关键词: MCM-41分子筛, 铝物种, 酸性调变, 吸附脱硫机制

Abstract: Al-MCM zeolites with different molar ratio of Si and Al, used as absorbents, were prepared by post-grafting method with MCM-41 molecular sieves as a subject and AlCl3 as an object and characterized by XRD, N2 adsorption-desorption techniques to investigate the textural properties of modified Al-MCM zeolites. The adsorptive desulfurization performance of FCC gasoline on these molecular sieves and the dynamic variation trend of sulfur compounds were investigated by dynamic adsorptive method, combined with GC-SCD technique. The adsorptive mechanisms of sulfur compounds on the molecular sieves were studied by NH3-TPD and Py-FTIR methods. The results show that Al species of Al-MCM-41 molecular sieves is well dispersed and combined with the silicon hydroxyls. The channel structure with 2D six-party rule arrangement is remained. The introduction of aluminum species can effectively modulate the acidic properties of mesoporous molecular sieves. The Lewis acid center is promoted obviously, while only a slightly increases of B acid center is found. The L acid centers related to the ligand unsaturated aluminum species without B acidity have a strong adsorption ability for 2, 3, 4-trimethylthiophene and C4 thiophenes, and promote the adsorption desulfurization efficiency.

Key words: MCM-41 molecular sieve, aluminum species, acidity modulation, adsorptive desulfurization mechanism