Burton H. Bartley

Dual function catalysis with the metal at a higher temperature than the support

Abstract Maintaining the metal and nonmetal sites of a dual function catalyst at different temperatures is termed differential heating. A way has been found to maintain a temperature difference between the catalytic sites of the iron portion and the sites of the silica-alumina portion of a dual function catalyst. A radiofrequency induction heater was used to keep the iron at a higher temperature than the silica-alumina. The iron particles supported upon the silica-alumina were heated directly by the induction unit, while the silica-alumina was heated only by conduction of heat away from the iron particles. The iron temperature was determined using the temperature dependence of the hydrogenation of propylene over the iron. The silica-alumina temperature was determined: (a) by using the temperature dependence of the isomerization of cyclopropane over the silica-alumina and (b) by the adsorption of hydrocarbon upon the catalyst. Under one set of conditions a temperature difference of 58 °C between the iron and the silica-alumina was indicated by the two reactions. The adsorption measurements had an even lower temperature for the silica-alumina. Among the important factors effecting an increase in temperature difference are: (a) increasing average catalyst temperature, (b) increasing ratio of carrier gas flow rate to catalyst weight, and (c) increasing the particle size and separating the two functional portions of the catalyst.