Ethylene polymerization with palygorskite supported nickel-diimine catalyst

A nickel-diimine catalyst [N, N'-bis(2,6-diisopropylphenyl)-1,4-diaza-2,3-dimethyl-1, 3-butadiene nickel dibromide, DMN] was supported on palygorskite clay for ethylene slurry polymerization. The effect of supporting methods on the catalyst impregnation was studied and compared. Pretreatment of the support with methylaluminoxane (MAO) followed by DMN impregnation gave higher catalyst loading and catalytic activity than the direct impregnation of DMN. Catalyst activity as high as 5.42 x 10(5) g PE-molNi(-1)-h(-1) was achieved at ethylene pressure of 6.87 x 10(5) Pa and polymerization temperature of 20 degrees C. In particular, the morphological change of the support during MAO treatment was characterized and analyzed. It was found that nano-fiber clusters formed during the support pretreatment, which increased the surface area of the support and favored the impregnation of the catalyst. The investigation of polymerization behavior of supported catalyst revealed that the polymerization rate could be kept at a relatively high level for a long time, different from the homogeneous catalyst. By analyzing the SEM photographs of the polymer produced by the supported catalyst, the morphological evolution of polymer particles was preliminarily studied.