International Journal of Hydrogen Energy, Vol.43, No.41, 18955-18976, 2018
An in depth investigation of deactivation through carbon formation during the biogas dry reforming reaction for Ni supported on modified with CeO2 and La2O3 zirconia catalysts
The dry reforming of biogas on a Ni catalyst supported on three commercially available materials (ZrO2, La2O3-ZrO2 and CeO2-ZrO2), has been investigated, paying particular attention to carbon deposition. The DRM efficiency of the catalysts was studied in the temperature range of 500-800 degrees C at three distinct space velocities, and their time-on stream stability at four temperatures (550, 650, 750 and 800 degrees C) was determined for 10 or 50 h operation. The morphological, textural and other physicochemical characteristics of fresh and spent catalysts together with the amount and type of carbon deposited were examined by a number of techniques including BET-BJH method, CO2 and NH3-TPD, XPS, SEM, TEM, STEM-HAADF, Raman spectroscopy, and TGA/DTG. The impact of the La2O3 and CeO2 modifiers on the DRM performance and time-on-stream stability of the Ni/ZrO2 catalyst was found to be very beneficial: up to 20 and 30% enhancement in CH4 and CO2 conversions respectively, accompanied with a CO-enriched syngas product, while the 50 h time-on-stream catalytic performance deterioration of-30-35% on Ni/ZrO2 was limited to less than-15-20% on the La2O3 and CeO2 modified samples. Their influence on the amount and type of carbon formed was substantial: it was revealed that faster oxidation of the deposited carbon at elevated temperatures occurs on the modified catalysts. Correlations between the La2O3 and CeO2-induced modifications on the surface characteristics and physicochemical properties of the catalyst with their concomitant support-mediated effects on the overall DRM performance and carbon deposition were revealed. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Keywords:Biogas reforming;Nickel-based catalysts;Ceria or lanthana modified zirconia;Catalytic stability;Carbon deposition;Multiwall carbon nanotubes