Silica supported tantalum alkyl as a self-activated catalyst for oligomerization/polymerization of ethylene

摘要

Over the last 50 years, the production of linear α-olefins ethylene oligomerisation has gained increasing interest in industrial and academic research. Presently, numerous studies in this field have been reported and developed into industrial production: titanium based catalysts for the di-merisation of ethylene (Alpha-butol, IFP); chromium based catalysts for the trimerisation of ethylene (Phillips Petroleum) and more recently Chromium bearing PNP ligand for ethylene tetrame-risation (SASOL). In contrast to these widely used homogeneous catalysts employing Cr and Ti, only few catalytic procedures for selective ethylene trimerisation using tantalum metal have been reported. In 2001, Sen employed Ta~((V)) chloride and an alkylating co-catalyst agent such as SnMe4, ZnMe2, AlMe3 or MeLi to generate TaMe2Cl3 in situ, which is an unstable species and postulated to be the precursor of active Ta~((III))species. Recently, Mashima reported the reduction of TaCl5 to an active catalyst by 3,6-bis(trimethylsilyl)-1,4-cyclohexadiene (BTCD). To avoid the use of co-catalyst, we envisage to employ surface organometallic chemistry to generate the postulated active tantalum precursor which is unstable in solution.