Diesel Truck Emissions

New diesel trucks (at least big, commercial ones) need to meet certain EPA emission standards.

One way some trucks are meeting the N-oxide specification is with a Selective Catalytic Reduction (SCR) system that uses a Diesel Exhaust Fluid (DEF).  DEF is a 32.5% mixture of urea, (H₂N)₂,CO, and water.

The process is pretty simple.  The engine exhaust goes through a filter to remove the carbon particulates (AKA soot).  The exhaust is then sent into the SCR where it is mixed with the DEF, where the N-Oxides are converted to nitrogen, carbon dioxide, and water.

I assume that the reaction would be:

2(H₂N)₂CO + 4NO + O₂ = 4N₂ + 2CO₂ + 4H₂O

If this works, it would be a pretty elegant solution to nitrogen oxide emissions.  I haven’t seen any data, though.

It seems like it’s an awful lot to ask of a pretty small reaction chamber.