Pub Date : 2015-06-26DOI: 10.2174/1876214x01508010001
Jairo M. Perdomo Cabrejo, Luisa Barrera, R. E. Prieto-Correa
A partially purified lipase from the Pseudomonas aeruginosa strain (PSA-01) isolated from the palm oil fruit Elaeis guineensis was used as biocatalyst to produce fatty acid methyl esters (FAME). Lyophilized lipase supernatant (LLS) was used during the first step to screen the main variables (pH, temperature, stoichiometric oil:methanol ratio, water content and type of oil). Other variables which were identified during the screening assays (scale of reaction recipient, LLS amount and use of hexane to solubilize methanol forming a methanol-oil microemulsion) were tested during a second step. The response variable was % molar yield of FAME. It was quantified by GC. Additionally, the LLS work parameters were optimized and compared to a partially purified lipase (PPL) during a final assay. The first-order interactions between the analyzed factors were significant (p<0.05). The highest yield was 4.16% w/w (respect to oil) using a partially purified lipase (PPL) with pH 8, refined, bleached, and deodorized oil (RBD), 5% water (by volume) in oil and 10% hexane (by volume), and a stoichiometric ratio of 1:170 oil:methanol. The final assay was carried out at 54°C and 200 rpm for 48 hours. It resulted in a 34.68% conversion using PPL. It also showed a 13-fold improvement versus the initial yield with LLS, suggesting the need for a better purification process. During this research, the lipase was partially purified and used at an alkaline pH. It showed resistance to organic compounds such as methanol and hexane. This implies great potential to act as an effective biocatalyst in the implementation of biodiesel production processes.
{"title":"Applied Biocatalysis with an Organic Resistant Partially Purified Lipasefrom P. aeruginosa During FAME Production","authors":"Jairo M. Perdomo Cabrejo, Luisa Barrera, R. E. Prieto-Correa","doi":"10.2174/1876214x01508010001","DOIUrl":"https://doi.org/10.2174/1876214x01508010001","url":null,"abstract":"A partially purified lipase from the Pseudomonas aeruginosa strain (PSA-01) isolated from the palm oil fruit Elaeis guineensis was used as biocatalyst to produce fatty acid methyl esters (FAME). Lyophilized lipase supernatant (LLS) was used during the first step to screen the main variables (pH, temperature, stoichiometric oil:methanol ratio, water content and type of oil). Other variables which were identified during the screening assays (scale of reaction recipient, LLS amount and use of hexane to solubilize methanol forming a methanol-oil microemulsion) were tested during a second step. The response variable was % molar yield of FAME. It was quantified by GC. Additionally, the LLS work parameters were optimized and compared to a partially purified lipase (PPL) during a final assay. The first-order interactions between the analyzed factors were significant (p<0.05). The highest yield was 4.16% w/w (respect to oil) using a partially purified lipase (PPL) with pH 8, refined, bleached, and deodorized oil (RBD), 5% water (by volume) in oil and 10% hexane (by volume), and a stoichiometric ratio of 1:170 oil:methanol. The final assay was carried out at 54°C and 200 rpm for 48 hours. It resulted in a 34.68% conversion using PPL. It also showed a 13-fold improvement versus the initial yield with LLS, suggesting the need for a better purification process. During this research, the lipase was partially purified and used at an alkaline pH. It showed resistance to organic compounds such as methanol and hexane. This implies great potential to act as an effective biocatalyst in the implementation of biodiesel production processes.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2015-06-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80959134","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-21DOI: 10.2174/1876214X01407010026
M. Sibi, H. Singh, A. Sinha
Selective catalysts for sustainable production of fuels and commodity chemicals are important due to the abundance of the raw materials in the nature. Most of these reactions require multiple active sites due to the complexity of the reactions involved. In view of this, we have synthesized a multifunctional catalyst for the selective synthesis of C 4 hydrocarbons from ethanol. The reason for selecting ethanol is due to the easy production and transformation of biomass, and the heavy demand in future for fuels. Here, we have synthesized nanometer sized nickel particles and protected it with a porous siliceous cover. The acidity of the catalyst has been tuned by introducing tantalum in the framework structure. The use of easily available metals for the synthesis of catalysts reduces the cost of making the catalyst and it also gives high temperature resistance characteristics. The physico-chemical characteristics of the catalysts were studied with various sophisticated instruments. We also investigated in detail the selective production of C 4 hydrocarbons, by tuning the reaction conditions.
{"title":"Porous Ni@Tantalum Silicate as a Tandem Catalyst for Selective Synthesisof C4 Hydrocarbons from Ethanol","authors":"M. Sibi, H. Singh, A. Sinha","doi":"10.2174/1876214X01407010026","DOIUrl":"https://doi.org/10.2174/1876214X01407010026","url":null,"abstract":"Selective catalysts for sustainable production of fuels and commodity chemicals are important due to the abundance of the raw materials in the nature. Most of these reactions require multiple active sites due to the complexity of the reactions involved. In view of this, we have synthesized a multifunctional catalyst for the selective synthesis of C 4 hydrocarbons from ethanol. The reason for selecting ethanol is due to the easy production and transformation of biomass, and the heavy demand in future for fuels. Here, we have synthesized nanometer sized nickel particles and protected it with a porous siliceous cover. The acidity of the catalyst has been tuned by introducing tantalum in the framework structure. The use of easily available metals for the synthesis of catalysts reduces the cost of making the catalyst and it also gives high temperature resistance characteristics. The physico-chemical characteristics of the catalysts were studied with various sophisticated instruments. We also investigated in detail the selective production of C 4 hydrocarbons, by tuning the reaction conditions.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"15 1","pages":"26-35"},"PeriodicalIF":0.0,"publicationDate":"2014-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86321366","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-18DOI: 10.2174/1876214X01407010018
Panagiotis Platanitis, G. D. Panagiotou, K. Bourikas, Christos Kodulis, A. Lycourghiotis
The influence of the composition of reduced CoMo, NiMo and NiW catalysts on the catalytic performance in hydrodeoxygenation (HDO) of phenol has been investigated. γ-Al 2 O 3 and TiO 2 were used as supports. Different activity orders were obtained over γ-Al 2 O 3 and TiO 2 supported catalysts reflecting the critical role of the support. NiMo catalyst supported on γ-alumina proved to be the most active followed by the CoMo catalyst supported on titania. CoMo and NiMo lab made catalysts were proved to be more active compared to a reduced industrial CoMo catalyst supported on γ- alumina. An increase of phenol conversion in the range 52-230% was obtained at 350°C. A series of CoMo, NiMo and NiW catalysts supported on TiO 2 was also prepared using the "Equilibrium - Deposition - Filtration" (EDF) method. The application of this technique, instead of the classical impregnation, increased considerably the activity of the CoMo catalyst supported on titania (48% increase of phenol conversion at 350°C). The most active lab catalysts (wet impregnated NiMo catalyst supported on alumina, EDF CoMo catalyst supported on titania) and the industrial CoMo catalyst were evaluated after sulfidation for simultaneous HDO of phenol and HDS of dibenzothiophene. These catalysts exhibited comparable HDO activities while the first one proved to be superior in HDS. Overall, taking into account the significantly higher loading of the industrial catalyst in the supported elements compared to the lab made catalysts, the latter seems to be quite promising, even in the frame of a co-processing strategy.
{"title":"Hydrodeoxygenation of Phenol Over Hydrotreatment Catalysts in their Reduced and Sulfided States","authors":"Panagiotis Platanitis, G. D. Panagiotou, K. Bourikas, Christos Kodulis, A. Lycourghiotis","doi":"10.2174/1876214X01407010018","DOIUrl":"https://doi.org/10.2174/1876214X01407010018","url":null,"abstract":"The influence of the composition of reduced CoMo, NiMo and NiW catalysts on the catalytic performance in hydrodeoxygenation (HDO) of phenol has been investigated. γ-Al 2 O 3 and TiO 2 were used as supports. Different activity orders were obtained over γ-Al 2 O 3 and TiO 2 supported catalysts reflecting the critical role of the support. NiMo catalyst supported on γ-alumina proved to be the most active followed by the CoMo catalyst supported on titania. CoMo and NiMo lab made catalysts were proved to be more active compared to a reduced industrial CoMo catalyst supported on γ- alumina. An increase of phenol conversion in the range 52-230% was obtained at 350°C. A series of CoMo, NiMo and NiW catalysts supported on TiO 2 was also prepared using the \"Equilibrium - Deposition - Filtration\" (EDF) method. The application of this technique, instead of the classical impregnation, increased considerably the activity of the CoMo catalyst supported on titania (48% increase of phenol conversion at 350°C). The most active lab catalysts (wet impregnated NiMo catalyst supported on alumina, EDF CoMo catalyst supported on titania) and the industrial CoMo catalyst were evaluated after sulfidation for simultaneous HDO of phenol and HDS of dibenzothiophene. These catalysts exhibited comparable HDO activities while the first one proved to be superior in HDS. Overall, taking into account the significantly higher loading of the industrial catalyst in the supported elements compared to the lab made catalysts, the latter seems to be quite promising, even in the frame of a co-processing strategy.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"41 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2014-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76275384","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-04-04DOI: 10.2174/1876214X01407010008
J. Vakros, K. Bourikas, C. Kordulis, A. Lycourghiotis
The mode of retention of Co(H 2 O) 6 2+ species at the "γ-alumina/aquatic solution" interface is refined using simulations, adsorption isotherm, potentiometric mass titrations and mainly proton - ion titrations jointly with diffuse reflectance spectroscopy. It was found that the increase in the Co(II) surface concentration affects considerably the kind of the Co(II) species deposited. Mononuclear/mono-substituted inner sphere Co(II) complexes are formed at extremely low Co(II) surface concentration. A mixed surface state involving mononuclear/mono-substituted and binuclear/bi-substituted Co(II) complexes is formed at relatively low Co(II) surface concentration. Only binuclear/bi-substituted Co(II) complexes are formed at intermediate Co(II) surface concentration. Finally, oligo-nuclear inner sphere Co(II) species are formed at relatively high Co(II) surface concentration, in addition to the bi-nuclear ones. The above species concern a range of surface Co(II) concentration extending from zero to 2.7 theoretical surface layers of (Co(H 2 O) 6 ) 2+ . The formation of Co(II) surface precipitate starts above these theoretical surface layers. The above indicates that one may control the surface Co(II) concentration, by adjusting the Co(II) concentration in the impregnating solution, and thus the Co(II) surface species formed. This control allows tailoring the preparation of cobalt catalysts supported on γ-alumina and thus the development of effective Co/γ-alumina catalysts.
{"title":"Structure of Co(II) Species Formed on the Surface of γ-Alumina Upon Interfacial Deposition","authors":"J. Vakros, K. Bourikas, C. Kordulis, A. Lycourghiotis","doi":"10.2174/1876214X01407010008","DOIUrl":"https://doi.org/10.2174/1876214X01407010008","url":null,"abstract":"The mode of retention of Co(H 2 O) 6 2+ species at the \"γ-alumina/aquatic solution\" interface is refined using simulations, adsorption isotherm, potentiometric mass titrations and mainly proton - ion titrations jointly with diffuse reflectance spectroscopy. It was found that the increase in the Co(II) surface concentration affects considerably the kind of the Co(II) species deposited. Mononuclear/mono-substituted inner sphere Co(II) complexes are formed at extremely low Co(II) surface concentration. A mixed surface state involving mononuclear/mono-substituted and binuclear/bi-substituted Co(II) complexes is formed at relatively low Co(II) surface concentration. Only binuclear/bi-substituted Co(II) complexes are formed at intermediate Co(II) surface concentration. Finally, oligo-nuclear inner sphere Co(II) species are formed at relatively high Co(II) surface concentration, in addition to the bi-nuclear ones. The above species concern a range of surface Co(II) concentration extending from zero to 2.7 theoretical surface layers of (Co(H 2 O) 6 ) 2+ . The formation of Co(II) surface precipitate starts above these theoretical surface layers. The above indicates that one may control the surface Co(II) concentration, by adjusting the Co(II) concentration in the impregnating solution, and thus the Co(II) surface species formed. This control allows tailoring the preparation of cobalt catalysts supported on γ-alumina and thus the development of effective Co/γ-alumina catalysts.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"4 1","pages":"8-17"},"PeriodicalIF":0.0,"publicationDate":"2014-04-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81822148","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-03-07DOI: 10.2174/1876214X01407010001
M. Almohalla, E. Asedegbega-Nieto, Á. Maroto-Valiente, B. Bachiller-Baeza, I. Rodríguez-Ramos, A. Guerrero-Ruíz
Catalytic bioethanol transformations over carbon nanomaterials (nanofibers and nanotubes) have been evaluated at atmospheric pressure and in the temperature range of 473-773 K. The pristine carbon materials were compared with these samples after surface modification by introducing sulfonic groups. The specific activity for ethanol dehydrogenation, yielding acetaldehyde, increases with the surface graphitization degree for these materials. This suggests that some basic sites can be related with specific surface graphitic structures or with the conjugated basic sites produced after removing acidic oxygen surface groups. Concerning the dehydration reaction over sulfonated samples, it is observed that catalytic activities are related with the amount of incorporated sulfur species, as detected by the evolution of SO 2 in the Temperature programmed Desorption (TPD) as well as by the analysis of sulfur by X-Ray Photoelectron Spectroscopy (XPS).
{"title":"Bioethanol Transformations Over Active Surface Sites Generated on Carbon Nanotubes or Carbon Nanofibers Materials","authors":"M. Almohalla, E. Asedegbega-Nieto, Á. Maroto-Valiente, B. Bachiller-Baeza, I. Rodríguez-Ramos, A. Guerrero-Ruíz","doi":"10.2174/1876214X01407010001","DOIUrl":"https://doi.org/10.2174/1876214X01407010001","url":null,"abstract":"Catalytic bioethanol transformations over carbon nanomaterials (nanofibers and nanotubes) have been evaluated at atmospheric pressure and in the temperature range of 473-773 K. The pristine carbon materials were compared with these samples after surface modification by introducing sulfonic groups. The specific activity for ethanol dehydrogenation, yielding acetaldehyde, increases with the surface graphitization degree for these materials. This suggests that some basic sites can be related with specific surface graphitic structures or with the conjugated basic sites produced after removing acidic oxygen surface groups. Concerning the dehydration reaction over sulfonated samples, it is observed that catalytic activities are related with the amount of incorporated sulfur species, as detected by the evolution of SO 2 in the Temperature programmed Desorption (TPD) as well as by the analysis of sulfur by X-Ray Photoelectron Spectroscopy (XPS).","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"1 1","pages":"1-7"},"PeriodicalIF":0.0,"publicationDate":"2014-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86825679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-11-29DOI: 10.2174/1876214X01306010037
S. Izhar, M. Nagai
Molybdenum catalysts carburized in CH4/H2 exhibited activity for methanol electrooxidation (MOR) in half cell measurements. Mo carburized at 773 and 873 K showed high electrooxidation of methanol compared to carburization at other temperatures. Catalyst characterization was carried out by XRD and TPC. The active carbide species responsible to facilitate the MOR was the Mo oxycarbide and � -Mo2C species.
{"title":"Oxidation of Methanol using Carburized Molybdenum Catalyst","authors":"S. Izhar, M. Nagai","doi":"10.2174/1876214X01306010037","DOIUrl":"https://doi.org/10.2174/1876214X01306010037","url":null,"abstract":"Molybdenum catalysts carburized in CH4/H2 exhibited activity for methanol electrooxidation (MOR) in half cell measurements. Mo carburized at 773 and 873 K showed high electrooxidation of methanol compared to carburization at other temperatures. Catalyst characterization was carried out by XRD and TPC. The active carbide species responsible to facilitate the MOR was the Mo oxycarbide and � -Mo2C species.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"19 1","pages":"37-40"},"PeriodicalIF":0.0,"publicationDate":"2013-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78707569","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-09-25DOI: 10.2174/1876214X01306010029
P. Tandon, Mamta Dhusia, A. Singh, S. Singh
Un-catalyzed oxidation of cyclic alcohols viz. cyclopentanol and cyclohexanol by hexacyanoferrate(III) in aqueous alkaline medium does not proceed to measurable extent even after 98 hr. Addition of traces of RhCl3, used as a homogeneous catalyst accelerates the reaction resulting in the formation of corresponding dicarboxylic acids. Correlating this result with previously reported results in the un-catalyzed oxidation of cyclopentanone to dicarboxylic acid indicates that hexacyanoferrate(III) in alkaline medium is incapable to oxidize cyclopentanol. Addition of catalyst initiates the initial conversion of cyclic alcohol into cyclic ketone which in turn is oxidized to dicarboxylic acid. Rate follows direct proportionality at low concentrations of catalyst, reaching to a maximum with increasing catalyst concentrations but further increase in RhCl3 concentration retards the reaction velocity. As the amount of catalyst is increased in the reaction mixture it also increases the amount of hydrochloric acid in which RhCl3 was prepared, resulting in the decrease in pH of the medium. At a particular pH, reactive species of catalyst Rh(OH)3(H2O)3, converts into the un-reactive RhCl3(H2O)3 and thus the reaction velocity decreases. Rate of the reaction shows first order kinetics in [OH ] and [cyclic alcohol], but it is one changing to zero order in oxidant concentrations. Increase in chloride ions and hexacyanoferrate(II) concentrations respectively increases and decreases the reaction velocity. Entropy, free energy and enthalpy values were calculated.
{"title":"Oxidation of Cyclic Alcohols by Hexacyanoferrate(III) in Alkaline Mediumin the Presence of Rhodium(III) Chloride as a Homogeneous Catalyst","authors":"P. Tandon, Mamta Dhusia, A. Singh, S. Singh","doi":"10.2174/1876214X01306010029","DOIUrl":"https://doi.org/10.2174/1876214X01306010029","url":null,"abstract":"Un-catalyzed oxidation of cyclic alcohols viz. cyclopentanol and cyclohexanol by hexacyanoferrate(III) in aqueous alkaline medium does not proceed to measurable extent even after 98 hr. Addition of traces of RhCl3, used as a homogeneous catalyst accelerates the reaction resulting in the formation of corresponding dicarboxylic acids. Correlating this result with previously reported results in the un-catalyzed oxidation of cyclopentanone to dicarboxylic acid indicates that hexacyanoferrate(III) in alkaline medium is incapable to oxidize cyclopentanol. Addition of catalyst initiates the initial conversion of cyclic alcohol into cyclic ketone which in turn is oxidized to dicarboxylic acid. Rate follows direct proportionality at low concentrations of catalyst, reaching to a maximum with increasing catalyst concentrations but further increase in RhCl3 concentration retards the reaction velocity. As the amount of catalyst is increased in the reaction mixture it also increases the amount of hydrochloric acid in which RhCl3 was prepared, resulting in the decrease in pH of the medium. At a particular pH, reactive species of catalyst Rh(OH)3(H2O)3, converts into the un-reactive RhCl3(H2O)3 and thus the reaction velocity decreases. Rate of the reaction shows first order kinetics in [OH ] and [cyclic alcohol], but it is one changing to zero order in oxidant concentrations. Increase in chloride ions and hexacyanoferrate(II) concentrations respectively increases and decreases the reaction velocity. Entropy, free energy and enthalpy values were calculated.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"85 1","pages":"29-36"},"PeriodicalIF":0.0,"publicationDate":"2013-09-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77222937","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-09-04DOI: 10.2174/1876214X20130729001
S. Al‐Sayari
Natural gas is catalytically converted into several bulk chemicals such as ammonia, methanol, dimethyl ether, and synthetic liquid fuels by Fischer-Tropsch synthesis and similar processes. The main step in the conversion of natural gas to these products is the production of synthesis gas with the desired composition ranging from H2/CO = 3:1 used for the production of ammonia to the 1:1 mixture preferred for production of dimethyl ether. Catalysts and catalytic processes are important in the production of synthesis gas from natural gas. In this work, relevant catalytic systems employed recently in the production of syngas by the catalytic partial oxidation of methane, as well as experimental evidences on the reaction mechanisms are examined. Differences in methane dissociation, binding site preferences, stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species are considered. The methane dissociation requires reduced metal sites, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H2 and CO (or C). The comparison of elementary reaction steps on Pt and Rh illustrates the fact that a key factor to produce hydrogen as primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H2 and CO as primary products is a low surface coverage of intermediates, such that the probability of O-H, OH-H and CO-O interactions is reduced.
{"title":"Recent Developments in the Partial Oxidation of Methane to Syngas","authors":"S. Al‐Sayari","doi":"10.2174/1876214X20130729001","DOIUrl":"https://doi.org/10.2174/1876214X20130729001","url":null,"abstract":"Natural gas is catalytically converted into several bulk chemicals such as ammonia, methanol, dimethyl ether, and synthetic liquid fuels by Fischer-Tropsch synthesis and similar processes. The main step in the conversion of natural gas to these products is the production of synthesis gas with the desired composition ranging from H2/CO = 3:1 used for the production of ammonia to the 1:1 mixture preferred for production of dimethyl ether. Catalysts and catalytic processes are important in the production of synthesis gas from natural gas. In this work, relevant catalytic systems employed recently in the production of syngas by the catalytic partial oxidation of methane, as well as experimental evidences on the reaction mechanisms are examined. Differences in methane dissociation, binding site preferences, stability of OH surface species, surface residence times of active species and contributions from lattice oxygen atoms and support species are considered. The methane dissociation requires reduced metal sites, but at elevated temperatures oxides of active species may be reduced by direct interaction with methane or from the reaction with H2 and CO (or C). The comparison of elementary reaction steps on Pt and Rh illustrates the fact that a key factor to produce hydrogen as primary product is a high activation energy barrier to the formation of OH. Another essential property for the formation of H2 and CO as primary products is a low surface coverage of intermediates, such that the probability of O-H, OH-H and CO-O interactions is reduced.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"8 1","pages":"17-28"},"PeriodicalIF":0.0,"publicationDate":"2013-09-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91080774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2013-04-03DOI: 10.2174/1876214X01306010008
Ajaya K. Singh, Ashok K. Singh, Vineeta Singh, S. Singh, B. Singh
The kinetics of the oxidation of Ru (III) catalyzed oxidation of tartaric acid by potassium bromate in aqueous perchloric acid medium at constant ionic strength was investigated in the temperature range 303- 318 K. The reactions exhibit first order kinetics at low concentration of bromate, tending to zero order at high concentration. Zero order kinetics with respect to (tartaric acid) and first order kinetics in (Ru (III)) were observed in the oxidation of tartaric acid. A positive effect on the rate of reaction has been found on the successive addition of (H + ) and (Cl - ). Variation in mercuric acetate concentration, (Hg(OAc)2) and ionic strength of the medium did not bring any significant change on the rate of reaction. The first order rate constant increases with decrease in the dielectric constant of the medium. The values of rate constants observed at four different temperatures were utilized to calculate the activation parameters. Formic acid and carbon dioxide have been identified as main oxidation products of the reaction. A plausible mechanism from the results of kinetic studies, reaction stoichiometry and product analysis has been proposed.
{"title":"Kinetics and Mechanism of Aquachlororuthenium (III) Catalyzed Oxidation of Tartaric Acid by Acid Bromate","authors":"Ajaya K. Singh, Ashok K. Singh, Vineeta Singh, S. Singh, B. Singh","doi":"10.2174/1876214X01306010008","DOIUrl":"https://doi.org/10.2174/1876214X01306010008","url":null,"abstract":"The kinetics of the oxidation of Ru (III) catalyzed oxidation of tartaric acid by potassium bromate in aqueous perchloric acid medium at constant ionic strength was investigated in the temperature range 303- 318 K. The reactions exhibit first order kinetics at low concentration of bromate, tending to zero order at high concentration. Zero order kinetics with respect to (tartaric acid) and first order kinetics in (Ru (III)) were observed in the oxidation of tartaric acid. A positive effect on the rate of reaction has been found on the successive addition of (H + ) and (Cl - ). Variation in mercuric acetate concentration, (Hg(OAc)2) and ionic strength of the medium did not bring any significant change on the rate of reaction. The first order rate constant increases with decrease in the dielectric constant of the medium. The values of rate constants observed at four different temperatures were utilized to calculate the activation parameters. Formic acid and carbon dioxide have been identified as main oxidation products of the reaction. A plausible mechanism from the results of kinetic studies, reaction stoichiometry and product analysis has been proposed.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"37 1","pages":"8-16"},"PeriodicalIF":0.0,"publicationDate":"2013-04-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79338632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2012-11-02DOI: 10.2174/1876214X01205010066
J. Aguilar-Pliego, P. Bosch, C. Zicovich-Wilson, G. Herrera-Pérez, V. Lara
Si-NMR, gas adsorption and SAXS results are discussed to determine if the geometry and the electronic properties of Si sites, present in the MCM-41walls, are more similar to three- than to four-fold coordinated sites. The features of Si-MCM-41, SBA-15, Y zeolite and silica (SiO2), characterized by several techniques, are compared. It is shown that the pre-polymer geometries are similar to those of the zeolite secondary building units, but, in the organization-polymerization step, the generation of partially saturated or quite stressed structures is favored.
{"title":"On Three-Fold Coordinated Si Sites in Mesoporous MCM-41 Catalysts","authors":"J. Aguilar-Pliego, P. Bosch, C. Zicovich-Wilson, G. Herrera-Pérez, V. Lara","doi":"10.2174/1876214X01205010066","DOIUrl":"https://doi.org/10.2174/1876214X01205010066","url":null,"abstract":"Si-NMR, gas adsorption and SAXS results are discussed to determine if the geometry and the electronic properties of Si sites, present in the MCM-41walls, are more similar to three- than to four-fold coordinated sites. The features of Si-MCM-41, SBA-15, Y zeolite and silica (SiO2), characterized by several techniques, are compared. It is shown that the pre-polymer geometries are similar to those of the zeolite secondary building units, but, in the organization-polymerization step, the generation of partially saturated or quite stressed structures is favored.","PeriodicalId":22755,"journal":{"name":"The Open Catalysis Journal","volume":"29 1","pages":"66-71"},"PeriodicalIF":0.0,"publicationDate":"2012-11-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74995354","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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