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...

M-Forming is a zeolite-based catalytic process which, when used in conjunction with naphtha reforming, produces a higher octane, lower aromatic content gasoline by selectively converting low octane normal and singly branched chain paraffins. It also allows increased reformer throughput and increased process flexibility to meet changing product quality demands. The process may be employed to process either full-range reformates from a low-pressure reformer or light reformates, boiling below 120 °C, which are difficult to reform. The reactions involved in the M-Forming process include (1) selective cracking of normal and singly branched paraffinic molecules, (2) formation of alkyl aromatics by the alkylation of benzene and toluene with olefinic cracked fragments, (3) aromatics formation via cyclization and hydrogen transfer, and (4) redistribution of alkyl aromatics to produce a spectrum of aromatic products.

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A novel and successful approach to the design of hydrogen-shift catalysts is presented. Detailed studies of 1-butene hydroisomerization reveal that a catalytic synergism exists in physical mixtures. Mixtures of FeCe/Grafoil and Pt/Grafoil (or Pd/Grafoil) display high selectivity (.Pt) and activity levels as much as ten times larger than the sum of the separately measured activities. Thus, it is demonstrated that highly selective and active isomerization catalysts can be created by physically mixing hydrogen atom generator surfaces (e.g. Pd) with highly selective but low-activity surfaces (e.g. FeCe).

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