摘要
烯烃催化氢化是研究得最彻底、也是应用最为广泛的一类催化反应。二烯和三烯烃部分氢化成单烯烃的反应在工业上是有吸引力的。目前,由于存在催化选择性不够理想以及产物与催化剂分离等问题,这一反应路线尚未为工业上所采用,但有很大的潜力。对于这类氢化反应,采用可溶性的小分子均相催化剂可得到较高的催化选择性,而传统的多相催化剂则选择性不好。H.Hirai等曾采用高分子保护过渡金属胶体催化剂,选择性和活性均较好,但也同样存在着类似于小分子均相催化剂的缺点,因而在工业应用上仍受到限制。 最近我们首次提出配位俘获法负载高分子保护过渡金属胶体合成多相金属催化剂的方法,即通过锚联在载体表面的配体与过渡金属胶粒表面原子间的配位作用。
A novel thioether-containing silica-supported metallic palladium catalyst was prepared via the coordination capture of polymer-protective palladium metal colloid with silica gel bearing thioether ligands. The catalyst shows high catalytic activity, stability and good selectivity for the partial hydrogenation of cyclodienes to monoenes, for example, the catalytic activity in hydrogenation of cyclopentadiene is 10-100 times higher than those of other supported catalysts reported in literature. This high catalytic activity is believed to be due to the fact that immobilization via coordination capture can create favourable conditions for easy access to- the substrates, preventing the colloidal particles from aggregating and thus forming a well dispersed catalyst. The selectivity to cyclopentene reached 99%, and a 100% selectivity for the partial hydrogenation of cis,cis-1 3-cyclooctadiene was obtained, narrowly dispersed ultrafine palladium metal particles with the modification of anchored thioether ligands is thought for causing the catalyst selective. During the course of catalytic reaction, the amounts of metal leaching are within the magnitude of ppb, and the total turnover numbers are larger than 80000.
Furthermore, this new route for catalyst preparation via coordination capture of metal colloids provides an approach to controlling or adjusting the particle size of metal particles within 1-10 nm, thus makes the inspection of the influences of different sulfur-containing group anchored on supported surface on the catalytic behaviors possible. In the partial hydrogenation the highest selectivity and activity were obtained when the n-propyl-thioether ligand was used. It can be expected that the new route for catalyst preparation will play an important role in the study of the interaction between the metal particles and supports.
出处
《分子催化》
EI
CAS
CSCD
1991年第2期189-192,共4页
Journal of Molecular Catalysis(China)
基金
北京中关村地区联合分析测试中心基金
