The optimization of Ni-Al2O3 catalyst with the addition of La2O3 for CO2-CH4 reforming to produce syngas

A series of La2O3-Ni-Al2O3 catalysts promoted by different loading of lanthanum were prepared via the hydrolysis-deposition method to improve the catalytic performance of nickel-based catalyst for CO2-CH4 reforming. The catalysts were characterized by N-2 adsorption - desorption, XRD, H-2-TPR, TG-DTG, TEM, Raman and TPH techniques. Results showed that the precursor of active component was mainly in the form of NiAl2O3 spinel, which almost disappeared after reduction process from XRD characterization, suggesting well reduction performance. The catalyst with La loading of 0.95 wt% (La-Ni-1) presented a small average Ni grain size of 7.71 nm and exhibited well catalytic performance at 800 degrees C, with CH4 conversion of 94.37%, CO2 conversion of 97.15%, H-2 selectivity of 75.01% and H-2/CO ratio of 0.92. The Ni grain size of La-Ni-1 increased only 5.84% to 8.16 nm after performance test, which was lower than that of others and indicated a well structure stability. Additionally, the strong carbon diffraction peak over La-Ni-0.5 and La-Ni-2 catalysts suggested the presence of crystalline carbon species accumulated on the catalysts, while there was no carbon peak over La-Ni-1 sample. A 150 h stability test for La-Ni-1 demonstrated that the conversion of CH4 was around 95%, higher than that of La-Ni-0 (without lanthanum addition) and La-Ni-4 (with La content of 3.82 wt%). The carbon deposition rate of La-Ni-1 was only 1.63 mg/(g(cat).h), lower than that of La-Ni-4 (2.20 mg/(g(cat).h)), showing both high activity and well stability. Therefore, the confinement effect of La2O3 to Ni crystalline grain would inhibit the sintering of active component, prevent the carbon deposition, and improve the catalytic reforming performance. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.