New cylinders for CNG cars offer longer journeys

Scientists at Rice University are looking at new materials for developing cylinders that can store compressed natural gas (CNG) at low pressure and at room temperature for longer, efficient journeys.

Rather than bulky high-pressure cylinders like those used in buses and trucks into light vehicles, they are trying cage-like synthetic macromolecules called metal organic frameworks (MOFs).

MOFs are nanoscale compounds of metal ions or clusters known as secondary building units (SBUs) and organic binding ligands, or linkers.

These linkers hold the SBUs together in a spongy network that can capture and store compressed natural gas aka methane molecules in a cylinder under pressure. As the pressure is relieved, the network releases the methane for usage. Lower pressures mean cylinders can be lighter and made to fit cars better.They may also offer the possibility that customers can tank up from household gas supply lines.

A team led by Rice University bioengineer Michael Deem used a custom algorithm to not only quickly design new MOF configurations able to store CNG with a high "deliverable capacity" but ones that can be reliably synthesised from commercial precursor molecules. "MOFs show potential for applications like drug delivery, sensing, purification and catalysis but methane storage for transportation is high on the US Department of Energy's (DoE) wish-list," Deem said.

"MOFs are being commercialised for methane storage in vehicles now," he added.
The results appeared in the American Chemical Society's Journal of Physical Chemistry C.