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

摘要

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/g_(cat) 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.