Preparation Of Biodiesel By Solid Acid Catalyst Modified By Rare Earth

As an ideal substitute for biodegradable,renewable,and green fossil fuels,biodiesel has been paid attention to by many countries.The previous studies of the research group have proved that Hangjin2^#clay can effectively increase the specific surface area of SO₄^2-/M_xO_ysolid acid catalyst for the transesterification of biodiesel（BD）.However,how to rationally regulate the interaction between metal centers and ligands to improve the catalytic activity and selectivity has always been a great challenge for this kind of catalyst.In this study,two kinds of catalysts,SO₄^2-/ZrO₂-La₂O₃-Hangjin2^#clay（SZLa-HJ）and SO₄^2-/ZrO₂-Ce O₂-Hangjin2^#clay（SZCe-HJ）,were prepared with La and Ce as cocatalysts,respectively.NH₃-TPD,Py-FTIR,and other characterization results show that the introduction of La and Ce can adjust the acidity distribution of SO₄^2-/ZrO₂-Hangjin2^#clay（SZ-HJ）,increase the number of Bronsted and Lewis acid sites,and keep more catalysts in Lewis acid sites to promote the occurrence of transesterification.The preparation of biodiesel using a rare-earth-modified clay-based catalyst is of great significance to improve the application of rare earth in catalyst modification,and also provides a reference for scholars to develop biodiesel.The main contents and research results are summarized as follows:1.SZLa-HJ and SZCe-HJ catalysts were prepared by the precipitation impregnation method.The three factors of rare earth dosage,sulfuric acid concentration,and calcination temperature were analyzed and fitted by CCD（Central Composite Design）experimental design method,and the mathematical model was obtained.After optimization,the preparation conditions of SZCe-HJ are as follows:the amount of rare earth Ce doping is 6.17wt.%,the concentration of sulfuric acid is 1.57mol/L,and the calcination temperature is 344℃.The average coversion rate of BD is 36.18%.The preparation conditions of SZLa-HJ:the amount of rare earth La doping is 3.7wt%,the concentration of sulfuric acid is 1.69 mol/L,and the calcination temperature is 357℃,and the average conversion rate of BD is 28.77%.2.The activity of SZCe-HJ and SZLa-HJ catalysts for biodiesel production was evaluated.The results showed that under the same conditions,the catalytic activity was:SZCe-HJ>SZLa-HJ,and SZCe-HJ was selected as the best catalyst to be used in the subsequent research on the biodiesel production process.At the same time,SEM,BET,XRD,XPS,NH₃-TPD,Py-FTIR and other characterization methods were used to characterize the crystal phase,thermal decomposition performance,pore structure,surface acidity and acid type of the catalyst.3.Based on the single factor results,the preparation process of soybean oil-based biodiesel catalyzed by SZCe-HJ was optimized by CCD experimental design.The results showed that the optimum process parameters were as follows:the molar ratio of alcohol to oil was 30:1,the amount of catalyst was 3.06wt%,and the reaction time was 178℃for6h.At this time,the average conversion rate of BD could reach 62.92%.In addition,it is found that the catalyst has good stability.By further comparing the catalytic performance of the catalyst,it is found that the conversion rate of biodiesel is SZCe-HJ>SZLa-HJ>SZ-Ti（contrast）>SZ（contrast）>SZ-HJ,which further proves the subject’s modification of the catalyst was successful.