FURAN SURFACTANT COMPOSITIONS AND METHODS
20220204467 · 2022-06-30
Inventors
- Shawn Eady (Seattle, WA)
- Sabrina Conrad (Seattle, WA, US)
- Trenton Wilke (Seattle, WA, US)
- Christoph Krumm (Seattle, WA)
Cpc classification
International classification
Abstract
Chemical compositions, and related methods for synthesizing furan, such as oleo-furan, surfactants, include calcium, magnesium, ammonium and/or lithium cations and one of a number of furan derivatives. Methods for synthesizing such furan surfactants containing calcium, magnesium, ammonium and/or lithium cations can include chemical reagents and purification procedures to prepare furan surfactants containing calcium, magnesium, ammonium and/or lithium cations. These furan surfactant compositions can be free of dioxane and ethoxylate.
Claims
1. A compound having the formula (1) ##STR00037## wherein M is selected from the group consisting of: NH.sub.4.sup.+, Li.sup.+, Ca.sup.2+, Na.sup.+, and Mg.sup.2+, wherein R is selected from the group consisting of: CH.sub.3 and other alkyl substituents, wherein y is selected from the group consisting of: 1, 2, and non-integer values between 1 and 2, and wherein n is an alkyl chain from 4 to 28 carbon atoms in length.
2. The compound of claim 1, wherein the alkyl chain includes a ketone functional group alpha to the furan ring.
3. The compound of claim 1, wherein R is CH.sub.3.
4. The compound of claim 1, wherein M is Na.sup.+ and y is 1.
5. The compound of claim 1, wherein M is NH.sub.4.sup.+ and y is 1.
6. The compound of claim 1, wherein M is Li.sup.+ and y is 1.
7. The compound of claim 1, wherein M is Ca.sup.2+ and y is 2.
8. The compound of claim 1, wherein M is Mg.sup.2+ and y is 2.
9. The compound of claim 1, wherein M is a mixture of Na.sup.+ and Ca.sup.2+ and y is a non-integer value between 1 and 2.
10. The compound of claim 1, wherein M is a mixture of Na.sup.+ and Li.sup.+ and y is 1.
11. The compound of claim 1, wherein M is a mixture of Na.sup.+ and NH.sub.4.sup.+ and y is 1.
12. The compound of claim 1, wherein M is a mixture of Na.sup.+ and Mg.sup.2+ and y is a non-integer value between 1 and 2.
13. The compound of claim 1, wherein n is 4, with 10 total carbon atoms in the alkyl chain.
14. The compound of claim 1, wherein n is 5, with 12 total carbon atoms in the alkyl chain.
15. The compound of claim 1, wherein the compound is: ##STR00038##
16. The compound of claim 15, wherein the compound is: ##STR00039##
17. The compound of claim 1, wherein the compound is: ##STR00040##
18. The compound of claim 17, wherein n is 5.
19. The compound of claim 1, wherein the compound is: ##STR00041##
20. The compound of claim 19, wherein n is 4.
Description
DETAILED DESCRIPTION
[0028] The following detailed description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the following description provides some practical illustrations for implementing exemplary embodiments of the present invention. Examples of elements, materials, compositions, and/or steps are provided below. Though those skilled in the art will recognize that many of the noted examples have a variety of suitable alternatives that are also within the scope of the present disclosure.
[0029] Embodiments described herein relate to surfactant compositions and related methods for synthesizing such surfactants. In particular, disclosed herein are embodiments including surfactant compositions free of dioxane and ethoxylate, produced from renewable sources, while providing similar performance as compared to SEES surfactants.
[0030] Sulfonation and sulfation reactions generally are the final process step in commercial surfactant manufacturing. Alkylfuran sulfonates, alkyldifuran sulfonates, and SLES are the product of sulfonation and sulfation reactions. From a chemical perspective, sulfonation describes the reaction of an organic surfactant precursor, such as alkyl benzene or the oleo-furan surfactant embodiments disclosed herein, with sulfur trioxide (SO.sub.3) to form a stable sulfur-carbon bond in the acid surfactant product (alkyl benzene sulfonic acid, embodiments of oleo-furan sulfonic acid disclosed herein). Due to the stability of the sulfur-carbon-bond, sulfonic acids can generally be isolated, stored, and shipped in their pure acid form. Sulfations, on the other hand, involve the reaction between an organic alcohol surfactant precursor, such as ethoxylated lauryl alcohol, find SO.sub.3 to form a hydrolytically instable carbon-oxygen-sulfur bond in the surfactant product (SLES). In order to avoid rapid decomposition of this unstable acid form, immediate neutralization and dilution of the sulfated product can be needed, resulting in high shipping costs for the dilute surfactant solution (30-70% active surfactant). Accordingly, one useful advantage of oleo-furan surfactant embodiments disclosed herein can be sulfonates and would thus be able to provide a stable concentrated acid form, leading to reduced shipping expenses and the possibility of on-site custom-neutralization by surfactant customers.
[0031] Commercially, there are multiple techniques for the production of detergent range sulfonates and sulfates. For all of them, major challenges are heat removal and control of the molar SO.sub.3 to organic precursor ratio, two process factors that are dictating the extent of side reactions and amount of byproducts formed due to the highly exothermic character of the reaction. In the past, this challenge has been tackled by using dilute or complexed SO.sub.3 precursors, reducing the rate of sulfonation or sulfation.
[0032] The following types of diluting/complexing SO.sub.3 reagents are commercially used (with an increase in usage in the order as they appear): sulfamic acid<chlorosulfuric acid<oleum<air/SO.sub.3. Sulfamic acid is used to sulfate alcohols and ethoxylated alcohols, such as SLES, and directly forms the ammonium neutralized salt. It is one of the mildest and most selective sulfating agents that does not react with aromatic rings, such as alkyl benzene or the proposed oleo-furan surfactant, and tends to be economically useful only for small batch processes due to the high cost of the SO.sub.3 precursor salt. Chlorosulfuric acid is also exclusively used to sulfate alcohols and ethoxylated alcohols, and reacts rapidly and stoichiometrically to the sulfated product, which requires immediate neutralization once the reaction is complete. Oleum (SO.sub.3.H.sub.2SO.sub.4), on the other hand, is predominantly used for sulfonations of aromatics, such as alkyl benzene, and can be used for embodiments disclosed herein, and has the advantage of low feedstock and capital equipment cost. The downside to this technique is that oleum-based sulfonation is an equilibrium process leaving large quantities of unreacted sulfuric acid behind that cannot be entirely separated leading to ca. 8% of sodium sulfate in the neutralized product. Lastly, the SO.sub.3/air process is generally used the most and has been steadily replacing the oleum process. The SO.sub.3/air-process is capable of both sulfonating and sulfating a wide range of organic feedstocks. Generally, the process is rapid and stoichiometric, produces high quality product under tight control of reaction conditions, and is best suited for large-scale continuous production. The organic feedstock, such as aromatics, alcohols or ethoxylated alcohols (i.e. SLES), is reacted with a mix of SO.sub.3 gas (typically sourced from sulfur) and very dry air. The resulting sulfonic or sulfuric acid is then combined with neutralizing agent (usually 50% sodium hydroxide), water as diluent and possible additives, producing a solution of neutral active surfactant (a slurry or paste) of the desired composition and pH. While immediate neutralization of SLES is inevitable to prevent decomposition, notably, stability of oleo-furan sulfonic acid could allow to omit neutralization and dilution after SO.sub.3/air sulfonation, resulting in the described benefits of lower shipping costs and on-site neutralization by formulators.
[0033] Feedstocks for this process may also include solvents or any other residual reagents or byproducts from the surfactant sulfonation process, as the neutralization may be applied directly to the sulfonation effluent stream. Preferably, the feedstock stream will contain only acid form oleo-furan sulfonates in the absence of solvent (neat).
[0034] Feedstocks used in the process can include but are not limited to alkylfuran sulfonates and alkyldifuran sulfonates with carbon chain lengths varying from (C.sub.4 to C.sub.28) that can be saturated or unsaturated (mono-, di-, or tri-). The alkylfuran sulfonate structure in the feedstocks may include, in part, a furan moiety or furan derivatives such as methylfuran, ethylfuran, or furfural.
[0035] The following provides a general description of an embodiment of an exemplary neutralization procedure. In general, neutralization of protic monoanionic or diprotic dianionic surfactant is achieved by addition (e.g., relatively slow addition) of a basic salt containing the cation of choice, including but not limited to calcium carbonate, or a mixture of basic metal salts, including but not limited to a calcium carbonate and sodium carbonate mixture, to a surfactant solution composed of a water and organic solvent mixture, wherein the ratio is 0-50% organic solvent by volume, and the organic solvent includes, but is not limited to acetonitrile. This process results in the surfactant salt with the selected cation in solution, which is then reduced to a solid by heating in a temperature range from 25-80° C. while optionally applying vacuum in the pressure range of 0.001-0.90 atm. Removal of residual sulfate or carbonate salts in the product mixture, which may be present in varying quantities depending on the sulfonation conditions and neutralization base salt selected, can be achieved by dissolving the solids in a minimum of water and adding sufficient organic solvent, including but not limited to acetone, to prepare all aqueous to organic solvent solution by volume. This solution is mixed thoroughly, then stored at a temperature between 0 and 15° C. for a period of time from 1-48 hours. The solid salt is then removed by filtration, and the liquid is removed by heating in a temperature range from 25-80° C. while optionally applying a vacuum in the pressure range of 0.001-0.99 atm. If unsulfonated organics or sulfated byproducts remain in the product mixture, removal can be achieved by recrystallization in organic solvent including but not limited to isopropanol, ethanol, methanol, acetonitrile, acetone, or mixtures composed of, but not limited to, the aforementioned solvents.
[0036] One exemplary embodiment of a neutralization process is depicted below as Scheme 1, and one exemplary embodiment of a composition formed from Scheme 1 is depicted below as General Structure 1.
##STR00008##
##STR00009##
[0037] Scheme 1 illustrates an exemplary neutralization of an acidic oleo-furan sulfonate (OFS) molecule with Ca, Mg, NH.sub.4, or Li cation base, such as CaCO.sub.3, to form a Ca, Mg, NH.sub.4, or Li salt of the General Structure 1, where each numbered position (1-4) designates a functional group, such as —H, —CH.sub.3, —CH.sub.2CH.sub.3, a longer alkyl chain of C.sub.4 to C.sub.28 chain length which may or may not contain a ketone functional group, and —SO.sub.3, this structure contains, at minimum, one longer alkyl chain C.sub.4 to C.sub.28 chain length containing a ketone functional group, and one —SO.sub.3 functional group. A complete list of possible substituents for General Structure 1 is included in Table 1 below. General Structure 1 may contain one or more alkylfuran sulfonates, one or more alkylfuran disulfonates, or any combination of the two; these anions may be balanced in charge with one or more monovalent cations including Na.sup.+, NH.sub.4.sup.+, or Li.sup.+, one or more divalent cations including Mg.sup.2+ or Ca.sup.2+ or any combination of the aforementioned monovalent and divalent cations. While preferred iterations of General Structure 1 will contain one monoanionic oleo-furan sulfonate anion per monovalent cation or two monoanionic oleo-furan sulfonate anions or one dianionic oleo-furan disulfonate per divalent cation, some iterations may not adhere to this ratio, particularly in iterations where mixed cation basic salts are used for neutralization.
[0038] Table 1 lists examples of substituents of the furan-based surfactant of General Structure 1.
TABLE-US-00001 TABLE 1 Furan Substituents (GS1)
[0039] The following describes preparation of dianionic calcium, magnesium, ammonium, and lithium surfactants of General Structure 1 are seen below and can be prepared from the corresponding acid forms according to Schemes 2 and 3, respectively.
[0040] One exemplars embodiment of preparing calcium, magnesium, ammonium, and lithium cation dianionic oleo-furan surfactants with a tailed alkyl chain is depicted below as Scheme 2.
##STR00020##
[0041] One exemplary embodiment of preparing calcium, magnesium, ammonium, and lithium cation dianionic oleo-furan surfactants with a bridging alkyl chain is depicted below as Scheme 3.
##STR00021##
[0042] In further embodiments of the above depicted Scheme 1, Scheme 2, and Scheme 3, a basic calcium salt, such as calcium hydroxide, can be used to neutralize the acid form surfactants.
[0043] One exemplary embodiment using a basic salt to neutralize the acid form surfactant of Scheme 1 is depicted below as Scheme 4.
##STR00022##
[0044] Scheme 4 shows surfactant preparation from a protic monoanionic oleo-furan sulfonate containing a tailed alkyl chain. The structure shown in Scheme 4 has a C.sub.12 alkoyl saturated carbon chain derived from lauric acid. Alternately, surfactants can also be derived from a distribution of fatty acids with varying alkyl chain length, and varying degrees of unsaturation can be used, such as those obtained from soybean oil, to produce surfactant mixtures of varying alkyl chain length, the final product of which may or may not contain chain unsaturation.
[0045] One exemplary embodiment using a basic salt to neutralize the acid form surfactant of Scheme 2 is depicted below as Scheme 5.
##STR00023##
[0046] Scheme 5 shows surfactant preparation from a protic dianionic oleo-furan sulfonate containing a tailed alkyl chain.
[0047] One exemplary embodiment using a basic salt to neutralize the acid form surfactant of Scheme 3 is depicted below as Scheme 6.
##STR00024##
[0048] Scheme 6 shows surfactant preparation from a protic dianionic oleo-furan sulfonate containing a bridging alkyl chain.
[0049] The following describes embodiments of surfactant structures, for instance that can result from process embodiments (e.g., neutralization scheme embodiments) described herein. The surfactant structure embodiments described as follows are based on General Structure 1, provided above. These surfactant structure embodiments can be part of a class of calcium, magnesium, ammonium, and lithium cation oleo-furan surfactant, for example with either one or two furan moieties acting as part of a hydrophilic head, and the hydrophobic alkyl chain as either a bridging or terminal carbon chain.
[0050] In each of these further surfactant structure embodiments based on General Structure 1, the alkyl chain length either on the terminal end of the furan moiety (e.g., as seen in Structures A and B of General Structure 1) or between furan molecules (e.g., as seen in Structure C of General Structure 1) can vary, for example, from C.sub.4 to C.sub.28 or in the alkyl chain range of C.sub.4 to C.sub.18 or in the alkyl chain range of C.sub.6 to C.sub.18 or in the alkyl chain range C.sub.8 to C.sub.14. The length of the alkyl chain can be an important surfactant structural feature and can significantly alter surfactant characteristics, including factors that impact performance in applications, such as laundry detergency. For these reasons, alkyl chain lengths in one range, e.g. C.sub.1-C.sub.3, are considered to produce surfactants with significantly different application performance than those in another range, e.g. C.sub.4-C.sub.28.
[0051] Referring back to General Structure 1, functional groups designated by number positions (1-4) can be —H, —CH.sub.3, —CH.sub.2CH.sub.3, a longer alkyl chain, —OH, polyglycoside, polyethoxylate, sulfate, sulfonate, or any of the other functional groups listed in Table 1 above.
[0052] One embodiment of a surfactant structure based on General Structure 1 is depicted below as Structure A of General Structure 1.
##STR00025##
[0053] Another embodiment of a surfactant structure based on General Structure 1 is depicted below as Structure B of General Structure 1.
##STR00026##
[0054] A further embodiment of a surfactant structure based on General Structure 1 is depicted below as Structure C of General Structure 1.
##STR00027##
EXAMPLE
[0055] The following provides illustrative, non-limiting experimental examples of methods of synthesis and related synthesized structures.
[0056] A monoanionic oleo-furan surfactant according to Structure A of General Structure 1 was prepared from the corresponding oleo-furan sulfonic acid as outlined in Scheme 4, and this calcium oleo-furan surfactant is shown below as Experimental Structure 1.
##STR00028##
[0057] Referring to Experimental Structure 1, neutralization of the oleo-furan sulfonic acid was performed by dissolving the acid in a 1:1 solution (v/v) of water and acetonitrile, followed by addition of calcium carbonate (>99%, Sigma), prompting release of CO.sub.2 gas. Addition of the calcium salt was continued until gas formation ceased and insoluble salt was observed. The pH of the solution was measured, and the mixture was allowed to stir until the pH was at least 6, or for approximately 12 hours. The mixture w as then filtered to remove excess carbonate salt, and reduced to a solid on a hot plate at 50° C. Further salt removal was achieved by dissolving in a 1:1 solution of water and acetone, chilling for 4 hours at 4° C., and filtering. After drying the filtrate to a solid by hot plate at 50° C., recrystallization in a 1:1 solution of isopropanol and acetone yielded the off-white solid product.
[0058] The following Table 2 provides selected surfactant physical characteristics and performance metrics relative to SLES.
TABLE-US-00002 TABLE 2 Ross High High Mlles Shear Shear Surface Foam Foam Foam Calcium Wetting Krafft CMC.sup.1 Tension.sup.2 Height.sup.3 Height.sup.4 Loss.sup.5 Tolerance.sup.6 Time.sup.7 Solubility.sup.8 Point Cation (ppm) (mN/m) (mm) (mm) (%) (ppm) (sec) (g/mL) (° C.) Na.sup.+ 1480 42 134/132 71/69 30.sup. >50,000 45 0.8 <0 Ca.sup.2+ 300 33 180/170 53/51 11.sup. >50,000 25 0.35 <0 Mg.sup.2+ — 38* 185/175 43/41 16.sup. >50,000 22 0.01 20 Li.sup.+ 1347 45 135/120 85/84 28.sup. >50,000 27 0.3 <0 NH.sub.4.sup.+ 3309 39 75/55 23/8 0.sup.8 >50,000 >300 1 <0 SLES.sup.† 449 32 160/150 50/48 42.sup. >50,000 14 ≥1 <0 .sup.1Critical micelle concentration .sup.2Surface tension at critical micelle concentration .sup.3Height of foam immediately after foam formation and after 5 minutes, performed according to ASTM D1173 .sup.4Height of foam in distilled water solution immediately after foam formation and after 5 minutes, performed according to ASTM D319-88 with a blend rate of 13,700 rpm and concentration of 0.1 wt % surfactant .sup.5Percent of high shear foam height lost when identical test is run in a 100 ppm hard water solution .sup.6Expressed as ppm of Ca.sup.2+ from a CaCl.sub.2 source salt at the concentration where sustained precipitate is noted .sup.7Wetting of cotton skein at 30° C. (Testfabrics) according to ASTM D2281 .sup.8Solubility in deionized water at 20° C. .sup.9Foam height increased with the addition of hard water *Recorded for saturated surfactant solution at 20° C. .sup.†Sodium laureth sulfate surfactant with 3 ethoxylates (Stepan STEOL CS 330) used as comparison
[0059] Synthesized surfactants including the structure depicted in Experimental Structure 1, as well as the corresponding Na, Li, NH.sub.4, and Mg surfactants, were tested to determine surfactant properties. These included the time required for the surfactant solution to wet cotton fabric, the amount of foam the surfactant generates when agitated, the tolerance of the surfactant to calcium ions in solution as a measure of surfactant performance in hard water, and the temperature below which the surfactant (brim a solid precipitate, known as the Krafft Point.
[0060] The results are listed in Table 2, above. These results show significant differences in performance as a function of cation. In particular, superior surface tension, critical micelle concentration, and wetting kinetics were observed with the calcium cation surfactants compared to sodium surfactants prepared in previous technology. The calcium and magnesium monoanionic surfactants w ere both observed to have high foaming and foam stability, which is attractive for a number of applications including home cleaning, personal care, detergents, cosmetics, ore floatation and oil recovery. In comparison to the common industrial surfactant SLES, which is known for its wide use across numerous home and personal care products despite the carcinogenic by product 1,4-dioxane, the calcium surfactant had very similar performance metrics, and even showed improvements in critical micelle concentration, foaming, and high shear foam stability in hard water. Stability of the oleo-furan surfactant, specifically the acid form oleo-furan sulfonic acid that is a precursor to the calcium and other cation surfactants, was measured over an eight week time course at room temperature and elevated temperatures, the results of which can be seen in FIG. 2. FIG. 2 is depicted below and shows stability tracking for oleo-furan sulfonic acid surfactant precursor.
[0061] In addition to having a unique cation from previous oleo-furan surfactants, the compositions disclosed herein can contain an additional short alkyl chain on the furan ring. While this change in structure can be minimal, the impact on resulting surfactant characteristics is substantial and would not have been predictable.
[0062] Table 3 depicted below shows selected surfactant physical characteristics and performance metrics for varying surfactant structures.
TABLE-US-00003 TABLE 3 Ross High High Mlles Shear Shear Surface Foam Foam Foam Ca.sup.2+ Wetting Krafft Hydrophilic Head CMC.sup.1 Tension.sup.2 Height.sup.3 Height Loss Tolerance.sup.4 Time.sup.5 Point Group Structure (ppm) (mN/m) (mm) (mm) (%) (ppm) (sec) (° C.)
[0063] As can be seen in Table 3, addition of a methyl short alkyl chain to the surfactant head group results in a change of sulfonation position from directly adjacent to the furan oxygen atom. This change in structure had been observed to elicit a significant decrease in critical micelle concentration. In addition, changes in surface tension, foam height, foam stability, calcium tolerance, wetting time and Krafft point were observed; in effect, every surfactant characteristic measured was altered due to the presence of a short alkyl chain on the furan ring. As these surfactant characteristics are useful to performance in application, this modification to the surfactant structure is highly relevant to use in everyday applications.
[0064] Table 4 shows the time taken to separate an emulsion comprised of an equal volume 0.1 wt % surfactant solution and soybean oil. The length of time a surfactant solution can maintain an oil-water emulsion is relevant to any application in cleaning, including in detergency, personal care, and industrial cleaning products, as well as for oilfield applications. As was seen for other surfactant properties, emulsion stability was seen to change significantly (18% increase) with the addition of a methyl group on the furan ring. The cation selection was also observed impact emulsion stability, with the calcium form of the methylfuran surfactant (OMFS-12-1/0) maintaining an emulsion nearly 5 times longer than the sodium form.
TABLE-US-00004 TABLE 4 Average Emulsion Separation Time, Surfactant 15 mL* (min)
[0065] Table 5 provides a comparison of stain removal performance of a furan surfactant (OFS-12-1/0) vs. the analogous methylfuran surfactant (OMFS-12-1/0) for hard set blood stains on cotton fabric. The stain removal index (SRI) is a measure of the amount of stain removed based on the change in RGB values before and after washing, with a higher SRI indicating more stain removal. When washed with a 0.1 wt % aqueous solution of surfactant, a significant difference in SRI was observed between the furan and methylfuran surfactants, providing further evidence the structure change on the furan moiety results in performance differences that would not be obvious to one skilled in the art.
TABLE-US-00005 TABLE 5 Stain Removal Index: Hard Set Blood on Surfactant Cotton Fabric.sup.†
[0066] Various examples have been described with reference to certain disclosed embodiments. The embodiments are presented for purposes of illustration and not limitation. One skilled in the art will appreciate that various changes, adaptations, and modifications can be made without departing from the scope of the invention.