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Applied Catalysis A, General (v.366, #2)
New and efficient procedure for the oxidation of dioxybenzylic alcohols into aldehydes with Pt and Pd-based catalysts under flow reactor conditions by A.L. Tarasov; L.M. Kustov; A.A. Bogolyubov; A.S. Kiselyov; V.V. Semenov (pp. 227-231).
We describe both selective and efficient catalysts for the oxidation of benzylic alcohols into the respective aldehydes. In a representative conversion, vanilline is prepared from vanilline alcohol under flow reactor conditions. Catalytic metals (Pt and Pd) retain their activity when immobilized on the modified carbon matrix. Catalysts can be regenerated via a combined treatment with basic water followed by acetone.Selective and efficient catalysts have been developed for the oxidation benzylic alcohols into the respective commercial aldehydes with air. Catalytically active metals (Pt and Pd) retained their activity when immobilized on the modified carbon carrier. To the best of our knowledge, this is the first example of synthesis of vanillin and piperonal from vanillyl and piperonyl alcohols under flow reactor conditions. Based on our evaluation we estimate that if the catalysts retain their activity for ca. 100h, the yield of vanillin will be over 120/1kg of the catalyst. Furthermore, we showed that the catalysts can be regenerated via a feasible treatment with basic water followed by acetone.
Keywords: Catalysis; Aromatic aldehydes; Vanillin
The hybrid plasma–catalytic process for non-oxidative methane coupling to ethylene and ethane by M. Młotek; J. Sentek; K. Krawczyk; K. Schmidt-Szałowski (pp. 232-241).
Non-oxidative methane coupling in hybrid plasma–catalytic reactors was studied. The hybrid system which combined the gliding discharge (GD) and mobile (spouted) bed of catalyst particles revealed high efficiency in the methane conversion. Two catalysts from Pt and Pd supported by alumina ceramics were prepared and tested. The methane conversion was investigated in two GD reactors supplied by 1-phase or 3-phase circuits (50Hz). In a homogeneous gas system and with a mobile bed of alumina–ceramic particles, mainly acetylene was produced from the CH4+H2 mixture with none or a minor share of other C2 hydrocarbons. The formation of non-volatile products (mainly soot) was also observed. In the presence of Pt and Pd catalysts, the soot formation was strongly reduced. Owing to these catalysts, ethylene and ethane became the main gaseous products replacing a major part of acetylene.Non-oxidative methane coupling in hybrid plasma–catalytic reactors was studied. The hybrid system which combined the gliding discharge (GD) and mobile (spouted) bed of catalyst particles revealed high efficiency in the methane conversion. In a homogeneous gas system and with a mobile bed of alumina–ceramic particles, mainly acetylene was produced from the CH4+H2 mixture. The formation of non-volatile products (mainly soot) was also observed. In the presence of Pt and Pd catalysts, the soot formation was strongly reduced. With these catalysts, ethylene and ethane became the main gaseous products replacing a major part of acetylene.
Keywords: Methane coupling; Gliding discharges; Metal catalysts; Ethylene; Ethane
Selective oxidation of CO in the presence of H2, CO2 and H2O, on different zeolite-supported Pt catalysts by V. Sebastian; S. Irusta; R. Mallada; J. Santamaría (pp. 242-251).
The selective oxidation of CO has been studied over different Pt/zeolite catalysts. The effect of H2O and CO2 in the reactor depended on the specific catalyst, with the stronger influence for Pt–ETS-10:CO2 strongly inhibited its activity and also caused a large decrease in its selectivity but these effects were completely reversed upon the introduction of water.The selective oxidation of CO in the presence of H2O and CO2 has been studied on Pt supported on different zeolitic materials (MOR, ZSM-5, FAU and ETS-10) using a range of operating conditions and a variety of characterization techniques. The behavior of the Pt–ETS-10 and Pt–FAU catalysts has been investigated in more depth and the results obtained have been compared and related to the different characteristics of the supports. The best results in the presence of H2O and CO2 were obtained with Pt–FAU catalysts, showing stable catalytic activity and complete conversion of CO ( λ=2) at 439K.
Keywords: CO SELOX; Selective oxidation; Microporous materials; ETS-10; Faujasite; Platinum; Fuel cells
Co/CeO2-ZrO2 catalysts prepared by impregnation and coprecipitation for ethanol steam reforming by Sean S.-Y. Lin; Hideo Daimon; Su Y. Ha (pp. 252-261).
Hydrogen production rate as a function of ethanol feeding rate for impregnated and coprecipitated 10% Co/CeO2-ZrO2 catalysts are tested. Steam-to-carbon ratio of 6.5 is used at the reaction temperature of 450°C. The impregnated catalyst is denoted as IM-10% Co/CeO2-ZrO2. The catalysts coprecipitated at pH=11.5, pH=12.2, and pH=13.1 are denoted as CP11-10% Co/CeO2-ZrO2, CP12-10% Co/CeO2-ZrO2 and CP13-10% Co/CeO2-ZrO2, respectively. A significant difference in the hydrogen production rate is actualized in various samples with increase of the ethanol feeding rate. IM-10% Co/CeO2-ZrO2 catalyst produces the highest amount of hydrogen at a high feeding rate of ethanol (0.0137mol/h).Co/CeO2-ZrO2 catalysts for the ethanol steam reforming were prepared by wet incipient impregnation and coprecipitation methods. These catalysts were characterized by nitrogen adsorption, TEM-EDX, XRD, H2-TPR, and CO chemisorption techniques. It was found that the catalyst reducibility was influenced by the preparation methods; catalysts with different reduction behaviors in the pre-reduction showed different catalytic activities toward hydrogen production. The H2-TPR studies suggested the presence of metal–support interactions in Co/CeO2-ZrO2 catalysts during their hydrogen pre-reduction, a necessary treatment process for catalysts activation. These interactions were influenced by the preparation methods, and the impregnation method is a favorable method to induce a proper metal–support effect that allows only partial reduction of the cobalt species and leads to a superior catalytic activity for the hydrogen production through ethanol steam reforming. At 450°C, the impregnated catalyst gives a hydrogen production rate of 147.3mmol/g-s at a WHSV of 6.3h−1 (ethanol) and a steam-to-carbon ratio of 6.5.
Keywords: Ethanol steam reforming; Cobalt; Wet incipient impregnation; Coprecipitation; Hydrogen production; Temperature-programmed reduction (TPR)
Brønsted acidity study of fiberglass materials by H/D-exchange by T.S. Glazneva; E.M. Sadovskaya; A.P. Suknev; V.B. Goncharov; L.G. Simonova; E.A. Paukshtis; B.S. Bal’zhinimaev (pp. 262-268).
The kinetics of hydrogen isotopic exchange over fiberglass materials and reference samples (HZSM-5, SiO2, H3PO4/SiO2) was studied under the dynamic adsorption–desorption equilibrium. The numerical modeling of H/D-exchange dynamics provided the number of different Brønsted acid sites (BAS) of fiberglass materials. Besides, for the first time the correlation between H/D-exchange rate and proton affinity scale was established. The strength of BAS in fiberglass materials was shown to be comparable to that of HZSM-5.The kinetics of hydrogen isotopic exchange over fiberglass materials and reference samples (SiO2, H3PO4/SiO2, and HZSM-5) was studied at 500°C under the dynamic adsorption–desorption equilibrium. The concentrations and H/D-exchange rates of different Brønsted acid sites (BAS) were determined using the numerical modeling of isotope exchange dynamics. The correlation between H/D-exchange rate of reference samples and their acidity determined by FTIR spectroscopy of adsorbed CO was established. Based on this correlation, the strength of BAS in fiberglass materials was shown to be comparable to that of HZSM-5 zeolite.
Keywords: Fiberglass materials; Brønsted acidity; H/D-exchange
Catalytic performance of silica-aluminas synthesised with the help of chitosan biopolymer by Marisa Falco; Jaime Retuert; Alexis Hidrobo; Cristian Covarrubias; Paulo Araya; Ulises Sedran (pp. 269-274).
Silica-aluminas synthesised with the help of chitosan biopolymer to form inorganic–organic composites, were compared to analogous catalysts synthesised conventionally. Evidences of stabilization in the physical and chemical properties were observed in the chitosan-containing catalysts. The catalytic performance was evaluated with the conversion of tri-isopropylbenzene to assess activity and accessibility, and cyclohexene to assess hydrogen transfer properties. The highest activity and accessibility was observed in the hydrotreated, chitosan-containing catalyst, while hydrogen transfer capabilities were similar to those of medium unit cell sizes, equilibrium commercial FCC catalysts.Mesoporous amorphous silica-aluminas were synthesised with standard aluminium and silicon sources by means of the formation of inorganic–organic composites with the addition of chitosan biopolymer, and compared to analogous catalysts synthesised conventionally. Some catalysts were subjected to hydrothermal treatment. The resulting specific surface areas were from 480 to 573m2/g in the untreated samples and 300–430m2/g in the hydrotreated catalysts, average pore sizes ranging from 32 to 100Å with sharp, unimodal distributions. The chitosan materials showed higher specific surface areas and larger pore sizes than those of their non-chitosan counterparts. The most important differences in the acidic properties were in the relationships between tetrahedral and octahedral aluminium atoms, the chitosan materials having higher relative amounts of tetrahedral aluminium than the conventional silica-aluminas. Evidences of stabilization in the physical and chemical properties were observed in the chitosan-containing catalysts. The catalytic performance was evaluated with the conversion of tri-isopropylbenzene at 400°C, to assess activity and accessibility, and cyclohexene at 300°C, to assess hydrogen transfer properties. The highest activity and accessibility was observed in the hydrotreated, chitosan-containing catalyst, while hydrogen transfer capabilities were similar to those of medium unit cell sizes, equilibrium commercial FCC catalysts.
Keywords: Silica-alumina; Chitosan; FCC
Iron-substituted polyoxotungstates as catalysts in the oxidation of indane and tetralin with hydrogen peroxide by Ana C. Estrada; Mário M.Q. Simões; Isabel C.M.S. Santos; M. Graça P.M.S. Neves; Artur M.S. Silva; José A.S. Cavaleiro; Ana M.V. Cavaleiro (pp. 275-281).
Tetrabutylammonium salts of iron(III)-substituted polyoxotungstates of general formula [XW11Fe(H2O)O39] n−, X=P, Si or B are shown to act as efficient catalysts for the homogeneous liquid phase oxidation of indane and tetralin with hydrogen peroxide, an environmentally clean and easy to handle oxidant, affording mainly the corresponding ketones.The homogeneous liquid phase oxidation of indane and tetralin with hydrogen peroxide catalysed by tetrabutylammonium salts of iron(III)-substituted polyoxotungstates of general formula [XW11Fe(H2O)O39] n−, X=P, Si or B is described. The system presented here gives rise to benzylic monooxygenation and dioxygenation products. Indane oxidation reactions produce also dehydrogenation and hydroperoxidation products. As a result, 1 H-indene and indane hydroperoxide are formed. Interestingly, tetralin gives rise to the cleavage of carbon–carbon bond, producing 4-(2-hydroxyphenyl)butanal. In the present conditions, this aldehyde is probably arising from tetralin hydroperoxide. Depending on the reaction conditions, moderate selectivities for the corresponding ketones are obtained, affording conversions as high as 59% and 34% for indane and tetralin, respectively. In order to understand the reactions pathway, the oxidation of 1-indanol, 1-indanone, 1 H-indene, 1-tetralol and 1-tetralone is also carried out with an iron(III)-substituted polyoxotungstate as catalyst and H2O2 as oxidant. The results show that 1-indanol and 1-tetralol give an important contribution for the formation of the corresponding ketones. As far as we know, the use of iron-substituted polyoxotungstates in the oxidation of these arenes is presented for the first time.
Keywords: Polyoxometalates; Polyoxotungstates; Oxidation; Hydrogen peroxide; Indane; Tetralin
Carbon-based monoliths for the catalytic elimination of benzene, toluene and m-xylene by Agustín F. Pérez-Cadenas; Sergio Morales-Torres; Francisco J. Maldonado-Hódar; Francisco Carrasco-Marín (pp. 282-287).
The catalytic behaviour of Pt supported on carbon-based monoliths was studied in the low-temperature catalytic combustion of benzene, toluene and m-xylene and compared with the corresponding behaviour of Pt supported on γ-Al2O3 coated monoliths. Carbon-based monoliths showed a much better catalytic performance which is ascribed to the fact that the carbon surface is more hydrophobic than the γ-Al2O3 one, and the release of water molecules produced during the combustion is favoured.The catalytic behaviour of Pt supported on carbon-based monoliths was studied in the low-temperature catalytic combustion of benzene, toluene and m-xylene and compared with the corresponding behaviour of Pt supported on γ-Al2O3 coated monoliths. Carbon-based monoliths showed a much better catalytic performance which is ascribed to the fact that the carbon surface is more hydrophobic than the γ-Al2O3 one.
Keywords: Carbon supports; Coating; Monolithic catalysts; BTX combustion; Platinum
Characterization and catalytic properties of the CuO/SiO2 catalysts prepared by precipitation-gel method in the hydrogenolysis of glycerol to 1,2-propanediol: Effect of residual sodium by Zhiwei Huang; Fang Cui; Haixiao Kang; Jing Chen; Chungu Xia (pp. 288-298).
The residual sodium in the CuO/SiO2 catalysts prepared by precipitation-gel method showed a negative effect on the chemical–physical properties but a promotion effect on the activity and stability of the catalysts in glycerol hydrogenolysis. A certain amount of sodium is needed for CuO/SiO2 catalyst to exhibit both high activity and good stability in glycerol reactions.The effect of residual sodium on the CuO/SiO2 catalysts prepared by precipitation-gel (PG) method has been investigated in correlation with the detailed characteristics of active component performance and catalytic performance in glycerol hydrogenolysis. Characterization of the catalysts showed that the residual sodium had a negative effect on the chemical–physical properties of the catalysts, such as the BET surface area, the dispersion of copper, and the reducibility of Cu2+ species as well as the adsorbility of reactant molecules. As a consequence, the conversion and selectivity of the catalysts in glycerol reactions generally decreased with increasing sodium content. The leaching of sodium from catalyst surface as a base could, however, on the one hand, weakly promote the activity of the catalyst, and on the other hand, could help retard the leaching of the active copper component and reduce the deactivation rate of the catalyst. The glycerol hydrogenolysis reaction is supposed to be a structure-sensitive reaction, in which copper particle sizes lower than a critical limit or those that did not fulfill a certain ensemble requirement were not active for glycerol reaction. Such details explained the lower TOFs of the catalysts with much smaller sizes. A certain amount of sodium is deduced to be needed for CuO/SiO2 catalyst to exhibit both high catalytic activity and good stability. In addition, a reaction mechanism based on the effect of sodium on the activity and selectivity in glycerol hydrogenolysis has been proposed.
Keywords: CuO/SiO; 2; catalyst; Sodium effect; Precipitation-gel method; Glycerol; Hydrogenolysis; Propanediol
Trimerization of isobutene over WO x/ZrO2 catalysts by Ji Sun Lee; Ji Woong Yoon; Shiva B. Halligudi; Jong-San Chang; Sung Hwa Jhung (pp. 299-303).
Isobutene can be trimerized very effectively over WO x/ZrO2 catalyst that is obtained by impregnation and high temperature calcination at 700°C. The WO x/ZrO2 catalyst having the tetragonal structure of zirconia is one of the best catalysts for the isobutene trimerization exhibiting stable and high conversion, high selectivity for trimers and facile regeneration.Trimerization of isobutene to produce isobutene trimers has been investigated over WO x/ZrO2 catalysts that were obtained by wet-impregnation and successive calcination at high temperatures. Very stable isobutene conversion and high selectivity for trimers are attained over a WO x/ZrO2 catalyst obtained by calcination at 700°C. From the XRD study it can be understood that tetragonal ZrO2 is beneficial for stable performance; however, monoclinic ZrO2 is not good for trimerization. Nitrogen adsorption and FTIR experiments suggest that amorphous WO x/ZrO2 is inefficient catalyst even though it has high surface area and high concentration of acid sites. The observed performance with the increased selectivity and stable conversion demonstrates that a WO x/ZrO2 having tetragonal zirconia, even with decreased porosity and acid sites, is one of the best catalysts to exhibit stable and high conversion, high selectivity for trimers and facile regeneration.
Keywords: WO; x; /ZrO; 2; Isobutene; Trimerization; Lewis acid site
Catalytic dehydration of 1,2-propanediol into propanal by Keitaro Mori; Yasuhiro Yamada; Satoshi Sato (pp. 304-308).
Vapor-phase catalytic dehydration of 1,2-propanediol was investigated over several catalysts, such as acidic oxides and supported heteropoly acids. These acids catalyze the dehydration of 1,2-propanediol to produce propanal. In particular, silica-supported silicotungstic acid showed the highest catalytic activity in the formation of propanal. Under optimum reaction conditions, 100% conversion was attained with propanal selectivity higher than 93mol% at 200°C.Vapor-phase catalytic dehydration of 1,2-propanediol was investigated over several catalysts, such as acidic oxides and supported heteropoly acids. These acids catalyze the dehydration of 1,2-propanediol to produce propanal. In particular, silica-supported silicotungstic acid showed the highest catalytic activity in the formation of propanal. At low conversions, however, propanal reacted with another 1,2-propanediol to produce a cyclic acetal (2-ethyl-4-methyl-1,3-dioxolane). Such acetal formation reduced the selectivity to propanal. Under optimum reaction conditions, 100% conversion was attained with propanal selectivity higher than 93mol% at 200°C.
Keywords: Dehydration; 1,2-Propanediol; Propanal; Heteropoly acid; Silicotungstic acid
Effective decolorizations and mineralizations of organic dyes over a silver germanium oxide photocatalyst under indoor-illumination irradiation by Shuxin Ouyang; Naoki Kikugawa; Zhigang Zou; Jinhua Ye (pp. 309-314).
A silver germanium oxide was developed as a photocatalyst which could work under the irradiation of white fluorescent lamp. Efficient decolorizations and mineralizations of the organic dyes were achieved over this material: 79% (90%) of the organic carbon in the Methylene Blue (Rhodamine B) solution was photooxidatized to inorganic carbon forms, when these dyes were totally decolorized.A silver germanium oxide, Ag2GeO3, was developed as a novel photocatalyst for degradation of organic dyes. The chemical composition of the sample was investigated via the SEM/EDX, ICP-AES, and TG-DTA techniques. The general activity of the material was characterized by testing the photodegradations of typical organic dyes, such as Methylene Blue (one of the heteropolyaromatic dyes), Rhodamine B (one of the xanthene dyes), Fuchsin Acid (one of the sulfonic dyes), and Orange II (one of the azoic dyes). All of these dyes were degraded more than 90% within 25min under the visible-light irradiation of Xe lamp. Besides, with a commercial white fluorescent lamp as testing light source (light intensity, 61μW/cm2), the efficient decolorizations and mineralizations of the organic dyes were achieved over this material: 79% (90%) of the organic carbon in the Methylene Blue (Rhodamine B) solution was photooxidatized to inorganic carbon forms, when these dyes were totally decolorized. The high performance of this material is due to the photophysical properties of the wide-visible-range absorption and response, and the sufficient oxidative potential of the top of the valence band.
Keywords: Photocatalysis; Silver germanium oxide; Dye degradation; Methylene Blue; Rhodamine B; Fuchsin Acid; Orange II
Synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification: Catalyst screening and reaction optimization by José R. Ochoa-Gómez; Olga Gómez-Jiménez-Aberasturi; Belén Maestro-Madurga; Amaia Pesquera-Rodríguez; Camilo Ramírez-López; Leire Lorenzo-Ibarreta; Jesús Torrecilla-Soria; María C. Villarán-Velasco (pp. 315-324).
The synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification is reported. Basic catalysts work much better than acidic ones. Catalytic activity is strongly dependent on base strength. After a catalyst screening study, CaO was selected as catalyst. Following an optimization study a ∼100% conversion and a 95% yield were achieved in 90min at 95°C, 0.06 catalyst:glycerol molar ratio and 3.5 dimethyl carbonate:glycerol molar ratio.The synthesis of glycerol carbonate from glycerol and dimethyl carbonate by transesterification is reported. Firstly, a catalyst screening has been performed by studying the influence of different basic and acid homogeneous and heterogeneous catalysts on reaction results. Catalytic activity is extremely low for acidic catalysts indicating that reaction rate is very slow. On the contrary, high conversions and yields are obtained for basic catalysts. Catalytic activity increases with catalyst basic strength. The best heterogeneous catalyst is CaO. Calcination of CaO increases dramatically its activity due to calcium hydroxide removal from its surface. A reaction optimization study has been carried out with CaO as catalyst by using a factorial design of experiments leading to operation conditions for achieving a 100% conversion and a >95% yield at 1.5h reaction time: 95°C, catalyst/glycerol molar ratio=0.06 and dimethyl carbonate/glycerol molar ratio=3.5. Carbonate glycerol can be easily isolated by filtering the catalyst out and evaporating the filtrate at vacuum. Leaching of catalyst in reaction medium was lower than 0.34%. Catalyst recycling leads to a quick decrease in both conversions and yields probably due to a combination of catalyst deactivation by CaO exposure to air between catalytic runs, and a decrease in the catalyst surface area available for reaction due to particle agglomeration.
Keywords: Glycerol carbonate; Base-catalyzed transesterification; Glycerol; Calcium oxide
An effect of iron(III) oxides crystallinity on their catalytic efficiency and applicability in phenol degradation—A competition between homogeneous and heterogeneous catalysis by Robert Prucek; Martin Hermanek; Radek Zbořil (pp. 325-332).
Nanocrystalline and amorphous Fe2O3 catalysts in phenol degradation are compared. Amorphous nanopowders are partially susceptible to leaching in acidic media and therefore act as mixed homogeneous/heterogeneous catalysts. Nanocrystalline Fe2O3 catalysts, on the other hand, remain stable during the phenol degradation process and act almost solely by a heterogeneous way.Catalytic efficiency, stability and environmental applicability of five iron(III) oxide nanopowders differing in surface area and crystallinity were tested in degradation of concentrated phenolic aqueous solutions (100g/L) at mild temperature (30°C), initially almost neutral pH and equimolar ratio of hydrogen peroxide and phenol. The catalyst properties were easily controlled by varying in reaction time during isothermal treatment of ferrous oxalate dihydrate in air at 175°C. Although the catalytic efficiency clearly increases with the surface area of the nanopowders, it is not due to the solely heterogeneous catalytic mechanism as would be expected. The amorphous Fe2O3 nanopowders possessing the largest surface areas (401m2g−1, 386m2g−1) are the most efficient catalysts evidently due to their highest susceptibility to leaching in acidic environment arising as a consequence of phenol degradation products. Thus, these amorphous samples act partially as homogeneous catalysts, which was confirmed by a high concentration of leached Fe(III) ions in the solution (∼19ppm). The crystalline hematite (α-Fe2O3) samples, varying in surface area between 337m2g−1 and 245m2g−1, are generally less efficient when compared to the amorphous powders, however their catalytic action is almost exclusively heterogeneous as only 3ppm of leached Fe(III) was found in the reaction systems catalyzed by nanohematite samples. A significant difference in relative contributions of heterogeneous and homogenous catalysis was definitely established in buffered reaction systems catalyzed by amorphous Fe2O3 and nanocrystalline hematite. The nanohematite sample exhibiting the highest heterogeneous action was tested at decreased initial phenol concentration (10g/L), which is closer to the real contents of phenol in waste waters, and at different hydrogen peroxide/phenol molar ratios to consider its environmental applicability. At the hydrogen peroxide/phenol ratio equal to 5, no traces of the leached iron were detected and the phenol conversion of 84% was reached. Moreover, such a high degree of conversion is accompanied by a decrease of the chemical oxygen demand (COD) from the initial value of 11.23g/L to 4.22g/L after 125min. This fact indicates that the considerable fraction of primary reaction products was totally degraded.
Keywords: Amorphous; Nanoparticles; Fenton; H; 2; O; 2; Phenol; Catalyst; Decomposition
Development of Ni-Pd bimetallic catalysts for the utilization of carbon dioxide and methane by dry reforming by Bernd Steinhauer; Mohan Reddy Kasireddy; Jörg Radnik; Andreas Martin (pp. 333-341).
CO2 reforming of methane using Ni-Pd bimetallic catalysts was investigated. Best conversions of CO2 of 78% and CH4 of 73% were obtained using a 7.5 wt% NiPd (80:20) ZrO2-La2O3 supported catalyst at 700°C. CO and H2 yields of 57% and 59%, resp, were obtained. The catalysts were characterized by XRD, ICP, XPS and TEM.The present research deals with catalyst development for the utilization of CO2 in dry reforming of methane with the aim of reaching highest yield of the main product synthesis gas (CO, H2) at lowest possible temperatures. Therefore, Ni-Pd bimetallic supported catalysts were prepared by simple impregnation method using various carriers. The catalytic performance of the catalysts was investigated at 500, 600 and 700°C under atmospheric pressure and a CH4 to CO2 feed ratio of 1. Fresh, spent and regenerated catalysts were characterized by N2 adsorption for BET surface area determination, XRD, ICP, XPS and TEM. The catalytic activity of the studied Ni-Pd catalysts depends strongly on the support used and decreases in the following ranking: ZrO2-La2O3, La2O3>ZrO2>SiO2>Al2O3>TiO2. The bimetallic catalysts were more active than catalysts containing Ni or Pd alone. A Ni to Pd ratio=4 at a metal loading of 7.5 wt% revealed the best results. Higher loading lead to increased formation of coke; partly in shape of carbon nanotubes (CNT) as identified by TEM. Furthermore, the effect of different calcination temperatures was studied; 600°C was found to be most favorable. No effect on the catalytic activity was observed if a fresh catalyst was pre-reduced in H2 prior to use or spent samples were regenerated by air treatment. Ni and Pd metal species are the active components under reaction conditions. Best conversions of CO2 of 78% and CH4 of 73% were obtained using a 7.5 wt% NiPd (80:20) ZrO2-La2O3 supported catalyst at a reaction temperature of 700°C. CO and H2 yields of 57% and 59%, respectively, were obtained.
Keywords: Dry reforming of methane; Syngas; Ni-Pd bimetallic supported catalyst; Carbon nanotubes; Coke formation; CO; 2; utilization
Characterization and carbonylic hydrogenation of methyl oleate over Ru-Sn/Al2O3: Effects of metal precursor and chlorine removal by David A. Echeverri; Juan M. Marín; Gloria M. Restrepo; Luis A. Rios (pp. 342-347).
Hydrogenation of methyl oleate to oleyl alcohol was evaluated over Ru-Sn/Al2O3 catalysts, prepared from different precursors, at 270°C and 5.0MPa. The best catalysts were obtained either from chlorine-free sources or after elimination of residual chlorine on metal-chloride-based catalysts. However, the most selective catalyst was obtained by NaBH4 reduction of catalyst prepared from chlorine precursors.Hydrogenation of methyl oleate to oleyl alcohol was evaluated over Ru-Sn/Al2O3 catalysts, prepared from different precursors, at 270°C and 5.0MPa. Two kinds of metal precursors were employed: chlorine-free precursors and inorganic chlorides. In addition, several methods for chlorine removal of metal-chloride-based catalysts were studied. Catalysts were characterized by EDX, XRF, DRX, BET and TPR analyses. Selectivity toward unsaturated alcohol was higher with the bimetallic catalyst based on chlorine-free precursors than with the catalyst based on metal chlorides, owing that chlorine avoids, at certain extent, an effective interaction between ruthenium and tin species. However, the most selective catalyst was the bimetallic one based on chloride precursors and reduced with NaBH4, due to elimination of residual chlorine and higher dispersion of Ru-Sn species.
Keywords: Oleyl alcohol; Hydrogenation; Ruthenium-tin catalysts; Fatty esters
Easy separation and reutilization of the Jacobsen's catalyst in olefin oxidation by Jairo Cubillos; Iván Montilla; Consuelo Montes de Correa (pp. 348-352).
A new method for recycling the Jacobsen's catalyst applied to the catalytic oxidation of R-(+)-limonene and cis-ethyl cinnamate at room temperature using in situ generated dimethyldioxirane (DMD) as oxidizing agent is presented. The strategy was to vary the solubility of the catalyst during reaction. The catalyst was quite stable towards oxidative degradation.A new method for recycling the Jacobsen's catalyst used for the catalytic oxidation of R-(+)-limonene and cis-ethyl cinnamate at room temperature by in situ generated dimethyldioxirane (DMD) as oxidizing agent is presented. Neither the immobilization of the catalyst to the solid support nor modification of its chemical structure is involved in this method. Therefore, the excellent catalytic properties of the Jacobsen's catalyst could be retained. Limonene diepoxide was the main product of the oxidation of R-(+)-limonene, whereas a single epoxide with good enanantioselectivity (78% ee) was obtained in the asymmetric oxidation of cis-ethyl cinnamate. On the other hand, R-(+)-limonene showed to be more reactive than cis-ethyl cinnamate. In both cases, the catalyst was recovered and recycled without appreciable loss of its initial catalytic activity.
Keywords: Catalytic oxidation; Jacobsen's catalyst; Dimethyldioxirane; Catalyst recovery; Catalyst reusability
Catalytic decomposition of alcohols over size-selected Pt nanoparticles supported on ZrO2: A study of activity, selectivity, and stability by S. Mostafa; Jason R. Croy; H. Heinrich; B. Roldan Cuenya (pp. 353-362).
This article describes H2 production by decomposition of C1–C4 alcohols over size-selected Pt-nanoparticles supported on nanocrystalline ZrO2. Alcohol conversion and H2 production were found to increase as ethanol<2-butanol<2-propanol2-supported size-selected Pt nanoparticles for the decomposition of methanol, ethanol, 2-propanol, and 2-butanol. The potential of each alcohol for the production of H2 and other relevant products in the presence of a catalyst is studied in a packed-bed mass flow reactor operating at atmospheric pressure. All the alcohols studied show some decomposition activity below 200°C which increased with increasing temperature. In all cases, high selectivity towards H2 formation is observed. With the exception of methanol, all alcohol conversion reactions lead to catalyst deactivation at high temperatures ( T>250°C for 2-propanol and 2-butanol, T>325°C for ethanol) due to carbon poisoning. However, long-term catalyst deactivation can be avoided by optimizing reaction conditions such as operating temperature.
Keywords: Pt; Nanoparticles; ZrO; 2; Catalyst; Methanol; Ethanol; Propanol; Butanol; Mass flow reactor; Mass spectrometry
Selective CO removal in a H2-rich stream over supported Ru catalysts for the polymer electrolyte membrane fuel cell (PEMFC) by Yun Ha Kim; Eun Duck Park; Hyun Chul Lee; Doohwan Lee (pp. 363-369).
We prepared various Ru catalysts supported on different supports such as yttria-stabilized zirconia (YSZ), ZrO2, TiO2, SiO2 and γ-Al2O3 with a wet impregnation method. We applied them to the selective CO removal in a hydrogen-rich stream via the preferential CO oxidation (PROX) and the selective CO methanation simultaneously. Among them, Ru/YSZ showed the highest CO conversion especially at low temperatures. Several measurements: the N2 physisorption, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), the CO chemisorptions, the temperature-programmed oxidation (TPO), the temperature-programmed reduction (TPR), the temperature-programmed desorption (TPD) of CO2 with mass spectroscopy and the transmission electron microscopy (TEM), were conducted to characterize the catalysts. No linear correlation can be found between the amount of CO chemisorbed at 300K and the PROX activity. On the other hand, the facile activation of O2 appeared to be closely related to the high PROX activity, judging by the TPO experiment. In addition, the strong adsorption of CO2 suppressed the low-temperature PROX activity. Ru/YSZ can be easily oxidized and also reduced at low temperatures. It is found that Ru/YSZ uptakes only small amounts of CO2, which can be desorbed at low temperatures. Ru/YSZ can reduce the high inlet CO concentration to be less than 10ppm even in the presence of H2O and CO2.Ru/YSZ showed the highest CO conversion among Ru catalysts supported on yttria-stabilized zirconia (YSZ), ZrO2, TiO2, SiO2 and γ-Al2O3. Ru/YSZ can be oxidized and also reduced at low temperatures. Ru/YSZ uptakes only small amounts of CO2 which can be desorbed at low temperatures. Ru/YSZ can reduce the high inlet CO concentration to be less than 10ppm even in the presence of H2O and CO2.
Keywords: Selective CO oxidation; PROX; Ru catalysts; PEMFC; Fuel cell