Highly Selective Gas-Phase Catalytic Hydrogenation of Acetone to Isopropyl Alcohol

Current industrial synthesis procedures of isopropyl alcohol (IPA), by the direct or indirect hydration of propylene in the gas or liquid phase, suffer from the low conversion of propylene, the requirement for high pressure, and the harmfulness to the environment. In this context, we report a single-step, gas-phase process for the green synthesis of IPA via acetone hydrogenation, in a fixed-bed reactor, under ambient pressure and within a temperature range of 100–350 °C. Composite catalysts with various ratios of ruthenium nanoparticles supported on activated charcoal and nano-zinc oxide (n-Ru/AC/n-ZnO) were used. Catalytic activity and selectivity were functions of n-Ru/AC/n-ZnO loading ratios, reaction temperature, and the hydrogen to acetone molar ratio. The composite catalysts were characterized by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), hydrogen temperature-programmed reduction (H2-TPR) analysis, and nitrogen physisorption. High yields of IPA were obtained over 3n-Ru/AC/2n-ZnO) catalyst, which showed the highest selectivity of 98.7% toward isopropyl alcohol and acetone conversion of 96.0% under a hydrogen to acetone mole ratio of 1.5 at 100 °C. Reaction rates, calculated from the model equation, were in reasonable agreement with those measured experimentally. The apparent activation energy (Ea) value for acetone hydrogenation was found to be 17.2 kJ/mol. This study proved that immobilized Ru catalysts were potential superior catalysts for the selective hydrogenation of acetone to IPA in exceptionally mild green synthesis conditions.