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A series of triflate derivatives (La(OTf)(3), tert-butyl-dimethyl-silyltrifluoromethane-sulfonate (BDMST) and triflic acid (HOTf)) embedded in a silica matrix were Used as heterogeneous catalysts for the acylation of alcohols and activated aromatic Compounds. Acylation of saturated alcohols and cyclohexanol resulted in O-acylated products. The acylation of the aromatic compounds was dependent on temperature and substituents. At low temperatures, for phenols and naphtols, acylation occurred mainly to O-acylated. Under these conditions, the presence of catalysts only enhanced the reaction rate. The increase of the temperature above 150 degrees C also led to C-acylation. For anisole and 1-methoxynaphtalene, acylation occurred at the aromatic ring even at low temperatures. (c) 2005 Elsevier B.V. All rights reserved.

Oxidative removal of toluene in a dielectric barrier discharge reactor combined with manganese catalysts downstream was investigated. Toluene input concentration was varied in the range of 415-2227 ppm. The discharge was operated in pulsed mode, with short pulses of 23-35 kV peak voltage. At 7 W average power, toluene conversion was 60%-70%, independent on the toluene input concentration and on the total gas flow rate in the range of 110-330 SCCM (SCCM denotes cubic centimeter per minute at STP). Toluene total oxidation was favored at high residence time of the gas in the discharge zone and low toluene concentration, when the main reaction product was CO2 with selectivities of 80%-85%. The addition of the catalysts led to a 15%-20% increase in toluene conversion with respect to the values obtained in the plasma, due to oxidation with ozone on the catalyst surface. (c) 2006 American Institute of Physics.

Mo-V-Te-Nb mixed oxides with a molar ratio of 1:0.30:0.20:0.15 were prepared by citrate and dry-up method, both associated with hydrothermal treatments in the presence of a cationic surfactant, (cetyl trimethylammonium bromide, CTAB), and tested in the ammoxidation of propane. The catalysts were characterized by adsorption-desorption isotherms of nitrogen at 77 K, particle size measurements, XRD, and XPS. By using the surfactant, the surface area increased significantly, and samples with surface area between 110 and 239 m(2)/g were obtained. These catalysts exhibited a propane conversion near 48% with selectivity to acrylonitrile of about 32% for a space velocity 30 times higher than generally reported. (c) 2005 Elsevier B.V. All rights reserved.

Supported LaCoO3 perovskites with 10 wt.% loading were prepared by impregnation of different supports containing ceria with a solution of La and Co nitrates and citric acid. All precursors were calcined at 700 degrees C for 5 h. XRD investigations indicated the perovskite formation via "citrate" precursor only on ceria support. All catalysts were tested for toluene total oxidation in the temperature range 100-600 degrees C. In spite of a large surface area, alumina-supported perovskites showed a lower global activity. It appears then the necessity of the presence of a perovskite phase for good oxidative activity. In terms of reaction rates higher reaction rates per perovskite weight were observed for all supported catalysts when compared to bulk LaCoO3. (c) 2005 Elsevier B.V. All rights reserved.

A dielectric barrier discharge (DBD) combined with Mn-based phosphate catalysts placed downstream of the plasma reactor was investigated experimentally for total oxidation of toluene in air. The discharge was initiated by high voltage pulses of 18 kV amplitude and 1213 ns rise time. The pulse frequency increased from 14 to 80 Hz, for applied voltages in the range 18-28 kV. Discharge currents up to 100 A and approximately 50 ns duration were obtained. No other hydrocarbons except toluene were detected in the effluent gas. The yield of carbon dioxide formed in the discharge was up to 24%. As catalysts, MnPO4, Mn-APO-5 and Mn-SAPO-11 were tested, for temperatures up to 400 degrees C. Under purely catalytic conditions, the best behavior for toluene total oxidation was found for Mn-SAPO-11, with a CO2 yield up to 33%, at 400 degrees C. The combined application of plasma and catalysis showed a remarkable synergetic effect, even at low temperature, up to 100 degrees C, where the catalysts alone are not active. In this range, the CO2 yield increased up to 41%, for the Mn-SAPO catalyst. At 400 degrees C the highest CO2 yield was obtained for MnPO4, reaching 68%. The synergetic effect observed for the plasma-catalyst combination is attributed to ozone radicals formed in the discharge, which decompose on the catalyst surface, greatly contributing to toluene total oxidation. (c) 2005 Elsevier B.V. All rights reserved.

Silica immobilized La(OTf)(3), tertbutyldimethylsilyl-triflate and triflic acid proved to be very efficient catalysts for the hydroquinone alkylation with tert-butanol. In solvent free conditons, the conversion was higher than 95% with the dialkylated product (2,5-DTBHQ) formed in high yields. When a polar solvent (1,4-dioxane) was used, the selectivity towards the monoalkylated product (2-TBHQ) increased up to 90%.

Ru-BEA catalysts with 1.0-2.5 wt.% Ru were prepared by ion exchange. The acidic properties of these catalysts were investigated using deuterated acetonitrile, pyridine, and 2,6-di-tert-butyl-pyridine. The deposited Ru was studied by CO-FTIR spectroscopy. The materials were tested as catalysts in the hydrogenation of a conjugated cyclic keto-enol, namely, 5-hydroxymethylene-5H-6,7-dihydrodibenzo[a,c]cyclohepten-6-one. Beside hydrogenation, hydrogenolysis products were identified by GC-MS and H-1 NMR techniques. Relations were sought between the selectivity and some physicochemical properties of the catalyst. (C) 2004 Elsevier B.V. All rights reserved.

Epoxidation of cyclohexene and indene with hydrogen peroxide was performed with peroxotungstic species complexed with phosphate groups at the surface of hydroxyapatite. Hydroxyapatite (HAp) was prepared from calcium acetate, diammonium phosphate, and ammonia in water. Tungsten was deposited on HAp using two procedures. In procedure A, HAp was suspended in different volumes of peroxotungstic acid either at room temperature or in an autoclave at 90 or 120 degreesC. In the later case, the peroxo form was regenerated by heating the catalyst suspension with 30% H2O2 for 6 h at 60 degreesC. In procedure B, HAp was suspended in a solution of (AliQ(+))(2)W2O11 in dichloromethane. The resulting materials were isolated by filtration, washed with CH,02, and dried overnight under vacuum. Some of the catalysts were lipophilized and buffered by a partial exchange with R4N+ from NBu4Cl. The catalytic materials were characterized by adsorption-desorption isotherms of N-2 at -196 degreesC, FT-IR, XRD, P-31 CP/MAS NMR, and XPS. The stability of the catalysts was checked by leaching and recycling tests. (C) 2003 Elsevier B.V. All rights reserved.

A series of SAPO, GaPSO, MgAPO and, GaPO's were prepared by hydrothermal. synthesis under autogeneous pressure. These catalysts were characterized by XRD, N-2 adsorption-desorption isotherms at 77 K, TG-DTA, NH3-DRIFT, XPS, and MAS NMR. They were tested under learn-burn conditions in the reduction of NO and NO2 Using isobutane and ethane as reductants. Under the investigated conditions, the reaction occurred selectively mainly to alkenes, namely, isobutene and ethene. The characterization of the tested catalysts indicated no changes for SAPO's and MgAPO, but only for gallium containing phosphates. However, both catalysts were stable in time.

A series of tantala-silica catalysts (15 wt.% Ta2O5) were prepared by sol-gel from tantalum and silica ethoxides. These syntheses were carried out using two families of quaternary ammonium salts, CnH2n+1(CH3)(3)NBr (n = 14, 16, 18) and (CnH2n+1)(4)NBr (n = 10, 12, 16, 18) were used as surfactants. The catalysts were characterized by adsorption-desorption isotherms of N-2 at 77 K, XRD, SAXS, DRUV-Vis, py and CDCl3-FTIR, and XPS. The catalytic tests were carried out in dioxane, methanol or CHCl3, and indicated that both conversion and selectivity depend on the size of tantalum nanoxide. Leaching investigation showed that part of Ta is extracted from the network, but it segregates on the support as Ta2O5. (C) 2004 Elsevier B.V. All rights reserved.

Mesoporous SO2 oxidation catalysts were prepared by impregnation of a sol-gel prepared vanadia-silica support with various amounts of cesium sulfate or mixtures of alkaline sulfate species (Na or K). The resulting catalysts were characterized by adsorption-desorption isotherms of nitrogen at 77 K, in situ evolution of crystallinity by X-ray diffraction, NH3-DRIFT, XPS, transmission electron microscopy, dispersive X-ray analysis, and X-ray fluorescence spectrometry. Catalytic tests in oxidation Of SO2 in diluted gases (1 vol.%) showed that these systems were very active. A dependence on the alkaline metal loading was also evidenced. (C) 2004 Published by Elsevier B.V.

Immobilized triflate derivatives (La(OTf)(3), AgOTf, tert-butyldimethylsilyltrifluoro-methanesulfonate), and triflic acid were found to be effective in the alkylation of phenol and naphthols with tert-butanol. The acidic strength and type of acidity (Lewis or Bronsted) are key factors controlling the conversion and product distribution.

The oxidation of 2-thiobeniyl-4,6-dimethyl-pyrimidine was investigated over catalysts based on MoO3, Mo suboxides and mixed Mo-Sb oxides to obtain 2-thiobenzyl-4,6-dimethyl-pyrimidine sulfoxide. The chemoselectivity was found to vary with the oxidation state of the Mo atoms, the morphology of the Mo oxide crystals and the concentration of Sb in the structure. The best chemoselectivity (about 80%) resulted from Mo8O23. The H2O2 efficiency was also found to depend on these parameters. For Mo suboxides the best efficiency was obtained on Mo8O23, which suggested that the efficient catalysts are those possessing Mo in a reduced oxidation state. The presence of Sb changed the behavior of the catalysts and the higher H2O2 efficiency resulted for the catalysts containing Mo in its highest oxidation state. (C) 2002 Elsevier Science B.V. All rights reserved.

Mixed vanadia-titania-silica catalysts (3 or 6wt% V2O5, and 16-34wt% TiO2) were one pot prepared by sol-gel and hydrothermal methods in the presence of different surfactants. Tetraethylortosilicate (TEOS) was used as precursor for silica, tetraisopropylorthotitanate (TIPOT) for titania, and vanadyl sulfate for vanadia. As surfactants were used cetyltrimethylammonium bromide (CTMABr) or octadecyl-trimethylammonium bromide (ODCABr). The catalysts were characterized by adsorption and desorption curves of N-2 at 77 K, NH3-DRIFTS, H-2-TPR, XRD, in-situ Raman spectroscopy, XPS, and TEM.

Silica-embedded tert-butyldimethylsilyltrifluoromethanesulfonate catalysts were synthesized by a sol-gel method in acidified CCl4, using hexadecyltrimethyl-ammonium bromide as a surfactant. The catalysts were characterized by nitrogen adsorption-desorption isotherms at 77 K; TG-DTA; H-1, C-13, and Si-29 solid state MAS/NMR; XRD; XPS; Raman spectroscopy; and FTIR after adsorption of NH3. The characterization data indicated mesoporous solids in which most of the silyl-triflate derivative keeps its integrity. The catalytic tests performed with the methyl ester of 1-cyclopentenylacetic acid in various solvents showed that the reaction selectively leads to 3-methylbenzaldehyde and is sensitive to the solvent accepting ability. (C) 2001 Academic Press.

Mesoporous zirconium oxides were obtained using the polymeric sol-gel procedure. The synthesis was carried out in the presence of two series of surfactants, namely, N(C-n)(4)Br and N(CH3)(3)CnBr, with n = 8-18, and C-n, the linear alkyl chain. Hydrolysis of zirconium isopropoxide was carried out both under acid and base catalysis, and also using acetylacetone (acac) as a stabiliser. In order to obtain information on the sol-gel procedure in the above conditions, the composition parameters: Zr/H2O and Zr/surfactant ratios were modified in a rather wide interval. Mesoporous textures were obtained, with surface areas and pore size distributions depending on the synthesis conditions. The evolution of the sol-gel process and the resulting oxides were characterised with several tools: nitrogen adsorption-desorption isotherms, TG-DTA, XRD. SAXS, FTIR, C-13-CP/MAS NMR, and XPS measurements. The results showed that the phase structure of ZrO2 is sensitive to the composition parameters, and confirmed that in the presence of surfactants, the synthesis occurred via a scaffolding mechanism. (C) 2001 Elsevier Science B.V. All rights reserved.

Mesoporous zirconium oxides were prepared by the sol-gel procedure under basic catalysis and in the presence of a series of surfactants: CnH2n+1N(CH3)(3)Br, with n = 8-18. Zirconium propoxide was used as a precursor. Basic conditions were created by NaOH (pH > 11) or ammonia (pH = 10). The influence of the preparation parameters was examined by modifying several parameters such as Zr:H2O and Zr:surfactant molar ratios. The sol-step and then the polymerization step were achieved at different temperatures. Drying of the samples was carried out by lyophilization, or in vacuum oven at 383 K for 48 h. Calcination of the materials was made on the basis of TG-DTA results. The oxides were characterized by adsorption-desorption isotherms of N-2 at 77 K, XRD, SAXS, solid-state C-13 CP/MAS NMR, FTIR, and SEM. (C) 2001 Elsevier Science B.V. All rights reserved.

Catalysts were prepared by exchange and co-exchange techniques following Iwamoto's procedure. Copper-exchange degree in the zeolites varied between 21.2% and 128% while the Sm content varied in inverse order, between 27.2% and 18.8%. The catalysts were characterized by NO-DRIFT, O-2-TPD, and XPS. Catalytic tests were performed in a microreactor in the temperature range 673-873 K. It was found that the presence of Cu in close proximity of the Al framework, i.e., in the exchangeable positions, is increased in the presence of Sm. The presence of Sm stabilizes the Cu(I)-O-Cu(II) "redox buffer," increasing the activity of this catalyst. This behavior is mainly observable for low Sm concentration. (C) 2000 Academic Press.

Co-Nb(2)Q(5)-SiO2 catalysts were prepared using three different sol-gel procedures: (i) the colloidal sol-gel method using NbCl5 and SiCl4 as precursors; (ii) the polymeric sol-gel method using niobium ethoxide and tetraethyl-orthosilicate (TEOS); (iii) an intermediate procedure between the colloidal and polymeric sol-gel method in which the precursors were those utilized in the CSG but dissolved in a mixture of anhydrous ethanol and CCl4. In all procedures, the elimination of the solvent carried out between 80 and 110 degrees C was followed by a reduction in hydrogen flow (30 ml min(-1)) at 773 K. Following these procedures, samples containing 10 wt.% Co and 15 wt.% niobium oxide (expressed as Nb2O5) were obtained. The characterization of the catalysts was performed using various techniques: N-2 adsorption and desorption curves at 77 K, NH3- and H-2-chemisorption, TPO, XPS, XRD, and solid state H-1 MAS-NMR. Hydrogenolysis of butane was evaluated. The low reaction rates are assigned to the effect of the metal size, whereas the isobutane selectivity as well as the relatively high stability is due to the acidity of the support. (C)2000 Elsevier Science B.V. All rights reserved.

Activation of amorphous zirconium phosphate powder by high temperature treatment under NH3 allows to prepare series of zirconium phosphate oxynitrides. The adjustment of the N/O ratio allows the tuning of the acid-base properties of these high surface area and amorphous catalysts. It is evidenced that the substitution of oxygen by nitrogen induces a decrease of the number and strength of acid site while the basic character of the surface increases. By increasing the nitrogen content in the ZrPON powders, the strong acidic centres of ZrPO precursor are modified and a "soft" surface is obtained with good equilibrium between acid and basic sites of medium strength. In ZrPON with high N content, the basicity clearly dominates as numerous strong basic centres are identified. The basicity enhancement is directly connected to the presence of nitrogen atoms N3- anions and hydrogenated nitrogen species in the zirconophosphate structure. It is then proposed that in addition to nitride N present at the surface and in the bulk, some oxygen species may be also responsible of the most strongest basic sites. (C) 1999 Elsevier Science B.V. All rights reserved.

Ru-zeolites prepared via deposition of aqueous solution of ruthenium chloride on X, L, ZSM-5 and APO-54 were investigated. The impregnated solids were characterized by the following techniques: N-2 sorption, H-2 chemisorption, TPR, XRD, XPS, EXAFS and Mossbauer spectroscopy. It was found that deposition of Ru is influenced by the pore structure and the chemical composition of the supports, in particular the concentration and strength of the protonic sites, with the formation of the different species. The packing of Ru as well as the degree of the reduction and the metal particle size are different according to the penetration depth of the metal and the nature of the zeolite. The amount of chlorine possibly remaining as adatoms of Ru is very low or inexistent. In calcined and reduced catalysts no chloride peak could be evidenced by XPS. The experiments confirmed that the use of large amounts of Ru chloride precursor leads to rather large metal particles. (C) 1999 Elsevier Science B.V. All rights reserved.

ZSM-5 containing Zr in the lattice was prepared following the procedure for ZSM-5 using ZrCl4 as zirconium precursor. Zr was substituted for Si in the ZSM-5 lattice and then this zeolite was loaded with Cu. Loading these catalysts with Cu was carried out following Iwamoto's procedure. An increase in Zr results in a decrease in Cu loading, although the exchange solutions were the same. The increased Zr loading and, hence, decreased Cu loading resulted in a decreased NO decomposition activity relative to the Zr-free ZSM-5 loaded with Cu. NO conversions, obtained on Cu-ZSM-5 zeolites in which zirconium replaced Si, were below 40%, which is about 30% lower than those recorded on Cu-exchanged pure zeolites. The amount of NO2 detected in the reaction products proved that, for total conversions lower than 20%, the reaction of NO takes place almost exclusively without decomposition to N-2 and O-2. The catalysts were characterized by DRIFTS and NO-DRIFTS, Raman spectroscopy, O-2 - TPD and XPS. The OH region observed in DRIFTS changed with an increase in Zr loading and, hence, Cu(II)-O-Cu(I) species cannot be formed. This may play a role in the decreased activity. Raman spectra showed that increased Zr also results in increased CuO which may lead to the decreased activity. Although the exposure of the samples with high Zr content to NO results in the apparent redispersion of CuO to isclated sites within the ZSM-5, the Cu moves to locations which are inactive and/or inaccessible to NO and, hence, the activity does not increase even though the Cu is dispersed. The formation of NO2 follows the mechanism proposed by Shelef. (C)1999 Elsevier Science B.V. All rights reserved.

Sulfate-zirconia catalysts were prepared via the colloidal-sol-gel method using ZrOCl2 as precursor. After precipitation and washing, the solids were peptized with a 1 : 1 mixture of CH3COOH and H2SO4. The promoters were introduced as gallium, indium, or thallium nitrates into the solution containing the zirconium sols. After a gel formation period, the samples were dried and calcined. The catalysts were characterized by chemical analysis, nitrogen sorption isotherms, FTIR analysis of adsorbed pyridine and deuterated acetonitrile, XRD, laser Raman and FTIR spectroscopy, and XPS. The catalytic tests were performed in a fixed-bed quartz microreactor using as reactant molecules hexane, cyclohexane, and methylcyclopentane. Characterization of the samples by the different techniques allowed us to propose that the main factors controlling the observed properties are the high sulfur content and the promoter effect. Low surface areas of the catalysts were related to the high sulfur contents. Sulfate species in different coordinations were indentified : isolated sulfate groups, polynuclear sulfate species, and sulfuric acid. Lewis acid sites as well as the polynuclear sulfate species determined the acidity of these solids. The presence of promoters contributed not only to the increase of the redox behavior of the catalysts, but also to a decrease of the population of polynuclear sulfates, in the order Tl > In > Ga. In the reaction conditions adopted, on unpromoted catalysts and (especially) Ga-promoted catalysts, dehydroizomerization and ring isomerization were the principal reaction pathways for hexane and methylcyclopentane, and for cyclohexane, respectively. Tl was found to promote ring cleavage. These data are consistent with previous studies pointing to the dehydrogenation activity of Ga embedded in zeolite matrices. (C) 1998 Academic Press.

ZrO2-SO42- catalysts with different sulfur contents were analysed with thermal methods coupled with mass spectrometry after exposure to mixtures of hexane, methylcyclopentane, and cyclohexane in argon. The reaction of the hydrocarbons led to carbonaceous deposits, but an important part of hydrocarbon remained chemisorbed as well. Heating these samples in He atmosphere provoked the decomposition of these deposits with evolution of CO2 and CO, and also of SO2 and SO. At the same time, COS was evidenced in the reaction products. The release of these molecules occurred below the activation temperature of the catalysts. The behavior of the catalysts depended both on reactant molecule and sulfur content. The analyses clearly evidenced the oxidation ability of ZrO2-SO42- catalysts.

Bicomponent Cu-Sm-ZSM-5 zeolites with different Cu and Sm contents have been investigated, and compared with monocomponent Cu-ZSM-5 and Sm-ZSM-5. Sm-ZSM-5 is almost inactive in NO decomposition, producing only N2O. Zeolites containing around 0.20 wt% Sm and between 2.2 and 2.7 wt% Cu are substantially more active than the pure Cu-ZSM-5, the increase in NO transformation per total Cu atoms reaching 100%. The catalysts were studied using XPS, O-2-TPD and FT-LR of adsorbed NO. In addition, the transient period between the first contact of the catalyst with NO and 3 h was monitored. The bicomponent Cu-Sm-ZSM-5 catalysts exhibit a very strong O-2-TPD band around 370 degrees C compared to the monocomponent catalysts. FT-IR shows a strong increase of NO adsorption in the (NO)(2) form, and a corresponding decrease of the bands of isolated adsorbed NO. The presence of Sm does not significantly prevent the loss of Cu dispersion during a heat treatment in helium, nor the Cu++/Cu+ ratio. Although it is impossible to conclude unequivocally, it seems that samarium has two roles. It modifies the exchange of copper with the zeolite and, consequently, the dispersion and aggregation of copper. (C) 1998 Elsevier Science B.V.

Colloidal and polymeric sol-gel, an intermediate technique between the colloidal and the polymeric sol-gel and the clasical incipient wetness impregnation method were used to prepare a set of Co-Nb2O5/SiO2 catalysts with various characteristics. Modifications in the preparation procedure and its parameters have determined significant changes of the texture and the acidity of the support as well as of the Co metal particle size. Textural and structural characterization and catalytic data from butane hydrogenolysis were used to reveal the main differences among the catalysts obtained by the various techniques applied for preparation.

The effect of coexchanging of Cu-M-ZSM-5 zeolites (M = Ce, Sn, Sm) upon the interaction with nitric oxide was investigated by FT-IR. Spectra recorded on Cu-ZSM-5, in the presence of NO and at room temperature, exhibit typical features, very well reported in the literature. During NO decomposition at 673 K in the presence of 50 mbar NO, the band assigned to (NO)(delta+) species exhibits both a splitting and a shift. This behavior was attributed both to some modification in the copper(II) state during the reaction and to the formation of N2O3 species, active in NO decomposition. The presence of a second metal influences this process, and the intensity of the effect depends both on the chemical nature of the second metal and on its loading. It was also found that in the presence of Ce or Sm, the bands assigned to gem-dinitrosyl and to Cu+-NO as well as those of the N2O3 species are more intense. These effects were correlated with a more intense activity of Ce or Sm-promoted zeolites compared to pure Cu-ZSM-5. It is noteworthy that this increase occurs simultaneously with a diminution of the intensity of the nitrate-nitrite species bands.

Cobalt-niobia catalysts were prepared using different variants of the colloidal sol-gel technique and wetness impregnation. Characterization of these catalysts by XRD, FT-IR, XPS and TEM showed that phases structure as well as superficial composition depended on the preparation route. It was found that niobia exhibits a strong metal support interaction effect and this effect depends on the dimension of the metallic cobalt on the support surface. Reactivity of these catalysts was checked in n-butane hydrogenolysis, a well known structural sensitive reaction. The catalytic tests showed the influence of the catalysts features both on the reaction rate and selectivity.