The Fatty Acid Methyl Esters Epoxidation Catalytic System

A heteropolyphosphatotungstate for the epoxidation of fatty acid methyl esters was prepared using sodium tungstate, phosphoric acid, hydrogen peroxide and cetyl pyridinium chloride. It was found that catalysts prepared by dissolving cetyl pyridinium chloride with ethyl acetate aggregate between the interface of organic phase and water phase. The catalyst was separated by simple filtration. The action of the title catalyst with H2O2 leads to a formation of homogeneous phase and an accelerated reaction rate. The catalyst will precipitate in solid particles with the consumption of H2O2 and the decreasing temperature, its recovery is up to 90% and catalytic activity is almost unchanged after eight consecutive uses. The catalyst structures before and after epoxidation reaction were characterized by FT-IR.Fatty acid methyl ester epoxide was synthesized and the effect of reaction conditions on the epoxidation and H2O2 utilization was investigated, respectively using using ethyl acetate and 1, 2-dichloroethane as solvent. Optimal synthesis conditions obtained using orthogonal design of experiments are as follows. For 1, 2-dichloroethane system, the product epoxy value is up to 5.78%, double bond epoxidation selectivity 81.9% and H2O2 utilization 86% under the conditions of reaction time 1 h,catalyst 0.1g,stepwise addition of 30wt% H2O2 1.57g,reaction temperature 65℃,1,2-dichloroethane 15mL and FAMEs 5.0g. For ethyl acetate system, the product epoxy value is up to 5.13% under the conditions of reaction time 2.5h,catalyst 0.3g,stepwise addition of 30wt% H2O2 3.5g(30.88mmol),reaction temperature 65℃,1,2-dichloroethane 20mL and FAMEs 5.0g(22.84mmol double bond).With formic acid as oxygen carriers, sulfuric acid as catalyst and hydrogen peroxide as oxidant, the influence of drops time of H2O2, reaction time, reaction temperature, H2O2 amount, formic acid amount and sulphuric acid dosage on the reaction was investigated. Results showed that suitable conditions are as follows: 40g FAMEs(iodine value=100), reaction temperature: 55℃, 35% H2O2 18.36g(corresponding with the ratio of H2O2 to double bond 1.2:1), 6g formic acid, stirring velocity :210r·min-1, drops time of H2O2:0.5 h, reaction time: 3h, the epoxy value of products could reach 4.27% and hydrogen peroxide utilization was 69.27%. After the highest epoxy value, the reaction continued to proceed for 2h and 3h, glycol yield could reach 88.05% and 95.17%, respectively. Kinetics of epoxidation were measured and well represented by the first-order reaction model, its apparent activation energy was 45.97 kJ/mol.