Intrinsic and global reaction rate of methanol dehydration over .gamma.-alumina pellets

Dehydration of methanol on y-Al,O, was studied in a differential fixed-bed reactor at a pressure of 146 kPa in a temperature range of 290-360 "C. A kinetic equation which describes a Langmuir-Hinshelwood surface controlled reaction with dissociative adsorption of methanol was found to fit the experimental results quite well. Coefficients in the equation follow the Arrhenius and the van't Hoff relation. The calculated value for the activation energy was found to be 143.7 kJ/mol, while calculated values for the heat of adsorption of methanol and water were 70.5 and 42.1 kJ/mol, respectively. The measured global reaction rates for 3-mm catalyst particles were compared to those calculated by means of intrinsic kinetics and transport processes within the particles. A reasonable agreement was found when the effective diffusion coefficients for reaction components were calculated using a parallel-pore model assuming that only Knudsen diffusion is important.

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