Study On Catalytic Systems And Reactive Mechanism Of Ethylene Trimerization To 1-Hexene

As an important comonomer in polyethylene, 1 -hexene is used in the production of high density polyethylene(HDPE) and linear density polyethylene(LLDPE). 1-Hexene modifies the processing and mechanical properties of the polymer, imparting greater strength and thoughness. It is estimated that the increases in 1-hexene capacity totaling about 250,000 metric tons are projected by 2005 to meet increased demand. Nowadays, 1-Hexene co-polymerization resin has been 55% percent of the total copolymer in many developed countries such as the United States, Europe and Japan, but it has not been produced in China.The research of ethylene trimerization to Hexene-1 was popular at the beginning of 1990s1.The catalyst systems of [Cr(2-ethylhexanoate)3/pyrrole/triethylaluminum] and[Cr(2-ethylhexanoate)3/2,5-dimethylpyrrole/triethylaluminum/tetrachloro ethane] were studied respectively. Because choloro compounds canincrease the catalytic activities and selectivities of ethylene trimerization reactions,the effects of them on the catalytic performance were examined. The choloro compounds with the structure ofCXnR:i-n (R') o were used as the fourth component in the chromium catalyst system.The catalytic efficiency is 920kg/gCr and the selectivity of Hexene-1 achieves 92% . The idea of the application of this kind of choloro compounds in chromium catalytic system is creative and this kind of choloro compounds are applied for a China invention patent.The component structure and coordinate mode of the catalyst system which is constituted by [Cr(EH)3/2,5-DMP/TEA/TCE] were studied using the infra-red spectra. The experimental results showed that the chromium compound coordinate with pyrrole. According to the research results, a new mechanism of ethylene trimerization is discussed.