Method for purifying amino acid surfactants

Abstract

The present invention relates to a process for producing a purified amino acid surfactant from a crude amino acid surfactant containing impurities, the process comprising the steps of: (i) providing the crude amino acid surfactant; and (ii) subjecting the crude amino acid surfactant to an ultrafiltration stage; and (iii) collecting the purified amino acid surfactant so produced wherein the ultrafiltration stage comprises a filter membrane having a separation limit molecular retention of from 1000 g / mol to 100,000 g / mol, preferably from 4000 g / mol to 50,000 g / mol, more preferably from 5000 g / mol to 30,000 g / mol. The method can produce purified amino acid surfactants with very low levels of impurities, especially inorganic salts, residual amino acids and polar organic solvents. Furthermore, the method provides a high filtration rate wherein the permeate has a relatively low polar organic solvent content.

Description

Technical Field

[0001] The present invention relates to a method for providing a purified amino acid surfactant from a crude amino acid surfactant containing impurities. Such impurities arise during the amino acid surfactant manufacturing process and often include residual amino acids, byproducts such as inorganic salts, and polar organic solvents. The method developed by the inventors involves ultrafiltration of the crude amino acid surfactant using a filter membrane having a specific molecular weight cut-off range. Background Art

[0002] Amino acid surfactants are typically long-chain acyl N-substituted amino acids. They are considered to be biocompatible and biodegradable surfactants and are found to be useful in a variety of applications such as personal care applications and biomedical applications. Amino acid surfactants have been used as preservatives in, for example, pharmaceuticals and cosmetics, and have antibacterial, antiviral and anti-yeast properties. Common applications of amino acid surfactants include skin care products, hair cleansing products, dental products, including shampoos, shower gels, shower gels, cosmetics, toothpastes and toiletries. Other applications can include products in the biological and medical fields; emulsifiers, defoamers and detergents in food applications; products in the agricultural field; products for mineral flotation and the oil field; bactericides; dispersants; and detergents.

[0003] Conventionally, amino acid surfactants are typically produced by reacting an amino acid (typically as an alkali metal salt, such as a sodium salt) with a long-chain acyl halide (suitably a long-chain acyl chloride) in the presence of water and a polar organic solvent. Typically, a molar excess of the amino acid will be used in the reaction to ensure complete consumption of the acyl halide. It can be assumed that the reaction product of the crude amino acid surfactant contains impurities produced by the reaction. This will include inorganic salts such as NaCl produced as a by-product; residual amino acid; and polar solvents such as isopropanol or 1,2-propylene glycol. In order for the amino acid surfactant to meet the application standards, these impurities need to be removed or at least reduced to an acceptable level.

[0004] A conventional method for separating impurities from amino acid surfactants comprises combining concentrated hydrochloric acid with a crude amino acid surfactant to separate soluble impurities, particularly NaCl, polar solvents, amino acids, and some water, and forming the amino acid surfactant in the form of an insoluble acid as a precipitated solid. These solids need to be fully washed with water and then filtered through appropriate equipment. Subsequently, the amino acid surfactant is treated with sodium hydroxide to produce a purified sodium salt. The disadvantage of this method is that concentrated mineral acids such as concentrated hydrochloric acid are highly corrosive. Therefore, additional safety measures for safely handling concentrated acid and using expensive hydrochloric acid-resistant reactors are prerequisites for this procedure.

[0005] An alternative method for purifying crude amino acid surfactants requires first acidifying the reaction mixture, typically with concentrated hydrochloric acid, to form two phases, one containing an inorganic salt (i.e., NaCl), a small amount of a polar solvent (e.g., isopropyl alcohol or 1,2-propylene glycol), and some water, and the other containing the amino acid surfactant. This phase is then subjected to phase separation between the product phase and a phase containing water-soluble byproducts. The amino acid surfactant-containing product phase is further treated with water, and the mixture is then subjected to high-temperature distillation to remove the polar solvent and leave the purified amino acid surfactant. This method also suffers from the aforementioned disadvantages of using concentrated hydrochloric acid. In addition, this phase separation method requires the use of a large amount of polar solvent during the reaction. This polar solvent partially remains in the amino acid surfactant product and must therefore be removed by distillation. This additional thermal stress during the distillation stage can lead to partial degradation of the product and the formation of soaps, amino acid salts, pyroglutamate, and / or solvent esters. Another disadvantage is that some of the amino acid surfactant product is lost during the water removal process during the washing process.

[0006] Japanese patent application JP 07002747 A (June 6, 1995) describes a method for purifying N-long chain acyl acidic amino acid salts. The method is included in a solution containing a mixture of water and a hydrophilic organic solvent at a pH of 8 to 13.5 in the presence of a base to condense an acidic amino acid and a long chain fatty acid halide with a saturated or unsaturated acyl group of 8 to 22 carbon atoms. It is said that a membrane separation method is used to obtain high-purity N-long chain acyl acidic amino acid salts. These examples describe neutralizing the mixture with hydrochloric acid and adjusting the pH to between 7.0 and 8.0, adding water and then using a polyamide-based ultrafiltration membrane with a molecular weight cut-off of 200 to 500 at 10 to 20 kg / cm 2 Under the operating pressure, at a temperature of 20 to 30 degrees Celsius and 13 to 15 L / m 2 The impurities were removed at a feed water rate of 1000 liters per hour for 2 hours. The amount of inorganic salts contained in the product was 0.1% or less.

[0007] A review by Jing Guo et al., “Review: Progress in synthesis, properties and application of amino acid surfactants,” Chemical Physics Letters 794 (2022) 139499, provides an overview of amino acid surfactant classes, their synthesis, and their applications in various fields. Amino acid surfactants are said to possess physicochemical properties (including surface activity), aggregates, gels, and biodegradation, and have applications in household chemicals, biomedicine, food, agriculture, and industry.

[0008] The present invention aims to provide a more efficient method for purifying amino acid surfactants. Another object is to develop a purification method that avoids the use of strong inorganic acids such as hydrochloric acid. The inventors have also sought to avoid filtration methods that require high pressure and low flow rates, which on an industrial scale would often require large and expensive filtration systems with large membrane areas. In addition, the present invention addresses the need for methods that avoid the risk of generating high levels of hazardous wastewater. The present invention also addresses the need for purification methods that can produce highly purified amino acid surfactants, particularly with very low levels of impurities such as inorganic salts and / or residual amino acids and / or organic solvents. Summary of the Invention

[0009] The present invention defines a method for producing a purified amino acid surfactant from a crude amino acid surfactant containing impurities, the method comprising the following steps

[0010] (i) providing the crude amino acid surfactant; and

[0011] (ii) subjecting the crude amino acid surfactant to an ultrafiltration stage; and

[0012] (iii) collecting the purified amino acid surfactant thus produced,

[0013] The ultrafiltration stage comprises a filter membrane having a separation limit molecular cut-off of 1000 g / mol to 100,000 g / mol, preferably 4000 g / mol to 50,000 g / mol, more preferably 5000 g / mol to 30,000 g / mol. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Schematic diagram of the high-pressure stirred tank used in the purification experiments of crude amino acid surfactant SG1 in Examples 1 to 11.

[0015] Figure 2Schematic diagram of the pilot plant unit used for the purification experiments of crude amino acid surfactant SG2 in Examples 12 to 16. DETAILED DESCRIPTION

[0016] The method of the present invention enables the convenient production of highly purified amino acid surfactants, thereby achieving the above-mentioned objectives. Specifically, this method avoids the necessity of handling strong inorganic acids and provides the following method, which can be scaled up to industrial levels to produce commercial quantities of products without the need for large, expensive filtration systems that occupy large floor spaces. In particular, the method enables the production of purified amino acid surfactants with extremely low levels of inorganic salts, residual amino acids, and organic solvents without generating high levels of hazardous wastewater.

[0017] Surprisingly, the method of the present invention is highly effective. According to the prior art, the molecular membrane cutoff for achieving high-purity amino acid surfactants via filtration is between 120 and 250 g / mol, with a maximum of 500 g / mol (CN 113 024 401, CN 113 135 833), and it is not expected that a membrane with a cutoff size much larger than the amino acid surfactant molecule would produce the same purity.

[0018] Crude amino acid surfactants will generally be produced by reacting an amino acid (including its alkali metal salt) with an acyl halide in an alkaline medium containing a polar organic solvent. The alkaline medium will generally completely neutralize the amino acid to produce a completely neutralized alkali metal salt of the amino acid.

[0019] The term crude amino acid surfactant refers to an unpurified amino acid surfactant produced by a manufacturing process containing impurities. Typically, the impurities contained in the crude amino acid surfactant include inorganic salts, polar organic solvents, and optionally amino acids. Inorganic salts are typically salts of alkali metals and halides, such as sodium chloride. Therefore, inorganic salts are produced as by-products from the condensation reaction of an acyl halide with an alkali metal salt of the amino acid. The inorganic salt produced depends on the base used and the halide of the acyl halide. Desirably, the base can be sodium hydroxide, and the acyl halide can be an acyl chloride, thus producing sodium chloride as the inorganic salt. The polar organic solvent can be any suitable polar organic solvent in which the amino acid and the amino acid surfactant are soluble or at least miscible. Desirably, the polar solvent can be any hydrophilic solvent that is miscible with water. Suitable polar solvents should also be substantially inert to the acyl halide, typically the acyl chloride, used in the reaction to produce the amino acid surfactant. Indicative examples of suitable polar organic solvents include methanol, ethanol, isopropanol, 1-propanol, tert-butanol, sec-butanol, isobutanol, n-butanol, ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, glycerol, acetone, methyl ethyl ketone, tetrahydrofuran, cyclohexanone, 1,4-dioxane, and the like, but isopropanol or 1,2-propylene glycol are preferred. Generally, the amino acid should be used in a molar excess relative to the acid halide to ensure that all of the acid halide is consumed. As a result, the crude amino acid surfactant may contain excess unreacted amino acid.

[0020] Thus, the crude amino acid surfactant will typically be produced by a process preceding the method of the present invention for producing the purified amino acid surfactant.

[0021] Such a process can generally be summarized as a method for preparing crude amino acid surfactants by reacting an amino acid (including its alkali metal salt) with an acyl halide in an aqueous alkaline medium containing a polar organic solvent. Preferably, the amino acid will be used in a molar excess of the acyl halide.

[0022] In a desirable embodiment of the present invention, the crude amino acid surfactant is contained in an aqueous medium.Preferably, the aqueous medium should have a pH within a range that avoids precipitation.

[0023] Desirably, the crude material amino acid surfactant is contained in an aqueous medium, preferably having a pH sufficient for at least one of the acid groups of the amino acid surfactant to be in salt form. In the case of a multiprotic amino acid surfactant (e.g., a diprotic amino acid surfactant), the aqueous medium should be sufficient at a pH at which only one acid group is in salt form.

[0024] Suitably, the pH of the aqueous medium may be in the range of greater than 4.0 to 14.0, 5.0 to 14.0, such as 6.0 to 13.5, 7.0 to 13.0, 8.0 to 12.5, 8.5 to 12.0, 8.5 to 11.5. The exact desired pH will depend on the specific amino acid surfactant in the aqueous medium.

[0025] For stearoyl glutamate, it is preferred that the aqueous medium has a pH greater than 8.0, such as greater than 8.0 to 13.5, such as 8.1 to 13.0, desirably 8.2 to 12.5, more desirably 8.3 to 12.0, suitably 8.3 to 11.5, 8.3 to 11.0, 8.5 to 11.0, 9.0 to 11.0.

[0026] In this preferred embodiment, the method avoids the risk of forming small spheres or agglomerates. This can be a particular problem at lower pH. In the case of stearoyl glutamate, a pH below 8.0 has been found to be problematic in terms of the formation of small spheres or agglomerates.

[0027] Avoiding such small spheres or aggregates should reduce the risk of clogging the filter membrane.

[0028] Desirably, the crude amino acid surfactant is diluted with an aqueous dilution medium. The aqueous dilution medium can be any suitable aqueous medium that is effective in providing sufficient dilution to the crude amino acid surfactant. Preferably, the aqueous dilution medium is water.

[0029] Preferably, the crude amino acid surfactant is diluted with the aqueous dilution medium in an amount ranging from 1:10 to 3:1, based on the weight of the crude amino acid surfactant to the weight of the aqueous dilution medium. More preferably, the dilution can be from 1:10 to 1:1, more preferably from 1:6 to 1:1. The amount by which the crude amino acid surfactant is diluted can depend on the initial concentration or solids content of the crude amino acid surfactant. The initial solids content of the crude amino acid surfactant prior to dilution can be, for example, up to 50% w / w, typically from 15% to 50%, or from 20% to 40%.

[0030] The ultrafiltration stage can adopt any of a variety of membranes for the method. Suitable filter membranes can be constructed from a variety of materials. A class of filter membranes includes polymer membranes. Examples of polymer membranes include symmetrical (polymer) membranes, which have uniform (pore) structures across the thickness of the membrane. Alternatively, asymmetric (polymer) membranes can be used. Typically, the filter membrane can be formed from polyethylene, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylonitrile, polyethersulfone, hydrophilized polyethersulfone, or any combination (e.g., as a composite material). Other polymer filter membranes include polyester membranes and polycarbonate membranes, which can be made from polymers such as polypropylene, polyamide, cellulose acetate, polyethersulfone, and polysulfone using radiation and etching processes. These polymer membranes can be used as tubular membranes or flat membranes. Preferably, these polymer membranes are used as flat spiral wound membrane modules.

[0031] Other suitable filter membranes can be made of inorganic materials (such as ceramics and metals). Suitable commercial ceramic membranes can be made by a slurry casting process. Typically, this consists of two steps and begins with preparing a dispersion of fine particles (called slurry), followed by deposition of the particles on a porous support. Inorganic membranes that are generally available and suitable for use in the present invention include composite materials containing a thin separation barrier on a support (e.g., a ceramic material such as titanium dioxide, zirconium oxide or aluminum oxide or a combination thereof). These ceramic membranes and metal membranes can be used as tubular membranes or flat membranes. Preferably, these ceramic membranes are used as tubular multichannel ceramic membrane elements.

[0032] Preferred filter membranes are composed of any material selected from the group consisting of polyacrylonitrile, polyethersulfone, hydrophilized polyethersulfone, and any combination of these materials.

[0033] The ultrafiltration stage can be applied in cross-flow or dead-end mode.In a preferred embodiment, the ultrafiltration stage comprises cross-flow filtration.

[0034] Preferably, the crude amino acid surfactant is in an aqueous medium, preferably an aqueous medium having a pH greater than 4.0. As previously described, the precise pH required will depend on the specific amino acid surfactant. Suitably, the pH should be sufficient to render at least one of the acid groups of the amino acid surfactant in salt form. Ultrafiltration preferably employs cross-flow filtration. Typically, the aqueous medium containing the crude amino acid surfactant flows tangentially across the surface of the filter membrane. Desirably, when using a spiral wound assembly, the surface velocity of the aqueous medium is in the range of 0.1 to 1.0 m / s, preferably 0.2 to 0.7 m / s, and more preferably 0.3 to 0.5 m / s. When using a tubular assembly, the surface velocity of the aqueous medium is in the range of 0.1 to 10.0 m / s, preferably 0.5 to 7 m / s, and more preferably 1 to 5 m / s. During this process, a portion of the aqueous medium passes through the filter membrane as permeate or filtrate, and the remaining portion of the aqueous medium that does not pass through the filter membrane is referred to as the retentate. The permeate should contain a high proportion of soluble impurities such as inorganic salts, polar organic solvents and optionally residual amino acids. The retentate should contain a high proportion of amino acid surfactant. The retentate can be recycled in a recirculation loop and combined with further incoming aqueous medium containing crude amino acid surfactant and then passed through the cross-flow filtration stage again.

[0035] In a preferred embodiment, the crude amino acid surfactant is contained in an aqueous medium that is passed through an ultrafiltration stage to form a permeate and a retentate, wherein impurities are removed through the permeate and the amino acid surfactant is preferentially retained in the retentate, which is recycled in a recirculation loop.

[0036] Suitable average total flux across the membrane filter may be 5 to 90 kg / m 2 / h or higher, such as 10 to 80 kg / m 2 / h or 10 to 70 kg / m 2 The desired average total flux across the selected membrane filter may depend on a number of factors affecting the specific process equipment employed and its operation.

[0037] The ultrafiltration stage suitably needs to the pressure applied to the aqueous medium comprising the crude amino acid surfactant to promote transmembrane flow. Usually, the average transmembrane pressure (TMP) will be at least 1.0 bar, typically at least 5.0 bar. The average transmembrane pressure (TMP) can be up to 90 bar, but will usually be no more than 50 bar, for example, up to 30 bar. Examples of suitable average transmembrane pressure (TMP) scopes include 1.0 to 30.0 bar, 5.0 to 90.0 bar.

[0038] The aqueous medium in the recirculation loop and the ultrafiltration stage will generally be at a temperature above ambient temperature to maintain sufficient fluidity of the aqueous medium and its components. Suitably, the aqueous medium will be at a temperature of 10°C to 95°C, 25°C to 90°C, 30°C to 70°C and preferably 35°C to 60°C.

[0039] In one embodiment, the crude amino acid surfactant included in the aqueous medium is subjected to at least one diafiltration step. Typically, in the diafiltration step, diafiltration medium (it can and is usually identical with the above-mentioned aqueous dilution medium) is fed in the recirculation loop with the substantially identical speed of the permeate flowing out from the ultrafiltration stage. Therefore, under diafiltration mode, the diafiltration medium (or aqueous dilution medium) that enters the recirculation loop and the permeate that leaves the ultrafiltration stage with substantially identical speed means that the volume and concentration of the amino acid surfactant will keep substantially the same. Therefore, diafiltration can be considered to a kind of washing stage for crude amino acid surfactant.

[0040] In an alternative embodiment, at least one diafiltration step can be avoided by adopting a high initial dilution of the crude amino acid surfactant. This will then require at least one concentration step to reduce the solids content to the desired level. Therefore, in this alternative embodiment, a similar washing stage of the crude amino acid surfactant should be implemented.

[0041] The filtration factor (DF) is defined as the mass of diafiltration medium used divided by the mass of the retentate. Preferably, the process employs at least one diafiltration step and has an overall filtration factor (DF) of 1 to 10, preferably 2 to 6.

[0042] In another more preferred embodiment, the crude amino acid surfactant in the aqueous medium is subjected to at least one concentration step. The concentration step typically comprises feeding no or substantially no dilution medium into the recirculation loop while the permeate is removed in the ultrafiltration stage, or feeding the aqueous dilution medium into the recirculation loop at a rate lower than the rate of permeate flowing out of the ultrafiltration stage.

[0043] The number by which the aqueous medium containing the crude amino acid surfactant becomes more concentrated during the concentration step is referred to as the concentration factor (CF). The concentration factor (CF) is defined as the mass of the retentate at the beginning of the concentration step divided by the mass of the retentate at the end of the concentration step. A concentration factor (CF) of exactly 1 means that the aqueous medium has not been concentrated. Thus, a concentration factor (CF) of any value greater than 1 means that the aqueous medium has become more concentrated due to that CF value.

[0044] More preferably, the crude amino acid surfactant in the aqueous medium is subjected to at least one diafiltration step and / or at least one concentration step. Particularly preferably, the aqueous medium will be subjected to a combination of diafiltration and concentration, performed sequentially.

[0045] Still more preferably, the aqueous medium comprising the crude amino acid surfactant is subjected to one or more diafiltration and / or concentration steps comprising the following steps

[0046] a) optionally initial diafiltration (D1);

[0047] b) optional initial concentration (C1);

[0048] c) optional diafiltration (D2); and

[0049] d) optional final concentration (C2),

[0050] The prerequisite is that at least one of steps a or c and / or at least one of steps b or d is included.

[0051] Particularly preferably, the aqueous medium comprising the crude amino acid surfactant is subjected to a series of diafiltrations and / or concentrations comprising, in sequence:

[0052] a) optionally initial diafiltration (D1);

[0053] b) optional initial concentration (C1);

[0054] c) optional diafiltration (D2); and

[0055] d) optional final concentration (C2),

[0056] The prerequisite is that at least one of steps a or c and at least one of steps b or d are included.

[0057] Still more preferably, the combination of diafiltration and concentration steps comprises at least steps b), c) and d) in sequence. In another preferred aspect, the combination of diafiltration and concentration steps comprises at least steps a), b), c) and d) in sequence.

[0058] Where an initial diafiltration (D1) step is employed, it is desirable that this is carried out with a diafiltration factor (DF1) of from 0.01 to 3.0. Preferably, the initial diafiltration (D1) is carried out with a diafiltration factor (DF1) of from 0.3 to 1.0.

[0059] In the preferred form of the invention where an initial concentration (C1 ) step is carried out, it is preferred that this will have a concentration factor (CF1 ) of from 1.01 to 10.0 and preferably from 1.3 to 2.0.

[0060] Preferably, a diafiltration (D2) step is employed and this will follow the initial concentration (C1 ) step.Desirably, the diafiltration (D2) step is carried out with a diafiltration factor (DF2) of from 0.01 to 10.0, preferably from 1.5 to 5.0.

[0061] Preferably, the process employs a final concentration (C2) step, which is typically performed after the diafiltration (D2) step. The final concentration (C2) step is typically performed with a concentration factor (CF2) of 1.1 to 4.0, preferably 1.2 to 3.0.

[0062] The process for producing the purified amino acid surfactant can be continuous, batch, semi-batch or fed-batch. Preferably, the process is performed in batch or fed-batch operation. Desirably, the fed-batch process will comprise placing the crude amino acid surfactant in an aqueous medium in a recirculation loop (e.g. a dilution vessel) and feeding aqueous dilution medium, aqueous diafiltration medium and / or retentate into the recirculation loop (e.g. dilution vessel) at a defined rate.

[0063] It is generally preferred that the amino acid surfactant is in the form of an alkali metal salt or an ammonium salt. The alkali metal salt can for example be a sodium salt or a potassium salt, but preferably the amino acid surfactant is in the form of a sodium salt.

[0064] Preferably, the amino acid surfactant is an N-substituted C8-C 30 - acyl amino acid, preferably an N-substituted C 12 - acyl amino acid, preferably an N-substituted C 20 - acyl amino acid, including alkali metal salts thereof, for example sodium salts. C8-C 30 The acyl moiety can be saturated or unsaturated.

[0065] Suitable N-substituted C8-C 20Examples of acylamino acids include the following compounds: N-octanoylglycine, N-nonanoylglycine, N-decanoylglycine, N-undecanoylglycine, N-lauroylglycine, N-tridecanoylglycine, N-myristoylglycine, N-pentadecanoylglycine, N-palmitoylglycine, N-heptadecanoylglycine, N-stearoylglycine, N-nonadecanoylglycine, N-arachidoylglycine, N-α-linolenoylglycine, N-stearidonoylglycine, N-eicosapentaenoylglycine, N-linoleoylglycine, N-γ-linolenoylglycine, N-dihomo-γ-linolenoylglycine, N-arachidonoylglycine, N-behenoylglycine, N-erucoylglycine Acid, N-octanoyl sarcosine, N-nonanoyl sarcosine, N-decanoyl sarcosine, N-undecanoyl sarcosine, N-lauroyl sarcosine, N-tridecanoyl sarcosine, N-myristoyl sarcosine, N-pentadecanoyl sarcosine, N-palmitoyl sarcosine, N-heptadecanoyl sarcosine, N-stearoyl sarcosine, N-nonadecanoyl sarcosine, N-arachidoyl sarcosine, N-α-linolenoyl sarcosine, N-stearoyl sarcosine, N-eicosapentaenoyl sarcosine, N-linoleoyl sarcosine, N-γ-linolenoyl sarcosine, N-dihomo-γ-linolenoyl sarcosine, N-arachidonoyl sarcosine, N-behenoyl sarcosine, N-erucyl sarcosine, N-octanoyl glutamate, N-nonanoyl glutamate, N-decanoyl glutamate, N- Undecanoyl glutamate, N-lauroyl glutamate, N-tridecanoyl glutamate, N-myristoyl glutamate, N-pentadecanoyl glutamate, N-palmitoyl glutamate, N-heptadecanoyl glutamate, N-stearoyl glutamate, N-nonadecanoyl glutamate, N-arachidoyl glutamate, N-α-linolenoyl glutamate, N-stearoyl glutamate, N-eicosapentaenoyl glutamate, N-linoleoyl glutamate, N-γ-linolenoyl glutamate, N-dihomo-γ-linolenoyl glutamate, N-arachidonoyl glutamate, N-behenoyl glutamate, N-erucyl glutamate, N-octanoyl alanine, N-nonanoyl alanine, N-decanoyl alanine, N-undecanoyl alanine, N-lauroyl alanine, N-tridecanoyl alanine, N -Myristoyl Alanine, N-Pentadecanoyl Alanine, N-Palmitoyl Alanine, N-Heptadecanoyl Alanine, N-Stearyl Alanine, N-N-Nonadecanoyl Alanine, N-Arachidoyl Alanine, N-α-Linoleyl Alanine, N-Stearyl Alanine, N-Eicosapentaenoyl Alanine, N-Linoleyl Alanine, N-γ-Linoleyl Alanine, N-Dihomo-γ-Linoleyl Alanine, N-Arachidonoyl Alanine, N-Behenoyl Alanine, N-Erucoyl Alanine, N-Capryloyl Arginine, N-N-Nonanoyl Arginine, N-Decanoyl Arginine, N-Undecanoyl Arginine, N-Lauroyl Arginine, N-Tridecanoyl Arginine, N-Myristoyl Arginine, N-Pentadecanoyl Arginine, N-Palmitoyl Arginine,N-α-linolenoylarginine, N-stearoylarginine, N-nontadecanoylarginine, N-arachidonoylarginine, N-α-linolenoylarginine, N-stearoylarginine, N-eicosapentaenoylarginine, N- linoleoylarginine, N-γ-linolenoylarginine, N-dihomo-γ-linolenoylarginine, N- arachidonoylarginine, N-behenoylarginine, N-eryaroylarginine, N-octanoylglutamic acid, N- nonanoylglutamic acid, N-decanoylglutamic acid, N-undecanoylglutamic acid, N- lauryloylglutamic acid, N-tridecanoylglutamic acid, N-myristoylglutamic acid, N- pentadecanoylglutamic acid, N-palmitoylglutamic acid, N-heptadecanoylglutamic acid, N- stearoylglutamic acid, N-nonadecanoylglutamic acid, N-arachidonoylglutamic acid, N- eicosapentaenoylglutamic acid, N-linoleoylglutamic acid, N-γ-linolenoylglutamic acid, N- dihomo-γ-linolenoylglutamic acid, N-arachidonoylglutamic acid, N-behenoylglutamic acid, N- eryaroylglutamic acid, N-octanoylhistidine, N-nonanoylhistidine, N-decanoylhistidine, N- undecanoylhistidine, N-lauryloylhistidine, N-tridecanoylhistidine, N-myristoylhistidine, N- pentadecanoylhistidine, N-palmitoylhistidine, N-heptadecanoylhistidine, N-stearoylhistidine, N- nonadecanoylhistidine, N-arachidonoylhistidine, N-eicosapentaenoylhistidine, N-linoleoylhistidine, N-γ-linolenoylhistidine, N-dihomo-γ-linolenoylhistidine, N-arachidonoylhistidine, N- behenoylhistidine, N-eryaroylhistidine, N-octanoylisoleucine, N-nonanoylisoleucine, N- decanoylisoleucine, N-undecanoylisoleucine, N-lauryloylisoleucine, N-tridecanoylisoleucine, N- myristoylisoleucine, N-pentadecanoylisoleucine, N-palmitoylisoleucine, N-heptadecanoylisoleucine, N-stearoylisoleucine, N-nonadecanoylisoleucine, N-arachidonoylisoleucine, N- eicosapentaenoylisoleucine, N-linoleoylisoleucine, N-γ-linolenoylisoleucine, N-dihomo-γ-N-eicosapentaenoyl isoleucine, N-linoleoyl isoleucine, N-γ-linolenoyl isoleucine, N-dihomo-γ-linolenoyl isoleucine, N-arachidonoyl isoleucine, N-behenoyl isoleucine, N-erucyl isoleucine, N-octanoyl leucine, N-nonanoyl leucine, N-decanoyl leucine, N-undecanoyl leucine, N-lauroyl leucine, N-tridecanoyl leucine, N-myristoyl leucine, N-pentadecanoyl leucine, N-palmitoyl leucine, N-heptadecanoyl leucine, N-stearoyl leucine, N-nonadecanoyl leucine, N-arachidonoyl leucine, N-α-linolenoyl leucine, N-stearoyl leucine, N-eicosapentaenoyl leucine, N-linoleoyl leucine, N -γ-linolenoyl leucine, N-dihomo-γ-linolenoyl leucine, N-arachidonoyl leucine, N-behenoyl leucine, N-erucyl leucine, N-octanoyl lysine, N-nonanoyl lysine, N-decanoyl lysine, N-undecanoyl lysine, N-lauroyl lysine, N-tridecanoyl lysine, N-myristoyl lysine, N-pentadecanoyl lysine, N-palmitoyl lysine, N-heptadecanoyl lysine, N-stearoyl lysine, N-nonadecanoyl lysine, N-arachidonoyl lysine, N-α-linolenoyl lysine, N-stearoyl lysine, N-eicosapentaenoyl lysine, N-linoleoyl lysine, N-γ-linolenoyl lysine, N-dihomo-γ-linolenoyl lysine, N-arachidonoyl lysine Acyl lysine, N-behenyl lysine, N-erucyl lysine, N-octanoyl methionine, N-nonanoyl methionine, N-decanoyl methionine, N-undecanoyl methionine, N-lauroyl methionine, N-tridecanoyl methionine, N-myristoyl methionine, N-pentadecanoyl methionine, N-palmitoyl methionine, N-heptadecanoyl methionine, N-stearoyl methionine, N-nonadecanoyl methionine, N-arachidoyl methionine, N-α-linolenoyl methionine, N-stearoyl methionine, N-eicosapentaenoyl methionine, N-linoleoyl methionine, N-γ-linolenoyl methionine, N-dihomo-γ-linolenoyl methionine, N-arachidonoyl methionine, N-behenyl methionine, N-erucyl methionine, N-octanoylphenylpropional N-nonanoyl phenylalanine, N-decanoyl phenylalanine, N-undecanoyl phenylalanine, N-lauroyl phenylalanine, N-tridecanoyl phenylalanine, N-myristoyl phenylalanine, N-pentadecanoyl phenylalanine, N-palmitoyl phenylalanine, N-heptadecanoyl phenylalanine, N-stearoyl phenylalanine, N-nonadecanoyl phenylalanine, N-arachidoyl phenylalanine, N-α-linolenoyl phenylalanine, N-stearoyl phenylalanine, N-eicosapentaenoyl phenylalanine, N-linoleoyl phenylalanine, N-γ-linolenoyl phenylalanine, N-diohomo-γ-linolenoyl phenylalanine, N-arachidonoyl phenylalanine, N-behenoyl phenylalanine, erucic acid phenylalanine, N-octanoyl proline, N-nonanoyl proline,N-decanoyl proline, N-undecanoyl proline, N-lauroyl proline, N-tridecanoyl proline, N-myristoyl proline, N-pentadecanoyl proline, N-palmitoyl proline, N-heptadecanoyl proline, N-stearoyl proline, N-nonadecanoyl proline, N-arachidoyl proline, N-α-linolenoyl proline, N-stearoyl proline, N-eicosapentaenoyl proline, N-linoleoyl proline, N-γ-linolenoyl proline, N-dihomo-γ-linolenoyl proline, N-arachidonoyl proline, N-behenoyl proline, N-erucyl proline, N-octanoylserine, N-nonanoylserine, N-decanoylserine, N-undecanoylserine, N-lauroylserine, N-Tridecanoylserine, N-myristoylserine, N-pentadecanoylserine, N-palmitoylserine, N-heptadecanoylserine, N-stearoylserine, N-nonadecanoylserine, N-arachidoylserine, N-α-linolenoylserine, N-stearoylserine, N-eicosapentaenoylserine, N-linoleoylserine, N-γ-linolenoylserine, N-dihomo-γ-linolenoylserine, N-arachidonoylserine, N-behenoylserine, N-erucylserine, N-octanoylthreonine, N-nonanoylthreonine, N-decanoylthreonine, N-undecanoylthreonine, N-lauroylthreonine, N-tridecanoylthreonine, N-myristoylthreonine, N-pentadecanoylthreonine N-palmitoylthreonine, N-heptadecanoylthreonine, N-stearoylthreonine, N-nonadecanoylthreonine, N-arachidoylthreonine, N-α-linolenoylthreonine, N-stearoylthreonine, N-eicosapentaenoylthreonine, N-cervonoylthreonine, N-linoleoylthreonine, N-γ-linolenoylthreonine, N-dihomo-γ-linolenoylthreonine, N-arachidonoylthreonine, N-behenoylthreonine, N-erucylthreonine, N-octanoyltryptophan, N-nonanoyltryptophan, N-decanoyltryptophan, N-undecanoyltryptophan, N-lauroyltryptophan, N-tridecanoyltryptophan, N-myristoyltryptophan, N-pentadecanoyltryptophan, N-palmitoyltryptophan, N -Heptadecanoyl tryptophan, N-stearoyl tryptophan, N-nonadecanoyl tryptophan, N-arachidoyl tryptophan, N-α-linolenoyl tryptophan, N-stearoyl tryptophan, N-eicosapentaenoyl tryptophan, N-linoleoyl tryptophan, N-γ-linolenoyl tryptophan, N-dihomo-γ-linolenoyl tryptophan, N-arachidonoyl tryptophan, N-behenoyl tryptophan, N-erucyl tryptophan, N-octanoyl tyrosine, N-nonanoyl tyrosine, N-decanoyl tyrosine, N-undecanoyl tyrosine, N-lauroyl tyrosine, N-tridecanoyl tyrosine, N-myristoyl tyrosine, N-pentadecanoyl tyrosine, N-palmitoyl tyrosine, N-heptadecanoyl tyrosine, N-stearoyl tyrosine, N-nonadecanoyl tyrosine,N-arachidoyl tyrosine, N-α-linolenoyl tyrosine, N-stearoyl tyrosine, N-eicosapentaenoyl tyrosine, N-linoleoyl tyrosine, N-γ-linolenoyl tyrosine, N-dihomo-γ-linolenoyl tyrosine, N-arachidonoyl tyrosine, N-behenoyl tyrosine, N-erucyl tyrosine, N-octanoyl valine, N-nonanoyl valine, N-decanoyl valine, N-undecanoyl valine, N-lauroyl valine, N-tridecanoyl valine, N-carnitine Myristoyl valine, N-pentadecanoyl valine, N-palmitoyl valine, N-heptadecanoyl valine, N-stearoyl valine, N-nonadecanoyl valine, N-arachidoyl valine, N-α-linolenoyl valine, N-stearoyl valine, N-eicosapentaenoyl valine, N-linoleoyl valine, N-γ-linolenoyl valine, N-dihomo-γ-linolenoyl valine, N-arachidonoyl valine, N-behenoyl valine and N-erucoyl valine. Preferably, these compounds will be in the form of an alkali metal salt, preferably a sodium salt. More preferably, the N-substituted acyl amino acid is N-stearoyl glutamic acid, still more preferably as an alkali metal salt, especially a sodium salt.

[0066] As given above, the crude amino acid surfactant will typically be obtained by the reaction of an amino acid and an acid halide under alkaline conditions and in the presence of a polar organic solvent.

[0067] Suitably, the acyl halide should be C6-C 30 -acyl halide, preferably C 12 -C 22 -acyl halide. Although the halide may be any halide, such as fluoride, chloride, bromide or iodide, it is preferred that the halide is chloride. 20 Suitable examples of acyl chlorides include octanoyl chloride, nonanoyl chloride, decanoyl chloride, n-undecanoyl chloride, lauroyl chloride, n-tridecanoyl chloride, myristoyl chloride, n-pentadecanoyl chloride, palmitoyl chloride, heptadecanoyl chloride, stearoyl chloride, n-nonadecanoyl chloride, arachidoyl chloride, α-linolenoyl chloride, stearyl chloride, eicosapentaenoyl chloride, linoleoyl chloride, γ-linolenoyl chloride, dihomo-γ-linolenoyl chloride, arachidonoyl chloride, behenoyl chloride and erucyl chloride.

[0068] Examples of suitable amino acids include glycine, sarcosine, glutamic acid, alanine, arginine, aspartic acid, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine and valine. Preferably, the amino acid is glutamic acid.

[0069] The following examples are intended to illustrate the invention but are not limiting.

[0070] Examples

[0071] Examples 1 to 10

[0072] The crude amino acid N-stearoylglutamate disodium salt is produced by reacting disodium glutamate and stearoyl chloride at low temperature in an aqueous alkaline medium containing 15% by weight of isopropanol. This is referred to as crude SG1.

[0073] Disodium N-stearoylglutamate is produced by feeding stearoyl chloride with an excess of sodium glutamate and a solids content of not more than 36 wt.-% to a stirred aqueous solution of sodium glutamate at pH>10 and containing 15 wt.-% isopropanol at a temperature of <20°C.

[0074] For Experiments 1 to 10, a high pressure stirred cell unit (see Figure 1 ). The apparatus consists of a retentate pool B1 installed in a thermostatically controlled water bath and a container B10 for crude SG1 feed or diafiltration medium. The membrane is installed at the bottom of pool B1 (as indicated in the figure). The liquid in pool B1 is stirred by a magnetic stirrer. By applying a pressure of up to 25 bar to container B10, the permeate is pressed through the membrane and collected in a bottle placed on a balance. In these experiments, 10 ultrafiltration membranes from three suppliers were tested as indicated in Table 1.

[0075] The experimental parameters are compiled in Table 1 and the experimental results are compiled in Table 2.

[0076] Table 1: Experiment at high pressure stirred cell temperature 65°C, feed crude SG1, assumed undiluted to have 36% solids.

[0077]

[0078]

[0079] Table 2 Experimental results at a high pressure stirred cell temperature of 65°C, crude SG1 feed, assumed to be undiluted

[0080]

[0081] Table 2 (Part 2):

[0082]

[0083] Example 11-Example 15

[0084] The crude amino acid surfactant, N-stearoylglutamate disodium salt, is produced by reacting disodium glutamate and stearoyl chloride in an aqueous alkaline medium containing isopropyl alcohol. This is referred to as crude SG2. The composition of crude SG2 is 3.7 wt% sodium chloride, 7.0 wt% isopropyl alcohol, 25.4 wt% sodium stearyl glutamate, 3.1 wt% sodium glutamate, and 2.6 wt% stearic acid, with the remainder being water.

[0085] Disodium N-stearoylglutamate is produced by feeding stearoyl chloride with an excess of sodium glutamate and not exceeding 36 wt.-% solids content to a stirred aqueous solution of sodium glutamate at pH>10 and containing 7 wt.-% isopropanol at a temperature of <20°C.

[0086] The pilot plant consists of a stainless steel container C001, a pressure pump (P) and membrane units F002 and F003. Figure 2 Connection: 1.5m 3 The vessel C001 is equipped with a stirrer, a heating mantle (HM), a level indicator (L) and a temperature indicator (T). A pressure pump (P) enables the dilute crude SG2 to be fed to the membrane units F003 and / or F002 and can be adjusted according to Figure 2 Automatic operation. Stainless steel membrane units F003 and F002 are suitable for accommodating two 4-inch spiral wound membranes and can be used Figure 2 Appropriate combinations of valves H02, H20, H21, H30, H31, H32, H33 shown in the figure operate in parallel and series modes.

[0087] For the pilot plant experiments, a stirred vessel C001 and a filtration unit were used. Vessel C001 was equipped with a retentate return line and a supply of diluted crude SG2 synthesis product and diafiltration (DF) medium (see Figure 2 The diafiltration (DF) medium was deionized water. The filling capacity of the vessel C001 was 1500 liters.

[0088] In Examples 11 to 15, the filter membrane used was a spiral wound module from Microdyn-Nadir. OY UP010 4040C (46 mil spacer, membrane area 6.0m 2 ), which has a nominal molecular weight cut-off of 10,000 Da.

[0089] Table 3 provides an overview of the pilot plant experiments for Examples 11-15.

[0090] Table 3: Process parameters for pilot plant experiments

[0091]

[0092]

[0093] *This material is diluted 1:1.

[0094] Initially, container C001 was filled with 1500 kg of diluted synthesis product.

[0095] In Example 011, the crude SG2 was diluted with deionized water (DI water) at a ratio of 1:5 to maintain the isopropanol concentration in the mixture below 1.4 wt% and the flash point above 80°C. In this example, the remaining raw material (approximately 1500 kg) was fed into the container via a fed-batch concentration process. In Example 016, after the initial concentration step, the raw material (200 kg) was filled into container C001.

[0096] In Examples 013 to 015, the filtration process began with an initial diafiltration step DF1 to reduce the concentration of isopropyl alcohol in the retentate. An initial concentration step was then performed to reduce the level in container C001. Examples 011 and 012 did not employ an initial diafiltration step DF1.

[0097] In all cases, sodium chloride and isopropyl alcohol were removed by the following diafiltration step. Finally, in a final concentration step, the purified product was concentrated to its final sodium stearyl glutamate content. Please find the diafiltration factor DF and concentration factor for the entire process in Table 3.

[0098] The filtration temperature is 40°C to 60°C. The cross flow of Example 011 is 2.8m 3 / h to 3.7m 3 / h. In Examples 012 to 015, 4.6m 3 / h of cross flow. The inlet pressure of the first module was kept constant at 10 bar. The transmembrane pressure (TMP) was between 9.5 and 9.9 bar.

[0099] Table 4: Overview of fluxes in the pilot plant example; membrane modules: OY UP010 4040C, 46 mil spacer; crude SG2 stock.

[0100] Example 011 012 013 014 015 Start dilution feed 1:5 1:2 1:2.7 2:3 1:2 <![CDATA[开始稀释因子 -1 ]]> 0.17 0.33 0.27 0.40 0.33 Average TMP [bar] 9.9 9.8 9.5 9.6 9.6 Temperature [°C] 59 59 42 40 45 Surface velocity [m / s] 0.3 / 0.4 0.5 0.5 0.5 0.5 Cross flow [kg / h] 2800 / 3700 4600 4600 4600 4600 Filtration time [h] 19 16 14 32 21 <![CDATA[平均通量DF1[kg / m 2 / h]]]> 53 37 30 <![CDATA[平均通量AK1[kg / m 2 / h]]]> 80 59 47 31 24 Average flux DF2 [kg / m 2 / h]]]> 66 48 32 15 22 <![CDATA[平均通量AK2[kg / m 2 / h]]]> 31 15 7 4 6 <![CDATA[平均总通量[kg / m 2 / h]]]> 60 41 25 11 19 <![CDATA[最大通量[kg / m 2 / h]]]> 120 73 60 39 62

[0101] The results presented in Table 5 below show that sodium chloride and isopropyl alcohol can be easily removed. Examples 011, 012, 014, and 015 show that no sodium chloride is found in the final retentate. In Example 013, the sodium chloride content in the column retentate is reduced to 0.2 wt.%. For all examples, the concentration of isopropyl alcohol in the final retentate is less than 0.4 wt.%. In all examples, no less than 16.9 wt.% and up to 23.4 wt.% of sodium stearoyl glutamate remains in the retentate. Sodium glutamate is removed from the retentate to a level below 0.1 wt.%.

[0102] Table 5: Concentrations in the final retentate, analytical values

[0103]

[0104] The permeates produced in Examples 11-15 had an isopropyl alcohol concentration below 2 wt. %, and therefore the flash point of the permeate was above 60°C.

[0105] These examples illustrate that amino acid surfactants containing very low levels of impurities (especially inorganic salts and amino acids such as sodium chloride and sodium glutamate) can be produced with high purity. Further, these examples have demonstrated high filtration flow rates. In addition, the permeate contains relatively low levels of polar organic solvents, which means that it can be used as wastewater disposal without a low flash point.

[0106] In the prior art, the molecular membrane cutoff value for achieving high-purity amino acid surfactants via filtration is between 120 and 250 g / mol, with a maximum of 500 g / mol.

[0107] Therefore, this result is highly unexpected since the molecular weight of the amino acid surfactant of 458 g / mol is much smaller than the used cut-off values ​​of 4 to 50 kD (4000 g / mol to 50,000 g / mol) for the filter membranes in the presented experiments.

[0108] Experiments with lauroyl glutamate (Mn 373 g / mol) in the process of the invention are ongoing but have shown the same surprising results as with stearoyl glutamate.

Claims

1. A method for producing a purified amino acid surfactant from a crude amino acid surfactant containing impurities, the method comprising the following steps (i) providing the crude amino acid surfactant; and (ii) subjecting the crude amino acid surfactant to an ultrafiltration stage; and (iii) collecting the purified amino acid surfactant thus produced, The ultrafiltration stage comprises a filter membrane having a separation limit molecular cut-off of 1000 g / mol to 100,000 g / mol, preferably 4000 g / mol to 50,000 g / mol, more preferably 5000 g / mol to 30,000 g / mol.

2. The method according to claim 1, wherein Impurities contained in the crude amino acid surfactant include inorganic salts, polar organic solvents and optionally amino acids.

3. The method according to claim 1 or claim 2, wherein: The filter membrane is composed of any material selected from the group consisting of polyacrylonitrile, polyethersulfone, hydrophilized polyethersulfone, and any combination thereof.

4. A method according to any preceding claim, wherein: The crude material amino acid surfactant is contained in an aqueous medium, preferably the aqueous medium has a pH greater than 4.

0.

5. A method according to any preceding claim, wherein: The crude amino acid surfactant is diluted with an aqueous dilution medium, preferably in an amount of 1:10 to 3:

1.

6. A method according to any preceding claim, wherein: This ultrafiltration stage involves cross-flow filtration.

7. The method according to claim 6, wherein: The crude amino acid surfactant is in an aqueous medium that flows through the ultrafiltration stage to form a permeate, wherein impurities are removed through the permeate and the amino acid surfactant is preferentially retained in the retentate, which is recycled in a recirculation loop.

8. The method according to claim 7, wherein: The crude amino acid surfactant in the aqueous medium is subjected to at least one diafiltration step, wherein diafiltration medium is fed into the recirculation loop at substantially the same rate as the rate at which permeate flows out of the ultrafiltration stage.

9. The method according to claim 8, wherein The at least one diafiltration step has an overall diafiltration factor of 1 to 10, preferably 2 to 6.

10. The method according to any one of claims 7 to 9, wherein The crude amino acid surfactant in the aqueous medium is subjected to at least one concentration step, wherein no dilution medium is fed into the recirculation loop or dilution medium is fed into the recirculation loop at a rate lower than the rate of the permeate emanating from the ultrafiltration stage.

11. The method according to claim 10, wherein: The crude amino acid surfactant in the aqueous medium is subjected to a combination of sequential diafiltration and concentration.

12. The method according to any one of claims 7 to 11, wherein The diafiltration and / or concentration steps are carried out sequentially and include a) optionally initial diafiltration (D1); b) optional initial concentration (C1); c) optional diafiltration (D2); and d) optional final concentration (C2), The prerequisite is that it includes at least one of steps a or c and at least one of steps b or d, preferably it includes at least steps b) to d), and more preferably it includes all steps a) to d).

13. The method according to claim 12, wherein: This optional initial diafiltration (D1) is performed with a diafiltration factor (DF1) of 0.01 to 3.0, preferably 0.3 to 1.

0.

14. The method according to claim 12 or claim 13, wherein: This initial concentration (C1) is carried out with a concentration factor (CF1) of 1.01 to 10.0, preferably of 1.3 to 2.

0.

15. The method according to any one of claims 12 to 14, wherein The diafiltration (D2) is carried out with a filtration factor (DF2) of 0.01 to 10.0, preferably 1.5 to 5.

0.

16. The method according to any one of claims 12 to 15, wherein This final concentration (C2) is carried out with a concentration factor (CF2) ranging from 1.1 to 4.0, preferably from 1.2 to 3.

0.

17. A method according to any preceding claim, wherein: The method is performed as a batch or fed-batch operation.

18. A method according to any preceding claim, wherein The amino acid surfactant is in the form of an alkali metal salt, preferably a sodium salt.

19. A method according to any preceding claim, wherein: The amino acid surfactant is an N-substituted C8-C 30 -acylamino acid, preferably N-substituted C 12 -C 20 -acylamino acids.

20. A method according to any preceding claim, wherein The crude amino acid surfactant has been obtained by reacting an amino acid and an acyl halide under alkaline conditions and in the presence of an organic polar solvent.

21. A method according to any preceding claim, wherein: The amino acid surfactant is derived from any amino acid, desirably selected from the group consisting of glycine, sarcosine, glutamic acid, alanine, arginine, aspartic acid, glutamine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine and valine, preferably glutamic acid.

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