A techno-economic evaluation of the feasibility of ... - Biocoup

NWBC 2011, Stockholm, March 22-24 

A Techno-Economic Evaluation on the Feasibility of Chemicals 

from Pyrolysis Oil 

André B. de Haan, G. Wytze Meindersma, Jeroen Nijenstein, Caecilia Vitasari 

1 Eindhoven University of Technology, The Netherlands, a.b.dehaan@tue.nl 

Abstract 

Pyrolysis liquid or pyrolysis oil contains more than 300 oxygenated components. Since 

acetic acid and glycolaldehyde are two of the most abundant valuable platform 

chemicals in wood-based pyrolysis oil, this paper presents a techno-economic 

evaluation of their recovery. All evaluated process concepts start with a water extraction 

that appeared capable of isolating acetic acid and glycoaldehyde quantitatively in the 

aqueous phase. Hereafter several conceptual process designs were established and 

evaluated for the recovery of both chemicals from the obtained aqueous phase. 

All evaluated designs were found to be profitable, but an integrated process for the 

combined recovery of acetic acid and glycoaldehyde appeared the most profitable route 

due to high recoveries combined with a 2.5 times lower energy requirement. Overall, it 

can be concluded that the integrated process combines the best profitability with the 

highest sustainability in terms of energy consumption. 

Introduction 

Biomass can be converted into different types of chemicals via thermochemical 

conversions, such as combustion, gasification and pyrolysis. Biomass pyrolysis 

typically yields 60-75% liquid, 15-25% char and 10-20% gas [1]. Pyrolysis liquid or 

pyrolysis oil contains 15-30 wt% water and more than 300 oxygenated components, 

such as acids, alcohols, sugars, phenols, aldehydes and ketones [2]. Since the market 

value of these chemicals is in most cases higher than the market value of fuels, their 

recovery is a promising route to increase the overall value of the forest bio-oil chain. 

The BIOCOUP FP6 Integrated Project is aimed at developing a chain of process steps 

to allow a range of different biomass feed stocks for co-feeding to a conventional oilrefinery 

to obtain liquid transport fuels and oxygenated chemicals. 

Chemicals 

Raw 

Biomass 

Water addition 

Pyrolysis 

Oil 

Polar aqueous 

phase 

Hydrogen 

Apolar 

oil-phase 

Oxygen 

removal 

Chemicals 

Chemicals 

Crude 

refinery 

Figure 1. Potential sources of chemicals


In Figure 1, a schematic overview of the envisaged overall process and separation routes 

is shown. There are three possible sources for the desired chemicals: the pyrolysis oil 

itself and, after water addition, the polar aqueous phase and the apolar oil phase. Acetic 

acid and glycolaldehyde are two of the most abundant valuable platform chemicals in 

wood-based pyrolysis oil with concentrations of 3.4-12 wt% and 5-13 wt% on dry 

basis, respectively [3]. Their recovery from the pyrolysis oil is relatively 

straightforward, since addition of a sufficient amount of water into the pyrolysis oil 

causes a phase separation that drives the more polar compounds towards the aqueous 

phase. Our extraction experiments showed that acetic acid, glycolaldehyde and acetol 

could be extracted nearly quantitatively into the aqueous phase. 

Therefore, the aim of this paper is to make a techno-economic evaluation on the 

recovery of acetic acid and glycoaldehyde for the aqueous phase obtained from forest 

residue pyrolysis oil. Acetic acid is a widely used industrial chemical and 

glycolaldehyde (hydroxyacetaldehyde) a potential intermediate chemical for producing 

renewable ethylene glycol. Figure 2 illustrates the overall approach followed. After 

water addition, first the acetic acid is recovered and hereafter several routes are 

evaluated to obtain the glycoaldehyde. In this paper, first the acid recovery technologies 

and their implication on glycoaldehyde recovery are evaluated. Subsequently, the 

various concepts for glycoaldehyde are analyzed and finally integrated into a whole 

concept for integrated acetic acid and glycoaldehyde recovery, which is analyzed in 

more detail on its economic viability. 

Figure 2. Overall approach for acetic acid and glycoaldehyde recovery 

Acetic Acid Recovery 

Acetic acid recovery from the aqueous mixture by reactive extraction was studied using 

20% TOA (tri-octylamine) in toluene or 2-ethylhexanol [4]. An important boundary 

condition is that the acid removal should not result in significant loss of glycolaldehyde. 

Figure 3 illustrates that for toluene 99% of acid extraction is reached at a solvent-to-feed 

ratio of 0.5, while for 2-ethylhexanol only 0.15 is required resulting in acid recoveries 

>90% for both solvents. Another important difference is that with toluene significantly 

less glycoaldehyde is co-extracted. However, in developing the flow sheets we observed 

that, due to the much lower boiling point of toluene, the acetic acid could not be 

separated by distillation while this was possible with 2-ethylhexanol. . As a result, in 

spite of the higher co-extraction with 2-ethylhexanol, the glycoaldehyde could be 

completely recycled to the acid extraction stage and losses were nearly completely 

prevented. Therefore, the 2-ethylhexanol route is taken as the acid removal step prior to 

the recovery of glycoaldehyde. The resulting flow sheet is depicted in Figure 4.


Figure 3: acetic acid and glycolaldehyde recovery at different S/F-ratios 

TOA-HEX is the solvent stream for the acid extraction in ACIDEXT. In distillation 

column B3, the TOA and part of the 2-ethylhexanol are separated from the acid. The 

remaining of the solvent and heavier impurities like glycolaldehyde is separated from 

the acid in distillation column B4. Distillation column B1 purifies the acid. As can be 

seen, the majority of the glycoaldehyde is recycled with the ethylhexanol from column 

B4, resulting in significantly lower loss compared to the toluene extraction. Overall less 

than 1% of the glycoaldehyde from the feed is lost. 

B4 

B1 

W+A+F 

B7 

B6 

ACID 

B3 

AC-HEX2 ETHYLH EX 

REMAKE 

WATEREXT 

ACIDEXT 

TOA-ACID 

AC-HEX1 

TOA-HEX3 

B5 

TOA-HEX 

B8 

2 

WATERRAF 

Figure 4: acetic acid recovery process scheme with TOA in 2-ethylhexanol 

WAT ERRAF 

V1 

V2 

AQ-WAST E 

FLASH1 

FLASH2 

B2 

GLYCOL 

L1 

L2 

WASTE 

Figure 5: glycoaldehyde process model multi-stage water evaporation 

Glycoaldehyde Recovery 

Three process concepts for glycoaldehyde recovery were compared. The aqueous 

mixture from the water extraction contains 7.5 wt% glycolaldehyde and 82 wt% water 

and needs to be concentrated before distillation. In the first configuration, illustrated in 

Figure 5, two flash drums evaporate 75 % of the feed at 200 mbar to reduce the water 

content of the glycolaldehyde. Distillation column B2 operates at 10 mbar to keep the


reboiler temperature below the decomposition temperature of glycoaldehyde, 100 °C. 

Although a glycoaldehyde purity of 97.5 wt% is obtained, the overall recovery from the 

feed stream to the first flash is only 64%, due to significant losses in the vapor streams 

from both flash drums. In the second configuration, an evaporator with a small reflux 

and a small number of stages (Figure 6) is applied and the recovery of glycoaldehyde 

improved to 81 wt% while maintaining the product purity at 97.5 wt%. 

WATERRAF 

V1 

AQWASTE 

B1 

B2 

GLYCOL 

L1 

WASTE 

Figure 6: water evaporation in evaporator with small reflux ratio and stages 

The third configuration uses extraction of glycoaldehyde with octanol as depicted in 

Figure 7. After extraction, the glycoaldehyde is recovered from the octanol by 

evaporation followed by back-extraction into water. The maximum operating pressure 

in the flash drum is 30 mbar to keep the temperature below 100 °C. The glycoaldehyde 

is subsequently obtained by water evaporation followed by distillation . The resulting 

glycoaldehyde purity is 96.5 wt%, but the overall recovery is only 68 wt%. These 

results clearly demonstrate that the highest recovery is obtained using evaporation with 

reflux. However, even then the maximum recovery (±80%) is relatively low, since 

significant amounts of glycolaldehyde are lost during the rigorous flash evaporation. 

OCT-EXT 

OCT 

WATERRAF 

AQUEOUS 

CONDENSO 

BACKEXT 

OCT-GLY1 

OCT-GLY2 

AQ-GLY 

B10 

AQWASTE 

AQWASTE2 

OCT-GLY 

B2 

WATER1 

AQ-GLY2 

B11 

OCT-SUG 

OCT1 

GLYCOL 

Figure 7: glycoaldehyde process scheme octanol extraction 

Integrated Acetic Acid and Glycoaldehyde Recovery 

To eliminate the costly, in terms of glycolaldehyde recovery, flash evaporation, the 

integration of glycolaldehyde and acetic acid production was evaluated. The acid 

extraction showed that the co-extracted glycolaldehyde is almost completely returned 

with the 2-ethylhexanol. When the solvent-to-feed ratio is increased, it can extract all of 

the glycolaldehyde. Since distillative separation of glycolaldehyde and 2-ethylhexanol 

appeared difficult due to an azeotrope, back extraction with water followed by 

distillation is applied to recover the glycoaldehyde. The resulting process flow diagram 

is shown in Figure 8. Increasing the solvent-to-feed ratio for the acid extraction step to 

>0.5 resulted in an acetic acid recovery of 89.4% and glycoaldehyde recovery of >99%. 

The purity of the acetic acid is 99.8 wt% and that of glycolaldehyde 97.5 wt%.


ACID1 

ACID2 

W+A+F 

AC-HEX1 

AC-HEX2 

B7 

B1 

TOA-HEX2 

B3 

B6 

B4 

ACID 

WATER1 

GLYCEXT 

TOA-HEX3 

WATEREXT 

ACIDEXT 

OIL 

WATEREXT 

WATER 

TOA-HEX1 

OILSTRIP 

WATERRAF 

B11 

REMAKE 

TOA-HEX4 

B5 

EHTYLHEX 

HEX1 

B8 4 

WAT-GLY 

B12 

WATER2 

GLYCOL 

Figure 8: process scheme for integrated acetic acid and 

glycolaldehyde recovery with 2-ethylhexanol 

Economic Evaluation 

All economic calculations are based on feeding 200.000 ton/yr pyrolysis oil to the water 

extraction and an operating time of 8000 hr/yr. To combine the capital and operating 

costs, the capital costs are converted to total annual cost (TAC) according to the method 

developed by Douglas (1988) [5]: 

TAC= (2.43 Kcap 0.19) Ccap 

Cop 

(1) 

were Ccap stands for the total installed capital cost of the equipment. Kcap is the capital 

charge factor that accounts for the time value of money; typical values are around 1/4 

yr -1 . Cop is calculated by adding heating and cooling costs and the difference in value 

between the products and the raw materials. The costs for heating are taken as €7.5/MW 

and for cooling €0.023/MW. As a first estimate, the costs of the pyrolysis oil are 

neglected since the products are recovered from a waste water stream. For acetic acid a 

price of 500 €/ton and glycoaldehyde 500 €/ton (75% of ethylene glycol price) were 

taken [6]. The profits of the product streams are included as a negative operation cost. 

This means that profitable operations are characterized by negative total annual costs 

(negative TAC). The results are summarized in Table 1. 

Table 1: Summary of economical evaluation conceptual process designs 

Process Concept 

Produced Produced 

acetic acid 

(ton/yr) 

glycoaldehyde 

(ton/yr) 

Energy 

(MW) 

TAC 

(M€/yr) 

Acetic acid with 20% 

TOA in 2-ethylhexanol 

10500 - 3.7 -4.4 

Glycoaldehyde flash - 8700 15.8 -3.3 

Glycoaldehyde flash 

with reflux 

- 11600 17.5 -5.0 

Glycoaldehyde octanol 

extraction 

- 9200 16.0 -3.2 

Integrated acetic acid & 

glycoaldehyde 

10200 13400 8.0 -12.0


From Table 1 it is evident that the integrated acetic acid/glycoaldehyde concept offers 

the highest profitability. This is the result of a combination of factors: highest 

glycoaldehyde recovery, low energy consumption through minimized need for 

evaporation and low capital costs through an integrated concept. All non-integrated 

combinations will suffer from high energy costs in the glycoaldehyde recovery part of 

the process and the relatively lower recoveries for glycoaldehyde. Therefore, the 

integrated concept is also the preferred option from a sustainability point of view. 

Conclusions 

Various conceptual process designs were established and evaluated for the recovery of 

acetic acid and glycoaldehyde from forest residue pyrolysis oil. All evaluated designs 

were found to be profitable, but an integrated process for the combined recovery of both 

chemicals from the aqueous phase originating from water extraction of the pyrolysis oil 

appeared the most profitable route due to high recoveries combined with a 2.5 times 

lower energy requirement. Overall, it can be concluded that the integrated process 

combines the best profitability with the highest sustainability in terms of energy 

consumption. 

Acknowledgements 

The authors would like to acknowledge the European Committee for funding this work 

as part of the 6 th framework integrated project BIOCOUP (www.biocoup.eu) 

References 

1. Mohan D., Charles U. and Steele P.H., (2006): Pyrolysis of wood/biomass for biooil: 

A critical review. Energy & Fuels, 20:3, p.848 

2. Oasmaa A., Leppämäki E., Koponen P., Levander J. and Tapola E., (1997): Physical 

characterization of biomass-based pyrolysis liquids: Application of standard fuel oil 

analyses. Espoo, Finland: Technical Research Centre of Finland, Report No.: 306. 

3. Bridgewater A.B., (2007): The production of biofuels and renewable chemicals by 

fast pyrolysis from biomass. Int. J. Glob. Energy Issues, 27:2, p. 160. 

4. De Haan A.B. et.al, (2009): Chemicals from the forest bio-oil chain. Proceedings 

NWBC2009, Helsinki, Finland, p. 

5. J.M. Douglas, Conceptual Design of Chemical Processes, Chapter 2, McGraw-Hill, 

New York 1988 

6. ICIS pricing:

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