Magnesium hydroxide–supported ruthenium as an efficient and stable catalyst for glycerol-selective hydrogenolysis without addition of base and acid additives

Abstract

In this work, Ru-based catalysts with the synthesized and commercial Mg(OH)₂ and MgO as supports such as Ru/Mg(OH)₂(S) (or Ru/Mg(OH)₂(B), Ru/MgO(S), and Ru/MgO(B)), S and B representing “synthesized” and “commercial”, respectively, were prepared at room temperature by a simple chemical reduction approach. The Ru/Mg(OH)₂(S) catalyst exhibited the best catalytic activity (TOF = 134 h⁻¹) and the highest selectivity to 1,2-propanediol (65%) for glycerol hydrogenolysis. Moreover, this reaction was performed over the as-prepared catalysts without adding any liquid acid (e.g., HCl) or base (e.g., NaOH). Selectivity of 1,2-propanediol increased with an increase in the reaction temperature or time, but that towards ethylene glycol did not show any obvious change. Characterization techniques such as XRD, SEM, XPS, TG, TEM, HRTEM, STEM, STEM-EDX elemental analysis (mapping and line-scanning), and CO₂-TPD were used to explore related properties of the as-synthesized catalysts to explain the difference in their catalytic activity and selectivity. The reasons for Ru/Mg(OH)₂(S) to exhibit high catalytic activity are as follows: Ru with high dispersion on the support, Mg(OH)₂ with a cotton-like morphology, numerous defect sites and strong basic active sites.