SLOW PYROLYSIS OF POTASSIUM DOPED XYLAN: A COMPARISON BETWEEN TWO DOPING APPROACHES

In this study, the effect of potassium ions on the slow pyrolysis of hemicellulose is assessed using xylan as a representative of hardwood hemicellulose. Thermogravimetric and pyrolysis tests, up to 973 K at a heating rate of 7 K/min, were conducted on different xylan samples: commercial xylan (X), demineralized xylan (DX), potassium doped xylan (DX_K) samples. Commercial xylan was demineralized through a cation exchange resin in order to reduce the presence of inherent inorganics. Subsequently, the demineralized sample was doped with a controlled amount of K ions (ca 1 wt%) by using two different approaches: wet impregnation and cation-exchange resin. The results show that the wet impregnation doping procedure affected negligibly the pyrolytic behavior of the demineralized sample, and thus it is not suitable for the study of the effect of salts ions on xylan pyrolysis. By comparing the results obtained from X, DX and _K doped DX through cation exchange method, it can be inferred that, overall, the presence of metal ions favored the gas production at the expense of pyrolysis liquids and the release rate of permanent gases (mainly CO2 and CO) along the temperature is greatly altered too.