Device and method for preparing aldehyde through carboxylic acid decarboxylation

Abstract

The invention discloses a device and a method for preparing aldehyde through carboxylic acid decarboxylation, and belongs to the technical field of electrochemistry. The membrane-free electrolytic tank is arranged, the electrolyte is electrolyzed through the specific cathode and anode in the electrolytic tank, oxygen needs to be introduced in the electrolysis process to provide an oxygen enrichment condition for the system, and the unique pore structure of the anode effectively promotes the liquid-phase mass transfer and interface adsorption process of O2; the unique carbon atom hybridization state promotes the bonding of alkyl free radicals and O2 on an interface, the high-selectivity synthesis of aldehyde is realized under the specific current density, the reaction mechanism is researched through isotopic tracing under the specific electrolysis condition, the synergistic reaction mechanism of carboxylic acid decarboxylation and oxygen atom insertion is disclosed, and the reaction efficiency is improved. By developing a novel electro-catalysis system, green and efficient conversion from biomass carboxylic acid to high-added-value aldehyde compounds is realized at normal temperature and normal pressure, and a new strategy is provided for preparation of fine chemicals.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, specifically to an apparatus and method for the decarboxylation of carboxylic acids to prepare aldehydes. Background Technology

[0002] Aliphatic aldehydes are a class of widely distributed and valuable compounds in nature. They play crucial physiological roles in the metabolism of organisms and are also indispensable intermediates in organic synthesis, particularly in the fine chemical industry, including fragrances, pharmaceuticals, and surfactants. Currently, the preparation methods for aliphatic aldehydes are mainly divided into oxidation and reduction methods. The oxidation method involves the oxidation of fatty alcohols, while the reduction method involves the catalytic conversion of carboxylic acids. Both methods have been industrialized. However, traditional preparation processes still have significant limitations in terms of raw materials and reaction conditions. For example, some routes rely on non-renewable fossil-based raw materials and often require harsh conditions such as high temperature and high pressure, resulting in high energy consumption and environmental pollution. While biomass-based alternatives based on natural product extraction align with green and sustainable principles, their industrialization is hampered by low conversion rates and high separation and purification costs.

[0003] Furthermore, in the traditional preparation of renewable fatty aldehydes, the fatty acid reduction method and the fatty alcohol oxidation method have the characteristic that the carbon chain length of the product remains consistent with the odd or even number of carbons in the raw material. That is, even-numbered carbon raw materials usually produce even-numbered carbon aldehydes. This characteristic leads to a bottleneck in the synthesis of odd-numbered carbon aldehydes. For example, Akakabe Y et al. in 1999, 40(6):1137-1140 Tetrahedron Letters The article "Enantioselective α-hydroperoxylation of long-chain fatty acids with crude enzyme of marine green alga Ulva pertusa" published in China mentions long-chain odd-numbered carbon aldehydes (C 15 C 17 ) can be mediated by oxygenase-mediated C 16 C 18 Fatty acid conversion was used to generate aldehydes, and a stepwise decarboxylation system for carboxylic acids using 2-hydroperoxyacid as an intermediate was developed based on this. Although some researchers have developed processes for preparing long-chain odd-carbon aldehydes using specific intermediates, inspired by biological metabolic pathways, the reaction conditions required for these processes are quite stringent, making them difficult to implement in practice.

[0004] Chinese patent CN118988285A discloses a heterojunction photocatalyst for the decarboxylation of fatty acids to aldehydes, its preparation method, and its application. The heterojunction photocatalyst is: (i) anatase titanium dioxide; or, (ii) a catalyst using anatase titanium dioxide as a support and one of Bi₂O₃, CeO₂, ZnO, or NiO as the active component. These catalysts can photocatalyze the removal of a carboxyl group from carboxylic acids to aldehydes at room temperature and pressure. This technical solution relies on a specific catalyst, and the preparation process of this catalyst is time-consuming. Subsequent catalytic processes also depend on photocatalysis, and the conditions are quite harsh.

[0005] CN118388328A discloses a catalyst-free photochemical decarboxylation synthesis method for aldehydes and ketones. This method uses inexpensive carboxylic acids as raw materials, air as an oxidant, 2,4,6-trimethylpyridine as a base, and tetrabutylammonium chloride as an amphoteric surfactant. It does not use exogenous photosensitizers. The synthesis of aldehydes and ketones involves the neutralization of the carboxylic acid with the base, followed by the formation of an EDA complex via an electron donor-acceptor (EDA) pathway. Electron transfer under light then mildly activates the carboxylic acid, leading to the synthesis of aldehydes and ketones. However, this technology suffers from low photocatalytic efficiency and is not suitable for large-scale preparation.

[0006] In summary, the methods for preparing aliphatic aldehydes by fatty acid decarboxylation have been extensively studied in the existing technology. However, due to the odd-even consistency in the preparation process, there are bottlenecks in the preparation of aliphatic aldehydes. The parameters required by existing photocatalysis or other decarboxylation methods are quite demanding and cannot be industrialized, or the selectivity of the obtained aliphatic aldehydes cannot meet the requirements of industrialization. Therefore, the high cost of raw materials, demanding preparation conditions, high energy consumption, pollution, low conversion rate, and high separation cost in the fatty acid decarboxylation process are still problems that urgently need to be solved. Summary of the Invention

[0007] To address the above problems, this invention provides an apparatus and method for preparing aldehydes by decarboxylation of carboxylic acids. The method uses electrocatalysis to catalyze the preparation of fatty acid aldehydes under specific conditions such as solvent, electrolyte, current density, and electrode type. The fatty acid aldehydes prepared by this method have high selectivity, high fatty acid conversion rate, simple preparation process, easy subsequent separation and purification process, and the entire process is green and pollution-free.

[0008] This invention provides an apparatus for the decarboxylation of carboxylic acids to prepare aldehydes. The apparatus includes an electrochemical workstation and an electrolytic cell. The electrolytic cell is a circular, membrane-free, dual-electrode electrolytic cell, specifically composed of an electrolytic cell, a cathode, and an anode. The electrolytic cell is filled with an electrolyte. The cathode is a titanium electrode, and the anode is one of a platinum sheet electrode, a mesh glassy carbon electrode (RVC), and a glassy carbon electrode. The electrolyte includes carboxylic acid, electrolyte, and solvent.

[0009] Furthermore, the electrolytic cell has a height of 8-12cm and a diameter of 2-5cm.

[0010] Furthermore, the dimensions of the cathode and the anode are (1-2cm) × (1-2cm).

[0011] Furthermore, the carboxylic acid is C4-C. 18 It consists of one or more of the saturated and unsaturated fatty acids.

[0012] Furthermore, the electrolyte is tetramethylammonium hydroxide (Me4N·OH).

[0013] Furthermore, the solvent is one or more of acetonitrile, methanol, ethanol, and acetone.

[0014] Furthermore, the working electrode of the electrochemical workstation is connected to the anode, and the counter electrode and reference electrode of the electrochemical workstation are connected to the cathode.

[0015] Furthermore, the electrochemical workstation uses 50-80 mA / cm 2 Constant current electrolysis was performed at a current density until the total charge was 1.3-1.5 F / mol.

[0016] The present invention also provides a method for decarboxylation of the apparatus used to prepare aldehydes from carboxylic acids, comprising the following steps: Step 1: Dissolve carboxylic acid and electrolyte in a solvent to obtain an electrolyte solution; Step 2: Place the electrolyte into an electrolytic cell. Under sealed conditions, first introduce an inert gas to remove dissolved oxygen, then continue to introduce O2. Electrolysis is carried out using an electrochemical workstation under constant current conditions. After stopping electrolysis, the product is obtained. Step 3: Acidify the product and then extract it with an extraction solution to obtain the upper aldehyde.

[0017] Furthermore, the concentration of the carboxylic acid in the electrolyte during step 1 is 0.1-0.8 mol / L.

[0018] Furthermore, the concentration of the electrolyte in the electrolyte solution in step 1 is 0.1-0.5 mol / L.

[0019] Furthermore, the carboxylic acid in step 1 is C4-C. 18 It consists of one or more of the saturated and unsaturated fatty acids.

[0020] Furthermore, the electrolyte in step 1 is tetramethylammonium hydroxide (Me4N·OH).

[0021] Furthermore, the solvent in step 1 is one or more of acetonitrile, methanol, ethanol, and acetone.

[0022] Furthermore, in step 2, the cathode of the electrolytic cell is a titanium electrode, and the anode is one of a platinum sheet electrode, a mesh glassy carbon electrode (RVC), or a glassy carbon electrode.

[0023] Furthermore, the inert gas is introduced for 10-30 minutes in step 2.

[0024] Furthermore, the inert gas in step 2 is nitrogen or argon, and the flow rate is 20-60 mL / min.

[0025] Furthermore, the flow rate of oxygen (O2) in step 2 is 20-60 mL / min.

[0026] Furthermore, the current density of the constant current in step 2 is 50-80 mA / cm². 2 .

[0027] Furthermore, in step 2, the electrolysis is carried out until the total charge is 1.3-1.5 F / mol.

[0028] Furthermore, in step 3, the hydrochloric acid (HCl) used for acidification has a concentration of 1-5 mol / L.

[0029] Furthermore, the volume ratio of the hydrochloric acid to the solvent in step 1 is (1-5):5.

[0030] Further, the volume ratio of the extract in step 3 to the solvent in step 1 is (1-10):5.

[0031] Furthermore, the extract in step 3 is ethyl acetate.

[0032] Furthermore, the conversion rate of the carboxylic acid in step 3 is 82-97%.

[0033] Furthermore, the selectivity of the aldehyde in step 3 is 34-70%.

[0034] Furthermore, the extraction in step 3 also includes byproducts, which include at least one or more of alcohols, alkenes, alkanes, ethers and esters.

[0035] The beneficial effects of this invention are: This invention employs a membrane-free electrolytic cell, in which the electrolyte is electrolyzed through specific anodes and cathodes. Oxygen is introduced during electrolysis to provide oxygen-rich conditions. The unique pore structure of the anode effectively promotes O2 liquid-phase mass transfer and interfacial adsorption. Its unique carbon atom hybridization promotes the interfacial binding of alkyl radicals with O2. Highly selective synthesis of aldehydes is achieved at specific current densities. Under specific electrolysis conditions, this invention investigated the reaction mechanism using isotope tracing, revealing a synergistic reaction mechanism of carboxylic acid decarboxylation and oxygen atom insertion. By developing a novel electrocatalytic system, the green and efficient conversion of biomass carboxylic acids into high-value-added aldehydes is achieved at ambient temperature and pressure, providing a new strategy for the preparation of fine chemicals. Attached Figure Description

[0036] Figure 1 This is a diagram of the apparatus for preparing aldehydes by decarboxylation of carboxylic acids as described in this invention; Figure 2 This is a graph showing the change in carboxylic acid conversion rate over time in Example 1. Figure 3 This is a graph showing the change in aldehyde and alcohol selectivity over time in Example 1. Figure 4 This is a graph showing the changes in reaction current efficiency and Faraday efficiency of the aldehyde over time in Example 1. Figure 5 These are the mass spectra of the aldehyde compounds obtained in Examples 2 and 3 of this study; Figure 6 The graphs show the changes in reaction current over time under different atmospheres in Example 1 and Comparative Example 1. Figure 7 This describes the reaction mechanism for the decarboxylation of carboxylic acids to prepare aldehydes in this invention. Detailed Implementation

[0037] The invention will be described in detail below with reference to the embodiments: This invention provides an apparatus and method for preparing aldehydes by decarboxylation of carboxylic acids. The method uses electrocatalysis to catalyze the preparation of fatty acid aldehydes under specific conditions such as solvent, electrolyte, current density, and electrode type. The fatty acid aldehydes prepared by this method have high selectivity, high fatty acid conversion rate, simple preparation process, easy subsequent separation and purification process, and the whole process is green and pollution-free.

[0038] Example 1 This embodiment provides an apparatus for the decarboxylation of carboxylic acids to prepare aldehydes. The apparatus includes an electrochemical workstation and an electrolytic cell. The electrolytic cell is a circular, membrane-free, dual-electrode electrolytic cell, specifically composed of an electrolytic cell, a cathode, and an anode. The electrolytic cell is filled with an electrolyte. The cathode is a titanium electrode, and the anode is a mesh glassy carbon electrode (RVC). The electrolyte includes carboxylic acid, electrolyte, and solvent.

[0039] In this embodiment, the electrolytic cell has a height of 10 cm and a diameter of 3 cm. The cathode and anode are 2 cm × 1 cm in size. The working electrode of the electrochemical workstation is connected to the anode, and the counter electrode and reference electrode of the electrochemical workstation are connected to the cathode. The electrochemical workstation uses a current of 50-80 mA / cm². 2 Constant current electrolysis was performed at a current density until the total charge was 1.5 F / mol.

[0040] like Figure 1 This is a diagram of the apparatus for preparing aldehydes by decarboxylation of carboxylic acids as described in this invention.

[0041] Example 2 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode (anode) and a 2cm × 1cm titanium sheet as the counter electrode (cathode). Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 93%, the selectivity of undecylaldehyde is 42%, and the selectivity of undecylol is 15%.

[0042] like Figure 2 The graph shows the change in carboxylic acid conversion rate over time in Example 1. As the reaction proceeds, the conversion rate of carboxylic acid is >90% when the charge reaches 1.5 F / mol. Further increasing the charge decreases the rate of increase, eventually reaching approximately 95%. However, when the charge exceeds 1.5 F / mol, the selectivity for the aldehyde decreases. Figure 3 ).

[0043] like Figure 3The graph shows the change in selectivity of aldehydes and alcohols over time in Example 1. The selectivity of aldehydes is close to 70% in the early stage of the reaction, but gradually decreases as the reaction proceeds. It can still maintain 60% selectivity at 1.0 F / mol. When the carboxylic acid is further converted, the selectivity of aldehydes decreases rapidly, and is below 40% at 2.0 F / mol. In contrast, the selectivity of alcohols remains almost unchanged, stabilizing at about 15%. This indicates that under higher potential conditions, due to the higher chemical reactivity of aldehydes, the probability of their adsorption and oxidation on the electrode surface increases, while alcohols are relatively stable.

[0044] like Figure 4 The graph shows the changes in reaction current efficiency and aldehyde's Faradaic efficiency over time in Example 1. The current efficiency initially shows an upward trend, possibly due to the time required for the formation of the electric double layer on the electrode surface and O2 diffusion. Once the charge efficiency stabilizes at around 63%, it remains stable until the lauric acid conversion rate reaches 90%. As the lauric acid conversion rate exceeds 90%, the current efficiency begins to decrease. The Faradaic efficiency of the aldehyde shows a similar trend to the current efficiency, but due to the gradual decrease in the selectivity of the aldehyde, its Faradaic efficiency decreases more significantly. This result indicates that reasonable control of the reaction time is crucial for improving the selectivity of the target product.

[0045] Example 3 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm×1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm×1cm titanium sheet as the counter electrode. Under sealed conditions, first pass N2 through at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue passing N2 through at a flow rate of 20mL / min. 18 O2, and at 60mA / cm 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 87%, the selectivity of undecylaldehyde is 40%, and the selectivity of undecylol is 17%.

[0046] like Figure 5 These are the mass spectra of the aldehyde compounds obtained in Examples 2 and 3. a represents Example 3, and b represents Example 2. Through spectral comparison and analysis, it was found that in Example 3, the aldehydes were...18 The O2 reaction products exhibit a clear... 18 O isotope labeling characteristics, similar to the oxygen introduced in Example 2 ( 16 Compared to the undecaldehyde produced after O2), the characteristic ion peak in the product spectrum shifted significantly from m / z 169 to m / z 171, resulting in a +2 mass deviation. 18 O replaced 16 The theoretical mass difference of O is in perfect agreement, and the above mass spectrometry behavior strongly proves that exogenous oxygen has successfully participated in the reaction and bound to the undecaldehyde molecule.

[0047] Example 4 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of methanol to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 85%, the selectivity of undecylaldehyde is 37%, and the selectivity of undecylol is 18%.

[0048] Example 5 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of ethanol to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 88%, the selectivity of undecylaldehyde is 42%, and the selectivity of undecylol is 19%.

[0049] Example 6 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetone to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 91%, the selectivity of undecylaldehyde is 34%, and the selectivity of undecylol is 16%.

[0050] Example 7 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 50mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid was 82%, the selectivity of undecylaldehyde was 58%, and the selectivity of undecylol was 26%.

[0051] Example 8 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 55mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 85%, the selectivity of undecylaldehyde is 51%, and the selectivity of undecylol is 14%.

[0052] Example 9 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 1 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 93%, the selectivity of undecylaldehyde is 42%, and the selectivity of undecylol is 15%.

[0053] Example 10 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of octanoic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper layer of heptanal; The conversion rate of the octanoic acid is 95%, and the selectivity of the heptanal is 40%.

[0054] Example 11 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of n-decanoic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper layer of nonanal; The conversion rate of the decanoic acid was 94%, and the selectivity of the nonanal was 42%.

[0055] Example 12 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol undecanoic acid and 0.5 mmol tetramethylammonium hydroxide (Me4N·OH) in 5 mL acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper layer of decanal; The conversion rate of undecanoic acid was 92%, and the selectivity of decanal was 43%.

[0056] Example 13 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of tetradecanoic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper layer of tridecanal; The conversion rate of the myristic acid was 93%, and the selectivity of the tridecanal was 45%.

[0057] Example 14 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol palmitic acid and 0.5 mmol tetramethylammonium hydroxide (Me4N·OH) in 5 mL acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper pentadecylaldehyde; The conversion rate of palmitic acid was 92%, and the selectivity of pentadecylaldehyde was 47%.

[0058] Example 15 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol stearic acid and 0.5 mmol tetramethylammonium hydroxide (Me4N·OH) in 5 mL acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper layer of heptadecanal; The conversion rate of stearic acid is 94%, and the selectivity of heptadecanal is 50%.

[0059] Example 16 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of 10-hydroxydecanoic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper layer of 9-hydroxynonanal; The conversion rate of 10-hydroxydecanoic acid was 92%, and the selectivity of 9-hydroxynonanal was 45%.

[0060] Example 17 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of monomethyl sebacate and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper layer of methyl 9-formylnonanoate; The conversion rate of the sebacic acid monomethyl ester is 90%, and the selectivity of the 9-formylnonanoate methyl ester is 40%.

[0061] Example 18 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of 10-undecenoic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper layer of 9-decenal; The conversion rate of 10-undecenoic acid was 88%, and the selectivity of 9-decenal was 42%.

[0062] Example 19 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of 10-undecynyl acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper layer of 9-decynyl aldehyde; The conversion rate of 10-undecynyl acid was 89%, and the selectivity of 9-decynyl aldehyde was 35%.

[0063] Example 20 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of 10-bromodecanoic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper layer of 9-bromononanal; The conversion rate of 10-bromodecanoic acid was 91%, and the selectivity of 9-bromononanal was 40%.

[0064] Example 21 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of oleic acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was performed using an electrochemical workstation under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and then extract with 5 mL of ethyl acetate to obtain the upper layer of 8-heptadecenal; The conversion rate of oleic acid was 93%, and the selectivity of 8-heptadecenal was 44%.

[0065] Example 22 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm×1cm platinum sheet as the working electrode and a 2cm×1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 92%, the selectivity of undecylaldehyde is 41%, and the selectivity of undecylol is 18%.

[0066] Example 23 This embodiment provides a method for decarboxylation using the apparatus of Embodiment 1, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 1cm×1cm glassy carbon electrode as the working electrode and a 2cm×1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 91%, the selectivity of undecylaldehyde is 42%, and the selectivity of undecylol is 20%.

[0067] Comparative Example 1 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, continuously introduce N2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl, then extract with 5 mL of ethyl acetate to obtain the byproduct; The conversion rate of lauric acid is 30%, the selectivity of undecylaldehyde is 0%, the selectivity of undecylol is 0%, and the selectivity of undecane, docosane, and terminal undecene in the byproducts (not all observed) is 10%, 70%, and 10%, respectively.

[0068] like Figure 6 The graph shows the change of reaction current over time under different atmospheres in Example 1 and Comparative Example 1. In the N2 environment, the current density drops rapidly from the initial stage and eventually approaches zero, indicating that the RVC electrode has extremely low catalytic ability for carboxylic acids under anaerobic conditions. In the O2 environment, the reaction current first rises to an extreme value and then slowly decreases. This trend indicates that the initial increase in current corresponds to the construction stage of the reaction, while the subsequent decrease is attributed to the gradual consumption of the substrate. To further verify the role of O2 in the reaction, a gas shift experiment was conducted. The reaction was started in a closed air atmosphere, and the current density dropped rapidly, but the decrease was slightly less than that in the N2 environment. When O2 was introduced into the system, the current rose rapidly in a short time, reaching the same level as in the O2 environment, and showed a trend consistent with the reaction in the O2 environment in the subsequent stages. This experimental result clearly proves that O2 is a necessary component of the reaction.

[0069] Comparative Example 2 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce air at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 30%, the selectivity of undecylaldehyde is 12%, the selectivity of undecyl alcohol is 7.5%, the selectivity of undecene in the byproducts (not all observed) is 40%, the selectivity of methyl ether and its derivatives is 20%, and the selectivity of undecyl laurate and its derivatives is 20%.

[0070] Comparative Example 3 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of N,N-dimethylformamide (DMF) to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 74%, the selectivity of undecylaldehyde is 6%, and the selectivity of undecylol is 16%.

[0071] Comparative Example 4 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of H2O to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 31%, the selectivity of undecylaldehyde is 6%, and the selectivity of undecylol is 4%.

[0072] Comparative Example 5 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 100mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 92%, the selectivity of undecylaldehyde is 30%, and the selectivity of undecylol is 10%.

[0073] Comparative Example 6 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 0.1 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 85%, the selectivity of undecylaldehyde is 25%, and the selectivity of undecylol is 15%.

[0074] Comparative Example 7 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 5 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm titanium sheet as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 95%, the selectivity of undecylaldehyde is 25%, and the selectivity of undecylol is 12%.

[0075] Comparative Example 8 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm 5wt% Pb / C electrode as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 93%, the selectivity of undecylaldehyde is 35%, and the selectivity of undecylol is 30%.

[0076] Comparative Example 9 This comparative example provides a method for preparing aliphatic aldehydes, comprising the following steps: Step 1: Dissolve 2 mmol of lauric acid and 0.5 mmol of tetramethylammonium hydroxide (Me4N·OH) in 5 mL of acetonitrile to obtain the electrolyte; Step 2: Place the electrolyte into an electrolytic cell, using a 2cm × 1cm mesh glassy carbon electrode (RVC) as the working electrode and a 2cm × 1cm 10wt% Pb / C electrode as the counter electrode. Under sealed conditions, first introduce N2 at a flow rate of 20mL / min for 10min to remove dissolved oxygen, then continue to introduce O2 at a flow rate of 20mL / min, and maintain a current of 60mA / cm. 2 Electrolysis was carried out under constant current conditions until the total charge in the system reached 1.5 F / mol, at which point the electrolysis was stopped to obtain the product. Step 3: Acidify the product with 2 mL of 3 mol / L HCl and extract with 5 mL of ethyl acetate to obtain the upper undecylaldehyde and the byproduct undecylol. The conversion rate of lauric acid is 92%, the selectivity of undecylaldehyde is 20%, and the selectivity of undecylol is 40%.

[0077] Table 1 shows the conversion rate and selectivity of the substances in the embodiments of this application.

[0078] Table 2 shows the conversion rate and selectivity of the substances in the comparative examples in this application.

[0079] like Figure 7 The diagram illustrates the oxygen-co-catalyzed reaction pathway in this invention. In the non-separated electrolytic cell system, carboxylate ions preferentially undergo decarboxylation on the RVC surface during the anodic oxidation reaction, simultaneously releasing CO2 and forming highly reactive alkyl radicals (R•). These radical species rapidly combine with O2 molecules in the presence of dissolved oxygen to generate peroxy radicals (ROO•). These peroxy radicals undergo rearrangement through intramolecular hydrogen migration to form a transition state structure containing a hydroperoxy group (HOOQ•). This high-energy intermediate then decomposes due to thermodynamic instability, ultimately transforming into aldehyde compounds.

[0080] Table 1 shows the conversion rate of carboxylic acids and the selectivity of aldehydes and alcohols in this embodiment. As can be seen from the table, the conversion rate of carboxylic acids in this embodiment is high, and the selectivity of aldehydes that can be obtained is also high. This method can be applied to a variety of carboxylic acids. In Comparative Example 1, no O2 was introduced, but N2 was introduced throughout the process. There were no peroxide free radicals in the system, which made it impossible to synthesize aldehydes. Therefore, the selectivity of aldehydes and alcohols was 0, and only byproducts appeared. In Comparative Example 2, after dissolving oxygen, air was introduced. Although aldehydes could still be synthesized due to the low oxygen content in the air, the selectivity for aldehydes was low. In Comparative Examples 3 and 4, the electrolyte solvents were DMF and water, and the selectivity of aldehydes was much lower than that of the present invention. Comparative Example 5 increased the current density during the electrolysis process. As the surface free radical concentration reached a certain threshold under high current density, and the supply and diffusion of O2 were insufficient, the coupling reaction of free radicals was promoted, resulting in a decrease in the selectivity of aldehydes and alcohols. In Comparative Examples 6 and 7, the substrate concentrations were too low and too high. At the lower concentrations, the selectivity of aldehydes was low, which may be due to the lower content of carboxylic acids in the solution system, making organic aldehydes more easily oxidized in the competitive reaction. However, when the substrate concentration was further increased to 1 mol, the selectivity of aldehydes also decreased. The possible reason is that the higher substrate concentration leads to a faster generation rate of organic aldehydes, which increases their concentration in the solution and makes them more easily oxidized on the RVC electrode surface, thereby reducing their relative selectivity. In Comparative Examples 8 and 9, replacing the counter electrode (cathode) with Pb / C electrodes of different concentrations resulted in a significant decrease in aldehyde selectivity.

[0081] As can be seen from the above, the apparatus and method for preparing aldehydes by decarboxylation of carboxylic acids described in this invention have a wide range of applications, low cost, and extremely high market prospects.

[0082] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any modifications or equivalent changes made based on the technical essence of the present invention shall still fall within the scope of protection claimed by the present invention.

Claims

1. An apparatus for the decarboxylation of carboxylic acids to prepare aldehydes, characterized in that, The device includes an electrochemical workstation and an electrolytic cell. The electrolytic cell is a circular, membrane-free, dual-electrode electrolytic cell, specifically composed of an electrolytic cell, a cathode, and an anode. The electrolytic cell is filled with an electrolyte. The cathode is a titanium electrode, and the anode is one of a platinum sheet electrode, a mesh glassy carbon electrode, and a glassy carbon electrode. The electrolyte includes carboxylic acid, electrolyte, and solvent.

2. A method for decarboxylation using the apparatus for preparing aldehydes from carboxylic acids according to claim 1, characterized in that, Includes the following steps: Step 1: Dissolve carboxylic acid and electrolyte in a solvent to obtain an electrolyte solution; Step 2: Place the electrolyte into an electrolytic cell. Under sealed conditions, first introduce an inert gas to remove dissolved oxygen, then continue to introduce O2. Electrolysis is carried out using an electrochemical workstation under constant current conditions. After stopping electrolysis, the product is obtained. Step 3: Acidify the product and then extract it with an extraction solution to obtain the upper aldehyde.

3. The method according to claim 2, characterized in that, The concentration of the carboxylic acid in the electrolyte during step 1 is 0.1-0.8 mol / L.

4. The method according to claim 2, characterized in that, The concentration of the electrolyte in the electrolyte solution in step 1 is 0.1-0.5 mol / L.

5. The method according to claim 2, characterized in that, The carboxylic acid in step 1 is C4-C. 18 It consists of one or more of the saturated and unsaturated fatty acids.

6. The method according to claim 2, characterized in that, The electrolyte in step 1 is tetramethylammonium hydroxide.

7. The method according to claim 2, characterized in that, The solvent in step 1 is one or more of acetonitrile, methanol, ethanol, and acetone.

8. The method according to claim 2, characterized in that, In step 2, the electrolysis is carried out until the total charge is 1.3-1.5 F / mol.

9. The method according to claim 2, characterized in that, The conversion rate of the carboxylic acid in step 3 is 80-97%.

10. The method according to claim 2, characterized in that, The selectivity of the aldehyde in step 3 is 34-70%.

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