Microwave-Assisted Oxidation of Organic Matter Using Diluted HNO 3 under O 2 Pressure: Rationalization of the Temperature Gradient Effect for Acid Regeneration

• Autor(a) principal: Bizzi,Cezar A.
• Data de Publicação: 2017
• Outros Autores: Barin,Juliano S., Oliveira,Jussiane S. S., Cravotto,Giancarlo, Flores,Erico M. M.
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Journal of the Brazilian Chemical Society (Online)
• Texto Completo: http://old.scielo.br/scielo.php?script=sci_arttext&pid=S0103-50532017000901673
• topic: microwave-assisted oxidation; diluted HNO3; IR thermal imaging; temperature gradient; gas phase reaction

Oxidation using diluted HNO3 solution is dependent on reactions taking place in the gas phase, resulting in HNO3 regeneration, thus allowing sub stoichiometric reactions (16.7 mmol of C oxidized with 10.4 mmol of HNO3). Reactions for HNO3 regeneration are dependent on temperature gradient along reaction vessel. Thermographic images were obtained of external vessel wall after 2.5, 5 and 7.5 min of heating. Temperature inside reaction vessel was directly measured using a sapphire thermocouple in four different depth (3, 6, 12 and 16 cm). Reactions under inert atmosphere (7.5 bar Ar) were evaluated and normally presented higher temperature gradient than that performed with O2 pressure, since HNO3 regeneration reactions are exothermic. A better understanding of the regeneration of HNO3 and the dependence on the whole reaction vessel temperature in this system was possible combined to residual carbon content and residual acidity measurements to estimate the extent of organic matter oxidation.