@article { ISI:000311698800036, title = {One-pot sol-gel preparation for efficient cobalt-molybdenum-titania hydrotreating catalysts}, journal = {Chemcatchem}, volume = {4}, number = {12}, year = {2012}, month = {DEC}, pages = {2112-2120}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

Titania-based hydrodesulfurization catalysts were prepared by using a one-pot solgel method with the titanium peroxo complex as titanium precursor and molybdenum and cobalt precursors dissolved in the aqueous hydrogen peroxide solution used during synthesis. Catalysts with MoO3 loadings varying from 5 to 40 wt?\% and a Co/Mo atomic ratio of 0.5 were prepared. Solids with molybdenum loadings below 20 wt?\% MoO3 demonstrated poor hydrodesulfurization activity for the model compound thiophene. This was attributed to the presence of a large amount of embedded cobalt and molybdenum species in the titania matrix. A significant increase in the catalytic activity was observed for solids containing 20 and 25 wt?\% of MoO3 on which active species appeared to be accessible on the titania surface. Furthermore, the highest conversion obtained on these solgel solids was superior to the highest conversion obtained on reference catalysts prepared through the impregnation of ammonium heptamolybdate and cobalt nitrate on commercial titania.

}, keywords = {cobalt, heterogeneous catalysis, Molybdenum, sol-gel process, titanium}, issn = {1867-3880}, doi = {10.1002/cctc.201200165}, author = {Nguyen, D. L. and Gillot, S. and Souza, D. O. and Blanchard, P. and Lamonier, Carole and Berrier, E. and Kotbagi, T. V. and Dongare, Mohan K. and Shubhangi B. Umbarkar and Cristol, S. and Payen, E. and Lancelot, Christine} } @article { ISI:000307308000020, title = {Transesterification of diethyl oxalate with phenol over sol-gel MoO3/TiO2 catalysts}, journal = {Chemsuschem}, volume = {5}, number = {8}, year = {2012}, month = {JUL}, pages = {1467-1473}, publisher = {WILEY-V C H VERLAG GMBH}, type = {Article}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

The transesterification of diethyl oxalate (DEO) with phenol to form diphenyl oxalate (DPO) has been carried out in the liquid phase over very efficient MoO3/TiO2 solid-acid solgel catalysts. A selectivity of 100?\% with a remarkable maximum yield of 88?\% were obtained, which opens the route to downstream phosgene-free processes for the synthesis of polycarbonates. Interpretation of the results of various acidity measurements (NH3 and pyridine desorption, methanol oxidation as a probe reaction) allowed us to identify the catalytic sites as Lewis acid sites.

}, keywords = {heterogeneous catalysis, Lewis acids, Oxidation, sol-gel processes, transesterification}, issn = {1864-5631}, doi = {10.1002/cssc.201100802}, author = {Kotbagi, Trupti and Duy Luan Nguyen and Lancelot, Christine and Lamonier, Carole and Thavornprasert, Kaew-Arpha and Zhu Wenli and Capron, Mickael and Jalowiecki-Duhamel, Louise and Shubhangi B. Umbarkar and Dongare, Mohan K. and Dumeignil, Franck} } @article { ISI:000319680800041, title = {Isolation, characterization, and identification of catalytically active species in the MoO3/SiO2 catalyst during solid acid catalyzed reactions}, journal = {Chemcatchem}, volume = {5}, number = {6}, year = {2013}, month = {JUN}, pages = {1531-1537}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

We report the isolation, characterization, and identification of the catalytically active species formed during various acid-catalyzed reactions if silica-supported MoO3 was used as a catalyst. We have reported previously the synthesis and extensive characterization of the silica-supported MoO3 catalyst prepared by the sol-gel process with ammonium heptamolybdate and ethyl silicate-40 as molybdenum and silica precursors, respectively. The TEM images showed uniformly distributed MoO3 nanoparticles on the high-surface area mesoporous silica support and high acidity (0.9mmolg-1) by using temperature-programmed desorption of ammonia (NH3-TPD) analysis. This catalyst has already shown high activity for various acid-catalyzed reactions. To understand the nature of catalytically active species formed during the reaction, the liquid-phase esterification of acetic acid and ethanol was studied as a probe reaction with very high acid conversion (83\%) in 8h. During esterification, the reaction mixture turned blue, which indicated a change in the nature of the catalyst under reaction conditions. These catalytically active species formed in the reaction mixture were isolated and extensively characterized by using FTIR, Raman, powder XRD, BET surface area, NH3-TPD, energy dispersive X-ray, and TEM analysis. The characterization results revealed the insitu formation of silicomolybdic acid on the silica surface in the presence of water, which acts as catalytically active species responsible for the acid-catalyzed reactions.

}, keywords = {esterification reactions, heterogeneous catalysis, Molybdenum, silicon, sol-gel processes}, issn = {1867-3880}, doi = {10.1002/cctc.201200662}, author = {Kotbagi, Trupti V. and Biradar, Ankush V. and Shubhangi B. Umbarkar and Dongare, Mohan K.} } @article { ISI:000365050700016, title = {Sol-gel synthesised WO3 nanoparticles supported on mesoporous silica for liquid phase nitration of aromatics}, journal = {Applied Catalysis B-Environmental}, volume = {182}, year = {2016}, month = {MAR}, pages = {142-152}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A series of WO3/SiO2 catalysts have been prepared by sol-gel method using ammonium metatungstate and ethyl silicate-40 (ES-40) as WO3 and SiO2 precursors respectively. The sol-gel method has led to the formation of WO3 nano-particles of 2-5 nm well dispersed on mesoporous silica along with some WO3{\textquoteright} agglomerates. Formation of monoclinic WO3 was seen on the catalysts above 5 wt\% WO3 loading by XRD analysis. Silica has shown very high surface area of 606 m(2)/g which decreased gradually upto 368 m(2)/g with 20 wt\% WO3 loading. 20 wt\% WO3/SiO2 catalyst has shown maximum acidity (0.56 mmol NH3/g) with presence of both Lewis and Bronsted acidity. UV-vis DRS analysis showed formation of polytungstate species along with WO3 on silica surface. The prepared catalysts were used for liquid phase nitration of aromatics using 70\% nitric acid as nitrating agent without using any sulfuric acid. Very high conversion (99\%) was obtained for p-cresol nitration with very high selectivity (99\%) for 2-nitro p-cresol. The water formed during the reaction was removed azeotropically using ethylene dichloride as solvent. In case of o-xylene 74\% conversion was obtained with 54\% selectivity for 4-nitro o-xylene. The effect of different WO3 precursors on nitration efficiency was studied using sodium tungstate and tungstic acid as precursors. However,ammonium metatungstate showed the highest acidity. Sodium tungstate showed formation of dimer of sodium tungstate which did not show any acidity and hence no activity for nitration. The mechanism for nitration using WO3/SiO2 has been proposed based on polarisation of water on tungsten centre generating Bronsted acidity which can further generate nitronium ion giving subsequently nitration of the aromatic ring. (C) 2015 Elsevier B.V. All rights reserved.

}, keywords = {Aromatic nitration, heterogeneous catalysis, Regioselective, Sol-gel synthesis, Water polarization}, issn = {0926-3373}, doi = {10.1016/j.apcatb.2015.09.020}, author = {Kulal, A. B. and Dongare, Mohan K. and Shubhangi B. Umbarkar} }