwig; Matthias Beller

2011-01-01

151

Catalytic decomposition of formic acid on oxide catalysts  

Microsoft Academic Search

In our previous paper [M.A. Borowiak, M.H. Jamróz, R. Larsson, J. Mol. Catal. A: Chem., 139 (1999) 97], an impulse-oscillation model (IOM) was used for a time description of catalytic acts in the reactions of catalytic decomposition of formic acid on oxide catalysts for unimolecular mechanism. In this paper the bimolecular mechanism were modelled for the same reactions. The results

Marek A Borowiak; Micha? H Jamróz; Ragnar Larsson

2000-01-01

152

The acrylation of glycerol over solid base catalysts: A precursor to functionalized lipids  

Technology Transfer Automated Retrieval System (TEKTRAN)

Transesterification of lipids using lipases is a common strategy used to incorporate novel acids into triacylglycerides. This approach, however, is limited to acids with pKa’s similar to common fatty acids. To overcome this limitation, we have used heterogeneous basic catalysts for the synthesis o...

153

A nanoparticle catalyst with superior activity for electrooxidation of formic acid  

Microsoft Academic Search

This paper reports the synthesis and characterization of a series of Pt-based nanoparticle catalysts with high activity for formic acid electrooxidation. The catalysts were prepared using spontaneous deposition to decorate platinum nanoparticles with controlled amounts of palladium and palladium\\/ruthenium. Among all the catalysts investigated, the Pt\\/Pd catalyst shows the best performance; the steady-state formic acid oxidation current is ca. 1mAcm?2

Piotr Waszczuk; Thomas M Barnard; Cynthia Rice; Richard I Masel; Andrzej Wieckowski

2002-01-01

154

BIFUNCTIONAL Nb\\/Ti-MCM-41 CATALYST IN OXIDATIVE ACIDIC REACTION OF CYCLOHEXENE TO DIOL  

Microsoft Academic Search

Bifunctional oxidative and acidic catalyst was prepared by incorporating titanium ion (Ti4+) and niobic acid in mesoporous molecular sieves MCM -41 structure. The catalyst is active both in oxidation, and acid-catalyzed reaction of olefin to diol. Nb\\/Ti-MCM -41 catalyst was prepared by first synthesizing Ti-MCM -41 by hydrothermal method, followed by subsequent impregnation of niobic acid (Nb) into Ti-MCM -41

Zainab Ramli; Mazidah Abdul Shukor; Didik Prasetyoko

155

Preyssler catalyst, [NaP 5W 30O 110] 14?: A green, efficient and reusable catalyst for esterification of salicylic acid with aliphatic and benzylic alcohols  

Microsoft Academic Search

A series of eco-friendly solid acid catalysts, including H14[NaP5W30O110], H14–P5, H14[NaP5W29MoO110], H14–P5Mo, and silica supported H14[NaP5W30O110], H14–P5\\/SiO2 have been used as catalysts for esterification of salicylic acid with aliphatic alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, t-butanol, 1-pentanol, and 2-pentanol) and benzylic alcohols (benzyl, 2-methylbenzyl, 2-chlorobenzyl, 4-bromobenzyl, 3-nitrobenzyl, and 4-methoxy benzyl) alcohol.The performance of different forms of Preyssler's anion in the

Fatemeh F. Bamoharram; Majid M. Heravi; Mina Roshani; Manochehr Jahangir; Ali Gharib

2006-01-01

156

Catalyst pretreatment for olefin hydration  

SciTech Connect

This patent describes an improvement in the process for the production of diisopropyl ether or isopropanol by hydration of feedstock containing propene, which comprises contacting the propene feedstock and water in a hydration zone with porous solid metal oxide acidic olefin hydration catalyst under olefins hydration conditions. The improvement comprises: pretreating the porous solid catalyst prior to contacting with the propene feedstock with a wetting agent containing at least one polar aliphatic oxygenated hydrocarbon to substantially wet the solid catalyst and sorb the wetting agent into pores of the solid catalyst.

Child, J.E.; Choi, B.C.; Ragonese, F.P.

1991-04-30

157

New catalysts and new electrolytes for acid fuel cells  

NASA Astrophysics Data System (ADS)

Based on the characterization studies and the behavior of the model systems, it appears that the promotion effect of oxides of Ti, V, Zr, Ta and Cr is probably not truly catalytic. The most probable mechanisms are changes in physical properties of the Pt catalyst in the dry state which result in improved electrode performance due to two effects: (1) at Pt crystallite shape/morphology effort, where the base metal oxide acts to impede Pt crystallite size growth (b coalescence) but alloys surface diffusion to occur and equilibrium shapes to form during heat treatment; and (2) the oxide acts as a flux for improving the wetability of the catalyst when fabricated into a gas diffusion electrode, resulting in higher catalyst layer effectiveness. Both of these effects have been discussed in the literature, but not with respect to how additives or promoters might relate to such effects. Recent work has shown that use of concentrated trifluoromethane sulfonic acid (TFMSA) in place of concentrated phosphoric acid enhances the activity of standard Pt electrodes for oxygen reduction by 40 mV (which could improve the heat rate of first-generation fuel cells by 400 Btu/kWh).

Ross, P. N.; Appleby, A. J.

1985-02-01

158

Role of surface-oxygen binding energy and surface acidity in the oxidation of o-xylene on vanadium-molybdenum oxide catalysts  

Microsoft Academic Search

using a thermostated metering tap. The acidity was determined as described in [ 9], the indicator reaction being cumene cracking. The method is based on the fact that, as is known, the activity of solid cumene-cracking catalysts is proportional to their surface acidity, as determined by measuring the adsorption of organic bases (butylamine, pyridine, quinoline, etc.) and other methods. In

Yu. I. Pyatnitskii; G. I. Golodets; T. G. Skorbilina; O. K. Biryukovich

1978-01-01

159

Catalytic reduction of U(VI) with formic acid in acid solutions on palladium catalysts  

Microsoft Academic Search

The kinetics of catalytic reduction of U(VI) with formic acid in H2SO4 solutions in the presence of Pd\\/SiO2 catalysts differing in the size of nanocrystallites of the active metal was studied. A decrease in the size of supported\\u000a Pd particles leads to a decrease in the specific activity of the catalyst, i.e., the catalytic centers located on large crystallites\\u000a exhibit

M. Yu. Boltoeva; V. P. Shilov; A. V. Anan’ev

2008-01-01

160

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts  

SciTech Connect

The research has involved the characterization of catalyst acidity, [sup 2]D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Not Available

1993-01-01

161

Application of solid ash based catalysts in heterogeneous catalysis  

Microsoft Academic Search

Solid wastes, fly ash, and bottom ash are generated from coal and biomass combustion. Fly ash is mainly composed of various metal oxides and possesses higher thermal stability. Utilization of fly ash for other industrial applications provides a cost-effective and environmentally friendly way of recycling this solid waste, significantly reducing its environmental effects. On the one hand, due to the

Shaobin Wang

2008-01-01

162

Synthesis and acid catalysis of cellulose-derived carbon-based solid acid  

Microsoft Academic Search

SO3H-bearing amorphous carbon, prepared by partial carbonization of cellulose followed by sulfonation in fuming H2SO4, was applied as a solid catalyst for the acid-catalyzed hydrolysis of ?-1,4 glucan, including cellobiose and crystalline cellulose. Structural analyses revealed that the resulting carbon material consists of graphene sheets with 1.5 mmol g?1 of SO3H groups, 0.4 mmol g?1 of COOH, and 5.6 mmol g?1 of phenolic OH groups. The

Satoshi Suganuma; Kiyotaka Nakajima; Masaaki Kitano; Daizo Yamaguchi; Hideki Kato; Shigenobu Hayashi; Michikazu Hara

2010-01-01

163

Catalytic synthesis of benzoic esters with carbon-based solid acid from coal tar  

Microsoft Academic Search

A new carbon-based solid acid catalyst (C- SO3H) was prepared by simultaneous cross- linking coal tar with benzaldehyde,hoist temperature -curing ,sulphonation in sulfuric acid and was characterized by FT-IR,TG-DTG,XRD and neutralization potentiometric titration, and SEM techniques. The results indicated that there is the high density of SO3H groups in forming amorphous coke consisting of polycyclic aromatic carbon sheets, and the

Haie Hao; Baojun Ma; Jinxin Ma; Sun Yuan; Wanyi Liu

2011-01-01

164

An Eco-Friendly Improved Protocol for the Synthesis of Bis(3-indolyl)methanes Using Poly(4-vinylpyridinium)hydrogen Sulfate as Efficient, Heterogeneous, and Recyclable Solid Acid Catalyst  

PubMed Central

Highly efficient and eco-friendly protocol for the synthesis of bis(3-indolyl)methanes by the electrophilic substitution reaction of indole with aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate was described. Excellent yields, shorter reaction times, simple work-up procedure, avoiding hazardous organic solvents, and reusability of the catalyst are the most obvious advantages of this method.

Banothu, Janardhan; Gali, Rajitha; Velpula, Ravibabu; Bavantula, Rajitha; Crooks, Peter A.

2013-01-01

165

An Eco-Friendly Improved Protocol for the Synthesis of Bis(3-indolyl)methanes Using Poly(4-vinylpyridinium)hydrogen Sulfate as Efficient, Heterogeneous, and Recyclable Solid Acid Catalyst.  

PubMed

Highly efficient and eco-friendly protocol for the synthesis of bis(3-indolyl)methanes by the electrophilic substitution reaction of indole with aldehydes catalyzed by poly(4-vinylpyridinium)hydrogen sulfate was described. Excellent yields, shorter reaction times, simple work-up procedure, avoiding hazardous organic solvents, and reusability of the catalyst are the most obvious advantages of this method. PMID:24052864

Banothu, Janardhan; Gali, Rajitha; Velpula, Ravibabu; Bavantula, Rajitha; Crooks, Peter A

2013-09-02

166

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones with a variety of aromatic and heteroaromatic hydrazines are accelerated upon irradiation in a household microwave overn in the absence of any catalyst, solid support or solvent thus providing an environmentally friendly pathw...

167

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-0nes with a variety of aromatic and heteroaromatic hydrazines are remarkably acceleterated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent. The approach provides an attractive...

168

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS  

EPA Science Inventory

The reaction of neat 5- or 8-oxobenzopyran-2(1H)-ones with a variety of aromatic and heteroaromatic hydrazines are remarkably accelerated upon irradiation in a household microwave oven in the absence of any catalyst, solid support or solvent. The approach provides an attractive a...

169

sup 13C solid-state NMR study of ethylene oxidation over supported silver catalysts.  

National Technical Information Service (NTIS)

Solid-state NMR has been used to study the interaction of ethylene with oxygen in the absence of promoters and moderators over silica-supported silver catalysts. Experiments using nitrous oxide and oxygen as the oxidants have been carried out over Ag/SiO(...

S. Hosseini

1992-01-01

170

Oxidation of glyoxal to glyoxylic acid by oxygen over V 2O 5\\/C catalyst  

Microsoft Academic Search

A novel vanadium oxide catalyst supported on active carbon was prepared by an incipient wetness impregnation method, and the precursor was obtained from oxalic acid aqueous solutions of NH4VO3. The catalyst was applied liquid phase oxidation of glyoxal to glyoxylic acid. It was found that V2O5\\/C catalyst exhibited obvious activity for glyoxal oxidation. Glyoxylic acid could be obtained without pH

Yu Lan Niu; Zheng Xu; Min Li; Rui Feng Li

2008-01-01

171

Synthesis of a Novel Carbon Based Strong Acid Catalyst Through Hydrothermal Carbonization  

Microsoft Academic Search

A novel carbon based strong acid catalyst has been synthesized through the sulfonation of the carbon materials from glucose.\\u000a The novel acid catalyst was obtained through the hydrothermal carbonization instead of the traditional heat treatment, which\\u000a made the carbonization process under much milder condition with higher yield. The novel heterogeneous catalyst owned the advantages\\u000a of high acidity as much as

Xuezheng Liang; Jianguo Yang

2009-01-01

172

Recovery of iron oxides from acid mine drainage and their application as adsorbent or catalyst.  

PubMed

Iron oxide particles recovered from acid mine drainage represent a potential low-cost feedstock to replace reagent-grade chemicals in the production of goethite, ferrihydrite or magnetite with relatively high purity. Also, the properties of iron oxides recovered from acid mine drainage mean that they can be exploited as catalysts and/or adsorbents to remove azo dyes from aqueous solutions. The main aim of this study was to recover iron oxides with relatively high purity from acid mine drainage to act as a catalyst in the oxidation of dye through a Fenton-like mechanism or as an adsorbent to remove dyes from an aqueous solution. Iron oxides (goethite) were recovered from acid mine drainage through a sequential precipitation method. Thermal treatment at temperatures higher than 300 °C produces hematite through a decrease in the BET area and an increase in the point of zero charge. In the absence of hydrogen peroxide, the solids adsorbed the textile dye Procion Red H-E7B according to the Langmuir model, and the maximum amount adsorbed decreased as the temperature of the thermal treatment increased. The decomposition kinetics of hydrogen peroxide is dependent on the H(2)O(2) concentration and iron oxides dosage, but the second-order rate constant normalized to the BET surface area is similar to that for different iron oxides tested in this and others studies. These results indicate that acid mine drainage could be used as a source material for the production of iron oxide catalysts/adsorbents, with comparable quality to those produced using analytical-grade reagents. PMID:22820746

Flores, Rubia Gomes; Andersen, Silvia Layara Floriani; Maia, Leonardo Kenji Komay; José, Humberto Jorge; Moreira, Regina de Fatima Peralta Muniz

2012-07-20

173

Enantioselective hydrogenation of isophorone over Pd catalysts in the presence of(?)-dihydroapovincaminic acid ethyl ester  

Microsoft Academic Search

The enantioselective heterogeneous catalytic hydrogenation of isophorone in the presence of apovincaminic acid ethyl ester was investigated. Various Pd black catalysts differing in their preparation method were studied. The catalysts were characterized by different methods such as physical adsorption and chemisorption, SEM and XPS. An explanation was created for the different enantioselectivity of the catalysts being precipitated by different reducing

G Farkas; É S??pos; A Tungler; A Sárkány; J. L Figueiredo

2001-01-01

174

Decarboxylative coupling of heptanoic acid. Manganese, cerium and zirconium oxides as catalysts  

Microsoft Academic Search

A series of catalysts containing 20wt.% of Mn, Ce and Zr oxides deposited on Al2O3, SiO2 and TiO2 has been studied in ketonisation of heptanoic acid. The most pronounced effect of alumina support on catalysts activity has been noted. Manganese oxide catalysts have shown the highest activity. The dependence of the concentration of MnO2 active phase on catalyst activity has

M Gli?ski; J Kije?ski

2000-01-01

175

Sonophotochemical Degradation of Bisphenol A with Solid Catalysts  

NASA Astrophysics Data System (ADS)

In order to investigate the degradation of bisphenol A (BPA) solution under sono, photo, sonocatalytic, photocatalytic and sonophotocatalytic processes, the BPA concentration and the total organic carbon (TOC) concentration were analyzed. The degradation rate of BPA was higher at high frequency (1 MHz) than at low frequency (300 kHz). At high frequency the acoustic period is shorter, and a high H2O2 concentration is therefore produced in aqueous solutions, which can enhance the degradation rate. The degradation rates of BPA were 0.0060, 0.0258, and 0.0451 min-1 under the sonocatalytic (1 MHz), photocatalytic and sonophotocatalytic processes respectively. The combined system of the sonochemical and photocatalytic processes can enhance the degradation rate of BPA compared with individual processes (sono and photocatalytic processes). The order of degradation of BPA (CuO>ZnO?TiO2) and TOC (TiO2>ZnO>CuO) differed for each of the three types of catalysts. The separation characteristics of catalysts were dissimilar for each of the two frequencies.

Myunghee Lim,; Younggyu Son,; Beomguk Park,; Jeehyeong Khim,

2010-07-01

176

Solid acids as fuel cell electrolytes.  

PubMed

Fuel cells are attractive alternatives to combustion engines for electrical power generation because of their very high efficiencies and low pollution levels. Polymer electrolyte membrane fuel cells are generally considered to be the most viable approach for mobile applications. However, these membranes require humid operating conditions, which limit the temperature of operation to less than 100 degrees C; they are also permeable to methanol and hydrogen, which lowers fuel efficiency. Solid, inorganic, acid compounds (or simply, solid acids) such as CsHSO4 and Rb3H(SeO4)2 have been widely studied because of their high proton conductivities and phase-transition behaviour. For fuel-cell applications they offer the advantages of anhydrous proton transport and high-temperature stability (up to 250 degrees C). Until now, however, solid acids have not been considered viable fuel-cell electrolyte alternatives owing to their solubility in water and extreme ductility at raised temperatures (above approximately 125 degrees C). Here we show that a cell made of a CsHSO4 electrolyte membrane (about 1.5 mm thick) operating at 150-160 degrees C in a H2/O2 configuration exhibits promising electrochemical performances: open circuit voltages of 1.11 V and current densities of 44 mA cm-2 at short circuit. Moreover, the solid-acid properties were not affected by exposure to humid atmospheres. Although these initial results show promise for applications, the use of solid acids in fuel cells will require the development of fabrication techniques to reduce electrolyte thickness, and an assessment of possible sulphur reduction following prolonged exposure to hydrogen. PMID:11309611

Haile, S M; Boysen, D A; Chisholm, C R; Merle, R B

2001-04-19

177

Hydrogenation of lactic acid to propylene glycol over copper-containing catalysts  

Microsoft Academic Search

Catalytic properties of different copper-containing catalysts synthesized from different precursors were studied in the hydrogenation\\u000a of lactic acid at mild conditions. The most active catalyst was found to be chrysocolla-like copper hydroxysilicate with the\\u000a copper loading of about 50 at%. At the optimal reaction conditions (T = 473 K, WHSV = 0.08 h?1), 95% conversion of lactic acid over this catalyst and 65% selectivity to 1,2-propylene glycol

Mikhail N. Simonov; Irina L. Simakova; Valentin N. Parmon

2009-01-01

178

Catalytic wet air oxidation of butyric acid solutions using carbon-supported iridium catalysts  

Microsoft Academic Search

Aqueous solutions of butyric acid were treated by catalytic wet air oxidation using carbon-supported iridium catalysts in a stirred reactor. Under the operating conditions of 6.9bar of oxygen partial pressure and 200°C of temperature, conversions up to 52.9% after 2h were obtained depending on the type of catalyst used. The effects of butyric acid initial concentration, loading of catalyst, oxygen

H. T Gomes; J. L Figueiredo; J. L Faria

2002-01-01

179

Sulfamic Acid as a Green, Efficient, Recyclable and Reusable Catalyst for Direct Addition of Aliphatic Acid with Cyclic Olefins  

Microsoft Academic Search

Sulfamic acid has been used as a catalyst for esterification of cyclic olefins with aliphatic acids, and good olefins conversion as well as excellent esters selectivity was obtained. The catalyst could be recycled easily by filtration and directly reused in the next run with satisfactory results.

Bo Wang; Yanlong Gu; Liming Yang; Jishuan Suo; Okamoto Kenichi

2004-01-01

180

On the strength of solid acids  

SciTech Connect

The objective of the present work was to establish the relative strengths of some common solid acids and to put them on a scale familiar to chemists. A modified spectrophotometric approach involving H{sub 0} and H{sub R} indicators was developed. The red-shifts of spectra from the adsorbed neutral forms of 4-nitrotoluene and 4-nitrofluorobenzene were used to deduce the equivalent H{sub 2}SO{sub 4} concentrations. Thus, values of 70 to 80%, and 90 to 98% H{sub 2}SO{sub 4} were determined for silica-alumina and HY preparations, respectively. HM preparations were found to be mild superacids (stronger than 100% H{sub 2}SO{sub 4}). On the other hand, H{sub 2}SO{sub 4}/ZrO{sub 2} preparations had surface acidities about equivalent to 100% H{sub 2}SO{sub 4}, and SbF{sub 5}/silica-alumina was a superacid with {minus}14.5 < H{sub 0} < {minus}13.7. These data were correlated with the catalytic activities of the solid acids expressed either as 1n (reaction rate) at 370{sup o}C or as the temperature required to obtain 0.5% conversion of isobutane. The extent and nature of the secondary reactions also varied with the acidity. These results demonstrate that the intensive factor of the acidity (acid strength) dominated over the extensive factor (surface concentration of Bronsted sites) in controlling the acidity, and therefore the catalytic properties, of these solids.

Umansky, B.; Engelhardt, J.; Hall, W.K. (Univ. of Pittsburgh, PA (USA))

1991-01-01

181

New Non-noble Metal Anode Catalysts for Acid Fuel Cells  

Microsoft Academic Search

NOBLE metals have been found to be the most suitable materials as anode catalysts for hydrogen oxidation in low temperature fuel cells containing an acid electrolyte. The one exception is tungsten carbide1, which is the only compound to have shown catalytic activity and sufficient resistance against corrosion in acid media under anodic polarization to act as an anode catalyst. In

Harald Böhm

1970-01-01

182

Influence of Catalyst (Citric Acid) Concentration on the Physical Properties of TEOS Silica Aerogels  

Microsoft Academic Search

In the present paper, the experimental results on the influence of catalyst (citric acid) concentration on the physical properties of TEOS silica aerogels, are reported. The aerogels have been prepared by hydrolysis and polycondensation of tetraethoxysilane (TEOS) using citric acid (CTA) as a new catalyst followed by supercritical drying in an autoclave. In order to obtain the best quality silica

P. B. Wagh; A. Venkateswara Rao; D. Haranath

1997-01-01

183

Silica-bonded N-propyl sulfamic acid as an efficient catalyst for the formylation and acetylation of alcohols and amines under heterogeneous conditions  

Microsoft Academic Search

A simple and efficient procedure for the preparation of silica-bonded N-propyl sulfamic acid (SBNPSA) by the reaction of 3-aminopropylsilica (1) and chlorosulfonic acid in chloroform is described. This solid acid is employed as a new catalyst for the formylation of alcohols and amines with ethyl formate under mild and heterogeneous conditions at room temperature with good to excellent yields. Also,

Khodabakhsh Niknam; Dariush Saberi

2009-01-01

184

Wet oxidation of acid brown dye by hydrogen peroxide using heterogeneous catalyst Mn-salen-Y zeolite: a potential catalyst.  

PubMed

Catalytic wet hydrogen peroxide oxidation of acid dye has been explored in this study. Manganese(III) complex of N,N'-ethylene bis(salicylidene-aminato) (salenH(2)) has been encapsulated in super cages of zeolite-Y by flexible ligand method. The catalyst has been characterized by FT-IR, XRD, TG/DTA and nitrogen adsorption studies. The effects of various parameters such as pH, catalyst and hydrogen peroxide concentration on the oxidation of dye were studied. The results indicate that after 20 min at 30 degrees C, 0.175 M H(2)O(2) and 3g/L catalyst, about 90% dye removal was obtained. These studies indicate that manganese-salen complex immobilized on zeolite framework can act as a good heterogeneous catalyst for removal of dye from wastewaters. PMID:16814465

Aravindhan, Rathinam; Fathima, Nishtar Nishad; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni

2006-05-26

185

Catalysts  

NSDL National Science Digital Library

There are two types of catalysis reactions: homogeneous and heterogeneous. In a homogeneous reaction, the catalyst is in the same phase as the reactants. In a heterogeneous reaction, the catalyst is in a different phase from the reactants. This activity addresses homogeneous catalysis.

Consortium, The C.

2011-12-11

186

Solid-state NMR characterization of Wilkinson's catalyst immobilized in mesoporous SBA-3 silica.  

PubMed

The Wilkinson's catalyst [RhCl(PPh(3))(3)] has been immobilized inside the pores of amine functionalized mesoporous silica material SBA-3 and The structure of the modified silica surface and the immobilized rhodium complex was determined by a combination of different solid-state NMR methods. The successful modification of the silica surface was confirmed by (29)Si CP-MAS NMR experiments. The presence of the T(n) peaks confirms the successful functionalization of the support and shows the way of binding the organic groups to the surface of the mesopores. (31)P-(31)P J-resolved 2D MAS NMR experiments were conducted in order to characterize the binding of the immobilized catalyst to the amine groups of the linkers attached to the silica surface. The pure catalyst exhibits a considerable (31)P-(31)P J-coupling, well resolvable in 2D MAS NMR experiments. This J-coupling was utilized to determine the binding mode of the catalyst to the linkers on the silica surface and the number of triphenylphosphine ligands that are replaced by coordination bonds to the amine groups. From the absence of any resolvable (31)P-(31)P J-coupling in off-magic-angle-spinning experiments, as well as slow-spinning MAS experiments, it is concluded, that two triphenylphosphine ligands are replaced and that the catalyst is bonded to the silica surface through two linker molecules. PMID:20446319

Grünberg, Anna; Yeping, Xu; Breitzke, Hergen; Buntkowsky, Gerd

2010-06-18

187

Advances in the Determination of the Architecture of Active Sites in Solid Catalysts  

Microsoft Academic Search

\\u000a We review some of the advances in the determination of the atomic architecture of solid catalysts, in particular using X-ray,\\u000a neutron scattering and spectroscopic techniques. The aim, wherever possible, is to arrive at such structures under operating\\u000a (catalytic) conditions. It is essential to retrieve such information in situ, because it then can serve as a realistic platform for the construction

G. Sankar; R. Raja; J. M. Thomas; D. Gleeson

188

Manipulating catalytic pathways: deoxygenation of palmitic acid on multifunctional catalysts.  

PubMed

The mechanism of the catalytic reduction of palmitic acid to n-pentadecane at 260 °C in the presence of hydrogen over catalysts combining multiple functions has been explored. The reaction involves rate-determining reduction of the carboxylic group of palmitic acid to give hexadecanal, which is catalyzed either solely by Ni or synergistically by Ni and the ZrO2 support. The latter route involves adsorption of the carboxylic acid group at an oxygen vacancy of ZrO2 and abstraction of the ?-H with elimination of O to produce the ketene, which is in turn hydrogenated to the aldehyde over Ni sites. The aldehyde is subsequently decarbonylated to n-pentadecane on Ni. The rate of deoxygenation of palmitic acid is higher on Ni/ZrO2 than that on Ni/SiO2 or Ni/Al2O3, but is slower than that on H-zeolite-supported Ni. As the partial pressure of H2 is decreased, the overall deoxygenation rate decreases. In the absence of H2, ketonization catalyzed by ZrO2 is the dominant reaction. Pd/C favors direct decarboxylation (-CO2), while Pt/C and Raney Ni catalyze the direct decarbonylation pathway (-CO). The rate of deoxygenation of palmitic acid (in units of mmol moltotal metal(-1) h(-1)) decreases in the sequence r(Pt black) ?r(Pd black) >r(Raney Ni) in the absence of H2 . In situ IR spectroscopy unequivocally shows the presence of adsorbed ketene (C=C=O) on the surface of ZrO2 during the reaction with palmitic acid at 260 °C in the presence or absence of H2. PMID:23519964

Peng, Baoxiang; Zhao, Chen; Kasakov, Stanislav; Foraita, Sebastian; Lercher, Johannes A

2013-03-20

189

Efficient dehydrogenation of formic acid using an iron catalyst.  

PubMed

Hydrogen is one of the essential reactants in the chemical industry, though its generation from renewable sources and storage in a safe and reversible manner remain challenging. Formic acid (HCO(2)H or FA) is a promising source and storage material in this respect. Here, we present a highly active iron catalyst system for the liberation of H(2) from FA. Applying 0.005 mole percent of Fe(BF(4))(2)·6H(2)O and tris[(2-diphenylphosphino)ethyl]phosphine [P(CH(2)CH(2)PPh(2))(3), PP(3)] to a solution of FA in environmentally benign propylene carbonate, with no further additives or base, affords turnover frequencies up to 9425 per hour and a turnover number of more than 92,000 at 80°C. We used in situ nuclear magnetic resonance spectroscopy, kinetic studies, and density functional theory calculations to explain possible reaction mechanisms. PMID:21940890

Boddien, Albert; Mellmann, Dörthe; Gärtner, Felix; Jackstell, Ralf; Junge, Henrik; Dyson, Paul J; Laurenczy, Gábor; Ludwig, Ralf; Beller, Matthias

2011-09-23

190

A sup 95 Mo solid-state NMR study of hydrodesulfurization catalysts. 1. Formation of fresh HDS catalyst precursors by adsorption of polyoxomolybdates onto. gamma. -alumina  

SciTech Connect

The solid-state {sup 95}Mo NMR of oxomolybdates and polyoxomolybdates adsorbed to {gamma}-alumina was utilized to characterize the molybdenum species present at circa monolayer coverages of molybdenum. This represents the first attempt at using solid-state NMR to look directly at the molybdenum species on the surface of 'fresh' hydrodesulfurization catalyst precursors. The selectively excited central {plus minus}1/2 transition line shapes were obtained, by the solid-echo technique, for several polyoxomolybdates, which are considered model compounds of the surface molybdena species, as well as for the uncalcined and calcined catalysts at various loadings. The spectra were obtained for static and magic angle spinning samples. Static sample spectra of the catalysts reveal inhomogeneously broadened lines owing to a range of surface species being present. Magic and angle spinning spectra show the presence of four possible species on the surface of the uncalcined catalysts and two possible species present on the surface of calcined catalysts. Spikelet echo spectra identified static adsorbed species (speculated to be predominantly adsorbed tetrahedral/octahedral molybdena, and perhaps Al{sub 2}(MoO{sub 4}){sub 3}), and a dynamic species (speculated to be disordered, surface-interactive tetrahedral and octahedral molybdates), in the uncalcined catalyst samples. Upon calcination the line widths of the static and MAS spectra are increased, indicating a polymerization of the surface species to form a MoO{sub 3}-like phase. 67 refs.

Edwards, J.C.; Adams, R.D.; Ellis, P.D. (Univ. of South Carolina, Columbia (United States))

1990-11-07

191

A kinetic model for activation-deactivation processes in solid catalysts  

SciTech Connect

In this paper a kinetic model is proposed to describe the activation-deactivation phenomena taking place simultaneously with the main reaction on a catalytic surface. Potentially active sites are transformed into active sites by the activation process. Simultaneously, catalyst deactivation gives rise to deactivated processes on the catalyst surface. When activation processes are present, this is a more rigorous alternative to studies that only take into account catalyst deactivation. Kinetic expressions have been obtained for activation processes coupled with reversible and irreversible deactivation, and a study of the influence of the different kinetic parameters has been carried out. Finally, the model developed has been applied to previous literature data on n-butane isomerization on an aluminum chloride/sulfonic acid resin.

Agorreta, E.L.; Pena, J.A.; Santamaria, J.; Monzon, A. (Dept. of Chemical Engineering, Faculty of Science, Univ. of Zaragoza, 50009 Zaragoza (ES))

1991-01-01

192

Organometallic catalysts for primary phosphoric acid fuel cells: Final report, 1981-1985  

SciTech Connect

Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 h in full cell at 160 to 200C in phosphoric acid (H3PO4), and was shown to provide stable performance.

Walsh, F.

1987-03-01

193

Selective Poisoning and Deactivation of Acid Sites on Sulfated Zirconia Catalysts for n-Butane Isomerization  

Microsoft Academic Search

Reaction kinetics measurements, selective poisoning, and microcalorimetry were used to study the activity, selectivity, and deactivation of acid sites on a sulfated zirconia catalyst forn-butane isomerization at 423 K. The sulfated zirconia catalyst has a distribution of acid site strengths, containing 50 ?mol\\/g of strong acid sites characterized by heats of ammonia adsorption from 125 to 165 kJ\\/mol. The strongest

G. Yaluris; R. B. Larson; J. M. Kobe; M. R. González; K. B. Fogash; J. A. Dumesic

1996-01-01

194

Synthesis of dioctyl phthalate using acid functionalized ionic liquid as catalyst  

Microsoft Academic Search

Dioctyl phthalate were synthesized by using acid functionalized ionic liquid as catalyst. The results indicated that HSO3-functionalized Brønsted acidic ionic liquids show better catalytic and reusable performance than non-functionalized ionic liquids or the combination of neutral ionic liquids and Brønsted acid. Under the optimum conditions, using 1-methyl-3-(3-sulfopropyl)-imidazolium hydrogen sulfate as catalyst, the conversion of phthalic anhydride was 98%. After easily

Hongliang Li; Shitao Yu; Fusheng Liu; Congxia Xie; Lu Li

2007-01-01

195

A green and efficient protocol for the synthesis of quinoxaline, benzoxazole and benzimidazole derivatives using heteropolyanion-based ionic liquids: as a recyclable solid catalyst.  

PubMed

In this paper, we introduce two nonconventional ionic liquid compounds which are composed of propane sulfonate functionalized organic cations and heteropolyanions as green solid acid catalysts for the highly efficient and green synthesis of 2,3-disubstitutedquinoxaline derivatives. These ionic liquids are in the solid state at room temperature and the synthesis is carried out via the one-pot condensation reaction of various o-phenylenediamine with 1,2-diketone derivatives. Benzoxazole and benzimidazole derivatives were also synthesized by these novel catalysts via the one-pot condensation from reaction orthoester with o-aminophenol (synthesis of benzoxazole derivatives) and ophenylenediamine (synthesis of benzimidazole derivatives). All experiments successfully resulted in the desired products. The described novel synthesis method has several advantages of safety, mild condition, high yields, short reaction times, simplicity and easy workup compared to the traditional method of synthesis. PMID:23547570

Vahdat, Seyed Mohammad; Baghery, Saeed

2013-09-01

196

Hydrogenation process using noble metal catalysts promoted by liquid fluorine containing acids  

Microsoft Academic Search

A process for the hydrogenation of unsaturated hydrocarbon fractions is described which comprises dissolving said unsaturated hydrocarbon fraction in a liquid acid system, said liquid acid system being selected from the group consisting of liquid HF, other liquid Bronsted acid containing fluorine, fluorine containing Friedel-Crafts catalyst (such as BFâ, TaFâ) in liquid HF or other liquid fluorine containing Bronsted acid

Wristers

1978-01-01

197

In vitro Dissolution Studies on Solid Dispersions of Mefenamic Acid.  

PubMed

Solid dispersions of mefanamic acid with a water-soluble polymer polyvinyl pyrrolidine and a super disintegrant, primojel were prepared by common solvent and solvent evaporation methods employing methanol as the solvent. The dissolution rate and dissolution efficiency of the prepared solid dispersions were evaluated in comparison to the corresponding pure drug. Solid dispersions of mefenamic acid showed a marked enhancement in dissolution rate and dissolution efficiency. At 1:4 ratio of mefenamic acid-primojel a 2.61 fold increase in the dissolution rate of mefenamic acid was observed with solid dispersion. The solid dispersions in combined carriers gave much higher rates of dissolution than super disintegrants alone. Mefanamic acid-primojel-polyvinyl pyrrolidine (1:3.2:0.8) solid dispersion gave a 4.11 fold increase in the dissolution rate of mefenamic acid. Super disintegrants alone or in combination with polyvinyl pyrrolidine could be used to enhance the dissolution rate of mefenamic acid. PMID:22303074

Rao, K R S Sambasiva; Nagabhushanam, M V; Chowdary, K P R

2011-03-01

198

Reactions of butadiene in zeolite catalysts by in situ variable-temperature solid-state nuclear magnetic resonance spectrometry  

SciTech Connect

The mechanisms by which butadiene oligomerizes in acidic zeolite catalysts leading to deactivation by pore blockage have been elucidated by using in situ {sup 13}C solid-state NMR spectroscopy with magic-angle spinning (MAS). Butadiene is found to oligomerize primarily by the 1,4-addition reaction upon adsorption at its melting point (164 K). Secondary reactions of the oligomers are strongly dependent upon the properties of the zeolite. The initially formed linear product undergoes cyclization reactions to form fused rings in zeolite HY, but isolated rings are formed in the smaller channels of zeolite HZSM-5. Branching reactions and/or 1,2 enchainment result in an appreciable methyl group content in the oligomers formed in zeolite HY. These results provide insight into the mechanisms by which oxide catalysts are deactivated by pore blockage. Neither carbenium ions nor any other reactive intermediates were observed spectroscopically, presumably because such intermediates reacted with either free butadiene or the oligomers so rapidly as to preclude a detectable steady state concentration.

Richardson, B.R.; Lazo, N.D.; Schettler, P.D.; White, J.L.; Haw, J.F. (Texas A and M Univ., College Station (USA))

1990-04-11

199

Synthesis of fatty acid methyl ester from palm oil (Elaeis guineensis) with Ky(MgCa)2xO3 as heterogeneous catalyst.  

PubMed

Fatty acid methyl esters (FAME) were produced from palm oil using eggshell modified with magnesium and potassium nitrates to form a composite, low-cost heterogeneous catalyst for transesterification. The catalyst, prepared by the combination of impregnation/co-precipitation was calcined at 830 °C for 4 h. Transesterification was conducted at a constant temperature of 65 °C in a batch reactor. Design of experiment (DOE) was used to optimize the reaction parameters, and the conditions that gave highest yield of FAME (85.8%) was 5.35 wt.% catalyst loading at 4.5 h with 16:1 methanol/oil molar ratio. The results revealed that eggshell, a solid waste, can be utilized as low-cost catalyst after modification with magnesium and potassium nitrates for biodiesel production. PMID:21983406

Olutoye, M A; Lee, S C; Hameed, B H

2011-09-16

200

Platinum nanoparticles–manganese oxide nanorods as novel binary catalysts for formic acid oxidation  

Microsoft Academic Search

The current study proposes a novel binary catalyst system (composed of metal\\/metal oxide nanoparticles) as a promising electrocatalyst in formic acid oxidation. The electro-catalytic oxidation of formic acid is carried out with binary catalysts of Pt nanoparticles (nano-Pt) and manganese oxide nanorods (nano-MnOx) electrodeposited onto glassy carbon (GC) electrodes. Cyclic voltammetric (CV) measurements showed that unmodified GC and nano-MnOx\\/GC electrodes

Mohamed S. El-Deab

201

Preparation and characterization of the phenolated wood using hydrochloric acid (HCl) as a catalyst  

Microsoft Academic Search

Summary  Birch (Betula maximowicziana Regel) wood meal was liquefied in the presence of phenol using hydrochloric acid (HCl) as a catalyst at a temperature of\\u000a 150 C for 2 h in an autoclave. It was found out that HCl acid could be used as an effective catalyst for the hydroxy phenylation\\u000a of wood under the experimental conditions. In this study the

M. H. Alma; M. Yoshioka; Y. Yao; N. Shiraishi

1995-01-01

202

Catalytic ketonization over oxide catalysts  

Microsoft Academic Search

Carboxylic acids were selectively reduced to aldehydes when their mixture with formic acid in the form of vapour had been passed over solid catalyst. The activities of 20?wt.% MO2\\/A catalysts, where M?=?Mn, Ce or Zr and A?=?Al2O3 have been studied in the mentioned reaction at the temperature range of 573–723?K. Hexanoic acid and its branched monomethyl and dimethyl isomers were

M. Gli?ski; A. Kozio?; D. ?omot; Z. Kaszkur

2007-01-01

203

Process for the generation of {alpha},{beta}-unsaturated carboxylic acids and esters using niobium catalyst  

SciTech Connect

A process using a niobium catalyst includes the step of reacting an ester or carboxylic acid with oxygen and an alcohol in the presence a niobium catalyst to respectively produce an {alpha},{beta}-unsaturated ester or carboxylic acid. Methanol may be used as the alcohol, and the ester or carboxylic acid may be passed over the niobium catalyst in a vapor stream containing oxygen and methanol. Alternatively, the process using a niobium catalyst may involve the step of reacting an ester and oxygen in the presence the niobium catalyst to produce an {alpha},{beta}-unsaturated carboxylic acid. In this case the ester may be a methyl ester. In either case, niobium oxide may be used as the niobium catalyst with the niobium oxide being present on a support. The support may be an oxide selected from the group consisting of silicon oxide, aluminum oxide, titanium oxide and mixtures thereof. The catalyst may be formed by reacting niobium fluoride with the oxide serving as the support. The niobium catalyst may contain elemental niobium within the range of 1 wt % to 70 wt %, and more preferably within the range of 10 wt % to 30 wt %. The process may be operated at a temperature from 150 to 450 C and preferably from 250 to 350 C. The process may be operated at a pressure from 0.1 to 15 atm. absolute and preferably from 0.5--5 atm. absolute. The flow rate of reactants may be from 10 to 10,000 liter/kg catalyst/h, and preferably from 100 to 1,000 liter/kg catalyst/h.

Gogate, M.R.; Spivey, J.J.; Zoeller, J.R.

1999-12-07

204

Highly efficient acid-treated cobalt catalyst for hydrogen generation from NaBH 4 hydrolysis  

Microsoft Academic Search

The effect of cobalt-based catalysts, i.e. CoCl2(20wt% Co)\\/Al2O3 treated by different acids, on NaBH4 hydrolysis was investigated. Five acids were used: oxalic acid, citric acid, acetic acid, sulfuric acid and hydrochloric acid. Two ways of acid treatment were considered: (i) ex-situ addition of acid to CoCl2(20wt% Co)\\/Al2O3 at room temperature and (ii) in-situ addition by mixing CoCl2, Al2O3 and acid

O. Akdim; U. B. Demirci; P. Miele

2009-01-01

205

Gas-phase decomposition of formic acid over Fe2O3 catalysts  

Microsoft Academic Search

Fe_2O_3 catalyst samples were used for the decomposition of formic acid, in the gas phase. These catalysts were produced by\\u000a calcination of Fe(NO_3)3 9H_2O for 5 h, in air, in the temperature range 200-600C. All catalysts were characterized by temperature-programmed\\u000a reduction (TPR) and X-ray diffraction (XRD). In addition, the surface area (SBET) of these samples as well as the acidity

S. A. Halawy; S. S. Al-Shihry; M. A. Mohamed

1997-01-01

206

Catalytic Ring Hydrogenation of Benzoic Acid with Supported Transition Metal Catalysts in scCO2  

PubMed Central

The ring hydrogenation of benzoic acid to cyclohexanecarboxylic acid over charcoal-supported transition metal catalysts in supercritical CO2 medium has been studied in the present work. The cyclohexanecarboxylic acid can be produced efficiently in supercritical CO2 at the low reaction temperature of 323 K. The presence of CO2 increases the reaction rate and several parameters have been discussed.

Wang, Hongjun; Zhao, Fengyu

2007-01-01

207

Application of nanostuctured materials as acid-catalysts in rice straw pyrolysis for bio-oil production  

NASA Astrophysics Data System (ADS)

Rice straw, a waste agro-byproduct, which is abundant lignocellulose products from rice production, is a renewable energy sources in Vietnam. Bio-oil from rice straw is produced by thermal and catalytic pyrolysis using a fixed-bed reactor with heating rate 15oC/min, nitrogen as sweeping gas with flow rate 120ml/min. Final temperature of the pyrolysis reaction is a significantly influence on product yield. The gas yield increased and the solid yield decreased as the pyrolysis temperature increasing from 400oC to 600oC. The bio-oil yield reached a maximum of 48.3 % at the pyrolysis temperature of 550oC. Mesoporous Al-SBA-15 was used as acid catalyst in pyrolysis of rice straw. The obtained results showed that, in the presence of catalyst, yield of gas products increased, whereas liquid yield decreased and solid product remained the same as compared to the non-catalytic experiments. The effect of nanostructured catalysts on the product yields and distribution was investigated.

Dang, Phuong T.; Le, Hy G.; Dinh, Thang C.; Hoang, Thang V.; Bui, Linh H. T.; Hoang, Yen; Tran, Hoa K. T.; Vu, Tuan A.

2008-12-01

208

A process to transesterify vegetable oil with methanol in the presence of quick lime bit functioning as solid base catalyst  

Microsoft Academic Search

As a precursor of the practical catalyst to utilize solid base catalysis of calcium oxide for biodiesel production, crushed lime stone whose size ranged from 1.0 to 1.7mm was used in this study. The precursor was turned into the practical catalyst by only calcination at 1173K. At 333K under atmospheric pressure, rapeseed oil was transesterified with methanol in the presence

Masato Kouzu; Jyu-suke Hidaka; Yoshiya Komichi; Haruhiko Nakano; Mitsuyo Yamamoto

2009-01-01

209

Study on the Condensation Reaction of preparing Vanillin from Guaiacol and Glyoxylic Acid by a novel Catalyst  

Microsoft Academic Search

As an intermediate for preparing vanillin derived from glyoxylic acid, 3-methoxy-4-hydroxymandelic acid (MHMA) was synthesized based on condensation of guaiacol with glyoxylic acid in the presence of a novel catalyst. The influence of the novel catalyst on the condensation reaction was investigated. The experimental results showed that the novel catalyst was suitable for the formation of 3-methoxy-4-hydroxymandelic acid from guaiacol

WEI Guo-feng; LIU Nai-qing

210

Surface properties of pillared acid-activated bentonite as catalyst for selective production of linear alkylbenzene  

NASA Astrophysics Data System (ADS)

Acid-activated and pillared montmorillonite were prepared as novel catalysts for alkylation of benzene with 1-decene for production of linear alkylbenzene. The catalysts were characterized by X-ray diffraction, FT-IR spectroscopy, N2 adsorption isotherms, temperature programmed desorption of NH3, scanning electron microscopy and elemental and thermal analysis techniques. It was found that acid-activation of clays prior to pillaring increased the porosity, total specific surface area, total pore volume and surface acidity of the catalysts. Optimization of the reaction conditions was performed by varying catalyst concentration (0.25-1.75 wt%), reactants ratio (benzene to 1-decene of 8.75, 12 and 15) and temperature (115-145 °C) in a batch slurry reactor. Under optimized conditions more than 98% conversion of 1-decene, and complete selectivity for monoalkylbenzenes were achieved.

Faghihian, Hossein; Mohammadi, Mohammad Hadi

2013-01-01

211

Chance and necessity in the selection of nucleic acid catalysts.  

PubMed

In Tom Stoppard's famous play [Rosencrantz and Guildenstern are Dead], the ill-fated heroes toss a coin 101 times. The first 100 times they do so the coin lands heads up. The chance of this happening is approximately 1 in 10(30), a sequence of events so rare that one might argue that it could only happen in such a delightful fiction. Similarly rare events, however, may underlie the origins of biological catalysis. What is the probability that an RNA, DNA, or protein molecule of a given random sequence will display a particular catalytic activity? The answer to this question determines whether a collection of such sequences, such as might result from prebiotic chemistry on the early earth, is extremely likely or unlikely to contain catalytically active molecules, and hence whether the origin of life itself is a virtually inevitable consequence of chemical laws or merely a bizarre fluke. The fact that a priori estimates of this probability, given by otherwise informed chemists and biologists, ranged from 10(-5) to 10(-50), inspired us to begin to address the question experimentally. As it turns out, the chance that a given random sequence RNA molecule will be able to catalyze an RNA polymerase-like phosphoryl transfer reaction is close to 1 in 10(13), rare enough, to be sure, but nevertheless in a range that is comfortably accessible by experiment. It is the purpose of this Account to describe the recent advances in combinatorial biochemistry that have made it possible for us to explore the abundance and diversity of catalysts existing in nucleic acid sequence space. PMID:11539421

Lorsch, J R; Szostak, J W

1996-02-01

212

[Experimental and kinetic modeling of acid/base and redox reactions over oxide catalysts]. Technical progress report  

SciTech Connect

The research has involved the characterization of catalyst acidity, {sup 2}D NMR studies of Bronsted acid sites, and kinetic, calorimetric, and spectroscopic studies of methylamine synthesis and related reactions over acid catalysts. Approach of this work was to explore quantitative correlations between factors that control the generation, type, strength, and catalytic properties of acid sites on zeolite catalysts. Microcalorimetry, thermogravimetric analysis, IR spectroscopy, and NMR spectroscopy have provided information about the nature and strength of acid sites in zeolites. This was vital in understanding the catalytic cycles involved in methylamine synthesis and related reactions over zeolite catalysts.

Not Available

1993-07-01

213

Consequences of acid strength for isomerization and elimination catalysis on solid acids.  

PubMed

We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and energies for intermediates and transition states and to relate them to acid strength. n-Hexane isomerization rates were limited by isomerization of alkoxide intermediates on bifunctional metal-acid mixtures designed to maintain alkane-alkene equilibrium. Isomerization rate constants were normalized by the number of accessible protons, measured by titration with 2,6-di-tert-butylpyridine during catalysis. Equilibrium constants for alkoxides formed by protonation of n-hexene increased slightly with deprotonation energies (DPE), while isomerization rate constants decreased and activation barriers increased with increasing DPE, as also shown for alkanol dehydration reactions. These trends are consistent with thermochemical analyses of the transition states involved in isomerization and elimination steps. For all reactions, barriers increased by less than the concomitant increase in DPE upon changes in composition, because electrostatic stabilization of ion-pairs at the relevant transition states becomes more effective for weaker acids, as a result of their higher charge density at the anionic conjugate base. Alkoxide isomerization barriers were more sensitive to DPE than for elimination from H-bonded alkanols, the step that limits 2-butanol and 1-butanol dehydration rates; the latter two reactions showed similar DPE sensitivities, despite significant differences in their rates and activation barriers, indicating that slower reactions are not necessarily more sensitive to acid strength, but instead reflect the involvement of more unstable organic cations at their transition states. These compensating effects from electrostatic stabilization depend on how similar the charge density in these organic cations is to that in the proton removed. Cations with more localized charge favor strong electrostatic interactions with anions and form more stable ionic structures than do cations with more diffuse charges. Ion-pairs at elimination transition states contain cations with higher local charge density at the sp(2) carbon than for isomerization transition states; as a result, these ion-pairs recover a larger fraction of the deprotonation energy, and, consequently, their reactions become less sensitive to acid strength. These concepts lead us to conclude that the energetic difficulty of a catalytic reaction, imposed by gas-phase reactant proton affinities in transition state analogues, does not determine its sensitivity to the acid strength of solid catalysts. PMID:19374417

Macht, Josef; Carr, Robert T; Iglesia, Enrique

2009-05-13

214

Stability of Supported Platinum Sulfuric Acid Decomposition Catalysts for use in Thermochemical Water Splitting Cycles  

SciTech Connect

The activity and stability of several metal oxide supported platinum catalysts were explored for the sulfuric acid decomposition reaction. The acid decomposition reaction is common to several sulfur based thermochemical water splitting cycles. Reactions were carried out using a feed of concentrated liquid sulfuric acid (96 wt%) at atmospheric pressure at temperatures between 800 and 850 °C and a weight hour space velocity of 52 g acid/g catalyst/hr. Reactions were run at these high space velocities such that variations in kinetics were not masked by surplus catalyst. The influence of exposure to reaction conditions was explored for three catalysts; 0.1-0.2 wt% Pt supported on alumina, zirconia and titania. The higher surface area Pt/Al2O3 and Pt/ZrO2 catalysts were found to have the highest activity but deactivated rapidly. A low surface area Pt/TiO2 catalyst was found to have good stability in short term tests, but slowly lost activity for over 200 hours of continuous operation.

Daniel M. Ginosar; Lucia M. Petkovic; Anne W. Glenn; Kyle C. Burch

2007-03-01

215

Carbon supported catalysts for oxygen reduction in acidic media prepared by thermolysis of Ru 3(CO) 12  

Microsoft Academic Search

Carbon supported catalysts for oxygen reduction in acidic media based on ruthenium and selenium have been prepared by thermolysis of Ru3(CO)12 in organic solvents. The mass specific activity of these catalysts is higher than that of the unsupported samples. The optimum loading of the supporting carbon with catalyst has been found to be about 10%; higher loadings lead to only

M Bron; P Bogdanoff; S Fiechter; M Hilgendorff; J Radnik; I Dorbandt; H Schulenburg; H Tributsch

2001-01-01

216

Evaluation of platinum-based catalysts for methanol electro-oxidation in phosphoric acid electrolyte  

Microsoft Academic Search

Carbon-supported catalysts of Pt, Pt\\/Ru, Pt\\/Ru\\/W, and Pt\\/Ru\\/Pd were evaluated for the electro-oxidation of methanol in phosphoric acid at 180 C. These catalysts were characterized using cyclic voltammetry and x-ray diffraction. Addition of Ru to a 0.5 mg\\/cm² Pt catalyst (1:1 atomic ratio) caused a large reduction in polarization. The open-circuit voltage was reduced by 100 mV and polarization at

Chunzhi He; H. R. Kunz; J. M. Fenton

1997-01-01

217

Manganese-Based Catalysts for the Catalytic Remediation of Phenolic Acids by Ozone  

Microsoft Academic Search

Manganese-based catalysts supported on Al2O3, TiO2, ZrO2 and CeO2 were tested for the catalytic ozonation of a simulated wastewater involving phenolic acids. Comparing the Mn-Ce catalysts preparation method, wetness impregnation and co-precipitation, the last one showed to be more active. Moreover, the increase of Mn\\/Ce molar proportion from 22\\/78 to 70\\/30 increased the ozonation efficiency. The catalysts stability in terms

Rui C. Martins; Rosa M. Quinta-Ferreira

2009-01-01

218

Supported organoiridium catalysts for alkane dehydrogenation  

DOEpatents

Solid supported organoiridium catalysts, a process for preparing such solid supported organoiridium catalysts, and the use of such solid supported organoiridium catalysts in dehydrogenation reactions of alkanes is provided. The catalysts can be easily recovered and recycled.

Baker, R. Thomas; Sattelberger, Alfred P.; Li, Hongbo

2013-09-03

219

Lanthanide(III) complexes of aromatic sulfonic acids as catalysts for the nitration of toluene  

Microsoft Academic Search

Ytterbium(III) complexes of benzenesulfonic acid, Yb(BSA)3, p-toluenesulfonic acid, Yb(Tos)3, and 2-naphthalenesulfonic acid, Yb(NSA)3, were prepared and tested as possible catalyst for the nitration of toluene. With a loading of 5–10mol% of Yb(BSA)3 and Yb(NSA)3, a quantitative conversion of toluene to nitrotoluene was achieved within 5h, while Yb(Tos)3 was slightly less active and 77% of nitrated products were obtained. The catalysts

Tatjana N. Parac-Vogt; Karen Deleersnyder; Koen Binnemans

2004-01-01

220

Study of kinetic laws of dehydration of dimethylvinylcarbinol of phosphoric acid catalyst  

SciTech Connect

The dehydration of dimethylvinylcarbinol (DMVC) to isoprene on phosphoric acid catalyst at 60-90/sup 0/C and in the concentrations range of 40-60 wt. % of the acid was studied by the microreactioning gas-chromatographic method. The overall consumption constants of DMVC with time were determined, as well as consumption constants of DMVC k/sub 1q/, taking into account the absorption of the reagent on the catalysts. It was shown that the dehydration reaction is irreversible, is first order with respect to DMVC, and the equation log k/sub 1q/ + H/sub 0/ = const, where H/sub 0/ is the acidity function holds.

Malinskii, V.S.; Vinnik, M.I.

1987-04-01

221

Sulfamic acid as a cost-effective catalyst instead of metal-containing acids for acetolysis of cyclic ethers  

Microsoft Academic Search

Sulfamic acid has been used as an efficient catalyst and green alternative for metal-containing acidic materials to promote the acetolysis reaction of THF to produce 1,4-diacetoxybutane. This method is also applicable to the acetolysis of other cyclic ethers, such as methyl substituted THF and tetrahydropyran and 1,4-dioxane, which is less reactive.

Bo Wang; Yanlong Gu; Weizhong Gong; Yuru Kang; Liming Yang; Jishuan Suo

2004-01-01

222

The role of acid sites in cobalt zeolite catalysts for selective catalytic reduction of NO x  

Microsoft Academic Search

The role of the acidic support in ion-exchanged cobalt-zeolite, lean NOx catalysts has been determined by studying the individual steps in the selective reduction pathway. At a GHSV of 10,000 and\\u000a reaction temperatures below 400C, NO oxidation is not sufficiently rapid to obtain equilibrium over, for example, 1–4 wt%\\u000a Co-mordenite catalysts. The NO oxidation rate increases in the order H+Co2+

J. T. Miller; E. Glusker; R. Peddi; T. Zheng; J. R. Regalbuto

1998-01-01

223

Epa’s Catalyst Research Program: Environmental Impact of Sulfuric Acid Emissions  

Microsoft Academic Search

A sulfuric acid review conference sponsored by EPA's automotive Catalyst Research Program was held recently at Hendersonville, NC, for researchers whose work is funded by EPA. Emissions characterization research indicated that in-use catalyst-equipped vehicles emit low levels of H2SO4, averaging 2.7 mg\\/mile for 49-state cars and 15 mg\\/mile for California cars. Research on measurement methodology for H2SO4 and other sulfate

Robert E. Lee Jr; F. Vandiver Duffield

1977-01-01

224

Novel Acidic Ionic Liquids as Efficient and Recyclable Catalysts for the Cyclotrimerization of Aldehydes  

Microsoft Academic Search

A mild, efficient, and eco-friendly procedure for cyclotrimerization of aldehydes was realized by using a series of novel Brönsted acidic ionic liquids (BAILs) consisting double –SO3H groups in cations as catalysts. High conversion of aldehydes and selectivity of trialkyl-1,3,5- trioxanes were achieved by using 1 mol% of BAILs. In addition, the catalyst system could be recycled and reused for at least

Heyuan Song; Jing Chen; Chungu Xia; Zhen Li

2011-01-01

225

Novel acidic ionic liquids mediated zinc chloride: Highly effective catalysts for the Beckmann rearrangement  

Microsoft Academic Search

A mild, efficient, and eco-friendly procedure for Beckmann rearrangement was catalyzed by a series of novel Brønsted acidic ionic liquids (ILs) consisiting double –SO3H cations mediated zinc chloride (ILs–ZnCl2) catalytic system. High yields of amides were achieved by using 5mol.% of ILs–ZnCl2 catalysts. In addition, the catalyst system could be recycled and reused for three times.

Xiaofei Liu; Linfei Xiao; Hugjiltu Wu; Zhen Li; Jing Chen; Chungu Xia

2009-01-01

226

Electrooxidation of formic acid on carbon supported Pt-Os catalyst  

Microsoft Academic Search

Pt-Os (3:1)\\/C catalyst was prepared through the route of thermal decomposition of metallic carbonyl cluster. TEM image showed Pt-Os nanoparticles were well dispersed on carbon substrate with an average particle size of 2.2±0.9nm. XRD pattern indicated Pt-Os has a face-centered cubic crystal structure. Characterized by cyclic voltammetry and chronoamperometry, Pt-Os (3:1)\\/C catalyst shows a superior electro-catalytic activity to formic acid

Wei Liu; Junjie Huang

2009-01-01

227

Sulfonic acid functionalised ordered mesoporous materials as catalysts for fine chemical synthesis.  

PubMed

The synthesis of highly active acid catalysts supported on ordered mesoporous materials has eluded chemists until 1998, when Wim M. Van Rhijn et al. explored three different routes to tether sulfonic acid on mesoporous silica. This viewpoint sheds light on this landmark and explores its significant impact on material science and green catalysis. PMID:23990025

El Kadib, Abdelkrim; Finiels, Annie; Brunel, Daniel

2013-08-30

228

Synthesis of 1- tert-butoxy-2-propanol (PGTBE) from propylene glycol and isobutene in a packed trickle-bed reactor on acid catalysts  

Microsoft Academic Search

1-tert-Butoxy-2-propanol has been synthesized from propylene glycol and isobutene over two solid acid catalysts, montmorillonite and Amberlyst 15, in a packed trickle-bed reactor operating under different experimental conditions, and its antiknock properties as an oxygenate gasoline additive have been evaluated. The reaction on Amberlyst 15 fitted first-order kinetics for isobutene (k?=0.37 h?1) for a molar ratio propylene glycol to isobutene

R Alcántara; L Canoira; C Fernández-Mart??n; M. J Franco; J. I Martinez-Silva; A Navarro

2000-01-01

229

Oligomerization of 2-methylpropene and transformation of 2,4,4-trimethyl-2-pentene over supported and unsupported perfluorinated resinsulfonic acid catalysts  

SciTech Connect

Oligomerization of 2-methylpropene was studied with two types of supported (on alumina and on silicon carbide) as well neat perfluorinated resinsulfonic acid catalysts. The heterogeneous reactions were carried out over the solid acid catalysts in a continuous flow reactor at temperatures between 85 and 170 C under atmospheric pressure. Under the studied conditions (85 to 105 C, 1 atm pressure, WHSV:1-3 g/g {center dot} h) all catalysts studied are suitable for oligomerization of 2-methyl-propene. Product distributions show regular temperature dependence: upon increasing temperature the molecular weight of oligomers decreases, with no difference in the selectivity of the catalysts. Transformation of 2,4,4-trimethyl-2-pentene in the liquid phase at room temperature shows surprising selectivity using either the hydrated or dehydrated forms of the resinsulfonic acids. In the case of the hydrated forms of the acids, only double bond isomerization takes place. With dehydrated acids oligomerization as well as isomerization occurs. Above 50 C the selectivity is lost.

Bucsi, I.; Olah, G.A. (Univ. of Southern California, University Park, Los Angeles (United States))

1992-09-01

230

PdBi\\/C and PtPb\\/C Bimetallic Catalysts for Direct Formic Acid Fuel Cells  

Microsoft Academic Search

An efficient methodology for comparing anode catalysts for direct formic acid fuel cells (DFAFCs) by employing a multi-anode, liquid-fed fuel cell is presented. PdBi\\/C bimetallic catalysts synthesized by co-depositing Pd and Bi on Vulcan XC-72 carbon black, as well as PtPb\\/C bimetallic catalysts synthesized by depositing Pb on a Pt\\/C catalyst, were systematically studied in a multi-anode DFAFC. The PdBi\\/C

Xingwen Yu; Peter G. Pickup

2009-01-01

231

Thermal stability of the active component of sulfuric acid catalysts  

Microsoft Academic Search

The authors study the melting point and thermal stability of the ternary system KâSOâ-KâSâOâ-VâOâ. The study was made by a thermogravimetric method. It is seen that higher potassium sulfate contents in the active component suppress the effects associated with the decomposition of the active component, and enhances the thermal stability of the catalyst.

V. M. Borisov; Yu. V. Azhikina; R. M. Stul

1987-01-01

232

Carbon nanotubes as electronic interconnects in solid acid fuel cell electrodes.  

PubMed

Carbon nanotubes have been explored as interconnects in solid acid fuel cells to improve the link between nanoscale Pt catalyst particles and macroscale current collectors. The nanotubes were grown by chemical vapor deposition on carbon paper substrates, using nickel nanoparticles as the catalyst, and were characterized using scanning electron microscopy and Raman spectroscopy. The composite electrode material, consisting of CsH2PO4, platinum nanoparticles, and platinum on carbon-black nanoparticles, was deposited onto the nanotube-overgrown carbon paper by electrospraying, forming a highly porous, fractal structure. AC impedance spectroscopy in a symmetric cell configuration revealed a significant reduction of the electrode impedance as compared to similarly prepared electrodes without carbon nanotubes. PMID:23942778

Varga, Aron; Pfohl, Moritz; Brunelli, Nicholas A; Schreier, Marcel; Giapis, Konstantinos P; Haile, Sossina M

2013-08-28

233

A solid-state NMR investigation of the structure of mesoporous silica nanoparticle supported rhodium catalysts  

SciTech Connect

A detailed study of the chemical structure of mesoporous silica catalysts containing rhodium ligands and nanoparticles (RhP-MSN) was carried out by multi-dimensional solid-state NMR techniques. The degree of functionalization of the rhodium-phosphinosilyl complex to the surface of the RhP-MSN channels was determined by {sup 29}Si NMR experiments. The structural assignments of the rhodium-phosphinosilyl complex were unambiguously determined by employing the novel, indirectly detected heteronuclear correlation ({sup 13}C-{sup 1}H and {sup 31}P-{sup 1}H idHETCOR) techniques, which indicated that oxidation of the attached phosphinosilyl groups and detachment of Rh was enhanced upon syngas conversion.

Rapp, Jennifer; Huang, Yulin; Natella, Michael; Cai, Yang; Lin, Victor S.-Y.; Pruski, Marek

2009-01-04

234

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS: JOURNAL ARTICLE (1437A)  

EPA Science Inventory

NRMRL-CIN-1437A Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. "Solid-State Synthesis of Heterocyclic Hydrazones using Microwaves under Catalyst-free Conditions http:///www.mdpi.net/ecsoc-5/." Fifth International Electronic Conference on Synthetic Organic Chemistry, h...

235

SOLID-STATE SYNTHESIS OF HETEROCYCLIC HYDRAZONES USING MICROWAVES UNDER CATALYST-FREE CONDITIONS: JOURNAL ARTICLE (1605)  

EPA Science Inventory

NRMRL-CIN-1605 Jeselnik, M., Varma*, R.S., Polanc, S., and Kocevar, M. Solid-State Synthesis of Heterocyclic Hydrazones using Microwaves under Catalyst-free Conditions. Green Chemistry (White, J.D. (Ed.), Cambridge, United Kingdom: Royal Society of Chemistry) (4):35-38 (2002). ...

236

A polyoxometalate-based Pd(II)-coordinated ionic solid catalyst for heterogeneous aerobic oxidation of benzene to biphenyl.  

PubMed

An ionic solid catalyst by pairing Keggin polyoxometalate-anions with Pd(II)-coordinated nitrile-tethered ionic liquid cations was synthesized, characterized, and tested for aerobic oxidation of benzene to biphenyl. A unique heterogeneous intramolecular electron transfer mechanism is proposed to understand its high activity. PMID:22543564

Zhao, Pingping; Leng, Yan; Zhang, Mingjue; Wang, Jun; Wu, Yajing; Huang, Jun

2012-04-30

237

Liquefaction of sawdust in 1-octanol using acidic ionic liquids as catalyst.  

PubMed

Acidic ionic liquids (AILs) as a novel catalyst in biomass liquefaction can accord with the demand of green chemistry and enhance the development of biomass thermal chemical conversion. A series of AILs containing HSO4- were synthesized by the imidazolium cation functionalization and applied to the Chinese fir sawdust liquefaction in 1-octanol in this paper. The experimental results showed that the liquefaction rate was gradually improved with the AILs acidity increasing, and reached 71.5% when 1-(4-sulfobutyl)-3-methylmidazolium hydrosulfate was used as catalyst with the 6:1 mass ratio of 1-octanol to sawdust at 423K after 60 min. Lignin, hemicellulose and cellulose were orderly desquamated, and then depolymerized and liquefied with the catalyst acidity increasing in the sawdust liquefaction process. The light oil was mainly composed of the octyl ether and the octyl ester compounds, suggesting that the solvent may play an important role in producing the high octane rating biofuel. PMID:23770997

Lu, Zexiang; Zheng, Huaiyu; Fan, Liwei; Liao, Yiqiang; Ding, Bingjing; Huang, Biao

2013-05-29

238

Evaluating acid and base catalysts in the methylation of milk and rumen fatty acids with special emphasis on conjugated dienes and total trans fatty acids  

Microsoft Academic Search

Milk analysis is receiving increased attention. Milk contains conjugated octadecadienoic acids (18?2) purported to be anticarcinogenic,\\u000a low levels of essential fatty acids, and trans fatty acids that increase when essential fatty acids are increased in dairy rations. Milk and rumen fatty acid methyl esters\\u000a (FAME) were prepared using several acid-(HCl, BF3, acetyl chloride, H2SO4) or base-catalysts (NaOCH3, tetramethylguanidine, diazomethane), or

John K. G. Kramer; Vivek Fellner; Michael E. R. Dugan; Frank D. Sauer; Magdi M. Mossoba; Martin P. Yurawecz

1997-01-01

239

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD)  

Microsoft Academic Search

Reductive desorption of sulfuric acid formed on the carbon catalyst in flue gas desulfurization (FGD) by heating with hydrogen at 3: 200°C converted the acid to gas-phase sulfur dioxide with a significant loss of the acid to hydrogen sulfide and elemental sulfur. These side reactions were suppressed and the temperature required for SOâ recovery was reduced by impregnating the charcoal

S. Yoshizawa; A. Karagiri; K. Watanabe

1979-01-01

240

Vapour phase hydrogenation of olefins by formic acid over a Pd\\/C catalyst  

Microsoft Academic Search

It has been found that ethylene and propylene could be effectively hydrogenated by formic acid vapour over a Pd\\/carbon catalyst at low temperatures (<440K). Surface hydrogen formation from formic acid is the rate-determining step for this hydrogenation reaction. Interaction of this hydrogen with the olefins is then fast. The conversion of formic acid in the presence of either of the

Dmitri A. Bulushev; Julian R. H. Ross

2011-01-01

241

Application of a supported iron oxyhydroxide catalyst in oxidation of benzoic acid by hydrogen peroxide  

Microsoft Academic Search

Oxidation of benzoic acid was studied via Fenton-like reaction using an innovative supported ?-FeOOH catalyst. The decomposition kinetics of hydrogen peroxide was investigated first. Oxidation of benzoic acid by hydrogen peroxide was performed to understand the effects of initial pH and hydrogen peroxide dosage. The treatment efficiency of benzoic acid at an initial pH of 3.2 was higher than at

Shanshan Chou; Chihpin Huang

1999-01-01

242

Acetylation of glycerol catalyzed by different solid acids  

Microsoft Academic Search

This work describes the acetylation of glycerol with acetic acid catalyzed by different solid acids. Reactions were carried out in batch mode under reflux. The kinetics of glycerol transformation and selectivity to the products, notably mono, di and triacetyl esters, were determined within 30min of reaction time to observe the primary products. The results showed that the acid exchange resin,

Valter L. C. Gonçalves; Bianca P. Pinto; João C. Silva; Claudio J. A. Mota

2008-01-01

243

Ammonolysis of esters of hydroxybenzoic acids on a boron phosphate catalyst  

SciTech Connect

In this investigation boron phosphate catalyst was used for ammonolysis of methyl and ethyl esters of salicylic and 4-hydroxybenzoic acids. It was shown that ammonolysis of methyl and ethyl esters of salicylic and 4-hydroxybenzoic acids in presence of boron phosphate catalyst at a ratio of 3-7 moles of ammonia per mole of ester in a contact time of 1-5 sec at 380-400/sub 0/ can be used for obtaining o- and p- hydroxybenzonitriles in yields of over 90% of the theoretical.

Suvorov, B.V.; Bukeikhanov, N.R.; Li, L.V.; Zulkasheva, A.Z.

1987-09-10

244

Degradation of oxalic acid from aqueous solutions by ozonation in presence of Ni\\/Al 2O 3 catalysts  

Microsoft Academic Search

The ozonation of oxalic acid has been carried out in an agitated slurry semi-batch reactor using NiO\\/Al2O3 as catalysts. The presence of catalysts in the ozonation processes significantly improves the oxalic acid removal rate, in comparison to the catalytic process. The influence of calcination temperature on the catalyst activity and on leaching of the active component was assessed. At the

Sorin Marius Avramescu; Corina Bradu; Ion Udrea; Nicoleta Mihalache; Florin Ruta

2008-01-01

245

Production of CO-Free H 2 by Formic Acid Decomposition over Mo 2 C\\/Carbon Catalysts  

Microsoft Academic Search

\\u000a Abstract  The vapor phase decomposition of formic acid was studied over supported Mo2C catalysts in a flow system. Mo2C deposited on silica is an effective catalyst for both the dehydrogenation of formic acid to yield H2 and CO2, and its dehydration to yield H2O and CO. The extent of the decomposition approached 100% at 623 K. Preparation of the Mo2C catalyst by

Ákos Koós; Frigyes Solymosi

2010-01-01

246

Dissociation and hydrolysis of ammonia-borane with solid acids and carbon dioxide: An efficient hydrogen generation system  

Microsoft Academic Search

Pure hydrogen generation under mild conditions in a controllable way is important for portable devices. Recently, we have found that an aq. ammonia-borane (NH3BH3) solution is a potential hydrogen source with noble metal catalysts. For practical use, the development of a low-cost, efficient and safe system is desired. In this study, we found that solid acids such as cation exchange

Manish Chandra; Qiang Xu

2006-01-01

247

Catalyst-assisted solution-liquid-solid synthesis of CdS/CdSe nanorod heterostructures.  

PubMed

We report the synthesis and characterization of axial nanorod heterostructures composed of cadmium selenide (CdSe) and cadmium sulfide (CdS). The synthesis employs a solution-liquid-solid (SLS) mechanism with the assistance of bismuth nanocrystals adhered to a substrate (silicon or a III-V semiconductor). Transmission electron microscopy (TEM) and diffraction studies show that CdSe and CdS segments exhibit the wurtzite (hexagonal) crystal structure with <5% stacking faults. Both of these segments grow along the [002] direction with an epitaxial interface between them. Energy-dispersive X-ray (EDX) spectrometry using a high-resolution TEM operating in scanning mode confirms the alloy-free composition modulation in the nanorod heterostructures, showing that Se and S are localized in the CdSe and CdS portions of the nanorod heterostructures, respectively. This study demonstrates that SLS synthesis provides an alternate route to prepare axial nanorod heterostructures that have been difficult to generate using either vapor-liquid-solid growth or catalyst-free solution-phase synthesis. PMID:17199292

Ouyang, Lian; Maher, Kristin N; Yu, Chun Liang; McCarty, Justin; Park, Hongkun

2007-01-10

248

An evaluation of Pt sulfite acid (PSA) as precursor for supported Pt catalysts  

SciTech Connect

As a catalyst precursor, platinum sulfite acid (PSA) is easy to use and not relatively expensive, and is a potentially attractive precursor for many types of supported catalysts. The ultimate usefulness for many catalyst applications will depend on the extent that Pt can be dispersed and sulfur eliminated. To our knowledge, there exists no detailed characterization in the catalysis literature of PSA and the nanoparticulate Pt phases derived from it during catalyst pretreatment. To this end a series of supports including alumina, silica, magnesia, niobia, titania, magnesia and carbon were contacted with PSA solutions and subsequently analyzed with extended x-ray absorption fine structure (EXAFS) and x-ray absorption near edge structure (XANES) analysis, and x-ray photoelectron spectroscopy (XPS) to characterize the Pt species formed upon impregnation, calcination, and reduction. While all catalysts show retention of some S, reasonably small particle sizes with relatively little Pt-S can in some instances be produced using PSA. The amount of retained sulfur appears to decrease with decreasing surface acidity, although even the most acidic supports (niobia and silica) display some storage of S even while only Pt-O bands are observed after calcination or reoxidation. More sulfur was eliminated by high temperature calcinations followed by reduction in hydrogen, at the expense of increasing Pt particle size.

Regalbuto, J.R.; Ansel, O.; Miller, J.T. (BP Res. Cntr.); (UIC)

2010-11-12

249

Performance improvement in direct formic acid fuel cells (DFAFCs) using metal catalyst prepared by dual mode spraying  

Microsoft Academic Search

In the present study, we investigate performance of direct formic acid fuel cells (DFAFCs) consisting of membrane electrode assembly (MEA) prepared by three different catalyst coating methods – direct painting, air spraying and dual mode spraying. For the DFAFC single cell tests, palladium (Pd) and platinum (Pt) are used as anode and cathode catalyst, respectively, and four different formic acid

S. M. Baik; Jinsoo Kim; Jonghee Han; Yongchai Kwon

2011-01-01

250

Selective poisoning and deactivation of acid sites on sulfated zirconia catalysts for n-butane isomerization  

SciTech Connect

Reaction kinetics measurements, selective poisoning, and microcalorimetry were used to study the activity, selectivity, and deactivation of acid sites on a sulfated zirconia catalyst for n-butane isomerization at 423 K. The sulfated zirconia catalyst has a distribution of acid site strengths, containing 50 {mu}mol/g of strong acid sites characterized by heats of ammonia adsorption from 125 to 165 kJ/mol. The strongest acid sites (heats from 145 to 165 kJ/mol) are responsible for the high initial activity of the catalyst, but these sites deactivate rapidly under reaction conditions. The acid sites exhibiting heats from 125 to 145 kJ/mol are less active than the stronger sites, but deactivate more slowly. Weaker sites have low activity and deactivate more rapidly after the intermediate sites are deactivated or poisoned. Broensted acidity is necessary for extended catalytic activity, although Lewis acid sites may play a role in generating the initial high activity. Acid sites with heats of ammonia adsorption from 125 to 165 kJ/mol show good selectivity for production of isobutane (ca. 93%), while sites with heats from 120 to 125 kJ/mol show lower isobutane selectivity (ca. 80%). 50 refs., 7 figs.

Yaluris, G.; Larson, R.B.; Kobe, J.M. [Univ. of Wisconsin, Madison, WI (United States)] [and others

1996-01-01

251

Cu–Cr–O nanocomposites: Synthesis and characterization as catalysts for solid state propellants  

Microsoft Academic Search

In this article we present the synthesis of Cu–Cr–O nanocomposites via a citric acid (CA) complexing approach and the evaluation of the as-synthesized Cu–Cr–O nanocomposites as additives for the catalytic combustion of AP (ammonium perchlorate)-based solid state propellants. Techniques of thermo-gravimetric\\/differential thermal analyzer (TG–DTA), X-ray diffraction (XRD), transmission electron microscopy (TEM) as well as scanning electron microscopy (SEM) have been

Wei Li; Hua Cheng

2007-01-01

252

Solid acid-catalyzed cellulose hydrolysis monitored by in situ ATR-IR spectroscopy.  

PubMed

The solid acid-catalyzed hydrolysis of cellulose was studied under elevated temperatures and autogenous pressures using in situ ATR-IR spectroscopy. Standards of cellulose and pure reaction products, which include glucose, fructose, hydroxymethylfurfural (HMF), levulinic acid (LA), formic acid, and other compounds, were measured in water under ambient and elevated temperatures. A combination of spectroscopic and HPLC analysis revealed that the cellulose hydrolysis proceeds first through the disruption of the glycosidic linkages of cellulose to form smaller cellulose molecules, which are readily observed by their distinctive C-O vibrational stretches. The continued disruption of the linkages in these oligomers eventually results in the formation and accumulation of monomeric glucose. The solid-acid catalyst accelerated the isomerization of glucose to fructose, which then rapidly reacted under hydrothermal conditions to form degradation products, which included HMF, LA, formic acid, and acetic acid. The formation of these species could be suppressed by decreasing the residence time of glucose in the reactor, reaction temperature, and contact with the metal reactor. The hydrolysis of regenerated cellulose proceeded faster and under milder conditions than microcrystalline cellulose, which resulted in increased glucose yield and selectivity. PMID:22315193

Zakzeski, Joseph; Grisel, Ruud J H; Smit, Arjan T; Weckhuysen, Bert M

2012-02-07

253

Catalytic membranes: alkene dimerisation by means of acidic porous thin-film composite membranes  

Microsoft Academic Search

Dimerisation of isobutene is of increasing interest to substitute oxygenated products such as MTBE or the like as fuel additives. Catalysts applied in commercial alkylation plants, e.g., hydrofluoric and sulfuric acid may be replaced by less harmful solid catalysts, for example by solid heteropolyacids (“super” acids) or polymeric sulfonic acids. To overcome decrease in catalyst performance by time and to

Igor Randjelovic; Gisela Bengtson; Detlev Fritsch

2002-01-01

254

Efficiencies of acid catalysts in the hydrolysis of lignocellulosic ...  

Treesearch

Among sulfuric, oxalic and maleic acid treatments, the amount of xylose released as ... In subsequent fermentations with pretreated biomass, the ethanol ... decay fungi, corn as fuel, biomass fuel, bioconversion, biorefining, alcohol, xylose, acid  ...

255

Active specie on vanadium-containing catalysts for the selective oxidation of ethane to acetic acid  

Microsoft Academic Search

Catalytic experiments on pure VPO phases and titania supported VPOx and VOx are presented for the selective oxidation of ethane to acetic acid. The effects of temperature, pressure, contact time and feed conditions are examined. The characterization of catalysts by several methods shows that different specie are present on titania according to the loading V\\/Ti. The correlation with catalytic results

L. Tessier; E. Bordes; M. Gubelmann-Bonneau

1995-01-01

256

Oxidizing of ferulic acid with the use of polyoxometalates as catalysts  

NASA Astrophysics Data System (ADS)

The kinetics of catalytic oxidation for ferulic acid with polyoxometalates used as catalysts was studied. The effect of pH and concentrations of the principal reacting components on the process kinetics was studied. A kinetic scheme of oxidation is proposed, and the values of a number of kinetic parameters of the process are determined.

Povarnitsyna, T. V.; Popova, N. R.; Bogolitsyn, K. G.; Beloglazova, A. L.; Pryakhin, A. N.; Lunin, V. V.

2010-12-01

257

Effects of deactivation and regeneration on the acidic function of commercial hydrocracking catalysts  

SciTech Connect

To determine the effects of deactivation and regeneration of the acidic function of a zeolite-containing hydrocracking catalyst, a series of fresh, commercially-deactivated, and regenerated catalysts were characterized using cumene transalkylation. Differential rate data obtained in a fixed-bed microreactor at a hydrogen or helium partial pressure of about 8.3 atm and temperatures ranging from 428 to 512/sup 0/K were extrapolated to zero time-on-stream to offset effects of catalyst deactivation during the experiments. These were classified into two categories such that the effects of unit cell size and wt% carbon on the cumene disproportionation activity could be assessed independently. As the unit cell size decreased, the adsorption equilibrium coefficient of the catalysts did not change, but the forward rate constant increased, went through a maximum, and decreased. The deactivation parameter on the other hand increased when the unit cell size decreased. At a constant unit cell size, the adsorption equilibrium coefficient of the regenerated catalysts did not change with wt% carbon, however, a linear relationship between the forward rate constant and wt% carbon was observed. This was attributed to the regeneration of the deactivated catalysts at highly diffusion-controlled conditions. At a constant unit cell size, the deactivated catalysts with high levels of coke (> 2 wt%) had similar activities. This was partially due to a reversible poison present on the surface of these deactivated catalysts. The decrease in the unit cell size during the deactivation and regeneration process was attributed to zeolite attack by water. In the regeneration process the water is formed as a byproduct of the coke oxidation reaction and, depending on the geometry of the bed, it can attack the zeolite framework.

Absil, R.P.L.

1984-01-01

258

Tritium labeling of amino acids and peptides with liquid and solid tritium  

SciTech Connect

Amino acids and peptides were labeled with liquid and solid tritium at 21/degree/K and 9/degree/K. At these low temperatures radiation degradation is minimal, and tritium incorporation increases with tritium concentration and exposure time. Ring saturation in L-phenylalanine does not occur. Peptide linkage in oligopeptides is stable toward tritium. Deiodination in 3-iodotyrosine and 3,5-diiodotyrosine occurs readily and proceeds in steps by losing one iodine atom at a time. Nickel and noble metal supported catalysts when used as supports for dispersion of the substrate promote tritium labeling at 21 K. Our study shows that both liquid and solid tritiums are potentially useful agents for labeling peptides and proteins.

Souers, P.C.; Coronado, P.R.; Peng, C.T.; Hua, R.L.

1988-01-01

259

An efficient green catalyst comprising 12-tungstophosphoric acid and MCM-41: synthesis characterization and diesterification of succinic acid, a potential bio-platform molecule  

Microsoft Academic Search

An efficient green catalyst comprising 12-tungstophosphoric acid (TPA) and MCM-41 was synthesized. The catalytic activity was evaluated for liquid phase solvent free diesterification of succinic acid. The support and the synthesized catalyst were characterized by various physico-chemical techniques. Fourier transform infrared, diffuse reflectance spectroscopy, and P NMR spectra indicate that the Keggin structure of TPA was not destroyed after anchoring

Varsha Brahmkhatri; Anjali Patel

2012-01-01

260

An efficient green catalyst comprising 12-tungstophosphoric acid and MCM-41: synthesis characterization and diesterification of succinic acid, a potential bio-platform molecule  

Microsoft Academic Search

An efficient green catalyst comprising 12-tungstophosphoric acid (TPA) and MCM-41 was synthesized. The catalytic activity was evaluated for liquid phase solvent free diesterification of succinic acid. The support and the synthesized catalyst were characterized by various physico-chemical techniques. Fourier transform infrared, diffuse reflectance spectroscopy, and P NMR spectra indicate that the Keggin structure of TPA was not destroyed after anchoring

Varsha Brahmkhatri; Anjali Patel

2011-01-01

261

Recyclable Lewis acid catalysts by tuning supercritical vs liquid carbon dioxide phases: lanthanide catalysts with tris(perfluorooctanesulfonyl)methide and bis(perfluorooctanesulfonyl)amide  

Microsoft Academic Search

Lanthanide tris(perfluorooctanesulfonyl)methide and bis(perfluorooctanesulfonyl)amide catalysts are shown to be continuously employed in supercritical carbon dioxide by changing supercritical vs. liquid carbon dioxide phases. The lanthanide complexes are thus extremely efficient Lewis acid catalysts even in supercritical carbon dioxide phase by virtue of the highly electron-withdrawing and solubilizing effect of tris(perfluorooctanesulfonyl)methide and bis(perfluorooctanesulfonyl)amide without any hydrocarbon spacer.

Joji Nishikido; Mayumi Kamishima; Hiroshi Matsuzawa; Koichi Mikami

2002-01-01

262

Synergistic chiral ion pair catalysts for asymmetric catalytic synthesis of quaternary ?,?-diamino acids.  

PubMed

The combination of a chiral phosphate anion with a silver ion has been demonstrated as a powerful and synergistic ion pair catalyst for the aza-Mannich reaction. A series of valuable quaternary ?,?-diamino acid derivatives was obtained in high yield, and with excellent diastereo- (up to 25:1 dr) and enantioselectivity (up to 99% ee). The adducts can be smoothly transformed into the corresponding protected chiral quaternary ?,?-diamino acids by a one-pot hydrolysis reaction. PMID:22472066

Shi, Shi-Hui; Huang, Fu-Ping; Zhu, Ping; Dong, Zhen-Wen; Hui, Xin-Ping

2012-04-03

263

Study of kinetic laws of dehydration of dimethylvinylcarbinol of phosphoric acid catalyst  

Microsoft Academic Search

The dehydration of dimethylvinylcarbinol (DMVC) to isoprene on phosphoric acid catalyst at 60-90°C and in the concentrations range of 40-60 wt. % of the acid was studied by the microreactioning gas-chromatographic method. The overall consumption constants of DMVC with time were determined, as well as consumption constants of DMVC k\\/sub 1q\\/, taking into account the absorption of the reagent on

V. S. Malinskii; M. I. Vinnik

1987-01-01

264

Lithium and lanthanum promoted NiAl 2O 3 as an active and highly coking resistant catalyst layer for solid-oxide fuel cells operating on methane  

Microsoft Academic Search

Ni-Al2O3 catalyst is modified with Li2O3, La2O3 and CaO promoters to improve its resistance to coking. These catalysts are used as the materials of the anode catalyst layer in solid-oxide fuel cells operating on methane. Their catalytic activity for the partial oxidation, steam reforming and CO2 reforming of methane at 600–850°C is investigated. Their catalytic stability and carbon deposition properties

Wei Wang; Ran Ran; Zongping Shao

2011-01-01

265

Transfer Hydrogenation Reaction Of Ketones And Formic Acid Under Hydrothermal Conditions Without A Catalyst  

NASA Astrophysics Data System (ADS)

The hydrothermal experiments with ketones and formic acid showed that the hydrogen transfer reduction of ketones can be conducted with formic acid as a hydride donor in the presence of NaOH at 300° C. The yield of alcohols was considerably higher at a much lower ratio of hydrogen source to ketones than the traditional Meerwein-Ponndorf-Verley reduction, reaching 60% for isopropanol from acetone and 70% for lactic acid from pyruvic acid. Water molecules as a catalyst may directly participate in the transition state by making a hydrogen-bond ring network with the substrate molecules.

Shen, Zheng; Zhang, Yalei; Zhou, Xuefei; Wu, Bing; Cao, Jianglin; Jin, Fangming

2010-11-01

266

A Modified Solid-State Reduction Method to Prepare Supported Platinum Nanoparticle Catalysts for Low Temperature Fuel Cell Application  

SciTech Connect

A modified solid state reduction (SSR) method, by which the platinum salt is reduced into platinum nanoparticles by sodium formate in solid state and under low temperature (below 180 C) conditions, is introduced here. The high performance catalysts based on carbon nanotubes (CNTs) supported platinum and platinum promoted by Mo (VI) and Si (IV) were prepared successfully by this method. The catalysts, with small particle size and uniform distribution were active toward the electrooxidation reaction of methanol. Among a few catalysts promoted by silicon, molybdenum and tungsten elements, catalysts co-promoted by silicon and molybdenum elements shows best performance. The particle size of promoted Pt/CNTs, calculated from XRD patterns, is small as 3.0 1.5 nm, and the results of transmission electron microscopy (TEM) revealed that the distribution of particle size is uniform. In comparison with the liquid-state synthesis, the advantages of SSR method include its environmental benefits due to less water usage and significantly reduced pollutants generation, as well as its suitability for large scale preparation.

Hu, Michael Z. [ORNL

2009-01-01

267

Low-cost catalysts for the control of indoor CO and PM emissions from solid fuel combustion.  

PubMed

Cu-Mn based mixed oxide type low-cost catalysts have been prepared in supported form using mesoporous Al(2)O(3), TiO(2) and ZrO(2) supports. These supports have been prepared by templating method using a natural biopolymer, chitosan. The synthesized catalysts have been characterized by XRD, BET-SA, SEM, O(2)-TPD and TG investigations. The catalytic activity for CO as well as PM oxidation was studied, in a view of their possible applications in the control of emissions from solid fuel combustion of rural cook-stoves. The trend observed for the catalytic activity of the synthesized catalysts for CO oxidation was ZrO(2)>TiO(2)>Al(2)O(3) while for PM oxidation it was observed to be TiO(2)>ZrO(2)>Al(2)O(3). The effect of CO(2), SO(2) and H(2)O on CO oxidation activity was also investigated, and despite partial deactivation, the catalysts show good CO oxidation activity. An effective regeneration treatment was attempted by heating the partially deactivated catalysts in presence of oxygen. Redox properties of TiO(2) and ZrO(2) and their structure appeared to be responsible for their promotional activity for CO and PM oxidation reactions. These unordered mesoporous materials could be useful for such reactions where mass transfer is more important than shape and size selectivity. PMID:21163572

Doggali, Pradeep; Kusaba, H; Einaga, H; Bensaid, S; Rayalu, S; Teraoka, Y; Labhsetwar, Nitin

2010-11-25

268

Catalyst-assisted vapor-liquid-solid growth of single-crystal Ga2O3 nanobelts.  

PubMed

Mass production of quasi-one-dimensional gallium oxide nanobelts is accomplished through graphite-thermal reduction of a mixture of gallium oxide powders and SnO2 nanopowders under controlled experimental conditions. Sn nanoparticles are located at or close to the tips of the nanobelts and served as the catalyst for the nanobelt growth by a vapor-liquid-solid mechanism. The morphology and microstructure of the nanobelts were characterized by scanning electron microscopy and high-resolution transmission electron microscopy. The Ga2O3 nanobelts grow along the [104] direction, the widths ranged from several tens to several hundreds of nanometers, and the lengths ranged from several tens to several hundreds of micrometers. The growth of Ga2O3 nanobelts is initiated by Sn nanoparticles via a catalyst-assisted vapor-liquid-solid process, which makes it possible to control the sizes of Ga2O3 nanobelts. PMID:16852636

Zhang, Jun; Jiang, Feihong; Yang, Yongdong; Li, Jianping

2005-07-14

269

Acid sites in sulfated and metal-promoted zirconium dioxide catalysts  

SciTech Connect

Unpromoted sulfated zirconia (SZ) and sulfated zirconia that was promoted with iron and manganese ions (FMSZ) have been tested as catalysts for the isomerization of n-butane to isobutane. FMSZ is the superior catalyst; its activity at 60{degrees}C is similar to that of SZ at 180{degrees}C. Both catalysts deactivate rapidly. FTIR analysis of adsorbed CO and acetonitrile reveals the presence of Lewis and Broensted sites in both catalysts. Acetonitrile is strongly adsorbed on FMSZ. Subsequent desorption is destructive; CO{sub 2}, SO{sub 2}, and O{sub 2} are formed, while temperature-programmed oxidation shows that no carbon-containing products are left on the surface. CO-FTIR reveals equal acidity, within experimental error, for the Lewis sites on SZ and FMSZ. Changes in proton NMR and FTIR parameters caused by adsorption of acetonitrile show that the acid strength of the Broensted sites of SZ and FMSZ is similar to that of the lower OH-frequency protons in HY, but weaker than that of the protons in HZSM-5. The results indicate that the remarkable activity of SZ and FMSZ is not caused by exceptionally strong acid sites, but by stabilization of the transition state complex at the surface. 34 refs., 8 figs., 2 tabs.

Adeeva, V.; Lei, G.D.; Schuenemann, V. [Northwestern Univ., Evanston, IL (United States)] [and others

1995-02-01

270

Characteristics of wet and solid ion exchanged Co–ferrierite catalysts for the reduction of NO using methane  

Microsoft Academic Search

A series of Co–ferrierite catalysts (Co–FERs) containing a variety of Co contents in the range 0.06solid-state ion exchange (SSIE) methods. Their activities of NOx reduction to N2 by CH4 over Co–FERs were examined over a fixed bed flow reactor in O2-rich condition to illustrate the distinctions of NO removal activity with

Joo-Hyoung Park; Chan Hee Park; In-Sik Nam

2004-01-01

271

Production of biodiesel from mixed waste vegetable oil using an aluminium hydrogen sulphate as a heterogeneous acid catalyst  

Microsoft Academic Search

Al(HSO4)3 heterogeneous acid catalyst was prepared by the sulfonation of anhydrous AlCl3. This catalyst was employed to catalyze transesterification reaction to synthesis methyl ester when a mixed waste vegetable oil was used as feedstock. The physical and chemical properties of aluminum hydrogen sulphate catalyst were characterized by scanning electron microscopy (SEM) measurements, energy dispersive X-ray (EDAX) analysis and titration method.

Kasirajan Ramachandran; Pandian Sivakumar; Tamilarasan Suganya; Sahadevan Renganathan

2011-01-01

272

Environmentally benign synthesis of h-phosphinic acids using a water-tolerant, recyclable polymer-supported catalyst.  

PubMed

[reaction: see text] A reusable polymer-supported hydrophosphinylation catalyst is described for the preparation of H-phosphinic acids. The polystyrene-based ligand is prepared in one step from commercially available compounds. The polymeric catalyst generally gives good yields for a variety of substrates and is water- and air-tolerant, although the scope of alkenes and alkynes which can be employed is somewhat narrower than with our original xantphos/Pd(2)dba(3) catalyst. PMID:15469354

Deprèle, Sylvine; Montchamp, Jean-Luc

2004-10-14

273

Autothermal reforming of methane over Ni catalysts supported over CaO–CeO 2–ZrO 2 solid solution  

Microsoft Academic Search

Ni catalysts supported on various solid solutions of ZrO2 with alkaline earth oxide and\\/or rare earth oxide were synthesized. The catalytic activities were compared for partial oxidation of methane and autothermal reforming of methane. For partial oxidation of methane, the Ni catalyst supported on a CaO–ZrO2 solid solution showed a high activity. Incorporation of CaO in the ZrO2 matrix was

Tatsuya Takeguchi; Shin-Nosuke Furukawa; Masashi Inoue; Koichi Eguchi

2003-01-01

274

MCM-48 as a support for sulfonic acid catalysts  

Microsoft Academic Search

The ordered mesoporous silica, MCM-48, has been functionalised with sulfonic acid. Its physico-chemical properties have been compared with those of sulfonated MCM-41 and SBA-15. A higher catalytic activity for the functionalised MCM-48 in the alkylation of toluene with benzyl alcohol suggests that MCM-48 behaves as a better sulfonic acid support than MCM-41 and SBA-15. Ammonia adsorption calorimetric data shows that

M. Bandyopadhyay; N. R. Shiju; D. R. Brown

2010-01-01

275

Catalytic pyrolysis of cellulose in sulfolane with some acidic catalysts  

Microsoft Academic Search

Catalytic pyrolysis of cellulose in sulfolane (tetramethylene sulfone) with sulfuric acid or polyphosphoric acid gave levoglucosenone,\\u000a furfural, and 5-hydroxymethyl furfural (5-HMF) up to 42.2%, 26.9%, and 8.8% (as mol% yield based on the glucose unit), respectively.\\u000a Pyrolysis behaviors of the intermediates indicated the conversion pathways, and the conversion: levoglucosenone ? furfural\\u000a was found to require water. The control of the

Haruo Kawamoto; Shinya Saito; Wataru Hatanaka; Shiro Saka

2007-01-01

276

Improved anode catalysts for coal gas-fueled phosphoric acid fuel cells  

NASA Astrophysics Data System (ADS)

The feasibility of adapting phosphoric acid fuel cells to operate on coal gas fuels containing significant levels of contaminants such as CO, H2S and COS was investigated. The overall goal was the development of low-cost, carbon-supported anode fuel cell catalysts that can efficiently operate with a fossil fuel-derived hydrogen gas feed contaminated with carbon monoxide and other impurities. This development would reduce the cost of gas cleanup necessary in a coal gas-fueled PAFC power plant, thereby reducing the final power cost of the electricity produced. The problem to date was that the contaminant gases typically adsorb on catalytic sites and reduce the activity for hydrogen oxidation. An advanced approach investigated was to modify these alloy catalyst systems to operate efficiently on coal gas containing higher levels of contaminants by increasing the alloy catalyst impurity tolerance and ability to extract energy from the CO present through (1) generation of additional hydrogen by promoting the CO/H2 water shift reaction or (2) direct oxidation of CO to CO2 with the same result. For operation on anode gases containing high levels of CO, a Pt-Ti-Zn and Pt-Ti-Ni anode catalyst showed better performance over a Pt baseline or G87A-17-2 catalyst. The ultimate aim was to allow PAFC-based power plants to operate on coal gas fuels containing increased contaminant concentrations, thereby decreasing the need for and cost of rigorous coal gas cleanup procedures.

Kackley, N. D.; McCatty, S. A.; Kosek, J. A.

1990-07-01

277

Transesterification of soybean oil catalyzed by fly ash and egg shell derived solid catalysts  

Microsoft Academic Search

A fly ash supported heterogeneous CaO catalyst has been developed using waste egg shell for transesterification of soybean oil to yield fuel grade biodiesel. The active metal precursor Ca(OH)2 of the catalyst has been economically derived from waste egg shell calcination and the mesoporous, high activity strong base catalyst has been prepared using wet-impregnation method. X-ray diffraction (XRD), scanning electron

R. Chakraborty; S. Bepari; A. Banerjee

2010-01-01

278

Establishing the feasibility of coupled solid-phase extraction-solid-phase derivatization for acidic herbicides.  

PubMed

The significance of this research is that it improves analytical methodology used for organic chemicals in aqueous solutions by establishing the feasibility of heterogeneous chemical derivatization at the liquid-solid interface (i.e., solid-phase reaction or solid-phase derivatization). A solid-phase derivatization method for determining chlorinated herbicide acids was developed. Solid-phase extraction was used to concentrate and retain analytes on sorbents for subsequent solid-phase derivatization. Background interferences were removed from the chromatograms by electronically subtracting the responses of blank, nonfortified analyses from spiked samples. Two extraction sorbents (octadecyl bonded silica and polystyrene-divinylbenzene) and two derivatizing reagents (BF3-MeOH and trimethylsilyldiazomethane) were investigated. Recovery of 13 chlorinated herbicide acids--including pentachlorophenol, dinoseb, and bentazon (having a derivatizable functional group, -OH or -NH, bonded directly to a phenyl group); dicamba, picloram, acifluorfen, 3,5-dichlorobenzoic acid, and dacthal (having a derivatizable functional group, -COOH, bonded directly to a phenyl group); and 2,4-D, 2,4,5-T, dichlorprop, 2,4,5-TP, and 2,4-DB (having a derivatizable functional group, -COOH, bonded directly to a sp3 carbon atom)--was tested. The analytical method developed was proven successful for determining acidic herbicides, except for the dacthal diacid metabolite, in aqueous samples. PMID:17214997

Yu, Lan Z; Wells, Martha J M

2006-12-22

279

Thickness effects of a carbon-supported platinum catalyst layer on the electrochemical reduction of oxygen in sulfuric acid solution  

Microsoft Academic Search

The influence of the thickness of a carbon-supported platinum catalyst layer on the oxygen reduction reaction (orr) has been studied in sulfuric acid solution by means of a thin-film rotating disk electrode. Pronounced changes in the Pt utilization, electrode activity and the orr kinetics have been observed upon varying the catalyst layer thickness. The thicker film electrode exhibits a higher

Junhua Jiang; Baolian Yi

2005-01-01

280

Catalytic decomposition of formic acid on oxide catalysts—an impulse-oscillation model approach to the unimolecular mechanism  

Microsoft Academic Search

An impulse-oscillation model (IOM) was used for a time description of catalytic acts in the reactions of catalytic decomposition of formic acid on oxide catalysts. The results of computation using the model show that for the dehydrogenation reaction the most important modes are the OCO bending in bidentate adsorbed formate ion and OH stretching on the catalyst surface while for

Marek A Borowiak; Micha? H Jamróz; Ragnar Larsson

1999-01-01

281

Structural organization of humic acid in the solid state.  

PubMed

Studies of the structural organization of humic acid in solution have suggested that it is composed of three fractions, two humic acid-like and one lipid-like, that have distinct roles in the process of its self-organization. The present work extends the study of humic acid's structural organization to the solid state by directly comparing its organization with a physical mixture composed of its three fractions using differential scanning calorimetry. Comparative measurements of the specific heat capacity as a function of temperature reveal differences between the original humic acid and the mixture with the same chemical composition. These differences provide direct evidence that humic acid's solid state structure is more than just a mixture of components and is determined by specific interactions between its components. This study indicates that humic acid in the solid state has a hierarchical or "structure within a structure" architecture. The lower-level structure is determined by the self-assembly of amphiphilic components of humic acid with lipids into a nanostructured composite material. A higher-level structure is formed by the association of this composite material with the nonamphiphilic components of humic acid. PMID:19408899

Chilom, Gabriela; Rice, James A

2009-08-18

282

Organometallic Catalysts for Primary Phosphoric Acid Fuel Cells.  

National Technical Information Service (NTIS)

A continuing effort by the U.S. Department of Energy to improve the competitiveness of the phosphoric acid fuel cell by improving cell performance and/or reducing cell cost is discussed. Cathode improvement, both in performance and cost, available through...

F. Walsh

1987-01-01

283

Effect of acidic and alkaline impurities on the activity of a low-temperature carbon monoxide conversion catalyst  

SciTech Connect

The results of a study of the dependence of the activity of low-temperature catalysts on the simultaneous presence of impurities of acidic and alkaline character are presented. The results of the study showed that poisioning of copper-containing catalysts by chlorine or sulfate ions cannot be prevented by adding alkali metal ions to the catalyst. However, with an increase in the concentration of the alkaline additives, the activity of the catalyst increases significantly at a temperature above 150/sup 0/C.

Sukhoruchkina, L.A.; Semenova, T.A.

1984-02-01

284

Aluminum chloride as a solid is not a strong Lewis acid.  

PubMed

Aluminum chloride is used extensively as Lewis acid catalyst in a variety of industrial processes, including Friedel-Crafts and Cl/F exchange reactions. There is a common misconception that pure AlCl3 is itself a Lewis acid. In the current study, we use experimental and computational methods to investigate the surface structure and catalytic properties of solid AlCl3. The catalytic activity of AlCl3 for two halide isomerization reactions is studied and compared with different AlF3 phases. It is shown that pure solid AlCl3 does not catalyze these reactions. The (001) surface of crystalline AlCl(3) is the natural cleavage plane and its structure is predicted via first principles calculations. The chlorine ions in the outermost layer of the material mask the Al3+ ions from the external gas phase. Hence, the experimentally found catalytic properties of pure solid AlCl3 are supported by the predicted surface structure of AlCl3. PMID:16623514

Murthy, J Krishna; Gross, Udo; Rüdiger, Stephan; Rao, V Venkat; Kumar, V Vijaya; Wander, A; Bailey, C L; Harrison, N M; Kemnitz, Erhard

2006-04-27

285

H 3 PO 4 - and H 2 SO 4 -treated niobic acid as heterogeneous catalyst for methyl ester production  

Microsoft Academic Search

The activity of solid niobic acid treated with sulfuric acid and with phosphoric acid was tested in the catalytic esterification\\u000a of oleic acid and in transesterification of soybean oil with methanol. X-ray diffraction studies revealed niobic acid treated\\u000a with sulfuric acid to be an amorphous solid, while niobic acid treated with phosphoric acid presented a crystalline phase,\\u000a probably due to

Mendelssolm K. de Pietre; Luiz C. P. Almeida; Richard Landers; Rita C. G. Vinhas; Fernando J. Luna

2010-01-01

286

Reduction of Np(V) with formic acid in acidic solutions in the presence of palladium catalysts  

Microsoft Academic Search

The kinetics of catalytic reduction of Np(V) with formic acid in HClO4 solutions in the presence of Pd\\/SiO2 catalysts differing in the Pd content and size of Pd nanocrystals was studied. The reaction is a structure-insenitive catalytic\\u000a process, i.e., the size effect is absent. An increase in the percentage of Pd on SiO2 leads to a decrease in the activity

M. Yu. Boltoeva; V. P. Shilov; A. V. Anan’ev

2008-01-01

287

Mesoporous silica containing sulfonic acid groups as catalysts for the alpha-pinene methoxylation  

Microsoft Academic Search

The methoxylation of a-pinene was studied over sulfonic acid-functionalized mesoporous silica (MCM-41, PMO) at 60°C. The support functionalization was achieved by the introduction of 3-(mercaptopropyl)trimethoxysilane onto the surface of these materials either by grafting or by co-condensation. The thiol groups were oxidized to SO3H by treatment with H2O2. All the catalysts were active in the studied reaction being the PMO-SO3H-g

José E. Castanheiro; Liliana Guerreiro; Isabel M. Fonseca; Ana M. Ramos; Joaquim Vital

2008-01-01

288

Dehydration of xylose into furfural over micro-mesoporous sulfonic acid catalysts  

Microsoft Academic Search

Surfactant-templated micro-mesoporous silicas possessing sulfonic acid groups (SAGs) have been prepared, characterized, and tested as catalysts in the dehydration of d-xylose to furfural. All of the materials possessed catalytic activity. In general, selectivity to furfural was lower for a poorly ordered microporous hybrid material, prepared via the co-condensation of (3-mercaptopropyl)trimethoxysilane with bis(trimethoxysilylethyl)benzene, than for mesoporous MCM-41 silica anchored with SAGs

Ana S. Dias; Martyn Pillinger; Anabela A. Valente

2005-01-01

289

Absolute acidities and site specific properties of zeolite catalysts modelled by advanced computational chemistry technology  

Microsoft Academic Search

Hartree–Fock structure predictions are made for two crystallographically distinct Brønsted sites, O1H and O3H, of the zeolite catalyst H-faujasite. The structure optimisation adopted very large cluster models without symmetry (163 atoms; 2033 basis function) and applied the parallel TURBOMOLE code on a multi-processor compute server. The predicted acidity strength of the two sites, 1166±10 kJ\\/mol, is the same within chemical

Joachim Sauer; Uwe Eichler; Ulrich Meier; Ansgar Schäfer; Malte von Arnim; Reinhart Ahlrichs

1999-01-01

290

Synthesis of bis(2-ethylhexyl) phthalate over methane sulfonic acid catalyst. Kinetic investigations  

Microsoft Academic Search

The kinetic model for the synthesis of bis(2-ethylhexyl) phthalate from phthalic anhydride and 2-ethylhexanol in the presence\\u000a of methane sulfonic acid as a catalyst has been derived, based on the investigation carried out in an isothermal, semibatch\\u000a reactor. The first step, the formation of mono(2-ethylhexyl) phthalate, is very fast and irreversible. The second step, the\\u000a esterification of monoester with 2-ethylhexanol,

Jerzy Skrzypek; Maria Lachowska; Maria Kulawska; Henryk Moroz

2008-01-01

291

WO 3\\/C hybrid material as a highly active catalyst support for formic acid electrooxidation  

Microsoft Academic Search

The hybrid material based on WO3 and Vulcan XC-72R carbon has been used as the support of Pd nanocatalysts. The resultant Pd–WO3\\/C catalysts in a large range of WO3 content exhibit excellent catalytic activity and stability for formic acid electrooxidation. The great improvement in the catalytic performance is attributed to the uniform dispersion of Pd with less particle sizes on

Zhonghua Zhang; Yunjie Huang; Junjie Ge; Changpeng Liu; Tianhong Lu; Wei Xing

2008-01-01

292

Deuteriation of benzoic acid in the presence of homogeneous potassium tetrachloroplatinate(II) catalyst  

Microsoft Academic Search

The kinetic behavior of deuteriation of benzoic acid with D2O acidified with HCl in the presence of homogeneous K2PtCl4 catalyst has been investigated in the 100–130°C temperature interval. The quasiunimolecular H\\/D rate constants at 100 and 130°C corresponding to an exchange process in ortho positions of the substituted benzene ring hydrogens were determined by1H NMR integration signal. These same constants

M. Ka?ska; R. Ka?ski

1992-01-01

293

Fatty Acid Methyl Ester Synthesis over Fe 3+ -Vanadyl Phosphate Catalysts  

Microsoft Academic Search

A heterogeneous acid catalyst, Fe3+-vanadyl phosphate, prepared by the isomorphous substitution of some VO3+ groups in vanadyl phosphate with trivalent metal Fe3+, was found to be active for the transesterification of soybean oil with methanol. When the transesterification reaction was\\u000a carried out with a molar ratio of methanol to oil of 30:1, a reaction temperature of 473 K, a reaction time

Hui Li; Wenlei Xie

2008-01-01

294

Pt/TiO2 (Rutile) Catalysts for Sulfuric Acid Decomposition in Sulfur-Based Thermochemical Water-Splitting Cycles  

SciTech Connect

Thermochemical cycles consist of a series of chemical reactions to produce hydrogen from water at lower temperatures than by direct thermal decomposition. All the sulfur-based cycles for water splitting employ the sulfuric acid decomposition reaction. This work reports the studies performed on platinum supported on titania (rutile) catalysts to investigate the causes of catalyst deactivation under sulfuric acid decomposition reaction conditions. Samples of 1 wt% Pt/TiO2 (rutile) catalysts were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different times on stream (TOS) between 0 and 548 h. Post-operation analyses of the spent catalyst samples showed that Pt oxidation and sintering occurred under reaction conditions and some Pt was lost by volatilization. Pt loss rate was higher at initial times but total loss appeared to be independent of the gaseous environment. Catalyst activity showed an initial decrease that lasted for about 66 h, followed by a slight recovery of activity between 66 and 102 h TOS, and a period of slower deactivation after 102 h TOS. Catalyst sulfation did not seem to be detrimental to catalyst activity and the activity profile suggested that a complex dynamical situation involving platinum sintering, volatilization, and oxidation, along with TiO2 morphological changes affected catalyst activity in a non-monotonic way.

L. M. Petkovic; D. M. Ginosar; H. W. Rollins; K. C. Burch; P. J. Pinhero; H. H. Farrell

2008-04-01

295

Consequences of Acid Strength for Isomerization and Elimination Catalysis on Solid Acids  

Microsoft Academic Search

We address here the manner in which acid catalysis senses the strength of solid acids. Acid strengths for Keggin polyoxometalate (POM) clusters and zeolites, chosen because of their accurately known structures, are described rigorously by their deprotonation energies (DPE). Mechanistic interpretations of the measured dynamics of alkane isomerization and alkanol dehydration are used to obtain rate and equilibrium constants and

Josef Macht; Robert T. Carr; Enrique Iglesia

2009-01-01

296

Mechanism of hydrodenitrogenation (Part 4) infrared spectroscopy of acidic molybdena catalysts. Fourth quarter report, July 1-September 30, 1990.  

National Technical Information Service (NTIS)

Mo oxide catalysts supported over a complete series of silica-aluminas have been characterized in the oxidic and reduced states, by means of total acidity measurements and by infrared spectroscopy. Ammonia chemisorption was used to titrate the total acidi...

R. Miranda

1990-01-01

297

Hydroaminations of unactivated alkenes with basic alkylamines: group 4 metal halide catalysts and Brønsted-acid organocatalysts.  

PubMed

Two distinct economical catalysts for intramolecular hydroaminations of electronically unactivated alkenes with basic amines are described, which are based on (a) group 4 metal halides under basic reaction conditions or (b) Brønsted-acid organocatalysts. PMID:17551648

Ackermann, Lutz; Kaspar, Ludwig T; Althammer, Andreas

2007-05-17

298

Transient optical absorption spectra in pulse irradiated solid amino acids  

Microsoft Academic Search

A preliminary pulse radiolytic study is reported on transient optical absorption spectra in solid amino acids. Spectra have been obtained by improved Cherenkov Light Self-absorption Method applied during 5.5 s pulses of 10 or 13 MeV linac electrons. Amino acids exhibit a very different type of behaviour: from lack of absorption signal (at the present sensitivity of the system) to

Z. P. Zagórski; Z. Tomasi?ski

1990-01-01

299

Pd/C Synthesized with Citric Acid: An Efficient Catalyst for Hydrogen Generation from Formic Acid/Sodium Formate  

PubMed Central

A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160?min and 64?mol H2 mol?1 catalyst h?1, respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells.

Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

2012-01-01

300

Pd/C synthesized with citric acid: an efficient catalyst for hydrogen generation from formic acid/sodium formate.  

PubMed

A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H(2) mol(-1) catalyst h(-1), respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells. PMID:22953041

Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

2012-08-23

301

Pd/C Synthesized with Citric Acid: An Efficient Catalyst for Hydrogen Generation from Formic Acid/Sodium Formate  

NASA Astrophysics Data System (ADS)

A highly efficient hydrogen generation from formic acid/sodium formate aqueous solution catalyzed by in situ synthesized Pd/C with citric acid has been successfully achieved at room temperature. Interestingly, the presence of citric acid during the formation and growth of the Pd nanoparticles on carbon can drastically enhance the catalytic property of the resulted Pd/C, on which the conversion and turnover frequency for decomposition of formic acid/sodium formate system can reach the highest values ever reported of 85% within 160 min and 64 mol H2 mol-1 catalyst h-1, respectively, at room temperature. The present simple, low cost, but highly efficient CO-free hydrogen generation system at room temperature is believed to greatly promote the practical application of formic acid system on fuel cells.

Wang, Zhi-Li; Yan, Jun-Min; Wang, Hong-Li; Ping, Yun; Jiang, Qing

2012-08-01

302

Comparison of sulfuric and hydrochloric acids as catalysts in hydrolysis of Kappaphycus alvarezii (cottonii).  

PubMed

In this study, hydrolysis of marine algal biomass Kappaphhycus alvarezii using two different acid catalysts was examined with the goal of identifying optimal reaction conditions for the formation of sugars and by-products. K. alvarezii were hydrolyzed by autoclave using sulfuric acid or hydrochloric acid as catalyst with different acid concentrations (0.1-1.0 M), substrate concentrations (1.0-13.5%), hydrolysis time (10-90 min) and hydrolysis temperatures (100-130 (°)C). A difference in galactose, glucose, reducing sugar and total sugar content was observed under the different hydrolysis conditions. Different by-product compounds such as 5-hydroxymethylfurfural and levulinic acid were also observed under the different reaction conditions. The optimal conditions for hydrolysis were achieved at a sulfuric acid concentration, temperature and reaction time of 0.2 M, 130 °C and 15 min, respectively. These results may provide useful information for the development of more efficient systems for biofuel production from marine biomass. PMID:21909670

Meinita, Maria Dyah Nur; Hong, Yong-Ki; Jeong, Gwi-Taek

2011-09-10

303

The glmS ribozyme cofactor is a general acid-base catalyst.  

PubMed

The glmS ribozyme is the first natural self-cleaving ribozyme known to require a cofactor. The d-glucosamine-6-phosphate (GlcN6P) cofactor has been proposed to serve as a general acid, but its role in the catalytic mechanism has not been established conclusively. We surveyed GlcN6P-like molecules for their ability to support self-cleavage of the glmS ribozyme and found a strong correlation between the pH dependence of the cleavage reaction and the intrinsic acidity of the cofactors. For cofactors with low binding affinities, the contribution to rate enhancement was proportional to their intrinsic acidity. This linear free-energy relationship between cofactor efficiency and acid dissociation constants is consistent with a mechanism in which the cofactors participate directly in the reaction as general acid-base catalysts. A high value for the Brønsted coefficient (? ~ 0.7) indicates that a significant amount of proton transfer has already occurred in the transition state. The glmS ribozyme is the first self-cleaving RNA to use an exogenous acid-base catalyst. PMID:23113700

Viladoms, Júlia; Fedor, Martha J

2012-11-09

304

Aerobic oxidation of aqueous ethanol using heterogeneous gold catalysts: Efficient routes to acetic acid and ethyl acetate  

Microsoft Academic Search

The aerobic oxidation of aqueous ethanol to produce acetic acid and ethyl acetate was studied using heterogeneous gold catalysts. Comparing the performance of Au\\/MgAl2O4 and Au\\/TiO2 showed that these two catalysts exhibited similar performance in the reaction. By proper selection of the reaction conditions, yields of 90–95% of acetic acid could be achieved at moderate temperatures and pressures. Based on

Betina Jørgensen; Sofie Egholm Christiansen; Marie Louise Dahl Thomsen; Claus Hviid Christensen

2007-01-01

305

Efficient, solventless N-Boc protection of amines carried out at room temperature using sulfamic acid as recyclable catalyst  

Microsoft Academic Search

A simple, rapid, and efficient protocol for the chemoselective N-Boc protection of amines using sulfamic acid as catalyst is described. N-Boc protection of various structurally diverse aliphatic, aromatic, alicyclic, and heterocyclic amines (1°, 2°, 3°) was carried out with (Boc)2O using sulfamic acid as catalyst (5mol%) at room temperature under solventless conditions. The advantages of this method are simplicity, shorter

Dharita J. Upadhyaya; Alessandro Barge; Rachele Stefania; Giancarlo Cravotto

2007-01-01

306

A Sulfated ZrO2 Hollow Nanostructure as an Acid Catalyst in the Dehydration of Fructose to 5-Hydroxymethylfurfural.  

PubMed

Mesoporous hollow colloidal particles with well-defined characteristics have potential use in many applications. In liquid-phase catalysis, in particular, they can provide a large active surface area, reduced diffusion resistance, improved accessibility to reactants, and excellent dispersity in reaction media. Herein, we report the tailored synthesis of sulfated ZrO2 hollow nanostructures and their catalytic applications in the dehydration of fructose. ZrO2 hollow nanoshells with controllable thickness were first synthesized through a robust sol-gel process. Acidic functional groups were further introduced to the surface of hollow ZrO2 shells by sulfuric acid treatment followed by calcination. The resulting sulfated ZrO2 hollow particles showed advantageous properties for liquid-phase catalysis, such as well-maintained structural integrity, good dispersity, favorable mesoporosity, and a strongly acidic surface. By controlling the synthesis and calcination conditions and optimizing the properties of sulfated ZrO2 hollow shells, we have been able to design superacid catalysts with superior performance in the dehydration of fructose to 5-hydroxymethyfurfural than the solid sulfated ZrO2 nanocatalyst. PMID:24023048

Joo, Ji Bong; Vu, Austin; Zhang, Qiao; Dahl, Michael; Gu, Minfen; Zaera, Francisco; Yin, Yadong

2013-09-10

307

Dehydration of aliphatic alcohols on phosphoric acid catalyst with the addition of calcium phosphate  

SciTech Connect

The kinetic regularities of dehydration of sec- and tert-butyl alcohols on a catalyst consisting of a mixture of calcium phosphate and H/sub 3/PO/sub 4/, deposited on molten quartz were studied by pulsed gas chromatography. At an equal water vapor pressure in the system, the activity of a catalyst consisting of a pure H/sub 3/PO/sub 4/ is higher than that of a catalyst with the addition of a salt. The experimentally observed dehydration rate constants and those determined with the retention volumes taken into account were measured. Activation energies, rate constants, and the heat of dissolution of tert-butyl alcohol on calcium phosphate catalyst were determined in the range of 80-110/sup 0/C. The dehydration of sec-butyl alcohol was studied at 140/sup 0/C. It was found that in a liquid phase, the reaction rate constant is not very dependent on the salt/acid ratio.

Obraztsov, P.A.; Batalin, O.E.; Malinskii, V.S.; Shubenok, L.F.; Vinnik, M.I.

1986-12-01

308

Nanorod vanadatesulfuric acid as a novel, recyclable and heterogeneous catalyst for the one-pot synthesis of tetrahydrobenzopyrans.  

PubMed

Vanadatesulfuric acid (VSA), as a novel and heterogeneous nanorod catalyst, was used for an efficient synthesis of tetrahydrobenzo[b]pyrans using an aldehydes, 1,3-cyclohexanediones or beta-ketoester and malononitrile in C2H5OH/H2O mixture under reflux conditions. VSA is prepared via the reaction of sodium metavanadate and chlorosulfonic acid in high purity. The catalyst was characterized by FT-IR, XRD, TEM and EDAX analysis. Compared to the conventional method, this method consistently has the advantage of high yields, simple workup, short reaction times and reusability of the catalyst. PMID:23901523

Nasr-Esfahani, Masoud; Abdizadeh, Tooba

2013-07-01

309

Moisture induced solid phase degradation of l-ascorbic acid  

Microsoft Academic Search

l-Ascorbic acid was found to degrade in the solid phase with discoloration under the influence of moisture in proportion to the moisture content. This degradation pattern was different to that in solution and followed zero order kinetics. The exclusion of air reduced the rate of reaction suggesting the degradation may proceed via an oxidative route but no evidence was found

Anthony B Shephard; Steven C Nichols; Alan Braithwaite

1999-01-01

310

Structural design and facile synthesis of a highly efficient catalyst for formic acid electrooxidation.  

PubMed

The pathway of formic acid electrooxidation strongly depends on the amount of three neighbouring Pt or Pd atoms in the surface of Pd- or Pt-based catalysts. Here, Pt decorated Pd/C nanoparticles (the optimal atomic ratio, Pd?:?Pt = 20?:?1) were designed and then synthesized through a facile galvanic replacement reaction where the amount of three neighbouring Pt or Pd atoms markedly decreased. As a result, discontinuous Pd and Pt atoms suppressed CO formation and exhibited unprecedented catalytic activity and stability toward formic acid electrooxidation while the cost was almost the same as that of Pd/C. PMID:21701741

Wang, Xiao-Ming; Wang, Ming-E; Zhou, Dan-Dan; Xia, Yong-Yao

2011-06-24

311

Graphene-Based Non-Noble-Metal Catalysts for Oxygen Reduction Reaction in Acid  

SciTech Connect

Non-noble-metal catalysts based on Fe-N-C moieties have shown promising oxygen reduction reaction (ORR) activity in proton exchange membrane fuel cells (PEMFCs). In this study, we report a facile method to prepare a Fe-N-C catalyst based on modified graphene (Fe-N-rGO) from heat treatment of a mixture of Fe salt, graphitic carbon nitride (g-C{sub 3}N{sub 4}), and chemically reduced graphene (rGO). The Fe-N-rGO catalyst was found to have pyridinic N-dominant heterocyclic N (40% atomic concentration among all N components) on the surface and have an average Fe coordination of {approx}3 N (Fe-N{sub 3,average}) in bulk. Rotating disk electrode measurements revealed that Fe-N-rGO had high mass activity in acid and exhibited high stability at 0.5 V at 80 C in acid over 70 h, which was correlated to low H{sub 2}O{sub 2} production shown from rotating ring disk electrode measurements.

H Byon; J Suntivich; Y Shao-Horn

2011-12-31

312

Oxidative steam reforming of methane under atmospheric and pressurized conditions over Pd\\/NiO–MgO solid solution catalysts  

Microsoft Academic Search

The effect of the Pd loading in NiO–MgO solid solution was investigated in oxidative steam reforming of methane under atmospheric and pressurized conditions. The small amounts of Pd addition on Ni0.2Mg0.8O can inhibit the oxidation of Ni species and the mixture can maintain the reforming ability at low W\\/F conditions under atmospheric pressure, where Ni0.2Mg0.8O catalyst deactivated. In addition, Ni0.2Mg0.8O

Mohammad Nurunnabi; Yuya Mukainakano; Shigeru Kado; Tomohisa Miyazawa; Kazu Okumura; Toshihiro Miyao; Shuichi Naito; Kimihito Suzuki; Ken-Ichiro Fujimoto; Kimio Kunimori; Keiichi Tomishige

2006-01-01

313

Characterization of iron counter-ion environment in bulk and supported phosphomolybdic acid based catalysts  

NASA Astrophysics Data System (ADS)

Extended X-ray absorption fine structure (EXAFS) was used to characterize the environment of iron counter-cations in Keggin type phosphomolybdic compounds used as catalysts for oxidation reactions. Iron doped compounds corresponding to bulk acid and to acid supported on the cesium salt were prepared and studied. Iron formed hexa-hydrated complex of both Fe3+ and Fe2+ in the bulk acid, whereas it was present as Fe(OH)2+ hydroxy-cations in the acid supported on the cesium salt. Upon heating the hexa-hydrated complex lost one molecule of water to bind to the Keggin anion through a terminal oxygen. (Fe O Mo bond). The environment of the iron hydroxy-cation changed upon heating while its closer coordination append to remained unchanged.

Huynh, Q.; Millet, J. M. M.

2005-05-01

314

High-temperature sulfuric acid decomposition over complex metal oxide catalysts  

SciTech Connect

Activity and stability of FeTiO3, MnTiO3, NiFe2O4, CuFe2O4, NiCr2O4, 2CuO•Cr2O3, CuO and Fe2O3 for the atmospheric decomposition of concentrated sulfuric acid in sulfur-based thermochemical water splitting cycles are presented. Catalyst activity was determined at temperatures from 725 to 900 °C. Catalytic stability was examined at 850 °C for up to one week of continuous operation. The results were compared to a 1.0 wt% Pt/TiO2 catalyst. Surface area by nitrogen physisorption, X-ray diffraction analyses, and temperature programmed desorption and oxidation were used to characterize fresh and spent catalyst samples. Over the temperature range, the catalyst activity of the complex oxides followed the general trend: 2CuO•Cr2O3 > CuFe2O4 > NiCr2O4 ˜ NiFe2O4 > MnTiO3 ˜ FeTiO3. At temperatures less than 800 °C, the 1.0 wt% Pt/TiO2 catalyst had higher activity than the complex oxides, but at temperatures above 850 °C, the 2CuO•Cr2O3 and CuFe2O4 samples had the highest activity. Surface area was found to decrease for all of the metal oxides after exposure to reaction conditions. In addition, the two complex metal oxides that contained chromium were not stable in the reaction environment; both leached chromium into the acid stream and decomposed into their individual oxides. The FeTiO3 sample also produced a discoloration of the reactor due to minor leaching and converted to Fe2TiO5. Fe2O3, MnTiO3 and NiFe2O4 were relatively stable in the reaction environment. In addition, CuFe2O4 catalyst appeared promising due to its high activity and lack of any leaching issues.

Daniel M. Ginosar; Harry W. Rollins; Lucia M. Petkovic; Kyle C. Burch; Michael J. Rush

2009-05-01

315

CaO–ZrO 2 Solid Solution: A Highly Stable Catalyst for the Synthesis of Dimethyl Carbonate from Propylene Carbonate and Methanol  

Microsoft Academic Search

CaO–ZrO2 prepared by co-precipitation showed to be a well-performed catalyst for the transesterification of propylene carbonate (PC) and methanol. The characterization by X-ray powered diffraction (XRD) and Raman spectroscopy indicated that CaO was doped into the lattice of ZrO2 to form CaO–ZrO2 solid solution. Such a solid solution was a strong solid base, which was proved by CO2 temperature program

Hui Wang; Mouhua Wang; Ning Zhao; Wei Wei; Yuhan Sun

2005-01-01

316

Advanced Electrodes for Solid Acid Fuel Cells by Platinum Deposition on CsH2PO4  

SciTech Connect

We demonstrate cathodes for solid acid fuel cells fabricated by vapor deposition of platinum from the metalorganic precursor Pt(acac)2 on the solid acid CsH2PO4 at 210 C. A network of platinum nanoparticles with diameters of 2-4 nm serves as both the oxygen reduction catalyst and the electronic conductor in the electrode. Electrodes with a platinum content of 1.75 mg/cm2 are more active for oxygen reduction than previously reported electrodes with a platinum content of 7.5 mg/cm2. Electrodes containing <1.75 mg/cm2 of platinum show significantly reduced catalytic activity and increased

Papandrew, Alexander B [ORNL; Chisholm, Calum R [ORNL; Elgammal, Ramez A [ORNL; Ozer, Mustafa M [ORNL; Zecevic, strahinja [LiOx, Inc., Pasadena, California 91106, United States

2011-01-01

317

Tungstic acid functionalized mesoporous SBA-15: a novel heterogeneous catalyst for facile one-pot synthesis of 2-amino-4H-chromenes in aqueous medium.  

PubMed

A new highly ordered mesoporous tungstic acid functionalized SBA-15, TAFMC-1 has been synthesized via post-synthesis modification of mesoporous SBA-15 with (3-chloropropyl) triethoxysilane followed by substitution reaction of chlorine atom of the 3-chloropropyl group by tungstic acid group under refluxing conditions in n-hexane. The tungstic acid functionalized mesoporous silica material has been characterized by using small angle powder X-ray diffraction, N2 sorption, HR-TEM, FE-SEM, FT-IR and solid state MAS NMR studies. TAFMC-1 catalyzes the facile one-pot catalytic three-component condensation reaction of resorcinol, aromatic aldehyde and malononitrile for the synthesis of a diverse range of 2-amino-4H-chromenes in aqueous medium. This heterogeneous catalyst can be recycled very efficiently for six consecutive reaction cycles without significant loss of catalytic activity. PMID:23760225

Kundu, Sudipta K; Mondal, John; Bhaumik, Asim

2013-08-01

318

Syngas production from methane reforming with CO 2\\/H 2O and O 2 over NiO–MgO solid solution catalyst in fluidized bed reactors  

Microsoft Academic Search

Catalyst performance of NiO–MgO solid solution catalysts for methane reforming with CO2 and H2O in the presence of oxygen using fluidized and fixed bed reactors under atmospheric and pressurized conditions was investigated. Especially, methane and CO2 conversion in the fluidized bed reactor in methane reforming with CO2 and O2 was higher than those in the fixed bed reactor over Ni0.15Mg0.85O

Keiichi Tomishige

2004-01-01

319

Solid-state NMR of a paramagnetic DIAD-FeII catalyst: sensitivity, resolution enhancement, and structure-based assignments.  

PubMed

A general protocol for the structural characterization of paramagnetic molecular solids using solid-state NMR is provided and illustrated by the characterization of a high-spin Fe(II) catalyst precursor. We show how good NMR performance can be obtained on a molecular powder sample at natural abundance by using very fast (>30 kHz) magic angle spinning (MAS), even though the individual NMR resonances have highly anisotropic shifts and very short relaxation times. The results include the optimization of broadband heteronuclear (proton-carbon) recoupling sequences for polarization transfer; the observation of single or multiple quantum correlation spectra between coupled spins as a tool for removing the inhomogeneous bulk magnetic susceptibility (BMS) broadening; and the combination of NMR experiments and density functional theory calculations, to yield assignments. PMID:17031968

Kervern, Gwendal; Pintacuda, Guido; Zhang, Yong; Oldfield, Eric; Roukoss, Charbel; Kuntz, Emile; Herdtweck, Eberhardt; Basset, Jean-Marie; Cadars, Sylvian; Lesage, Anne; Copéret, Christophe; Emsley, Lyndon

2006-10-18

320

New polystyrene sulfonic acid resin catalysts with enhanced acidic and catalytic properties  

Microsoft Academic Search

The effects of halogenation of polystyrene sulfonic acid resins on acidic and catalytic properties have been evaluated. Four polystyrene-co-divinylbenzene sulfonic acid resins from Rohm and Haas (Amberlyst 70, Amberlyst 15, Amberlyst 35 and Amberlyst 36) have been characterised in terms of their acidities (both strength and acid site concentrations) by ammonia adsorption flow microcalorimetry, their thermal and hydrothermal stabilities, and

P. F. Siril; H. E. Cross; D. R. Brown

2008-01-01

321

Enantioselective hydrogenation of isophorone with titania supported Pd catalysts modified by (?)-dihydroapovincaminic acid ethyl ester effect of the support and the reduction method  

Microsoft Academic Search

Enantioselective hydrogenation of isophorone was investigated over Pd\\/TiO2 catalysts in the presence of (?)-dihydroapovincaminic acid ethyl ester. The used supports were different in crystalline form and in surface area. The influence of the catalyst preparation method on the optical purity was studied. The catalysts were characterized by H2 adsorption and SEM.

É. S??pos; G. Farkas; A. Tungler; J. L. Figueiredo

2002-01-01

322

Apparatus and method for a solid catalyst and fluid dynamic eruption reaction  

US Patent & Trademark Office Database

An apparatus and method for use in conducting an eruption reaction are disclosed. The apparatus includes a catalytic solids container with a mouth and fluid egress opening and a trigger device or mechanism that allows for the controlled release of catalytic solid into an eruptible fluid. The catalytic solids container may be adapted to be coupled to container for an eruptible fluid.

2011-07-05

323

New catalytic functions of heteropoly compounds as solid acids  

Microsoft Academic Search

Our recent developments in catalysis of heteropoly compounds as solid acids have been described. “Water-tolerant catalysis” is one of novel catalytic functions of an acidic Cs salt, Cs2.5H0.5PW12O40 (Cs2.5). Comparison of adsorption amounts of water and benzene led to the following order of hydrophobicity; HZSM-5 (Si\\/Al=628)>silica>Cs3>H-ZSM-5 (Si\\/Al=40)?Cs2.5>silica-alumina>alumina. Owing to the hydrophobicity, Cs2.5 was highly active for organic reactions like hydration

Toshio Okuhara

2002-01-01

324

Solid state lighting using deoxyribonucleic acid-phosphor blend  

NASA Astrophysics Data System (ADS)

Commercial white solid state lighting consists of a blue light emitting diodes (LEDs) that excites a yellow-emitting phosphor powder, which is encapsulated with epoxy on top of the LED die. In this paper, we present the results of replacing the epoxy, with a promising new material, a deoxyribonucleic acid (DNA)-based biopolymer. Using this DNA-biopolymer as the host, has shown the potential for improving both the brightness and color of the light output.

Grote, James G.; Gorman, Timothy; Ouchen, Fahima

2012-10-01

325

Liquid Hydrofluoric Acid Sorption Using Solid Media - Part 1  

Microsoft Academic Search

The conversion of the uranium hexafluoride (UFâ) which is removed from the Molten Salt Reactor Experiment (MSRE), into a stable oxide for long-term storage will produce a significant amount of slightly contaminated, concentrated aqueous hydrofluoric acid (HF). Sin&the handling of this HF is complicated and dangerous, it was decided to transform it into a stable solid fluoride (e.g., CaFâ, AlFâ,

Osborne

2000-01-01

326

Isoselenazolones as catalysts for the activation of bromine: bromolactonization of alkenoic acids and oxidation of alcohols.  

PubMed

Isoselenazolones were synthesized by a copper-catalyzed Se-N bond forming reaction between 2-halobenzamides and selenium powder. The catalytic activity of the various isoselenazolones was studied in the bromolactonization of pent-4-enoic acid. Isoselenazolone 9 was studied as a catalyst in several reactions: the bromolactonization of a series of alkenoic acids with bromine or N-bromosuccinimide (NBS) in the presence of potassium carbonate as base, the bromoesterification of a series of alkenes using NBS and a variety of carboxylic acids, and the oxidation of secondary alcohols to ketones using bromine as an oxidizing reagent. Mechanistic details of the isoselenazolone-catalyzed bromination reaction were revealed by (77)Se NMR spectroscopic and ES-MS studies. The oxidative addition of bromine to the isoselenazolone gives the isoselenazolone(IV) dibromide, which could be responsible for the activation of bromine under the reaction conditions. Steric effects from an N-phenylethyl group on the amide of the isoselenazolone and electron-withdrawing fluoro substituents on the benzo fused-ring of the isoselenazolone appear to enhance the stability of the isoselenazolone as a catalyst for the bromination reaction. PMID:23046286

Balkrishna, Shah Jaimin; Prasad, Ch Durga; Panini, Piyush; Detty, Michael R; Chopra, Deepak; Kumar, Sangit

2012-10-18

327

Acid catalysts based on Cu/Ru alumina: Conversion of butyraldehyde to dibutyl ether  

SciTech Connect

A system made by combining two nonalloying metals, ruthenium and copper, using alumina as the oxide support was studied. This bimetallic supported catalyst has been used mainly in hydrogenoloysis, dehydrogenation, and oxidation reactions of hydrocarbons. The preparation of such materials has been proposed to effect the selectivity and activity of a highly active metal by inclusions of a second less active metal. The samples were characterized by electron paramagnetic resonance spectrometry (EPR), X-ray diffraction (XRD), surface area, and surface acidities. The techniques EPR and XRD are ideal for studying the electronic and structural changes of the samples at different temperatures and concentrations. The primary reaction involved in this study was the hydrogenation of an aldehyde to the corresponding alcohol. A secondary reaction occurred as well. The acid catalyzed, substitution or bimolecular dehydration of the alcohol to the dibutyl ether was observed under certain catalytic conditions. These catalysts appeared to act as acid/base. Therefore this reaction to produce the ether is of special importance. A correlation between the electronic, structural and catalytic properties has been made to understand molecular processes` role in catalytic phenomena. 44 refs., 6 figs., 5 tabs.

Jansen, S.; Palmieri, M.; Gomez, M. [Temple Univ., Philadelphia, PA (United States); Lawrence, S. [Saginaw Valley State Univ., University Center, MI (United States)

1996-10-01

328

Photodegradation of nalidixic acid assisted by TiO(2) nanorods/Ag nanoparticles based catalyst.  

PubMed

Two different nanosized TiO2-based catalysts supported onto glass with tailored photocatalytic properties upon irradiation by UV light were successfully employed for the degradation of nalidixid acid, a widely diffused antibacterial agent of environmental relevance known to be non-biodegradable. Anatase rod-like TiO2 nanocrystals (TiO2NRs) and a semiconductor oxide-noble metal nanocomposite TiO2 NRs/Ag nanoparticles (NPs), synthesized by colloidal chemistry routes, were cast onto glass slide and employed as photocatalysts. A commercially available catalyst (TiO2 P25), also immobilized onto a glass slide, was used as a reference material. It was found that both TiO2 NRs/Ag NPs composite and TiO2 NRs demonstrated a photocatalytic efficiency significantly higher than the reference TiO2 P25. Specifically, TiO2 NRs/Ag NPs showed a photoactivity in nalidixic acid degradation 14 times higher than TiO2 P25 and 4 times higher than bare TiO2 NRs in the first 60min of reaction. Several by-products were identified by HPLC-MS along the nalidixic acid degradation, thus getting useful insight on the degradation pathway. All the identified by-products resulted completely removed after 6h of reaction. PMID:23466278

Petronella, F; Diomede, S; Fanizza, E; Mascolo, G; Sibillano, T; Agostiano, A; Curri, M L; Comparelli, R

2013-03-05

329

Transition metal complexes — A new class of catalysts of interfacial alkylation for the asymmetrical synthesis of ?-amino acids  

Microsoft Academic Search

A new class of catalysts of interfacial asymmetrical alkylation is suggested for the synthesis of a-amino acids — positively charged complexes of the transition metals Cu(II), Ni(II), and Pd(II). These complexes consist of several fragments, by variation of which the structure of the catalysts can readily be modified. The complexes are chiral on account of (S)proline derivatives contained in them

V. I. Maleev; S. O. Videnskaya; M. B. Saporovskaya; V. A. Tsyryapkin; V. M. Belikov

1991-01-01

330

Use of functionalized PEG with 4-aminobenzoic acid stabilized platinum nanoparticles as an efficient catalyst for the hydrosilylation of alkenes.  

PubMed

A catalyst containing functionalized polyethylene glycol with 4-aminobenzoic acid (PEG-AMB) stabilized platinum nanoparticles has been synthesized and characterized, and its application in the hydrosilylation of alkenes investigated. It is shown that the functionalized PEG-stabilized Pt nanoparticles form a very efficient catalyst for the hydrosilylation of alkenes. The Pt nanoparticles can be fully immobilized in the PEG-AMB and recycled at least nine times without any obvious loss of catalytic activity. PMID:23295024

Bai, Ying; Zhang, Shufang; Deng, Yuan; Peng, Jiajian; Li, Jiayun; Hu, Yingqian; Li, Xiaonian; Lai, Guoqiao

2012-12-12

331

Catalytic conversion of canola oil to fuels and chemicals: roles of catalyst acidity, basicity and shape selectivity on product distribution  

Microsoft Academic Search

Studies were performed at atmospheric pressure in a fixed-bed microreactor at temperatures of 400 and 500°C over HZSM-5, silicalite, silica, silica-alumina, ?-alumina, calcium oxide and magnesium oxide catalysts to determine the various roles of catalyst acidity, basicity and shape selectivity on canola oil conversion and product distribution. Results showed that the initial decomposition of canola oil to long chain hydrocarbons

Raphael O. Idem; Sai P. R. Katikaneni; Narendra N. Bakhshi

1997-01-01

332

Chiral dendritic bis(oxazoline) copper(II) complexes as Lewis acid catalysts for enantioselective aldol reactions in aqueous media  

Microsoft Academic Search

A series of copper(II) complexes, with chiral bis(oxazoline) ligands disubstituted at the carbon atom linking the two oxazolines by Fréchet-type polyether dendrimers, have been designed and synthesized. These complexes were used as Lewis acid catalysts in enantioselective aldol reactions in aqueous media. Good yields and moderate enantioselectivities were achieved, which are comparable with those resulting from the corresponding smaller catalysts.

Bai-Yuan Yang; Xiao-Min Chen; Guo-Jun Deng; Yi-Li Zhang; Qing-Hua Fan

2003-01-01

333

MoV-based catalysts in ethane oxidation to acetic acid: Influence of additives on redox chemistry  

Microsoft Academic Search

The formation of acetic acid and\\/or ethylene by oxidation of ethane is strongly dependent on X additives or Y promotor added to MoVO-based catalysts. MoV0.4X0.12Y?Oz (X=Nb; Y=Pd; ?=10?4) catalysts were prepared by the slurry method and their structural properties were studied by in situ (redox conditions) XRD, Raman and XPS techniques. The reactivity during reduction and reoxidation was analysed by

M. Roussel; S. Barama; A. Löfberg; S. Al-Sayari; K. Karim; E. Bordes-Richard

2009-01-01

334

Effects of acidic treatments on the pore and surface properties of Ni catalyst supported on activated carbon  

Microsoft Academic Search

Activated carbon as catalyst support was treated with HCl, HNO3, and HF and the effects of acid treatments on the properties of the activated carbon support were studied by N2 adsorption, mass titration, temperature-programmed desorption (TPD), and X-ray photoelectron spectrometry (XPS). Ni catalysts supported on untreated and treated activated carbons were prepared, characterized and tested for the reforming reaction of

Shaobin Wang

1998-01-01

335

Microwave-accelerated energy-efficient esterification of free fatty acid with a heterogeneous catalyst.  

PubMed

This paper shows energy-efficiency of microwave-accelerated esterification of free fatty acid with a heterogeneous catalyst by net microwave power measurement. In the reaction condition of 5 wt% sulfated zirconia and 1:20 M ratio of oil to methanol at 60°C and atmospheric pressure, more than 90% conversion of the esterification was achieved in 20 min by microwave heating, while it took about 130 min by conventional heating. Electric energy consumption for the microwave heating in this accelerated esterification was only 67% of estimated minimum heat energy demand because of significantly reduced reaction time. PMID:21144741

Kim, Daeho; Choi, Jinju; Kim, Geun-Ju; Seol, Seung Kwon; Ha, Yun-Chul; Vijayan, M; Jung, Sunshin; Kim, Bo Hyun; Lee, Gun Dae; Park, Seong Soo

2010-11-21

336

Photodissociation of Formic Acid Isolated in Solid Parahydrogen  

NASA Astrophysics Data System (ADS)

The in situ photochemistry of dopant molecules isolated in solid parahydrogen (pH_2) typically differs from analogous studies in rare gas crystals for two main reasons: (1) solid pH_2 has a negligible cage effect so that photodissociation of a precursor molecule can lead efficiently to well-separated fragments, and (2) radical fragments can potentially react with the pH_2 matrix. Our group is currently studying the 193 nm photochemistry of a number of precursor molecules isolated in solid pH_2 via high-resolution FTIR spectroscopy. In this talk I will present results for the 193 nm photolysis of formic acid (FA) in solid pH_2. In rare gas matrices, the analogous FA photochemistry proceeds via the CO+H_2O and CO_2+H_2 photodissociation channels. In solid pH_2, in addition to these channels we observe the production of HCO and HOCO. Further, after the UV laser is turned off, the HOCO concentration continues to increase with a slow first-order rate constant for a period of 10 hours. At this point, we still do not have a full explanation of the chemical mechanism leading to the post-photolysis increase in the HOCO concentration. J. Lundell, M. Räsänen, J. Mol. Struct. 436-437, 349 (1997).

Anderson, David T.; Paulson, Leif O.

2011-06-01

337

Transient response study of the formaldehyde oxidation to formic acid on V–Ti–O catalyst: FTIR and pulse study  

Microsoft Academic Search

The mechanism of the formaldehyde oxidation to formic acid on a V–Ti–O catalyst has been studied by pulse and spectrokinetic (in situ FTIR) methods. Bidentate symmetrical formates and asymmetric formates are observed by formaldehyde adsorption both in the presence and in the absence of dioxygen in the temperature range between 100 and 200°C. Formic acid may form by two parallel

Galina Ya. Popova; Tamara V. Andrushkevich; Yurii A. Chesalov; Valentin N. Parmon

2007-01-01

338

One-Pot synthesis of phosphorylated mesoporous carbon heterogeneous catalysts with tailored surface acidity  

SciTech Connect

Soft-templated phosphorylated mesoporous carbons with homogeneous distributions of phosphate groups were prepared by a 'one-pot' synthesis method using mixtures of phosphoric acid with hydrochloric, or nitric acids in the presence of Pluronic F127 triblock copolymer. Adjusting the various ratios of phosphoric acid used in these mixtures resulted in carbons with distinct adsorption, structural and surface acidity properties. The pore size distributions (PSDs) from nitrogen adsorption at -196 C showed that mesoporous carbons exhibit specific surface areas as high as 551 m{sup 2}/g and mesopores as large as 13 nm. Both structural ordering of the mesopores and the final phosphate contents were strongly dependent on the ratios of H{sub 3}PO{sub 4} in the synthesis gels, as shown by transmission electron microscopy (TEM), X-ray photoelectron (XPS) and energy dispersive X-ray spectroscopy (EDS). The number of surface acid sites determined from temperature programmed desorption of ammonia (NH{sub 3}-TPD) were in the range of 0.3-1.5 mmol/g while the active surface areas are estimated to comprise 5-54% of the total surface areas. Finally, the conversion temperatures for the isopropanol dehydration were lowered by as much as 100 C by transitioning from the least acidic to the most acidic catalysts surface.

Fulvio, Pasquale F [ORNL; Mahurin, Shannon Mark [ORNL; Mayes, Richard T [ORNL; Bauer, Christopher [ORNL; Wang, Xiqing [ORNL; Veith, Gabriel M [ORNL; Dai, Sheng [ORNL

2012-01-01

339

Mass transfer effects in the oxidation of aqueous organic compounds over a hydrophobic solid catalyst  

Microsoft Academic Search

The use of a Carberry-type reactor has been investigated for the complete oxidation by oxygen of various water-soluble organic compounds over a platinum on porous polydivinylbenzene catalyst. Studies with aqueous formaldehyde as the test reactant reveal important details of reactor hydrodynamics and possible reaction pathways. Two routes for the transfer of oxygen are apparent in this reaction system. At low

K Lavelle; J. B McMonagle

2001-01-01

340

A review on solid oxide derived from waste shells as catalyst for biodiesel production  

Microsoft Academic Search

The waste eggs and mollusk shells are found to be the richest sources of calcium carbonate and have been utilized for various purposes after proper treatments. When calcined at a proper temperature calcium carbonate converts into CaO, which is a metal oxide. Researchers have found that the CaO prepared from the waste shells can be used as catalyst in biodiesel

Jutika Boro; Dhanapati Deka; Ashim J. Thakur

341

Fundamental investigation of catalyst utilization at the electrode\\/solid polymer electrolyte interface  

Microsoft Academic Search

The active layer of gas diffusion electrodes, widely used in low temperature polymer electrolyte fuel cells, contains either metal-blacks (mostly Pt-black) or metallic nanoparticles (mostly Pt particles or Pt based alloy particles) supported on high surface area carbon. Depending on the nature of the catalyst in the active layer and the applied pretreatment of the gas diffusion electrodes, cyclic voltammetry

U. A. Paulus; Z. Veziridis; B. Schnyder; M. Kuhnke; G. G. Scherer; A. Wokaun

2003-01-01

342

BIOINSPIRED CATALYSTS: SYNTHESIS, CHARACTERISATION AND SOME APPLICATIONS  

Microsoft Academic Search

Our recent work concerning the synthesis, characterisation and some applications of bioinspired electron-transfer catalysts is reviewed in this contribution. The catalysts were various mono- or heterobimetallic complexes having either Cu(II) or Cu(II) and Zn(II) as central ions and amino acids, their derivatives or various N- containing organic molecules as ligands. Emphasis was based upon the solid support immobilised versions of

István Pálinkó

343

One-pot synthesis of 5-hydroxymethylfurfural directly from starch over SO(4)(2-)/ZrO2-Al2O3 solid catalyst.  

PubMed

The synthesis of 5-hydroxymethylfurfural (HMF) directly from starch was studied in dimethyl sulfoxide-water. The effects of catalyst variation, reaction time, water content, catalyst loading and temperature on the reaction were investigated. The SO(4)(2-)/ZrO(2)-Al(2)O(3) catalyst was found to act as a bifunctional catalyst with high activity for both hydrolysis and dehydration of starch. HMF yield of 55% was obtained after 6h at 423K for the reaction of starch (the molar ratio of water to glucose in starch is 44/1) over the SO(4)(2-)/ZrO(2)-Al(2)O(3) catalyst, which bears high acidity and moderate basicity with Zr/Al molar ratio of 1:1. PMID:22534374

Yang, Yu; Xiang, Xi; Tong, Dongmei; Hu, Changwei; Abu-Omar, Mahdi M

2012-03-30

344

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor.  

PubMed

Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2-3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3. PMID:24062830

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe; Verboom, Willem

2013-08-16

345

Gallium-containing polymer brush film as efficient supported Lewis acid catalyst in a glass microreactor  

PubMed Central

Summary Polystyrene sulfonate polymer brushes, grown on the interior of the microchannels in a microreactor, have been used for the anchoring of gallium as a Lewis acid catalyst. Initially, gallium-containing polymer brushes were grown on a flat silicon oxide surface and were characterized by FTIR, ellipsometry, and X-ray photoelectron spectroscopy (XPS). XPS revealed the presence of one gallium per 2–3 styrene sulfonate groups of the polymer brushes. The catalytic activity of the Lewis acid-functionalized brushes in a microreactor was demonstrated for the dehydration of oximes, using cinnamaldehyde oxime as a model substrate, and for the formation of oxazoles by ring closure of ortho-hydroxy oximes. The catalytic activity of the microreactor could be maintained by periodic reactivation by treatment with GaCl3.

Munirathinam, Rajesh; Ricciardi, Roberto; Egberink, Richard J M; Huskens, Jurriaan; Holtkamp, Michael; Wormeester, Herbert; Karst, Uwe

2013-01-01

346

A solid form of ambazone with lactic acid  

NASA Astrophysics Data System (ADS)

In recent years, much research has been carried out on the preparation of pharmaceutical solid forms due to their improved physical-chemical parameters such as solubility, dissolution rate of the drug, chemical stability, melting point and hygroscopic parameter. The aim of this study was to obtain and to investigate the structural properties of the ambazone (AMB) with lactic acid (LA) solid form. The solid form was obtained starting from the mixture of ambazone with lactic acid (1:1), by grinding method at constant temperature. The obtained compound was investigated via X-ray powder diffraction (PXRD), thermal analysis (DSC, TG-DTA) and infrared (FTIR) spectroscopy. The difference between the patterns of AMB•LA and of the starting compounds evidenced a new compound. Using X-ray powder diffraction method, by indexing procedure the unit cell and the lattice parameters were determined. Thermal and FTIR measurements on the pure compounds and on the (1:1) ground mixture of AMB with LA confirm the new salt form formation.

Borodi, Gh.; Muresan-Pop, M.; Kacsó, I.; Bratu, I.

2012-02-01

347

The primary zone in the combustion of solid propellants containing catalysts  

Microsoft Academic Search

Using a scanning electron microscope and an x-ray microprobe analyzer, we investigated the structure and composition of the combustion surface of the N propellant containing catalysts (PbO2, CuO, PbO2+CuO) which was extinguished at various pressures. Based on the obtained results, the heat-transfer coefficient was calculated for the layer above the catalyzed propellant combustion surface and found to be greater than

A. P. Denisyuk; L. A. Demidova; V. I. Galkin

1995-01-01

348

On the Structure of Activated Hydrotalcites as Solid Base Catalysts for Liquid-Phase Aldol Condensation  

Microsoft Academic Search

Hydrotalcites (HTs) of different, well-defined platelet sizes were hydrothermally synthesized. Activation via calcination and rehydration resulted in highly active catalysts. Their activities in the self-condensation of acetone at 273 K showed a linear increase with the amount of accessible Brønsted basic sites as determined by CO2 adsorption. The number of accessible sites, based on the CO2\\/Al ratio, was below 5%.

J. C. A. A. Roelofs; D. J. Lensveld; A. J. van Dillen; K. P. de Jong

2001-01-01

349

Kinetic relationships in conversion of 3-methyl-1,3-butanediol on phosphoric acid catalyst with added sodium phosphate  

Microsoft Academic Search

By means of pulse chromatography on a phosphoric acid catalyst consisting of a mixture of phosphoric acid and sodium phosphates supported on quartz, a study has been made of the acid-catalyzed conversions of 3-methyl-1,3-butanediol (MBD) at 120-150°C. It has been established that the principal products are isoprene and isopropenylethyl alcohol; at long contact times, the alcohol is also dehydrated to

V. S. Malinskii; M. I. Vinnik

1988-01-01

350

Fluidized catalyst process for production and hydration of olefins  

SciTech Connect

A continuous multi-stage process is described for increasing octane quality and yield of liquid hydrocarbons from an integrated fluidized catalytic cracking unit and hydration reaction zone comprising: contacting heavy hydrocarbon feedstock in a primary fluidized bed reaction stage with cracking catalyst comprising particulate solid large pore acid aluminosilicate zeolite catalyst at conversion conditions to produce a hydrocarbon effluent comprising gas containing C2-C6 olefins, intermediate hydrocarbons in the gasoline and distillate range, and cracked bottoms; regenerating primary stage zeolite cracking catalyst in a primary stage regeneration zone and returning at least a portion of regenerated zeolite cracking catalyst to the primary reaction stage; reacting an olefinic stream containing at least one iso-olefin with water in a secondary fluidized bed hydration reactor stage in contact with a closed fluidized bed of acid zeolite catalyst particles comprising solid acid zeolite under hydration reaction conditions to effectively convert said isoolefin to alkyl alkanol; adding fresh acid zeolite particles to the secondary stage reactor in an amount sufficient to maintain average equilibrium catalyst particle activity for effective alkanol synthesis reaction without regeneration of the secondary catalyst bed; withdrawing a portion of equilibrium catalyst from the secondary fluidized bed reactor stage; and passing said withdrawn catalyst portion to the primary fluidized bed reaction stage for contact with the petroleum feedstock.

Harandi, M.N.

1993-08-03

351

[Denitrification using polylactic acid as solid carbon source].  

PubMed

Polylactic acid (PLA) was used as solid carbon source and biofilm support simultaneously, to investigate the applicability of PLA in the denitrification process. The effect of temperature on denitrification performance was also studied. The IR analysis and SEM observation were performed to investigate the PLA surface structure and biofim morphology. The results showed that when the initial concentration of nitrate nitrogen was 50 mg/L and the temperature was 30 degrees C, the average denitrification rate was 2.6 x 10(-1) mg/(g x h) and nitrate could be completely removed within 13h. Temperature had a significant influence on the denitrification rate. The IR analysis and SEM observation of PLA surface structure confirmed the feasibility of PLA as solid carbon source. The SEM observation of biofim showed that the biofilm was thin and mainly consisted of cocci. PMID:19799294

Fan, Zhen-xing; Wang, Jian-long

2009-08-15

352

Catalytic pyrolysis of oil fractions separated from food waste leachate over nanoporous acid catalysts.  

PubMed

Oil fractions, separated from food waste leachate, can be used as an energy source. Especially, high quality oil can be obtained by catalytic cracking. In this study, nanoporous catalysts such as Al-MCM-41 and mesoporous MFI type zeolite were applied to the catalytic cracking of oil fractions using the pyrolysis gas chromatography/mass spectrometry. Mesoporous MFI type zeolite showed better textural porosity than Al-MCM-41. In addition, mesoporous MFI type zeolite had strong Brönsted acidity while Al-MCM-41 had weak acidity. Significant amount of acid components in the food waste oil fractions were converted to mainly oxygenates and aromatics. As a result of its well-defined nanopores and strong acidity, the use of a mesoporous MFI type zeolite produced large amounts of gaseous and aromatic compounds. High yields of hydrocarbons within the gasoline range were also obtained in the case of mesoporous MFI type zeolite, whereas the use of Al-MCM-41, which exhibits relatively weak acidity, resulted in high yields of oxygenates and diesel range hydrocarbons. PMID:22121679

Kim, Seung-Soo; Heo, Hyeon Su; Kim, Sang Guk; Ryoo, Ryong; Kim, Jeongnam; Jeon, Jong-Ki; Park, Sung Hoon; Park, Young-Kwon

2011-07-01

353

Catalyst Activity and Post-operation Analyses of Pt/TiO2 (Rutile) Catalysts Used in the Sulfuric Acid Decomposition Reaction  

SciTech Connect

Production of hydrogen by splitting of water at lower temperatures than by direct thermal decomposition can be achieved by a series of particular chemical reactions that establish a thermochemical cycle [1]. Among the high number of thermochemical water-splitting cycles proposed in the literature [2], the sulfur-based group is of considerable interest. All the sulfur-based cycles employ the catalytic decomposition of sulfuric acid into SO2 and O2. The produced O2 corresponds to the O2 generated from water in the overall cycle. Research performed at the Idaho National Laboratory [3] has found that even one of the most stables catalysts, Pt supported on low surface area titania, deactivates with time on stream (TOS). To develop an understanding of the factors that cause catalyst deactivation, samples of 1% Pt supported on titania (rutile) catalyst were submitted to flowing concentrated sulfuric acid at 1123 K and atmospheric pressure for different TOSs between 0 and 548 h and a number of chemical and spectroscopic analyses applied to the spent samples.

Lucia M. Petkovic; Daniel M. Ginosar; Harry W. Rollins; Kyle C. Burch; Patrick J. Pinhero; Helen H. Farrell

2007-06-01

354

Synthesis and characterization of porous layered solid acids  

NASA Astrophysics Data System (ADS)

Four types of zirconium phosphonates with interesting texture have been synthesized and characterized, including zirconium biphenylenebis(phosphonates), zirconium terphenylenebis(phosphonates), zirconium phosphate biphenylenebis-(phosphonates) and zirconium phenylphosphonates. These compounds have been characterized by thermogravimetric analysis, X-ray powder diffraction (XRD), surface area analysis, elemental analysis, 31P solid state NMR, transmission electron microscopy (TEM) and scanning electron microscopy (SEM). When HF and 100% excess Zr were used in the synthesis, the resulting zirconium biphenylenebis-(phosphonates) (Zr-P2-Ph2) compounds have microporosity (10--20 A) and high surface areas (˜400 m2/g). The micropore diameters range from 13 to 18 A, depending on the solvents and the amount of HF used. Zirconium 4,4?-terphenylenebis(phosphonates) (Zr-P2-Ph3) also have mostly microporous properties (11--17 A) if 100% excess Zr was used. SEM and TEM studies revealed that these samples have a stacked layer pattern, instead of a "house of cards" arrangement. A novel model is therefore proposed to explain the porosity and surface area data of these compounds. A number of porous sulfonated zirconium phosphonates, namely, sulfonated zirconium phenylphosphonate, sulfonated zirconium biphenylenebis(phosphonate) and sulfonated zirconium terphenylenebis(phosphonate), have been successfully synthesized. The use of SO3 as the sulfonation agent instead of fuming H2SO4 virtually eliminates the possibility of water contact with the sulfonated samples. The surface acidity of these materials has been characterized in great detail by solid state MAS NMR studies of probe molecules. The results suggest that the acidity of several sulfonated samples is close to 100% H2SO4. The syntheses of structurally stable Al-pillared montmorillonites (Al-mont), Zr-pillared montmorillonites (Zr-mont), phosphated Al-mont, phosphated Zr-mont, sulfated Al-mont and sulfated Zr-mont have been successfully achieved. XRD and surface area analysis (SA) have been used mainly for structural characterization. The modified clays exhibit good thermal stability and surface area values of ˜300 m2/g, and some samples retain their d-spacings after modification if prepared carefully. The acidity strength of the modified pillared samples has been investigated by solid state MAS NMR spectroscopy with acetone-2-13C adsorption. The phosphated Al-pillared montmorillonites have slightly weaker acidity after modification, but the phosphated Zr-pillared montmorillonites have much stronger acidity. Some of the acid sites in one sample even exhibit superacidity.

Wang, Zhike

355

Ultra-fast vapour-liquid-solid synthesis of Si nanowires using ion-beam implanted gallium as catalyst.  

PubMed

The feasibility of gallium as a catalyst for vapour-liquid-solid (VLS) nanowire (NW) growth deriving from an implantation process in silicon by a focused ion beam (FIB) is investigated. Si(100) substrates are subjected to FIB implantation of gallium ions with various ion fluence rates. NW growth is performed in a hot wall chemical vapour deposition (CVD) reactor at temperatures between 400 and 500?°C with 2% SiH(4)/He as precursor gas. This process results in ultra-fast growth of (112)- and (110)-oriented Si-NWs with a length of several tens of micrometres. Further investigation by transmission electron microscopy indicates the presence of a NW core-shell structure: while the NW core yields crystalline structuring, the shell consists entirely of amorphous material. PMID:21891844

Hetzel, Martin; Lugstein, Alois; Zeiner, Clemens; Wójcik, Tomasz; Pongratz, Peter; Bertagnolli, Emmerich

2011-09-02

356

Preparation of heat-resistant BaAl 12 O 19 combustion catalyst by solid-state reaction combined with sub-micron grinding  

Microsoft Academic Search

Heat-resistant barium hexaaluminate combustion catalyst was prepared by a conventional solid-state reaction combined with sub-micron grinding. The barium hexaaluminate thus prepared retained almost the same high surface area at high temperatures as the one prepared by the alkoxide method, exhibiting high activity in the catalytic combustion of methane.

S. Imamura I; S. Ishida; E. Ebata; K. Tsurumi; T. Nishikawa; K. Tanaka; I. Koshiga

1994-01-01

357

Production of biodiesel from mixed waste vegetable oil using an aluminium hydrogen sulphate as a heterogeneous acid catalyst.  

PubMed

Al(HSO(4))(3) heterogeneous acid catalyst was prepared by the sulfonation of anhydrous AlCl(3). This catalyst was employed to catalyze transesterification reaction to synthesis methyl ester when a mixed waste vegetable oil was used as feedstock. The physical and chemical properties of aluminum hydrogen sulphate catalyst were characterized by scanning electron microscopy (SEM) measurements, energy dispersive X-ray (EDAX) analysis and titration method. The maximum conversion of triglyceride was achieved as 81 wt.% with 50 min reaction time at 220°C, 16:1 molar ratio of methanol to oil and 0.5 wt.% of catalyst. The high catalytic activity and stability of this catalyst was related to its high acid site density (-OH, Brönsted acid sites), hydrophobicity that prevented the hydration of -OH group, hydrophilic functional groups (-SO(3)H) that gave improved accessibility of methanol to the triglyceride. The fuel properties of methyl ester were analyzed. The fuel properties were found to be observed within the limits of ASTM D6751. PMID:21621409

Ramachandran, Kasirajan; Sivakumar, Pandian; Suganya, Tamilarasan; Renganathan, Sahadevan

2011-05-06

358

Ozonation of trichloroethylene in acetic acid solution with soluble and solid humic acid.  

PubMed

The combined flushing and oxidation process using acetic acid and ozone has been used successfully to remove trichloroethylene (TCE) completely from contaminated soil. In this study, the effects of humic acid, a fraction of the organic matter in soil, over the performance of TCE decomposition was evaluated. TCE decomposition by ozone was enhanced by the presence of humic acid at concentrations lower than 8mgCL(-1) and then inhibited at higher concentrations. It is possible that the presence of the soluble humic acid fraction during the ozonation of TCE in acetic acid solutions produces hydroxyl radicals during the TCE ozonation which appears to be the reason for the enhanced TCE decomposition rate. Solid humic acid reduced TCE decomposition rate by acting as an ozone scavenger. Similarly, sorbed TCE reduced the amount of TCE available for decomposition by ozone in solution. PMID:18511186

Alcántara-Garduño, Martha E; Okuda, Tetsuji; Nishijima, Wataru; Okada, Mitsumasa

2008-03-30

359

Fluorescence emission from rhodamine-B lactone adsorbed at solid catalysts  

NASA Astrophysics Data System (ADS)

Fluorescence emission of RBL depends strongly on the polarity of the solvents and the emission maximum shifts to the red with increasing polarity of the solvent. However, RBL adsorbed at the surfaces of Y Zeolites (both HY and NaY) and ZSM-5 show two fluorescence bands at 440 nm and 580 nm where the peak at 440 nm is a new emission peak. The fluorescence intensities of both peaks were found to vary with the loading level of the probe to the catalyst surface.

El-Rayyes, Ali A.; Al-Betar, A.; Htun, Than; Klein, Uwe K. A.

2005-10-01

360

Solid-state forms of zoledronic acid: polymorphism in hydrates.  

PubMed

Solid-state forms of zoledronic acid, a nitrogen-containing bisphosphonate used for treatment of bone diseases are studied using different experimental techniques (DSC, TG, and XRD). Two degrees of hydration have been obtained, containing one and three water molecules per zoledronic acid molecule. The crystal structure of the trihydrated form is reported. Two different anhydrated forms have been obtained when the hydrated ones were heated. Besides, during the dehydration process, an amount of metastable amorphous phase appears, as a function of the dehydration rate. The stability of the obtained crystalline forms is examined under high humidity and a different trihydrated form was obtained, setting clear that the same degree of hydration (trihydrated) can be obtained in two different crystalline forms, and then very different thermal behaviors have been observed. PMID:20533554

Ruscica, Romina; Bianchi, Micaela; Quintero, Mariano; Martinez, Andrea; Vega, Daniel R

2010-12-01

361

The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation  

NASA Astrophysics Data System (ADS)

Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N2 adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization.

Yu, Xiaofang; Yu, Xiaobo; Wu, Shujie; Liu, Bo; Liu, Heng; Guan, Jingqi; Kan, Qiubin

2011-02-01

362

Silica-bonded N-propyl sulfamic acid used as a heterogeneous catalyst for transesterification of soybean oil with methanol.  

PubMed

The transesterification of soybean oil with methanol was carried out, to produce biodiesel, over silica-bonded N-propyl sulfamic acid in a heterogeneous manner. Results showed that a maximum conversion of 90.5% was achieved using a 1:20 M ratio of soybean oil to methanol and a catalyst amount of 7.5 wt.% at 423 K for 60 h. It was found that the free fatty acid (FFA) and water present in the feedstock had no significant influence on the catalytic activity to the transesterification reaction. Besides, the catalyst also showed activities towards the esterification reaction of FFAs, in terms of the FFA conversion of 95.6% at 423 K for 30 h. Furthermore, the catalyst could be recovered with a better reusability. PMID:21871795

Xie, Wenlei; Yang, Dong

2011-08-09

363

Cooperative catalysis: combining an achiral metal catalyst with a chiral brønsted Acid enables highly enantioselective hydrogenation of imines.  

PubMed

Asymmetric hydrogenation of imines leads directly to chiral amines, one of the most important structural units in chemical products, from pharmaceuticals to materials. However, highly effective catalysts are rare. This article reveals that combining an achiral pentamethylcyclopentadienyl (Cp*)-iridium complex with a chiral phosphoric acid affords a catalyst that allows for highly enantioselective hydrogenation of imines derived from aryl ketones, as well as those derived from aliphatic ones, with ee values varying from 81 to 98?%. A range of achiral iridium complexes containing diamine ligands were examined, for which the ligands were shown to have a profound effect on the reaction rate, enantioselectivity and catalyst deactivation. The chiral phosphoric acid is no less important, inducing enantioselection in the hydrogenation. The induction occurs, however, at the expense of the reaction rate. PMID:24019056

Tang, Weijun; Johnston, Steven; Li, Chaoqun; Iggo, Jonathan A; Bacsa, John; Xiao, Jianliang

2013-09-09

364

The primary zone in the combustion of solid propellants containing catalysts  

SciTech Connect

Using a scanning electron microscope and an x-ray microprobe analyzer, we investigated the structure and composition of the combustion surface of the N propellant containing catalysts (PbO{sub 2}, CuO, PbO{sub 2} + CuO) which was extinguished at various pressures. Based on the obtained results, the heat-transfer coefficient was calculated for the layer above the catalyzed propellant combustion surface and found to be greater than that of the gas by factors ranging from 1.5 to 15. The calculation of the C-phase heat balance for the N propellant with additives showed that the rise in the combustion rate is caused by the increased quantity of heat entering into the C-phase from the zone above the combustion surface. Plus, the driving stage in the combustion of catalyzed propellants is the zone above the combustion surface and not the C-phase reaction layer, as in the case of the propellants without any catalysts.

Denisyuk, A.P.; Demidova, L.A.; Galkin, V.I. [D.I. Mendeleev Russian Chemical Methodology Univ., Moscow (Russian Federation)

1995-09-01

365

Oxidation of ethane to ethylene and acetic acid by MoVNbO catalysts  

Microsoft Academic Search

The influence of niobium on the physicochemical properties of the MoVO system and on its catalytic properties in the oxidation of ethane to ethylene and acetic acid is examined. Solids based on MoV0.4Ox and MoV0.4Nb0.12Oy composition and calcined at 350 or 400°C were studied by X-ray diffraction, and by laser Raman and X-ray photoelectron spectroscopies. Their reactivity during reduction and

M. Roussel; M. Bouchard; E. Bordes-Richard; K. Karim; S. Al-Sayari

2005-01-01

366

A novel direct and one-pot Mannich synthesis of fluorinated ?-aminobutanones with sulfamic acid as a green catalyst  

Microsoft Academic Search

A variety of fluorinated ?-aminobutanones could be obtained in good to excellent yields at room temperature through the direct and three-component Mannich reactions of unmodified acetone with aldehydes and fluorinated anilines in one-pot procedure. Among the catalysts screened, sulfamic acid was tested to the best in aspect of outstanding stability, inexpensive cost, ready recovery and excellently catalytic activity. All the

Min Xia; Yue-Dong Lu

2006-01-01

367

Green and Efficient Procedure for the Trimethylsilylation of Hydroxy Groups and Their Regeneration Using Sulfamic Acid as Recyclable Catalyst  

Microsoft Academic Search

Structurally diverse alcohols and phenols were efficiently transformed into their corresponding trimethylsilyl ethers with hexamethyldisilazane (HMDS) in the presence of catalytic amounts of sulfamic acid (SA) at room temperature under both acetonitrile and solvent-free conditions. Deprotection of these trimethylsilyl ethers to their parent alcohols and phenols was also achieved using this catalyst in water at room temperature.

Amin Rostami; Firoz Ahmad-Jangi; Mohammad Rezgar Zarebin; Jamal Akradi

2010-01-01

368

Niobic acid and niobium phosphate as highly acidic viable catalysts in aqueous medium: Fructose dehydration reaction  

Microsoft Academic Search

The catalytic properties of niobic acid (Nb2O5·nH2O) and niobium phosphate (NbOPO4) surfaces were studied in the reaction of fructose dehydration carried out in water. The reaction was performed in a continuous reactor at different temperatures 90–110°C and pressures (from 2 to 6bar). Superior activity and selectivity to 5-hydroxymethyl-2-furaldehyde (HMF) of niobium phosphate compared to niobic acid was observed. The initial

Paolo Carniti; Antonella Gervasini; Serena Biella; Aline Auroux

2006-01-01

369

Copper active sites for the selective reduction of nitrogen monoxide by propane on Cu-MFI catalysts and non-zeolitic supported-copper solids  

Microsoft Academic Search

The selective reduction of NO by C3H8 is performed on copper-based catalysts: Cu\\/Al2O3, Cu\\/SiO2, Cu\\/SiO2–Al2O3 solids, fresh and hydrothermally-treated Cu-MFI with various Si\\/Al ratios. For all the Cu-MFI solids and for the non-zeolitic\\u000a supported-copper solids with low copper loadings, O2 promotes the reduction of NO. The C3H8–NO reaction rate correlates with the number of accessible and isolated Cun+ ions deduced

Zakaria Chajar; Valérie Le Chanu; Michel Primet; Hélène Praliaud

1998-01-01

370

Continuous Isosorbide Production From Sorbitol Using Solid Acid Catalysis  

SciTech Connect

This is a final report for a project funded by the US Department of Agriculture and managed by the US Department of Energy. The Iowa Corn Promotion Board was the principal contracting entity for the grant. The Iowa Corn Promotion Board subcontracted with General Electric, Pacific Northwest National Lab and New Jersey Institute of Technology to conduct research in this project. The Iowa Corn Promotion Board and General Electric provided cost share for the project. The purpose of this diverse collaboration was to integrate both the conversion and the polymer applications into one project and increase the likelihood of success. This project has led to additional collaborations among other polymer companies. The goals of the project were to develop a renewable route to isosorbide for commercialization that is economically competitive with all existing production technologies and to develop new applications for isosorbide in various products such as polymers and materials. Under this program a novel process for the production of isosorbide was developed and evaluated. The novel process converts corn based sorbitol into isosorbide using a solid catalyst with integrated water removal and product recovery. In addition the work under this program has identified several novel products based on isosorbide chemistries. These market applications include: epoxy resins, UV stabilizers, plasticizers and polyesters. These market applications have commercial interest within the current polymer industry. This report contains an overview summary of the accomplishments. Six inventions and four patent applications have been written as a result of this project. Additional data will be published in the patent applications. The data developed at New Jersey Institute of Technology was presented at two technical conferences held in June of 2006. Several companies have made inquiries about using this material in their products.

Williamson, R.; Holladay,J.; Jaffe, M.; Brunelle, D.

2006-09-29

371

Hydrotreating of coker light gas oil on Ti-HMS supported heteropolytungstic acid catalysts  

Microsoft Academic Search

Ti-HMS substrates were synthesized by using dodecylamine as structure-directing agents. A series of HPW\\/Ti-HMS catalysts with different Si\\/Ti ratios, promoted by Ni was prepared using Keggin-type heteropolyacids (H3PW12O40) as active phase precursors. These catalysts were compared with corresponding NiW\\/HMS catalysts prepared from the traditional precursors (ammonium metatungstate). Prepared supports and catalysts were characterized by small- and wide-angle XRD, N2 physisorption,

K. Soni; P. E. Boahene; K. Chandra Mouli; A. K. Dalai; J. Adjaye

2011-01-01

372

Organometallic catalysts for primary phosphoric acid fuel cells: Final report, 1981-1985  

Microsoft Academic Search

Cathode improvement, both in performance and cost, available through the use of a class of organometallic cathode catalysts, the tetraazaannulenes (TAAs), was investigated. A new mixed catalyst was identified which provides improved cathode performance without the need for the use of a noble metal. This mixed catalyst was tested under load for 1000 h in full cell at 160 to

Walsh

1987-01-01

373

Liquefaction of cellulose in the presence of phenol using p-toluene sulfonic acid as a catalyst  

Microsoft Academic Search

The kinetics of p-toluene sulfonic acid (PTSA)-catalyzed cellulose liquefaction in the presence of phenol were investigated at 130, 140 and 150°C. The resulting liquefied products were also analyzed to evaluate the effectiveness of PTSA as a catalyst during the phenol liquefaction. The liquefaction rate of PTSA was slightly lower than that of sulfuric acid (SA), which was used as a

Sung Phil Mun; Jeong Phil Jang

2009-01-01

374

Characterisation and acid properties of some modified combustion catalysts: Pt\\/alumina with barium and Pt\\/zirconia with yttrium  

Microsoft Academic Search

Platinum was deposited on alumina and zirconia, subjected or not to addition of barium or yttrium, respectively. Surface acidic properties were probed by ammonia adsorption followed by FT-IR spectroscopy and temperature-programmed desorption (TPD) using an original inductive set-up for fast heating of the sample.The Pt\\/alumina sample exhibits 0.34 acid site per nm2. The addition of barium (14.8wt%) to this catalyst

V. Labalme; B. Béguin; F. Gaillard; M. Primet

2000-01-01

375

Design of reflective tantala optical coatings using sol-gel chemistry with ethanoic acid catalyst and chelator  

Microsoft Academic Search

Sol-gel processing of Ta(OC2H5)5 to produce tantala highly reflective (HR) coating has been systematically studied in the absence of inorganic anions using an ethanoic acid catalyst in part using IR. In the presence of ethanoic acid, both hydrolysis and chelation co-exist, depending on the preparative parameters; most of the precursor was found to be converted into an amorphous chemically modified

Y. Sun; P. A. Sermon; M. S. W. Vong

1996-01-01

376

Decomposition of Carboxylic Acids in Water by O3, O3\\/H2O2, and O3\\/Catalyst  

Microsoft Academic Search

This paper studies the decomposition of formic, oxalic and maleic acids by O3, O3\\/catalyst, and O3\\/H2O2. The catalytic effect of Co, Ni, Cu, Mn, Zn, Cr, and Fe ions is investigated. The results showed that—Co and Mn have the highest catalytic activity for the decomposition of oxalic acid while the catalytic effect of the studied ions is insignificant on the

Ahmed A. Abd El-Raady; Tsuyoshi Nakajima

2005-01-01

377

New solid superacid catalysts for n-butane isomerization: ?-Al 2O 3 or SiO 2 supported sulfated zirconia  

Microsoft Academic Search

Solid superacid catalysts SO42?\\/ZrO2 (SZ) supported on ?-Al2O3 and SiO2 (named SZ\\/Al2O3 and SZ\\/SiO2, respectively) were prepared by an impregnation method. Their catalytic behaviors of for n-butane isomerization at low temperature in steady state system and at high temperature in flow system were studied. Large improvements of catalytic activities were observed on the SZ\\/Al2O3 catalysts. In the flow system, the

T Lei; J. S Xu; Y Tang; W. M Hua; Z Gao

2000-01-01

378

Nanosized metal catalysts in electrodes for solid polymeric electrolyte fuel cells: an XPS and XRD study  

Microsoft Academic Search

Solid polymeric fuel cells (SPFC) are devices that are able to convert chemical energy into electric energy continuously without any ambient pollution. The electrodes of this type of cells are layered structures, composed of a carbon support, a diffusive layer and a catalytic layer, usually platinum clusters dispersed on amorphous carbon microparticles, whose properties, at atomic and molecular level, determine

R. Giorgi; P Ascarelli; S Turtù; V Contini

2001-01-01

379

Optimization of the preparation method of HSO 3-functionalized MCM-41 solid catalysts  

Microsoft Academic Search

In this work, a systematic study of the acid extraction of the surfactant present in MCM-41 mesoporous materials was carried out. Two organic solvent\\/acid mixtures were used at various temperatures and for different periods of time. Propylthiol groups were subsequently grafted onto the surface by reacting the mesoporous silica with 3-mercaptopropyltrimethoxysilane. The resulting organic matter loading is compared with the

Marcelo Boveri; Julia Aguilar-Pliego; Joaquín Pérez-Pariente; Enrique Sastre

2005-01-01

380

The influence of metal and carrier natures on the effectiveness of catalysts of the deoxygenation of fatty acids into hydrocarbons  

NASA Astrophysics Data System (ADS)

The activity and selectivity of palladium, copper, platinum, and nickel catalysts in the decarbonylation of stearic acid into hydrocarbons were studied at a 14 atm hydrogen pressure and temperatures of 300-350°C. If ?-alumina was used as a carrier, the catalysts formed the series Pd > Cu > Pt > Ni according to desired product yields. Quantum-chemical simulation was performed to show that the free energy of activation increased in the same series. The same metals deposited on mixed tungsten and zirconium oxides catalyzed decarbonylation with a low yield of C17 hydrocarbons, likely because such a superacidic carrier could catalyse cracking of olefins or their oligomers formed.

Berenblyum, A. S.; Shamsiev, R. S.; Podoplelova, T. A.; Danyushevsky, V. Ya.

2012-08-01

381

Selektive Reaktionsfuehrung an festen Katalysatoren. Bericht 1989-1991. (Selective reactions on solid state catalysts. Report 1989-1991).  

National Technical Information Service (NTIS)

This report of the Special Research Department 250 of Karlsruhe University describes catalyst production, catalyst, and reactors for hydrocarbon conversion. After a general outline, the individual projects are described. (BBR).

1991-01-01

382

Pt, Pd and Au nanoparticles supported on a DNA-MMT hybrid: efficient catalysts for highly selective oxidation of primary alcohols to aldehydes, acids and esters.  

PubMed

Novel DNA-MMT hybrid supported metal nanoparticle catalysts, such as Pt/DNA-MMT, Pd/DNA-MMT, Au/DNA-MMT, were prepared for application in highly selective aerobic oxidation of primary alcohols to aldehydes, acids and esters, respectively. Taking advantage of the water-soluble reversibility of these catalysts, all the transformations could be performed smoothly in water and reuse of the catalysts has also been accomplished by a very simple phase separation process. PMID:23628847

Tang, Lin; Guo, Xuefeng; Li, Yunfeng; Zhang, Shuai; Zha, Zhenggen; Wang, Zhiyong

2013-06-01

383

Model reaction for the in situ characterization of the hydrogenating and acid properties of industrial hydrocracking catalysts  

SciTech Connect

A kinetic study of o-xylene transformation was carried out on a sulfided NiMo on Y zeolite catalyst during the hydrocracking of a model compound (n-heptane) under the following conditions of the process: high hydrogen pressure (5.7 MPa), presence of nitrogen and sulfur-containing compounds. o-Xylene inhibits n-heptane transformation, which can be explained by a competition for the adsorption on the acid sites between o-xylene and the olefinic intermediates of hydrocracking. The products of o-xylene transformation are the following: p- and m-xylenes (isomerization), toluene and trimethylbenzenes (disproportionation), and saturated C{sub 8} naphthenes (dimethylcyclohexane and trimethylcyclopentanes). It is shown that 1,3- and 1,4-dimethylcyclohexanes (and trimethylcyclopentanes) result from the isomerization of m- and p-xylenes. Therefore, the hydrogenating activity of hydrocracking catalysts can be characterized by the formation of dimethylyclohexanes and trimethylcyclopentanes. Furthermore, the isomerization of xylenes, which occurs through an acid mechanism, can be used for characterizing the acid activity of hydrocracking catalysts. This is not the case for disproportion whose rate depends on hydrogen pressure. The validity of o-xylene transformation for characterizing the acid and hydrogenating activities of bifunctional hydrocracking catalysts was confirmed by the use of a series of catalysts having either the same content of NiMo and different contents of zeolite or the same content of zeolite and different contents of NiMo. While the isomerization activity is strictly proportional to the zeolite content and independent of the NiMo content, and the hydrogenating activity is proportional to the NiMo content and independent of the zeolite content. 27 refs., 17 figs., 3 tabs.

Guisnet, M.; Thomazeau, C.; Lemberton, J.L. [Laboratoire de Catalyse en Chimie Organique, Poitiers (France); Mignard, S. [Institut Francais du Petrole, Rueil-Malmaison (France)

1995-01-01

384

High activity of acid-treated quail eggshell catalysts in the transesterification of palm oil with methanol.  

PubMed

The transesterification of palm oil with methanol was investigated over calcium oxide catalysts prepared by calcining eggshells of quail and chicken. Compared to chicken eggshell, the palisade layer of quail eggshell had more closely dispersed micron-sized pores. Following treatment with 0.005M HCl solution for 2h to remove its dense cuticle layer and subsequent calcination above 800 degrees C, the quail eggshell had a large amount of strong basic sites and showed high catalytic activity comparable to that of potassium methoxide in the transesterification. The acid-treated, quail eggshell catalyst steadily maintained high conversions of over 98% during repeated fivefold usage at 65 degrees C with a reactant composed of methanol/oil (as mol)=12/1 and oil/catalyst (as g)=2/0.03. PMID:20621469

Cho, Yung Bok; Seo, Gon

2010-11-01

385

Stepwise engineering of a Pichia pastoris D-amino acid oxidase whole cell catalyst  

PubMed Central

Background Trigonopsis variabilis D-amino acid oxidase (TvDAO) is a well characterized enzyme used for cephalosporin C conversion on industrial scale. However, the demands on the enzyme with respect to activity, operational stability and costs also vary with the field of application. Processes that use the soluble enzyme suffer from fast inactivation of TvDAO while immobilized oxidase preparations raise issues related to expensive carriers and catalyst efficiency. Therefore, oxidase preparations that are more robust and active than those currently available would enable a much broader range of economically viable applications of this enzyme in fine chemical syntheses. A multi-step engineering approach was chosen here to develop a robust and highly active Pichia pastoris TvDAO whole-cell biocatalyst. Results As compared to the native T. variabilis host, a more than seven-fold enhancement of the intracellular level of oxidase activity was achieved in P. pastoris through expression optimization by codon redesign as well as efficient subcellular targeting of the enzyme to peroxisomes. Multi copy integration further doubled expression and the specific activity of the whole cell catalyst. From a multicopy production strain, about 1.3 × 103 U/g wet cell weight (wcw) were derived by standard induction conditions feeding pure methanol. A fed-batch cultivation protocol using a mixture of methanol and glycerol in the induction phase attenuated the apparent toxicity of the recombinant oxidase to yield final biomass concentrations in the bioreactor of ? 200 g/L compared to only 117 g/L using the standard methanol feed. Permeabilization of P. pastoris using 10% isopropanol yielded a whole-cell enzyme preparation that showed 49% of the total available intracellular oxidase activity and was notably stabilized (by three times compared to a widely used TvDAO expressing Escherichia coli strain) under conditions of D-methionine conversion using vigorous aeration. Conclusions Stepwise optimization using a multi-level engineering approach has delivered a new P. pastoris whole cell TvDAO biocatalyst showing substantially enhanced specific activity and stability under operational conditions as compared to previously reported preparations of the enzyme. The production of the oxidase through fed-batch bioreactor culture and subsequent cell permeabilization is high-yielding and efficient. Therefore this P. pastoris catalyst has been evaluated for industrial purposes.

2010-01-01

386

Nature of the acid sites of supported sulfate catalysts for the skeletal isomerization of n-pentenes  

SciTech Connect

The influence of the degree of dehydration of a sample of NiSO/sub 4//SiO/sub 2/ (7.3% Ni) on its activity in the skeletal isomerization of n-pentenes, the total acidity, and the ratio between the brnsted (B) and Lewis (L) sites, which was determined from the IR spectra of chemisorbed pyridine, has been studied. As the calcination temperature of the catalyst is increased from 150 to 300 degree C, the total acidity, as well as the B/L ratio, change only slightly, but they decrease sharply at higher calcination temperatures. It may be postulated that the decrease in the total acidity of the catalyst is due to the reduction of the number of B sites. The symbatic variation of the activity shows that the B sites are responsible for the occurrence of skeletal isomerization.

Isagulyants, G.V.; Gitis, K.M.; Kharson, M.S.; Kornyshev, V.N.

1985-10-01

387

Generation of WO{sub 3}-ZrO{sub 2} catalysts from solid solutions of tungsten in zirconia  

SciTech Connect

WO{sub 3}-ZrO{sub 2} samples were obtained by precipitating zirconium oxynitrate in presence of WO{sub 4} {sup =} species in solution from ammonium metatungstate at pH=10.0. Samples were characterized by atomic absorption spectroscopy, thermal analysis, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy and energy filtered-TEM. The ammonia retained in the dried sample produced a reductive atmosphere to generate W{sup 5+} ions coexisting with W{sup 6+} ions to produce a solid solution of tungsten in the zirconia lattice to stabilize the zirconia tetragonal phase when the sample was annealed at 560 deg. C. When the sample was annealed at 800 deg. C, the W atoms near crystallite surface were oxidized to W{sup 6+}, producing patches of WO{sub 3} on the zirconia crystallite. The HR-TEM analysis confirmed the existence of the solid solution when the sample was annealed at 560 deg. C, and two types of crystalline regions were identified: One with nearly spherical morphology, an average diameter of 8 nm and the atomic distribution of tetragonal zirconia. The second one had a non-spherical morphology with well-faceted faces and dimensions larger than 30 nm, and the atom distribution of tetragonal zirconia. When samples were annealed at 800 deg. C two different zirconia crystallites were formed: Those where only part of the dissolved tungsten atoms segregated to crystallite surface producing patches of nanocrystalline WO{sub 3} on the crystallite surface of tetragonal zirconia stabilized with tungsten. The second type corresponded to monoclinic zirconia crystallites with patches of nanocrystalline WO{sub 3} on their surface. The tungsten segregation gave rise to the WO{sub 3}-ZrO{sub 2} catalysts. - Graphical abstract: WO {sub x} -ZrO{sub 2} catalysts were obtained by precipitating zirconium oxynitrate in presence of WO{sub 4} {sup =}species. Initially, the W atoms remained inside the crystallite after annealing at 560 deg. C in a reduced oxidation state (W{sup 5+}), whereas, the sample annealed at 800 deg. C, the W atoms migrate from the bulk to the surface, forming a layer of W atoms on a ZrO{sub 2} core, with the consequent oxidation to W{sup 6+}, producing patches of nanocrystalline WO{sub 3} with dimension smaller than 3 nm.

Cortes-Jacome, Maria A. [Instituto Mexicano del Petroleo. Prog. Ingenieria Molecular, Eje Central L. Cardenas 152, 07730 Mexico D.F. (Mexico); Angeles-Chavez, Carlos [Instituto Mexicano del Petroleo. Prog. Ingenieria Molecular, Eje Central L. Cardenas 152, 07730 Mexico D.F. (Mexico); Bokhimi, Xim [Institute of Physics, National University of Mexico (UNAM), A. P. 20-364, 01000 Mexico D.F. (Mexico); Toledo-Antonio, J.A. [Instituto Mexicano del Petroleo. Prog. Ingenieria Molecular, Eje Central L. Cardenas 152, 07730 Mexico D.F. (Mexico)]. E-mail: jtoledo@imp.mx

2006-08-15

388

Brown algae hydrolysis in 1-n-butyl-3-methylimidazolium chloride with mineral acid catalyst system.  

PubMed

The amenability of three brown algal species, Sargassum fulvellum, Laminaria japonica and Undaria pinnatifida, to hydrolysis were investigated using the ionic liquid (IL), 1-n-butyl-3-methylimidazolium chloride ([BMIM]Cl). Compositional analyses of the brown algae reveal that sufficient amounts of sugars (15.5-29.4 wt.%) can be recovered. Results from hydrolysis experiments show that careful selection of the type of mineral acid as catalyst and control of acid loading could maximize the recovery of sugars. Optimal reaction time and temperature were determined from the kinetic studies on the sequential reducing sugar (TRS) formation and degradation. Optimal reaction times were determined based on the extent of furfurals formation as TRS degradation products. X-ray diffraction and environmental scanning electron microscopy confirmed the suitability of [BMIM]Cl as solvent for the hydrolysis of the three brown algae. Overall results show the potential of brown algae as renewable energy resources for the production of valuable chemicals and biofuels. PMID:22721878

Malihan, Lenny B; Nisola, Grace M; Chung, Wook-Jin

2012-05-26

389

Production of methacrylic acid by vapor-phase aldol condensation of propionic acid with formaldehyde over silica-supported metal phosphate catalysts  

Microsoft Academic Search

The vapor-phase aldol condensation of propionic acid (PA) with formaldehyde (HCHO) to form methacrylic acid (MAA) was performed with a PA\\/HCHO molar ratio of 2 using various silica-supported metal phosphate catalysts. In the absence of water, a silica-supported tin phosphate with Sn\\/Si\\/P atomic ratio of 1\\/8\\/2.3 showed the same level of performance as a silica-supported vanadium phosphate with V\\/Si\\/P atomic

Mamoru Ai; Hideyuki Fujihashi; Sanae Hosoi; Akiyo Yoshida

2003-01-01

390

The outer-coordination sphere: incorporating amino acids and peptides as ligands for homogeneous catalysts to mimic enzyme function  

SciTech Connect

Great progress has been achieved in the field of homogeneous transition metal-based catalysis, however, as a general rule these solution based catalysts are still easily outperformed, both in terms of rates and selectivity, by their analogous enzyme counterparts, including structural mimics of the active site. This observation suggests that the features of the enzyme beyond the active site, i.e. the outer-coordination sphere, are important for their exceptional function. Directly mimicking the outer-coordination sphere requires the incorporation of amino acids and peptides as ligands for homogeneous catalysts. This effort has been attempted for many homogeneous catalysts which span the manifold of catalytic reactions and often require careful thought regarding solvent type, pH and characterization to avoid unwanted side reactions or catalyst decomposition. This article reviews the current capability of synthesizing and characterizing this often difficult category of metal-based catalysts. This work was funded by the DOE Office of Science Early Career Research Program through the Office of Basic Energy Sciences. Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.

Shaw, Wendy J.

2012-10-09

391

Catalytic Synthesis of Oxygenates: Mechanisms, Catalysts and Controlling Characteristics  

SciTech Connect

This research focused on catalytic synthesis of unsymmetrical ethers as a part of a larger program involving oxygenated products in general, including alcohols, ethers, esters, carboxylic acids and their derivatives that link together environmentally compliant fuels, monomers, and high-value chemicals. The catalysts studied here were solid acids possessing strong Br�������¸nsted acid functionalities. The design of these catalysts involved anchoring the acid groups onto inorganic oxides, e.g. surface-grafted acid groups on zirconia, and a new class of mesoporous solid acids, i.e. propylsulfonic acid-derivatized SBA-15. The former catalysts consisted of a high surface concentration of sulfate groups on stable zirconia catalysts. The latter catalyst consists of high surface area, large pore propylsulfonic acid-derivatized silicas, specifically SBA-15. In both cases, the catalyst design and synthesis yielded high concentrations of acid sites in close proximity to one another. These materials have been well-characterization in terms of physical and chemical properties, as well as in regard to surface and bulk characteristics. Both types of catalysts were shown to exhibit high catalytic performance with respect to both activity and selectivity for the bifunctional coupling of alcohols to form ethers, which proceeds via an efficient SN2 reaction mechanism on the proximal acid sites. This commonality of the dual-site SN2 reaction mechanism over acid catalysts provides for maximum reaction rates and control of selectivity by reaction conditions, i.e. pressure, temperature, and reactant concentrations. This research provides the scientific groundwork for synthesis of ethers for energy applications. The synthesized environmentally acceptable ethers, in part derived from natural gas via alcohol intermediates, exhibit high cetane properties, e.g. methylisobutylether with cetane No. of 53 and dimethylether with cetane No. of 55-60, or high octane properties, e.g. diisopropylether with blending octane No. of 105, and can replace aromatics in liquid fuels.

Kamil Klier; Richard G. Herman

2005-11-30

392

Alkali Doping Heterogeneous Catalysts.  

National Technical Information Service (NTIS)

Alkali doping mechanisms were considered: catalytic action of the alkali; creation of basic centers; neutralization of acid centers; alteration of the electronic properties of the catalyst surface; remedies for catalyst preparation; influencing the physic...

W. D. Mross

1983-01-01

393

Physically mixed LiLaNi–Al 2O 3 and copper as conductive anode catalysts in a solid oxide fuel cell for methane internal reforming and partial oxidation  

Microsoft Academic Search

Different concentrations of copper are added to LiLaNi–Al2O3 to improve the electronic conductivity property for application as the materials of the anode catalyst layer for solid oxide fuel cells operating on methane. Their catalytic activity for the methane partial oxidation, steam and CO2 reforming reactions at 600–850 °C is systematically investigated. Among the three catalysts, the LiLaNi–Al2O3\\/Cu (50:50, by weight) catalyst

Wei Wang; Chao Su; Ran Ran; Hee Jung Park; Chan Kwak; Zongping Shao

2011-01-01

394

Oxidation of sulfur dioxide over supported solid V 2O 5\\/SiO 2 and supported molten salt V 2O 5–Cs 2SO 4\\/SiO 2 catalysts: molecular structure and reactivity  

Microsoft Academic Search

The molecular structure and reactivity of supported solid V2O5\\/SiO2 catalysts with 6.5 wt% V content and surface densities in the range 0.97–2.04 V atoms\\/nm2 have been studied by in situ Raman spectroscopy and activity measurements for the oxidation of SO2. Different sol–gel routes, resulting in variations of surface area and pore volume, were used for preparing the catalysts. These catalysts

Ioanna Giakoumelou; Vasile Parvulescu; Soghomon Boghosian

2004-01-01

395

Solvolysis and isomerization of phenyloxirane catalyzed with niobic acid  

Microsoft Academic Search

Solvolysis and isomerization of phenyloxirane were studied with niobic acid (Nb2O5.xH2O) as catalyst. In aqueous solution, niobic acid showed much higher hydrolysis performances in activity and selectivity than other solid acid catalysts. Selectivity of alcoholysis with methanol was much higher than that with other alcohols because of simultaneous isomerization and dehydration of alcohol.

Taka-aki Hanaoka; Kazuhiko Takeuchi; Takehiko Matsuzaki; Yoshihiro Sugi

1990-01-01

396

Solar photocatalytic treatment of landfill leachate using a solid mineral by-product as a catalyst.  

PubMed

The treatment of municipal solid waste landfill leachate in a pilot plant made up of solar compound parabolic collectors, using a solid industrial titanium by-product (WTiO(2)) containing TiO(2) and Fe(III) as a photocatalyst, was investigated. In the study evidence was found showing that the degradation performed with WTiO(2) was mainly due to the Fe provided by this by-product, instead of TiO(2). However, although TiO(2) had very little effect by itself, a synergistic effect was observed between Fe and TiO(2). The application of WTiO(2), which produced coupled photo-Fenton and heterogeneous catalysis reactions, achieved a surprisingly high depuration level (86% of COD removal), higher than that reached by photo-Fenton using commercial FeSO(4) (43%) in the same conditions. After the oxidation process the biodegradability and toxicity of the landfill leachate were studied. The results showed that the leachate biodegradability was substantially increased, at least in the first stages of the process, and again that WTiO(2) was more efficient than FeSO(4) in terms of increasing biodegradability. PMID:22633861

Poblete, Rodrigo; Prieto-Rodríguez, Lucia; Oller, Isabel; Maldonado, Manuel I; Malato, Sixto; Otal, Emilia; Vilches, Luis F; Fernández-Pereira, Constantino

2012-05-23

397

Catalyst functionalized buffer sorbent pebbles for rapid separation of carbon dioxide from gas mixtures  

DOEpatents

A method for separating CO.sub.2 from gas mixtures uses a slurried media impregnated with buffer compounds and coating the solid media with a catalyst or enzyme that promotes the transformation of CO.sub.2 to carbonic acid. Buffer sorbent pebbles with a catalyst or enzyme coating are provided for rapid separation of CO.sub.2 from gas mixtures.

Aines, Roger D.

2013-03-12

398

Kinetic relationships in conversion of 3-methyl-1,3-butanediol on phosphoric acid catalyst with added sodium phosphate  

SciTech Connect

By means of pulse chromatography on a phosphoric acid catalyst consisting of a mixture of phosphoric acid and sodium phosphates supported on quartz, a study has been made of the acid-catalyzed conversions of 3-methyl-1,3-butanediol (MBD) at 120-150/sup 0/C. It has been established that the principal products are isoprene and isopropenylethyl alcohol; at long contact times, the alcohol is also dehydrated to isoprene. It has been shown that the reaction of MBD conversion is irreversible and is first-order with respect to the reactant. Rate constants have been determined for individual stages of the process.

Malinskii, V.S.; Vinnik, M.I.

1988-01-01

399

Preparation of high energy fuel JP-10 by acidity-adjustable chloroaluminate ionic liquid catalyst  

Microsoft Academic Search

The isomerization of endo-tetrahydrodicyclopentadiene (endo-THDCPD) to its exo-isomer (JP-10) has been investigated by using chloroaluminate ionic liquids (ILs) as catalysts. The catalyst activity and selectivity could be optimized by varying the mole fraction of AlCl3 in the IL. Undesirable by-products derived from side-reactions such as skeletal rearrangement, alkylation, cracking, and dimerization could be minimized by appropriate catalyst design and adjustment

Ming-Yu Huang; Jung-Chung Wu; Fuh-Sheng Shieu; Jiang-Jen Lin

2011-01-01

400

Dehydration of aliphatic alcohols on phosphoric acid catalyst with the addition of calcium phosphate  

Microsoft Academic Search

The kinetic regularities of dehydration of sec- and tert-butyl alcohols on a catalyst consisting of a mixture of calcium phosphate and HâPOâ, deposited on molten quartz were studied by pulsed gas chromatography. At an equal water vapor pressure in the system, the activity of a catalyst consisting of a pure HâPOâ is higher than that of a catalyst with the

P. A. Obraztsov; O. E. Batalin; V. S. Malinskii; L. F. Shubenok; M. I. Vinnik

1986-01-01

401

High efficient electrocatalytic oxidation of formic acid on Pt\\/polyindoles composite catalysts  

Microsoft Academic Search

Four novel composite catalysts have been developed by the electrodeposition of Pt onto glassy carbon electrode (GCE) modified with polyindoles: polyindole, poly(5-methoxyindole), poly(5-nitroindole) and poly(5-cyanoindole). As-formed composite catalysts are characterized by SEM, XRD and electrochemical analysis. Compared with Pt nanoparticles, respectively, deposited on the bare GCE and on the GCE modified with polypyrrole, the four newly developed composite catalysts exhibit

Weiqiang Zhou; Yukou Du; Hongmei Zhang; Jingkun Xu; Ping Yang

2010-01-01

402

Resonance Raman and surface- and tip-enhanced Raman spectroscopy methods to study solid catalysts and heterogeneous catalytic reactions.  

SciTech Connect

Resonance Raman (RR) spectroscopy has several advantages over the normal Raman spectroscopy (RS) widely used for in situ characterization of solid catalysts and catalytic reactions. Compared with RS, RR can provide much higher sensitivity and selectivity in detecting catalytically-significant surface metal oxides. RR can potentially give useful information on the nature of excited states relevant to photocatalysis and on the anharmonic potential of the ground state. In this critical review a detailed discussion is presented on several types of RR experimental systems, three distinct sources of so-called Raman (fluorescence) background, detection limits for RR compared to other techniques (EXAFS, PM-IRAS, SFG), and three well-known methods to assign UV-vis absorption bands and a band-specific unified method that is derived mainly from RR results. In addition, the virtues and challenges of surface-enhanced Raman spectroscopy (SERS) are discussed for detecting molecular adsorbates at catalytically relevant interfaces. Tip-enhanced Raman spectroscopy (TERS), which is a combination of SERS and near-field scanning probe microscopy and has the capability of probing molecular adsorbates at specific catalytic sites with an enormous surface sensitivity and nanometre spatial resolution, is also reviewed.

Kim, H.; Kosuda, K. M.; Van Duyne, R. P.; Stair, P. C. (Chemical Sciences and Engineering Division); (Northwestern Univ.)

2010-01-01

403

Noble metal catalysts highly-dispersed on Sm-doped ceria for the application to internal reforming solid oxide fuel cells operated at medium temperature  

Microsoft Academic Search

Steam reforming of CH4 on microcrystalline metal catalysts dispersed on Sm-doped ceria (SDC) was investigated with the intention of the application to an anode for internal reforming-type solid oxide fuel cells to be operated at medium temperature. Ru- or Ir-dispersed SDC exhibited high catalytic activities and low activation energies; these are potential candidates for that application. The high dispersion of

Margarida J. Saeki; Hiroyuki Uchida; Masahiro Watanabe

1994-01-01

404

A comprehensive evaluation of a Ni–Al 2O 3 catalyst as a functional layer of solid-oxide fuel cell anode  

Microsoft Academic Search

An inexpensive 7wt.% Ni–Al2O3 composite is synthesized by a glycine–nitrate process and systematically investigated as anode catalyst layer of solid-oxide fuel cells operating on methane fuel by examining its catalytic activity towards methane partial oxidation, steam and CO2 reforming at 600–850°C, cell performance, mechanical performance, and carbon deposition properties. Ni–Al2O3 shows comparable catalytic activities to Ru–CeO2 for the above three

Wei Wang; Chao Su; Yuzhou Wu; Ran Ran; Zongping Shao

2010-01-01

405

Catalytic oxidation of methane over CeO 2-ZrO 2 mixed oxide solid solution catalysts prepared via urea hydrolysis  

Microsoft Academic Search

In this study, CeO2-ZrO2 mixed oxide catalysts were prepared via urea hydrolysis and tested for methane oxidation. Highly uniform solid solution particles of ceria-zirconia were obtained under the conditions of this study. The incorporation of Zr into the CeO2 lattice was found to promote the redox properties. The methane oxidation activity of the mixed oxides was found to be dependent

Sitthiphong Pengpanich; Vissanu Meeyoo; Thirasak Rirksomboon; Kunchana Bunyakiat

2002-01-01

406

Heterogeneous liquid-phase hydration of isobutene by heteropoly acid–polymer composite film catalyst  

Microsoft Academic Search

H3PMo12O40-polymer composite film catalysts were prepared by blending these two materials using a methanol–chloroform mixture by a membrane\\u000a preparation technique. Polyphenylene oxide (PPO), polyethersulfone (PES) and polysulfone (PSF) were used as blending polymers.\\u000a A H3PMo12O40-PPO composite catalyst coated on Al2O3 was also prepared. These catalysts were used as heterogeneous catalysts for the liquid-phase tert-butanol (TBA) synthesis\\u000a from isobutene and water.

Seong Soo Lim; Yong Heon Kim; Gyo Ik Park; Wha Young Lee; In Kyu Song; Hyun Ki Youn

1999-01-01

407

Nano-Structured Solids and Heterogeneous Catalysts: Powerful Tools for the Reduction of CBRN Threats  

NASA Astrophysics Data System (ADS)

In the field of non-conventional CBRN weapons, the recent rapid development of nanotechnology and catalysis over nanosized solids provides innovative tools for the detection, protection and decontamination against these threats. By improving the efficiency of the countermeasures and by minimizing the negative effects of a deliberate use of CBRN agents, the practical application of the new technologies will readily represent a step forward in lowering the vulnerability of the civilian populations and in preventing the use of mass destruction weapons by terrorist groups or by `rogue states' supporting terrorists' activity. In such scenario, some relevant examples of nanosystems applied to the defense from non-conventional warfare agents will be here presented and commented. The key role of nanotechnology and heterogeneous catalysis for a multidisciplinary approach in counteracting CBRN threats will be highlighted too.

Guidotti, M.; Rossodivita, A.; Ranghieri, M. C.

408

Effect of sulfation methods on TiO 2–SiO 2 sol–gel catalyst acidity  

Microsoft Academic Search

A series of x TiO2–SiO2 (x=1.7, 4.0 and 6.7wt.% TiO2) binary mixed oxides was prepared by a sol–gel method in acidic and basic conditions. In order to upgrade the acidic properties of the obtained solids, their sulfation was carried out in three different ways: (1) by in situ (H2SO4 was admixed with the gel), (2) impregnating the dried solids with

T López; P Bosch; F Tzompantzi; R Gómez; J Navarrete; E López-Salinas; M. E Llanos

2000-01-01

409

Azido Acids in a Novel Method of SolidPhase Peptide Synthesis  

Microsoft Academic Search

Azido acids were produced from ?-branched acids by ?-bromination with NBS followed by substitution with sodium azide and the products were used in a novel method of solid-phase synthesis. The azido acids were transformed into the highly activated acid chlorides and used synthesis of extremely hindered peptides containing up to four successive diphenyl glycine or Aib residues. By reaction of

Maria A Juliano; Anita M Jansson

1997-01-01

410

Synthesis of methyl esters from palm (Elaeis guineensis) oil using cobalt doped MgO as solid oxide catalyst.  

PubMed

The potential of Mg(x)Co(2-)(x)O(2) as heterogeneous reusable catalyst in transesterification of palm oil to methyl ester was investigated. The catalyst was prepared via co-precipitation of the metal hydroxides at different Mg-Co ratios. Mg(1.7)Co(0.3)O(2) catalyst was more active than Mg(0.3)Co(1.7)O(2) in the transesterification of palm oil with methanol. The catalysts calcined at temperature 300 °C for 4 h resulted in highly active oxides and the highest transesterification of 90% was achieved at methanol/oil molar ratio of 9:1, catalyst loading of 5.00 wt.%, reaction temperature of 150 °C and reaction time of 2 h. The catalyst could easily be removed from reaction mixture, but showed 50% decrease in activity when reused due to leaching of active sites. PMID:21855332

Rahman, Nur Ashikin Ab; Olutoye, M A; Hameed, B H

2011-07-22

411

Dynamic behavior of reaction intermediates on catalyst surfaces in the working state: Behavior of formate ion during the decomposition of formic acid on Ni\\/SiO 2 catalyst  

Microsoft Academic Search

The reactivity of the formate ions on Ni\\/SiO2 catalyst was examined during the course of the formic acid decomposition. It is of great interest to note that the reactivity was markedly increased by the presence of formic acid in the ambient gas compared to that at the same coverage under vacuum. It is accordingly suggested that the formate ion behaves

Keiko Takahashi; Etsuko Miyamoto; Kikuo Shoji; Kenzi Tamaru

1988-01-01

412

N -alkylation of aniline with ethanol over an industrial niobic acid catalyst – influence of water formation on kinetics and selectivity  

Microsoft Academic Search

The reaction of aniline with ethanol was carried out over an industrial niobic acid catalyst in a fixed bed reactor at atmospheric pressure and 220–260 °C. The main products, N-ethylaniline and N,N-diethylaniline were formed consecutively. A kinetic study including a model discrimination between several Hougen\\/Watson type rate equations led to an Eley\\/Rideal mechanism, where the reaction of gas phase aniline with

B. Frank; D. Habel; R. Schomäcker

2005-01-01

413

Photocatalytic degradation of Acid Red 1 dye using ZnO catalyst in the presence and absence of silver  

Microsoft Academic Search

The investigation of the degradation of Acid Red 1 (AR1) dye was carried out in an aqueous suspension photoreactor. Different parameters that affect the degradation of AR1 dye such as the presence and absence of a photocatalyst, light source, air, catalyst loading, initial substrate concentration were studied. The activity of Ag-doped ZnO prepared by photoreduction of Ag ion on ZnO

B. H. Hameed; U. G. Akpan; K. P. Wee

2011-01-01

414

A Simple, Efficient Synthesis of 2-Aryl Benzimidazoles Using Silica Supported Periodic Acid Catalyst and Evaluation of Anticancer Activity  

PubMed Central

A new, efficient method for the synthesis of 2-aryl substituted benzimidazole by using silica supported periodic acid (H5IO6-SiO2) as a catalyst has been developed. The salient feature of the present method includes mild reaction condition, short reaction time, high yield and easy workup procedure. The synthesized benzimidazoles exhibited potent anticancer activity against MCF7 and HL60 cell lines.

Sontakke, Vyankat A.; Ghosh, Sougata; Lawande, Pravin P.; Chopade, Balu A.; Shinde, Vaishali S.

2013-01-01

415

One-pot three-component Mannich-type reactions using Sulfamic acid catalyst under ultrasound irradiation  

Microsoft Academic Search

Sulfamic acid (NH2SO3H, SA) was used as an efficient, inexpensive, non-toxic and recyclable green catalyst for the ultrasound-assisted one-pot Mannich reaction of aldehydes with ketones and amines. This ultrasound protocol has advantages of high yield, mild condition, no environmental pollution, and simple work-up procedures. Most importantly, ?-aminocarbonyl compounds with ortho-substituted aromatic amines are obtained in acceptable to good yields by

Hongyao Zeng; Hua Li; Huawu Shao

2009-01-01

416

Double bond isomerization of olefin-containing feeds with minimal oligomerization using surface acidity deactivated zeolite catalysts  

SciTech Connect

A method is described for double bond isomerization of alpha-olefin-containing organic feedstock with minimal oligomerization which comprises contacting said feedstock under double bond isomerization conditions with a double bond isomerization catalyst comprising a zeolite having a Constraint Index of 1 to 12 whose surface has been at least partially deactivated for acid catalyzed reactions by chemisorption of an alkyl-substituted pyridine surface-deactivating agent which possesses an average cross section diameter greater than that of the zeolite pores.

Haag, W.O.; Heck, R.H.; Santiesteban, J.G.; Shihabi, D.S.

1993-08-17

417

Double bond isomerization of olefin-containing feeds with minimal oligomerization using surface acidity deactivated zeolite catalysts  

Microsoft Academic Search

A method is described for double bond isomerization of alpha-olefin-containing organic feedstock with minimal oligomerization which comprises contacting said feedstock under double bond isomerization conditions with a double bond isomerization catalyst comprising a zeolite having a Constraint Index of 1 to 12 whose surface has been at least partially deactivated for acid catalyzed reactions by chemisorption of an alkyl-substituted pyridine

W. O. Haag; R. H. Heck; J. G. Santiesteban; D. S. Shihabi

1993-01-01

418

Catalytic Reduction of Nitrate by Pd\\/SnO2 Catalyst Using Formic Acid as Reducing Agent  

Microsoft Academic Search

In current study, the Pd\\/SnO2 catalyst had been prepared successfully by using precipitation method and its characters were analyzed by XRD (X-ray diffraction), SEM (Transmission electron microscopy) and Specific surface area analyzer etc. The catalytic reduction of nitrate (100ppm) in deionized water was investigated in a batch reactor at room temperature and atmospheric pressure, with formic acid (FA) used as

Yibao Wu; Yongyou Hu; Jianhua Cheng; Yanni Guo

2010-01-01

419

Solvent-Free Tetrahydropyranylation of Alcohols with Sulfamic Acid as Reusable Catalyst  

Microsoft Academic Search

An efficient H2NSO3H-catalyzed solvent-free tetrahydropyranylation of various alcohols at room temperature was investigated. The features of mild conditions, cost-efficient catalyst, simple work-up, and the recyclability of the catalyst were displayed in this article.

Bo Wang; Li-Ming Yang; Ji-Shuan Suo

2003-01-01

420

Aluminum Chlorhydroxide-Phosphoric Acid Catalyst System for Flash Cure Treatments to Give Improved Durable-Press Properties in Cellulose-Containing Textiles.  

National Technical Information Service (NTIS)

In this patent application an aluminum chlorhydroxide-phosphoric acid catalyst system has been devised that is practical for treatments of cellulose-containing textile materials with formaldehyde and formaldehyde-amide adducts under flash curing condition...

R. M. H. Kullman R. M. Reinhardt

1976-01-01

421

Arenesulfonic acid functionalized mesoporous silica as a novel acid catalyst for the liquid phase Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam  

Microsoft Academic Search

Beckmann rearrangement of cyclohexanone oxime to ?-caprolactam was performed in liquid phase for the first time on arenesulfonic acid-functionalized SBA-15 (SBA-ar-SO3H) mesoporous silica with different loadings of the acid. The catalysts were prepared via co-condensation of 2-(4-chlorosulfonylphenyl)ethyltrimethoxysilane (CSPTMS) and tetraethyl orthosilicate (TEOS) in the presence of Pluronic 123 (EO20PO70EO20) and characterized by XRD, N2 adsorption–desorption, TGA, EA and acid–base titration

Xueguang Wang; Chin-Chang Chen; Shih-Yuan Chen; Yun Mou; Soofin Cheng

2005-01-01

422

The effect of the distance between acidic site and basic site immobilized on mesoporous solid on the activity in catalyzing aldol condensation  

SciTech Connect

Acid-base bifunctional heterogeneous catalysts containing carboxylic and amine groups, which were immobilized at defined distance from one another on the mesoporous solid were synthesized by immobilizing lysine onto carboxyl-SBA-15. The obtained materials were characterized by X-ray diffraction (XRD), N{sub 2} adsorption, Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), scanning electron micrographs (SEM), transmission electron micrographs (TEM), elemental analysis, and back titration. Proximal-C-A-SBA-15 with a proximal acid-base distance was more active than maximum-C-A-SBA-15 with a maximum acid-base distance in aldol condensation reaction between acetone and various aldehydes. It appears that the distance between acidic site and basic site immobilized on mesoporous solid should be an essential factor for catalysis optimization. -- Graphical abstract: Proximal-C-A-SBA-15 with a proximal acid-base distance and maximum-C-A-SBA-15 with a maximum acid-base distance were synthesized by immobilizing lysine onto carboxyl-SBA-15. Display Omitted Research highlights: {yields} Proximal-C-A-SBA-15 with a proximal acid-base distance. {yields} Maximum-C-A-SBA-15 with a maximum acid-base distance. {yields} Compared to maximum-C-A-SBA-15, proximal-C-A-SBA-15 was more active toward aldol condensation reaction between acetone and various aldehydes.

Yu Xiaofang [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Yu Xiaobo [China Pharmaceutical University, Nanjing 210009 (China); Wu Shujie; Liu Bo; Liu Heng [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Guan Jingqi, E-mail: guanjq@jlu.edu.c [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China); Kan Qiubin, E-mail: catalysischina@yahoo.com.c [College of Chemistry, Jilin University, Jiefang Road 2519, Changchun 130023 (China)

2011-02-15

423

Sulfonic Acid Functionalized Nano-?-Al2O3: A New, Efficient, and Reusable Catalyst for Synthesis of 3-Substituted-2H-1,4-Benzothiazines  

PubMed Central

A simple and efficient synthetic protocol has been developed for the synthesis of 3-substituted-2H-1,4-benzothiazines by using a novel sulfonic acid functionalized nano-?-Al2O3 catalyst, devoid of corrosive acidic, and basic reagents. The developed method has the advantages of good to excellent yields, short reaction times, operational simplicity, and a recyclable catalyst. The catalyst can be prepared by a simple procedure from inexpensive and readily available nano-?-Al2O3 and has been shown to be recoverable and reusable up to six cycles without any loss of activity.

Li, Wei Lin; Tian, Shuan Bao; Zhu, Feng

2013-01-01

424

Recovery of coal liquefaction catalysts  

SciTech Connect

Metal constituents are recovered from the heavy bottoms produced during the liquefaction of coal and similar carbonaceous solids in the presence of a catalyst containing a metal capable of forming an acidic oxide by burning the heavy bottoms in a combustion zone at a temperature below the fusion temperature of the ash to convert insoluble metal-containing catalyst residues in the bottoms into soluble metal-containing oxides; contacting the oxidized solids formed in the combustion zone with an aqueous solution of a basic alkali metal salt to extract the soluble metal-containing oxides in the form of soluble alkali metal salts of the metal-containing oxides and recycling the soluble alkali metal salts to the liquefaction zone. In a preferred embodiment of the invention, the bottoms are subjected to partial oxidation, pyrolysis, coking, gasification, extraction or a similar treatment process to recover hydrocarbon liquids and/or gases prior to the burning or combustion step.

Francis, J.N.; Veluswamy, L.R.

1983-11-29

425

Acidity and acid catalysis of polyatom-substituted H n PW 11 M 1 O 40 (M=V, Nb, Ta, and W) Keggin heteropolyacid catalysts  

Microsoft Academic Search

Acidity of polyatom-substituted H\\u000a n\\u000a PW11M1O40 (M=V, Nb, Ta, and W) Keggin heteropolyacids (HPAs) was measured by NH3-TPD experiments. Acidity decreased in the order of H3PW11W1O40>H4PW11V1O40>H4PW11Nb1O40>H4PW11Ta1O40. Vapor-phase dehydration of cyclohexanol was conducted as a model reaction to correlate the acidity with the acid catalysis\\u000a of HPA catalysts. Yield for cyclohexene (a product by acid catalysis) increased with increasing acidity of

Dong Ryul Park; Ung Gi Hong; Sun Ho Song; Jeong Gil Seo; Sung-Hyeon Baeck; Jin Suk Chung; In Kyu Song

2010-01-01

426

p-Hydroxybenzoic acid degradation by Fe\\/Pd-HNT catalysts with in situ generated hydrogen peroxide  

Microsoft Academic Search

Pd- and Fe\\/Pd-HNT were elaborated by successive ionic exchange and wet impregnation at room temperature of hydrogenotitanate nanotubes (HNT) nanomaterials. Hydrogen peroxide was generated in situ via reaction of oxygen and formic acid (FA) over Fe\\/Pd-HNT catalysts. A high p-hydroxybenzoic acid (p-HBz) mineralization was achieved (52%) using Fe\\/Pd-HNT\\/FA\\/O2\\/UV system compared to the simulated reaction using Fe\\/Pd-HNT\\/H2O2\\/UV system (34%). The rate

Asma Turki; Hafedh Kochkar; Gilles Berhault; Abdelhamid Ghorbel

2010-01-01

427

Catalytic wet-air oxidation of aqueous solutions of formic acid, acetic acid and phenol in a continuous-flow trickle-bed reactor over Ru\\/TiO 2 catalysts  

Microsoft Academic Search

Catalytic wet-air oxidation of aqueous solutions of formic acid, acetic acid and phenol was carried out in a trickle-bed reactor at T=328–523K and total pressures up to 50bar over various Ru\\/TiO2 catalysts. Complete oxidation of formic acid was obtained at mild operating conditions, and no catalyst deactivation occurred that could be attributed to the dissolution of active ingredient material. It

Albin Pintar; Jurka Batista; Tatjana Tišler

2008-01-01

428

Catalytic reactions of formate. 3. Noble metal chlorides as catalyst precursors for formic acid reactions  

Microsoft Academic Search

Noble metal chlorides (‘RuCl3·xH2O’, ‘RhCl3·3H2O’, PdCl2 and ‘IrCl3·xH2O’) have been evaluated as catalyst precursors for the decomposition (HCO2H ? H2 + CO2), dehydration (HCO2H ? H2O + CO) and air oxidation (2HCO2H + O2 ? 2H2O + 2CO2) of 88% HCO2H at 75–80 °C. RhCl3 under these conditions is an active oxidation catalyst but not an active decomposition catalyst. However,

R. Bruce King; Allen D. King; Nripendra K. Bhattacharyya

1995-01-01

429

Niobium, catalyst repair kit  

Microsoft Academic Search

This paper reports that niobium oxides, when small amounts are added to known catalysts, enhance catalytic activity and selectivity and prolong catalyst life. Moreover, niobium oxides exhibit a pronounced effect as supports of metal or metal oxide catalysts. Recently we found that the surface acidity of hydrated niobium pentoxide, niobic acid (NbâOâ {center dot} nHâO), corresponds to the acidity of

Tanabe

1991-01-01

430

Glutamic acid 160 is the acid-base catalyst of ?-xylosidase from Bacillus stearothermophilus T-6: a family 39 glycoside hydrolase  

Microsoft Academic Search

A ?-xylosidase from Bacillus stearothermophilus T-6 was cloned, overexpressed in Escherichia coli and purified to homogeneity. Based on sequence alignment, the enzyme belongs to family 39 glycoside hydrolases, which itself forms part of the wider GH-A clan. The conserved Glu160 was proposed as the acid-base catalyst. An E160A mutant was constructed and subjected to steady state and pre-steady state kinetic

Tsafrir Bravman; Adva Mechaly; Smadar Shulami; Valery Belakhov; Timor Baasov; Gil Shoham; Yuval Shoham

2001-01-01

431

Acid-base properties of copper(I) halides and their solid solutions  

SciTech Connect

Surface acidity and basicity of copper(I) halides and solid solutions of the CuBr-CuI system were studied. The nonuniformity of the surface with respect to acid-base properties was discovered. Surface acidity and basicity decrease in the sequence copper(I) bromide ..-->.. solid solutions ..-->.. copper(I) iodide. Concentrations and strengths of the acidic and basic centers were found. It was established that the principal contribution to surface acidity comes from Lewis centers, which are at the same time catalytically active centers for the decomposition of isopropyl alcohol.

Belousova, V.N.; Bugerko, L.N.

1987-03-01

432

Catalysts and Processes for Formaldehyde-Free Durable Press Finishing of Cotton Textiles with Polycarboxylic Acids.  

National Technical Information Service (NTIS)

The invention relates to new esterification catalysts and esterification processes for crosslinking cellulose as a means of imparting wrinkle resistance and smooth drying properties to cellulosic textiles without the use of formaldehyde or derivatives tha...

C. M. Welch B. K. Andrews

1988-01-01

433

Extraction of zirconium and hafnium from nitric acid solutions by solid extractant based on tributyl phosphate  

SciTech Connect

A study has been made of extraction equilibrium and kinetics and the influence of temperature and aqueous phase acidity on the extraction of zirconium and hafnium from nitric acid solutions by a solid extractant based on tributyl phosphate. Results are presented from pilot-plant experiments on Zr and Hf extraction from acidic pulps with high silicon contents, using pulsed columns.

Korovin, V.Yu.; Yagodin, G.A.; Savel`eva, V.I. [Dnieper Scientific Center, Dneprodzerzhinsk (Ukraine)

1994-10-20

434

An unprecedented (3,4,24)-connected heteropolyoxozincate organic framework as heterogeneous crystalline Lewis acid catalyst for biodiesel production  

PubMed Central

A novel 3D hexadecanuclear heteropolyoxozincate organic framework, IFMC-200, has been successfully synthesized based on a late transition metal-oxygen cluster. IFMC-200 not only represents the first example of (3,4,24)-connected framework but also contains the first 24-connected single metal cluster in a crystal structure. It exhibits superior thermal stability, good water-stability, and even insensitivity to the existence of acid and base within a certain range of pH values. Furthermore, it performs as a heterogeneous crystalline Lewis acid catalyst with good activity for the conversion of long-chain fatty acids rather than short-chain ones, and high recycling efficiency for esterification reaction of fatty acids with alcohols to produce biodiesel.

Du, Dong-Ying; Qin, Jun-Sheng; Sun, Zhong; Yan, Li-Kai; O'Keeffe, Michael; Su, Zhong-Min; Li, Shun-Li; Wang, Xiao-Hong; Wang, Xin-Long; Lan, Ya-Qian

2013-01-01

435

An unprecedented (3,4,24)-connected heteropolyoxozincate organic framework as heterogeneous crystalline Lewis acid catalyst for biodiesel production.  

PubMed

A novel 3D hexadecanuclear heteropolyoxozincate organic framework, IFMC-200, has been successfully synthesized based on a late transition metal-oxygen cluster. IFMC-200 not only represents the first example of (3,4,24)-connected framework but also contains the first 24-connected single metal cluster in a crystal structure. It exhibits superior thermal stability, good water-stability, and even insensitivity to the existence of acid and base within a certain range of pH values. Furthermore, it performs as a heterogeneous crystalline Lewis acid catalyst with good activity for the conversion of long-chain fatty acids rather than short-chain ones, and high recycling efficiency for esterification reaction of fatty acids with alcohols to produce biodiesel. PMID:24019078

Du, Dong-Ying; Qin, Jun-Sheng; Sun, Zhong; Yan, Li-Kai; O'Keeffe, Michael; Su, Zhong-Min; Li, Shun-Li; Wang, Xiao-Hong; Wang, Xin-Long; Lan, Ya-Qian

2013-09-10

436

Carbon-supported, selenium-modified ruthenium-molybdenum catalysts for oxygen reduction in acidic media.  

PubMed

The stability and oxygen reduction activity of two carbon-supported catalyst materials are reported. The catalysts, Se/Ru and Se/(Ru-Mo), were prepared by using a chemical reduction method. The catalyst nanoparticles were evenly dispersed onto globular amorphous carbon supports, and their average size was ca. 2.4 nm. Thermal treatment at 500 °C for 2 h in an inert argon atmosphere resulted in coarsening of the nanoparticles, and also in some decrease of their activity. A gradual reduction of activity was also observed for Se/Ru during potential-cycle experiments. However, the incorporation of small amounts of Mo into the Se/Ru catalysts considerably improved the stability of the catalyst against dissolution. The Mo-containing samples showed excellent oxygen reduction activities even after cycling the potential 1000 times between 0.7 and 0.9 V. Furthermore, they showed excellent fuel-cell behavior. The performance of the Se/Ru catalysts is greatly improved by the addition of small amounts of elemental Mo. Possible mechanisms responsible for the improvement of the activity are discussed. PMID:19554605

Guinel, Maxime J-F; Bonakdarpour, Arman; Wang, Biao; Babu, Panakkattu K; Ernst, Frank; Ramaswamy, Nagappan; Mukerjee, Sanjeev; Wieckowski, Andrzej

2009-06-24

437

New chitosan microspheres supported [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] as efficient catalysts for colour degradation in the presence of hydrogen peroxide  

Microsoft Academic Search

This paper concerns the immobilisation of either [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] (I) or ruthenium chloride (RuCl3) (II) on chitosan microspheres (catalyst I and catalyst II, respectively). These heterogenised catalysts were used for the oxidative degradation of two acid dyes, i.e. [Calmagite (Calma) and Acid Blue 25 (AB25)] in aqueous solution at pH 7.0 in the presence of hydrogen peroxide (H2O2). Prepared solid supports

Mahjoub Jabli; Ridha Touati; Yakdhane Kacem; Bechir Ben Hassine

2012-01-01

438

New chitosan microspheres supported [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] as efficient catalysts for colour degradation in the presence of hydrogen peroxide  

Microsoft Academic Search

This paper concerns the immobilisation of either [bis(2-methylallyl)(1,5-cyclooctadienne)ruthenium(II)] (I) or ruthenium chloride (RuCl3) (II) on chitosan microspheres (catalyst I and catalyst II, respectively). These heterogenised catalysts were used for the oxidative degradation of two acid dyes, i.e. [Calmagite (Calma) and Acid Blue 25 (AB25)] in aqueous solution at pH 7.0 in the presence of hydrogen peroxide (H2O2). Prepared solid supports

Mahjoub Jabli; Ridha Touati; Yakdhane Kacem; Bechir Ben Hassine

2011-01-01

439

ZrO 2 promoted with sulfate, iron and manganese: a solid superacid catalyst capable of low temperature n -butane isomerization  

Microsoft Academic Search

A sulfated oxide of zirconium, iron and manganese is prepared and shown to isomerizen-butane to isobutane at 35°C with rates approximately 2–3 orders of magnitude greater than sulfated zirconia as claimed by workers at Sun Refining and Marketing Company. Temperature programmed desorption of benzene is used to investigate the acidity of this remarkable catalyst. Adsorbed benzene is oxidized to CO2

Anup Jatia; Clark Chang; Jason D. MacLeod; Tatsuya Okubo; Mark E. Davis

1994-01-01

440

Spent catalyst waste management: A review  

Microsoft Academic Search

Solid catalysts containing metals, metal oxides or sulfides, which play a key role in the refining of petroleum to clean fuels and many other valuable products, become solid wastes after use. In many refineries, the spent catalysts discarded from hydroprocessing units form a major part of these solid wastes. Disposal of spent hydroprocessing catalysts requires compliance with stringent environmental regulations

M. Marafi; A. Stanislaus

2008-01-01

441

Esterification of sodium 4-hydroxybenzoate by ultrasound-assisted solid-liquid phase-transfer catalysis using dual-site phase-transfer catalyst.  

PubMed

The catalytic esterification of sodium 4-hydroxybenzoate with benzyl bromide by ultrasound-assisted solid-liquid phase-transfer catalysis (U-SLPTC) was investigated using the novel dual-site phase-transfer catalyst 4,4'-bis(tributylammoniomethyl)-1,1'-biphenyl dichloride (BTBAMBC), which was synthesized from the reaction of 4,4'-bis(chloromethyl)-1,1'-biphenyl and tributylamine. Without catalyst and in the absence of water, the product yield at 60°C was only 0.36% in 30min of reaction even under ultrasound irradiation (28kHz/300W) and 250rpm of stirring speed. When 1cm(3) of water and 0.5mmol of BTBAMBC were added, the yield increased to 84.3%. The catalytic intermediate 4,4'-bis(tributylammoniomethyl)-1,1'-biphenyl di-4-hydroxybenzoate was also synthesized to verify the intrinsic reaction which was mainly conducted in the quasi-aqueous phase locating between solid and organic phases. Pseudo-first-order kinetic equation was used to correlate the overall reaction, and the apparent rate coefficient with ultrasound (28kHz/300W) was 0.1057min(-1), with 88% higher than that (0.0563min(-1)) without ultrasound. The esterification under ultrasonic irradiation using BTBAMBC by solid-liquid phase-transfer catalysis was developed. PMID:23972326

Yang, Hung-Ming; Chu, Wei-Ming

2013-08-13

442

Hydrogen-bonding 2D metal-organic solids as highly robust and efficient heterogeneous green catalysts for Biginelli reaction.  

PubMed

Two new Zn(II) and Cd(II) MOFs have been synthesized. These MOFs have been applied as heterogeneous catalysts for the green synthesis of a variety of dihydropyrimidinone derivatives through the Biginelli reaction and the desired products were obtained in high yields with short reaction time under mild solvent- free conditions. Moreover, the MOF catalysts may be readily recovered after the reaction and reused for many cycles. PMID:22043110

Li, Peng; Regati, Sridhar; Butcher, Raymond J; Arman, Hadi D; Chen, Zhenxia; Xiang, Shengchang; Chen, Banglin; Zhao, Cong-Gui

2011-11-23

443

Atmospheric secondary aerosol formation by heterogeneous reactions of aldehydes in the presence of a sulfuric acid aerosol catalyst.  

PubMed

Particle growth by the heterogeneous reaction of aldehydes was evaluated in 0.5 m3 Teflon film bags under darkness in the presence of background seed aerosols. The aldehydes used were as follows: glyoxal, butanal, hexanal, octanal, and decanal. To study acid catalyst effects on aldehyde heterogeneous reactions, one of the Teflon bags was initially filled with seed aerosols composed of ammonium sulfate-aerosol acidified with sulfuric acid. These results were compared to particle growth reactions that contained only ammonium sulfate as a background seed aerosol. The gas-phase aldehydes were then added to the Teflon bags. In selected experiments, 1-decanol was also added to the Teflon bags with aldehydes to clarify particle growth via a heterogeneous hemiacetal/acetal formation in the presence/absence of an acid catalyst. The particle size distribution and growth were measured using a scanning mobility particle sizer (TSI-SMPS), and the results were applied to predicting aerosol growth and size distribution changes by condensation and heterogeneous reactions. Aerosols created from the heterogeneous reactions of aldehydes were collected directly on an ungreased zinc selenide (ZnSe) FTIR disk (25 mm in diameter) by impaction. The ZnSe disks were directly analyzed for product functional groups inthe aerosol phase using a Fourier transform infrared (FTIR) spectrometer with a deuterated triglycine sulfate (DTGS) detector. Aerosol growth by heterogeneous aldehyde reactions proceeds via a hydration, polymerization process, and hemiacetal/acetal formation from the reaction of aldehydes with alcohols. These aldehyde heterogeneous reactions were accelerated in the presence of an acid catalyst, H2SO4, and led to higher aerosol yields than when H2SO4 was not present in the seed aerosol. The FTIR spectra obtained from the growing aerosol, also illustrated aldehyde group transformation in the particle phase as a function of the heterogeneous reaction. It was concluded that aldehydes, which can be produced by atmospheric photochemical reactions, can significantly contribute on secondary aerosol formation through heterogeneous reactions in the presence of an acid catalyst. PMID:11775150

Jang, M; Kamens, R M

2001-12-15

444

Influence of the starting aluminum salt on the surface and acid properties of AlPO/sub 4/ catalysts precipitated with ammonium hydroxide  

SciTech Connect

In this paper, the influence of the starting aluminum salt (chloride, nitrate, or sulfate) and the pretreatment temperature (773-1273 K) on textural properties, crystal structure, and surface acidity of AlPO/sub 4/ (Al/P = 1) catalysts was studied in order to learn how preparation conditions affect catalyst activity in organocationic reactions. The catalysts were characterized using nitrogen adsorption, X-ray diffraction, infrared spectroscopy, and thermogravimetric analyses. The surface acid properties were determined using a dynamic method that consists of determining the AlPO/sub 4/'s catalytic activity in cyclohexene skeletal isomerization (CSI), a reaction that requires the presence of strong surface acid sites. Catalytic activity (as apparent rate constants), activation energies, and selectivities to 1-methylcyclopentene (1-MCP) were calculated in terms of Bassett-Habgood's kinetic model for first-order processes in which the surface reaction is the controlling step and the partial pressure of the reactant is low. Significant differences in structure, texture, surface acidity, and catalytic activity in CSI were found, showing that the aluminum starting salt plays an important role in the final properties of AlPO/sub 4/ (Al/P molar ratio = 1) catalysts. Thus, aluminum nitrate yielded material with higher surface area and low activity for CSI while aluminum sulfate resulted in higher surface acidity, and hence catalytic activity for CSI, although the sample is highly crystalline exhibiting low surface area. Aluminum chloride produces porous catalysts although they are less acidic.

Campelo, J.M.; Garcia, A.; Luna, D.; Marinas, J.M.

1988-05-01

445

Solid polymer electrolyte water electrolysis  

Microsoft Academic Search

Electrocatalyst performances and bonding to solid polymer electrolytes used for water electrolysis are investigated. Noble metal and metal alloy catalysts were plated to Nafion perfluorosulfonic acid polymer membranes without a binder by the use of a reducing agent solution held on the opposite side of the membrane from a metal salt solution. It was found that pretreatment of the membrane

H. Takenaka; E. Torikai; Y. Kawami; N. Wakabayashi

1981-01-01

446

Radiation-induced reactions of amino acids adsorbed on solid surfaces  

NASA Astrophysics Data System (ADS)

The purpose of this work is to study the adsorption of compounds such as amino acids on clays and carbon nanotubes (CNTs) as a possible phase in the chemical evolution that may have occurred on the primitive Earth or in extraterrestrial environments. We further study the behavior of amino acids adsorbed on these solid surfaces at different conditions of pH and levels of irradiation, simulating a high-radiation field at early Earth conditions. The relevance of this work is to explain the possible contribution of solids (clays and CNTs) as promoters of polymerization and as shields for the adsorbed organic compounds against external sources of energy. To this end, tryptophan, aspartic acid, and glutamic acid were adsorbed on fixed amounts of solid surfaces and were irradiated by a 60Co source for different periods of time at fixed dose rates. After irradiation, the amino acids were extracted from the solid and analyzed with UV and IR spectroscopes and high-performance liquid chromatography. The most efficient surface for adsorption of amino acids was clay, followed by CNTs. Studies of the gamma irradiation of amino acids adsorbed on clay (in the solid phase) show a low yield of recovery of the amino acid.

López-Esquivel Kranksith, L.; Negrón-Mendoza, A.; Mosqueira, F. G.; Ramos-Bernal, Sergio

2010-07-01

447

Supported Molecular Catalysts: Synthesis, In-Situ Characterization and Performance  

SciTech Connect

The objectives of our work are: (i) to create solid catalysts with active sites that can function in a cooperative manner to enhance reactivity and selectivity, and (ii) to prepare solid catalysts that can perform multiple reactions in a network that in some cases would not be possible in solution due to the incompatibilities of the various catalytic entities (for example an acid and a base). We carried out extensive reactions to test the nature of the cooperative effect caused by thiol/sulfonic acid interactions. The acid/thiol combination provided an example where the two organic groups should be positioned as close to one another as possible. We also studied a system where this is not possible (acid-base). We investigated simultaneously incorporating acid and base groups into the same material. For the case of acid and bases, there is an optimal separation distance (too close allows for neutralization while too far eliminates any cooperative behavior).

Davis, Mark E.

2009-03-13

448

The enrichment of n?3 polyunsaturated fatty acids using aminopropyl solid phase extraction columns  

Microsoft Academic Search

A rapid, simple and reliable method is described for the preparation of concentrates of methyl or ethyl esters of n?3 polyunsaturated\\u000a fatty acids by solid phase extraction using aminopropyl bonded silica columns. After applying mixtures of fatty acid esters\\u000a in hexane, saturated and monounsaturated fatty acid esters are preferentially eluted with hexane whereas polyunsaturated fatty\\u000a acids (PUFA) can subsequently be

Robert Wilson; R. James Henderson; Ivan C. Burkow; John R. Sargent

1993-01-01

449

Synthesis and characterization of a novel nano-scale magnetic solid base catalyst involving a layered double hydroxide supported on a ferrite core  

Microsoft Academic Search

A nano-scale magnetic solid base catalyst MgAl-OH-LDH\\/MgFe2O4 (where LDH denotes layered double hydroxide) composed of MgAl-OH-LDH Brønsted base catalytic layers coated on MgFe2O4 spinel cores has been prepared. A magnetic precursor MgAl-CO3-LDH\\/MgFe2O4 was prepared by a method involving separate nucleation and aging steps, and subsequently calcined to give a mixed metal oxide composite MgAl(O)\\/MgFe2O4 which was rehydrated to give MgAl-OH-LDH\\/MgFe2O4.

Hui Zhang; Rong Qi; David G Evans; Xue Duan

2004-01-01

450

Combustion-synthesized Ru–Al 2O 3 composites as anode catalyst layer of a solid oxide fuel cell operating on methane  

Microsoft Academic Search

Ru–Al2O3 composites with varied Ru contents were synthesized by a glycine–nitrate combustion technique. Their potential application as anode catalyst functional layer of a solid–oxide fuel cell operating on methane fuel was investigated. Catalytic tests demonstrated the 3–7 wt.% Ru–Al2O3 composites had high catalytic activity for methane partial oxidation and CO2\\/H2O reforming reactions, while 1 wt.% Ru–Al2O3 had insufficient activity. The 3 wt.% Ru–Al2O3

Wei Wang; Ran Ran; Zongping Shao

2011-01-01

451

Catalyst development gets federal funding  

SciTech Connect

Despite the threat of Republican-led budget cuts, the National Institute of Standards and Technology`s (Gaithersburg, MD) Advanced Technology Program (ATP) has awarded backing to a handful of US chemical companies to conduct long-term projects to develop novel catalysts. The projects--which read like a wish list of next generation catalyst technology--includes $16 million to Eastman Chemical and Genencor International (Rochester, NY), Eastman`s joint venture with Cultor (Helsinki), to develop biocatalysts to make industrial chemicals from renewable resources. Eastman hopes the project will allow it to commercialize fine and specialty chemical products based on biocatalysts in three to five years and eventually pay off in new processes to make commodity chemicals. ATP also plans to provide $10 million to Amoco for further work on metallocene catalysts to make elastomeric homopolymer polypropylene (EHPP). The research, which also involves Stanford University and Fiberweb North America, aims to further develop EHPP to compete with a range of flexible polyolefins. Other ATP-funded projects include long-time industry goals such as the direct oxidation of propylene to propylene oxide, a solid-acid catalyst for alkylation, and a single-step oxidation of alkanes to acrylic acid. The ATP funding, however, is endangered by proposed Congressional budget cuts that would reduce ATP spending this year and eliminate the program thereafter.

Rotman, D.

1995-09-20

452

Liquid Hydrofluoric Acid Sorption Using Solid Media - Part 1  

SciTech Connect

The conversion of the uranium hexafluoride (UF{sub 6}) which is removed from the Molten Salt Reactor Experiment (MSRE), into a stable oxide for long-term storage will produce a significant amount of slightly contaminated, concentrated aqueous hydrofluoric acid (HF). Sin&the handling of this HF is complicated and dangerous, it was decided to transform it into a stable solid fluoride (e.g., CaF{sub 2}, AlF{sub 3}, and MgF{sub 2}). Tests have been performed to identify the best media to use for trapping the HF. These tests are described in this report. The first series of tests evaluated 37 trapping materials using a 6 wt % solution of HF. The solution was pumped through a 3.8-cm-diam column at a slow rate, and samples were taken in 100-mL batches until it was determined that the media could no longer neutralize the solution. Each bed volume of media was evaluated for its retention of fluoride and for its plugging problems. Mixtures of calcium hydroxide and blast furnace slag (BFS) with high Surface areas (18-30 mesh) performed the best. A mixture of 80 wt % calcium hydroxide and 20 wt % BFS was capable of loading 0.134 g HF per cubic centimeter (cm{sup 3}) of media. Other media that performed well were (a) mixtures of calcium hydroxide and portland cement and (b) pure calcium hydroxide. The second series of tests evaluated media using a 33 wt % HF solution. The best performing media from the first series and some new ones were tested. A 2.54-cm-diam, clear, polyvinyl chloride pipe was used as the column, and solution was introduced to different types or sizes of media using slugs from a pipette or constant flow of {approx}10.7 mL/min from a metering pump. The transparent PVC allowed for observation of acid-media interaction and provided a glimpse into how the media and cartridge were performing in this highly corrosive environment. Results from the second series of tests showed that many of the best performing media from the first series of tests would not do well under the more concentrated solutions of HF. Plugging and vigorous reactions were common in the second series, and calcium hydroxide-based media was ruled out due to its disintegration at any size (1.25-cm diam to 30 mesh). The best performing media was mid-sized (4-18 mesh) soda and lime (soda lime). This media not only stood up well in the HF solution, but it also had great neutralization capability, effectively neutralizing up to {approx}0.5 g HF/cm{sup 3} of media. It is expected that a cartridge of this sorbent will be capable of handling approximately seven batches of HF from the uranium conversion.

Osborne, P.E.

2000-09-14

453

Preparation of microporous solids by acid treatment of a saponite  

Microsoft Academic Search

A ferrous saponite (griffithite) from Griffith Park (CA, USA) was treated with solutions of HCl (0.62, 1.25 and 2.5%, w\\/w) at 25°C for 2, 6, 24 and 48 h. The characterization of the resulting solids shows the destruction of the silicate structure and generation of free silica by the treatments. The specific surface areas increase greatly in activated solids, with

M. A. Vicente Rodríguez; J. de D. López González; M. A. Bañares Muñoz

1995-01-01

454

Hydrogen storage and delivery: immobilization of a highly active homogeneous catalyst for the decomposition of formic acid to hydrogen and carbon dioxide  

Microsoft Academic Search

The homogeneous catalytic system, based on water-soluble ruthenium(II)–TPPTS catalyst (TPPTS = meta-trisulfonated triphenylphosphine),\\u000a selectively decomposes HCOOH into H2 and CO2 in aqueous solution. Although this reaction results in only two gas products, heterogeneous catalysts could be advantageous\\u000a for recycling, especially for dilute formic acid solutions, or for mobile, portable applications. Several approaches have\\u000a been used to immobilize\\/solidify the homogeneous ruthenium–TPPTS catalyst based

Weijia Gan; Paul J. Dyson; Gábor Laurenczy

2009-01-01

455

Hazardous waste to materials: recovery of molybdenum and vanadium from acidic leach liquor of spent hydroprocessing catalyst using alamine 308.  

PubMed

Recovery of valuable materials/metals from waste goes hand in hand with environmental protection. This paper deals with the development of a process for the recovery of metals such as Mo, V, Ni, Al from spent hydroprocessing catalyst which may otherwise cause a nuisance if dumped untreated. A detailed study on the separation of molybdenum and vanadium from the leach solution of spent hydroprocessing catalyst of composition: 27.15% MoO?, 1.7% V?O?, 3.75% NiO, 54.3% Al?O?, 2.3% SiO? and 10.4% LOI is reported in this paper. The catalyst was subjected to roasting under oxidizing atmosphere at a temperature of about 550 °C and leaching in dilute sulphuric acid to dissolve molybdenum, vanadium, nickel and part of aluminium. Metals from the leach solution were separated by solvent extraction. Both molybdenum and vanadium were selectively extracted with a suitable organic solvent leaving nickel and dissolved aluminium in the raffinate. Various parameters such as initial pH of the aqueous feed, organic to aqueous ratio (O:A), solvent concentration etc. were optimized for the complete extraction and recovery of Mo and V. Molybdenum and vanadium from the loaded organic were stripped by ammonia solution. They were recovered as their corresponding ammonium salt by selective precipitation, and were further calcined to get the corresponding oxides in pure form. PMID:23644591

Sahu, K K; Agrawal, Archana; Mishra, D

2013-05-03

456

SO{sub 4}{sup 2{minus}}/TiO{sub 2}-SiO{sub 2} mixed oxide catalyst. 1: Synthesis, characterization, and acidic properties  

SciTech Connect

A series of sulfate-doped titania-silica mixed oxides have been prepared by immersing titania-silica gel in the required volume of sulfuric acid, followed by drying. The mixed oxide gel is obtained by hydrolyzing an equimolar mixture of tetraethylorthosilicate (TEOS) and tetrabutylorthotitanate (TBOT) at pH 3. The materials, after calcining at 723 K for 4 h, are characterized by XRD, FT-IR, the BET method, and surface acid strength by the Hammett indicator method. The catalytic activity tests are carried in a fixed bed catalytic reactor (i.e. = 10 mm) for alcohol conversion, whereas cumene cracking/dehydrogenation reactions are carried out in a micropulse reactor. XRD results shows that the titania-silica mixture is amorphous and the crystallization starts with sulfation. The surface of the mixed oxide contains both bridged and normal hydroxyl groups, as observed from FT-IR data. The surface area of the material is not much altered by sulfation and lies within 50 m{sup 2}/g. The acid strength of 4 wt% SO{sub 4}{sup 2{minus}}/TiO{sub 2}-SiO{sub 2} is found to be stronger than that of 100% concentrated H{sub 2}SO{sub 4}. In the case of 2-propanol conversion, low acetone selectivity indicates the presence of weak basic sites, whereas methanol conversion over all solids shows that dehydration follows a parallel and consecutive pathway. A good correlation is found between the cumene cracking and the acidity of the catalysts.

Parida, K.M.; Samantaray, S.K.; Mishra, H.K. [CSIR, Orissa (India). Regional Research Lab.

1999-08-01

457

Nanoporous PdNi Alloy Nanowires As Highly Active Catalysts for the Electro-Oxidation of Formic Acid.  

PubMed

Highly active and durable catalysts for formic acid oxidation are crucial to the development of direct formic acid fuel cell. In this letter, we report the synthesis, characterization, and electrochemical testing of nanoporous Pd(57)Ni(43) alloy nanowires for use as the electrocatalyst towards formic acid oxidation (FAO). These nanowires are prepared by chemically dealloying of Ni from Ni-rich PdNi alloy nanowires, and have high surface area. X-ray diffraction data show that the Pd(57)Ni(43) nanowires have the face-centered cubic crystalline structure of pure Pd, whereas X-ray photoelectron spectroscopy confirm the modification of electronic structure of Pd by electron transfer from Ni to Pd. Electrocatalytic activity of the nanowires towards FAO exceeds that of the state-of-the-art Pd/C. More importantly, the nanowires are highly resistant to deactivation. It is proposed that the high active surface area and modulated surface properties by Ni are responsible for the improvement of activity and durability. Dealloyed nanoporous Pd(57)Ni(43) alloy nanowires are thus proposed as a promising catalyst towards FAO. PMID:21192691

Du, Chunyu; Chen, Meng; Wang, Wengang; Yin, Geping

2010-12-30

458

Highly efficient and convenient Strecker reaction of carbonyl compounds and amines with TMSCN catalyzed by MCM-41 anchored sulfonic acid as a recoverable catalyst  

Microsoft Academic Search

MCM-41 anchored sulfonic acid (MCM-41–SO3H) was found to be a highly efficient and recoverable heterogeneous catalyst for the three-component Strecker reaction of aldehydes or ketones and diverse amines using trimethylsilyl cyanide (TMSCN) to afford the corresponding ?-amino nitriles under mild conditions in high to quantitative yields. The simple experimental procedure along with easy recovery and reusability of the catalyst has

Mohammad G. Dekamin; Zahra Mokhtari

459

Pd-modified Au on carbon as an effective and durable catalyst for the direct oxidation of HMF to 2,5-furandicarboxylic acid.  

PubMed

Mixed noblility: We show that the modification of a gold/carbon catalyst with platinum or palladium produces stable and recyclable catalysts for the selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA): the support and nanoparticle chemistry directly mediate the selective oxidation of terminal hydroxyl groups in bio-derived HMF. This finding is a significant advance over current conversion technology because of the technological importance of FDCA. PMID:23495091

Villa, Alberto; Schiavoni, Marco; Campisi, Sebastiano; Veith, Gabriel M; Prati, Laura

2013-03-11

460

Suzuki-Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported N-heterocyclic carbene-palladium complex catalyst  

PubMed Central

Summary The Suzuki–Miyaura cross-coupling reaction of 1-aryltriazenes with arylboronic acids catalyzed by a recyclable polymer-supported Pd–NHC complex catalyst has been realized for the first time. The polymer-supported catalyst can be re-used several times still retaining high activity for this transformation. Various aryltriazenes were investigated as electrophilic substrates at room temperature to give biaryls in good to excellent yields and showed good chemoselectivity over aryl halides in the reactions.

Nan, Guangming; Ren, Fang

2010-01-01

461

Silica Phosphoric Acid (SPA) as a Highly Active, Reusable, Heterogeneous Catalyst for the Synthesis of 2Amino\\/Anilino5ARYL1,3,4Thiadiazine Bromide Derivatives  

Microsoft Academic Search

Silica phosphoric acid has been found to be an efficient catalyst for the synthesis of 2-amino\\/anilino-5-aryl-1,3,4-thiadiazine bromide derivatives from the reaction of thiosemicarbazide and ?-bromoketones in acetonitrile at room temperature. The catalyst can be reused for four times without any significant loss of catalytic activity. The experimental procedure is simple, and the products are obtained in high yield.

Shahnaz Rostamizadeh; Ali Mohammad Amani; Nasrin Shadjou

2012-01-01

462

The effect of chiral solvent and various kinds of chiral organic salts on the asymmetric hydrogenation of methyl acetoacetate over an improved tartaric acid modified Raney nickel catalyst  

Microsoft Academic Search

The influence of the chiral ionic liquid (CIL) on the asymmetric hydrogenation of methyl acetoacetate (MAA) over an improved\\u000a tartaric acid-modified Raney nickel catalyst using it as reaction medium was investigated. At the same time, we also studied\\u000a the effect of up to eight chiral ionic salts, and ionic liquids on this reaction using these ionic salts as co-catalyst. Although

Chaofeng Wang; Yunfeng Zheng; Shunli Cai; Jiantai Ma; Rong Li

2008-01-01

463

One-pot three-component Mannich-type reactions using sulfamic acid catalyst under ultrasound irradiation.  

PubMed

Sulfamic acid (NH(2)SO(3)H, SA) was used as an efficient, inexpensive, non-toxic and recyclable green catalyst for the ultrasound-assisted one-pot Mannich reaction of aldehydes with ketones and amines. This ultrasound protocol has advantages of high yield, mild condition, no environmental pollution, and simple work-up procedures. Most importantly, beta-aminocarbonyl compounds with ortho-substituted aromatic amines are obtained in acceptable to good yields by this methodology for the first time. PMID:19394889

Zeng, Hongyao; Li, Hua; Shao, Huawu

2009-03-27

464

Infrared study of the adsorption of formic acid on clean and Ca-promoted Pd\\/SiO 2 catalysts  

Microsoft Academic Search

The adsorption and decomposition of formic acid on a highly dispersed supported Pd\\/SiO2 catalyst (2wt.% Pd) prepared via ion exchange (IE) of [Pd(NH3)4]2+ in alkaline solution, together with two Ca-promoted preparations (Ca\\/Pd=2at.\\/at.) where calcium was added either to the prereduced Pd crystallites or to the diammine palladium complex, were studied by FTIR at 298–653K.On the support, HCOOH is mostly adsorbed

Griselda C Cabilla; Adrian L Bonivardi; Miguel A Baltanás

2003-01-01

465

Effects of acid catalyst type on structural, morphological, and optoelectrical properties of spin-coated TiO2 thin film  

NASA Astrophysics Data System (ADS)

The effects of different acid catalysts of nitric acid, hydrochloric acid, sulfuric acid, phosphoric acid, boric acid, acetic acid, and citric acid on structural, morphological, and optoelectrical properties of nanocrystalline spin-coated TiO2 thin films synthesized via alkoxide sol-gel route were investigated. It was found that only the sols with HNO3 and HCl are suitable for film preparation. The X-ray diffractometry and Raman analysis showed that crystalline phases could be controlled by the type of acid catalyst. Although the H2SO4 sol shows good stability, it causes extremely different morphology to form due to its different sol nature and high contact angle. Fourier transformed infrared spectra confirmed the presence of acid anion species in all samples even after calcination. Furthermore, it was inferred from UV-visable absorption spectra that although the band gap and thickness of the films are independent of acid catalyst type, the refractive index and porosity of the films are strongly affected by the type of acids.

Golobostanfard, Mohammad Reza; Abdizadeh, Hossein

2013-03-01

466

Sulfamic Acid as a Cost-Effective Catalyst for Synthesis of ? -acyloxyacrylate Esters as Candidate Monomers for Bio-Based Polymers by Acylation of Pyruvate Esters  

Microsoft Academic Search

Sulfamic acid was used as an efficient catalyst and green alternative for metal-containing acidic material to promote the acylation of pyruvate esters to produce ? -acyloxyacrylate esters which were candidate monomers for bio-based polymers. Polymers from these monomers were useful materials for bio-based plastics which showed high heat resistance and transparency. A series of ? -acyloxyacrylate esters were converted from

Zhenxin Zhang; Baochun Ma; Qianqian Zhu; Yong Ding; Changming Wang; Wenfeng Song

2012-01-01

467

Vanadium-molybdenum phosphates supported by TiO 2 -anatase as new catalysts for selective oxidation of ethane to acetic acid  

Microsoft Academic Search

Dispersion of vanadium and molybdenum phosphates on titanium oxide (anatase) below the monolayer gives good catalysts for direct oxidation of ethane to acetic acid. By comparison with the dispersion of only vanadium phosphate, the higher selectivity to acetic acid for vanadium and molybdenum phosphates has been explained by an interaction between molybdenum and vanadium as it can be deduced from

Magalie Roy; Michel Gubelmann-Bonneau; Hervé Ponceblanc; Jean-Claude Volta

1996-01-01

468

X-ray diffraction evidence of the single solid solution character of bi-metallic Pt-Pd catalyst particles on an amorphous SiO 2 substrate  

NASA Astrophysics Data System (ADS)

An X-ray diffraction study was carried out on powders of a series of catalysts prepared from aqueous solutions of H 2PtCl 6 and PdCl 4 and amorphous SiO 2 with different concentrations in weight of Pt and Pd at about 4% in overall metallic weight. Measurements of the position of high angle Bragg reflections in the diffractograms show evidence of the fact that the small catalyst particles are bi-metallic Pt-Pd crystals having a face-centred cubic Bravais lattice. The lattice constant of these crystals was found to change with the relative concentration of Pt and Pd by following the Vegard's rule. This correlation leads to the conclusion that the bi-metallic catalyst particles are made of a single solid solution of Pt and Pd atoms in the whole range of relative concentrations. Relative concentrations of these metals in the samples under study were determined by using energy dispersive X-ray spectrometry and their values were found to be close to the stochiometric relative concentrations in weight of the metals in the precursor aqueous solution. An average size of about 96 Å was estimated for the bi-metallic particles from the full-width at half-maximum value measured for the (2 0 0) diffractometric curve.

Cordero-Borboa, A. E.; Sterling-Black, E.; Gómez-Cortés, A.; Vázquez-Zavala, A.

2003-12-01

469

Waste shells of mollusk and egg as biodiesel production catalysts.  

PubMed

The solid oxide catalysts derived from waste shells of egg, golden apple snail, and meretrix venus were employed to produce biodiesel from transes