CN110713437A - Device and method for preparing oxalic acid by hydrolyzing oxalate - Google Patents
Device and method for preparing oxalic acid by hydrolyzing oxalate Download PDFInfo
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- C07C51/09—Preparation of carboxylic acids or their salts, halides or anhydrides from carboxylic acid esters or lactones
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- C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
- C07C29/09—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrolysis
- C07C29/095—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring by hydrolysis of esters of organic acids
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- C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
- C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
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- C—CHEMISTRY; METALLURGY
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- C07C51/42—Separation; Purification; Stabilisation; Use of additives
- C07C51/43—Separation; Purification; Stabilisation; Use of additives by change of the physical state, e.g. crystallisation
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Abstract
The invention relates to a device for preparing oxalic acid by hydrolyzing oxalate, which comprises a batching tank, a pre-reaction kettle, a reaction rectifying tower, a methanol refining tower and a crystallization kettle which are mutually connected through pipelines. The invention combines the pre-reaction and the reactive distillation technology, realizes the high-efficiency hydrolysis of oxalate by the circulation of the oxalic acid mother liquor and the autocatalysis of oxalic acid, and obtains the high-purity oxalic acid product.
Description
Technical Field
The invention relates to a device and a method for preparing oxalic acid by hydrolyzing oxalate, belonging to the technical field of oxalate hydrolysis.
Background
Oxalic acid is an important chemical raw material and is widely used in the industries of medicine, printing and dyeing, plastics and the like. As a precipitant, oxalic acid can also be used to separate and purify rare earth elements. With the rapid development of the fields of aerospace, new energy, new materials and the like, the application field of oxalic acid is more and more extensive, and the demand of oxalic acid is gradually increased year by year. The preparation method of oxalic acid mainly comprises a synthesis method and a hydrolysis method, wherein the hydrolysis method is to hydrolyze oxalic ester under an acidic condition to prepare oxalic acid, the hydrolysis reaction process of the oxalic ester is formed by two steps of reactions, firstly, oxalic acid diester is rapidly hydrolyzed to generate oxalic acid monoester, then, the oxalic acid monoester is continuously hydrolyzed to generate oxalic acid, the reaction rate of the second step is slow, the control step of the whole hydrolysis reaction is realized, and the oxalic acid solution after hydrolysis can be cooled and crystallized to obtain an oxalic acid product.
However, since oxalic acid diester and oxalic acid monoester have low solubility in water and high melting point, if oxalic acid ester is not hydrolyzed completely, oxalic acid monoester or oxalic acid diester remaining in the crystallization kettle is crystallized together with oxalic acid, and thus an acceptable oxalic acid product cannot be obtained.
Patent CN 1094922C discloses a method for preparing oxalic acid by direct hydrolysis of diethyl oxalate, wherein a reactive rectifying tower is used for hydrolysis of diethyl oxalate, and oxalic acid solution produced at the bottom of the tower is crystallized. However, the conversion rate of diethyl oxalate by adopting the method is 97%, the yield of oxalic acid is only 87%, and the possible reasons are that the hydrolysis reaction rate of the monoethyl oxalate is slow, and the retention time of the monoethyl oxalate in the reaction section of the rectifying tower is insufficient. Patent CN 104892389B discloses a process for preparing oxalic acid by hydrolyzing dimethyl oxalate through continuous reaction rectification, which takes dimethyl oxalate as a raw material to prepare oxalic acid through autocatalytic hydrolysis in a continuous reaction rectification bulkhead tower. Although the conversion rate of the method reaches 99%, the process still has some defects, and the industrial application of the process is influenced. Firstly, the structure of the bulkhead reaction rectifying tower is complex, the equipment cost is high, and the equipment control is complex; the flow of the whole process is complicated, and unit processes such as a methanol refining tower, a light component removal tower and the like are needed besides a bulkhead reaction rectifying tower; secondly, the oxalic acid crystal is obtained by adopting a mode of evaporation, concentration and crystallization, and the energy consumption of the system is high; and finally, the oxalic acid generated by the reaction is used for autocatalysis, the reaction rate is slow, and the equipment of a reaction rectifying tower is large. Therefore, a new process for preparing oxalic acid by hydrolyzing oxalate needs to be developed to solve the problem of preparing oxalic acid by hydrolyzing oxalate at present.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a device and a method for preparing oxalic acid by hydrolyzing oxalate, which have the characteristics of quick reaction, high hydrolysis rate and good selectivity.
In order to solve the technical problems, the technical scheme of the invention is as follows: the device for preparing oxalic acid by hydrolyzing oxalate comprises a batching tank, a pre-reaction kettle, a reaction rectifying tower, a methanol refining tower and a crystallization kettle which are mutually connected through pipelines.
Preferably, one side of the upper part of the mixing tank is communicated with a water inlet and an oxalate inlet, a top inlet pipeline of the mixing tank is communicated with a top outlet of the crystallization kettle, a bottom outlet pipeline of the mixing tank is communicated with an inlet of one side of the upper part of the pre-reaction kettle, a bottom outlet of the pre-reaction kettle is communicated with a pre-reaction material inlet of the reaction rectifying tower through a first centrifugal pump, a bottom outlet of the reaction rectifying tower is communicated with an inlet of a first cooler through a second centrifugal pump, an outlet pipeline of the first cooler is communicated with an inlet of the crystallization kettle, a top outlet pipeline of the reaction rectifying tower is communicated with an inlet of the methanol rectifying tower, and a bottom outlet of the methanol rectifying tower is communicated with a water inlet of the mixing tank through a pipeline; a second cooler is arranged between one side and the top of the upper part of the reactive distillation tower in series, so that a condensation reflux loop is formed at the top of a tower kettle of the reactive distillation tower; and a third cooler is connected between one side of the upper part of the methanol refining tower and the top of the methanol refining tower in series, so that a condensation reflux loop is formed at the top of a tower kettle of the methanol refining tower.
Preferably, a reaction rectifying tower reboiler is arranged between the bottom of the reaction rectifying tower and one side of the lower part of the reaction rectifying tower in series, so that a reflux loop is formed at the bottom of a tower kettle of the reaction rectifying tower; a methanol refining tower reboiler is arranged between the bottom of the methanol refining tower and one side of the lower part of the methanol refining tower in series, so that a reflux loop is formed at the bottom of a tower kettle of the methanol refining tower.
Preferably, a pre-reaction material inlet of the reactive distillation tower is positioned at 1/4-1/2 of the height of the tower body; the inlet of the methanol refining tower is located at 2/5-2/3 of the height of the tower body.
Preferably, the reactive distillation column is of a combined structure of one or two of a plate column and a packed column, and the number of theoretical plates of the reactive distillation column is 25-50.
Preferably, the methanol refining tower is a combined structure of one or two of a plate tower and a packed tower, and the number of theoretical plates of the methanol refining tower is 20-32.
A preparation method of a device for preparing oxalic acid by hydrolyzing oxalate comprises the following steps:
step (1): introducing a mixture with a molar ratio of 4: 1-5: 1, water and the raw material oxalate to obtain a solution; uniformly mixing the solution and the oxalic acid mother liquor obtained in the step (6) to obtain a mixed solution; the raw material of the oxalate is one of dimethyl oxalate, monomethyl oxalate, diethyl oxalate or monoethyl oxalate; the molar ratio of water to oxalate in the mixed solution is 3: 1-6: 1;
step (2): introducing the mixed solution in the batching tank into a pre-reaction kettle for preliminary hydrolysis reaction, wherein the preliminary hydrolysis rate of the oxalate is 80-90%; obtaining a pre-reaction material, wherein the reaction temperature is 60-110 ℃, and the reaction time is 30-100 min;
pressurizing the pre-reaction material by a first centrifugal pump, introducing the pre-reaction material into a reaction rectifying tower, and further hydrolyzing in the reaction rectifying tower to obtain crude oxalic acid and alcohol, wherein the tower top temperature of the reaction rectifying tower is 50 ~ 70 ℃, and the tower kettle temperature is 90 ~ 110 ℃;
step (4), introducing the crude alcohol product extracted from the top of the reactive rectifying tower into a methanol refining tower for rectification to obtain a methanol product and water, wherein the tower top temperature of the methanol refining tower is 60 ~ 70 ℃, and the tower bottom temperature is 90 ~ 110 ℃;
step (5), pressurizing the oxalic acid solution extracted from the bottom of the reactive rectifying tower (3) by a second centrifugal pump (8) and cooling by a first cooler (5) in sequence to obtain a cooled oxalic acid solution, wherein the temperature of the cooled oxalic acid is 60 ~ 70 ℃;
and (6): introducing the cooled oxalic acid solution into a crystallization kettle (6) for cooling crystallization to obtain oxalic acid crystals and oxalic acid mother liquor, introducing the oxalic acid mother liquor into a proportioning tank (1), extracting the oxalic acid crystals and carrying out centrifugal drying; the crystallization temperature of the crystallization kettle is 20-40 ℃;
the oxalic acid product with the purity of more than or equal to 99.5 percent is obtained by the steps of (1) ~ and (6) the hydrolysis rate of the raw material oxalic ester is 99.5 percent, ~ 99.8.8 percent.
Preferably, the condensation reflux ratio of the top of the methanol refining tower passing through the third condenser in the step (4) is 1.8-4.
Preferably, the condensation reflux ratio of the top of the reaction rectifying tower in the step (3) to the second condenser is 2 ~ 4.
Preferably, the water at the bottom of the refined methanol refining tower in the step (4) is conveyed to a water inlet at one side of the upper part of the batching tank through a pipeline.
Compared with the prior art, the invention has the following beneficial effects:
(1) the raw material oxalate is dissolved in the batching tank by utilizing the circulating oxalic acid mother liquor, and the raw material oxalate does not need to be heated and melted, so that the problem of conveying the solid oxalate in a pipeline is solved; meanwhile, the oxalic acid mother liquor is recycled, so that oxalic acid with the mass concentration of more than or equal to 10% is always contained in the hydrolysis reaction process of the oxalic ester, and the higher concentration of the oxalic acid can improve the hydrolysis reaction speed of the oxalic ester.
(2) The pre-reaction kettle and the reaction rectifying tower are combined for use, so that the hydrolysis rate of the oxalate raw material is ensured to reach more than 99.5 percent. And carrying out preliminary hydrolysis reaction in a pre-reaction kettle, so that 80-90% of oxalate reacts, the load of the reaction rectifying tower is reduced, and the size of the reaction rectifying tower is favorably reduced.
(3) The oxalic acid crystal product is obtained by adopting a cooling crystallization mode, and compared with evaporative crystallization, the energy consumption can be saved by more than 90%.
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
Drawings
FIG. 1 is a schematic configuration diagram of an embodiment of the present invention.
Detailed Description
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.
As shown in figure 1, the device for preparing oxalic acid by hydrolyzing oxalic ester comprises a dosing tank 1, a pre-reaction kettle 2, a reaction rectifying tower 3, a methanol refining tower 4 and a crystallization kettle 6 which are connected with each other through pipelines.
In the embodiment of the invention, one side of the upper part of a batching tank 1 is communicated with a water inlet and an oxalate inlet, a top inlet pipeline of the batching tank 1 is communicated with a top outlet of a crystallization kettle 6, a bottom outlet pipeline of the batching tank 1 is communicated with an inlet of one side of the upper part of a pre-reaction kettle 2, a bottom outlet of the pre-reaction kettle 2 is communicated with a pre-reaction material inlet of a reaction rectifying tower 3 through a first centrifugal pump 7, a bottom outlet of the reaction rectifying tower 3 is communicated with an inlet of a first cooler 5 through a second centrifugal pump 8, an outlet pipeline of the first cooler 5 is communicated with an inlet of the crystallization kettle 6, a top outlet pipeline of the reaction rectifying tower 3 is communicated with an inlet of a methanol rectifying tower 4, and a bottom outlet of the methanol rectifying tower 4 is communicated with a water inlet of the batching tank 1 through a pipeline; a second cooler 9 is arranged between one side and the top of the upper part of the reactive distillation tower 3 in series, so that a condensation reflux loop is formed at the top of the tower kettle of the reactive distillation tower 3; and a third cooler 10 is arranged between one side and the top of the upper part of the methanol refining tower 4 in series, so that a condensation reflux loop is formed at the top of the tower kettle of the methanol refining tower 4.
In the embodiment of the invention, a reactive distillation column reboiler 31 is arranged in series between the bottom of the reactive distillation column 3 and one side of the lower part of the reactive distillation column 3, so that a reflux loop is formed at the bottom of the column bottom of the reactive distillation column 3; a methanol refining tower reboiler 41 is arranged between the bottom of the methanol refining tower 4 and one side of the lower part of the methanol refining tower 4 in series, so that a reflux loop is formed at the bottom of a tower kettle of the methanol refining tower 4.
In the embodiment of the invention, a pre-reaction material inlet of the reactive distillation column 3 is positioned at 1/4-1/2 of the height of the column body; the inlet of the methanol refining tower 4 is positioned at 2/5-2/3 of the height of the tower body.
In the embodiment of the invention, the reactive distillation column 3 is a combined structure of one or two of a plate column and a packed column, and the number of theoretical plates of the reactive distillation column 3 is 25-50.
In the embodiment of the invention, the methanol refining tower 4 is a combined structure of one or two of a plate tower and a packed tower, and the number of theoretical plates of the methanol refining tower 4 is 20-32.
A preparation method of a device for preparing oxalic acid by hydrolyzing oxalate comprises the following steps:
step (1): introducing a mixture with a molar ratio of 4: 1-5: 1, water and the raw material oxalate to obtain a solution; uniformly mixing the solution and the oxalic acid mother liquor obtained in the step 6 to obtain a mixed solution; the raw material of the oxalate is one of dimethyl oxalate, monomethyl oxalate, diethyl oxalate or monoethyl oxalate; the molar ratio of water to oxalate in the mixed solution is 3: 1-6: 1;
step (2): introducing the mixed solution in the batching tank 1 into a pre-reaction kettle 2 for preliminary hydrolysis reaction, wherein the preliminary hydrolysis rate of the oxalate is 80-90%; obtaining a pre-reaction material, wherein the reaction temperature is 60-110 ℃, and the reaction time is 30-100 min;
step (3), pressurizing the pre-reaction material by a first centrifugal pump 7, introducing the pre-reaction material into a reaction rectifying tower 3, and further hydrolyzing in the reaction rectifying tower 3 to obtain crude oxalic acid and alcohol, wherein the tower top temperature of the reaction rectifying tower 3 is 50 ~ 70 ℃, and the tower bottom temperature is 90 ~ 110 ℃;
step (4), introducing the crude alcohol product extracted from the top of the reactive distillation tower 3 into a methanol refining tower 4 for rectification to obtain a methanol product and water, wherein the tower top temperature of the methanol refining tower 4 is 60 ~ 70 ℃, and the tower kettle temperature is 90 ~ 110 ℃;
step (5), pressurizing the oxalic acid solution extracted from the bottom of the reactive rectifying tower (3) by a second centrifugal pump (8) and cooling by a first cooler (5) in sequence to obtain a cooled oxalic acid solution, wherein the temperature of the cooled oxalic acid is 60 ~ 70 ℃;
and (6): introducing the cooled oxalic acid solution into a crystallization kettle (6) for cooling crystallization to obtain oxalic acid crystals and oxalic acid mother liquor, introducing the oxalic acid mother liquor into a proportioning tank (1), extracting the oxalic acid crystals and carrying out centrifugal drying; the crystallization temperature of the crystallization kettle is 20-40 ℃;
the oxalic acid product with the purity of more than or equal to 99.5 percent is obtained by the steps of (1) ~ and (6) the hydrolysis rate of the raw material oxalic ester is 99.5 percent, ~ 99.8.8 percent.
In the embodiment of the invention, the condensation reflux ratio of the top of the methanol refining tower 4 in the step (4) through the third condenser 10 is 1.8-4.
In the present embodiment, the condensed reflux ratio of the top of the reactive distillation column 3 in the step (3) through the second condenser 9 is 2 ~ 4.
In the embodiment of the invention, in the step (4), the water at the bottom of the refined methanol refining tower 4 is conveyed to a water inlet at the upper part of the batching tank 1 through a pipeline.
The specific implementation process comprises the steps that the inside of the reaction rectifying tower 3 is of a tower structure formed by combining a plate tower structure and a packed tower structure, the reaction rectifying tower 3 corresponding to the position above the pre-reaction material inlet is of a packed tower structure, the number of theoretical plates is 15 (the height of the packing is 4 ~ 5 m), the inside of the reaction rectifying tower 3 corresponding to the position below the pre-reaction material inlet is of a plate tower structure, the number of theoretical plates (tower plates) is 30, the packing material is a ceramic material resistant to oxalic acid corrosion, the number of theoretical plates of the methanol rectifying tower 4 is 28 (the height of the packing is 6 ~ 7 m), and the packing material is a ceramic material or a metal material.
Step (1): 328kg/hr dimethyl oxalate and 210kg/hr water are introduced into the batching tank 1, and the molar ratio of the water to the dimethyl oxalate is 4.2; and (4) simultaneously introducing the oxalic acid mother liquor obtained in the step (6) and saturated at the temperature of 30 ℃ and the flow rate of 600kg/hr, and stirring and mixing uniformly to obtain a mixed solution.
Step (2): introducing the mixed solution in the batching tank 1 into a pre-reaction kettle 2 for preliminary hydrolysis reaction to obtain a pre-reaction material; the pre-reaction kettle 2 is heated by steam, the reaction temperature is about 80 ℃, and the reaction time is 80 min.
And (3): pressurizing the pre-reaction material by a first centrifugal pump 7, introducing the pre-reaction material into a reaction rectifying tower 3 at the flow rate of 1138kg/hr, and further hydrolyzing in the reaction rectifying tower 3 to respectively obtain crude oxalic acid and methanol; the reaction rectifying tower 3 is operated under normal pressure, the temperature of the tower top is 68.9 ℃, the temperature of the tower bottom is 104.7 ℃, and the condensation reflux ratio of the top is 2.5; 188kg/hr of crude methanol containing 5.2% water is extracted from the top of the reactive distillation column 3, and 950kg of oxalic acid is extracted from the bottom of the column.
And (4): introducing a methanol crude product extracted from the top of the reaction rectifying tower 3 into a methanol refining tower 4 for rectification to respectively obtain a methanol product and water; the tower top temperature of the methanol refining tower 4 is 65.5 ℃, the tower bottom temperature is 100.4 ℃, and the top condensing reflux ratio of the methanol refining tower 4 is 2.2; 180kg/hr of methanol product is obtained from the top of the methanol refining tower 4, and the water obtained from the tower bottom is sent to a material mixing tank for recycling.
And (5): the oxalic acid solution extracted from the tower kettle of the reactive distillation tower 3 is pressurized by a second centrifugal pump 8 and cooled by a first cooler 5 in sequence to obtain a cooled oxalic acid solution, and the temperature of the cooled oxalic acid is 65 ℃;
and (6): and introducing the cooled oxalic acid solution into a crystallization kettle 6 for cooling crystallization, wherein the crystallization temperature of the crystallization kettle is 30 ℃, and 350kg/hr of oxalic acid crystals and oxalic acid mother liquor are obtained.
And returning the liquid-phase oxalic acid mother liquor to the batching tank 1 for recycling, and sending the solid-phase oxalic acid crystal to a subsequent centrifugal drying process.
The hydrolysis rate of the dimethyl oxalate in the step (1) ~ (6) is 99.8 percent, and the purity of the oxalic acid product is 99.6 percent.
The hydrolysis reaction formula of the oxalate is as follows:
the present invention is not limited to the above-described preferred embodiments, and any one can find out other various types of apparatuses and methods for producing oxalic acid by hydrolyzing oxalic ester, according to the teaching of the present invention. All equivalent changes and modifications made according to the claims of the present invention should be covered by the present invention.
Claims (10)
1. The utility model provides a device of oxalic acid ester hydrolysis preparation oxalic acid which characterized in that: comprises a proportioning tank (1), a pre-reaction kettle (2), a reaction rectifying tower (3), a methanol refining tower (4) and a crystallization kettle (6) which are connected with each other through pipelines.
2. The apparatus for preparing oxalic acid by hydrolyzing oxalic ester according to claim 1, wherein: one side of the upper part of the batching tank (1) is communicated with a water inlet and an oxalate inlet, a top inlet pipeline of the batching tank (1) is communicated with a top outlet of a crystallization kettle (6), a bottom outlet pipeline of the batching tank (1) is communicated with an inlet on one side of the upper part of a pre-reaction kettle (2), a bottom outlet of the pre-reaction kettle (2) is communicated with a pre-reaction material inlet of a reaction rectifying tower (3) through a first centrifugal pump (7), a bottom outlet of the reaction rectifying tower (3) is communicated with an inlet of a first cooler (5) through a second centrifugal pump (8), an outlet pipeline of the first cooler (5) is communicated with an inlet of the crystallization kettle (6), a top outlet pipeline of the reaction rectifying tower (3) is communicated with an inlet of a methanol refining tower (4), and a bottom outlet of the methanol refining tower (4) is communicated with a water inlet of the batching tank (1) through a pipeline; a second cooler (9) is arranged between one side and the top of the upper part of the reactive distillation column (3) in series, so that a condensation reflux loop is formed at the top of the tower kettle of the reactive distillation column (3); and a third cooler (10) is connected in series between one side of the upper part and the top of the methanol refining tower (4), so that a condensation reflux loop is formed at the top of the tower kettle of the methanol refining tower (4).
3. The apparatus for preparing oxalic acid by hydrolyzing oxalic ester according to claim 1, wherein: a reaction rectifying tower reboiler (31) is arranged between the bottom of the reaction rectifying tower (3) and one side of the lower part of the reaction rectifying tower in series, so that a reflux loop is formed at the bottom of a tower kettle of the reaction rectifying tower (3); a methanol refining tower reboiler (41) is arranged between the bottom of the methanol refining tower (4) and one side of the lower part of the methanol refining tower in series, so that a reflux loop is formed at the bottom of a tower kettle of the methanol refining tower (4).
4. The apparatus for preparing oxalic acid by hydrolyzing oxalic ester according to claim 1, wherein: a pre-reaction material inlet of the reactive distillation tower (3) is positioned at 1/4-1/2 of the height of the tower body; the inlet of the methanol refining tower (4) is located at 2/5-2/3 of the height of the tower body.
5. The apparatus for preparing oxalic acid by hydrolyzing oxalic ester according to claim 1, wherein: the reactive distillation tower (3) is of a combined structure of one or two of a plate tower and a packed tower, and the number of theoretical plates of the reactive distillation tower (3) is 25-50.
6. The apparatus for preparing oxalic acid by hydrolyzing oxalic ester according to claim 1, wherein: the methanol refining tower (4) is of a combined structure of one or two of a plate tower and a packed tower, and the number of theoretical plates of the methanol refining tower (4) is 20-32.
7. A method for preparing an apparatus for preparing oxalic acid by hydrolyzing oxalic ester according to any of claims 1 to 6, comprising the steps of:
step (1): introducing a mixture with a molar ratio of 4: 1-5: 1, water and the raw material oxalate to obtain a solution; uniformly mixing the solution and the oxalic acid mother liquor obtained in the step (6) to obtain a mixed solution; the raw material of the oxalate is one of dimethyl oxalate, monomethyl oxalate, diethyl oxalate or monoethyl oxalate; the molar ratio of water to oxalate in the mixed solution is 3: 1-6: 1;
step (2): introducing the mixed solution in the batching tank (1) into a pre-reaction kettle (2) for preliminary hydrolysis reaction, wherein the preliminary hydrolysis rate of the oxalate is 80-90%; obtaining a pre-reaction material, wherein the reaction temperature is 60-110 ℃, and the reaction time is 30-100 min;
pressurizing the pre-reaction material by a first centrifugal pump (7) and introducing the pre-reaction material into a reaction rectifying tower (3), and further hydrolyzing in the reaction rectifying tower (3) to obtain crude oxalic acid and alcohol, wherein the tower top temperature of the reaction rectifying tower (3) is 50 ~ 70 ℃, and the tower kettle temperature is 90 ~ 110 ℃;
step (4), introducing the crude alcohol product extracted from the top of the reaction rectifying tower (3) into a methanol refining tower (4) for rectification to obtain a methanol product and water, wherein the tower top temperature of the methanol refining tower (4) is 60 ~ 70 ℃, and the tower kettle temperature is 90 ~ 110 ℃;
step (5), pressurizing the oxalic acid solution extracted from the bottom of the reactive rectifying tower (3) by a second centrifugal pump (8) and cooling by a first cooler (5) in sequence to obtain a cooled oxalic acid solution, wherein the temperature of the cooled oxalic acid is 60 ~ 70 ℃;
and (6): introducing the cooled oxalic acid solution into a crystallization kettle (6) for cooling crystallization to obtain oxalic acid crystals and oxalic acid mother liquor, introducing the oxalic acid mother liquor into a proportioning tank (1), extracting the oxalic acid crystals and carrying out centrifugal drying; the crystallization temperature of the crystallization kettle is 20-40 ℃;
the oxalic acid product with the purity of more than or equal to 99.5 percent is obtained by the steps of (1) ~ and (6) the hydrolysis rate of the raw material oxalic ester is 99.5 percent, ~ 99.8.8 percent.
8. The method according to claim 7, wherein the device for preparing oxalic acid by hydrolyzing oxalic ester comprises: and (3) in the step (4), the condensing reflux ratio of the top of the methanol refining tower (4) passing through a third condenser (10) is 1.8-4.
9. The method for preparing a device for preparing oxalic acid by hydrolyzing oxalate according to claim 7, characterized in that the condensing reflux ratio of the top of the reactive distillation column (3) in the step (3) through the second condenser (9) is 2 ~ 4.
10. The method according to claim 7, wherein the device for preparing oxalic acid by hydrolyzing oxalic ester comprises: and (3) conveying the water at the bottom of the refined methanol refining tower (4) in the step (4) to a water inlet at one side of the upper part of the batching tank (1) through a pipeline.
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| CN111036158A (en) * | 2019-12-28 | 2020-04-21 | 邯郸市瑞田农药有限公司 | 2 chlorine-5 chloromethyl thiazole synthesis reaction system |
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