Alkane reforming on partially sulfided CeO2 (1 1 1) surfaces

Abstract

a b s t r a c tCleanup of biomass gasification effluent requires a catalyst that can reform methane and larger hydrocarbons while tolerating the presence of H 2 S or, ideally, that can act as a sulfur sorbent while reforming hydrocarbons. We utilize density functional theory (DFT) methods to examine the impact of oxide sulfidation on the reforming of methane and the initial steps of propane reforming, using M-doped CeO 2 catalysts. On a ceria oxy-sulfide surface, surface oxygen atoms remain active for CAH bond activation via hydride abstraction whereas surface sulfur atoms are significantly less active. Methyl adsorption is slightly favored at a surface sulfur site, and though subsequent dehydrogenation steps remain viable, the final steps of methane decomposition may lead to carbon buildup on the surface. However, surface sulfur sites will be less active globally for the initial rate limiting H abstraction step, and these sites can nucleate carbon buildup. Doping CeO 2 with Mn accelerates CAH bond activation, aids eventual CO product desorption, and may induce sulfur tolerance by motivating CH x intermediates to bind to surface O atoms rather than surface S atoms. This work represents an initial step in the development of S-tolerant oxide catalysts for hydrocarbon reforming.

Sulfur-Accelerated Ceria Catalyst for Efficient CH4/CO2 Reforming: Unraveling the Special Role of Redox Functions and Its Reaction Mechanism

“…However, the remaining question is whether such a mechanism can be applied in the present work and whether this strategy can be extended to the activation of other alkane molecules. Furthermore, the reaction mechanism during alkane reforming over sulfated CeO 2 surface was also reported by them, which illustrated that there was a slight preference for CH 3 * species to bind to surface sulfur atoms . More recently, the sulfur-accelerated ceria catalyst was reported for deNO x reaction, and it is revealed that Brønsted acid sites originated from the protons on surface sulfates were created by sulfation treatment .…”

Rare Earth/Transition Metal Oxides for Syngas Tar Reforming: A Model Compound Study

“…For Pd/Ce7 the slightly more negative order results suggest some competitive inhibition by water, due possibly to elimination of oxygen vacancies. For La/Ce3 and Re/Ce3/Zr54, the high negative orders signify that the water greatly changed the catalyst structure resulting in the elimination of oxygen vacancies that according to DFT studies constitute the initial active sites. ,, …”

“…For La/Ce3 and Re/Ce3/ Zr54, the high negative orders signify that the water greatly changed the catalyst structure resulting in the elimination of oxygen vacancies that according to DFT studies constitute the initial active sites. 10,11,57 Most researchers have reported some increase in tar reforming activity and lower coke deposition when the partial pressure of water is increased. 22,25,51,58−60 However, there appears to exist an optimum water partial pressure, for most catalysts.…”

Ru nanoparticles supported on hydrophilic mesoporous carbon catalyzed low-temperature hydrodeoxygenation of microalgae oil to alkanes at aqueous-phase

“…The selective hydrodeoxygenation (HDO) of lipid was performed using sulfur-and non-sulfur-containing metal catalysts due to their relatively high stability in non-polar phases [1,14]. Ni-and Co-based catalysts are used for the HDO of fatty acids and lipids into alkanes at ca.…”