Biogas to syngas conversion without carbonaceous deposits via the dry reforming reaction using transition metal catalysts
•High OSC of CeZrO2 solid solution provides the functionality to oxidize formed coke.•Marginal improvement in catalytic activity is obtained with excessive NiCo loading.•No coke had accumulated after 400 h TOS at 1023 K and equimolar CH4/CO2 feed.•CH4/CO2 feed ratio higher that 1 drastically accelerates coke accumulation.
This study investigates how morphology, active metal content and oxygen storage capacity of various bimetallic NiCo/CeZrO2 materials influence their catalytic activity and stability in the methane dry reforming reaction. Catalyst preparation procedure and chemical composition were steered to finally obtain materials, which do not accumulate carbon during the CH4/CO2 reforming reaction. Oxygen storage capacity of the CeZrO2 catalyst support was identified to play a vital role in retarding carbon accumulation over the tested NiCo/CeZrO2 materials. This property can be fully developed when a nanocrystalline solid solution of CeO2 and ZrO2 is formed. Secondly, a high dispersion of nickel and cobalt is crucial for two reasons: (i) catalysts which contain larger NiCo bimetallic particles (for example with 12–18 wt.% active metal loading) exhibit a low metal-support interphase that results in enhanced coke formation rates; (ii) additionally, only a marginal gain in methane reforming rates are achieved at higher loadings, compared to catalysts with a 3–6 wt.% active metal content. We demonstrated that a NiCo/CeZrO2 catalyst under relevant operating conditions after 400 h TOS maintains 79 and 84% conversion of CH4 and CO2, with negligible coke accumulation.
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Journal: Catalysis Today - Volume 253, 15 September 2015, Pages 155–162