Most liquid fuels used in transportation today are derived from petroleum and burned in internal combustion engines. These fuels are attractive because of their high energy density and current economics, but they remain partially reliant on imported petroleum and are highly carbon intensive. Domestically produced carbon-neutral liquid fuels (CNLFs), such as dimethyl ether (DME) that is a potential drop-in replacement for diesel engines, can address both of these challenges. Typical fuel production processes require huge capital investments and supporting infrastructure, including base-load power to run continuously. Technology enabling the small- and medium-scale synthesis of liquid fuels can move the production of the fuels closer to the consumer, and - if renewable sources are used - the fuels can be produced in a carbon neutral manner. However, significant technical challenges remain in either changing these processes for smaller scale use or developing alternative electrochemical processes for fuel development. New methods would also have to employ variable rates of production to match the intermittent generation of renewable sources. Improvements in these areas could dramatically reduce the energy and carbon intensity of liquid fuel production. By taking better advantage of intermittent renewable resources in low-population areas and transporting that energy as a liquid fuel to urban centers, we can more fully utilize domestically available resources.
Project Innovation + Advantages:
Gas Technology Institute (GTI) will develop a process for producing dimethyl ether (DME) from renewable electricity, air, and water. DME is a clean-burning fuel that is easily transported as a liquid and can be used as a drop-in fuel in internal combustion engines or directly in DME fuel cells. Ultimately carbon dioxide (CO2) would be captured from sustainable sources, such as biogas production, and fed into a reactor with hydrogen generated from high temperature water splitting. The CO2 and hydrogen react on a bifunctional catalyst to form methanol and a subsequently DME. To improve conversion to DME, GTI will use a novel catalytic membrane reactor with a zeolite membrane. This reactor improves product yield by shifting thermodynamic equilibrium towards product formation and decreases catalyst deactivation and kinetic inhibition due to water formation. The final DME product is separated and the unreacted chemicals are recycled back to the catalytic reactor. Each component of the process is modular, compact, and requires no additional inputs aside from water, CO2, and electricity, while the entire system is designed from the ground up to be compatible with intermittent renewable energy sources.
If successful, developments from REFUEL projects will enable energy generated from domestic, renewable resources to increase fuel diversity in the transportation sector in a cost-effective and efficient way.
The U.S. transportation sector is heavily dependent on petroleum for its energy. Increasing the diversity of energy-dense liquid fuels would bolster energy security and help reduce energy imports.
Liquid fuels created using energy from renewable resources are carbon-neutral, helping reduce transportation sector emissions.
Fuel diversity reduces exposure to price volatility. By storing energy in hydrogen-rich liquid fuels instead of pure hydrogen in liquid or gaseous form, transportation costs can be greatly reduced, helping make CNLFs cost-competitive with traditional fuels.