Novel Efficient Mesoporous Solid Acid Catalyst UDCaT-4:  Dehydration of 2-Propanol and Alkylation of Mesitylene

Abstract

A novel mesoporous solid acid catalyst named UDCaT-4 was synthesized by incorporating superacidic centers of persulfated alumina and zirconia into highly ordered and well-defined hexagonal mesoporous silica. The catalyst is well characterized, and its properties are compared with those of bulk persulfated alumina and zirconia (PAZ) by FTIR spectroscopy, X-ray diffraction, Brunauer-Emmett-Teller surface area, pore size analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and ammonia temperature-programmed desorption. UDCaT-4 is more acidic than PAZ. The dehydration processes of 2-propanol, diisopropyl ether, and n-propanol were studied independently including a mixture of n-propanol and 2-propanol to throw light on kinetics and mechanism. For alkylation of mesitylene with 2-propanol, UDCaT-4 exhibits superior catalytic activity in comparison with PAZ and also it shows remarkable stability toward coke formation. Kinetic interpretations of the observed rate data are presented for all reactions, and mechanistic models are developed. The results are novel.

Synthesis of carvacrol by Friedel–Crafts alkylation of o‐cresol with isopropanol using superacidic catalyst UDCaT‐5

“…Temperature programmed desorption (TPD) profiles of PAZ and UDCaT-4 show that although UDCaT-4 possesses both weak and medium acid sites, the total acid sites of UDCaT-4 (0.56 mmol g −1 ) are greater than those of PAZ (0.09 mmol g −1 ). 17,20 Scanning electron micrographs (SEM) of UDCaT-4 revealed that similar to the morphology of HMS, UDCaT-4 is made up of sub-micrometer sized free standing or aggregated sphere shaped particles. SEM analysis further supports the argument that active centers of the PAZ are successfully embedded in HMS and the structural integrity of HMS is unaltered even after it is converted to UDCaT-4.…”

“…GD Yadav, SB Kamble it followed second-order kinetics. The analysis of earlier published reports 7,17,28 on the dehydration of isopropanol suggests that there is a production of ether and also two types of site should be involved in the reaction. Thus, a model based on two catalytic sites was proposed according to which IPA (A) is adsorbed onto two different sites S 1 and S 2 .…”

“…20 Characterization of catalysts UDCaT-4, 17 UDCaT-5, 18 UDCaT-6, 19 and sulfated zirconia 13,14 were characterized by X-ray diffraction (XRD), Brunauer-EmmettTeller (BET) surface area and Fourier transform infrared (FTIR) spectroscopy: details are published elsewhere. Only a few salient features thought to be important are reported here.…”

“…We have recently reported alkylation of several substituted aromatics using linear and branched alcohols, and ethers using a variety of solid acid catalysts, wherein a free olefin and water are generated in-situ as a co-product, along with the C-or/and O-alkylated products. 7,27,28 The dehydration of IPA to propylene is remarkably dependent on the temperature and was studied independently on UDCaT-4 17 , which is a superacid. There was no coking in the temperature range covered in this work.…”

“…The dehydration of IPA was found to obey an overall second-order kinetics contrary to the expected first-order kinetics for weakly adsorbed species. 17 Furthermore, it was found that the alkylation of o-cresol also followed a second-order reaction. Thus mechanistic models were needed to describe IPA dehydration to diisopropyl ether (DIPE), propylene and water and alkylation of o-cresol with IPA.…”