Levulinate ester composition comprising an antioxidant

Abstract

This invention relates to a levulinate ester composition comprising a levulinate ester; and at least one antioxidant. The present invention also relates to the use of at least one antioxidant to reduce or avoid the color development in levulinate ester compositions.

Description

TITLE: LEVULINATE ESTER COMPOSITION COMPRISINGAN ANTIOXIDANTFIELD OF THE INVENTION

[0001] This invention relates to a levulinate ester composition comprising a levulinate ester; and at least one antioxidant. The present invention also relates to the use of at least one antioxidant to reduce or avoid the color development in levulinate ester compositions.BACKGROUND

[0002] Levulinates are important chemicals (Ejaz Ahmad, et al., “Catalytic and mechanistic insights into production of ethyl levulinate from biorenewable feedstocks”, Green Chem., 2016, 18, 4804-4823,) utilized as solvents across various markets, including paints and coatings, agro-industry, cleaning and cosmetics. They are also used as intermediates for producing other valuable products such as succinic acid, methyltetrahydrofuran and gammavalerolactone. The latter can be used to make chemicals such as adipic acid and caprolactam, which in turn serve as monomers for polyesters and polyamides. Additionally, levulinic acid esters themself can be used as fuel or fuel additives for both gasoline based and diesel engines. For several of these applications, a colorless and color-stable levulinic acid ester is a requirement or preferred.

[0003] Levulinic acid-based esters can be produced through several methods. One approach involves esterification of levulinic acid (e.g., US 2,029,412; Sindi Baco, et al. , “Solvent effect investigation on the acid-catalyzed esterification of levulinic acid by ethanol aided by a Linear Solvation Energy Relationship”, Chemical Engineering Science, 2022, pp.117928). Another approach is the direct conversion of hexose sugars in the presence of alcohols to produce levulinate esters (e.g., Yao-Bing Huang, et al., “Facile and high-yield synthesis of methyl levulinate from cellulose”, Green Chem., 2018, 20, 1323-1334; Anna Maria Raspolli Galletti, et al., “Direct Alcoholysis of Carbohydrate Precursors and Real Cellulosic Biomasses to Alkyl Levulinates a critical review”, Catalysts, 2020, 10(10): 1221). Additionally, levulinic acidbased esters can be synthesized by converting furfuryl alcohol in the presence of alcohols (US 2023 / 0322655 Al, Rudy Parton and Arie de Rijke, “Process for the conversion of furfuryl alcohol into a levulinate ester”), as byproduct in the synthesis of alkoxymethyl furfuraldehyde (R.J.H. Grisel, et al., “Acid catalysed alcoholysis of wheat straw Towards second generation furan-derivatives”, Catalysis Today, 2014, 223, 3- 10). Another approach is the conversion of hydroxymethylfurfural (HMF) or its derivatives with alcohols. Aside from these renewableroutes, a petrochemical method exists through the saponification of acetyl succinates (e.g., US 5,189,215). Furthermore, levulinic acid esters can be transesterified with alcohols to produce various levulinates.

[0004] Although levulinic esters are virtually colorless immediately after synthesis and purification, they tend to develop a yellow color over time, even following state-of-the-art fractional distillation. Additionally, several methods that produce colorless products immediately after synthesis do not ensure that they will remain colorless over time (e.g., US 2,349,514).

[0005] Most technologies for removing the color have been developed for levulinic acid. For example, in CN113929571 A, colored species in levulinic acid are removed via adsorption on onto activated carbon or activated clay in an adsorption column, or by oxidization with hypochlorite. Prior to adsorption, the pH of the levulinic acid solution is adjusted with inorganic strong bases. Following treatment, the solution is filtered on a nanofiltration membrane and further purified via distillation. This technology entails considerable additional investment costs. Various other methods have been developed for reducing the color in levulinic acid. They for example involve double extraction combined with a membrane filtration (EP 3823952B1), nanofiltration (WO 2014 / 037560 Al), crystallization (US 2,305,738, US 2016 / 0031788 Al, US 10,550,067 B2), treatment withe sunlight (CN112794800A). While these methods effectively reduce the color of the levulinic acid immediately after treatment, they do not guarantee that the color will not re-develop, potentially occurring relatively quickly over time.

[0006] Very few technologies address color stability over time. One exception is described in US 2,349,514 where both unwanted odor and undesirable color in levulinic acid are addressed through a treatment with hypochlorite. While the treatment effectively removes the odor, the color tends to reappear rapidly. The yellow color can be more permanently removed via a treatment with hydrogen peroxide. However, the procedure is time consuming and not recommended.

[0007] For levulinic acid esters, also known as levulinates, there is very little prior art available. In 1967, Quaker Oats (US 3,358,014) developed a process to make color stable levulinates from furfuryl alcohol-derived levulinates. The method involves treating the color unstable ester at an elevated temperature (above 75°C, preferably 110°C) for an hour in the presence of sulfuric acid (above 0.2 wt.%, preferably 1 wt.%), followed by neutralization and distillation. Not only this technology involves a corrosive process step, but it also entailsconsiderable additional investment costs. Alternatively, adsorption on a column with activated carbon (US 2,029,412) has been described. However, the technology does not address the issue of color stability over time.

[0008] Levulinic acid esters are generally considered to be stable and not particularly prone to radical reactions. However, impurities may be present in levulinate esters depending on the manufacturing processes and raw materials used. These impurities may possess different properties that can impact the overall stability of the product, particularly affecting its color. The color of the levulinate ester products may also be impacted by the temperature at which the products are stored. The specific nature of these impurities and what triggers color changes in levulinate esters are not well understood, creating challenges in managing their impact on the levulinate ester product’ s performance.

[0009] The object of the present invention is to reduce or avoid the color development in levulinate ester compositions while minimizing equipment investment and requiring as few additional process steps as possible. The solution provided must not only be easy and cost- effective to implement but must also perform satisfactorily across various temperature conditions, as it should produce a positive impact on the product after manufacturing but also generally contribute to an overall improvement in the levulinate ester products shelf life.BRIEF SUMMARY

[0010] The present invention relates to a levulinate ester composition comprising a levulinate ester; and at least one antioxidant.

[0011] In some embodiments, the amount of levulinate ester in the composition is at least 95 wt.%, based on the total weight of the composition.

[0012] In some embodiments, the amount of antioxidant is from 10 ppm to 5,000 ppm, based on the total weight of the composition.

[0013] The present invention also relates to the use of at least one antioxidant to reduce or avoid the color development in levulinate ester compositions.DETAILED DESCRIPTION

[0014] In the present application:- the expression “comprised between ... and ...” or “from ... to...” should be understood as including the limits;- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present invention;- where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component recited in a list of elements or components may be omitted from such list; and- any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents.

[0015] Definitions

[0016] The term “antioxidant” refers to any compound that prevents or slows the oxidation of other molecules through various mechanisms, including but not limited to radical scavenging. This term highlights the overall function of preventing oxidative damage, which can involve chelating metal ions, decomposing peroxides, or enhancing the activity of other antioxidants.

[0017] The term “radical scavenger” denotes a compound that neutralizes free radicals by donating an electron or a hydrogen atom, emphasizing the action of capturing and neutralizing these radicals. Therefore, in the context of the present invention, the term “radical scavenger is encompassed by the term “antioxidant”.

[0018] The term “levulinate ester” should be interpreted as having its broadest meaning in the context of the present invention. As such, the levulinate ester may be a levulinate ester with one ester group (also called levulinate monoester), a dilevulinate ester (i.e., a compound formed when levulinate ester is esterified with a glycol), or a multilevulinate ester (i.e., a compound formed when levulinate ester is esterified with a polyol, for example with sorbitol). Preferably, the levulinate ester is a levulinate monoester or a mixture of levulinate monoesters.

[0019] The antioxidant used in the present invention may be characterized by the presence of a certain group, radical or function. For example, the antioxidant may be an amine-based antioxidant. In this case, the term “amine -based antioxidant” refers herein to an antioxidant, the structure of which comprises at least one amine function. This means that the antioxidant generally comprises other groups or moieties. The nature and number of additional groups or moieties is not limited. The same holds true for all antioxidant described herein, including forantioxidant which qualify, for example, as carotenoids, glutathione or nitroxide-based antioxidant (among all of the other antioxidants described herein).

[0020] The term “derivative” or “derivative of antioxidant” refers to a chemically modified version of the antioxidant of the present invention, retaining the same technical effect. Derivatives may include, for example, salts, esters, ethers, or other chemical modifications that maintain the antioxidant properties of the original compound.

[0021] The term “about” means the recited number ± 10%. For example, "about 100" means 90-110, inclusive.

[0022] The term “aliphatic” means non-aryl and encompasses non-aromatic rings (e.g., a cycloaliphatic ring). It may be linear or branched, saturated or unsaturated, cyclic or acyclic. An aliphatic ligand may be substituted by one or more groups, for example selected from alkyl, hydroxyl, halogen (Br, Cl, I), isocyanate, carbonyl (=0), amine, carboxylic acid, -C(=O)-OR’, -C(=O)-O-C(=O)-R’, each R’ being independently a C1-C6 alkyl. It may comprise one or more bonds selected from ether, ester, amide, urethane, carbo amide, carbonate, organosiloxane, and mixtures thereof. Examples of aliphatic groups are C1-C6, C1-C10 and C1-C20 aliphatic chains.

[0023] The term “aryl” means comprising an optionally substituted polyunsaturated aromatic group. The aryl may contain a single ring (i.e. phenyl) or more than one ring wherein at least one ring is aromatic. When the aryl comprises more than one ring, the rings may be fused or linked via a direct bond (for example biphenyl). The aromatic ring may optionally comprise one to two additional fused rings (i.e. cycloalkyl, heterocycloalkyl or heteroaryl). Examples include phenyl, naphtyl, biphenyl, phenanthrenyl and naphthacenyl.

[0024] The term “heteroaryl” means comprising an optionally substituted polyunsaturated aromatic group wherein one or more of the ring atoms is a heteroatom such as O, N and S.

[0025] The term “aralkyl” means an aryl substituted by an alkyl group. An example of an aralkyl group is tolyl.

[0026] The term “alkaryl” means an alkyl substituted by an aryl group. An example of an alkaryl group is benzyl (-CFL-Phenyl).

[0027] The term “heteroaralkyl” means an aralkyl group in which the aryl contains at least one heteroatom, such as O, N or S.

[0028] The term “alkheteroaryl” means an heteroaryl group substituted by an alkyl.

[0029] Levulinate ester composition

[0030] The present invention relates to a levulinate ester composition. This levulinate ester composition comprises a levulinate ester and at least one antioxidant. The composition of the present invention is a liquid.

[0031] The inventors have found that adding an antioxidant to levulinate ester products has an effect in minimizing or preventing yellowing of the products. The solution not only produces an effect on the products immediately after manufacturing, but also over time as it has been shown to attenuate the increase in yellow color over time (e.g., after 35 days). The addition of antioxidant(s) in levulinate ester compositions, which are stored at high temperatures (i.e., temperatures higher than room temperature, e.g., temperatures above 30°C), has also been shown to be effective in attenuating the increase in color compared to compositions not comprising the antioxidant.

[0032] The addition of an antioxidant to levulinate ester products meets the objectives of the present invention, as the solution is easy to implement, cost-effective as it does not require significant equipment investments. The invention is inventive and addresses the technical problem effectively.

[0033] In some embodiments, the levulinate ester component is the primary or major component in the composition of the present invention. In other words, it forms the largest portion compared to other components in the composition described in the present invention. For example, the amount of levulinate ester in the composition may be at least 95 wt.%, based on the total weight of the composition.

[0034] In some other embodiments, the amount of levulinate ester in the composition may be at least about 98.0 wt.%, about 98.5 wt.%, at least about 99.0 wt.%, at least about 99.5 wt.%, based on the total weight of the composition.

[0035] The levulinate ester composition comprises less than 100 wt.% of levulinate ester. In some embodiments, the amount of levulinate ester in the composition may be less than about 99.99 wt.%, less than about 99.95 wt.% or less than about 99.90 wt.%, based on the total weight of the composition.

[0036] According to the present invention, the levulinate ester is a levulinate ester with one ester group (also called levulinate monoester). The levulinate ester may also be a dilevulinate ester, which is a compound formed when levulinate ester is esterified with a glycol. It may also be a multilevulinate ester, which is a compound formed when levulinate ester is esterified witha polyol (alcohol with 2 or more hydroxyl groups), for example with sorbitol. Preferably, the levulinate ester is a levulinate monoester or a mixture of levulinate monoesters.

[0037] The composition of the present invention may comprise several distinct levulinate esters, for example two, three or four distinct levulinate esters. The composition of the present invention may comprise one levulinate ester only. The composition of the present invention may comprise a mixture of levulinate esters.

[0038] The composition of the present invention also comprises at least one antioxidant.

[0039] In some embodiments, the antioxidant constitutes the minor component in the composition. In other words, the antioxidant forms a small or lesser portion of the overall composition. It is not the primary or major component but is present in a smaller quantity relative to the levulinate ester component and other optional components in the mixture. For example, the amount of antioxidant may be from 10 ppm to 5,000 ppm, based on the total weight of the composition.

[0040] In some other embodiments, the amount of antioxidant in the composition is from about 50 ppm to about 3,000 ppm, from about 100 ppm to about 2,000 ppm or from about 200 ppm to about 1,500 ppm, based on the total weight of the composition.

[0041] The composition of the present invention may comprise several distinct antioxidants, for example two, three or four distinct antioxidants, for example a combination of distinct antioxidants.

[0042] The composition of the present invention may comprise several distinct antioxidants. For example, the composition of the present invention may comprise a combination of an antioxidant (or several) qualifying in one category of antioxidants described herein and an antioxidant (or several) qualifying in another category of antioxidants described herein. Additionally, the composition of the present invention may comprise a combination of an antioxidant (or several) qualifying in one category of antioxidants described herein and an antioxidant (or several) not described herein. Examples of antioxidants which are not described herein but may be used in combination with the antioxidant listed in the present application are phenolic antioxidants. Examples of these antioxidants not described herein, but which can be used in addition to the antioxidants described herein, are tocopherol, derivatives of tocopherol, tocotrienol, hydroquinone, alkyl phenol, butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tertiary butylated hydroxyquinone (TBHQ), propyl gallate (PG), octyl gallate (OG), dodecyl gallate (DG), catechin, benzoic acid, hydroxybenzoic acid,dihydroxybenzoic acid, p-hydroxybenzoic acid and derivatives (Bas, p-HBAs, DHBAs ), vanillic acid (VA), gallic acid (GA), salicylic acid, syringic acid, hydroxycinnamic acid and derivatives (e.g., caffeic acid, ferulic acid, sinapic acid, p-coumaric acid, o-coumaric acid), stilbenoid and derivatives of the aglycone type (e.g., resveratrol) and derivatives of the glycoside type (e.g., piceid), tannins and hydrolysable derivatives (e.g., ellagitannins, gallotannins) and condensates derivatives (e.g., proanthocyanidins), lignans, lignins, and any derivative of such compounds, and mixtures or combinations thereof.

[0043] In the context of the present invention, more precisely with respect to combinations of antioxidants, the term “combination” herein involves blending several antioxidants to achieve a synergistic effect where the properties of each antioxidant enhance the effects of the others.

[0044] The composition of the present invention preferably comprises, or consists essentially of, one, two or three levulinate esters and one or several antioxidants.

[0045] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one of vitamin C, carotenoids, flavonoids, benzopyrones, naphthoquinone, glutathione, coenzyme Q, ubiquinone, lipoic acid, a nitroxide-based antioxidant, a phosphite-based antioxidant, a phosphonite-based antioxidant, an amine-based antioxidant, and mixtures or combinations thereof.

[0046] In some embodiments, the antioxidant used in the composition of the present invention comprises at least vitamin C or derivatives thereof. In these embodiments, the antioxidant may for example be at least one of ascorbyl glucoside, ascorbyl palmitate, sodium ascorbyl phosphate, magnesium ascorbyl phosphate, ascorbyl sorbate, tetrahexyldecyl ascorbate, ascorbyl tetraisopalmitate, 3-O-ethyl ascorbate, mono-, di-, tri-, or tetrafunctionalized esters, a salt of vitamin C, any of their derivatives, or a mixture or a combination thereof.

[0047] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one carotenoid or a derivative thereof. In these embodiments, the antioxidant may for example be at least one of [3-carotene, lycopene, lutein, zeaxanthin, astaxanthin, any of their derivatives, or a mixture or a combination thereof.

[0048] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one flavonoid or a derivative thereof. In these embodiments, the antioxidant may for example be at least one of flavones (e.g., luteolin and apigenin),isoflavones (e.g., genistein, daidzein and glycitein), flavonols and dihydroflavonols (e.g., quercetin, kaempferol, myricetin), flavanones (e.g., naringenin, eriodictyol, hesperetin), flavanonols and flavanols (e.g., proanthocyanidins, catechins), aurones and chaicones, anthocyanidins (e.g., cyanidin, pelagonidin, dihydrochalcones anthocyanins), any of their derivatives, or a mixture or a combination thereof.

[0049] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one benzopyrone or a derivative thereof. In these embodiments, the antioxidant may for example be at least one of coumarins, seselin, psoralens, warfarin, any of their derivatives, or a mixture or a combination thereof.

[0050] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one benzopyrone or a derivative thereof. In these embodiments, the antioxidant may for example be at least one of vitamin KI (phylloquinone) or vitamin K2 (menaquinone), any of their derivatives, or a mixture or a combination thereof.

[0051] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one amine -based antioxidant. In these embodiments, the antioxidant may for example be at least one of an aromatic cyclic amine, hydroxylamine, heterocyclic amine, oxygenated aromatic amine functionalized with (CH3)nor (CH2)n, wherein n ranges between 1 and 6, pyran amine, alkyl dimeric fatty amine, or a Schiff base amine, any of their derivatives, or a mixture or a combination thereof.

[0052] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one amine -based antioxidant. In these embodiments, the antioxidant may for example be at least one of 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO), 2,2,5,5-tetramethyl-l-pyrrolidinyloxy (PROXYL), any of their derivatives, or a mixture or a combination thereof.

[0053] In some embodiments, the antioxidant used in the composition of the present invention comprises at least one phosphite-based antioxidant or a phosphonite-based antioxidant. In these embodiments, the antioxidant may for example be at least one of triphenylphosphite (TPP), tris(2,4-di-tert-butylphenyl)phosphite, tris(2,4-di-tert- butylphenyl)phosphite, di-tert-butylphenylphosphite, 2,4-di-tert-butylphenyl phosphite, tris(2,4-di-tert-butylphenyl)phosphonite and bis(2,4-di-tert-butylphenyl)phosphonite. any of their derivatives, or a mixture or a combination thereof.

[0054] The composition of the present invention may comprise other components and / or impurities.

[0055] The term “component” refers to a substance that is intentionally included in the composition. Other components may be present in the composition of the present invention; if they are included in the composition of the present invention, they are typically included in low amounts, for example less than about 5.0 wt.% or less than about 4.0 wt.% (and even lower).

[0056] In contrast, the term “impurity” refers to a substance that is not intentionally included in the composition and which is usually present in a very low amount. Impurities can arise from various sources, such as raw materials, manufacturing processes, or storage conditions. While impurities may affect the quality, safety, or efficacy of the final product, it is generally acceptable that compositions comprise low amounts of such impurities. The amount of such impurities and the nature of such impurities generally depend on the intended application, as different applications may tolerate varying levels of impurities based on the required quality standards and performance criteria.

[0057] In some embodiments, the composition of the present invention comprises less than about 50,000 ppm of impurities, for example less than about 20,000, less than about 10,000 or less than about 5,000, based on the total weight of the composition.

[0058] The composition of the present invention may comprise one or several impurities arising from the raw materials and manufacturing processes used for preparing the levulinate ester. The composition of the present invention generally comprises at least one such impurity.

[0059] Examples of impurities which may be present in the composition of the invention are water, lactone derivatives of levulinic acid, levulinic ester, furanics, functionalyzed furanics, derivatives of furfuryl alcohol, pseudo-ethyl levulinate, angelicalactone, and levulinic acid. This list is, however, not meant to be limiting.

[0060] In some embodiments, the levulinate ester is obtained from the esterification of levulinic acid with alcohols. Levulinic acid is typically derived from biomass, especially through the degradation of cellulose. This process involves treating cellulose with acid catalysts to produce levulinic acid, along with other by-products. Levulinic acid can be transformed into a wide range of valuable derivatives, including levulinate esters, gamma- valerolactone, methyltetrahydrofuran, diphenolic acid and 5 -aminolevulinic acid.

[0061] As explained above, levulinate esters can be produced through several methods. The methods and raw materials used to produce the levulinate esters impact the purity of the finalproduct, including the color of the final product, as well as the color stability of the product over time.

[0062] The esterification of levulinic acid with alcohols to prepare levulinate esters typically requires the presence of an acid catalyst (such as sulfuric acid) to accelerate the process and improve the yield of the ester. The reaction is usually carried out under reflux conditions to ensure complete conversion. The alcohol used in the esterification process is not limited. It may be either a monohydric alcohol or a polyhydric alcohol (alcohol having multiple hydroxyl groups). Monohydric alcohols, such as methanol, ethanol, propanol, and butanol, can for example be used. Polyhydric alcohols, including ethylene glycol, propylene glycol, and glycerol, can also be used to prepare other levulinate ester products, such as di- or triesters. Higher alcohols and branched alcohols, such as isopropanol, isobutanol, and tert-butanol, yield esters with branched chains. Within the scope of the present invention, the levulinate ester can also result from the esterification of levulinic acid with unsaturated alcohols, like allyl alcohol, and aromatic alcohols, such as phenol. Specialty alcohols, including cetyl and stearyl alcohols, can be used for application in cosmetics and personal care products; sugar alcohols like sorbitol and mannitol can be used to prepare biocompatible and biodegradable esters.

[0063] In some embodiments, the levulinate ester used in the composition of the present invention derives from the esterification of levulinic acid with a monohydric or a polyhydric alcohol, for example having a number of hydroxyl groups ranging from 1 to 20, for example from 1 to 10 or from 1 to 5.

[0064] In some preferred embodiments, the alcohols used for preparing the levulinate ester is ethanol (ethyl levulinate), butanol (butyl levulinate), isoamyl alcohol (isoamyl levulinate), isobutanol (isobutyl levulinate), or 2-ethylhexanol (ethylhexyl levulinate).

[0065] Under certain conditions, the reaction may be represented according to the following equations:(eq.1 with polyhydric alcohol) or(eq.2 with monohydric alcohol) wherein:R is substituted or unsubstituted aliphatic, aryl, aralkyl, alkaryl, heteroaralkyl, alkheteroaryl, or heteroaryl group, preferably a substituted or unsubstituted C1-C20 aliphatic group; m is an integer > 1, preferably m ranges from 1 to 20, from 1 to 10 or from 1 to 6; n is an integer > 1, preferably n ranges from 1 to 20, from 1 to 10 or from 1 to 6.

[0066] In some preferred embodiments, in equations 1-2, as well as equations 3-4 below, R is C2H5 (ethanol), C4H9 (butanol), C5H11 (isoamyl alcohol), C4H9 (branched, isobutanol), or CsHiv (2-ethylhexanol).

[0067] In some embodiments, the levulinate ester is obtained from the conversion of furfuryl alcohol in the presence of alcohols (e.g., methanol, ethanol, etc.). Alcohols which can be used according to these embodiments are as described above. Furfuryl alcohol is an organic compound derived from the hydrogenation of furfural. Furfural may typically be obtained from the processing of biomass, such as agricultural waste. Furfuryl alcohol contains a furan ring C4H3O with an attached hydroxymethyl group. The conversion or furfuryl alcohol typically takes place under acidic conditions, which act as a catalyst.

[0068] Under certain conditions, the reaction may be represented according to the following equations:(eq.3 with polyhydric alcohol) or(eq.4 with monohydric alcohol) wherein:R is substituted or unsubstituted aliphatic, aryl, aralkyl, alkaryl, heteroaralkyl, alkheteroaryl, or heteroaryl group, preferably a substituted or unsubstituted C1-C20 aliphatic group; m is an integer > 1, preferably m ranges from 1 to 20, from 1 to 10 or from 1 to 6; n is an integer > 1, preferably n ranges from 1 to 20, from 1 to 10 or from 1 to 6.

[0069] For example, the conversion of furfuryl alcohol in the presence of methanol produces methyl levulinate; the conversion of furfuryl alcohol in the presence of ethanol produces ethyl levulinate.

[0070] In some embodiments, the levulinate ester is obtained from the transesterification of levulinic acid-based esters. The reaction is generally conducted in the presence of an acid or base catalyst. This reaction involves exchanging the alkoxy group of a first ester with the alcohol group, forming a new ester and a by-product alcohol. Alcohols which can be used according to these embodiments are as described above. They can be monohydric alcohols or poly hydric alcohols.

[0071] Under certain conditions, the reaction may be represented according to the following equation:wherein:Ri and R2 are distinct and independently substituted or unsubstituted aliphatic, aryl, aralkyl, alkaryl, heteroaralkyl, alkheteroaryl, or heteroaryl group, preferably a substituted or unsubstituted C1-C30 aliphatic group.

[0072] In some preferred embodiments, in equation 5, Ri and R2 are independently C2H5 (ethanol), C4H9 (butanol), C5H11 (isoamyl alcohol), C4H9 (branched, isobutanol), or CsHn (2- ethylhexanol).

[0073] According to one example, methyl levulinate is converted into ethyl levulinate in the presence of ethanol.

[0074] In some embodiments, the levulinate ester is a byproduct of the synthesis of 5- methoxymethyl furfuraldehyde (5-MMF) or derivative thereof (e.g., 5 -alkoxy methyl furfuraldehyde). More precisely, the conversion of sugars such as fructose to 5-MMF involvesdehydration of fructose to form furfural typically achieved through the use of acid catalysts, and subsequently the methylation of furfural with methanol under acidic conditions to introduce a methoxymethyl group at the 5 -position of the furan ring to lead to 5-MMF. In these embodiments, levulinate esters are the by-product arising from the reaction conditions used in the synthesis of 5-MMF.

[0075] The levulinate ester may preferably be an alkyl levulinate. In some embodiments, the levulinate ester is methyl levulinate, ethyl levulinate, butyl levulinate, isoamyl levulinate, isobutyl levulinate, ethylhexyl levulinate or a mixture thereof.

[0076] The inventors have found that adding an antioxidant to levulinate ester products has an effect in minimizing or preventing yellowing of these products. The solution has also been shown to attenuate the increase in yellow color over time (e.g., after 35 days).

[0077] In some embodiments, the composition of the present invention presents a color on Alpha Scale of less than 100, after 50 days of storage at room temperature, as measured using Lovibond® EComparator 2000 for Pt-Co APHA Color scale, according to ASTM D1209. For example, the color is less than 90, less than 70, less than 50, or less than 40 after 50 days of storage at room temperature.

[0078] Levulinate ester compositions may be stored at high temperatures (i.e., temperatures higher than room temperature, e.g., temperatures above 30°C). Therefore, it is important that the technical effect of the antioxidant on the levulinate ester compositions remains true across different temperature ranges.

[0079] In some embodiments, the composition of the present invention presents a color on Alpha Scale of less than 180, after 35 days of storage at 50°C, as measured using Lovibond® EComparator 2000 for Pt-Co APHA Color scale, according to ASTM D1209. For example, the color is less than 170, less than 160, less than 165, or less than 160, after 35 days of storage at 50°C.

[0080] In some embodiments, the composition of the present invention comprises about 0.05 to about 5.0 mmol / L of antioxidant(s). For example, the composition may comprise from about 0.1 to about 4.0 mmol / L, from about 0.15 to about 3.0 mmol / L or from about 0.2 to about 2.0 mmol / L of antioxidant(s).

[0081] Method for preparing the levulinate ester composition

[0082] The composition of the present invention can be prepared using a variety of mixing equipment, with the choice of equipment depending on the volume of the composition beingproduced. For example, laboratory-scale mixers may be used for small-scale preparations, while high-shear mixers are suitable for applications requiring thorough mixing and dispersion. For larger scale production, industrial blenders, such as ribbon blenders or fluidized bed mixers stirred vessels or static mixers, can be employed. Additionally, continuous mixers may be utilized for processes that involve constant production and blending of large volumes.

[0083] Other aspects

[0084] The present invention also generally relates to the use of at least one antioxidant to reduce or avoid the color development in levulinate ester compositions.

[0085] All the embodiments described above in relation to the compositions apply similar to the present aspect of the invention.

[0086] The color-stable levulinate ester compositions described herein may be used in many and diverse end-use applications. The following markets can be mentioned, without the list being intended to be limited in scope: pesticides, herbicides, soil conditioners, drug delivery systems, pharmaceutical compositions, flavoring agents, food additives, cosmetics, personal care, fragrances, solvents, plasticizers, biofuels.ASPECTS OF THE INVENTION

[0087] The invention may be according to the following aspects:Aspect 1. A levulinate ester composition comprising:- a levulinate ester; and- at least one antioxidant.Aspect 2. The composition of aspect 1, wherein the amount of levulinate ester in the composition is at least about 95.0 wt.%, based on the total weight of the composition, preferably at least about 98.0 wt.%, about 98.5 wt.%, at least about 99.0 wt.%, at least about 99.5 wt.%, based on the total weight of the composition.Aspect 3. The composition of any one of aspects 1-2, wherein the amount of antioxidant is from about 10 ppm to about 5,000 ppm, based on the total weight of the composition, preferably from about 50 ppm to about 3,000 ppm, from about 100 ppm to about 2,000 ppm or from about 200 ppm to about 1,500 ppm, based on the total weight of the composition.Aspect 4. A levulinate ester composition comprising:- at least about 95.0 wt.% of a levulinate ester; and- from about 10 ppm to about 5,000 ppm of at least one antioxidant, based on the total weight of the composition.Aspect 5. The composition of any one of aspects 1-4, wherein the antioxidant comprises at least one of vitamin C, carotenoids, flavonoids, benzopyrones, naphthoquinone, glutathione, coenzyme Q, ubiquinone, lipoic acid, a nitroxide-based antioxidant, a phosphite-based antioxidant, a phosphonite-based antioxidant, an amine-based antioxidant, and mixtures or combinations thereof.

[0088] The composition of any one of aspects 1-5, wherein the antioxidant may for example be at least one of ascorbyl glucoside, ascorbyl palmitate, sodium ascorbyl phosphate, magnesium ascorbyl phosphate, ascorbyl sorbate, tetrahexyldecyl ascorbate, ascorbyl tetraisopalmitate, 3-O-ethyl ascorbate, mono-, di-, tri-, or tetra-functionalized esters, a salt of vitamin C, any of their derivatives, or a mixture or a combination thereof.Aspect 6. The composition of any one of aspects 1-6, wherein the antioxidant is at least one of [3-carotene, lycopene, lutein, zeaxanthin, astaxanthin, any of their derivatives, or a mixture or a combination thereof.Aspect 7. The composition of any one of aspects 1-7, wherein the antioxidant is at least one of flavones, isoflavones, flavonols, dihydroflavonols, flavanones, flavanols, flavanonols, aurones, chaicones, anthocyanidins, any of their derivatives, or a mixture or a combination thereof.Aspect 8. The composition of any one of aspects 1-8, wherein the antioxidant is at least one of coumarins, seselin, psoralens, warfarin, any of their derivatives, or a mixture or a combination thereof.Aspect 9. The composition of any one of aspects 1-9, wherein the antioxidant is at least one of phylloquinone and menaquinone, any of their derivatives, or a mixture or a combination thereof.Aspect 10. The composition of any one of aspects 1-10, wherein the antioxidant is an amine-based antioxidant and is at least one of at least one of an aromatic cyclic amine, hydroxylamine, heterocyclic amine, oxygenated aromatic amine functionalized with (CtTh or (CH2)n, wherein n ranges between 1 and 6, pyran amine, alkyl dimeric fatty amine, or a Schiff base amine, any of their derivatives, or a mixture or a combination thereof.Aspect 11. The composition of any one of aspects 1-11, wherein the antioxidant is at least one of 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO), 2,2,5,5-tetramethyl-l-pyrrolidinyloxy (PROXYL), any of their derivatives, or a mixture or a combination thereof.Aspect 12. The composition of any one of aspects 1-13, wherein the antioxidant is at least one of phosphite-based antioxidant or phosphonite-based antioxidant and is at least one oftriphenylphosphite (TPP), tris(2,4-di-tert-butylphenyl)phosphite, tris(2,4-di-tert- butylphenyl)phosphite, di-tert-butylphenylphosphite, 2,4-di-tert-butylphenyl phosphite, tris(2,4-di-tert-butylphenyl)phosphonite and bis(2,4-di-tert-butylphenyl)phosphonite. any of their derivatives, or a mixture or a combination thereof.Aspect 13. The composition of any one of aspects 1-13, wherein the levulinate ester is obtained from the esterification of levulinic acid with alcohols.Aspect 14. The composition of any one of aspects 1-13, wherein the levulinate ester is obtained from the conversion of furfuryl alcohol in the presence of alcohols.Aspect 15. The composition of any one of aspects 1-13, wherein the levulinate ester is obtained from the transesterification of levulinic acid-based esters.Aspect 16. The composition of any one of aspects 1-13, wherein the levulinate ester is a byproduct of the synthesis of 5 -alkoxymethyl furfuraldehyde-or derivative thereof.Aspect 17. The composition of any one of aspects 1-17, wherein the levulinate ester is an alkyl levulinate.Aspect 18. The composition of any one of aspects 1-18, wherein the levulinate ester is methyl levulinate, ethyl levulinate, butyl levulinate, isoamyl levulinate, isobutyl levulinate, ethylhexyl levulinate or a mixture thereof.Aspect 19. The composition of any one of aspects 1-19, wherein the composition comprises at least one of ethyl levulinate, butyl levulinate, isoamyl levulinate, isobutyl levulinate, ethylhexyl levulinate or a mixture thereof, and at least one antioxidant.Aspect 20. The composition of any one of aspects 1-20, wherein the composition presents a color on Alpha Scale of less than 100, after 50 days of storage at room temperature, as measured using Lovibond® EComparator 2000 for Pt-Co APHA Color scale, according to ASTM D1209.Aspect 21. The composition of any one of aspects 1-21, wherein the composition presents a color on Alpha Scale of less than 180, after 35 days of storage at 50°C, as measured using Lovibond® EComparator 2000 for Pt-Co APHA Color scale, according to ASTM DI 209.Aspect 22. The composition of any one of aspects 1-22, wherein the composition comprises at least two distinct antioxidants.Aspect 23. Use of at least one antioxidant to reduce or avoid the color development in levulinate ester compositions.Aspect 24. The use of aspect 25, wherein the levulinate ester compositions comprises at least about 95.0 wt.% of a levulinate ester, based on the total weight of the composition.Aspect 25. The use of any one of aspects 24-25, wherein the antioxidant is present in an amount ranging from about 10 ppm to about 5,000 ppm, based on the total weight of the composition.

Claims

CLAIMS1. A levulinate ester composition comprising:- at least 95.0 wt.% of a levulinate ester; and- from 10 ppm to 5,000 ppm of at least one antioxidant, based on the total weight of the composition.

2. The composition of claim 1, wherein the levulinate ester is an alkyl levulinate, preferably a methyl levulinate, an ethyl levulinate, a butyl levulinate, an isoamyl levulinate, an isobutyl levulinate, an ethylhexyl levulinate or a mixture thereof.

3. The composition of any one of claims 1-2, wherein the levulinate ester is:(i) obtained from the esterification of levulinic acid with alcohols,(ii) obtained from the conversion of furfuryl alcohol in the presence of alcohols,(iii) obtained from the transesterification of levulinic acid-based esters; or(iv) a byproduct of the synthesis of 5 -alkoxy methyl furfuraldehyde-or derivative thereof.

4. The composition of any one of claims 1-3, wherein the antioxidant comprises at least one of vitamin C, carotenoids, flavonoids, benzopyrones, naphthoquinone, glutathione, coenzyme Q, ubiquinone, lipoic acid, a nitroxide-based antioxidant, a phosphite- based antioxidant, a phosphonite-based antioxidant, an amine-based antioxidant, and mixtures or combinations thereof.

5. The composition of any one of claims 1-4, wherein the antioxidant is at least one of ascorbyl glucoside, ascorbyl palmitate, sodium ascorbyl phosphate, magnesium ascorbyl phosphate, ascorbyl tetraisopalmitate, 3-O-ethyl ascorbate, mono-, di-, tri-, or tetrafunctionalized esters, a salt of vitamin C, any of their derivatives, or a mixture or a combination thereof.

6. The composition of any one of claims 1-4, wherein the antioxidant is at least one of -carotene, lycopene, lutein, zeaxanthin, astaxanthin, any of their derivatives, or a mixture or a combination thereof.

7. The composition of any one of claims 1-4, wherein the antioxidant is at least one of flavones, isoflavones, flavonols, dihydroflavonols, flavanones, flavanonols, aurones, chaicones, anthocyanidins, any of their derivatives, or a mixture or a combination thereof.

8. The composition of any one of claims 1-4, wherein the antioxidant is at least one of coumarins, seselin, psoralens, warfarin, any of their derivatives, or a mixture or a combination thereof.

9. The composition of any one of claims 1-4, wherein the antioxidant is at least one of phylloquinone and menaquinone, any of their derivatives, or a mixture or a combination thereof.

10. The composition of any one of claims 1-4, wherein the antioxidant is an amine-based antioxidant and is at least one of at least one of an aromatic cyclic amine, hydroxylamine, heterocyclic amine, oxygenated aromatic amine functionalized with (CtTh or (CH2)n, wherein n ranges between 1 and 6, pyran amine, alkyl dimeric fatty amine, or a Schiff base amine, any of their derivatives, or a mixture or a combination thereof.

11. The composition of any one of claims 1-4, wherein the antioxidant is at least one of 2,2,6,6-tetramethyl-l-piperidinyloxy (TEMPO), 2,2,5,5-tetramethyl-l- pyrrolidinyloxy (PROXYL), any of their derivatives, or a mixture or a combination thereof.

12. The composition of any one of claims 1-4, wherein the antioxidant is at least one of phosphite-based antioxidant or phosphonite-based antioxidant and is at least one of triphenylphosphite (TPP), tris(2,4-di-tert-butylphenyl)phosphite, tris(2,4-di-tert- butylphenyl)phosphite, di-tert-butylphenylphosphite, 2,4-di-tert-butylphenyl phosphite, tris(2,4-di-tert-butylphenyl)phosphonite and bis(2,4-di-tert-butylphenyl)phosphonite. any of their derivatives, or a mixture or a combination thereof.

13. The composition of any one of claims 1-12, comprising at least two distinct antioxidants.

14. Use of at least one antioxidant to reduce or avoid the color development in levulinate ester compositions comprising at least 95 wt.% of a levulinate ester, based on the total weight of the composition.

15. The use of claim 14, wherein the antioxidant is present in an amount ranging from 10 ppm to 5,000 ppm, based on the total weight of the composition.

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