Oligomerization of Lower Olefins on Micro- and Mesoporous Aluminosilicates for the Production of Fuel Fractions Fuel Fractions (A Review)

Data on the oligomerization of lower olefins on micro- and mesoporous aluminosilicates and on regular trends observed in the process are summarized. The oligomerization mechanisms for individual components are presented. Propylene oligomerization on structured microporous materials, zeolites of BEA, MOR, SSZ, FER, and TON structures, mainly yields propylene dimers (65–85%) and trimers (15–25%); the yield of tetramers does not exceed 7%. To obtain С12–С16 hydrocarbons, it is necessary to use as the feed 1-butene and 2-butene; the selectivity of the formation of the С12–С16 fraction is 60–65 wt % on MFI zeolite and 45–50 wt % on BEA and MOR zeolites. Amorphous aluminosilicate SIRAL and aluminated mesoporous silicates (Al-MCM-41, Al-SBA-15, Al-HMS, Al-KIT-6) modified with nickel were mainly studied in ethylene and propylene oligomerization. Their use allows the reaction to be carried out at a lower temperature than with zeolites. Under otherwise identical conditions, the silicate structure influences to a greater extent the feed conversion and the specific yield of the oligomerization products, whereas the product composition is determined by the procedure for introducing aluminum and nickel and by their concentration. Nickel is responsible for the formation of Lewis acid sites and for the initial activity in the reaction proceeding via a metal-complex mechanism, and aluminum is responsible for the formation of Brønsted acid sites, oligomer chain growth, and deactivation rate. In the flow-through reaction mode, the product formation selectivity is described by the Schulz–Flory distribution with the shift toward di- and trimers: In ethylene oligomerization, the product formation selectivity decreases in the order С4 (55–60%) > C6 (23–25%) > C8 (14–16%) > C10 (8–12%). In propylene oligomerization, C6 (90–95%) and C9 (5–10%) hydrocarbons are mainly formed; the initial structure of the mesoporous material influences the isomer ratio in the oligomerizate.