Evolution of gaseous products from biomass pyrolysis in the presence of phosphoric acid

Slow pyrolysis experiments of China fir (Cunninghamia lanceolata) wood were performed in a vertical tubular furnace at various heating rates. The raw material was pretreated by impregnation with phosphoric acid solutions of various concentrations for given times. The evolution of the gaseous products CO, CO2, H2 and CH4 was analyzed online by using gas spectrometry to investigate the effect of phosphoric acid on the pyrolytic gaseous products of biomass. The addition of phosphoric acid was shown to significantly reduce the pyrolysis temperature necessary for the production of CO, CO2 and H2 gases, and the pyrolysis variables exerted an influence on the amount of the gases released. Moreover, phosphoric acid appreciably depressed the CO, CO2 and CH4 production, and promoted H2, especially when a higher heating rate was employed. This suggested that phosphoric acid catalyzed both the primary thermal decomposition of biopolymers and the secondary reactions that took place among the pyrolytic vapor products.