A material made of a mixture of silica and water (Figure 1) promises to provide a convenient and inexpensive way to store methane, say researchers at the University of Liverpool, Liverpool, U.K. While solids that trap methane are well known — methane gas hydrates are abundant, e.g., in marine sediments, they form slowly and only when methane contacts water under pressure.

Figure 1. Promising powder -- White silica-based powder may provide an attractive means to store methane. Source: University of Liverpool.

“To counteract these difficulties, we used a method to break water up into tiny droplets to increase the surface area in contact with the gas. We did this by mixing water with a special form of silica [hydrophobic fumed silica] — a material similar to sand — which stops the water droplets from coalescing. This ‘dry water’ powder soaks up large quantities of methane quite rapidly at around water’s normal freezing point,” explains Andy Cooper, director of the university’s Centre for Materials Discovery.

The crystalline methane gas hydrate physically retains the methane by trapping it in cages of water molecules. The fine white powder smears and feels cold to the touch, he notes.

The researchers are investigating how to store larger quantities of methane at higher temperatures and lower pressures, with funding from the U.K. Engineering and Physical Sciences Research Council.