Carbon monoxide release mechanism in cellulose combustion using reactive forcefield. (1st June 2020)

• Record Type: Journal Article
• Authors: Hao, Huali; Chow, Cheuk Lun; Lau, Denvid
• Is Part Of: Fuel. Volume 269(2020)
• Publication Date: 2020-06-01
• Subjects: Carbon monoxide -- Cellobiose oxidation -- Reaction pathway -- Reactive forcefield; Fuel -- Periodicals; Coal -- Periodicals; Coal; Fuel; Periodicals; 662.6
• DOI: 10.1016/j.fuel.2020.117422
• Languages: English
• ISSNs: 0016-2361

Abstract

Graphical abstract: Highlights: The chemical reaction pathway of cellobiose oxidation is figured out. The amount of CO depends on the concentration of carboxyl and formyl groups. C=O related bonds increase to over 80% while C-O bonds decrease during pyrolysis. Hydroxyl group dominates the critical reaction steps of cellobiose oxidation. Simulated and experimental results have shown a good agreement. Abstract: The generation of carbon monoxide, that can cause loss of human life, is unavoidable during combustion of wood related biomass fuels. A correct understanding of reactions associated with carbon monoxide formation during cellulose combustion is critical for the safe application of biomass fuels. Although bench-scale experiments have been applied to quantify products generated during cellulose combustion, the details of reactions are still very hard to be figured out. In this work, a fundamental approach using molecular dynamics simulations equipped with reactive forcefield has been adopted to study reactions in the oxidation process of a major pyrolyzed product of cellulose called cellobiose. The effect of temperature on the reaction mechanism has also been studied. By tracking the reaction details during cellobiose oxidation, the predicted reaction pathway is in good agreement with experimental results. The initiation stage of oxidation involves the decomposition of cellobiose with the formation of formyl and carboxyl groups, and the formation of carbon monoxide is highly dependent on the concentration of these groups. Subsequently, the formed carbon monoxide is oxidized into carbon dioxide, where reaction steps for the formation and decomposition of carboxyl group are involved. A higher temperature promotes the decomposition of cellobiose with the formation of more formyl and carboxyl groups causing more carbon monoxide to be released. The simulation results help to figure out critical reaction steps, important intermediate products and free radicals that dominate the formation of carbon monoxide. Carbon monoxide formation can be slowed by reducing the concentration of these critical free radicals.