Insights into CeO2-modified Ni–Mg–Al oxides for pressurized carbon dioxide reforming of methane

Abstract

• NiO, MgO, and Al 2 O 3 mixed oxide (NMA) was prepared from hydrotalcite precursors. • NMA was modified by co-precipitated (NMACe) and impregnated CeO 2 (Ce/NMA). • Ce/NMA and NMACe were evaluated for pressurized CO 2 reforming of CH 4 (CDR). • Sharply reduced coke deposition and greatly inhibited Ni sintering of Ce/NMA. • Highly active and stable Ce/NMA was obtained for CDR under severe conditions. The mixed oxide of NiO, MgO, and Al 2 O 3 (NMA) with a MgO/Al 2 O 3 molar ratio of 3 was prepared from the hydrotalcite-like precursor, and ceria was introduced into NMA with Ce/Al molar ratios between 0.1 and 1.0 via the co-precipitation (NMACe) and the incipient impregnation (Ce/NMA) method, respectively. The NMACe and Ce/NMA were comparatively investigated to reveal the impact of ceria on NMA for carbon dioxide reforming of methane (CDR) under severe conditions. All of the catalysts were highly active for the pressurized CDR. On the contrary, a significant impact of the content and introduction method of CeO 2 on the catalytic stability was observed. Thus, the calcined, reduced, and/or used catalysts were systematically characterized by spectroscopic and adsorption techniques. Results indicate that the H 2 -TPR pattern of NMA was significantly influenced by the addition of CeO 2 , the extent of which is dependent on its content and introduction method. As a result, the degree of reduction and dispersion of Ni were clearly varied for different catalysts. Although the (1 1 1) planes of cubic CeO 2 were preferentially exposed over all of the catalysts, the content of Ce 3+ over Ce/NMA was apparently higher than that over NMACe, and the appropriate interactions between Ni and NMA were achieved over Ce/NMA with a Ce/Al ratio of 0.5. Because of the inhibited coke deposition, the alleviated graphitization of the deposited coke, and the delayed sintering of Ni, Ce/NMA with a Ce/Al ratio of 0.5 showed highly active and stable performance for the titled reaction under highly demanding operation conditions.