Recovery of acetic acid from an aqueous pyrolysis oil phase by reactive extraction using tri-n-octylamine, C.B. Rasrendra, B. Girisuta, H.H. van de Bovenkamp, J.G.M. Winkelman, E.J. Leijenhorst, R.H. Venderbosch, M. Windt, D. Meier, H.J. Heeres, Chemical Engineering Journal 176– 177 (2011) 244– 252
Acetic Acid Recovery from Fast Pyrolysis Oil. An Exploratory Study on Liquid-Liquid Reactive Extraction using Aliphatic Tertiary Amines, FH Mahfud, F van Geel, RH Venderbosch, HJ Heeres, 2008, Separation Science and Technology, 43 (11-12), p. 3056-3074
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Bio-materials & chemicals
Pyrolysis oil from biomass & residues contains a large amount of different components and can be the basis for a huge number of new products and chemicals.
BTG is actively exploring and developing different new products by using pyrolysis oil as the raw material. Examples of these are:
- Pyrolytic lignin as a substitute for fossil phenol in phenol-formaldehyde resins
- Pyrolytic lignin as a replacement for fossil bitumen in e.g. asphalt
- Recovery of organic acids
- Production of mono-phenolics
- Pyrolytic sugars as a renewable feedstock for platform chemicals and fuels e.g. bio-ethanol
Pyrolysis oil fractionation
Pyrolysis oil is a mixture of cracked components originating from the pyrolysis of the three main building blocks of biomass; cellulose, hemicellulose and lignine. Pyrolysis is a good pretreatment to facilitate the fractionation of biomass. After pyrolysis the oil can easily be fractionated into three product streams namely; pyrolytic lignin (from lignin), pyrolytic sugars (from cellulose) and a watery phase containing smaller organic components e.g. acetic acid (mainly from hemicellulose).
At BTG a pilot setup-up was developed which can process 5-20 kg/h of pyrolysis oil in a continuous mode to produce pyrolytic lignin. Processing the pyrolysis oil in this separator will typically yield about 20-30 wt% of pyrolytic lignin with a water content of about 10-11 wt%. The pyrolytic lignin obtained from this device is a highly viscous liquid.
In several experiments the obtained pyrolytic lignin showed to be a potential substituent for fossil phenol in phenol/formaldehyde resins. These types of resins are widely used in wood products like particle boards, plywood etc. It has been demonstrated that the phenol in phenol/formaldehyde resins can be substituted up to 75 wt% by pyrolytic lignin and still meet the D4 (NEN-EN 204/205) standards for this type of resin.
Another interesting application of the pyrolytic lignin is in the replacement of fossil bitumen in various bitumen based materials e.g. in asphalt. Also the pyrolytic lignine could be used in the production of green phenolic (mono-) derivatives, as a possible raw material for various coatings, composites and preservatives.
Subsequently from the remaining bio-oil obtained after pyrolytic lignin separation, the pyrolytic sugars and small organics can be extracted. The pyrolytic sugar phase, containing high amounts of levoglucosan, cellobiosan and larger sugar molecules can be concentrated in the pilot set-up to obtain a thick syrup (up to 30 wt% of the original oil).
This sugar phase could be a renewable source for the production (via glucose) of e.g. bio-ethanol, levulinic acid, polyols etc. It has a high potential as a renewable sugar source due to the fact that it is not extracted from food sources like corn, sugarcane etc. Exploratory experiments showed that a substantial amount of the pyrolytic sugars can be converted to fermentable sugar monomers (especially C6 sugars). Subsequently, fermentation of this phase by means of a yeast culture resulted in the production of ethanol.
From the last fraction, the water phase, acetic acid can be produced by means of an extraction step followed by simple distillation, in this way an acetic acid stream with a concentration up to 90 wt% can be produced in the pilot set-up. Applications of this acetic acid could for example be in the production of acetate salts, as a cleaning agent etc.