Structure and thermal properties of tar from gasification of agricultural crop residue

Abstract

This study was carried out to elucidate chemical composition and thermal decomposition behavior of bio-tar from the gasification of agricultural crop residue, facilitating its further processing and utilization. Structural characterization by gas chromatography mass spectroscopy (GC–MS), Fourier transform infrared spectroscopy, and elemental analysis indicated that the bio-tar was mainly composed of phenols and polycyclic aromatic hydrocarbons. It contained more oxygenated and less aromatic compounds compared with fossil pitches. Thermogravimetric measurements demonstrated that the tar decomposed rapidly within the temperature range of 183–252 °C under nitrogen atmosphere. The apparent activation energy values obtained from the Friedman method and distributed activation energy model showed the same trend. The activation energy values from both methods nearly unchanged within the conversion rate of 0.1–0.6, with average values of 107 and 85 kJ mol−1, respectively. The activation energy increased quickly when the conversion rate was larger than 0.6. The change of reaction mechanism from parallel single reactions or uniform multiple reactions at lower conversion rates to multiple-step reactions at higher conversion rates indicated the complex nature of the bio-tar. The developed chemical and thermal degradation data of the tar can facilitate the design and manufacture of tar-containing polymeric composites.