油脂水素添加反応中の銅クロム酸化物触媒の不連続被毒

抄録

It had been found that ordinary-pressure hydrogenation of whale oil with copperchromium oxide catalyst is of zero order with respect to the initial concentration of the substrate. However, hydrogen absorption frequently followed an apparent first-order reaction formula with respect to the concentration of the substrate. This fact suggests the formation of a catalyst poison in proportion to the degree of hydrogenation.
The present series of experiments has shown that there is no formation of a catalyst poison even when the oil and the catalyst are heated for a fairly long time at 180° in vacuum or in carbon dioxide atmosphere prior to hydrogenation. This fact supports the above assumption that there is a close relationship between the formation of a catalyst poison and hydrogenation.
A detailed examination was then made on the poisoning of the catalyst during hydrogenation of whale oil with copper-chromium oxide catalyst at 180° in ordinary-pressure of hydrogen. The rate decreasing curve followed an apparent first-order reaction formula but seemed to be composed of many straight lines. In fact, the reaction rate maintains a constant value for a certain range of hydrogenation but drops suddenly, and these phenomena are repeated successively. These experimental facts indicate that there is a discontinuous adsorption of the poison on the active site of the catalyst, or that there is a hysteresis in the adsorption of catalyst poison or desorption of the substrate.
A similar phenomenon had been observed in the ordinary-pressure hydrogenation of ethylene with the same catalyst and a hysteresis in desorption of ethylene and hydrogen was described earlier.