关键词: 多级孔结构, SSZ-32分子筛, 无机/有机混合碱改性, 加氢异构

Abstract: To address the issues of narrow micropores, high diffusion resistance, and low utilization of active sites in traditional n-alkane hydroisomerization catalysts, a series of hierarchical porous Pt/SSZ-32 catalysts were prepared by inorganic/organic mixed base modification. The effects of different modification times on the phase structure, pore structure, acidity and acid content of the hierarchical porous catalyst, as well as the catalytic performance in the hydroisomerization of n-hexadecane were investigated. The results showed that the addition of an organic base avoided excessive desilication and dealumination of the molecular sieve framework by the inorganic strong base, resulting in smaller and more uniform mesopores, reducing loss of acid sites, and improving the accessibility of active sites within the molecular sieve and the mass transfer capacity of the reaction products. With the increase of mixed base modification time, the pore volume and specific surface area of the modified mesopores continuously increase, while the proportion of framework Al decreases and the proportion of non-framework Al increases. This leads to a decrease in both the acidity and acid strength of the catalyst, resulting in a decline in catalyst activity. The optimal mixed base modification time for the molecular sieve is 10 min. Under this modification condition, the catalyst prepared exhibits the highest selectivity for hydroisomerization and the lowest selectivity for cracking reactions, achieving a 73.6% yield of isohexadecaneat 270 ℃. Therefore, the hydroisomerization activity and selectivity of the catalyst can be effectively controlled by adjusting the mixed base modification time.

Key words: hierarchical, SSZ-32 zeolite, inorganic/organic mixed alkali modification, hydroisomerization