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Applied Catalysis A, General (v.363, #1-2)

Contents (pp. iii-x).

Editorial Board (pp. co2).

Solid heterogeneous catalysts for transesterification of triglycerides with methanol: A review by Z. Helwani; M.R. Othman; N. Aziz; J. Kim; W.J.N. Fernando (pp. 1-10).

Hydrotalcite consisted of positively charged layers in lamellar structures with divalent/trivalent cations at the centers of presumably octahedral sites of the hydroxide sheets whose vertexes contain hydroxide ions promoted dissociation of triglycerides into diglyceride and monoglyceride, leading to methyl ester and glycerol generation in the vicinity of interlayer spacing or within the two sublayers.Increasing number of researches focusing on the use of solid heterogeneous catalysts for the production of biodiesel provides evidence that these catalysts continue to evolve as viable alternatives. While liquid alkaline metal alkoxides remain to be appealing in the industries, it is expected that solid base catalyst will soon become more attractive due to the economics and environmental concern. Limited researches have shown that the conversion by solid base catalysts was comparable to that of the existing alkoxide system. This paper reviews various types of heterogeneous solid acids and bases in the production of biodiesel from transesterification of triglycerides. Unconventional enzymatic and non-catalytic supercritical methanol transesterification are also presented. The yields and conversion from various catalytic systems are compared, and the advantages and disadvantages of the systems discussed.

Keywords: Biodiesel; Transesterification; Hydrotalcites; Alkaline solid catalysts; Metal hydroxides

Benzene reduction in gasoline by alkylation with olefins: Effect of the feedstock on the catalyst deactivation by Georgina C. Laredo; Jesus Castillo; Jesus O. Marroquin; Fidencio Hernandez (pp. 11-18).

The production of a more environmentally suitable gasoline by removing substantial portions of benzene by alkylation with propylene using zeolite Beta as catalyst was studied on four feedstocks with different chemical composition. With the increase of benzene concentration in the feedstock, benzene conversions improved. Presence of olefin compounds even in traces caused oligomers formation and finally catalyst deactivation.The production of a more environmentally suitable gasoline by removing substantial portions of benzene by alkylation with propylene was studied on three real feedstocks with different chemical composition. Nine consecutive tests of 1h were carried out for each feedstock, in a batch system with a 2/1 benzene:propylene mole ratio at 220°C using the same Beta catalyst. The results obtained were compared with pure benzene alkylation reactions. With the increase of benzene concentration in the feedstock, benzene conversions improved. Presence of olefin compounds even in traces caused oligomers formation and finally catalyst deactivation.

Keywords: Gasoline; Benzene; Alkylation; Propylene; Cumene; Zeolite Beta

Benzene reduction in gasoline by olefin alkylation: Effect of the catalyst on a C₆-reformate heart-cut by Georgina C. Laredo; Jesus O. Marroquin; Jesus Castillo; Patricia Perez-Romo; Juan Navarrete-Bolaños (pp. 19-26).

The production of a more environmentally suitable gasoline by removing substantial portions of benzene by alkylation with propylene was studied on a real feedstock with Beta, ZSM-5 and Beta:ZSM-5 composites as catalysts. Beta catalyst was associated with higher benzene conversions and cumene and di-isopropylbenzene (DIPB) isomers formation. Lower conversions with high oligomers production were obtained with a ZSM-5 catalyst.The study presented here compares the performance of different zeolite catalysts (Beta, ZSM-5 and Beta:ZSM-5 composites) for benzene alkylation by propylene with a benzene enriched reformate heart-cut (13wt% benzene). The experiments were carried out in a batch system with a 1/1 benzene:propylene mole ratio at 220°C for 1h. The results showed that an increase in conversion produced decreases in cumene selectivity and oligomers formation. These results were associated to Beta contained catalysts. Lower conversions related to a higher oligomers production and lower di-isorpropylbenzene isomers formation, were obtained with a ZSM-5 catalyst. Results were compared with pure benzene/propylene alkylation tests carried out at similar experimental conditions.

Keywords: Benzene; Gasoline; Aromatic; Alkylation; Olefin; Propene; Zeolites; Beta; ZSM-5

Catalytic oxidation of tetralin by biologically active copper and palladium complexes by Maribel Navarro; Alexis Escobar; Vanessa R. Landaeta; Gonzalo Visbal; Francisco Lopez-Linares; Miguel Luis Luis; Alberto Fuentes (pp. 27-31).

The biologically active complexes [Cu(CTZ)₄]Cl₂, [Cu(CTZ)₂Cl₂]₂ and Pd(CTZ)₂Cl₂ were evaluated as catalyst precursors for the homogeneous oxidation of tetralin under aerobic conditions. Copper complexes were found to perform better than the palladium complexes under the studied conditions, leading to higher conversions and selectivity towards α-tetralone.The biologically active complexes [Cu(CTZ)₄]Cl₂ (1), [Cu(CTZ)₂Cl₂]₂ (2) and Pd(CTZ)₂Cl₂ (3) were evaluated as catalyst precursors for the homogeneous oxidation of tetralin under aerobic conditions. The catalytic reaction was carried out using the following conditions determined for [Cu(CTZ)₄]Cl₂: T=373K, P_air=35.0atm, substrate/catalyst ratio=700, reaction time=9h. These complexes were effective catalyst precursors for the selective oxidation of tetralin to α-tetralone and α-tetralol. Copper complexes1 and2 performed better than the palladium complex both in conversion (over 50%) and selectivity towards the production of α-tetralone (one/ol=3).

Keywords: Oxidation; Tetralin; Copper(II) complexes; Palladium(II) complexes

Ethylbenzene oxidation to its hydroperoxide in the presence of N-hydroxyimides and minute amounts of sodium hydroxide by P.P. Toribio; A. Gimeno-Gargallo; M.C. Capel-Sanchez; M.P. de Frutos; J.M. Campos-Martin; J.L.G. Fierro (pp. 32-39).

N-hydroxyimides were used in ethylbenzene oxidation with air under soft reaction conditions. The ethylbenzene conversion increase in the presence of the organocatalysts. On the other hand, the hydroperoxide yield increased dramatically with the addition of a minute quantity of sodium hydroxide to the reaction mixture. Combination of NHPI and NaOH produce the highest yield to hydroperoxide reported.N-hydroxyimides of the type N-hydroxyphthalimide (NHPI), N-hydroxysuccinimide (NHSI), N-hydroxymaleinimide (NHMI) and N-hydroxynaphthalimide (NHNI) were used in ethylbenzene oxidation with air under soft reaction conditions. The ethylbenzene conversion profile was found to increase almost linearly with time, and the rate of ethylbenzene conversion was the highest in the presence of NHNI. Nevertheless, the selectivity reached in all cases is still far from the values required for industrial application. On the other hand, the hydroperoxide yield increased dramatically with the addition of minute amounts of sodium hydroxide to the reaction mixture. It is worth noting that this increase can be associated to an enhancement in the selectivity to hydroperoxide because, in fact, ethylbenzene conversion slightly decreased with the addition of sodium. Indeed, this behavior is puzzling, because the amount of sodium is very small regarding ethylbenzene (0.005mol%) and yet its effect is enormous. Finally, a tenfold increase in the concentration of N-hydroxyimide yielded only a slight increase in ethylbenzene conversion, but no improvement in hydroperoxide concentration. This behavior is related to the participation ofNO radicals in the formation of by-products (alcohols and ketones) from hydroperoxide. Up to date, the combination of NHPI and NaOH produces the highest hydroperoxide yield reported.

Keywords: Autoxidation; Organocatalysis; Homogeneous catalysis; Sodium hydroxide; Hydrocarbons; NHPI

Sc and Zn-catalyzed synthesis of cyclic carbonates from CO₂ and epoxides by Angelica Ion; Vasile Parvulescu; Pierre Jacobs; Dirk de Vos (pp. 40-44).

Scandium and zinc can efficiently catalyze the solventless reaction of terminal epoxides with carbon dioxide in the presence of cetyltrimethylammonium bromide (CTAB) to give the corresponding five-membered cyclic carbonates in very high yields.Scandium can efficiently catalyze the solventless reaction of terminal epoxides with carbon dioxide in the presence of cetyltrimethylammonium bromide (CTAB) to give the corresponding five-membered cyclic carbonates in very high yields. Metal-exchanged montmorillonites proved to be an excellent and highly effective solution for the immobilization of Sc and Zn in this reaction.

Keywords: Scandium; Zinc; CTAB; Montmorillonite; Carbon dioxide; Cyclic carbonate; Epoxide

Unsupported Ni-Mo-W sulphide HDS catalysts with the varying nickel concentration by J. Bocarando; R. Huirache-Acuña; W. Bensch; Z.-D. Huang; V. Petranovskii; S. Fuentes; G. Alonso-Núñez (pp. 45-51).

Ni-Mo-W catalysts were prepared varying the nickel concentration. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and BET specific surface area measurements.It was found that the nickel concentration has a positive effect on the catalytic activity in the hydrodesulphurization (HDS) of dibenzothiophene (DBT).Unsupported Ni-Mo-W sulphide hydrodesulphurization (HDS) catalysts were prepared by ex-situ decomposition of trimetallic Ni-Mo-W precursors varying the nickel concentration. Firstly, the trimetallic precursors were treated in a stainless steel vessel of 45mL volume at 523K for 2h under argon atmosphere. Subsequently, the respective thiosalt was decomposed under a reductive atmosphere of H₂S/H₂ (15vol.% H₂S) from room temperature to 673K. A series of four catalysts was tested in HDS of dibenzothiophene (DBT). The catalysts were labeled as Ni0.5, Ni1 and Ni2 according with the molar ratio of Ni in the sample. In addition, a precursor with a molar ratio Ni-Mo-W of 2:1:2 was prepared varying the concentration of tungsten, named as W2. The catalysts were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD) and BET specific surface area measurements.The ex-situ activation method leads to catalysts with a distribution of specific surface areas from 8 to 34m²/g, showing type IV adsorption–desorption isotherms of nitrogen typical for mesoporous materials, and poorly crystalline structures with different morphology, and varying phase composition. The Ni:Mo:W atomic ratios for the trimetallic catalysts show variations and are slightly smaller than those expected. The sample labeled as Ni-Mo-W2 showed the highest catalytic activity in the HDS of DBT ( k=12×10⁻⁷mol/gs).

Keywords: Trimetallic Ni-Mo-W; Ex-situ; activation; Hydrodesulphurization

Ni/Mg–Al mixed oxide catalyst for the steam reforming of ethanol by L.J.I. Coleman; W. Epling; R.R. Hudgins; E. Croiset (pp. 52-63).

Ni-loaded Mg–Al mixed oxide supported catalysts were evaluated for the production of hydrogen via the steam reforming of ethanol. Mg–Al mixed oxide supported nickel catalysts exhibited superior activity, H₂ and CO_x product selectivity, and improved catalyst stability compared to the pure oxide supported catalysts. Performance was dependent upon the Al and Mg content of the support.A series of 10wt% Ni-loaded Mg–Al mixed oxide supported catalysts were evaluated for the production of hydrogen via the steam reforming of ethanol. Mg–Al mixed oxide supported nickel catalysts were found to give superior activity, H₂ and CO_x product selectivity, and improved catalyst stability compared to the pure oxide supported nickel catalysts. Performance was dependent upon the Al and Mg content of the support. At 923K, the mixed oxide supported catalysts exhibited the highest H₂ and CO_x yields and were stable, showing no signs of deactivation after 20h of operation. The improved performance of these catalysts was related to the incorporation of the pure oxides, MgO and Al₂O₃, into a MgAl₂O₄ phase. The formation of MgAl₂O₄ reduced nickel incorporation into the supports leaving nickel in its active form. In addition, the formation of MgAl₂O₄, a slightly basic material, exhibited moderate acidic and basic site strength and density compared to the pure oxide supported catalysts. Moderation of the acid–base properties improved the activity, selectivity, and stability of the catalysts by reducing activity for by-product reactions.

Keywords: Ethanol steam reforming; Hydrogen production; Nickel; Hydrotalcite; Mixed oxide support

Optimization of thermally impregnated Ni–olivine catalysts for tar removal by Zhongkui Zhao; Nandita Lakshminarayanan; John N. Kuhn; Allyson Senefeld-Naber; Larry G. Felix; Rachid B. Slimane; Chun W. Choi; Umit S. Ozkan (pp. 64-72).

Thermally impregnated Ni–olivines are potential catalysts for hot cleanup of tars generated in fluidized bed biomass gasifiers. The present study examined the influence of synthesis parameters, namely Ni precursor, preparation temperature, and olivine support upon the physiochemical and catalytic properties of Ni–olivine catalysts prepared by thermal impregnation.Thermally impregnated Ni–olivines are potential catalysts for hot cleanup of tars generated in fluidized bed biomass gasifiers. The present study examined the influence of synthesis parameters, namely Ni precursor, preparation temperature, and olivine support upon the physiochemical and catalytic properties of Ni–olivine catalysts prepared by thermal impregnation. Catalytic activity and stability was monitored by reforming naphthalene, a model tar compound in simulated biomass-derived syngas and by reforming methane. Physiochemical properties, which include both structural (XRD, TPR, and Raman spectroscopy) and surface measurements (BET surface area and XPS), were evaluated for both fresh and spent catalysts. Choice of Ni precursor (NiO or Ni) demonstrated minimal influence upon physiochemical properties and catalytic activity and stability for naphthalene- and methane-steam reforming. The synthesis temperature (1100 and 1400°C) and olivine support, however, did have an impact. Large structural changes and deactivation were observed when lower synthesis temperatures were used, which indicated that this formulation was not desirable. The use of the Washington olivine as the support demonstrated improved catalytic performance and stability compared to two other olivine supports and further characterization showed that treatments are important in determining the final structural features.

Keywords: Tar removal; Biomass gasification; Ni–olivine; Catalytic stability/activation; Catalyst characterization

Influence of the preparation procedure of NSR monolithic catalysts on the Pt-Ba dispersion and distribution by Beñat Pereda-Ayo; Rubén López-Fonseca; Juan R. González-Velasco (pp. 73-80).

The preparation procedure of a NSR structured catalyst is investigated by optimizing washcoating of ceramic monoliths and subsequent incorporation of Pt and Ba as the active phases. Endurance and firm adherence of the alumina washcoat to the substrate has been achieved. A relation between good NO_x storage behavior and Pt-Ba dispersion and distribution, and the preparation procedure has been established.The preparation procedure of a structured NO_x storage/reduction catalyst is investigated by optimizing washcoating of ceramic monoliths and subsequent incorporation of Pt and Ba as the active phases. Endurance and firm adherence of the alumina washcoat to the substrate has been achieved. Incorporation of platinum from Pt(NH₃)₄(NO₃)₂ has been studied by impregnation (filling the monolith channels) and adsorption from solution (ion exchange). Highly dispersed and well distributed platinum were obtained by the adsorption procedure at pH 11–12 and calcination temperature no higher than 450–500°C. Barium was incorporated by dry or wet impregnation. The dry impregnation procedure led to a more homogeneous barium distribution on the surface of washcoat. The sample prepared by adsorption from solution and dry impregnation, for incorporation of Pt and Ba respectively, showed the best storage capacity, ca. around 2.1μmol NO_x per mg of BaO for a feedstream with 380ppm NO and 6% O₂ in nitrogen, and a space velocity of 32,100h⁻¹, and also complete release and reduction of the stored NO_x when oxygen was shifted to 2.3% H₂. Thus, a relation between good NO_x storage behavior and Pt dispersion and Pt-Ba distribution, and the preparation procedure has been established.

Keywords: NSR; NO; _x; storage; Lean burn engines; Catalyst preparation; Washcoating; Platinum; Barium

NO₂⁻ adsorption onto denitration catalysts by Akane Miyazaki; Toru Asakawa; Ioan Balint (pp. 81-85).

2mmolL⁻¹ NaNO₂ was reduced by H₂ gas on 0.1wt% Pt/Al₂O₃ catalyst. The decrease of NO₂⁻ (○) was found to be caused by catalytic conversion to N₂ or NH₄⁺, and by adsorption onto alumina (▵). The result suggests that a significant amount of NO₂⁻ can be adsorbed by alumina and this should be considered when we discuss catalytic conversion and selectivity.The performance of denitration catalysts is usually evaluated according to the concentrations of NO₃⁻, NO₂⁻ and NH₄⁺ ions. Catalytic conversion is conventionally calculated from the decrease of NO₃⁻ and NO₂⁻ in the reaction solution. In this study, batch experiments were performed by contacting NO₂⁻ with Pt/Al₂O₃ under the presence or absence of H₂ flow. Significant amounts of NO₂⁻ in the reaction solution disappeared even in the absence of H₂, i.e., under conditions where reduction did not occur. This phenomenon is explained by NO₂⁻ adsorption onto Al₂O₃. The equilibrium amount of adsorbed NO₂⁻ showed a linear decrease with the increase of Pt particles. The adsorption of NO₂⁻ onto Al₂O₃ should be considered when the performance of denitration catalysts is evaluated. In addition, utilizing the high adsorption capacity of Al₂O₃ for NO₂⁻ may realize its potential as a scavenger for the removal of NO₂⁻ ions in waste water.

Keywords: Nitrite; Alumina; Pt/Al; ₂; O; ₃; Adsorption

The role of molybdenum in Fe–Mo–Al₂O₃ catalyst for synthesis of multiwalled carbon nanotubes from butadiene-1,3 by V.V. Chesnokov; V.I. Zaikovskii; A.S. Chichkan; R.A. Buyanov (pp. 86-92).

MoO₃–Fe₂O₃–Al₂O₃ catalysts were prepared by co-precipitation of mixed hydroxides from soluble salts. It was found that the 55%Fe₂O₃–Al₂O₃ aluminum–iron catalyst calcined in air at 500–700°C consisted of a solid solution based on hematite where a part of iron atoms was substituted for aluminum. The modification of the aluminum–iron catalyst with molybdenum results in the formation of a solid solution based on hematite where a part of iron atoms is substituted for aluminum and molybdenum ions. At 700°C the MoO₃–Fe₂O₃–Al₂O₃ catalysts are reduced under the action of the feed. The dependence of the multiwalled carbon nanotube (MWNT) yield over MoO₃–Fe₂O₃–Al₂O₃ catalysts on the molybdenum concentration has a maximum. Small concentrations of MoO₃ (up to 6.5wt.%) added to the aluminum–iron catalyst increase the dispersity of the active metal particles and alter their properties due to the formation of a Fe–Mo alloy. Its formation leads to the decrease of the nanotube growth rate and makes the catalyst more stable. The overall yield of the carbon nanotubes increases. Further increase of the molybdenum concentration leads to the decrease of the nanotube yield because the catalytically active Fe–Mo particles are enriched too much with molybdenum. In addition, excess molybdenum forms molybdenum carbide α-Mo₂C, in which part of the molybdenum atoms are substituted for iron atoms, and which is inactive in the MWNT growth.A maximum has been observed on the dependence of the carbon nanotube yield over MoO₃–Fe₂O₃–Al₂O₃ catalysts on the molybdenum concentration. Small concentrations of molybdenum (up to 5.2wt.%) added to the aluminum–iron catalyst increase the dispersity of the metal particles, makes the catalyst more stable and increases the overall yield of the carbon nanotubes.

Keywords: Molybdenum; Iron oxide; Catalyst; Carbon nanotubes; Butadiene-1,3

Conversion of mono/di/polysaccharides into furan compounds using 1-alkyl-3-methylimidazolium ionic liquids by Sérgio Lima; Patrícia Neves; Maria M. Antunes; Martyn Pillinger; Nikolai Ignatyev; Anabela A. Valente (pp. 93-99).

The ionic liquid [EMIM][HSO₄] is promising for furfural and 5-hydroxymethyl-2-furaldehyde production from xylose, fructose or related polysaccharides, under relatively mild conditions. For more challenging polysaccharides such as cellulose and starch, the addition of [EMIM][HSO₄] to the system cellulose/[BMIM][Cl]/CrCl₃ enhances 5-hydroxymethyl-2-furaldehyde yields. Reaction/solvent extraction and reaction/evaporation systems were investigated for simultaneous reaction and product separation, and for both the acidic medium could be reused successfully.The one-pot hydrolysis/dehydration of mono/di/polysaccharides into furfural (FUR) or 5-hydroxymethyl-2-furaldehyde (HMF) in the presence of an acidic ionic liquid, 1-ethyl-3-methylimidazolium hydrogen sulfate ([EMIM][HSO₄]), at 100°C, was investigated and the results were compared with those using 1-butyl-3-methylimidazolium chloride ([BMIM][Cl]), with or without CrCl₃ or H₂SO₄. The ionic liquid [EMIM][HSO₄] is effective in converting xylose and fructose or related polysaccharides into FUR (e.g. from xylose: 84% yield at 6h) or HMF (e.g. from fructose: 88% yield at 30min), but not glucose and polymers containing these units, which contrasts to that observed for the [BMIM][Cl]/CrCl₃ system. The latter is quite effective in converting glucose and related disaccharides into HMF, but not the polysaccharides cellulose and starch. For the latter feedstocks, the addition of H₂SO₄ or [EMIM][HSO₄] to cellulose/[BMIM][Cl]/CrCl₃ enhances HMF yields, presumably by accelerating the hydrolysis step, although the selectivity of the dehydration of glucose monomers seems rather poor (HMF yield<13wt.%). In the case of the xylose to FUR conversion in [EMIM][HSO₄], two systems involving the reaction and simultaneous separation of the target product were investigated, namely reaction/solvent extraction and reaction/evaporation systems, and for both the ionic liquid could be recovered and reused without a significant drop in FUR yield in recycling runs.

Keywords: Ionic liquids; Saccharides; Acid catalysis; Hydrolysis; Dehydration; Furfural; 5-Hydroxymethyl-2-furaldehyde

Dodecylbenzene transformations: Dealkylation and disproportionation over immobilized ionic liquid catalysts by Alice L. Petre; Wolfgang F. Hoelderich; Martin L. Gorbaty (pp. 100-108).

AlCl₃-based ionic liquids (ILs) supported on silica and MCM-41 were used in the disproportionation and dealkylation of dodecylbenzene (DDB). Up to 55mol% conversion and benzene selectivity of up to 60mol% at 120°C after 2h reaction time were found. Yield ratios between didodecylbenzenes and benzene showed that a part of 1-dodecylbenzene was catalytically dealkylated and not disproportionated.AlCl₃-based ionic liquids (ILs) supported on silica and MCM-41 have been used for disproportionation and dealkylation of dodecylbenzene (DDB) at low reaction temperature. AlCl₃-based ionic liquids supported on MCM-41 were highly active for the conversion of DDB. Up to 55mol% conversion and selectivity to benzene at 120°C after 2h reaction time were found for DDB transformation. Yield ratios between didodecylbenzenes and benzene are lower than 1 over such AlCl₃-based ionic liquids supported on MCM-41. That means a part of the 1-dodecylbenzene is catalytically dealkylated and not disproportionated. An induction period has been found for such a catalyst. The catalytic dealkylation of DDB requires a high density of very strong Lewis acid sites. A detrimental influence of n-decane (used as solvent) on DDB conversion was observed. The presence of an increased amount of naphthalene in the initial reaction mixture led to a strong decrease of selectivity towards didodecylbenzenes in favor of selectivity for benzene and formation of dodecylnaphthalene.

Keywords: Dealkylation; Disproportionation; 1-Dodecylbenzene; Alkylaromatics; Immobilized ionic liquids

Chemicals from ethanol—The ethyl acetate one-pot synthesis by A.B. Gaspar; A.M.L. Esteves; F.M.T. Mendes; F.G. Barbosa; L.G. Appel (pp. 109-114).

The direct synthesis of ethyl acetate from ethanol was studied using PdO/SiO₂ catalysts and the oxidative route. It was inferred that this synthesis occurs via ethanol oxidation followed by the condensation reaction of acetaldehyde and ethanol or etoxide species. This work shows that the ethyl acetate synthesis by the oxidative route can be considered as a very promising new process.The direct synthesis of ethyl acetate from ethanol, a renewable raw material, was studied using PdO/SiO₂ catalysts and the oxidative route. These catalysts were prepared by ionic exchange and also by impregnation. They were characterized by XPS, UV–vis, XRD, chemical analysis and BET. These catalysts were tested under different experimental conditions using a conventional system with a fixed bed reactor at atmospheric pressure. It was inferred that the ethyl acetate synthesis occurs via ethanol oxidation followed by the condensation reaction of acetaldehyde and ethanol or ethoxide species. It can be suggested that the rate limiting step of the synthesis change according to the rate of ethanol consumption. For low rates, the limiting step is the ethanol oxidation to acetaldehyde, and for the high ones, it is the condensation reaction. It was verified that the catalysts preparation conditions modify the PdO distribution on the support and its particle sizes, therefore, changing the ethanol consumption rate, and consequently, the selectivities to acetaldehyde, ethyl acetate, acetic acid and CO₂. This work shows that the ethyl acetate synthesis by the oxidative route using PdO/SiO₂ catalyst can be considered as a very promising new process.

Keywords: Ethyl acetate; Ethanol; PdO/SiO; ₂; Palladium; Oxidation; Acetaldehyde; Silica

Reactions of methanol and higher alcohols over H-ZSM-5 by Amit C. Gujar; Vamshi Krishna Guda; Michael Nolan; Qiangu Yan; Hossein Toghiani; Mark G. White (pp. 115-121).

The reaction of methanol to gasoline range hydrocarbons over H-ZSM-5 was studied as a function of time, temperature, total pressure and H₂ partial pressure in a batch reactor. Total gasoline yields were studied as a function of these process variables. The gasoline yield was improved at higher pressures in inert He. The presence of H₂ increased the gasoline yield and decreased the formation of polyaromatic compounds. The presence of H₂ also led to less coking and lighter gasoline color. The methanol to gasoline (MTG) reaction was also studied over a composite catalyst containing H-ZSM-5 and mixed oxide (Cu–Co–Cr) alcohol synthesis catalyst. The use of segregated beds of zeolite+mixed oxide catalyst gave good gasoline yields whereas the use of a single well mixed bed containing zeolite+mixed oxide catalyst gave negligible gasoline yields. Other alcohols (C₂–C₄) were also studied for their reaction over H-ZSM-5. Higher alcohols were found to produce higher yields of gasoline compared to methanol. It was found that tertiary and secondary alcohols had an increased tendency to form aromatics compared to primary alcohols. A continuous flow reactor was employed to produce a sufficient quantity of gasoline so as to perform an engine knock test.***H⁺ZSM-5 has been found active for alcohol conversion to gasoline-range hydrocarbons mainly composed of alkyl-substituted aromatics and lower branched and cyclized alkanes. Higher yields of hydrocarbon liquids were realized when the substrates were either propyl or butyl alcohols in place of methanol.

Keywords: Synthesis gas; Catalytic; Gas to liquids; Gasoline

Efficient preparation of silver nanoparticles supported on hybrid films and their activity in the oxidation of styrene under microwave irradiation by Violeta Purcar; Dan Donescu; Cristian Petcu; Rafael Luque; Duncan J. Macquarrie (pp. 122-128).

Ag nanoparticles supported on hybrid organic–inorganic films were synthesized and their activities were investigated in the oxidation of styrene under microwave irradiation. Materials were found to be differently active and selective depending on the composition of the support and exhibited high activities and selectivities to styrene epoxide under microwave irradiation at mild reaction conditions (<200°C) and very short times of reaction (<30min).Hybrid films containing different loadings of silver nanoparticles (0.5, 1 and 2.5wt.%) have been prepared using a sol–gel method. Three types of materials were prepared in order to compare their properties: Ag nanoparticles (NPs) on hybrid film containing methyltrimethoxysilane (Ag-MeTMS), a similar hybrid material containing both MeTMS and 3-mercaptopropyltrimethoxysilane (MPTMS) as modifier (Ag-MeTMS/MPTMS) and finally a Ag-MeTMS film to which starch was added as modifier/reducing agent (Ag-MeTMS/starch). Characterized materials by TEM showed that, in general, Ag materials had a bimodal particle size distribution, with sizes of 7–8, 12–16nm as well as some bigger agglomerates (on some of them) of 24–25nm present at increasing silver loadings. The catalytic properties of the supported Ag NP were investigated in the oxidation of styrene. Ag-MeTMS/MPTMS materials were comparatively more active and selective than Ag-MeTMS or Ag-MeTMS/starch, regardless of the Ag content in the materials, providing high conversions and selectivities to styrene oxide.

Keywords: Sol–Gel process; Silver nanoparticles; Heterogeneous catalysis; Oxidation of styrene

Hydrogenation of a hydroformylated naphtha model (mixture of specific aldehydes) catalysed by Ru/TPPTS complex in aqueous media by Nikolaos C. Kokkinos; Anastasia Lazaridou; Nikolaos Nikolaou; Georgios Papadogianakis; Nikolas Psaroudakis; Alexis K. Chatzigakis; Christos E. Papadopoulos (pp. 129-134).

Aqueous biphasic hydrogenation of a mixture of aldehydes, all met in a hydroformylated naphtha (the feedstock of gasoline production) implemented with ruthenium complex containing the water-soluble ligand TPPTS, generated in situ. A high activity under mild conditions was observed. The hydrogenation of a hydroformylated naptha would upgrade the combustion properties of the gasoline, in an environmentally friendly process.Aqueous biphasic hydrogenation of a mixture of 2-methylvaleraldehyde, 2-ethylbutyraldehyde, hexanal, heptaldehyde, 2-phenylpropionaldehyde and hydrocinnamaldehyde, which are all met in a hydroformylated naphtha (the feedstock of gasoline production) in high yield (mol%) according to the literature, was carried out with ruthenium complex containing the water-soluble ligand TPPTS (TPPTS=P[m-C₆H₄SO₃Na]₃, trisodium salt of m-trisulfonated triphenyl phosphine). Ru/TPPTS catalytic system was generated in situ by direct addition of RuCl₃· xH₂O catalyst precursor to TPPTS in aqueous media; and appears to have high activity under mild conditions (80°C, 20bar) in the hydrogenation of the above hydroformylated naphtha model to the production of the corresponding alcohols. Thus, the aqueous biphasic hydrogenation of a hydroformylated fuel would upgrade the combustion properties of the ultimate fuel, while at the same time the whole process would be characterised as environmentally friendly. The effect of the reaction pressure, temperature and time, as well as the influence of the organic solvent, the agitation speed, the TPPTS/Ru and aldehydes/Ru molar ratios were investigated.

Keywords: Hydrogenation; Ruthenium; TPPTS; Aldehydes mixture; Aqueous biphasic catalysis

New Cu-based mixed oxides obtained from LDH precursors, catalysts for methane total oxidation by Serghei Tanasoi; Nathalie Tanchoux; Adriana Urdă; Didier Tichit; Ioan Săndulescu; François Fajula; Ioan-Cezar Marcu (pp. 135-142).

The methane total oxidation was studied over high surface area mesoporous Cu–Mg–Al mixed oxide catalysts obtained from layered double hydroxides precursors. The best results were obtained with the catalysts containing 10 and 20at.% Cu, total conversion being achieved at temperatures lower than 525°C in these cases.The methane total oxidation was studied over high surface area mesoporous Cu–Mg–Al mixed oxide catalysts obtained from layered double hydroxides (LDHs) precursors. XRD and H₂-TPR revealed that both CuO and CuAl₂O₄ phases were present in the calcined catalysts. The best results were obtained with the catalysts containing 10 and 20at.% Cu, total conversion being achieved at temperatures lower than 525°C in these cases. The catalyst containing 10% Cu showed the best specific activity per unit mass of copper. The influences of the contact time and of the methane concentration in the feed gas on the catalytic performances have also been investigated. The stability of the copper-based catalysts during the catalytic test was evidenced.

Keywords: Cu-containing mixed oxides; Layered double hydroxide; Methane; Total oxidation

An iron molybdate catalyst for methanol to formaldehyde conversion prepared by a hydrothermal method and its characterization by Andrew M. Beale; Simon D.M. Jacques; Elena Sacaliuc-Parvalescu; Matthew G. O’Brien; Paul Barnes; Bert M. Weckhuysen (pp. 143-152).

A one-step, low-temperature hydrothermal method has been successfully employed to prepare iron molybdate catalysts with Mo:Fe ratios ranging from 1.5:1 to 3.0:1. The resulting materials were characterized using a number of techniques including: XRD, Raman, N₂ adsorption, SEM/EDX, DTA, EDXRD and combined XRD/XAS. The catalytic oxidative dehydrogenation of methanol to formaldehyde has been used as a test reaction. For Mo:Fe∼1.5, phase-pure Fe₂(MoO₄)₃ resulted from syntheses performed at temperatures as low as 100°C in under 4h. For samples with a Mo:Fe∼3 detailed analysis of XRD, Raman and EXAFS data revealed the formation of a high surface area possessing, mixed phase material consisting of a poorly crystalline Mo₅O₁₄ and an amorphous Fe₂(MoO₄)₃ type precursor. Both phases proved to be thermally unstable above a calcination temperature of 300°C, going on to form high surface area mixed Fe₂(MoO₄)₃/MoO₃. Continued heating of this mixed oxide material resulted in sintering and to a decrease in the surface area. When both mildly (200°C) and then more severely calcined (300°C), this mixed phase sample showed a higher selectivity for formaldehyde production than a conventionally prepared (via co-precipitation) iron molybdate catalyst.A one-step, low-temperature hydrothermal method has been successfully employed to prepare high surface area iron molybdate catalysts with Mo:Fe ratios of 1.5:1–3:1. Syntheses performed with a Mo:Fe∼3 resulted in a mixed crystalline Mo₅O₁₄/amorphous FeMo oxide phase, with the chemical formula which was unstable above a calcination temperature of 300°C, forming mixed Fe₂(MoO₄)₃/MoO₃. The Mo:Fe∼3 phase after both mild (200°C) and more severe calcinations (300°C), showed a higher selectivity for formaldehyde production than a conventionally prepared (via co-precipitation) iron molybdate catalyst.

Keywords: Iron molybdate; Hydrothermal; Methanol-to-formaldehyde

Zn(II)–Cr(III) mixed oxide as efficient bifunctional catalyst for dehydroisomerisation of α-pinene to p-cymene by Fahd Al-Wadaani; Elena F. Kozhevnikova; Ivan V. Kozhevnikov (pp. 153-156).

Zn(II)–Cr(III) mixed oxide possessing acid and dehydrogenation functions catalyses one-step dehydroisomerisation of α-pinene to yield 78% of p-cymene in the gas phase process. The catalyst shows stable performance for over 30h without co-feeding hydrogen.Zn(II)–Cr(III) mixed oxide possessing acid and dehydrogenation functions is an efficient, noble-metal-free catalyst for the one-step dehydroisomerisation of α-pinene to p-cymene. This reaction is a good example of the use of heterogeneous multifunctional catalysis for the conversion of renewable feedstock into value-added chemicals. It involves acid-catalysed α-pinene isomerisation followed by dehydrogenation of p-cymene precursor(s). The reaction is carried out over a fixed catalyst bed in the gas phase at 350°C. Amongst Zn–Cr oxides studied (Zn/Cr=20:1–1:30), the preferred catalyst is Zn–Cr (1:1) oxide which produces p-cymene with a 78% yield at 100% α-pinene conversion. This catalyst shows stable performance for over 30h without co-feeding hydrogen to the reactor.

Keywords: α-Pinene; p-Cymene; Zn–Cr mixed oxide; Bifunctional catalysis

Comparison of non-catalytic and catalytic ozonation processes of three different aqueous single dye solutions with respect to powder copper sulfide catalyst by Saltuk Pirgalıoğlu; Tülay A. Özbelge (pp. 157-163).

Catalytic ozonation of single dye solutions of Acid Red-151, Remazol Brilliant Blue-R (RBBR), and Reactive Black-5 was investigated with CuS catalyst. Effects of pH, initial dye concentration, ozone and catalyst dosages on kinetics and mechanism of reactions were determined. Using scavenger decreased total organic carbon removal in catalytic ozonation, indicating importance of hydroxyl radicals in the oxidation process. Figure is for RBBR at pH 3.Treatment of textile wastewaters containing dyes has not been very successful by conventional methods such as biological treatment. In order to overcome this problem, ozonation based on the oxidation of organic pollutants has been studied by researchers. Catalytic ozonation and advanced oxidation processes (AOPs) are used in order to increase the efficiency of sole ozonation further. In this work, catalytic ozonation in the presence of copper sulfide (CuS) powder as a catalyst was investigated in the treatment of aqueous single dye solutions, namely solutions of Acid Red-151 (AR-151), Remazol Brilliant Blue-R (RBBR) and Reactive Black-5 (RB-5). In the catalytic ozonation experiments, the effects of important ozonation parameters such as solution pH, ozone and catalyst dosages and the initial concentration of each dye on reaction kinetics and mechanism were studied.The catalyst CuS increased the oxidation rates of ozonation side-products measured by the decrease in the total organic carbon (TOC) values of the treated dye solutions. The dye removal rates were enhanced in the treatment of RB-5 dye solutions, while no significant effects were observed on the dye removal rates of RBBR and AR-151 aqueous solutions. The TOC removals above 90% were observed in the catalytic ozonation with CuS for each of the dyes separately at pH 10 and at an initial dye concentration of 100mg/L. The most important effect of the catalyst addition was observed at pH 3, where TOC removals without catalyst were low. Copper sulfide addition increased the percent TOC removals at the end of a reaction period of 80min by 123%, 65% and 58% in the treatment of 100mg/L RBBR, RB-5 and AR-151 aqueous solutions, respectively, at pH 3. Catalytic ozonation kinetics and mechanism were discussed in detail.

Keywords: C; atalytic ozonation; Copper sulfide; Remazol Brilliant Blue-R (RBBR); Reactive Black-5 (RB-5); Acid Red-151 (AR-151); Advanced oxidation processes (AOPs)

Biodiesel production using heteropoly acid-derived solid acid catalyst H₄PNbW₁₁O₄₀/WO₃–Nb₂O₅ by Naonobu Katada; Tsubasa Hatanaka; Mitsuo Ota; Kazuhiro Yamada; Kazu Okumura; Miki Niwa (pp. 164-168).

A heteropoly acid-derived solid acid catalyst H₄PNbW₁₁O₄₀/WO₃–Nb₂O₅ calcined at 773K was found to have a high catalytic activity for transesterification between triolein and ethanol into the biodiesel. In a fixed-bed continuous-flow reaction, its potential as an insoluble catalyst is suggested.A heteropoly acid-derived solid acid catalyst, H₄PNbW₁₁O₄₀/WO₃–Nb₂O₅ calcined at 773K (HPNbW/W-Nb), showed a higher catalytic activity for transesterification between triolein and ethanol into ethyloleate compared to the activities of conventional solid acid catalysts. The HPNbW/W-Nb was insoluble to the reaction mixture, while such heteropoly acids as H₄PNbW₁₁O₄₀ and H₃PW₁₂O₄₀ showed high activities but were dissolved into the reaction mixture. The activity was sensitive to calcination temperature, and calcination around 773K provided a highly active catalyst. The reaction rate showed the maximum at 10–30 of the ethanol/triolein molar ratio. The activity was observed in the co-presence of water and oleic acid. The reaction rate was high when methanol was used in place of ethanol. In a fixed-bed continuous-flow reaction, its potential as an insoluble catalyst is suggested by its stable activity during at least 4 days of the reaction.

Keywords: Biodiesel; Transesterification; Heteropoly acid-derived solid acid catalyst; H; ₄; PNbW; ₁₁; O; ₄₀; /WO; ₃; –Nb; ₂; O; ₅

“Green” preparation of “intelligent” Pt-doped Ni/Mg(Al)O catalysts for daily start-up and shut-down CH₄ steam reforming by Dalin Li; Yingying Zhan; Kazufumi Nishida; Yasunori Oumi; Tsuneji Sano; Tetsuya Shishido; Katsuomi Takehira (pp. 169-179).

Trace amounts of Pt-doped Ni/Mg(Al)O catalysts prepared by sequential impregnation with Ni(II) and Pt(VI) starting from commercial Mg3.5–Al hydrotalcites (HTs) exhibited “intelligent” behavior, i.e., self-activation and self-regenerative activity in the DSS steam reforming of CH₄. Mg(Al)O periclase that originated from Mg–Al HTs played an important role in the regenerative activity of the catalysts via reversible reduction–oxidation between Ni⁰ and Ni²⁺ on/in Mg(Al)O assisted by hydrogen spillover from Pt.“Green” preparation of “intelligent” catalysts for daily start-up and shut-down steam reforming of CH₄ for the reformer of the PEFCs has been investigated; trace Pt-doped Ni/[Mg_xAl]O ( x=0.5, 1.3 and 3.5) catalysts were prepared starting from commercial Mg_x–Al hydrotalcites (HTs) by adopting a “memory effect” of HT. The Mg_x–Al HTs were calcined to the mixed oxides, i.e., [Mg_xAl]O, and were sequentially impregnated with aqueous solutions of Ni(II) nitrates and Pt(IV) nitrates. When [Mg_3.5Al] HT was calcined to [Mg_3.5Al]O at 850°C, well grown Mg(Al)O periclase structure was formed. After impregnating [Mg_3.5Al]O powders in Ni(II) nitrate solution at 80°C for 2h, 10wt% Ni was completely incorporated by reconstituting Mg(Ni)–Al HT due to the “memory effect”, resulting in a high and sustainable activity due to the formation of self-regenerative Ni(-Pt) particles after 0.05wt% Pt doping. The catalyst exhibited “intelligent” properties, i.e., self-activation and self-regenerative activity; the finely dispersed Ni(-Pt) particles were effectively self-regenerated via a reversible reduction–oxidation between Ni⁰ and Ni²⁺ on/in Mg(Ni,Al)O periclase. An increased Ni loading to 16wt% on [Mg_3.5Al]O produced Ni(OH)₂ separately from the Mg(Ni,Al)O lattice, leading to the formation of non self-regenerative Ni(-Pt) particles even after 0.1wt% Pt doping. We conclude that the well grown Mg(Ni,Al)O periclase structure acts as an effective Ni reservoir, through which Ni(-Pt) particles were self-redispersed via oxidative Ni incorporation and reductive Ni release assisted by steam and hydrogen spillover, respectively.

Keywords: Pt/Ni/Mg(Al)O catalyst; Mg–Al hydrotalcites; CH; ₄; steam reforming; Self-activation; Self-regeneration

Photocatalytic H₂ evolution over basic zincoxysulfide (ZnS1− x−0.5_yO_x(OH)_y) under visible light irradiation by Yuexiang Li; Gangfeng Ma; Shaoqin Peng; Gongxuan Lu; Shuben Li (pp. 180-187).

A basic zincoxysulfide (ZnS1− x−0.5_yO_x(OH)_y) solid solution was prepared through co-precipitation. Hydroxide groups are very important to the formation and stabilization of the solid solution. With 1:1 calculated molar ratio of ZnS to ZnO (or Zn(OH)₂), ZnS1− x−0.5_yO_x(OH)_y prepared via co-precipitation at 373K and calcination at 673K under N₂ atmosphere, exhibits the highest activity.A composite visible light photocatalyst was prepared through co-precipitation of Zn(NO₃)₂ in the mixed solution of aqueous Na₂S and NaOH, and calcination in N₂ atmosphere. The photocatalyst was characterized by thermogravimetric and differential thermal analysis (TG–DTA), X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), BET and electrochemistry measurements. Its activity was evaluated by hydrogen production from an aqueous solution containing Na₂S and Na₂SO₃ as hole scavengers under visible light ( λ≥420nm) irradiation. The photocatalyst is a mixture of basic zincoxysulfide (ZnS1− x−0.5_yO_x(OH)_y) solid solution and ZnO or only the solid solution. ZnS1− x−0.5_yO_x(OH)_y, which was visible light active, was a solid solution of ZnS with dissolved oxygen and hydroxide groups. Hydroxide groups are very important in the formation and stabilization of the solid solution. The precipitation and calcination temperatures as well as the precursor composition of ZnS1− x−0.5_yO_x(OH)_y have great influence on the photocatalytic activity. With 1:1 calculated molar ratio of ZnS to ZnO (or Zn(OH)₂), ZnS1− x−0.5_yO_x(OH)_y photocatalyst prepared via co-precipitation at 373K and calcination at 673K under N₂ atmosphere exhibits the highest activity. Its apparent quantum yield without noble metal cocatalyst is ca. 3.0% under visible light irradiation.

Keywords: Basic zincoxysulfide; Solid solution; Photocatalyst; Visible light; Hydrogen evolution

Gas phase hydrogenation of nitrobenzene over acid treated structured and amorphous carbon supported Ni catalysts by Antonio Nieto-Márquez; Sonia Gil; Amaya Romero; José Luis Valverde; Santiago Gómez-Quero; Mark A. Keane (pp. 188-198).

Gas phase hydrogenation of nitrobenzene generated aniline as the sole product where the specific rate constant increased in the order Ni/CNFi.e. carbon nanofibers (CNF, 129m²g⁻¹) and nanospheres (CNS, 15m²g⁻¹), and one unstructured, i.e. activated carbon (AC, 686m²g⁻¹), supports were used. The three supports were treated with HNO₃+H₂SO₄ to generate oxygen-containing surface groups that served as anchoring sites for Ni introduction. The supports and Ni catalysts have been characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), temperature-programmed reduction (TPR), temperature-programmed decomposition (TPD), Raman spectroscopy, N₂ adsorption–desorption and acid/base titrations, which have established distinct morphological, graphitic and porous characteristics. CNS and CNF exhibited significant graphitic character when compared with AC, which was essentially microporous in contrast to mesoporous CNF and CNS. Pore volumes were lowered after the HNO₃+H₂SO₄ treatment, a result that we associate with the incorporation of surface acidity. TPR of the three Ni/C samples resulted in low (620–630K) and high (823–910K) temperature hydrogen consumption due to a combined reduction of the Ni precursor and partial decomposition of surface acid groups. Surface area weighted mean Ni particle diameters (post-activation at 623K) were in the range 7.7–10.4nm. The three catalysts were tested in the gas phase ( T=523K) hydrogenation of nitrobenzene to aniline. Application of pseudo-first order kinetics has delivered the following sequence of increasing specific (permNi2) activity: Ni/CNF

Keywords: Activated carbon; Carbon nanofibers; Carbon nanospheres; Carbon supported Ni; Surface acidity; Nitrobenzene hydrogenation

Influence of nickel crystal domain size on the behaviour of Ni and NiCu catalysts for the methane decomposition reaction by J.L. Pinilla; I. Suelves; M.J. Lázaro; R. Moliner; J.M. Palacios (pp. 199-207).

Ni and NiCu catalysts have been prepared by the fusion method using different textural promoters and their performance in methane decomposition have been studied in a thermobalance at different operating temperatures. Nickel crystal domain sizes measured after the reaction have been correlated with catalysts performance. The morphology and structural properties of carbon deposited after the reaction are also presented.In the present work, Ni and NiCu catalysts have been prepared by the fusion method using different textural promoters, and their performances in catalytic methane decomposition have been studied in a thermobalance tester at different operating temperatures. The nickel crystal domain sizes, as determined from their respective powder XRD patterns, have been correlated with the catalyst performance measured by the carbon deposition rate and the amount of accumulated carbon at the end of the test. The best performances were for those catalysts showing nickel domain sizes after reaction tests in the range of 10–20nm, the lowest domain sizes achieved with the fusion method, indicating that lower nickel particle size leads to better catalytic performance in the methane decomposition reaction. Ni/MgO catalysts doped with copper had the best performances in terms of carbon accumulation capacity (40g/g_cat at 600°C). The effect of copper on the catalyst performance, however, is highly dependent on the textural promoter used. The morphology and structural properties of carbon deposited after the reaction tests revealed by XRD and TEM of different catalysts are also presented.

Keywords: Hydrogen production; Nickel catalyst; Textural promoter; Crystal size; Carbon nanofiber

Characterization and catalytic performance of Cu/CeO₂ and Cu/MgO-CeO₂ catalysts for NO reduction by CO by Jinfa Chen; Junjiang Zhu; Yingying Zhan; Xingyi Lin; Guohui Cai; Kemei Wei; Qi Zheng (pp. 208-215).

The addition of MgO into Cu/CeO₂ promotes the formation of Cu-O-Ce solid solution. The formation of Cu-O-Ce solid solution in Cu/MgO-CeO₂ is further improved when treated by a redox process. The sample with more Cu-O-Ce solid solution shows higher NO conversion (Cu/CeO₂22).Copper supported on ceria and ceria-magnesia catalysts were synthesized and used for NO reduction by CO. The supports and the subsequent Cu catalysts were prepared by citric acid sol–gel and impregnation methods, respectively. Based on XRD, TPR and EPR measurements, it is found that the Mg addition promotes not only the dispersion of CuO, but also the doping of copper ions into CeO₂ matrix. A redox treatment favors some of copper ions in the octahedral sites of CeO₂ substituting the lattice sites of Ce⁴⁺. Combining the results of activity test, we found that the formation of copper-substituted Cu-O-Ce solid solution promotes the catalytic activity of the catalysts. Also, the ways that MgO acts on the dispersion of CuO and the formation of Cu-O-Ce solid solutions were investigated with the aid of TEM, TGA and XRD techniques. The results of these studies suggest that magnesia crystallites undergo a phase evolvement during the preparation process of Cu/MgO-CeO₂, leading to the reconstitution of the support and hence the improvement of copper dispersion, BET surface area, pore volume, as well as the doping of copper ions into the CeO₂ matrix.

Keywords: Copper; Ceria; Magnesia-ceria; NO reduction by CO

Efficient photodecomposition of gaseous organics catalyzed by titanium(IV) oxide encapsulated in a hollow silica shell with high porosity by Shigeru Ikeda; Hideyuki Kobayashi; Tomohiko Sugita; Yoshimitsu Ikoma; Takashi Harada; Michio Matsumura (pp. 216-220).

A composite of titanium(IV) oxide (TiO₂) particles (core) and nanoporous silica (shell) was prepared. The composite showed high photocatalytic activity for gas phase decomposition of acetone under a diluted condition due to condensation of acetone on the lateral silica shell. Such condensation resulted in enhancing the collision frequency between the substrate and the TiO₂ surface.A composite of titanium(IV) oxide (TiO₂) particles (core) and nanoporous silica (shell) was prepared by successive coating of a carbon layer and an octadecyl-functionalized silica layer on TiO₂, followed by heat treatment to remove the organic components. Transmission electron microscope (TEM) observation and nitrogen (N₂) sorption analyses showed that the composite has a unique rattle-type structure, i.e., TiO₂ particles were encapsulated in the hollow silica shell having well-developed porosity. When the photocatalytic activity for gas phase decomposition of acetone over the composite was compared with that over naked TiO₂ without the lateral silica shell, the activity over the composite tended to become higher than that over naked TiO₂ as the initial amount of acetone in the system was reduced. The enhancement of decomposition rate under a diluted condition was due to condensation of acetone on the lateral silica shell, which resulted in enhancement of the collision rate between the substrate and the surface of the TiO₂ core.

Keywords: Photocatalysis; Titanium(IV) oxide; Core–shell structure; Hollow porous silica; Condensation of substrates; Gaseous photodecomposition; Carbon dioxide

AgBr-Ag-Bi₂WO₆ nanojunction system: A novel and efficient photocatalyst with double visible-light active components by Lisha Zhang; Kin-Hang Wong; Zhigang Chen; Jimmy C. Yu; Jincai Zhao; Chun Hu; Chiu-Yeung Chan; Po-Keung Wong (pp. 221-229).

An AgBr-Ag-Bi₂WO₆ nanojunction was obtained using the deposition-precipitation method, where two visible-light active components (AgBr, Bi₂WO₆) and the electron-transfer system (Ag) are spatially fixed. Due to its double visible-light active components, the AgBr-Ag-Bi₂WO₆ nanojunction exhibits a high photocatalytic activity, even far exceeding the sum of the activities of two individual photocatalysts (AgBr-Ag-TiO₂ and Bi₂WO₆) containing same weight of AgBr or Bi₂WO₆.A semiconductor-based photocatalyst system, consisting of two visible-light-driven (VLD) components and one electron-transfer system, has a great potential to efficiently photocatalytically degrade pollutants. In this paper, we have reported a simple strategy for constructing an all-solid-state AgBr-Ag-Bi₂WO₆ nanojunction by a facile deposition-precipitation method with Bi₂WO₆ as the substrate. Two visible-light active components (AgBr, Bi₂WO₆) and the electron-transfer system (Ag) are spatially fixed in this nanojunction system. Due to the presence of double visible-light active components, such a AgBr-Ag-Bi₂WO₆ nanojunction system has the broadened visible-light photo-response range, and it also exhibits higher photocatalytic activity than photocatalysts containing single visible-light active component, such as Bi₂WO₆, Ag-Bi₂WO₆ and AgBr-Ag-TiO₂ composite, for the degradation of the azo dye, Procion Red MX-5B and colorless pollutant pentachlorophenol. In addition, the initial dye concentration and pH value could greatly affect its photocatalytic activity, and the recycling experiments confirm that it is essentially stable during the photocatalytic process. In particular, the photocatalytic activity of AgBr-Ag-Bi₂WO₆ nanojunction is superior to the sum of the activities of two individual photocatalysts (AgBr-Ag-TiO₂ and Bi₂WO₆) that contain the same weight of AgBr or Bi₂WO₆, indicating the presence of a synergic effect between two visible-light active components in AgBr-Ag-Bi₂WO₆ nanojunction. On the basis of the photocatalytic results and energy band diagram, the photocatalytic process that may have occurred on the AgBr-Ag-Bi₂WO₆ nanojunction system is proposed; the vectorial electron transfer driven by the two-step excitation of both VLD components (AgBr and Bi₂WO₆) contributes to its high photocatalytic activity. Therefore, this work provides some insight into the design of novel and efficient photocatalysts with multi-visible-light active components for enhancing VLD photocatalytic activity.

Keywords: AgBr-Ag-Bi; ₂; WO; ₆; Nanojunction; Double visible-light active; Photocatalysis

Catalytic hydrogenation of aromatic nitriles and dinitriles with nickel compounds by Paulina Zerecero-Silva; Isai Jimenez-Solar; Marco G. Crestani; Alma Arévalo; Rigoberto Barrios-Francisco; Juventino J. García (pp. 230-234).

The catalytic hydrogenation of benzonitrile and benzodinitriles was achieved under relatively mild conditions to mainly produce the corresponding Schiff base. In the case of terephthalonitrile, the use of an increased loading of catalyst permitted the isolation of a double Schiff base. The hydrogenation of the 1,2-benzodinitrile, phthalonitrile, did not yield any product either derived from hydrogenation or condensation.Nickel(0) catalysts of the type, [(dippe)Ni(η²– NC–R)] (R=–Ph, –PhCN) prepared in situ from the nickel(I) dimmer, [(dippe)Ni(μ-H)]₂ (1) in the presence of benzonitrile or the benzodinitriles (1,2-, 1,3- or 1,4-dicyanobenzenes) were used to hydrogenate these substrates. In the case of benzonitrile, 100% conversion was achieved after 72h at 140°C while pressurizing a reactor vessel with 60psi of H₂. N-Benzyl-benzylimine was obtained in 97% yield, accompanied by a small amount of dibenzylamine (2%). Hydrogenation of dicyanobenzenes was found to require more forceful conditions. In the case of 1,4-dicyanobenzene a 62% conversion of the substrate was achieved at 180°C and 60psi of H₂ after 72h. Hydrogenation of 1,3-dicyanobenzene yielded only a 38% conversion, which could only be achieved at 180°C while pressurizing at 120psi. The major products from these reactions, 4-{[(4-cyanobenzyl)imino]methyl}benzonitrile and 3-{[(3-cyanobenzyl)imino]methyl}benzonitrile, were obtained in 97 and 98% yield respectively. The 1,2-dicyanobenzene did not show any reactivity under the conditions used for the other two substrates.

Keywords: Nitrile; Hydrogenation; Homogeneous catalysis; Nickel; Amines; Imines

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Applied Catalysis A, General (v.363, #1-2)