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

Silicon oxycarbonitride ceramic containing nickel nanoparticles: from design to catalytic application

“…The formation of nickel silicide and the sintering of nickel particles can result, to some degree, in catalyst deactivation. 53,88 This deactivation is soft for the time on stream tested as proved by the catalytic tests previously. Surface carbon formation resulting from CO disproportionation or CH4 decomposition (Eq.(3)-Eq.…”

“…( 5)) has been claimed to deactivate the catalyst or also to be involved in the reaction mechanism, 53,85,86 although an excess carbon can plug the reactor. 87 Another option can be the transformation of the active metal nickel nanoparticles to its silicide phases, 88 which displays a diminished activity toward syngas formation. The occurrence of the different potential deactivation mechanisms will be later discussed using post-catalytic XRD, XPS, and TEM data.…”

Engineering Thermally Resistant Catalytic Particles for Oxidative Coupling of Methane Using Spray-Drying and Incorporating SiC

“…For a dry reforming of methane, the SiO 2 layer on the Ni/SiC catalyst was shown to prevent formation of silicides and contributed toward the higher activity. 64 The transformation of the α-cristobalite phase to quartz along with the reduced surface area for the used catalyst are the results for deactivation in the IMP SiO 2 catalyst. 58,65 This applies to the IMP SiO 2 catalyst in particular, for which the S BET dropped 38% from 2.64 m 2 g −1 to 1.64 m 2 g −1 , compared to SD SiO 2 − SiC, for which S BET decreased 25% from 5.44 m 2 g −1 to 4.07 m 2 g −1 .…”

Monolithic silicon carbide with interconnected and hierarchical pores fabricated by reaction‐induced phase separation

“…Porous silicon carbide (SiC) monoliths attract increasing attentions in catalyst/catalyst support, electromagnetic absorption, heat exchanger, hot gas separation, porous media combustion, and metal/ceramic composite areas, owing to their excellent properties including high‐temperature stability, good mechanical strength, low thermal expansion coefficient, high thermal conductivity, and chemical inertness. In light of their promising applications, numerous methods have been developed for the fabrication of porous SiC monoliths, such as oxidation bonding, freeze‐drying, sacrificial templating, direct foaming, and sol‐gel method combined with carbothermal reduction.…”