02440nas a2200253 4500008004100000022001400041245010300055210006900158260007300227300000900300490000800309520155700317653001401874653001501888653001201903653001801915653002501933653002401958653001401982653001301996100002202009700002802031856012702059 2006 eng d a1381-116900aEffect of calcination temperature on the catalytic activity of zirconia-supported heteropoly acids0 aEffect of calcination temperature on the catalytic activity of z aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL a8-150 v2533 a

Zirconia-supported silicotungstic acid (15% STA) catalyst with different calcination temperatures (600-850 degrees C) was prepared by suspending zirconium oxyhydroxide in methanol solution of STA followed by drying and calcination. These catalysts were characterized by XRD, FTIR pyridine adsorption and DRUV-vis spectroscopy. The catalysts showed both Bronsted as well as Lewis acidity and 15% STA on zirconia calcined at 750 degrees C (15 SZ-750) had the highest Bronsted acidity. Characterization of 15 SZ-750 catalyst by Raman spectroscopy showed the presence of zirconia-anchored mono-oxotungstate as the major tungsten species present in this catalyst. These catalysts were used in benzoylation of veratrole with benzoic anhydride and 15 SZ-750 catalyst showed the highest activity. For catalyst with support calcined at different temperatures before HPA impregnation, catalytic activity decreases as the support calcination temperature increases due to the decrease in Bronsted acidity. Comparison of the catalytic activity of 15 SZ-750 with that of zirconia-supported phosphotungstic acid (15%, calcined at 750 degrees C, 15 PZ-750) in benzoylation of veratrole with benzoic anhydride, acylation of anisole with acetic anhydride and in alkylation of diphenylether with 1-dodecene showed that 15 SZ-750 catalyst has higher activity and deactivation resistance due to its higher Bronsted acidity. The deactivated catalyst could be regenerated by calcination without appreciable loss in activity. (c) 2006 Elsevier B.V. All rights reserved.

10aAcylation10aAlkylation10aAnisole10adiphenylether10aPhosphotungstic acid10aSilicotungstic acid10averatrole10aZirconia1 aDevassy, Biju, M.1 aHalligudi, Shivaraj, B. uhttps://library.ncl.res.in/content/effect-calcination-temperature-catalytic-activity-zirconia-supported-heteropoly-acids-001722nas a2200229 4500008004100000022001400041245014100055210006900196260007300265300001200338490000800350520085900358653001601217653001101233653001301244653001401257653002101271100002601292700002101318700002801339856012501367 2007 eng d a1387-181100aEffect of pretreatment conditions on the catalytic activity of nano-sized TPA/ZrO2 dispersed in SBA-15 channels in acetylation reactions0 aEffect of pretreatment conditions on the catalytic activity of n aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAY a223-2330 v1023 a

Acetylation of an aromatic compounds such as veratrole (1,2-dimethoxybenzene), anisole, thioanisole, isobutyl benzene and 2-methoxynaphthalene with acetic anhydride has been investigated over a nano-sized 12-tungstophosphoric acid (TPA)/22.4 wt.%ZrO2/SBA- 15 catalysts in the liquid phase conditions. Catalysts with different (%) TPA and zirconia loadings calcined at different temperatures were prepared by wet-impregnation and characterized by XRD, N-2 adsorption-desorption, FT-Rarnan, X-ray photoelectron spectroscopy (XPS). The acidic behavior of the catalyst was studied by TPD of ammonia and FT-IR pyridine adsorption. Among the catalysts, 15 wt.%TPA/22.4 wt.%ZrO2/SBA- 15 calcined at 1123 K had the highest acidity and was the most active catalyst in veratrole acetylation with acetic anhydride. (C) 2007 Elsevier Inc. All rights reserved.

10aacetylation10aSBA-1510aTPA/ZrO210averatrole10awet-impregnation1 aSawant, Dhanashri, P.1 aHartmann, Martin1 aHalligudi, Shivaraj, B. uhttps://library.ncl.res.in/content/effect-pretreatment-conditions-catalytic-activity-nano-sized-tpazro2-dispersed-sba-1502330nas a2200277 4500008004100000022001400041245013000055210006900185260009500254300001100349490000800360520129000368653001001658653003501668653001901703653002001722653001801742653002901760653002301789653002801812100001701840700001901857700001701876700002801893856013101921 2008 eng d a0021-951700aEnantioselective hydrogenation of olefins by chiral iridium phosphorothioite complex covalently anchored on mesoporous silica0 aEnantioselective hydrogenation of olefins by chiral iridium phos a525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USAbACADEMIC PRESS INC ELSEVIER SCIENCEcFEB a91-1000 v2543 a

Chiral monodentate phosphorous-based ligands have proven effective for the enantioselective hydrogenation of olefins. Binol-derived monodentate phosphorothioite (PS) ligand was synthesized from binol and thiopropyltriethoxysilane, and its iridium complex was covalently anchored to mesoporous silica supports like SBA-15, MCM-41, and MCM-48. These catalysts were characterized by different physicochemical techniques and assessed for their catalytic performances in the heterogeneous asymmetric hydrogenation of itaconic acid and its derivatives. It was found that the catalytic activities and enantioselectivities of the heterogenized iridium complex (IrPSSBA-15) in the hydrogenation reactions were comparable to its homogeneous analogue. Binol-derived monodentate phosphorothioite ligand in heterogeneously anchored form (iridium complex) is a more effective catalyst than the reported monodentate phosphorous ligand systems in the hydrogenation reactions, possibly due to the changes in electronic properties around the iridium metal center. The effects of substrate-to-catalyst molar ratio, solvents, and temperature on substrate conversions and enantioselectivities, of the products were investigated in hydrogenation reactions. (c) 2007 Elsevier Inc. All rights reserved.

10abinol10aEnantioselective hydrogenation10aImmobilization10airidium complex10aitaconic acid10aMesoporous silica SBA-1510amonodentate ligand10aphosphorothioite ligand1 aSahoo, Suman1 aKumar, Pradeep1 aLefebvre, F.1 aHalligudi, Shivaraj, B. uhttps://library.ncl.res.in/content/enantioselective-hydrogenation-olefins-chiral-iridium-phosphorothioite-complex-covalently-0