Catalytic performance on upgrading saudi medium crude oil over Ag-Ga/ZSM-5 catalyst and the formation mechanistic study of light aromatics product

Key words:  heavy oil upgrading  methane activation  catalyst  model compound  light aromatics

Abstract:

Catalysts for heavy oil upgrading were prepared through incipient wetness impregnation method using one commercial ZSM-5 zeolite as a carrier with Ag-Ga loadings. The catalysts were characterized by XRD, Py-FTIR, N₂ adsorption-desorption isotherms and temperature-programmed desorption of ammonia. The effects of reaction temperature (380-420 ℃) on Saudi medium crude oil upgrading and light aromatics production under methane were studied. The results indicate that the supported metals such as Ag and Ga are highly dispersed on the Ag-Ga/ZSM-5 catalyst, and there are less Brnsted acid sites and more Lewis acid sites. It is found that the synergistic effect of highly dispersed supported metal species, the generated Lewis acid sites and Brnsted acid sites on the supports can achieve good performance for crude oil upgrading. Also, proper increasing of reaction temperature (380-400 ℃) is favorable to upgrading performance. However, high temperature (410-420 ℃) will reduce the liquid yield of product oil and cause serious coke formation. The best upgrading performance is obtained when the reaction temperature is 400 ℃, at which the properties of the product oil can be significantly improved and the mass fraction of light aromatics increased by 11.32%. The catalysts with highly dispersed Ag, Ga metal species, less Brnsted acid and more Lewis acid can effectively activate methane, which participates in the co-aromatization and alkylation of gasoline fractions and the cracking of diesel fractions to produce a large number of light aromatics.