Catalytic adsorptive desulfurization of mercaptan, sulfide and disulfide using bifunctional Ti-based adsorbent for ultra-clean oil

Ultra-deep desulfurization of transformer oil is of great demand among power industry. In this work, the effective and deep removal of various types of organosulfurs, including mercaptan, sulfide and disulfide via catalytic adsorptive desulfurization (CADS) using bifunctional Ti-based adsorbent is reported. Compared to adsorptive desulfurization (ADS), dramatically improvement of the organosulfur uptakes were achieved under CADS process. The equilibrium adsorption capacity at 5 μg∙g⁻¹ S reached up to 15.7, 33.4, 11.6 and 11.9 mg∙g⁻¹ for propyl mercaptan(n-PM), dimethyl sulfide(DMS), di-t-butyl disulfide (DTBDS) and dibenzyl disulfide (DBDS), which was 262, 477, 97 and 128 times to that of ADS process, respectively, and was the highest among the reported desulfurization adsorbents. Moreover, it achieved superior breakthrough capacity of 2050, 530 and 210 ml F·(g A)⁻¹ at the breakthrough S concentration of 1 μg∙g⁻¹ of the commercial transformer oil S containing 10, 50 and 150 μg∙g⁻¹, respectively. The effectiveness of CADS is associated to the transformation of sulfur species to higher polar sulfonic species with the assistance of mild oxidant, which can be readily captured by silanol groups on SiO₂ through H-bonding interaction. The excellent recyclability of the adsorbent can be realized through solvent washing or oxidative air treatment. This work provides an effective and economic approach for the elimination of trace amount of mercaptan, sulfide and disulfide from transformer oil.