Reduction of Magnesium Oxide

1. Solar Thermochemical Ammonia: A More Sustainable Way to Feed the World 1,2,3Brian Peterson, 2Ronny Michalsky, 2Peter Pfromm • 1NSF REU Program, 2Kansas State University Center for Sustainable Energy 3Missouri University of Science and Technology Department of Chemical Engineering Brian Peterson Introduction Corrosion of Calcium Nitride Reduction of Magnesium Oxide • Conclusions from Figure 1: • Higher ratios of Carbon to Magnesium Oxide heavily influence Magnesium Nitride • Chromium(III) Oxide appears to have a stronger influence than Iron(III) Nitride on the production of Magnesium Nitride • H2 • NH3. Ammonia is critical as a source of fixed nitrogen as fertilizer for agriculture globally. It has been estimated that between one third and one half of the world’s population could not be sustained without chemical processes that synthetically produce ammonia from nitrogen in the air. The current standard for ammonia production is the Haber-Bosch process. This 100-year-old process consumes large quantities of fossil fuels and requires large amounts of energy (accounts for nearly 2% of energy usage globally). It is imperative to study alternative, sustainable processes to feed both the growing world population and the growing biofuel industry. • H2O • NH3. ← ← ← ← Ca Nitride + H2 → “Ca solids”+ NH3 Mg Nitride + H2O → Mg Oxide + NH3 Tab1: Percent of Magnesium atoms that left the system at different reaction times which correlates to Magnesium reduced. Ca Nitride← “Ca solids” + N2 Mg Nitride +CO ← Mg Oxide + C +N2 ← ← ← ← ← ← N2 N2 CO C (Biomass/Charcoal) Methods Goal • React Calcium Nitride with H2 at various temperatures using an indoor reactor and determine the composition of the solids • Gather kinetics data for the reaction at 700°C Reduce Magnesium Oxide into the form of Magnesium Metal or Magnesium Nitride Methods Comparison Goal • Conclusions from Table 1: • Heavy error exists, most likely in the X-Ray Diffraction analysis of solid composition • Better analytical techniques might be considered • Make different molar combinations of 3 solid reactants Maximize the production of Ammonia Results and Conclusions • React Nitrogen using Solar Concentrator and reactor. • Gather data on kinetics of 3 mixtures, one with Iron(III) Oxide added, one with Chromium (III) Oxide added, and a reference without additional oxides. Run using an indoor furnace and reactor Fig2: Mol percent of Nitrogen atoms that left the system, presumably as Ammonia at different reaction temperatures Fig3: Mass percent of Calcium Hydride in the solid phase after reactions at various temperatures • In general, the Solar Ammonia process utilizes a metal nitride which is corroded with a hydrogen source (either H2or H2O). When water is used, the metal nitride corrodes very easily at room temperature and atmospheric pressure, but a rather unreactive metal oxide is formed. The more difficult step is recycling the metal oxide because it requires much higher temperatures and a reducing agent such as carbon. Solar Concentrator Results and Conclusions • Conclusions from Figure 2: • As expected, more Ammonia is produced (Nitrogen liberated) at higher temperatures, but levels off after 700 °C • Flow rate experiments (Figure 4) should be performed at 700 °C Fig1: Yield of 8 mixtures using Solar Concentrator Tasks Fig4: Molpercent of Nitrogen atoms liberated, likely as Ammonia at different Hydrogen flows • Reduction of Magnesium Oxide • Test effects of the addition of Iron(III) Oxide and Chromium(III) Oxide at 1200 °C • Analyze kinetics of best case mixtures • Conclusions from Figure 3: • More Calcium Hydride is produced at higher temperatures • Also Calcium Hydride is vaporized at the higher temperatures and exits the system • Corrosion of Calcium Nitride • Identify composition of solids after reaction • Analyze the kinetics at various H2 flow rates • Conclusions from Figure 4: • Hydrogen flow rate has little effect on Ammonia formation • Thus this is likely a diffusion limited reaction