Anhydrous ammonia (NH3) is produced by the Haber-Bosch
process that involves combining hydrogen and nitrogen under heat and pressure
with the presence of a catalyst.
Urea is produced commercially by the dehydration of
ammonium carbamate at elevated temperature and pressure. Ammonium carbamate is
obtained by direct reaction of ammonia with carbon dioxide. These reactions are
normally carried out simultaneously in a high pressure reactor.
Ammonium nitrate is produced by the reaction of nitric acid
with anhydrous ammonia.
UAN, commonly known as 32-0-0, is actually the combination
of urea (U) and ammonium nitrate (AN) with water.