Аңдатпа
In the present study, the activities and selectivities of HZSM-5 and Zn/HZSM-5 catalysts in the aromatization of a mixture of butanes and butenes were investigated. Conversion of the feedstock over HZSM-5 proceeds with low selectivity toward benzene, toluene, and xylenes; cracking products are formed predominantly. The concentration of butanes decreases during the first 4 hours of the reaction, after which it increases continuously, exceeding the initial feed concentration after 16 hours. The concentration of butenes also decreases during the first 4 hours and then increases steadily, reaching 22.63% after 24 hours of reaction. The formation of methane and ethane reaches a maximum (29.52%) after 4 hours of reaction, while propane formation reaches a maximum after 8 hours (61.66%) and then gradually decreases. Molecular hydrogen is not observed in the gas phase. Catalytic activity and selectivity toward aromatic hydrocarbons are maintained during the first 12 hours of operation, after which they gradually decline to 14.63% after 24 hours. After 12 hours of operation, aliphatic hydrocarbons in the C5– C10 range are predominantly formed, reaching 78% after 20 hours. Experimental data indicate that the bifunctional Zn/HZSM-5 catalyst provides higher hydrocarbon conversion and greater selectivity toward aromatic hydrocarbons compared with the monofunctional HZSM-5 catalyst. When the HZSM-5 catalyst is used for 24 hours at 450 °C and a pressure of 8 atm, the fraction of aromatic hydrocarbons in the liquid product averages about 30%, with xylene yields predominating. Over the Zn/HZSM-5 catalyst, after 24 hours of operation at 450 °C and atmospheric pressure, the yield of aromatic hydrocarbons reaches 70%, with toluene being the main product. On the HZSM-5 catalyst, oligomerization proceeds in parallel with the aromatization process, resulting in an increased content of aliphatic hydrocarbons in the C9–C10 and C10+ fractions.