Highly Dispersed Ni/Silica by Carbonization-Calcination of a Chelated Precursor for Coke-Free Dry Reforming of Methane

Catalyst deactivation by coke deposition is one of the primary challenges for dry reforming of methane (DRM) to produce syngas. In this study, we report the synthesis of highly dispersed Ni/silica catalysts (similar to 2.3 nm Ni particles) that exhibit excellent resistance to coke formation and deactivation in DRM by virtue of very small metal particle size, strong metal-support interaction, and sinter resistance, which hinders the formation and growth of filamentous coke. A facile citric acid-chelated nickel impregnation method followed by sequential carbonization/calcination treatment is developed to synthesize this highly dispersed catalyst. Compared to reference Ni/silica catalysts prepared by the impregnation method, the reported catalyst exhibits 2.5 times specific DRM activity and remarkably high coke resistance with stable performance and negligible coke formation after 100 h on stream. Extensive material characterization using extended X-ray absorption fine structure, high-resolution transmission electron microscopy, Raman, Fourier transform infrared spectroscopy, H-2 temperature-programmed reduction, and mass spectrometry analyses reveals insights into the effect of the synthesis process on the metal dispersion in the catalyst. The reported synthesis method is also observed to increase the density of basic surface sites on the catalyst, which are beneficial for CO2 activation and coke removal in DRM. The simplicity of the synthesis process and the excellent coke resistance of the resultant catalyst make it promising for large-scale application in DRM and other reforming reactions.