Reaction performance of partial oxidation of methane over Ni/SiO 2 catalysts using monodisperse silica sol as supporting precursor

Abstract

The reaction performance of partial oxidation of methane (POM) by air over Ni/SiO 2 catalysts was investigated using monodisperse silica sol [H.E. Bergna, in: H.E. Bergna (Ed.), The Colloid Chemistry of Silica, Adv. Chem. Ser. 234, The American Chemical Society Press, Washington, DC, 1994, p. 1.] as supporting precursor in a fixed micro-reactor at atmospheric pressure. The distribution of SiO 2 particles in silica sol was imaged by transmission electron microscopy (TEM). Ni/silica-sol catalyst has an excellent performance during partial oxidation of methane, and methane oxidation greatly depends on the concentration of O 2. At 800 °C, when the CH 4/O 2 molar ratio is ca. 2, about 96% of CH 4 conversion is achieved, and the selectivities of H 2 and CO are above 98% and 95%, respectively. The reaction products are mainly H 2, H 2O and CO 2 at low temperature; a large amount of heat is released to sustain the POM reactions for a long time while the temperature of the surroundings is close to room temperature. The facts indicate that the catalyst has high activity and that the POM reaction can be ignited by H 2 injection at low temperature. The structure and the reducing properties of these catalysts were characterized by BET, temperature programmed reduction (TPR) and powder X-ray diffraction (XRD) methods. XRD patterns also indicate that oxygen is completely consumed on the top layer of the catalysts; and the active species of catalyst can fully sustain Ni 0 phase under low reaction temperature in water-rich product mixtures.