Abstract
Alkali compounds contained in wood have been said to significantly influence the wood reaction. Although many researchers reported wood and cellulose gasification with alkali catalysts, the detailed reaction mechanism of alkali metals on pyrolysis of biomass is not yet clear.
Pyrolysis of wood with/without potassium carbonate (K2CO3) under relatively high temperature increasing rate was carried out to elucidate the role of alkali metals on wood pyrolysis. Gaseous species produced by wood pyrolysis were measured by TCD and FID gas chromatographs. Tar was analyzed to quantify polycyclic aromatic hydrocarbons (PAHs) by GC/MS. Changes in chemical bonds in solid residue(char) were analyzed by 13C-NMR.
By adding alkaline salts, gaseous products increased and tar decreased. The gas products except for ethylene and light PAHs increased while heavier PAHs decreased. Without potassium carbonate, saccharide structure contained in cellulose remained in the char obtained from pyrolysis at 500°C but with potassium carbonate, the structure dramatically changed, for example C-O bond disappeared. It was suggested that not only K2CO3 but also K2O produced around 300°C - 400°C by pyrolysis of K2CO3 caused such effects on pyrolysis. From results of various measurements, effects of alkaline on the pyrolysis process were discussed.
