Effect of pyrolysis temperature and thermal conditioning on the coke-forming potential of bio-oils

MELISA BERTERO; GABRIELA DE LA PUENTE; ULISES SEDRAN

ENERGY & FUELS (PRINT)

AMER CHEMICAL SOC

Lugar: Washington; Año: 2011 vol. 25 p. 1267 - 1275

0887-0624

Bio-oil from the pyrolysis of pine sawdust was subjected to a thermal conditioning process aimed at inducing changes in its composition and physicochemical properties. The objective was to facilitate the co-processing of bio-oil together with conventional feedstocks in FCC. The pyrolysis was performed at different conditions (heating ramp 15 ºC/min, final temperatures from 300 to 650 ºC), yielding varying proportions of gases, tar, char and bio-oil. The maximum bio-oil yield (43.7 wt%) was obtained at 550 ºC. Bio-oil showed a high concentration of oxygenated compounds (about 48 wt%) including acids, esthers, aldehydes, ketones, furans, alcohols, sugars, phenols and ethers, together with hydrocarbons and close to 50 wt% of water. The thermal treatments included different conditions (final temperatures from 350 to 550 ºC, and heating ramps from 8 to 12 ºC/min), and the most important consequences were that the concentrations of compounds believed to be coke precursors, such as phenols decreasesd significantly (between 30 and 50 %, and particularly some phenolic ethers, up to 90 %), and high molecular weight compounds (between 50 and 65 %). Some physicochemical properties in the bio-oil changed positively, the CCR decreasing from 4.8 wt% to about 1.5 wt%, and the effective hydrogen index increasing by 30 %. Most of the carbon and the hydrogen remained in the liquid phase after the thermal treatment, while about 40 % of the oxygen was removed. The by-products in the thermal process (tar, gases and pyrolytic lignin), represented an overall yield of about 5 wt%, and the overall yield of conditioned liquid was 38.7 wt% based on the sawdust raw material.