PHYSICO-CHEMICAL FEATURES OF AROMATIZATION OF LOWER ALKANE С3 – С4 ON HIGH SILICA ZEOLITE CATALYSTS MODIFIED WITH Zn, LA AND P ADDITIVES

Abstract

The physicochemical characteristics of zeolite-containing catalysts modified by the introduction of zinc, lanthanum and phosphorus, as well as their activity in the aromatization of propane-butane fractions, have been studied. The maximum amount of aromatic hydrocarbons (43.6%) in the processing of the propane-butane fraction is formed on the Zn-La-P-ZSM-Al2 O3 catalyst at 500 °C, while the selectivity for aromatic hydrocarbons is 80.0%. When processing the propane- propylene fraction in the temperature range of 400-600°C, the yield of aromatic hydrocarbons on the Zn-La-P-ZSM-Al2O3 catalyst is significantly higher compared to other studied catalysts. The activity of catalysts in the processing of light hydrocarbons mainly depends on the structure and state of active centers and the conditions of the process. The results of the study of catalysts by electron microscopy and thermal desorption of ammonia showed that acid sites coexist with metal sites on the surface of the developed catalysts. The composition of acid sites can include metals in various degrees of oxidation, fixed both inside the zeolite cavities and on their outer side. The most active, stable KTG-4 catalyst (Zn-La-P-ZSM-Al2 O3 ) is recommended for pilot testing at gas and oil refineries when processing propane-butane fraction and gases released during catalytic cracking into aromatic hydrocarbons.