Influence of Support Acidity on the HDS Performance over β-SBA-16 and Al-SBA-16 Substrates: A Combined Experimental and Theoretical Study

A novel composite material beta-SBA-16 is successfully synthesized and utilized as the support for the development of hydrodesulfurization (HDS) catalyst. The supports and the corresponding catalysts were characterized by a variety of techniques involving X-ray diffraction, N-2 physisorption, Al-27 NMR, Raman, pyridine IR, X-ray photoelectron spectra, and high-resolution transmission electron microscopy. The activity evaluation results displayed that the NiMo/beta-SBA-16 catalyst possessed the highest dibenzothiophene HDS efficiency of 97.3% at weight hourly space velocity of 20 h(-1) compared with the catalysts supported on the Al-modified SBA-16 and the conventional Al2O3. Furthermore, the HDS efficiency of NiMo/beta-SBA-16 is almost 1.5 times that of the other two catalysts at 150 h(-1) which was considered to be closely linked to the acidic properties of the supports. Correspondingly, the results of pyridine IR exhibited that NiMo/beta-SBA-16 possessed larger amounts of total acidity and higher B/L acidities ratio. Furthermore, density functional theory calculations were performed to explore the Bronsted acid strength generated by the incorporation of beta seeds or Al atoms. The calculation results indicated that Si atoms located in the 5- or 6-membered rings of beta-zeolite were more easily substituted by Al atoms, and the generated Si-OH-Al group played an important role in providing stronger Bronsted acid sites. Therefore, both experimental and theoretical results have shown that the incorporation of beta seeds contributed more to produce the Bronsted acid sites of SBA-16 materials.