Mechanism analysis and chemical equilibrium modelling for liquid phase glycerol hydrogenolysis

Abstract

In this work, the chemical equilibrium of the glycerol (GLY) hydrogenolysis in the liquid phase was studied from the mechanism of the C–O and C–C bond cleavage and hydrogenation reactions using the commercial simulator UniSim Design ® in the range T = 423–533 K, P = 4–10 MPa and molar ratios H2/reactant = 0.4–2. The equilibrium constants were calculated from the Gibbs free energy, enthalpy and entropy of the reactions involved, employing the group contribution method to estimate the formation properties of the compounds. The results showed that the formation of EG through GLY and the hydrogenation reactions of acetol (AcOH) and 3- hydroxypropionaldehyde (3-HPA) to produce 1,2-propylene glycol (1,2-PG) and 1,3-propylene glycol (1,3-PG) respectively, are limited by thermodynamic equilibrium. For glycols, the formation of 1,2-PG is favored over that of 1,3-PG, and for propanols, the formation of 2-propanol (2-POH) is favored over that of 1-propanol (1-POH). In addition, the formation of EG from 1,2-PG is more feasible, and the formation of ethanol (EtOH) and methanol(MeOH) depend on alternative routes involving EG and 1,3-PG as intermediates, respectively. These results not only show good agreement with previously reported experimental data, but also provide relevant information for the design of bifunctional catalysts that are active and selective towards specific products in the liquid phaseglycerol hydrogenolysis.