Illuminating solid gas storage in confined spaces - methane hydrate formation in porous model carbons.

Lars Borchardt,Dirk Wallacher,Mirian Casco,Simon Krause,Irena Senkovska,Nico Grimm,Winfried Nickel,Volodymyr Bon,Joaquín Silvestre-Albero

doi:10.1039/c6cp03993f

Abstract

Methane hydrate nucleation and growth in porous model carbon materials illuminates the way towards the design of an optimized solid-based methane storage technology. High-pressure methane adsorption studies on pre-humidified carbons with well-defined and uniform porosity show that methane hydrate formation in confined nanospace can take place at relatively low pressures, even below 3 MPa CH4, depending on the pore size and the adsorption temperature. The methane hydrate nucleation and growth is highly promoted at temperatures below the water freezing point, due to the lower activation energy in ice vs. liquid water. The methane storage capacity via hydrate formation increases with an increase in the pore size up to an optimum value for the 25 nm pore size model-carbon, with a 173% improvement in the adsorption capacity as compared to the dry sample. Synchrotron X-ray powder diffraction measurements (SXRPD) confirm the formation of methane hydrates with a sI structure, in close agreement with natural hydrates. Furthermore, SXRPD data anticipate a certain contraction of the unit cell parameter for methane hydrates grown in small pores.

Highlights

Recent studies performed by Casco et al have shown that the kinetic limitations of methane hydrate growth can be overcome using high-surface area activated carbons as a host structure.[3]
The uniform pore size is validated by the type IV N2 isotherm with a H1 hysteresis (Fig. 2), and visualized by Scanning electron microscopy (SEM) and Scanning transmission electron microscopy (STEM) images (Fig. 3)
This observation is in close agreement with the slow methane hydrate nucleation and growth process, preferentially when water is in liquid-like phase, i.e. for sample Cmeso-1 and Cmicro above 0 1C

Summary

Introduction

Recent studies performed by Casco et al have shown that the kinetic limitations of methane hydrate growth can be overcome using high-surface area activated carbons as a host structure.[3].

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Results

Conclusion