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Catalytic oxidation of phenol in aqueous solution over supported copper oxide was studied in the batchwise mode at atmospheric and above-atmospheric pressure and between 369 and 419°K. The reaction undergoes an induction period and transition to a much higher, steady-state activity regime. The reaction is first order with respect to phenol in both regimes, but the oxygen dependency decreases from first to one-half order in shifting from the induction period to the steady-state activity regime. The rate shows other than first-order behavior with respect to catalyst loading. The reaction is proposed to involve a free-radical mechanism. Oxidation rates at atmospheric pressure conditions are too slow to be of practical interest but can easily be brought into the range of practical importance by only moderate increases in temperature and operating pressure.

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Mathematical models are developed which account for simultaneous heat transfer, mass transfer, and chemical reaction in the oxidation of carbon monoxide over platinum containing monoliths. A two-dimensional model is shown to predict unusual behavior of the Nusselt number in the presence of rapid reaction. However, a simpler one-dimensional model is adequate for predicting monolith behavior. Department of Chemical EngineeringUniversity of Delaware Newark, Delaware 1971 1 SCOPEThe oxidation of carbon monoxide and hydrocarbons is the principal reaction in an automobile catalytic converter. Half of the 1975 automobiles are equipped with monolithic converters in which platinum and palladium catalysts are deposited on the walls of a bundle of parallel ceramic tubes. The oxidation kinetics exhibits a negative reaction order with respect to carbon monoxide concentration, and the reactions are highly exothermic.This paper describes a theoretical analysis of these unusual kinetics in monoliths. Steady state and transient temperature and concentration profiles are investigated, with numerical techniques used to solve the partial differential equations. The effects of inlet carbon monoxide concentration, inlet gas temperature, gas velocity, tube geometry, and diameter are investigated.Young and Finlayson (1974) have shown that there is a significant difference between a one-dimensional model, where only axial gradients are considered, and a twodimensional model, where both axial and radial gradients are considered. They have shown that in the two-dimensional model the Nusselt number shows an unusual behavior in the presence of rapid reactions. It would appear that the far more time consuming two-dimensional model must be used for the monolithic catalyst.Overheating of the monolith in road use is often observed, to temperatures above the melting point of the ceramic material (about 1 4OO0C), even when the adiabatic flame temperature of the inlet gas is far below this temperature. An explanation for this phenomenon is needed. CONCLUSIONS AND SIGN I FICANCEThis study confirmed the unusual behavior of the Nusselt number when the wall cools the gas in one section but heats the gas in a subsequent section. Despite this spectacular variation in the Nusselt number, the one-and two-dimensional models predict similar performance of the monolithic reactor (measured by the concentration profile). Thus, the simpler one-dimensional model is adequate for predicting monolith behavior during the crucial warm-up of an automobile from a cold start.The monolithic reactor behavior is dominated by the position of the light-off point, where the catalytic wall temperature takes an upward leap, the wall concentration falls to zero, and the reaction becomes mass transport limited. In a typical 1975 automobile, with a rich exhaust during idle or deceleration, the position of the light-off point is dominated by the inlet gas temperature. At a sufficiently low inlet temperature, light-off does not occur, and the conversion is very low. For a very narrow...