Glycerol Hydrogenolysis To 1,3-propanediol Over Pt/Nb₂O₅-SiO₂ Catalyst

A series of Nb2O5-SiO2 supports were synthesized by sol-gel method and Pt/Nb2O5-SiO2 catalysts were prepared by impregnation method.These catalysts were examined in a 100mL stainless steel autoclave in glycerol hydrogenolysis.The physiochemical properties of the catalysts were investigated by the techniques of X-ray diffraction,H2 temperature-programmed reduction,transmission electron microscopy,NH3 temperature-programmed desorption and in-situ CO adsorption diffuse reflectance infrared Fourier transform spectroscopy.The parametric study of glycerol hydrogenolysis,effect of Nb2O5 content and preparation technology on Pt/Nb2O5-SiO2 catalyst have been extensively investigated.The results and conclusions are as follows:1.The effect of reaction conditions on the catalytic performance of Pt/Nb2O5-SiO2 catalyst was investigated.Optimal reaction parameters for catalyst evaluation was obtained as:reaction time 12h,reaction temperature 150?,hydrogen pressure 5.6MPa.2.The effect of Nb2O5 content on the structural properties and catalytic activity of Pt/Nb2O5-SiO2 catalyst was studied.A volcanic curve relationship between Nb2O5 content and catalyst activity was established.Highest catalyst activity was observed for 5wt%(Nb2O5 content),while too much Nb2O5 on the surface of catalysts would change the electronic structure of active constituent so that part of Pt would exist as oxidation state,thus resulting the decreased catalyst activity.3.Five Nb2O5 supports prepared by different preparation technologies were employed as catalyst supports for Pt/Nb2O5-SiO2 catalyst in glycerol hydrogenolysis.Results showed that in the process of preparing Nb2O5-SiO2 supports by sol-gel method or impregnation method,Nb would be doped into SiO2 lattice to promote synergy between the support and Pt which could generate active sites,thus enhanced the catalytic activity of glycerol hydrogenolysis.However,Nb2O5-SiO2 support obtained by physical mixing did not have this promotion effect for the reason that Nb2O5 and SiO2 were independent of each other.In addition,Nb2O5-SiO2 supports prepared by different silicon sources under the same preparation method would also result in different metal dispersion and metal-support interaction,therefore the agglomeration degree of Pt during the calcination is quite different,thus resulting catalytic performances variance in glycerol hydrogenolysis.