Hydrogenation of ethylene over chromia–alumina catalysts. Electron spin resonance and kinetic studies

Abstract

The hydrogenation of ethylene over chromia–alumina catalysts containing known amounts of Cr²⁺ and Cr³⁺ has been investigated at temperatures between – 78 and 200 °C. The activity of the catalyst depends strongly on the presence of Cr³⁺(determined by e.s.r.), in as much as increasing Cr³⁺ concentration is accompanied by a considerable increase in the rate of hydrogenation. Preliminary kinetic studies show that the reaction rate is zeroth order in hydrogen at –78 °C and first order at higher temperatures (> 0 °C). The e.s.r. signal ascribed to Cr³⁺(g= 1.986) undergoes some changes under the reaction conditions when exposed to a 1 : 1 mixture of hydrogen and ethylene at 100 °C.