Oxidation of 2,6-di-tert-butylphenol with tert-butyl hydroperoxide catalyzed by iron porphyrin tetrasulfonate, iron porphyrin tetracarboxylate and their supported analogues in a water-methanol mixture

Highlights: • An effective oxidation of DTBP was achieved. • Highest TON and TOF values were obtained by porphyrin catalysts. • The TON and TOF values were 4300 and 8600 (h⁻¹), respectively. • Complete conversion of DTBP was achieved in 30 min. • Ecotoxicity tests indicated less toxic reaction mixture. -- Abstract: In this study, two water-soluble iron porphyrins bearing sulfonate and carboxylate functionalities (FePTS and FePTC, respectively) and their supported analogues were used as catalysts for the oxidation of 2,6-di-tert-butylphenol (DTBP) in a water-methanol mixture. tert-Butyl hydroperoxide (TBHP) was the oxidant and the volume ratio of water to methanol in the mixture was 1–8. The major products of the DTBP oxidation were 3,3,5,5-tetra-tert-butyl-4,4-diphenoquinone (DPQ) and 4,4′-dihydroxy-3,3′,5,5′-tetra-tert- butylbiphenyl (H₂DPQ). Also 2,6-di-tert-butyl-1,4-benzoquinone (BQ) was the minor product of the oxidation. The results showed that FePTC was more catalytically active than FePTS in the oxidation and gave the highest TON and TOF values in comparison to those for metalloporphyrin and metallophthalocyanine based catalysts in the DTBP oxidation given in the literature. In addition, the ecotoxicity tests of the DTBP oxidation mixtures before and after oxidative catalytic treatment toward Artemia salina were performed. It was found that the toxicity of the catalytically treated DTBP mixture containing residual DTBP and products was lower than the catalytically untreated DTBP mixture.