02005nas a2200253   4500008004100000022001400041245009000055210006900145260007300214300001200287490000800299520111400307653001101421653002401432653002001456653001301476100002201489700002101511700002601532700002201558700002601580700002801606856011701634       2005                        eng d  a1381-116900aSilicotungstate-modified zirconia as an efficient catalyst for phenol tert-butylation0 aSilicotungstatemodified zirconia as an efficient catalyst for ph  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAY  a141-1460 v2333 a<p>The alkylation of phenol with tert-butanol was investigated using zirconia modified with silicotungstic acid (STA) as catalysts. The catalysts with different STA loading (5-25 wt.% calcined at 750 degrees C) and calcination temperature (15 wt.% calcined from 350 to 850 degrees C) were prepared and characterized by X-ray diffraction and NH3-TPD measurements. The XRD results indicate that STA stabilizes the tetragonal phase of zirconia. The catalyst with 15% STA on ZrO2 calcined at 750 degrees C shows the highest acidity and hence highest activity. Under the reaction conditions of 140 degrees C, tert-butanol/phenol molar ratio of 2 and LHSV of 4 h(-1), phenol conversion was 95.4% with selectivity to 2-tert-butyl phenol 4.3%, 4-tert-butyl phenol 59.2% and 2,4-di-tert-butyl phenol 35.8%. The reaction was studied as a function of time for 50 It without appreciable change in phenol conversion and product selectivity. The deactivated catalyst could be regenerated by calcination with out appreciable lose in catalytic activity and product selectivity. (c) 2005 Elsevier B.V. All rights reserved.</p>10aphenol10aSilicotungstic acid10atert-butylation10aZirconia1 aDevassy, Biju, M.1 aShanbhag, G., V.1 aMirajkar, Subhash, P.1 aBohringer, Walter1 aFletcher, Jack, C. Q.1 aHalligudi, Shivaraj, B.  uhttps://library.ncl.res.in/content/silicotungstate-modified-zirconia-efficient-catalyst-phenol-tert-butylation-002031nas a2200217   4500008004100000022001400041245006700055210006400122260007300186300001000259490000800269520130600277653001301583653002001596653001901616653001301635100001501648700002201663700002801685856010001713       2005                        eng d  a1381-116900atert-Butylation of p-cresol over WOx/ZrO2 solid acid catalysts0 atertButylation of pcresol over WOxZrO2 solid acid catalysts  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJUL  a44-510 v2353 a<p>The tert-butylation of p-cresol with tert-butanol was carried out over WO3/ZrO2 catalysts under flow conditions, The catalysts were prepared by wet impregnation method using zirconium oxyhydroxide and ammonium metatungstate. Catalysts with different WO3 loading (5-30 wt.%) were prepared and calcined at 800 degrees C and catalyst with 15% WO,, was calcined from 600 to 900 C. The catalysts were characterized by surface area, XRD, FTIR and TEM. The catalyst 15% WO3/ZrO2 calcined at 800 degrees C found to be the most active in the reaction. The effect of temperature, space velocity and molar ratio of the reactants on the conversion of p-cresol and products selectivities were studied. Under the optimized reaction conditions of 130 degrees C, tert-butanol/p-cresol molar ratio of 3 and flow rate of 10 ml h(-1). p-cresol conversion was 69.8% with selectivity to 2-tert-butyl-p-cresol 92.4%, 2,6-di-tert-butyl-p-cresol 6.3% and p-cresol tert-butyl ether 1.3%. The catalytic activity is compared with sulfated zirconia, USY, H beta zeolites and montmorillonite K-10 under the optimized reaction conditions The activity of sulfated zirconia is lower than that of 15% WO3/ZrO2 catalyst calcined at 800 C and other catalysts showed very low activity, (c) 2005 Elsevier B.V.. All rights reserved.</p>10ap-Cresol10atert-butylation10atungsten oxide10aZirconia1 aSarish, S.1 aDevassy, Biju, M.1 aHalligudi, Shivaraj, B.  uhttps://library.ncl.res.in/content/tert-butylation-p-cresol-over-woxzro2-solid-acid-catalysts-002264nas a2200217   4500008004100000022001400041245008600055210006900141260007300210300001200283490000800295520148700303653003001790653001101820653002001831653001301851100002201864700001901886700002001905856012101925       2006                        eng d  a1381-116900aPhenol tert-butylation over zirconia-supported 12-molybdophosphoric acid catalyst0 aPhenol tertbutylation over zirconiasupported 12molybdophosphoric  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAR  a162-1700 v2473 a<p>The alkylation of phenol with tert-butanol was investigated using zirconia-supported 12-molybdophosphoric acid (MPA) as catalyst. The catalysts with different MPA loading (5-25 wt.% calcined at 700 degrees C) and calcination temperature (15 wt.% calcined from 500 to 750 degrees C) were prepared by suspending zirconium oxyhydroxide in methanol solution of MPA followed by drying and calcination. These catalysts were characterized by X-ray diffraction and (31)p MAS NMR spectroscopy measurements. The XRD results indicated that MPA stabilizes the tetragonal phase of zirconia. (31)p MAS NMR spectra showed the presence of three types of phosphorous species, phosphomolybdate in interaction with zirconia, decomposition product of MFPA and an unidentified species. IFTIR pyridine adsorption on 15% MPA catalyst calcined at different temperatures showed the presence of both Bronsted and Lewis acidity and the catalyst calcined at 700 degrees C showed the highest relative Bronsted acidity. Under the reaction conditions of 140 degrees C, tert-butanol/phenol molar ratio of 2 and LHSV of 4 h(-1), the phenol conversion was 80.6% at 2 h (selectivity to 2-TBP 11.5%, 2,4-DTBP 55.2%, and 4-TBP 25.7%), which decreased slowly with time and at 31 h, it was 58.5% (selectivity to 2-TBP 15.2%, 2,4-DTBP 41.6%, and 4-TBP 38.4%). The major reason for the catalyst deactivation was the reduction and leaching of MPA from the catalyst surface. (c) 2005 Elsevier B.V. All rights reserved.</p>10a12-molybdophosphoric acid10aphenol10atert-butylation10aZirconia1 aDevassy, Biju, M.1 aShanbhag, G.V.1 aHalligudi, S.B.  uhttps://library.ncl.res.in/content/phenol-tert-butylation-over-zirconia-supported-12-molybdophosphoric-acid-catalyst