Raw N₂O from ammonium nitrate decomposition contains numerous impurities that must be removed to achieve the required purity specifications for pharmaceutical, food, and electronic grades. Modern purification trains combine multiple separation technologies.
Impurity Profile
Raw reactor output typically contains: water vapor (2–5%), nitrogen (0.5–2%), nitrogen oxides (NOₓ: 50–500 ppm), ammonia (10–100 ppm), carbon monoxide (trace), and particulates. Each target grade requires specific impurity limits.
Purification Train
A typical purification sequence includes: alkaline scrubbing for NOₓ removal, catalytic NOₓ reduction (if needed), drying with molecular sieves (3Å), activated carbon adsorption for organic removal, and cryogenic fractional distillation for final N₂/O₂ separation.
Cryogenic distillation operates at approximately −90°C and 40 bar, leveraging the 10.2°C difference in boiling points between N₂O (−88.5°C) and N₂ (−195.8°C).