Hierarchically Porous ZSM-5/SBA-15 Zeolite: Tuning Pore Structure and Acidity for Enhanced Hydro-Upgrading of FCC Gasoline

Abstract

The pore structure and acid sites of the catalysts are demonstrated as the main factors for the hydro-upgrading of fluid catalytic cracking (FCC) gasoline. Herein, we report a general synthesis of ZSM-5/SBA-15 composite zeolites with tunable pore structure and acid sites. The effects of the pore structure and acid sites of these catalysts on their hydro-upgrading performance were systematically investigated. The platelet CoMo/AZS-PL (CoMo/ZS-PL-γ-Al2O3) catalyst with the short mesochannels, appropriate Co–Mo–S phase, and suitable acidity exhibited the excellent preservation ability of research octane number (RON) and hydrodesulfurization (HDS) performance, which was better than those of CoMo/AZS-SR (CoMo/ZS-SR-γ-Al2O3), CoMo/AZS-HP (CoMo/ZS-HP-γ-Al2O3), and CoMo/AZS-LR (CoMo/ZS-LR-γ-Al2O3) catalysts. The relationship between the physicochemical properties (acidity, morphology, pore structure, and sulfided active metal) of the catalysts and their isomerization (ISO), aromatization (ARO), as well as HDS abilities were explored in detail.

Hydrotreatment of FCC Gasoline Catalyzed by CoMo Bifunctional Catalysts: The Effects of Acidity on Catalytic Performance

“…These results indicate that the addition of HZSM-5 and MCM-41 improved the specific area of the catalysts while decreased the average diameter of pores. However, narrow channels may cause inhibitory effects on the diffusion of reactants and products, which is disadvantageous to HDS and olefin isomerization. , …”

“…Compared with the obtained bifunctional catalysts, the reference CoMo/Al 2 O 3 catalyst has the shortest average slab length and stacking number equivalent to 2.2 and 1.7 nm, respectively, resulting in the highest dispersion of active species ( D ). According to ref , the surface of γ-Al 2 O 3 contains a great number of hydroxyl groups, which can benefit the formation of Mo–O–Al bonds to increase the interactions between Mo species and hydroxyl groups to reduce HDS activity. The presence of molecular sieves in CoMo bifunctional catalysts leads to an obvious increase of the average slab length and stacking number, resulting in little poorer dispersion of active species.…”

“…The acidity of catalysts is an important factor in hydrotreating reactions. , As can be seen in Table , the CoMo/Al 2 O 3 catalyst contains only LAS, which will facilitate the removal of sulfur compounds and the hydrogenation of olefins into the corresponding paraffins . However, catalysts with different strengths of BAS and different BAS/LAS ratios show apparent differences in catalytic performance.…”

“…With the increasing recognition of environmental protection, many countries and regions have adopted more stringent regulations for the sulfur content level of commercial gasoline, which brings a severe challenge for the modern refining industry to manufacture clean gasoline. − FCC gasoline is one of the main components in the gasoline pool and contributes to approximately 90% sulfur of commercial gasoline. , Hence, the reduction of the sulfur content in FCC gasoline is of great significance to produce clean gasoline. Currently, hydrodesulfurization (HDS) has still been widely regarded as an effective process to remove sulfur compounds from FCC gasoline in refineries.…”

“…Nevertheless, due to the lack of BAS on conventional CoMo/Al 2 O 3 catalysts, many studies have focused on the acidity modification of HDS catalysts to preserve RON. Lv et al synthesized ZSM-5/SBA-15 composite zeolites as the supports of HDS catalysts. The results revealed that the relative content of i -paraffins increased by 2.4 wt % with the increasing number of total acid sites from 88.9 to 127.7 μmol g –1 .…”