| To solve the problems of homogeneous catalyst residue and high raw material price in the synthesis of C22-tricarboxylic acid, using oleic acid as the raw material, Lewis acid as catalyst, the Alder-ene addition reaction of oleic acid and maleic anhydride was realized, and C22-tricarboxylic acid was obtained after hydrolysis. The synthesis conditions of C22-tricarboxylic acid were optimized and the product was identified, and its product was neutralized to prepare C22-tribasic acid sodium surfactant and its surface properties were studied. The results showed that the optimal conditions for C22-tricarboxylic acid synthesis were obtained as follows: with Lewis acid FePO4 as catalyst, dosage of catalyst 3% (calculated by the mole of oleic acid ), molar ratio of maleic anhydride to oleic acid 3∶ 1, reaction temperature 180℃, and reaction time 10 h. Under the optimal conditions, the yield of C22-tricarboxylic acid could reach 78% and oleic acid conversion rate was 77.4%. It was proved that C22-tricarboxylic acid was obtained through mass spectrometry and nuclear magnetic resonance characterization. There was no obvious decrease in activity of catalyst after 5 times of recycling. The critical micelle concentration of C22-tribasic acid sodium surfactant prepared by C22-tricarboxylic acid was 3.61×10-3 mol/L, and the surface tension(γ) reached 28.39 mN/m. In conclusion, the preparation process of C22-tricarboxylic acid by the Alder-ene addition reaction of oleic acid and maleic anhydride with FePO4 as catalyst is green and the cost of materials is low， and the C22-tricarboxylic acid prepared can used as good material for surfactant preparation. |
