THE LATEST RESEARCH AND DEVELOPMENT NEWS IN MANUFACTURING AND TECHNOLOGYTECH FRONT New Nanoscale Compounds for Better CNG Storage t R
esearchers at Rice University (Houston) have published a new study on nanoscale materials composed of metal organic frameworks (MOF) that could be used to devise more practical storage systems used with com- pressed natural gas (CNG) vehicles. Today’s CNG-powered buses and trucks typically use very bulky tanks that store natural gas at very high pressure. But the Department of Energy (DOE) is encourag- ing researchers to develop newer methods of storage that would allow light vehicles to store the gas at room temperature and at much lower pressures. The Rice research focused on MOFs—nanoscale compounds of metal ions or clusters known as second- ary building units and organic ligands, or linkers—that hold the materials together. A research team led by Rice bioengineer Michael Deem used a custom algorithm to quickly design new MOF confi gurations able to store compressed natural gas, or methane, with a high “deliverable capac- ity,” which can be reliably synthesized from commercial precursor molecules. Deem and his colleagues at Rice, the
Lawrence Berkeley National Laboratory and the University of California-Berkeley reported their results in December in the American Chemical Society’s Journal of Physical Chemistry C. MOFs show poten- tial for applications like drug delivery, sensing, purifi cation and catalysis, but methane storage for transportation is high on the DOE’s wish list, Deem said. “MOFs are being commer- cialized for methane storage in vehicles now,” he said. The advantages to using MOFs as a storage medium
are many and start with increased capacity over the heavy, high-pressure cylinders in current use. The Rice study found 48 MOFs that beat the best currently available, a compound
An example of metal organic frameworks discovered by researchers at Rice University that could be used in creating more practical compressed natural gas storage systems.
called MOF-5, by as much as 8%, and the program adhered to standard DOE conditions that an ideal MOF would store methane at 65 bar (atmospheric pressure at sea level is one bar) and release it at 5.8 bar, all at 298 kelvins (about 77° F). That pressure is signifi cantly less than standard CNG tanks, and the temperature is far higher than liquid natural gas tanks that must be cooled to minus 260° F. Lower pressures mean tanks can be lighter and made to fi t cars better, Deem said.
February 2015 |
AdvancedManufacturing.org 37
Image courtesy of the Deem Research Group/Rice University
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