WO2018229342A1

WO2018229342A1 - Extraction of furfural and optionally (an) organic acid(s) from their aqueous solution

Info

Publication number: WO2018229342A1
Application number: PCT/FI2018/050462
Authority: WO
Inventors: Juha-Pekka POKKI; Herbert Sixta; Olga ERSHOVA; Anna ZAITSEVA
Original assignee: Aalto University Foundation Sr
Priority date: 2017-06-15
Filing date: 2018-06-14
Publication date: 2018-12-20

Abstract

A method for extracting furfural and optionally (an) organic acid(s) from an aqueous solution is disclosed. The method may comprise extracting of furfural and optionally (an) organic acid(s) from an aqueous solution using isophorone as an extracting agent.

Description

EXTRACTION OF FURFURAL AND OPTIONALLY (AN) ORGANIC ACID(S) FROM THEIR AQUEOUS SOLUTION

TECHNICAL FIELD

The present disclosure relates to a method for extracting furfural and optionally (an) organic acid(s) from an aqueous solution using isophorone as an extracting agent. BACKGROUND

Furfural is a platform chemical produced from plant pentosans. It is utilized in chemical industry for synthesizing solvents, adhesives, pharmaceutical products, textile fibers (Nylon) and plastics. Nowa- days furfural is produced by acid catalyzed dehydra^¬ tion of pentoses which are released during the hydrol^¬ ysis of pentose-rich lignocellulosic substrates such as corn cob, bagasse, wheat and rice straw or birch wood. When the dehydration reaction is carried out in purely aqueous solution, the formed furfural is pre^¬ sent in a rather low concentration. Several other industrial processes, such as biomass hydrolysis and pretreatment for further processing, produce dilute aqueous solutions comprising low amounts of furfural and carboxylic acids. These compounds are known to in^¬ hibit the following fermentation reactions for example in ethanol production. Nevertheless, the removal of furfural by distillation is energy consuming, technically challenging and economically inefficient in cas- es of diluted aqueous solutions or even impossible in case of complex mixtures were direct heating is inap^¬ propriate .

Furfural and the carboxylic acids are sepa^¬ rated from its dilute aqueous solutions and concen- trated by an extractant which is insoluble in water and its boiling temperature shows a big enough gap from the boiling point of the target component. The economical way of furfural and carboxylic acids recov^¬ ery from dilute water mixtures typically involves liq^¬ uid-liquid extraction as a first stage followed by a stripping column to recycle the extractant (solvent) and to separate the extracted substances as pure com^¬ pounds. Due to environmental and economical reasons the recovery of furfural and carboxylic acids has be^¬ come increasingly interesting nowadays. The separation of various organic chemicals from complex mixtures may be based on liquid-liquid extraction processes. In the literature, different organic solvents have been stud^¬ ied for furfural and carboxylic acids extraction from its aqueous solutions. In most of the publications, solvents were proposed to either extract carboxylic acids with good yield or to extract furfural, as for example extraction with supercritical C02 (Gairola & Smirnova 2012; Games et al . 1997), methyl-isobutyl ke^¬ tone (MIBK) (Croker & Bowrey 1984), alcohols (Cabezas & Barcena 1988; Zautsen et al . 2009), ionic liquids (Pei et al . 2008) and others (Coca & Diaz 1980; Demesa et al . 2014) . Several solid adsorbents such as poly^¬ meric adsorbents and activated carbon have been inves^¬ tigated for their ability to remove the furfural from water (Gupta et al . 2001; Sahu et al . 2008; Weil et al . 2002) but further furfural separation from these adsorbents is questionable.

The highest partition coefficients (m_p = Worg/w_aq , were m_p is the partition coefficient, w_aq is the mass fraction of component in aqueous phase and Worg is the mass fraction of component in organic phase) of furfural were published as high as 16-12 for certain ionic liquids (Pei et al . 2008) . However, due to their high costs, the industrial application of such ionic liquids is not realistic.

Another interesting solution for furfural and carboxylic acids extraction suggested is the applica- tion of supercritical C0₂ (Gairola & Smirnova 2012; Games et al . 1997), which requires high pressure equipment (65 bars) .

The usage of methyl-isobutyl ketone (MIBK) has been also proposed in the scientific literature for furfural extraction due to its high partition coefficient with furfural of about 8 in the temperature range of 20 to 80 °C (Croker & Bowrey 1984) . Its com^¬ mercial utilization is however doubtful due to its high flammability .

US 2013/0232854 Al describes the process for separating furfural from a liquid aqueous phase com^¬ prising furfural and one or more organic acids using one or more aromatic hydrocarbon compounds such as al- kyl benzenes or naphthalene (Haan 2011) . The document focused on the selective extraction of furfural and doesn't discuss the extraction of organic acids such as formic acid or acetic acid.

The patent application WO2013/064751 and US patent US2014/0275581A1 discloses the extraction of furfural and carboxylic acid from a dilute aqueous mixture thereof using derivatives of methyltetrahydro- furan such as 2-methyltetrahydrofuran, 3- methyltetrahydrofuran, 2 , 2-methyltetrahydrofuran or 2 , 5-methyltetrahydrofuran . These compounds have boiling temperature lower than that for furfural and evap^¬ orate first during the distillation process. Moreover, the 2-methyltetrahydrofuran is a highly flammable liquid and thus difficult to handle.

The separation of furfural and acetic acid from acidic hydrolyzates and spent sulfite liquors is described in US 4,401,514 (Kanzler & Schedler 1983). The authors propose the use of the polar water- insoluble tri-n-octylphosphine oxide (TOPO) as an ex- tractant dispersed in n-undecane. The only commercial application based on this technology is successfully implemented by Lenzing AG (Austria) . However, TOPO is a solid below 50-54 °C, meaning that extraction using TOPO is not feasible below this temperature. Moreover, this extraction method is applicable only for acidic solutions .

SUMMARY

A method for extracting furfural and optionally (an) organic acid(s) from an aqueous solution is disclosed. The method comprises extraction using isophorone as an extracting agent.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the embodiments and constitute a part of this specification, illustrate various embodiments. In the drawings:

Fig. 1 illustrates a schematic diagram of a method for extracting furfural according to one embodiment .

Fig. 2 illustrates a schematic diagram of a method for extracting furfural with recovery of the extraction solvent according to one embodiment.

Fig. 3 illustrates a schematic diagram of a method for extracting furfural with the optional recovery of the extraction solvent and water according to one embodiment.

DETAILED DESCRIPTION

A method for extracting furfural and optionally (an) organic acid(s) from an aqueous solution using isophorone as an extracting agent is disclosed .

In one embodiment the method comprises subjecting the aqueous solution comprising furfural and (an) organic acid(s) to extraction with isophorone as an extracting agent, wherein the mass ratio of the aqueous solution to isophorone is between 0.1 and 10, and wherein the extraction takes place at a temperature between 10° C and 95° C, forming an extract comprising an organic phase, and a raffinate comprising an aqueous phase.

In the context of this specification, the term "extraction" may refer to liquid-liquid extraction. The terms "extraction method" and "extraction process" may be interchangeably in this specification

The term "aqueous solution" may refer to a dilute aqueous solution/mixture comprising low amounts of furfural and optionally low amounts of (an) organic acid(s) . The aqueous solution is suitable for liquid extraction allowing amount of solids low enough for not disturbing the extraction process. The terms "aqueous solution" and "aqueous mixture" may be interchangeably in this specification.

By the term "extract" is meant the organic phase formed after extracting comprising the extracting agent, furfural, traces of water and optionally traces of (an) organic acid(s).

By the term "extractant" is meant the extracting agent. The term "extracting solvent" may also be used when referring to the extracting agent.

By the term "raffinate" is meant the aqueous phase formed after extracting comprising essentially water.

In the context of this specification, the expression "extracting furfural" may refer to extracting furfural from the liquid aqueous solution into a liquid organic phase comprising isophorone to form the extract comprising furfural. The expression "extracting furfural and optionally (an) organic acid(s)" may refer to extracting furfural and optionally (an) organic acid(s) from the liquid aqueous solution into a liquid organic phase comprising isophorone to form the extract comprising furfural and optionally (an) organic acid(s).

Isophorone is an a, β-unsaturated cyclic ketone, a colorless to yellowish liquid with a characteristic peppermint-like smell. It has a density of 0.9255 g/cm3 and a boiling point at 215.32 °C. Isophorone is only slightly soluble in water (1.2 g/100 mL at 20 °C) . It is widely used as an intermediate in organic synthesis and solvent for concentrated vinyl chloride/acetate-based coating systems (Papa & Sherman 1981) . The isophorone has a low solubility in water resulting in fast phase separation without additional salting out or sugaring out methods. Furfural has boiling temperature lower than that for isophorone and evaporates first during the distillation. Isophorone aids in water removal by forming azeotrope with water and it is fully regenerable by distillation. Isophorone is an efficient furfural solvent and an extracting agent.

In an embodiment the aqueous solution comprises 0.1 wt% to 10 wt % of furfural based on the total weight of the aqueous solution. In an embodiment the aqueous solution comprises 0.1 wt% to 7 wt % of furfural based on the total weight of the aqueous solution .

In an embodiment the aqueous solution comprises 0.1 wt% to 10 wt% of (an) organic acid(s) based on the total weight of the aqueous solution. In an embodiment the aqueous solution comprises 0.1 wt% to 7 wt% of (an) organic acid(s) based on the total weight of the aqueous solution.

The method may further comprise recovering or removing furfural from the extract.

In an embodiment the method comprises recovering or removing furfural and (an) organic acid(s from the extract. Furfural and (an) organic acid(s) may be extracted simultaneously.

In an embodiment the organic acid is acetic acid. In an embodiment the organic acids are acidic acid and formic acid.

In an embodiment the aqueous solution/mixture originates from biomass treatment processes. The aqueous solution may originate from biomass hydrolysis. In an embodiment the aqueous mixture is hydrolysate from hardwood prehydrolysis or a sulfite spent liquor.

In an embodiment the method is an industrially suitable method for the extraction of furfural and optionally the organic acid(s) from a diluted aqueous mixture or mixture originated from biomass treatment/fractionation processes using isophorone as extracting agent. The method is also applicable for the extraction of furfural and optionally the organic acid(s) during the pentosans conversion into furfural.

In an embodiment the extraction takes place in a continuous extraction column. In an embodiment the extraction takes place in a continuous contraflow extractor .

In an embodiment isophorone as an extracting agent is fed into the continuous extraction column from the top of the extraction column and the aqueous solution comprising furfural and (an) organic acid(s) is fed from the bottom of the continuous extraction column.

In an embodiment the extraction takes place at a temperature of 20 °C to 80 °C, or at a temperature of 20 °C to 65 °C. In an embodiment the extraction takes place at a room temperature. The elevation of the temperature can increase heat integration . The extraction may take place in ambient pressure. In an embodiment the extraction takes place at a temperature from about 10 to about 95 °C, more preferably from 20 to 80 °C, and ambient pressure.

In an embodiment the mass ratio of the aqueous solution/mixture to isophorone in the feed is from 0.2 to 4, or from 0.5 to 4. Lowering the mass ratio of the aqueous solution/mixture to isophorone in the feed promotes extraction, i.e. the amount of recovered furfural and optionally (a) organic acid(s) increases .

By the method as described in this application the furfural is removed or recovered from an aqueous mixture in at least 80 wt% yield, preferably at least 90 wt%, more preferably at least 95 wt%. The obtained furfural extraction yield is dependent on the concentration of furfural in the mixture where from furfural is to be separated and the chosen operating parameters such as temperature, pressure, and aqueous feed and isophorone ratio.

In an embodiment the aqueous solution is heated prior to the extraction. In an embodiment the aqueous solution is heated prior to entering the extraction column.

In an embodiment the method further comprises recycling the raffinate separated from the extraction process .

In an embodiment the raffinate separated from the extraction process is purified with membrane or activated carbon filtration.

In an embodiment furfural is extracted by feeding an aqueous solution containing furfural and acetic acid from the bottom of the continuous extraction column, feeding isophorone as an extracting agent into said extraction column from the top to make the aqueous feed to isophorone feed ratio to be between 0.1 and 10, operating the said extraction column in a manner such that the temperature of said column is between 10 °C and 95 °C, resulting in an organic phase comprising said extracting agent, furfural, traces of water and organic acids (acetic and formic acids) , and an aqueous phase comprising essentially water.

In an embodiment furfural and (an) organic acid(s) are recovered or removed from said extract by distillation .

In an embodiment the organic extract comprising water, furfural, (an) organic acid(s) is purified from water by an azeotropic distillation. In an embodiment the organic extract containing water, furfural, acetic acid and formic acid, or acetic acid is purified from water by an azeotropic distillation.

In an embodiment the recovery or the removal of the mixture comprising furfural, (an) organic acid(s), water and a small amount of isophorone in the form of an azeotrope from the extract by distillation takes place at a temperature of the top part of the distillation column.

In an embodiment the distillation takes place at a temperature from about 55 °C to about 150 °C at pressure of 0.2 bars. In an embodiment the recovery or the removal of the mixture comprising furfural, acetic acid, water and a small amount of isophorone in the form of an azeotrope from the extract by distillation takes place at a temperature of the top part of the distillation column from about 55 °C to about 150 °C at pressure of 0.2 bars.

In an embodiment the organic extract comprising furfural, (an) organic acid(s) and an extracting agent is subjected to stripping distillation wherein the major part of the extracting agent is removed as a bottom stream. The distillate from the top part of the stripper may be mixed with solvent such as isopropanol forming low-boiling azeotrope with water. Water and isopropanol may be removed as an azeotrope by distillation.

In an embodiment the distillate, drawn from the top part of the distillation column comprising essentially (an) organic acid(s), furfural and some amount of isophorone is subjected to a further distillation whereby a bottom stream obtained from distillation, comprising the extracting agent, isophorone, and a top stream comprising (an) organic acid(s) and furfural is obtained. In an embodiment the distillate comprises acetic acid, formic acid, furfural and some amount of isophorone and a top stream comprising formic acid, acetic acid and furfural is obtained, or the distillate comprises acetic acid, furfural and some amount of isophorone and a top stream comprising acetic acid and furfural is obtained.

In an embodiment the next steps comprise the separation of (an) organic acid(s) and furfural from the formed water-free mixture by distillation. In an embodiment the next steps comprise the separation of acetic acid and furfural from the water-free mixture by distillation.

By first removing or recovering the furfural and optionally (an) organic acid(s) such as acetic acid from the dilute aqueous solution by liquid-liquid extraction and subsequent distillation gives a concentrated industrial grade platform chemical.

In an embodiment isophorone is further recycled to the extraction process. In an embodiment the bottom stream of the first distillation column, or further distillation column comprising the separated isophorone, goes back to the extraction stage.

The method as described in this application provides a method for efficient separation of furfural and (an) organic acid(s) from a diluted aqueous solution. The method has added utility of quantitative furfural and acetic acid extraction from a diluted aqueous solution. Further, the method as described in this application has the added utility of simultaneous recovery or removal of furfural and (an) organic acid(s) from a dilute aqueous solution with a single extraction solvent. The method as described in this application has the added utility of removing furfural from an aqueous solution in at least 80 wt% yield. EXAMPLES

Reference will now be made in detail to various embodiments, an example of which is illustrated in the accompanying drawing.

The description below discloses some embodiments in such a detail that a person skilled in the art is able to utilize the embodiments based on the disclosure. Not all steps or features of the embodiments are discussed in detail, as many of the steps or features will be obvious for the person skilled in the art based on this specification.

For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.

Fig. 1 illustrates a schematic diagram of a method for extraction of furfural according to one embodiment described in this description. From Fig. 1 one can see an extraction unit 1, EXTRCOL, where furfural and (an) organic acid(s) are extracted by isophorone from dilute aqueous solution. Based on the layout of Fig. 1, a feed comprising or consisting of dilute aqueous solution comprising furfural, and (an) organic acid(s) is fed into an extraction unit 1, which may be batch mode extractor or a contraflow extractor, together with solvent SOLV comprising or consisting of the extracting agent. Formed extract EXTR comprising furfural, (an) organic acid(s) and the extracting agent is recovered or removed. Formed extract EXTR may comprise furfural, acidic acid and the extracting agent. Formed extract EXTR may also comprise furfural, formic acid, acidic acid and the extracting agent. Raffinate RAFF comprising essentially water is drawn from the bottom of the extraction unit 1. Water may also have tiny amount of extracting agent and furfural and/or (an) organic acid(s) left, which amounts come from the phase equilibrium.

In the embodiment of Fig. 2, a feed comprising or consisting of dilute aqueous solution comprising furfural is fed into an extraction unit 1, which may be a contraflow extractor, together with a solvent SOLV comprising or consisting of the extracting agent. The solvent may be a fresh extracting agent and/or a recycled extracting agent. Fresh and recycled extracting agents may be mixed with a mixer 3. The formed extract EXTR comprising furfural is directed to first distillation unit 2, DIST1, where the extracting agent is separated from water, furfural and optional organic acids. The bottom stream SOLV-REC comprising the extracting agent is recycled back to the extraction unit 1 and the distillate is split in two phases, the aqueous rich (top stream AQ-RICH) and furfural rich (F-RICH) phase. The formed top stream AQ-RICH is fed to further distillation unit 4, DIST- AQ, to separate the water and to form the residue/bottom product. The formed stream PURE WATER comprises pure water. The other formed top stream F- RICH from the first distillation unit 2 is fed to the further distillation unit 5, DIST-F, to give furfural. The formed stream DIST-F-FURF comprises furfural. The dashed line illustrates a further distillation unit where the stream DIST-F-FURF comprising furfural may be fed to further purify furfural. The stream AQ-WASTE from the distillation unit 4 and/or the stream DIST-F- AQ from the distillation unit 5 may be purified to get very pure water. Streams AQ-WASTE and DIST-F-AQ may be purified by using membrane or activated carbon filtration. The stream S2 from the distillation unit 4 may be mixed with F-RICH stream from the distillation unit 2 before the distillation unit 5, DIST-F. The distillation units may be distillation columns.

In the embodiment of Fig. 2 where the feed comprises or consists of dilute aqueous solution comprising furfural and organic acid(s), the extraction unit 1 is connected to a distillation unit 2, DIST1, for the distillation of the extract provided by the extraction unit 1 comprising furfural and (an) organic acid(s) and further connected to multiple distillation units, the distillation unit 4, DIST-AQ, and the distillation unit 5, DIST-F, for additional distillation of the top streams AQ-RICH and F-RICH comprising furfural and (an) organic acid(s) from the distillation unit 1, DIST1, to separate (an) organic acid(s) and furfural.

In the embodiment of Fig. 3, a feed comprising or consisting of dilute aqueous solution comprising furfural and (an) organic acid(s) is fed into an extraction unit 1, which may be a contraflow extractor, together with solvent SOLV comprising or consisting of the extracting agent. The solvent may be a fresh extracting agent and/or a recycled extracting agent. The extract (EXTR) from the extraction unit 1 is fed to a stripping column 6, STRIPCOL, via a heat exchanger. The major part of the extracting agent, isophorone is removed as a bottom stream of the stripping column 6, STRIPCOL. The bottom stream ISOPH1 consists highly pure isophorone and can be recycled back to the extraction unit 1. The top stream from stripping column 6 in a vapor form is condensed in a heat exchanger and mixed with solvent IPAADD forming low-boiling azeotrope with water. The mixture of the streams is fed to the first distillation unit 7, WATERDIS, where the water and solvent IPAADD forming low-boiling azeotrope with water are removed as an azeotrope from the top of the distillation unit 7. The recycling of solvent IPAADD forming a low-boiling azeotrope with water is possible after the separation of water.

The bottom stream of the distillation unit 7 comprising isophorone, furfural and acetic acid is fed to a second distillation unit 8, ACIDDIST, where (an) organic acid(s) such as acetic acid is removed as product with high purity. The bottom stream from the distillation unit 8, ACIDDIST, comprising isophorone and furfural is fed to a distillation unit 51, FURFDIST, where furfural is removed as highly pure product in stream, FURFOUT, leaving highly pure isophorone in a bottom stream ISOPH2, which can be send to the extraction unit 1 for solvent recycling.

The raffinate RAFF from the extraction unit 1, EXT-COL, is the aqueous stream comprising small amounts of isophorone and (an) organic acid(s) such as acetic acid as impurities. This raffinate stream is fed to the series of two distillation unit 81, RAFFDIST1, and 82, RAFDIST2, where water and some small amounts of (an) organic acid(s) such as acetic acid are separated as a bottom stream ACIDWATE. The top streams of the distillation units 81 and 82 are the organic streams and the aqueous streams. These top streams are separated from each other by density difference. The separation can be carried out by decantation. The organic streams are mixed with the extractant EXTR and fed to the stripping unit 6. The aqueous stream from the distillation unit 82 is fed to the heat exchanger after the stripping unit 6. The distillation units may be distillation columns. Example 1

Aqueous solution (909 g) , which contained 6.0 wt-% acetic acid and 6 wt-% furfural was fed to the batch mode extractor where it was extracted during 1 h of mixing with 923 g of isophorone. Mass ratio of aqueous to organic feed was 0.98. The resulting mixture was allowed to settle down during 1 h after mixing has been stopped. Extraction temperature was 35 °C . The composition of the extract was 4.4 wt-% acetic acid, 5.2 wt-% furfural, 13.2 wt-% water and the rest was isophorone. The extraction yield (calculated as (m^feed-m^raff) *100/m^feed, where m^feecl and m^raf are the amounts of components in g in aqueous feed or raffinate, respectively) for acetic acid was 40 % and furfural 87.6 %. Table 1 shows material flows (wt-%) of the extraction unit according to Figure 1.

Table 1. The material flows (wt-%) of the extraction unit according to Figure 1

Example 2

Aqueous solution with the flow rate 34.78 kg/sec, which contained 1 wt-% acetic acid and 1 wt-% furfural was fed to the contraflow extractor where it was extracted with 55.28 kg/sec of isophorone. Mass ratio of aqueous to organic feed was 0.63. Extraction temperature was 30 °C . The composition of the extract was determined as follows: 0.58 wt-% acetic acid, 0.6 wt-% furfural, 4.1 wt-% water and the rest was isophorone. The extraction yield (calculated as described in Example 1) for acetic acid was 96.6 % and furfural 99.9 %. Table 2 shows material flows (wt-%) of the extraction unit according to Figure 1.

Table 2. The material flows (wt-%) of the extraction unit according to Figure 1

Example 3

Aqueous solution with the flow rate 12.481 g/min, which contained 0.98 wt-% acetic acid and 0.95 wt-% furfural was fed to the contraflow extractor where it was extracted with 7.674 g/min of isophorone. Mass ratio of aqueous to organic feed was 0.62. Extraction temperature was 22 °C . The composition of the extract was determined as follows: 0.84 wt-% acetic acid, 0.61 wt-% furfural, 4.1 wt-% water and the rest was isophorone. The extraction yield (calculated as described in Example 1) for acetic acid was around 94 % and furfural over 99.9 %. Table 3 shows material flows (wt-%) of the extraction unit according to Figure 1.

Table 3. The material flows (wt-%) of the extraction unit according to Figure 1 FEED SOLVent

(Aqueous (Ex- EXTRact RAFFinate solution) tractant )

Mass Flow,

7.68 12.48 13.14 6.42 G/MIN

Temperature, C 22 22 22 22

Component mass fraction, wt%

Isophorone 0 100 94.45 1.23

Furfural 0.95 0 0.61 0

Acetic acid 0.98 0 0.84 0.07

Water 98.07 0 4.10 98.70

Example 4

Aqueous solution with the flow rate 12.536 g/min, which contained 0.7 wt-% acetic acid and 0.92 wt-% furfural was fed to the contraflow extractor where it was extracted with 21.966 g/min of isophorone. Mass ratio of aqueous to organic feed was 1.75. Extraction temperature was 22 °C . The composition of the extract was determined as follows: 1.74 wt-% acetic acid, 1.35 wt-% furfural, 4.33 wt-% water and the rest was isophorone. The extraction yield (calculated as described in Example 1) for acetic acid was around 67.7 % and furfural over 99.9 %. Table 4 shows material flows (wt-%) of the extraction unit according to Figure 1.

Table 4. The material flows (wt-%) of the extraction unit according to Figure 1

FEED SOLVent

(Aqueous (Ex- EXTRact RAFFinate solution) tractant )

Mass Flow,

21.96 12.54 12.96 21.00 G/MIN

Temperature,

22 22 22 22 C

Component mass fraction, wt%

Isophorone 0 100 92.58 1.25

Furfural 0.92 0 1.74 0.00

Acetic acid 0.70 0 1.35 0.27

Water 98.18 0 4.33 98.48

Example 5

Aqueous solution with the flow rate 12.51 g/min, which contained 1.02 wt-% acetic acid and 0.87 wt-% furfural was fed to the contraflow extractor where it was extracted with 51.141 g/min of isophorone. Mass ratio of aqueous to organic feed was 4.08. Extraction temperature was 22 °C . The composition of the extract was determined as follows: 1.48 wt-% acetic acid, 4.07 wt-% furfural, 4.37 wt-% water and the rest was isophorone. The extraction yield (calculated as described in Example 1) for acetic acid was around 33.4 % and furfural over 99.9 %. Table 5 shows material flows (wt-%) of the extraction unit according to Figure 1.

Table 5. The material flows (wt-%) of the extraction unit according to Figure 1

FEED SOLVent

(Aqueous (Ex- EXTRact RAFFinate solution) tractant )

Mass Flow,

51.12 12.54 13.20 49.62 G/MIN

Temperature,

22 22 22 22 C

Component mass fraction, wt%

Isophorone 0 100 90.08 1.27

Furfural 0.87 0 4.07 0.00

Acetic acid 1.02 0 1.48 0.70

Water 98.07 0 4.37 98.03

Example 6

Aqueous solution with the flow rate 34,7 kg/sec (FEED) (Figure 2), which contained 1 wt-% furfural was fed to the contraflow extractor (EXTRCOL) where it was extracted with 54,8 kg/sec of isophorone. Mass ratio of aqueous to organic feed was 0.6. Extraction temperature was 35 °C . The composition of the extract (EXTR) was determined as follows: 0,6 wt-% furfural, 4,15 wt-% water and the rest was isophorone. The extraction yield for furfural is 99,9 %. Table 6 shows material flows (wt-%) of the extraction unit according to Figure 2.

The extract (EXTR) after the extraction unit is fed to the distillation column DIST1. The distillation occurs at 153-155 °C under pressure 20kPa. The bottom stream (SOLV-REC) contains almost pure isophorone (99,999 wt-%) and recycled back to the extraction unit. Two top streams of the first distillation column AQ-RICH and F-RICH are fed to the further distillation columns DIST-AQ and DIST-F to give pure water and 91% pure furfural, respectively (streams PURE WATER and DIST-F-FURF) . The furfural distillation efficiency is about 70%. The streams containing furfural after DIST-F column optionally could be send to further distillation stages to obtain pure final product. The streams AQ-WASTE, DIST-F-AQ can be optionally additionally purified using membrane or activated carbon filtration to get very pure water. The stream S2 can be optionally mixed with F-RICH stream before DIST-F distillation column.

Table 6. The material flows (wt-%) of the extraction unit and distillation units according to Figure 2.

Example 7

Aqueous solution (FEED) (Figure 3) , containing 0.85 wt% furfural and 0.86 wt% acetic acid with the total flow rate 65 kg/sec is fed to the contraflow extractor (EXTR-COL) where it is extracted with 19.7 kg/sec isophorone (SOLVENT). Extraction temperature is 60 °C . The extract (EXTR) after the extraction unit is fed to the stripping column (STRIPCOL) via heat exchanger. The major part of the isophorone is removed as a bottom stream of the STRIPCOL. This stream ISOPH1 consists of at least 99.9 wt% pure isophorone and can be recycled back to the extraction unit. The top stream from stripping column in a vapor form is condensed in heat exchanger and mixed with isopropanol or other solvent forming a low- boiling azeotrope with water. The mixture of the streams is fed to the first distillation column WATERDIS where the water and isopropanol are removed as an azeotrope from the top of the distillation column. The separation of isopropanol and water is a widely used industrial process and the recycling of isopropanol is possible after the separation of water.

The bottom stream of the water distillation column containing isophorone, furfural and acetic acid is fed to the second distillation column ACIDDIST where acetic acid is removed as product with at least 99.9wt% purity. The bottom stream from ACIDDIST column containing isophorone and furfural is send to the FURFDIST distillation column where furfural is removed as at least 99.9wt% pure product leaving 99.9% pure isophorone in a bottom stream, which can be send to the extraction unit for solvent recycling.

The raffinate (RAFF) from the extraction unit (EXT-COL) is the aqueous stream containing 1.7 wt% of isophorone and 0.8wt% of acetic acid as impurities. This stream is sent to the series of two distillation column RAFFDIST1 and RAFDIST2 where water and some small amounts of acetic acid are separated as bottom stream (ACIDWATE) . The top streams of the distillation columns are the organic streams RAFD1(2)0RG and the aqueous streams RAFD1(2)AQ separated from each other by density difference. Organic streams are mixed with EXTR and fed to the stripping column. RAFD2AQ is fed to the heat exchanger after the stripping column. Table 7. The material flows (wt-%) of the extraction unit and distillation units according to Figure 3.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea may be implemented in various ways. The embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.

The embodiments described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined together to form a further embodiment. A product, a system, a method, or a use, disclosed herein, may comprise at least one of the embodiments described hereinbefore. It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item refers to one or more of those items. The term "comprising" is used in this specification to mean including the feature (s) or act(s) followed thereafter, without excluding the presence of one or more additional features or acts. References

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Claims

1. A method for extracting of furfural and optionally (an) organic acid(s) from an aqueous solution using isophorone as an extracting agent.

2. The method according to claim 1, wherein the method comprises subjecting the aqueous solution comprising furfural and (an) organic acid(s to extraction with isophorone as an extracting agent, wherein the mass ratio of the aqueous solution to isophorone is between 0.1 and 10, and wherein the extraction takes place at a temperature between 10° C and 95° C, forming an extract comprising an organic phase, and a raffinate comprising an aqueous phase.

3. The method according to any of claims 1 or 2, wherein the method further comprises recovering or removing furfural from the extract.

4. The method according to any of claims 1 -

3, wherein the method comprises recovering or removing furfural and (an) organic acid(s) from the extract.

5. The method according to any of claims 1 -

4, wherein the organic acid is acetic acid, or the organic acids are acidic acid and formic acid.

6. The method according to any of claims 1 -

5, wherein the aqueous solution originates from biomass treatment processes.

7. The method according to any of claims 1 -

6, wherein the extraction takes place in a continuous extraction column.

8. The method according to any of claims 1 - 7, wherein isophorone as an extracting agent is fed into the continuous extraction column from the top of the extraction column and the aqueous solution comprising furfural and (an) organic acid(s) is fed from the bottom of the continuous extraction column.

9. The method according to any of claims 1 -

8, wherein the extraction takes place at a temperature of 20 °C to 80 °C.

10. The method according to any of claims 1 -

9, wherein the mass ratio of the aqueous solution to isophorone in the feed is from 0.2 to 4, or from 0.5 to 4.

11. The method according to any of claims 1 -

10, wherein the aqueous solution is heated prior to entering the extraction column.

12. The method according to any of claims 1 -

11, wherein the method further comprises recycling the raffinate separated from the extraction process.

13. The method according to any of claims 1 -

12, wherein the raffinate separated from the extraction method is purified with membrane or activated carbon filtration.

14. The method according to any of claims 1 -

13, wherein furfural and said organic acid(s) are recovered or removed from said extract by distillation .

15. The method according to any of claims 1 - 14, wherein recovering or removing a mixture comprising furfural, (an) organic acid(s), water and a small amount of isophorone (in the form of an azeotrope) from the extract by distillation takes place at a temperature of the top part of the distillation column.

16. The method according to any of claim 14 or 15, wherein the distillation takes place at a temperature from about 55 °C to about 150 °C at pressure of 0.2 bars.

17. The method according to any of claims 1 -

16, wherein isophorone is further recycled to the extraction process.

18. The method according to any of claims 14 -16, wherein the distillate, drawn from the top part of the distillation column comprising essentially (an) organic acid(s), furfural and some amount of isophorone is subjected to further distillation whereby a bottom stream obtained from distillation, comprising the extracting agent, isophorone, and a top stream comprising (an) organic acid(s) and furfural is obtained .