Enhanced Adsorption Desulfurization Performance over Mesoporous ZSM-5 by Alkali Treatment

The adsorption sulfur capacity and selectivity are two key challenges for adsorption desulfurization technology of FCC gasoline. In order to improve the above issues, the mesopores were first introduced into ZSM-5 zeolites by a NaOH alkali treatment method to reduce the diffusion limitations and increase the sulfur capacity, in which the effects of the alkali concentration, treatment time, and temperature on the pore properties of zeolites were well discussed. The desulfurization performance was tested in a fixed-bed reactor using model fuel. The results demonstrated that the alkali treatment time was the most influential factor for the sulfur capacity. The mesoporous ZSM-5 adsorbents prepared under the conditions of 0.5 M NaOH, 150 min, and 75 °C showed the maximal sulfur capacity, the breakthrough and saturation sulfur capacities of which were 14.00 and 17.46 mg of S/g of adsorbent, respectively. In addition, Ni 2+ ions were exchanged into mesoporous ZSM-5 zeolites to enhance the sulfur selectivity. The results proved that the selectivity of sulfur could be improved by an introduced metal ion because the Brönsted acid sites were decreased while the Lewis acid sites were increased.