A self - contained heat - exchange graphite - filled bipolar electrolytic synthesis device for succinic acid

Abstract

The present invention belongs to the field of electrolysis devices, and discloses a self - heat - exchanging graphite - filled bipolar electrolytic synthesis device for succinic acid. The bipolar electrode is composed of a lead - alloy frame, a lead - alloy basket, filled graphite particles and a cooling system; one side of the lead - alloy frame is the working electrode (cathode); on the other side, a lead - alloy basket is welded and filled with graphite particles (anode); cooling water is passed through the cavity of the lead - alloy frame for heat exchange to regulate and stabilize the temperature of the electrolyte. The electrolysis device of the present invention is applicable to large - scale industrial electrolytic synthesis of succinic acid with an annual output of more than 500 tons. The applicable range is that the electrolyte temperature is 15 - 85 °C and the current density is 100 - 1000 A / m<supgt;2< / supgt>; the loss of the graphite anode is 8 - 10 kg / ton of succinic acid, and the power consumption is < 2600 kwh / ton of succinic acid; it can greatly reduce the electrode investment and electrode consumption of lead - alloy anodes and iridium - titanium coated anodes in the current industry, and can be applied to the electrolytic synthesis of succinic acid industry with a scale of more than ten thousand tons.

Description

Technical Field

[0001] The present invention belongs to the field of electrolysis devices, and relates to an electrode and a device for diaphragm-free electrolytic synthesis of succinic acid, in particular to a self-cooling graphite-filled bipolar electrolytic synthesis device for succinic acid. Background Art

[0002] Succinic acid, commonly known as amber acid, is an important synthetic intermediate for pharmaceuticals and fine chemicals, and is widely used in the synthesis of plastics, rubbers, pharmaceuticals, protective coatings and other industries. Succinic acid has most of the typical reactions of dibasic acids, such as halogenation, dehydration, esterification, polycondensation, iodination, acylation, oxidation, reduction, etc. Using succinic acid as a substrate, a series of mono-esters and di-esters can be prepared. For example, succinic acid can be esterified with starch, cellulose and polyols; succinic acid and 1,4-butanediol can undergo a polycondensation reaction to synthesize polybutylene succinate (PBS), which is a biodegradable plastic with very broad market promotion prospects. In recent years, with the implementation of the national plastic ban, the domestic market for succinic acid is expected to exceed an annual output of more than 200,000 tons; currently, the domestic market scale is about 20,000 tons, and the annual production capacity of the largest domestic production enterprise does not exceed 5,000 tons. Therefore, expanding the production scale is an inevitable requirement for the rapid development of the current succinic acid market.

[0003] The main industrial methods for preparing succinic acid are catalytic hydrogenation reduction of maleic acid (ester), biochemical method and electrolytic reduction method. Among them, the catalytic hydrogenation method requires maleic acid ester as a raw material, the product is complex, and the conversion rate is low; while the biochemical method has a large amount of process wastewater, and there are multiple monoacids in the product, which cannot be used for the polymerization reaction of PBS; currently, the electrolytic method is widely used by domestic and foreign manufacturers and is the main method for the production of succinic acid at home and abroad.

[0004] Industrially, the electrolytic synthesis device for succinic acid usually adopts a diaphragm-free electrolysis device. The cathode material generally uses a lead alloy electrode with a high oxygen evolution overpotential to improve the selectivity of the reaction. The anode material is usually an insoluble anode material, including iridium-titanium noble metal coated electrodes (Shandong Feiyang Chemical Co., Ltd., Shanxi Jinhui Zhaolong Co., Ltd.); and lead alloy electrodes (Anqing Hexing Chemical Co., Ltd., Anhui Sanxin Chemical Co., Ltd.), etc. However, for the lead alloy anode material, the electrode is severely corroded during electrolysis, the service life is short (3-6 months), the maintenance cost of the electrolytic cell is high, and the product quality is poor; at the same time, limited by the current density, the current density is only between 100-250 A / m 2 2, and when applied to large-scale production, especially for a production capacity of 10,000 tons, a large number of electrolysis devices and electrode materials are required, and the investment cost is high; the lead alloy electrode as the anode also has the disadvantages of high oxygen evolution overpotential, high cell voltage and high energy consumption. The iridium-titanium coated electrode is an electrocatalytic oxygen evolution electrode, which has very good oxygen evolution activity and a large working current, and the current density is between 400-600 A / m 2When the temperature is 50 - 60°C, the service life of the electrolyte of 10% sulfuric acid + 10% succinic acid can reach 2 years; however, the price of this electrode is expensive. The total price of the coating per square meter and the titanium mesh substrate exceeds 10,000 yuan. The investment in the electrode is large. For an anode electrode with an annual output scale of 10,000 tons, the investment exceeds 30 million yuan. Moreover, the electrode life is limited by temperature. When the electrolyte temperature rises to 80°C, the electrode life drops sharply (not exceeding 6 months). Therefore, the anode material for electrolytic synthesis of succinic acid in industry has become an important bottleneck restricting the large-scale production of succinic acid.

[0005] Due to the resistance of the electrolyte, the solution heats up significantly during electrolysis. Especially under high-current conditions, the temperature of the electrolytic synthesis of succinic acid solution rises particularly significantly. The temperature can reach and exceed 80°C for the electrode within a few hours, causing a sharp decline in the electrode life and current efficiency. Usually, the method of external heat exchanger is adopted, such as enamel laminated heat exchanger, stainless steel heat exchanger and graphite heat exchanger. However, these heat exchangers cool the electrode by cooling the electrolyte and maintain the constant temperature of the electrolyte, which requires a large heat transfer area and is severely corroded and blocked.

[0006] Aiming at the problems in the anode material of the electrolytic synthesis of succinic acid device, such as the easy corrosion of the lead alloy anode material, low current density, poor product quality; and the large investment in the noble metal anode and its inapplicability to high-temperature media, as well as the difficult control of constant temperature due to the unstable heat generation during electrolysis and other practical industrial problems, the present invention proposes an industrialized electrolytic succinic acid device filled with graphite particles with self-heat exchange. This device can effectively solve practical problems such as the corrosion of lead alloy anodes, the high cost of iridium-titanium coated electrodes, the reduction of electrode life caused by electrode heating, and the difficulty in selecting heat exchangers, providing the core electrolytic device technology for large-scale electrolytic production of succinic acid, especially for the electrolytic production of succinic acid at the 10,000-ton level. Summary of the Invention

[0007] The purpose of the present invention is to solve the practical problems of the existing industrial electrolytic synthesis of succinic acid, such as the easy corrosion of the lead alloy anode material, the large investment in the iridium-titanium coated anode, the high temperature of the electrolyte and the difficulty in control. A bipolar electrolytic device for industrialized electrolytic production of succinic acid with self-heat exchange is proposed, which has the characteristics of self-heat exchange, less investment, low power consumption, long electrode life and high product quality, and is especially suitable for the production of large-scale electrolytic synthesis of succinic acid above the 10,000-ton level.

[0008] In order to achieve the above invention purpose, the present invention provides the following technical solutions:

[0009] A self - contained heat - exchange graphite - filled bipolar electrolytic synthesis device for succinic acid. The electrolytic device mainly consists of an electrolytic cell body and several bipolar electrodes. The bottom surface of any bipolar electrode is closely placed on a plastic backing plate at the bottom of the electrolytic cell body. The bipolar electrodes at both ends are respectively closely attached to the corresponding side walls of the electrolytic cell. One is connected to the positive pole of the power supply, and the other is connected to the negative pole of the power supply, forming a plate - frame bipolar electrolytic device. The lead - alloy clamping edges on both sides of any bipolar electrode are embedded in the grooves on both side plates of the electrolytic cell body, dividing the interior of the electrolytic cell body into several bipolar unit electrolytic cells. A unit electrolytic cell cavity is formed between any two adjacent bipolar electrodes. On the lower part of one side of the electrolytic cell body corresponding to any unit electrolytic cell cavity, there is an electrolyte inlet, and on the upper part of the opposite side, there is an electrolyte overflow port.

[0010] Preferably, any of the bipolar electrodes includes a lead - alloy frame and a lead - alloy basket. The lead - alloy frame is a closed cuboid frame, which has the functions of heat exchange and bipolar electrode. One side of the lead - alloy frame is a lead - alloy cathode surface, and the other side is welded to the lead - alloy basket. The lead - alloy basket is an open basket structure. The basket ribs are lead - alloy basket lead rods. A plastic net is arranged inside the lead - alloy basket, which can prevent the graphite particles filled inside from falling off. The graphite particles are added or replenished from the opening of the lead - alloy basket.

[0011] Preferably, a cooling water inlet pipe joint is arranged at the lower part of the lead - alloy frame, and a cooling water outlet pipe joint is arranged at the upper part of the lead - alloy frame. Cooling water enters the cavity of the lead - alloy frame from the cooling water inlet pipe joint, exchanges heat with the external electrolyte, and then flows out from the cooling water outlet pipe joint, playing a heat - exchange role.

[0012] Preferably, the plastic backing plate and the plastic net are made of insulating materials such as polypropylene PP or nylon.

[0013] Preferably, the size of the plastic backing plate matches and closely fits any bipolar electrode. The plastic backing plate is welded to the bottom of the electrolytic cell body. The plastic backing plate can prevent the dropped graphite powder from causing micro - short - circuit between the electrodes.

[0014] Preferably, a spray pipe is arranged at the upper part inside the lead - alloy basket. The spray pipe is connected to an electrolyte pump. The spray pipe can wash the electrolyzed graphite particles to dissolve a small amount of deposited succinic acid crystals.

[0015] Preferably, part of the graphite particles are consumed during electrolysis. The consumed graphite particles are replenished from the upper opening of the lead - alloy basket. The graphite powder dropped due to electrolysis is filtered and recovered by an electrolyte circulation pump to a filtering device outside the electrolytic cell.

[0016] Preferably, the electrolytic device contains 5 - 100 bipolar electrodes, and multiple electrolytic devices are connected in series or in parallel for industrial electrolytic synthesis of succinic acid.

[0017] The self - heat - exchange graphite - filled bipolar electrolytic synthesis device for succinic acid described in the present invention is applicable to large - scale industrial electrolytic synthesis of succinic acid with an annual output of more than 500 tons. The applicable range of the bipolar electrode is that the electrolyte temperature is 15 - 85 °C and the current density is 100 - 1000 A / m 2 .

[0018] At present, graphite - filled electrodes have not been used as anodes in the industrial electrolytic synthesis of succinic acid. At the same time, an external - tank heat exchanger is used in industry to control the electrolyte temperature. Compared with the existing electrolytic devices, the beneficial effects of the present invention are as follows:

[0019] (1) Using graphite - filled electrodes as anodes significantly reduces the electrode investment cost. The anode investment is only one - half of that of lead - alloy anodes and one - tenth of that of iridium - titanium coated electrodes;

[0020] (2) Reduces the electrode depreciation cost. The depreciation of lead - alloy anodes is 600 - 900 yuan / ton of succinic acid, and the depreciation of iridium - titanium coated electrodes is 900 - 1500 yuan / ton of succinic acid, while the graphite supplementation is only 25 yuan / ton of succinic acid;

[0021] (3) The self - heat - exchange device uses lead - alloy electrode materials, which plays a role in cathodic protection, directly cools the electrodes, has good heat - exchange effect and few side reactions, solves the corrosion and blockage problems of enamel laminated and graphite heat exchangers, and has very significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic diagram of an industrial self - heat - exchange graphite - filled bipolar electrolytic synthesis device for succinic acid of the present invention;

[0023] Figure 2 is a schematic diagram of a bipolar electrode of an industrial self - heat - exchange graphite - filled bipolar electrolytic synthesis device for succinic acid of the present invention;

[0024] Figure 1 In, 1 - electrolytic cell tank body, 2 - electrolytic cell side wall, 3 - bipolar electrode, 4 - plastic backing plate, 5 - electrolyte inlet, 6 - electrolyte overflow port;

[0025] Figure 2 In, 4 - plastic backing plate, 7 - lead - alloy frame, 8 - lead - alloy basket, 9 - lead - alloy cathode surface, 10 - lead rod of lead - alloy basket, 11 - plastic mesh, 12 - graphite particles, 13 - cooling water inlet pipe joint, 14 - cooling water outlet pipe joint, 15 - lead - alloy clamping edge, 16 - spray pipe. DETAILED DESCRIPTION OF THE INVENTION

[0026] The technical solutions of the present invention will be further specifically described below through specific embodiments and in combination with the drawings.

[0027] Example 1

[0028] Reference Figure 1-2 Schematic diagram. An industrial self-heat-exchanging graphite-filled bipolar electrolytic synthesis device for succinic acid. The device includes a number of bipolar electrodes 3. The bipolar electrodes 3 are placed on a plastic backing plate 4 at the bottom of the electrolytic cell body 1. The bipolar electrodes 3 at both ends are respectively in close contact with the corresponding side walls 2 of the electrolytic cell. One is connected to the positive pole of the power supply, and the other is connected to the negative pole of the power supply, forming a plate-frame bipolar electrolytic device. The lead alloy edges 15 on both sides of any bipolar electrode 3 are embedded in the grooves on both side plates of the electrolytic cell body 1, fixed inside the electrolytic cell body 1, and divide the inside of the electrolytic cell body 1 into a number of unit electrolytic cells. A unit electrolytic cell cavity is formed between any two adjacent bipolar electrodes 3. An electrolyte inlet 5 is provided at the lower part of one side of the electrolytic cell body 1 corresponding to any unit electrolytic cell cavity, and an electrolyte overflow port 6 is provided at the upper part of the opposite side.

[0029] Among them, any of the bipolar electrodes 3 includes a lead alloy frame 7 and a lead alloy basket 8. The lead alloy frame 7 is a closed cuboid frame, which has the functions of heat exchange and bipolar electrode. One side of the lead alloy frame 7 is a lead alloy cathode surface 9, and the other side is fixedly welded to the lead alloy basket 8. The lead alloy basket 8 is an open basket structure. The basket ribs are lead alloy basket lead rods 10. A plastic net 11 is arranged inside the lead alloy basket 8. Graphite particles 12 are added into the lead alloy basket 8 from the opening, and the plastic net 11 can prevent the graphite particles 12 from falling off.

[0030] A cooling water inlet pipe joint 13 is arranged at the lower part of the lead alloy frame 7, and a cooling water outlet pipe joint 14 is arranged at the upper part of the lead alloy frame 7. Cooling water enters the cavity of the lead alloy frame 7 from the cooling water inlet pipe joint 13, exchanges heat with the electrolyte outside, and then flows out from the cooling water outlet pipe joint 14, playing a role in heat exchange.

[0031] The graphite particles 12 are cylindrical graphite particles, and the size is matched with the hole size of the plastic net 11.

[0032] The opening rate of the plastic net 11 > 90%, which is used to fix the graphite particles 12.

[0033] The plastic backing plate 4 and the plastic net 11 are made of polypropylene PP.

[0034] The size of the plastic backing plate 4 is matched with any bipolar electrode 3 and is in close contact. The plastic backing plate 4 is welded to the bottom of the electrolytic cell body 1. The plastic backing plate 4 can prevent the dropped graphite powder from causing a micro short circuit between the electrodes.

[0035] A spray pipe 16 is provided at the upper part of the lead alloy basket 8, and the spray pipe 16 is connected to an electrolyte pump. The spray pipe 16 can rinse the electrolyzed graphite particles 12 and dissolve a small amount of deposited succinic acid crystals.

[0036] The graphite particles are partially consumed during electrolysis, and the consumed graphite particles are added from the upper opening of the lead alloy basket 8; the graphite powder dropped due to consumption is recovered through the electrolyte filtering device.

[0037] The electrolysis device contains 40 bipolar electrodes, forming an electrolysis device containing 40 unit electrolysis cells. Three electrolysis devices are connected in series (a total of 120 unit electrolysis cells) and are applied to the industrial electrolysis synthesis of succinic acid.

[0038] The bipolar electrolysis specifications are as follows: the lead alloy frame 7 has a size of 1000mm*1000mm*60mm, and the lead alloy cathode surface 9 has an area of 1m 2 The lead alloy basket 8 with an opening at the top has a size of 950mm*950mm*100mm, with a PP net fixed outside. The electrolytic cylindrical graphite particles filled in the lead alloy basket 8 have a total mass of 70kg and a total effective area of more than 100m 2 ; The distance between any two bipolar electrodes is 30 mm.

[0039] The electrolyte temperature is controlled by cooling water which is connected from the cooling water inlet joint 13 at the lower part of one side of the lead alloy frame 7 and overflows from the cooling water outlet joint 14 at the upper part of the other side. The cooling water inlet temperature is 32±2°C, and the cooling water flow rate is adjusted to control the electrolyte temperature to 70±2°C.

[0040] The electrolyte composition is 8% sulfuric acid + 10% maleic acid (initial concentration of feed), and the cathode current density is 600A / m 2 (current value is 600A), graphite anode current density <10A / m 2 The electrolyte is input from the electrolyte inlet 5 by a pump connected to the electrolyte circulation tank. After participating in the electrolysis reaction in the cavity between the two electrodes, it overflows from the upper part of the electrolytic cell and returns to the electrolyte circulation storage tank. The electrolysis is terminated after the constant current combined with the variable current control to a specific time. The discharge pipe is connected to the pump and transported to the filter device to recover the graphite powder. The filtered electrolyte is crystallized, washed, recrystallized, dried and other processes to obtain the succinic acid product. After each batch of electrolysis discharge, the graphite particles are sprayed with a spray pipe 16 to dissolve a small amount of succinic acid crystals deposited on the surface of the graphite electrode due to heat exchange.

[0041] The above process was run for 100 batches, and the main production experimental results obtained are shown in Table 1.

[0042] Table 1 Production results of succinic acid synthesized by graphite filled bipolar electrolysis succinic acid synthesis device with self-contained heat exchange

[0043] Project Test results Temperature control 70±2℃ Cooling water inlet / outlet temperature 32℃ / 37℃ Cooling water flow rate <![CDATA[32m 3 / h]]> Graphite consumption 9.15 kg / ton succinic acid Total power consumption 2582 kwh / ton succinic acid Unit consumption 0.848 tons maleic anhydride / ton succinic acid

[0044] Example 2-3

[0045] According to the method of Example 1, take two of the electrolytic cells as the experimental electrolytic device. Replace the packed graphite with massive graphite particles or large-grained graphite balls respectively. The cooling water flow rate is 6m 3 / h, the inlet / outlet temperature of the cooling water is 32°C / 37°C, the electrolyte temperature is controlled at 70±2°C, and it runs for 10 batches. The test results are statistically calculated per ton of product based on 100 kg of succinic acid product, and the results are shown in Table 2.

[0046] Table 2 Influence of Graphite Filling Materials on the Synthesis of Succinic Acid by a Multi-polar Electrolytic Device

[0047]

[0048] The results in Table 2 show that the filling of graphite particles with different shapes has little influence on the electrolytic synthesis of succinic acid.

[0049] Examples 4-11

[0050] According to the electrolytic device of Example 1, take two of the electrolytic cells as the experimental electrolytic device, adjust the electrolyte temperature and current density, run for 10 batches, and statistically calculate the test results per ton of product based on 100 kg of succinic acid product. The results are shown in Table 3.

[0051] Table 3 Influence of Different Controls and Currents of a Multi-polar Electrolytic Device on the Industrial Synthesis of Succinic Acid

[0052]

[0053] The results in Table 3 show that the multi-polar electrolytic device with self-heat exchange can better control the temperature. The graphite electrode loss per ton of succinic acid is less than 10 kg. It can adapt to large-scale production, especially to work under the electrolytic conditions above 70°C, and can significantly reduce the power consumption and the loss of anode materials. It is a production device that can be used for the electrolytic synthesis of succinic acid at the ten-thousand-ton level.

[0054] The above-described embodiments are only preferred solutions of the present invention, and do not impose any form of limitation on the present invention. There are other variations and modifications without exceeding the technical solutions recorded in the claims.

Claims

1. A graphite-filled bipolar electrolytic synthesis device for succinic acid with self-heat exchange, characterized in that, The device mainly consists of an electrolytic cell body (1) and a plurality of bipolar electrodes (3); the bottom surface of any bipolar electrode (3) is tightly placed on a plastic pad (4) at the bottom of the electrolytic cell body (1), and the bipolar electrodes (3) at both ends are tightly fitted with the corresponding electrolytic cell side walls (2), one connected to the positive pole of the power supply, and the other connected to the negative pole of the power supply; the lead alloy clamping edges (15) on both sides of any bipolar electrode (3) are embedded in the grooves of the two side plates of the electrolytic cell body (1), dividing the inside of the electrolytic cell body (1) into a plurality of bipolar unit electrolytic cells, and a unit electrolytic cell cavity is formed between any two adjacent bipolar electrodes (3); an electrolyte inlet (5) is arranged at the lower part of one side of the electrolytic cell body (1) corresponding to any unit electrolytic cell cavity, and an electrolyte overflow port (6) is arranged at the upper part of the opposite side; Any of the bipolar electrodes (3) is composed of a lead alloy frame (7) and a lead alloy basket (8); the lead alloy frame (7) is a closed rectangular parallelepiped frame, one side of the lead alloy frame (7) is a lead alloy cathode surface (9), and the other side is welded to the lead alloy basket (8); the lead alloy basket (8) is an open basket structure, the basket ribs are lead alloy basket lead rods (10), a plastic net (11) is arranged on the inner side of the lead alloy basket (8), and graphite particles ( 12), graphite particles (12) are added or supplemented from the opening of the lead alloy basket (8), a cooling water inlet pipe joint (13) is arranged at the lower part of the lead alloy frame (7), and a cooling water outlet pipe joint (14) is arranged at the upper part of the lead alloy frame (7); the graphite particles (12) are cylindrical graphite particles, block graphite particles or large-grain graphite balls; the size of the plastic pad (4) matches and fits tightly to any bipolar electrode (3), and the plastic pad (4) is welded to the bottom of the electrolytic cell body (1).

2. The self - heat - exchanging graphite - filled bipolar electrolytic synthesis device for succinic acid according to claim 1, wherein, A spray pipe (16) is provided at the upper part of the lead alloy basket (8).

3. The self - heat - exchanging graphite - filled bipolar electrolytic synthesis device for succinic acid according to claim 1, wherein, The device contains 5-100 bipolar electrodes.

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