Rotary micro-gap electrolytic cell and method for preparing aromatic diacetal by using rotary micro-gap electrolytic cell

Abstract

The rotary micro-gap electrolytic cell comprises a cell body, a rotating shaft is arranged in the cell body, and the top end of the rotating shaft extends out of the cell body and is provided with a rotating motor; the rotating shaft is sequentially and alternately sleeved with the fixed electrodes and the rotating electrodes at intervals from top to bottom; the fixed electrode is of an annular plate structure, is coaxial with the rotating shaft, is spaced from the rotating shaft and is fixedly arranged with the groove wall; the rotating electrode is of an annular plate structure, is coaxial with the rotating shaft and is fixedly arranged, and is spaced from the groove wall; and cathode and anode access points and liquid inlet and outlet pipes are arranged on the tank wall. The invention also provides a method for preparing aromatic diacetal by using the electrolytic cell, which comprises the following steps: feeding a mixture of a substituted toluene-containing substance, an organic solvent and an electrolyte into the electrolytic cell in an inert atmosphere, and electrolyzing under the rotation of the rotating electrode, so that substituted methyl on the substituted toluene-containing substance is subjected to oxidation reaction to obtain aryl diacetal. According to the electrolytic cell and the method, aromatic diacetal can be prepared through electrolysis, the feeding pressure in the preparation process is low, and the electrodes can be automatically cleaned.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrolytic synthesis of aromatic diacetals, and particularly relates to a rotary micro-gap electrolytic cell and a method for preparing aromatic diacetals by using the same. Background Art

[0002] Aromatic diacetals are the main category of acetal spices and are also widely used in daily and edible spices. For example, anisaldehyde diacetal is a floral and fruity spice stronger than anisaldehyde and is currently commercially applied in both food and daily products as a new type of spice. The aroma of phenylacetaldehyde dimethyl acetal is dry green - floral, fruity, citrus and cocoa - like flavors. While phenylacetaldehyde diisobutyl acetal has a sweet aroma, honey and glutinous rice candy - like fragrance, with a hint of floral and hyacinth - like feeling. It can be used in aromatic and fruity formulations, such as in the applications of fig, artemisia, strawberry, chocolate or tropical fragrances. On the other hand, luteolin has a delicate and strong hyacinth, narcissus and reseda aroma, accompanied by sweet pea, green bean and green - like feelings.

[0003] Currently, there are mainly two processes for industrial production of aromatic diacetals. One is to react aromatic aldehydes with diol compounds to generate aromatic diacetals and water; the other is to use an electrolytic method, using the corresponding alcohol as a solvent to electrolytically generate diacetals. Among them, the process for producing diacetals by electrolysis has been industrialized by BASF in Germany.

[0004] In US04539081, Dieter Degner et al. from BASF invented a method for preparing aromatic diacetals by electrolysis. In this method, in a methanol solution, substituted toluene and an electrolyte containing a sulfonic acid group are used for electrolytic reaction to produce aromatic diacetals. The use of a rigid graphite electrode as the electrode material is mentioned in the article, but the use of a capillary gap electrolytic cell is not mentioned, and it is speculated that the electrode spacing of 0.5 mm affects the mass transfer effect of the electrolyte, and most of the current efficiencies in the reaction are lower than 67%, resulting in a high production cost.

[0005] In EP0011712A2, Dieter Degner et al. from BASF proposed a static capillary gap electrolytic cell with 7 segmented graphite electrodes, and the electrolytic yield is only 36 - 62%, and the current efficiency is only 31 - 85%.

[0006] Although BASF has achieved the industrialization of aromatic dialdehyde using a capillary gap electrolyzer, due to the fact that the capillary gap of the electrolysis electrode and the electrode plate are basically in a static state, and the electrode gap of the capillary gap causes a large pressure drop, it is necessary to increase the feeding pressure to ensure that it flows over the electrode plate surface at an appropriate linear velocity to achieve the purpose of mass transfer. Therefore, this capillary gap electrolyzer has high requirements for the pressure at the pump outlet, resulting in a great waste of energy. At the same time, due to the relative stillness of the cathode and anode, a small amount of solid impurities deposited on the electrode surface cannot be removed in real time, resulting in the need to disassemble the electrolyzer every about six months for cleaning the pollutants on the electrode surface. Frequent disassembly and assembly will bring greater safety risks and waste of human resources, which is not conducive to cost reduction and efficiency improvement in industrial production. Currently, these technical problems cannot be solved.

[0007] Therefore, finding an electrolyzer that can reduce the feeding pressure and whose electrodes can be self-cleaned is the key to large-scale continuous production of high-quality aromatic dialdehyde, which has very important significance. Summary of the Invention

[0008] The first object of the present invention is to provide a rotary micro-gap electrolyzer, which can be used for electrolytic preparation of aromatic dialdehyde, and during its use, the feeding pressure is low and the electrodes can be self-cleaned;

[0009] The second object of the present invention is to provide a method for preparing aromatic dialdehyde by using the aforementioned rotary micro-gap electrolyzer. This method is simple and easy to operate, can use the aforementioned rotary micro-gap electrolyzer to prepare aromatic dialdehyde, and during the preparation process, the feeding pressure is low and the electrodes can be self-cleaned.

[0010] To achieve the first object of the present invention, the following technical solutions are adopted:

[0011] A rotary micro-gap electrolyzer includes a cell body, and the cell body is a cylindrical cell body with both ends sealed;

[0012] A rotating shaft is arranged along the vertical central axis of the cell body, and the top end of the rotating shaft extends out of the cell body and is equipped with a rotating motor for driving the rotating shaft to rotate;

[0013] The rotating shaft is successively and alternately sleeved with fixed electrodes and rotating electrodes from top to bottom at intervals, and there is one more fixed electrode than rotating electrode, and a micro-gap is formed between adjacent fixed electrodes and rotating electrodes;

[0014] The fixed electrode is in the structure of an annular plate, and the diameter L2 of the central circular hole thereof is larger than the diameter L1 of the rotating shaft; the fixed electrode is coaxially arranged with the rotating shaft with a gap, and its outer edge is fixedly arranged with the cell wall of the cell body;

[0015] The rotating electrode is in the structure of an annular plate, and the diameter L3 of the central circular hole thereof is equal to the diameter L1 of the rotating shaft; the rotating electrode is coaxially and fixedly arranged with the rotating shaft to rotate together with the rotating shaft, and a clearance is provided between its outer edge and the groove wall of the groove body;

[0016] An anode access point and a cathode access point are respectively arranged at corresponding different positions on the groove wall of the groove body; the anode access point is arranged corresponding to the first fixed electrode or the last fixed electrode of the rotating shaft from top to bottom; the cathode access point is arranged corresponding to the last fixed electrode or the first fixed electrode of the rotating shaft from top to bottom;

[0017] A liquid inlet pipe and a liquid outlet pipe are respectively arranged on the groove wall of the groove body, and the liquid inlet pipe and the liquid outlet pipe are arranged oppositely.

[0018] In the rotating micro-gap electrolytic cell of the present invention, preferably, the distance between adjacent fixed electrodes and the rotating electrode is 0.5 - 5 mm.

[0019] In the rotating micro-gap electrolytic cell of the present invention, preferably, the diameter of the liquid inlet pipe is 5 - 10 mm; and / or, the diameter of the liquid outlet pipe is 5 - 10 mm.

[0020] In the rotating micro-gap electrolytic cell of the present invention, preferably, there are multiple liquid inlet pipes, and they are sequentially arranged at intervals from top to bottom along the groove wall of the groove body; preferably there are 2 - 8; and / or,

[0021] There are multiple liquid outlet pipes, and they are sequentially arranged at intervals from top to bottom along the groove wall of the groove body; preferably there are 2 - 8.

[0022] In the rotating micro-gap electrolytic cell of the present invention, preferably, the material of the rotating electrode is a metal material and / or a non-metal material; the metal material includes any one or a combination of multiple of copper, nickel, silver, manganese, iron, lead, cadmium and their alloys, preferably stainless steel; the non-metal material includes a carbon material and / or a silicon material; and / or,

[0023] The material of the fixed electrode is a metal material and / or a non-metal material; the metal material includes any one or a combination of multiple of copper, nickel, silver, manganese, iron, lead, cadmium and their alloys, preferably stainless steel; the non-metal material includes a carbon material and / or a silicon material.

[0024] To achieve the second object of the present invention, the following technical solution is adopted:

[0025] A method for preparing aromatic dialdehyde using a rotary micro-gap electrolytic cell. In this method, under an inert atmosphere, a mixture of a substance containing substituted toluene, an organic solvent, and an electrolyte is fed from the inlet pipe into the rotary micro-gap electrolytic cell. Electrolysis is carried out under the rotation of the rotary electrode, causing the substituted methyl group on the substance containing substituted toluene to undergo an oxidation reaction to obtain aryl dialdehyde, which is output from the outlet pipe along with the electrolyte solution.

[0026] In the method of the present invention, preferably, in the mixture, the mixing ratio of the substance containing substituted toluene, the organic solvent, and the electrolyte is 1:(1.2 - 9):(0.0007 - 0.003) by weight.

[0027] In the method of the present invention, preferably, the electrolysis conditions include: the temperature is 10 - 40 °C; and / or, the pressure is normal pressure; and / or, the current density is 1000 - 2000 A / m 2 .

[0028] In the method of the present invention, preferably, the rotation speed of the rotating shaft is 50 - 10000 r / min; and / or, the inert gas in the inert atmosphere includes any one or a combination of nitrogen, helium, neon, argon, and krypton.

[0029] In the method of the present invention, preferably, in the substance containing substituted toluene, the substituents include any one or a combination of alkyl, alkenyl, alkynyl, halogen atom, ester group, and ether; and / or,

[0030] the organic solvent includes any one or a combination of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, dimethyl carbonate, ethyl acetate, dichloromethane, and dimethylformamide; and / or,

[0031] the electrolyte includes any one or a combination of halide salts, quaternary ammonium salts, and benzenesulfonates.

[0032] The beneficial effects of the present invention are as follows:

[0033] In the rotary micro-gap electrolytic cell of the present invention, during use, a microfilm can be formed at the gap between the adjacent rotary electrode and the fixed electrode through the rotation of the rotary electrode. And due to the real-time dynamic rotation between the anode and the cathode (i.e., between the adjacent fixed electrode and the rotary electrode), the mass transfer effect can be significantly improved, the feeding pressure can be reduced, the electrode can be kept self-cleaning, and the raw material liquid can be continuously introduced under normal pressure. Compared with the traditional static capillary gap electrolytic cell, the rotary micro-gap electrolytic cell of the present invention can not only significantly reduce the feeding pressure and the energy consumption of material transportation, but also significantly improve the electrode life, the selectivity of the electrolytic reaction for preparing aromatic dialdehyde products, and the electrolytic reaction efficiency, which is beneficial to industrialization;

[0034] The method for preparing aromatic dialdehyde by using a rotary micro-gap electrolytic cell according to the present invention can feed a mixture of a substance containing substituted toluene, an organic solvent, and an electrolyte into the rotary micro-gap electrolytic cell, perform electrolysis through the rotary micro-gap electrolytic cell, and form a microfilm at the gap between the anode and the cathode (i.e., the gap between the adjacent fixed electrode and the rotary electrode) through the rotation of the rotary electrode. The substituted methyl in the substance containing substituted toluene undergoes an oxidation reaction to generate aryl dialdehyde, and hydrogen is generated at the cathode. Due to the real-time dynamic rotation between the anode and the cathode (i.e., between the adjacent fixed electrode and the rotary electrode), the mass transfer effect can be significantly improved, the feeding pressure can be reduced, and continuous feeding can be carried out under normal pressure. Moreover, the electrode can be kept self-cleaning, which can greatly reduce the energy consumption of material transportation and extend the electrode life. Therefore, the selectivity of the electrolytic reaction for preparing aromatic dialdehyde products and the electrolytic reaction efficiency are greatly improved compared with the traditional method, which is beneficial to industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 is a longitudinal sectional structural schematic diagram of the rotary micro-gap electrolytic cell of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] The technical solutions and their effects of the present invention will be further described below in conjunction with specific embodiments / Examples and the drawings. The following embodiments / Examples are only used to illustrate the content of the present invention, and the present invention is not limited to the following embodiments or Examples. Any simple changes made to the present invention using the concept of the present invention are within the scope of the present invention claimed.

[0037] The present invention provides a rotary micro-gap electrolytic cell, as Figure 1 shown, the rotary micro-gap electrolytic cell includes a cell body 3, and the cell body 3 is a cylindrical cell body with both ends sealed;

[0038] A rotating shaft 2 is arranged along the vertical central axis of the cell body 3, and the top end of the rotating shaft 2 extends out of the cell body 3 and is provided with a rotating motor 1 for driving the rotating shaft 2 to rotate;

[0039] The rotating shaft 2 is alternately and spacedly sleeved with fixed electrodes 6 and rotary electrodes 5 from top to bottom in sequence, and the number of fixed electrodes 6 is one more than that of the rotary electrodes 5, and a micro-gap is formed between the adjacent fixed electrode 6 and the rotary electrode 5;

[0040] The fixed electrode 6 is of an annular plate structure, and the diameter L2 of the central circular hole thereof is greater than the diameter L1 of the rotating shaft 2; the fixed electrode 6 is coaxially arranged with the rotating shaft 2 with a gap therebetween, and its outer edge is fixedly arranged with the cell wall of the cell body 3;

[0041] The rotating electrode 5 is of an annular plate structure, and the diameter L3 of the central circular hole thereof is equal to the diameter L1 of the rotating shaft 2; the rotating electrode 5 is coaxially and fixedly arranged with the rotating shaft 2 to rotate together with the rotating shaft 2, and a clearance is provided between its outer edge and the groove wall of the groove body 3;

[0042] Anode access points 7 and cathode access points 9 are respectively arranged at corresponding different positions on the groove wall of the groove body 3; the anode access point 7 is arranged corresponding to the first fixed electrode 6 or the last fixed electrode 6 of the rotating shaft 2 from top to bottom; the cathode access point 9 is arranged corresponding to the last fixed electrode 6 or the first fixed electrode 6 of the rotating shaft 2 from top to bottom;

[0043] A liquid inlet pipe 8 and a liquid outlet pipe 4 are respectively arranged on the groove wall of the groove body 3, and the liquid inlet pipe 8 and the liquid outlet pipe 4 are arranged oppositely.

[0044] Those skilled in the art understand that the groove body 3 is an insulating groove body, such as a plastic groove body, so as to avoid its conductivity.

[0045] In the rotating micro-gap electrolytic cell of the present invention, during use, a microfilm can be formed at the gap between adjacent rotating electrodes and fixed electrodes through the rotation of the rotating electrode, and due to the real-time dynamic rotation between the anode and the cathode (i.e., between adjacent fixed electrodes and rotating electrodes), the mass transfer effect can be greatly improved, the feeding pressure can be reduced, the electrolysis can be kept self-cleaning, and the raw material liquid can be continuously introduced under normal pressure. Compared with the traditional static capillary gap electrolytic cell, the rotating micro-gap electrolytic cell of the present invention can not only greatly reduce the feeding pressure and the energy consumption of material transportation, but also greatly improve the electrode life, the selectivity of the electrolysis reaction for preparing aromatic dialdehyde products and the electrolysis reaction efficiency, which is beneficial to industrialization.

[0046] In one embodiment, the bottom end of the rotating shaft 2 is movably placed on the bottom surface inside the groove body 3.

[0047] In one embodiment, a ball structure is arranged at the bottom end of the rotating shaft 2, so as to reduce the friction force between it and the bottom surface inside the groove body 3 during rotation.

[0048] In one embodiment, a concave pit is correspondingly arranged at the position of the rotating shaft 2 on the bottom surface inside the groove body 3 for cooperatively placing the bottom end of the rotating shaft 2, so as to avoid the displacement of the bottom end of the rotating shaft 2 and cause damage during the rotation of the rotating shaft 2.

[0049] In one embodiment, the concave pit is an arc-shaped surface concave pit, so as to cooperate with the ball structure at the bottom end of the rotating shaft 2 to further reduce the friction force between the rotating shaft 2 and the bottom surface inside the groove body 3 during rotation.

[0050] In one embodiment, a ring-shaped insulating plate 10 is disposed around the outer edge of the fixed electrode 6. The inner edge of the ring-shaped insulating plate 10 is fixedly arranged with the outer edge of the fixed electrode 6, and the outer edge of the ring-shaped insulating plate 10 is fixedly arranged with the groove wall of the groove body 3, so as to realize the fixed arrangement of the fixed electrode 6 on the groove wall of the groove body 3.

[0051] Those skilled in the art understand that the ring-shaped insulating plate 10 can be a ring-shaped plastic plate.

[0052] In one embodiment, the distance between the adjacent fixed electrode 6 and the rotating electrode 5 is 0.5 - 5 mm, that is, the distance of the micro-gap formed between the adjacent fixed electrode 6 and the rotating electrode 5 is 0.5 - 5 mm, such as 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm and 4.5 mm.

[0053] In one embodiment, the diameter of the liquid inlet pipe 8 is 5 - 10 mm, such as 6 mm, 7 mm, 8 mm and 9 mm.

[0054] In one embodiment, the diameter of the liquid outlet pipe 4 is 5 - 10 mm, such as 6 mm, 7 mm, 8 mm and 9 mm.

[0055] In one embodiment, there are a plurality of liquid inlet pipes 8, and they are sequentially arranged at intervals from top to bottom along the groove wall of the groove body 3; preferably, there are 2 - 8, such as 3, 4, 5, 6, 7.

[0056] In one embodiment, there are a plurality of liquid outlet pipes 4, and they are sequentially arranged at intervals from top to bottom along the groove wall of the groove body 3; preferably, there are 2 - 8, such as 3, 4, 5, 6, 7.

[0057] In one embodiment, the material of the rotating electrode 5 is a metal material and / or a non-metal material; the metal material includes any one or a combination of more than one of copper, nickel, silver, manganese, iron, lead, cadmium and their alloys (such as Monel nickel-copper, nickel-cadmium alloy, nickel-iron alloy, lead-silver alloy, lead-cadmium alloy, etc.); the non-metal material includes carbon materials (such as isostatic graphite, glassy carbon, carbon felt, carbon fiber, etc.) and / or silicon materials (such as silicon carbide, silicon nitride, etc.).

[0058] In one embodiment, the material of the fixed electrode 6 is a metal material and / or a non-metal material; the metal material includes any one or a combination of more than one of copper, nickel, silver, manganese, iron, lead, cadmium and their alloys (such as Monel nickel-copper, nickel-cadmium alloy, nickel-iron alloy, lead-silver alloy, lead-cadmium alloy, etc.); the non-metal material includes carbon materials (such as isostatic graphite, glassy carbon, carbon felt, carbon fiber, etc.) and / or silicon materials (such as silicon carbide, silicon nitride, etc.).

[0059] The present invention also provides a method for preparing aromatic dialdehyde acetals by using a rotary micro-gap electrolytic cell. As Figure 1 shown, in an inert atmosphere, a mixture of a substance containing substituted toluene, an organic solvent, and an electrolyte is fed from the feed pipe 8 into the aforementioned rotary micro-gap electrolytic cell, and electrolysis is carried out under the rotation of the rotary electrode 5, so that the substituted methyl group on the substance containing substituted toluene undergoes an oxidation reaction to obtain aryl dialdehyde acetals, and the electrolytic solution is output from the outlet pipe 4.

[0060] Those skilled in the art understand that during electrolysis, the rotary micro-gap electrolytic cell needs to be connected to direct current. In the present invention, the connection of direct current is achieved by connecting the anode connection point 7 and the cathode connection point 9 to the positive and negative electrodes of a direct current electrolysis device respectively.

[0061] Those skilled in the art understand that during electrolysis, the rotation of the rotary motor 1 is turned on to drive the rotation of the rotary shaft 2, and then drive the rotation of the rotary electrode 5.

[0062] In the method for preparing aromatic dialdehyde acetals by using a rotary micro-gap electrolytic cell of the present invention, a mixture of a substance containing substituted toluene, an organic solvent, and an electrolyte can be fed into the rotary micro-gap electrolytic cell, electrolysis is carried out by the rotary micro-gap electrolytic cell, and a microfilm is formed at the anode-cathode gap (i.e., the gap between adjacent fixed electrodes and the rotary electrode) through the rotation of the rotary electrode. The substituted methyl group in the substance containing substituted toluene undergoes an oxidation reaction to generate aryl dialdehyde acetals, and hydrogen is generated at the cathode. Due to the real-time dynamic rotation between the anode and the cathode (i.e., between adjacent fixed electrodes and the rotary electrode), the mass transfer effect can be greatly improved, the feeding pressure can be reduced so that continuous feeding can be carried out under normal pressure, and the electrode can be kept self-cleaning, which can greatly reduce the energy consumption of material transportation and improve the electrode life. Therefore, the selectivity of the electrolytic reaction for preparing aromatic dialdehyde acetal products and the electrolytic reaction efficiency are greatly improved compared with the traditional method, which is beneficial to industrialization.

[0063] In the traditional method for preparing by using a gap electrolytic cell, since the electrodes are all fixed and the gap between the electrodes is very small, a large pressure needs to be applied to feed the raw material liquid, resulting in high energy consumption.

[0064] The method of the present invention is carried out by using the aforementioned rotary micro-gap electrolytic cell. In the aforementioned rotary micro-gap electrolytic cell, due to the rotation of the rotating electrode, a micro-gap is formed between the adjacent fixed electrode and the rotating electrode. The raw material liquid forms a micro-film in this micro-gap, which improves the conductivity of the raw material liquid. Moreover, since the two electrodes are very close to each other, a double-layer superposition will also be formed, further improving the conductivity of the raw material liquid, thereby reducing the power consumption. It not only saves electricity, but also due to the rotation of the rotating electrode, the flow of materials is caused, and the raw material liquid can be fed under normal pressure, reducing the feeding pressure. The reduction of the feeding pressure avoids the occurrence of excessive electrolysis and reduces side reactions, resulting in a high selectivity for the electrolytic production of aryl diacetal products. In one embodiment, during feeding, to overcome the pressure caused by the liquid level in the electrolytic cell, the feeding is at a slightly positive pressure, and this pressure is not greater than 15 kPa (gauge pressure).

[0065] In the traditional method, since organic solvents are non-conductive, a large amount of electrolytes need to be added to meet the conductivity requirements of the raw material liquid.

[0066] However, the method of the present invention is carried out by using the aforementioned rotary micro-gap electrolytic cell. In the aforementioned rotary micro-gap electrolytic cell, due to the rotation of the rotating electrode, a micro-gap is formed between the adjacent fixed electrode and the rotating electrode. The raw material liquid forms a micro-film in this micro-gap, which improves the conductivity of the raw material liquid. Moreover, since the two electrodes are very close to each other, a double-layer superposition will also be formed, further improving the conductivity of the raw material liquid. Therefore, only a very small amount of electrolyte needs to be added to achieve good conductivity, reducing the amount of electrolyte used and the preparation cost. In one embodiment, in the mixture, the mixing ratio of the substance containing substituted toluene, the organic solvent, and the electrolyte is 1:(1.2 - 9):(0.0007 - 0.003) by weight, for example, 1:(1.2, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5, 7, 7.5, 8, 8.5, or 9):(0.0007, 0.001, 0.0015, 0.002, 0.0025, or 0.003).

[0067] In one embodiment, the electrolysis conditions include:

[0068] The temperature is 10 - 40 °C, such as 15 °C, 20 °C, 25 °C, 30 °C, and 35 °C; and / or,

[0069] The pressure is normal pressure; and / or,

[0070] The current density is 1000 - 2000 A / m 2 , such as 1100 A / m 2 , 1200 A / m 2 , 1300 A / m 2 , 1400 A / m 2 , 1500 A / m2 、1600 A / m 2 、1700 A / m 2 、1800 A / m 2 and 1900 A / m 2 。

[0071] Those skilled in the art understand that low rotational speed is not conducive to the escape of hydrogen and will increase the electrolysis power consumption. In one embodiment, the rotational speed of the rotating shaft 2 is 50 - 10000 r / min, such as 100 r / min, 500 r / min, 1000 r / min, 2000 r / min, 3000 r / min, 4000 r / min, 5000 r / min, 6000 r / min, 7000 r / min, 8000 r / min, 9000 r / min.

[0072] In one embodiment, the inert gas of the inert atmosphere includes any one or a combination of more than one of nitrogen, helium, neon, argon, and krypton.

[0073] In one embodiment, in the substance containing substituted toluene, the substituents include alkyl groups (such as p - isopropyltoluene, p - tert - butyltoluene, etc.), alkenyl groups (such as p - vinyltoluene, m - vinyltoluene, 4-(1 - methylpropenyl)toluene, etc.), alkynyl groups (such as p - ethynyltoluene, o - ethynyltoluene, etc.), halogen atoms (such as p - chlorotoluene, p - fluorotoluene, m - bromotoluene, etc.), ester groups (such as p - acetoxytoluene, etc.), and ethers (such as p - methoxytoluene, etc.), and any one or a combination of more than one of them.

[0074] In one embodiment, the organic solvent includes any one or a combination of more than one of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, dimethyl carbonate, ethyl acetate, dichloromethane, and dimethylformamide.

[0075] In one embodiment, the electrolyte includes any one or a combination of more than one of halogen salts, quaternary ammonium salts, and benzenesulfonates; preferably, the halogen salts include any one or a combination of more than one of sodium bromide, ammonium fluoride, and potassium chloride; preferably, the quaternary ammonium salts include any one or a combination of more than one of tetrabutylammonium tetrafluoroborate, tetraethylammonium hexafluorophosphate, and tetrabutylammonium perchlorate; preferably, the benzenesulfonates include sodium dodecylsulfonate and / or sodium p - toluenesulfonate.

[0076] The rotary micro - gap electrolytic cell of the present invention and the method for preparing aromatic diacetal using the same can be used for electrolytic preparation of aromatic diacetal, with low feed pressure, the electrodes can self - clean, which can ensure the continuity of the preparation, and can reduce the power consumption, improve the selectivity of the aromatic diacetal product in the electrolytic reaction and the electrolytic reaction efficiency, and contribute to the realization of industrialization.

[0077] The present application will be further illustrated by specific examples and comparative examples below.

[0078] The sources of the raw materials used in the following examples and comparative examples are as follows:

[0079] All the raw materials used are conventional raw materials in the art, and the purity specifications used are analytical pure or chemically pure. If not otherwise specified, they are all obtained from ordinary commercial sources;

[0080] Substituted toluene-containing substance 1, p-methoxytoluene, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0081] Substituted toluene-containing substance 2, p-isopropyltoluene, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0082] Substituted toluene-containing substance 3, p-chlorotoluene, was purchased from Aladdin Reagent, with a purity > 99 wt%, AR;

[0083] Substituted toluene-containing substance 4, p-tert-butyltoluene, was purchased from Aladdin Reagent, with a purity > 99 wt%, AR;

[0084] Organic solvent 1, absolute ethanol, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0085] Organic solvent 2, tetrahydrofuran, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0086] Organic solvent 3, ethyl acetate, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0087] Organic solvent 4, dichloromethane, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0088] Electrolyte 1, sodium dodecyl sulfate, was purchased from Aladdin Reagent, with a purity > 98 wt%, AR;

[0089] Electrolyte 2, tetrabutylammonium tetrafluoroborate, was purchased from Aladdin Reagent, with a purity > 98 wt%;

[0090] Electrolyte 3, potassium chloride, was purchased from Aladdin Reagent, with a purity > 98 wt%;

[0091] Electrode material 1, copper, was purchased from the High-Purity Metal Research Institute, with a purity > 99 wt%;

[0092] Electrode material 2, Monel 400 copper-nickel alloy, was purchased from the High-Purity Metal Research Institute, with a total metal element purity > 99 wt%;

[0093] Electrode material 3, isostatic graphite, was purchased from Fangda Carbon, with a purity > 99.5 wt%.

[0094] The test methods used in the following examples and comparative examples are as follows:

[0095] Content of aryl dialdehyde in the electrolyte output from the liquid outlet pipe 4: Determined by the external standard curve method of gas chromatography; among them, the gas chromatography instrument model is Shimadzu GC2010, the injector is an automatic injector; the detector is an FID detector, the chromatographic column is a DB-5 chromatographic column, the injection volume is 2 μL, and the quantitative method uses the external standard curve method;

[0096] Selectivity of aryl dialdehyde: According to selectivity = m 实际产量 / m 理论产量 The selectivity of aryl dialdehyde is calculated;

[0097] Electrolysis efficiency: According to the electrolysis time t and Faraday's second law n 理论 zF = It (where n 理论 is the theoretical molar amount of the product, z is the number of transferred electrons, F is the Faraday constant, I is the electrolysis current, and t is the electrolysis time), calculate the theoretical molar amount n of aryl dialdehyde 理论 , according to n 实际 = m 实际产量 / M 分子量 Calculate the actual molar amount n of aryl dialdehyde 实际 , and then according to η = n 实际 / n 理论 Calculate the electrolysis efficiency η of aryl dialdehyde;

[0098] Energy consumption: Measure the electrolysis voltage V, and calculate the energy consumption W according to W = kV / η (k is the theoretical power consumption for generating the product, in the unit of kAh·t -1 ; V is the electrolysis voltage, which is also the cell voltage; η is the electrolysis efficiency, which is also the current efficiency);

[0099] Electrode manual cleaning cycle: By monitoring the change of the electrolytic cell voltage, when the voltage rises to 120% or more of the original voltage, the electrode needs to be manually cleaned.

[0100] Device Example 1 (Device S1)

[0101] A rotary micro-gap electrolytic cell A1 as Figure 1 shown, including a cell body 3, and the cell body 3 is a cylindrical cell body with both ends sealed;

[0102] A rotating shaft 2 is arranged along the vertical central axis of the cell body 3, and the top end of the rotating shaft 2 extends out of the cell body 3 and is equipped with a rotating motor 1 for driving the rotating shaft 2 to rotate;

[0103] The rotating shaft 2 is successively and alternately sleeved with fixed electrodes 6 and rotating electrodes 5 from top to bottom at intervals, and there is one more fixed electrode 6 than the rotating electrode 5. A micro-gap is formed between adjacent fixed electrodes 6 and rotating electrodes 5.

[0104] The fixed electrode 6 is of an annular plate structure, and the diameter L2 of the central circular hole thereof is larger than the diameter L1 of the rotating shaft 2; the fixed electrode 6 is coaxially arranged with the rotating shaft 2 with a gap therebetween, and its outer edge is fixedly arranged on the groove wall of the groove body 3.

[0105] The rotating electrode 5 is of an annular plate structure, and the diameter L3 of the central circular hole thereof is equal to the diameter L1 of the rotating shaft 2; the rotating electrode 5 is coaxially arranged and fixedly arranged with the rotating shaft 2 to rotate together with the rotating shaft 2, and its outer edge is arranged with a gap from the groove wall of the groove body 3.

[0106] An anode access point 7 and a cathode access point 9 are respectively arranged on the groove wall of the groove body 3.

[0107] The anode access point 7 is arranged corresponding to the first fixed electrode 6 from top to bottom of the rotating shaft 2; the cathode access point 9 is arranged corresponding to the last fixed electrode 6 from top to bottom of the rotating shaft 2.

[0108] A liquid inlet pipe 8 and a liquid outlet pipe 4 are also respectively arranged on the groove wall of the groove body 3, and the liquid inlet pipe 8 and the liquid outlet pipe 4 are oppositely arranged.

[0109] Wherein, the distance between adjacent fixed electrodes 6 and rotating electrodes 5 is 2.5 mm.

[0110] There are 5 fixed electrodes 6 and 4 rotating electrodes 5.

[0111] There are 4 liquid inlet pipes 8, which are successively arranged at intervals from top to bottom along the groove wall of the groove body 3; the diameter of the liquid inlet pipe 8 is 7.5 mm.

[0112] There are 4 liquid outlet pipes 4, which are successively arranged at intervals from top to bottom along the groove wall of the groove body 3; the diameter of the liquid outlet pipe 4 is 7.5 mm.

[0113] The materials of the rotating electrode 5 and the fixed electrode 6 are both isostatic graphite.

[0114] Device Embodiment 2 (Device S2)

[0115] A rotary micro-gap electrolytic cell A2, which is different from the rotary micro-gap electrolytic cell A1 in Device Embodiment 1 in that:

[0116] The distance between adjacent fixed electrodes 6 and rotating electrodes 5 is 0.5 mm.

[0117] The diameter of the liquid inlet pipe 8 is 5 mm;

[0118] The diameter of the liquid outlet pipe 4 is 5 mm;

[0119] The materials of the rotating electrode 5 and the fixed electrode 6 are both copper.

[0120] Device Embodiment 3 (Device S3)

[0121] A rotary micro-gap electrolytic cell A3, which is different from the rotary micro-gap electrolytic cell A1 in Device Embodiment 1 in that:

[0122] The distance between adjacent fixed electrodes 6 and rotating electrodes 5 is 5 mm;

[0123] The diameter of the liquid inlet pipe 8 is 10 mm;

[0124] The diameter of the liquid outlet pipe 4 is 10 mm;

[0125] The materials of the rotating electrode 5 and the fixed electrode 6 are both Monel 400.

[0126] Device Embodiment 4 (S4)

[0127] A rotary micro-gap electrolytic cell A4, which is different from the rotary micro-gap electrolytic cell A1 in Device Embodiment 1 in that:

[0128] A ball structure is provided at the bottom end of the rotating shaft 2.

[0129] Method Embodiment 1 (Method S1)

[0130] A method for preparing aromatic dialdehyde acetals using a rotary micro-gap electrolytic cell, the method comprising:

[0131] Under an inert atmosphere, a mixture of a substance containing substituted toluene, an organic solvent, and an electrolyte is fed from the liquid inlet pipe 8 into the rotary micro-gap electrolytic cell, and electrolysis is carried out under the rotation of the rotating electrode 5 to cause an oxidation reaction of the substituted methyl group on the substance containing substituted toluene to obtain aryl dialdehyde acetals, which are output from the liquid outlet pipe 4 along with the electrolyte; wherein,

[0132] The rotary micro-gap electrolytic cell used is the rotary micro-gap electrolytic cell A1 obtained in Device Embodiment 1;

[0133] The substance containing substituted toluene is p-methoxytoluene, and the dosage is 20 g;

[0134] The organic solvent is ethanol, and the dosage is 100 g;

[0135] The electrolyte is sodium dodecyl sulfate, and the dosage is 0.02 g;

[0136] The electrolysis conditions include: temperature is 25 °C; pressure is atmospheric pressure; current density is 1500 A / m 2 ;

[0137] The rotation speed of the rotating shaft 2 is 5000 r / min;

[0138] The inert gas is nitrogen.

[0139] Method Example 2 (Method S2)

[0140] Prepare the aromatic dialdehyde according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0141] The substance containing substituted toluene is p-methoxytoluene, and the dosage is 20 g;

[0142] The organic solvent is ethanol, and the dosage is 180 g;

[0143] The electrolyte is sodium dodecyl sulfate, and the dosage is 0.014 g.

[0144] Method Example 3 (Method S3)

[0145] Prepare the aromatic dialdehyde according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0146] The substance containing substituted toluene is p-methoxytoluene, and the dosage is 20 g;

[0147] The organic solvent is ethanol, and the dosage is 24 g;

[0148] The electrolyte is sodium dodecyl sulfate, and the dosage is 0.06 g.

[0149] Method Example 4 (Method S4)

[0150] Prepare the aromatic dialdehyde according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0151] The electrolysis conditions include: temperature is 10 °C; pressure is atmospheric pressure; current density is 1000 A / m 2 .

[0152] Method Example 5 (Method S5)

[0153] Prepare the aromatic dialdehyde according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0154] The electrolysis conditions include: temperature is 40 °C; pressure is atmospheric pressure; current density is 2000 A / m 2 .

[0155] Method Example 6 (Method S6)

[0156] The aromatic dialdehyde is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0157] The rotation speed of the rotating shaft 2 is 50 r / min;

[0158] The inert gas is neon.

[0159] Method Example 7 (Method S7)

[0160] The aromatic dialdehyde is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0161] The rotation speed of the rotating shaft 2 is 10,000 r / min;

[0162] The inert gas is argon.

[0163] Method Example 8 (Method S8)

[0164] The aromatic dialdehyde is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0165] The substance containing substituted toluene is p-isopropyltoluene, and the amount used is 20 g;

[0166] The organic solvent is tetrahydrofuran, and the amount used is 100 g;

[0167] The electrolyte is tetrabutylammonium tetrafluoroborate, and the amount used is 0.02 g.

[0168] Method Example 9 (Method S9)

[0169] The aromatic dialdehyde is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0170] The substance containing substituted toluene is p-chlorotoluene, and the amount used is 20 g;

[0171] The organic solvent is ethyl acetate, and the amount used is 100 g;

[0172] The electrolyte is sodium dodecylsulfonate, and the amount used is 0.02 g.

[0173] Method Example 10 (Method S10)

[0174] The aromatic dialdehyde is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0175] The substance containing substituted toluene is p-tert-butyltoluene, and the amount used is 20 g;

[0176] The organic solvent is dichloromethane, and the amount used is 100 g;

[0177] The electrolyte is potassium chloride and the dosage is 0.02 g.

[0178] Method Example 11 (Method S11)

[0179] The aromatic dialdehyde acetal is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0180] The rotary micro-gap electrolytic cell used is the rotary micro-gap electrolytic cell A2 obtained in Device Example 2.

[0181] Method Example 12 (Method S12)

[0182] The aromatic dialdehyde acetal is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0183] The rotary micro-gap electrolytic cell used is the rotary micro-gap electrolytic cell A3 obtained in Device Example 3.

[0184] Method Example 13 (Method S13)

[0185] The aromatic dialdehyde acetal is prepared according to the method of Method Example 1. Compared with Method Example 1, there are only the following differences:

[0186] The rotary micro-gap electrolytic cell used is the rotary micro-gap electrolytic cell A4 obtained in Device Example 4.

[0187] Results:

[0188] The electrolyte output from the liquid outlet pipe 4 in Method Examples 1-13 (Methods S1-13) is sampled and analyzed, and the analysis results are shown in Table 1;

[0189] The calculation results of the electrolysis efficiency and energy consumption in Method Examples 1-13 (Methods S1-13) are shown in Table 2;

[0190] The measurement results of the manual cleaning cycle of the electrode and the inspection and maintenance cycle of the rotating shaft in Method Examples 1-13 (Methods S1-13) are shown in Table 3.

[0191] Table 1 Sampling analysis results of the electrolyte output from the liquid outlet pipe 4

[0192]

[0193] Table 2 Calculation results of the electrolysis efficiency and energy consumption

[0194]

[0195] Table 3 Measurement results of the manual cleaning cycle of the electrode and the maintenance cycle of the rotating shaft

[0196]

[0197]

[0198] As can be seen from Table 1-3, in the method for preparing aromatic diacetal by using the rotary micro-gap electrolytic cell of the present invention, in the electrolytic solution obtained after electrolysis, the content of aryl diacetal is as high as 25.8 wt%, the selectivity of aryl diacetal is as high as 92%, the electrolysis efficiency is as high as 91%, the energy consumption is as low as 2610 kWh / t, the manual cleaning period of the electrode is as long as 60 months, the electrode can effectively clean itself, and the maintenance period of the rotating shaft is as long as 60 months, so that the long-term stable operation of the rotary micro-gap electrolytic cell can be maintained.

Claims

1. A rotary micro-gap electrolytic cell, characterized in that, It includes a trough body (3), and the trough body (3) is a cylindrical trough body with both ends sealed; A rotating shaft (2) is arranged along the vertical central axis of the trough body (3). The top end of the rotating shaft (2) extends out of the trough body (3) and is equipped with a rotating motor (1) for driving the rotation of the rotating shaft (2); The rotating shaft (2) is successively and alternately sleeved with fixed electrodes (6) and rotating electrodes (5) at intervals from top to bottom, and there is one more fixed electrode (6) than the rotating electrode (5). A micro-gap is formed between adjacent fixed electrodes (6) and rotating electrodes (5); The fixed electrode (6) is of an annular plate structure, and the diameter L2 of the central circular hole thereof is larger than the diameter L1 of the rotating shaft (2); the fixed electrode (6) is coaxially arranged with the rotating shaft (2) with a gap, and its outer edge is fixedly arranged on the trough wall of the trough body (3); The rotating electrode (5) is of an annular plate structure, and the diameter L3 of the central circular hole thereof is equal to the diameter L1 of the rotating shaft (2); the rotating electrode (5) is coaxially arranged with the rotating shaft (2) and fixedly arranged to rotate together with the rotating shaft (2), and its outer edge is arranged with a gap from the trough wall of the trough body (3); An anode access point (7) and a cathode access point (9) are respectively arranged at different positions on the trough wall of the trough body (3); the anode access point (7) is arranged corresponding to the first fixed electrode (6) or the last fixed electrode (6) of the rotating shaft (2) from top to bottom; the cathode access point (9) is arranged corresponding to the last fixed electrode (6) or the first fixed electrode (6) of the rotating shaft (2) from top to bottom; A liquid inlet pipe (8) and a liquid outlet pipe (4) are respectively arranged on the trough wall of the trough body (3), and the liquid inlet pipe (8) and the liquid outlet pipe (4) are arranged oppositely.

2. The rotary micro-gap electrolytic cell according to claim 1, characterized in that, The distance between adjacent fixed electrodes (6) and rotating electrodes (5) is 0.5 - 5 mm.

3. The rotary micro-gap electrolytic cell according to claim 1 or 2, characterized in that the diameter of the liquid inlet pipe (8) is 5 - 10 mm; and / or, the diameter of the liquid outlet pipe (4) is 5 - 10 mm.

4. The rotary micro-gap electrolytic cell according to any one of claims 1 - 3, characterized in that there are multiple liquid inlet pipes (8), and they are successively arranged at intervals from top to bottom along the trough wall of the trough body (3); preferably there are 2 - 8; and / or, there are multiple liquid outlet pipes (4), and they are successively arranged at intervals from top to bottom along the trough wall of the trough body (3); preferably there are 2 - 8.

5. The rotary micro-gap electrolytic cell according to any one of claims 1 - 4, characterized in that the material of the rotating electrode (5) is a metal material and / or a non-metal material; the metal material includes any one or a combination of multiple of copper, nickel, silver, manganese, iron, lead, cadmium and their alloys; the non-metal material includes a carbon material and / or a silicon material; and / or, the material of the fixed electrode (6) is a metal material and / or a non-metal material; the metal material includes any one or a combination of multiple of copper, nickel, silver, manganese, iron, lead, cadmium and their alloys; the non-metal material includes a carbon material and / or a silicon material.

6. A method for preparing aromatic diacetals using the rotary micro-gap electrolytic cell according to any one of claims 1-5, characterized in that, The method is to feed a mixture of a substance containing substituted toluene, an organic solvent and an electrolyte from the feed pipe (8) into the rotary micro-gap electrolytic cell, and perform electrolysis under the rotation of the rotary electrode (5) to oxidize the substituted methyl group on the substance containing substituted toluene to obtain aryl dialdehyde acetals, which are output from the liquid outlet pipe (4) along with the electrolyte solution.

7. The method according to claim 6, characterized in that In the mixture, the mixing ratio of the substance containing substituted toluene, the organic solvent and the electrolyte is 1:(1.2 - 9):(0.0007 - 0.003) by weight.

8. The method according to claim 6 or 7, characterized in that The electrolysis conditions include: the temperature is 10 - 40 °C; and / or, the pressure is atmospheric pressure; and / or, the current density is 1000 - 2000 A / m 2 .

9. The method according to any one of claims 6 - 8, characterized in that the rotation speed of the rotating shaft (2) is 50 - 10000 r / min; and / or the inert gas of the inert atmosphere includes any one or a combination of more than one of nitrogen, helium, neon, argon and krypton.

10. The method according to any one of claims 6 - 9, characterized in that in the substance containing substituted toluene, the substituent includes any one or a combination of more than one of alkyl, alkenyl, alkynyl, halogen atom, ester group and ether; and / or the organic solvent includes any one or a combination of more than one of methanol, ethanol, isopropanol, tetrahydrofuran, dioxane, dimethyl carbonate, ethyl acetate, dichloromethane and dimethylformamide; and / or the electrolyte includes any one or a combination of more than one of halide salts, quaternary ammonium salts and benzenesulfonates; preferably, the halide salts include any one or a combination of more than one of sodium bromide, ammonium fluoride and potassium chloride.

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