Effects of hydrothermal carbonization on products from fast pyrolysis of cellulose

Abstract

In the first step of this study, the hydrothermal carbonization (HTC) of cellulose was performed at 225 and 250 °C for 4, 8 and 12 h. The effect of temperature and residence time on hydrochar (HC) yields and characteristics was investigated, and the highest hydrochar yield had a heating value of 21.06 MJ/kg. In the second step, cellulose and hydrochar-derived cellulose was subjected to fast online pyrolysis at 500, 600 and 700 °C, using a pyrolysis-gas chromatography-mass spectrometry system. The HTC process significantly affected the pyrolysis products. The major decomposition product resulting from the fast pyrolysis of cellulose was levoglucosan, but at all tested temperatures, 2-methylfuran was the major product from hydrochars. Increasing the pyrolysis temperature caused a decrease in the relative yield of 2-methylfuran. Another prominent compound observed in pyrolyzates was 2,5-dimethylfuran. The relative yields of these two compounds decreased when the residence time of the HTC process was increased. The highest 2-methylfuran selectivity was 67.4%, while the highest 2,5-dimethylfuran selectivity among the furanic compounds was 24.0%. This study demonstrated that, by combining HTC and pyrolysis processes, fine chemicals can be produced from cellulose.