Role of ceria in Ti 0.9Ce 0.1O 2 materials for adsorptive desulfurization

Michael John Janik, Siddharth Sitamraju, Jiahua Guo, Chunshan Song

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Fuel cell systems efficiently convert chemical energy to electrical energy. The reforming and water-gas shift catalysts used to produce hydrogen and the fuel cell electrodes are all sensitive to the sulfur compounds in the fuels. Conventional desulfurization methods, i.e. hydrodesulfurization (HDS), consume large amounts of energy to reach sulfur concentrations low enough for fuel cells. Adsorptive desulfurization (ADS) is a promising method being developed to produce ultra-low sulfur fuels. A Ti xCe 1-xO 2 material has been reported by the Song group at Penn State to be a potential adsorbent for ADS due to its good selectivity and regenerability. The ratios of Ti:Ce were optimized to 9:1 for the maximum adsorption capacity. Comparing Ti 0.9Ce 0.1O 2 to TiO 2, the 10% CeO 2 addition significantly increases the capacity, despite only a slight surface area increase. We have applied density functional theory (DFT) calculations to examine the role of Ce addition to TiO 2 in promoting the adsorption of thiophenic molecules. A number of possible contributions of Ce addition were evaluated, including 1) stabilization of TiO 2 surfaces that adsorb thiophene strongly, 2) stronger adsorption to Ce-doped TiO 2 surfaces, 3) stabilization of reduced or over-oxidized sites on Ce-doped TiO 2, and 4) increased oxygen storage capacity to promote formation of adsorbed sulfone-like complexes. We find that Ce-doping of the surface can offer adsorption sites with stronger binding of thiophene, and can stabilize the anatase (100) surface which demonstrates strong adsorption affinity. Ceria may also serve as an oxygen reservoir to promote formation of adsorbed sulfone species to the TiO 2 surface. Thiophene adsorption energies are compared with cyclopentene to probe adsorption selectivity, and substitution of both thiophene and cyclopentene is considered to evaluate variations in selectivity. Calculations using DFT and dispersion corrected DFT, DFT+D, are compared.

Original languageEnglish (US)
Title of host publication11AIChE - 2011 AIChE Annual Meeting, Conference Proceedings
StatePublished - 2011
Event2011 AIChE Annual Meeting, 11AIChE - Minneapolis, MN, United States
Duration: Oct 16 2011Oct 21 2011

Other

Other2011 AIChE Annual Meeting, 11AIChE
CountryUnited States
CityMinneapolis, MN
Period10/16/1110/21/11

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)

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