Hydrogenolysis of Glycerol to Lower Alcohols over Bifunctional Copper Catalysts

The hydrogenolysis of glycerol was investigated in a fixed-bed catalyst reactor over bifunctional catalysts containing 15 wt % copper supported on SAPO-11, Al-HMS (20), BEA-38, and Al-SBA-15(20); the industrial copper chromite catalyst CuCr2O4 was used as a reference sample. The physicochemical properties of the catalysts (acidity, textural characteristics, and metallic copper dispersion) as well as their catalytic performance in the temperature range of 180–260°C at pressures up to 6 MPa were compared. It was shown that the distribution of hydrogenolysis products depends on the type of aluminosilicate used and the ratio of acid to metal sites. The 15% Cu/SAPO-11 catalyst in the range of 220–240°C provided preferential formation of 1,2-propanediol, whereas systems with a larger number of acid sites (15% Cu/BEA-38 and 15% Cu/Al-HMS (20)) at elevated temperature promoted sequential hydrogenolysis to propyl alcohols. An increase in pressure above 4 MPa and in the hydrogen/feed ratio above 500–1000 Nm3/m3 did not lead to a substantial improvement in the performance. Differential IR spectroscopy data for the surface of the spent catalysts indicated the absence of carbonaceous deposits. Organic compounds present on the surface were represented by aliphatic and aromatic oxygenates (predominantly ethers and acetals); their presence were not the cause of catalyst deactivation, which was instead due to agglomeration of copper particles.