Theoretical Study on the Evolution Mechanism of NOX and COX During the Pyrolysis of Nitric Acid and Glucopyranose

Abstract

Sugar, as a denitration agent, has broad application prospects in the field of high-level radioactive liquid waste (HLLW) treatment. Understanding the interaction mechanism between nitric acid and sugar is crucial for the development of HLLW treatment. This study presents a detailed reaction mechanism, revealing key intermediates (HNO₂) and pathways (generation of carboxyl groups) leading to critical products (NO₂, NO, CO₂, and CO). The work shows five different paths leading to the ring-opening of β-D-glucopyranose. The results indicate that the ring-opening path involving the interaction of H₃O⁺ with glycosidic oxygen has the greatest kinetic advantage, with lower energy of highest point (EHP) (63.6 kJ/mol) and lower highest energy barrier (HEB) (49.2 kJ/mol). Furthermore, carbon oxides, as key gaseous products, exhibit a synergistic relationship with the generation pathways of nitrogen oxides, promoting each other. In addition, through thermodynamic analysis of the four reaction products (NO₂, NO, CO₂, and CO), the study shows that the reactions producing NO₂ and NO are spontaneous exothermic reactions, while the reactions generating CO₂ and CO are non-spontaneous endothermic reactions. The study aims to elucidate the atomic-scale interaction mechanism between sugar-based denitration agents and nitric acid, providing a theoretical basis for the application of natural polysaccharides in HLLW, while also opening new avenues for the design of reducing agents and byproduct control strategies in industrial denitration processes.