Chemical Composition Optimization and Characterization of the NiO/B2O3-Al2O3 System As a Catalyst for Ethylene Oligomerization

The samples of the NiO/B2O3-Al2O3 system with NiO contents from 0.48 to 38.30 wt % were synthesized by the impregnation of borate-containing alumina (20 wt % B2O3). It was found that nickel oxide occurred in an X-ray amorphous state in the samples containing to 23.20 wt % NiO. At a NiO content of 4.86 wt % or higher, the support was blocked by the modifier to cause a decrease in the specific surface area from 234 to 176 m(2)/g and in the amount of acid sites from 409-424 to 333 mu mol/g. An extremal character of the dependence of catalyst activity in ethylene oligomerization on NiO content was found with a maximum in the range of 4.86-9.31 wt %. Based on spectroscopic data, it was found that ethylene activation on the NiO/B2O3-Al2O3 catalyst can be associated with the presence of Ni2+ cations, which chemically interact with the support. The catalyst containing 4.86 wt % NiO at 200 degrees C, a pressure of 4 MPa, and an ethylene supply rate of 1.1 h(-1) provided almost complete ethylene conversion at the yield of liquid oligomerization products to 90.0 wt %; the total concentration of C8+ alkenes in these products was 89.0 wt %.