Applied Catalysis A, General (v.392, #1-2)
Editorial Board (CO2).
Synthesis and characterization of Pt/Fe–Zr catalysts for the CO selective oxidation by Martin Schmal; Ricardo Scheunemann; Nielson F.P. Ribeiro; Jose Fernando Bengoa; Sergio Gustavo Marchetti (1-10).
▪.▶ Pt/Fe2O3 and Pt/Fe x Zr(1−x)O2 catalysts were prepared for selective CO + H2 oxidation. ▶ X-ray and Mössbauer showed solid solution and segregated mixed oxides with phases. ▶ Zr4+ substitute Fe3+ ions in the lattice and Fe3+ diffuse in the zirconia lattice. ▶ Catalytic tests showed maximum CO conversion and total oxygen conversion. ▶ Interfacial Fe3+/Pt° sites improve the oxidation either for CO and H2 oxidation.Catalysts of Pt on Fe2O3 and mixed oxides Fe x Zr(1−x)O2 were prepared for the selective CO + H2 oxidation. X-ray diffraction and Mössbauer spectroscopy showed α-Fe2O3 in pure support, a solid solution for x = 0.25 and mixed oxides with segregated phases for higher “x” values. Mössbauer results showed also that with increasing the Zr content Zr4+ ions substitute the Fe3+ ions in the α-Fe2O3 lattice, and also Fe3+ ions diffusing into the zirconia lattice. The Pt/Fe0.25Zr0.75O2(p) exhibited only Fe3+ inside the ZrO2 lattice. After reduction, Fe3O4 was found in the catalysts, which decreased with increasing zirconium loading. It is interesting to note that the corresponding precursor presents 83% of Fe3+ located in the ZrO2 lattice and the remaining 17% corresponds to hematite.Catalytic tests for the preferential oxidation of CO containing H2 showed a maximum CO conversion at different temperatures after reaching total oxygen conversion. The CO conversion decreased with increasing iron content in the mixed oxide. The Pt/Fe2O3 catalyst is the most active compared to the other Pt/mixed oxide and Pt/ZrO2. Results showed the following order: Pt/Fe2O3(c) > Pt/Fe0.75Zr0.25O2(c) > Pt/Fe0.25Zr0.75O2(c) > Pt/ZrO2. The Pt/Fe0.25Zr0.75O2(c) presented high selectivity (56%) at 90 °C and is 2-fold higher compared to the Pt/Fe2O3 and Pt/ZrO2 catalyst.
Keywords: Mixed oxides; Iron–zirconia; Iron catalyst; Mössbauer; SELOX reaction;
Oxidation of α-pinene over gold containing bimetallic nanoparticles supported on reducible TiO2 by deposition-precipitation method by S. Ajaikumar; J. Ahlkvist; W. Larsson; A. Shchukarev; A.-R. Leino; K. Kordas; J.-P. Mikkola (11-18).
Display Omitted▶ Heterogeneous catalysis. ▶ Synthesis and characterisation of gold containing bimetallic catalysts. ▶ Fine chemical synthesis from renewable sources. ▶ Studying the oxidation of α-pinene using efficient gold containing bimetallic catalysts. ▶ Optimisation of reaction parameters.A series of bimetallic catalysts Au–M (where M = Cu, Co and Ru) were supported on a reducible TiO2 oxide via deposition-precipitation (DP) method with a slow decomposition of urea as the precipitating agent. The characteristic structural features of the prepared materials were characterized by various physico-chemical techniques such as X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). XPS results indicated the formation of alloyed bimetallic particles on the TiO2 support. TEM results confirmed the fine dispersion of metal nanoparticles on the support with an average particle size in the range of 3–5 nm. An industrially important process, oxy-functionalization of α-pinene was carried out over the prepared bimetallic heterogeneous catalysts under liquid phase conditions. Reaction parameters such as the reaction time, temperature, and the effect of solvent were studied for optimal conversion of α-pinene into verbenone. The major products obtained were verbenone, verbenol, α-pinene oxide and alkyl-pinene peroxide. The activity of the catalysts followed the order; AuCu/TiO2 > AuCo/TiO2 > Cu/TiO2 > Au/TiO2 > AuRu/TiO2. Upon comparison of the various catalysts, AuCu/TiO2 was found to be an active and selective catalyst towards the formation of verbenone. The temperature, nature of the catalysts and the choice of solvents greatly influenced the reaction rate.
Keywords: AuCu/TiO2; α-Pinene oxidation; Vebenone; Verbenol; α-Pinene oxide; Heterogeneous; Liquid phase conditions;
Comparative dehydrogenation of cyclohexanol to cyclohexanone with commercial copper catalysts: Catalytic activity and impurities formed by Arturo Romero; Aurora Santos; Daniel Escrig; Ernesto Simón (19-27).
Display Omitted▶ Commercial copper-based catalysts have been tested. ▶ Impurities from dehydration and dehydrogenation have been identified and quantified by GC/MS. ▶ Higher activity is obtained with catalyst containing Cu–Zn which is in agreement with the smaller copper crystallite size. ▶ Impurities from dehydration reaction are due to alumina or chromium in the catalyst.Catalytic dehydrogenation of cyclohexanol to cyclohexanone has been carried out on phase gas in a continuous fixed bed reactor under atmospheric pressure. Copper chromite and copper zinc oxide catalysts have been checked. Effect of temperature (in the range 250–290 °C) and spatial time in reactor have been studied. The catalytic activity has been evaluated in terms of cyclohexanone yields and impurities from secondary reactions of dehydration and dehydrogenation of cyclohexanol have also been identified and quantified by GC/MS.Catalysts have been characterized by X-ray diffraction, temperature programmed desorption of ammonia and BET surface area measurement. High activity was confirmed by copper-based catalysts under the operating conditions, concerning the size and dispersion of the copper specie. It was also found that catalysts with alumina and chromium exhibit higher dehydration capacity, being cyclohexene the main impurity obtained. For a given cyclohexanone yield the impurities from dehydrogenation reactions showed similar trends for the three catalysts tested. Phenol was the main impurity obtained by dehydrogenation.
Keywords: Alumina; Catalyst; Chromium; Copper; Cyclohexanol; Cyclohexene Cyclohexanone; Dehydrogenation; Phenol; Zinc;
Silica supported transition metal substituted polyoxotungstates: Novel heterogeneous catalysts in oxidative transformations with hydrogen peroxide by Ana C. Estrada; Isabel C.M.S. Santos; Mário M.Q. Simões; M. Graça P.M.S. Neves; José A.S. Cavaleiro; Ana M.V. Cavaleiro (28-35).
Display Omitted▶ Fe- and Mn-polyoxotungstate based catalysts were prepared and characterized. ▶ Alkylammonium-functionalized silica was used as support for the polyoxotungstates. ▶ The novel materials were used in catalytic oxidations with hydrogen peroxide. ▶ Catalytic oxidation of model hydrocarbons was achieved. ▶ Some catalysts were reused several times without noticeable loss of activity.The preparation and characterization (FT-IR, FT-Raman, diffuse reflectance, elemental analysis) of novel catalysts with iron or manganese substituted polyoxotungstates [XMIII(H2O)W11O39] n− (X = P, M = Fe or Mn; X = Si or B, M = Fe) immobilized on a functionalized silica matrix are reported. The new materials were tested as heterogeneous catalysts in the oxidation of cis-cyclooctene and cyclooctane at 80 °C, using environmentally safe hydrogen peroxide as oxidant and acetonitrile as solvent. Some of these novel heterogeneous catalysts could be reused several times without appreciable loss of catalytic activity.
Keywords: Oxidation; Hydrogen peroxide; Fe; Mn; Supported metal-substituted polyoxometalates;
Effect of Ce/Zr composition and noble metal promotion on nickel based Ce x Zr1−x O2 catalysts for carbon dioxide methanation by Fabien Ocampo; Benoit Louis; Lioubov Kiwi-Minsker; Anne-Cécile Roger (36-44).
Display Omitted▶ 5 wt% Ni based Ce x Zr1−x O2 with C/Z mass ratios ranging from 4 to 0.25 and Ru or Rh promoted Ce0.72Zr0.28O2 catalysts were successfully synthesized. ▶ C/Z and noble metal addition effects were evaluated on catalyst structural properties and catalytic activity in CO2 methanation reaction. ▶ Impressive CO2 conversion and extremely high selectivity to methane (superior to 98%). ▶ Both incorporated Ni2+/Ni0 ratio optimization and noble metal addition boosted the catalyst performance. ▶ 5Ni(60–40) appeared to be the best catalytic system.Carbon dioxide methanation was carried out over a series of Ni–Ce x Zr1−x O2 catalysts prepared by a pseudo sol–gel method. The influence of CeO2/ZrO2 mass ratio and noble metal addition was investigated. The catalysts were subsequently characterized by means of XRD, TPR, BET, H2-TPD and SEM-EDX. The modification of structural and redox properties of these materials was evaluated in relation with their catalytic performances. All catalysts gave impressive CO2 conversion and extremely high selectivity to methane (superior to 98%). Ni2+ incorporation into the CZ structure was proved to enhance catalysts specific activity. The global performance of the studied systems depended not only on the surface of available metallic nickel but also on the composition of the support and on its modification by Ni2+ doping. As a result of these two phenomena, the Ni-based mixed oxide having a CeO2/ZrO2 = 60/40 exhibited the highest catalytic activity, owing to an optimal Ni2+/Ni0 ratio. Noble metal addition led to higher Ni dispersion, resulting in a raise of both activity and catalyst life-time. It did not modify the support intrinsic activity. The deactivation was shown not to be due to carbon deposits but rather to nickel particles sintering. The investigated parameters thus allowed an improvement of the previously studied 5 wt% Ni–Ce0.72Zr0.28O2 system.
Keywords: Methanation; Carbon dioxide; Mixed oxides; Ceria–zirconia; Synthetic fuels;
Combustion of diesel soot in NO/O2 presence. Cesium nitrate and gold catalysts by María L. Ruiz; Ileana D. Lick; Marta I. Ponzi; Enrique Rodriguez-Castellón; Antonio Jiménez-López; Esther N. Ponzi (45-56).
Display Omitted▶ CsNO3 and gold catalysts show a good activity for soot oxidation. ▶ The gold addition increases the selectivity in CO2. ▶ Evidences of the nitrate/nitrite redox cycle are shown.The diesel soot combustion was studied using catalysts prepared by impregnation with cesium nitrate and/or gold on zirconium oxide (ZrO2), hydrated zirconium oxide and silica (SiO2). Catalysts were characterized by colorimetry, elemental analysis, atomic absorption spectrophotometry, XRD, FTIR, TPR and XPS. Measurements of catalytic activity were performed in a thermobalance with air and in a fixed bed reactor with a NO/O2 feed. All catalysts containing cesium nitrate exhibit a good activity for soot oxidation and the addition of gold substantially increases the CO2 generation leading the selectivity to 100% in CO2.
Keywords: Diesel soot; Cesium nitrate; Gold; Combustion;
Liquid phase aldol condensation reactions with MgO–ZrO2 and shape-selective nitrogen-substituted NaY by Wenqin Shen; Geoffrey A. Tompsett; Karl D. Hammond; Rong Xing; Fulya Dogan; Clare P. Grey; W. Curtis Conner; Scott M. Auerbach; George W. Huber (57-68).
Display Omitted▶ Nitrogen-substituted NaY shows much increased base strength compared to NaY. ▶ Nit-NaY is highly active for liquid phase aldol condensation reactions of furfural/HMF with acetone/propanal, comparable to a strong solid base MgO–ZrO2. ▶ Nit-NaY shows shape selectivity towards aldol monomer product due to the FAU-typed crystal structure. ▶ Nit-NaY is unstable due to the leaching of framework nitrogen under current operation conditions, while MgO–ZrO2 shows good recyclability.The aldol condensation reactions of furfural/hydroxymethylfurfural (furfurals) with acetone/propanal in water–methanol solvents were studied over the solid base catalysts MgO–ZrO2, NaY and nitrogen-substituted NaY (Nit-NaY). The reactions were conducted at 120 °C and 750 psig of He in batch reactors. Nit-NaY exhibited catalytic activity for aldol condensation comparable to MgO–ZrO2 and much higher than that of NaY, indicative of the increased base strength after replacing the bridging oxygen with the lower electronegativity nitrogen over Nit-NaY. The aldol condensation of furfurals with acetone produces two different products, the monomer and the dimer. The monomer is formed from reaction of furfurals with acetone. The dimer is formed from reaction of the monomer with furfurals. MgO–ZrO2 had a higher selectivity towards dimer formation. In contrast, Nit-NaY was more selective towards the monomer product due to the cage size in the FAU structure, indicating that Nit-NaY is a shape selective base catalyst. Increasing the water concentration in the feed solution or increasing the feed concentration led to both increased catalytic activity and dimer selectivity. The Nit-NaY catalyst was not stable and lost catalytic activity when recycled due to leaching of the framework nitrogen. Different characterization techniques, including XRD, high resolution Ar adsorption isotherm, basic sites titration, CO2 TPD-MS, TGA and 29Si SP MAS NMR, were used here to characterize the fresh and spent catalysts. The results show that Nit-NaY maintains only part of the FAU-type crystal structure. Furthermore, the base strength over Nit-NaY was found to be between that of Mg2+–O2− pair and Mg(OH)2. The reaction mechanism over Nit-NaY was discussed.
Keywords: Nitrogen-substituted zeolite; MgO–ZrO2; Aldol condensation; High-throughput reactor; Shape-selective base catalyst;
Selective oxidation of arabinose to arabinonic acid over Pd–Au catalysts supported on alumina and ceria by Elena Smolentseva; Bright T. Kusema; Sergey Beloshapkin; Miguel Estrada; Eunice Vargas; Dmitry Yu. Murzin; Felipe Castillon; Sergio Fuentes; Andrey Simakov (69-79).
Display Omitted▶ Au or Au–Pd species covered with PdO show synergetic effect in arabinose oxidation. ▶ Interactions of Au and Pd with ceria coexist with the mutual interaction between them. ▶ Au metallic nanoparticles are responsible for arabinose activation. ▶ Easy redox transformations of Pd species provoke oxygen activation.Selective oxidation of arabinose to arabinonic acid was carried out isothermally in a shaker reactor at moderate conditions of 60 °C and pH 8 on Pd–Au catalysts supported on nanosized alumina and ceria. The gold (4 wt.%) was supported by deposition–precipitation (DP) using HAuCl4 and urea with subsequent chemisorption of palladium (1 wt.%) using PdCl2. Before catalytic tests, samples were treated in hydrogen or oxygen at 300 °C, or by aqueous solution of formaldehyde at room temperature. Synthesized bimetallic Pd–Au catalysts are characterized with higher activity in the selective aqueous phase oxidation of arabinose to arabinonic acid by molecular oxygen in comparison with monometallic ones. Activity and selectivity of catalysts depend on the sample treatment and the nature of the support used. Pd–Au/CeO2 catalyst reduced by formaldehyde manifests the highest activity and selectivity. The synthesized bimetallic catalysts have been characterized by TEM, XPS and UV–vis techniques under different stages of sample activation. Mutual interactions of supported gold and palladium species depending on the support nature and sample treatment were observed. A more pronounced interaction between gold and palladium species was observed for Pd–Au/Al2O3 catalyst, while interactions of Au and Pd with reducible ceria coexist with the mutual interaction between these metals. Gold metallic species seem to be responsible for activation of arabinose while an easy redox transformation of Pd species can provoke oxygen activation. Thus, gold species or Au–Pd alloy covered with thin PdO film manifest a synergetic effect in the selective arabinose oxidation by molecular oxygen.
Keywords: Palladium; Gold; Nanocatalysts; Sol–gel; Arabinose; Arabinonic acid;
Preparation of well-crystallized Pd20Te7 alloy nanoparticulate catalysts with uniform structure and composition in liquid-phase by Hideyuki Takahashi; Norikazu Konishi; Hironobu Ohno; Kazunari Takahashi; Yuichiro Koike; Kiyotaka Asakura; Atsushi Muramatsu (80-85).
Display Omitted▶ Solution condition can be controlled by the metal complex calculations using the critical stability constants. ▶ Pd20Te7 alloy can be synthesized from the solution containing specific metal complexes. ▶ Well-crystallized Pd20Te7 alloy nanoparticles with a quite narrow content range were obtained only in the pores of SiO2.The synthesis system of uniform and well-crystallized alloy nanoparticulate catalysts has been studied based on the calculation of pH dependent metal complex concentrations in an aqueous solution. Results of both the prediction based on calculation and EXAFS analysis clearly demonstrated that [Pd2+(EDTA)] and Te-citric acid complex species were generated independently in the solution. Since the formations of metal complexes are restricted to [Pd2+(EDTA)] and Te-citric acid complexes in the pH range between 5 and 10, only Pd20Te7 was successfully synthesized when the reducing agent was introduced into the [Pd2+(EDTA)] complex/Te-citric acid complex system at room temperature. Moreover, PdTe nanoparticles can be synthesized predominantly in pores of silica-gel by controlling the temperature of the Pd-EDTA/Te-citric acid/hydrazine mixed solution with a metal loading of 0.5 wt% Pd. The main phase of the well-crystallized alloy nanoparticles formed in the pores was Pd20Te7, leading to remarkable stability in catalytic activity, compared with those of the conventional catalysts.
Keywords: Well-crystallized Pd20Te7 alloy nanoparticles; Predicted concentration; Metal complexes; Uniform structure; Uniform composition;
Mesoporous NiO–Al2O3 catalyst for high pressure partial oxidation of methane to syngas by Junpei Horiguchi; Yasukazu Kobayashi; Seishiro Kobayashi; Yuichiro Yamazaki; Kohji Omata; Daisuke Nagao; Mikio Konno; Muneyoshi Yamada (86-92).
Display Omitted▶ Mesoporous NiO–Al2O3 catalyst shows high activity of oxidative reforming of methane at 650 °C and 1 MPa. ▶ The limited diffusivity of reactant gas in mesopores resulted in the high tolerance of nickel species against oxidation. ▶ The limited diffusivity of reactant gas in mesopores resulted in the high syngas selectivity.Mesoporous NiO–Al2O3 catalysts were applied to catalytic partial oxidation of methane at 650 °C, 1 MPa with a feed composition of CH4/O2/N2/Ar = 5.2 vol.%/2.6 vol.%/4.9 vol.%/balance. In order to investigate the effect of mesopore of the catalyst on the catalytic activity, we used various types of organic reagents, such as P123, F127, PEG6000, and some carboxylic acids, to prepare bulk NiO–Al2O3 catalysts. Among the organic reagents P123, F127, and PEG6000 were effective for the formation of mesopores.As a result of activity tests, the catalyst prepared by using P123 showed the highest oxidative activity and selectivity; the values were higher than those of NiO catalyst supported on α-Al2O3 or γ-Al2O3. Results of pulse reaction indicated that the oxidation tolerance of NiO–Al2O3 prepared with P123 was high under reaction conditions. The effect of pore size of the catalyst was predominant because in the mesopores the diffusion values of the reactant gases are different and the CH4/O2 ratio in the pores was kept high. These factors contributed to the high selectivity of the mesoporous NiO–Al2O3 catalysts.
Keywords: Partial oxidation of methane; Syngas formation; Oxidative reforming of methane; NiO–Al2O3 catalyst; Short contact time reaction; Mesoporous;
Understanding the complexity of a catalyst synthesis: Co-precipitation of mixed Cu,Zn,Al hydroxycarbonate precursors for Cu/ZnO/Al2O3 catalysts investigated by titration experiments by Malte Behrens; Daniel Brennecke; Frank Girgsdies; Stefan Kißner; Annette Trunschke; Nurain Nasrudin; Salamiah Zakaria; Nur Fadilah Idris; Sharifah Bee Abd Hamid; Benjamin Kniep; Richard Fischer; Wilma Busser; Martin Muhler; Robert Schlögl (93-102).
.Display Omitted▶ Precipitation of Cu, Zn and Al species proceed sequentially in nitrate solution. ▶ Microdroplet-technique or complexing anions can lead to a homogeneous distribution. ▶ Conditions have been optimized for the zincian malachite precursor. ▶ New precursors require renewed optimization of the synthesis conditions.Co-precipitation of Cu,Zn,(Al) precursor materials is the traditional way of synthesizing Cu/ZnO/(Al2O3) catalysts for industrial methanol synthesis. This process has been investigated by titration experiments of nitrate and formate solutions. It was found that the solidification of the single components proceeds sequentially in case of nitrates: Cu2+ is precipitated at pH 3 and Zn2+ (as well as Al3+) near pH 5. This behavior prevents a homogeneous distribution of all metal species in the initial precipitate upon gradual increase of pH and requires application of the constant pH micro-droplet method.This effect is less pronounced if formate instead of nitrate is used as counter ion. This can be explained by the strong modification of the hydrolysis chemistry of the metal ions due to the presence of formate anions, which act as ligands and buffer.A formate-derived Cu/ZnO/Al2O3 catalyst was more active in methanol synthesis compared to a nitrate-derived sample although the same crystallographic phases were present in the precursor after co-precipitation and ageing.The effect of precipitation temperature was studied for the binary CuZn nitrate model system. Increasing the temperature of co-precipitation above 50 °C leads to down-shift of the precipitation pH of Zn2+ by a full unit. Thus, in warm solutions more acidic conditions can be used for complete co-precipitation, while in cold solutions, some Zn2+ may remain dissolved in the mother liquor at the same precipitation pH. The higher limit of temperature is given by the tendency of the initial Cu precipitate towards formation of CuO by oxolation. On the basis of these considerations, the empirically determined optimal pH and temperature conditions of the industrially applied synthesis can be rationalized.
Keywords: Cu/ZnO/Al2O3 catalyst; Preparation; Co-precipitation; Precursor; Methanol synthesis;
Kinetic studies on ammonia decomposition over zirconium oxynitride by T. Otremba; N. Frenzel; M. Lerch; T. Ressler; R. Schomäcker (103-110).
The kinetics of ammonia decomposition has been studied using a zirconium oxynitride catalyst, which has been synthesized via ammonolysis of zirconia. The catalyst was characterized with BET, XRD and hot gas extraction. The conversion of NH3 was measured as a function of residence time, temperature, partial pressures of H2 and NH3 in the inlet flow, respectively, via infrared spectrometry. The activation energy of the rate determining step and adsorption enthalpies were determined for a 3 and a 5-step reaction mechanism, considering an interaction between NH3 and the oxygen vacancies of the catalyst. A comparison with theoretically predicted values offered a good agreement and led to a refinement of the mechanism.▶ Reaction mechanism for decomposition of ammonia over zirconium oxynitride. ▶ Determining of equilibrium constants and activation energy. ▶ Link between theoretical works and experiment.
Keywords: Ammonia decomposition; Zirconium oxynitride; Reaction mechanism; Energy level diagram;
Ga-TUD-1: A new heterogeneous mesoporous catalyst for the solventless expeditious synthesis of α-aminonitriles by Bikash Karmakar; Apurba Sinhamahapatra; Asit Baran Panda; Julie Banerji; Biswajit Chowdhury (111-117).
.Display Omitted▶ Ga-TUD-1, a new mesoporous catalyst developed by non hydrothermal sol–gel method. ▶ Characterized by TEM, atom mapping, XRD, NH3 TPD, 29Si NMR, BET SSA method. ▶ Found to be highly acidic having large number of Bronsted and Lewis acid sites. ▶ The catalyst applied in multicomponent organic synthesis of α-aminonitriles. ▶ Reused several times with reproducible activity.The high surface area three-dimensional porous catalyst has been prepared and characterized by TEM, BET S.A, low angle XRD, 29Si MAS NMR, NH3 TPD techniques. A simple, efficient and rapid method for the green synthesis of α-aminonitriles has been demonstrated over a new mesoporous gallosilicate catalyst Ga-TUD-1. The solventless technique has been applied for the synthesis of a range of compounds with variable functionality with excellent yield and selectivity. The catalyst has been recycled four times with reproducible yield.
Keywords: Mesoporous gallosilicate; Strecker reaction; Multicomponent synthesis; Recyclable;
Fe–Mo interactions and their influence on Fischer–Tropsch synthesis performance by Shaodong Qin; Chenghua Zhang; Jian Xu; Yong Yang; Hongwei Xiang; Yongwang Li (118-126).
.Display Omitted▶ In Fe–Mo bimetallic catalysts, Mo interacts with Fe species via Fe–O–Mo bridge bonds. ▶ Fe–Mo interaction improves the dispersion of Fe species. ▶ Fe–Mo interaction leads to an electron transfer from Fe to Mo. ▶ The dispersion effect on the Fischer–Tropsch synthesis activity and methane selectivity is opposite to the electronic transfer effect.Fe–Mo interactions and their effect on Fischer–Tropsch synthesis (FTS) performance were investigated over Fe–Mo catalysts. The interaction between Fe and Mo is in the form of Fe–O–Mo structure in as-prepared catalysts and remains largely undestroyed after activation. This interaction leads to increased charge transfer between Fe and Mo species and electron-deficient Fe species with increasing Mo content. The electron-deficient Fe species is responsible for the poor reduction and high methane selectivity in FTS reactions. Meanwhile, Mo incorporation increases the dispersion of iron oxides. The Mo dispersion effect inhibits the aggregation of active iron particles in the heat-treatment. Under the combined action of the electron transfer effect and dispersion effect, the FTS activity of catalysts exhibits a parabola-like trend as a function of Mo content and passes through a minimum at Mo/Fe ratio of 10/100. In contrast, the methane selectivity demonstrates an opposite tendency to FTS activity.
Keywords: Fischer–Tropsch synthesis; Fe–Mo catalyst; Fe–Mo interaction; Electron transfer; Reduction; Dispersion; Particle-size-effect;
Reactions for the partial oxidation of propane over Pt-on-Ceria by Dady B. Dadyburjor; Tapan K. Das; Edwin L. Kugler (127-135).
.Display Omitted▶ H2 from C3H8 studied using Pt on low-surface-area and high-surface-area CeO2. ▶ The number of independent reactions is 4, per Gauss elimination. ▶ CO and H2 formed at the start of the reactor. ▶ CO2 and H2O formed at the end of the reactor.The sequence of reactions for the formation of hydrogen from propane has been studied using a supported 1% Pt catalyst, with either a low-surface-area CeO2 or a high-surface-area CeO2 as support. The catalytic experiments were carried out in a fixed-bed reactor at 600 °C at different contact times. Flow rates were varied (100, 200, 300, and 400 sccm), as were the catalyst loadings (0.01 g and 0.02 g). Six species (CO, H2, CO2, C3H8, C3H6 and O2) were analyzed at the exit of the reactor. Using the Gauss-elimination procedure, it was found that the number of independent reactions is four. A material balance of the exit species can be used to determine a set of independent reactions which are physically meaningful under a given set of conditions. (Of course, dependent reactions are obtained by algebraic manipulations of the independent reactions chosen.) The set of reactions comprising partial oxidation, total oxidation, water formation and dehydrogenation is a possible sequence of reactions for the low-surface-area catalyst. For the high-surface-area catalyst, the same set of reactions is also a possibility for the 0.01 g loading, but not for the 0.02 g loading. For that case, there is a net loss of water, so the water-formation reaction in the set above is replaced by the water-gas-shift (WGS) reaction. The net loss of water is shown to be due to the effect of the ceria support. To confirm the choice of the above sets, independent runs involving WGS, dry reforming and steam reforming were carried out over the catalysts. Neither dry reforming nor steam reforming can take place in appreciable amounts over any of the catalysts, while WGS occurs over the catalyst with the largest total surface area. This is consistent with the choice of reaction sets above. Finally, the nature and relative importance of the reactions in these sets indicate that the amount of propane reacting via partial oxidation increases with loading and also with flow rate, while the amount of propane reacting via total oxidation increases only slightly with loading and decreases with flow rate. This implies that partial oxidation takes place first, as compared to total oxidation. Microreactors, with small contact times, would be preferred for such processes.
Keywords: Propane; Synthesis gas; Partial oxidation; Platinum; Ceria; Sequence of reactions;
Catalytic ethanolysis of soybean oil with immobilized lipase from Candida antarctica and 1H NMR and GC quantification of the ethyl esters (biodiesel) produced by Isac G. Rosset; Maria Cecília H. Tavares; Elisabete M. Assaf; André Luiz M. Porto (136-142).
Display Omitted▶ Catalytic ethanolysis of soybean oil by lipase from Candida antarctica. ▶ The parameters investigated were the quantity of biocatalyst, the reaction time, the amount of water added and turnover of lipase. ▶ The highest yields of biodiesel were obtained (87% by 1H NMR; 82.9% by GC). ▶ The quantification methods were efficient for determination of yields of ethyl esters (biodiesel) in mixtures with MAG, DAG, TAG.The catalytic ethanolysis of soybean oil with commercial immobilized lipase type B from Candida antarctica to yield ethyl esters (biodiesel) has been investigated. Transesterification was monitored with respect to the following parameters: quantity of biocatalyst, reaction time, amount of water added and turnover of lipase. The highest yields of biodiesel (87% by 1H NMR; 82.9% by GC) were obtained after a reaction time of 24 h at 32 °C in the presence of lipase equivalent to 5.0% (w/w) of the amount of soybean oil present. The production of ethyl esters by enzymatic ethanolysis was not influenced by the addition of water up to 4.0% (v/v) of the alcohol indicating that it is possible to use hydrated ethanol in the production of biodiesel catalyzed by lipase. The immobilized enzyme showed high stability under moderate reaction conditions and retained its activity after five production cycles. The 1H NMR methodology elaborated for the quantification of biodiesel in unpurified reaction mixtures showed good correlations between the signal areas of peaks associated with the α-methylene groups of the ethyl esters and those of the triacylglycerides in residual soybean oil. Monoacylglycerides, diacylglycerides and triglycerides could also be detected and quantified in the crude biodiesel using 1H NMR spectroscopic and GC-FID chromatographic methods. The biodiesel production by enzymatic catalysis was promising. In this case, was produced a low concentration of glycerol (0.74%) and easily removed by water extraction.
Keywords: Biodiesel; Enzymatic ethanolysis; Quantitative 1H NMR analysis; Quantitative GC-FID analysis;
Behavior of titania-supported vanadia and tungsta SCR catalysts at high temperatures in reactant streams: Tungsten and vanadium oxide and hydroxide vapor pressure reduction by surficial stabilization by David M. Chapman (143-150).
Display Omitted▶ Bulk vanadia and tungsta relative vapor pressures: V4O10 ∼ WO2(OH)2 > VO(OH)3 > (WO3)3. ▶ Without H2O, no V or W oxides vaporize from TiO2 surface. ▶ With H2O, WO2(OH)2 is much more volatile than VO(OH)3 on TiO2 surface. ▶ TiO2 surface lowers W-, V-oxide vapor pressures. ▶ W-, V-oxide vapor pressures are negligible on TiO2 supports with improved stability.In order to meet impending regulations for soot and NOx reduction from mobile diesel engines, advanced emission control systems may require SCR catalysts with substantially improved thermal durability. State of the art vanadia-based SCR catalysts are composed of vanadia, tungsta, and possibly silica, present at relatively low mass fraction and supported on high-surface-area titania. Concern over the possible emission of metals such as vanadia from diesel vehicles fitted with vanadia-based catalysts limits their potential utility. Vanadia and tungsta oxide and hydroxide vapor pressures over the bulk oxides under conditions relevant for the simulated lifetime exposure of catalysts in the mobile SCR application were estimated on the basis of literature data, and the vapor pressures can be consequential. For the bulk tungsta and vanadia, the most volatile component is WO2(OH)2, formed from the reaction of tungsta with water, followed by V4O10 and then VO(OH)3, also a reaction product. An experimental method was developed to measure the vapor-phase transport (a manifestation of vapor pressure) of such inorganic components over real catalysts in representative gas streams by collection on high-surface-area alumina at exposure temperature. In the absence of water at 750 °C, only V4O10 was anticipated as the volatile species. However, no V was observed downstream of the catalyst, so that the vapor pressure of titania-supported vanadia was strongly suppressed relative to the bulk oxide. In the presence of water, the results depended on the support. In the case of a support that underwent substantial loss of surface area during exposure, amounts of W were collected consistent with equilibrium vaporization as WO2(OH)2. However, the amounts of V collected were below the amount expected based on equilibrium vaporization as either V4O10 or VO(OH)3. Thus, the reaction of titania-supported vanadia with water at high temperatures was also suppressed. The vapor pressures of the vanadia and tungsta, and the extent of their reaction with water, can be reduced by varying degrees by reducing loss of the surface area of the titania support during exposure and by minimizing the mass fractions of the surficial oxides. New, highly stable titania supports with optimized compositions were found to virtually eliminate the loss of vanadia and tungsta.
Keywords: Titania; Vanadia; Tungsta; SCR catalyst; Vaporization; Surface stabilization;
Cobalt–iron magnetic composites as heterogeneous catalysts for the aerobic oxidation of thiols under alkali free conditions by Luciano Menini; Márcio C. Pereira; André C. Ferreira; José D. Fabris; Elena V. Gusevskaya (151-157).
Display Omitted▶ A simple method for the liquid-phase aerobic oxidation of thiols has been developed. ▶ Co–Fe inexpensive magnetic materials are used as efficient heterogeneous catalysts. ▶ Disulfides can be obtained in high yields at low catalyst loading (0.008 mol%). ▶ The catalyst does not undergo leaching and can be recovered magnetically and reused. ▶ The reaction occurs under mild alkali free conditions using air as an oxygen source.Cobalt–iron magnetic composites prepared by the thermal treatment of an iron oxide-rich soil in the presence of sucrose and cobalt(II) sulfate are efficient heterogeneous catalysts for the liquid-phase aerobic oxidation of thiols into disulfides. The materials have been characterized by Mössbauer spectroscopy, XRD, N2 adsorption–desorption, and elemental analysis. It has been shown that the isomorphic substitution of iron by cobalt occurs preferentially in the framework of the wüstite (FeO) phase and strongly affects the catalytic behavior of the material. The choice of a solvent is critically important for the efficiency of the reaction. In weakly basic solvents, such as dimethylformamide and dimethylacetamide, disulfides can be obtained in near-quantitative yields at low catalyst loading (0.008 mol%). A significant practical advantage of this environment-friendly process is the use of inexpensive magnetically recoverable materials as catalysts and oxygen as a final oxidant as well as mild alkali free conditions. Of particular note are the stability of the catalyst toward leaching and the possibility of catalyst recycling without any special treatment.
Keywords: Cobalt; Magnetic catalysts; Oxidation; Oxygen; Thiols;
Potassium effect on the thermal stability and reactivity of NOx species adsorbed on Pt,Rh/La2O3 catalysts by B.S. Sánchez; C.A. Querini; E.E. Miró (158-165).
Display Omitted▶ K decreases the noble metals capacity to decompose NOx species, especially for Pt. ▶ In the presence of Pt and/or Rh the trapped NOx are reduced at lower temperature. ▶ With catalysts containing K but no noble metals, the only reduction product is N2. ▶ The activity for soot combustion is improved by the presence of adsorbed nitrate species.In this paper we analyzed the effect of potassium on the thermal stability of NOx species adsorbed on lanthanum supported catalysts. Catalysts containing only noble metals (Pt and/or Rh) or noble metals and potassium were prepared. The soot combustion process in the presence of NOx species previously adsorbed on the catalysts has also been studied in order to evaluate the possibility of using these materials for the simultaneous abatement of soot and nitrogen oxides.It was shown that lanthanum supported catalysts containing Pt and/or Rh exhibited great capacity to decompose previously adsorbed nitrate species in an inert atmosphere. When potassium was added to the formulation this capacity was modified, which proves the existence of a strong interaction between the potassium and noble metals. Such interaction was much stronger in the case of platinum and, therefore, the Pt–K catalyst was able to decompose only a small fraction of the adsorbed compounds in helium stream. However, when decomposition took place in reducing atmosphere (H2), the NOx species were reduced at a lower temperature in the presence of platinum.For all the lanthanum supported catalysts under study, the activity for soot combustion increased in the presence of previously adsorbed nitrate species, even though some of the samples were not very effective for NOx decomposition. This indicates that NOx species are capable of reacting with soot in oxidant atmosphere without the need for their previous decomposition, as previously observed in an inert stream.
Keywords: Potassium; NOx reduction; Pt; Rh;
Structural characterization and catalytic performance of alkali (K) and metal (Co and Rh)-promoted MoS2 catalysts for higher alcohols synthesis by Venkateswara Rao Surisetty; Yongfeng Hu; Ajay Kumar Dalai; Janusz Kozinski (166-172).
Display Omitted▶ Co and Rh promotion to the sulfided Mo–K catalyst improved higher alcohols yield. ▶ Alkali promotion to the MoS2 reduced the crystalline nature of the catalyst. ▶ Co (Rh)–Mo–S species were evident in the XANES spectra of the catalysts.A series of alkali and metal (Rh and Co) promoted MoS2 catalysts were prepared for the higher alcohols synthesis reaction. The effects of alkali and metal promoters on the performance and structure of molybdenum-sulfided catalysts were studied using the BET, X-ray diffraction (XRD), and X-ray absorption near edge structure (XANES) at the S K-edge and Mo L3-edge. Alkali (K) promotion to trimetallic (Co–Rh–Mo) catalyst supported on multi-walled carbon nanotubes (MWCNTs) showed less CO conversion compared to that of the catalyst without K. The promotion of alkali reduces the hydrogenation ability of alkyl species to form alkanes and increases the active sites for the formation of alcohols, which is consistent with the observation of higher surface area and larger pore diameters in the K-promoted catalysts. XRD patterns showed that alkali-promoted catalysts were less crystalline compared to that of the catalyst not promoted with K. More oxidized S and Mo species were observed by XRD and XANES in the K-promoted catalysts, indicating the formation of more Mo oxide with the addition of K, thus increasing the active sites. The alkali-promoted trimetallic catalysts using two different supports, MWCNTs and active carbon (AC), showed very different catalytic performances. The activity of the AC-supported alkali-promoted trimetallic catalyst was lower than that supported on MWCNTs. More intense features corresponding to the oxidized S and Mo species were observed in both S K-edge and Mo L3-edge spectra of the MWCNT-supported catalysts. Finally, formation of Co (Rh)–Mo–S species was evident in the XANES spectra of bimetallic and trimetallic alkali-promoted MoS2 catalysts, in agreement with their improved catalytic performance.
Keywords: Higher alcohols synthesis; X-ray absorption near-edge structures; Alkali-promoted molybdenum catalyst; Multi-walled carbon nanotubes; Rh promotion; Co promotion; Trimetallic catalyst;
Non-thermal RF plasma effects on surface properties of Pd/TiO2 catalysts for selective hydrogenation of acetylene by Yanan Li; Ben W.L. Jang (173-179).
Display Omitted▶ RF plasma is an alternative to reduce supported Pd species at room temperature. ▶ SMSI phenomenon can be induced at a lower temperature with plasma treatment. ▶ The support and palladium interaction can be measured by the H2-DSC technique. ▶ The distribution of Pd planes has been changed due to plasma treatments.Non-thermal RF plasma modification has been applied to Pd/TiO2 catalysts for selective hydrogenation of acetylene in the presence of ethylene. High ethylene selectivity and high acetylene conversion were obtained over the plasma-treated catalysts. To understand the plasma effect, the catalysts were characterized by differential scanning calorimetry in hydrogen (H2-DSC), pulse H2 chemisorption, X-ray photoelectron spectroscopy (XPS), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) with CO and temperature-programmed desorption with ethylene (C2H4-TPD). XPS and H2-DSC results confirmed that supported Pd precursors could be effectively reduced to the metallic state during the room temperature plasma treatment. Plasma treatments also enhanced the surface active sites of Pd/TiO2 catalysts and improved the dispersion of Pd metal particles. In addition, DRIFTS and C2H4-TPD results indicated that plasma treatments could induce strong metal-support interaction with lower reduction temperature (200 °C), which lead to an enhanced catalytic performance on selective hydrogenation of acetylene. It demonstrates that the RF non-thermal plasma treatment is an effective way to manipulate surface properties and the interaction between metals and supports of supported Pd catalysts for selective hydrogenation.
Keywords: Palladium catalyst; Titanium oxide; Non-thermal plasma; DSC; SMSI; Acetylene hydrogenation;
Esterification of lactic acid over TiO2–ZrO2 catalysts by Kuo-Tseng Li; Chih-Kai Wang; Ikai Wang; Chih-Ming Wang (180-183).
Display Omitted▶ Catalyst with a Ti/Zr atomic ratio of 3/1 had the best activity. ▶ Catalyst with a Ti/Zr atomic ratio of 1/1 had the maximum acidity and area. ▶ Turnover frequency correlated well with surface acidic site density. n-Butyl lactate was synthesized with a good yield by the reaction between lactic acid and n-butanol over TiO2–ZrO2 catalysts. These catalysts had various Ti/(Ti + Zr) atomic ratios and were prepared by a co-precipitation method. XRD, n-butylamine/acetic acid adsorption, nitrogen adsorption, and SEM/EDS were used to characterize the oxides. The maximum activity was found for the catalyst with Ti/(Ti + Zr) ratio = 0.75 (TZ31), which had smaller surface area and acid amount than the catalyst with Ti/(Ti + Zr) ratio = 0.5. In general, turnover frequency (TOF) increased with increasing areal concentration of acid sites. The superiority performance of TZ31 (with a maximum product yield of 94.2%) was ascribed to the cooperation of TOF, acid site density, and specific surface area.
Keywords: Solid acid catalysts; Lactic acid esterification; TiO2–ZrO2 catalysts; Acid site density;
Hydrogen production by methanol steam reforming on NiSn/MgO–Al2O3 catalysts: The role of MgO addition by A. Penkova; L. Bobadilla; S. Ivanova; M.I. Domínguez; F. Romero-Sarria; A.C. Roger; M.A. Centeno; J.A. Odriozola (184-191).
Display Omitted▶ The incorporation of MgO to Al2O3 results in the formation of MgAl2O4 spinel. ▶ The acidity of the catalysts decreases when increasing the MgO content. ▶ NiSn/MgO/Al2O3 catalysts are active in steam reforming of methanol. ▶ The addition of Sn improves the resistance to coke formation. ▶ Higher the basicity, lower the level of the carbonaceous deposit formed.The effect of the magnesia loading on the surface structure and catalytic properties of NiSn/MgO–Al2O3 catalysts for hydrogen production by methanol steam reforming has been investigated. The catalysts have been obtained by impregnation of γ-Al2O3 by the incipient wetness method, with variation of the MgO content. X-ray diffraction (XRD), BET surface area and H2-temperature programmed reduction (TPR) have been used to characterise the prepared catalysts. From this, it has been concluded that the incorporation of MgO results in the formation of MgAl2O4 spinel, which modifies the acid–base properties of the catalysts. The formation of Ni–Sn alloys after the reductive pre-treatment has also been evidenced.The influence of the temperature of reaction and of the MgO loading on the hydrogen production by reforming of methanol has been established. Moreover, tests of catalytic stability have been carried out for more than 20 h. The carbonaceous deposits have been examined by temperature-programmed oxidation (TPO). The analysis of the catalysts after reaction has confirmed the low level of carbon formation on these catalysts. In no case, carbon nanotubes have been detected on the solids.
Keywords: H2 production; Methanol; Steam reforming; Nickel catalysts; Magnesia; Alumina;
Spatially and chemically resolved measurement of intra- and inter-particle molecular diffusion in a fixed-bed reactor by D. Weber; D.J. Holland; L.F. Gladden (192-198).
Display Omitted▶ New technique for measurement of spatially and chemically resolved diffusion. ▶ Discrimination between inter- and intra-particle diffusion is achieved. ▶ Esterification of ethanol and acetic acid over an ion-exchange resin is studied. ▶ Concentration gradients consistent with a mass transfer limitation are observed. ▶ Measurement is generic and can be applied to other catalyst systems.This work demonstrates for the first time the ability to spatially and chemically resolve inter- and intra-particle apparent diffusion coefficients in a packed bed during reaction using Nuclear Magnetic Resonance. The measurements were performed using a diffusion preconditioned one-dimensional chemical shift imaging pulse sequence; all the data are recorded within a single measurement. The reaction studied was the continuous liquid phase esterification of acetic acid and ethanol to form ethyl acetate and water over an ion-exchange resin at ambient temperature and pressure. Inter- and intra-particle apparent diffusivities of the hydrocarbons were resolved at four different spatial positions along the length of the catalyst bed. Absolute composition measurements were obtained of the liquid in the inter-particle space of the bed. Relative concentration measurements of the chemical species in the intra-particle space are also reported. The development of these measurement methods advances our ability to characterise mass transfer limitations in situ within a working fixed-bed reactor.
Keywords: Nuclear Magnetic Resonance; Diffusion; Reaction; Ion-exchange; Esterification; Imaging;
Investigation of the electrical and catalytic properties of materials with Cs x (Mo,Nb)5O14 composition by Anikó Simon; Evgenii V. Kondratenko (199-207).
.Display Omitted▶ Cs x (Mo,Nb)5O14 (x = 0–1) structured materials are mainly ionic conductors with minor electronic conductivity. ▶ Cs promotion increases ionic conductivity and promotes changing the electronic conductivity from n-type to p-type. ▶ Cs x (Mo,Nb)5O14 n-type conductors are more active in the oxidative dehydrogenation of C2–C4 alkanes than the p-type ones. ▶ Consecutive alkene oxidation is increasingly inhibited with rising n-type electronic conductivity in Cs x (Mo,Nb)5O14.The influence of the concentration of Cs and the ratio of Mo/Nb in materials with Cs x (Mo,Nb)5O14 (x = 0, 0.47, 0.53, 0.86, and 1.2) stoichiometry on their electronic properties was elucidated by performing alternating current measurements at various partial oxygen pressures and temperatures. All materials feature mainly ionic conductivity rather than electronic one at 523 K. The ionic contribution decreases in favor of a rising electronic type for most of the materials with further increase in temperature. Upon cesium promotion, the total conductivity generally increases, while the electronic conductivity changes from the n- to the p-type. The individual differences in the electronic properties of the investigated catalysts were related to their activity and selectivity in the oxidative dehydrogenation of C2–C4 alkanes. It appears that the n-type conductivity is crucial for high catalytic activity. Mechanistic investigations on the two best-performing catalyst systems, Mo1.6Nb3.4O m and Mo2.3Nb2.7O m , in the oxidative dehydrogenation of ethane disclosed, that secondary (non-selective) oxidation reactions are inhibited progressively with rising contributions of the n-type conductivity.
Keywords: Conductivity; Oxidative dehydrogenation; Ethane; Propane; n-Butane; Iso-butane; Molybdenum; Niobium; Cesium;
Catalytic performance in selective hydrogenation of citral of bimetallic Pt–Sn catalysts supported on MgAl2O4 and γ-Al2O3 by Patricia D. Zgolicz; Virginia I. Rodríguez; Irene M.J. Vilella; Sergio R. de Miguel; Osvaldo A. Scelza (208-217).
Display Omitted▶ The highest Sn content added to Pt increases the selectivity to UA. ▶ PtSn(3 wt%)/Al2O3 catalyst displays the highest selectivity value to UA (88%). ▶ For PtSn/Al2O3, both dilution and electronic effects were found. ▶ For PtSn/MgAl2O4 only geometric effects appear to take place. ▶ The presence of alloy particles in PtSn/Al2O3 would increase selectivity values.The liquid phase citral hydrogenation, using Pt and PtSn catalysts supported on MgAl2O4 and γ-Al2O3, was studied in a stirred reactor at 70 °C and atmospheric pressure. It was found that the addition of Sn to the Pt catalysts increases the selectivity to double unsaturated alcohols for both catalyst series. Besides, monometallic catalysts hydrogenate the α,β-unsaturation with a high selectivity in absence of cyclization secondary products. The performance of these catalysts in the citral hydrogenation was related with the characteristics of the metallic phase. Results from test reactions – cyclohexane dehydrogenation (CHD) and cyclopentane hydrogenolysis (CPH) – H2 chemisorption, 2-propanol dehydration, temperature programmed reduction (TPR) and X-ray photoelectron spectroscopy (XPS), were used to explain the influence of the support and the Sn loading and postulate the models of the catalytic metallic surface. Results indicated that, a fraction of ionic Sn would be deposited near Pt, thus increasing the polarization of the carbonyl group, and a fraction of metallic Sn could form Pt–Sn alloy phases that would hinder the hydrogenation of the olefinic bonds and would be active to the hydrogenation of the carbonyl group. Both effects contribute to a higher selectivity to unsaturated alcohols in bimetallic PtSn/Al2O3 catalysts than PtSn/MgAl2O4 ones, which display a low alloy formation.
Keywords: Citral selective hydrogenation; Supported PtSn catalysts; MgAl2O4; γ-Al2O3; Characterization of the metallic phase;
Copper on boehmite: A simple, selective, efficient and reusable heterogeneous catalyst for oxidation of alcohols with periodic acid in water at room temperature by S. Ganesh Babu; P. Aruna Priyadarsini; R. Karvembu (218-224).
Display Omitted▶ Catalytic oxidation of alcohols to carbonyl compounds by Cu/AlO(OH). ▶ Catalytic reaction was carried out in water solvent and at room temperature. ▶ Conversion and selectivity are good. ▶ Reusability of the catalyst is good. ▶ Primary alcohols are chemoselectively oxidized in presence of secondary alcohols.Oxidation of various aliphatic, aromatic, alicyclic, benzylic and allylic alcohols to corresponding carbonyl compounds is studied in water at room temperature over copper on boehmite [Cu/AlO(OH)] catalyst which is prepared from CuCl2·2H2O, pluronic P123 and Al(O-sec-Bu)3. The prepared catalyst was characterized by HR-TEM, SEM-EDX and IR spectroscopy. The reaction conditions for catalytic oxidation of alcohols are optimized with different mole ratio, solvents, and oxidants using 1-phenylethanol system as a model. The scope of the reaction is extended to various types of alcohols. Chemoselectivity, heterogeneity and reusability tests were performed. The use of water as a solvent at room temperature makes the reaction interesting from both an economic and environmental point of view.
Keywords: Oxidation; Alcohols; Cu/AlO(OH); Periodic acid; Water; Room temperature;
Anchoring of copper(II) complexes onto the organically modified MCM-41: Preparation, characterization and catalytic epoxidation by Sreyashi Jana; Susmita Bhunia; Buddhadeb Dutta; Subratanath Koner (225-232).
.Display Omitted▶ Anchoring of copper(II) diamine complexes onto MCM-41. ▶ Heterogeneous catalytic epoxidation. ▶ Bulkiness of diamine ligands dictates the catalytic efficacy. ▶ Possible reaction mechanisms are outlined.[Cu(diamine)(NO3)2] complexes have been anchored by substituting easily replaceable nitrate ligand with the amine groups of the organic-modified MCM-41. The amine group containing organic moiety (3-aminopropyl)triethoxysilane has been first anchored on the surface of MCM-41 via silicon alkoxide route. Then the [Cu(diamine)(NO3)2] [where diamine = N,N′-dimethyl-1,2-ethanediamine (NN′dmen) N,N-dimethyl-1,2-ethanediamine (NNdmen), and N,N-diethyl-1,2-ethanediamine (NNdeten)] complex was allowed to react with the modified MCM-41 for tethering the complexes onto mesoporous silica matrix. Copper complexes containing different substituted diamine ligands viz. N,N′-dimethyl-1,2-ethanediamine, N,N-dimethyl-1,2-ethanediamine, and N,N-diethyl-1,2-ethanediamine have also been prepared to compare the catalytic efficiency. The prepared catalysts have been characterized by infrared (FT–IR) and UV–vis spectroscopic, electron paramagnetic resonance (EPR), small-angle X-ray diffraction and N2 sorption study. The catalytic efficacy in the epoxidation reaction depends on the bulkiness of the substituted group in diamine. Notably, styrene shows an impressive conversion (94%) with tert-butylhydroperoxide (tert-BuOOH) over the Cu(NNdmen)-MCM-41 catalyst. Whereas, conversion in styrene to styrene-oxide reaction were only 78% and 48% with Cu(NNdeten)-MCM-41 and Cu(NN′dmen)-MCM-41 catalysts, respectively.
Keywords: Catalytic epoxidation; MCM-41; Copper(II) diamine complex; Tert-butylhydroperoxide; Olefins;
Heteropolyacid salts as self-separation and recyclable catalysts for transesterification of trimethylolpropane by Kaixin Li; Li Chen; Honglin Wang; Weibin Lin; Zongcheng Yan (233-237).
Display Omitted▶ An eco-friendly procedure for transesterification of trimethylolpropane is investigated. ▶ The heteropolyacid salts as catalysts present a self-separation performance in the reaction. ▶ The self-separation performance facilitates the reaction and the recovery of catalysts.A series of heteropolyacid (HPA) salts as catalysts were prepared and characterized. Transesterifications of trimethylolpropane (TMP) were carried out using these catalysts. The influence of organic cations and heteropolyanions on the reaction, optimization of reaction conditions, and catalytic reusability were investigated. The results show that the heteropolyacid (HPA) salts present a self-separation performance after reaction, which can be easily recovered and quite steadily reused as demonstrated by a eight-run recycling test. Moreover, the pyridinium with PW12O40 3− as the anion ([PyBS]3PW12O40) showed the best catalytic performance among the heteropolyacid salts for the transesterification of trimethylolpropane with various methyl esters.
Keywords: Heteropolyacid salts; Trimethylolpropane; Transesterification; Self-separation; Catalyst;
Catalytic synthesis of a high aspect ratio carbon nanotubes bridging carbon felt composite with improved electrical conductivity and effective surface area by Kun Wang; Kambiz Chizari; Yu Liu; Izabela Janowska; Simona Maria Moldovan; Ovidiu Ersen; Antoine Bonnefont; Elena R. Savinova; Lam D. Nguyen; Cuong Pham-Huu (238-247).
Display Omitted▶ Catalytic synthesis of macroscopic composite carbon nanotubes. ▶ High external surface area carbon nanotubes composite for use as catalyst support. ▶ High mechanical strength macroscopic carbon–carbon composite. ▶ Carbon–carbon composite with high electrical and thermal conductivities. ▶ Fully accessible surface with low residual porosity.High aspect ratio (>5000) composite with macroscopic shape consisted of multi-walled carbon nanotubes bridging a 3D network of the micrometers carbon felt host structure was synthesized by means of the chemical vapour deposition technique. Such carbon-based nano-macro composite material displays a high mechanical strength, high electrical conductivity along with a high and fully accessible effective surface area (>100 m2 g−1), which allows it to be efficiently employed as structured catalyst support, in fixed-bed catalytic reactions, without the problem of pressure drop as encountered with the nanoscopic carbon support materials. The nanoscopic structure also provides a high degree of mixing of the reactant mixture which strongly increases the effective surface contact between the reactants and the active sites. In addition, the total effective surface area of the composite can be finely tuned, depending to the downstream application, as a function of the carbon nanotubes intake.
Keywords: Carbon nanotubes; Carbon-based composite; Catalysis; Structured reactors;
Catalytic performance and characterization of Ni-Fe catalysts for the steam reforming of tar from biomass pyrolysis to synthesis gas by Lei Wang; Dalin Li; Mitsuru Koike; Shuichi Koso; Yoshinao Nakagawa; Ya Xu; Keiichi Tomishige (248-255).
Display Omitted▶ Addition of the optimum amount of Fe to Ni/Al2O3 enhanced the catalyst activity and stability of Ni/Al2O3 in the steam reforming of tar derived from the pyrolysis of cedar wood. ▶ Fe atoms added were alloyed with Ni and they tended to be located on the surface of the Ni-Fe alloy particles. ▶ Suggested mechanism of high performance in the tar steam reforming is due to the synergy between high tar decomposition activity on Ni atoms and activation of H2O on Fe atoms.Catalytic performance of Ni-Fe/Al2O3 catalysts with the optimum composition was much higher than corresponding monometallic Ni and Fe catalysts in the steam reforming of tar from the pyrolysis of cedar wood. According to the catalyst characterization, the Ni-Fe alloys were formed and the Fe atoms on the alloys tend to be enriched on the surface, and it was suggested that the structure was maintained mainly during the reaction. The surface Fe atoms supply oxygen species, enhancing the reaction of tar and suppressing the coke formation. Excess Fe addition decreased the catalytic activity by decreasing the surface Ni atoms.
Keywords: Biomass; Tar; Steam reforming; Ni; Fe; Alloy; Synthesis gas;