Kinetic study of the liquid-phase selective hydrogenation of 1-butyne in presence of 1-butene over a commercial palladium-based catalyst

Abstract A kinetic investigation of the liquid-phase selective hydrogenation of 1-butyne in presence of 1-butene was performed over a commercial palladium-based/alumina catalyst of the eggshell type. This investigation is aimed at validating a kinetic expression to describe 1-butyne hydrogenation under experimental conditions around the typical operating conditions of industrial C 4 cuts hydrorefining processes. Seven levels of temperature between 27 °C and 62 °C were explored. 1-Butyne and n-butene initial mole fractions amounted to ca. 8% and 9% and hydrogen partial pressure was set between 0.85 atm and 7.82 atm. Experimental data and data analysis were extended to 1-butyne total conversion. Palladium proved to be quite selective towards 1-butyne hydrogenation. However, the intrinsic palladium selectivity is impaired by the presence in our experiments of severe intracatalyst diffusion limitations. This result turns the attention to the crucial influence of hydrogen partial pressure level on selectivity because unnecessary hydrogen excesses severely lessen selectivity when 1-butyne becomes the limiting reactant inside the catalyst. A kinetic expression of the Langmuir–Hinshelwood–Hougen–Watson type was proposed to describe the hydrogenation of 1-butyne. 1-Butene hydrogenation rate was described by a zero-order and first-order kinetic expression with respect to 1-butene and hydrogen, respectively. The kinetic model predicts experimental data with an average deviation of 17.1%. The relative inference intervals of the kinetic parameter estimates were less than ±14.8%.