@article { ISI:000240365800049, title = {Heteropoly acid supported on titania as solid acid catalyst in alkylation of p-cresol with tert-butanol}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {256}, number = {1-2}, year = {2006}, month = {AUG}, pages = {324-334}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Butylation of p-cresol with tert-butanol was investigated on titania modified with 12-tungstophosphoric acid (TPA/TiO2) catalyst under vapor phase conditions. Catalysts with different TPA loadings (10-25 wt.\%) and calcination temperatures (650-750 degrees C) were prepared by suspending titanium hydroxide in methanol solution of TPA followed by drying and calcination. These catalysts were characterized by surface area, XRD, P-31 MAS NMR, XPS, NH3-TPD, and FTIR pyridine adsorption. XRD results indicated that the presence of TPA retarded the crystallization of titania and stabilized TiO2 in anatase phase. P-31 MAS NMR indicated the presence of TPA in various forms (dispersed, highly fragmented and Keggin intact). These catalysts showed both Bronsted and Lewis acidity, and 20\% TPA on TiO2 calcined at 700 degrees C (from here after words 20\% TT 700) had the highest Bronsted as well as total acidity. Further, the catalytic activities were examined in tert-butylation of p-cresol with tent-butanol. The catalytic activity depended on TPA coverage, and the highest activity corresponded to the monolayer of TPA on titania. The most active catalyst 20\% TT-700 gave 82\% conversion of p-cresol and 89.5\% selectivity towards 2-tert-butyl cresol (TBC), 2,6-di-tert-butyl cresol (DTBC) 7.5\% and cresol-tert-butyl ether (CTBE) 3\% under optimized conditions. The activity was always higher than that of WO3/ZrO2, sulfated zirconia (SZ), USY, H-beta zeolites and montmorillonite K-10 (K-10mont) under similar conditions. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {2, 2-tert-butyl-p-cresol, 6-di-tert-butyl-p-cresol, Alkylation, heteropoly acid, p-Cresol, tert-butanol, titania}, issn = {1381-1169}, doi = {10.1016/j.molcata.2006.05.024}, author = {Kumbar, Suresh M. and Shanbhag, G. V. and Lefebvre, F. and Halligudi, Shivaraj B.} } @article { ISI:000245961800012, title = {Tungstophosphoric acid supported on titania: a solid acid catalyst in benzylation of phenol with benzylalcohol}, journal = {Catalysis Communictions}, volume = {8}, number = {5}, year = {2007}, month = {MAY}, pages = {800-806}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

{Benzylation of phenol with benzylalcohol was carried out in liquid phase over tungstophosphoric acid (TPA) supported on titania. The catalysts were prepared with different TPA (10-25\%) loading by wet impregnation method, were calcined at 700 degrees C and characterized by XRD, surface area, FTIR and acidity of the catalysts was measured by temperature programmed desorption of NH(3)-TPD, FTIR pyridine adsorption. The catalysts have been represented by a general formula as xPTiO(2)-Y (where x = wt\%

}, keywords = {benzyl ether, benzyl phenol, benzylalcohol, Heteropolyacid, phenyl benzyl ether, titania, tungstophosphoric acid}, issn = {1566-7367}, doi = {10.1016/j.catcom.2006.08.027}, author = {Kumbar, Suresh M. and Halligudi, Shivaraj B.} } @article { ISI:000253450900068, title = {Alkene epoxidation catalyzed by vanadomolybdophosphoric acids supported on hydrated titania}, journal = {Catalysis Communications}, volume = {9}, number = {5}, year = {2008}, month = {MAR}, pages = {931-938}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Vanadomolybdophosphoric acids wet-impregnated oil hydrated titania (TiO(2) - xH(2)O), make ail efficient catalytic system for the epoxidation of a variety of alkenes with organic solvent extracted TBHP as the oxidant. By,in appropriate choice of solvent, the catalyst call be reused at least three times without much loss in the activity for subsequent runs. XRD shows that the heteropoly acid is uniformly dispersed over the support and up to 15 wt\% loading of the heteropoly acid, no additional peak of the same call be seen in the XRD pattern of the catalyst. The reactivity varied with the nature of alkene but the major product was always the corresponding epoxide. The catalytic system is free of high temperature calcination steps and tedious multi-step procedures, normally encountered in the heter-ogenization of heteropoly acids. (c) 2007 Elsevier B.V. All rights reserved.

}, keywords = {alkenes, epoxidation, heteropoly acids, TBHP, titania, vanadomolybdophosphoric acids}, issn = {1566-7367}, doi = {10.1016/j.catcom.2007.09.022}, author = {Ingle, Rohit H. and Vinu, A. and Halligudi, Shivaraj B.} } @article { ISI:000257016800018, title = {Titania supported silicotungstic acid: an efficient solid acid catalyst for veratrole acylation}, journal = {Catalysis Communications}, volume = {9}, number = {10}, year = {2008}, month = {JUN}, pages = {2026-2029}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Titania supported silicotungstic acid (STA) with different STA loading (10-25 wt\%) and calcination temperature (650-750 degrees C) were prepared by wet impregnation method. The catalysts have been represented by a general formula xSTiO(2)y (where x denotes wt\%, S denotes STA and y denotes calcination temperature in degrees C). These catalysts were characterized by techniques such as X-ray diffraction, surface analysis, FTIR-pyridine and TPD-NH(3) and were used as heterogeneous solid acid catalysts in the liquid phase acylation of veratrole with acetic anhydride (Ac(2)O). It was found that 20STiO(2)700 gave the highest activity in acylation reaction due to its highest acidity. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {acetic anhydride, Acylation, Silicotungstic acid, titania, veratrole}, issn = {1566-7367}, doi = {10.1016/j.catcom.2008.03.043}, author = {Waghmare, Nilesh G. and Kasinathan, Palraj and Amrute, Amol P. and Lucas, Nishita and Halligudi, Shivaraj B.} }