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Abstract: Vanadium-substituted ordered mesoporous silicates (V-OMS) were synthesized hydrothermally using two common silica sources, viz. fumed silica and tetraethyl orthosilicate, and their surface properties and catalytic activities were evaluated in the liquid phase oxidation of 1-napthol using aqueous H2O2 as an oxidant. The catalysts were characterized by XRD, N 2 adsorption–desorption, DRUV–vis and TPR to evaluate the mesostructural ordering and the local environment of vanadium in the MCM-41 matrix. Characterization data of the fresh calcined catalysts reveal a more ordered hexagonal structure for the V-MCM-41 catalyst prepared by using tetraethyl orthosilicate as the silica source while spent catalyst showed that the material is less stable than the V-MCM-41 catalyst prepared by using fumed silica as the silica source. Further, the observed differences in the selectivity behavior of extracted and calcined forms of both vanadium catalysts shows that the treatment conditions had a decisive role in the formation of extra framework metal species and further in the mesoscopic structural ordering. [Copyright &y& Elsevier]

Abstract: A simple wet-impregnation method and controlled calcination process was used for preparing nano-sized silicotungstic acid (STA) supported on zirconia embedded inside the various mesoporous silicas such as SBA-15, MCM-41 and MCM-48. Catalysts with different (%) STA loadings were also synthesized and characterized by XRD, N2 adsorption–desorption, TEM, 29Si-MAS NMR, FT-Raman spectroscopic techniques. The acidic behavior of the catalysts was studied by TPD of ammonia and FT-IR pyridine adsorption technique. The effect of calcination temperature on the textural parameters of the catalysts and the integrity of STA on the surface of the catalyst were also examined. Moreover, the performance of these catalysts was investigated in the esterification of isoamyl alcohol (IAA) with acetic acid (AA). Catalytic activities were correlated with the acidity of the catalysts. Effects of reaction parameters such as mole ratio of reactants, reaction temperature, catalyst concentration and reusability of the catalyst were studied to get higher substrate conversions and product selectivities. Among the catalysts, 15wt.% STA/22.4wt.% ZrO2/SBA-15 calcined at 1123K was found to be the most active and acidic catalyst, showing higher conversion and selectivity than neat 15wt.% STA/ZrO2 in esterification of IAA by AA. The reaction was found to be heterogeneously catalyzed and no contribution from homogeneous (leached) STA into the medium under the reaction conditions was observed. [Copyright &y& Elsevier]

Abstract: The alkylation of phenol with tert-butanol was investigated using zirconia modified with silicotungstic acid (STA) as catalysts. The catalysts with different STA loading (5–25wt.% calcined at 750°C) and calcination temperature (15wt.% calcined from 350 to 850°C) were prepared and characterized by X-ray diffraction and NH3-TPD measurements. The XRD results indicate that STA stabilizes the tetragonal phase of zirconia. The catalyst with 15% STA on ZrO2 calcined at 750°C shows the highest acidity and hence highest activity. Under the reaction conditions of 140°C, tert-butanol/phenol molar ratio of 2 and LHSV of 4h−1, phenol conversion was 95.4% with selectivity to 2-tert-butyl phenol 4.3%, 4-tert-butyl phenol 59.2% and 2,4-di-tert-butyl phenol 35.8%. The reaction was studied as a function of time for 50h without appreciable change in phenol conversion and product selectivity. The deactivated catalyst could be regenerated by calcination with out appreciable lose in catalytic activity and product selectivity. [Copyright &y& Elsevier]

Abstract: A series of vanadia-alumina catalysts with different vanadia contents were prepared by a wet impregnation method. The influence of the local structure of vanadia in these catalysts on the oxidative dehydrogenation of ethylbenzene with nitrous oxide was investigated. The use of N2O as a co-feed remarkably enhanced the styrene yield compared with the use of N2. Characterization of these vanadia catalysts by XRD, FTIR, UV–vis, TPR, XPS, and 51V NMR techniques suggests that the nature of the VO x species depends on the vanadia loading; the predominant species are monomeric vanadia at lower loadings, two-dimensional polyvanadates at intermediate loadings, and bulk-like V2O5 and AlVO4 at higher loadings. The rate of oxidative dehydrogenation (ODH) of ethylbenzene per vanadium atom increases with vanadia loading and reaches a maximum at 10 wt%, the loading at which the surface predominantly contains polyvanadate species. The observed variation in the selectivity of products with vanadium loading indicates that the monomeric V5+ species favors dehydrogenation, whereas bulk-like V2O5 preferentially participates in the dealkylation of ethylbenzene. The vanadium species remains at a higher oxidation state in the presence of N2O, leading to a higher styrene yield, than in a N2 atmosphere. The ODH turnover rates increased with decreasing energy of the absorption edge in the UV–vis spectrum, at low VO x coverages of less than one monolayer on the Al2O3 surface. [Copyright &y& Elsevier]

Abstract: The liquid-phase acylation of veratrole with acetic anhydride and alkylation of toluene with 1-dodecene were carried out over WO x /ZrO2 solid acid catalysts. The catalysts were prepared by wet impregnation method using zirconium oxyhydroxide and ammonium metatungstate. Catalysts with different WO3 loading (5–30wt.%) were prepared and calcined at 800°C and catalyst with 15% WO3 was calcined from 650 to 850°C. All the catalysts were characterized by nitrogen adsorption, XRD and NH3-TPD. The catalyst with 15% WO3 calcined at 800°C (15 WZ-800) was found to be the most active in acylation and alkylation reactions. The effect of temperature, molar ratio and catalyst weight on the conversions of acetic anhydride and dodecene were studied in detail. The catalyst 15 WZ-800 gave 67% acetic anhydride conversion in veratrole acylation under the reaction conditions of 70°C, veratrole/acetic anhydride molar ratio 2, time 4h and 99% dodecene conversion with >99% monododecyl toluene selectivity at 100°C, toluene/1-dodecene molar ratio 10 and time 1h. [Copyright &y& Elsevier]

The synthesis of Ce–MCM-41, Al–MCM-41 and Ce–Al–MCM-41-type mesoporous materials was carried out hydrothermally by refluxing the gel with magnetic stirring under atmospheric pressure for 24–36h. The samples were characterized thoroughly in order to obtain the structural and textural properties, which reveal the presence of well-ordered M41S-type materials. The Ce–MCM-41 samples were used for catalytic acylation of alcohols, thiols, phenols and amines show good activity and selectivity including high chemoselectivity towards selective monofunctional acylation of bifunctional compounds. Quite importantly the acylation of bulky molecules such as cholesterol, ergesterol and β-sitosterol could be achieved using Ce–MCM-41 as solid catalyst. The presence of Ce along with Al in Ce–Al–MCM-41 was found to have synergistic effect as Ce–Al–MCM-41samples were more active catalysts for alkylation of naphthalene compared to either Ce–MCM-41 or Al–MCM-41 with comparable Si/Al or Si/Ce molar ratio. [Copyright &y& Elsevier]

The protonic forms of zeolite beta (H/β) with different crystallinities were obtained by postsynthesis modification of phases that were obtained by varying crystallization periods during progressive crystallization from a (TEA)2O–Na2O–SiO2–Al2O3–H2O system at 413 K. These catalytic materials were characterized using powder X-ray diffraction, 27Al MAS NMR, nitrogen adsorption, temperature-programmed ammonia desorption (TPAD), sorption of benzene probe molecules, and chemical composition. Evaluation of the catalysts for isopropylation of benzene reaction using isopropanol as alkylating agent was carried out in a continuous, down–flow, fixed-bed reactor at 483 K, liquid hour space velocity (LHSV) of 2.5 h-1, and feed (isopropanol: benzene) molar ratios ranging from 1:6.5 to 4:6.5. The effect of time on stream on the benzene conversion and cumene selectivity was also studied. The pore volume accessible to benzene in catalyst was found to provide a more realistic measure for screening the catalyst as compared to percentage XRD crystallinity. A catalyst, which is XRD amorphous in nature, has exhibited nearly 27% benzene conversion and 48% cumene selectivity when compared with fully crystalline catalyst. Cumene selectivity was found to increase with increase in time on stream when the feed used contained a IPA/benzene molar ratio below 0.31. The number of strong Brönsted acid sites was found to increase with the increase in the crystallinity up to 85% XRD crystallinity. Above 85% XRD crystallinity, no considerable improvement was observed in catalyst activity as far as benzene conversion and cumene selectivity are concerned. [Copyright &y& Elsevier]

ZSM-5 type of zeolite was synthesized using two different techniques, first by conventional hydrothermal (C-H) method and another by exposing the hydrogel to microwave radiation followed by C-H method. In the case of microwave treated gel the crystallization period is reduced substantially (nearly half) to that of crystallization period by C-H method. ZSM-5 zeolites synthesized by these two methods have been characterized by different characterization techniques like X-ray diffraction, IR, TG/DTA, sorption and MASNMR. By both the techniques the ZSM-5 synthesized was similar in all the respects however; the M-T synthesis technique is time saving. [Copyright &y& Elsevier]

Cu-ZSM-5 and Cu-AlTS-1 catalysts were prepared by solid state ion exchange and studied in DeNOx reactions. A NO3 type surface complex was found to be an active intermediate in the decomposition of NO and N2O. Copper was oxidized to Cu2+ in the decomposition reactions. Oscillations at full N2O conversion were observed in the gas phase O2 concentration, without any change in the N2 concentration. The oscillation was synchronized by gas phase NO formed from the NO3 complex. The same complex seems to be an active intermediate also in NO selective catalytic reduction (SCR) by methane, whereas carbonaceous deposits play a role in NO SCR by propane. TPD reveals that only 10–20% of the total copper in the zeolites participates in the catalytic cycles. [Copyright &y& Elsevier]