01967nas a2200229 4500008004100000022001400041245010400055210006900159260007300228300001000301490000800311520116300319653001401482653001101496653001501507653001401522653001301536100001601549700002601565700001801591856012801609 2005 eng d a1381-116900aInfluence of silica source in the catalytic activity and heterogenity of mesoporous vanadosilicates0 aInfluence of silica source in the catalytic activity and heterog aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcSEP a57-630 v2393 a

Vanadium-substituted ordered mesoporous silicates (V-OMS) were synthesized hydrothermally using two common silica sources, viz. fumed silica and tetraethyl orthosilicate, and their surface properties and catalytic activities were evaluated in the liquid phase oxidation of 1-napthol using aqueous H2O2 as an oxidant. The catalysts were characterized by XRD, N-2, adsorption-desorption, DRUV-vis and TPR to evaluate the mesostructural ordering and the local environment of vanadium in the MCM-41 matrix. Characterization data of the fresh calcined catalysts reveal a more ordered hexagonal structure for the V-MCM-41 catalyst prepared by using tetraethyl orthosilicate as the silica source while spent catalyst showed that the material is less stable than the V-MCM-41 catalyst prepared by using fumed silica as the silica source. Further, the observed differences in the selectivity behavior of extracted and calcined forms of both vanadium catalysts shows that the treatment conditions had a decisive role in the formation of extra framework metal species and further in the mesoscopic structural ordering. (c) 2005 Elsevier B.V. All rights reserved.

10a1-napthol10aMCM-4110aMesoporous10aOxidation10aVanadium1 aShylesh, S.1 aMirajkar, Subhash, P.1 aSingh, A., P. uhttps://library.ncl.res.in/content/influence-silica-source-catalytic-activity-and-heterogenity-mesoporous-vanadosilicates-002025nas a2200229 4500008004100000022001400041245016600055210006900221260007300290300001200363490000700375520113600382653002101518653001801539653001101557653001401568100002401582700001601606700002601622700001801648856012901666 2006 eng d a1387-181100aOxidation of ethyl benzene and diphenyl methane over ordered mesoporous M-MCM-41 (M = Ti, V, Cr): synthesis, characterization and structure-activity correlations0 aOxidation of ethyl benzene and diphenyl methane over ordered mes aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcOCT a154-1630 v953 a

Transition metals (M = Ti, V, Cr) were incorporated into the MCM-41 framework by surfactant-assisted direct hydrothermal (DHT) methods and were characterized in detail by XRD, N-2 adsorption-desorption, TG-DTG/DTA, SEM/TEM, DR UV-Vis, XPS and EPR. The structural regularity as well as the textural properties of the M-MCM-41 materials was confirmed by XRD, TEM and adsorption-desorption techniques. Nature of metal species and the percentage of framework as well as extra framework metal sites in the MCM-41 matrix are discussed in detail by various spectroscopic techniques. The catalytic activity as well as the selectivity of the M-MCM-41 catalysts were explored in the one-step liquid-phase oxidation reaction of ethyl benzene and diphenyl methane. Reaction data showed that the oxidation activity is more when H2O2 was used an oxidant, acetonitrile as solvent and V-MCM-41 as catalyst. However, the selectivity towards the desired keto derivatives (ethyl benzene to acetophenone and diphenyl methane to benzophenone) follows the order, Ti-MCM-41 > V-MCM-41 > Cr-MCM-41. (c) 2006 Elsevier Inc. All rights reserved.

10adiphenyl methane10aEthyl benzene10aMCM-4110aOxidation1 aJha, Ratnesh, Kumar1 aShylesh, S.1 aBhoware, Shrikant, S.1 aSingh, A., P. uhttps://library.ncl.res.in/content/oxidation-ethyl-benzene-and-diphenyl-methane-over-ordered-mesoporous-m-mcm-41-m-ti-v-cr-002664nas a2200241 4500008004100000022001400041245013100055210006900186260007300255300001000328490000800338520179500346653002502141653001302166653001602179653001102195653001402206100001602220700002102236700001802257700002102275856012602296 2008 eng d a1387-181100aBridging the gap between micropores and mesopores by the controlled transformation of bifunctional periodic mesoporous silicas0 aBridging the gap between micropores and mesopores by the control aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB a29-400 v1083 a

Novel bifunctional periodic mesoporous silicas having high content of organic groups in the pore channels and chromium in the frame wall has been synthesized by direct co-condensation method, using organo trialkoxysilanes (chloro propyl, vinyl, methyl), chromium nitrate and tetraethyl orthosilicate, in presence of cetyltrimethyl ammonium surfactants. The obtained materials show one main peak in the XRD patterns up to a molar ratio of 1: 1 between TEOS and organosilane in the synthesis gel and N-2 adsorption-desorption analysis shows that the mesopore structure remains intact after the surfactant removal process. Among the organosilanes, chloro propyl and vinyl pendant chromium samples shows a shift in the main peak to higher 2-theta values with a corresponding decrease in pore volume and pore diameter, with the percentage of organosilane functionalization. Small-pore silicas and chromium silicas can be prepared from the large pore mesoporous MCM-41, by effectively removing the organic groups by calcination. By this method, the pore size of the material can be tailored into the super-microporous region, without changing the chain length of the surfactant used in the assembly process. The shrinkage in pore size is dependent on the nature and percentage of the organic pendant groups that the chloro propyl and vinyl pendant mesoporous materials show the maximum pore size shrinkage than the small chain length methyl units. Because of the tailorable pore size and with better textural characteristics, chromium-silica materials find applications in the field of shape selective heterogeneous catalysis, as demonstrated in the oxidation reaction of cyclohexane, than the conventional metal-containing mesoporous materials. (c) 2007 Elsevier Inc. All rights reserved.

10abifunctional silicas10achromium10aCyclohexane10aMCM-4110aOxidation1 aShylesh, S.1 aSrilakshini, Ch.1 aSingh, A., P.1 aAnderson, B., G. uhttps://library.ncl.res.in/content/bridging-gap-between-micropores-and-mesopores-controlled-transformation-bifunctional-0