Nanoporous silicon carbide as nickel support for the carbon dioxide reforming of methane

Abstract

Fumed silica is used as a template in the nanocasting approach towards nanoporous silicon carbide, and it can then be applied as a catalyst support. By varying the pyrolysis temperature between 1000 and 1500 °C, the structural parameters of the resulting silicon carbide materials DUT-87 (DUT = Dresden University of Technology) can be controlled. A specific surface of 328 m² g⁻¹ is obtained. Furthermore, the oxidation behaviour of such nanoporous SiCs is investigated. The materials are distinguished by an impressive thermal stability at 900 °C for at least 12 h, which is allowed by the presence of a passive oxidation even for such highly porous SiCs. Hence, nickel (10 wt%) was supported on the fresh DUT-87 as well as controlled oxidized DUT-87preox samples, and the influence of the different support properties on the characteristics of the catalyst samples which are used in the carbon dioxide reforming of methane was investigated. The SiO₂ layer on the SiC for the DUT-87preox samples could prevent the formation of nickel silicide to a large extent at temperatures up to 850 °C. This resulted in higher activities during the dry reforming of methane at 800 °C and the performance of the siliceous supports was significantly exceeded, emphasizing the beneficial effect of SiC. Effective methane reaction rates of 1.2 mmol g⁻¹ s⁻¹ were obtained for KPK1ox which was based on DUT-87 pyrolysed at 1300 °C and oxidative treatment prior to nickel insertion. Furthermore, a stable conversion level was reached over the whole time on stream of 8 h.