Deep Desulfurization By The Adsorption Process Of FCC Diesel Over Mesoporous Material MCM-41

Deep desulfurization of fuel oils has become an environmental urgent subject worldwide due to very stringent environmental regulations. Although the hydrodesulfurization (HDS) technique is highly effective in removing thiols, sulfides, and disulfides but less effective for the removal of thiophene and thiophene derivatives, which constitute as much as 85% of the sulfur content in diesel fuel. Therefore, deep desulfurization by means of adsorption technique has attracted considerable attention recently.Al-MCM-41 adsorbents with different SiO₂/Al₂O₃ molar ratios were prepared by hydrothermal synthesis and used for desulfurization of a commercial diesel fuel (sulfur content: 1786 ppm) at 100℃. The adsorbents were characterized by means of techniques, such as XRD, N2 adsorption isotherm, FT-IR and HRTEM. The results showed the existence of fine crystalline structure and long-rang ordered hexagonal structure in Al-MCM-41(50) and Al-MCM-41(30) adsorbents, as well as large specific surface areas and narrow pore-size distribution. The adsorption capacity for sulfur-containing compounds was found to follow the order: Al-MCM-41(50) > Al-MCM-41(30) > Al-MCM-41(100). The efficiency of sulfur removal is 95% over Al-MCM-41(50) (0.4 g) at the initial state and is still above 75% after a cumulative effluent volume of 17 ml.In addition, the effect of adsorption temperature on adsorption capacity and the regenerability of Al-MCM-41(100) were investigated too. The results indicate that high temperature is disadvantageous for desulfurization. After the regeneration of a spent Al-MCM-41(100) sample, there is good recovery of adsorption capacity, indicating a good regenerability of this adsorbent.Furthermore, the adsorption capacity of Al-MCM-41 within Cu⁺ ions was also investigated. It showed that there is an enhancement in adsorption capacity and sulfur removal efficiency with the presence of Cu⁺ ions in Al-MCM-41 at 100℃. The effect can be related to the formation ofÏ€-complexation between sulfur-containing compounds and Cu⁺ ions.