Ordered mesoporous carbon CMK-5 as a potential sorbent for fuel desulfurization: Application to the removal of dibenzothiophene and comparison with CMK-3

摘要

In this study, a mesoporous carbon with large surface area (CMK-5) was studied for the first time for adsorption of dibenzothiophene (DBT) as a model sulfur compound, and its performance was compared with that of CMK-3. The mesoporous carbon was synthesized from mesoporous silica SBA-15 as the hard template and furfuryl alcohol as the carbon source. The structural and textural properties of the synthesized samples were characterized by means of X-ray diffraction, transmission electron microscopy and nitrogen adsorption-desorption techniques. The CMK-5 afforded a maximum adsorption capacity of 125 mg DBT g~(-1) of the adsorbent at the optimized conditions (adsorbent dose, 2gL~(-1); contact time, 1 h; temperature, 25 °C), which was twice of that observed for CMK-3 (62.5 mg DBT g~(-1)). The higher adsorption capacity of CMK-5 compared to CMK-3 is ascribed to its unique structure composed of ordered arrays of carbon nanopipes separated by ordered arrays of mesoporous channels in a bimodal pore system. Kinetic studies revealed that the sorption process achieved equilibrium within 60 min and followed a pseudo-second-order rate equation. Langmuir isotherm best represented the equilibrium adsorption of DBT onto CMK-5. The negative value of Gibbs free energy (-15.3 kj mol~(-1)) for CMK-5 indicated that the adsorption occurs via a spontaneous process. The CMK-5 adsorbent could be easily regenerated by washing with toluene. The regenerated adsorbent afforded 86.3%, and 86.0% of the initial adsorption capacity after the first two regeneration cycles, respectively. The corresponding values for CMK-3 were 76.9% and 75.2%.