Effect of NH 3 Alkalization and MgO Promotion on the Performance of Ni/SBA-15 Catalyst in Combined Steam and Carbon Dioxide Reforming of Methane

摘要

In this work, 31.4?wt.% Ni/SBA-15 (Ni/SBA-15) nonpromoted and alkalized with ammonia solution and by MgO promoter catalysts were prepared and used for combined steam and CO 2 reforming of CH 4 (bireforming). Effect of concentration of ammonia solution (NH 3(aq) ) (10–25?vol.%) and Mg content (3–12?wt.%) on the properties of the Ni/SBA-15 catalysts was investigated by low-angle and powder X-ray diffraction (XRD), N 2 -BET isothermal adsorption, SEM, TEM, EDS mapping, H 2 -TPR, and CO 2 -TPD methods. The performance of the catalysts in bireforming was assessed in the temperature range of 550–800°C. The enhancement of dispersion of NiO particles, reducibility, and basicity of alkalized Ni/SBA-15 catalysts were responsible for improving the catalytic performance of this catalyst. The results revealed that the Ni/SBA-15 treated with 15-25% NH 3(aq) solution and promoted with 3-9% Mg exhibited high activity for CH 4 conversion. Meanwhile, Ni6Mg/SBA-15 showed the highest CO 2 conversion. Among tested catalysts, Ni/SBA-15-20NH 3 and Ni9Mg/SBA-15 samples had an almost equal activity with a CH 4 conversion of nearly 97% and a CO 2 conversion of about 84% at 700°C thanks to its moderate affinity with both CO 2 and CH 4 . However, the H 2 /CO ratio of the product mixture remained at 2.02 on the Ni/SBA-15-20NH 3 catalyst and almost 1 on the Ni9Mg/SBA-15 sample. These results might be related to the fact that the alkalization of the Ni/SBA-15 catalyst by NH 3(aq) solution had an advantage over using MgO because side reactions were unlikely to occur.