WO2020220183A1 - Multi-stage electrocatalytic membrane reactor, and use thereof and method therefor in organic electrochemical reaction - Google Patents

Abstract

The present application provides a multi-stage electrocatalytic membrane reactor, and use thereof and a method therefor in an organic electrochemical reaction. The multi-stage electrocatalytic membrane reactor comprises: a reactor body, having a chamber for performing an electrochemical reaction; two or more stages of porous membrane electrode pairs, provided in the chamber; a feeding unit, provided on one side of the reactor body, being in communication with the chamber, and used for supplying reaction raw materials to the chamber; and a product collecting unit, provided on the other side of the reactor body, being in communication with the chamber, and used for collecting products generated in the chamber; and a power supply, the positive electrode and the negative electrode thereof being respectively connected to a porous membrane electrode and an auxiliary electrode or an auxiliary electrode and a porous membrane electrode of each stage of the porous membrane electrode pair, so as to form electrode pairs. The multi-stage electrocatalytic membrane reactor of the present application has the advantages of a high conversion rate and high stability, and being safe, reliable, green, environmentally friendly, and reusable.

Description

Multi-stage electrocatalytic membrane reactor and its application and method in organic electrochemical reaction Technical field

This application belongs to the technical field of organic electrochemical synthesis, and in particular relates to a multi-stage electrocatalytic membrane reactor and its application and method in organic electrochemical reactions.

Background technique

Organic electrochemical synthesis, known as green synthesis technology, uses electrons as reagents. It is a new technology that realizes the synthesis of organic substances through the gains and losses of electrons. It is called "ancient method, new technology" and has been widely used in medicine, Perfume, auxiliary agent, dye intermediate and other industries. As a new type of separation technology with high efficiency, energy saving and environmental friendliness, membrane separation has been widely used in various fields such as petroleum, chemical industry, medicine, biology, food and water treatment. The electrochemical technology and membrane separation technology are combined to construct an electrocatalytic membrane reactor. The high specific surface area of the porous membrane electrode is used to load more catalysts to further increase the number of active sites. At the same time, the process of reactants passing through the membrane surface strengthens the The flow mass transfer effect increases the efficiency of electron transfer, and the product is separated from the membrane surface in time to prevent excessive oxidation, while improving the conversion rate of raw materials and the selectivity of target products.

There are many types of reactors in the chemical industry. Traditional reactors include: tubular reactors, tank reactors, tower reactors, fixed bed reactors, fluidized bed reactors, etc. These reactors will involve one or more problems of high temperature, high pressure, oxidant, reducing agent, and catalyst loss. In the future energy saving, green and high efficiency process requirements, there is an urgent need to develop new and efficient new reactors.

Chinese invention patent CN101597096A discloses an electrocatalytic membrane reactor, which includes adjustable DC stabilized power supply, connecting wires, electrocatalytic composite membrane, auxiliary electrode, liquid tank, vacuum gauge, peristaltic pump, permeate tank and other parts.

Chinese invention patent CN102634815A discloses a method for preparing sodium tetrafluoropropionate by oxidation of tetrafluoropropanol by electrocatalytic membrane. It is characterized in that reaction and separation are integrated to synthesize sodium tetrafluoropropionate. The invention uses a titanium-based electrocatalytic membrane as an anode and an auxiliary electrode as a cathode to form an electrocatalytic membrane reactor; the reactant or feed liquid is a mixed aqueous solution of tetrafluoropropanol and sodium salt. Under certain working voltage and current density conditions, four The fluoropropanol is catalyzed and oxidized to the intermediate product tetrafluoropropionic acid on the surface of the membrane. The tetrafluoropropionic acid reacts with the electrolyte sodium salt in the feed solution to produce sodium tetrafluoropropionate. Under the condition of high volume, the reactant tetrafluoropropanol and the product sodium tetrafluoropropionate are separated in real time; the membrane permeate is collected, the pH value is adjusted to about 7-8, and then concentrated to obtain the sodium tetrafluoropropionate product.

Chinese invention patent CN103436910A discloses a method for preparing gluconic acid and glucaric acid by electrocatalytic membrane oxidation of glucose. The utility model is characterized in that the electrocatalytic membrane is used as the anode, and the auxiliary electrode is used as the cathode. The electrocatalytic membrane reactor is constructed by connecting with a stabilized voltage through a wire to catalyze the oxidation of glucose.

Chinese invention patent CN104032327A discloses a method for preparing cyclohexanol and cyclohexanone by electrocatalytic oxidation of alkanes. The method uses a porous metal electrocatalytic membrane loaded with metal oxides as the anode, and the auxiliary electrode is the cathode to form an electrocatalytic membrane reactor; the reaction raw material liquid is a mixed aqueous solution of cyclohexane, organic solvent and electrolyte, at a certain working voltage and current Under density conditions, cyclohexane is catalyzed and oxidized by metal oxides on the membrane surface and in the pores to the products cyclohexanol and cyclohexanone. At the same time, through the negative pressure generated by the peristaltic pump, under certain membrane permeation flux conditions, The product is pumped to the permeate side, real-time online separation or transfer is realized, the membrane permeate is separated and purified, and the products cyclohexanol and cyclohexanone are finally obtained.

However, the disadvantages of the above methods and technologies are: 1) There is only a single membrane electrode pair, which cannot achieve high conversion rates; 2) Continuous production and operation cannot be realized; 3) The function is single, which only provides the function of electrochemical oxidation. And method.

Summary of the invention

In view of the above problems, this application proposes a multi-stage electrocatalytic membrane reactor and its application and method in organic electrochemical reactions.

One aspect of this application provides a multi-stage electrocatalytic membrane reactor, including:

The reactor body, which has a chamber for electrochemical reaction;

A pair of porous membrane electrodes of two or more stages are arranged in the chamber; the pair of porous membrane electrodes includes a porous membrane electrode and an auxiliary electrode arranged oppositely; the porous membrane electrode includes a supporting membrane and a support on the Support the catalyst on the membrane;

A feeding unit, which is arranged on one side of the reactor body and communicates with the chamber, and is used to provide reaction raw materials to the chamber;

A product collection unit, which is arranged on the other side of the reactor body and communicates with the chamber, and is used to collect products generated in the chamber; and

The power source, the positive electrode and the negative electrode of which are respectively connected to the porous membrane electrode and the auxiliary electrode, or the auxiliary electrode and the porous membrane electrode of each stage of the porous membrane electrode pair, to form an electrode pair.

Preferably, the porous membrane electrode pairs of two or more stages are arranged in a manner such that the cathode and the anode are staggered with each other, and the step spacing of adjacent porous membrane electrode pairs is 1-100 mm.

Preferably, the supporting membrane is one of a titanium membrane, a nickel membrane, and a carbon membrane, and the porous membrane electrode has an average pore diameter of 0.1-10 μm, a thickness of 1-20 mm, and a porosity of 5-40%.

Preferably, the catalyst is an electrochemical oxidation catalyst or an electrochemical reduction catalyst; the electrochemical oxidation catalyst includes CeO ₂ , MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , MoO ₃ , PbO ₂ , SnO ₂ , TiO _2. At least one of V ₂ O ₅ ; the electrochemical reduction catalyst includes at least one of Au, Pb, In, Cd, Sn, Zn, Ru, Cu, and oxides thereof.

Preferably, the auxiliary electrode is one of stainless steel or titanium metal.

Preferably, a sampling point for sampling is provided between each stage of the porous membrane electrode pair or multiple stages of the porous membrane electric stage pair.

Preferably, the multi-stage electrocatalytic membrane reactor is further provided with a temperature control device, and the temperature control device is arranged outside the feeding unit and/or the reactor body.

Preferably, the feeding unit is in communication with the lower end of the chamber, and the product collection unit is in communication with the upper end of the chamber, so that the entire system circulates in a bottom-up path.

Preferably, a pump is provided on the communication path between the feeding unit and the chamber for pumping reaction raw materials into the chamber of the reactor body.

Another aspect of this application provides an application of the multi-stage electrocatalytic membrane reactor described in any one of the above in organic electrochemical oxidation or organic electrochemical reduction reactions.

Preferably, the organic matter oxidized in the organic electrochemical oxidation reaction includes alcohols, aldehydes, alkanes, and phenols; the alcohols include methanol, ethanol, propanol, butanol, cyclohexanol, benzyl alcohol, etc. The aldehydes include one of benzaldehyde and pentahydroxymethyl furfural; the alkanes include one of pentane, hexane, cyclohexane, and octane; the phenols include phenol.

Preferably, the organic matter reduced in the organic electrochemical reduction reaction includes acid gas and organic acid; the acid gas includes CO ₂ ; the organic acid includes formic acid, acetic acid, butyric acid, benzoic acid, fatty acid, and unsaturated fatty acid Or a kind of grease.

Another aspect of the present application provides a method for performing organic electrochemical oxidation or organic electrochemical reduction in the multi-stage electrocatalytic membrane reactor according to any one of the above, and the method includes the following steps:

Configure the porous membrane electrode pair: According to the product, select the support membrane of the porous membrane electrode and the type of the catalyst supported on it, and confirm the auxiliary electrode type; the two or more porous membrane electrode pairs are cathode and anode Arranged in a staggered manner in the chamber of the reactor body;

Preparation of reaction raw materials: According to the electrochemical reaction to be carried out, the reaction raw materials are selected and placed in the feeding unit, and the corresponding electrolyte solution is placed in the chamber;

Turn on the power supply to provide a stable current to each porous membrane electrode pair;

Turn on the pump, and continuously pump the reaction raw materials from the feeding unit into the chamber of the reactor body; and

The product generated in the chamber is collected by the product collection unit.

Preferably, the reaction raw materials are pumped in through the lower end of the chamber, and sequentially pass through various levels of porous membrane electrode pairs from bottom to top to perform a multi-stage catalytic electrochemical reaction, and the product is collected by the product collection unit through the upper end of the chamber.

Preferably, the operating voltage range of the control power supply is 0.5-20V, and the control current density range is 0.5-20mA/cm ² .

Preferably, the residence time of the reaction raw materials in the chamber is controlled by a pump to be 1 to 50 minutes.

Preferably, the method further includes controlling the temperature in the feeding unit and/or the chamber to be 0-80°C through a temperature control device arranged outside the feeding unit and/or the reactor body.

Preferably, the method further includes the step of collecting samples at different positions for detection by sampling points arranged between the porous membrane electrode pairs at each stage or the porous membrane electrical stage pairs at multiple stages.

Compared with the prior art, the advantages and positive effects of this application are:

(1) The catalyst is immobilized on a supporting membrane with good conductivity to form a porous membrane electrode, which has good stability and can be used repeatedly, and the electrochemical oxidation or reduction reaction can be achieved by installing two or more porous membrane electrode pairs. High efficiency.

(2) It is safe and reliable to operate under normal temperature and pressure.

(3) Using electrons as "reagents", no strong oxidizing or strong reducing reagents are used to pollute any pollutant discharge, which is green and environmentally friendly.

(4) The reaction is mainly controlled by voltage or current density, the voltage or current density used is low, and the energy consumption is low.

(5) Continuous operation, with the advantages of high efficiency, high selectivity, simple operation, etc., suitable for industrial implementation.

Description of the drawings

Fig. 1 is a schematic diagram of the structure of a multi-stage electrocatalytic membrane reactor of this application.

The above figures: 1. Reactor body; 11. Chamber; 2. Porous membrane electrode pair; 21. Anode; 22. Cathode; 3. Feeding unit; 4. Product collection unit; 5. Power supply; 6. Sampling Point; 7. Temperature control device; 8. Pump; 9. Control valve; 10. Pressure gauge.

Detailed ways

Hereinafter, the present application will be described in detail through exemplary implementations. However, it should be understood that, without further description, the units, structures, and features in one embodiment can also be beneficially combined into other embodiments.

In the description of this application, it should be noted that the directions or positional relationships indicated by the terms "inner", "outer", "upper", "lower", "front", "rear", etc. are based on the drawings shown The positional relationship is only for the convenience of describing the application and simplifying the description, rather than indicating or implying that the device or unit referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the application. In addition, the number of stages of the porous membrane electrode pair in this application means the number of pairs of the porous membrane electrode.

On the one hand, the embodiments of the present application provide a multi-stage electrocatalytic membrane reactor, as shown in FIG. 1, including:

The reactor body 1 has a chamber 11 for electrochemical reaction;

The porous membrane electrode pair 2 of two or more stages is arranged in the chamber 11; the porous membrane electrode pair includes a porous membrane electrode and an auxiliary electrode arranged oppositely; the porous membrane electrode includes a supporting membrane and a load Catalyst on the supporting membrane;

A feeding unit 3, which is arranged on one side of the reactor body 1 and communicates with the chamber 11, and is used to provide reaction raw materials to the chamber 11;

The product collection unit 4, which is arranged on the other side of the reactor body 1 and communicates with the chamber 11, is used to collect the products generated in the chamber 11; and

The power supply 5 has its positive electrode and negative electrode respectively connected to the porous membrane electrode and the auxiliary electrode, or the auxiliary electrode and the porous membrane electrode of each stage of the porous membrane electrode pair 2 to form an electrode pair.

It should be noted that 21 in FIG. 1 is an anode connected to the positive electrode of the battery, and 22 is a cathode connected to the negative electrode of the battery. When the organic electrochemical reduction reaction is carried out, the porous membrane electrode in the porous membrane electrode pair 2 is used as the cathode 22, and the auxiliary electrode is used as the anode 21; when the organic electrochemical oxidation reaction is carried out, the porous membrane electrode in the porous membrane electrode pair 2 It is used as the anode 21, and the auxiliary electrode is used as the cathode 22.

The multi-stage electrocatalytic membrane reactor provided by the above-mentioned embodiments is provided with two or more porous membrane electrode pairs, and the catalyst is immobilized on the supporting membrane, which has good stability and can be used repeatedly, and the reactants will gradually Grade through the porous membrane electrode pair to carry out the organic electrosynthesis reaction, to achieve the high efficiency of electrochemical oxidation or reduction; use electrons as the "reagent", do not use strong oxidizing or strong reducing reagents, polluting any pollutant discharge, and environmental protection; It has the advantages of high efficiency, high selectivity, simple operation, etc., and is suitable for industrial production and application.

As a preferred embodiment, the porous membrane electrode pairs 2 of two or more stages are arranged in such a way that the cathode 22 and the anode 21 are staggered with each other, and the step distance between adjacent porous membrane electrode pairs 2 is 1-100 mm. As shown in FIG. 1, in this embodiment, the electrode pairs are arranged in the manner of anode 21, cathode 22, anode 21, cathode 22, etc., to achieve stepwise oxidation or reduction reactions. In addition, by controlling the stage spacing within the above range, on the one hand, the overall volume of the reactor can be controlled, and on the other hand, the continuity of the stepwise organic electrosynthesis reaction can be ensured; it is understandable that the adjacent porous membrane electrode pair 2 The spacing can also be 20mm, 40mm, 60mm, 80mm, etc., and those skilled in the art can select within the above range.

As a preferred embodiment, the supporting membrane is one of a titanium membrane, a nickel membrane, and a carbon membrane, and the porous membrane electrode has an average pore diameter of 0.1-10 μm, a thickness of 1-20 mm, and a porosity of 5~ 40%. In this embodiment, a material with good conductivity is selected as the supporting film to ensure the progress of the electrochemical reaction and can be used repeatedly. Controlling the average pore size, thickness and porosity of the porous membrane electrode within the above range can ensure that the reactants smoothly permeate the porous membrane electrode for electrochemical reactions, and are beneficial to the screening and adsorption of the membrane, and increase electrons. The transfer efficiency is enhanced by convection and mass transfer. It is understandable that the average pore diameter of the porous membrane electrode can also be 0.5μm, 1μm, 2μm, 5μm, 6μm, 8μm, etc., the thickness can also be 5mm, 10mm, 15mm, etc., and the porosity can also be 10%, 20%. %, 30%, etc., a person skilled in the art can choose within the above ranges according to actual needs.

As a preferred embodiment, the catalyst is an electrochemical oxidation catalyst or an electrochemical reduction catalyst; the electrochemical oxidation catalyst includes CeO ₂ , MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , MoO ₃ , PbO ₂ At least one of SnO ₂ , TiO ₂ , and V ₂ O ₅ ; the electrochemical reduction catalyst includes at least one of Au, Pb, In, Cd, Sn, Zn, Ru, Cu and their oxides . In this embodiment, high-activity electrochemical oxidation catalyst and reduction catalyst are selected, and on the basis of the prior art, the reduction function of the reactor is realized. According to actual reaction requirements, those skilled in the art can choose the above oxidation or reduction catalysts to be uniformly supported on the supporting membrane, which not only has physical adsorption, but also has strong chemical bond effect, good stability, and can improve the conversion efficiency and yield of raw materials.

As a preferred embodiment, the auxiliary electrode is one of stainless steel or titanium metal.

As a preferred embodiment, each stage of the porous membrane electrode pair 2 or multiple stages of the porous membrane electrode pair 2 is provided with a sampling point 6 for sampling, which can detect samples taken at different positions, thereby Control the reaction process, in addition to kinetic studies.

As a preferred embodiment, the multi-stage electrocatalytic membrane reactor is further provided with a temperature control device 7 which is provided outside the feed unit 3 and/or the reactor body 1. The temperature affects the conversion rate of the electrochemical reaction and the catalytic efficiency of the catalyst. In this embodiment, the temperature control device 7 is provided to better realize the control of the organic electrochemical synthesis reaction. Optionally, the temperature control device 7 may be an ordinary instrument or be controlled by PLC.

As a preferred embodiment, the feeding unit 3 communicates with the lower end of the chamber 11, and the product collection unit 4 communicates with the upper end of the chamber 11, so that the entire system is in a bottom-up manner. Path circulation. This embodiment takes fluid mechanics into consideration and is verified by experiments. The bottom-up path shown in Fig. 1 has the best effect. As a result, the reaction raw materials enter the chamber 11 from the lower end of the reactor body 1, and pass through the porous membrane electrode pair 2 from bottom to top to chemically react, and the final product enters the product collection unit 4 from the upper end of the chamber 11. However, it is understandable that in addition to the bottom-to-up path of the reaction materials in this embodiment, other circulation paths (such as left to right, right to left, front to back, back to front, top to bottom) are also feasible. of.

As a preferred embodiment, a pump 8 is provided on the communication path between the feeding unit 3 and the chamber 11 for pumping reaction raw materials into the chamber 11 of the reactor body 1. In this embodiment, by setting a pump instead of one-time feeding, continuous feeding is realized, which is beneficial to realizing continuous production.

As a preferred embodiment, a control valve 9 is provided on the communication path between the chamber and the feed unit 3 and the product collection unit 4 to control the supply of reaction raw materials and the output of products.

In addition, other suitable measuring devices, such as the pressure gauge 10 shown in FIG. 1, can be provided to measure the pressure in the reactor body 1.

Another aspect of the embodiments of the present application provides an application of the multi-stage electrocatalytic membrane reactor according to any of the above embodiments in organic electrochemical oxidation or organic electrochemical reduction reactions.

In particular, the organic matter oxidized in the organic electrochemical oxidation reaction in the above application includes alcohols, aldehydes, alkanes, and phenols; the alcohols include methanol, ethanol, propanol, butanol, cyclohexanol, and benzyl alcohol. The aldehydes include one of benzaldehyde and pentahydroxymethyl furfural; the alkanes include one of pentane, hexane, cyclohexane, and octane; the phenols include phenol.

The organic matter reduced in the organic electrochemical reduction reaction of the above application includes acid gas and organic acid; the acid gas includes CO ₂ ; the organic acid includes formic acid, acetic acid, butyric acid, benzoic acid, fatty acid, unsaturated fatty acid or A kind of grease.

Another aspect of the embodiments of the present application provides a method for performing organic electrochemical oxidation or organic electrochemical reduction in the multi-stage electrocatalytic membrane reactor according to any of the above embodiments. The method includes the following steps:

Configure the porous membrane electrode pair 2: According to the product, select the support membrane of the porous membrane electrode and the type of the catalyst supported on it, and confirm the auxiliary electrode type; as shown in Figure 1, the two or more porous The membrane electrode pair 2 is arranged in the chamber 11 of the reactor body 1 in a manner that the cathode and the anode are staggered with each other;

Preparation of reaction raw materials: According to the electrochemical reaction to be performed, the reaction raw materials are selected and placed in the feeding unit 3, and the corresponding electrolyte solution is placed in the chamber;

Turn on the power supply 5 to provide a stable current to each porous membrane electrode pair 2;

Turn on the pump 8, and continuously pump the reaction raw materials from the feeding unit 3 into the chamber 11 of the reactor body 1; and

The product generated in the chamber 11 is collected by the product collection unit 4.

As a preferred embodiment, the reaction raw materials are pumped in through the lower end of the chamber 11, and pass through the porous membrane electrode pairs 2 at various levels from bottom to top to perform a multi-stage catalytic electrochemical reaction, and the product is processed through the upper end of the chamber 11. The collection unit 4 collects.

As a preferred embodiment, the operating voltage range of the control power supply 5 is 0.5-20 V, and the control current density range is 0.5-20 mA/cm ² . The reaction is mainly controlled by voltage or current density, the voltage or current density used is low, and the energy consumption is low.

As a preferred embodiment, the method further includes controlling the temperature in the feeding unit 3 and/or the chamber 11 to be 0 through a temperature control device 7 provided outside the feeding unit 3 and/or the reactor body 1. ～80℃.

As a preferred embodiment, the residence time of the reaction raw materials in the chamber 11 is controlled by the pump 8 to be 1-50 min.

As a preferred embodiment, the method further includes collecting samples at different positions for detection by setting a sampling point 6 between each stage of the porous membrane electrode pair 2 or multiple stages of the porous membrane electric stage pair 2 A step of.

The electrochemical oxidation or reduction method provided in the above embodiments is carried out using a multi-stage electrocatalytic membrane reactor. The type, number, and distribution of porous membrane electrodes are controlled, and the voltage range, current density, and raw materials of the reaction are controlled. Residence time, temperature, etc., so as to control the conversion rate of raw materials and the yield of products, and realize the high efficiency of electrochemical oxidation or reduction. In addition, it operates under normal temperature and pressure, and does not use strong oxidants or strong reducing agents. It is highly efficient, green, simple to operate, safe and reliable, suitable for industrial implementation, and can be widely used in the organic electrosynthesis industry.

The following describes the multi-stage catalytic membrane reactor described in the present application and the method of applying it for organic electrochemical synthesis reaction in conjunction with specific embodiments.

Example 1

Electrochemical reduction of acetic acid to produce ethanol

The porous titanium film with in-situ supported Cu nano-catalyst is used as the cathode (high electrochemical reduction activity), and the auxiliary conductive titanium metal mesh is used as the anode (only as the counter electrode, forming a current path, electrochemical oxidation is small), and the cathode is used A five-stage electrocatalytic membrane reactor is assembled in a staggered manner with the anode, which has a strong electrochemical reduction effect. Stable current is provided by the DC power supply. The raw material liquid enters the chamber from the bottom of the reactor body under the action of the peristaltic pump, and gradually penetrates each pair of porous membrane electrode pairs to realize the multi-stage catalytic electrochemical reaction, and finally enters the permeate Tank (product collection unit). Under normal pressure, in the acetic acid solution, the electrolyte is 15g/L Na ₂ SO ₄ , the initial concentration of acetic acid is 20 mmol/L, the current density of the membrane reactor is 1.0 mA/cm ² , and the residence time is 10 min.

In this embodiment, the temperature is used as a variable to control the multi-stage electrocatalytic membrane reactor. It can be seen from Table 1 that the temperature increased from 15°C to 35°C, correspondingly, the conversion rate of acetic acid first increased and then decreased. Among them, when the temperature is 25°C, the conversion rate of acetic acid reaches 95.5%, and the selectivity of ethanol is greater than 99%.

Table 1 The influence of temperature on the reduction efficiency of acetic acid

Temperature(℃)	Acetic acid conversion rate (%)	Ethanol selectivity (%)
15	68.0	>99
20	76.5	>99
25	95.5	>99
30	86.5	>99
35	76.1	>99

Example 2

Electrochemical reduction of CO _{2 to} produce formic acid and CO

The porous titanium film with Au nano-catalyst supported in situ is used as the cathode (high electrochemical reduction activity), and the auxiliary conductive titanium metal mesh is used as the anode (only as the counter electrode, forming a current path, with little electrochemical oxidation), using the cathode A forty-stage electrocatalytic membrane reactor is assembled in a staggered manner with the anode, which has a strong electrochemical reduction effect. Stable current is provided by the DC power supply. The raw material liquid enters the chamber from the bottom of the reactor body under the action of the peristaltic pump, and gradually penetrates each pair of porous membrane electrode pairs to realize the multi-stage catalytic electrochemical reaction, and finally enters the permeate tank. Under normal pressure, the Na ₂ CO ₃ solution is fed with a saturated CO ₂ solution, the current density of the membrane reactor is 1.0 mA/cm ² , and the residence time is 20 min. When the temperature is 25°C, the CO ₂ conversion rate reaches 96.0%, and the selectivity between formic acid and CO is 95%, of which CO accounts for about 10%.

Example 3

Electrochemical catalytic oxidation of cyclohexanol to cyclohexanone

The porous titanium membrane with in-situ supported V ₂ O ₅ nano-catalyst is used as the anode (with high electrochemical oxidation activity), and the auxiliary conductive stainless steel mesh is used as the cathode (only as the counter electrode, forming a current path, electrochemical reduction effect is small), A ten-stage electrocatalytic membrane reactor is assembled in a staggered cathode and anode manner, which has strong electrochemical oxidation. Stable current is provided by the DC power supply. The raw material liquid enters the chamber from the bottom of the reactor body under the action of the peristaltic pump, and gradually penetrates each pair of porous membrane electrode pairs to realize the multi-stage catalytic electrochemical reaction, and finally enters the permeate tank. Under normal pressure, the initial concentration of cyclohexanol is 5mmol/L, the electrolyte is 5g/L NaOH, the residence time is 40min, and the reaction temperature is 30°C.

In this embodiment, the current density is used as a variable to control the multi-stage electrocatalytic membrane reactor. It can be seen from Table 2 that as the current density increases, the conversion efficiency first increases and then decreases. Among them, when the current density is 2.0 mA/cm ² , the conversion rate of cyclohexanol reaches 95.0%, and the selectivity of cyclohexanone is as high as 99.4%. The good performance is better than most precious metal catalysts reported in the literature.

Table 2 The effect of current density on the efficiency of cyclohexanol oxidation

Current density

Cyclohexanol conversion rate (%)

Cyclohexanone selectivity (%)

(mA cm -2 )	To	To
0.5	53.8	>99
1.0	71.4	>99
2.0	95.0	>99
2.5	85.7	>99
3.0	78.9	>99

Example 4

Electrochemical catalytic oxidation of cyclohexane to produce cyclohexanol and cyclohexanone

The porous titanium membrane with in-situ supported V ₂ O ₅ nano-catalyst is used as the anode (with high electrochemical oxidation activity), and the auxiliary conductive stainless steel mesh is used as the cathode (only as the counter electrode, forming a current path, electrochemical reduction effect is small), The multi-stage electrocatalytic membrane reactor is assembled separately by adopting the alternate method of cathode and anode. Stable current is provided by the DC power supply. The raw material liquid enters the chamber from the bottom of the reactor body under the action of the peristaltic pump, and gradually penetrates each pair of porous membrane electrode pairs to realize the multi-stage catalytic electrochemical reaction, and finally enters the permeate tank. Under normal pressure, in the cyclohexane-acetic acid-water miscible system, the initial concentration of cyclohexane is 20mmol/L, the electrolyte is 5g/L NaOH, the current density of the membrane reactor is 1.0mA/cm, the residence time is 10min, and the temperature is 30 ℃.

In this embodiment, the multi-stage reactor is controlled with the number of porous membrane electrode pairs (number of porous membrane electrode pairs) as a variable. It can be seen from Table 3 that the more stages of the porous membrane electrode pair, the higher the conversion efficiency. Among them, when the number of reactor stages is 50, the conversion rate of cyclohexane reaches 96.0%, and the total selectivity of cyclohexanol and cyclohexanone is as high as 99.9%.

Table 3 Catalytic efficiency of different reactor stages

Number of reactor stages	Cyclohexane conversion rate (%)	KA oil selectivity (%)
Level 10	34.0	>99
Level 20	53.5	>99
Level 30	65.2	>99

Level 40	80.6	>99
Level 50	96.0	>99

Cyclohexane is a bulk chemical raw material. Cyclohexanone and cyclohexanol (KA oil) are prepared by oxidation of cyclohexane, and adipic acid is further oxidized to produce nylon 66. At present, the industrially oxidizing cyclohexane to prepare KA oil mainly includes cobalt salt oxidation, boric acid oxidation, and non-catalytic oxidation. However, due to the high stability of CH bond, it is difficult to be oxidized, resulting in low conversion rate (<15% ), low selectivity (75-91%), high energy consumption, and high pollution, as shown in Table 4, are internationally recognized large-scale chemical processes with the lowest efficiency, which severely restricts the development of nylon and other related industries.

Table 4 Process of oxidizing cyclohexane in industry

Chinese invention patent CN104032327A also discloses a method for preparing cyclohexanol and cyclohexanone by electrocatalytic oxidation of alkanes, but the conversion rate of cyclohexane is only 9.37%, and the total selectivity of cyclohexanol and cyclohexanone is 94.2%.

Based on the above, it can be concluded that the conversion rate of cyclohexane in this example is much higher than the conversion rate of the existing method, and can be as high as 96.0%, which can realize the efficient conversion of cyclohexane. The total selectivity of cyclohexanol and cyclohexanone is as high as 99.9%, the reaction efficiency is obviously improved, the good performance is better than most cyclohexane oxidation processes reported in the literature, and it has a wide range of application prospects.

The above are only preferred embodiments of the application, and are not intended to limit the application in other forms. Any person familiar with the profession may use the technical content disclosed above to change or modify the equivalent to equivalent changes. The embodiments are applied to other fields, but any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the application without departing from the content of the technical solutions of the application still fall within the protection scope of the technical solutions of the application.

Claims (18)

1. A multi-stage electrocatalytic membrane reactor, characterized in that it comprises:

   The reactor body, which has a chamber for electrochemical reaction;

   A pair of porous membrane electrodes of two or more stages are arranged in the chamber; the pair of porous membrane electrodes includes a porous membrane electrode and an auxiliary electrode arranged oppositely; the porous membrane electrode includes a supporting membrane and a support on the Support the catalyst on the membrane;

   A feeding unit, which is arranged on one side of the reactor body and communicates with the chamber, and is used to provide reaction raw materials to the chamber;

   A product collection unit, which is arranged on the other side of the reactor body and communicates with the chamber, and is used to collect products generated in the chamber; and

   The power source, the positive electrode and the negative electrode of which are respectively connected to the porous membrane electrode and the auxiliary electrode, or the auxiliary electrode and the porous membrane electrode of each stage of the porous membrane electrode pair, to form an electrode pair.
2. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein the porous membrane electrode pairs of two or more stages are arranged in a manner that the cathode and anode are staggered with each other, and the adjacent porous membrane electrode pairs The step spacing is 1～100mm.
3. The multi-stage electrocatalytic membrane reactor of claim 1, wherein the supporting membrane is one of a titanium membrane, a nickel membrane, and a carbon membrane, and the average pore diameter of the porous membrane electrode is 0.1-10 μm, The thickness is 1-20mm, and the porosity is 5-40%.
4. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein the catalyst is an electrochemical oxidation catalyst or an electrochemical reduction catalyst; the electrochemical oxidation catalyst comprises CeO ₂ , MnO ₂ , Mn ₂ O ₃ , Mn ₃ O ₄ , MoO ₃ , PbO ₂ , SnO ₂ , TiO ₂ , V ₂ O ₅ at least one of; the electrochemical reduction catalyst includes Au, Pb, In, Cd, Sn, Zn, Ru, Cu At least one of elemental metal and its oxide.
5. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein the auxiliary electrode is one of stainless steel or titanium.
6. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein a sampling point for sampling is provided between the pair of porous membrane electrodes at each stage or the pair of porous membrane electric stages at each stage.
7. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein the multi-stage electrocatalytic membrane reactor is further provided with a temperature control device, and the temperature control device is provided in the feeding unit and/or The outside of the reactor body.
8. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein the feeding unit is in communication with the lower end of the chamber, and the product collection unit is in communication with the upper end of the chamber, so that the entire The system circulates in a bottom-up path.
9. The multi-stage electrocatalytic membrane reactor according to claim 1, wherein a pump is provided on the communication path between the feeding unit and the chamber for pumping into the chamber of the reactor body Reaction materials.
10. An application of the multi-stage electrocatalytic membrane reactor according to any one of claims 1-9 in organic electrochemical oxidation or organic electrochemical reduction reaction.
11. The application according to claim 10, wherein the organic matter oxidized in the organic electrochemical oxidation reaction includes alcohols, aldehydes, alkanes, and phenols; the alcohols include methanol, ethanol, propanol, butane One of alcohols, cyclohexanol, benzyl alcohol, etc.; the aldehydes include one of benzaldehyde and pentahydroxymethyl furfural; the alkanes include pentane, hexane, cyclohexane, and octane One; the phenols include phenol.
12. The application according to claim 10, wherein the organic matter reduced in the organic electrochemical reduction reaction includes acid gas and organic acid; the acid gas includes CO ₂ ; and the organic acid includes formic acid, acetic acid, butane One of acid, benzoic acid, fatty acid, unsaturated fatty acid or grease.
13. A method for organic electrochemical oxidation or organic electrochemical reduction in a multi-stage electrocatalytic membrane reactor according to any one of claims 1-9, wherein the method comprises the following steps:

    Configure the porous membrane electrode pair: According to the product, select the support membrane of the porous membrane electrode and the type of the catalyst supported on it, and confirm the auxiliary electrode type; the two or more porous membrane electrode pairs are cathode and anode Arranged in a staggered manner in the chamber of the reactor body;

    Preparation of reaction raw materials: According to the electrochemical reaction to be carried out, the reaction raw materials are selected and placed in the feeding unit, and the corresponding electrolyte solution is placed in the chamber;

    Turn on the power supply to provide a stable current to each porous membrane electrode pair;

    Turn on the pump, and continuously pump the reaction raw materials from the feeding unit into the chamber of the reactor body; and

    The product generated in the chamber is collected by the product collection unit.
14. The method according to claim 13, characterized in that the reaction raw materials are pumped in through the lower end of the chamber, pass through the porous membrane electrode pairs of various levels sequentially from bottom to top to carry out a multi-stage catalytic electrochemical reaction, and the product passes through the upper end of the chamber Collected by the product collection unit.
15. The method according to claim 13, wherein the operating voltage range of the control power supply is 0.5-20V, and the control current density range is 0.5-20mA/cm ² .
16. The method according to claim 13, characterized in that the residence time of the reaction raw materials in the chamber is controlled by a pump to be 1-50 min.
17. The method according to claim 13, characterized in that the method further comprises controlling the temperature in the feeding unit and/or the chamber to be 0 to 0 through a temperature control device provided outside the feeding unit and/or the reactor body. 80°C.
18. The method according to claim 13, characterized in that the method further comprises collecting samples at different positions by sampling points arranged between the pairs of the porous membrane electrodes at each stage or the pairs of the porous membrane electric stages at each level. Steps for testing.

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