Ammonia has real promise as a green renewable fuel; however its use is not without some of the drawbacks endemic to high temperature combustion processes. Chief among them is the potential for NOx formation in nitrogen-rich oxidizing environments. Nitric and nitrous oxides are prime culprits that plague both entrenched hydrocarbon internal combustion technology but also emerging technologies like ammonia-as-a-fuel. Nitric oxide is implicated in photochemical ground-level ozone production in urban areas. Nitrous oxide is its own double-edged environmental sword, being both a potent tropospheric green-house gas as well as a principle agent in renewed stratospheric ozone-depletion (Science 2009, v326, p. 123). Successful ammonia-as-a-fuel initiatives must deal with these realities or risk marginalization before reaching maturity.
Fortunately considerable research exists on the interrelationship of NOx and ammonia. These lessons come from current exhaust treatments for lean-burn gasoline and diesel engines and model studies of the pure gases in both catalyzed and uncatalyzed environments. This presentation will survey some of these lessons with the goal of informing the ammonia-as-a-fuel community of possible solutions to the NOx / ammonia problem.
