Influence of temperature and time on initial pyrolysis of cellulose and xylan

Abstract

The aim of this study was to investigate the effects of temperature and reaction time on the primary pyrolysis of cellulose and xylan. Fast pyrolysis of cellulose and xylan was carried out with a micropyrolyser connected to a gas chromatograph-mass spectrometer/flame ionisation detector (GC–MS/FID) to separate and identify volatile components, both qualitatively and quantitatively. This set-up meant a minimum amount of secondary reactions, low impact of the heating period and at the same time provided rapid and accurate analyses. The two biomass components investigated were: cellulose and hemicellulose (represented by xylan). They were pyrolysed during 0.5, 1, 2 and 5 s (s) and within a temperature range of 400–600 °C. The results showed that levoglucosan (1, 6-anhydro β-D-glucopyranose) is the main chemical compound released during cellulose pyrolysis. It increased with increasing temperature and time. The main volatile compounds produced from pyrolysis of xylan are: 1-hydroxy-2-butanone, 4-hydroxy-5, 6-dihydro-(2 H)-pyran-2-one, 1-hydroxy-2-propanone (acetol), acetaldehyde and hydroxyacetaldehyde (HAA). HAA was the most abundant chemical compound released during xylan pyrolysis, increasing with higher temperatures and time. Acetol and acetaldehyde also showed similar behaviour. The chemical compounds released from cellulose and xylan fast pyrolysis are primary products and assumed to be produced directly from both cellulose and xylan molecules and not from secondary degradation. In this study, possible reaction routes during biomass primary pyrolysis are also suggested based on the product distribution from the thermal decomposition of cellulose and xylan.