Kinetic and Isotopic Study of Ethane Dehydrogenation over a Semicommercial Pt,Sn/Mg(Al)O Catalyst

Abstract

Mechanistic and kinetic information on the ethane dehydrogenation reaction over a semicommercial Pt,Sn/Mg(Al)O catalyst has been elucidated from catalytic testing and isotopic labeling experiments under reaction conditions close to those used in the commercial dehydrogenation process (C2H6/H2/H2O/inert = 10/1.5/2/32 or C2H6/H2/CO2/inert = 10/2/5/83, 600−630 °C reaction temperature, atmospheric pressure). From kinetic measurements, a negative dependence of the reaction rate in H2 and C2H4 partial pressures was observed, while the dependence on steam partial pressure was positive. Isotopic labeling experiments showed that the negative effect of H2 and C2H4 could not be attributed to the reverse reaction, but rather to competitive adsorption at the active sites for dehydrogenation. The observed reaction rate with respect to C2H6 was close to first order. By fitting the experimental data to the rate equation derived from the elementary steps of ethane dehydrogenation, the observed deviation from the first ord...