Chromia-Pillared α-Zirconium Phosphate Materials as Catalysts for Thiophene Hydrodesulfurization

Chromia-pillared α-zirconium phosphate materials have been prepared by two different methods: series a, using as precursor a preswelled phosphate prepared by neutralization up to 70% of the exchange capacity with n -propylamine in aqueous solution, and series b, preswelling the phosphate with n -propylamine vapors up to saturation. Sulfidation of the pillared materials with a H 2 S mixture at 673 K did not result in the formation of isolated chromium sulfide phases but in partial sulfided chromium-oxide-pillared phosphate. The catalysts have been characterized by nitrogen adsorption, X-ray photoelectron spectroscopy (XPS), and oxygen chemisorption. After sulfidation, the modification of textural parameters observed was negligible and slightly different in both series, probably due to higher sulfidation in the pillars of series b. The higher dispersion of chromia in materials of series b detected by XPS was corroborated by the oxygen chemisorption study of the sulfided-pillared materials. Sulfur is found to be present as S 2 - species. The sulfided catalysts exhibited a high activity and stability for thiophene hydrodesulfurization (HDS), particularly the sulfide−CrZrP-3b material, which, despite its deactivation, after 6 h on stream is very active. However, the oxidic pillars showed an unusual activity, similar to those of sulfided materials. So, the chromia-pillared catalysts, above all those of series b, do not need the initial sulfidation to achieve a considerable activity. The optimal sulfidation temperature and reaction temperature was 673 K. The thiophene hydrodesulfurization exclusively gives rise to the formation of butane and butenes. The constants for hydrogenation of butenes to n -butane have also been calculated.