Highly selective Ni/SiO2 catalyst for the reverse water-gas shift reaction: effect of ageing and adding a second metal (bimetallic Ni-Pd)
EMSL Project ID
50697
Abstract
The reverse water-gas shift (RWGS) can be understood as a model reaction to probe the properties of heterogeneous catalysts, besides it can be a way to convert CO2, a greenhouse gas, to CO that can be further used in Fisher-Tropsch processes. Selectivity is an important issue on Ni catalysts, which can favor the complete hydrogenation of CO2/CO to CH4. The selectivity can be governed by nanoparticle structure. Although small nanoparticles tend to avoid methanation, the stability of such catalysts can be an important issue. The modification of Ni sites by either changing specific sites that promotes one reaction at the expenses of another, or changing the electronic structure by adding a different component are strategies applied in order to improve selectivity. Herein we plan to study classical Ni/SiO2 impregnated catalysts, and NixPdy bimetallic pre-formed nanoparticles by decomposition of organometallic precursors onto SiO2 catalysts under RWGS conditions. The as-prepared and reduced Ni/SiO2 catalysts are active for CO2-CO hydrogenation to CH4 at low temperatures, but we observed that after thermal treatments under different atmospheres, the CH4 formation is suppressed. This can be related to poisoning of the most active sites for CH4 formation. After some surface analysis by XPS, we suggested that carbon deposits on the top of Ni nanoparticle are the key to addressing selectivity towards RWGS reaction, which might be a very important finding in the CO2 conversion to chemicals. However, the type and stability of carbon specie remains unclear. We also found that NixPdy (x and y is the molar proportion of each atom) are selective to CO formation in RWGS, with the best selectivity achieved for Ni1Pd1 bimetallic compound. The formation of homogeneous alloy decreases the activation barrier for CO2 reduction to CO. The decreasing of CO binding energy to the NiPd surface can improves CO desorption, decreasing the activity for CO hydrogenation to CH4. Nevertheless, the mechanisms that lead to the improved selectivity in the alloy are still not proved.
Project Details
Project type
Limited Scope
Start Date
2019-02-25
End Date
2019-04-27
Status
Closed
Released Data Link
Team
Principal Investigator
Co-Investigator(s)
Related Publications
Braga A.H., N.J. Costa, K. Philippot, R.V. Goncalves, J. Szanyi, and L. Rossi. 2020. "Structure and activity of supported bimetallic NiPd nanoparticles: influence of preparation method on CO2 reduction." ChemCatChem. PNNL-SA-152908. doi:10.1002/cctc.201902329. [Unpublished]
Bruno H. Arpini, Adriano H. Braga, Thalita S. Galhardo, Renato V. Gonçalves, Caetano R. Miranda, Liane M. Rossi, János Szanyi, Bruno F. Zornio. 2021. "Optimizing Active Sites for High CO Selectivity during CO2 Hydrogenation over Supported Nickel Catalysts." Journal of the American Chemical Society 143 (11):4268-4280. 10.1021/jacs.0c12689
Bruno H. Arpini, Lais R. Borges, Adriano H. Braga, Renato V. Gonçalves, Liane M. Rossi, János Szanyi, Pedro Vidinha. 2022. "Tuning CO2 Hydrogenation Selectivity by N-Doped Carbon Coating over Nickel Nanoparticles Supported on SiO2." ACS Sustainable Chemistry & Engineering 10.1021/acssuschemeng.1c05847
Gustavo A. S. Alves, Laís R. Borges, Adriano H. Braga, Renato V. Gonçalves, Maitê L. Gothe, Nágila E. C. Maluf, Liane M. Rossi, János Szanyi, Pedro Vidinha. 2021. "Zeolitic‐Imidazolate Framework Derived Intermetallic Nickel Zinc Carbide Material as a Selective Catalyst for CO
2
to CO Reduction at High Pressure." European Journal of Inorganic Chemistry 2021 (44):4521-4529. 10.1002/ejic.202100530