After synthesis, ammonia can be selectively absorbed by calcium chloride; nitrogen and hydrogen are not absorbed. The kinetics of release seem to be diffusion controlled. The kinetics of absorption are consistent with a first-order reaction after an initial period of a higher-order reaction, which may indicate a nucleation event. At 225 °C, both absorption and release show half-lives of around 10 min if the ammonia partial pressure is swung from 2 to 1 bar, which allows design of an absorber for the periodic separation of ammonia. When this absorber replaces the ammonia condenser in a conventional ammonia synthesis, the ammonia production at low pressure can have the same rate as the conventional process operating at higher pressure.
Bibliographical noteFunding Information:
This work was funded in part by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000804; in part by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR,/ ML 2015, CH 76, SEC 2, SUBD 07A); and in part by the MnDRIVE initiative of the University of Minnesota (MNT11). The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. Giang Le is acknowledged for assistance.
© 2018 American Chemical Society.
- Metal halide
- Pressure swing absorption