Selective Ethylene Oligomerization with Chromium-Based Metal Organic Framework MIL-100 Evacuated under Different Temperatures

MIL-100(Cr) was synthesized and evacuated under different temperatures to generate a series of heterogeneous catalysts for ethylene oligomerization. These catalysts showed moderate catalytic activities for ethylene oligomerization but high selectivities to low carbon olefins C6, C8, and C10. Moreover, the oligomer distribution was different depending on the evacuation temperature. The XPS results showed the reduction of some Cr-III active sites in the MIL-100(Cr) structure to Cr-II active sites, which made the catalysts show polymerization activities. The MIL-100(Cr)250 catalyst evacuated at 250 degrees C exhibited the highest oligomerization and polymerization activities up to 9.27 X 10(5) g/(molCr.h) and 0.99 x 10(5) g/(molCr.h) respectively. The oligomerization selectivity to low carbon olefins C6, C8, and C10 was about 99%. The byproduct polymer from MIL-100(Cr)-250 belonged to linear polyethylene with ultrahigh molecular weight and broad molecular weight distributions. This work demonstrated that MOFs containing coordinatively unsaturated metal sites might be a promising selective catalyst for ethylene slurry oligomerization.