Massive growth of a fibrous gas hydrate from surface macropores of an activated carbon

Abstract

Venet et al., reported unprecedented, bundled growth of ≈ 1-10mm long, hollow gas hydrate fibres, diameter ≈ 1-10μm, on an activated carbon close to a guest-water interface, circumventing the hydrate growth bottleneck. Here, in situ video microscopy traces growth (2-3μms-1 at 0.5°C) to surface macropores of similar diameter, further exhibited by confocal and scanning electron microscopies. X-ray radiography shows fluid exchange to a depth of ≈ 50-100μm in a total porous fraction 40% (gravimetric porometry). Computed X-ray microtomography reveals a belt of organised peripheral porosity of aligned ≈5μm pores. These structures explain the origin of the comb or whalebone-like appearance of the hydrate. Whereas hydrate promotion by porous media is usually assumed to proceed inside the materials, like tiny hydrate storage warehouses, we find that the substrate behaves more like a ’lean’ or ’just in time’ production line, with hydrate extruded as fast as it is produced near the surface.