@article { ISI:000231197500017, title = {Vanadium-containing ordered mesoporous silicas: synthesis, characterization and catalytic activity in the hydroxylation of biphenyl}, journal = {Applied Catalysis A - General}, volume = {290}, number = {1-2}, year = {2005}, month = {AUG}, pages = {148-158}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A series of vanadium-containing ordered mesoporous MCM-41 materials (V-OMS) have been synthesized by direct hydrothermal (VMCM-41) and grafting (V/MCM-41) methods using hexadecyl trimethyl ammonium bromide (HDTMABr) as the structure-directing agent. The physico-chemical properties of the vanadium-containing materials were characterized in detail by ICP-OES, XRD, Fr-IR, N-2 adsorption-desorption, DRUV-VIS, TPR, XPS and SEM techniques. The redox performances of the vanadium-modified mesoporous materials were tested in the hydroxylation of biphenyl using aqueous H2O2 (30 wt.\%) as oxidant. For a better exploitation of the catalytic activity, the reaction parameters are optimized in terms of temperature, solvent, oxidant, etc. A comparison between the catalytic activity values of the vanadium-containing mesoporous materials prepared by the two routes shows that vanadium-substituted (V-MCM-41) materials had increased activity and improved selectivity for mono hydroxyl products in the hydroxylation reaction of biphenyl compared to the V/MCM-41 catalysts. The heterogenity of the catalysts was verified by a series of leaching studies. Both the catalysts enhance the leaching of active vanadia species during the reaction; among them, V/MCM-41 shows the least heterogenity. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {biphenyl, heterogenity, MCM-41, Mesoporous molecular sieves, Vanadium}, issn = {0926-860X}, doi = {10.1016/j.apcata.2005.05.012}, author = {George, J. and Shylesh, S and Singh, AP} } @article { ISI:000239077500019, title = {Chemo-, regio- and stereo-selective aerial oxidation of limonene to the endo-1,2-epoxide over Mn(Salen)-sulfonated SBA-15}, journal = {Applied Catalysis A-General}, volume = {309}, number = {1}, year = {2006}, month = {JUL}, pages = {144-154}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Mn(Salen) complexes immobilized on sulfonic acid-functionalized SBA-15 molecular sieves (SBA-15-pr-SO3-Mn(Salen)) catalyze the Mukaiyama-type oxidation of R-(+)-limonene selectively to the 1,2-epoxide with molecular oxygen at 298 K (Salen = N,N-ethylenebis(salicylidenaminato)). The endo-diastereomer is formed with a diasteromeric excess of 39.8\%. This catalyst exhibited higher catalytic activity than {\textquoteleft}{\textquoteleft}neat{\textquoteright}{\textquoteright} Mn(Salen) complexes directly supported on SBA-15 or zeolite-Y. A change in the oxidation state of Mn from +3 in the {\textquoteleft}{\textquoteleft}neat{\textquoteright}{\textquoteright} complex to +2 when immobilized on the sulfonated surface is a probable cause for the observed enhancement of catalytic activity. A part of the Mn complexes was leached out of the solid phase during the reaction. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {aerial oxidation of limonene, catalysis by Mn(Salen) complexes, chemo-, immobilized Mn Schiff base complexes, Mesoporous molecular sieves, Mukaiyama-type oxidation, regio- and stereo-selective epoxidation, sulfonic acid-functionalized SBA-15}, issn = {0926-860X}, doi = {10.1016/j.apcata.2006.05.011}, author = {Saikia, Lakshi and Srinivas, D. and Ratnasamy, Paul} } @article {52}, title = {Characterization and catalytic activity of cobalt containing MCM-41 prepared by direct hydrothermal, grafting and immobilization methods}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {266}, number = {1-2}, year = {2007}, month = {APR}, pages = {118-130}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

{Cobalt containing hexagonal mesoporous molecular sieves (MCM-41) were prepared by different methods viz., direct hydrothermal synthesis, grafting and immobilization. The calcined material was characterized by various spectroscopic tools such as powder X-ray diffraction (XRD), N-2 adsorption-desorption isotherms, Fourier transformed infra-red (Fr-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance UV-vis and X-ray photoelectron spectroscopy (XPS). The XRD patterns show the highly intense (100) reflection peak in the range 2-3 degrees (2 theta angle), characteristic of mesoporous material. Higher order reflection peaks suggest highly ordered mesoporous structure. N2 adsorption-desorption isotherms are of type IV according to IUPAC classification and the steep rise in the isotherms in the narrow range 3.5-4.5 of relative pressure (P/P-0) is due to the condensation of N-2 gas molecules in the pores (characteristic of mesoporous structure). In FT-IR increase in the intensity of band at 960 cm(-1) with the increase of the cobalt content in Co-MCM-41 samples indicate the incorporation of cobalt ions in the framework of MCM-41. SEM and TEM reveal spherical morphology for the cobalt substituted MCM-41. UV-vis spectra demonstrate the characteristic features of framework and extraframework cobalt in MCM-41. Cobalt is in +2 oxidation state as evidenced from UV-vis and XPS. The catalysts were tested for the side chain oxidation of ethylbenzene using 70 wt.\% tert-butyl hydrogen peroxide as an oxidant with and without the use of solvent. Solvents have effect in the catalytic activity and selectivity. In the absence of solvent, substituted cobalt [

}, keywords = {2-butanol, cyclohexanone, Mesoporous molecular sieves, MPV reduction}, issn = {1381-1169}, doi = { 10.1016/j.molcata.2006.09.031}, author = {Bhoware, Shrikant S. and Singh, A. P.} } @article { ISI:000265237700014, title = {Synthesis, characterization and catalytic performance of Sn-MCM-48 in solvent-free Mukaiyama-type aldol condensation reactions}, journal = {Applied Catalysis A-General}, volume = {358}, number = {1}, year = {2009}, month = {APR}, pages = {88-94}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The influence of various synthesis variables on the physico-chemical properties of mesoporous stannosilicate molecular sieves with MCM-48 structure (Sn-MCM-48) has been investigated. Sn-MCM48 has been used as a new heterogeneous catalyst in solvent-free Mukaiyama-type aldol reactions. Invariably, the beta-hydroxy ester selectivity was found to be 100\% irrespective of the conversion level. The product yield was found to increase, to reach a maximum (70\%), and then to decrease with the increase in tin content. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {Characterization, heterogeneous catalysis, Hydrothermal synthesis, Mesoporous molecular sieves, Mukaiyama-aldol condensation, Sn-MCM-48}, issn = {0926-860X}, doi = {10.1016/j.apcata.2009.02.001}, author = {Taralkar, U. S. and Kalita, Pranjal and Kumar, Rajiv and Joshi, P. N.} }