The effect of pyrolysis temperature on recovery of bio-oil as distinctive stage fractions

• The effect of pyrolysis temperature on recovery of various products collected in stage fractions (SF) was investigated.
• The highest moisture content, over 91% total moisture, was collected in SF 5 at 550 °C.
• The majority of sugars were collected in SF 1–2 with the maximum production at 450 °C.
• Highest production of phenolic compounds occurred at 400 °C at 29.4 wt% db with most collected as oligomers in SF 1–2.
• Relative molecular weight distribution of the majority of heavy ends bio-oil (SF 1–2) ranged from monomers to tetramers.

The goal of this study was to investigate the effect of pyrolysis temperature on the recovery of various products from the pyrolysis of red oak using a fractionating bio-oil recovery system. Within the temperature range investigated, the maximum bio-char yield of 31.1 wt% occurred at 350 °C, the maximum bio-oil yield of 66.7 wt% occurred at 400 °C and the maximum non-condensable gas (NCG) yield of 26.3 wt% occurred at 550 °C. The maximum production of sugar from cellulose and hemicellulose of 13.5 wt% occurred at 450 °C. The sugars, in the form of anhydrosugars, were condensed in stage fractions (SF) 1–2. Production of phenolic compounds was highest at 400 °C yielding 29.4 wt% dry basis (db) with the majority collected as oligomers in SF 1–2. Moisture content was highest at 550 °C yielding 57.9% in SF5, which is 91% of the total moisture. Gel permeation chromatography (GPC) indicated that the majority of compounds found in the heavy ends of bio-oil (SF 1–2) ranged from oligomeric monomers to tetramers.