Abstract
La-promoted NiMgAl mixed-oxide catalysts derived from hydrotalcite were synthesized by coprecipitation for the carbon dioxide reforming of methane. X-ray diffraction, thermogravimetric analysis, temperature-programmed reduction, X-ray photoelectron spectroscopy, temperature-programmed desorption of carbon dioxide, hydrogen chemisorption and transmission electron microscopy were used to investigate the structure and deactivation characteristics of the catalysts. The catalysts exhibited a narrow Ni-metal particle-size distribution between 5 and 11nm. The presence of lanthanum evidently improved reforming activity in the temperature range of 600–700°C, because the introduction of lanthanum into the NiMgAl catalysts increased the total amount of basic sites and the surface Ni content. The activity of the Ni0.5Mg2.5Al0.9La0.1O4.5 catalyst was slightly higher than those of the other lanthanum-containing catalysts. The addition of lanthanum improved the stability of the NiMgAl catalysts significantly because of the suppression of coke deposition. Lanthanum effectively inhibited coking by increasing the basicity of the catalysts, forming the La2O2CO3 phase and improving nickel metal dispersion.
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