| AVS 66th International Symposium & Exhibition | |
| Plasma Science and Technology Division | Thursday Sessions |
| Session PS+SS-ThA |
| Session: | Plasma Conversion and Enhanced Catalysis for Chemical Synthesis |
| Presenter: | Joseph Toth, Case Western Reserve University |
| Authors: | J.R. Toth, Case Western Reserve University D.J. Lacks, Case Western Reserve University J. Renner, Case Western Reserve University R.M. Sankaran, Case Western Reserve University |
| Correspondent: | Click to Email |
Alternative approaches are sought to the high-pressure, high-temperature Haber-Bosch (H-B) process for nitrogen fixation in order to enable distributed synthesis from renewable feedstocks. A potentially promising reactive strategy is plasma excitation which was historically the first method to fix nitrogen by reacting nitrogen and oxygen in air. More recently, plasmas have been combined with solid catalyst materials to synthesize ammonia at atmospheric pressure and lower temperatures than the H-B process. However, most of these reactions still require hydrogen gas which remains linked to fossil fuels and leads to both high cost and environmental consequences.
Here, we present a novel plasma-aerosol droplet reactor to synthesize ammonia from nitrogen and water at atmospheric pressure and near room temperature. Introducing the water as droplets instead of water vapor increases the throughput that can be achieved and also simplifies the system, eliminating the need for heated lines to avoid condensation on the walls. The plasma was formed as a dielectric barrier discharge inside a quartz tube with an outer ring electrode and an inner wire electrode. The water droplets were generated using a commercial nebulizer via a high nitrogen flow rate causing a Venturi effect which siphoned the water into the gas stream. The products were collected by bubbling the gas effluent leaving the reactor through a concentrated sulfuric acid bath and condensing in a second trap chilled to -40 oC. The ammonia was then measured by the o-phthalaldehyde colometric assay technique. The ammonia production rate was found to be a function of the power and flow rate with production rates up to 600 µg/hr at 70 W. Controls were run with an argon plasma and with no water droplets to verify that no ammonia was produced without both nitrogen and water. In addition to ammonia, we also tested for nitrites/nitrates (NOx) and measured up to 3000 µg/hr total production rate. The efficiency, power consumption, and potential reaction mechanisms will also be discussed.