01522nas a2200193   4500008004100000022001400041245015000055210006900205260007300274300001200347490000600359520073500365100002301100700002101123700002401144700001801168700001301186856012901199       2005                        eng d  a1566-736700aTextural/structural, stability and morphological properties of mesostructured silicas (MCM-41 and MCM-48) prepared using different silica sources0 aTexturalstructural stability and morphological properties of mes  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAY  a361-3660 v63 a<p>A series of MCM-41 and MCM-48 samples have been synthesized under hydrothermal and static conditions using different silica sources (fumed silica, silica sot and ethyl silicate) and characterized by powder XRD, scanning electron microscopy and N-2 adsorption. The silica source reactivity trend observed was as: ethyl silicate &gt; fumed silica &gt; silica sot. However, the extent of contraction caused by calcination, magnitude of the wall thickness and stability were found to depend not only upon the type of silica source used but also on the type of structure formed. Noticeable morphological differences were observed in case of only MCM-41 when silica sources were varied. © 2005 Elsevier B.V. All rights reserved.</p>1 aGaydhankar, T., R.1 aTaralkar, U., S.1 aJha, Ratnesh, Kumar1 aJoshi, P., N.1 aKumar, R  uhttps://library.ncl.res.in/content/texturalstructural-stability-and-morphological-properties-mesostructured-silicas-mcm-41-001997nas a2200253   4500008004100000022001400041245013800055210006900193260007300262300001200335490000800347520105500355653002101410653001301431653003301444653001101477653001401488653002401502653002201526100002101548700002401569700001801593856013201611       2007                        eng d  a0022-309300aStructural evolutions of hydrothermally prepared mesostructured MCM-48 silica using differently manufactured amorphous silica powders0 aStructural evolutions of hydrothermally prepared mesostructured   aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcFEB  a194-1990 v3533 a<p>The hydrothermal synthesis of Si-MCM-48 mesoporous molecular sieves was carried out using a ternary SiO2:CTAOH:H2O System wherein differently manufactured amorphous silica powders such as fumed silica (FMDS), spray dried precipitated silica (SDPS) and flash dried precipitated silica (FDPS) were used as silica source materials. The changes in structural/textural properties were evaluated using powder XRD, N-2 adsorption-desorption and scanning electron microscopy techniques. Studies on the progressive development of MCM-48 mesophases revealed that, the reactivity of the silica source follow the trend: FMDS &gt; SDPS &gt; FDPS. MCM-48 synthesized using low cost FDPS has exhibited thicker pore walls but poorer orderness, while MCM-48 prepared from relatively expensive FMDS has thinner pore walls and more ordered structure. Moreover, the extent of contraction caused by calcinations, agglomerate size and structural stability were found to depend on the reactivity of the silica source used. (c) 2006 Elsevier B.V. All rights reserved.</p>10along-range order10amicelles10ascanning electron microscopy10asilica10asilicates10asol-gels (xerogels)10aX-ray diffraction1 aTaralkar, U., S.1 aJha, Ratnesh, Kumar1 aJoshi, P., N.  uhttps://library.ncl.res.in/content/structural-evolutions-hydrothermally-prepared-mesostructured-mcm-48-silica-using-differently01689nas a2200169   4500008004100000022001400041245007300055210006900128260010600197300001400303490000700317520103500324100002101359700002001380700001801400856010101418       2008                        eng d  a0022-369700aInfluence of synthesis conditions on structural properties of MCM-480 aInfluence of synthesis conditions on structural properties of MC  aTHE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLANDbPERGAMON-ELSEVIER SCIENCE LTDcAUG  a2075-20810 v693 a<p>The influence of synthesis variables such as time, cetyltrimethyl ammonium hydroxide (CTAOH) concentration, water content, pH, temperature and silica source on the structural properties of Si-MCM-48 is investigated. Time-dependent studies on the progressive development of MCM-48 have indicated that synthesis time is a crucial parameter, which influences the unit cell parameter. The formation of different mesophases was observed when the concentration of CTAOH and pH of the initial gel were varied. The Si-29 MASNMR results showed that the (Q(2) +W-3)/Q(4) ratio decreases with the increase in synthesis temperature. On account of increase in W units at high-temperature synthesis run, Si-MCM-48 with highly polymerized silica walls with lower surface area was obtained when compared with Si-MCM-48 prepared at lower temperature. Such effect was not significant when Si-MCM-48 was synthesized at the same temperature but using silica sol as a source in place of fumed silica. (c) 2008 Elsevier Ltd. All rights reserved.</p>1 aTaralkar, U., S.1 aKasture, M., W.1 aJoshi, P., N.  uhttps://library.ncl.res.in/content/influence-synthesis-conditions-structural-properties-mcm-48-001532nas a2200253   4500008004100000022001400041245013100055210006900186260007300255300001000328490000800338520056900346653002100915653002800936653002700964653003200991653003301023653001401056100002101070700002001091700001701111700001801128856013201146       2009                        eng d  a0926-860X00aSynthesis, characterization and catalytic performance of Sn-MCM-48 in solvent-free Mukaiyama-type aldol condensation reactions0 aSynthesis characterization and catalytic performance of SnMCM48   aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAPR  a88-940 v3583 a<p>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.</p>10aCharacterization10aheterogeneous catalysis10aHydrothermal synthesis10aMesoporous molecular sieves10aMukaiyama-aldol condensation10aSn-MCM-481 aTaralkar, U., S.1 aKalita, Pranjal1 aKumar, Rajiv1 aJoshi, P., N.  uhttps://library.ncl.res.in/content/synthesis-characterization-and-catalytic-performance-sn-mcm-48-solvent-free-mukaiyama-type-001866nas a2200241   4500008004100000022001400041245009100055210006900146260007400215300001200289490000700301520101100308653002301319653002301342653001401365653001901379653002501398653002401423100002101447700002201468700001801490856011601508       2009                        eng d  a0928-070700aSynthesis of Si-MCM-41 from ternary SiO2-CTAOH-H2O system via dry gel conversion route0 aSynthesis of SiMCM41 from ternary SiO2CTAOHH2O system via dry ge  aVAN GODEWIJCKSTRAAT 30, 3311 GZ DORDRECHT, NETHERLANDSbSPRINGERcAUG  a244-2500 v513 a<p>Steam assisted dry gel conversion method was employed for the synthesis of Si-MCM-41 from ternary SiO2:CTAOH:H2O systems wherein fumed silica was used as a source of silica. The influence of synthesis time, molar ratios of CTAOH/SiO2 in dry gel and the water content at the bottom of autoclave on the quality and formation of mesophases has been investigated. Powder XRD, N-2 adsorption-desorption, TEM and hydrothermal stability test were the techniques used for sample characterization. Keeping molar ratio of CTAOH/SiO2 constant, shorter synthesis time, lower unit cell parameter and d spacing were observed when steam assisted dry gel conversion method was employed in place of conventional hydrothermal method. There exists an optimum lower limit for water content at the bottom of autoclave for reducing the synthesis period. Keeping synthesis temperature and CTAOH/SiO2 molar ratio fixed, Si-MCM-41 with improved hydrothermal stability was obtained by steam assisted dry gel conversion route.</p>10aDry gel conversion10apowder diffraction10aSi-MCM-4110aSol-gel growth10aStructural stability10aTextural properties1 aTaralkar, U., S.1 aNiphadkar, P., S.1 aJoshi, P., N.  uhttps://library.ncl.res.in/content/synthesis-si-mcm-41-ternary-sio2-ctaoh-h2o-system-dry-gel-conversion-route-0