Preparation Of Modified Calcium-Based Solid Base Catalyst And Catalytic Performance Study In Transesterification For Biodiesel Production

Biodiesel perform better renewable and environmental performance than traditional fossil fuels.In recent years,the government has increased its support and the biodiesel industry has developed rapidly.The characteristics of the solid base catalyst represented by CaO,such as mild transesterification conditions,high product quality,and good reusability,have become the focus of biodiesel catalyst research in recent years.This article is supported by the National Natural Science Foundation of China(51876106),Primary Research&Development Plan of Shandong Province,China(2018GGX104027)and Young Scholars Program of Shandong University(2015WLJH33),using dolomite or calcium carbonate as the calcium source,and using different modification methods to achieve calcium-based solid base catalyze,and used to catalyze transesterification to produce biodiesel.At the same time,combined with XRD,N2 adsorption and desorption,XPS,CO2-TPD,SEM,EDS,FTIR,alkali content alkali density measurement and other systematic characterization methods,the phase composition,micropores and surface of the modified calcium-based solid alkali catalyst are analyzed Chemistry and other characteristics.In this paper,the single-factor method and response surface method are used to optimize the working parameters of the modified calcium-based solid base catalyst for transesterification,and to explore the catalyst's reusability and deactivation reasons.The results of this study provide a theoretical basis for the development of transesterified calcium-based solid base catalysts and the industrial application of catalytic synthesis of biodiesel.(1)A transition metal cerium-modified calcium-based solid base catalyst was prepared,and its catalytic synthesis of biodiesel was discussed.Using dolomite as the calcium source and cerium as the modified active agent,a cerium-modified calcium-based solid base catalyst based on dolomite was prepared by three methods:wet impregnation method,solid mechanical-mixing method,and improved wet impregnation method.The results show that the catalyst obtained by the improved wet impregnation method has the highest catalytic transesterification activity,and the optimized molar ratio of cerium to calcium is 0.6.Through characterization and analysis,the alkali density of the catalyst prepared under this condition can reach 2.21mmol/g,the specific surface area of the catalyst is 19.34m2/g,and the pore size distribution is between 2nm-20nm.Cerium causes the catalyst to have an irregular sheet structure.Coexists in the catalyst in two forms,Ce3+ and Ce4+.Through single variable exploration,the best working condition parameters of cerium-modified calcium-based solid base-catalyzed transesterification are catalyst addition amount 5wt.%,Alcohol-oil molar ratio 15:1,transesterification temperature 65? and transesterification time 2h,corresponding The highest yield of biodiesel can reach 97.21%.And due to the strong synergy between CaO and CeO2,the cerium modification greatly reduces the leaching rate of calcium-based active sites in the liquid transesterification product,and the stability of the catalyst reuse is greatly improved.After 5 reuses,the biodiesel recovery The rate can still be maintained at 88.63%.At the same time,the physicochemical indicators of the biodiesel obtained by catalysis meet the ASTM D 6751 standards,and have the potential for commercial application.(2)Ca-Zn-Al-Ce solid base catalysts of calcium zinc aluminum aluminum cerium type were prepared,and the working conditions parameters of catalytic transesterification were optimized by response surface methodology.The Ca-Zn-Al-Ce catalyst was prepared by three methods,namely,the wet impregnation method,co-precipitation method,and hydrothermal synthesis method,and the amount of calcium added was optimized.Finally,the Ca:Zn:Ce:Al molar ratio was 5:4:1:1 hydrothermal method is used to synthesize catalyst.Through characterization and analysis,the total alkalinity of the catalyst was 0.922mmol/g,and the amount of strong base reached 0.794mmol/g.The crystallinity of the catalyst was high.The average pore size and specific surface area were 14.99nm and 3.231m2/g,respectively.The catalyst has good stability,and the yield of biodiesel that is reused 5 times can still reach 87.37%,and the physical and chemical indexes of the produced biodiesel meet the standard.Using response surface method combined with central composite design(RSM-CCD)for optimizing transesterification parameters and constructing a prediction model of biodiesel yield,the best working condition parameters of the catalyst reaction were 66.12? for transesterification temperature and 8.19wt.%,The molar ratio of alcohol to oil is 18.53:1,and the corresponding biodiesel yield can reach 99.44%.Through three repeated experiments,the deviation from the model prediction result is 0.03%,which proves that the regression model is stable and reliable.