Device for preparing stannous octoate through electrolytic method and preparation method of stannous octoate

Abstract

The invention provides a device for preparing stannous octoate through an electrolytic method and a preparation method of the stannous octoate, and belongs to the technical field of stannous octoate preparation. The device comprises an electrolytic bath, a cathode electrolysis region and an anode electrolysis region which are respectively arranged on two sides of the electrolytic bath, and a bucket-shaped collector arranged below the middle position of the bottom of the electrolytic bath, the cathode electrolysis area is composed of four layers of cathode DSA electrodes and three layers of cathode PVC partition plates which are sequentially arranged close to the wall side of the electrolytic bath and are connected in parallel to connect a circuit; the anode electrolysis region consists of three layers of anode DSA electrodes, one layer of tin anode plate and one layer of anode PVC partition plate which are sequentially arranged close to the wall side of the electrolytic bath and are connected in parallel to connect a circuit; a liquid level sensor is arranged at the upper part of the bucket-shaped collector, a pneumatic ball valve is arranged at the bottom of the bucket-shaped collector, a double-channel peristaltic pump is arranged on the side wall of the bucket-shaped collector, and two pump pipes are respectively led to the cathode electrolysis area and the anode electrolysis area. According to the method, anode passivation is not prone to occurring, little sponge tin is generated on the cathode, and high-quality and low-loss stannous octoate production can be achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of organic metal electrochemical synthesis, in particular to a stannous octoate continuous electrolysis preparation device and method based on electrode function separation and multi-stage reaction flow channel design, which solves the industrialization problems of anode passivation, cathode tin deposition and low reaction efficiency caused by high viscosity products. BACKGROUND

[0002] Stannous octoate (Sn(C7H 15 As an important and efficient catalyst in the polyurethane industry, stannous octoate mainly plays a role in accelerating the urethane reaction (gel reaction) between isocyanate (-NCO) and polyol (-OH) and the foaming reaction (urea reaction) between isocyanate and water, thereby achieving a precise balance of foam expansion and crosslinking. With its unique catalytic selectivity, stannous octoate has been widely used in soft polyurethane foam (such as furniture, car seats, etc.), rigid thermal insulation materials (such as building insulation layers), and room temperature vulcanized silicone rubber, etc., and the global demand is growing. As an environmentally friendly organotin compound, stannous octoate has lower volatility (flash point > 160℃) and thermal stability (suitable temperature range is -20℃ to 150℃) than traditional amine catalysts.

[0003] There are mainly two technical routes for industrial production of stannous octoate: 1. Saponification synthesis method, that is, isooctanoic acid reacts with sodium hydroxide to form sodium octoate, which then undergoes a double decomposition reaction with stannous chloride to produce the target product. This method has wide raw material adaptability, but due to the reaction in a strong alkaline environment, there are many side reactions (yield is less than 85%), and high-salinity wastewater (sodium chloride concentration is greater than 10%, treatment cost accounts for 30% of production cost) is generated, as disclosed in Chinese patent CN108947808A. 2. Electrochemical method, which uses tin as the anode and stainless steel as the cathode in an electrolyte containing isooctanoic acid to generate the product through electrolysis, as disclosed in Chinese patent CN110938833A. This method avoids the introduction of chloride ions and has the characteristics of simple operation, but has the problems of cathode deposition of sponge tin (tin direct yield is only 89%) and anode passivation, and high direct current consumption. SUMMARY

[0004] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a device for preparing stannous octoate by electrolysis which is not prone to anode passivation and has less sponge tin produced at the cathode, thereby achieving high-quality and low-loss production of stannous octoate.

[0005] The technical solutions adopted by the present application are as follows: The device for preparing stannous octoate by electrolysis method comprises a rectangular electrolytic tank (1), a cathode electrolysis area and an anode electrolysis area arranged at two sides of the electrolytic tank respectively, and a hopper-shaped collector (2) arranged below the middle position of the bottom of the electrolytic tank; the cathode electrolysis area is composed of 4 layers of cathode DSA electrodes (3) arranged in sequence and connected in parallel on the side close to the tank wall of the electrolytic tank, 3 layers of cathode PVC separators (4) arranged behind the last layer of cathode DSA electrodes in sequence, and the 4 layers of cathode DSA electrodes and the 3 layers of cathode PVC separators are arranged at intervals to form 7-stage cathode series reaction pools (5); the anode electrolysis area is composed of 3 layers of anode DSA electrodes (6) arranged in sequence and connected in parallel on the side close to the tank wall of the electrolytic tank, 1 layer of tin anode plate (7) arranged behind the last layer of anode DSA electrodes, and 1 layer of anode PVC separator (8) arranged behind the tin anode plate, and the 3 layers of anode DSA electrodes, the 1 layer of tin anode plate and the 1 layer of anode PVC separator are arranged at intervals to form 5-stage anode series reaction pools (9); a liquid level sensor (10) is arranged at the upper part of the hopper-shaped collector (2), a pneumatic ball valve (11) linked with the liquid level sensor (10) is arranged at the bottom, a double-channel peristaltic pump (12) is arranged at the side wall of the hopper-shaped collector, and two pump pipes are connected to the cathode electrolysis area and the anode electrolysis area respectively.

[0006] Further, the 4 layers of cathode DSA electrodes of the cathode electrolysis area are arranged alternately and staggered.

[0007] The method for preparing stannous octoate by electrolysis method adopts the device, and potassium nitrate electrolyte is introduced into the electrolytic tank (1), the double-channel peristaltic pump is started, the electrolyte is pumped to the anode electrolysis area and the cathode electrolysis area in circulation, then octanoic acid is injected into the cathode electrolysis area from the top of the electrolytic tank for electrolysis, stannous octoate precipitate is gradually produced and falls into the hopper-shaped collector, when the liquid level sensor (10) detects that the thickness of the precipitate layer reaches the set thickness, the pneumatic ball valve (11) is automatically opened to discharge the precipitate, the precipitate is collected and washed, then vacuum drying is carried out to obtain the stannous octoate product.

[0008] Further, the concentration of the potassium nitrate electrolyte is 0.01M.

[0009] Further, the current density of electrolysis is 70-100 A / m², the double-channel peristaltic pump pumps the electrolyte to the anode electrolysis area and the cathode electrolysis area in circulation at a flow rate of 0.2 L / min, and the addition rate of octanoic acid is 0.5 L / h.

[0010] Compared with the prior art, the device has the following beneficial effects: 1. The core process problem is solved, and the product quality and yield are improved.

[0011] 1) Effectively prevent anode passivation, ensure continuous and stable reaction. The electrolysis device of the present application adopts a composite design of "3 layers of DSA electrode + 1 layer of tin anode" in the anode electrolysis area. When the DSA electrode is powered on, H⁺ is generated by electrolyzing water to form a local acidic environment. The acidic environment inhibits the hydrolysis of octanoic acid (C7H 15 COOH), thereby greatly reducing the possibility of directly generating stannous octoate and adsorbing on the surface of the tin anode in the anode area. This fundamentally solves the problem of anode passivation caused by product adhesion, ensures the continuous and stable dissolution of the tin anode to generate Sn²⁺, and improves the continuity and stability of the reaction.

[0012] 2) Significantly reduce the cathode deposition of sponge tin, improve the direct yield of tin. In the cathode electrolysis area, 4 layers of DSA electrode electrolyze water to generate OH⁻, forming an alkaline environment. On the one hand, OH⁻ rapidly reacts with the incoming octanoic acid to generate octanoate ions; on the other hand, Sn²⁺ in the alkaline environment will coordinate with OH⁻. Sn²⁺-OH⁻ coordination increases the overpotential of tin ion deposition on the cathode, i.e. increases the difficulty of tin metal deposition, thereby effectively inhibiting the deposition of metal tin (sponge tin) on the cathode. This not only reduces the waste of raw material tin, but also avoids the interference of sponge tin on the electrode and the reaction, greatly improving the direct yield of tin and the purity of the product.

[0013] 3) Promote complete reaction, improve reaction efficiency and product quality. The cathode electrolysis area is designed as a 7-stage series mixed reaction channel, and 4 layers of DSA electrodes are arranged in staggered manner. The multi-stage series design significantly prolongs the residence time of the reactants in the cathode electrolysis area, ensuring that the saponification reaction of octanoic acid and OH⁻ is more complete. The staggered arrangement of the electrodes generates disturbances in the solution flow process, similar to stirring, which enhances the mass transfer process, allowing the generated octanoate ions to more fully combine with Sn²⁺ migrated from the anode area in the settling area to generate the target product stannous octoate, thereby improving the reaction efficiency and product yield.

[0014] 2, The electrolysis device has a reasonable structure, realizing efficient and automatic separation of the product 1) Efficient settling and automatic collection. The electrolysis device is designed with a bucket-shaped collector at the bottom, equipped with a liquid level sensor and a linked pneumatic ball valve. The inclined wall of the bucket-shaped collector is conducive to the sliding and aggregation of the high-viscosity stannous octoate product to the bottom. When the thickness of the settled product layer reaches the preset height (6 cm), the liquid level sensor automatically triggers, and the control system controls the pneumatic ball valve to open, realizing automatic discharge of the product. This avoids manual intervention, realizes continuous and automated production, and improves production efficiency.

[0015] 2) Optimize the circulation system to ensure uniformity of the reaction. The clear liquid (rich in ions) above the sedimentation zone is pumped back to the anode electrolysis zone and the cathode electrolysis zone at a flow rate of 0.2 L / min using a double-channel peristaltic pump, which maintains the uniformity of ion concentration in the electrolyte, ensures the stable progress of the electrolysis reaction, and also helps to remove the reaction heat and maintain the stability of the reaction temperature.

[0016] 3. Improve the overall process performance and reduce production costs 1) Reduce energy consumption. By preventing anode passivation and inhibiting cathode tin deposition, the efficiency of the electrode is significantly improved. At an optimized current density range (70-100 A / m²), electrical energy can be more effectively used for the target reaction, thereby reducing the consumption of direct current and reducing energy costs.

[0017] 2) Reduce by-products and pollution. Compared with the traditional saponification synthesis method, this method avoids the use of stannous chloride and the generation of a large amount of salt (NaCl) wastewater, and the process is cleaner, reducing the cost and environmental pressure of subsequent wastewater treatment.

[0018] 3) Improve production safety. Compared with the direct synthesis method at high temperature and high pressure, the electrolysis method is carried out at normal temperature and pressure or under mild conditions, avoiding safety hazards such as hydrogen explosion, and the production process is safer and more reliable. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a schematic diagram of the front view of the device of the present application; Figure 2 is a left view of the device of the present application; Figure 3 is a top view of the device of the present application. DETAILED DESCRIPTION

[0020] The content of the present application will be described below in conjunction with the drawings of the specification. Obviously, the described embodiments are only a part of the embodiments, not all the embodiments. Based on these embodiments, the embodiments of equivalent alternative technical means obtained by those skilled in the art without creative labor should belong to the scope of protection of the present application.

[0021] Figure 1 、 Figure 2 、 Figure 3 The device for preparing stannous octoate by the electrolysis method of the present application is shown in the figure, which includes a rectangular electrolytic cell 1, a cathode electrolysis zone A and an anode electrolysis zone B respectively arranged on both sides of the electrolytic cell, and a hopper-shaped collector 2 arranged below the middle position of the bottom of the electrolytic cell. The area between the cathode electrolysis zone A and the anode electrolysis zone B is the reaction sedimentation zone C.

[0022] The cathode electrolysis area A is composed of 4 layers of cathode DSA electrodes 3 arranged in sequence close to the side of the electrolytic cell tank wall, 3 layers of cathode PVC partitions 4 arranged in sequence behind the last layer of cathode DSA electrodes. The 4 layers of cathode DSA electrodes and the 3 layers of cathode PVC partitions are arranged alternately and staggered and connected in parallel circuit. The 4 layers of cathode DSA electrodes and the 3 layers of cathode PVC partitions are arranged at intervals to form 7-stage cathode series reaction pools 5.

[0023] The anode electrolysis area B is composed of 3 layers of anode DSA electrodes 6 arranged in sequence close to the side of the electrolytic cell tank wall, 1 layer of tin anode plate 7 arranged behind the last layer of anode DSA electrodes, and 1 layer of anode PVC partition 8 arranged behind the tin anode plate. The 3 layers of anode DSA electrodes, the 1 layer of tin anode plate and the 1 layer of anode PVC partition are arranged alternately and staggered, and the 3 layers of anode DSA electrodes are connected in parallel circuit. The 3 layers of anode DSA electrodes, the 1 layer of tin anode plate and the 1 layer of anode PVC partition are arranged at intervals to form 5-stage anode series reaction pools 9.

[0024] A liquid level sensor 10 is arranged at the upper part of the bucket-shaped collector 2, and a pneumatic ball valve 11 is arranged at the bottom part and linked with the liquid level sensor 10. Both the liquid level sensor 10 and the pneumatic ball valve 11 are connected with a PLC controller.

[0025] A double-channel peristaltic pump 12 is arranged at the height of 8 cm of the side wall of the bucket-shaped collector 2, a first pump pipe 13 is connected to the cathode electrolysis area, and a second pump pipe 14 is connected to the anode electrolysis area.

[0026] The liquid level sensor, the pneumatic ball valve, the PLC controller and the double-channel peristaltic pump used in the electrolysis device are all prior art devices, and the installation and use methods are also common prior art. The DSA electrode is a titanium-based metal oxide coating electrode, and the cathode DSA electrode and the anode DSA electrode of the present application are both titanium-based ruthenium-iridium coating electrodes coated with a mixture of ruthenium oxide and iridium oxide (purchased from Shaanxi Jinshikaite New Material Technology Co., Ltd.). The electrolytic cell of the present embodiment is made of PPH material, and the total size is 80 cm long x 48 cm wide x 32 cm high.

[0027] The bucket-shaped collector is 40 cm long, 48 cm wide and 12 cm high, and the liquid level sensor is installed at the height of 6 cm of the side.

[0028] The components, materials and sizes, and layout parameters of the electrode system are shown in the following table: The method for preparing stannous octoate by electrolysis using the electrolysis device, a 0.01 M potassium nitrate electrolyte is injected into the electrolytic cell 1, a double-channel peristaltic pump 12 is started to pump the electrolyte to the anode electrolysis area B and the cathode electrolysis area A, and the circulation pump flow is controlled to be 0.2 L / min. Then, octanoic acid is injected into the cathode electrolysis area at a flow rate of 0.5 L / h from the top of the electrolytic cell for electrolysis, and the current density of electrolysis is controlled to be 70 ± 5 A / m 2 In the reaction settling area C, stannous octoate precipitates gradually and falls into the hopper-shaped collector 2.

[0029] The cathode electrolysis area uses 4 layers of cathode DSA electrodes to generate an alkaline environment, at this time, C7H 15 COOH in the environment undergoes saponification reaction, and then C7H 15 COO - reacts with Sn 2+ . The 3 layers of cathode PVC separators arranged in the cathode area are to prolong the reaction time, ensure the completion of the saponification reaction, and indirectly ensure the completion of the reaction of C7H 15 COO - with Sn 2+ . In the alkaline aqueous solution environment, Sn 2+ coordinates with OH - , increases the overpotential of tin deposition in the cathode, and thus reduces the generation of sponge tin.

[0030] In the electrolysis process, the following reactions occur on the cathode DAS electrode of the cathode electrolysis area: 2H + + 2e - → H2, H + mainly comes from C7H 15 COOH and H2O, C7H 15 COOH and H2O hydrolyze to generate H + , and then the hydrogen evolution reaction occurs in the electrolysis process; and when polarization occurs, higher voltage makes C7H 15 COOH dissociate to generate H2. After H2 is generated in the aqueous solution, the remaining OH⁻ makes the saponification reaction of octanoic acid occur, and accelerates the reaction rate of octanoate and Sn 2+ in the reaction settling area. In addition, Sn 2+ coordinates with OH - in the cathode electrolysis area, which improves the polarization degree of the cathode, thereby reducing the generation of sponge tin. The staggered arrangement can achieve the stirring effect during the solution flow. In addition, the cathode has more plates than the anode, so the OH - generated by the cathode is more than the H + generated by the anode, which can provide an alkaline atmosphere for the system in the subsequent reaction, and promote the subsequent Sn 2+ + 2C7H 15 COO- =Sn(C7H 15 COO)2 The 3-layer anode DSA electrode used in the anode electrolysis zone is used to generate an acidic solution environment, which can prevent Sn 2+ from hydrolysis and oxidation, and on the other hand, the hydrolysis degree of octanoic acid is low, which can prevent the generation of stannous octoate in the anode zone, which is adsorbed on the surface of the tin anode, causing anode passivation.

[0031] The anode DSA electrode (electrolysis of water: 2H2O→O2↑+4H⁺) and the tin anode (Sn→Sn²⁺+2e⁻) in the anode electrolysis zone, the 3-layer anode DSA electrode shares 70% of the current to prevent passivation. The 1-layer tin anode can reduce the amount of stannous, thereby reducing the generation of cathode sponge tin caused by tin excess. The 3-layer anode DSA electrode generates an acidic environment through electrolysis, and the acidic environment is not easy to hydrolyze octanoic acid, thereby reducing the generation rate of stannous octoate and reducing the passivation caused by the attachment of stannous octoate on the tin anode. The staggered arrangement is used to achieve the stirring effect during the solution flow. H + and NO3 - in the solution can form HNO3, and the generated HNO3 has a low concentration and a gentle oxidation, which is more suitable for use as an oxidizing tin anode to prevent the generation of Sn 4+ .

[0032] Considering the low electrolysis efficiency of the cathode and the anode, the prepared OH - needs to match the generation rate of Sn 2+ in the anode, and the ratio of the number of cathode DSA electrodes, the number of anode DSA electrodes and the number of tin anodes is set to 4:3:1. The anode zone forms a 5-stage series reaction tank and the cathode zone forms a 7-stage series reaction tank, and the reaction residence time can be prolonged and the reaction is more complete.

[0033] When the liquid level sensor 10 detects that the thickness of the precipitate layer is ≥6 cm, the pneumatic ball valve 11 is controlled to open by the PLC controller, and the precipitate is discharged. A collection container is arranged below the hopper-shaped collector to collect the precipitate and wash it with deionized water for 3 times, and then vacuum dried at 60°C for 6 h to obtain stannous octoate product. The product indexes are shown in the following table: The device and method of the present application can effectively reduce the generation of by-products and improve the reaction efficiency, and high-quality stannous octoate is prepared, which not only improves the product quality, but also significantly reduces the energy consumption, and is suitable for industrial scale production.

Claims

1. An apparatus for preparing stannous octoate by electrolysis, characterized in that, The electrolytic cell includes a rectangular electrolytic cell (1), a cathode electrolytic zone and an anode electrolytic zone respectively located on both sides of the electrolytic cell, and a bucket-shaped collector (2) located below the middle of the bottom of the electrolytic cell; the cathode electrolytic zone consists of four layers of cathode DSA electrodes (3) arranged in sequence and connected in parallel near the wall of the electrolytic cell, and three layers of cathode PVC partitions (4) arranged in sequence behind the last layer of cathode DSA electrodes. The four layers of cathode DSA electrodes and the three layers of cathode PVC partitions are spaced apart to form a seven-stage cathode series reaction cell (5); the anode electrolytic zone consists of three layers of anode electrodes arranged in sequence and connected in parallel near the wall of the electrolytic cell. The system consists of a DSA electrode (6), a 1-layer tin anode plate (7) placed behind the last layer of anode DSA electrode, and a 1-layer anode PVC partition plate (8) placed behind the tin anode plate. The three layers of anode DSA electrodes, the 1-layer tin anode and the 1-layer anode PVC partition plate are arranged alternately to form a 5-stage anode series reaction tank (9). A liquid level sensor (10) is provided at the top of the bucket-shaped collector (2), and a pneumatic ball valve (11) linked with the liquid level sensor (10) is provided at the bottom. A dual-channel peristaltic pump (12) is provided on the side wall of the bucket-shaped collector, and the two pump pipes are respectively connected to the cathode electrolysis zone and the anode electrolysis zone.

2. The apparatus for preparing stannous octoate by electrolysis according to claim 1, characterized in that, The four layers of cathode DSA electrodes in the cathode electrolysis zone are arranged alternately and staggered.

3. A method for preparing stannous octoate by electrolysis using the apparatus described in claim 1 or 2, characterized in that, Potassium nitrate electrolyte is introduced into the electrolytic cell (1), and a dual-channel peristaltic pump is started to circulate the electrolyte to the anode electrolysis zone and the cathode electrolysis zone. Then, octanoic acid is injected from the top of the electrolytic cell into the cathode electrolysis zone for electrolysis, gradually producing stannous octanoate precipitate which falls into the funnel-shaped collector. When the liquid level sensor (10) detects that the precipitate layer thickness has reached the set thickness, the pneumatic ball valve (11) is automatically opened to release the precipitate. The precipitate is collected and washed, and then vacuum dried to obtain the stannous octanoate product.

4. The method for preparing stannous octoate by electrolysis according to claim 3, characterized in that, The molar concentration of the potassium nitrate electrolyte is 0.01M.

5. The method for preparing stannous octoate by electrolysis according to claim 3, characterized in that, The current density for electrolysis is 70-100 A / m², and a dual-channel peristaltic pump circulates the electrolyte to the anodic and cathodic electrolysis zones at a flow rate of 0.2 L / min; the addition rate of octanoic acid is 0.5 L / h.

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