Intrinsic reaction rate kinetics for the oxidation of methanol have been determined by an experimental investigation conducted using two catalysts. The catalysts used are silver crystals and silver supported on a-alumina. A differential tubular reactor at a pressure of 1.14 atmospheres and a temperature range of 267-320°C was employed to study the chemical kinetics of this reaction. The oxidation of methanol was found to be less than first order with respect to oxygen and greater than first order with respect to methanol for both the supported and unsupported catalysts. Water was found to have an inhibiting effect. Empirical power function, Langmuir-Hinshelwood (LH), Eley-Rideal (ER) and redox type reaction models were invoked to correlate the experimental data. A modified redox type rate expression is proposed for both catalysts. This expression is based on a steady state between two reaction steps: (a) adsorption of oxygen on the catalyst surface and (b) reduction of the catalyst by reaction of adsorbed oxygen with methanol. One and two dimensional reactor models were used to predict industrial reactor performance employing the rate expressiion determined in the experimental study. The prediction of temperature runaway at inlet temperatures above 425°C and inlet methanol partial pressures greater than 0.385 atmospheres are consistent with the operation of an adiabatic reactor. The dimensions of the industrial reactor (i.e. a large, shallow catalyst bed) are such that the simulations obtained with the two dimensional model are in accord with predictions for an adiabatically operated reactor.
|Date of Award||1983|