A comparison of Al₂O₃ and SiO₂ supported Ni-based catalysts in their performance for the dry reforming of methane

Dry reforming of methane (DRM) with CO₂ is of great significance in the environmental protection and the utilization of natural gas. SiO₂ and Al₂O₃ are two typical catalyst supports used in DRM. To elucidate the effect of these two supports on the catalytic performance, in this work, Ni/SiO₂ and Ni/Al₂O₃ catalysts are prepared by the incipient wetness method and characterized by BET, TEM, H₂-TPR, XRD, TG and Raman technologies. The results indicate that the performance of Ni-based catalyst is closely related to the properties of support and the Ni/SiO₂ and Ni/Al₂O₃ catalysts are rather different in their DRM performance. Ni/SiO₂ catalyst exhibits higher initial activity but poor stability; its catalytic activity decreases rapidly in 15 h for DRM at 800℃. Because of the weak metal-support interaction, Ni species on the Ni/SiO₂ catalyst is present as large Ni particles, which may promote the formation of coke precursors, viz., the multi-carbon C_n species, leading to the fast carbonaceous deposition and catalyst deactivation. In contrast, the Ni/Al₂O₃ catalyst displays a lower activity but a much higher stability; its activity in DRM keeps stable in 50 h. Although Ni particles in the Ni/Al₂O₃ catalyst is much smaller, the strong metal-support interaction promotes the formation of NiAl_xO_y species during the catalyst preparation process, which may lead to a decrease in the content of active Ni species and give the Ni/Al₂O₃ catalyst a relatively low catalytic activity in DRM; however, the strong metal-support interaction between Ni and Al₂O₃ is also of benefit to the formation and stabilization of small Ni particles, which can alleviate the carbanceous deposition and afford the Ni/Al₂O₃ catalyst a better stability.