朕接有硫醚基的二氧化硅固载的钯金属催化剂对环戊二烯的选择性氢化

SELECTIVE HYDRO GENATION OF CYCLOPENTADIENE TO CYCLOPENTENE OVER HIGHLY-DISPERSED METALLIC PALLADIUM PARTICLE SUPPORTED ON SILICA POSSESSING THIOETHER GROUPS

本文合成了联接有硫醚基的二氧化硅固载的金属钯催化剂.结果表明:(1)该催化剂在常温常压下对环戊二烯具有较高的催化氢化活性,并能选择性地生成环戊烯.在环戊二烯转化100%时,生成环戊烯的选择性达97.7%.(2)该催化剂有良好的稳定性,可多次重复使用,保持高活性和选择性不变.经透射电镜观察,远红外分析以及X—光光电子能谱分析测定,催化剂的活性中心是颗粒大小为10—60(?)的钯金属微粒.

A highly dispersed palladium catalyst was prepared by coordinating palladium chloride on silica possessing thioether groups(pre-catalyst) ,followed by reduction with aqueous solution of hydrazine at room temperature (catalyst) .Cyclopentadiene is hydrogcnatcd over this catalyst .to cyclopenteae in 97. 9% selectivity at 100% conversion of cyclopcntadicnc in methanol under 0.1MPa hydrogen at 30℃ .The catalyst shows high activity which is about 5 times higher than that of colloidal palladium supported on chelate resin containing iminodiacetic acid groups reported by Hirai.The catalyst also exhibits excellent stability and can be used more than 10 times without losing its activity and selectivity.From FT-IR, XPS data and TEM observation combined with the mercury poison experiment, it can be shown that the palladium (Ⅱ) complex pre-catalyst is unactive for hydrogenation and the active species of the catalyst are metallic palladium particles ranging from 10 to 60 A in diameter. The difference of adsorption ability between cyclopentadicnc ( CPD) and cyclopeutene (CPE) on active species is found to be the main reason for such a high selectivity of this catalyst, although the hydrogenation rate ratio of these two compounds, V_CPD / VCPE, is only 1,5.It is noted that the metal particle size, its dispersion and electron state arc controlled by the sulfur ligand , which results in the excellent activity, selectivity and stability of the catalyst.