Ammonia is becoming more crucial for the energy transition as renewable-power producers look to its potential as a means for energy storage. Typically made using the energy-intensive Haber Bosch (HB) process, solutions for decarbonizing NH3 typically involve the adoption of carbon-capture systems, or the use of “green” H2. Now, a new method for NH3 synthesis relies on microwaves as its energy source. Developed at the National Energy Technology Laboratory (NETL; www.netl.doe.gov), in partnership with West Virginia University (both Morgantown, W.Va.; www.wvu.edu) and Malachite Technologies (San Francisco, Calif.; www.malachitetech.com), the Microwave Assisted Synthesis (MAS) process uses microwave energy and a patented catalyst to produce NH3 at much lower temperature and pressure than the HB process. “MAS is a fully electric system that can respond quickly to energy changes. That means it can be paired with renewable power and adjust to the energy input. The HB process cannot vary production output in this way without losing efficiency,” explains NETL researcher Christina Wildfire.
The microwave energy is applied directly to the catalyst, heating it rapidly and evenly, which enables significantly faster startup times than with large industrial processes. The direct application of energy is also what allows MAS to run at lower temperature and pressure. “The microwaves enhance the chemical reaction and selectively heat the metal sites on the catalyst, providing accelerated electron transfer. The technology will support a very different business model for NH3 synthesis, going from very large, centralized production to smaller, distributed production closer to the use site, reducing the need for transport,” says Wildfire.
The team has demonstrated MAS at 1-kg/d scale and plans to build a 100-kg/d reactor system and test catalyst durability. Ultimately, Wildfire expects MAS to scale up to around 3-ton/d modules, which would match the typical electrical output of a wind turbine.