Effects of metal content on activity and stability of Ni-Co bimetallic catalysts for CO2 reforming of CH4

Ni-Co bimetallic catalyst with a general formula of Ni-Co-Al-Mg-O prepared using coprecipitation has shown excellent stability and high activity for CO2 reforming of CH4 in our previous research. This paper focuses on the effects of Ni-Co content of the catalyst, attempting to avoid carbon formation on the catalyst. Catalyst samples with Ni and Co loadings ranging between 1.83 and 14.5 wt.% and 2.76 and 12.9 wt.%, respectively, were prepared and the activity and stability for CO2 reforming of CH4 was tested at 750 °C and 1 atm using a high GHSV of 180,000 mL/gcat h. The results show that catalysts with lower Ni-Co content (1.83–3.61 wt.% for Ni and 2.76–4.53 wt.% for Co) had higher and more stable activity with no deactivation and no detectable carbon formation and that those of higher Ni-Co content (5.28–14.5 wt.% for Ni and 7.95–12.9 wt.% for Co) experienced apparent deactivation with significant carbon formation in 250 h time-on-stream tests. Catalyst characterizations using TEM, XRD, H2-TPR, TG/DTG-TPO, N2-physisorption, and CO-chemisorption indicate that catalyst with lower Ni-Co content has larger surface area, smaller metal particles and better metal dispersion and therefore gives rise to better catalytic performance. The absence of large metal particles (>10 nm) is believed essential to the complete suppression of the carbon formation during reaction.

Graphical abstractThis work focuses on the effects of Ni-Co content of the catalyst, attempting to avoid carbon formation on the catalyst by selecting proper metal ensemble size. Catalyst samples with different Ni and Co loadings were prepared, and the activity and stability for CO2 reforming of CH4 was tested at 750 °C, 1 atm and GHSV of 180,000 mL/gcat h. The results with 250 h time-on-stream show that catalysts of lower Ni-Co content had high and stable activity with no deactivation and no detectable carbon formation and that those of higher Ni-Co content experienced apparent deactivation with significant carbon formation. Characterizations indicate that catalyst with lower Ni-Co content has larger surface area and better metal dispersion and therefore gives rise to smaller metal particles (<10 nm) which is essential to the complete suppression of the carbon formation on catalyst. Figure optionsDownload full-size imageDownload as PowerPoint slide