膦化聚2,6-二甲基1,4-苯醚负载钯催化剂的表征及其催化性能

Catalytic Behavior and Structure Characterization of Phosphinated Poly(2,6-Dimethyl-1,4-Phenylene Oxide) Supported Palladium Catalysts

报道了四种不同P/Pd摩尔比的膦化聚2,6-二甲基1,4-苯醚负载把催化剂的加氢和异构化性能;通过XPS、电镜和远红外对催化剂进行了表征;并考察了溶剂和温度对催化剂活性的影响.

Palladium catalysts supported on phosphinated poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) with different P/Pd mole ratios were prepared and their catalytic behavior for hydrogenation and isomerization were investigated. The activity of these catalysts for the hydrogenation of both cyclopentadiene and phyenylethyne varies with the P/Pd mole ratio. The selectivity in the hydrogenation of cyclopentadiene is not influenced by the P/Pd mole ratio, but in the hydrogenation of phenylethyne it decreases with the decrease of P/Pd mole ratio. It was also found that the selectivity of these catalysts for cyclopentadiene to cyclopentene is higher than that for phenylethyne to styrene. The reason is that the ability of cyclopentadiene inhibiting the further hydrogenation of cyclopentene is higher than that of phenylethyne inhibiting the futher hydrogenation of styrene. The effect of solvent and reaction temperature on the catalytic activity in the hydrogenation and isomerization of olefins was also investigated. The hydrogenation rate of 1-octene in pure ethanol is higher than that in pure benzene or the mixture of ethanol and benzene. Both the hydrogenation rate and isomerization rate increase with the increase of reaction temperature. Under suitable reaction conditions, the total yield of inner hexenes in the isomerization of 1-hexene can reach 91%. So, these phosphinated PPO supported palladium catalysts can be used to catalyze both the hydrogenation and isomerization of olefins under different reaction conditions. From IR, XPS data and TEM observation, it is shown that the palladium valence state in the catalysts depends on the P/Pd mole ratio. With a high P/Pd mole ratio, the palladium exists in the Pd2+ state coordinated with the phosphine ligands in support, but with a low P/Pd mole ratio Pd2+, Pd0 and metallic palladium particles coexist, in which Pd2+ and Pd0 are coordinated with the phosphine ligands in support.