Direct Partial Oxidation of Methane to Synthesis Gas by Cerium Oxide

Otsuka, Kiyoshi; Wang, Ye; Sunada, Eiyuh; Yamanaka, Ichiro

doi:10.1006/jcat.1998.1985

Cited by 324 publications

(191 citation statements)

References 20 publications

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“…Recently, Otsuka et al [50][51][52] showed that ceria can also directly convert methane to syngas with H 2 :CO = 2 at temperatures higher than 600 • C. In this work, we examined the activity of Ce(La)O x in fuelrich methane oxidation with a CH 4 :O 2 molar feed ratio of 2 in the absence of SO 2 . In agreement with Otsuka et al [50][51][52], partial oxidation products, i.e. CO and H 2 , were observed on Ce(La)O x at temperatures higher than 650 • C as shown in Fig.…”

Section: Catalyst Activity and Selectivitymentioning

confidence: 97%

Ceria-based catalysts for the recovery of elemental sulfur from SO2-laden gas streams

Flytzani‐Stephanopoulos

Zhu

2000

Catalysis Today

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The catalytic reduction of SO 2 to elemental sulfur by CO or CH 4 over ceria-based catalysts under demanding operating conditions is reported in this paper. Cu-or Ni-containing ceria catalysts have been shown before to be highly active and selective for SO 2 reduction by CO in dry gas streams or in the presence of low amounts of H 2 O. In this work, the activity/selectivity of 10 at.%La-doped ceria, Ce(La)O x , and Cu-or Ni-containing Ce(La)O x for the (SO 2 + CO) reaction was tested in gas streams containing 10-45 mol%H 2 O at high space velocities (>80,000 h −1 ). The addition of 5 at.% (∼2.5 wt.%) copper or nickel significantly improved the low-temperature (<500 • C) reactivity of Ce(La)O x . This was correlated with the improved reducibility of ceria in the metal-ceria catalysts and the ensuing low-temperature activity for the water-gas-shift (WGS) reaction. The combined reduction of SO 2 and NO by CO was also studied in this work over the same catalysts. In dilute gas mixtures containing 0.1-1.0 mol%SO 2 and NO, stoichiometric amount of CO and in the presence of 40%H 2 O, the NO presence in the feed gas enhances both the SO 2 conversion and the elemental sulfur yield. At 550 • C, in the presence of NO, SO 2 conversion and sulfur yield over the 5%Ni-Ce(La)O x catalyst were 0.94 and 0.77, respectively, the NO conversion to N 2 was complete, and the CO 2 produced was the sum of the SO 2 and NO reduction reactions by CO. Ceria-based materials are also active for SO 2 reduction by methane to elemental sulfur at temperatures higher than 550 • C. The addition of Cu or Ni has a different effect on the sulfur selectivity of ceria under fuel-rich conditions. The Cu-ceria system is a complete oxidation catalyst to a much higher temperature than Ni-ceria. Over Ni-CeO 2 , dissociation of methane begins at <550 • C, and side reactions favor H 2 S production over elemental sulfur. However, the 5 at.%Ni-Ce(La)O x catalyst showed remarkable resistance to carbon deposition, both in the SO 2 -methane reaction as well as in partial oxidation of methane by O 2 to synthesis gas with a 2:1 H 2 :CO ratio. This is attributed to the high dispersion of nickel in this catalyst and the fast rate of oxygen supply from ceria to the nickel interface. Catalysts were characterized by temperature-programmed-reduction, XPS and STEM/EDS.

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Section: Catalyst Activity and Selectivitymentioning

confidence: 97%

Ceria-based catalysts for the recovery of elemental sulfur from SO2-laden gas streams

Flytzani‐Stephanopoulos

Zhu

2000

Catalysis Today

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“…To suppress complete oxidation, CeO2-supported catalysts can achieve selective partial oxidation due to the lattice oxygen without complete oxidation 51) . Furthermore, Pt black supported on CeO2 promoted this reaction 52) . CeO2 and CexZr1-xO2 solid solutions were used to achieve higher activity as CeO2 supports 53), 54) .…”

Section: Chmentioning

confidence: 89%

Methane Conversion Assisted by Plasma or Electric Field

Oshima

Sekine

2013

J. Jpn. Petrol. Inst.

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Direct conversion of methane to other valuable products such as ethylene, methanol, benzene, carbon, hydrogen, and syngas has been widely investigated. Such conversion requires high temperatures because of the strong C-H bond in CH4, and such high-temperature reactions present various problems: sequential reaction to decrease the selectivity to target products, need for multiple heat exchangers to use or recover high-temperature waste heat, materials that are stable at high temperatures, etc. To solve these problems, several trials have been undertaken to lower reaction temperatures using plasma, Non-Faradaic Electrochemical Modification of Catalytic Activity (NEMCA), and electric fields. This review describes recent trends in methane conversion, and describes our methods to lower the reaction temperature.

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“…The limitation for the reduction of only one hypothetical reduced ceria layer by CO cannot be attributed to the oxygen diffusion since the reduction degree of ceria was not significantly influenced by a temperature between 400 and 580 • C. The role of ceria in the reduction of CO 2 to CO had been widely studied in the field of solar cells [12][13][14]. CO 2 can also re-oxidise reduced ceria, thereby forming CO.…”

Section: Reduction Of Ceria By Co and Hmentioning

confidence: 99%