| AVS 65th International Symposium & Exhibition | |
| Surface Science Division | Friday Sessions |
| Session SS+AS+HC-FrM |
| Session: | Near/Ambient Pressure and Bridging Gaps between Surface Science and Catalysis |
| Presenter: | Evgeny Vovk, ShanghaiTech University, China |
| Authors: | E.I. Vovk, ShanghaiTech University, China X. Zhou, ShanghaiTech University, China Z. Liu, ShanghaiTech University, China C. Guan, ShanghaiTech University, China Y. Yang, ShanghaiTech University, China W. Kong, Shanghai Advanced Research Institute, China R. Si, Shanghai Synchrotron Radiation Facility, Shanghai Institute of Applied Physics, Chaina |
| Correspondent: | Click to Email |
Dry reforming of methane (DRM) is an environmentally favored process transferring two greenhouse gases (CH4 and CO2) into syn-gas (H2+CO). Ni-based catalysts demonstrate good potential in this application because of comparable reactivity and low cost. DRM is highly endothermic reaction which requires high operating temperatures. At high temperatures sintering is a common issue of catalyst deactivation. Deactivation of Ni catalyst in DRM process is also accompanied by carbon deposition (coking) induced by methane decomposition and CO disproportionation (Boudouard reaction).
In the current work we investigated catalyst obtained by encapsulating Ni clusters (2.5±0.2 nm) into microporous silicalite-1 (aluminum free zeolite with MFI structure). No deactivation and coking under a wide range of conditions where carbon formation is thermodynamically favorable were observed for this sample. This atom-economical Ni/silicalite-1 catalyst was compared with Ni/SiO2 catalyst prepared by impregnation method. XPS study has been performed in ThermoFischer ESCALAB 250X photoelectron spectrometer. The gas treatments of catalysts (up to 1 bar) was performed in high pressure gas cell (Model HPGC 300, Fermi Instruments) connected to the spectrometer.
XPS analysis of Ni/silicalite-1 demonstrates the presence of a peak with binding energy (BE) 856.2 eV in Ni 2p3/2 region. Nickel silicate has a similar spectrum shape with close BE. The presence of this peak in Ni/silicalite-1 sample suggests of the Ni-O-Si species and strong metal-support interaction. After oxidation of this sample at 400°C there are no changes of the Ni-O-Si species. At the same time nickel in Ni/SiO2 catalyst which has shown mostly metallic Ni0 state with minor content of Ni-O-Si upon oxidation transforms into NiO. Reduction of Ni/silicalite-1 catalyst in hydrogen at 650°C leads to partial reduction of nickel into Ni0 while a significant portion of Ni-O-Si still remains. The behavior of Ni-O-Si feature in both oxidizing and reducing conditions clearly indicates its very high stability. We attribute this feature to the Ni-O-Si formed at the interface between Ni nanoparticles and the silicalite support. The Ni/silicalite-1 novel oxygen-philic interfacial catalyst system consists of very small metallic Ni clusters intercalated into silicalite framework and surrounded by Ni-O-Si species. Ni-O-Si provides high stability of Ni nanoparticles and prevents sintering and carbon deposition making this catalyst also very interesting for commercial application.