@article { ISI:000230713100019, title = {Alkylation of benzene with alpha-olefins over zirconia supported 12-silicotungstic acid}, journal = {Journal of Molecular Catalysis A - Chemical}, volume = {237}, number = {1-2}, year = {2005}, month = {AUG}, pages = {137-145}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Liquid phase alkylation of benzene to linear alkyl benzene (LAB) with alpha-olefins has been investigated with 12-silicotungstic acid supported on zirconia (STA/ZrO2) as the catalyst. Among the catalysts, 15 wt.\% STA/ZrO2 calcined at 750 degrees C was found to be most active than others in the alkylation reaction. The total amount of acid sites of different STA loaded catalysts were estimated by TPD of NH3 and 15 wt.\% STA/ZrO2 calcined at 750 degrees C was found to have the highest acidity and more active in the reaction. The optimization of reaction conditions of alkylation of benzene with 1-dodecene was performed with 15 wt.\% STA/ZrO2 calcined at 750 degrees C by varying catalyst concentration (1-5 wt.\% of reaction mixture); temperature, 373-423 K and benzene: 1-dodecene (1-dd) molar ratio, 5-15 in a Parr autoclave under N-2 pressure. Under the optimized reaction conditions, conversion of 1-dodecene (50.8\%) gave high selectivity to 2-phenyl dodecane (47.1\%) and the remaining 3-, 4-, 5- and 6-phenyldodecanes in 4 h. The reaction was found to be heterogeneously catalyzed and no contribution from homogeneous (leached) STA into the reaction medium. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {1-dodecene, 12-silicotungstic acid, Alkylation, Benzene, LAB, Zirconia}, issn = {1381-1169}, doi = {10.1016/j.molcata.2005.04.042}, author = {Sawant, D. P. and Halligudi, Shivappa B.} } @article { ISI:000228699400021, title = {Benzylation of benzene and other aromatics by benzyl chloride over mesoporous AlSBA-15 catalysts}, journal = {Microporous and Mesoporous Materials}, volume = {80}, number = {1-3}, year = {2005}, month = {MAY}, pages = {195-203}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Aluminum-containing mesoporous molecular sieves AISBA-15 with different n(Si)/n(Al), ratios and AIMCM-41 have been synthesized hydrothermally and characterized in detail by physicochemical methods, viz. XRD, N(2) adsorption and (27)Al NMR spectroscopy. The low angle XRD and N2 adsorption measurements reveal that the structural order of SBA-15 was retained after the incorporation of Al. The increase of the unit cell parameter with increasing aluminum content and (27)Al MAS NMR spectroscopy confirm the incorporation of aluminum in the framework. Benzylation of benzene and substituted benzenes reaction employing benzyl chloride as the alkylating agent over AISBA-15 and AIMCM-41 have been investigated. The influence of various reaction parameters such as reaction temperature, reactant feed ratio and catalyst amount affecting the activity and selectivity of AISBA-15, have been studied. Among the mesoporous catalysts studied, AISBA-15(45), where the number in parentheses indicates the molar nsilnA, ratio, shows both high conversion and high selectivity for the benzylation of benzene. The activity of this catalyst for the benzylation of different aromatic compounds is in the following order: benzene \> toluene \> p-xylene \> mesitylene \> anisole. Kinetics of the benzene benzylation over different catalysts have also been investigated. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {Alkylation, AlSBA-15, Benzylation, SBA-15}, issn = {1387-1811}, doi = {10.1016/j.micromeso.2004.12.012}, author = {Vinu, A. and Sawant, D. P. and Ariga, Katsuhiko and Hartmann, Martin and Halligudi, Shivappa B.} } @article { ISI:000230389700019, title = {Bis(2-[alpha-hydroxyethyl]benzimidazolato)copper(II) anchored onto chloromethylated polystyrene for the biomimetic oxidative coupling of 2-aminophenol to 2-aminophenoxazine-3-one}, journal = {Journal of Molecular Catalysis A - Chemical}, volume = {236}, number = {1-2}, year = {2005}, month = {JUL}, pages = {132-138}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

2-(alpha-Hydroxyethyl)benzimidazole (Hhebmz) has been covalently anchored to chloromethylated polystyrene cross-linked with 5\% divinylbenzene. This polymer-anchored chelating resin reacts with cupric acetate in presence of Hhebmz to give polymer-anchored copper(II) complex PS-[Cu(hebmz)(2)]. Elemental analyses, FT-IR, electronic, scanning electron micrographs (SEM) and TGA-DTA pattern have been used to characterize the complex. Oxidative coupling of 2-aminophenol (OAP) to 2-aminophenoxazine-3-one (APX) catalyzed by PS-[Cu(hebmz)(2)] in presence of air at 70 degrees C in DMF gave 62\% substrate conversion over a period of 8 h. Kinetics of the above reaction indicated that the rate of oxidative coupling of OAP has a first order dependence with respect to substrate, catalyst and air pressure (dissolved O-2) concentrations in the range of conditions evaluated. Based on these observations, a plausible mechanism for the above reaction has been proposed. From, the study on the effect of temperature on the rates of oxidative coupling, an activation energy 34.2 kcal/degree mole was evaluated from Arrhenius plot of -ln rate versus 1/T. Enthalpy, entropy and free energy were calculated using standard thermodynamic equations for the above reaction. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {2-aminophenol, 2-aminophenoxazine-3-one, bis(2-[alpha-hydroxyethyl]benzimidazolato)copper(II), chloromethylated polystyrene, oxidative coupling}, issn = {1381-1169}, doi = {10.1016/j.molcata.2005.02.034}, author = {Maurya, Mannar R. and Sikarwar, S. and Joseph, Trissa and Halligudi, Shivappa B.} } @article { ISI:000229488700014, title = {Bronsted acidic ionic liquids: a green, efficient and reusable catalyst system and reaction medium for fischer esterification}, journal = {Journal of Molecular Catalysis A - Chemical}, volume = {234}, number = {1-2}, year = {2005}, month = {JUN}, pages = {107-110}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Bronsted acidic ionic liquid containing nitrogen-based organic cations 1-methylimidazole and 1-butyl-3-methylimidazolium and inorganic anions of the type BF4-, PF6- and PTSA(-) has been synthesized in good yields and used as a catalysts and reaction medium for Fischer esterification of alcohols with acids. These were characterized using FTIR and NMR spectroscopy. Ionic liquids as catalyst afforded good alcohol conversion and excellent ester selectivity. Fischer esterification of acetic acid with benzyl alcohol with different Bronsted acidic ionic liquids was carried out. Maximum substrate conversion 100 \% and product selectivity 100 \% was observed on using [BMIM](+)PTSAas catalyst over a period of 2 h. The ester was easily separated from the reaction mixture and the ionic liquid was reused four times after removing water. No significant loss in catalytic activity was observed on recycling. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {acids, alcohol and reaction medium, Fischer esterification, Ionic liquid}, issn = {1381-1169}, doi = {10.1016/j.molcata.2005.03.005}, author = {Joseph, Trissa and Sahoo, S. and Halligudi, Shivappa B.} } @article { ISI:000230389700020, title = {Copper(II) ion-exchanged montmorillonite as catalyst for the direct addition of N-H bond to CC triple bond}, journal = {Journal of Molecular Catalysis A - Chemical}, volume = {236}, number = {1-2}, year = {2005}, month = {JUL}, pages = {139-144}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

An efficient synthesis of phenyl-(1-phenylethylidene)amine using copper-exchanged montmorillonite clay (Cu K-10) is demonstrated. The catalyst was characterized using UV-vis, XRD, BET surface area measurements, pyridine adsorption etc. The XRD and surface area measurement show that the structural characteristics of the support montmorillonite K-10 (K-10) are preserved after Cu exchange. The hydroamination of phenyl acetylene with aniline was carried out in toluene under reflux condition in N-2 atmosphere at 393 K. The reaction is highly regio-selective for only Markovnikoff{\textquoteright}s addition of an-tine to CC multiple bond and proceeded smoothly to completion. The reaction conditions were optimized to obtain complete conversion with respect to phenyl acetylene. Reaction data showed that the activity of the catalyst in hydroamination reaction is greater at higher reaction temperatures and nonpolar solvents and NZ pressure promotes the reaction drastically. (c) 2005 Elsevier B.V. All rights reserved.

}, keywords = {alkyne, Aniline, Catalyst, hydroamination, K-10 montmorillonite clay, phenyl acetylene}, issn = {1381-1169}, doi = {10.1016/j.molcata.2005.04.022}, author = {Joseph, Trissa and Shanbhag, G. V. and Halligudi, Shivappa B.} } @article { ISI:000232743700020, title = {Direct synthesis of well-ordered and unusually reactive FeSBA-15 mesoporous molecular sieves}, journal = {Chemistry of Materials}, volume = {17}, number = {21}, year = {2005}, month = {OCT}, pages = {5339-5345}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Large-pore hexagonal SBA-15 molecular sieves partially substituted with iron(III) have been synthesized for the first time in highly acidic media. The degree of iron(III) incorporation into SBA-15 can easily be controlled by a simple adjustment of the molar ratio of water and hydrochloric acid. All the materials have been characterized by XRD, N-2 adsorption, UV-Vis DRS, ESR, and XANES spectroscopy. The characterization of the FeSBA-15 materials by UV-Vis DRS, ESR, and XANES spectroscopies suggests that the iron atoms are highly dispersed and mostly occupy isolated tetrahedral sites. XANES studies revealed that the proportion of tetrahedrally coordinated Fe atoms decreases with decreasing n(Si)/n(Fc) ratios. Benzylation of benzene (or substituted benzenes) using benzyl chloride as the alkylating agent over FeSBA-15 with different n(Si)/n(Fe) ratios was investigated as was the same reaction using AISBA-15 as catalyst. The influence of parameters such as reaction temperature, reactant feed ratio, and the presence of electron-donating substituents on the activity and selectivity of AISBA-15 was studied. Under optimized reaction conditions, the FeSBA-15 catalyst showed a superior catalytic performance in the benzylation of benzene and other aromatics using benzyl chloride, with a clean conversion of benzyl chloride to the monoalkylated product (100\% selectivity) with a very high rate constant when compared to other mesoporous materials such as AISBA-15 and FeHMS. Interestingly, use of FeSBA-15(21) resulted in quantitative conversion of benzyl chloride with a high rate constant of 2420.5 x 10(-4) min(-1) under the optimized reaction conditions.

}, issn = {0897-4756}, doi = {10.1021/cm050883z}, author = {Vinu, A. and Sawant, D. P. and Ariga, Katsuhiko and Hossain, K. Z. and Halligudi, Shivappa B. and Hartmann, Martin and Nomura, M.} } @article { ISI:000232815700010, title = {Formation of nanosized zirconia-supported 12-tungstophosphoric acid in mesoporous silica SBA-15: a stable and versatile solid acid catalyst for benzylation of phenol}, journal = {Journal of Catalysis}, volume = {235}, number = {2}, year = {2005}, month = {OCT}, pages = {341-352}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

A nanosized zirconia-supported 12-tungstophosphoric acid (TPA) in SBA-15 composite was prepared by wet impregnation of TPA/ZrO2 nanoparticles inside the mesoporous channels of SBA-15. The resulting composite material was calcined at 1123 K and characterized by elemental analysis, powder X-ray diffraction, nitrogen adsorption isotherms, transmission electron microscopy (TEM), scanning electron microscopy (SEM), solid-state P-31 CP-MAS NMR, Si-29 MAS NMR, UV-vis diffuse reflectance spectra, FTIR, TPD of ammonia, FTIR pyridine adsorption, and thermogravimetric analysis (TG-DTG). The synthesized TPA/ZrO2/SBA-15 showed a well-ordered hexagonal inesoporous structure and mesoporous support SBA-15 stabilized ZrO2-t (tetragonal) phase with crystal size in the range of 3-4 nm. SBA-15 was a better support than MCM-41 and MCM-48 because it retained its mesostructure even after high TPA loading and high calcination temperatures. Mesoporous silica support plays an important role in stabilizing the catalytically active tetragonal phase of zirconia, which gave the most active catalysts. The catalysts were examined for their catalytic activities in the liquid phase benzylation of phenol with benzyl alcohol and the catalyst 15 wt\% TPA/ 22.4 wt\% ZrO2/SBA-15 calcined at 1123 K was found to have high acidity and to be 10 times more active than neat TPA/ZrO2 Under the reaction conditions studied in benzylation of phenol. (c) 2005 Elsevier Inc. All rights reserved.

}, keywords = {nanosized, phenol benzylation reaction, terragonal phase, TPA/ZrO2}, issn = {0021-9517}, doi = {10.1016/j.jcat.2005.08.010}, author = {Sawant, D. P. and Vinu, A. and Jacob, Nalini E. and Lefebvre, F. and Halligudi, Shivappa B.} } @article { ISI:000227266100034, title = {Oxyfunctionalization of limonene using vanadium complex anchored on functionalized SBA-15}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {229}, number = {1-2}, year = {2005}, month = {MAR}, pages = {241-247}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

VO(Salten) complexes, where Salten = 3-[N,N{\textquoteright}-bis-3(salicylidenamino)ethyltriamine], have been covalently anchored on to functionalized SBA-15. The formation and integrity of the complex have been confirmed by elemental analysis, Fr-IR, X-ray diffraction (XRD) and BET measurements and the complex was used for the oxyfunctionalization of limonene in presence of urea hydroperoxide (UHP) as the oxidizing agent. The oxyfunctionalization of limonene resulted in limonene oxide, carvone, carvacrol and carveol. Anchored complex showed better catalytic activity than the neat complex, while the neat complexes has deactivated in the reaction due to formation of inactive alpha-oxo-bridged dimers, the covalently anchored complexes remained stable throughout the reaction. The anchored complex could be easily separated from the products and could be reused. (C) 2004 Elsevier B.V. All rights reserved.

}, keywords = {covalently anchored vanadium complex, functionalized Si-SBA-15, limonene, oxofunctionalization, UHP}, issn = {1381-1169}, doi = {10.1016/j.molcata.2004.12.008}, author = {Joseph, Trissa and Halligudi, Shivappa B.} } @article { ISI:000228779100008, title = {Synthesis, characterization and catalytic potentials of polymer anchored copper(II), oxovanadium(IV) and dioxomolybdenum(VI) complexes of 2-(alpha-hydroxymethyl)benzimidazole}, journal = {Reactive \& Functional Polymers}, volume = {63}, number = {1}, year = {2005}, month = {MAR}, pages = {71-83}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

{2-(alpha-Hydroxymethyl)benzimidazole (Hhmbmz) has been covalently anchored to chloromethylated polystyrene cross-linked with 5\% divinylbenzene. This chelating resin reacts with cupric acetate, vanadyl sulphate and [MoO(2)-(acac)(2)] (Hacac = acetylacetone) in presence of Hhmbmz to give complexes PS-[Cu(hmbmz)(2)], PS-[VO(hmbmz)(2)] and PS-[MoO(2)(hmbmz)(2)] (where

}, keywords = {2-(alpha-hydroxymethyl)benzimidazole, oxidation of styrene and ethyl benzene, oxidative bromination of salicylaldehyde, polymer anchored-complexes}, issn = {1381-5148}, doi = {10.1016/j.reactfunctpolym.2005.02.008}, author = {Maurya, Mannar R. and Sikarwar, S. and Joseph, Trissa and Manikandan, Palanichamy and Halligudi, Shivappa B.} } @article { ISI:000237318000033, title = {Chemoselective anti-Markovnikov hydroamination of alpha,beta-ethylenic compounds with amines using montmorillonite clay}, journal = {Journal of Molecular Catalysis A-Chemical}, volume = {250}, number = {1-2}, year = {2006}, month = {MAY}, pages = {210-217}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

The catalytic activity of montmorillonite clays as a catalyst for the hydroamination of alpha,beta-ethylenic compounds with amines was tested. Aniline and substituted amines reacted with alpha,beta-ethylenic compounds in the presence of catalytic amount of commercially available clay to afford exclusively anti-Markovnikov adduct in excellent yields. Aniline reacted with ethyl acrylate to yield only anti-Markovnikov adduct N-[2-(ethoxycarbonyl)ethyl] aniline (mono-addition product). No Markovnikov adduct (N-[1-(ethoxycarbonyl)ethyl]aniline and double addition product N,N-bis[2-(ethoxycarbonyl)ethyl]aniline were formed under selected reaction conditions. For a better exploitation of the catalytic activity in terms of increased activity and improved selectivity for the mono-addition product, the reaction parameters were optimized in terms of temperature, solvent, reactant mole ratio. Under optimized reaction conditions, montmorillonite clay K-10 showed a superior catalytic performance in the hydroamination of ethyl acrylate with aniline with a conversion of aniline to mono-addition product (almost 100\% chemoselectivity) with a high rate constant 0.3414 min(-1) compared to the reported protocols. The dependence of conversion of aniline over different types of montmorillonite clays (K-10, K-20, K-30, Al-Pillared clay and untreated clay) has also been discussed. The activities of clay for the hydroamination of different aromatic and aliphatic amines have also been investigated. Under harsh reaction conditions (increased temperature and long reaction time) small amounts of di-addition products were observed. The kinetics data has been interpreted using the initial rate approach model. (c) 2006 Elsevier B.V. All rights reserved.

}, keywords = {alpha, amines, anti-Markovnikov addition product, beta-ethylenic compounds, chemo-selective, hydroamination, K-10 montmorillonite clay}, issn = {1381-1169}, doi = {10.1016/j.molcata.2006.01.062}, author = {Joseph, Trissa and Shanbhag, G. V. and Sawant, D. P. and Halligudi, Shivappa B.} } @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:000258800700002, title = {Highly selective catalytic hydrogenation of arenes using rhodium nanoparticles supported on multiwalled carbon nanotubes}, journal = {Journal of Physical Chemistry C}, volume = {112}, number = {35}, year = {2008}, month = {SEP}, pages = {13317-13319}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

Rhodium nanoparticles (RhNPs; 4.9 +/- 0.4 nm) supported on multiwalled carbon nanotubes (Rh/MWNT), prepared by simple microwave treatment, show a remarkable catalytic activity for arene hydrogenation with enhanced turnover numbers of similar to 10000; disubstituted arenes show selective conversion of thermodynamically less favorable cis products (\>80\%). A series of arenes have been tested using various Rh-based catalysts, and a comparison of the results with that of reported rhodium catalysts shows unique selectivity under mild conditions.

}, issn = {1932-7447}, doi = {10.1021/jp804843h}, author = {Kakade, Bhalchandra A. and Sahoo, Suman and Halligudi, Shivappa B. and Pillai, Vijayamohanan K.} } @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} } @article {47410, title = {Direct synthesis of mesoporous siliceous phosphotungstic acid and its superior catalytic activity on the cyclohexylation of phenol}, journal = {Journal of Physical Chemistry C }, volume = {125}, year = {2021}, month = {APR }, pages = {6723-6734}, type = {Article}, abstract = {

The synthesis of highly active and reusable mesoporous siliceous phosphotungstic acid materials (mPTA-Si) which are prepared through a simple self-assembly between phosphotungstic acid (PTA), the polymeric surfactant, and the silica precursor assisted by KCl for cyclohexylation of phenol is reported. The surface area and the acidity of these materials are tuned with a simple adjustment of PTA in the silica framework. The prepared samples exhibit mesoporous structure with a high surface area, but the structure is collapsed when the loading of PTA is high. It is established that the Keggin structure of PTA is retained on the final mPTA-Si. mPTA-Si with different loadings of PTA are employed as the catalysts for the cyclohexylation of phenol under liquid phase conditions. Among the catalysts studied, 10.0-mPTA-8.3Si calcined at 350 degrees C is found to be highly active, selective, and recyclable and offers 100\% conversion of phenol with the highest selectivity for p-cyclohexylphenol (96.8\%).

}, issn = {1932-7447}, doi = {10.1021/acs.jpcc.1c01596}, author = {Ilbeygi, Hamid and Sawant, Dhanashri P. and Ruban, Sujanya M. and Reshma, Kokane S. and Umbarkar, Shubhangi B. and Halligudi, Shivappa B. and Vinu, Ajayan} }