Selective Adsorptive Desulfurization with Alkaline-Earth Metal-Modified Zeolites in Oil in the Presence of Olefin

Adsorptive desulfurization (ADS) was a hopeful method for deep desulfurization of oil in mild conditions. In this paper, based on the alkaline-earth (AE) metal-modified Y zeolite (AEY), synthesis, systematic characterization, ADS performance test, and analysis of related adsorption mechanisms were carried out. The crystal and pore structure of Y zeolite were not damaged after ion exchange of AE, while the amount of acid sites and the ratio of Lewis/Bronsted acid sites were both decreased. Although surface acid sites on zeolites were believed to be active sites for ADS, the performance test results showed that AEY adsorbents had rather good S adsorption capacity compared to NaY. Moreover, the S adsorption selectivity in the presence of hexene-1 in oil was also desirable for all AEY adsorbents. Based on these experimental results and previously proposed mechanisms for S-containing compound adsorption, a new adsorption mechanism was proposed for AEY, and this mechanism was further supported by the aid of DFT calculations. The good S-removal performance of AEY adsorbents as well as the new proposed adsorption mechanism may help people design and synthesize further improved S-compound adsorbents for ADS processes in an oil refinery.