Persistent adsorptive desulfurization enhancement of TiO2 after one-time ex-situ UV-treatment

- One-time ex-situ UV-treatment before breakthrough experiments improved desulfurization performance of TiO2 by 50%.
- TiO2 was able to maintain excellent desulfurization performance after ex-situ UV-treatment.
- Sulfur removal species generated after photo-treatment on TiO2 were proven to be stable after the thermal regeneration step.
- Photo-induced sulfur removal active sites on TiO2 were observed via in-situ IR and XPS.

Adsorptive desulfurization (ADS) of hydrocarbon fuels at ambient pressure over TiO2 adsorbents following an ex-situ one-time UV-treatment have been investigated in this work. Based on our previous study, TiO2 adsorbent showed high adsorptive capacity (5.63 mg S/g adsorbent) when UV-treatment was applied in-situ during the adsorption step. In the current study, Ultra-violet (λ = 365 nm) treatment at 2.0 mW/cm2 was applied before the breakthrough experiment. And, research results indicate that one-time ex-situ UV-treatment before sulfur adsorption also increased the desulfurization breakthrough capacity of TiO2 by ca. 50%, from 3.90 mg S/g adsorbent to 5.95 mg S/g adsorbent. Moreover, for multiple adsorption, desorption and regeneration/calcination cycles (at 450 °C in air for 120 min), the stability of the UV-enhanced sulfur adsorption sites (once created) was persistent for subsequent cycles. In-situ IR and XPS were employed to investigate the effect of ex-situ UV treatment on the TiO2 adsorbent. Based on these IR and XPS results, the photo-enhanced desulfurization capacity of TiO2 was attributed to an increase in the total number of terminal acidic Ti(IV)OH groups.