Bio-oil from pyrolysis of wood pellets using a microwave multimode oven and different microwave absorbers

Wood pellets were pyrolyzed using a microwave oven and different microwave power, apparatus set-up and microwave absorbers (none, Fe, and carbon). Pyrolysis was realized in a short time in the presence of Fe or carbon and the shape of the pellets remains unaltered. Otherwise if the absorber was absent pyrolysis was low, incomplete and pellets were disaggregated. Three fractions were collected from each pyrolysis: a gas, a liquid also called bio-oil and a solid called bio-char. Two phases were present in the bio-oil and they were quantitatively characterized through a GC/MS-FID procedure using an internal standard according to a previously reported method. HPLC/MS, FTIR and 1H-NMR spectroscopy were also employed for characterization of these liquids. Cellulose pyrolysis products were present in the upper phase such as water, acetic acid, furans (such as furfural), carbohydrates and their derivatives. Compounds from pyrolysis of lignin such as phenols and veratric acid were present in the bottom phase. The microwave assisted pyrolysis showed the possibility to efficiently convert wood pellets in different products. The main economical important components of the bio-oil may be separated and used as chemicals, natural drugs or pesticides, while the remaining components may be used as liquid fuel for energy production. Solid may be used for carbon sequestration, absorbent or energy production.