Reduction of nitric oxide in diesel exhaust with the addition of methylamine

A chemical gas-phase process capable to reduce the nitric oxide in diesel e ngine exhaust was studied. In this process, monomethylamine (CH3NH2) was ad ded to the exhaust gas in a molar ratio to NO varying between 1:1 and 4:1. Experiments were conducted in electrically heated quartz reactors in a temp erature range of 200 degrees C to 600 degrees C. Diesel exhaust gas and sim ulated exhaust gas were used in this experiment. The results showed thoroug h mixing of methylamine into the exhaust effectively breaks NO down into ni trogen and water, enabling more than 80 percent NO reduction in a reactor t emperature range of 400 degrees C to 540 degrees C and at a molar ratio of 1. On the other hand, imperfect mixing between methylamine and exhaust gase s results in excess ammonia and reduced NO decomposition. Consequently, it is suggested that the mixing is a very important factor in this technique. The results also show that the coexisting gases such as carbon monoxide, ca rbon dioxide, hydrocarbons, and water vapor in the diesel exhaust have no e ffect on NO reduction by methylamine. However, the presence of oxygen in ex cess of 10 percent in the exhaust is needed for an 80 percent NOx reduction . Furthermore, the mechanisms of the methylamine process were discussed.