02980nas a2200289   4500008004100000022001400041245013400055210006900189260007600258300001400334490000700348520191000355653001902265653002502284653001702309653001902326653002402345100002602369700001902395700003502414700002102449700002402470700002002494700002802514700001702542856013102559       2008                        eng d  a0947-653900aHeteropoly acid encapsulated SBA-15/TiO(2) nanocomposites and their unusual performance in acid-catalysed organic transformations0 aHeteropoly acid encapsulated SBA15TiO2 nanocomposites and their   aCOMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USAbWILEY-BLACKWELLcFEB  a3200-32120 v143 a<p>The preparation of SBA-15/TiO(2) nanocomposites with different loadings of Keggin-type 12-tungsto-phosphoric acid (TPA) nanocrystals in their mesochannels through a simple and effective vacuum impregnation method is reported for the first time. The catalysts have been characterised by various sophisticated techniques, including XRD, HRSEM, and TEM. It has been found that the acidity and the textural parameters of the nanocomposites can be controlled by simply changing the loadings of TPA and TiO(2) or the calcination temperature. TPA and TiO(2) loadings of 15 and 22.4 wt %, respectively, and a calcination temperature of 1123 K have proved to be optimal for obtaining mesoporous nanocomposite materials with the highest acidity. Moreover, the activities of these catalysts in promoting hydroamination as well as Mannich and Claisen rearrangement reactions have been extensively investigated. The results show that the amount of TPA has a great influence on the activity of the nanocomposites in all of the reactions studied. The effects of other reaction parameters, such as temperature and reaction time, on the conversion and product selectivity have also been studied in detail. A kinetic analysis of the formation of the products under various reaction conditions is presented. It has been found that the activity of the nanocomposite composed of 15 wt % TPA deposited on 22.4 wt of TiO(2) on SBA-15 in promoting the studied reaction is remarkably higher than the catalytic activities shown by pure TPA, TiO(2)-loaded SBA-15, or TPA-loaded SBA-15. The results obtained have indicated that the acidity and the structural control of the nanocomposite materials are highly critical for obtaining excellent catalytic activity, and the presented highly acidic nanocomposites are considered to show great potential for use as catalysts in promoting many acid-catalysed organic transformations.</p>10aBronsted acids10amesoporous materials10ananoreactors10ananotechnology10asupported catalysts1 aSawant, Dhanashri, P.1 aJustus, Josena1 aBalasubramanian, Veerappan, V.1 aAriga, Katsuhiko1 aSrinivasu, Pavuluri1 aVelmathi, Sivan1 aHalligudi, Shivappa, B.1 aVinu, Ajayan  uhttps://library.ncl.res.in/content/heteropoly-acid-encapsulated-sba-15tio2-nanocomposites-and-their-unusual-performance-acid-002420nas a2200289   4500008004100000022001400041245011000055210006900165260007700234300001400311490000600325520138300331653002101714653001901735653002501754653001801779100002801797700003501825700002101860700001901881700001701900700001901917700002401936700002801960700001701988856012502005       2014                        eng d  a1867-388000aTitania nanoparticles stabilized HPA in SBA-15 for the intermolecular hydroamination of activated olefins0 aTitania nanoparticles stabilized HPA in SBA15 for the intermolec  aBOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcDEC  a3347-33540 v63 a<p>A liquid phase hydroamination (HA) of alpha,beta-ethylenic compounds with amines was investigated with TiO2 nanoparticles stabilized 12-tungstophosphoric acid (TPA) in SBA-15. The catalysts were prepared by wet impregnation of TPA/TiO2 nanoparticles into the SBA-15 and calcined at different temperatures. The characterization results reveal that the textural properties and the acidity of the prepared catalysts can be finely controlled with the simple adjustment of the calcination temperature and the structure of the support, decorated with the TiO2 and TPA nanoparticles, was intact even after the modification. The prepared catalysts were investigated for HA of ethyl acrylate with different aromatic and aliphatic amines over a wide range of reaction conditions to optimize the yield and the selectivity of product. It was found that this process is 100% atom efficient and the catalytic performance depended significantly on the loading of TPA over the catalyst and the calcination temperature. Under optimized reaction conditions, the best catalyst, 15 wt% TPA/22.4 wt% TiO2/SBA-15 calcined at 1123 K, offered the highest conversion of p-ethylaniline (70%) with 100% chemo-selectivity to the anti-Markovnikov product, i.e., the mono-addition product. The reaction was heterogeneously catalyzed and no contribution from leached TPA into the reaction was observed.</p>10aheteropoly acids10ahydroamination10amesoporous materials10ananocatalysts1 aSawant-Dhuri, Dhanashri1 aBalasubramanian, Veerappan, V.1 aAriga, Katsuhiko1 aPark, Dae-Hwan1 aChoy, Jin-Ho1 aCha, Wang, Soo1 aAl-deyab, Salem, S.1 aHalligudi, Shivappa, B.1 aVinu, Ajayan  uhttps://library.ncl.res.in/content/titania-nanoparticles-stabilized-hpa-sba-15-intermolecular-hydroamination-activated-0