文献类型：期刊文献

英文题名：Selective Ethylene Tri-/Tetramerization by in Situ-Formed Chromium Catalysts Stabilized by N,P-Based Ancillary Ligand Systems

作者：Yang, Yun[1,2];Liu, Zhen[1];Liu, Boping[1];Duchateau, Robbert[2]

机构：[1]E China Univ Sci & Technol, State Key Lab Chem Engn, Shanghai 200237, Peoples R China;[2]Eindhoven Univ Technol, Dept Chem Engn & Chem, NL-5600 MB Eindhoven, Netherlands

年份：2013

卷号：3

期号：10

起止页码：2353

外文期刊名：ACS CATALYSIS

收录：;EI(收录号：20134216859250);WOS:【SCI-EXPANDED(收录号:WOS:000326320000024)】；

基金：We thank the Chinese Scholarship Council, the Natural Science Foundation of China (21174037), and the Eindhoven University of Technology for financial support.

语种：英文

外文关键词：selective ethylene oligomerization; ethylene tetramerization; chromium catalyst; ligand design; solvent effect; DFT calculation

摘要：A series of N,P-based ancillary ligands have been synthesized, and the corresponding catalysts, formed in situ by mixing one of the N,P-ligands, Cr(acac)(3) and MAO, have been tested for ethylene oligomerization. Under standard ethylene oligomerization conditions (30 bar ethylene, 60 degrees C, methylcyclohexane solvent), all of the in situ formed complexes show catalytic activity, producing oligomers together with varying amounts of polyethylene (PE). Of all these combinations, only the catalyst formed by mixing N-pyrrolyldiphenylphosphine with Cr(acac)(3) and MAO is capable of selectively oligomerizing ethylene, producing a mixture of 1-hexene and 1-octene in varying ratios alongside a small amount of PE. Further investigations on this catalyst system revealed that the presence of a low concentration of toluene favors the production of 1-octene. However, in pure toluene as the solvent, the selectivity toward 1-hexene/1-octene is lost and a statistic mixture of alpha-olefins is produced. Moreover, the choice of the cocatalyst is to dramatically influence the composition of the liquid products. By careful adjustment of the reaction conditions (temperature, ethylene pressure, catalyst loading, and ligand/Cr ratio), the 1-hexene/1-octene molar ratio can be tuned from 0.3 to 20 and a selectivity for 1-octene formation of up to 74% can be achieved.