Ultra-Deep Adsorptive Desulfurization of Light-Irradiated Diesel Fuel over Supported TiO₂–CeO₂ Adsorbents

Abstract

This study investigates ultra-deep adsorptive desulfurization (ADS) from light-irradiated diesel fuel over supported TiO2–CeO2 adsorbents. A 30-fold higher desulfurization capacity of 95 mL of fuel per gram of adsorbent (mL-F/g-sorb) or 1.143 mg of sulfur per gram of adsorbent (mg-S/g-sorb) was achieved from light-irradiated fuel over the original low-sulfur fuel containing about 15 ppm by weight (ppmw) of sulfur. The sulfur species on spent TiO2–CeO2/MCM-48 adsorbent was identified by sulfur K-edge XANES as sulfones and the adsorption selectivity to different compounds tested in a model fuel decreases in the order of indole > dibenzothiophenesulfone ≫ dibenzothiophene > 4-methyldibenzothiophene > benzothiophene > 4,6-dimethyldibenzothiophene > phenanthrene > 2-methylnaphthalene ∼ fluorene > naphthalene. The results suggest that during ADS of light-irradiated fuel, the original sulfur species were chemically transformed to sulfones, resulting in the significant increase in desulfurization capacity. For different supports for TiO2–CeO2 oxides, the ADS capacity increases with a decrease in the point of zero charge (PZC) value; for silica-supported TiO2–CeO2 oxides (the lowest PZC value of 2–4) with different surface areas, the ADS capacity increases monotonically with increasing surface area. The supported TiO2–CeO2/MCM-48 adsorbent can be regenerated using oxidative air treatment. The present study provides an attractive new path to achieve ultraclean fuel more effectively.

Selective adsorption of thiophenic compounds from fuel over TiO2/SiO2 under UV-irradiation

“…At the C e of 15 ppmw-S, the q e were 5.15, 2.45 and 0.31 mg/g for 0.3TiO 2 /0.7SiO 2 -UV, Cu-BTC and MIL-100(Fe), respectively. The greatest q e at low C e (0-50 ppmw-S) on 0.3TiO 2 /0.7SiO 2 -UV suggested that the 0.3TiO 2 /0.7SiO 2 adsorbent under UV-irradiation can be a promising approach for the effective deep desulfurization of fuel for ultra-clean fuel production, i.e., <15 ppmw-S (U.S. EPA regulation [2a]), or <1 ppmw-S (on-board fuel cell applications [15]). …”

“…Metal oxide-based adsorbents have caught attentions with plausible regenerability by air oxidation treatment [15]. Watanabe et al [16] developed regenerable mixed TiO 2 -CeO 2 adsorbent that demonstrated high ADS capacity from real fuel, and the adsorption selectivity was enhanced by tuning the Ti/Ce ratio.…”

“…Watanabe et al [16] developed regenerable mixed TiO 2 -CeO 2 adsorbent that demonstrated high ADS capacity from real fuel, and the adsorption selectivity was enhanced by tuning the Ti/Ce ratio. Recently, Xiao et al [17] reported a two-step ADS approach using TiO 2 -CeO 2 /MCM-48 adsorbent for selective removal of thiophenic compounds in light-irradiated diesel, which achieved a high desulfurization capacity (1.143 mg-S per g-Ads) of 14.5 ppmw-S real diesel, and the enhanced adsorption selectivity of thiophenic compounds was due to the conversion of low-polar thiophenic compounds to the corresponding polar sulfones on the adsorbent [15]. Previous work suggested that converting thiophenic compounds to sulfones over an adsorbent can be an effective approach to enhance ADS selectivity.…”

Adsorption diffusion behaviour of 4,6‐DMDBT from diesel fuel

“…There are several methods for the treatment of sulphur‐containing fuel, such as hydrodesulphurization (HDS), oxidation, extraction, and adsorption for ultra‐deep desulphurization of fuels. Among the above techniques, adsorptive desulphurization (ADS) is recognized as an emerging alternative technology for ultra‐deep desulphurization due to its simplicity and adaptability to different fuel processors …”

“…Among the above techniques, adsorptive desulphurization (ADS) is recognized as an emerging alternative technology for ultra-deep desulphurization due to its simplicity and adaptability to different fuel processors. [7][8][9][10] Amorphous silica from natural resources is widely used as an adsorbent due to its high surface area and high adsorption capacities. [11] The silver supported on TiO 2 -SiO 2 is effective for removing sulphur compounds from diesel fuel.…”