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Impact of Surface Composition of SrTiO 3 Catalysts for Oxidative Coupling of Methane
Author(s) -
Bai Lei,
PoloGarzon Felipe,
Bao Zhenghong,
Luo Si,
Moskowitz Benjamin M.,
Tian Hanjing,
Wu Zili
Publication year - 2019
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201900159
Subject(s) - catalysis , selectivity , perovskite (structure) , oxidative coupling of methane , methane , chemistry , base (topology) , raman spectroscopy , inorganic chemistry , low energy ion scattering , analytical chemistry (journal) , ion , crystallography , organic chemistry , physics , optics , mathematical analysis , mathematics
Oxidative coupling of methane (OCM) to C 2 hydrocarbons (C 2 H 6 and C 2 H 4 ) have regained much attention due to the shale gas revolution. Perovskite catalysts have shown promising activity and selectivity to C 2 hydrocarbons. Here, we investigate the effect of surface reconstruction (leading to different surface compositions) of perovskites on the OCM by using SrTiO 3 (STO) as a model catalyst. Different surface densities of Sr (25–96 %) were attained via various treatments of STO. Low energy ion scattering (LEIS) and UV‐Raman results are in good agreement on the surface and subsurface composition of the reconstructed STO. From H 2 ‐TPR, the same H 2 consumption of STO samples allows relating their catalytic performances with surface acid‐base properties (quantified by NH 3 ‐/CO 2 ‐TPD). At 600–800 °C, the surface Sr enrichment was found to enhance CH 4 conversion, C 2 selectivity and the ratio C 2 H 4 /C 2 H 6 up to Sr/(Sr+Ti) of 0.66 and then levels off. Furthermore, the relative concentration of basic sites, base/(base+acid), is found as a better descriptor for STO catalytic performances. This work shows the clear correlation between surface reconstruction, relative basicity/acidity and OCM catalytic performance over perovskite catalysts. The trends here are similar to those for CH 4 combustion over the reconstructed STO in our recent work.[1][F. Polo Garzon, 2018] Overall, we suggest that tuning surface reconstruction/composition of perovskites can be an effective approach to control CH 4 activation and conversions.