Abstract
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. Overall, we suggest that tuning surface reconstruction/composition of perovskites can be an effective approach to control CH 4 activation and conversions.
| Original language | English |
|---|---|
| Pages (from-to) | 2107-2117 |
| Number of pages | 11 |
| Journal | ChemCatChem |
| Volume | 11 |
| Issue number | 8 |
| DOIs | |
| State | Published - Apr 18 2019 |
Funding
The authors acknowledge financial support from National Science Foundation CBET supplemental intern funding 1511818, West Virginia Higher Education Policy Commission, under the Grant Number HEPC.dsr.18.7. FPG, ZB, SL and ZW were supported by U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division. BMM acknowledges support from the U.S. Department of Energy, Office of Science, Office of Workforce Development for Teachers and Scientists, Office of Science Graduate Student Research (SCGSR) Program. The SCGSR program is administered by the Oak Ridge Institute for Science and Education (ORISE) for the DOE. ORISE is managed by ORAU under contract number DE-SC0014664. This work was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.
| Funders | Funder number |
|---|---|
| DOE Office of Science user facility | |
| National Science Foundation CBET | 1511818 |
| Office of Basic Energy Sciences | |
| Office of Science Graduate Student Research | |
| SCGSR | |
| West Virginia Higher Education Policy Commission | HEPC.dsr.18.7 |
| U.S. Department of Energy | |
| Office of Science | |
| Workforce Development for Teachers and Scientists | |
| Oak Ridge Associated Universities | DE-SC0014664 |
| Oak Ridge Institute for Science and Education | |
| Chemical Sciences, Geosciences, and Biosciences Division |
Keywords
- Base/Acid sites
- Kinetics
- Oxidative Coupling of Methane
- Strontium Titanate
- Surface Reconstruction