Support interaction of Ni nanocluster based catalysts applied in CO2 reforming

Abstract

Surface-tuned mesoporous alumina has been prepared using a template-assisted solvo thermal method, and Ni nanoclusters (4–5nm) have been synthesized on this support using a very facile organic matrix decomposition approach to dry reforming of methane. The catalyst system demonstrates very good catalytic activity toward CH4 and CO2 conversion (>90%), with a H2/CO ratio in syngas of almost unity, remarkable stability for more than 100h, and is proven to be a very interesting catalyst system in dry reforming with methane. Both fresh and spent catalyst have been thoroughly characterized using different techniques such as N2 physisorption studies, X-ray diffraction, X-ray photoelectron spectroscopy, high-resolution transmission electron microscopy, temperature-programmed reduction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and thermogravimetric analysis to determine the structure–activity relationship. Characterization results show that Ni nanoclusters are highly dispersed on the surface of modified alumina. In addition, an excellent metal-support interaction evolves that clearly enhances the stability of the Ni clusters, providing better resistivity toward sintering. The presence of balanced acidic and basic sites in the surface-modified alumina drastically lowers coke formation and enhances the catalyst lifetime. The structures of adsorbed methane and carbon dioxide on the catalyst surface and the corresponding energy of adsorption have been computed using density functional theory calculations. It has been found that CO2 is adsorbed and dissociated into CO and O, while methane is adsorbed as CH3∗ and H∗ on the catalyst system.