Air-Promoted Adsorptive Desulfurization of Diesel Fuel Over Ti-Ce Mixed Metal Oxides

Air-promoted adsorptive desulfurization (ADS) of commercial diesel fuel over a Ti-Ce mixed oxide adsorbent in a flow system is investigated in this work. The fresh/spent adsorbents were characterized using X-ray absorption near edge structure spectroscopy. Results show that sulfoxide species are formed during air-promoted ADS over Ti0.9Ce0.1O2 adsorbent. Adsorption selectivity of various compounds in fuel follows the order of dibenzothiophene sulfone>dibenzothiophene similar or equal to benzothiophene>4-methyldibenzothiophene> 4,6-dimethyldibenzothiophene>phenanthrene>methylnaphthalene>fluorene>naphthalene. The high adsorption affinity of sulfoxide/sulfone is attributed to stronger Ti-OSR2 than Ti-SR2 interactions, resulting in significantly enhanced ADS capacity. Adsorption affinity was calculated using ab initio methods. For Ti-Ce mixed oxides, reduced surface sites lead to O-vacancy sites for O-2 activation for oxidizing thiophenic species. Low temperature is preferred for air-promoted ADS, and the Ti-Ce adsorbent can be regenerated via oxidative air treatment. This study paves a new path of designing regenerable adsorbents. (c) 2014 American Institute of Chemical Engineers AIChE J, 61: 631-639, 2015