Method for simultaneously synthesizing isooctanal and isocaprylic acid through paired electrolysis method

Abstract

The invention relates to the technical field of organic synthesis, in particular to a method for simultaneously synthesizing isooctanal and isocaprylic acid through a paired electrolysis method. According to the method, isooctenal serves as a cathode starting raw material, isooctanal serves as an anode starting raw material, isooctanal and isocaprylic acid are synthesized through paired anodic oxidation and cathode reduction electrolytic reaction, high temperature and high pressure are not needed, reaction conditions are milder and controllable, safety risks are lower, meanwhile, due to paired electrolysis, electrolysis power consumption is greatly reduced, and the method is suitable for industrial production. Meanwhile, one set of electrolysis equipment can be used for producing two products with high additional values, the yield of the two products is high, the current efficiency is high, clean electrons are used for replacing oxygen oxidation and hydrogen reduction, and the reaction process is greener, more environmentally friendly and safer.

Description

Technical Field

[0001] The invention relates to the technical field of organic synthesis, and in particular to a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by a paired electrolysis method. Background Art

[0002] Isooctylaldehyde (full name 2-ethylhexanal) is an important chemical intermediate. It can be oxidized to generate isooctyl acid for use as a coating and resin modifier, and can also be reduced to generate isooctyl alcohol for the production of plasticizer dioctyl phthalate. At the same time, isooctylaldehyde is also a flavor additive used in soaps and synthetic detergents. At present, the main industrial methods for the preparation of isooctylaldehyde are propylene carbonyl synthesis and acetaldehyde aldol condensation.

[0003] Propylene and synthesis gas are used as raw materials to prepare butyraldehyde through propylene hydroformylation. Butyraldehyde undergoes aldol condensation reaction under alkaline conditions to obtain isooctylaldehyde enriched liquid, which is directly and selectively hydrogenated to prepare isooctylaldehyde without separation. Isooctylaldehyde has two types of double bonds: carbon-carbon double bonds and carbon-oxygen double bonds. The difficulty of this process is to achieve high conversion rate and high selectivity for the hydrogenation reaction of carbon-carbon double bonds. At the same time, the polymerized heavy components in the butyraldehyde condensation liquid are also the main reason for the deactivation of the hydrogenation catalyst. Therefore, the synthesis of efficient catalysts is the key to realizing this technology.

[0004] Isooctanoic acid (full name 2-ethylhexanoic acid) is an important fine chemical organic product. Since its salts are widely used in coating driers, catalysts and stabilizers for polymer products, its economic status has become more important. In recent years, the process and technology of domestic production of isooctanoic acid have made a qualitative leap, and the product quality is comparable to that of imported products.

[0005] The current mainstream process route is to use isobutylene aldehyde to selectively hydrogenate and reduce to obtain isooctyl aldehyde, and then obtain isooctyl acid through air / oxidation. Patent CN111054437A uses a polyacid cross-linked polymer matrix to load the precious metal palladium, and uses a high-pressure reactor at a reaction temperature of 50-130°C and a reaction pressure of 1-5MPa to achieve high-selectivity conversion. However, the polymer matrix mentioned in the invention is difficult to control the degree of cross-linking during the long-term production process, and the reaction activity is difficult to maintain stability. The literature also reports a method for selective hydrogenation of isooctyl aldehyde with a Pd / γ-Al2O3 catalyst. At a reaction temperature of 85-95°C, a reaction pressure of 2.45MPa, and an air velocity of 0.15-0.3h -1 Under the above conditions, highly selective conversion can be achieved. The overall yield of this method is high, but the catalyst processing capacity is low and the cost is high. At the same time, γAl2O3 has strong acidity, and the high tar content of isooctylaldehyde raw materials can easily lead to carbon deposition and deactivation of the catalyst.

[0006] Electrochemical synthesis technology uses electrons as redox reagents, does not require the use of other oxidants or reductants, and the reaction is carried out at room temperature and pressure, which is a green and environmentally friendly synthesis process. A method for preparing isooctanoic acid by electrochemical oxidation of isooctyl alcohol has been reported in the prior art. The method uses Pb-PbO2 as an anode and a copper sheet as a cathode. The electrochemical oxidation reaction is carried out in an electrolyte containing potassium chromium sulfate. The reaction uses a high-valent chromium salt as an electrocatalyst, which will have heavy metal residues and have a great impact on product quality. The current efficiency of the target product is low. Too low current efficiency will lead to excessive power consumption, and the electrical energy cannot be effectively utilized. Summary of the invention

[0007] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art that a high temperature, high pressure environment or low electrolysis efficiency is required, thereby providing a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by a paired electrolysis method.

[0008] To this end, the present application provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, comprising the following steps:

[0009] Step S1: adding a cathode electrolyte to the cathode chamber and adding an anolyte to the anode chamber, wherein the cathode electrolyte comprises an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the anolyte comprises an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the cathode chamber and the anode chamber are separated by a cation exchange membrane;

[0010] Step S2: After power is turned on, an electrolytic reaction is carried out, in the cathode chamber, isooctyl aldehyde undergoes a reduction reaction to obtain a cathode liquid containing isooctyl aldehyde, and in the anode chamber, isooctyl aldehyde undergoes an oxidation reaction to obtain an anode liquid containing isooctyl acid.

[0011] Further, the concentration of isooctyl aldehyde in the cathode electrolyte added in step S1 is 0.1 to 1 mol / L; and / or the concentration of isooctyl aldehyde in the anode electrolyte added in step S1 is 0.1 to 1 mol / L.

[0012] Furthermore, the mass percentage of the conductive salt added to the anolyte or catholyte in step S1 is 0.1-10%, preferably 1-5%.

[0013] Furthermore, in the cathode electrolyte and / or the anode electrolyte, the volume percentage of alcohol in the alcohol aqueous solution is 20-80%, preferably 40-60%.

[0014] Furthermore, the alcohol aqueous solution includes one or more of an ethanol aqueous solution, a methanol aqueous solution, and an ethylene glycol aqueous solution; and / or the conductive salt includes a quaternary ammonium salt and / or a quaternary phosphonium salt; and / or the paired electrolysis method is a continuous electrolysis method or an intermittent electrolysis method.

[0015] Furthermore, the conductive salt includes one or more of tetrabutylammonium tetrafluoroborate and tetrabutylphosphine hexafluorophosphate.

[0016] Further, the cathode is selected from a metal electrode; optionally, the metal electrode includes nickel, lead, copper, stainless steel, a nickel alloy electrode, a lead alloy electrode or a copper alloy electrode; optionally, the cathode structure is selected from a cylindrical shape, a flat plate shape or a porous mesh shape. The porous mesh shape can be a porous mesh shape formed by stretching, weaving or sintering.

[0017] Furthermore, the anode is selected from a metal electrode or a carbon electrode; and / or the structure of the anode is selected from a flat plate or a porous mesh; and / or the cation exchange membrane is selected from one or more of cation exchange membrane N117, cation exchange membrane N221, cation exchange membrane N427, cation exchange membrane N 551, cation exchange membrane HF-1, cation exchange membrane CM001, cation exchange membrane N324, and cation exchange membrane N982.

[0018] Furthermore, the metal electrode is selected from one of nickel, lead, platinum, DSA electrode, lead alloy electrode and platinum alloy electrode. The carbon electrode is selected from graphite electrode.

[0019] Further, at least one step S3 is included, which includes: the anolyte containing isooctyl acid obtained in the previous step is led out, the cathode liquid containing isooctyl aldehyde obtained in the previous step is added to the anode chamber, the cathode electrolyte is added to the cathode chamber again, and the electrolysis reaction is carried out after power is turned on, isooctyl aldehyde undergoes a reduction reaction in the cathode chamber to obtain a cathode liquid containing isooctyl aldehyde, isooctyl aldehyde undergoes an oxidation reaction in the anode chamber to obtain an anolyte containing isooctyl acid and is combined with the anolyte containing isooctyl acid obtained in the previous step; optionally, when the conversion rate of isooctyl aldehyde in the cathode liquid is greater than or equal to 99%, the anolyte containing isooctyl acid is led out, and the cathode liquid containing isooctyl aldehyde is added to the anode chamber. For example, step S3 can be repeated 1 to 10 times.

[0020] Furthermore, in step S2, the current density of the electrolysis reaction is 500 to 3000 A / m 2 ; and / or, the cell voltage of the electrolysis reaction is 3.2 to 8.7 V; and / or, the temperature of the cathode electrolyte or the anode electrolyte in the electrolysis reaction is 25 to 55°C.

[0021] Furthermore, in step S3, the current density of the electrolysis reaction is 500 to 3000 A / m 2 ; and / or, the cell voltage of the electrolysis reaction is 3.2 to 8.7 V; and / or, the temperature of the cathode electrolyte or the anode electrolyte in the electrolysis reaction is 25 to 55°C.

[0022] Furthermore, in step S2, after the electrolysis reaction, the step of purifying the cathode liquid and the anode liquid to obtain pure isooctyl aldehyde and pure isooctyl acid is also included; optionally, the purification method includes extraction or distillation.

[0023] Furthermore, in step S3, after the electrolysis reaction, the cathode liquid and the anode liquid are purified to obtain pure isooctyl aldehyde and pure isooctyl acid; optionally, the purification method includes extraction or distillation. The cathode liquid is extracted by conventional extraction methods in the art, for example, ethyl acetate is used for extraction. The anode liquid is distilled by conventional distillation methods in the art, with a tower top temperature of 86-92°C, a tower bottom temperature of 150-156°C, a tower operating pressure of 1.8-2.1 kPa, and a reflux ratio of 1.8-2.5:1.

[0024] The technical solution of the present invention has the following advantages:

[0025] 1. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis provided by the present invention comprises the following steps: Step S1: adding a cathode electrolyte into a cathode chamber, and adding an anolyte into an anode chamber, wherein the cathode electrolyte comprises an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the anolyte comprises an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the cathode chamber and the anode chamber are separated by a cation exchange membrane; Step S2: performing an electrolytic reaction after power is turned on, wherein isooctyl aldehyde undergoes a reduction reaction in the cathode chamber to obtain a cathode liquid containing isooctyl aldehyde, and isooctyl aldehyde undergoes an oxidation reaction in the anode chamber to obtain an anode liquid containing isooctyl acid. The present invention uses isooctyl aldehyde as a cathode starting material and isooctyl aldehyde as an anode starting material, and simultaneously synthesizes isooctyl aldehyde and isooctyl acid through paired anodic oxidation and cathode reduction electrolysis reactions, without the need for high temperature and high pressure, and the reaction conditions are more mild and controllable, with lower safety risks, and simultaneously due to paired electrolysis, electrolysis power consumption is greatly reduced, and a set of electrolysis equipment can produce two high value-added products, both of which have high yields and high current efficiency, and utilizes clean "electrons" to replace oxidation and reduction reagents, so that the reaction process is greener, more environmentally friendly, and safer. The cathode electrolyte includes an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the anolyte includes an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, so that the matching of paired anodic oxidation and cathode reduction electrolysis reactions is good, and the electrolysis efficiency is significantly improved.

[0026] 2. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis provided by the present invention can significantly improve the anodic electrolysis efficiency while increasing the yield of isooctyl acid by controlling the mass percentage of the conductive salt in the anolyte or cathode electrolyte added in step S1 to 0.1-10%, preferably 1-5%.

[0027] 3. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis provided by the present invention can significantly improve the cathode and anode electrolysis efficiencies while increasing the yields of isooctyl acid and isooctyl aldehyde by controlling the volume percentage of alcohol in the alcohol aqueous solution in the cathode electrolyte and / or the anode electrolyte to be 20-80%, especially 40-60%.

[0028] 4. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis provided by the present invention also includes at least one S3 step, wherein the S3 step includes: extracting the anolyte containing isooctyl acid obtained in the previous step, adding the catholyte containing isooctyl aldehyde obtained in the previous step into the anode chamber, adding the catholyte into the cathode chamber, and conducting an electrolytic reaction after powering on, wherein isooctyl aldehyde undergoes a reduction reaction in the cathode chamber to obtain a catholyte containing isooctyl aldehyde, and isooctyl aldehyde undergoes an oxidation reaction in the anode chamber to obtain an anolyte containing isooctyl acid and is combined with the anolyte containing isooctyl acid obtained in the previous step. By using the catholyte containing isooctyl aldehyde obtained in the previous step as the anolyte, there is no need to prepare the anolyte again by purchasing commercial isooctyl aldehyde, so that the subsequent reaction only needs to use the starting material of isooctyl aldehyde, thereby reducing the cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 It is an intermittent diaphragm electrolyzer provided in the specific implementation method of the present application;

[0031] Figure 2 It is a continuous diaphragm electrolyzer provided in the specific implementation method section of this application.

[0032] Reference numerals:

[0033] 1. Anode; 2. Cathode; 3. Diaphragm; 4. Anode chamber; 5. Cathode chamber; 6. Anode electrolyte tank; 7. Cathode electrolyte tank; 8. Anode liquid circulation pump; 9. Cathode liquid circulation pump; 10. Paired electrolysis circulation pumps; 11. Raw material feed pump; 12. Electrolyte discharge pump. DETAILED DESCRIPTION

[0034] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0035] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0036] 1. The purity of isooctanoic acid in pure isooctanoic acid is measured by gas chromatography (GC), and the yield of isooctanoic acid is calculated. The purity of isooctyl aldehyde in pure isooctyl aldehyde is measured by gas chromatography (GC), and the yield of isooctyl aldehyde is calculated. The conversion rate of isooctyl aldehyde in the cathode liquid is measured by gas chromatography (GC). Yield = actual yield × purity / theoretical yield × 100%.

[0037] Gas chromatograph model: Agilent 8890; Injector: automatic injector; Detector: FID detector; Chromatographic column: HP-5 (30m×0.25mm×0.25μm); Temperature program: 40°C for 5 minutes, increase the temperature to 300°C at 10°C / min, and hold for 10 minutes.

[0038] 2. Electrolysis efficiency, also known as current efficiency, is determined by Faraday's second law It=nZF, and the percentage of theoretical power consumption to actual power consumption is used to obtain the electrolysis efficiency.

[0039] Example 1

[0040] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, using a monopolar diaphragm electrolyzer (intermittent diaphragm electrolyzer) for intermittent electrolysis reaction, see Figure 1 , a flat nickel plate is used as the anode 1, and nickel foam is used as the cathode 2. The cathode surface area is 100 cm 2 The apparent area of ​​the anode is 95 cm 2 , the inter-electrode distance is 1 cm, and N117 perfluorosulfonic acid resin membrane cation exchange membrane is used as the diaphragm 3, specifically comprising the following steps:

[0041] (1) An ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the volume percentage of ethanol is 50%) is taken as a cathode electrolyte and placed in a cathode electrolyte tank 7. An ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the volume percentage of ethanol is 40%) is taken as an anode electrolyte and placed in an anode electrolyte tank 6.

[0042] (2) 2000 mL of cathode electrolyte and 2000 mL of anolyte are respectively introduced from the cathode electrolyte tank and the anolyte tank into the cathode chamber 5 and the anode chamber 4. 。 After power is turned on, constant current electrolysis is performed with a current density of 1000A / m 2 , the average cell voltage is 4.2V; during the electrolysis reaction, the temperatures of the cathode electrolyte and the anode electrolyte are both 30°C, isooctyl aldehyde undergoes a reduction reaction in the cathode chamber to obtain a cathode liquid containing isooctyl aldehyde, and isooctyl aldehyde undergoes an oxidation reaction in the anode chamber to produce isooctyl acid. The electrolysis is stopped after 2.2 hours to obtain an anode liquid containing isooctyl acid.

[0043] (3) The cathode liquid in the cathode chamber was collected, evaporated (temperature 60°C, time 3h), extracted with ethyl acetate, separated, and the upper organic phase was collected to obtain 48.64g of pure isooctylaldehyde, with a yield of 95% and a purity of 99.5%. The cathode electrolysis efficiency was 92%.

[0044] (4) The anolyte in the anode chamber was collected, and the pH of the anolyte was adjusted to 3 with 5% by volume dilute sulfuric acid, and the liquid was separated, and the upper oil phase was collected. After distillation (tower top temperature 89°C, tower bottom temperature 154°C, tower operating pressure 2kPa, reflux ratio 2:1), 55.30g of pure isooctanoic acid was obtained, with a yield of 95% and a purity of 99.2%. The anode electrolysis efficiency was 98%.

[0045] Example 2

[0046] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, using a monopolar diaphragm electrolytic cell, graphite as the anode, metal lead as the cathode, and the cathode surface area of ​​100 cm 2 The apparent area of ​​the anode is 92 cm 2 , the inter-electrode distance is 1 cm, and N324 perfluorosulfonic acid resin membrane cation exchange membrane is used as the diaphragm, specifically comprising the following steps:

[0047] (1) A methanol aqueous solution (the volume percentage of methanol is 60%) containing 0.8 mol / L isooctyl aldehyde and 5 wt% tetrabutylphosphine hexafluorophosphate (CAS No. 111928-21-3) is taken as a cathode electrolyte and placed in a cathode electrolyte tank. An ethanol aqueous solution (the volume percentage of ethanol is 40%) containing 0.8 mol / L isooctyl aldehyde and 5 wt% tetrabutylphosphine hexafluorophosphate is taken as an anode electrolyte and placed in an anode electrolyte tank. 2000 mL of the cathode electrolyte and 2000 mL of the anode electrolyte are respectively input into the cathode chamber and the anode chamber from the cathode electrolyte tank and the anode electrolyte tank.

[0048] (2) 2000 mL of cathode electrolyte and 2000 mL of anolyte are introduced into the cathode chamber and anode chamber from the cathode electrolyte tank and the anode electrolyte tank, respectively. After power is turned on, constant current electrolysis is performed with a current density of 2000 A / m 2 , the average cell voltage is 7.5V, the temperatures of the cathode electrolyte and the anode electrolyte are 35°C; in the cathode chamber, isooctyl aldehyde undergoes a reduction reaction to obtain a cathode liquid containing isooctyl aldehyde, and in the anode chamber, isooctyl aldehyde undergoes an oxidation reaction to produce isooctyl acid. After 4.5 hours of electrolysis, the electrolysis is stopped to obtain an anode liquid containing isooctyl acid.

[0049] (3) Collecting the cathode liquid from the cathode chamber, evaporating the cathode liquid (temperature 60° C., time 3 h), adding ethyl acetate for extraction, separating the liquids, and collecting the upper organic phase to obtain pure isooctyl aldehyde.

[0050] The anolyte in the anode chamber was collected, and the pH of the anolyte was adjusted to 3 with 5% by volume dilute sulfuric acid. The liquids were separated, and the upper oil phase was collected. After distillation treatment (tower top temperature 89°C, tower bottom temperature 154°C, tower operating pressure 2kPa, reflux ratio 2:1), pure isooctanoic acid was obtained.

[0051] Example 3

[0052] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Embodiment 1, except that the mass percentage of tetrabutylammonium tetrafluoroborate in the cathode electrolyte and the anode electrolyte is different, both of which are 0.5% in this embodiment.

[0053] Example 4

[0054] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Embodiment 1, except that the mass percentage of tetrabutylammonium tetrafluoroborate in the cathode electrolyte and the anode electrolyte is different, which is 8% in this embodiment.

[0055] Example 5

[0056] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Embodiment 1, except that the volume percentage of alcohol in the alcohol aqueous solution in the cathode electrolyte and the anode electrolyte is different, which is 20% in this embodiment.

[0057] Example 6

[0058] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Embodiment 1, except that the volume percentage of alcohol in the cathode electrolyte and the anode electrolyte is different, which is 80% in this embodiment.

[0059] Example 7

[0060] The present embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis. Steps (1) and (2) of the present embodiment are respectively the same as steps (1) and (2) of embodiment 1. Steps (3) and (4) are also included after step (2). Step (3) is: the anolyte in the anode chamber is led out, the cathode liquid in the cathode chamber is collected, and the cathode liquid is introduced into the anode chamber as the anolyte. 2000 mL of an ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the volume percentage of ethanol is 50%) is taken as the cathode electrolyte and introduced into the cathode chamber. After power is turned on, constant current electrolysis is performed, and the current density is 1000 A / m 2 , the average cell voltage is 4.2V; during the electrolysis reaction, the temperature of the cathode electrolyte and the anode electrolyte are both 30°C, isooctylaldehyde undergoes a reduction reaction in the cathode chamber to obtain a cathode liquid containing isooctylaldehyde, and isooctylaldehyde undergoes an oxidation reaction in the anode chamber to generate isooctyl acid. After 2.2 hours of electrolysis, the electrolysis is stopped to obtain an anode liquid containing isooctyl acid. Then, the anode liquids obtained in step (2) and step (3) are combined, and the cathode liquid in the cathode chamber is collected to perform step (4). Step (4) of this embodiment is the same as step (3) of embodiment 1.

[0061] Example 8

[0062] This embodiment provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, using a continuous diaphragm electrolyzer for continuous electrolysis reaction, see Figure 2 , including an anode chamber 4 and an anode 1 located in the anode chamber 4, a cathode chamber 5 and a cathode 2 located in the cathode chamber 5, and the cathode chamber 5 is separated from the anode chamber 4 by a diaphragm 3. The upper and bottom of the anode chamber 4 are also connected to an anode electrolyte tank 6, and the bottom of the anode electrolyte tank is connected to an anode chamber with an anode liquid circulation pump 8, which is used to transport the anode electrolyte in the anode electrolyte tank to the anode chamber, continue to transport the anode electrolyte, and the liquid in the anode chamber flows back into the anode electrolyte tank to realize the circulation of the liquid between the two. The upper and bottom of the cathode chamber are also connected to a cathode electrolyte tank 7. A cathode liquid circulation pump 9 is provided between the cathode electrolyte tank and the cathode chamber, which is used to transport the cathode electrolyte in the cathode electrolyte tank to the cathode chamber, continue to transport the cathode electrolyte, and the liquid in the cathode chamber flows back into the cathode electrolyte tank to realize the circulation of the liquid between the two. A pair of electrolysis circulation pumps 10 are provided between the cathode electrolyte tank and the anode electrode liquid tank, which are used to transport the cathode liquid containing isooctylaldehyde to the anode electrolyte tank. The anode electrolyte tank is connected to an anode liquid delivery pipeline, on which a raw material feed pump 11 is provided for outputting the anode liquid produced by electrolysis. The cathode electrolyte tank is connected to a cathode electrolyte delivery pipeline, on which an electrolyte discharge pump 12 is provided for delivering cathode electrolyte to the cathode electrolyte tank.

[0063] In this embodiment, a flat plate of nickel is used as the anode 1, and a nickel foam is used as the cathode 2. The cathode surface area is 100 cm 2 The apparent area of ​​the anode is 95 cm 2 , the inter-electrode distance is 1 cm, and N117 perfluorosulfonic acid resin membrane cation exchange membrane is used as the diaphragm 3, specifically comprising the following steps:

[0064] (1) Take 2000 mL of an ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the volume percentage of ethanol is 50%) as a cathode electrolyte and place it in a cathode electrolyte tank 7. Take 2000 mL of an ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the volume percentage of ethanol is 40%) as an anode electrolyte and place it in an anode electrolyte tank 6.

[0065] (2) Turn on the anolyte circulation pump and the cathode circulation pump to continuously feed the cathode electrolyte and the anolyte from the cathode electrolyte tank and the anolyte tank into the cathode chamber 5 and the anode chamber 4 at a flow rate of 200 L / h, respectively. Turn on the power supply and perform constant current electrolysis at a current density of 1000 A / m 2 , the average cell voltage is 4.2V; during the electrolysis reaction, the temperatures of the cathode electrolyte and the anode electrolyte are both 30°C, and isooctyl aldehyde undergoes a reduction reaction in the cathode chamber to obtain a cathode liquid containing isooctyl aldehyde, and isooctyl aldehyde undergoes an oxidation reaction in the anode chamber to produce isooctyl acid. After 2.2 hours of electrolysis, an anode liquid containing isooctyl acid is obtained.

[0066] (3) The raw material feed pump 11, the paired electrolysis circulation pump 10 and the electrolyte discharge pump 12 are sequentially used to continuously deliver the cathode electrolyte to the cathode electrolyte tank at a flow rate of 913 mL / h, and the cathode liquid containing isooctylaldehyde is continuously delivered to the anode at the same flow rate; and the anode liquid is continuously output at the same flow rate. After continuing the electrolysis for 2.2 hours, the electrolysis is stopped, and the anode liquid circulation pump, the cathode liquid circulation pump, the paired electrolysis circulation pump, the raw material feed pump and the electrolyte discharge pump are turned off.

[0067] (4) Collecting the cathode liquid from the cathode electrolyte tank and the cathode chamber, evaporating the cathode liquid (temperature 60° C., time 3 h), adding ethyl acetate for extraction, separating the liquids, and collecting the upper organic phase to obtain pure isooctyl aldehyde.

[0068] The anolyte in the anolyte tank and the anolyte chamber and the anolyte discharged from the anolyte tank were collected, and the pH of the anolyte was adjusted to 3 with 5% by volume dilute sulfuric acid. The liquids were separated, and the upper oil phase was collected. After distillation treatment (tower top temperature 89°C, tower bottom temperature 154°C, tower operating pressure 2kPa, reflux ratio 2:1), pure isooctanoic acid was obtained.

[0069] Comparative Example 1

[0070] This comparative example provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Example 1, except that the cathode electrolyte and the anode electrolyte are different, and an aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate is used as the cathode electrolyte and placed in the cathode electrolyte tank. An aqueous solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate is taken as the anode electrolyte and placed in the anode electrolyte tank.

[0071] Comparative Example 2

[0072] This comparative example provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Example 1, except that the cathode electrolyte and the anode electrolyte are different, and an ethanol solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the solvent is pure ethanol) is used as the cathode electrolyte and placed in the cathode electrolyte tank. An ethanol solution containing 0.2 mol / L isooctyl aldehyde and 2 wt% tetrabutylammonium tetrafluoroborate (the solvent is pure ethanol) is taken as the anode electrolyte and placed in the anode electrolyte tank.

[0073] Comparative Example 3

[0074] This comparative example provides a method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, which is basically the same as Example 1, except that the cathode electrolyte and the anode electrolyte are different, and an ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde (the volume percentage of ethanol is 50%) is used as the cathode electrolyte and placed in the cathode electrolyte tank. An ethanol aqueous solution containing 0.2 mol / L isooctyl aldehyde (the volume percentage of ethanol is 40%) is taken as the anode electrolyte and placed in the anode electrolyte tank.

[0075] Table 1 Electrolysis results

[0076]

[0077]

[0078] It can be seen from the results in the above table that, compared with Comparative Examples 1-3, the embodiments of the present application not only significantly improve the yield of isooctyl aldehyde and isooctyl acid, but also improve the electrolysis efficiency of the cathode and the anode.

[0079] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis, characterized in that: The steps include: Step S1: adding a cathode electrolyte to the cathode chamber and adding an anolyte to the anode chamber, wherein the cathode electrolyte comprises an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the anolyte comprises an alcohol aqueous solution containing isooctyl aldehyde and a conductive salt, and the cathode chamber and the anode chamber are separated by a cation exchange membrane; Step S2: After power is turned on, an electrolytic reaction is carried out, in the cathode chamber, isooctyl aldehyde undergoes a reduction reaction to obtain a cathode liquid containing isooctyl aldehyde, and in the anode chamber, isooctyl aldehyde undergoes an oxidation reaction to obtain an anode liquid containing isooctyl acid.

2. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to claim 1, characterized in that: The concentration of isooctyl aldehyde in the cathode electrolyte added in step S1 is 0.1 to 1 mol / L; and / or the concentration of isooctyl aldehyde in the anode electrolyte added in step S1 is 0.1 to 1 mol / L.

3. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to claim 1 or 2, characterized in that: The mass percentage of the conductive salt added to the anolyte or cathode electrolyte in step S1 is 0.1-10%, preferably 1-5%.

4. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to any one of claims 1 to 3, characterized in that: In the cathode electrolyte and / or the anode electrolyte, the volume percentage of alcohol in the alcohol aqueous solution is 20-80%, preferably 40-60%.

5. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to any one of claims 1 to 4, characterized in that: The alcohol aqueous solution includes one or more of an ethanol aqueous solution, a methanol aqueous solution, and an ethylene glycol aqueous solution; and / or the conductive salt includes a quaternary ammonium salt and / or a quaternary phosphonium salt; and / or the paired electrolysis method is a continuous electrolysis method or an intermittent electrolysis method.

6. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to any one of claims 1 to 5, characterized in that: The cathode is selected from a metal electrode; optionally, the metal electrode includes nickel, lead, copper, stainless steel, a nickel alloy electrode, a lead alloy electrode or a copper alloy electrode; optionally, the structure of the cathode is selected from a flat plate or a porous mesh.

7. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to any one of claims 1 to 6, characterized in that: The anode is selected from a metal electrode or a carbon electrode; and / or the structure of the anode is selected from a flat plate or a porous mesh; and / or the cation exchange membrane is selected from one or more of cation exchange membrane N117, cation exchange membrane N221, cation exchange membrane N427, cation exchange membrane N551, cation exchange membrane HF-1, cation exchange membrane CM001, cation exchange membrane N324, and cation exchange membrane N982.

8. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to any one of claims 1 to 7, characterized in that: The method further includes at least one S3 step, wherein the S3 step includes: conducting anode liquid containing isooctyl acid obtained in the previous step, adding cathode liquid containing isooctyl aldehyde obtained in the previous step into the anode chamber, re-adding the cathode electrolyte into the cathode chamber, conducting an electrolytic reaction after power is turned on, reducing isooctyl aldehyde in the cathode chamber to obtain cathode liquid containing isooctyl aldehyde, oxidizing isooctyl aldehyde in the anode chamber to obtain an anode liquid containing isooctyl acid and combining the anode liquid containing isooctyl acid obtained in the previous step; optionally, when the conversion rate of isooctyl aldehyde in the cathode liquid is greater than or equal to 99%, conducting anode liquid containing isooctyl acid and adding cathode liquid containing isooctyl aldehyde into the anode chamber.

9. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to any one of claims 1 to 8, characterized in that: In step S2, the current density of the electrolysis reaction is 500-3000 A / m 2 ; and / or, the cell voltage of the electrolysis reaction is 3.2 to 8.7 V; And / or, the temperature of the cathode electrolyte or the anode electrolyte in the electrolysis reaction is 25-55°C.

10. The method for simultaneously synthesizing isooctyl aldehyde and isooctyl acid by paired electrolysis according to claim 1, characterized in that: In step S2, after the electrolysis reaction, the step of purifying the cathode liquid and the anode liquid to obtain pure isooctyl aldehyde and pure isooctyl acid is also included; optionally, the purification method includes extraction or distillation.

Images