Selective oxidation of methane to methanol in acetic acid solvent over Pd-CuPc/Y catalyst

The CuPc/Y which is copper phthalocyanine encapsulated inside the supercage of zeolite-Y was prepared with copper dichloride, ammonium molybdate, phthalic anhydride, urea and NaY molecular sieve by means of phthalic anhydride-urea solid state synthesis method. By using CuPc/Y as support, Pd-CuPc/Y composite catalyst was prepared by equivalent-volumetric impregnation method. The catalytic activity of the composite catalyst for selective aerobic oxidation of methane to methanol in acetic acid solvent was investigated. The results showed that the catalytic performance of the composite catalyst was related to reaction temperature, volume ratio of CH₃COOH to H₂O in acetic acid solvent, amount of p-benzoquinone and reaction time. The optimal yield of methanol was 1 840 μmol under the reaction conditions: 0.5 g of 0.5%Pd-0.5%CuPc/Y, 4 to 1 of volume ratio of CH₃COOH to H₂O in acetic acid solvent, 1 000 μmol of p-benzoquinone, 3 h of reaction time and 150 ℃ of reaction temperature. Pd-CuPc/Y catalyst could be reused repeatedly. However, the catalytic activity of reused catalyst decreased by catalyst loss and Pd particle aggregation. The selective oxidation of methane catalyzed by Pd-CuPc/Y catalyst in acetic acid solution possibly involved electrophilic substitute reaction and reactive oxygen species oxidation reaction.