Structure-Controlled Pyrolysis of Biomass with Sodium Hydroxide for Suppression of Tar Formation

Abstract

Pyrolysis of NaOH-loaded Douglas fir and cellulose has been carried out to determine the effect of sodium hydroxide on the pyrolysis profile. A tar yield of 0 wt% and the char yield of 32 wt% were obtained at a final pyrolysis temperature of 500°C. It was revealed that the amount of hydroxyl groups in the residue significantly decreased at 200°C and that the structure of cellulose was distorted via cross-linking at the same temperature through spectroscopic analyses and diffraction patterns. The cross-linking led to the increase in char yield at 500°C. A detailed analysis showed that char yield from cellulose at 500°C correlated linearly with the degree of cross-linking calculated from the amount of dehydration at 200°C. These results showed a possibility that the pyrolysis profile of biomass may be controlled through an appropriate pretreatment to change the structure of the intermediate.