Synthesis of Silicon-Modified Pseudoboehmite with High Specific Surface Area by the Nitric Acid Method

As a significant source of catalyst support for FCC (Fluid Catalytic Cracking), pseudoboehmite is widely applied in the petrochemical industry. In FCC processes, the performance of catalyst supports is often limited by insufficient pore volume and surface area, which hinders the dispersion of active components and reduces accessibility for large hydrocarbon molecules. Therefore, developing pseudoboehmite with improved textural properties is essential for high-performance FCC units. In this paper, pseudoboehmite with a high specific surface area and large pore volume is prepared using nitric acid and sodium aluminate as raw materials, and sodium silicate as a pore-expanding agent. During the reaction process, the silicon atoms enter the crystal lattice of the product to cause changes in the pore structure. The results show that the pore parameters of the pseudoboehmite are improved to varying degrees with different amounts of silicon (0, 6, 9, 12, 18, and 24 wt % Si). Compared with the addition amount of 0 wt %, the pseudoboehmite produced with 9 wt % silicon has the largest specific surface area, reaching 506.67 m² g^-1 (increased by 33%), with a pore volume of 1.134 cm³ g^-1 (increased by 253%) and an average pore size of 8.279 nm (increased by 120%). It is found that silicon promotes the formation of AlO₄ coordination and disrupts the lamellar structure of the product. Additionally, it inhibits the growth of crystals along the (020) face and alters the morphology of the product. The incorporation of silicon facilitates pore enlargement and mitigates particle agglomeration, leading to a more developed pore structure and a marked increase in the specific surface area, pore volume, and pore size of pseudoboehmite. Pseudoboehmite with enhanced textural properties can significantly improve the conversion efficiency of FCC units, thereby supporting productivity gains in the petrochemical industry and offering strong potential for practical industrial applications.