@article { ISI:000262658000018, title = {Montmorillonite for selective hydroxyalkylation of p-cresol}, journal = {Applied Clay Science}, volume = {43}, number = {1}, year = {2009}, month = {JAN}, pages = {113-117}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Performances of montmorillonite titanium silicate (TS-1) and dodecatungstophosphoric acid (DTP) were compared for the hydroxyalkylation of p-cresol into dihydroxydiarylmethane (DAM). Ammonia TPD studies of various catalysts showed that an appropriate combination of both strong and weak acid sites of montmorillonite was mainly responsible rather than only the stronger acidity of bulk DTP for its highest catalytic activity for selective hydroxyalkylation of p-cresol to DAM. The selectivity to DAM could be enhanced by adjusting reaction conditions like mole ratio of p-cresol to formaldehyde, reaction temperature, catalyst concentration, solvent and reaction time. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Ammonia TPD, Dihydroxydiarylmethane, Hydroxyalkylation, Montmorillonite, Solid acids}, issn = {0169-1317}, doi = {10.1016/j.clay.2008.07.015}, author = {Garade, Ajit C. and Mate, Vivek R. and Rode, C. V.} } @article { ISI:000263491600023, title = {Selective hydroxyalkylation of phenol to bisphenol F over dodecatungstophosphoric acid (DTP) impregnated on fumed silica}, journal = {Applied Catalysis A-General}, volume = {354}, number = {1-2}, year = {2009}, month = {FEB}, pages = {176-182}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The catalyst activity of various solid acids, such as fumed Silica (SiO(2)) dodecatungstophosphoric acid (DTP), DTP impregnated on SiO(2), amberlyst-15 and montmorillonite KSF/0, was studied for the hydroxyalkylation of phenol to bisphenol F. A well-dispersed DTP on SiO2 catalyst was prepared by the wet impregnation method. The effect of DTP loading on SiO(2) was also compared with bulk DTP and other solid acid catalysts. 20\% DTP/SiO(2) catalyst gave the highest products yield of 34.2\% and selectivity of 90.1\% to bisphenol F, at 353 K and with a phenol-to-formaldehyde mole ratio of 5:1. Ammonia TPD studies of various catalysts showed that an appropriate combination of both strong and weak acid sites of DTP/SiO(2) Was mainly responsible, rather than only the stronger acidity of bulk DTP, for its highest catalytic activity and selectivity. The effect of various reaction parameters like mole ratio, catalyst concentration, temperature and reaction time on product yield and bisphenol F selectivity was also investigated. The catalyst recycle was established by catalyst activity testing. (C) 2008 Elsevier B.V. All rights reserved.

}, keywords = {Bisphenol F, Hydroxyalkylation, NH(3)-TPD, Reaction pathways, solid acid catalysts}, issn = {0926-860X}, doi = {10.1016/j.apcata.2008.11.025}, author = {Garade, Ajit C. and Kshirsagar, V. S. and Rode, C. V.} } @article { ISI:000270338700005, title = {Solid acid catalysts: modification of acid sites and effect on activity and selectivity tuning in various reactions}, journal = {Catalysis Surveys from Asia}, volume = {13}, number = {3}, year = {2009}, month = {SEP}, pages = {205-220}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The effects of acidity and variation in concentration of acid sites of dodecatungstophosphoric acid (DTP), supported DTP and montmorillonite-K catalysts were studied for various organic reactions such as the hydroxyalkylation of phenols to bisphenols, intramolecular rearrangement of benzyl phenyl ether (BPE) to 2-benzyl phenol (2-BP) and selective cleavage of tert-butyldimethylsilyl (TBDMS) ether into the corresponding alcohol. Both dodecatungstophosphoric acid (DTP) impregnated on silica (SiO(2)) and montmorillonite catalysts showed the highest catalyst activity with 90-95\% selectivity to bisphenol for the hydroxyalkylation of phenols to give bisphenol. Temperature Programmed Desorption (TPD) of ammonia and activity results of various catalysts showed that an appropriate combination of both strong and weak acidic sites in the catalyst was highly desirable for high bisphenol selectivity. A 10\% DTP/SiO(2) catalyst was found to be highly selective for the cleavage of TBDMS ether into the corresponding alcohol at room temperature giving a high TON of 9.5 x 10(5) even after the 4th recycle. DTP was also found to be a promising solid acid catalyst for the intramolecular rearrangement of BPE giving 2-BP.

}, keywords = {Acidity tuning, Catalytic cleavage, Hydroxyalkylation, Intramolecular rearrangement, solid acid catalysts}, issn = {1571-1013}, doi = {10.1007/s10563-009-9078-4}, author = {Rode, C. V. and Garade, Ajit C. and Chikate, Rajeev C.} } @article { ISI:000276010700025, title = {Acidity tuning of montmorillonite K10 by impregnation with dodecatungstophosphoric acid and hydroxyalkylation of phenol}, journal = {Applied Clay Science}, volume = {48}, number = {1-2, SI}, year = {2010}, month = {MAR}, pages = {164-170}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Acidity tuning of montmorillonite K10 (mont K10) was achieved by impregnating with dodecatungstophosphoric acid (DTP). The effect on the hydroxyalkylation of phenol was studied at 353 K with phenol to formaldehyde molar ratio of 5. The nature and strength of acid sites were determined by NH(3)-TPD measurement while the distribution of Brensted and Lewis acid sites expressed as B/L ratio, was determined by pyridine IR technique. Among various loadings of DTP (5-60\%) studied for the hydroxyalkylation of phenol, 20\% DTP/mont K10 showed the highest catalyst activity (90\% selectivity to bisphenol F with 28\% conversion of phenol). Both total concentration of acid sites and the distribution of acid sites in a high temperature region were required for the high bisphenol F selectivity. Our catalyst (20\% DTP/Mont K10) could be recycled three times. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Acidity tuning, Dodecatungstophosphoric acid/Montmorillonite K10, Hydroxyalkylation, Impregnation, Temperature programmed desorption}, issn = {0169-1317}, doi = {10.1016/j.clay.2009.11.042}, author = {Garade, Ajit C. and Kshirsagar, V. S. and Mane, R. B. and Ghalwadkar, Ajay A. and Joshi, U. D. and Rode, C. V.} } @article { ISI:000279333000002, title = {Structure-activity studies of dodecatungstophosphoric acid impregnated bentonite clay catalyst in hydroxyalkylation of p-cresol}, journal = {Catalysis Communications}, volume = {11}, number = {11}, year = {2010}, month = {JUN}, pages = {942-945}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Bentonite clay impregnated with dodecatungstophosphoric acid (20\% DTP/BNT) showed an excellent activity, selectivity and stability [95\% product yield with 94\% selectivity to 2, 2{\textquoteright}-methylenebis (4-methylphenol), DAM] for the hydroxyalkylation of p-cresol with formaldehyde at 353 K and for a mole ratio of 5. Ammonia-TPD results showed that an increase in total concentration of acid sites from 4.9 of parent bentonite to 11.6 micromoles per surface area NH(3) (mu molS(-1) NH(3)) of 20\% DTP/BNT was due to a strong interaction of protons of bulk DTP with surface hydroxyl groups of BNT as evidenced by (31)P NMR studies. (C) 2010 Elsevier B.V. All rights reserved.

}, keywords = {(31)P CPMAS NMR, Bentonite, Hydroxyalkylation, p-Cresol, surface modification}, issn = {1566-7367}, doi = {10.1016/j.catcom.2010.04.008}, author = {Garade, Ajit C. and Kshirsagar, V. S. and Jha, Ajay and Rode, C. V.} } @article { ISI:000328665300008, title = {Effect of SnO2/Al2O3 ratio of Si-based MFI on its acidity and hydrophobicity: application in selective hydroxyalkylation of p-cresol}, journal = {Catalysis Communications}, volume = {44}, number = {SI}, year = {2014}, month = {JAN}, pages = {29-34}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Silica based MR type molecular sieves with various SnO2/Al2O3 ratios were synthesized from gels having molar compositions SiO2:xSnO(2):yAl(2)O(3):0.23(TPA)(2)O:35H(2)O where 0 \<= x \<= 0.02 and 0 \<= y \<= 0.01. Recyclable, Al-free Sn-MFI catalyst showed 31\% conversion of formaldehyde with 100\% selectivity to 2,2{\textquoteright}-methylenebis(4-methylphenol) in hydroxyalkylation of p-cresol with formaldehyde on account of moderate acidity and higher hydrophobicity. (C) 2013 Elsevier B.A. All rights reserved.

}, keywords = {Al-27 MAS NMR, Hydroxyalkylation, Molecular sieves, p-Cresol, Stannosilicate}, issn = {1566-7367}, doi = {10.1016/j.catcom.2013.08.002}, author = {Garade, Ajit C. and Malwadkar, A. V. and Niphadkar, P. S. and Jha, Ratnesh Kumar and Joshi, P. N. and Rode, C. V.} }