THE INFLUENCE OF POSTSYNTHETIC ALKALINE TREATMENT AND MODIFICATION WITH NICKEL NANOPOWDER ON THE PROPERTIES OF A ZEOLITE CATALYST FOR GASOLINE UPGRADING

Abstract

Postsynthetic treatment of ZSM-5 zeolite with an aqueous solution of NaOH was carried out, followed by the modification of the treated zeolite with nanosized nickel powder. Nickel powder is introduced into the zeolite by dry mechanical mixing. The textural, acidic and catalytic properties of the original ZSM-5 zeolite and zeolite-based samples after alkaline treatment and modification are studied. The catalytic activity of zeolites has been studied in the process of conversion of straight-run gasoline fraction of oil. Along with determining the characteristics of the target reaction products - high-octane gasolines, an analysis of the resulting gaseous hydrocarbons and carbon compaction products (coke) was carried out. It has been established that alkaline treatment of zeolite and its subsequent mixing with nickel nanopowder leads to a decrease in the total specific surface area and total specific pore volume, a decrease in the concentration of acid sites and an increase in their strength. The enhancement of the combined effect of alkaline treatment and modification with nickel nanopowder on the textural and acidic properties of zeolite catalysts was determined. It has been shown that modification of zeolite catalysts has almost no effect on the composition of gaseous products formed in the conversion of straight-run gasoline fraction of oil. Post-synthetic alkaline treatment of ZSM-5 zeolite significantly reduces its aromatising and cracking activity, resulting in an increased yield of high-octane gasoline with improved environmental characteristics. The introduction of nickel nanopowder into alkali-treated zeolite enhances this trend, although not significantly. On modified zeolites, the amount of carbon compaction products is reduced, which will increase the time of stable operation of the resulting catalysts and improve the conditions for their regeneration.