Direct synthesis of highly loaded and well-dispersed NiO/SBA-15 for producer gas conversion

Abstract

To design a new Ni based catalyst for producer gas (CO₂ + H₂) conversion with high conversion and selectivity, highly loaded and well-dispersed NiO/SBA-15 was obtained for the first time by the direct synthesis method. The NiO particles were dispersed into the SiO₂ structure of SBA-15, unlike when prepared by the post synthesis method. The NiO/SBA-15 exhibited excellent efficiency and selectivity for producer gas conversion, comparable to that obtained by the post synthesis method. The synthesis method affected the CO selectivity. The temperature and H₂/CO₂ ratio played an important role in CO₂ conversion, indicating that a high temperature and high H₂/CO₂ ratio favored CO₂ conversion. The NiO loading did not affect the CO₂ conversion. Although there was no difference in the CO selectivity when the NiO loading was increased at high temperature, it was influenced greatly by NiO loading at low temperature as a result of CH₄ formation. In NiO/SBA-15 with low NiO loading, it can be considered that the NiO particles were separated into single NiO particles, which only catalyzed the reverse water gas shift (RWGS) reaction, regardless of the temperature, resulting in a CO selectivity of 100%. However, in NiO/SBA-15 with high NiO loading, the NiO particles aggregated to result in one or more NiO particles existing near each other. In this case only the RWGS reaction could occur at high temperature, and both methanation and the RWGS reaction were catalyzed at low temperature, resulting in a CO selectivity of less than 100%.