Effect of Pyrolysis Temperature and Thermal Conditioning on the Coke-Forming Potential of Bio-oils

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 coprocessing of bio-oil together with conventional feedstocks in catalytic cracking of hydrocarbons (FCC). The pyrolysis was performed at different conditions (heating ramp 15 degrees C/min, final temperatures from 300 to 650 C), yielding varying proportions of gases, tar, char, and bio-oil. The maximum bio-oil yield (43.7 wt %) was obtained at 550 C. 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 SO wt % of water. The thermal treatments included different conditions (final temperature from 350 to 550 degrees C and heating ramps from 8 to 12 degrees C/min), and the most important consequences were that the concentrations of compounds believed to be coke precursors, such as phenols decreased significantly (between 30 and 50%, and particularly some phenolic ethers, up to 90%), and high molecular weight,compounds (between SO and 65%) Some physicochemical properties in the bio-oil changed positively, the CCR decreasing from 4.8 to-about 1.5 wf%, 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 byproduct 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.