Heterogeneous Catalysts for Glycerol Biorefineries: Hydrogenolysis to 1,2-Propylene Glycol

Abstract

Research on the use of biomass resources for the generation of energy and chemical compounds is of great interest worldwide. The development and growth of the biodiesel industry has led to a parallel market for the supply of glycerol, its main by-product. Its wide availability and relatively low cost as a raw material make glycerol a basic component for obtaining various chemical products and allows for the development of a biorefinery around biodiesel plants, through the technological integration of different production processes. This work proposes a review of one of the reactions of interest in the biorefinery environment: the hydrogenolysis of glycerol to 1,2-propylene glycol. The article reviews more than 300 references, covering literature from about 20 years, focusing on the heterogeneous catalysts used for the production of glycol. In this sense, from about 175 catalysts, between bulk and supported ones, were revised and discussed critically, based on noble metals, such as Ru, Pt, Pd, and non-noble metals as Cu, Ni, Co, both in liquid (2–10 MPa, 120–260 °C) and vapor phase (0.1 MPa, 200–300 °C). Then, the effect of the main operational and decision variables, such as temperature, pressure, catalyst/glycerol mass ratio, space velocity, and H2 flow, are discussed, depending on the reactors employed. Finally, the formulation of several kinetic models and stability studies are presented, discussing the main deactivation mechanisms of the catalytic systems such as coking, leaching, and sintering, and the presence of impurities in the glycerol feed. It is expected that this work will serve as a tool for the development of more efficient catalytic materials and processes towards the future projection of glycerol biorefineries.

Glycerol Hydrogenolysis to Bio-Propanol: Catalytic Activity and Kinetic Model for Ni/C Modified with Al(H2PO4)3

“…As it can be seen, glycerol conversion decreases as the water concentration increases. This behavior is expected as water is a by-product of the reaction, so its formation shifts the equilibrium towards the reactants [51]. It has been reported that in the presence of Rh 0.02 Cu 0.4 /Mg 5.6 Al 1.98 O 8.57 catalyst, glycerol conversion decreases from 91% to 69% when the water content increases from 0 wt.% to 40 wt.%, using ethanol as a solvent at 180 • C and 2 MPa of H 2 [52].…”

“…the reaction, so its formation shifts the equilibrium towards the reactants [51]. It has be reported that in the presence of Rh0.02Cu0.4/Mg5.6Al1.98O8.57 catalyst, glycerol conversion creases from 91% to 69% when the water content increases from 0 wt.% to 40 wt.%, us ethanol as a solvent at 180 °C and 2 MPa of H2 [52].…”

Crude Glycerol Hydrogenolysis to Bio-Propylene Glycol: Effect of Its Impurities on Activity, Selectivity and Stability

“…In this context, it has been extensively reported in the literature that glycerol hydrogenolysis allows for the production of bio-propylene glycol (1,2-PG), a product employed in the pharmaceutical, cosmetics, food industries and in the chemical industry in general. At present, 1,2-PG is obtained through a petrochemical process, so the production of 1,2-PG from glycerol is an environmentally friendly alternative, which, in the near future, could allow for decreasing the present dependence on fossil resources as raw materials [3].…”