醋酸溶液中Pd-CuPc/Y催化甲烷选择氧化制甲醇

以氯化铜、钼酸铵、苯酐、氯化铵、尿素和NaY分子筛为原料,采用苯酐-尿素法制备了酞菁铜/分子筛复合物CuPc/Y.采用等体积浸渍法将金属钯担载在CuPc/Y上制备了Pd-CuPc/Y催化剂,并在醋酸水溶液中考察了其催化甲烷选择氧化合成甲醇反应的性能,结果表明,催化性能与反应温度、溶剂中CH₃COOH与H₂O的混合比例、对苯醌用量、反应时间等因素有关,在0.5%Pd-0.5%CuPc/Y添加量0.5 g、CH₃COOH与H₂O体积比4∶1、对苯醌用量1 000 μmol、反应时间3 h、反应温度150 ℃的条件下,甲醇的最佳生成量为1 840 μmol.Pd-CuPc/Y催化剂可以多次循环使用,但由于催化剂流失和催化剂表面的钯粒子聚集的原因,循环使用后的催化剂催化活性有所下降.Pd-CuPc/Y在醋酸溶液中催化甲烷选择氧化合成甲醇是亲电取代反应和活性氧物种氧化共同作用的结果.

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.