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Applied Catalysis A, General (v.452, #)
Photoinduced reactions occurring on activated carbons. A combined photooxidation and ESR study by Leticia F. Velasco; Valter Maurino; Enzo Laurenti; Isabel M. Fonseca; Joao C. Lima; Conchi O. Ania (pp. 1-8).
Display Omitted► Ash-free carbons photooxidize phenol from solution. ► UV light/carbon interactions generated radical species. ► Hydroxyl radicals have been detected by ESR. ► Ash content increased phenol photodegradation yield. ► Hydroxyl radicals as a key factor in the photoactivity of carbon materials.This work demonstrates the ability of ash-free activated carbons to interact with UV light to promote the photooxidation of phenol in solution through the formation of radical species. Our results show that in the absence of inorganic impurities or semiconductor additives, the photodegradation efficiency of the studied activated carbons has to be ascribed to the carbon matrix itself. Hydroxyl radicals have been detected by spin trapping electron spin resonance spectroscopy upon UV irradiation of the activated carbon suspensions in aqueous solution. Although the ability to photogenerate radicals upon irradiation is well known in inorganic semiconductors (such as titanium dioxide) or carbon/semiconductor composites, we herein demonstrate the capacity of the carbon matrix alone to interact with UV light, generating reactive species that would be responsible for the observed photoinduced reaction using carbons alone in the absence of semiconductor additives. Thus, the conventional interpretation of the enhanced photodegradation efficiency of carbon/semiconductor photocatalysts -so far attributed to synergistic and confinement effects, and minimized surface recombination of the charge carriers- should be reconsidered to account for the radicals photogenerated when the carbons are exposed to UV light.
Keywords: Hydroxyl radicals; Ash-free materials; Activated carbon; Photooxidation; Electron spin resonance
Partial hydrogenation of benzene on Ru catalysts: Effects of additives in the reaction medium by Raphael Soeiro Suppino; Richard Landers; Antonio José Gomez Cobo (pp. 9-16).
Display Omitted► Impregnation methods induce remarkable effects on Ru/Al2O3 catalytic performance. ► Formaldehyde is a fine reduction agent for wet-impregnated catalysts. ► Ru/Al2O3 leads to higher cyclohexene yields compared to Ru/CeO2. ► Presence of amines or alcohols in the reaction medium increases cyclohexene yield.The partial hydrogenation of benzene is an interesting chemical reaction mostly because of cyclohexene, a compound that can be part of the production chain of many other chemicals. In the present work, it was investigated the effects of additives in the reaction medium on the performance of Ru/Al2O3 and Ru/CeO2 catalysts for the partial hydrogenation of benzene in liquid phase. The Ru catalysts were prepared by incipient impregnation or wet impregnation, both from aqueous solution of the precursor RuCl3· xH2O. The catalysts prepared by incipient impregnation were reduced at 573K under H2 flow, whereas formaldehyde was used to reduce the catalysts prepared by wet impregnation. The solids were characterized by potentiometric titration, N2 physisorption, SEM, TEM, EDX, XPS and TPR. The catalytic performance in the liquid phase was evaluated using a slurry Parr reactor at 373K and under 5MPa of H2 pressure. The additives studied were the following: ethylenediamine, ethyl acetate, n-methyl-2-pyrrolidone, monoethyleneglycol and monoethanolamine. The results indicate that the Ru/Al2O3 catalyst, prepared by wet impregnation, leads to the highest values of activity and selectivity. The yield of cyclohexene follows the order: monoethanolamine>monoethyleneglycol>n-methyl-2-pyrrolidone≫ethyl acetate>without additive≫ethylenediamine.
Keywords: Benzene hydrogenation; Ruthenium catalyst; Cyclohexene; Additive
2,3,5-Trimethylphenol oxidation over Co-based solid catalysts by Clara Saux; Luis R. Pizzio; Liliana B. Pierella (pp. 17-23).
Display Omitted► Trimethylphenol selective oxidation to trimethylbenzoquinone and trimethylhydroquinone. ► K6[CoW12O40]·6H2O supported on ZSM-5 presents best behavior as oxidation catalyst. ► The estimate activation energy for trimethylphenol oxidation is 94.19kJ/mol.2,3,5-Trimethylphenol (TMP) was oxidized with hydrogen peroxide employing cobalt based solid materials. K6[CoW12O40]·6H2O (CoW12) was probed as selective catalyst for the oxidation obtaining better results when it was supported over ZSM-5 zeolites (CoW12-ZSM-5). CoW12-ZSM-5 was found to be an efficient catalyst in the oxidation of TMP to 2,3,5-trimethylbenzoquinone (TMBQ) and 2,3,5-trimethylhydroquinone (TMHQ) under mild reaction conditions. Liquid phase reaction parameters were evaluated obtaining better results employing hydrogen peroxide as oxidant, with an oxidant/substrate molar ratio of 5, methanol as solvent and 60°C as reaction temperature. An apparent activation energy of 94.19kJ/mol was obtained.
Keywords: 2,3,5-Trimethylphenol; 2,3,5-Trimethylbenzoquinone; 2,3,5-Trimethylhydroquinone; Hydrogen peroxide; Co-based solid catalysts
Multi-walled carbon nanotubes functionalized with a palladium(II)-Schiff base complex: A recyclable and heterogeneous catalyst for the copper-, phosphorous- and solvent-free synthesis of ynones by Mozhgan Navidi; Barahman Movassagh; Saeed Rayati (pp. 24-28).
Multi-walled carbon nanotubes functionalized with a palladium(II)-Schiff base complex: a recyclable and heterogeneous catalyst for the copper-, phosphorous- and solvent-free synthesis of ynones.Display Omitted► A heterogeneous, air-moisture stable and reusable catalyst is utilized.► The reaction is performed under a very low catalyst loading.► A copper-, phosphorous- and solvent-free CC coupling reaction is reported.The air-moisture stable and reusable multi-walled carbon nanotubes (MWCNTs) functionalized with a palladium(II)-Schiff base complex was synthesized by covalently anchoring a hydroxyl functionalized palladium(II)-Schiff base complex to modified MWCNTs. This heterogeneous catalyst exhibited effective catalytic activities by affording ynones in excellent yields from coupling reactions of acid chlorides with terminal alkynes under copper-, phosphorous- and solvent-free conditions in air.
Keywords: Ynones; MWCNTs-Pd(II)-Schiff base; C; C coupling; Terminal alkynes; Acyl chlorides
Sulfated tungstate catalyzed selective N-monoalkylation of primary amines with alcohol by Sagar P. Pathare; Krishnacharya G. Akamanchi (pp. 29-33).
Display Omitted► Sulfated tungstate is mildly acidic, stable, eco-friendly heterogeneous catalyst. ► The catalyst is easy to prepare and well characterized. ► Efficient for selective N-monoalkylation of primary amines. ► The catalyst can be easily recovered and recycled several times.We have developed an environmentally benign protocol for N-monoalkylation of primary amines with alcohols using sulfated tungstate as heterogeneous catalyst. Elimination of formation of overalkylated amines as by-products, use of alcohols as alkylating agent has resulted in high atom-economy transformation. In addition efficient, mild reaction conditions, easy product isolation and reusability of the catalyst are attractive features. The developed protocol has been successfully applied for N-monoalkylation of aromatic as well aliphatic amines with different alcohols.
Keywords: N; -monoalkylation; Sulfated tungstate; Heterogeneous catalysis; Amines; Alcohol
Liquid-phase dehydration of sorbitol to isosorbide using sulfated zirconia as a solid acid catalyst by Nazmul Abedin Khan; Dinesh Kumar Mishra; Imteaz Ahmed; Ji Woong Yoon; Jin-Soo Hwang; Sung Hwa Jhung (pp. 34-38).
Display Omitted► Isosorbide is produced in liquid-phase dehydration of sorbitol. ► The liquid-phase dehydration is carried out firstly with solid inorganic catalysts. ► Sulfated zirconia is suggested as a potential catalyst for the isosorbide production.Sulfated zirconia catalysts have been prepared with zirconium (IV) hydroxide and sulfuric acid as the sources of zirconia and sulfate group, respectively. In this study, liquid-phase dehydration of sorbitol to isosorbide is investigated in the presence of the catalysts under various reaction conditions including reaction temperature, time, catalyst dosage and sulfur content/acidity of the catalysts. The results show that sulfated zirconia, with high sulfur content and a tetragonal crystalline structure, is a promising solid acid catalyst that can be used at least four times in the dehydration of sorbitol to isosorbide.
Keywords: Sorbitol dehydration; Isosorbide; Solid acid; Zirconia; Sulfation
Simultaneous synthesis of styrene and aniline over activated carbon catalysts. Influence of the surface chemistry by Anna Malaika; Paulina Rechnia; Beata Krzyżyńska; Agnieszka Tolińska; Adriana Kawałko; Mieczysław Kozłowski (pp. 39-47).
Display Omitted► Oxidised activated carbons were prepared using different precursors. ► Activity of carbons in dehydrogenation/hydrogenation coupled process was determined. ► Oxidised samples were more effective catalysts in this process than the initial ones. ► Activity of the catalysts is probably affected by the carbonyl/quinone groups.Activated carbons prepared from different precursors and two commercial carbons were applied as catalysts of ethylbenzene dehydrogenation carried out in the presence of nitrobenzene as an oxidiser (ODE-N process). Using of nitrobenzene enabled obtaining not only styrene, but also second industrially important product – aniline. Prior to the reaction some activated carbon samples were modified by oxidation with an air/helium mixture in order to generate carbonyl (quinone) structures on their surfaces, which are expected to be active centres of the process. The results obtained show that all samples prepared catalysed the ODE-N reaction and both surface texture and surface chemistry are important in the catalytic behaviour of activated carbons in this process.
Keywords: Dehydrogenation of ethylbenzene; Hydrogenation of nitrobenzene; Activated carbons
Pt-Mg-Ir/Al2O3 and Pt-Ir/HY zeolite catalysts for SRO of decalin. Influence of Ir content and support acidity by Silvana A. D’Ippolito; Laura B. Gutierrez; Carlos R. Vera; Carlos L. Pieck (pp. 48-56).
Display Omitted► Decalin ring opening using Pt-Ir/HY and Pt-Mg-Ir/Al2O3 catalysts were studied. ► Pt-Ir/HY catalyst was substantially more acid than Pt-Mg-Ir/Al2O3. ► Increasing the Ir content produced an increase of the hydrogenolytic activity. ► Pt-Ir/HY catalysts are better for SRO of decalin than those supported on alumina. ► Higher Ir content favored the formation of ring-opening products in all cases.Pt-Ir/HY and Pt-Mg-Ir/Al2O3 catalysts were studied and tested in the reaction of ring opening of decalin. The acidity of the alumina support was modified by addition of 3% Mg and the acidity of the zeolite by ion exchange with NH4Cl. The Pt content of the catalysts was fixed at 1% (mass basis) while the Ir content was adjusted between 0.1 and 0.6%. The catalysts were characterized by temperature programmed reduction, temperature programmed desorption of pyridine and FTIR of adsorbed CO. They were further tested with the reactions of cyclohexane dehydrogenation, cyclopentane hydrogenolysis and n-C5 isomerization.It was found that the Pt-Ir/HY catalyst was substantially more acid than Pt-Mg-Ir/Al2O3. Increasing the Ir content produced an increase of the hydrogenolytic activity and a decrease of the dehydrogenating activity of both catalysts. The n-pentane isomerization reaction results revealed that in the case of the alumina catalyst increasing the Ir content promoted both the catalyst stability and the cracking selectivity to C5 isomers. The opposite was found for the Pt-Ir/HY zeolite catalysts. The zeolite supported Pt-Ir catalysts performed better for decalin ring opening than those supported on alumina. Higher Ir content favored the formation of ring-opening products in all cases.
Keywords: Selective ring opening; Decalin; Pt–Ir; Diesel
Modified polystyrene anion exchange resins with long chain alkyl groups to enhance the aldolization reaction selectivity by Jiexiang Wang; Qiang Wang; Yu Deng; Yunhua Li; Bing H. Chen; Ruyun Zhang (pp. 57-63).
Display Omitted► Anion exchange resin as solid base catalysts for aldol condensation. ► Surfactants addition and Soxhlet extraction enhance the reaction. ► A direct graft of one or two long alkyl chains onto the commercial resins. ► Resins with addition of alkyl groups increased the yield significantly.The aldolization of formaldehyde and acetone to form 4-hydroxy-2-butanone over anion exchange resins with and without modifications is investigated in this work. Attempts such as surfactants addition and Soxhlet extraction are taken aiming to improve the aldolization selectivity thus the product yield. Subsequently, resins grafted long alkyl chains intrigue us for its steric hindrance effect and the synergic effect of weak and strong basic sites. Two types of modifications are carried out (1) one long alkyl chain on the copolymer tertiary amine via Menshutkin N-alkylation reaction; (2) two long alkyl chains: one on polystyrene aromatic ring through Friedel–Crafts alkylation under the circumstances of tertiary amine and the other on the copolymer tertiary amine using the Menshutkin N-alkylation reaction. The reaction results indicate that the yield for 4-hydroxy-2-butanone can be increased from 44.3% to around 50% for the resin with one long alkyl chain (the first case), while this can achieve up to 71.3% for the resin with two long alkyl chains.
Keywords: Solid base; Aldol condensation; Anion exchange resin; 4-Hydroxy-2-butanone
Performance and deactivation of Ir-based catalyst during hydroxylammonium nitrate catalytic decomposition by Rachid Amrousse; Toshiyuki Katsumi; Yosui Niboshi; Nobuyuki Azuma; Ahmed Bachar; Keiichi Hori (pp. 64-68).
Display Omitted► Uniform distribution of nano-size iridium particles into the alumina before test. ► Deactivation of iridium catalyst after HAN decomposition. ► Deactivation phenomena was caused by oxidation of iridium. ► Severe sintering of iridium catalyst after HAN decomposition reaction.The catalytic performance of Ir-based catalyst for the decomposition of high energetic liquid propellant was investigated in a monopropellant thruster. The changes of ignition delay, catalyst bed temperature and chamber pressure with the numbers of pulse-injection were demonstrated to be effective signposts of catalyst bed efficiencies. The catalyst in fresh state and that after its deactivation were characterized by N2-physisorption, XRD, H2-chemisorption, TEM, H2-TPR and XPS. It was noted that the particle distribution and oxidation state of iridium are the major indicators of catalyst deactivation.
Keywords: Thruster; Deactivation; HAN; Liquid propellant
Strong influence of structures around aluminum centers constructed in polyoxotungstates for catalytic oxidation of alcohols with dioxygen in water by Chika Nozaki Kato; Masaru Nagami; Nami Ukai (pp. 69-74).
Display Omitted► Alcohols were oxidized by Al-coordinated polyoxotungstates with dioxygen in water. ► The activities were affected by the structures around the aluminum sites in polyoxoanions. ► [PW11{Al(OH2)}O39]4− exhibited high turnover numbers with >99% selectivity. ► [PW11{Al(OH2)}O39]4− was remarkably stable for oxidations with long time intervals.Water-soluble aluminum-coordinated polyoxotungstates, Cs4[α-PW11{Al(OH2)}O39]·8H2O (Cs-1), [(CH3)4N]4[α-PW11{Al(OH2)}O39]·8H2O (TMA-1), K6Na[(A-PW9O34)2{W(OH)(OH2)}{Al(OH)(OH2)}{Al(μ-OH)(OH2)2}2]·19H2O (KNa-2), and K7[α2-P2W17{Al(OH2)}O61]·14H2O (K-3), were used as homogeneous catalysts or catalyst precursors for the oxidation of alcohols with 1atm molecular oxygen in a water–alcohol biphasic medium. The catalytic activities and the stabilities of polyoxoanions were significantly affected by the structures around the aluminum sites constructed in the polyoxotungstates. In particular, polyoxoanion1 exhibited high turnover numbers and high selectivities of the corresponding carbonyl products, and the molecular structure of1 was remarkably stable for oxidations with long time intervals.
Keywords: Aluminum complex; Polyoxometalate; Alcohol oxidation; Molecular oxygen; Water
One-pot preparation and characterization of bifunctional Ni-containing ZSM-5 catalysts by Gerardo Vitale; Hebert Molero; Eumir Hernandez; Samuel Aquino; Viola Birss; Pedro Pereira-Almao (pp. 75-87).
Display Omitted► Convenient method of nickel incorporation to produce a bifunctional Ni-zeolite catalyst. ► Incorporation of nickel in the zeolite synthesis gel produces a well dispersed hydrogenating site. ► Prepared H-Ni-ZSM-5 is sulfur tolerant and active for hydrocracking of toluene.A convenient method for the incorporation of nickel into an aluminosilicate MFI type zeolite, which avoids the impregnation of nickel, drying and further calcinations steps, to produce a bifunctional catalyst in a cost efficient way, is presented. The one step preparation involves the addition of the nickel source in the zeolite preparation step and anchoring it during the crystallization process. After calcination to remove the organic template, the composite zeolite is ion exchanged to produce the acid form, which already has the nickel incorporated and no further steps are required. The incorporation of high contents of nickel (up to 5wt% nominal) induced important modifications in the produced materials. As the amount of nickel increases, the textural properties are modified and lower micropore area and volume and higher mesopore and total volumes are observed. The amount of acidic sites decreased and the sites seem to be of the Brønsted kind. The nickel seems to be well dispersed or anchored in the prepared material and then high temperatures are used to reduce the oxidation state of nickel in the material; however, the catalyst with 1wt% nickel incorporated showed good physical–chemical properties and was as active as other catalysts for the hydroconversion of toluene. The tested catalyst had a good tolerance to sulfur, indicating that part of the nickel incorporated is hindered from sulfur poisoning but is active for the dissociation of hydrogen during hydrogenation in the presence of sulfur.
Keywords: Ni-ZSM-5; Bifunctional catalysts; Hydroconversion; Toluene hydrogenation; Hydrothermal synthesis
Effect of structure of CuO/ZnO/Al2O3 composites on catalytic performance for hydrogenation of fatty acid ester by Limin He; Haiyang Cheng; Guanfeng Liang; Yancun Yu; Fengyu Zhao (pp. 88-93).
Display Omitted► The CuO/ZnO/Al2O3 with LDHs structure showed high catalytic activity and selectivity. ► The high activity was due to the high reducibility and small crystal particle size of catalyst. ► Cu+/Cu0 were supposed to be the active species for the hydrogenation of fatty acid esters. ► Fatty alcohol was produced with a yield >98%, it is the best one by comparing to literature.In this work, CuO/ZnO/Al2O3 catalysts were prepared by adjusting the initial alkali concentration in the process of co-precipitation. The correlation between the structure and catalytic activity was studied, and the catalyst derived from LDHs (layered double hydroxides) structure exhibited the highest activity in the hydrogenation of fatty esters as well as high selectivity to fatty alcohol, producing fatty alcohol with a yield above 98%. The high catalytic performance was attributed to relatively high dispersion (small crystal size) and the high reducibility of copper species. In addition, the active species was discussed and the Cu+/Cu0 were supposed to be the active site for the present hydrogenation.
Keywords: CuO/ZnO/Al; 2; O; 3; Layered double hydroxide; Hydrogenation; Fatty ester; Higher alcohol
Sm-CeO2 supported gold nanoparticle catalyst for benzyl alcohol oxidation using molecular O2 by Sandip Mandal; Kyoko K. Bando; Chiranjit Santra; Sudip Maity; Olusola O. James; Devinder Mehta; Biswajit Chowdhury (pp. 94-104).
Display Omitted► Design of nanocrystalline samarium doped ceria catalyst. ► Use of samarium doped ceria catalyst as a support of gold nanocluster. ► Change in redox property of the ceria support after gold deposition. ► Evaluation of catalytic activity for alcohol oxidation reaction using molecular O2. ► Role of oxygen vacancies toward the catalytic activity.Supported gold nanoparticles perform as a potential catalyst for CO oxidation, propylene epoxidation and hydrogenation reactions, while using them for alcohol oxidation reaction in the presence of molecular oxygen is a challenging task. Nanocrystalline ceria supported gold catalysts are suitable candidates for alcohol oxidation reaction under mild condition. In this study, ceria based mixed oxides were prepared by modified sol–gel method using triethanolamine/water mixture where the defect sites were created by doping Sm3+ cation to cerium oxide. The catalysts were characterized by XRD, FT-RAMAN, TPR, TPD, XPS, XAFS, and HRTEM techniques. Strong gold–support interaction facilitates the easy removal of capping oxygen ions present in the Sm3+ doped cerium oxide surface as observed by XPS and TPR studies. The acid–base property of the CeO2 oxide after incorporation of samarium and gold deposition was observed from TPD studies. The Au/Sm-CeO2 catalyst was active for benzyl alcohol oxidation reaction using molecular O2 under mild condition.
Keywords: Rare earth; Gold; Nanoparticle; Oxidation
Comparison of the activity stabilities of nanosized and microsized zeolites based Fe–Mo/HZSM-5 catalysts in the non-oxidative CH4 dehydroaromatization under periodic CH4–H2 switching operation at 1073K by Yuebing Xu; Yoshizo Suzuki; Zhan-Guo Zhang (pp. 105-116).
Display Omitted► Nano- and micro-zeolites based Mo/HZSM-5catalysts exhibit similar maximum activities. ► Fe modification improves only the activity stability of nano-zeolite based catalyst. ► Preferential coking on nano-zeolite agglomerates to enhance the catalyst deactivation. ► Fe-induced CNT growth forces agglomerates to disagglomerate and increases diffusivity. ► More crystals inside the agglomerates are involved and the catalyst stability improves.The activities and stabilities of three series of Fe-modified 5%Mo/HZSM-5 catalysts based on a nano-zeolite and two micro-zeolites in the fixed-bed non-oxidative CH4 dehydroaromatization reaction were compared at the condition of 1atm, 1073K and 10,000mL/g/h under periodic CH4–H2 switch operation mode. The activity evaluation tests showed that 0.1–2wt% Fe co-impregnated modification improves remarkably the benzene formation activity stability of the nanosized zeolite-based catalyst while it had little influence on those of the two microsized zeolites-based catalysts. Then, another series of Fe-modified 5%Mo/HZSM-5 catalysts based on a ball-milled, nanosized zeolite sample were prepared and tested at the same condition. The results confirmed that the maximum improving effect of Fe modification achieves at a properly small Fe addition of 0.5wt%. SEM observation of all fresh and spent catalyst samples revealed that carbon nanotubes formed over all Fe-modified catalysts but disagglomeration of zeolite agglomerates caused by carbon nanotube formation and growth occurred only to the nano-zeolite based, Fe-modified catalysts. Further, TPO measurement of all spent samples revealed that the amounts of accumulated coke per unit external surface area in the spent nano-zeolite based catalysts were much smaller than those in the micro-zeolite based catalysts. Moreover, well consistent BET measurement confirmed that all nano-zeolite based, Fe-modified catalysts exhibited a similarly smaller degree of decrease in their microporosity than all micro-zeolite based catalysts. All these suggest that the preferential coke formation on the external surfaces and/or in the outer layers of zeolite agglomerates took place under the test condition and enhanced the deactivation of the nano-zeolite based, Fe-unmodified catalysts, and that the disagglomeration of zeolite agglomerates caused by Fe-induced carbon nanotube formation and growth in the reaction was the origin of Fe modification improving the activity stability of the nano-zeolite based Mo/HZSM-5 catalysts. The improvement mechanism is discussed in detail in the article.
Keywords: Methane dehydroaromatization; Mo/HZSM-5; Nanosized zeolite; Fe modification; Carbon nanotube
Fundamentals, properties and applications of solid catalysts prepared by solution combustion synthesis (SCS) by Sergio L. González-Cortés; Freddy E. Imbert (pp. 117-131).
Display Omitted► Solution combustion synthesis (SCS) is an effective method for preparing robust solid catalysts. ► Multi-functional and nano-structured catalysts can be prepared by SCS method. ► SCS-prepared catalysts can be synthesized under controlled or uncontrolled thermal treatment. ► O/C ratio can rationalize the presence or absence of residual carbon in the SCS-prepared catalysts.The recent progress in solution combustion synthesis (SCS)-based preparation approaches in the synthesis of solid catalysts is discussed. This integrated overview includes not only the current understanding of the SCS chemistry and catalyst properties but also catalyst applications. SCS-based methods have had a variety of applications in heterogeneous catalysis including oxidation reactions, exhaust emission control, hydrogenation reactions, hydrogen production, and photocatalytic processes. The effects of using the fuel as chelating agent and reducing agent for the production of nanosized catalysts are also presented. Finally, the future of this important topic is discussed.
Keywords: Solution combustion synthesis; Solid catalysts preparation; Novel approaches for preparing catalysts
Disordered mesoporous V/TiO2 system for ambient oxidation of sulfides to sulfoxides by Sanjay Singh Negi; Kumarsrinivasan Sivaranjani; Anand Pal Singh; Chinnakonda S. Gopinath (pp. 132-138).
Display Omitted► V has been incorporated into the TiO2 lattice position. ► Ti1− xV xO2 exhibit disordered mesoporosity. ► Ti1− xV xO2 evaluated for oxidation of sulfides to sulfoxides at ambient and at 278K with environmentally benign H2O2.High sulfide conversion and predominant sulfoxide yield has been observed with 0.1% vanadium doped disordered mesoporous Ti1− xV xO2 material at ambient and sub ambient temperatures using environmentally green H2O2 oxidant. Ti1− xV xO2 materials were prepared by one-pot solution combustion method in less than 15min and thoroughly characterized by X-ray diffraction, HRTEM, Raman spectra and other physicochemical techniques. Different sulfides, such as, phenylsulfide, methyl- p-tolylsulfide, ethylsulfide, thioanisole, were converted into the corresponding sulfoxide. Isolated V5+ incorporated in the TiO2 lattice is likely to be the active species for the sulfide oxidation reaction. Catalyst recycling studies indicates the robustness of the catalyst.
Keywords: Heterogeneous catalysis; Mesoporous TiO; 2; Sulfoxidation; Hydrogen peroxide; Combustion synthesis; Ambient oxidation; Sulfoxide
The CuZnZrAl hydroxycarbonates as copper catalyst precursors—Structure, thermal decomposition and reduction studies by Paweł Kowalik; Marcin Konkol; Małgorzata Kondracka; Wiesław Próchniak; Robert Bicki; Paweł Wiercioch (pp. 139-146).
Display Omitted► HT-XRD studies of two series of complex CuZnZrAl hydroxycarbonates as copper catalyst precursors. ► Influence of the Zr/Al ratio on the formation of hydrotalcite-like phases of the CuZnAl hydroxycarbonates. ► With increasing ZrO2 content CuO crystallites form at higher temperatures during calcination. ► Decrease of CuO crystallite size at the calcination temperatures up to ca. 400°C upon addition of zirconium oxide.The transformations of a series of complex CuZnZrAl hydroxycarbonates as copper catalyst precursors have been investigated. The materials have been prepared by the coprecipitation method and characterized by means of XRD, ICP-OES, TG-MS, TPR and N2O chemisorption. The results reveal that the Zr/Al ratio has got an influence on the formation of hydrotalcite-like phases of copper–zinc–aluminum hydroxycarbonates. The increase of ZrO2 content results in the increase of amorphous phase content in the hydroxycarbonate precursors. Moreover, the increase of ZrO2 content causes the formation of CuO crystallites at higher temperatures during calcination. At the lower calcination temperatures (up to ca. 400°C) the incorporation of zirconium oxide results in the decrease of CuO crystallite size in the calcined mixed oxides compared to the Zr-free sample. At higher calcination temperatures a reversed effect was observed. Two different thermal decomposition pathways of the precursors with and without alumina were observed.
Keywords: Copper catalyst precursor; Methanol synthesis; CuZnZrAl hydroxycarbonates; Mixed metal oxides; XRD studies
Oxidative coupling of methane using catalysts synthesized by solution combustion method by Ranjita Ghose; Hyun Tae Hwang; Arvind Varma (pp. 147-154).
Display Omitted► Solution combustion is successfully used for synthesis of OCM catalysts. ► Sr–Al, La2O3, La–Sr–Al mixed oxides and Na2WO4–Mn/SiO2 are effective catalysts. ► The double perovskite phase in the Sr–Al oxides is active for OCM. ► Na2WO4–Mn/SiO2 shows highest catalytic activity, maximum C2 yield ∼25%.Solution combustion synthesis (SCS) is a one-step technique for the preparation of nanostructured complex metal oxides. In the present study, SCS was used for the synthesis of several promising oxidative coupling of methane (OCM) catalyst series with varying metal ratios: (a) Sr–Al complex oxides, (b) La2O3, (c) La–Sr–Al complex oxides and (d) Na2WO4–Mn/SiO2. The C2 yield and ethylene/ethane ratio were measured for each catalyst over a wide range of temperatures. It was found that the double perovskite phase is active for OCM in the Sr–Al complex oxide series. The Na2WO4–Mn/SiO2 catalyst synthesized by SCS was stable and also showed high ethylene/ethane ratio ∼2 along with high C2 yield ∼25%, which is among the highest value reported in the literature, indicating that SCS is a promising method to prepare OCM catalysts.
Keywords: Oxidative coupling; Solution combustion synthesis (SCS); Ethylene; Methane; Complex oxide catalysts
Formation of 3-pentanone via ethylene hydroformylation over Co/activated carbon catalyst by Xiangen Song; Yunjie Ding; Weimiao Chen; Wenda Dong; Yanpeng Pei; Juan Zang; Li Yan; Yuan Lu (pp. 155-162).
Display Omitted► 3-pentanone was formed from ethylene hydroformylation over Co/AC catalyst. ► Micropore and carbonaceous materials are key factors in the formation of ketones. ► Cobalt carbonyl was responsible for the formation of ketone. ► High dispersion of cobalt favored the formation of cobalt carbonyl species.In ethylene hydroformylation over Co/activated carbon (AC) catalyst, in addition to propanal, 3-pentanone was formed for the first time as one of a main product over heterogeneous cobalt catalyst. It was interesting to find that the properties of the supports, including both micropore proportion and the carbonaceous materials, are key factors in the formation of ketones. Based on the characterization results, cobalt carbonyl species was confirmed to be related with the formation of ketones on the surface of heterogeneous Co based catalysts. The small particle of cobalt and the high ratio of chemisorbed CO/H2 might favor the formation of cobalt carbonyl clusters on the activated carbon supported cobalt catalysts.
Keywords: Ethylene hydroformylation; Cobalt carbonyl; Activated carbon; 3-Pentanone
Spectroscopic characterization of Ni/Al2O3 catalytic materials for the steam reforming of renewables by Gabriella Garbarino; Serena Campodonico; Alvaro Romero Perez; Maria M. Carnasciali; Paola Riani; Elisabetta Finocchio; Guido Busca (pp. 163-173).
Display Omitted► Ni/Al2O3 catalysts active in steam reforming of renewables have been characterized. ► XRD, skeletal IR and Raman, IR of adsorbed CO, UV–vis–NIR techniques have been used. ► Isolated Ni2+, NiO nanoparticles and normal NiO particles predominate at different loadings. ► Hexagonal Ni metal is found on spent catalyst together with easily oxidizable species.Ni/alumina catalytic materials (with 0, 5, 16, 39, 125 and ∞ % wtNi/Wsupport, using a 5% silica-containing alumina with 170m2/g surface area) have been characterized by XRD, IR, MicroRaman, UV–vis–NIR techniques. Three types of nickel oxide species have been identified: i) isolated Ni2+ species dispersed and strongly interacting with the support surface, predominant when the NiO coverage is well below that of the ‘theoretical monolayer’. (ii) Ni oxide-like particles having a vibrational environment similar to that of NiO nanoparticles, but with different Raman and UV spectra, predominant near or well above the ‘theoretical monolayer’. (iii) normal NiO particles at even higher Ni oxide contents, characterized by (2M) magnonic and several phononic peaks in the Raman spectrum and normal position for the optical gap (absorption edge at ca. 300nm). IR spectra of adsorbed CO recorded after reduction in hydrogen suggest that species i) predominantly gives rise to isolated Nio atoms, producing Nio polycarbonyls, while species ii) gives rise by reduction to Ni metal particles, over which unusually CO adsorbs producing only terminal species, without any formation of bridging CO species. This may be due to an unusual structure or morphology of these particles. The catalysts have been tested in the steam reforming of ethanol–phenol mixture as well as of pure ethanol. XRD, UV–vis–NIR and Raman studies show that the spent catalysts are largely reduced to metal with the appearance of hexagonal nickel, although unreduced or easily oxidixable centers are also detected.
Keywords: Steam reforming of tars; Biomass tar; Ethanol steam reforming; Hydrogen production; Ni/Al; 2; O; 3; catalysts; Catalyst deactivation; Raman spectroscopy; MicroRaman Spectroscopy; IR spectroscopy; Nickel oxides; Electronic properties
Effects of preparation conditions of Ni/TiO2 catalysts for selective CO methanation in the reformate gas by Kohei Urasaki; Yuta Tanpo; Yuta Nagashima; Ryuji Kikuchi; Shigeo Satokawa (pp. 174-178).
Display Omitted► Catalytic performance of Ni/TiO2 was affected by preparation conditions. ► Increasing nickel contents promotes CO methanation at low temperature range. ► Increasing nickel contents declined CO/CO2 selectivity at high temperature range. ► Temperature window for selective CO methanation can be controlled by nickel contents.Selective CO methanation in the reformate gas over Ni/TiO2 catalyst was carried out. Nickel metal salts (nitrate, sulfate, acetate, chloride and formate) used as a precursor of nickel, calcination temperatures (400–700°C), reduction temperatures (350–650°C) and nickel contents (1–30wt%) affected to the CO methanation activity and CO/CO2 selectivity over the obtained Ni/TiO2 catalysts. The appropriate nickel precursors were nitrate and acetate and suitable calcination and reduction temperatures were 400–500°C and 450–550°C, respectively. An increase of nickel contents in the Ni/TiO2 catalysts improved to the CO methanation activity. Reverse water gas shift reaction activity was extremely low regardless of nickel contents. As a result, temperature window of Ni/TiO2 catalyst was constant and it could be shifted to desired position by changing nickel content.
Keywords: Selective methanation; Nickel catalyst; Titania; Reformate gas
Synthesis of Ni/Al2O3 and Ni–Co/Al2O3 coatings onto AISI 314 foams and their catalytic application for the oxidative dehydrogenation of ethane by J.P. Bortolozzi; L.B. Gutierrez; M.A. Ulla (pp. 179-188).
Display Omitted► Ni and NiCo/Al2O3 coatings onto a foam were active and selective for ODE. ► There is an optimal Co/Ni ratio to improve the ethylene production. ► The catalytic features depend on the concentration solutions and impregnation cycles. ► The metal distribution affects the structured catalyst activity and selectivity.The aim of this work was to obtain alumina-supported Ni and Ni–Co oxide catalytic coating onto an AISI 314 foam (60ppi) so as to produce a good distribution of the catalytic components and reproduce characteristics of their interactions similar to those observed in the powder catalysts. These catalytic systems were characterized by different techniques (Laser Raman spectroscopy, X-ray diffraction, temperature-programmed reduction, scanning electron microscopy and energy-dispersive X-ray analysis). The oxidative dehydrogenation of ethane was used as test reaction. The results indicated that the Ni and Ni–Co/Al2O3 powder catalysts were active and selective for this reaction. For the active metal loading used (15wt%), the addition of cobalt with an atomic ratio of Co/Ni=0.114 slightly improved the ethylene productivity, possibly due to the enhancement of Ni dispersion. However, the addition of a higher amount (Co/Ni=0.253) led to a lower productivity, probably due to the presence of cobalt compounds and to the increase in the NiO crystal size. The structured systems showed a performance similar to that of the corresponding powder forms and they also showed good adhesion of the catalytic layer onto the metallic foams.The features of the resulting structured systems are very sensitive to the variables which involve the deposition method. Therefore, it is necessary to take into account the control of such parameters in order to obtain good, repetitive depositions of the active components and a correct distribution of the support in the coverage. In the same sense, the achievement of a constant relationship between the active metals is significant because, otherwise, the activity and selectivity of these systems could be affected.
Keywords: Structured catalyst; AISI 314 foam; Ni/Al; 2; O; 3; Ni–Co/Al; 2; O; 3; Oxidative dehydrogenation
Production of biodiesel from soybean oil on CaO/Al2O3 solid base catalysts by Nagaraju Pasupulety; Kamalakar Gunda; Yuanqing Liu; Garry L. Rempel; Flora T.T. Ng (pp. 189-202).
Display Omitted► CaO/Al2O3 solids were synthesized by wet impregnation of CaO on acidic, basic and neutral Al2O3. ► Formation of calcium diglyceroxide on Al2O3 as an active species for transesterification was identified first time. ► FAME formation influenced by (1) nature of Al2O3 and (2) CDG formation and its role in the ester formation. ► This study explains the effect of methanol to oil mole ratio on the formation of CDG on CaO/n-Al2O3. ► This study helps in designing highly active and stable solid bases for the production of biodiesel.Transesterification of soybean oil was carried out over calcium oxide supported on Al2O3 as solid base catalysts. Solid base catalysts were synthesized by wet impregnation of CaO on acidic, basic and neutral Al2O3. Solid basic catalysts investigated in this study were characterized by BET surface area, XRD, FTIR, CO2-TPD and TG/DTA techniques. Formation of fatty acid methyl esters (FAME) in this study was influenced by the nature of the catalyst prepared on different Al2O3 supports. CaO supported on neutral-Al2O3 exhibited higher FAME yield and the activation energy was determined to be 30.7kJ/mol. The formation of the calcium diglyceroxide (CDG), on the surface of CaO supported on neutral Al2O3 was established by13C NMR spectroscopy. The catalytic system (with CaO+CDG) on neutral Al2O3 showed higher activity in the transesterification of soybean oil. Among the catalysts studied the conversion of soybean oil to FAME formation was as follows: CaO/neutral-Al2O3>CaO/basic-Al2O3>CaO/acidic-Al2O3. The presence of CDG on neutral Al2O3 probably contributes to the higher activity. To our knowledge, this is the first report on identifying the formation of CDG on neutral Al2O3 during the production of biodiesel.
Keywords: Key words; Biodiesel; Calcium oxide; Calcium diglyceroxide; Impregnation; Transesterification
Particle size effect in methane activation over supported palladium nanoparticles by Antje Ota; Edward L. Kunkes; Jutta Kröhnert; Martin Schmal; Malte Behrens (pp. 203-213).
Display Omitted► A series of supported Pd catalysts was prepared from Hydrotalcite precursors. ► The particle size of Pd Nanoparticles have been tuned from 1.7 to 3.8nm. ► The methane chemisorptions capacity was largely enhanced for particles <2nm. ► For 2nm the capacity scaled with the Pd loading.A synthesis method for producing MgAl oxide supported uniform palladium nanoparticles with varying diameters has been developed. The method consists of reductive-thermal decomposition of a PdMgAl hydrotalcite-like compound, formed via co-precipitation of metal nitrate salts and sodium carbonate. The hydrotalcite–like precursors were characterized by XRD, TG-MS and SEM, and were found to contain a well-defined crystalline structure and a uniform distribution of all constituent elements. The resulting catalysts were characterized by XRD, TEM, Chemisorption of CO and in situ IR measurements of CO, and were found to consist of partially oxide-embedded Pd nanoparticles with diameters ranging from d=1.7 to 3.3nm and correspond dispersions of 67–14%. Furthermore, the particle size was found to be inversely related to Pd loading. The palladium catalysts were studied for methane activation via chemisorption at 200 and 400°C followed by a temperature programmed surface hydrogenation. The most disperse catalyst ( d=1.7nm) possessed an intrinsic methane adsorption capacity, which was an order of magnitude larger than that of other catalysts in the series, indicating a strong structure sensitivity in this reaction. Additionally, the methane adsorption capacity of the hydrotalcite-derived Pd catalysts was nearly two orders of magnitude higher than that of catalysts derived through other synthesis pathways such as colloidal deposition or sonochemical reduction.
Keywords: Palladium; Hydrotalcites; Co-precipitation; Methane activation; Non-oxidative coupling
Exploring anatase-TiO2 doped dilutely with transition metal ions as nano-catalyst for H2O2 decomposition: Spectroscopic and kinetic studies by M.I. Zaki; A. Katrib; A.I. Muftah; T.C. Jagadale; M. Ikram; S.B. Ogale (pp. 214-221).
Display Omitted► 3at% doping of anatase-TiO2 was affected with Nb, Cr, Fe, Ni, Mn, Co or Cu ions. ► The anatase structure is maintained but the crystallite size decreases down 8–3nm. ► Only the Mn, Co or Cu ions form dopant–O–Ti linkages. ► Consequently, anatase-TiO2 is rendered a visible light absorber. ► Consequently, anatase-TiO2 is rendered a H2O2 decomposition heterogeneous catalyst.Pure and dilutely doped nano anatase-TiO2 with 3at% Nb, Cr, Fe, Ni, Mn, Co or Cu ions were prepared by sol–gel processing. The doping was found by X-ray diffractometry and laser Raman spectroscopy to reduce the average crystallite size of the titania (8nm) down to <8–3nm without formation of separate or mixed oxide phases and without deviation from the anatase structure of the titania. Ion scattering spectroscopy observed surface exposure of the dopant ions, but only Mn, Co or Cu dopant ions were found by X-ray photoelectron spectroscopy to form oxygen-mediated bonds with titanium ions. The likely facilitation of d–d electron exchange interactions via such dopant–O–Ti linkages is suggested to provide the necessary bulk and surface attributes for the observed rendering of the host anatase-TiO2 a visible light absorber (as revealed by UV-visible diffuse reflectance spectroscopy) and an active heterogeneous catalyst for H2O2 decomposition (as revealed by gravimetric gasometry of the decomposition reaction). These two dopant-mediated behaviors were exhibited uniquely by the anatase-TiO2 nanoparticles after doping with Mn, Co or Cu ions.
Keywords: Transition metal; Dopants; Anatase-TiO; 2; Catalysis; H; 2; O; 2; decomposition