Selective hydrogenolysis of glycerol to propylene glycol on Cu–ZnO catalysts

Abstract

Hydrogenolysis of biomass-derived glycerol is an alternative route to sustainable production of propylene glycol. Cu-ZnO catalysts were prepared by coprecipitation with a range of Cu/Zn atomic ratio (0.6-2.0) and examined in glycerol hydrogenolysis to propylene glycol at 453-513 K and 4.2 MPa H 2 . These catalysts possess acid and hydrogenation sites required for bifunctional glycerol reaction pathways, most likely involving glycerol dehydration to acetol and glycidol intermediates on acidic ZnO surfaces, and their subsequent hydrogenation on Cu surfaces. Glycerol hydrogenolysis conversions and selectivities depend on Cu and ZnO particle sizes. Smaller ZnO and Cu domains led to higher conversions and propylene glycol selectivities, respectively. A high propylene glycol selectivity (83.6%), with a 94.3% combined selectivity to propylene glycol and ethylene glycol (also a valuable product) was achieved at 22.5% glycerol conversion at 473 K on Cu-ZnO (Cu/Zn = 1.0) with relatively small Cu particles. Reaction temperature effects showed that optimal temperatures (e.g. 493 K) are required for high propylene glycol selectivities, probably as a result of optimized adsorption and transformation of the reaction intermediates on the catalyst surfaces. These preliminary results provide guidance for the synthesis of more efficient Cu-ZnO catalysts and for the optimization of reaction parameters for selective glycerol hydrogenolysis to produce propylene glycol.

Improved Utilization of Crude Glycerol By-Product from Biodiesel Production

“…They also observed that addition of a phosphonium salts improved the selectivity and rate toward 1,2-propanediol. S. Wang & Liu (2007) converted glycerol to 1,2-propanediol on Cu-ZnO catalysts in temperatures between 180-240 o C and high hydrogen pressure 42 bar. They found that glycerol conversion and 1,2-propanediol selectivity depends on Cu and ZnO particle sizes.…”

Glycerol Hydrogenolysis over Co Catalysts Derived from a Layered Double Hydroxide Precursor

“…The hydrogenolysis of glycerol to propanediol is a promising option [1,2]. Until now, supported Cu [3], Co [4], Ni [5], Ru [6], Pt [7], Rh [8] and Ir [9] catalysts have been reported to be active towards glycerol hydrogenolysis. However, the sintering of the metal particles during the course of the reaction often resulted in catalyst deactivation [10][11][12][13].…”

Selective Conversion of Glycerol into 1,2-Propanediol at Ambient Hydrogen Pressure

“…[5][6][7][8][9][10][11][12][13][14][15][16] In liquid-phase hydrogenolysis under hydrogen pressure, glycerol is converted into 1,2-PDO and 1,3-PDO in the presence of supported Rh, 5 Ru, [6][7][8]9 In the vapor-phase hydrogenolysis of glycerol, Cu catalyzes 1,2-PDO formation in the presence of high hydrogen pressure. [10][11][12][13] Since the hydrogenolysis requires elevated hydrogen pressure, 5-11 side reactions occur to form several by-products, including ethylene glycol (EG), propanol, lactic acid, and propanoic acid. Hydroxyacetone (HA) is an intermediate product in the conversion of glycerol into 1,2-PDO through the dehydration-hydrogenation reactions.…”

“…[5][6][7][8][9][10][11][12][13][14][15][16] In liquid-phase hydrogenolysis under hydrogen pressure, glycerol is converted into 1,2-PDO and 1,3-PDO in the presence of supported Rh, 5 Ru, [6][7][8] or Pt. 8,9 In the vapor-phase hydrogenolysis of glycerol, Cu catalyzes 1,2-PDO formation in the presence of high hydrogen pressure.…”