Effects of CaO addition on Ni/CeO2-ZrO2-Al2O3 coated monolith catalysts for steam reforming of N-decane

A series of 10 wt%Ni/CeO2-ZrO2-Al2O3 (10%Ni/CZA) coated monolith catalysts modified by CaO with the addition amount of 1 wt%similar to 7 wt% are prepared by incipient-wetness co-impregnation method. Effects of CaO promoter on the catalytic activity and anti-coking ability of 10%Ni/CZA for steam reforming of n-decane are investigated. The catalysts are characterized by N-2 adsorption-desorption, XRD, SEM-EDS, TEM, NH3-TPD, XPS, H-2-TPR and Raman. The results show that specific surface area and pore volume of as-prepared catalysts decrease to some extent with the increasing addition of CaO. However, the proper amounts of CaO (<= 3 wt%) significantly enhance the catalytic activity in terms of n-decane conversion and H-2 selectivity mainly due to the improved dispersion of NiO particles (precursor of Ni particles). As for anti-coking performance, reducibility of CeO2 in composite oxide support CZA is promoted by CaO resulting in providing more lattice oxygen, which favors suppressing coke formation. Moreover, the addition of CaO reduces the acidity of 10%Ni/CZA, especially the medium and strong acidity. But far more importantly, a better dispersion of NiO particles obtained by proper amounts of CaO addition is dominant for the lower carbon formation, as well as the higher catalytic activity. For the spent catalysts, amorphous carbon is the main type of coke over 10%Ni-3%CaO/CZA, while abundant filamentous carbon is found over the others. (C) 2020 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.