Synthesis Of CaO-CeO₂ Catalysts By Soft Template Methods And Research For Its Catalytic Application

Biodiesel can be produced through transesterification of vegetable oils and fats with methanol in the presence of a suitable catalyst.Compared to conditional petroleum-based fuel,biodiesel is biodegradable,renewable,non-toxic,higher flash point and can be blended with fossil diesel fuel.The conventional catalysts for this transesterification reaction are homoge-neous strong bases or homogeneous acids.Due to their fast reaction rates and less corrosive properties,bases are preferred to acid catalysts.Unfortunately,removal of the base after reac-tion is problematic.Therefore,efforts in recent years have been directed towards to the de-velopment of heterogeneous catalyst systems to produce biodiesel.In this study,through two kinds of methods,the preparation of CaO-CeO2 catalyst for biodiesel synthesis using PDMS-PEO as a structure-directing agent has been investigated.Compared to catalysts prepared by citric acid method,catalysts prepared by EISA have higher activity and better stability,thus have good potential in commercial applications.The syner-gistic effect of macropores and mesopores on the templated catalysts functioned efficiently as a catalyst for transesterification.The macropores in CaO-CeO2 enable bulky triglycerides to deeply penetrate and approach to active catalytic sites on the inner CaO-Ce02 surface by mass transport.And the mesopores cause more catalytic sites on the CaO-CeO2 surface.At the same time,due to the Ce added,the activity of CaO-CeO2 catalysts declined a little,but the stability of catalyst had a remarkable improvement.Among them,the catalyst 0.15-1073(Ce/Ca molar ratio:0.15,calcination temperature:1073 K)has the best compositive performance.At the reaction conditions:mass fraction of catalyst is 15 wt%,methanol/oil molar ratio is 30:1,reaction time is 6 h,reaction temperature is 60℃,the yield of biodiesel can reach 97.5%while metal leaching is 117.7 ppm.Using the response surface method to optimize the experimental parameters.The best pro-cess conditions are as follow:mass fraction of catalyst is 12.0 wt%,methanol/oil molar ratio is 34.1:1 and reaction temperature is 334 K.The accuracy of the model was validated with triplicate experiments.The mean value of the yield of methyl ester was 99.2%,which agreed with the predicted value 99.7%well.As a result,the model from BBD was considered to be accurate and reliable for predicting the yield of methyl ester.