SUBSTITUENT EFFECTS ON THE RATE OF DEHYDROGENATION OF PRIMARY AND SECONDARY ALCOHOLS

The kinetics of catalytic dehydrogenation of eight secondary alcohols to ketones on a ZnO-Cr2O3 catalyst has been studied in a flow reactor at 360-degrees-C and atmospheric pressure. The experimental data were fitted to several kinetic models using a nonlinear least-squares method. The most suitable model was found to be a Langmuir-Hinshelwood-type equation, assuming single-site adsorption of alcohol and surface reaction as the rate-determining step. Reaction rate constants and adsorption coefficients of dehydrogenation of secondary alcohols were correlated by the Taft equation with structural parameters characterizing polar or steric effects of substituents in R1-CH(OH)-R2. Similar data, obtained previously, on nine primary alcohols were included in this correlation. The reaction mechanism is discussed.