Glycerol hydrogenolysis over Ru-Cu bimetallic catalysts supported on modified zirconias

Ruthenium-copper bimetallic catalysts supported on modified zirconia (m-ZrO2, 2%CaO-ZrO2, 3%SO4-ZrO2 and 10%WO3-ZrO2) were investigated in hydrogenolysis of glycerol in aqueous solution to produce 1,2-propanediol (1,2-PDO). Catalysts were characterized by N-2 physisorption (BET), H-2 and CO chemisorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Active metallic phase consists of Ru-Cu nanoparticles with average diameter of 1.2 nm when supported on m-ZrO2 and 2%CaO-ZrO2, and larger particles on 3%SO4-ZrO2 and 10%WO3-ZrO2. In all cases, the addition of Cu to the Ru-based catalysts resulted in a decrease in glycerol conversion and increase in selectivity to 1,2-PDO. At 453 K, the best performing catalyst was bimetallic Ru-Cu/m-ZrO2. The catalysts supported on 3%SO4-ZrO2 showed activity well below expectations, likely due to sulfur poisoning. On the other hand, catalysts supported on 2%CaO-ZrO2 or 10%WO3-ZrO2 showed adequate activity. An increase in 40% in H-2 pressure decreased 1,2-PDO selectivity but caused a ten-fold increase in TOF over Ru-Cu/10%WO3-ZrO2, to around 0.11 s(-1). Cu addition to Ru lead to site blockage, with a beneficial effect on tuning selectivity towards C-O cleavage, and depressing C-C cleavage.