Catalytic activity of the 1:1:1 Zn, Cr and Fe mixed oxide: Mechanistic study of the ketonization of acetic acid

Abstract

The catalytic activity of a ternary oxide mixture of Zn, Cr and Fe in 1:1:1 atomic concentration has been studied using ketonization of acetic acid. The Arrhenius plot for the reaction shows a break around 673 K indicating the dependence of the reaction mechanism on temperature. Electrical conductance measurement also shows a change in the electronic nature of the catalyst around 673 K. The utilization of dehydration and dehydrogenation active sites of the catalyst for the ketonization process is established by the mutual effect of isopropyl alcohol and acetic acid on each others reaction on the catalyst. Competitive reaction study shows that ketonization follows Langmuir-Hinshelwood mechanism where as esterification follows Rideal-Eley mechanism. Product inhibition studies and infrared spectral studies show that the reaction is between two adsorbed acetate ions above 673 K and between one adsorbed acetate ion and an adsorbed acyl carbonium ion below 673 K.