@article { ISI:000254872600028, title = {Heteropoly acid encapsulated SBA-15/TiO(2) nanocomposites and their unusual performance in acid-catalysed organic transformations}, journal = {Chemistry-A European Journal}, volume = {14}, number = {10}, year = {2008}, month = {FEB}, pages = {3200-3212}, publisher = {WILEY-BLACKWELL}, type = {Article}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

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.

}, keywords = {Bronsted acids, mesoporous materials, nanoreactors, nanotechnology, supported catalysts}, issn = {0947-6539}, doi = {10.1002/chem.200701562}, author = {Sawant, Dhanashri P. and Justus, Josena and Balasubramanian, Veerappan V. and Ariga, Katsuhiko and Srinivasu, Pavuluri and Velmathi, Sivan and Halligudi, Shivappa B. and Vinu, Ajayan} } @article { ISI:000254979800027, title = {Highly efficient and chemo selective catalyst system for the synthesis of blossom orange fragrance and flavoring compounds}, journal = {Catalysis Communications}, volume = {9}, number = {7}, year = {2008}, month = {APR}, pages = {1671-1675}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

{Acetal and acylal formation reactions of organic compounds are efficiently catalyzed by zirconia-supported mixed oxide systems under liquid-phase reaction conditions. 15WZ-750 (where

}, keywords = {Acetal, acylal, Silicotungstic acid, tungsten oxide, tungstophosphoric acid, Zirconia}, issn = {1566-7367}, doi = {10.1016/j.catcom.2008.01.025}, author = {Justus, Josena and Vinu, Ajayan and Devassy, Biju M. and Balasubramanian, Veerappan V. and Bohringer, Walter and Fletcher, Jack C. Q. and Halligudi, Shivaraj B.} } @article { ISI:000254450600014, title = {Novel three dimensional cubic Fm3m mesoporous aluminosilicates with tailored cage type pore structure and high aluminum content}, journal = {Advanced Functional Materials}, volume = {18}, number = {4}, year = {2008}, month = {FEB}, pages = {640-651}, publisher = {WILEY-V C H VERLAG GMBH}, address = {PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY}, abstract = {

Novel three dimensional cubic Fm3m mesoporous aluminosilicates (AIKIT-5) with very high structural order and unprecedented loadings of Al in the silica framework have been successfully prepared for the first time by using non ionic surfactant as a template in a highly acidic medium. The obtained materials have been unambiguously characterized in detail by several sophisticated techniques such as XRD, N, adsorption, HRTEM, HRSEM, EDS, elemental mapping, Al-27 MAS NMR, and NH3-TPD. We also demonstrate that the nature, and the amount of Al incorporation in the silica framework can easily be controlled by simply varying the n(H2O)/n(HCl) and the n(Si)/n(Al), ratios, and the Al sources in the synthesis gel. Among the Al sources examined, the Al isopropoxide (AiPr) is superior over other Al sources. Al-27 MAS NMR results reveal that the amount of tetrahedral Al in the framework can be controlled by simply adjusting the nSi/nAl ratio in the synthesis gel, which increases with increasing the Al incorporation. One of the interesting findings in the work is the increase of the specific surface area, specific pore volume and the pore diameter of AIKIT-5 with increasing the Al incorporation in the silica framework (up to n(Si)/n(Al), ratio of 10) while retaining the well-ordered three dimensional cage type porous structure, and the mechanism for the unusual behavior has been discussed in detail. Finally, the acidity and the catalytic activity in the acetylation of veratrole of the AIKIT-5 catalysts have been studied and the results have been compared with the several zeolites catalysts. Among the catalysts examined, AIKIT-5(10) is found to be superior over the zeolites catalysts such as mordenite, zeolite H-Y, zeolite H-beta, and ZSM-5.

}, issn = {1616-301X}, doi = {10.1002/adfm.200701027}, author = {Srinivasu, Pavuluri and Alam, Sher and Balasubramanian, Veerappan V. and Velmathi, Sivan and Sawant, Dhanashri P. and Boehlmann, Winfred and Mirajkar, Subhash P. and Ariga, Katsuhiko and Halligudi, Shivappa B. and Vinu, Ajayan} } @article { ISI:000253450900027, title = {Synthesis of biodiesel over zirconia-supported isopoly and heteropoly tungstate catalysts}, journal = {Catalysis Communications}, volume = {9}, number = {5}, year = {2008}, month = {MAR}, pages = {696-702}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The liquid-phase synthesis of biodiesel by transesterification of sunflower oil with methanol is carried out by using zirconia-supported isopoly and heteropoly tungstates (HPAs) as catalysts. The isopoly and heteropoly tungstate catalysts were prepared by suspending zirconium oxyhydroxide in water/methanol solution of ammonium metatungstate/silicotungstic acid, phosphotungstic acid (WO3/HPA loading, 15\%,,) followed by drying and calcination at 750 degrees C. The catalysts were characterized by XRD, Raman spectroscopy, IR spectroscopy, NH3-TPD and FTIR pyridine adsorption spectroscopy. XRD results indicate that the presence of isopoly and heteropoly tungstates stabilizes ZrO2 in tetragonal phase. Raman and IR spectra of the catalysts show that tungstate species exist as zirconia-anchored octahedral mono-oxotungstate. The acidity measurements by NH3-TPD and FTIR pyridine adsorption spectroscopy show that zirconia-supported phosphotungstate has the highest total acidity and zirconia-supported isopoly tungstate has the highest Bronsted acidity. The zirconia-supported isopoly tungstate shows superior catalytic performance compared to zirconia-supported heteropoly tungstate catalysts. Under the reaction conditions of 200 degrees C and methanol/oil molar ratio 15, 15\% WO3/ZrO2 calcined at 750 degrees C gave 97\% conversion of oil. This catalyst also efficiently catalyzes methanolysis of other vegetable oils like mustard oil and sesame oil. The deactivated catalyst could be regenerated by calcination without appreciable loss in activity. (c) 2007 Elsevier B.V. All rights reserved.

}, keywords = {Biodiesel, phosphotungstic acids, Silicotungstic acid, transesterification, tungsten oxide, Zirconia}, issn = {1566-7367}, doi = {10.1016/j.catcom.2007.08.007}, author = {Sunita, G. and Devassy, Biju M. and Vinu, Ajayan and Sawant, Dhanashri P. and Balasubramanian, Veerappan V. and Halligudi, Shivappa B.} } @article { ISI:000345975300012, title = {Titania nanoparticles stabilized HPA in SBA-15 for the intermolecular hydroamination of activated olefins}, journal = {ChemCatChem}, volume = {6}, number = {12}, year = {2014}, month = {DEC}, pages = {3347-3354}, publisher = {WILEY-V C H VERLAG GMBH}, address = {BOSCHSTRASSE 12, D-69469 WEINHEIM, GERMANY}, abstract = {

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.

}, keywords = {heteropoly acids, hydroamination, mesoporous materials, nanocatalysts}, issn = {1867-3880}, doi = {10.1002/cctc.201402449}, author = {Sawant-Dhuri, Dhanashri and Balasubramanian, Veerappan V. and Ariga, Katsuhiko and Park, Dae-Hwan and Choy, Jin-Ho and Cha, Wang Soo and Al-deyab, Salem S. and Halligudi, Shivappa B. and Vinu, Ajayan} }