Sorption and diffusion in heteropolyoxometalates : I. Aromatic hydrocarbons |
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| Authors: | V. S. Nayak J. B. Moffat |
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| Affiliation: | 1. Department of Chemistry and Guelph-Waterloo Centre for Graduate Work in Chemistry, University of Waterloo, Waterloo, Ontario, Canada N2L, 3G1;1. Guangxi Key Laboratory of Clean Pulp & Papermaking and Pollution Control, College of Light Industry and Food Engineering, MOE Key Laboratory of New Processing Technology for Nonferrous Metals and Materials, School of Chemistry and Chemical Engineering, Guangxi University, Nanning 530004, China;2. Guangzhou Key Laboratory for New Energy and Green Catalysis, School of Chemistry and Chemical Engineering, Guangzhou University, Guangzhou 510006, China;3. Institute of Chemical Sciences, University of Peshawar, 25120 KP, Pakistan;1. School of Chemical Engineering, Faculty of Engineering, University of Tehran, P.O.Box:11155/4563 Tehran, Iran;2. Adsorption, Modeling and Nanomaterial Laboratory, School of Chemical Engineering, College of Engineering, University of Tehran, Iran |
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| Abstract: | The sorption capacities and diffusivities of benzene, toluene, xylene, mesitylene, and m-diethylbenzene have been measured at 293, 308, and 323 K on three solid heteropolyoxometalates, 12-tungstophosphoric, 12-molybdophosphoric, and 12-tungstosilicic acids, and their ammonium salts. Heats of adsorption were calculated from the former data. The microporous salts show considerably larger sorption capacities than the nonporous solid acids, not surprisingly, and the former show sorption properties which are evidently related to both the micropore size distributions and the nature of the sorbate molecules. Diffusivities of aromatic hydrocarbons were found to decrease with the increase in molecular weight and kinetic diameter, and were also dependent on the particular heteropolyoxometalate being examined. Heats of adsorption, in general, show no evidence of chemisorption effects. However, the sorption of mesitylene and of m-diethylbenzene on ammonium 12-tungstosilicate was found to be irreversible. Little or no evidence was found for the penetration of aromatic hydrocarbons into the bulk structure of the solid heteropolyacids. |
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