@article { ISI:000242130100007, title = {Heterogenized vanadyl cations over modified silica surfaces: a comprehensive understanding toward the structural property and catalytic activity difference over mesoporous and amorphous silica supports}, journal = {Journal of Catalysis}, volume = {244}, number = {1}, year = {2006}, month = {NOV}, pages = {52-64}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

Using a postsynthesis grafting method, 3-aminopropyltriethoxysilane (3-APTS) was functionalized over silica gel and mesoporous silica materials like SBA-15 and MCM-41. Vanadyl cations were then immobilized over the functionalized amino groups of the silica samples and used as a catalyst in the liquid-phase oxidation reaction of cyclohexane. Elemental analysis, PXRD, TEM, N-2 adsorption-desorption isotherms, FTIR, C-13 and Si-29 MAS NMR, UV-vis, and EPR techniques were used to characterize the developed materials. Characterization results suggest that the percentage of 3-APTS grafting depends on the number of isolated and genlinal silanol sites of the support material, the solvents used during the grafting reactions, and the sample pretreatment conditions. We found that using toluene as the dispersing medium and Si-MCM-41 as a support provides the maximum amount of amine functionalization, and thereby the highest percentage of vanadium immobilization. Catalytic activity and metal leaching studies show that vanadium-immobilized mesoporous solids are more active and stable than the silica gel-functionalized vanadium catalyst and a framework-substituted V-MCM-41 catalyst. The enhanced activity and stability of the immobilized vanadium catalysts compared with the V-MCM-41 and silica gel samples are attributed to the active metal site isolations, as well as to the spatial restrictions imparted from the concave silica surfaces of the mesoporous solids rather than the convex silica surfaces of the silica gel sample. (c) 2006 Published by Elsevier Inc.

}, keywords = {3-APTS, mesoporous solids, Oxidation, Silica gel, Vanadium}, issn = {0021-9517}, doi = {10.1016/j.jcat.2006.08.002}, author = {Shylesh, S. and Singh, A. R.} } @article { ISI:000311935400073, title = {Influence of contact medium and surfactants on carbon dioxide clathrate hydrate kinetics}, journal = {Fuel}, volume = {105}, year = {2013}, month = {MAR}, pages = {664-671}, publisher = {ELSEVIER SCI LTD}, address = {THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND}, abstract = {

Carbon dioxide (CO2) hydrate formation kinetic was investigated in a fixed bed crystallizer at constant pressure (3.55 MPa) and temperature (274 K). Porous media of three different silica gels were used, with a mesh size of 60-120, 100-200 and 230-400 having different surface area. The observed trends indicate that silica gel with larger surface area leads to higher gas consumption as well as reduces the induction time. The effect of pore diameter and particle size distribution has already been reported in a previous study [1]. In this study the effect of additives on hydrate formation kinetics were also investigated. The additives studied were nonionic surfactant Tween-80 (T-80), cationic dodecyltrimethylammonium chloride (DTACl) and anionic Sodium Dodecyl Sulphate (SDS). Out of the three surfactants used in this study, SDS was found to be most effective in enhancing the rate of hydrate formation as well as reducing the induction time. The current result shows significant improvement in water to hydrate conversion in silica gel media compared to quiescent water or surfactant-water system under similar conditions. (C) 2012 Elsevier Ltd. All rights reserved.

}, keywords = {Carbon dioxide capture, Clathrate hydrate, kinetics, Silica gel, Surfactants}, issn = {0016-2361}, doi = {10.1016/j.fuel.2012.10.031}, author = {Kumar, Asheesh and Sakpal, Tushar and Linga, Praveen and Kumar, Rajnish} } @article { ISI:000344439400007, title = {Regioselective acylation of 2-methoxy naphthalene catalyzed by supported 12-phosphotungstic acid}, journal = {Applied Catalysis A-General}, volume = {486}, year = {2014}, month = {SEP}, pages = {55-61}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

12-Phosphotungstic acid supported on silica gel, zirconium sulfate, and a combination of silica gel and zirconium sulfate (50\% w/w) were employed as solid acid catalysts for regioselective acylation of 2-methoxynaphtalene with acetic anhydride. 1-(6-Methoxynaphthalen-2-yl)ethanone (2,6-AMN), a commercially important intermediate for production of Naproxen, was obtained with excellent selectivity (\>98\%) at 67-68\% conversion using 12-phosphotungstic acid supported on silica gel 20\% (w/w) in refluxing tetrachloroethane. The unreacted starting material can be easily separated from the product by a simple crystallization from nonane. (C) 2014 Elsevier B.V. All rights reserved.

}, keywords = {Acylation, Naproxen, Phosphotungstic acid, Silica gel, Supported, Zirconium sulfate}, issn = {0926-860X}, doi = {10.1016/j.apcata.2014.08.026}, author = {Kumaraguru, Thenkrishnan and Devi, Ayala Vedamayee and Siddaiah, Vidavalur and Rajdeo, Kishor and Fadnavis, Nitin W.} } @article {47049, title = {Hydrate-based carbon capture process: assessment of various packed bed systems for boosted kinetics of hydrate formation}, journal = {Journal of Energy Resources Technology-Transactions of the ASME}, volume = {143}, year = {2021}, month = {MAR }, pages = {033005}, type = {Article}, abstract = {

The case for developing novel technologies for carbon dioxide (CO2) capture is fast gaining traction owing to increasing levels of anthropogenic CO2 being emitted into the atmosphere. Here, we have studied the hydrate-based carbon dioxide capture and separation process from a fundamental viewpoint by exploring the use of various packed bed media to enhance the kinetics of hydrate formation using pure CO2 as the hydrate former. We established the fixed bed reactor (FBR) configuration as a superior option over the commonly used stirred tank reactor (STR) setups typically used for hydrate formation studies by showing enhanced hydrate formation kinetics using the former. For the various packing material studied, we have observed silica gel with 100 nm pore size to return the best kinetic performance, corresponding to a water to hydrate conversion of 28 mol\% for 3 h of hydrate growth. The fundamental results obtained in the present study set up a solid foundation for follow-up works with a more applied perspective and should be of interest to researchers working in the carbon dioxide capture and storage and gas hydrate fields alike.

}, keywords = {air emissions from fossil fuel combustion, Carbon dioxide capture, combustion of waste, Fixed bed reactor, fuel combustion, Gas hydrate, hydrates, kinetics, Silica gel}, issn = {0195-0738}, doi = {10.1115/1.4048304}, author = {Arora, Amit and Kumar, Asheesh and Bhattacharjee, Gaurav and Balomajumder, Chandrajit and Kumar, Pushpendra} }