How do the main components influence the VOCs emission characteristics and formation pathways during moso bamboo heat treatment?

Bamboo heat treatment will cause plenty of release of volatile organic compounds (VOCs) into the atmosphere which are important precursors for ozone (O3) formation. In this study, dewaxed bamboo was heat-treated at 180 °C for 2 h to investigate the emission characteristics and the formation pathways of VOCs during heat treatment by removing different main components. The results showed that aldehydes (22.61%-57.54%) and esters (14.64%-38.88%) are the primary VOCs released during heat treatment. These compounds mainly originate from the degradation of hemicellulose, lignin, cellulose, and the linkage bonds between them in bamboo. During the bamboo heat treatment, the degradation of CO, CH, and CO bonds in hemicellulose results in the release of 5-hydroxymethylfurfural, 3-furfural, and 1-(+)-ascorbic acid 2,6-dihexadecanoate. The breakage of benzene ring group and the CO and CH bonds of lignin leading to the emission of VOCs including m-Formylphenol, Vanillin, and Syringaldehyde. The degradation of aliphatic CH, CC, and CO bonds in the amorphous region of cellulose contributes to an enhanced release of alcohols, olefins, and alkanes. It is calculated that acids (28.92%-59.47%), esters (10.10%-22.03%) and aldehydes (17.88%-39.91%) released during heat treatment contributed more to Ozone Formation Potential (OFP).

Influence of ultrasound-assisted extraction on the pyrolysis characteristics and kinetic parameters of eucalyptus.

In this study, the influence of ultrasound-assisted extraction on eucalyptus samples with special focus on pyrolysis characteristics and kinetic parameters was explored. Ultrasound and Soxhlet extraction were used to pretreat samples respectively, then samples were assayed by component analysis, TG-FTIR, and kinetic analysis. Ultrasound-assisted extraction did change the physiochemical characteristics of eucalyptus samples, particularly in regards to the quantity of extractives obtained. In TG and DTG curves, ultrasound-extracted samples reflected lower residual weight ratio (17.77%) and higher maximum weight loss rate (-22.92%/min), and were accompanied by a slight shift in the weight loss rate peak to lower temperature (366°C). The volatiles produced during pyrolysis and the discrepancies of product distribution between experimental and controlled groups were explored based on TG-FTIR spectra. According to kinetic analysis results, ultrasound-treated samples showed higher activation energy at the primary portion of thermal degradation with an average of 206.09kJ/mol.