Selective Hydrogenation Of Natural Oils And Fatty Acids To Fatty Alcohols Catalyzed Over Co/HAP Catalyst

With the increasing demands of fossil fuels for the industrial production and human life and the exhaustion of fossil resource,it forced people to develop the renewable resources since the 21st century.Biomass resource as a kind of renewable clean energy with abundant reserves is crucial for the production of green fuels and chemicals in the future.Naturally much attention has been paid to natural lipid biomass,which is an important green renewable raw material in current chemical production.Its special structure and properties make it worthy for further high value utilization.Fatty alcohols,as important derivative products in the transformation process of natural oils and fatty acids,are used in the production of various kinds of surfactants products and other fine chemicals.The traditional catalysts for the preparation of fatty alcohols from natural oils and fatty acids are mainly copper-chromium catalysts.The copper-chromium catalysts can cause environmental pollution in the process of synthesis and the reaction conditions are very harsh.The new developed catalytic system is mainly the precious metal catalysis system.The synthesis cost of precious metal catalyst is high and it is not suitable for large-scale industrial production.The catalyst synthesis in the non-precious metal catalytic system is more complex and the reaction conditions are also relatively high.Therefore,it is of great significance to develop a simple,green and efficient non-precious metal catalytic system for the selective hydrogenation of fatty acids and natural oils to fatty alcohols.In this study,a new efficient non-precious metal-based catalytic system was developed for the selective hydrogenation of fatty acids into fatty alcohols under mild conditions in aqueous phase.The non-precious cobalt,which has the proper hydrogenation activity,was used as the hydrogenated metal,and stearic acid was used as the model compound of fatty acid.The hydrogenation of stearic acid was performed over cobalt-based catalysts with different supports including HZSM-5,CeO2,ZrO2,SiO2,Al2O3,TiO2 and hydroxyapatite(HAP).Among these catalysts,Co/HAP exhibited the highest activity and 97.1%yield of 1-octadecanol was obtained at 190? and 4 MPa H2 in water.Additionally,the Co/HAP was capable of directly hydrogenating the natural oil,Jatropha oil,to fatty alcohols without any preprocessing and better result could be achieved.83.1 wt%Yield of alcohols was obtained at 190? and 4 MPa H2.Co/HAP catalyst can also catalyze the full hydrodeoxygenation of stearic acid and Jatropha oil to alkanes when dodecane was used as solvent.The catalysts were characterized by a series of methods(TEM,XRD,H2-TPR,NH3-TPD and FT-IR),and the high catalytic activity of Co/HAP could be due to its desired acidity,cobalt particle dispersion,and stronger metal-support interaction.Meanwhile,the high efficiency of Co/HAP could also be due to the absorption of fatty acid on catalyst which thus promotes the hydrogenation process over surface active site of cobalt particle.The experimental parameters(temperature and pressure)of the reaction were also optimized,and the possible reaction pathway was also proposed by tracking the reaction process intermediates.In the process of catalyst circulation,metal leaching and serious aggregation of metal particles could be the main reason for the inactivation of catalyst.This catalytic system will provide reference for other selective catalytic hydrogenation of biomass.