02110nas a2200229   4500008004100000022001400041245012000055210006900175260007500244300001200319490000700331520122900338653001901567653002301586653002201609653003301631653002501664100001701689700002101706700002401727856012901751       2009                        eng d  a1571-101300aSolid acid catalysts: modification of acid sites and effect on activity and selectivity tuning in various reactions0 aSolid acid catalysts modification of acid sites and effect on ac  a233 SPRING ST, NEW YORK, NY 10013 USAbSPRINGER/PLENUM PUBLISHERScSEP  a205-2200 v133 a<p>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.</p>10aAcidity tuning10aCatalytic cleavage10aHydroxyalkylation10aIntramolecular rearrangement10asolid acid catalysts1 aRode, C., V.1 aGarade, Ajit, C.1 aChikate, Rajeev, C.  uhttps://library.ncl.res.in/content/solid-acid-catalysts-modification-acid-sites-and-effect-activity-and-selectivity-tuning-001904nas a2200265   4500008004100000022001400041245012400055210006900179260007300248300001200321490000700333520090600340653001901246653005301265653002201318653001701340653003801357100002101395700002301416700001701439700002501456700001801481700001701499856012201516       2010                        eng d  a0169-131700aAcidity tuning of montmorillonite K10 by impregnation with dodecatungstophosphoric acid and hydroxyalkylation of phenol0 aAcidity tuning of montmorillonite K10 by impregnation with dodec  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAR  a164-1700 v483 a<p>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.</p>10aAcidity tuning10aDodecatungstophosphoric acid/Montmorillonite K1010aHydroxyalkylation10aImpregnation10aTemperature programmed desorption1 aGarade, Ajit, C.1 aKshirsagar, V., S.1 aMane, R., B.1 aGhalwadkar, Ajay, A.1 aJoshi, U., D.1 aRode, C., V.  uhttps://library.ncl.res.in/content/acidity-tuning-montmorillonite-k10-impregnation-dodecatungstophosphoric-acid-and-0