Catalytic Partial Oxidation of Ethane to Acetic Acid over Mo1V0.25Nb0.12Pd0.0005Ox: II. Kinetic Modelling

The kinetics of the oxidation of ethane to acetic acid was modelled based on experimental data obtained in a fixed-bed reactor using the title catalyst at temperatures between 500 and 580 K and elevated pressures from 1.3 to 2.8 MPa. The kinetic data were fitted. Two different models taking into account surface processes such as catalyst reduction by ethane or ethylene and reoxidation by oxygen and surface hydroxylation were suggested; the models were discriminated on the basis of experimental data. For the superior kinetic model two different catalytic centres were assumed, i.e., one for the oxidative dehydrogenation of ethane and one for the heterogeneous Wacker oxidation of ethylene to acetic acid. The activity of the Wacker centre strongly depends on the presence of water. The analysis of the kinetic results leads to the conclusion that ethane activation is the rate determining step for oxidising ethane and that the formation of the Wacker centre by water adsorption is rate determining for converting ethylene to acetic acid.