Coating the Internal Surface of a Capillary Microreactor for the Selective Hydrogenation of 2-Methyl-3-Butyn-2-ol by PdxZn1 – x/TiO2 Catalysts: A Kinetic Study

Abstract

The kinetics of the liquid-phase hydrogenation of 2-methyl-3-butyn-2-ol (MBI) on the thin films of Pd₅₀Zn₅₀/TiO₂, Pd₈₀Zn₂₀/TiO₂, and Pd/TiO₂ was studied in a temperature range of 308–333 K at MBI concentrations of 0.1–0.6 mol/L. The films were applied to the internal walls of silica capillaries with an inside diameter of 530 μm. The reaction of MBI hydrogenation at its initial stage was of first order with respect to hydrogen, and the orders of reaction with respect to MBI on Pd₅₀Zn₅₀/TiO₂, Pd₈₀Zn₂₀/TiO₂, and Pd/TiO₂ were 0.3, 0.4, and 0.5, respectively. The yield of the target product 2-methyl-3-buten-2-ol on the bimetallic films was higher than that on Pd/TiO₂. The highest yield (94%) was achieved on the film of Pd₅₀Zn₅₀/TiO₂ at a conversion of 99%, a temperature of 313 K, and a partial hydrogen pressure of 1 atm. The higher selectivity of the reaction, which occurred according to the Langmuir–Hinshelwood mechanism, on the bimetallic films was explained by a decrease in the alkene/alkyne and alkene/alkane ratios of adsorption constants and by a decrease in the rate constants of 2-methyl-3-buten-2-ol hydrogenation.