WO2020094526A1

WO2020094526A1 - Process for the recovery of furfural

Info

Publication number: WO2020094526A1
Application number: PCT/EP2019/079990
Authority: WO
Inventors: Juben Nemchand Chheda; Jean Paul Andre Marie Joseph Ghislain LANGE
Original assignee: Shell Internationale Research Maatschappij B.V.; Shell Oil Company
Priority date: 2018-11-05
Filing date: 2019-11-01
Publication date: 2020-05-14

Abstract

The present invention relates to a process for the extraction of furfural from a biphasic dehydration reaction mixture in a resource- and energy-efficient manner by the use of one or more adsorption units to increase the recovery of furfural and enrich the furfural content of an organic solvent stream.

Description

PROCESS FOR THE RECOVERY OF FURFURAL

Field of the Invention

The present invention relates to a process for the extraction of furfural from a biphasic dehydration reaction mixture in a resource- and energy-efficient manner by the use of one or more adsorption units to enrich the furfural content of an organic solvent stream.

Background of the Invention

Furfural is a useful precursor for industrial chemicals such as in producing furan and its derivatives.

Furfural may be produced from the hydrolysis of feedstock including lignocellulosic biomass. Lignocellulosic biomass includes mainly cellulose, hemicelluloses and lignin, and smaller amounts of protein. Hemicelluloses are a branched polysaccharide of heterogeneous monosaccharide content whose molecular structure includes the five-carbon monosaccharides (otherwise generically referred to as“pentoses”) xylose and arabinose, as well as the six-carbon monosaccharides (otherwise generically referred to as“hexoses”) mannose, galactose and rhamnose. Due to their xylose and arabinose content, hemicelluloses are a suitable source of monomeric and polymeric pentoses. In comparison, cellulose is a linear- polysaccharide made up of polymerised glucose (a six-carbon

monosaccharide/hexose). Compared to cellulose, hemicelluloses are easier to breakdown into their constituent monosaccharides.

A commercially available feedstock comprising lignocellulosic biomass includes bagasse which is the fibrous matter that remains after sugarcane or sorghum stalks are crushed and their juices are extracted.

An established continuous process for the production of furfural from bagasse is the Rosenlew process, the details of which are discussed in“The Chemistry and Technology of Furfural and its Many By-Products”, lst Edition, K. Zeitsch, pages 48-51 and 303-306. However, other processes for the production of furfural also exist.

For example, W02012041990 describes the production of furfural from bagasse-derived hemicellulose, via its gaseous acid catalysed hydrolysis to pentoses, which are then dehydrated to produce furfural.

For example, WO2016025678 describes the production of furfural, where initially hemicellulose is hydrolysed in a solution comprising a-hydroxysulfonic acid, a portion of the a-hydroxysulfonic acid is then removed from the hydrolysis reaction product to produce an acid-removed stream, and finally the acid-removed stream is subjected to a dehydrating step to produce furfural.

For example, WO2016025679 describes a hydrolysis step, which is buffered to less than pH 1, followed by a dehydrating step to produce furfural.

In both WO2016025678 and WO2016025679, during the dehydration reaction step, a“biphasic” dehydration reaction mixture is formed by the addition of “a water-immiscible organic phase” (i.e. a solvent) into the dehydration reaction mixture. The solvent extracts a portion of the furfural produced in the biphasic dehydration reaction mixture. The biphasic dehydration reaction mixture is then separated into an aqueous product stream and an organic product stream comprising a portion of furfural. However, WO2016025678 and WO2016025679 do not disclose how furfural can be fully recovered and purified from the organic product stream comprising furfural. Further, it is not clear from the disclosures in

WO2016025678 and WO2016025679 how the efficiency of furfural recovery from the dehydration reaction mixture can be improved.

Lee S.C & Park S. (2016) have disclosed in Biotechnology 216, pages 661- 668, that powdered activated charcoal may be used to remove contaminants such as furans from simulated biomass hydrolysates. The example of a furan provided is furfural. However, Lee & Park does not discuss furfural recovery from the biphasic dehydration reaction mixtures/compositions comprising organic solvent(s) and does not disclose how to selectively desorb furfural from the powdered activated charcoal.

Palkovits (2014) has disclosed in ACS Sustainable Chem. Eng. 2, pages 2407-2415, that hyper-branched carbon polymers made by crosslinking alkylation of dichloro -biphenyl have a very high surface area, pore volume and hydrophobicity, and will adsorb hydroxymethylfurfural with high selectivity and with a high uptake. However, Palkovits does not discuss furfural recovery from the biphasic dehydration reaction mixtures/compositions comprising organic solvent(s) and does not disclose how to selectively desorb the furfural from the hyper-branched carbon polymer.

It would, therefore, be advantageous to provide a process for the recovery of furfural in which the efficiency of furfural recovery from the biphasic dehydration reaction mixture can be improved, for example by recovering residual furfural from the biphasic dehydration reaction mixture’s aqueous phase, and transferring such furfural into such reaction mixture’s organic phase, thus increasing the furfural content of the organic solvent stream used to extract furfural from the biphasic dehydration reaction mixture, leading to the lowering the energy duty of furfural extraction from such organic solvent.

Summary of the Invention

Accordingly, the present invention provides a process for a process for the extraction of furfural from a biphasic composition having an organic phase comprising furfural and an organic solvent. The process includes subjecting the biphasic composition to a liquid-liquid separation step in a liquid-liquid separator to provide an organic phase including the organic solvent and a portion of the furfural and an aqueous phase including a remainder portion of the furfural. The process also includes conveying a portion of the aqueous phase to an adsorption unit to adsorb a first amount of the remainder portion of the furfural and to form a furfural- depleted stream. The process further includes conveying a portion of the organic phase to the adsorption unit to desorb a second amount of the first amount of the remainder portion of the furfural into a furfural-rich stream.

Brief Description of the Drawing

Figure 1 shows a simplified schematic diagram of an embodiment of the process according to the invention with a solvent having a boiling point higher than furfural.

Figure 2 shows a simplified schematic diagram of an embodiment of the process according to the invention with a solvent having a boiling point lower than furfural.

Figure 3 shows a simplified schematic diagram of another embodiment of the process according to the invention with a solvent having a boiling point higher than furfural.

Figure 4 shows a simplified schematic diagram of another embodiment of the process according to the invention with a solvent having a boiling point lower than furfural. Detailed Description of the Invention

The following description of the variations is merely illustrative in nature and is in no way intended to limit the scope of the disclosure, its application, or uses. The description and examples are presented herein solely for the purpose of illustrating the various embodiments of the disclosure and should not be construed as a limitation to the scope and applicability of the disclosure.

The terminology and phraseology used herein is for descriptive purposes and should not be construed as limiting in scope. Language such as“including,” “comprising,”“having,”“containing,” or“involving,” and variations thereof, is intended to be broad and encompass the subject matter listed thereafter, equivalents, and additional subject matter not recited.

Also, as used herein any references to“one embodiment” or“an embodiment” means that a particular element, feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. The appearances of the phrase“in one embodiment” in various places in the specification are not necessarily referring to the same embodiment.

The present inventors have found that the process for the extraction of furfural according to the present invention provides a higher yield of furfural than known processes, consumes less energy to produce each tonne of furfural, and consumes less material, in particular, less organic solvent, suitably, by enhancing the extraction of furfural from the biphasic dehydration reaction mixture (i.e. enhancing the level of furfural contained in the‘organic phase’ before the organic phase is distilled), and by reducing the loss of furfural via the aqueous waste by reducing the level of furfural remaining in the‘aqueous phase’.

In the process according to the present invention, furfural is extracted from the“biphasic” dehydration reaction mixture referred to in WO2016025678 and WO2016025679. The biphasic dehydration reaction mixture comprises an aqueous phase and an organic phase comprising furfural and an organic solvent.

The biphasic dehydration reaction mixture can be derived from a pentose dehydration step wherein monomeric and polymeric pentoses are dehydrated at an elevated temperature.

In turn, the monomeric and polymeric pentoses used for said dehydration step may be produced by hydrolysing lignocellulosic biomass in the presence of at least one inorganic acid, as described in WO2016025678 and WO2016025679.

Preferably, the pentose dehydration step is carried out at elevated

temperatures of at least l00°C, more preferably at least 11 CPC, and even more preferably at least l40°C. Preferably, the pentose dehydration step is carried out at elevated temperatures of at most 250°C, more preferably at most 200°C, and even more preferably at most l50°C.

Preferably, the pentose dehydration step is carried out for a period of at least 1 second, more preferably at least 5 minutes, even more preferably at least 10 minutes and most preferably at least 30 minutes. Preferably, the pentose dehydration step is carried out for a period of at most 24 hours, more preferably at most 12 hours, even more preferably at most 5 hours and most preferably at most 2 hours.

The biphasic dehydration reaction mixture comprises furfural, water, an organic solvent, and aqueous components. The organic solvent may have a boiling point higher than the boiling point of furfural or lower than the boiling point of furfural. In a preferred embodiment, the organic solvent has a boiling point higher than the boiling point of furfural. The organic solvent may be an aromatic solvent, a phenolic solvent, or mixtures thereof.

Due to the immiscibility of the organic solvent with the aqueous components of the dehydration reaction mixture, the organic solvent’s presence in the dehydration reaction mixture leads to the formation of the biphasic dehydration reaction mixture. If this mixture is allowed to settle, the organic solvent will separate from the aqueous phase of the dehydration reaction mixture to form an organic phase that is distinct from the aqueous phase.

Suitably, furfural formed in the aqueous phase has a preference to partition into the organic solvent rather than remain in the aqueous phase. The partitioning of furfural into the organic solvent forms the organic phase. The extent of this partitioning depends on the partition coefficient of furfural with respect to water and the selected organic solvent. Such partitioning is not absolute, and depending on the selected organic solvent, the proportion of furfural in the organic phase in

comparison to its proportion in the aqueous phase will vary, such that not all the furfural from the dehydration reaction mixture will partition into the organic phase, leading to an amount of unextracted furfural remaining in the aqueous phase. For example, in the presence of equal parts by weight of water and an aromatic solvent, about 80% of the furfural will partition into the aromatic solvent, while the remaining about 20% will remain in the aqueous phase. The partition coefficient may also depend on temperature.

In one embodiment, the organic solvent may be added to the aqueous dehydration reaction mixture at the start of the pentose dehydration step, or part way through it.

In other embodiments, the organic solvent may also be added after the completion of the pentose dehydration step, to the aqueous dehydration product stream, such as if the pentose dehydration step did not occur in the presence of the organic solvent.

In some embodiments, the source of the organic solvent added to the dehydration reaction mixture may be from a fresh source of the organic solvent, or may be from a stream recycled from one or more steps downstream of the biphasic dehydration reaction. The organic solvent may also be a mixture in varying proportions of both fresh and recycled organic solvent.

If the organic solvent is added to the biphasic dehydration reaction mixture at the start of, or part way through the pentose dehydration step, simultaneous with its production, furfural will partition predominantly into the organic phase. The level of furfural partitioning into the organic phase will continue to the extent possible in accordance with the relevant partitioning coefficient.

Adding the organic solvent to the biphasic dehydration reaction mixture at the start of, or part way through the pentose dehydration step, enables the simultaneous extraction of furfural from the dehydration reaction mixture, thus protecting furfural from degradation by removing it from the dehydration reaction mixture.

In some embodiments, the aqueous phase to total organic solvent phase has a ratio of at least 1: 0.05 by volume, more preferably said ratio is at least 1 : 0.1 by volume, even more preferably said ratio is at least 1 : 0.25 by volume, most preferably said ratio is at least 1 : 0.4 by volume.

In some embodiments, the aqueous phase to total organic solvent ratio is at most 1 : 2.5 volume, more preferably said ratio is at most 1 : 1.25 volume, even more preferably said ratio is at most 1 : 0.75 volume, most preferably said ratio is at most 1 : 0.6 volume.

In some embodiments, a mixture of organic solvents may include organic solvents having a boiling point higher than furfural and organic solvents having a boiling point lower than furfural. In a preferred embodiment, a mixture of organic solvents, each with a boiling point higher than that of furfural, may be used.

In some embodiments, the aromatic solvent is selected from compounds such as, but not limited to, l-ethyl-2,3-dimethylbenzene,l-ethyl-2,5- dimethylbenzene, 1 -ethyl-2, 4-dimethylbenzene, l-ethyl-3,4-dimethylbenzene,

1 ,2,3,5-tetramethylbenzene, 1 ,2,3,4-tetramethylbenzene, 1 ,2,4,5-tetramethylbenzene, naphthalene, l-methylnaphthalene, 2-methylnaphthalene, n- and sec-propyl- methyl benzenes (with the methyl group located in 2-, 3-, 4- or 5- position) n- and sec-butyl benzene and n- and sec-pentyl benzene. The aromatic solvent may also be selected from compounds such as, but not limited to, dimethyl naphthalene, ethyl

naphthalene, diethyl naphthalene, methyl ethyl naphthalene, propyl naphthalene, butyl naphthalene, pentyl naphthalene, hexyl naphthalene, methyl propyl

naphthalene, methyl butyl naphthalene, methyl pentyl naphthalene, methyl hexyl naphthalene. Suitable alkylated naphthalenes can also include, for example,

AROMATIC® 200 fluid, AROMATIC® 200 ND fluid, AROMATIC® 150 fluid, or AROMATIC® 150 ND fluid, all available from Exxon-Mobil. Suitable alkylated naphthalenes also include AROMATIC® 100 fluid available from Shell Oil

Company. The aromatic solvent may also be selected from compounds such as toluene, benzene, m-, p-, o- xylenes, cymene, and cumene.

In some embodiments, the aromatic solvent has a ratio of aromatic carbons to aliphatic carbons of greater than 1. If the aromatic solvent is a pure compound, the ratio of aromatic carbons to aliphatic carbons will be evident to the skilled person. However, if the aromatic solvent is a mixture of one or more of such compounds, a method of determining the ratio of aromatic carbons to aliphatic carbons may be by subjecting the aromatic solvent mixture to ¹³C NMR analysis and obtaining a ratio of the peaks representing the aromatic and aliphatic moieties by techniques known in the art. In some embodiments, the aromatic solvent is selected from benzene, alkyl benzene compounds of 7 or more carbons, naphthalene, and alkyl naphthalene compounds of 11 or more carbons.

In some embodiments, the phenolic solvent may be selected from the group consisting of, but not limited to, propyl guaiacol, propyl syringol, guaiacyl propanol, syringyl propanol, nonyl phenol, o-, m-, p- substituted cresols, guaiacol, 2-methoxy- 4-propylphenol, eugenol, sec-butyl phenol, 2,6-xylenol, 2,5-xylenol, tert-butyl phenol, pentyl phenol, hexyl phenol, and dodecyl phenol.

In one embodiment, the phenolics solvent may be sec-butyl phenol or tert- butyl phenol.

In another embodiment, the organic solvent is a mixture of aromatic and phenolic solvents, in particular, a mixture of alkylated naphthalene and alkylated phenolic solvents.

In embodiments of the invention, the organic phase includes the organic solvent, a portion of the furfural, and heavy soluble by-products and the aqueous phase comprises a remainder portion of the furfural, the aqueous dehydration reaction mixture, heavy soluble by-products and the other reactants of the

dehydration reaction mixture, such as water and organic acids. The aqueous phase may also comprise a small fraction of the organic solvent.

To increase the overall yield of furfural production, instead of the remainder portion of furfural in the aqueous phase being discarded as a waste stream, the furfural content in the aqueous phase can be extracted by conventional means such as distillation, which is energy intensive due to factors such as the formation of a furfural-water azeotrope that has a boiling point very close to that of water and is, thereby, difficult to separate from water. Further, additional hardware, such as distillation column(s), will be needed to undertake the extraction of the remainder portion of furfural from the aqueous phase. Therefore, a simpler and a more energy efficient way is needed to recover the residual furfural in the aqueous phase.

In some embodiments, an adsorption unit which can adsorb furfural from an aqueous environment, and release furfural to an organic environment, can be used to adsorb furfural from the aqueous phase, and release it into the organic phase. Such adsorption unit, therefore, can be deployed in the process to enrich the furfural content of the organic phase by transferring some of the remainder portion of furfural in the aqueous phase into the organic phase. By such transfer, the furfural concentration of the organic phase can increase, and lead to, for example, a more energy efficient distillation of furfural from the organic phase.

Figure 1 shows a simplified schematic process line up diagram of an embodiment of a process according to the present invention, illustrating the supply of a biphasic dehydration reaction mixture (2) from the dehydration reactor (1) to a liquid-liquid separator (3), wherein the latter phase separates to provide an aqueous phase (4) and an organic phase (5).

The organic phase (5) comprises the organic solvent and a portion of the furfural. The aqueous phase (4) comprises a remainder portion of the furfural.

Preferably, the liquid- liquid separator (3) may be operated at a temperature of at most 200°C, more preferably at a temperature of at most l80°C, even more preferably at a temperature of at most l60°C, even more preferably at a temperature of at most l40°C, so long as the liquid separates into two phases at the separation temperature.

Preferably, the liquid- liquid separator (3) may be operated at a temperature of at least ambient temperature, more preferably at a temperature of at least 20°C, even more preferably at a temperature of at least 60°C, even more preferably at a temperature of at least 90°C, and most preferably at a temperature of at least l00°C, so long as the liquid separates into two phases at the separation temperature.

The liquid-liquid separation step is carried out in any suitable liquid-liquid separator as would be known to the person skilled in the art.

Prior to entering the liquid- liquid separation step, optionally the biphasic dehydration reaction mixture (2) may be routed through a solid/liquid separation step to remove any insoluble matter that may have been formed during the dehydration step, and which may otherwise negatively interfere with the separation of the organic phase from the aqueous phase, or a later separation or purification steps.

In some embodiments, the adsorption unit (6) may be operated in a swing- type operation. Following phase separation, as a first step, a quantity of the aqueous phase (4) is conveyed from the liquid- liquid separator (3) via a line to an adsorption unit (6). As the aqueous phase (4) flows through the adsorption unit (6), a quantity of the furfural from the aqueous phase (4) is adsorbed and retained by the adsorption unit (6), resulting in the production of a furfural-depleted (aqueous) stream (8) that exits the adsorption unit (6).

To increase the furfural content of the organic phase (5), after the absorption unit (6) adsorbs and retains a quantity of furfural from the aqueous phase (4) that has flowed through it, the adsorbed/retained furfural can be desorbed into the organic phase. To achieve this, as a second step, the flow of the aqueous phase (4) to the absorption unit (6) is stopped, and instead, only the organic phase (5) is conveyed from the liquid- liquid separator (3) to the adsorption unit (6) via a line.

The furfural that was adsorbed/retained by the adsorption unit (6) can thus be desorbed/released into the organic phase, and a furfural-rich stream is produced (7).

When to stop the flow of the aqueous phase (4) and start the flow of the organic phase (5) may be determined by one of ordinary skill in the art. In some embodiments, an unacceptable level of furfural may be detected in the furfural- depleted (aqueous) stream (8), prompting a swing-type operation to commence.

Preferably, the adsorption may be carried out at a temperature of at least 30°C, more preferably at a temperature of at least 40°C, and most preferably at a

temperature of at least 50°C.

Preferably, the adsorption may be carried out at a temperature of at most l20°C, more preferably at a temperature of at most l00°C, and most preferably at a temperature of at most 70°C.

Preferably, the desorption may be carried out at a temperature of at least 30°C, more preferably at a temperature of at least 60°C, and most preferably at a

temperature of at least 70°C.

Preferably, the desorption may be carried out at a temperature of at most l20°C, more preferably at a temperature of at most l00°C, and most preferably at a temperature of at most 90°C.

Figure 1 depicts an embodiment having the organic solvent with a boiling point higher than furfural. The furfural-rich stream (7) exits the adsorption unit (6) and is conveyed to a distillation column (9) to distill the furfural from the furfural- rich stream as a top stream (10). The distillation column (9) may be an atmospheric distillation column or a vacuum distillation column. The distillation of the furfural- rich stream (7) also produces a bottom stream (11) comprising the organic solvent.

Figure 2, depicts an embodiment having the organic solvent with a boiling point lower than furfural. The furfural-rich stream (7) exits the adsorption unit (6) and is conveyed to a distillation column (9) to distill the furfural from the furfural- rich stream as a bottom stream (10). The distillation of the furfural-rich stream (7) also produces a top stream (11) comprising the organic solvent. Reference numbers remain the same throughout the figures for items identical or similar to those of Fig.

1.

The adsorption unit (6) contains a solid adsorbent. In some embodiments, the solid adsorbent has a high surface area and/or high pore volume. The solid adsorbent may be a metal oxide (such as a zirconia, a silica or a titania) or a mixed oxide (such as aluminosilicates). The metal oxide may be micro-, meso-, or mega-porous. In some embodiments, the solid adsorbent may also comprise polymers or polymeric resins. In other embodiments, the solid adsorbent may also comprise carbon, such as in the form of soot, carbon black, activated carbon, carbon nanotubes, hyper branched polymeric, graphene or graphitic carbon.

Activated carbon is a form of carbon processed to have high surface area or microporosity. For example, one gram of activated carbon may have a surface area in excess of 500 m².

Activated carbon may be produced from materials of biological origin such as peat, wood, nutshells, coconut husk or coir, as well as from mineralised matter such as coal and lignite. Such materials are subjected to either‘physical’ reactivation, and/or to‘chemical’ reactivation, both as known in the art.

The‘activation’ of the carbon is a result of either exposure to an oxidising atmosphere (during physical reactivation,) or to an acid, strong base or a salt followed by carbonisation (during chemical reactivation).

Whichever way active carbon is produced, the high microporosity makes activated carbon an excellent candidate for its use as an adsorption medium, as its ability to adsorb, bind or interact with other compounds is enhanced by its activated high surface area.

Carbon black on the other hand is produced by the incomplete combustion or thermal decomposition of gaseous or liquid hydrocarbons. It typically has a lower surface area than active carbon.

Depending on the production method, the solid adsorbent comprising carbon in the adsorption unit (6) may have hydrophilic or hydrophobic surface properties.

Suitably, the activated carbon, the carbon black, graphite, the carbon nanotubes or the carbon nanofibers that may be used as the carbon absorbent can be sourced from commercial suppliers known to the skilled person.

In some embodiments, the carbon may be in the form of powder. The fineness of the powder may vary, and the fineness may be chosen according to how a given powder in a given adsorption unit affects the flow pressure across the adsorption unit. Carbon in the form of larger grains or pellets may be chosen if the resistance to flow through the adsorption unit is to be reduced.

The adsorption unit (6) may be fixed-bed or a suspended bed. In the suspended bed case, the suspended bed may contain a liquid-solid disengagement zone based on hydrocyclone, settler, membrane or any other option known to persons skilled in the art.

In the embodiment described above, the supply of the aqueous phase (4) and the supply of the organic phase (5) to the adsorption unit (6) may be performed as a swing-type operation, requiring the alternating supply of the aqueous phase (4) and the organic phase (5) to the same adsorption unit (6) to enable alternating cycles of furfural adsorption and desorption to take place. This however can limit the processing capacity of the process, as during the supply of the aqueous phase (4) to the adsorption unit (6), the flow of the organic phase (5) must cease, and vice versa during the supply of the organic phase (5) to the adsorption unit (6).

Figures 3 and 4 show simplified schematic process line up diagram of an alternate embodiment of a process according to the present invention, wherein the assigned reference numerals refer to the same steps/streams as in Figures 1 and 2, except that the furfural-depleted (aqueous) stream (8), has been omitted from the Figures 3 and 4 solely to avoid crowding the figure. However, Figures 3 and 4 additionally depicts a second adsorption unit (6’), wherein both adsorption units (6 and 6’) may have a furfural-depleted (aqueous) stream (8) exiting it. In some embodiments, there may be multiple adsorption units (6, 6’, 6”, etc.)

In these embodiments, as an alternative to the swing-type operation of alternating supply of the aqueous phase (4) and the organic phase (5) to the adsorption unit (6), the aqueous phase (4) and the organic phase (5) may be continuously supplied to multiple adsorption units (6, 6’, 6” etc.), each working in parallel with the other(s), thus providing continuous operation.

In such embodiments, the flow of the aqueous phase (4) and the organic phase (5) are directed to, and continuously supplied to, a different adsorption unit, with the flow to a given adsorption unit switching between continuous rounds of a quantity of the aqueous phase (4) followed by an amount of the organic phase (5).

For example, in such an embodiment, during the same time as a quantity of the aqueous phase (4) is supplied to adsorption unit (6), a quantity of the organic phase (5) is supplied to another adsorption unit (6’). Once such quantities of the aqueous phase (4) and the organic phase (5) are supplied as such, the flow direction of each phase switches, such that, a quantity of the aqueous phase (4) is now supplied to adsorption unit (6’), a quantity of the organic phase (5) is now supplied to adsorption unit (6). Such a supply cycle is then continuously repeated, thereby allowing each adsorption unit (6 and 6’) to go through alternating rounds of furfural adsorption from the aqueous phase and desorption into the organic phase.

Deploying more than one adsorption unit provides advantages that at least, firstly, the process can be operated continuously thereby increasing the throughput, and at least, secondly, pairs of adsorption units can be taken out of use and serviced without shutting down the process of the present invention.

Other than having more than one adsorption unit, and the supply of the aqueous phase (4) and the organic phase (5) to such more than one adsorption units being arranged as described above, all other aspects of the process and the process line-up of the embodiments in Figures 3 and 4 are the same as in the embodiments of Figures 1 and 2, respectively.

In some embodiments, following desorption of the furfural from the adsorption unit(s) (6, 6’ etc.) by the organic phase (5), the adsorption unit may undergo a solvent removal step to remove any residual organic phase / solvent remaining in the adsorption unit, so that the residual organic phase / solvent in the adsorption unit does not interfere with the next adsorption step. The solvent removal step may be a heating step or a vacuum step to evaporate any residual organic phase / solvent from the adsorption unit, or it may be a washing step, wherein a portion of the biphasic composition (2) is flushed through the adsorption unit and then recycled into the liquid-liquid separator (3) and/or the dehydration reactor (1). The heating step may be carried out by supplying an inert gas at a temperature above the boiling point of the organic solvent through the adsorption unit (6), or by other methods known to the skilled person, such the use of a heat jacket surrounding the adsorption unit.

Example 1

A process line up as depicted in Figure 1 was assessed for furfural extraction/separation/recovery using process modelling Aspen plus (Version 7.3) software licensed from Aspen Technology Inc., MA. The modelled process line-up was representative of a furfural extraction scheme according to the present invention from a biphasic composition / process stream comprising furfural.

The results obtained in this Example are representative of expected furfural recovery rates, fraction of furfural recovery from feed stream, furfural purity, heat duty (MW), and steam usage measured in tonne of steam/tonne of furfural produced.

Thermodynamic data contained in‘NRTL-HOC property method’ set was used in this simulation.

Steam consumption in the process line up was determined on the basis of using 4.48 MPa high pressure steam.

The biphasic dehydration reaction mixture (2) from the dehydration reactor (1) comprises water, furfural, acetic acid (HAC-D), and 1 -methyl naphthalene (1- MNP) (representative of an organic solvent with a boiling point higher than that of furfural).

After the phase separation in liquid-liquid separator (3), the aqueous phase (4) is passed through an adsorption bed (6) to adsorb the remainder portion of furfural in the aqueous phase (4).

Once, the furfural is adsorbed, the organic phase (5) is then passed through the adsorption bed (6) to desorb the furfural in the organic phase thereby increasing the furfural concentration into the furfural-rich stream (7).

To make the process continuous, multiple adsorption bed can be used wherein one bed could be in the adsorption mode while the other bed is in the desorption mode.

This separation scheme enables the extraction of furfural from the biphasic dehydration reaction mixture, produces a furfural composition with high purity and allows for the recycle of solvent for re-use in the same process, either in the dehydration reactor and/or the absorber.

Table 1 presents all the process stream data output.

Tables 2 and 3 give process operating conditions and a results summary for distillation column (9) and liquid-liquid separators (3) used in the process line-up. Table 4 presents the summary of results for furfural extraction/separation scheme.

Based on this simulation, the results set out in Table 1 show that the furfural- rich stream (7) is enriched with a further 25% of the furfural which was in the dehydration reaction mixture (2), and which would otherwise have remain unextracted in the aqueous phase (4), thus increasing the overall yield of the process according to the present invention.

Based on this simulation output, the separation process line up according to the present invention consumes about 2.8 tonne steam/tonne furfural produced. This is about 72% reduction in steam usage compared to consumption of 10 tonne steam/tonne furfural produced in the state-of-the-art Rosenlew’s process for commercial furfural production.

Table 1: Stream Summary Results

Table 2: Distillation Column Summary

Table 3: Liquid- Liquid Separator Summary

Table 4: Separation Scheme Results Summary

Example 2

About 1 g of furfural was added to 100 g water in a screw-top sealable glass bottle to make an aqueous furfural solution, to represent the‘aqueous phase’. About

10 g of activated charcoal Norit® (Norit CA1, from wood, chemically activated, powder from Sigma- Aldrich) was added this aqueous furfural solution, and the mixture was stirred for about 1 hour.

The mixture was then kept still for about 24 hours allowing the activated charcoal to settle to the bottom of the bottle.

The aqueous furfural solution was then removed from the bottle and submitted for HPLC analysis for furfural concentration. HPLC analysis of the samples of the aqueous furfural solution after charcoal treatment (representing the ‘aqueous phase’) showed that its furfural concentration dropped from 1 wt% to 0.009 wt%, indicating that over 99% of furfural was adsorbed by the activated charcoal.

To the activated charcoal remaining in the bottle, a solvent mixture containing about 50 g of 4 wt% furfural in A200ND (Aromatic 200 ND solvent) was added and stirred for about an hour and then left still for about 24 hours, all at ambient temperature. A 2 ml sample was removed for GC analysis for furfural concentration. The GC results of the room temperature solvent mixture (representing the‘organic phase’) showed that its furfural concentration increased from 4 wt% to 4.72 wt% after“washing” of the activated charcoal.

To understand the effect of heat on the desorption/recovery of furfural from the activated charcoal, the remaining charcoal/solvent mixture was heated at about 60 °C for about 4 hours in a capped glass. After four hours, a sample of the hot solvent mixture, was taken and analysed by GC.

After increasing the temperature, the GC results of the 60 °C solvent mixture (representing the‘organic phase’) showed that its furfural concentration had increased to 5.16 wt% after heating. Together, these represent about 36% furfural recovery from the charcoal at room temperature, and about 58% furfural recovery from the charcoal upon heating to 60 °C.

Example 3

About 1.4 g of furfural was added to 100 g water in a screw-top sealable glass bottle to make an aqueous furfural solution, to represent the‘aqueous phase’. About 10 g of activated charcoal Norit® (Norit CA1, from wood, chemically activated, powder from Sigma- Aldrich) was added this aqueous furfural solution, and the mixture was stirred for about 1 hour.

The aqueous furfural solution was then removed from the from the bottle and submitted for HPLC analysis for furfural concentration. HPLC analysis of the samples of the aqueous furfural solution (representing the‘aqueous phase’) showed that its furfural concentration dropped from 1.4 wt% to 0.02 wt%, indicating that over 99% of furfural was adsorbed on the activated charcoal.

To the activated charcoal remaining in the bottle, a solvent mixture containing about 50 g pure toluene was added and stirred for about 1 hour, then left still for about 24 hours, all at ambient room temperature. A 2 ml sample of the room temperature solvent mixture (representing the‘organic phase’) showed that its furfural concentration increased from 0 wt% to 1 wt%, representing about 35% furfural recovery at room temperature after“washing” of the activated charcoal.

Applicants theorize that by utilizing an adsorption unit which can adsorb furfural from an aqueous environment, and release furfural to an organic

environment, a more energy efficient process can increase recovery of furfural.

Although a few embodiments of the disclosure have been described in detail above, those of ordinary skill in the art will readily appreciate that many

modifications are possible without materially departing from the teachings of this disclosure. Accordingly, such modifications are intended to be included within the scope of this disclosure as defined in the claims.

Claims

1. A process for the extraction of furfural from a biphasic composition (2)

comprising furfural and an organic solvent, said process comprising:

(a) subjecting the biphasic composition (2) to a liquid-liquid separation step in a liquid-liquid separator (3) to provide:

an organic phase (5) comprising the organic solvent and a portion of the furfural, and

an aqueous phase (4) comprising a remainder portion of the furfural;

(b) conveying a portion of the aqueous phase (4) to an adsorption unit (6) to adsorb a first amount of the remainder portion of the furfural and to form a furfural-depleted stream (8); and

(c) conveying a portion of the organic phase (5) to the adsorption unit (6) to desorb a second amount of the first amount of the remainder portion of the furfural into a furfural-rich stream (7).

2. A process according to Claim 1, wherein steps (b) and (c) are repeated with

further portions of the aqueous phase (4) and the organic phase (5).

3. A process according to Claims 1 or 2, wherein steps (b) and (c) are carried out using more than one adsorption unit.

4. A process according to any of Claims 1 to 3, wherein the furfural-rich stream (7) is subjected to a distillation step (9) to provide:

a stream (10) comprising furfural, and

a stream (11) comprising the organic solvent.

5. The process according to any of Claims 1 to 4, wherein the organic solvent has a boiling point higher than furfural.

6. The process according to any of Claims 1 to 4, wherein the organic solvent has a boiling point lower than furfural.

7. The process according to any of Claims 1 to 6, wherein the organic solvent is an aromatic solvent, a phenolic solvent, or a mixture thereof.

8. The process according to Claim 7, wherein the aromatic solvent is selected from the group consisting of 1 -ethyl-2, 3-dimethylbenzene,l -ethyl-2, 5-dimethylbenzene, 1 -ethyl-2, 4-dimethylbenzene, l-ethyl-3,4-dimethylbenzene, 1, 2,3,5- tetramethylbenzene, 1 ,2,3,4-tetramethylbenzene, 1 ,2,4,5-tetramethylbenzene, naphthalene, l-methylnaphthalene, 2-methylnaphthalene, n- and sec-propyl- methyl benzenes (with the methyl group located in 2-, 3-, 4- or 5- position) n- and sec-butyl benzene and n- and sec-pentyl benzene, dimethyl naphthalene, ethyl naphthalene, diethyl naphthalene, methyl ethyl naphthalene, propyl naphthalene, butyl naphthalene, pentyl naphthalene, hexyl naphthalene, methyl propyl naphthalene, methyl butyl naphthalene, methyl pentyl naphthalene, methyl hexyl naphthalene, toluene, benzene, m-, p-, o- xylenes, cymene, cumene or any combination thereof.

9. The process according to Claim 7, wherein the phenolic solvent is selected from the group consisting of, but not limited to, propyl guaiacol, propyl syringol, guaiacyl propanol, syringyl propanol, nonyl phenol, o-, m-, p- substituted cresols, guaiacol, 2-methoxy-4-propylphenol, eugenol, sec-butyl phenol, 2,6-xylenol, 2,5- xylenol, tert-butyl phenol, pentyl phenol, hexyl phenol, dodecyl phenol or any combination thereof.

10. The process according to any of Claims 1 to 9, wherein following step (c), the adsorption unit (6) undergoes a solvent removal step to remove any residual organic phase in the adsorption unit.

11. The process according to any of Claims 1 to 10, wherein the organic solvent is a mixture comprising alkylated phenols and alkylated naphthalenes.

12. The process according to any of Claims 1 to 10, wherein the organic solvent comprises alkylated naphthalenes.

13. The process of claim 4, wherein the stream (11) comprising the organic solvent is recycled to a biphasic dehydration reactor.