Pyrolysis of fast growing wood Macaranga gigantea: Product characterisation and kinetic study

Abstract

Fast-growing wood Macaranga gigantea has been pyrolyzed and its pyrolysis products have been characterized and their formation kinetics studied. Pyrolysis of M. gigantea wood was carried out by varying the temperature and time of pyrolysis to determine the effect of these two parameters on product yields and product characteristics. In general, an increase in pyrolysis temperature and time increased the yield of liquid and gas products, the concentration of cellulose, hemicellulose and lignin-derived compounds, but decreased the biochar yield. The organic phase liquid pyrolysis products mainly contained phenolic compounds and their derivatives, eugenols, furans, aldehydes and ketones. Fourier-transform infrared spectroscopy and pyrolysis–gas chromatography–mass spectrometry analyses of biochar showed that thermal decomposition of M. gigantea required temperatures higher than 300 °C to optimize thermal decomposition and carbonization of lignin, cellulose and hemicellulose. The concentration of phenols and benzenediols in biochar decreased with an increase in pyrolysis temperature. M. gigantea pyrolysis kinetics studies showed that wood pyrolysis occurred through four main stages with activation energy (Eα) values, based on calculations by the Friedman and Kissinger-Akahira-Sunose methods, of 28.1–99.0 kJ/mol and 35.6–104.9 kJ/mol, respectively. The spectra produced by thermogravimetric analyzer coupled with a Fourier-transform infrared spectroscopy showed that H2O and CO2 were produced during pyrolysis and the volatile compounds produced were predominantly phenolic compounds, in accord with characterization results of the liquid products by gas chromatography–mass spectrometry and nuclear magnetic resonance spectroscopy.