The nature of permeability anisotropy and catalytic activity |
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Authors: | I. M. Kurchatov N. I. Laguntsov M. V. Tsodikov A. S. Fedotov I. I. Moiseev |
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Affiliation: | 1.OAO Akvaservis,Moscow,Russia;2.Moscow Institute of Engineering Physics,Moscow,Russia;3.Topchiev Institute of Petrochemical Synthesis,Russian Academy of Sciences,Moscow,Russia;4.Kurnakov Institute of General and Inorganic Chemistry,Russian Academy of Sciences,Moscow,Russia |
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Abstract: | The phenomena of permeability anisotropy and an increase in the rates of catalytic reactions in porous membranes modified with highly dispersed catalytic systems were analyzed. A model of stochastic gas motions was proposed; this model is based on the hypothesis of the specific interaction of molecules with the inner surface of pores resulting in a nonisotropic distribution of molecules over traveling directions. The effects of asymmetric gas transfer in porous and gradient-porous membranes were considered to explain differences in the rates of heterogeneous catalytic reactions in a nanoporous membrane reactor under changes in the direction of supplying a reaction mixture. From the model proposed, it follows that the transversal diffusion of gas molecules is most probable in the porous medium of a ceramic membrane with a pore-size distribution gradient from large to small pores along the flow direction. This diffusion results in an increase in the frequency of molecular collisions with the wall of a microchannel and, correspondingly, in an increase in the contact time. The model proposed explains the intensification of a number of heterogeneous catalytic reactions performed in the porous media of catalytic porous membranes. |
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