Pyrolysis of pine wood in a slowly heating fixed-bed reactor: Potassium carbonate versus calcium hydroxide as a catalyst

Catalytic pyrolysis of pine wood was carried out in a fixed-bed reactor heated slowly from room temperature to 700 °C under a stream of purging argon to examine the effects of the physically mixed K2CO3 or Ca(OH)2 on the pyrolysis behaviors. K2CO3 demonstrated a stronger catalysis for decomposition of hemicellulose, cellulose and lignin constituents, leading to the reduced yield of liquid product in conjunction with the increased yields of gaseous and char products because of the promoted secondary reactions of liquid product. With the addition of 17.7 wt.% of K2CO3, none of saccharides, aldehydes and alcohols was formed and the formation of acids, furans and guaiacols was substantially reduced, whereas the yields of alkanes and phenols were increased. Potassium led to an increase in the cumulative yields of H2, CO2 and CO at 700 °C. Ca(OH)2 somewhat promoted the decomposition of cellulose and lignin constituents, and the effect of Ca(OH)2 on the yields of liquid and char was opposite to that of K2CO3. With the addition of 22.2 wt.% Ca(OH)2, some groups of liquid product such as acids and aldehydes disappeared completely and the yields of saccharides, furans and guaiacols were somewhat reduced, while the yield of alcohols was remarkably increased in contrast to the result of K2CO3. The addition of Ca(OH)2 did not significantly change the total yield of gaseous product at 700 °C but enhanced the yield of H2.