Preparation of Nanoporous Silicon Carbide Materials for High Temperature Gas Separation Applications
Steam gasification of biomass is one potential technique for the large scale synthesis of hydrogen. Biomass gasification produces a gaseous mixture primarily containing hydrogen, carbon dioxide, carbon monoxide and methane. In situ separation of hydrogen during gasification using membranes is a promising approach to large-scale hydrogen synthesis, however, at the present time, there are material durability issues due to the hydrothermal conditions within the gasifier. Silicon carbide has been proposed as a suitable material for this high temperature application due to its favourable thermal and mechanical properties as well as its chemical inertness. However, the formation of nanoporous silicon carbide has received very little attention in the literature, and is comparatively difficult to synthesize compared with mesoporous silica. We have prepared porous silicon carbide materials using four separate techniques; i) pre-ceramic polymer pyrolysis, ii) chemical vapour deposition, iii) sacrificial templating using an aligned carbon nanotube template and iv) particle bonding techniques. The synthesised materials have been evaluated as potential membrane materials for hydrogen separation under hydrothermal conditions. To quantify the properties of the porous SiC materials we used nitrogen adsorption, mercury porosimetry, thermogravimetric analysis, infrared spectroscopy and high resolution scanning electron microscopy.