Applied Catalysis A, General (v.384, #1-2)
Editorial Board (CO2).
Study of nanostructured Ni/CeO2 catalysts prepared by combustion synthesis in dry reforming of methane by Víctor M. Gonzalez-Delacruz; Fátima Ternero; Rosa Pereñíguez; Alfonso Caballero; Juan P. Holgado (1-9).
This work reports the study of several catalysts of Ni–CeO2 active for dry methane reforming process (CH4 + CO2 → 2CO + 2H2). The use of Ni as active phase is highly preferred, due to its availability, high activity and low cost, although its main lack is the coke formation on the surface of Ni metal particles, resulting in a severe deactivation. Here we report a new synthesis method that allows a simple, effective and fast way to prepare Ni–CeO2 catalysts, in a wide range of metallic loadings, resulting in all the cases in well-formed NiO crystallites with sizes in the range of 12–18 nm. The use of CeO2 as a support has been based on its massive use in TWC catalysts formulations, where it is recognized to activate CH4 and lower hydrocarbon dissociation. Moreover, CeO2 has been reported to have an intrinsic activity in the CH4 reforming reaction. Besides the metallic loading, several factors that control the preparation method of the catalyst have been varied, in order to optimize their performance. Most of the catalysts prepared show activity and selectivity values close to thermodynamic ones, maintaining a good stability on long periods of time and severe conditions. Nevertheless, formation of some carbon nano-fibers has been observed, which could result in a drawback for their application at large scale.
Keywords: Methane reforming; Syngas; Hydrogen production; Heterogeneous catalysts; Nanoparticles;
Effect of promoter on Ni/MgO catalyst in C8H18 autothermal reforming in solid oxide fuel cell system by Yun Tae Kim; Ji Hyun Um; Sung Ho Kim; Tae-Hoon Lim; Ho-In Lee (10-17).
. In Ni/MgO catalysts combined with various promoters such as Ag, Cr, and Cu, Cr which did not make an alloy with Ni acted as a blocker for Ni sintering and then gave good dispersion of Ni. For this reason, Ni–Cr/MgO catalyst showed the most desirable characteristics in the aspects of its activity, stability, and resistance to carbon deposition.Display Omitted▶ The formation of NiO–MgO solid solution resulted in loss of active Ni metal. ▶ Among Ag, Cr, and Cu promoters for Ni/MgO catalysts, Cr acted as a blocker for Ni sintering not forming an alloy with Ni unlike Ag and Cu. ▶ Cr-promoted Ni/MgO catalyst, Ni–Cr/MgO, showed stably the highest activity. ▶ An optimal condition of octane ATR was 1.5 and 0.5 for steam-to-carbon ratio and oxygen-to-carbon ratio, respectively.Autothermal reforming, which is a combined process of steam reforming and partial oxidation reforming, has excellent coke resistance and high efficiency in reforming reactions. Octane autothermal reforming was carried out over Ni-supported catalysts. The catalysts were prepared by normal precipitation and promoters were added by impregnation. The formation of NiO–MgO solid solution was accomplished during calcination of the Ni/MgO catalyst at 900 °C, resulting in loss of the active Ni metal and very low catalytic activity. Therefore, all catalysts were treated by a reduction process without calcination in order to prevent the formation of NiO–MgO solid solution. Among Ni/MgO catalysts combined with various promoters such as Ag, Cr, and Cu, Ni–Cr/MgO catalyst showed the most desirable characteristics in the aspects of its activity, stability, and resistance to carbon deposition. We found an optimal condition for octane autothermal reforming when steam-to-carbon ratio and oxygen-to-carbon ratio were 1.5 and 0.5, respectively.
Keywords: Octane autothermal reforming; Carbon deposition; Ni/MgO; Cr promoter; NiO–MgO solid solution;
Regioselective bromination of organic substrates by LDH-CO3 2−–Br− promoted by V2O5–H2O2 by M. Ghiaci; M.E. Sedaghat; S. Ranjbari; A. Gil (18-26).
Display Omitted▶ Regioselective monobromination of aromatic compounds by hydrotalcites. ▶ New heterogeneous catalytic system for selective bromination of aromatic compounds. ▶ New method for substituting quaternary ammonium tribromides.An efficient, fast, simple, mild, and selective monobromination of aromatic compounds, with high para-selectivity, is reported. The catalytic system is readily prepared from a Mg–Al-layered double hydroxide-CO3 2−–Br− (LDH-CO3 2−–Br−) as the source of bromide, V2O5 as a promoter and hydrogen peroxide as the oxidant. The use of hydrogen peroxide as a synthetically useful oxidizing agent is reported for generating electrophilic bromine in situ from easily available KBr as a bromine source, to brominate electron rich aromatic compounds, employing LDH-CO3 2−–Br3 − as the phase-transfer catalyst. The phase-transfer catalyst leads to nearly complete bromination in 3 h at room temperature with high selectivity. The reaction rate of p-bromoanisole and p-bromotoluene formation by LDH-CO3 2−–Br3 − in a triphasic system was studied. The heterogeneity of the reaction system facilitates the recovery and recycling of the catalyst, and the reagent components are environmentally acceptable. The catalyst, LDH-CO3 2−–Br3 −, and its precursors, LDH-CO3 2−–Br− and LDH-CO3 2−, were characterized by powder XRD, FT-IR and UV–vis spectroscopy.
Keywords: Bromination; Aromatic compounds; LDH; Phase-transfer catalyst;
Catalytic decomposition of hydrocarbons on cobalt, nickel and iron catalysts to obtain carbon nanomaterials by U. Narkiewicz; M. Podsiadły; R. Jędrzejewski; I. Pełech (27-35).
Hydrocarbons decomposition was investigated on cobalt, nickel and iron catalysts under atmospheric pressure and in the temperature range of 500–700 °C. In lower temperatures, the cobalt catalyst revealed the highest activity, whereas in higher temperatures, larger carbon amounts were obtained on the nickel and iron catalysts. On the cobalt and iron, MWNTs at 700 °C were obtained, but on the nickel many disordered carbon structures and Ni nanocapsules coated with a graphite layer were found.Hydrocarbons decomposition was investigated on cobalt, nickel and iron catalysts under atmospheric pressure and in the temperature range of 500–700 °C. As a carbon source, methane, ethane and ethylene were used. In lower temperatures, the cobalt catalyst revealed the highest activity, whereas in higher temperatures, larger carbon amounts were obtained on the nickel and iron catalysts. According to the observed results the decomposition of hydrocarbons on the cobalt sample led to the formation of a stable form of fcc-Co in room temperature. On the cobalt and iron catalysts, multiwalled carbon nanotubes at 700 °C were obtained, but on the nickel catalyst many disordered carbon structures and Ni nanocapsules coated with a graphite layer were found.
Keywords: Nanostructures; Metal carbides; Phase transitions; Chemical vapor deposition;
Qualitative treatment of catalytic hydrolysis of alkyl formates by Olatunde Jogunola; Tapio Salmi; Kari Eränen; J.-P. Mikkola (36-44).
Display Omitted▶ Formic acid increases reaction rate but suppresses yield slightly. ▶ The additive, X increases both reaction rate and yield. ▶ Internal diffusion is present in the large particle of the resin. ▶ The catalyst can be used more than once.Liquid-phase hydrolysis of alkyl formates was performed in a stirred batch reactor using formic acid as a homogenous catalyst, cation exchange resin as heterogeneous catalyst and an additive as a complexation agent. The catalysts increased the rate of the reaction considerably, but the equilibrium conversion was slightly suppressed by the homogenous catalyst. The additive not only accelerated the reaction rate, but also improved the yield significantly. The effect of external and internal mass transfer limitations present in the heterogeneous reaction steps was investigated and it was observed that there is the existence of internal diffusion limitation for the largest catalyst particles. Other parameters such as temperature, catalyst pre-treatment, catalyst loading and stirring speed were investigated in order to optimize the process. The experiments also demonstrated that the ion exchange resin can be reused more than once.
Keywords: Additive; Alkyl formate hydrolysis; Amberlite IR-120 resin; Formic acid;
Hydrogenation of polystyrene in CO2-expanded liquids: The effect of catalyst composition on deactivation by Laura Beth Dong; Gary B. McVicker; Douglas J. Kiserow; George W. Roberts (45-50).
Display Omitted▶ Pd catalyst deactivation occurs when PS is hydrogenated in CO2-expanded solvents. ▶ Reverse water-gas shift reaction forms CO, which poisons Pd hydrogenation sites. ▶ Ni and Ru catalysts can be used to reduce CO levels. ▶ Mixtures of mesoporous Pd & Ru or Ni catalysts are ineffective in hydrogenation. ▶ Bimetallic catalyst (Pd/Ru or Ni on same particle) is effective in PS hydrogenation.The effect of catalyst composition on the hydrogenation of the aromatic rings of polystyrene dissolved in carbon dioxide-expanded decahydronaphthalene (CO2-DHN) was studied using a slurry reactor at 150 °C. Catalyst deactivation occurred within 15 min of the addition of CO2 to the reactor when 5% Pd/SiO2 or 5% Pd/Al2O3 was used as the catalyst. The deactivation is believed to be a consequence of CO formation via the reverse water-gas shift reaction, as CO was observed at the end of each hydrogenation reaction. In an effort to convert CO to CH4 before the poisoning of Pd sites occurred, a methanation catalyst such as 5% Ru/Al2O3 or 65% Ni/SiO2–Al2O3 was physically mixed with 5% Pd/SiO2 or 5% Pd/Al2O3 and used to hydrogenate PS. Carbon monoxide concentrations decreased, but no significant improvements in aromatic ring hydrogenation were observed. When a catalyst containing both a hydrogenation and methanation function in a single catalyst particle (1.6% Ru/4.2% Pd/SiO2) was used, the degrees of hydrogenation in CO2-DHN matched those obtained when neat DHN was the solvent. Furthermore, no CO was detected when the reaction was catalyzed by the bimetallic catalyst. These results suggest that the methanation function must be proximate to the hydrogenation (reverse water-gas shift) function in order for aromatic ring hydrogenation to proceed as rapidly in a CO2-expanded solvent as in the unexpanded solvent.
Keywords: Polystyrene; Carbon dioxide-expanded liquid; Reverse water-gas shift reaction; Hydrogenation; Catalyst deactivation;
Influence of support acidity of NiMoS catalysts in the activity for hydrogenation and hydrocracking of tetralin by Sheila G.A. Ferraz; Fatima M. Zanon Zotin; Lucia R. Raddi Araujo; José Luiz Zotin (51-57).
Display Omitted▶ NiMoS with similar dispersion prepared on Al2O3, SiO2–Al2O3 and Al2O3-Y zeolite. ▶ Tetralin ring opening and cracking is favored on NiMoS/Al2O3-Y zeolite. ▶ Support acidity also promotes hydrogenation activities. ▶ Electronic effect or alternative reaction pathway over acidic supports are proposed.Three NiMo sulfided catalysts with the same active phase content and deposited on different supports (alumina, silica–alumina and alumina-Y zeolite) were prepared aiming to obtain bifunctional catalysts with different acidities and good dispersion of the sulfide phase for analyzing the role of the support acidity on the hydrogenation and hydrocracking activities for the conversion of tetralin. Support acidity promotes the ring opening of tetralin, increasing the yields of aromatic compounds among the reaction products of silica–alumina and alumina-Y zeolite supported catalysts. However, these catalysts also presented high activities for both ring opening/cracking and hydrogenation reactions, respectively associated to the support and to sulfided metal phase, as compared to alumina supported one, which presented essentially hydrogenated products. Although the hydrogenation activity of sulfided catalysts can be modified by neighboring acid sites, the complex reaction network for the tetralin conversion, involving series and parallel steps on both acid and hydrogenation sites, has to be taken in account for explaining the present results.
Keywords: Tetralin; Hydrogenation; Hydroconversion; Ring opening; Acidity;
Factors affecting activity and selectivity during cyclohexanone hydrogenation with colloidal platinum nanocatalysts by Kimberly A. Manbeck; Nathan E. Musselwhite; Lindsay M. Carl; Carrie A. Kauffman; Oliver D. Lyons; Jason K. Navin; Anderson L. Marsh (58-64).
Display Omitted▶ Catalytic activity for the aqueous-phase hydrogenation of cyclohexanone using colloidal platinum nanocatalysts increases with reaction temperature, reactant concentration, hydrogen pressure, and nanoparticle size. ▶ Catalytic activity for the aqueous-phase hydrogenation of cyclohexanone using colloidal platinum nanocatalysts does not depend on the capping agent molecular weight, regardless of nanoparticle size. ▶ Under these mild conditions, the reaction proceeds via a Langmuir-Hinshelwood mechanism with 100% selectivity to cyclohexanol.The hydrogenation of cyclohexanone was carried out with 100% selectivity to cyclohexanol by utilizing 1–10 nm size poly(vinylpyrrolidone)-capped colloidal platinum nanocatalysts dispersed in the aqueous-phase. Particle sizes for these synthesized nanocatalysts were determined by transmission electron microscopy (TEM), and open adsorption sites on the metal nanoparticle surface were established through attenuated total reflectance infrared (ATR-IR) spectroscopic studies of chemisorbed carbon monoxide. The effect of the reaction conditions (temperature, hydrogen pressure, and cyclohexanone concentration) on turnover frequencies (TOFs) was examined to calculate apparent activation energies and reaction orders. In addition, platinum nanoparticle size and PVP molecular weight were varied to investigate effects of nanocatalyst properties on catalytic activity and reaction selectivity. In situ ATR-IR spectroscopy was used to verify adsorbed cyclohexanone as being present on the nanocatalyst surface during the reaction. Combining kinetic parameters with identification of adsorbed species is essential for developing a molecular-level mechanism for the reaction, thereby allowing factors controlling activity and selectivity in these aqueous-phase hydrogenations to be elucidated. Taken together, these results permit the ingredients essential for a highly active and selective catalyst to be discerned.
Keywords: Ketone; Hydrogenation; Colloidal platinum; Nanocatalyst;
Continuous production of 5-hydroxymethylfurfural from simple and complex carbohydrates by Clayton V. McNeff; Daniel T. Nowlan; Larry C. McNeff; Bingwen Yan; Ronald L. Fedie (65-69).
Display Omitted▶ A continuous flow biphasic reactor converts sugars to 5-HMF using TiO2. ▶ Glucose, fructose, sucrose, corn syrup and honey are converted to 5-HMF. ▶ An approach to the continuous conversion of cellulose to 5-HMF is described.▶ Cellulose is converted to HMF in 35% yield with 87% cellulose consumption.The synthesis of biofuels and biopolymers from cellulosic feedstocks has been a focus of many renewable energy research groups primarily due to the desire to use inedible sources of biomass for the production of liquid biofuels. Here we describe the continuous production of 5-hydroxymethylfurfural (HMF) from sources of both simple and complex sugars such as fructose, glucose, starch and cellulose using a fixed bed porous metal oxide-based catalytic process. Specifically, a two liquid phase continuous method was developed using a fixed bed catalytic reactor that resulted in the production of HMF with yields up to 29%. The organic extracting solvent used in the system was found to have a significant effect on the efficiency of HMF production. An approach to the continuous depolymerization of cellulose and subsequent conversion to HMF is described using a single catalytic reactor resulting in high consumption of the cellulose (87%) and good HMF yields (35%). The catalysts studied were spherical, porous zirconia and titania, which were both found to be stable over a variety of operating conditions and reusable through a simple pyrolytic regeneration process.
Keywords: HMF; Cellulose; Continuous; Metal oxide; Biphasic;
Characterization of alumina- and niobia-supported gold catalysts used for oxidation of glycerol by Karolina Musialska; Elisabetta Finocchio; Izabela Sobczak; Guido Busca; Robert Wojcieszak; Eric Gaigneaux; Maria Ziolek (70-77).
Display Omitted▶ Gold-supported niobia-active catalyst in selective oxidation of glycerol with O2. ▶ The generation of active oxygen on the interface between Au particles and niobia. ▶ Au/Nb2O5 after reduction in hydrogen — able to convert CO into CO2 at 153–193 K.Gold catalysts supported on niobia and alumina are active in glycerol oxidation performed in liquid basic solution in the presence of oxygen. Niobia-supported gold is only slightly less active than commercial Au/TiO2 catalyst. XPS data allow to characterize gold nanoparticles on both supports. IR studies show that CO adsorbs on gold particles loaded on niobia producing well characterized terminal carbonyls whose C–O stretching frequency shifts up by decreasing CO coverage, an usual behaviour for gold carbonyls. Two families of gold nanoparticles on niobia are characterized by CO stretching frequencies of adsorbed CO at 2098–2112 cm−1 after reduction at 573 K and at 2108–2120 and 2125–2135 cm−1 after reduction at 773 K. However, after both reduction pretreatments such gold metal particles coexist with strongly oxidizing gold species which are able to convert CO into CO2 at 153–193 K. Based on IR and XPS experiments, the lower activity of alumina-supported gold may be due to a lower density of corner and edge sites on Au nanoparticles, associated to the minor dispersing ability of alumina for gold.
Keywords: Gold catalysts; Alumina-supported gold; Niobia-supported gold; Glycerol oxidation; IR spectroscopy; XPS spectroscopy; Carbon monoxide probe;
Relevance of sulfiding pretreatment on the performance of Re/ZrO2 and Re/ZrO2-sulfated catalysts for the hydrodeoxygenation of guayacol by P.E. Ruiz; K. Leiva; R. Garcia; P. Reyes; J.L.G. Fierro; N. Escalona (78-83).
Display Omitted▶ Effect of the sulfiding pretreatment (H2/H2S and N2/H2S mixture) on Re/ZrO2 and Re/ZrO2-sulfated catalysts for the hydrodeoxygenation of guayacol were investigated. ▶ It was found that Re/ZrO2 and Re/ZrO2-S catalysts sulfided under N2/H2S mixture increases the activity of guayacol hydrodeoxygenation. ▶ The increase in the H2S partial pressure decreases the activity of guayacol hydrodeoxygenation and changes the (phenol/cathecol) ratio, favoring the formation of cathecol.The effect of the sulfiding mixture (H2/H2S and N2/H2S) over Re/ZrO2 and Re/ZrO2-sulfated catalysts in the hydrodeoxygenation (HDO) of 2-methoxyphenol (guayacol) in the presence of CS2 has been studied. The catalysts were prepared by wet impregnation and characterized by X-ray diffraction (XRD), BET surface area, X-ray photoelectron spectroscopy (XPS) and surface acidity techniques. The reaction was carried out in a batch reactor at 300 °C and 5 MPa. Reaction rates for both catalysts increased upon sulfiding in N2/H2S mixture. This N2/H2S mixture promotes the formation of ReS(2 − x) species over support surfaces and leads to an increase in the rate of direct demethoxylation and an enhancement in the phenol/cathecol ratio. An increase in the concentration of CS2 leads to an increase in the HDO and cathecol and inhibits the demethoxylation of guayacol.
Keywords: Re sulfided; Hydrodeoxygenation; ZrO2 support; Methoxyphenol;
Bio-inspired Mo(II) complexes as active catalysts in homogeneous and heterogeneous olefin epoxidation by Cristina I. Fernandes; Nuno U. Silva; Pedro D. Vaz; Teresa G. Nunes; Carla D. Nunes (84-93).
Display Omitted▶ Low valent Mo(II) complexes with amino acid ligands in oxidation catalysis. ▶ Ligands hold amine moieties inducing deactivation. ▶ Clay catalysts circumvent deactivation yielding stable and active catalysts. ▶ Epoxidation of cyclooctene is completely selective whereas for styrene is not. ▶ Benzaldehyde is formed by oxidative cleavage with epoxide as intermediary.New hydrotalcite clay materials functionalized with molybdenum(II) complexes holding potential catalytic properties were prepared by a stepwise procedure. The material was first calcined at 823 K for 4 h, to eliminate all the carbonate ions; the layered structure was reconstructed after treatment with a solution of either tryptophane (trpH) or phenylalanine (pheH) in a KOH aqueous solution of dmf at 343 K. Subsequent impregnation with a solution of the organometallic precursor [MoI2(CO)3(NCCH3)2] led to substitution of the nitriles by the ligands affording the organometallic derivatized clays. The equivalent homogeneous phase complexes [MoI2(CO)3L] (L = trpH or pheH) were also prepared for comparison purposes. All the materials were characterized by powder X-ray diffraction, FTIR and 13C CP MAS-DD solid state NMR. The complexes were also characterized by FTIR, UV/vis, elemental analysis, and 1H and 13C solution NMR accordingly. Both the complexes and these new materials, the latter containing 3.90 wt.% and 5.42 wt.% of Mo, respectively for HT–trp–Mo and HT–phe–Mo materials, catalyzed the epoxidation of cyclooctene and styrene at 328 K. The heterogeneous catalytic systems performed better showing that the presence of the clay is not innocent. In addition, further oxidation of styrene yielding benzaldehyde has occurred. A possible mechanism is proposed based on the detection of two reaction intermediaries by GC/MS.The heterogeneous catalysts also show superior handling capabilities due to Mo increased resistance to moisture and to separation from reaction medium.
Keywords: Molybdenum; Amino acids; Clays; Heterogeneous catalysis; Oxidation catalysis;
Al-promoted Pt/SO4 2−/ZrO2 with low sulfate content for n-heptane isomerization by Ying-Chieh Yang; Hung-Shan Weng (94-100).
Display Omitted▶ The sulfur content in Pt/SZA catalyst greatly affected its performance. ▶ Lowering sulfate content resulted in remarkably enhanced iso-C7 selectivity. ▶ The selectivity could increase from 25% up to 83% without a loss of activity. ▶ Pt/SZA catalysts with low sulfur content had low acidity and high Pt dispersion. ▶ High Pt dispersion in Pt/SZA with low sulfur content benefited a higher selectivity.To reduce the occurrence of cracking reactions and obtain high activity for n-heptane isomerization, we performed this study, aimed at improvements of the Al-promoted Pt/SO4 2−/ZrO2 (Pt/SZ) catalyst. The effect of sulfur content was studied and it was found that lowering sulfate content in the Al-promoted Pt/SZ resulted in remarkably enhanced selectivity towards iso-C7 formation from 25% up to 83% compared with Pt/SZ without a loss of activity. The results of catalyst characterizations revealed that the tetragonal phase of ZrO2 and its acidity were responsible for the higher activity, and that aluminum helped to stabilize the tetragonal phase in Al-promoted Pt/SZ and hence maintained catalytic activity at low sulfate content, while the low acidity and high Pt dispersion resulted in a high ratio of metal sites to acid sites and hence benefited a higher selectivity for iso-C7.
Keywords: Sulfated zirconia; Al- and Pt-promoted; Sulfur content; n-Heptane isomerization; Selectivity;
Heteropoly tungstate supported on tin oxide catalysts for liquid phase benzylation of anisole with benzyl alcohol by Ch. Ramesh Kumar; P.S. Sai Prasad; N. Lingaiah (101-106).
Display Omitted▶ Tin oxide supported heteropoly tungstates are efficient catalysts for benzylation. ▶ The acidity of the catalysts varies with the amount of heteropoly tungstate. ▶ The catalysts activity related to surface and structural characteristics. ▶ The structural and surface modifications depend on the calcination temperatures.A series of 12-tungstophosphoric acid supported on tin oxide catalysts were prepared and characterized by FT-Infra red, X-ray diffraction, Laser Raman spectroscopy and temperature programmed desorption of ammonia. The characterization results suggest the presence of Keggin ions and the generation of strong acidic sites on the support. The catalysts were evaluated for benzylation of anisole with benzyl alcohol as benzylating agent. The benzylation activity depends on the content of TPA on tin oxide; the catalyst with 15 wt% loading of tungstophosphoric acid showed highest activity. The structural and surface modifications and their influence on benzylation activities were studied by treating the catalysts at different calcination temperatures. The benzylation activity varied with the change in stability of the Keggin ion structure, which depended upon treatment conditions. The alcohol conversion and selectivity were also dependent on the anisole-to-benzyl alcohol ratio, reaction temperature, reaction time and catalyst weight.
Keywords: Tungstophosphoric acid; Tin oxide; Benzylation; Anisole; Benzyl alcohol;
Surface and structural properties of titania-supported Ru catalysts for hydrogenolysis of glycerol by M. Balaraju; V. Rekha; B.L.A. Prabhavathi Devi; R.B.N. Prasad; P.S. Sai Prasad; N. Lingaiah (107-114).
Display Omitted▶ Titania-supported Ru is efficient catalysts for glycerol hydrogenolysis. ▶ The activity of the catalyst depends on the nature of Ru particles on titania. ▶ The structural and surface properties depend on the catalyst preparation method. ▶ The catalyst is reusable and active even for crude bio-glycerol hydrogenolysis.A series of catalysts with different Ru contents supported on titania were prepared by conventional impregnation (IM) and deposition–precipitation (DP) methods. These catalysts were characterized by X-ray diffraction, temperature programmed reduction, transmission electron microscopy, X-ray photoelectron spectroscopy and CO chemisorption. The catalysts were evaluated for selective hydrogenolysis of glycerol. The glycerol conversion and the selectivity towards 1,2-propanediol depend on the method of catalyst preparation and on the Ru content. The catalyst with low Ru content exhibited maximum conversion, in turn was related to its dispersion. The catalysts prepared by DP method showed stable activity even with crude glycerol containing alkali salts as impurity. The catalyst exhibited consistent activity upon reuse. The high activity of Ru/TiO2 catalyst is due to the presence of well-dispersed nano size Ru particles on titania. The low activity of the IM catalyst is because of large domains of Ru and because of the presence of residual Cl− ions.
Keywords: Glycerol; Ruthenium; Titania; Hydrogenolysis; 1,2-Propanediol; Deposition–precipitation;
Benzene reduction in gasoline by alkylation with olefins: Effect of the experimental conditions on the product selectivity by Georgina C. Laredo; Jesus Castillo; Hector Armendariz-Herrera (115-121).
Display Omitted▶ Formation of by-products could not be avoided by changing experimental conditions. ▶ A maximum benzene conversion was obtained at 220 °C (1/1 B/P). ▶ Formation of by-products decreased at lower temperatures. ▶ Benzene conversion decreased drastically at higher B/P molar ratios. ▶ IPB selectivity increased slightly at higher B/P molar ratios.The production of a more environmentally friendly gasoline by removing substantial portions of benzene by alkylation with propylene was studied. One step experiments were performed with a real feedstock (20 wt% benzene) varying temperatures (120, 180, 220 and 320 °C) and benzene/propylene molar ratios (1, 2, 3, 5 and 7) in a batch system using Beta zeolite as catalyst. The highest benzene content reduction (52%) was achieved at 220 °C and B/P of 1, although the preferred i-propylbenzene production was attached to high molecular weight poly-alkylated by-products and olefin oligomers, which can trigger catalyst deactivation. The effect of this procedure on the reformation gasoline and on the final gasoline blendstock is also presented.
Keywords: Gasoline; Benzene; Alkylation; Propylene; i-Propylbenzene; Beta zeolite;
The Ritter reaction under incredibly green protocol: Nano magnetically silica-supported Brønsted acid catalyst by Leila Ma’mani; Akbar Heydari; Mehdi Sheykhan (122-127).
Display Omitted▶ Magnetically recoverable catalyst leading to enhancement simplicity and product purity. ▶ Capable biocompatible and green catalyst. ▶ Mild, cost-effective and applicable efficient reusable heterogeneous catalyst. ▶ Economically and environmentally benign procedure for synthesis of amides from alcohols.HClO4-functionalized silica-coated magnetic nanoparticles [γ-Fe2O3@SiO2-HClO4] (2.5 mol%) has been found to be a capable biocompatible and recyclable catalyst for highly efficient conversion of a variety of alcohols to corresponding amides via modified Ritter reaction in good to excellent yields. Since this heterogeneous catalyst can be simply removed by using an external magnetic device then recovered, it also enhances product purity and promises economic.
Keywords: Functionalized silica-coated magnetic nanoparticle; Silica-supported perchloric acid; Biocompatible and recoverable catalyst; Modified Ritter reaction;
Mineralization of 2,6-dimethylaniline by photoelectro-Fenton process by Nalinrut Masomboon; Chavalit Ratanatamskul; Ming-Chun Lu (128-135).
Display Omitted▶ Our study applied a new approach to promoting ferric reduction efficiency using electrochemical, photoreduction and photo-assisted electrochemical processes. ▶ The target chemical is 2,6-dimethylaniline which is a new chemical for photoelectro-Fenton process and from literature review we found that no one uses it before. ▶ Moreover, the energy cost, reaction mechanism and intermediates identification of 2,6-dimethylaniline degradation were also determined in this study and gave a valuable knowledge. ▶ The technologies that we applied in our study are a clean technology, using cheap chemicals, available in environment and non-toxic. Therefore, we believe that our research is useful not only for the scientific knowledge but also for the environment.A new approach to promoting ferric reduction efficiency using electrochemical, photoreduction and photo-assisted electrochemical processes has been developed. The use of UVA irradiation and electric current as electron donors can efficiently initiate a Fenton reaction called the photoelectro-Fenton process. 2,6-Dimethylaniline was the target compound in this study. Parameters including initial pH, ferrous ion dosage, hydrogen peroxide concentration, the electric current applied and the number of UVA lamps used were investigated to evaluate the performance of the photoelectro-Fenton process. The removal efficiencies of 2,6-dimethylaniline, COD, TOC and initial degradation rate were determined in this study. The optimum condition for 1 mM of 2,6-dimethylaniline degradation was achieved when using 1 mM of ferrous ions, 20 mM of hydrogen peroxide at pH 2 and 2 A of electric current applied with four UVA lamps used. The energy cost, reaction mechanism and intermediates identification of 2,6-dimethylaniline degradation have also been determined in this study.
Keywords: 2,6-Dimethylaniline; Advanced oxidation processes; Photoelectro-Fenton process; Hydroxyl radical;
Novel alkoxysilane pentacoordinate O＝V(IV) complexes as supported catalysts for cyclohexane oxidation with dioxygen by Gopal S. Mishra; Anil Kumar; Suman Mukhopadhyay; Pedro B. Tavares (136-146).
Display Omitted▶ Synthesis and well characterization of newly alkoxysilane pentacoordinate Oxovanadium(IV) complexes. ▶ Covalently anchored Oxovanadium(IV) complexes on the surface of SiO2 and/or Al2O3 as supported catalysts. ▶ Supported V-catalysts showed high catalytic efficiency (high TONs, ca. 5.0 × 103) in the selective oxidation of cyclohexane with molecular O2. ▶ Significantly improved yield was obtained by pyrazinecarboxylic acid as a co-catalyst.A variety of newly synthesized and well characterized alkoxysilane pentacoordinate Oxovanadium(IV) complexes, VO[Sal(PMeOSi)DPTA] 3[a], VO[Cl-Sal(PMeOSi)DPTA] 3[b], VO[Sal(PMeOSi)DETA] 6[a] and VO[Cl-Sal(PMeOSi)DETA] 6[b], (Sal = salicylaldehyde, DPTA = bis(aminopropyl)amine, DETA = diaminoethylamine), have been anchored by covalent bond into the surface of SiO2 and/or Al2O3 via silicon-alkoxide route by a condensation process as supported catalysts. These solid supported catalysts (abbreviated as catalysts A to H) showed high catalytic efficiency in the selective oxidation reaction of cyclohexane using molecular oxygen under relatively mild condition in a micro-batch reactor. The Catalyst C (SiO2/3[a] complex) system exhibits best activity, overall yield 38.5% (TONs, ca. 5.0 × 103) as well as high selectivity 98% (cyclohexanol 74%, cyclohexanone 24%). Notably, cyclohexane shows significantly improved yield 44.0%, by the addition of pyrazinecarboxylic acid as a co-catalyst. The TGA indicates these catalysts are stable up to maximum reaction temperature, ca. 473 K and ICP analysis shows there is negligible vanadium loss from the supported catalyst after the reaction, allowing further use of the V-catalyst. The various factors influences (i.e. temperature, O2 pressure, reaction time, catalyst amount) were also investigated in the systematic way, to optimize the reaction processes. The impact of radical traps and detection of intermediate peroxy radical were also investigated to establish a radical mechanism.
Keywords: V-complexes; Covalent bond anchoring; Supported catalysts; Cyclohexane; Oxygen;
Activation of trimethylsilyl cyanide and mechanistic investigation for facile cyanosilylation by solid acid catalysts under mild and solvent-free conditions by Boningari Thirupathi; Meghshyam K. Patil; Benjaram M. Reddy (147-153).
Display Omitted▶ Sulfated-zirconia is found to be a highly efficient heterogeneous solid catalyst in activating trimethylsilyl cyanide (TMSCN) for facile cyanosilylation of aldehydes. ▶ A unifying explanation is provided for the cyanosilylation reactions.Sulfated-zirconia is found to be a highly efficient heterogeneous solid catalyst in activating trimethylsilyl cyanide (TMSCN) for facile cyanosilylation of aldehydes. A unifying explanation is provided for the cyanosilylation reactions. The unique role of sulfated-zirconia consists of rendering cyanide anions from TMSCN to C＝O of aldehydes and providing the corresponding cyanohydrin silyl ethers in quantitative yields under mild and solvent-free conditions.
Keywords: Cyanosilylation; Sulfated-zirconia; Mechanistic investigations; Solid acids; Solvent-free synthesis;
Quantum chemical insights into the initiation mechanism of transition metal catalysed polymerisation of isobutene by Hugh Chaffey-Millar; Fritz E. Kühn (154-164).
Display Omitted• First quantum chemical study into the room temperature, transition metal catalysed polymerisation of isobutene. • None of the previously proposed mechanisms are viable exactly as originally given. • Mechanisms involving Ziegler–Natta style monomer insertion reactions at the complex core may be possible. • The role of the counter-ion in facilitating some mechanisms has not been ruled out.During the polymerisation of isobutene using highly active Lewis-base initiators such as AlCl3, it has typically been necessary to polymerise isobutene at temperatures between −80 and −20 °C, sometimes in the presence of chlorinated solvents, to minimise the effects of unwanted side reactions. However, a transition metal based catalyst system which enables polymerisation at room temperature and without chlorinated solvents has recently been discovered. In the current manuscript, the first molecular level insights into the previously proposed mechanisms for the polymerisation process are presented based on an ab initio/density functional theory study. Using hexakis-acetonitrile-manganese(II) as a model system, reaction enthalpies and barriers are calculated to determine which mechanisms may or may not be possible. The formation of a hydrogen or alkyl group bonded directly to the manganese may lead to polymerisation, but the proposed mechanisms to generate such a species, as well as other proposed mechanisms, have not been found to be feasible (at least in the exact form originally proposed).
Keywords: Manganese; Poly(isobutene); Polymerisation; Quantum chemistry; Mechanism; Homogenous catalysis; DFT;
Catalytic synthesis of dialkyl carbonate from low pressure CO2 and alcohols combined with acetonitrile hydration catalyzed by CeO2 by Masayoshi Honda; Shintaro Kuno; Noorjahan Begum; Ken-ichiro Fujimoto; Kimihito Suzuki; Yoshinao Nakagawa; Keiichi Tomishige (165-170).
Display Omitted▶ Diethyl and dipropyl carbonate were synthesized from low pressure CO2 and corresponding alcohols. ▶ These reactions were catalyzed by a heterogeneous CeO2. ▶ The removal of H2O from the system remarkably enhanced the yield of these carbonates.Dialkyl carbonates have attracted much attention from the viewpoint of sustainable chemistry because they are useful intermediates and solvents and can be synthesized from renewable resources. One promising synthesis method of the dialkyl carbonates is the reaction of CO2 with the corresponding alcohols. Direct synthesis of diethyl carbonate and dipropyl carbonate from ethanol + CO2 and 1-propanol + CO2 was promoted remarkably by the combination of acetonitrile hydration. The yield based on CO2 reached 42 and 33% for diethyl carbonate and dipropyl carbonate, respectively. All the reactions were catalyzed by CeO2 as a heterogeneous catalyst. It is characteristic that the combination with in situ dehydration enabled the conversion of low pressure CO2 to dialkyl carbonate.
Keywords: CO2 utilization; Organic carbonate; Acetonitrile hydration;
Synthesis of nitrile coordinated Lewis acids Al(OC(CF3)2R)3 and their application in catalytic epoxide ring-opening reactions by Yang Li; Yi Tan; Eberhardt Herdtweck; Mirza Cokoja; Fritz E. Kühn (171-176).
Display Omitted▶ Aluminum-based Lewis acids catalyze epoxide ring opening with amines. ▶ The Al catalysts are more efficient than borane analogues. ▶ The shape and basicity of the amine influence the product yield.Four nitrile ligated aluminum-based Lewis acids PhCNAl(OC(CF3)2PhCH3)3 (1), CH3CNAl(OC(CF3)2PhCH3)3 (2), PhCNAl(OC(CF3)2Ph)3 (3), CH3CNAl(OC(CF3)2Ph)3 (4) were synthesized and characterized by nuclear magnetic resonance and infrared spectroscopy, as well as X-ray crystallography. The ring-opening reactions of epoxides with aromatic/aliphatic amines were efficiently catalyzed by compounds 1–4 as catalysts in a concentration of 1 mol% under solvent-free conditions at room temperature, affording 2-amino alcohols in high yields (up to 99%) within 4 h. Compound 1, being the best catalyst, yields 70% product within 10 min.
Keywords: Homogeneous catalysis; Lewis acid; Ring-opening reaction; Epoxides; Aluminum;
Light olefin transformation over ZSM-5 zeolites with different acid strengths – A kinetic model by P. Oliveira; P. Borges; R. Ramos Pinto; M.A.N.D.A. Lemos; F. Lemos; J.C. Védrine; F. Ramôa Ribeiro (177-185).
Display Omitted▶Polanyi-type equations correlate the activity with acid strength distribution. ▶ Ammonia TPD can be used to obtain the acid strength distribution of acid catalysts. ▶ A single kinetic mechanism and set of parameters describe all experiments. ▶This all reactants and all catalysts used.In this study, we analysed the influence of the acidity of a ZSM-5 catalyst on the catalytic transformation of various short-chain olefins (ethylene, propylene and 1-butene). Four ZMS-5 catalysts with different acid strength distributions were studied at different temperatures and partial pressures. The results were fitted using a kinetic model based on a network mechanism, which details the products by type (olefins, paraffins and aromatics) and number of carbon atoms. Polanyi-type equations, supported on quantum chemical calculations, were used to derive quantitative relations between the ammonia adsorption energy, used as a measure of the acidity of a given acid site, and the energetics of the various steps involved in the reaction. It was observed that, although the qualitative aspects of the reactivity differs from olefin to olefin and according to the catalyst's acidity, the model is able to describe both activity and product distribution for all catalysts, reactants and conditions using a single reaction scheme and a single set of kinetic parameters.
Keywords: Olefin transformation; Acid catalysis; ZSM-5 zeolite; Kinetic model;
Catalytic degradation of polyethylene using nanosized ZSM-2 zeolite by C. Covarrubias; F. Gracia; H. Palza (186-191).
Display Omitted▶ Nanosized zeolites are highly efficient in the catalytic degradation of polyethylene. ▶ The catalytic degradation activity depends on the acidity and structure of the crystal structure. ▶ Polyethylene can be efficiently recycled by means of nanosized zeolite of high acidities.Nanosized ZSM-2 zeolite with crystal size of ∼100 nm was synthesized and ion exchanged in order to characterize its behaviour in the catalytic degradation of polyethylene (PE) in a semi-batch reactor. The starting ZSM-2 allowed a reduction in the PE degradation temperature of more than 80 °C as quantified by dynamic thermogravimetric analysis (TGA). By either proton or Lanthanum exchanges, the nanozeolite increased the acidity improving even more these degradation processes. The starting nanometric catalyst was dramatically more active than a micrometric Y-zeolite displaying lower onset temperatures of PE degradation due to its higher external surface area. These differences nevertheless were reduced by ion-exchanging the Y-catalysts. Our results confirm the relevance of both the zeolite acidity and other parameters, such as crystal size and crystallinity of the zeolite framework, on the catalytic efficiency. Regarding the degradation products during the catalytic process, both zeolites increased the production of low boiling compounds being more efficient the ZSM-2 based catalysts reaching a yield about 90%. Higher amount of accessible sites active for cracking on the external surface of the nanosized crystals would be responsible of this high gas yield. Furthermore, ZSM-2-based zeolites were highly selective to propylene and C4 compounds compared with Y-based zeolites. These results open up the use of nanosized ZSM-2 zeolites in the catalytic degradation of PE with relevant energetic applications.
Keywords: Catalytic degradation; ZSM-2 zeolite; Nanozeolites; Polyethylene;
The influence of carbon laydown on selectivity in the hydrogenation of pentenenitriles over supported-nickel catalysts by James McGregor; Arran S. Canning; Scott Mitchell; S. David Jackson; Lynn F. Gladden (192-200).
Display Omitted▶ Five distinct active sites identified on the surface of Ni/θ-Al2O3. ▶ Pentenenitrile hydrogenation proceeds via a cyclic intermediate over nickel sites. ▶ θ-Al2O3 is catalytically active for the hydrogenation of pentenenitriles. ▶ Different pentenenitrile isomers show different activity and selectivity profiles. ▶ Coke directs selectivity by preferentially deactivating groups of active sites.Pentenenitriles contain two-reducible functionalities: a carbon–carbon double bond and a nitrile group, either of which may undergo hydrogenation during reaction. In this work we show how the deposition of hydrocarbonaceous material on the catalyst surface during pentenenitrile hydrogenation over 16 wt.% Ni/Al2O3 and 10 wt.% Ni/SiO2 catalysts has a significant impact on the observed catalytic activity and selectivity. The role of carbon laydown in controlling catalytic performance in this system has been evaluated through activity measurements and mechanistic studies employing a Tapered Element Oscillating Microbalance (TEOM) and a conventional flow-through reactor. TEOM data indicating the deposition of carbonaceous material during reaction are correlated with kinetic analysis which provides a description of catalyst deactivation in terms of the deactivation of groups of active sites. Specifically five distinct active sites are shown to exist on Ni/Al2O3 including a hydrogenation site on the support, which is not present in the case of Ni/SiO2. The nature and strength of these sites are discussed. Furthermore, deuteration studies provide mechanistic insights suggesting that the hydrogenation reaction proceeds via a cyclic intermediate. The reported data identify a correlation between mass laydown on specific active sites and deactivation, thereby demonstrating the influence of hydrocarbonaceous deposits on selectivity. Both the location and the nature of such deposits are crucial in determining its influence on reaction.
Keywords: Catalytic hydrogenation; cis-2-Pentenenitrile; trans-3-Pentenenitrile; Kinetic analysis; TEOM; Alumina; Coke; Deactivation;
Phosphorus-modified ZSM-5 for conversion of ethanol to propylene by Zhaoxia Song; Atsushi Takahashi; Isao Nakamura; Tadahiro Fujitani (201-205).
Display Omitted▶ Propylene selectivity depends on the phosphorus content. ▶ Phosphorus modification leads to a decrease of strong acid sites. ▶ Reduction of strong acid sites enhances propylene selectivity. ▶ Phosphorous modification improves catalytic stability.In this work, phosphorus-modified ZSM-5 zeolites were used to transform ethanol to propylene. The selectivity of propylene formation depended strongly on the phosphorus content in the zeolites; the highest propylene yield (32%) was observed over H-ZSM-5(80) modified with phosphorus at a P/Al molar ratio of 0.5. The enhancement of propylene selectivity with increasing phosphorus content was attributed to reduction of strong acid sites on the H-ZSM-5. Modification of the zeolite with phosphorous also improved the material's catalytic stability.
Keywords: ZSM-5; Phosphorus; Ethanol conversion; Propylene; Dealumination;
Comparison of canola oil conversion over MFI, BEA, and FAU by Daichuan Chen; Noah I. Tracy; Daniel W. Crunkleton; Geoffrey L. Price (206-212).
Display Omitted▶ Canola oil cracked on three different types of zeolite, BEA, FAU, and MFI showed that MFI gave the highest yield of gasoline range products. ▶ Coke formation was significantly higher on FAU and BEA compared to MFI which can be attributed to larger pores in the FAU and BEA materials. ▶ Coke formation was reduced on materials as SiO2/Al2O3 increased. ▶ The gasoline fraction produced on MFI was primarily aromatic in nature.The catalytic conversion of canola oil was performed at atmospheric pressure with a weight hourly space velocity of 1.0 h−1 in a fixed-bed reactor at temperatures of 400 °C and 450 °C over MFI, BEA, and FAU, and with different SiO2/Al2O3 ratios for BEA and FAU. Simulated distillation of the organic liquid product showed that MFI gave the highest gasoline range product (39%, 450 °C) and lowest coke (3.2%, 450 °C) yields compared to the other zeolites. MFI produced the most C3 hydrocarbons, while BEA produced the most C4s and FAU generated the most C5s. As SiO2/Al2O3 in BEA increased from 25 to 300, the gasoline fraction yield increased from 18.5% to 25.0% at 400 °C.
Keywords: Canola oil; Catalytic cracking; BEA; FAU; MFI; Simulated distillation;
Epoxidation of soybean oil using a homogeneous catalytic system based on a molybdenum (VI) complex by Maritana Farias; Márcia Martinelli; Diana Pagliocchi Bottega (213-219).
Display Omitted▶ Vegetable oil epoxidation is promoted by MoO2(acac)2 catalyst. ▶ Selectivity for epoxidized products improves with temperature. ▶ Monoepoxidized products are selectivity obtained at 80 °C and short reaction times. ▶ Epoxidation products are identified and quantified by 1H NMR.The ability of bis(acetyl-acetonato)dioxo-molybdenum (VI) [MoO2(acac)2] to catalyse the epoxidation of soybean oil in the presence of tert-butyl hydroperoxide as oxidizing agent has been investigated. The influence of reaction time and temperature in the course of the epoxidation reaction was evaluated by quantitative 1H NMR. When epoxidation was carried out in refluxing toluene at 110 °C for 2 h, a 70.1% conversion of substrate was obtained, producing 54.1% epoxidation with a selectivity of 77.2%. The 1H NMR spectroscopic method selected for the purpose of this work allowed a simple and rapid evaluation of the mono- and diepoxides obtained following the epoxidation of soybean oil.
Keywords: Molybdenum (VI) acetylacetonate complex; Epoxidation; Homogeneous catalysis; Soybean oil; 1H NMR;
Insight on the promoting effect of Zr and Ti on the catalytic properties of Rh/SiO2 for partial oxidation of methane by Alejandro Karelovic; Ximena García; Robert Wojcieszak; Patricio Ruiz; Alfredo L. Gordon (220-229).
Display Omitted▶ Ti and Zr addition to Rh/SiO2 catalyst enhances its activity and stability in partial oxidation of methane. ▶ The promoters change the oxidation states of Rh, improving its performances in various ways. ▶ Ti enhances the dispersion of Rh promoting its oxidation while Zr can help to maintain Rh in a reduced state. ▶ Grafting of Zr and Ti leads to the formation of TiO2 and ZrO2 in strong interaction with SiO2 which stabilizes these elements on the surface.Partial oxidation of methane over Rh supported catalysts was investigated. Supports were prepared by organic grafting of Zr and Ti on SiO2-based supports of the Ti-SiO2, Zr-SiO2 and Zr-Ti-SiO2 type. The Rh catalysts (1 wt.%) were prepared by humid impregnation on those supports and on SiO2 as a comparison. Grafting of Ti and Zr leads to the formation of Ti-O-Si and Zr-O-Si species, as well as nanoparticles of the respective oxides when there is a high concentration of TiO2 and/or ZrO2. The promotion of silica with Ti and/or Zr results in a significant increase of the catalysts stability, under high spatial velocity, as compared with the catalyst of Rh-supported on pure silica. The catalysts with better performance were those obtained using Ti as promoter. This would be related to the capacity of Ti to better disperse the Rh and keep it at an adequate oxidized state. On the other hand, Zr does not increase dispersion, but is able to keep Rh in a more reduced state, thus avoiding the deactivation which occurs with Rh/SiO2 catalysts. The experiments carried out with varying spatial velocities in the reactor indicate that the predominant mechanism with these catalysts is methane combustion followed by reforming of the remaining methane. Nevertheless, at high spatial velocities the Rh/Ti-SiO2 catalyst could promote a mechanism of direct methane oxidation.
Keywords: Partial oxidation of methane; Syngas; Rhodium catalysts; XPS characterization;
Selective catalytic reduction of nitrogen oxide by ammonia on substituted strontium ferrites by Marina V. Bukhtiyarova; Aleksandra S. Ivanova; Elena M. Slavinskaya; Lyudmila M. Plyasova; Vasily V. Kaichev; Pavel A. Kuznetsov (230-240).
Display Omitted▶ The ferrites calcined at 700 °C are multiphase. ▶ The specific surface area of the samples lies in the range of 27–59 m2/g. ▶ The main components on the surface are in the oxidized states: Mn3+, Fe3+, Ce4+, W6+. ▶ SCR of NO by NH3 was carried out in accordance with light-off test. ▶ Activity of catalysts is determined by atomic ratio of [Mn]/[Fe] and O2 reactivity.Substituted Sr-ferrites Sr1−x Ce x Mn6−y W y Fe4Al2O19 (x = 0; 0.2; y = 0; 0.28; 0.56; 0.84) with the components ratio typical for Sr-hexaferrite obtained by co-precipitation and calcined at 700 °C have been characterized by thermal analysis (TG-DTA), X-ray diffraction (XRD), Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and adsorption method. Ferrites have been studied in the selective catalytic reduction of NO by ammonia (SCR) using temperature-programmed desorption of ammonia (NH3-TPD) and temperature-programmed reaction of ammonia (NH3-TPR) techniques. It was shown that the substituted Sr-ferrites are multiphase. Its specific surface area is 27–59 m2/g. Surface concentrations of elements in the samples differ from the bulk chemical contents. According to XPS data, the surface of the samples is enriched by strontium. The main components on the surface are in oxidized states: Sr2+, Mn3+, Fe3+, Al3+, Ce4+ and W6+. The surface acidity of the samples determined by NH3-TPD increases from 0.023 to 0.071–0.082 mmol/g when Ce and W ions are introduced in SrMn6Fe4Al2O19. The most active (XNO ≈ 100%) and selective with respect to N2 catalyst is the Sr0.8Ce0.2Mn5.16W0.84Fe4Al2O19 ferrite obtained by the precipitation of the soluble nitrates of Sr, Fe, Mn, Al, Ce using ammonium para-tungstate and ammonium hydrocarbonate as precipitating agents. This sample is characterized by the highest surface acidity, the highest atomic ratio of [Mn]/[Fe] and the lowest oxygen reactivity.
Keywords: Ferrites; XPS; NO reduction; NH3-TPD; NH3-TPR;
Microstructure of leached Al-Cu-Fe quasicrystal with high catalytic performance for steam reforming of methanol by Toyokazu Tanabe; Satoshi Kameoka; An Pang Tsai (241-251).
Display Omitted▶ Leached Al-Cu-Fe quasicrystal showed high activity for steam reforming of methanol. ▶ Fe species in leached layer enhance catalytic activity and stability. ▶ Microstructure of leached layer is controlled by the dissolution rate of Al. ▶ Low dissolution rate of Al from quasicrystal produces a homogeneous leached layer.The catalytic performance of steam reforming of methanol (SRM), cross-sectional microstructure and leaching process of an Al63Cu25Fe12 quasicrystal (QC) catalyst were studied. The QC catalyst was prepared by the NaOH leaching. The leaching of the QC alloy generated a homogeneous leached layer composed of Cu, Fe, Al, and their oxides. The activity and stability of the QC catalyst for the SRM was much superior to those of related crystalline alloy catalysts, because the highly dispersed Fe species in the homogeneous leached layer of the QC catalyst enhances the catalytic activity and suppresses the aggregation of Cu particles. The quasiperiodic structure of the Al-Cu-Fe QC was stable against leaching and had a relatively low dissolution rate of Al among the Al-Cu-Fe alloys, which resulted in the formation of a homogeneous leached layer that was responsible for the high activity and stability for SRM.
Keywords: Quasicrystal; Methanol steam reforming; Cross-sectional TEM; Cu catalyst; Raney catalyst;