WO2018011741A1

WO2018011741A1 - Synthesis of ketals and levulinates

Info

Publication number: WO2018011741A1
Application number: PCT/IB2017/054223
Authority: WO
Inventors: Alexander Stanislaus; Girish KORIPELLY; Santosh GANJI; Venkata Ramanarayanan Ganapathy Bhotla; Ravichander Narayanaswamy; Krishna Kumar RAMAURTHY
Original assignee: Sabic Global Technologies B.V.
Priority date: 2016-07-15
Filing date: 2017-07-12
Publication date: 2018-01-18

Abstract

Disclosed are methods for preparing a levulinic acid mixture in a reaction vessel that is, for example, suitable for use in synthesizing a glyceryl ketal of levulinic acid or an ester of levulinic acid comprising distilling a combination comprising levulinic acid, formic acid, sulphuric acid, and water with an organic solvent in order to separate water and formic acid from the combination, thereby forming the levulinic acid mixture. The levulinic acid mixtures that are prepared according to such methods may therefore be used to produce high yields of a glyceryl ketal of levulinic acid or an ester of levulinic acid that have a high level of purity relative to prior art compounds.

Description

SYNTHESIS OF KETALS AND LEVULINATES

TECHNICAL FIELD

[0001] The present disclosure relates to simplified methods for preparing ketals and esters of levulinic acid.

BACKGROUND

[0002] Levulinic acid can be converted to a wide range of value-added derivatives like gamma valerolactone, methyl tetrahydrofuran, diphenolic acid, amino levulinic acid, and others. Levulinic acid esters, like methyl levulinate and ethyl levulinate, have been used as fragrance ingredients, green solvents, and additives for transport fuel. Importantly, ketals of levulinic acid, like glyceryl ketals, have assumed a significant role as alternatives to phthalate plasticizers, which are typically used during the manufacture of polyvinyl chloride (PVC).

[0003] Traditionally, ketals and esters of levulinic acid are prepared in two steps, including isolation of levulinic acid in pure form by various methods, such as flash vapor mixture separation (U.S. Pat. No. 8,426,619), reactive distillation (U.S. Pat. No. 7,718,039), reactive extraction (U.S. Pat. No. 7,378,549; U.S. Pub. No. 2010/0312006), solvent extraction (U.S. Pub. No. 2012/0302764; EP2773437), membrane separation (U.S. Pub. No. 2008/0217247; WO 2013/034763), biphasic systems (U.S. Pub. No. 2011/0071306; EP2684875; WO

2015/034964), decarboxylation (U.S. Pub. No. 2010/0281763), fractional distillation

(EP481798), wipe film evaporation (U.S. Pub. No. 2014/0316161), separation by molecular sieve (id), crystallization (id), or precipitation (id), followed by ketal or ester formation.

[0004] However, these multi-step synthesis methods are associated with certain drawbacks, such as increased time, and the need for more equipment and reagents, which render such methods more expensive and vulnerable to error and reduced recovery efficiency. The need exists for a more streamlined process for preparing ketals and esters of levulinic acid that would overcome such disadvantages.

[0005] These and other shortcomings are addressed by aspects of the present disclosure.

SUMMARY

[0006] Aspects of the disclosure relate to methods for preparing a levulinic acid mixture in a reaction vessel that is suitable for use in synthesizing a glyceryl ketal of levulinic acid or an ester of levulinic acid. The method comprises distilling a combination comprising levulinic acid, formic acid, sulphuric acid, and water with an organic solvent in order to separate water and formic acid from the combination, thereby forming the levulinic acid mixture. [0007] Aspects of the disclosure further relate to methods for synthesizing a glyceryl ketal of levulinic acid comprising combining a levulinic acid mixture that is prepared according to the instant methods with glycerol, forming a ketal intermediate by a condensation reaction between the levulinic acid in the mixture and the glycerol, recovering the ketal intermediate from the ketal intermediate containing mixture, and forming the glyceryl ketal of levulinic acid by a transesterification reaction between the ketal intermediate and an alcohol.

[0008] Glyceryl ketals of levulinic acid that are prepared according to such methods are also described herein. Thermoplastic polymers comprising such glyceryl ketals of levulinic acid are also disclosed.

[0009] The present disclosure also relates to methods for synthesizing an ester of levulinic acid comprising combining the levulinic acid mixture that is prepared according to the instant methods with an alcohol in a reaction vessel, and forming the ester of levulinic acid by an esterification reaction between the levulinic acid in the mixture and the alcohol.

[0010] Esters of levulinic acid that are prepared according to such methods are also described herein, as are fragrances, solvents, plasticizers, or a fuel additives comprising such esters of levulinic acid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 illustrates the reaction flow scheme described in Example 1 for the preparation of a levulinic acid mixture and a glyceryl ketal.

[0012] FIG. 2 depicts a gas chromatogram of the glyceryl ketal produced pursuant to Example 1.

[0013] FIG. 3 provides the ¾ NMR spectrum corresponding to the glyceryl ketal obtained pursuant to Example 1.

[0014] FIG. 4 provides the ¹³C NMR spectrum corresponding to the glyceryl ketal obtained pursuant to Example 1.

[0015] FIG. 5 illustrates the reaction flow scheme described in Example 2 for the preparation of a levulinic acid mixture and methyl levulinate.

[0016] FIG. 6 depicts a gas chromatogram of the methyl levulinate produced pursuant to Example 2.

[0017] FIG. 7 shows a gas chromatogram of the glyceryl ketal prepared in Example 8.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[0018] It is to be understood that the terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting. As used in the specification and in the claims, the term "comprising" can include the embodiments "consisting of and "consisting essentially of." Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0019] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural equivalents unless the context clearly dictates otherwise. Thus, for example, reference to "an organic solvent" includes mixtures of two or more such solvents.

[0020] As used herein, the term "combination" is inclusive of blends, mixtures, alloys, reaction products, and the like.

[0021] Ranges can be expressed herein as from one value (first value) to another value (second value). When such a range is expressed, the range includes in some aspects one or both of the first value and the second value. Similarly, when values are expressed as approximations, by use of the antecedent "about", it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. It is also understood that there are a number of values disclosed herein, and that each value is also herein disclosed as "about" that particular value in addition to the value itself. For example, if the value "10" is disclosed, then "about 10" is also disclosed. It is also understood that each unit between two particular units are also disclosed. For example, if 10 and 15 are disclosed, then 11, 12, 13, and 14 are also disclosed.

[0022] As used herein, the terms "about" and "at or about" mean that the amount or value in question can be the designated value, approximately the designated value, or about the same as the designated value. It is generally understood, as used herein, that it is the nominal value indicated ±10% variation unless otherwise indicated or inferred. The term is intended to convey that similar values promote equivalent results or effects recited in the claims. That is, it is understood that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but can be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. In general, an amount, size, formulation, parameter or other quantity or characteristic is "about" or "approximate" whether or not expressly stated to be such. It is understood that where "about" is used before a quantitative value, the parameter also includes the specific quantitative value itself, unless specifically stated otherwise. [0023] Disclosed are the components to be used to prepare the compounds of the disclosure as well as the compounds themselves. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed that while specific reference of each various individual and collective combinations and permutation of these materials cannot be explicitly disclosed, each is specifically contemplated and described herein. For example, if a particular material is disclosed and discussed and a number of modifications that can be made to a number of molecules including the compounds are discussed, specifically contemplated is each and every combination and permutation of the material and the modifications that are possible unless specifically indicated to the contrary. Thus, if a class of molecules A, B, and C are disclosed as well as a class of molecules D, E, and F and an example of a combination molecule, A-D is disclosed, then even if each is not individually recited each is individually and collectively contemplated meaning combinations, A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered disclosed. Likewise, any subset or combination of these is also disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E would be considered disclosed. This concept applies to all aspects of this application including, but not limited to, steps in methods of making and using the compositions of the disclosure. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific aspect or combination of aspects of the methods of the disclosure.

[0024] References in the specification and concluding claims to parts by weight, of a particular element or component in a composition or article, denotes the weight relationship between the element or component and any other elements or components in the composition or article for which a part by weight is expressed. Thus, in a compound containing 2 parts by weight of component X and 5 parts by weight component Y, X and Y are present at a weight ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound.

[0025] As used herein the terms "weight percent," "wt. %," and "wt. %" of a component, which can be used interchangeably, unless specifically stated to the contrary, are based on the total weight of the formulation or composition in which the component is included. For example if a particular element or component in a composition or article is said to have 8% by weight, it is understood that this percentage is relative to a total compositional percentage of 100% by weight.

[0026] All cited patents, patent applications, and other references are incorporated herein by reference in their entirety. [0027] While typical aspects have been set forth for the purpose of illustration, the foregoing descriptions should not be deemed to be a limitation on the scope herein.

Accordingly, various modifications, adaptations, and alternatives can occur to one skilled in the art without departing from the spirit and scope herein.

[0028] Traditional methods for isolating levulinic acid (e.g. , involving the use of solvent extraction, molecular sieves, crystallization, distillation, thin film evaporation, or precipitation) are characterized by incomplete segregation of the target compound within a single phase of the reaction mixture, resulting in low yield and undesirable levels of impurities. The present disclosure relates to methods that result in effectively complete segregation of levulinic acid within one physical phase, which enables the production of derivatives of levulinic acid (e.g., ketals, levulinates) at beneficially high yield and levels of purity. The presently disclosed methods, compositions, compounds, and products are therefore highly improved relative to their traditional counterparts.

[0029] Accordingly, provided are methods for preparing a levulinic acid mixture in a reaction vessel that is, for example, suitable for use in synthesizing, a glyceryl ketal of levulinic acid or an ester of levulinic acid comprising distilling a combination comprising levulinic acid, formic acid, sulphuric acid, and water with an organic solvent in order to separate water and formic acid from the combination, thereby forming the levulinic acid mixture. The levulinic acid mixtures that are prepared according to such methods may therefore be used to produce a high yield of a glyceryl ketal of levulinic acid or an ester of levulinic acid that have a high level of purity relative to prior art compounds.

[0030] In accordance with the instant methods, the combination may be a hydrolysate mixture resulting from hydrolysis of cellulosic or lignocellulosic matter. Sources of these materials are well known and can include, for example: naturally occurring terrestrial plants such as trees, bushes, and grass; waste biomass, e.g. , from agriculture or forestry, such as corn stover, sugarcane bagasse, straw, saw mill waste, cellulosic cotton waste, used paper, and paper mill discards; and energy crops with high yield of lignocellulosic biomass, such as switch grass (Panicum virgatum) and elephant grass.

[0031] Exemplary organic solvents for use in the distillation of the combination include cyclohexane, toluene, benzene, pentane, cyclopentane, ethyl benzene, hexane, heptane, or any combination thereof. Other organic solvents may be selected based on the specific requirements of the distillation, for example, formation of an azeotrope. The organic solvent may be selected based on whether the levulinic acid phase or the formic acid phase that result from the distillation is to be miscible with the organic solvent, as described more fully below. When the distillation is an azeotropic distillation, the organic solvent is selected such that the azeotropic mixture (comprising water, formic acid and the solvent) has a low boiling point. The use of this type of solvent prevents the levulinic acid from being subjected to high temperatures, which would degrade the levulinic acid, resulting in yield loss of the desired final product.

[0032] The distillation of the combination may produce (i) a residue that is a mixture of the levulinic acid, sulphuric acid, and optionally, the organic solvent, and (ii) a distillate that is a mixture of formic acid, water and the organic solvent. In certain aspects, the mixture including levulinic acid and sulphuric acid is immiscible with the organic solvent. In other aspects, the mixture of formic acid and water is immiscible with the organic solvent in the distillate.

[0033] The instant methods may further comprise separating the organic solvent from the residue, the distillate, or both (for example, by decantation of the organic solvent), and leaving the levulinic acid and the sulphuric acid in the residue and formic acid and water in the distillate. Accordingly, one of the criteria for the selection of the organic solvent is the ease of separation from the distillate. Another criterion is, as described above, the ability of the organic solvent to form a low-boiling azeotrope with formic acid and water.

[0034] In certain aspects, the distillation of the combination comprising levulinic acid, formic acid, sulphuric acid, and water with an organic solvent may be an azeotropic distillation.

[0035] As described above, the levulinic acid mixture that is formed in accordance with the instant methods is suitable, and indeed represents a highly favorable starting material, for use in synthesizing a glyceryl ketal of levulinic acid or an ester of levulinic acid. Advantageously, all or virtually all of the levulinic acid from the starting combination of levulinic acid, formic acid, sulphuric acid, and water may be segregated within the levulinic acid mixture that is formed in accordance with the present methods, which attests to the high degree of efficiency with which derivatives of levulinic acid can be produced from a starting combination comprising levulinic acid. This is in comparison to prior art methods in which levulinic acid could not be quantitatively recovered. The successful segregation of all or virtually all of the levulinic acid from the starting combination into a mixture of the levulinic acid, sulphuric acid, and organic solvent is illustrated in the examples of the present disclosure, discussed below.

Glyceryl Ketals

[0036] Accordingly, also disclosed herein are methods for synthesizing a glyceryl ketal of levulinic acid comprising combining a levulinic acid mixture that is prepared according the methods described above with glycerol, forming a ketal intermediate by a condensation reaction between the levulinic acid in the mixture and the glycerol, optionally recovering the ketal intermediate from the ketal intermediate containing mixture, and forming the glyceryl ketal of levulinic acid by a transesterification reaction between the ketal intermediate and an alcohol.

[0037] The combination of the levulinic acid mixture with glycerol may be performed simply by adding the glycerol to the levulinic acid mixture. The reaction of the levulinic acid mixture with glycerol may optionally be conducted in the same vessel as a subsequent reaction for the formation of the final ketal product. The efficiency of the present methods is enhanced by the fact that there is minimal to no loss of levulinic acid due to separation issues as mentioned elsewhere in the literature. The amount of glycerol that is combined with the levulinic acid mixture may be such that there is up to about 1 : 1 mole ratio of glycerol to levulinic acid. The inclusion of glycerol in an amount exceeding this mole ratio (i.e., greater than 1 mole glycerol relative to 1 mole levulinic acid) could complicate separation of the final product.

[0038] The formation of the ketal intermediate by a condensation reaction may be performed in the absence or in the presence of water.

[0039] The ketal intermediate, once formed, may be subjected to washing and extraction of any washing reagents. The washing step is particularly useful if the

transesterification is performed in a basic medium using sodium methoxide. If the

transesterification reaction is performed in acidic medium, utilizing the sulphuric acid that is present in the reaction mixture, then washing the intermediate is not necessary. When needed, the washing may be performed using a sodium bicarbonate solution. A solution containing 5% sodium bicarbonate may be used as the neutralizing reagent.

[0040] The step of recovering the ketal intermediate from ketal intermediate containing mixture is optional, and is carried out when the transesterification reaction is not performed in an acidic medium (as in Example 1, below). When the transesterification reaction is performed in an acidic medium (as in Example 8, below), the step of recovering the ketal intermediate need not be performed.

[0041] The glyceryl ketal is formed using a transesterification reaction between the ketal intermediate and an alcohol. In some aspects, the alcohol is a primary alcohol, examples of which include any Ci to C₂₀ alcohol or combinations thereof, such as methanol, ethanol, butanol, pentanol, hexanol, octanol, decanol, hexadecanol, and the like. The alcohol is typically provided in amount that is in excess of the quantity of ketal intermediate. The conditions for a transesterification reaction between the ketal intermediate and the alcohol can otherwise be determined by routine procedures. Transesterification can be performed in a basic medium using sodium methoxide, under which conditions the sulphuric acid present in the mixture must be neutralized. If the reaction is performed in acidic medium, then the sulphuric acid present in the reaction mixture can be utilized, and therefore neutralization of the solution containing the intermediate polymeric material is not necessary. The time over which the ketal intermediate and the alcohol are reacted can be from about 12 to about 36 hours. For example, the reaction between the ketal intermediate and the alcohol may be conducted over about 12 hours, about 14 hours, about 16 hours, about 18 hours, about 20 hours, about 22 hours, about 23 hours, about 24 hours, about 25 hours, about 26 hours, about 27 hours, about 28 hours, about 29 hours, about 30 hours, about 32 hours, about 34 hours, or about 36 hours.

[0042] The temperature of the reaction medium for the reaction between the ketal intermediate and the alcohol is kept low in some aspects to avoid degradation of the polymeric material. In addition, during the formation of the polymeric material, water is removed as an azeotrope with the organic solvent. Taking this into consideration, the temperature required is that at which water that is formed by condensation of glycerol with levulinic acid distills out as an azeotrope. Those of ordinary skill in the art can readily determine appropriate temperatures and temperature ranges for these purposes.

[0043] The present disclosure also provides glyceryl ketals of levulinic acid that are prepared according to the above-described methods, as well as thermoplastic polymers comprising such glyceryl ketals of levulinic acid. For example, the thermoplastic polymer comprising the glyceryl ketal of levulinic acid may be a vinyl chloride polymer, poly(3- hydroxyyalkanoate) polymer, poly(lactate) polymer, or polysaccharide polymer.

Esters of Levulinic Acid

[0044] The present disclosure also provides methods for synthesizing an ester of levulinic acid comprising combining the levulinic acid mixture that is prepared according to the instant methods with an alcohol in a reaction vessel, and forming the ester of levulinic acid by an esterification reaction between the levulinic acid in the mixture and the alcohol.

[0045] The combination of the alcohol with the levulinic acid mixture may be performed simply by adding the alcohol to the reaction vessel in which the levulinic acid mixture was formed. The efficiency of the present methods is enhanced by the fact that a single reaction vessel may be used for the formation of both the levulinic acid mixture and subsequently, the ester final product. In addition, there is no loss of levulinic acid due to separation issues, as contrasted with conventional methods. When implementing a batch process, the same reaction vessel may be used for both the formation of the levulinic acid mixture and for the formation of an ester of levulinic acid. When implementing a continuous process, separate reaction vessels can be used for formation of levulinic acid and for the formation of the ester of the final product, respectively. [0046] The esterification reaction may be performed in the absence or in the presence of water. The reaction may be performed at room temperature. In some aspects, the alcohol is a primary alcohol, examples of which include any Ci to C₂₀ alcohol or combinations thereof, such as methanol, ethanol, butanol, pentanol, hexanol, octanol, decanol, hexadecanol, and the like. In some aspects, the alcohol is methanol, and the esterification reaction produces methyl levilinate. The alcohol is typically provided in amount that is in excess of the quantity of the levulinic acid in the levulinic acid mixture. The other conditions for the esterification reaction between the levulinic acid mixture and the alcohol can otherwise be determined by routine procedures.

[0047] Esters of levulinic acid that are prepared according to the above-described methods are also provided herein. The esters can be used as components of fragrances, solvents, plasticizers, or fuel additives.

Aspects

[0048] In various aspects, the present disclosure relates to and includes at least the following aspects.

[0049] Aspect 1. A method for preparing a levulinic acid mixture in a reaction vessel that is suitable for use in synthesizing a glyceryl ketal of levulinic acid or an ester of levulinic acid comprising distilling a combination comprising levulinic acid, formic acid, sulphuric acid, and water with an organic solvent in order to separate water and formic acid from the combination, thereby forming the levulinic acid mixture.

[0050] Aspect 2. The method according to aspect 1, wherein the combination is a hydrolysate mixture resulting from hydrolysis of cellulosic or lignocellulosic matter.

[0051] Aspect 3. The method according to aspect 1 or 2 wherein the distilling produces a residue that is a mixture of the levulinic acid, sulphuric acid, and optionally, the organic solvent, and a distillate that is a mixture of formic acid, water and the organic solvent.

[0052] Aspect 4. The method according to aspect 3 wherein the mixture of levulinic acid and sulphuric acid is immiscible with the organic solvent in the distillate.

[0053] Aspect 5. The method according to aspect 3 wherein the mixture of formic acid and water is immiscible with the organic solvent in the distillate.

[0054] Aspect 6. The method according to aspect 3 further comprising separating the organic solvent from the residue, the distillate, or both, by decantation of the organic solvent, leaving the levulinic acid and the sulphuric acid in the residue and formic acid and water in the distillate.

[0055] Aspect 7. The method according to any one of aspects 1-6 wherein the distillation is azeotropic distillation. [0056] Aspect 8. A method for synthesizing a glyceryl ketal of levulinic acid comprising combining the levulinic acid mixture that is prepared according to any one of aspects 1-7 with glycerol forming a ketal intermediate by a condensation reaction between the levulinic acid in the levulinic acid mixture and the glycerol; optionally recovering the ketal intermediate from the resulting ketal intermediate -containing mixture; and forming the glyceryl ketal of levulinic acid by a transesterification reaction between the ketal intermediate and an alcohol.

[0057] Aspect 9. The method of aspect 8 wherein the alcohol is a primary alcohol.

[0058] Aspect 9a. The method of

[0059] Aspect 10. The method according to aspect 9 wherein the primary alcohol is a Ci to C₂₀ alcohol or any combination thereof.

[0060] Aspect 11. The method according to any one of aspects 8-10 wherein the alcohol is methanol.

[0061] Aspect 12. The method according to any one of aspects 8-11, wherein the ketal intermediate is formed in the absence of water.

[0062] Aspect 13. The method according to any one of aspects 8-11, wherein the ketal intermediate is formed in the presence of water.

[0063] Aspect 14. The method according to any one of aspects 8-13, wherein the ketal intermediate containing mixture is neutralized prior to the transesterification reaction in basic medium.

[0064] Aspect 15. The method according to aspect 14 wherein the neutralization is performed using a sodium bicarbonate solution.

[0065] Aspect 16. The method according to any of aspects 8-13, wherein the ketal intermediate-containing mixture is processed without neutralizing and is taken up for acid catalyzed transesterification.

[0066] Aspect 17. The method according to any of aspects 8-16, wherein the ketal intermediate formed with higher molecular weight build up results in ketal of higher purity

[0067] Aspect 18. A method for synthesizing an ester of levulinic acid comprising combining the levulinic acid mixture that is prepared according to any one of aspects 1-7 with an alcohol in the reaction vessel; and forming the ester of levulinic acid by an esterification reaction between the levulinic acid in the mixture and the alcohol.

[0068] Aspect 19. The method according to aspect 18, wherein the esterification reaction is performed in the absence of water.

[0069] Aspect 20. The method according to aspect 18 or 19, wherein the esterification reaction is performed at room temperature. [0070] Aspect 21. The method according to any one of aspects 18-20, wherein the alcohol is a primary alcohol.

[0071] Aspect 22. The method according to aspect 21, wherein the primary alcohol is a Ci to C₂₀ alcohol or any combination thereof.

[0072] Aspect 23. The method according to any one of aspects 18-22, wherein the alcohol is methanol, and the esterification reaction produces methyl levulinate.

[0073] Aspect 24. The method according to any one of aspects 1-23, wherein the organic solvent is cyclohexane, toluene, benzene, pentane, cyclopentane, ethyl benzene, hexane, heptane, or any combination thereof.

[0074] Aspect 25. The method according to any one of aspects 1-7 or the method according to any one of aspects 8-23, wherein the organic solvent is cyclohexane.

[0075] Aspect 26. A levulinic acid mixture that is prepared according to any one of aspects 1-7.

[0076] Aspect 27. A glyceryl ketal of levulinic acid that is prepared according to any one of aspects 8-15 or 24-25.

[0077] Aspect 28. A thermoplastic polymer comprising a glyceryl ketal of levulinic acid according to aspect 27.

[0078] Aspect 29. The thermoplastic polymer according to aspect 28 comprising vinyl chloride polymer, poly (3- hydroxyyalkanoate) polymer, poly(lactate) polymer, or polysaccharide polymer.

[0079] Aspect 30. An ester of levulinic acid that is prepared according to any one of aspects 18-25.

[0080] Aspect 31. A fragrance, a solvent, a plasticizer, or a fuel additive comprising an ester of levulinic acid according to aspect 30.

[0081] Aspect 32. The method according to aspect 8 wherein the higher purity of ketal is obtained after transesterification by increasing the molecular weight of the ketal intermediate

[0082] Aspect 33. The method according to any one of aspects 8-13, where in the ketal intermediate containing mixture need not be neutralized prior to transesterification in an acidic medium.

Examples

[0083] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, processes and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary of the disclosure and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, temperature is expressed in degrees Celsius (°C) or is at ambient temperature, and pressure is at or near atmospheric. The disclosed methods can be carried out in a single vessel pursuant to a batch process, where the various steps of distillation, separation, condensation and transesterification can be sequenced. The disclosed methods can alternatively be carried out pursuant to a continuous process, in which different vessels/equipment are used for convenience of operation and control of the process.

Example 1 - Formation of Glyceryl Ketal of Levulinic Acid From a Hydrolysate Mixture

[0084] To form a levulinic acid mixture, 97 grams (g) of the feed containing levulinic acid (44.4 g), formic acid (17 g), sulphuric acid (0.5 g) in water (35.5 g) was treated with 200 g of cyclohexane, which forms an azeotropic mixture with water (mole fraction of cyclohexane in the binary mixture is 0.3), and was transferred into a round bottom flask fitted with a Dean-Stark apparatus. The mixture was brought up to reflux by heating using an oil bath. The reaction mixture temperature was measured to be 70 °C. It was refluxed for about 5 hours.

[0085] Most of the water and formic acid was then collected in the Dean- Stark apparatus and separated. Presence of water in the mixture would not drive the ketal formation in the forward direction and the water was thus removed. The azeotropic distillation with cyclohexane not only separated out water but also carried away formic acid from the hydrolysate mixture, leaving behind levulinic acid, sulphuric acid and traces of formic acid and water (1.7 g formic acid and <0.1 g water). Cyclohexane can be replaced by toluene to carry out azeotropic distillation. Once water and formic acid were removed from the mixture, 35.2 g glycerol was added and the reaction temperature maintained at 100 °C. The condensed water formed during the reaction of glycerol with levulinic acid was collected in the Dean-Stark apparatus. The reaction was then stopped when no further water was collected, the polymeric phase separated, and 68 g of the polymeric material was isolated and was taken up for transesterification reaction.

[0086] Glyceryl formate was not observed as a byproduct. Glyceryl formate is formed when only glycerol and formic acid alone are subjected to condensation. In a mixture containing formic acid and levulinic acid, glyceryl formate was not observed as a byproduct along with glyceryl levulinate.

[0087] To the polymeric material, 200 g of ethyl acetate was added and dissolved. The material was then washed with 100 g of 5 wt% NaHCC>3 solution to neutralize the sulphuric acid. The ethyl acetate layer was then separated, dried with anhydrous sodium sulphate and distilled using a Rotavac to purify and recover the polymeric material. [0088] The polymeric material obtained from the above step was subjected to transesterification reaction with methanol and sodium methoxide at room temperature in a round bottom flask. After stirring for 5 hours, the reaction was stopped. The mixture was then quenched with water and methanol was removed using a Rotavac. Ethyl acetate was added to extract the product, and was then dried with anhydrous sodium sulphate, and filtered. The solvent was then separated using a Rotavac, and the final product was dried and weighed to be 61 g.

[0089] FIG. 1 illustrates the reaction scheme described above for the preparation of a levulinic acid mixture and glyceryl ketal.

[0090] Gas chromatograph results confirmed purity of 89% glyceryl ketal (mixture of two stereoisomers 50.3 and 38.6% respectively), 10% methyl levulinate and 1% other impurities (FIG. 2). Yield of ketal based on levulinic acid used for the reaction was 70%. Since the methods were conducted in lab scale, better yield entitlements are anticipated when the method is scaled-up. The ketal structure was also confirmed by ^:H and ¹³C NMR (FIGS. 3 and 4, respectively).

[0091] Other methods, such as high vacuum distillation, can be used as an alternative workup procedure to remove the ketal from the methanolic mixture. Molecular sieves can be used to remove the traces of water and later distilled to isolate the ketal from methanol.

Example 2 - Formation of Methyl Levulinate From a Hydrolysate Mixture Containing Levulinic Acid

[0092] The procedure was carried out according to Example 1, except that instead of glycerol, 91 g of methanol was added and stirred at room temperature for the levulinic acid to be esterified into methyl levulinate. After stirring for 5 hours the reaction was stopped. The mixture was quenched with water and methanol was removed using a Rotavac. Ethyl acetate was added to extract the product, dried with anhydrous sodium sulphate, and filtered. The solvent was then separated using a Rotavac, and the final product was dried and weighed to be 40 g. FIG. 5 illustrates the reaction scheme described above for the preparation of a levulinic acid mixture and methyl levulinate. As illustrated in FIG. 6, gas chromatography results confirm methyl levulinate with 98.9% purity. Yield calculated based on the amount of levulinic acid used for the reaction was 81%. The loss of levulinic acid was due to the small scale lab experiments, and better efficiencies can be realized in a large-scale plant.

Example 3 - Alternative Procedure for Producing Glyceryl Ketal

[0093] A further procedure was carried out according to Example 1, except that the intermediate polymeric material formed was dissolved in 90 g of dichloromethane (DCM) instead of ethyl acetate by stirring at room temperature. A clear solution was obtained to which water was added for phase separation. Unlike in Example 1, there was no phase separation instead it formed an emulsion. The DCM and water was removed using a Rotavac, and the polymeric material was processed as described in Example 1 to obtain the glyceryl ketal.

Example 4 - Alternative Procedure for Producing Glyceryl Ketal

[0094] An additional procedure was carried out according to Example 1 to obtain 69 g of the intermediate polymeric material. 25 g of this material was dissolved in 100 g of ethyl acetate by stirring at room temperature. Equal quantity of water was added to the mixture for phase separation. No phase separation was observed with water. To another 25 g of the material dissolved in 100 g of ethyl acetate, 100 g of 5% NaHCC was added, and the combination was stirred at room temperature. On being allowed to stand, the aqueous layer separated from the organic layer. The organic layer was washed and dried over anhydrous sodium sulphate, and ethyl acetate was removed using a Rotavac. The transesterification was carried out as in Example 1.

Example 5 - Extent of Conversion of Levulinic Acid Without Separation By Inventive Method

[0095] To monitor the extent of conversion of levulinic acid in the hydrolysate mixture without isolation from water and formic acid, Example 5 was conducted using 97 g of the feed containing levulinic acid (44.4 g), formic acid (17 g), sulphuric acid (0.5 g) in water (35.5 g) and 35 g of glycerol was transferred into the round bottom flask fitted with a condenser. The mixture was brought up to reflux by heating using an oil bath. The bath temperature was measured to be 100 °C. Aliquots of sample were taken and analyzed for the levulinic acid conversion to the polymeric material. Results demonstrated that the conversion was only up to 22% even after 12 hours of refluxing.

Example 6 - Demonstration of Separation of H₂0 and Formic Acid

[0096] The procedure of Example 5 was repeated except that about 50% of the water and formic acid were removed prior to the addition of glycerol. The mixture was then brought up to reflux by heating using an oil bath. The reaction temperature is measured to be 100 °C.

Aliquots of sample have been taken and analyzed for the levulinic acid conversion to the polymeric material. Results show that even after the removal of sufficient water and formic acid, conversion was only up to 27% even after 12 hours of refluxing.

[0097] Table 1, below, shows the amount of levulinic acid over time pursuant to the procedures of Examples 5 and 6, respectively: Table 1

[0098] This data represents experimental evidence demonstrating that in some aspects it is preferable to remove water and formic acid before addition of glycerol for the ketal adduct to be formed. The presence of water hinders ketal formation.

Example 7 - Extent of Conversion of Levulinic Acid Into Ketal, Monitored Over Time and For Purity

[0099] The procedure was followed as per Example 1, except that after glycerol was added into the reaction flask, aliquots of samples were acquired to monitor the molecular weight buildup of the polymeric intermediate formed. These samples were further processed through transesterification as in Example 1 to form the ketal. The results of the purity of the ketal versus molecular buildup (based on a gas chromatograph (GC) analysis) are shown in Table 2, which demonstrates that it is possible to generate high purity ketal (94%) hitherto not shown in prior art through transesterification of high molecular weight build polymeric material:

Table 2

Example 8 - Producing Ketal Through Acid Catalyzed Transesterification

[00100] The procedure was carried out according to Example 1, except that the polymeric material-containing mixture was not neutralized with 5% NaHCC>3 solution. The sulphuric acid present in the mixture was utilized for acid catalyzed transesterification. The solvent cyclohexane was decanted and 200 g of methanol was added into the mixture containing the polymeric material and sulphuric acid. The mixture was refluxed for 8 hours and then cooled. Methanol was evaporated using a Rotavac. The product mixture was then neutralized with 5% NaHC0₃ solution. Ethyl acetate was added to extract the product, and was then dried with anhydrous sodium sulphate, and filtered. The ethyl acetate was then separated using a Rotavac, and the final product was dried and weighed to be 52 g. Gas chromatography results confirmed purity of 77.8% glyceryl ketal (mixture of two stereoisomers 44.1 and 33.7% respectively), 17.6% methyl levulinate and 4.6% other impurities (FIG. 7). The yield of ketal based on levulinic acid used for the reaction was 52.5%. As the methods were conducted in lab scale, better yield entitlements are anticipated when the process is scaled-up.

Claims

What is Claimed:

1. A method for preparing a levulinic acid mixture in a reaction vessel that is suitable for use in synthesizing a glyceryl ketal of levulinic acid or an ester of levulinic acid comprising: distilling a combination comprising levulinic acid, formic acid, sulphuric acid, and water with an organic solvent in order to separate water and formic acid from the combination,

thereby forming the levulinic acid mixture.

2. The method according to claim 1, wherein the combination is a hydrolysate mixture resulting from hydrolysis of cellulosic or lignocellulosic matter.

3. The method according to claim 1 or 2 wherein the distilling produces a residue that is a mixture of the levulinic acid, sulphuric acid, and optionally, the organic solvent, and a distillate that is a mixture of formic acid, water, and the organic solvent.

4. The method according to claim 3 further comprising separating the organic solvent from the residue, the distillate, or both, by decantation of the organic solvent, leaving the levulinic acid and the sulphuric acid in the residue and formic acid and water in the distillate.

5. The method according to any one of claims 1-4 wherein the distilling is azeotropic distillation.

6. A method for synthesizing a glyceryl ketal of levulinic acid comprising:

combining the levulinic acid mixture that is prepared according to any one of claims 1-5 with glycerol;

forming a ketal intermediate by a condensation reaction between the levulinic acid in the mixture and the glycerol;

optionally recovering the ketal intermediate; and

forming the glyceryl ketal of levulinic acid by a transesterification reaction between the ketal intermediate and an alcohol.

7. The method according to claim 6, wherein the ketal intermediate-containing mixture is neutralized prior to base catalyzed transesterification.

8. The method according to claim 6, wherein the ketal intermediate-containing mixture is processed without neutralizing and is taken up for acid catalyzed transesterification.

9. The method according to any one of claims 6-8, wherein the ketal intermediate formed with higher molecular weight build up results in ketal of higher purity

10. A method for synthesizing an ester of levulinic acid comprising:

combining the levulinic acid mixture that is prepared according to any one of claims 1-5 with an alcohol; and

forming the ester of levulinic acid by an esterification reaction between the levulinic acid in the mixture and the alcohol.

11. The method according to claim 10, wherein the esterification reaction is performed in the absence of water.

12. The method according to claim 10 or claim 11, wherein the esterification reaction is performed at room temperature.

13. The method according to any one of claims 10-12 wherein the alcohol is methanol, and the esterification reaction produces methyl levulinate.

14. The method according to any one of claims 1-13, wherein the organic solvent is cyclohexane, toluene, benzene, pentane, cyclopentane, ethyl benzene, hexane, heptane, or any combination thereof.

15. A levulinic acid mixture that is prepared according to any one of claims 1-5.

16. A glyceryl ketal of levulinic acid that is prepared according to any one of claims 6-8.

17. A thermoplastic polymer comprising a glyceryl ketal of levulinic acid according to claim 16.

18. The thermoplastic polymer according to claim 17 comprising vinyl chloride polymer, poly(3- hydroxyyalkanoate) polymer, poly(lactate) polymer, or polysaccharide polymer.

19. An ester of levulinic acid that is prepared according to any one of claims 10-13.

20. A fragrance, a solvent, a plasticizer, or a fuel additive comprising an ester of levulinic acid according to claim 19.