WO2021178329A1

WO2021178329A1 - Separation of furan-containing compounds

Info

Publication number: WO2021178329A1
Application number: PCT/US2021/020331
Authority: WO
Inventors: Shawn EADY; Sabrina CONRAD; Trenton WILKE; Christoph Krumm
Original assignee: Sironix Renewables Inc
Current assignee: Sironix Renewables Inc
Priority date: 2020-03-03
Filing date: 2021-03-01
Publication date: 2021-09-10
Anticipated expiration: 2022-09-03

Abstract

A method of forming an immobilized and separated Diels-Alder adduct is disclosed. This method includes a Diels-Alder reaction between a surface-supported dienophile and a furan-based diene to form an immobilized and separated Diels-Alder adduct. The reversible Diels-Alder reaction can separate a furan-containing compound in a mixed chemical stream with the surface-supported dienophile being a n-propylmaleimide alkylated on a silica support and a furan-based diene being methyl furan.

Description

SEPARATION OF FURAN-CONTAINING COMPOUNDS

RELATED APPLICATION

[1] This disclosure claims priority to US provisional patent application number 62/984,388, filed on March 3, 2020.

TECHNICAL FIELD

[2] This disclosure generally relates to methods for separating biomass-derived furanics as well as compositions including furan.

BACKGROUND

[3] Furanics, which can be produced from multiple bio-renewable feedstocks including sugars and cellulose, are difficult to separate from their biomass reactant streams. Despite decades of reaction development, conversion of the biomass feedstocks to furanics remains non-quantitative, typically having limits at approximately 50-60% for products such as hydroxymethylfurfural (HMF).

[4] While these reactivity limitations have not completely impeded the scaling of biomass-derived furanic production, they have made chemical separation of the product and reactant stream an additional engineering hurdle in sourcing bio-renewable consumer products and fuels. However, separation of the furanic products from the reaction stream remains a challenge, and several components including Cri and Ce sugars, sugar degradation products, and lignin are particularly difficult to separate. The presence of these residual reactants in the product stream has a negative impact on further chemical processing and creates challenges for applications requiring high purity furanics.

SUMMARY

[5] The present disclosure describes embodiments that can improve the efficiency of separations for biomass-derived furanics. Such embodiments can be useful in a variety of applications, including in a range of consumer products and fuels.

[6] Furanics, or structures containing the furan chemical moiety, such as HMF and furfural have a wide range of applications in multiple major chemical industries, including use in polymers, pharmaceuticals, fuels, wood treatment, agriculture and as chemical solvents. End products derived from furanics also have many applications; levulinic acid is used in fuels, fragrances, flavoring, animal feed, and antifreeze products; formic acid is used in leather tanning, decalcification, and deicing; caprolactone is used in coatings, adhesives, bioplastics and foams.

[7] Design of efficient separation technologies for furanics from mixtures serves to improve scalability of existing chemical production routes such as dehydration of sugars, pyrolysis of biomass, and enzyme catalysis. Examples of processes benefitting from improved efficiency in chemical separations are: (1) complex chemical mixtures such as those obtained from biomass pyrolysis are unstable and temperature sensitive, and (2), chemical reactions with limited conversion, such as those to convert sugars to HMF, and (3), chemical product mixtures containing compounds that cannot be efficiently separated via traditional methods (e.g. distillation, crystallization). Better separation efficiency improves process economics for production of furanics, enabling application for use in fuels, polymers, bioproducts, surfactants, solvents, and other common furanics applications.

[8] One exemplary embodiment includes a method of forming an immobilized and separated Diels-Alder adduct. This method embodiments includes a Diels-Alder reaction between a surface-supported (e.g., tethered) dienophile and a furan-based diene to form an immobilized and separated Diels-Alder adduct. The following reaction scheme shows one example of such a method embodiment, where a reversible Diels-Alder reaction separates a furan-containing compound in a mixed chemical stream with the surface-supported (e.g., tethered) dienophile being a n-propylmaleimide alkylated on a silica support and a furan- based diene being methyl furan:

DielS_"Akier adduct

[9] Another method embodiment includes the step of performing a Diels-Alder reaction between a dienophile and a furan-based diene. This method embodiment also includes the step of forming an immobilized and separated Diels-Alder adduct from the Diels-Alder reaction.

[10] In a further embodiment of this method, the dienophile is selected from the group consisting of dienophiles set forth in Table 1.

[11] In a further embodiment of this method, the dienophile is a surface-supported dienophile. [12] In a further embodiment of this method the furan-based diene is selected from the group consisting of dienes set forth in Table 1.

[13] In a further embodiment of this method, the Diels-Alder reaction is a reversible Diels- Alder reaction. In one application of this embodiment, the reversible Diels-Alder reaction separates a furan-containing compound in a mixed chemical stream. In another application of this embodiment, the dienophile includes a n-propylmaleimide alkylated on a silica support, and the furan-based diene includes a methyl furan or an alkoylmethylfuran. As one such example, the alkoylmethylfuran includes 2-Dodecoyl 5-Methylfuran. In an additional application of this embodiment, the furan-based diene includes an alkylfuran.

[14] In a further embodiment of this method, the Diels-Alder reaction is performed at a temperature range from 0-100°C. As one such example, the Diels-Alder reaction is performed at a temperature range from 0-60°C (e.g., at room temperature).

[15] In a further embodiment of this method, a molar ratio of the dienophile to the furan- based diene is in the range of 2-100.

[16] In a further embodiment of this method, the dienophile is supported on a heterogeneous support, and the Diels-Alder reaction is performed by passing the furan-based diene over the dienophile at the heterogeneous support. As one such example, when the dienophile is saturated with the furan-based diene, the passing of the furan-based diene over the dienophile is terminated. As an additional such example, when the dienophile is saturated with the furan-based diene, a temperature at the heterogeneous support is increased (e.g., increased from room temperature). For instance, when the temperature is increased, a retro Diels-Alder reaction can be performed. Performing the retro Diels-Alder reaction can release a pure furan-based product.

DETAILED DESCRIPTION

[17] The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides some practical illustrations for implementing exemplary embodiments of the present invention. Examples of elements, materials, compositions, and/or steps are provided below. Though those skilled in the art will recognize that many of the noted examples have a variety of suitable alternatives that are also within the scope of the present disclosure.

[18] As described herein, embodiments of the present disclosure can improve the efficiency of separations for biomass-derived furanics. As a result, furan-containing compounds may be able to be more cost competitive with traditional, non-renewable (e.g., petrochemical) compounds, thereby increasing the number of applications in which furan- containing compounds can be utilized.

[19] One exemplary embodiment of a synthesis process is depicted below as Scheme 1. Scheme 1 illustrates an exemplary reaction for a reversible Diels-Alder reaction for separation of a furan-containing compound in a mixed chemical stream.

Scheme 1

[20] The exemplary embodiment shown in Scheme 1 shows the Diels-Alder reaction between a surface-supported (e.g., tethered) dienophile, in this example shown as a n- propylmaleimide alkylated on a silica support, and a furan-based diene, in this example methyl furan, to form an immobilized and separated Diels-Alder adduct.

Scheme 2

[21] Another exemplary embodiment of a synthesis process is depicted below in Scheme 2. Scheme 2 illustrates the Diels-Alder reaction between a unsupported dienophile, in this example l,T-(Methylenedi-4,l-phenylene)bismaleimide, and a furan-based diene, in this example 2-dodecylfuran, which comprise the two soluble components that react in solution to afford an insoluble Diels-Alder adduct which may then be separated from the reaction effluent.

[22] Any variant of the general maleimide structure with Diels-Alder reactivity may be used, including, but not limited to, alternative maleimide derivatives such as n- pentylmaleimide and n-octylmaleimide. Other variants of the maleimide structure include bismaleimide compounds which contain two maleimide rings in a single molecule, including but not limited to l,l'-(Methylenedi-4,l-phenylene)bismaleimide. In addition, alternative dienophiles with Diels-Alder reactivity may be used, including, but not limited to, other cyclic alkenes such as maleic anhydride and benzoquinone, aliphatic alkenes and alkynes substituted with functional groups including, but not limited to, cyano groups, alcohols, aldehydes, carboxylic acids, esters, amines, and halides, as well as cyclic and aliphatic azo functional groups. A list of potential furanic and dienophile examples for use in the reversible Diels-Alder separation process is listed in Table 1. The support to which the dienophile is tethered and with which the furanic will reversibly bind to form the Diels-Alder adduct may also be varied, and may include, though not be limited to, zeolites such as silica, alumina, resins, and polymers. Supports may also include materials in which the dienophiles are integrated into the chemical structure; examples include polymers containing a dienophile repeating unit such as maleimide, maleic anhydride, or aliphatic alkene, alkyne or azo functional groups

[23] A list of furanics (dienes) and dienophiles that can be used in the reversible Diels- Alder separation process (e.g., of Scheme 1) is included in Table 1. References in this disclosure to “diene” can refer to any one or more of the dienes listed below in Table 1, and references in this disclosure to “dienophile” can refer to any one or more of the dienophiles listed below in Table 1. A list of possible supports for the immobilization of furanics in the separation process (e.g., of Scheme 1) is included in Table 2.

Table 1

Table 2

[24] One preferred iteration of the process, shown in Scheme 1, can use a silica-supported dienophile, in this preferred iteration the commercially-available silica-supported n- propylmaleimide, to form the Diels-Alder adduct with a furan-based compound, in this preferred iteration 2-methylfuran.

[25] An additional application for the method embodiments described herein is for the separation of furan-containing surfactant structures or precursors from other reagents or solvents, such as those found in the production process of oleo-furan sulfonate surfactants. Reversible Diels-Alder chemistry can be used for furan-containing intermediate molecules for producing surfactants, such as 2-dodecylfuran 2-dodecanoylfuran and 2 -methyl-5 - dodecanoylfuran (or any structural isomers or any similar structures with variable chain length or branching), as well as surfactant molecules such as 2-dodecylfuran-5-sulfonate, 2- dodecanoylfuran-5-sulfonate and 2-methyl-5-dodecanoylfuran-sulfonate (or any structural isomers or any similar structures with variable chain length or branching). A process for separating surfactants precursors such as alkylfurans from other reagents such as lauric acid could involve immobilized (e.g., tethered) maleimide molecules (or another dieneophile) on a solid substrate such as silica placed in a flow reactor held at a temperature conducive to Diels-Alder addition. Effluent from a reaction process step, such as the acylation of lauric acid with furan to produce alkylfurans, is fed to the dieneophile reaction bed, where alkylfurans react in a Diels-Alder reaction with the dieneophile. Other components of the mixture, such as lauric acid, readily flow through the reactor bed for recycle. Once the dieneophile material is saturated with alkylfuran product, the feed is stopped and the bed temperature is raised to promote the retro Diels-Alder reaction to release a pure alkylfuran product stream. This process is then repeated to produce semi-batch volumes of pure alkylfuran product. Practical iterations of this would have numerous parallel beds sequentially performing the same Diels-Alder separations process using the effluent from one continuous-flow reactor (e.g. acylation reaction).

[26] The following description provides exemplary details relating to reactions steps included in the embodiments, such as Scheme 1, described previously.

[27] As noted, various embodiments, such as Scheme 1, can include a Diels-Alder Reaction. The reaction of furan-based dienes with supported dienophiles typically involves the interaction of 4 p-electrons from the diene and 2 p-electrons from the dienophile initiating a cycloaddition step to form new s-bonds, resulting in the cyclized adduct.

[28] The reaction can be performed in a temperature range from 0-100°C in a variety of organic solvents, including acetone and methylethylketone, hydrocarbons including but not limited to pentane, hexane, and heptane, cyclohexane, and cyclopentane, aromatic organics including benzene, toluene, organic nitriles including acetonitrile, propionitrile, and butyronitrile, organic chlorocarbons including dichloromethane, dichloroethane, chloroform, alcohols including but not limited to methanol, ethanol, and isopropanol, ethereal solvents including but not limited to dimethyl ether, diethyl ether, and tetrahydrofuran, esters including but not limited to methyl acetate and ethyl acetate, water and finally the absence of solvent (neat).

[29] More preferably, solvent use will be limited to reviewed to be preferable by one or more solvent selection guides outlined by Byrne and coworkers, including but not limited to acetone, heptane, cyclohexane, toluene, xylene, acetontrile, methanol, ethanol, isopropanol,

1 -butanol, ethyl acetate and isopropyl acetate, cyclopentyl methyl ether, 2- methyltetrahydrofuran, tetrahydrofuran, water and finally the absence of solvent (neat).

[30] Most preferably solvent use will be limited to those reviewed to be preferable by all solvent selection guides outlined by Byme and co workers, including 1 -butanol, isopropylacetate, water and finally the absence of solvent (neat).

[31] The furanic compound is dissolved in the solvent or neat, and the dienophile is supported on a macromolecule that is dissolved in solution, supported on a heterogeneous solid in contact with the solution, or is integrated into the chemical structure of a macromolecule dissolved in solution or on the surface of a solid in contact with the reaction solution. This reaction has not to our knowledge been reported for use in separation of biomass-derived furanics from their reactant feedstocks, and it is not believed to be intuitive to someone skilled in the art to do so. Catalysts may be added to expedite the separation process, such as Lewis acids including but not limited to AgTOf, Hf(TOf)4, Ce(TOf)4, Sc(OTf2)3, BF3, and SnCh. Br0nsted acids including but not limited to HC1, H2S04, HCIO3, acetic acid, thiourea, amidinium salts, and Amberlyst-15, and Br0nsted bases including but not limited to Et3N, cinchonidine, cinchonine, quinidine, and n-butyl lithium.

[32] Reaction in the absence of catalyst is preferable to minimize the complexity of the separation process and avoid adding additional components, while the use of moderately low temperatures (0-60°C) is preferable to avoid reaction conditions that begin to favor the more endothermic retro-Diels-Alder reaction. Use of excess molar equivalents of the supported dienophile is preferable to improve conversion and assure more complete separation, with molar ratios of 2-100 of the dienophile to the furanic compound. Most preferably, the reaction would proceed at room temperature in the absence of catalyst and externally added solvent, being facilitated with a dienophile on a heterogeneous support as the biomass- derived furanic effluent stream is passed over the heterogeneous support, resulting in the Diels-Alder adduct supported on the solid and an effluent free of furanic product.

[33] As noted, various embodiments, such as Scheme 1, can include a retro-Diels-Alder Reaction. To reclaim the separated furanic products from the support, the retro-Diels-Alder reaction can proceed via a single step concerted cycloreversion mechanism yielding the two original reagents. The reaction can be performed in a temperature range from 60-200°C in a variety of organic solvents, including but not limited to all solvents listed for the Diels-Alder reaction above, or in the absence of solvent (neat). Catalysts may be added to expedite the separation process, including but not limited to the same catalysts used for the Diels-Alder reaction above. The Diels-Alder adduct immobilized on a support is heated to the desired temperature, initiating the retro-Diels-Alder reaction to release the furan-based compound in liquid or gaseous form, and allowing for recovery of the immobilized dienophile on/in its support. The furan compound may be recovered from the reaction solvent by distillation or in the absence of solvent may be condensed to liquid phase for collection.

[34] The proposed Diels-Alder and/or retro-Diels-Alder reactions can be carried out using any of the catalysts listed in Table 3. Table 3 lists possible catalyst classes and types which can be used for the reaction of the noted separations.

Table 3

Examples

[35] The following provides illustrative, non-limiting examples of both methods of synthesis and synthesized structures.

[36] A silica-supported Diels-Alder adduct was prepared following a combination of procedures. Diels-Alder reaction with n-propylmaleimide (1 g, 0.67 mmol/g loading, Sigma Aldrich) and 2-methylfuran (0.41 g, 5 mmol) was carried out at 60°C in n-heptane (Alfa Aesar). After 24 hours, the silica was removed by filtration and stirred with fresh n-heptane for 1 hour to remove weakly adsorbed 2-methylfuran. The silica was filtered a second time and dried en vacuo at room temperature (-0.1 MPa, 2 hours) to remove residual solvent. Thermal Gravimetric Analysis (TGA) coupled with Differential Scanning Calorimetry (DSC) showed an endothermic event at approximately 120°C. This is consistent with the retro-Diels- Alder reaction between furan and maleimide moieties. This signal was not present when testing unmodified silica without the maleimide moiety, nor was it present when unmodified silica was stirred with an identical concentration of 2-methylfuran at 60°C for 24 hours. Results for the TGA/DSC analysis of the resulting silica materials can be seen in Figure 1 below.

[37] Figure 1 shows plots of differential Scanning Calorimetry of silica modified with n- propylmaleidime after mixing with 2-methylfuran (lefthand plot of A) and 2-ethylfuran (lefthand plot of B), as well as for the unmodified silica control after mixing with 2- methylfuran (righthand plot of A) and 2-ethylfuran (righthand plot of B). Experiments were performed on a Mettler Toledo TGA/DSC 3+. Samples (ca. 10 mg) were loaded into 70 uL alumina crucibles and heated to 250°C at 10 min. A

Figure 1

[38] A Diels-Alders adduct that is self-separating from solution was prepared following a combination of procedures. Diels- Alder reaction with l,T-(Methylenedi-4,l- phenylene)bismaleimide (0.036 g, 50 mmol loading, Sigma Aldrich) and excess 2- dodecylfuran (0.07 g, 150 mmol) was carried out at 40°C in deuterated acetone (2 mL, Sigma Aldrich). The reaction started to precipitate a solid corresponding to the Diels-Alder adduct shortly after the components were combined in solution. After 24 hours, the solid was filtered, rinsed with fresh acetone, and dried en vacuo at room temperature (-0.1 MPa, 2 hours) to remove residual solvent. 'H NMR analysis of the solid dissolved in deuterated chloroform confirmed signals corresponding to the Diels-Alder adduct, while the analogous analysis of the reaction solvent showed nearly complete consumption of the bis-maleimide starting material. [39] Figure 2 shows a 'H NMR spectra of the precipitate formed (self-separating from solution) upon addition of the diene (dodecylfuran) and dienophile (bismaleimide compound). Signals corresponding to both individual compounds are largely preserved, as would be expected for the Diels-Alder adduct. Importantly, the development of signal(s) in the 5 to 5.5 ppm range (5.3 ppm in Figure 2 below) is unique to the stereoisomers of the Diels-Alder adduct, and is not present for either compound independently. This serves as evidence the separated solid is the formed Diels-Alder adduct.

Figure 2

[40] Various examples have been described with reference to certain disclosed embodiments. The embodiments are presented for purposes of illustration and not limitation. One skilled in the art will appreciate that various changes, adaptations, and modifications can be made without departing from the scope of the invention.

Claims

What is claimed is:

1. A method comprising the steps of: performing a Diels-Alder reaction between a dienophile and a furan-based diene; and forming an immobilized and separated Diels-Alder adduct from the Diels-Alder reaction.

2. The method of claim 1, wherein the dienophile is selected from the group consisting of dienophiles set forth in Table 1.

3. The method of claim 1, wherein the dienophile is a surface-supported dienophile.

4. The method of claim 1, wherein the furan-based diene is selected from the group consisting of dienes set forth in Table 1.

5. The method of claim 1, wherein the Diels-Alder reaction is a reversible Diels-Alder reaction.

6. The method of claim 5, wherein the reversible Diels-Alder reaction separates a furan- containing compound in a mixed chemical stream.

7. The method of claim 5, wherein the dienophile comprises a n-propylmaleimide alkylated on a silica support.

8. The method of claim 7, wherein the furan-based diene comprises a methyl furan.

9. The method of claim 7, wherein furan-based diene comprises an alkoylmethylfuran.

10. The method of claim 9, wherein the alkoylmethylfuran comprises 2-Dodecoyl 5- Methylfuran.

11. The method of claim 7, wherein the furan-based diene comprises an alkylfuran.

12. The method of claim 1, wherein the Diels-Alder reaction is performed at a temperature range from 0-100°C.

13. The method of claim 12, wherein the Diels-Alder reaction is performed at a temperature range from 0-60°C.

14. The method of claim 1, wherein a molar ratio of the dienophile to the furan-based diene is in the range of 2-100.

15. The method of claim 1, wherein the dienophile is supported on a heterogeneous support, and wherein the Diels-Alder reaction is performed by passing the furan-based diene over the dienophile at the heterogeneous support.

16. The method of claim 15, wherein, when the dienophile is saturated with the furan-based diene, terminating the passing of the furan-based diene over the dienophile.

17. The method of claim 15, wherein, when the dienophile is saturated with the furan-based diene, increasing a temperature at the heterogeneous support.

18. The method of claim 17, further comprising: when the temperature is increased, performing a retro Diels-Alder reaction.

19. The method of claim 18, wherein performing the retro Diels-Alder reaction releases a pure furan-based product.

20. The method of claim 17, wherein the temperature is increased from room temperature.