Reaction Performance Of Glycerol Hydrogenolysis Over Supported Pt Catalyst

Biodiesel, as renewable and pollution-free alternative diesel fuel, has been receiving a lot of concern throughout the world due to the energy needs and environmental awareness. At present, biodiesel, i.e. fatty acid methyl ester, is produced through transesterification of triglyceride and methanol with glycerol as a by-product in the reaction. Meanwhile, due to the increased expansion of biodiesel and the sharp decrease of glycerol prices, much attention was focusing on converting glycerol into value-added chemicals.In this work, catalysts were prepared with Pt as active component and γ-Al2O3 as the support by impregnation method. And then, Fe, Co, Ni, Cu, Zn, Cr were added to Pt catalyst to evaluate their performance on glycerol hydrogenolysis reaction via fixed-bed reactor. The results showed that the Pt-Ni/y-Al2O3 bimetallic catalyst gives the highest selectivity to ethylene glycol. Further, the properties of Pt-Ni/y-Al2O3 with the addition of the third metal components (Fe, Co, Cu, Zn, Cr), rare-earth oxides (La2O3, CeO2, Y2O3) and acids (H2WO4, (NH4)2MoO4, H3BO3) were investigated.The effect of the content of Pt and Ni, calcination temperature and calcination time on the distribution of products were evaluated in the process of glycerol hydrogenolysis. The results suggest that 2%Pt-15%Ni/γ-Al2O3 exhibits excellent catalytic activity and high selectivity to ethylene glycol. The impacts of the reaction conditions on 2%Pt-15%Ni/y-Al2O3 were evaluated in the temperature range of 453-493 K, H2 pressure range of 3.0-6.0 MPa, glycerol concertration range of 20%-60%wt, LSV range of 0.261-2.609 h-1, GSV range of 2608.69-7826.1 h-1. The results show that the highest selectivity to ethylene glycol is 21.11%, with 97.28% conversion to glycerol,64.96% selectivity to 1,2-PDO under the condition of 473 K,3.0 MPa,20%wt of glycerol concertration, LSV=1.304 h-1, GSV=5217.4h-1.The 2%Pt-10%Ni/y-Al2O3 and 2%Pt-15%Ni/y-Al2O3 were characterized using powder X-ray diffraction (XRD), N2 physical adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), temperature-programmed reduction (TPR) and X-ray photoelectron spectra (XPS). The results of XRD, TPR and XPS suggest the formation of PtNi alloy cluster.The metal-metal interaction and the formation of PtNi alloy cluster in Pt-Ni bimetallic catalyst come into being the synergistic effect and thus obtain a much higher selectivity to ethylene glycol.