Deep desulfurization by the adsorption process of fluidized catalytic cracking (FCC) diesel over mesoporous Al-MCM-41 materials

Al-MCM-41 adsorbents with different SiO₂/Al₂ O₃ molar ratios (100, 50, and 30) were synthesized and used for desulfurization of a commercial diesel fuel (sulfur content = 1786 ppmw) at 373 K. The adsorbents were characterized by means of X-ray diffraction, N₂ adsorption isotherm, Fourier transform infrared, and high-resolution transmission electron microscopy techniques. 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 number in parentheses is the SiO₂/ Al₂O₃ ratio hereafter). The efficiency of sulfur removal is 95% over Al-MCM-41(50) at the initial state and still above 75% after a cumulative effluent volume of 17 mL. The effect of the adsorption temperature on the adsorption capacity of Al-MCM-41(100) was investigated. The results indicate that high temperature is disadvantageous for desulfurization. After the regeneration of a spent Al-MCM-41(100) sample (calcined at 823 K for 6 h), there is good recovery of the adsorption capacity. In addition, with the presence of Cu⁺ ions in Al-MCM-41, there is enhancement in the adsorption capacity and sulfur removal efficiency at 373 K and the effect can be related to the formation of Π complexation between sulfur-containing compounds and Cu⁺ions.