One-pot Synthesis of Ordered Mesoporous NiCeAl Oxide Catalysts and a Study of Their Performance in Methane Dry Reforming

摘要

Ordered mesoporous NiAl and NiCeAl catalysts with different Ce/Al molar ratios were facilely synthesized by using the improved evaporation-induced self-assembly method. The characterization results confirmed that the ordered mesoporous structure was well sustained in the Ce-incorporated NiAl materials (Ce/Al molar ratio<4%). Compared with NiAl mesoporous materials, Ce-incorporated mesoporous materials demonstrated higher specific surface areas, larger pore volumes, and more uniform pore sizes. The catalytic test conducted by using methane dry reforming revealed that compared with NiAl catalysts, all the Ce-promoted catalysts demonstrated improved initial catalytic activity, which was due to the high dispersion and the high reduction degree of active Ni species in NiCeAl catalysts. The stable alumina framework, confinement effect of ordered mesopores, and high oxygen mobility contributed to the improved catalytic stability of NiCeAl catalysts. For comparison, the mesoporous NiCeAl catalyst (denoted as NiCeAl-IMP) was also prepared by using the conventional impregnation method. The agglomeration of Ni particles was observed during the stability test for the Ni-impregnated catalyst, which accelerated the rate of carbon deposition. The NiCeAl catalyst (Ce/Al molar ratio=1%) demonstrated excellent resistance to the formation of graphitic carbon species owing to the redox property, while a large amount of graphitic carbon species was deposited over the NiAl sample, which was responsible for deactivation.