A Study On The Hydrothermal/mechanical Stability Of Bulk MoNi Composite Oxide Catalysts For Hydrogenation

With the petroleum resources shortage and awareness of environmental protection increasing,it has been considerably concerned that the study on the production of second generation biodiesel which is environmentally friendly and a substitute for fossil fuels by means of hydrodeoxygenation of renewable animal fats and vegetable oils.The common hydrodeoxygenation catalysts at present have the main problems of the low catalytic activity and poor hydrothermal stability,so the development of hydrodeoxygenation catalysts with high activity and high hydrothermal/mechanical stability becomes an important issue in the biodiesel study.The unsupported Mo Ni composite oxide catalysts were preparation by the sol-gel method in this thesis,were characterized by XRD,BET,Py-IR,NH3-TPD,and using the solution of 20 wt% jatropha curcas oil+80wt% n-octane as the feed,the HDO performance of the catalysts were evaluated in a continuous flow fixed-bed reactor.The influences of the adhesive and amount of the pore-enlarging additive as well as the modifying agents on the properties and hydrothermal/mechanical stability of the catalysts were investigated.In addition,the influences of reaction temperature,reaction pressure and the moral ratio of Mo/Ni on hydrodeoxygenation reaction path of jatropha curcas oil over the catalysts were also investigated.The study results of the influences of the adhesive on hydrothermal/mechanical stability of the catalysts showed that using a suitable adhesive,it not only can to maintain a high hydrodeoxygenation catalysts activity but also can significantly improve hydrothermal/mechanical stability;adding diatomite into the catalyst could effectively improve the hydrothermal/mechanical stability of the catalysts,adding molecular sieve adhesive could effectively improve the mechanical stability of the catalysts in the catalyst molding process,Using mass ratio is 1:2 of molecular sieve adhesive/magnesia-alumina spinel as adhesive could significantly improve the hydrothermal/mechanical stability of the catalyst.Comparison of the properties of the catalysts made respectively using mass ratio is 1:2 of molecular sieve adhesive/ magnesia-alumina spineland aluminum hydroxide as adhesive showed that the former affected slightly on the crystalline phase of the catalyst,but increased its pore size,reduced its specific surface area and the total amount of acid.The results of pore-enlarging study of the unsupported Mo Ni composite oxide catalyst indicated that within the range studied of the added amount,with increasing the ?-cyclodextrin amount,the catalyst hydrodeoxygenation activity increased slightly,while the hydrothermal/mechanical stability decreased slightly,therefore,it can reduce the amount of ?-cyclodextrin appropriately,thereby improving the hydrothermal/mechanical stability of catalyst,and the suitable amount was of 5g ?-cyclodextrin/(Mo+Ni)mol.The addition of ?-cyclodextrin had no effect on hydrodeoxygenation reaction path of jatropha curcas oil over the catalysts.The study results of modifying agent cerium nitrate,lanthanum nitrate on the performance and properties of the catalysts showed that within the range examined of the amount addition,with increasing the amount of modifying agent,hydrothermal stability of the catalyst significantly improved at first,but not change significantly later,the mechanical stability of the catalyst decreased slightly;and the suitable amount was 3.75 g modifying agent/(Mo+Ni)mol;The adding of cerium nitrate or lanthanum nitrate could increase the fraction of decarboxylation and decarbonylation.The experimental results of modified catalyst stability showed that the HDO activity of the catalyst was basically stable during a period of 120 h,the average deoxydeoxygenation percentage of refined jatropha curcas oil was greater than 99.9%,which indicated that the catalyst has a excellent stability for a longer time.With the prolongation of the reaction time,the fraction of direct hydrodeoxygenation increased gradually.The influences of reaction conditions and the Mo/Ni moral ratio on hydrodeoxygenation reaction path of jatropha curcas oil over the catalysts were investigated,the study result showed that high temperature and low pressure is favor to the hydrogenation decarboxylation,decarbonylation;high pressure and low temperature is favor to the direct hydrodeoxygenation;It almost only occuerred decarboxylation and decarbonylation on Ni/Al2O3 catalyst,with the moral ratio of Mo/Ni increasing,the fraction of direct hydrodeoxygenation increased gradually.