Well-defined meso/macroporous materials as a host structure for methane hydrate formation: Organic versus carbon xerogels

A series of xerogels with a properly designed porous structure and surface chemistry have been synthesized and evaluated as a host structure to promote the nucleation and growth of methane hydrates. Organic xerogels (OGs) have been synthesized from resorcinol-formaldehyde mixtures using a sol-gel approach and microwave heating. These xerogels are hydrophilic in nature and possess designed meso/macrocavities in the pore size range 5-55 nm. Carbon xerogels (CGs) have been synthesized from their organic counterparts after a carbonization treatment at high temperature. Interestingly, the carbonization process does not alter/modify substantially the porous network of the parent xerogels, while developing new micropores. Under water-supplying conditions, the two types of xerogels exhibit a large improvement in the methane adsorption capacity compared to the pure physisorption process taking place in dry conditions (up to 200% improvement), and associated with a significant hysteresis loop. These excellent values must be associated with the promoting effect of these xerogels in the water-to-hydrate conversion process. The comparison of OGs and CGs as a host structure anticipates that surface chemistry, total pore volume and pore size are critical parameters defining the extent and yield of the methane hydrate formation process.