EXTENDED KINETIC ISOTOPE METHOD——ITS APPLICATION TO THE ANALYSIS OF BUTENE OXIDATIVE DEHYDROGENATION REACTION NETWORK OVER THREE CATALYSTS

Abstract

The "Extended Kinetic Isotope Method" (EKIM) is presented in this paper in detail. The EKIM is applied to the analysis of butene oxidative dehydrogenation reaction network over Bi-Mo-P, Sn-P-Li and ferrite catalysts, including reversible isomerization between the three n-butene isomers, selective oxidation of n-butenes to butadiene, and totaI oxidation of n-butenes and butadiene. The reaction orders of selective and total oxidation reactions, as well as the rate constants of the 13 step reactions, have been estimated. From the results obtained, it is suggested that the rate determining step in the selective oxidation of butenes over the Bi-Mo-P and Sn-P-Li catalysts should be the abstraction of first hydrogen to form allyl intermediate. However, over the ferrite catalyst, the second H-abstraction from allyl intermediate rather than the first one might be the rate determining step. Mechanisms of selective oxidation and isomcrization reactions over the three catalysts are also discussed.