Pyrolysis of different wood species: Impacts of C/H ratio in feedstock on distribution of pyrolysis products

Abstract

In this study, pyrolysis of the wood samples with varied C/H ratio on distribution of the products was investigated. The results show that C/H ratio in the biomass drastically affects the yields of char, tar and gas. Poplar has a higher C/H content, and consequently it produces a higher yield of char and the lower yield of tar. Pine wood has the lower C/H ratio, and the pyrolysis produces the lower char but higher gas and tar yields. Furthermore, the C/H ratio in the feedstock affects the elemental composition and the stability of the tar. The higher C/H ratio in biomass resulted in the tar with a higher stability during pyrolysis of the tar. The C/H ratio also affected the formation of the aromatic ring structures in the tar. The pyrolysis of poplar with the highest C/H content produced more aromatics with smaller ring size in the tar, while that from pine with the lowest C/H content produced more aromatics with bigger ring size. The tars produced from the feedstock with the different C/H ratio show a large similarity in terms of distribution of the functionalities but with varied intensities. The TG-MS characterisation showed that the organics in the tar did not reach the equilibrium and could continue to decompose during heating, producing CO2 via decarboxylation, CO via decarbonylation and H2 via dehydrogenation reactions. The DRIFTS study of heating char in inert atmosphere showed that the char originated from the different biomasses had distinct stabilities and distinct tendencies towards aromatisation.