Method for producing 5,5-dimethylhydantoin

Abstract

The invention provides a method for preparing 5,5-dimethylhydantoin from tail gas which contains ammonia and carbon dioxide and is produced during industrial production of melamine and sodium cyanate. The tail gas which contains the ammonia and the carbon dioxide is fed into a bubbling reactor to react with an acetone cyanohydrin aqueous solution at the temperature of 95-100 DEG C for 20-30 min, the yield is 99.6%, and the product content is 99.7% (HPLC). With the adoption of the method, the tail gas which contains the ammonia and the carbon dioxide can be combined with fine chemicals, the 5,5-dimethylhydantoin with the high added value can be produced, environmental pollution can be reduced, and harmful gases are turned into useful things.

Description

technical field [0001] The invention relates to the field of chemical engineering, in particular to a method for producing 5,5-dimethylhydantoin by using tail gas containing ammonia and carbon dioxide produced in the industrial production process of melamine, sodium cyanate and nitrogen fertilizer. Background technique [0002] In the industrial production process of chemical raw materials such as melamine, sodium cyanate and nitrogen fertilizer, a large amount of ammonia and carbon dioxide tail gas are often involved. [0003] Such as the reaction equation for preparing melamine: [0004] 6CO(NH 2 ) 2 →C 3 N 3 (NH 2 ) 3 +3 CO 2 ↑ +6 NH 3 ↑ [0005] Such as the reaction equation for preparing sodium cyanate: [0006] Na 2 CO 3 +3 CO(NH 2 ) 2 →2NaCNO+CO 2 ↑ +2 NH 3 ↑ +H 2 o ↑ [0007] Direct discharge of ammonia and carbon dioxide tail gas into the atmosphere will pollute the environment and affect people's quality of life. The country has explicitly pr...

AI Technical Summary

Problems solved by technology

Therefore, the separation and recycling of ammonia and carbon dioxide tail gas has always been a problem that cannot be ignored.

[0009] NH 3 -CO 2 -H 2 The direct use of O ternary system solution is very small, and direct discharge will pollute the environment, often because it cannot be sold and used in time, overflow tanks, leakage, etc.

On the one hand, the mixed gas containing ammonia and carbon dioxide will generate ammonium carbamate (NH 2 COONH 4 , referred to as methylamine), its crystallization will block the pipeline and hinder the condensation of ammonia, so it is necessary to start from NH 3 -CO 2 -H 2 It is also very difficult to directly separate pure ammonia and carbon dioxide from the O ternary system for utilization.

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