Effect of sulfur on the oxidative coupling of methane over a lanthana catalyst

Campbell, Ian; Saricilar, Süreyya; Hoare, Ian C.; Bhargava, Suresh K.

doi:10.1016/0926-860x(92)80002-t

Cited by 5 publications

(3 citation statements)

References 23 publications

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“…Sulfur and lead compounds are often found at low percentage in natural gas, which are well-known poisoning components for many catalysts. Since La 2 Ce 2 O 7 catalyst shows good OCM performance at low temperature region (below 750 °C) and has certain application potential, its resistance to these poisoning agents has been tested.…”

Section: Resultsmentioning

confidence: 99%

“…This indicates that SO 2 molecules adsorbed reversibly on La 2 Ce 2 O 7 surface and occupied only a small amount of active sites for the reaction, which can be desorbed easily when SO 2 is removed from the reaction feed, and poses no any permanent damage to the catalyst. Generally, individual La and Ce oxides can react with sulfur oxides at high temperatures to form sulfates or sulfites. , It is apparent that, after forming La 2 Ce 2 O 7 compound, the La and Ce cations have been protected by the potent and stable La 2 B 2 O 7 lattice, thus La 2 Ce 2 O 7 showing potent sulfur resistance during high-temperature OCM reaction.…”

Section: Resultsmentioning

confidence: 99%

“…11,25 In order to estimate the contribution of the B-site metal oxides to the OCM reaction, the reactivity of the individual TiO 2 , ZrO 2 , and CeO 2 , which were also prepared by the same sol−gel method and calcined at 800 °C, have been tested. As depicted in Figure S6 in the Supporting Information, XRD and Raman results have proven that pure rutile-phase TiO 2 , baddeleyite ZrO 2 , and cubic fluorite CeO 2 have been successfully achieved, but with very low surface area (see Sulfur and lead compounds are often found at low percentage in natural gas, 50 which are well-known poisoning components for many catalysts. Since La 2 Ce 2 O 7 catalyst shows good OCM performance at low temperature region (below 750 °C) and has certain application potential, its resistance to these poisoning agents has been tested.…”

Section: Resultsmentioning

confidence: 99%

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Constructing La₂B₂O₇ (B = Ti, Zr, Ce) Compounds with Three Typical Crystalline Phases for the Oxidative Coupling of Methane: The Effect of Phase Structures, Superoxide Anions, and Alkalinity on the Reactivity

et al. 2019

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To probe the phase structure–reactivity relationship of A2B2O7 catalysts for the oxidative coupling of methane (OCM), three model La2B2O7 compounds with Ti4+, Zr4+, or Ce4+ at the B-site have been purposely designed. By decreasing the r A/r B ratios in the order of La2Ti2O7 > La2Zr2O7 > La2Ce2O7, typical monoclinic layered perovskite, cubic ordered pyrochlore, and disordered defective cubic fluorite phase are formed, respectively. The reaction performance of the catalysts based on CH4 conversion and C2 product yield follow the order of La2Ce2O7 > La2Zr2O7 > La2Ti2O7. It has been discovered that superoxide O2 – is the active oxygen species detected on all the catalysts and is responsible for the OCM reaction, whose amount follows also the sequence of La2Ce2O7 > La2Zr2O7 > La2Ti2O7. Moreover, the surface alkalinity related to the superoxide anions observes the same order. This testifies that the amount of surface superoxide O2 – determines the OCM reaction performance over the La2B2O7 compounds. On the basis of the characterization results, the formation of active O2 – species could follow two pathways. For La2Zr2O7 and La2Ce2O7 possessing intrinsic 8a oxygen vacancies, O2 – anions are formed by activating the oxygen species entering into the vacancies in the bulk and then migrating to the catalyst surface. For La2Ti2O7 possessing no oxygen vacancies, they are formed directly by transforming the O2 molecules adsorbed on its surface. Usually, the former pathway generates more abundant O2 – species than the latter one. La2Ce2O7 displays not only promising reaction performance in the low-temperature region, but also potent sulfur and lead poisoning resistance, thus having the potential for application after further optimization.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%