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Microwave-assisted hydrolysis of nitroglycerine (NG) under mild alkaline conditons : New insight into the degradation pathway

 
 
Affiliation:
National Research Council Canada (NRC-CNRC); NRC Biotechnology Research Institute
Language:
English
Type:
Article
Published in:
Chemosphere
Date:
2010
Pages :
228-232
NRCC #:
50010
NPArC #:
14756483
Keywords:
Nitroglycerin; Alkaline hydrolysis; Microwave; 2-Hydroxypropanedial; Degradation pathway
Abstract:
Nitroglycerin (NG), a nitrate ester, is widely used in the pharmaceutical industry and as an explosive in dynamite and as propellant. Currently NG is considered as a key environmental contaminant due to the discharge of wastewater tainted with the chemical from the military and pharmaceutical industry. The present study describes hydrolytic degradation of NG (200 μM) at pH 9 using either conventional or microwave-assisted heating at 50 °C. We found that hydrolytic degradation of NG inside the microwave chamber was much higher than its degradation using conventional heating. Products distributions in both heating systems were closely related and included nitrite, nitrate, formic acid, and the novel intermediates 2-hydroxypropanedial (O=CHCH(OH)HC=O) and glycolic acid (CH₂(OH)COOH). Two other intermediates glycolaldehyde (CH₂(OH)CHO) and glyoxylic acid (CHOCOOH) were only detected in the microwave treated samples. The molar ratio of nitrite to nitrate in the presence and absence of microwave heating was 2.5 and 2.8, respectively. In both microwave assisted and conventional heating a nitrogen mass balance of 96% and 98% and a carbon mass balance of 58% and 78%, respectively, were obtained. The lower C mass recovery might be attributed to further unknown reactions, e.g., polymerization of the aldehydes CH₂(OH)CHO, CHOCOOH and O=CHCH(OH)HC=O. A hydrolytic degradation pathway for NG was proposed involving denitration (loss of 2 NO-₂ ) from the two primary carbons and the loss of one nitrate from the secondary carbon to produce 2-hydroxypropanedial.
 
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