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Applied Catalysis A, General (v.360, #2)

Contents (pp. iii-vii).

Editorial Board (pp. co2).

Steam resistant CoLa-mordenite catalysts for the SCR of NO_x with CH₄ by Laura Gutierrez; Eduardo A. Lombardo (pp. 107-119).

The stabilization of Co-mordenite catalysts through lanthanum exchange was studied for the SCR of NO_x with CH₄. A battery of characterization techniques allowed us to suggest that the presence of exchanged lanthanum seems to preserve the integrity of the zeolite structure preventing the migration of cobalt ions with the subsequent formation of cobalt oxides.The stabilization of Co-mordenite catalysts through lanthanum exchange is reported here. The effect of exchange order and calcination conditions upon the reduction of NO_x to N₂ at 500°C was tracked during 400h on a stream containing NO_x, CH₄, O₂ and 10% H₂O. Both the fresh and used catalysts were characterized through TPR, Raman spectroscopy, FTIR spectroscopy using CO as probe molecule, and XPS. These techniques revealed that the CoLa-mordenite catalysts which were not affected by the severe hydrothermal treatment showed no sign of Co or La migration out of the exchange positions. Instead, those that rapidly deactivated showed the formation of cobalt oxides and, in some cases, the migration of the cations to other exchange positions. The presence of exchanged lanthanum seems to preserve the integrity of the zeolite structure preventing the migration of cobalt ions with the subsequent formation of cobalt oxides which favors the reaction of methane with O₂, thus decreasing N₂ production.

Keywords: Mordenite stability; Co-mordenite deactivation; Zeolite hydrothermal stability; NO; _x; elimination

Effect of micropores diffusion on kinetics of CH₄ decomposition over a wood-derived carbon catalyst by A. Dufour; A. Celzard; B. Ouartassi; F. Broust; V. Fierro; A. Zoulalian (pp. 120-125).

In order to optimise hydrogen production from biomass gasification, catalytic conversion of methane contained in a surrogate biomass syngas (CH₄ 14%; CO 19%; CO₂ 14%; H₂ 16%; H₂O 30%; N₂ 7%) is investigated over a fixed bed of porous wood char as a function of temperature (800–1000°C) and space time (1.6–6.2mingL⁻¹). Determination of Thiele modulus evidences a change of kinetic regime from chemically- to diffusion-controlled when the temperature increases; this finding is particularly relevant when porous chars having an average pore width of 1nm are used as catalysts. Mass diffusion transfers are accounted for by a model introducing an internal effectiveness factor. Knudsen diffusion in micropores is shown to limit the conversion rate of methane per unit mass of catalyst, and explains why such a rate is not proportional to the BET surface area, especially when the latter is higher than typically 300m²/g. It is concluded that diffusion limitations in micropores should be taken into account, otherwise underestimated activation energy and intrinsic kinetic constant are obtained in some experimental conditions.In order to optimise hydrogen production from biomass gasification, catalytic conversion of methane contained in a surrogate biomass syngas (CH₄ 14%; CO 19%; CO₂ 14%; H₂ 16%; H₂O 30%; N₂ 7%) is investigated over a fixed bed of porous wood char as a function of temperature (800–1000°C) and space time (1.6–6.2mingL⁻¹). Determination of Thiele modulus evidences a change of kinetic regime from chemically- to Knudsen diffusion-controlled when the temperature increases. Mass diffusion transfers are accounted for by a model introducing an internal effectiveness factor.

Keywords: Hydrogen production; Biomass; Methane decomposition; Carbon; Catalysis; Effective diffusivity

Polystyrene with half-titanocene/MAO catalysts: Influence of 2,6-diisopropylphenol by Sutapa Ghosh; Hideaki Hagihara (pp. 126-129).

Styrene polymerization was carried out using half-titanocene complexes CpTiCl₃ and Cp*TiCl₃ combined with methylaluminoxane as a cocatalyst. The effects of addition of 2,6-diisopropylphenol derivatives on the catalytic activity and the microstructure of this polymer were investigated by characterizations of the polymer by¹³C NMR, GPC and DSC.Styrene polymerization was carried out by a simple half-titanocene complex [cyclopentadienyltitanium trichloride] (CpTiCl₃) and pentamethyl [cyclopentadienyltitanium trichloride] (Cp*TiCl₃) combined with methylaluminoxane (MAO) as a cocatalyst. The effects of addition of 2,6-diisopropylphenol on the catalytic activity of the above catalytic systems and the microstructure of the resulting polymer were investigated. The results of the above experiments showed that the addition of the 2,6-diisopropylphenol changed the catalytic performance of the above catalytic systems, in terms of catalytic activity of the metal complexes and microstructure, molecular weight and molecular weight distribution of polystyrene synthesized. The yields of polystyrene of the above polymerization reactions indicated that the 2,6-diisopropylphenol enhanced the catalytic activity of both the CpTiCl₃/MAO and Cp*TiCl₃/MAO catalyst systems. Further Soxhlet extraction of the polymer was conducted by boiling acetone for 6h to get pure syndiotactic polystyrene. The microstructure of polystyrene obtained by the above polymerization reactions was investigated by¹³C NMR, GPC and DSC. Results indicated the formation of syndiotactic polystyrene in the absence of phenol and in low concentration of phenol. On the other hand, in the presence of excess phenol, the polystyrene produced was found to be completely atactic in nature. The appearance of monomodal peaks and narrow polydispersity in the GPC results of polystyrenes obtained in all the above polymerizations indicated that the polymerization was only coordination in nature.

Keywords: Half-titanocene; Microstructure; Syndiotactic polystyrene; Atactic polystyrene

Preparation of Co–Mo/B₂O₃/Al₂O₃ catalysts for hydrodesulfurization: Effect of citric acid addition by Nino Rinaldi; Usman; Khalida Al-Dalama; Takeshi Kubota; Yasuaki Okamoto (pp. 130-136).

This research studied the effect of citric acid (CA) addition on the hydrodesulfurization (HDS) of thiophene over Co–Mo/(B)/Al₂O₃ catalysts prepared by a simultaneous impregnation method. The HDS activity enhanced up to the CA/Mo mole ratio of 1 and leveled off by the addition of more CA. The dispersion of MoS₂ particles is increased by the simultaneous presence of Mo, Co, and CA.The effect of citric acid (CA) addition was studied on the HDS of thiophene over Co–Mo/(B)/Al₂O₃ catalysts. The catalysts were characterized by means of LRS, Mo K-edge EXAFS, NO adsorption capacity measurements, and UV–vis spectra. The catalysts were subjected to a chemical vapor deposition (CVD) technique using Co(CO)₃NO as a precursor of Co in order to get deeper insights into the effect of citric acid addition. It was shown that the HDS activity was enhanced by the citric acid addition up to the CA/Mo mole ratio of around 1 and leveled off with further addition. The amount of Co anchored by the CVD was increased by the addition of citric acid, suggesting an increase in the dispersion of MoS₂ particles on the catalyst by the simultaneous presence of Co, Mo and citric acid, in conformity with the increase in the NO adsorption capacity. In contrast to Co–Mo catalysts, the edge dispersion of MoS₂ particles in Mo/B/Al₂O₃ was not affected by the addition of citric acid. The LRS, UV–vis spectra and Mo K-edge EXAFS showed that Co–CA and Mo–CA surface complexes are formed by the addition of citric acid. The Co–CA surface complex is more preferentially formed on CoMo/Al than on CoMo/B/Al, in agreement with a greater promoting effect of citric acid at a lower CA/Mo mole ratio for CoMo/Al than for CoMo/B/Al.

Keywords: Catalyst preparation; Citric acid; Hydrodesulfurization; Co–Mo sulfide catalysts; EXAFS; LRS; Chelating agent; Boria-alumina

Liquid phase reactions catalyzed by Fe- and Mn-sulphated ZrO₂ by S. Ardizzone; C.L. Bianchi; G. Cappelletti; R. Annunziata; G. Cerrato; C. Morterra; P. Scardi (pp. 137-144).

Fe- and Mn-doped ZrO₂–SO₄ (ZS) powders were prepared both by a sol–gel reaction and by impregnation of the zirconia hydrous precursor. Surface functionalities were investigated by XPS,¹H MAS NMR and FTIR analyses. The liquid medium catalytic activity was tested with respect to both the esterification of benzoic acid to methylbenzoate and the benzylation of toluene.Fe- and Mn-promoted ZrO₂–SO₄ (ZS) powders were prepared both by a single step sol–gel reaction and by impregnation of the zirconia hydrous precursor. The samples were calcined at 890K and characterized for the structural (XRD) and morphological features (BET method). Surface functionalities were investigated by XPS,¹H MAS NMR and FTIR analyses. The liquid medium catalytic activity was tested with respect to both the esterification of benzoic acid to methylbenzoate and the benzylation of toluene. The acidity features appeared not to be significantly different among the various samples while all surface characterizations showed a lower affinity to retain water by the metal-promoted samples with respect to ZS, the more so in the case of iron-containing samples. The presence of Mn reduced the surface area and depressed the catalytic activity. Iron-doped catalysts appeared, instead, to be more efficient than ZS especially for the benzylation of toluene.

Keywords: Metal-promoted sulphated zirconia; Liquid media catalyst; Surface functionalities; Structural characterizations; ¹; H MAS NMR

Heterogeneously Pd/C catalysed procedure for the vinylation of aryl bromides by Lionel Joucla; Giuseppe Cusati; Catherine Pinel; Laurent Djakovitch (pp. 145-153).

Heterogeneous Pd/C catalyst was applied to the vinylation of various aryl and heteroaryl halides giving useful isolated yields under aerobic and mild reaction conditions. The catalyst was proved to be stable upon several catalytic cycles given that base was added in the reaction mixture. Hot-filtration experiment indicates that the activity was mainly due to leached Pd-species.Heterogeneous Pd/C catalyst was applied to the Suzuki–Miyaura vinylation of various aryl and heteroaryl halides under aerobic and mild reaction conditions [1.0mmol aryl halide, 1.5mmol potassium vinyltrifluoroborate, 3.0mmol K₃PO₄·H₂O, 0.1mol% Pd/C_(EVO), 1mL NMP, 100°C, 24h]. Useful isolated yields (57–73%) were achieved. In some cases, the catalytic system should be tuned to face the reactivity of the aryl halides: while 0.1mol% Pd/C is sufficient for almost all aryl bromides, 1.0mol% Pd/C was used for free phenols.The heterogeneous catalyst was proved to be stable upon several catalytic cycles; however, the results showed that this was dependent on addition of the base. Hot-filtration experiment indicates that the activity was mainly due to leached Pd-species, indicating that the Pd/C catalyst acts as a palladium reservoir.

Keywords: Styrenes; Vinylation; Heterogeneous palladium catalyst; Potassium vinyltrifluoroborate; Suzuki–Miyaura cross-coupling

Deposition and characterisation of TiO₂ coatings on various supports for structured (photo)catalytic reactors by Philippe Rodriguez; Valérie Meille; Stéphanie Pallier; Mohamad Ali Al Sawah (pp. 154-162).

Different types of aqueous TiO₂–P25 suspensions were prepared and their properties were studied. Then, TiO₂ suspensions were used to elaborate TiO₂ coatings on various substrates (cordierite monolith, stainless steel plates andβ-SiC foam) using a dip-coating method. Finally, the photocatalytic properties of the materials have been determined by studying the photooxidation of aqueous ammonia.Different types of aqueous TiO₂–P25 suspensions were prepared and their properties, including rheological behaviour and zeta potential, were studied. Then, TiO₂ suspensions were used to elaborate TiO₂ coatings on various substrates (cordierite monolith, stainless steel plates andβ-SiC foam) using a dip-coating method. The relationship between the suspension stability and the coating adhesion has been considered. The structural and morphological characterisation of TiO₂ coatings has been performed using scanning electron microscopy, X-ray diffraction and other methods. Finally, the photocatalytic properties of the materials have been determined by studying the photooxidation of aqueous ammonia.

Keywords: Structured reactors; Titanium dioxide; Dip-coating; β; -SiC foam; Stainless steel; Cordierite monolith

Oil transesterification over calcium oxides modified with lanthanum by Shuli Yan; Manhoe Kim; Steven O. Salley; K.Y. Simon Ng (pp. 163-170).

A single-step method was developed for biodiesel production from unrefined or waste oils using a series of heterogeneous calcium and lanthanum mixed oxides. The catalyst activity was closely correlated with the surface basicity and specific surface area. A high yield (96%) of FAME was obtained within 3h even using unrefined or waste oils.Investigations were conducted on a series of calcium and lanthanum oxides catalyst for biodiesel production. Mixed oxides catalyst showed a superior transesterification activity over pure calcium or pure lanthanum oxide catalysts. The catalyst activity was correlated with surface basicity and specific surface areas. The effects of water and free fatty acids (FFA) levels in oil feedstock, water and CO₂ in air, mass ratio of catalyst, molar ratio of oil to methanol, and reaction temperature on fatty acid methyl ester (FAME) yield were investigated. Under optimal conditions, FAME yields reached 94.3% within 60min at 58°C. Mixed CaO-La₂O₃ catalyst showed a high tolerance to water and FFA, and could be used for converting pure or diluted unrefined/waste oils to biodiesel.

Keywords: Biodiesel; Unrefined and waste oils; Transesterification; Solid base catalyst

A novel and efficient catalytic epoxidation of monoterpenes by homogeneous and heterogeneous methyltrioxorhenium in ionic liquids by Raffaele Saladino; Roberta Bernini; Veronica Neri; Claudia Crestini (pp. 171-176).

A convenient and efficient synthesis of monoterpene epoxides by application of methyltrioxorhenium and heterogeneous poly(4-vinylpyridine)/methyltrioxorhenium and microencapsulated polystyrene/methyltrioxorhenium catalytic systems in ionic liquids is described here. It was found that even highly sensitive terpenic epoxides were obtained in excellent yields. Environmentally friendly, easily available and low cost (UHP) urea hydrogen peroxide adduct was used as the primary oxidant. Catalysts were stable systems for at least four recycling oxidations. Experimental results showed that the reactions performed in ionic liquids were more selective and efficient than the ones performed in molecular solvents.A convenient and efficient synthesis of monoterpene epoxides by application of methyltrioxorhenium and heterogeneous poly(4-vinylpyridine)/methyltrioxorhenium and microencapsulated polystyrene/methyltrioxorhenium systems in ionic liquids is described here. Environment friendly, easily available, and low cost urea hydrogen peroxide adduct was used as the primary oxidant. Catalysts were stable systems for at least four recycling oxidations. Experimental results showed that the oxidations performed in (ILs) ionic liquids were more selective and efficient than the ones in molecular solvents.

Keywords: Methyltrioxorhenium; Heterogeneous catalysis; Epoxidation of terpenes; Ionic liquids

Preparation of recoverable Ru catalysts for liquid-phase oxidation and hydrogenation reactions by Marcos J. Jacinto; Osvaldo H.C.F. Santos; Renato F. Jardim; Richard Landers; Liane M. Rossi (pp. 177-182).

We here report the synthesis, characterization and catalytic performance of new supported Ru(III) and Ru(0) catalysts. In contrast to most supported catalysts, these new developed catalysts for oxidation and hydrogenation reactions were prepared using nearly the same synthetic strategy, and are easily recovered by magnetic separation from liquid phase reactions. The catalysts were found to be active in both forms, Ru(III) and Ru(0), for selective oxidation of alcohols and hydrogenation of olefins, respectively. The catalysts operate under mild conditions to activate molecular oxygen or molecular hydrogen to perform clean conversion of selected substrates. Aryl and alkyl alcohols were converted to aldehydes under mild conditions, with negligible metal leaching. If the metal is properly reduced, Ru(0) nanoparticles immobilized on the magnetic support surface are obtained, and the catalyst becomes active for hydrogenation reactions.We here describe the preparation of a new supported Ru(III) and Ru(0) catalysts with fast recovery and negligible metal leaching for green chemical processes covering both alcohol oxidation and olefin hydrogenation reactions. The reactions were performed under mild conditions with H₂ and O₂ as green reducing and oxidizing agents, respectively.

Keywords: Magnetite nanoparticles; Magnetic recovery; Ruthenium; Hydrogenation; Oxidation

The interaction of cobalt species with alumina on Co/Al₂O₃ catalysts prepared by atomic layer deposition by L.B. Backman; A. Rautiainen; M. Lindblad; A.O.I. Krause (pp. 183-191).

Alumina supported cobalt catalysts were prepared by atomic layer deposition of cobalt acetylacetonate precursors. The interaction between cobalt species and the alumina support was studied. Calcination decreased the reducibility of the Co/Al₂O₃ catalysts due to formation of a cobalt oxide phase strongly interacting with the support and probably aluminate type surface species. The dispersion was also found to decrease due to calcination. The catalytic activity for toluene hydrogenation correlated with the cobalt surface area.Alumina supported cobalt catalysts were prepared by atomic layer deposition (ALD) of cobalt acetylacetonate precursors (Co(acac)₂ and Co(acac)₃). The main modes of interaction between the acetylacetonate precursors and the support were found to be the exchange reaction between the alumina OH-groups and the acac-ligands of the precursor and dissociative adsorption on coordinatively unsaturated Al³⁺ sites. The amount of precursor that could adsorb on the support was determined by steric hindrance. Samples were prepared using 1–5 reaction cycles, i.e. subsequent precursor addition (Co(acac)₂) and calcination, resulting in catalysts containing ca. 3–10wt.% Co. Samples were also prepared where the last calcination step was omitted, i.e. uncalcined catalysts. Calcination at 450°C decreased the reducibility of the Co(acac)₂/Al₂O₃ catalysts due to formation of a cobalt oxide phase strongly interacting with the support and aluminate type surface species. The reducibility increased with metal loading on both calcined and uncalcined catalysts; however the reducibility of the calcined catalysts remained lower than of the uncalcined ones. The dispersion was found to be lower on the calcined catalysts. The cobalt particle sizes on the calcined samples was ca. 8nm and on the uncalcined 4–5nm, for cobalt loadings of ca. 6–10wt.%. Catalytic activity was tested by gas phase hydrogenation of toluene in temperature programmed mode (30–150°C).

Keywords: Cobalt catalysts (supported); Alumina; Atomic layer deposition; ALD; Reducibility; Dispersion; Calcination; Toluene hydrogenation

Polymerization of ethylene using zirconocenes supported on swellable cation-exchanged fluorotetrasilicic mica by Hideki Kurokawa; Satoru Morita; Michiko Matsuda; Hidenori Suzuki; Masa-aki Ohshima; Hiroshi Miura (pp. 192-198).

Supported catalysts consisting of Cp₂ZrCl₂ and cation-exchanged fluorotetrasilicic mica (M n⁺-mica, M n⁺=Na⁺, Mg²⁺, Fe³⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺) were prepared and employed in the ethylene polymerization or ethylene/1-hexene copolymerization in the presence of R₃Al. The catalysts consisting of swellable Mg²⁺-mica and Zn²⁺-mica (both calcined at 200°C) and Cp₂ZrCl₂ displayed high activity for the polymerization reaction. By contrast, when Mg²⁺-mica and Zn²⁺-mica were calcined above 250°C, the swellability was lost, and the activities of Cp₂ZrCl₂ supported on these non-swellable micas were significantly reduced. The relationship between the activity and swellability of mica was clearly observed both in ethylene polymerizations employing ( n-BuCp)₂ZrCl₂ in place of Cp₂ZrCl₂ and in ethylene/1-hexene copolymerizations using Cp₂ZrCl₂. The role of M n⁺-mica for the activation of the metallocene complex was investigated by surface observation using a scanning electron microscope and by XRD measurements of the catalysts after polymerization of ethylene for a short time. The results of the surface observations indicated that polyethylene was produced on the edges of M n⁺-mica lamellas at the initial stage of the polymerization. The XRD measurements show that the regularity of the stacked lamellas was immediately lost at this stage. The catalyst prepared by removing free Cp₂ZrCl₂ (i.e., unsupported Cp₂ZrCl₂, Cp₂ZrCl₂ dissolved into the catalyst slurry) showed extremely low activity, suggesting that the most of the active sites were formed through the reactions of M n⁺-mica and free Cp₂ZrCl₂. These results indicate that the lamellas of M n⁺-mica are peeled off at the initial stage of the polymerization and that exposed metal cations react with free-Cp₂ZrCl₂ to form additional active species. The swellability of M n⁺-mica strongly affects the formation of additional active sites, and therefore the supported catalysts based on non-swellable M n⁺-mica displayed only low activities.The catalyst Cp₂ZrCl₂ supported on cation-exchanged fluorotetrasilicic mica showed a high activity for ethylene polymerization in the presence of R₃Al. The results of SEM observation for the catalyst surface after polymerization for a short time indicated that the polymerization began on Cp₂ZrCl₂ located at the edges of the mica sheet.

Keywords: Metallocene catalyst; Ethylene/1-hexene copolymerization; Swellability of mica

Secondary ketonization of primary alcohol over LaMn-based mixed oxides with perovskite-like structure by Roman Klimkiewicz; Janusz Trawczyński (pp. 199-204).

Binary mixed oxide LaMnO₃ with perovskite-like structure, bulk and supported on La–Al₂O₃, dehydrogenate n-butanol to an aldehyde which undergoes a secondary reaction to produce a symmetrical ketone. Incorporation of Cu, V or Sr into LaMnO₃ structure enables to control the acid–base surface properties. The degree of n-butanol conversion depends on the total concentration of basic and acidic sites. Selectivity to butyraldehyde depends on the share of basic sites. Selectivity to dipropyl ketone can be related both with the share and concentration of acidic sites.LaMnO₃-based mixed oxides with perovskite-like structure both bulk and supported on La–Al₂O₃, show high catalytic activity in dehydrogenation of n-butanol to an aldehyde, which then undergoes a secondary reaction to produce a symmetrical ketone. Partial substitution of Cu, V or Sr into LaMnO₃ structure does not destroy the perovskite-like structure and enables to control the acid–base surface properties. It allows linking up these qualitative and quantitative features with activity and selectivity of these materials. The degree of n-butanol conversion depends on the total concentration of basic and acidic sites. Selectivity to butyraldehyde can be related with the share of basic sites. Selectivity to dipropyl ketone is affected both by the acidity and concentration of acidic sites. LaMnO₃/La–Al₂O₃ seems to posses an optimum set of surface characteristics for the examined ketonization of a primary alcohol.

Keywords: Lanthanum manganite; Perovskite; Basic sites; Acidic sites; Primary alcohol; Ketonization

Catalytic oxidation of sulfur and nitrogen compounds from diesel fuel by Wladmir F. de Souza; Iara R. Guimarães; Mário César Guerreiro; Luiz C.A. Oliveira (pp. 205-209).

The oxidation of nitrogen or sulphur pollutants was monitored with electrospray ionization mass spectrometry. Quinoline, dibenzothiophene and methylene blue were found to be oxidized through a successive hydroxylation mechanism. These results strongly suggest that highly reactive hydroxyl radicals, generated during the reaction of H₂O₂ on the catalyst surface, are responsible for the oxidation.The oxidation of nitrogen or sulfur pollutants, using organic substrates as model compounds, was monitored with electrospray ionization mass spectrometry. Quinoline, dibenzothiophene and methylene blue were found to be oxidized through a successive hydroxylation mechanism. These results strongly suggest that highly reactive hydroxyl radicals, generated during the reaction of H₂O₂ on the catalyst surface, are responsible for this oxidation, and confirm that the material is an efficient heterogeneous Fenton-like catalyst, which is able to eliminate around 90% of the sulfur molecules. This is, therefore, an important and useful tool for the elimination of refractory sulfur in the hydrotreatment process with potential application to meet future environmental legislation indexes. It is important to remember that only the heteroatom fraction is degraded, preserving the hydrocarbons of interest in the diesel flows. The catalyst showed activity in successive oxidation cycles presenting a high regeneration capacity.

Keywords: Pollutant; Oxidation process; Natural iron oxide; Electrospray ionization

Amphiphilic cerium(III) β-diketonate as a catalyst for reducing diesel/biodiesel soot emissions by Paulo. C. de Sousa Filho; Luciano F. Gomes; Kleber T. de Oliveira; Cláudio R. Neri; Osvaldo A. Serra (pp. 210-217).

The amphiphilic β-diketonate Ce(hdacac)₃(Hhdacac)₃·2H₂O was synthesized and characterized as a potential metal fuel additive. Due to its expressive solubility in non-polar fuels, this complex can act as a homogeneous precursor for CeO₂ nanoparticles, which efficiently catalyze the oxidation of soot derived from diesel/biodiesel combustion. These properties were confirmed in studies comprising carbon black oxidation and combustions of additived diesel/biodiesel blends.This work reports on the synthesis, characterization and applications of the new cerium(III) β-diketonate Ce(hdacac)₃(Hhdacac)₃·2H₂O (where hdacac and Hhdacac denote, respectively, the hexadecylpentane-2,4-dionate and hexadecylpentane-2,4-dione ligands) as catalyst for the reduction of automotive emissions. Due to its amphiphilic character, this complex can be solubilized in non-polar fuels, thus generating cerium(IV) oxide particles, which efficiently catalyze the oxidation of diesel/biodiesel soot.The synthesized complex was characterized by microanalysis (C, H), thermal analysis, and infrared spectroscopy. Scanning electron microscopy, X-ray diffractometry, and specific surface area measurements attested that the complex can act as a soluble precursor of homogeneous CeO₂ spherical nanoparticles. The efficiency of this compound as catalyst for the reduction of soot emission was evaluated through static studies (comprising carbon black oxidation), which confirmed that increasing concentrations of the complex result in lower carbon black oxidation temperatures and lower activation Gibbs free energies. Dynamic studies, which embraced the combustion of diesel/biodiesel blends containing different amounts of the solubilized complex in a stationary motor, allowed a comparative evaluation of the soot emission through diffuse reflectance spectroscopy. These analyses provided very emphatic evidences of the efficiency of this new cerium complex for the control of soot emission in diesel/biodiesel motors.

Keywords: β-Diketonates; Cerium; Diesel; Biodiesel; Soot

Cu(II) bipyridine and phenantroline complexes: Tailor-made catalysts for the selective oxidation of tetralin by B. Louis; C. Detoni; N.M.F. Carvalho; C.D. Duarte; O.A.C. Antunes (pp. 218-225).

Mononuclear 2,2′-bipyridine and 1,10-phenantroline mononuclear Cu(II) complexes have been synthesized, and their structure determined by ESI-MS. These complexes have been tested in the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene), using hydrogen peroxide as oxidant in acetonitrile/water solvent. [Cu(bipy)₂Cl]Cl catalyst was able to oxidize tetralin at room temperature, at 62.1% conversion into 1-tetralol and 1-tetralone at 91% selectivity (81% in 1-tetralone).Mononuclear Cu(II) complexes have been synthesized, and their structure thoroughly characterized by electrospray ionization mass spectrometry (ESI-MS). These 2,2′-bipyridine and 1,10-phenantroline mononuclear Cu(II) complexes have been tested as catalysts in the partial oxidation of tetralin (1,2,3,4-tetrahydronaphthalene), using hydrogen peroxide as oxidant in acetonitrile/water as solvent.The complexes [Cu(bipy)₃]Cl₂·6H₂O (1), [Cu(bipy)₂Cl]Cl·5H₂O (2), [Cu(bipy)Cl₂] (3), [Cu(phen)₃]Cl₂·6H₂O (4), [Cu(phen)₂Cl]Cl·5H₂O (5), [Cu(phen)Cl₂] (6) were able to oxidize tetralin at room temperature, at high degrees of conversion (62.1% with2) into α-tetralol and α-tetralon at 91% selectivity (81% in 1-tetralon).Depending on nature and number of ligands (bipyridine or phenantroline) surrounding Cu²⁺ cation, one was able to tailor both the activity toward tetralin oxidation, and the selectivity toward 1-tetralol and 1-tetralone products, but also to raise the yield in valuable α-tetralone.

Keywords: Tetralin; Partial oxidation; Mononuclear Cu(II) complexes; 2,2′-Bipyridine; 1,10-Phenantroline; Hydrogen peroxide

The steady state methanol decomposition reaction over Cu/Zn and Cu/Cr catalysts: Pretreatment, operando EXAFS, and activity study by Shawn D. Lin; Ting C. Hsiao; Li-Chung Chen (pp. 226-231).

Two commercial Cu catalysts, Cu/Zn and Cu/Cr, were pretreated to produce calcined, partially reduced and completely reduced catalysts, and tested for methanol decomposition. The pretreatments resulted in different initial Cu states based on extended X-ray absorption fine structure (EXAFS) morphological analysis, but only metallic Cu was found after methanol decomposition tests. Pretreatment was found to affect catalytic activity only during the initial transient period, when atom balance analysis showed the presence of excess oxygen in the effluent. The excess oxygen is attributed to the participation of lattice oxygen in the reaction leading to CO₂ and H₂O formation. When there was no excess oxygen present in the effluent, a steady state was achieved and a similar catalytic performance was obtained regardless of catalyst pretreatment conditions.Commercial Cu/Zn and Cu/Cr catalysts were pretreated to different degrees of reduction and tested for methanol decomposition. The catalytic activity was affected by pretreatment only during the initial transient period, when atom balance analysis showed the presence of excess oxygen in the effluent. As the steady state was achieved, a similar catalytic performance was obtained regardless of catalyst pretreatment conditions.

Keywords: Methanol decomposition; Cu/Zn; Cu/Cr; Pretreatment; EXAFS

Kinetic study of ethanol reforming in a microreactor by O. Görke; P. Pfeifer; K. Schubert (pp. 232-241).

In a microchannel reactor it was possible to produce hydrogen by ethanol reforming even with a low steam to carbon ratio of 2 with low methane by-product concentrations below 1%. For temperatures above 625°C, very high H₂ space time yield of 400mmolgmin⁻¹ was reached, four times more than the highest values reported in the literature.The applied microreactor was excellently suitable for the determination of kinetic data of the ethanol reforming reaction.We have demonstrated the successful application of a microchannel reactor to produce hydrogen by ethanol reforming. Microchannels coated with Rh/CeO₂ catalyst were used at residence times of 9–42ms. Reaction temperatures were 350–660°C, and the steam to carbon ratio was varied between 2 and 4. Even with a low steam to carbon ratio of 2 it was possible to ensure low methane by-product concentrations below 1% by lowering the residence time in the microreactor to 9ms. For temperatures above 625°C, a H₂ space time yield of 400mmolgmin⁻¹ was reached, four times more than the highest values reported in the literature. Negligible coke formation was found in the metallic microreactor even at low steam to carbon ratios of 2. This can be attributed to superior heat supply compared to conventional reactors and the low acidity of the applied catalyst.The applied microreactor was suitable for the determination of kinetic data of the ethanol reforming reaction. It was shown that neither mass nor heat transport limitations falsify the experimentally determined kinetic parameters. Consequently, the excellent isothermal behaviour of the microchannel reactor is supposed to be responsible for a good fit of the calculated values of the selected models to the experimental results. The model and experiments were in good agreement for a wide range of ethanol and water partial pressures, steam to carbon ratios, and temperatures. Rate determining steps in the models were CO₂ desorption, dissociative ethanol adsorption and reaction of adsorbed methane with steam from the gas phase for the identified main reactions, i.e. water gas shift, ethanol decomposition and methane steam reforming, respectively.

Keywords: Microreactor; Ethanol steam reforming; Methane formation; Kinetics; Rhodium; Ceria

Hydrodeoxygenation of bio-crude in supercritical hexane with sulfided CoMo and CoMoP catalysts supported on MgO: A model compound study using phenol by Yun Yang; Allan Gilbert; Chunbao (Charles) Xu (pp. 242-249).

Hydrodeoxygenation of bio-crude was investigated using phenol as the model compound in supercritical hexane at 300–450°C and 5.0MPa hydrogen (cold pressure) with MgO-supported sulfided CoMo with and without phosphorous as the catalyst promoter. With CoMoP/MgO for 60 min and at 450°C, the treatment of phenol yielded a product containing approximately 65wt.% benzene.Hydrodeoxygenation (HDO) of bio-crude was investigated using phenol as a model compound in supercritical hexane at temperatures of 300–450°C and cold pressure of hydrogen 5.0MPa with MgO-supported sulfided CoMo with and without phosphorus as a catalyst promoter. The oily products after hydro-treatment were characterized by GC/MS and FTIR. Both MgO-supported catalysts proved to be effective for hydrodeoxygenation of phenol leading to significantly increased yields of reduced hydrocarbon products, such as benzene and cyclohexyl-aromatics, at temperatures higher than 350°C, while CoMoP/MgO showed superior activity in HDO of phenol. With the presence of CoMoP/MgO for 60min and at 450°C, the treatment of phenol yielded a product containing approximately 65wt.% benzene and >10wt.% cyclohexyl-compounds. The fresh and spent catalysts were thoroughly characterized by ICP-AES, N₂ isothermal adsorption, XRD, XPS and TGA, and the effects of the phosphorus as the catalyst promoter and MgO as a basic support were discussed.

Keywords: Bio-crude; Phenol; Hydrodeoxygenation; CoMo/MgO; CoMoP/MgO; Sulfided catalysts

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Applied Catalysis A, General (v.360, #2)

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Applied Catalysis A, General (v.360, #2)