Carbon intermediates during CO2 reforming of methane over Ni-CaO-ZrO2 catalysts: A temperature-programmed surface reaction study

The carbon intermediates for dry reforming of methane over Ni-CaO-ZrO2, catalysts during the initial reaction period were studied by temperature-programmed surface reaction (TPSR) techniques, including temperature-programmed hydrogenation (TPH), temperature-programmed CO2 reaction (TPRn CO2) and temperature-programmed oxidation (TPO). Three carbon species were detected on the catalysts surface during dry reforming, namely C alpha, C beta and C gamma. However, due to the different redox properties of Ni-CaO-ZrO2 catalysts, the individual carbon intermediate amount and interaction with the catalyst surface was distinct, which in turn led to the different reaction performance of both catalysts. The TPH-TPO and TPRn CO2-TPO tests showed that H-2 and CO2 had weaker elimination ability than O-2 and their elimination ability was lied on the carbon intermediate properties and the interaction with the support. According to the TPSR results, a possible mechanism of coking for dry reforming over Ni-CaO-ZrO2 catalysts was proposed, based on which the carbon intermediates might convert to the others or dissolve on the metal sites forming carbon deposits. (C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.