Preparation Of Functionalized Ca-based Solid Base Catalyst And Capability Optimization Of Transesterification In Catalyzing High Acid Oil

Compared with petrochemical diesel,biodiesel,which is clean and renewable,has excellent physical and chemical properties.Biodiesel is an important part of sustainable production,and generally produced through transesterification.A series of solid base catalysts represented by calcium-based catalysts,which can catalyze transesterification under mild conditions,are easy to separate,reusable,and not easy to cause corrosion to equipment.Therefore,they become the focus of the research.The source oil for domestic biodiesel production is mostly waste cooking oil(WCO),which has a high content of free fatty acid(FFA).The traditional method requires esterification for acid reduction treatment first,causes complicated process and high cost.Therefore,the development of acid-resistant solid base catalysts has become a hot spot.This article was funded by the National Natural Science Foundation of China(51876106),the Shandong Provincial Key Research and Development Program(2018GGX104027),and the Shandong University Young Scholars Future Program Funding Project(2015WLJH33).In this paper,the calcium-based solid base catalysts are prepared using Fe2O3 and ZnO as acid active sites and applied to the synthesis of methanol and acidulated palm oil to explore its catalytic activity.The reusability of the calcium-based solid base catalysts is studied,and the reasons for the deactivation and instability of the catalysts are analyzed.The phase and element composition,microscopic morphology,pore structure and other characteristics of the catalyst are analyzed through XRD,XPS,SEM-EDX,nitrogen adsorption,CO2/NH3-TPD,TG,TEM,FTIR and Raman,etc.Different methods are used to optimize the reaction parameters of the transesterification.In the part of the calcium-based solid base catalyst supported on the iron-containing solid waste,the central composite design in the response surface method(RSM-CCD)and the genetic algorithm-back propagation(GA-BP)neural network model are adopted to study the influence of reaction temperature,catalyst amount and methanol-to-oil molar ratio on the biodiesel yield.In the part of the zinc-modified halloysite-supported calcium-based solid base catalysts,GA-BP model is used to optimize the reaction parameters.The obtained best parameters are verified.(1)Using iron-containing solid waste from iron and steel plants as raw materials,impregnated with calcium nitrate and calcined to form an acid-resistant calcium-based solid base catalyst.Mix palm oil with oleic acid to synthesis high acid value source oil.The acid resistance and reusability of the catalyst are investigated.The SW-Ca3 catalyst has the highest catalytic activity and acid resistance when the Ca to Fe molar ratio is 1.26.When the acid value increases to 8.9 mg KOH/g,the yield can still reach 88.21%.Based on various characteristics,the pore structure,acidity and basicity of SW-Ca3 catalyst are the most ideal,which is conducive to showing the acid resistance and catalytic activity.The biodiesel meets relevant standards.SW-Ca3 catalyst shows good reusability.After 3 cycles,the biodiesel yield can still reach 82.54%.Finally,the RSM-CCD and GA-BP models are used to optimize the parameters of the transesterification reaction temperature,catalyst amount and the methanol-to-oil molar ratio.The prediction parameters are stable,and the predicted biodiesel yield is relative to the experimental value.The errors of the models are 0.13%and 0.07%,respectively.The experimental results are in good agreement with the predicted values,and the model is reliable.After evaluate the two models with the correlation coefficient(R),the determination coefficient(R2),the mean square error(MSE),the root mean square error(RMSE),the mean absolute error(MAE)and the mean absolute percentage error(MAPE),the GA-BP neural network model is more accurate,and more suitable for this research.(2)Using cheap and easily available halloysite as carrier,impregnated with calcium nitrate and zinc nitrate to form an acid-resistant calcium-based solid base catalyst with developed pore structure.The acid resistance and reusability of the catalyst with acidulated oil are investigated.The HNTs-Ca/Zn1.5 catalyst has the highest catalytic activity when the Zn to Ca molar ratio is 1.5.When the acid value of the source oil is as high as 26.02 mg KOH/g,the catalytic activity of the HNTs-Ca/Zn1.5 catalyst can still remain stable,and the biodiesel yield can reach 92.66%.The catalyst has a high specific surface area,well-developed pore structure,and abundant acid-base active sites,which greatly increases the contact area.The produced biodiesel meets relevant standards.The HNTs-Ca/Zn1.5 catalyst has good reusability,and the yield can reach 85.88%after 3 reused cycles.Finally,the GA-BP neural network model is used to optimize the parameters of the transesterification reaction,such as the reaction temperature,catalyst amount and the methanol-to-oil molar ratio.The model is proved to be stable.Experimental verification shows that the relative error between the predicted yield of biodiesel and the experimental value is 0.11%,and the model is reliable.