Conversion of the Components of Natural and Associated Petroleum Gases over Modified Zeolite Catalysts

The laws governing the conversion of components of natural and associated petroleum gases into aromatic hydrocarbons over zeolite catalysts modified with active metal additives are investigated. According to the data obtained, the catalysts under study exhibit high activity in the course of the aromatization of lower C-2-C-4 alkanes. For almost complete conversion of the feedstock, the selectivity towards the formation of aromatic hydrocarbons over GaAC and Zn-ZSM-5 samples at 550 degrees C is 44.6 and 37.8 %, respectively. The highest catalytic activity and selectivity in the conversion of natural gas into aromatic hydrocarbons is exhibited by Zn-containing zeolites. The yield of aromatic hydrocarbons over them reaches 26.7 % at 650 degrees C. This is higher by 9.0 and 19.0 % than the yield over Ga-containing and unmodified zeolites, respectively. The revealed differences in the behaviour of the catalysts are due to various functional features of their active sites formed when metals are introduced into the zeolite matrix. The yield of aromatic hydrocarbons from the conversion of a mixture of C-2-C-4 alkanes over zeolite-containing catalysts is significantly higher than that in the case of natural gas conversion, which is due to the high thermodynamic stability of its major component - methane. The nature of coke deposits formed on the surface of the catalysts under study during the aromatization of low-molecular C-2-C-4 paraffins was studied by means of differential thermal analysis. The stability of Zn-ZSM-5 in this process was determined to be higher than that of the Ga-containing zeolite.