The effect of oxygen on in-situ evolution of chemical structures during the autothermal process of tobacco

Autothermal process which involves the introduction of oxygen to the pyrolysis process has been regarded as a better option for commercialization of biomass pyrolysis technologies. The presence of oxygen in the pyrolysis system will inevitably affect the thermal decomposition process, especially the release of products. However, few attentions have been paid to the influence of oxygen on in-situ evolution of chemical structure and emission of different product as pyrolysis process proceeded which are helpful for us to understand the role played by oxygen. Herein, we systematically demonstrated the effect of oxygen on the thermal decomposition of tobacco, a special lignocellulosic biomass material. The influential mechanisms of oxygen on the thermal decomposition process were explored via a series of in-situ characterization techniques including in-situ DRIFTS, in-situ XPS, Raman, and TG-MS. We found that the presence of oxygen was beneficial to oxygen and hydrogen removal process (e.g., dehydration, decarboxylation and de-carbonylation) during biomass pyrolysis, thus promoting the generation of aromatic char structure. In addition, the char formed under oxygen exhibited a more ordered structure with the larger aromatic crystallite size. Oxygen influenced the relative content of volatile and semivolatile products, despite not affecting their types.

Automated summary

The presence of oxygen in the pyrolysis system affects the removal of oxygen and hydrogen during biomass pyrolysis, promoting the generation of aromatic char structures with more ordered and larger aromatic crystallite sizes. Oxygen influences the relative content of volatile and semivolatile products, but not their types.