One-pot tandem processing of glycerol stream to 1,2-propanediol with methanol reforming as hydrogen donor reaction

Abstract

1,2-propanediol is formed efficiently using bio-glycerol feedstock via hydro-deoxygenation reaction with H2 formed in-situ by a novel reaction cycle. The new catalytic route presented here includes the reformation of methanol, remained unreacted after transesterification, for the production of the active H2 which is consumed in the tandem reaction of glycerol hydrogenolysis. The overall process proceeds in liquid phase over Pt or Cu based catalysts at 220–250°C and 3.5MPa initial N2 pressure for 1 and 4h reaction time. The test over Pt/SiO2 catalyst resulted in 1,2-propanediol yield of 21.4%. The yield to the desired product in the presence of Al2O3 supported Pt is further limited due to the high extent of the over-hydrogenolysis reactions to propanols, which are promoted by the catalyst acidity. Cu:Zn:Al catalysts showed promising performance in the combined reaction cycle. The Cu bulk catalyst (with 49wt% Cu) synthesized by the oxalate gel co-precipitation route exhibits ∼35% yield to 1,2-propanediol at the standard reaction conditions. Further increase to 1,2-propanediol yield (up to ∼45%) was achieved by tuning the reaction conditions. Experiments with labeled 13CH3OH shed light into the H2 formation origin and proved that ∼70% of the total H2 is indeed produced from the reformation of methanol.