Study On Solid Basic Catalysts Derived From Ca-based Wastes For Fatty Acid Methyl Ester Production

In this study,three different kinds of calcium-based wastes（egg shell,clam shell and crab shell）was used as raw materials to prepare low-cost,high-efficiency solid base catalysts for the transesterification of methanol and rapeseed oil to produce fatty acid methyl esters.The influence of preparation conditions and reaction conditions of the catalyst on the yield of fatty acid methyl esters was investigated.By characterization of the catalyst（XRD,N₂ adsorption-desorption,CO₂-TPD and SEM）;the factors influencing the catalytic activity of the catalyst were analyzed.The waste egg shell was used as calcium source to prepare Ca-based catalyst.The waste egg shell was pre-treated with 0.005 mol/L hydrochloric acid for 2 hours and calcined at 800 ℃ for 6 hours.The experimental results showed that the yield of fatty acid methyl esters can reached 98.27%at the following reaction conditions:reaction temperature of 65℃,oil/methanol molar ratio of 1:10,catalyst loading of 3%,reaction time of 4 hours.The waste clam shell was used as calcium source to prepare Ca-based catalyst.The waste clam shell was calcined at 900℃ for 6 h.The experimental results showed that the yield of fatty acid methyl esters can reached 92.47%at the following reaction conditions:reaction temperature of 65℃,oil/methanol molar ratio of 1:6,the amount of catalyst of 5%,reaction time of4 hours.The waste crab shell was used as calcium source to prepare Ca-based catalyst.The waste crab shell was calcined at 800℃ for 6 h.The experimental results showed that the yield of fatty acid methyl esters can reached 93.82%at the following reaction conditions:reaction temperature of 65℃,oil/methanol molar ratio of 1:8,the amount of catalyst of 5%,reaction time of 1.5 hours.The N₂ adsorption-desorption and CO₂-TPD characterization results of the three types ofcatalysts showed that the catalytic activity of the catalyst was main affected by the calcination temperature and has a great influence on the basicity,BET surface,pore size and pore volume of the catalyst.The SEM results show that the catalysts prepared from these three calcium-based wastes have special surface morphology and have a certain influence on the activity of the catalyst compared with chemical pure calcium oxide.The order of the catalytic activity of the three types of catalysts was:eggshell>crab shell>clam shell.The catalytic activity of these catalysts depends on the basicity,BET surface,and pore volume of the catalyst after calcination.Compared with chemical pure calcium oxide,the solid basic catalysts derived from Ca-based wastes was more efficiency.Hydrotalcite-derived solid base catalysts were prepared by co-precipitation method and impregnation method at the following preparation conditions:Mg/Al molar ratio of 2:1,K₂CO₃ loading of 20%,and calcination temperature of 450℃.The experimental results showed that the yield of fatty acid methyl esters can reached 99.74%at the following reaction conditions:reaction temperature of 65℃,oil/methanol molar ratio of 1:12,the amount of catalyst of 4%,reaction time of 30 minutes.The characterization results showed that the Mg/Al molar ratio,K2CO3 loading,and calcination temperature all affect the basicity of catalyst and depended on its K2CO3 loading highly.