LAUSR

Persistent free radicals (PFRs) may cause negative impacts to human health and the environment, due to the induced reactive oxygen species. We expect that PFRs could be generated in the condensable volatiles formed during lignocellulose biomass pyrolysis. Elucidating the structural origin and formation mechanism of PFRs is important for an in-depth understanding on air pollutant from the pyrolysis or combustion of lignocellulose biomass. This work selected rice straw (RS) and pine sawdust (PS) to represent agricultural and forest biomass residues. The pyrolysis mechanism, volatile components, and PFRs generation were discussed based on the analysis of TG-FTIR-MS, Py-GC/MS and ESR. Levoglucosan, furans, and 2-methoxyphenols were the main pyrolytic compounds for cellulose (CL), hemicellulose (HC), and lignin (LG), respectively. Obvious ESR signals were detected in the condensable volatiles of LG, while no ESR signals was detected for that of CL and HL. Higher ESR signals were detected in lignocellulose with higher content of LG. Therefore, LG was the main structural basis to generate PFRs in lignocellulose condensable volatiles, mostly attributed to the methoxyphenol components. This study provides useful information regarding the generation mechanisms of and the structures related to PFRs, which is essential to understand the risks of lignocellulose pyrolytic volatiles.