Production, Physicochemical and Catalytic Properties
of Gallium-Containing Zeolite Catalysts
A.V. Vosmerikov, L.N. Vosmerikova, Ya.E. Barbashin
Institute of Petroleum Chemistry, Akademichesky Ave. 3, Tomsk 634021, Russia
Crystalline galloalumino- and gallosilicates with pentasil structure were synthesised under hydrothermal conditions. The influence of gallium concentration and binder amount both on physicochemical and catalytic properties of a zeolite in the process of C2-C4 light alkanes aromatization and on catalyst deactivation due to carbidization has been studied. Acidic properties of gallium-containing pentasils with different composition were studied using the method of thermoprogrammed ammonia desorption. The formation of strong aproton acidic sites whose composition includes gallium ions was found. It has been shown that isomorphic aluminium replacement by gallium in the pentasil lattice leads to a significant increase in aromatizing activity and period of stable catalyst operation. A decrease in intensity of coking and the formation of less condensed coke deposits with a wide distribution by the structure are observed with the increase in gallium concentration. The introduction of a binder to galloaluminosilicate results in a significant increase in mechanical strength of a catalyst. It was established that the most efficient catalyst of the above process is a zeolite containing 2.2% of gallium oxide and 1.3% of aluminium oxide and mixed with 20% of the pseudobeumite. The selectivity of the formation of aromatic hydrocarbons reaches 55-60%, the period of stable operation exceeds 350 h. In accordance with the data obtained suggested are the principles of the selection of efficient catalysts of light alkanes aromatization and optimum conditions of the process.