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Issue 15, 2017
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Elucidation of the higher coking resistance of small versus large nickel nanoparticles in methane dry reforming via computational modeling

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Abstract

Dry reforming of methane (DRM) is a promising utilization process of greenhouse gases, namely CO2 and CH4. Nickel-based catalysts are the most popular ones for DRM, because they are inexpensive and relatively active but deactivate rapidly mainly due to carbon formation. Carbon gasification by either partial or complete oxidation is considered to be the main route for carbon-free catalysis. To clarify the competition between carbon deposition and carbon gasification in this computational study, we modeled the formation of C–C and C–O bonds on large and small Ni-nanoparticles (∼1 nm). We found that C prefers to penetrate into the subsurface, whereas O prefers to adsorb on the surface of both large and small nickel particles. The formation of CO at low concentrations is significantly more exothermic than C2 formation but the C2 moiety is formed faster than CO. At low carbon concentrations, the formation of the C–C bond is not favorable with respect to the two C species located in the subsurface region. However, at high C concentrations, on the large metal particles, multicarbon Cn species are formed; those species are potential precursors of carbon deposits such as graphene or coke. On the other hand, the flexibility of the small nickel nanoparticles allows separation of monoatomic C to remain stable as subsurface species. Thus, Cn species, considered to be precursors of carbon deposits leading to catalyst deactivation, are found to preferably form on large rather than on small Ni nanoparticles.

Graphical abstract: Elucidation of the higher coking resistance of small versus large nickel nanoparticles in methane dry reforming via computational modeling

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Publication details

The article was received on 19 Apr 2017, accepted on 02 Jul 2017 and first published on 17 Jul 2017


Article type: Paper
DOI: 10.1039/C7CY00773F
Citation: Catal. Sci. Technol., 2017,7, 3339-3347
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    Elucidation of the higher coking resistance of small versus large nickel nanoparticles in methane dry reforming via computational modeling

    H. A. Aleksandrov, N. Pegios, R. Palkovits, K. Simeonov and G. N. Vayssilov, Catal. Sci. Technol., 2017, 7, 3339
    DOI: 10.1039/C7CY00773F

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