Deep removal of thiophene and benzothiophene in low-sulfur fuels over the efficient CeAlSBA-15 adsorbent synthesized by sequential alumination and cerium incorporation

Abstract

Deep removal of thiophenic sulfur compounds in the low-sulfur concentration fuels (e.g., < 50 μg/g S) has been facing a great challenge. Ce-containing adsorbents as a typical representation of “S-M” bonding mechanism have performed an excellent adsorption selectivity, while it cannot be unsatisfactory for the sulfur capacity due to the ambiguous and complexity of effective adsorption active sites. Herein, we aim to address the above difficulty, employing the CeAlSBA-15 materials that are synthesized for the first time by the sequential alumination and Ce incorporation. The data results of XRD, Ar adsorption, TEM and EDX mapping indicate that the Ce species can be highly dispersed onto the micro-mesoporous surface of CeAlSBA-15 by the induction of Al species. Moreover, the UV–vis, XPS and in situ FTIR spectra further reveal that the isolated Ce(III) species (e.g., -Al-O-Ce-O-Si-) located onto the CeAlSBA-15 adsorbents can be considered as effective adsorption active sites, rather than the Ce(IV) species (e.g., -Ce-O2-Ce-) that is difficult to be touched due to the steric hindrance. For the model fuels of thiophene and benzothiophene, 90 and 65 mL/g of sulfur-free fuels can be produced by using the CeAlSBA-15(NH4+) adsorbent, respectively, which are much superior to the best one reported. In particular, the adsorbent shows an excellent regeneration performance after three cycles (90.8% sulfur capacity recovered), and also can perform an outstanding adsorption selectivity (36.7%) in the presence of 5 wt% benzene. The contribution of this work can pave a way for further developing more excellent desulfurization adsorbents with effective adsorption active sites.