Production of limonene epoxides from tire pyrolysis oil by polyoxometalate immobilized on SBA-15

The goal of producing limonene epoxide and separating p -cymene from tire pyrolysis oil (TPO) could be achieved after epoxidation . However, the existing catalytic epoxidation process has the problem of cumbersome catalyst separation process, which is not conducive to industrial applications. In this work, the heterogeneous catalysts polyoxometalate-SBA-15 were prepared with the point of simplifying separation process. Heteropoly acid anions (phosphotungstic acid or peroxophosphotungstic acid) with catalytic active successfully enter the mesoporous pores of SBA-15, exhibiting high limonene conversion in the TPO system. The PW 4 species produced by phosphotungstic acid after oxidation of H 2 O 2 was favorable for improving the selectivity of epoxidation. The catalyst S- D -PW 4 prepared showed high catalytic activity and epoxidation selectivity with the condition of H 2 O 2 as an oxidant and free of solvent. Furthermore, A statistical experimental approach was used to comprehensively evaluate the reaction conditions. The conversion of limonene in TPO could reach 99.78%, and the yield of 1,2-limonene epoxide and diepoxide were 67.96% and 20.16%, respectively. A variety of characterization techniques such as 31 P NMR, XPS, and ICP were employed to analyze the difference in catalyst before and after epoxidation. S- D -PW 4 could be easily separated and the catalytic activity and epoxidation selectivity remained high after 5 cycles.