Method for electrolytic synthesis of strawberry acid
The electrolytic synthesis method utilizes anodic electrochemical oxidation to generate oxygen for the direct oxidation of 2-methyl-2-pentenal, solving the problems of heavy metal residues and environmental pollution in strawberry acid production. This method achieves high selectivity and high yield of strawberry acid, with product purity and yield exceeding 80%, in line with green chemistry principles.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-31
- Publication Date
- 2026-03-31
AI Technical Summary
Existing strawberry acid production methods suffer from high risks of heavy metal residues, poor oxidation selectivity, severe side reactions, poor batch stability of products, and significant environmental pollution, resulting in high production costs, heavy pollution, and poor product consistency.
An electrolytic synthesis method was adopted, which utilizes anodic electrochemical oxidation to generate oxygen in situ in an aqueous medium as a clean oxidant to directly oxidize 2-methyl-2-pentenal. The conversion of the aldehyde group to acid is achieved through an electron transfer mechanism. The reaction conditions are precisely controlled by combining proton membrane isolation and a saturated calomel reference electrode. High-purity strawberry acid is then obtained through extraction and separation.
This method achieves the production of strawberry acid with no heavy metal residue, high selectivity, and high yield. The process is clean and the separation is simple. The product purity and yield both reach over 80%, which is in line with the principles of green chemistry and solves the problems of heavy metal pollution and side reactions that exist in traditional methods.
Smart Images
Figure CN121759970A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of pharmaceutical manufacturing intermediates, and more specifically to a method for the electrolytic synthesis of strawberry acid. Background Technology
[0002] Strawberry acid (2-methyl-2-pentenoic acid) is a key α,β-unsaturated organic acid flavoring. Its conjugated double bonds and branched methyl groups in its molecular structure impart a unique, fresh fruity aroma reminiscent of strawberry and apple juice, while also possessing a sweet note of nuts, caramel, and maltol. As a food-grade flavoring, strawberry acid is widely used in blending edible flavorings such as maple, strawberry, and caramel. It can also be used to prepare derivative flavorings such as ethyl strawberry acid through esterification. It enjoys stable market demand in the food, beverage, and daily chemical industries. The chemical structural formula of strawberry acid is as follows: .
[0003] Industrially, strawberry acid is produced using a two-step process: propionaldehyde self-aldol condensation followed by selective oxidation. First, two molecules of propionaldehyde undergo aldol condensation under an alkaline catalyst to generate the intermediate 2-methyl-2-pentenal. Subsequently, the aldehyde group of this intermediate is selectively oxidized to a carboxyl group, while retaining the α,β-unsaturated double bond structure. However, the current oxidation technology reported by Minkyung Lim et al. in 2007 has fundamental flaws: while the palladium-on-carbon catalytic air oxidation method achieves a yield of 87%, palladium catalysts are expensive, the reaction requires pressurized conditions, resulting in large equipment investments and high operational safety risks. More importantly, palladium, as a heavy metal, poses a very high risk of residue in food-grade products, making it difficult to meet the stringent requirements of food safety regulations. Traditional silver nitrate or silver oxide oxidation methods, although simple, suffer from poor oxidation selectivity, resulting in a single-pass yield of less than 60%. Double bonds are easily oxidized and broken or epoxidized, and the large amount of silver salt used is difficult to recover, generating large amounts of heavy metal-containing wastewater, leading to high environmental remediation costs.
[0004] The core deficiency of existing technologies lies in the dual contradiction of the difficulty in precisely controlling oxidation selectivity and the poor stability of intermediates. The aldehyde group in the 2-methyl-2-pentenal molecule has similar chemical reactivity to the α,β-unsaturated double bond, making it prone to competitive reactions under oxidant conditions. More seriously, this intermediate is extremely unstable under alkaline or heated reaction conditions: it readily condenses via the Michael addition pathway to form high-molecular-weight byproducts such as dimers and trimers; simultaneously, trace amounts of active hydrogen species in the reaction system can hydrogenate and reduce the aldehyde double bond to 2-methylpentanal, which is further oxidized to the byproduct 2-methylpentanoic acid. These side reactions not only lead to low product yield and poor batch stability but also make product separation and purification extremely difficult, requiring multiple crystallizations to obtain food-grade purity. Furthermore, precious metal catalysts have limited reuse and are prone to deactivation, while silver salt oxidation generates large amounts of wastewater containing heavy metals, resulting in extremely high end-of-pipe treatment costs. These problems collectively lead to high costs, heavy pollution, and poor product consistency in strawberry acid production, severely restricting its green and large-scale application. Therefore, developing an environmentally friendly oxidation process with no heavy metal residues, high selectivity, high yield, and controllable side reactions, to optimize reaction selectivity and suppress polymerization side reactions from the source, and to achieve clean production of strawberry acid, has become a technical challenge that needs to be overcome in the field of fragrance synthesis. Summary of the Invention
[0005] The purpose of this invention is to provide a method for the electrolytic synthesis of strawberry acid, which uses anodic electrochemical oxidation to generate oxygen in situ as a clean oxidant to directly oxidize 2-methyl-2-pentenal in an aqueous medium. This solves the technical problems of high risk of heavy metal residue in traditional palladium-carbon catalytic oxidation method, serious side reactions and low yield in silver salt oxidation method, poor batch stability of products and large environmental pollution.
[0006] The present invention is achieved through the following technical solution: The present invention provides a method for electrolytic synthesis of strawberry acid, comprising an electrolytic oxidation reaction in the anodic cell of an electrolytic cell, wherein the oxidant of the electrolytic oxidation reaction includes oxygen generated by anodic electrolytic oxidation, and the anolyte in the anodic cell includes a mixture of 2-methyl-2-pentenal and an aqueous medium, wherein the aqueous medium includes water or an inorganic solution.
[0007] In one alternative embodiment, the mass ratio of 2-methyl-2-pentenal to the aqueous medium is 1:(10~50).
[0008] As an optional implementation, the solute of the inorganic solution includes at least one selected from NaOH, KOH, (NH4)2SO4, NaHSO4, MgCl2, Na2SO4, K2SO4, (NH4)2CO3, NH4Cl, NaCl, HCl, and H2SO4.
[0009] As an optional implementation, the concentration of the inorganic solution is 0~20 wt%. As an alternative implementation, the synthetic route of the strawberry acid is as follows: .
[0010] As an optional implementation, the cathode electrolyte in the cathode cell of the electrolytic cell includes an aqueous solution, and the cathode cell and the anode cell are separated by a proton exchange membrane.
[0011] As an optional implementation, the electrolytic cell uses a saturated calomel electrode as a reference electrode.
[0012] As an optional implementation, the current density of the electrolytic oxidation reaction is 100~500 mA / dm². 2 .
[0013] As an optional implementation, the temperature of the electrolytic oxidation reaction is 25~80℃, the reaction time is 3~5h, and the ambient pressure of the electrolytic oxidation reaction is 0~0.5 MPa.
[0014] As an optional implementation, the method further includes, after the electrolytic oxidation reaction, lowering the temperature to room temperature, adjusting the pH of the anode pool to 2-3, and extracting and separating the product with 1,2-dichloroethane at room temperature, with the dichloroethane phase being desolventized by rotary evaporation to obtain strawberry acid.
[0015] Compared with the prior art, the embodiments of the present invention have the following advantages and beneficial effects: 1. The core principle of the electrolytic synthesis of strawberry acid provided in this embodiment of the invention is to use the active oxygen species generated in situ during the electrochemical anodic oxidation process as a clean oxidant, which directly acts on the aldehyde functional group in the 2-methyl-2-pentenal molecule, and realizes the conversion from aldehyde to acid through the electron transfer mechanism.
[0016] Specifically, under energized conditions, the surface of the anode electrode oxidizes water molecules to produce oxygen with oxidizing activity. This active oxygen undergoes selective oxidation with 2-methyl-2-pentenal, which is homogeneously or heterogeneously dispersed in an aqueous medium, under the mass transfer effect enhanced by the electric field. Since the generation and consumption of the oxidant are completed simultaneously in the anode cell of the electrolytic cell, the problems of heavy metal residues, side reactions, and material separation caused by the addition of external oxidants in traditional chemical oxidation methods are avoided. At the same time, the use of an aqueous system for the anode electrolyte conforms to the principles of green chemistry. The introduction of inorganic solutions can adjust the conductivity and pH of the system to optimize the reaction. This process transforms the source of the oxidant into an electrochemical in-situ reaction, fundamentally changing the oxidation pathway of strawberry acid synthesis, making it possible to milden the reaction conditions, clean the oxidant, and make the process continuous.
[0017] 2. This invention achieves high-efficiency conversion through the integrated design of an electrochemical oxidation system and the synergistic effect of reaction and separation: In the anode cell, 2-methyl-2-pentenal is dispersed in an aqueous medium at a mass ratio of 1:(10~50). This ensures sufficient contact between the organic reactants and the active oxygen species generated in situ on the electrode surface, while maintaining the electrolyte conductivity and proton transfer capacity through the absolute dominance of water. This avoids the risks of phase separation and electrode passivation caused by a low proportion, and also prevents a decrease in mass transfer efficiency and an aggravation of side reactions caused by a high proportion. Proton exchange membrane isolation and a saturated calomel reference electrode work together to achieve precise potential control, ensuring that oxidation selectively targets the aldehyde group rather than destroying the α,β-unsaturated double bond. After the reaction, a three-step post-treatment process of cooling, acidification, and extraction is performed, utilizing pH... The characteristic of strawberry acid changing from ionic to molecular state under 2-3 conditions is utilized to efficiently extract the product with 1,2-dichloroethane, while eliminating polar byproducts and inorganic salt impurities. Finally, strawberry acid with a purity >80% and a yield >80% is obtained by desolvation. The entire process is completed under mild conditions, the oxidant is clean and the separation is simple, avoiding the heavy metal residues and environmental pollution problems of traditional chemical oxidation methods. Attached Figure Description
[0018] To more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of the present invention and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings: Figure 1 This is a simplified diagram of the electrolysis apparatus according to an embodiment of the present invention; Figure 2 The hydrogen spectrum of strawberry acid prepared in Example 1 of this invention; Figure 3 This is the carbon spectrum of strawberry acid prepared in Example 1 of the present invention. Detailed Implementation
[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments.
[0020] Therefore, the detailed description of the embodiments of the present invention provided below is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
[0021] This invention provides a method for the electrolytic synthesis of strawberry acid. The key points of the invention and the points requiring protection are as follows: (Refer to...) Figure 1 As shown, this is the first time that electrochemical oxidation has been applied to the synthesis of strawberry acid, no longer limited to existing chemical oxidation methods. The key feature of this process is that active oxygen generated by anodic electrolysis acts on 2-methyl-2-pentenal, oxidizing it to strawberry acid. The anodic electrolyte is a homogeneous or heterogeneous solution formed by a certain amount of 2-methyl-2-pentenal and water or an inorganic salt solution of a certain concentration; the cathode is an aqueous solution of a certain concentration; the cathode and anodic cells are separated by a proton exchange membrane, and a saturated calomel electrode is used as a reference electrode. Electrolytic oxidation is carried out under specific current, temperature, and pressure conditions. After the electrolytic oxidation reaction, the temperature is lowered to room temperature, the pH of the anodic cell is adjusted to 2-3, and 1,2-dichloroethane is used for extraction and separation at room temperature. The dichloroethane phase is then dissolved by rotary evaporation to obtain strawberry acid.
[0022] The inorganic salt solution can be one or more of the following: NaOH, KOH, (NH4)2SO4, NaHSO4, MgCl2, Na2SO4, K2SO4, (NH4)2CO3, NH4Cl, NaCl, HCl, and H2SO4.
[0023] The concentration of the inorganic salt solution is 0~20wt%, preferably 5~15wt%.
[0024] The mass ratio of 2-methyl-2-pentenal to water or a solution of inorganic salts of a certain concentration is 1:(10~50), preferably 1:(20~40).
[0025] The current density is 100~500 mA / dm 2 Preferably 150 ~ 400 mA / dm 2 ; The temperature is 25~80℃, preferably 40~60℃; The pressure is 0~0.5 MPa, preferably 0~0.3 MPa.
[0026] Example 1: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to a 500mL anode cell. Add 300mL of 10wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 150mA / dm. 2The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 5 hours with an electric current applied. The current was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to yield 14.25 g of strawberry acid. The 1H NMR spectrum is shown below. Figure 1 As shown, the carbon spectrum is as follows Figure 2 As shown, the GC purity is 82.33%, the content is 68%, and the yield is 85%.
[0027] Example 2: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: 9.81 g of 2-methyl-2-pentenal was added to 200 mL of 20 wt% KOH solution (mass ratio 1:24.2), and stirred to form a heterogeneous solution. This solution was then added to a 500 mL anode tank, and 300 mL of 20% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then the power supply was connected to conduct electricity at a current density of 100 mA / dm³. 2 Under conditions of 40℃ and 0.3 MPa gauge pressure, the reaction was carried out under heat and electricity for 5 hours. The electricity was then stopped, the temperature was lowered, the pH was adjusted to 2 with concentrated hydrochloric acid, and the mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 13.05 g of strawberry acid with a GC purity of 80.22%, a content of 70%, and a yield of 80%.
[0028] Example 3: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid (pH 2-3 unadjusted), comprising the following: 9.81 g of 2-methyl-2-pentenal was added to 200 mL of 10 wt% sulfuric acid solution (mass ratio 1:21.8), and stirred to form a heterogeneous solution. This solution was then added to a 500 mL anode tank, and 300 mL of 10 wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then the power supply was connected to conduct electricity at a current density of 150 mA / dm³. 2 The reaction was carried out at 50℃ and normal pressure for 5 hours with the power applied. The power was then turned off, the temperature was lowered, and the mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 7.48 g of strawberry acid with a GC purity of 72.03% and a content of 64%, yielding a yield of 42%.
[0029] Example 4: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: 9.81 g of 2-methyl-2-pentenal was added to 200 mL of 10 wt% NaOH solution and stirred to form a heterogeneous solution. This solution was then added to a 500 mL anode tank, and 300 mL of 10 wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then a power supply was connected to conduct electricity at a current density of 150 mA / dm². 2The reaction was carried out at 70℃ and normal pressure for 3 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 12.13 g of strawberry acid with a GC purity of 73.24%, a content of 65%, and a yield of 69%.
[0030] Example 5: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: 9.81 g of 2-methyl-2-pentenal was added to 200 mL of 10 wt% NaOH solution and stirred to form a heterogeneous solution. This solution was then added to a 500 mL anode tank, and 300 mL of 10 wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then a power supply was connected to conduct an energization at a current density of 400 mA / dm². 2 The reaction was carried out at 60℃ and atmospheric pressure for 3 hours with the power applied. The power was then turned off, the temperature was lowered, the pH was adjusted to 3 with concentrated hydrochloric acid, and the mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid was separated, and the dichloroethane phase was desoluble by rotary evaporation to obtain 14.35 g of strawberry acid with a GC purity of 78.79%, a content of 69%, and a yield of 87%.
[0031] Example 6: 22g of 2-methyl-2-pentenal was added to 200ml of 10wt% NaOH solution (mass ratio 1:10), and stirred to form a heterogeneous solution. This solution was then added to a 500mL anode tank, and 300mL of 10wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then a power supply was connected to conduct electricity at a current density of 150mA / dm². 2 The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 5 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 33.46 g of strawberry acid with a GC purity of 76.73%, a content of 65%, and a yield of 85%.
[0032] Example 7: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 4.4 g of 2-methyl-2-pentenal to 200 mL of 10 wt% NaOH solution (mass ratio 1:50), stir to form a heterogeneous solution, then add to a 500 mL anode cell. Add 300 mL of 10 wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 150 mA / dm². 2The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 5 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 6.47 g of strawberry acid with a GC purity of 74.25%, a content of 68%, and a yield of 86%.
[0033] Example 8: 24g of 2-methyl-2-pentenal was added to 200ml of 10wt% NaOH solution and stirred to form a heterogeneous solution. This solution was then added to a 500mL anode tank, and 300mL of 10wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then a power supply was connected to conduct electricity at a current density of 150mA / dm². 2 The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 12 hours with an electric current applied. The current was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 34.16 g of strawberry acid with a GC purity of 73.33% and a content of 67%, yielding a (supplementary) 82%.
[0034] Example 9: 4g of 2-methyl-2-pentenal was added to 200ml of 10wt% NaOH solution and stirred to form a heterogeneous solution. This solution was then added to a 500mL anode tank, and 300mL of 10wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then a power supply was connected to conduct electricity at a current density of 150mA / dm². 2 The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 16 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 5.80 g of strawberry acid with a GC purity of 74.62% and a content of 65%, yielding a (supplementary) 81%.
[0035] Example 10: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to a 500mL anode cell. Add 300mL of 10wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 150mA / dm. 2The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 5 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 1.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 29.86 g of strawberry acid with a GC purity of 60% and a content of 42%, yielding a recovery rate of 87%.
[0036] Example 11: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to a 500mL anode cell. Add 300mL of 10wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 150mA / dm. 2 The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 5 hours with an electric current applied. The current was then stopped, the temperature was lowered, and the pH was adjusted to 3.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 17.56 g of strawberry acid (supplementary), with a GC purity of 63.35%, a content of 52%, and a yield of 80%.
[0037] Example 12: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to a 500mL anode cell. Add 300mL of 10wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 150mA / dm. 2 The reaction was carried out at 25℃ and atmospheric pressure (0 MPa) for 9 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 12.27 g of strawberry acid with a GC purity of 73.26%, a content of 67%, and a yield of 72%.
[0038] Example 13: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: 9.81 g of 2-methyl-2-pentenal was added to 200 mL of 25 wt% KOH solution and stirred to form a heterogeneous solution. This solution was then added to a 500 mL anode tank, and 300 mL of 20% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then a power supply was connected to conduct electricity at a current density of 150 mA / dm². 2Under normal temperature and pressure conditions, the reaction was carried out with electricity for 4 hours. The electricity was then stopped, the temperature was lowered, the pH was adjusted to 2.5 with concentrated hydrochloric acid, and the mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The mixture was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 12.59 g of strawberry acid (GC purity 81.27%, content 68%, yield 75%).
[0039] Example 14: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to a 500mL anode cell. Add 300mL of 10wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 150mA / dm. 2 Under conditions of 50℃ and 0.4 MPa gauge pressure, the reaction was carried out under heat and electricity for 3 hours. The electricity was then stopped, the temperature was lowered, the pH was adjusted to 2.5 with concentrated hydrochloric acid, and the mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 11.23 g of strawberry acid with a GC purity of 72.21%, a content of 63%, and a yield of 62%.
[0040] Example 15: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: 9.81 g of 2-methyl-2-pentenal was added to 200 ml of distilled water and stirred to form a heterogeneous solution. This solution was then added to a 500 mL anode tank, and 300 mL of 10 wt% NaCl aqueous solution was added to the cathode tank. Stirring was started, and then the power supply was turned on. The reaction was carried out at a current density of 150 mA / dm², a temperature of 50 °C, and a normal pressure (0 MPa) for 12 h. The power supply was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 min. The liquid was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 15.10 g of strawberry acid with a GC purity of 75.62%, a content of 65%, and a yield of 86%.
[0041] Example 16: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to a 500mL anode cell. Add 300mL of 10wt% NaCl aqueous solution to the cathode cell. Start stirring, then connect the power supply and apply current at a density of 80mA / dm. 2The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 20 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 12.84 g of strawberry acid with a GC purity of 73.65%, a content of 64%, and a yield of 72%.
[0042] Example 17: This embodiment of the invention provides a method for electrolytic synthesis of strawberry acid, comprising the following: Add 9.81g of 2-methyl-2-pentenal to 200ml of 10wt% NaOH solution (mass ratio 1:22.4), stir to form a heterogeneous solution, then add to 500mL of the anode tank. Add 300mL of 10wt% NaCl aqueous solution to the cathode tank. Start stirring, then connect the power supply and apply current at a density of 550mA / dm. 2 The reaction was carried out at 50℃ and atmospheric pressure (0 MPa) for 4 hours with the power applied. The power was then stopped, the temperature was lowered, and the pH was adjusted to 2.5 with concentrated hydrochloric acid. The mixture was extracted with 1,2-dichloroethane at room temperature for 15 minutes. The liquid-liquid phase was separated, and the dichloroethane phase was removed by rotary evaporation to obtain 11.76 g of strawberry acid with a GC purity of 75.63%, a content of 65%, and a yield of 67%.
[0043] Data Analysis: As can be seen from Example 3, after the electrolytic oxidation reaction, without using concentrated hydrochloric acid to adjust the pH, the purity of the prepared strawberry acid was quite good, but the yield was significantly reduced. This is because strawberry acid is more easily extracted from water by organic solvents under acidic conditions.
[0044] A comparison of Examples 1, 4, 5, and 12 shows that the electrolytic oxidation reaction temperature is optimal within the range of 40°C to 60°C. When the reaction temperature is below 40°C (Example 12), the electrolysis time is prolonged, impurities are generated during electrolysis, and the raw materials themselves polymerize, leading to a decrease in yield. When the reaction temperature is above 60°C (Example 4), the yield drops to 69%. This is because the raw material 2-methyl-2-pentenal becomes impurities at excessively high temperatures under electrolysis conditions, resulting in a decrease in product yield.
[0045] A comparison of Example 8 and Example 1 shows that when the 2-methyl-2-pentenal content in the anolyte is too high, the electrolysis process is exothermic and the electrolysis time is prolonged, resulting in increased impurities and a lower yield. A comparison of Example 9 and Example 1 shows that when the 2-methyl-2-pentenal content in the anolyte is too low, the electrolysis time is prolonged, impurities increase, and the yield decreases. Therefore, a mass ratio of 2-methyl-2-pentenal to the aqueous medium of 1:(10~50) is preferred.
[0046] A comparison of Examples 10 and 11 with Example 1 shows that after the electrolytic oxidation reaction, when the pH is adjusted to less than 2 with concentrated hydrochloric acid, the yield remains basically unchanged. However, a low pH will extract impurities and reduce purity, increasing the difficulty of subsequent purification processes. When the pH is adjusted to greater than 3 with concentrated hydrochloric acid, the yield decreases. When the pH is less than 2.5, the product is difficult to extract completely in the aqueous phase.
[0047] A comparison of Example 13 and Example 1 shows that when the concentration of inorganic solution in the anolyte is greater than 20%, the concentration of inorganic solvent is too high, the conductivity is better, the raw material reaction is faster, the heat generation is more uncontrollable, impurities increase, and the yield decreases. Therefore, an inorganic solution concentration of 0~20wt% is better.
[0048] A comparison of Example 14 and Example 1 shows that when the gauge pressure of the electrolytic oxidation reaction is greater than 0.3 MPa, the reaction rate will be accelerated by increasing the pressure, and the exothermic reaction process will be uncontrollable, resulting in increased impurities and reduced yield. Therefore, an environmental pressure of 0~0.3 MPa is more favorable for the electrolytic oxidation reaction.
[0049] A comparison of Examples 16 and 17 with Example 1 shows that when the current density of the electrolytic oxidation reaction is too high, the exothermic reaction is more pronounced, impurities increase, and the yield decreases. Conversely, when the current density is too low, the electrolysis is insufficient, leaving residual raw materials and further reducing the yield. Therefore, the current density is controlled between 100 and 500 mA / dm³. 2 It is even better at that time.
[0050] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for electrolytic synthesis of strawberry acid, characterized in that, The method includes an electrolytic oxidation reaction carried out in the anolyte of an electrolytic cell, wherein the oxidant of the electrolytic oxidation reaction includes oxygen generated by anolytic oxidation, and the anolyte in the anolyte of the anolyte includes a mixture of 2-methyl-2-pentenal and an aqueous medium, wherein the aqueous medium includes water or an inorganic solution.
2. The method for electrolytic synthesis of strawberry acid according to claim 1, characterized in that, The mass ratio of 2-methyl-2-pentenal to the aqueous medium is 1:(10~50).
3. A method for electrolytic synthesis of strawberry acid according to claim 1 or 2, characterized in that, The solute in the inorganic solution includes at least one of NaOH, KOH, (NH4)2SO4, NaHSO4, MgCl2, Na2SO4, K2SO4, (NH4)2CO3, NH4Cl, NaCl, HCl, and H2SO4.
4. The method for electrolytic synthesis of strawberry acid according to claim 3, characterized in that, The concentration of the inorganic solution is 0~20wt%.
5. The method for electrolytic synthesis of fructooligosaccharide according to claim 4, characterized in that, The synthetic pathway of the fructose acid is as follows: 。 6. The method for electrolytic synthesis of strawberry acid according to claim 1, characterized in that, The cathode electrolyte in the electrolytic cell includes an aqueous solution, and the cathode cell and the anode cell are separated by a proton exchange membrane.
7. The method for electrolytic synthesis of strawberry acid according to claim 6, characterized in that, The electrolytic cell uses a saturated calomel electrode as a reference electrode.
8. The method for electrolytic synthesis of strawberry acid according to claim 7, characterized in that, The current density of the electrolytic oxidation reaction is 100~500 mA / dm. 2 .
9. The method for electrolytic synthesis of fructooligosaccharide according to claim 7, characterized in that, The electrolytic oxidation reaction is carried out at a temperature of 25~80℃ for 3~5 hours, and the environmental pressure is 0~0.5 MPa.
10. The method for electrolytic synthesis of fructooligosaccharide according to claim 9, characterized in that, The process also includes lowering the temperature to room temperature after the electrolytic oxidation reaction, adjusting the pH of the anode pool to 2-3, and extracting and separating the product with 1,2-dichloroethane at room temperature. The dichloroethane phase is then desolvated by rotary evaporation to obtain strawberry acid.