What happens when urea is heated to 160 degrees?
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When producing controlled-release urea, it is necessary to heat the urea; if the heating is not properly controlled, black lumps will form at around 160 degrees Celsius. What are they?
It decomposes at 160°C, producing ammonia while turning into cyanic acid
What is the pressure when heating? In addition to the side effects mentioned by Moderator Luo, biuret may also be formed. However, it’s a bit confusing as to how black blocks are generated. Were any other substances added during the heating process?
When producing large-grained urea, a small amount of formaldehyde is added to the urine in order to enhance the strength of the urea particles; if the urea you use is produced using this process, it will naturally turn black when heated. Haha, I think what was said earlier wasn’t clear enough, so I’ll add more details.
Urea is thermally unstable; when heated to 150–160°C, it loses ammonia to form biuret. If heated rapidly, it undergoes deamination and trimerizes to form the six-membered cyclic compound cyanuric acid. (Mechanism: First, deamination occurs to produce isocyanic acid (HN=C=O), followed by trimerization.) ）
This post was last edited by yss5180 on 2010-2-3 at 14:53. 6# huaandhua: The urea used as raw material for producing melamine should be industrial urea (free of formaldehyde), not agricultural urea (which contains formaldehyde added artificially).