Physicochemical properties of biochars prepared from raw and acetone-extracted pine wood

Biochars can be used in a wide range of applications, serving as soil additives, sorbents, fuels, catalyst supports or as catalysts themselves. There is however, a vast range of variables influencing the properties of biochars and their performance as catalysts. One of the characteristic features of pine wood is its high extractives content which is known to influence the pyrolysis process, therefore it can also affect the properties of the derived biochar. In this paper, raw and acetone-extracted pine wood was used to prepare steam-activated biochars. The changes in physicochemical properties of the chars upon the feedstock treatment were examined, including the analysis of surface area, porosity, acidic sites distribution, metals content and surface characterisation by FTIR and SEM techniques. A toluene pyrolytic conversion experiment was carried out to determine the chars' potential towards tar removal. At the initial stage of the process, toluene removal was higher for extracted than non-extracted pine char, and with time-on-stream their performance became similar. It was concluded that the removal of the extractives affected wood pyrolysis, creating char with significantly higher microporosity and increased acidity. Upon steam activation, the microporosity and acidity of both chars were enhanced in general while the difference between the samples diminished, while still improving toluene conversion in the early stages of the process.