Making ammonia from renewable wind energy at a competitive price may be possible if the conventional ammonia condenser is replaced with an ammonia absorber. Such a process change requires an ammonia selective absorbent. Supported metal halide sorbents for this separation display outstanding dynamic capacity close to their equilibrium thermodynamic limits. Alkaline earth chlorides and bromides supported on silica and zeolite Y are the most promising. MgCl2 and CaBr2 at 40% loading on silica show capacities of 60-70 mgNH3/gsorbent at 150 °C and 4 bar. Overall, cations with smaller atomic numbers show more affinity to ammonia; bromides hold ammonia more strongly than chlorides. Different solvents and metal halide mixtures do not show significant changes in the absorption capacity. These absorbents can be incorporated into ammonia reaction-absorption syntheses to achieve faster production rates.
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. Other support came from the Institute for Renewable Energy and the Environment (IREE) at the University of Minnesota, Undergraduate Research Opportunities Program (UROP) at the University of Minnesota, and the Camille & Henry Dreyfus Foundation. Parts of this work were carried out in the Characterization Facility (CharFac), University of Minnesota, which receives partial support from NSF through the MRSEC program. We are grateful to Nick Seaton of the CharFac for training and guidance in SEM.
- Metal halides
- Wind energy