Epoxidation of vietnam rubber seed oil by using peroxophosphatotungstate catalyst complex based on Na2WO4/H3PO4/H2O2 with the presence of phase-transfer catalyst

Abstract

• Peroxophosphatotungstate based on Na 2 WO 4 /H 3 PO 4 /H 2 O 2 is formed in the aqueous phase. • The acid value of rubber seed oil strongly affects the epoxidation reaction. • Higher the acid value, higher conversion but smaller yield and selectivity. • The epoxidation takes place very quickly because of its high catalytic activity. • The epoxy ring opening occurs when the epoxidation is done for more than one hour. Rubber seed oil (RSO) with a high acid value was esterified under mild conditions with methanol to convert the free fatty acids in the RSO into methylesters in the esterified rubber seed oil (RSO E ) and minimize the acid value as well. The peroxophosphatotungstate complexes were formed in the aqueous phase from the reaction between Na 2 WO 4 , H 3 PO 4 , and H 2 O 2 . Thanks to a cation exchange reaction with the phase-transfer catalyst (PTC), the catalytic complexes moved from phase to phase to perform their catalytic role. By studying a variety of factors influencing the epoxidation via the determination of oxirane oxygen, yield, conversion, and catalytic selectivity, the optimum conditions are found. They are as DB (double bond)/H 2 O 2 /Na 2 WO 4 ratio of 1/2/0.0065, Na 2 WO 4 /PTC/H 3 PO 4 ratio of 1/0.55/3 with RSO E , and 1/0.25/3 with RSO at 60°C for just one hour. The epoxidized rubber seed oil (ERSO) had an oxirane oxygen of 6.36% when 92.97% of the double bonds in the RSO were broken and 75.09% of the double bond was converted to the epoxide. These parameters would be 7.53%, 91.82%, and 88.91%, respectively for epoxidized esterified rubber seed oil (ERSO E ). The catalyst selectivity for these reactions was significantly different, which was 0.81 for the high acid value RSO but 0.97 for the low acid value RSO E . Through the FTIR and NMR study, the success of the epoxidation has been shown.