Fast pyrolysis of lignin proceeds in two consecutive stages. The first stage, termed primary pyrolysis, results in the thermal degradation of lignin’s macromolecular structure, releasing an initial volatile product collectively called bio-oil or tar. This tar product is comprised of a complex mixture of oxygenated compounds. Upon release, the tar is subject to the second stage of pyrolysis, wherein it undergoes vapor-phase thermal cracking to primarily produce permanent gases and aromatic hydrocarbons. This secondary pyrolysis stage plays a significant role in both fast pyrolysis and gasification processes. In fast pyrolysis, tar cracking controls the distribution of products, and in gasification, tar and condensable products from tar cracking are detrimental to process equipment.  In this current study, we investigate the vapor-phase thermal decomposition pathways of the lignin tar compounds 4-methylguaiacol (4MG) and guaiacol (GUA). We use a laminar-flow reactor to conduct pyrolysis experiments at temperatures between 300-900°C and a residence time of one second.  We discuss thermal decomposition pathways in terms of the product distribution comparisons complemented by computational chemistry calculations.

Thermal decomposition pathways of guaiacol and 4-methylguaiacol under fast pyrolysis and gasification conditions

253rd National Meeting (2017)

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