Nickel based catalysts derived from hydrothermally synthesized 1:1 and 2:1 phyllosilicates as precursors for carbon dioxide reforming of methane

Abstract: Hydrothermally synthesized Ni-containing 1:1 and 2:1 phyllosilicates (PS) were used as catalyst precursors for the CO2 reforming of CH4 to synthesis gas. The textural properties of the reduced and unreduced Ni-based PS were determined by N2 sorption analyses. In situ X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) experiments were used to characterize the generated Ni0 nanoparticles after reduction of the Ni-containing PS under various conditions such as H2 concentration and temperature. In the case of thermally stable PS (2:1 type), the reduction of structural nickel led to the formation of nanometric Ni0 particles over the surface of the remaining unreduced PS, while for Ni 1:1 PS phases nickel particles were supported on silica only. All catalysts were also investigated in the reverse water gas shift (RWGS) reaction to elucidate the effect of RWGS on the reforming reaction. The catalytic results obtained over reduced Ni-containing 1:1 and 2:1 PS confirmed that CH4 conversion was favored by very small Ni0 particles size, whereas CO2 conversion was catalyst support dependent. Our study demonstrated that a number of side reactions can compete with CO2 reforming of CH4 over Ni-containing phyllosilicates. However, by choosing the suitable phyllosilicate structure as catalyst precursor, as well as appropriate reduction conditions and reaction temperature, it may be possible to suppress the parallel reactions to some extent, thereby increasing the selectivity towards the products of the reforming reaction (H2 and CO). Reduced Ni-containing 2:1 PS proved to be stable even at high temperature. Highly dispersed homogeneously sized supported nanometric Ni0 particles over the remaining unreduced 2:1 PS structure are the key factors for high catalytic activity in CO2 reforming of CH4. [ABSTRACT FROM AUTHOR]