Epoxidation of methyl oleate in a TiO2 coated-wall capillary microreactor

In the present work, a catalytic coated-wall microreactor was developed and tested for producing epoxidized methyl oleate in a solvent-free system. TiO2 was coated inside the microcapillary reactor wall by a static method, while H2O2 and ethylenediaminetetraacetic acid (EDTA) were used as oxidant and stabilizer, respectively. The weight percent of oxirane oxygen was determined according to ASTM D1652 and the reaction performance was evaluated as oxirane oxygen yield and selectivity. Without TiO2 coated catalyst or formic acid, trace oxirane yield were obtained. Without EDTA as stabilizer, decomposition of H2O2 occurred as bubbles formation causing system operation failure. The results indicated that TiO2 coated catalyst as well as the presences of EDTA and formic acid were crucial for epoxidation reaction, and oxirane yield of 43.1% could be achieved at the optimal reaction temperature of 60 °C and residence time of 2.7 min. The results were compared with the data obtained from a batch reactor. Microcapillary reactor offers continuous operation with 23 times higher reaction rate of epoxide production than batch reactor. However, TiO2 coated layer was partially peeled off over 3 h lead to decrease in epoxide yield.