CO₂ Solubility in Fast Pyrolysis Bio-oil

Abstract

Preheating and the use of additives, such as alcohols, are common strategies to treat fast pyrolysis bio-oil after production or before its intended use. Such strategies lower the viscosity of bio-oil and slow chemical reactions occurring in bio-oil during storage. Furthermore, they influence the physicalchemical properties, environmental performance, and cost of the final product. This work suggests the use of CO 2 as an alternative and environmental strategy. In contrast to other additives, CO 2 has the advantage of being a byproduct of the pyrolysis process. To assess CO 2 as an additive and solvent for bio-oil, solubility data on CO 2 in acetol, pure bio-oil, and mixtures of bio-oil with an added compound are provided. Experiments were conducted at 50 °C and pressures of 20−100 bar. As additional compounds, acetic acid, acetol, furfural, guaiacol, and water are deployed. The results showed that the CO 2 solubility is below 0.1 wt % at subcritical pressures but elevated at supercritical pressures. At 95 bar, the CO 2 solubility equates to 0.45 wt %. This is below the CO 2 solubility of butanol, which accounts for 0.6−0.7 wt % at the same pressure and is generally higher than the solubility in bio-oil. The CO 2 solubility in pure fast pyrolysis bio-oil and its mixtures can be well described by the SRK-EoS. This is a basis to draw a connection between the CO 2 solubility and its effects on the properties and further treatment.

Viscosity Reduction of Fast Pyrolysis Bio-Oil by Using CO2 as an Additive

“…Pressurized CO 2 at 50 bar reduces the original viscosity of the wheat-straw-based FPBO used here by 70–80%, as does 5 wt % ethanol in FPBO. Further measurements have shown that a comparable viscosity reduction is achieved by the same mass fraction of solved CO 2 . Since the molar mass of CO 2 and ethanol is quite similar, this implies a similar mole fraction.…”

Involvement of Acid-Leachable Inorganics in Pyrolysis of Pig Manure

“…11,12 Bio-oil is seen as a potential feedstock for the production of biofuel. 13,14 Gases from pyrolysis could be combusted for providing heat required for pyrolysis. 15,16 As a waste in livestock production, pig manure production is relatively stable and has no seasonal fluctuations.…”