Hydrodesulfurization of fluid coke was studied in a hydrogen flow at temperatures ranging from 550 to 850°C. The desulfurization to remove 40% of sulfur took place very slowly at 550°C in 20 h. At 650°C desulfurization was more rapid until 35% of sulfur was removed after 2 h; then it became slower but steady to achieve 70% removal after 20 h. In a hydrogen atmosphere at 750 and 850°C, the initial rates of desulfurization were much the same as the rate at 650°C, however, the former rate became very slow after 1 h, and after 10 h, only 30 and 25% removals were achieved at 750 and 850°C, respectively (Fig. 1). Grinding and airoxidation of the coke before desulfurization enhanced the initial rate and the percentage of desulfurization at 650°G. However, such effects were diminished rather in the early stages of desulfurization at 750 and 850°C (Figs. 3,5). Heat-treatment at 850°C in nitrogen before desulfurization retarded the percentage of desulfurization very much at 650°C (Fig. 2). Such observations suggest that contacting hydrogen with the sulfur atoms in the polycyclic aromatic ring systems govern the desulfurization reaction. Any pretreatment which can increase the accessibility of coke to molecular hydrogen can enhance desulfurization. Heat-treatment before or during desulfurization brought about a significant shrinkage of the coke structure, reducing its surface area available to hydrogen, thereby retarding the hydrodesulfurization reaction.
All Science Journal Classification (ASJC) codes
- Fuel Technology
- Energy Engineering and Power Technology