CN112851492A - Method for recovering benzoic acid from sodium benzoate-containing wastewater - Google Patents
Method for recovering benzoic acid from sodium benzoate-containing wastewater Download PDFInfo
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- CN112851492A CN112851492A CN202110228448.9A CN202110228448A CN112851492A CN 112851492 A CN112851492 A CN 112851492A CN 202110228448 A CN202110228448 A CN 202110228448A CN 112851492 A CN112851492 A CN 112851492A
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- sodium benzoate
- benzoic acid
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- WPYMKLBDIGXBTP-UHFFFAOYSA-N benzoic acid Chemical compound OC(=O)C1=CC=CC=C1 WPYMKLBDIGXBTP-UHFFFAOYSA-N 0.000 title claims abstract description 92
- 239000005711 Benzoic acid Substances 0.000 title claims abstract description 46
- 235000010233 benzoic acid Nutrition 0.000 title claims abstract description 46
- 239000002351 wastewater Substances 0.000 title claims abstract description 37
- 238000000034 method Methods 0.000 title claims abstract description 35
- WXMKPNITSTVMEF-UHFFFAOYSA-M sodium benzoate Chemical compound [Na+].[O-]C(=O)C1=CC=CC=C1 WXMKPNITSTVMEF-UHFFFAOYSA-M 0.000 title claims abstract description 35
- 235000010234 sodium benzoate Nutrition 0.000 title claims abstract description 35
- 239000004299 sodium benzoate Substances 0.000 title claims abstract description 35
- 239000013078 crystal Substances 0.000 claims abstract description 27
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims abstract description 19
- 238000002425 crystallisation Methods 0.000 claims abstract description 18
- 230000008025 crystallization Effects 0.000 claims abstract description 18
- 238000001816 cooling Methods 0.000 claims abstract description 14
- 239000002002 slurry Substances 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 9
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 claims abstract description 8
- 238000001914 filtration Methods 0.000 claims abstract description 7
- 239000007787 solid Substances 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 6
- 238000001291 vacuum drying Methods 0.000 claims abstract description 6
- 239000011780 sodium chloride Substances 0.000 claims abstract description 4
- 238000001704 evaporation Methods 0.000 claims description 14
- 230000008020 evaporation Effects 0.000 claims description 12
- 238000004064 recycling Methods 0.000 claims description 9
- 238000006243 chemical reaction Methods 0.000 claims description 8
- 238000007599 discharging Methods 0.000 claims description 6
- 239000000047 product Substances 0.000 abstract description 21
- 238000011084 recovery Methods 0.000 abstract 2
- 239000000155 melt Substances 0.000 abstract 1
- 238000004321 preservation Methods 0.000 abstract 1
- 150000003839 salts Chemical class 0.000 abstract 1
- 239000012265 solid product Substances 0.000 abstract 1
- 239000002245 particle Substances 0.000 description 9
- 238000012512 characterization method Methods 0.000 description 4
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000005265 energy consumption Methods 0.000 description 3
- 239000012065 filter cake Substances 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 238000002844 melting Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 2
- 235000013305 food Nutrition 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- XNGIFLGASWRNHJ-UHFFFAOYSA-N phthalic acid Chemical compound OC(=O)C1=CC=CC=C1C(O)=O XNGIFLGASWRNHJ-UHFFFAOYSA-N 0.000 description 2
- 230000010287 polarization Effects 0.000 description 2
- 238000000926 separation method Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 238000005903 acid hydrolysis reaction Methods 0.000 description 1
- 230000000844 anti-bacterial effect Effects 0.000 description 1
- 150000004945 aromatic hydrocarbons Chemical class 0.000 description 1
- 230000003385 bacteriostatic effect Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000002537 cosmetic Substances 0.000 description 1
- 239000003722 gum benzoin Substances 0.000 description 1
- 238000002329 infrared spectrum Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 230000009965 odorless effect Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000003755 preservative agent Substances 0.000 description 1
- 230000002335 preservative effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 159000000000 sodium salts Chemical class 0.000 description 1
- 239000000606 toothpaste Substances 0.000 description 1
- 229940034610 toothpaste Drugs 0.000 description 1
- 230000001988 toxicity Effects 0.000 description 1
- 231100000419 toxicity Toxicity 0.000 description 1
- 239000002699 waste material Substances 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- 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
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/02—Treatment of water, waste water, or sewage by heating
- C02F1/04—Treatment of water, waste water, or sewage by heating by distillation or evaporation
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C51/00—Preparation of carboxylic acids or their salts, halides or anhydrides
- C07C51/02—Preparation of carboxylic acids or their salts, halides or anhydrides from salts of carboxylic acids
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Crystallography & Structural Chemistry (AREA)
- Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
Abstract
The invention provides a method for recovering benzoic acid from sodium benzoate-containing wastewater, which comprises the following steps: continuously adding a certain volume of filtered wastewater into an evaporative crystallizer, heating the wastewater under a certain negative pressure, and carrying out evaporative crystallization at a certain stirring rate; preserving heat, filtering and separating sodium chloride to obtain a sodium benzoate concentrated solution; and simultaneously, continuously adding a hydrochloric acid solution at a certain feeding rate, cooling to obtain a crystal slurry containing benzoic acid, and carrying out heat preservation, filtration and vacuum drying on the discharged crystal slurry to obtain a benzoic acid solid product. The method for recovering the benzoic acid from the sodium benzoate-containing wastewater provided by the invention separates and purifies the sodium chloride in the wastewater to form industrial salt and obtain benzoic acid solid, so that the engineering target is achieved, the recovery rate is high, the batch difference of product quality is eliminated, and the obtained benzoic acid has high purity, large granularity and good fluidity. Compared with the melt crystallization process, the invention also has the advantages of simple operation, low temperature, less pollution and high recovery rate.
Description
The technical field is as follows:
the invention relates to the field of wastewater treatment, in particular to a method for recovering benzoic acid from wastewater containing sodium benzoate.
Background art:
benzoic acid (C)6H5COOH), english name: benzoic acid, originally made from benzoin gum, is also known as Benzoic acid, sodium benzoate as its sodium salt (C)6H5COONa). Benzoic acid melting point 122.13 deg.C, relative density (15/4 deg.C.) 1.2659. The appearance is white needle-like or scaly crystal. Benzoic acid and sodium benzoate have bactericidal and bacteriostatic effects and are low in toxicity and odorless, and thus they are widely used in pharmaceutical manufacturing; it is widely used as preservative in food industry, pharmaceutical, cosmetic, toothpaste, etc. The purity, particle size, etc. of industrial benzoic acid vary from application to application, and especially the purity of food grade benzoic acid is increasingly required. Common methods for producing benzoic acid in the reported patents include a toluene oxidation method, a phthalic acid hydrolysis method, a rectification-melting combined crystallization, and the like, depending on the field of application.
In the above-mentioned preparation method, there has been an improvement in the technique for obtaining crude benzoic acid, but there has been reported a method for treating impurities in the production process accompanied by mixing of poorly soluble and soluble impurities. The invention aims to provide a method for purifying benzoic acid, which aims at solving the problem that the purification process of the benzoic acid containing sodium benzoate impurities still has low purity. The method has the advantages of achieving good separation effect by using very low energy consumption. The method provided by the invention is simple to operate, and the obtained benzoic acid has large particle size and good fluidity. The method basically achieves the standard of zero discharge of wastewater, and the obtained benzoic acid product has high purity and can meet the production requirements of various fields.
The invention content is as follows:
in view of the above problems, the present invention aims to provide a method for recycling wastewater containing sodium benzoate, which is simple and convenient to operate and can obtain a high-purity and high-yield benzoic acid product.
The technical scheme of the invention is as follows:
a method for recovering benzoic acid from sodium benzoate-containing wastewater comprises the following steps:
(1) continuously placing the wastewater containing sodium benzoate in an evaporation crystallizer, and heating the wastewater to an evaporation temperature;
(2) filtering and separating sodium chloride at a constant temperature to obtain a sodium benzoate concentrated solution, continuously adding a hydrochloric acid solution at a certain feeding rate, reacting and crystallizing to obtain a concentrated solution of benzoic acid, and discharging crystal mush in evaporative crystallization at a certain rate;
(3) cooling, crystallizing and vacuum drying the discharged crystal slurry to obtain a benzoic acid crystal product;
further, in the reduced pressure evaporation process in the step (1), the reduced pressure evaporation temperature is controlled to be 75-80 ℃; the feeding speed of continuously adding the wastewater containing sodium benzoate into the evaporative crystallization is 80 ml/h-200 ml/h.
Further, the concentration of the hydrochloric acid in the step (2) is 5.6-6.6mol/l, the reaction crystallization temperature is controlled at 80 ℃, the feeding rate of the hydrochloric acid is 50-160 ml/h, and the solid content of the crystal mush is kept at 20-30%.
Further, the discharge rate of the crystal mush in the step (3) is 110-400 ml/h; and finally, the stirring speed in the cooling crystallization process is 250-400 rpm, and the temperature is controlled to be 10-15 ℃.
The invention has the advantages and beneficial effects that:
(1) the invention has low energy consumption in the evaporation process and can obtain good separation effect under the condition of low cost.
(2) The invention can react with sodium benzoate by adding hydrochloric acid, thereby not only achieving the comprehensive utilization of waste water, but also obtaining high-purity benzoic acid.
(3) The method for recovering the benzoic acid from the sodium benzoate-containing wastewater provided by the invention is simple and convenient to operate and high in yield, solves the problem of discharge of the sodium benzoate waste liquid, produces a product with large granularity and good fluidity after reaching balance, and eliminates the batch difference of product quality; compared with the traditional melting crystallization process, the invention also has the advantages of low temperature, low energy consumption and less pollution in the crystallization process.
Description of the drawings:
FIG. 1 XRD spectra of benzoic acid products obtained from examples 1-3 and a control;
FIG. 2 is a graph of the solid infrared characterization of the benzoic acid product obtained from example 3;
FIG. 3 polarization microscope characterization of the benzoic acid product obtained from example 3;
FIG. 4 is an off-line particle size characterization plot of the benzoic acid product obtained from example 3.
The specific implementation mode is as follows:
the present invention is further illustrated by the following specific examples, which are intended to be illustrative, not limiting and are not intended to limit the scope of the invention.
Example 1
1) Continuously adding wastewater containing sodium benzoate into an evaporative crystallizer at a feeding rate of 90ml/h, wherein the sodium benzoate accounts for 33.47% of the total mass of the solution, the benzoic acid accounts for 0.4% of the total mass of the solution, starting stirring, and heating the crystallizer to enable the temperature of the crystallizer to reach 79 ℃;
2) when the temperature of the wastewater reaches the evaporation temperature, adjusting a vacuum pump to maintain the absolute vacuum degree in the crystallizer at 400mbar, and evaporating the wastewater to ensure that the solid content of the crystal mush is 20-30%;
3) adding 6.0mol/l of dilute hydrochloric acid solution into a crystallizer at a feeding rate of 90ml/h, and controlling the reaction crystallization temperature to be 80 ℃; discharging crystal slurry at 110ml/h after reaction, uniformly cooling at a stirring speed of 300rpm and a cooling speed of 7 ℃/h, cooling to 10 ℃, and standing for 1h at constant temperature;
4) and filtering the crystal slurry, and drying a filter cake in a vacuum drying oven at 60 ℃ to obtain a crystal product with the average particle size of 492.879 mu m.
Example 2
1) Continuously adding wastewater containing sodium benzoate into an evaporative crystallizer at a feeding rate of 100ml/h, wherein the sodium benzoate accounts for 30.50% of the total mass of the solution, and the benzoic acid accounts for 1.5% of the total mass of the solution, starting stirring, and heating the crystallizer to enable the temperature of the crystallizer to reach 80 ℃;
2) when the temperature of the wastewater reaches the evaporation temperature, adjusting a vacuum pump to maintain the absolute vacuum degree in the crystallizer to be 350mbar, and enabling the solid content of the crystal mush to be 20% -30% after the wastewater is evaporated;
3) adding 6.5mol/l of dilute hydrochloric acid solution into a crystallizer at a feeding rate of 100ml/h, and controlling the reaction crystallization temperature to be 80 ℃; discharging crystal slurry at a rate of 130ml/h after reaction, uniformly cooling at a stirring speed of 260rpm and a cooling speed of 7 ℃/h, cooling to 10 ℃, and standing at constant temperature for 1 h;
4) and filtering the crystal slurry, and drying a filter cake in a vacuum drying oven at 60 ℃ to obtain a crystal product with the average particle size of 500.879 mu m.
Example 3
1) Continuously adding wastewater containing sodium benzoate into an evaporative crystallizer at a feeding rate of 80ml/h, wherein the sodium benzoate accounts for 25.33% of the total mass of the solution, and the benzoic acid accounts for 0.5% of the total mass of the solution, starting stirring, and heating the crystallizer to enable the temperature of the crystallizer to reach 81 ℃;
2) when the temperature of the wastewater reaches the evaporation temperature, adjusting a vacuum pump to maintain the absolute vacuum degree in the crystallizer at 410mbar, and evaporating the wastewater to ensure that the solid content of the crystal mush is 20-30%;
3) adding 7.0mol/l of dilute hydrochloric acid solution into a crystallizer at a feeding rate of 80ml/h, and controlling the reaction crystallization temperature to be 80 ℃; discharging crystal slurry at 120ml/h after reaction, uniformly cooling at a stirring speed of 300rpm and a cooling speed of 7 ℃/h, cooling to 10 ℃, and standing at constant temperature for 1 h;
4) and filtering the crystal slurry, and drying a filter cake in a vacuum drying oven at 60 ℃ to obtain a crystal product with the average particle size of 498.879 mu m.
And (3) effect testing:
as shown in fig. 1, XRD spectrograms of the benzoic acid products and the standard products obtained in examples 1 to 3 show that the XRD spectrograms of the three products and the standard substance (benzoic acid with purity of 99.99% or more) used as a reference have the same main peak position, and are consistent with the main characteristic peak position of the XRD spectrogram of benzoic acid reported in the literature, which indicates that the crystalline products obtained by the present invention are all high-purity benzoic acid.
As shown in FIG. 2, the crystal infrared spectrum of the benzoic acid product obtained in example 3, in which 705cm is present in the fingerprint region-1And 662cm-1Is a characteristic absorption peak of the deformation vibration of the monosubstituted benzene C-H; in the radical frequency region, at 1760cm-1The peak of C ═ O stretching vibration appears at 1638cm-1The peak is C ═ C skeleton stretching vibration peak at 3010cm-1The peak of C-H stretching vibration of aromatic hydrocarbon is in the range of 3400-2400 cm-1The O-H stretching vibration peak of the acid is consistent with the characteristic peak position of the benzoic acid in the literature report.
As shown in FIG. 3, the polarization microscope characterization chart of the benzoic acid product obtained in example 3 shows that the product is in the form of plate-like crystals.
As shown in FIG. 4, the particle size distribution of the benzoic acid product obtained in example 3 is characterized by a normal distribution, a single peak state, and a mean particle size of 500.02 μm with a coefficient of variation of 0.28, indicating that the degree of crystallization is more complete and the degree of crystallization is high, and the obtained sample is a crystalline substance with large and uniform particle size.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept, and these changes and modifications are all within the scope of the present invention.
Claims (9)
1. A method for recovering benzoic acid from sodium benzoate-containing wastewater is characterized in that: the method comprises the following steps:
(1) continuously placing the wastewater containing sodium benzoate in an evaporation crystallizer, and heating the wastewater to an evaporation temperature;
(2) filtering and separating sodium chloride at a constant temperature to obtain a sodium benzoate concentrated solution, continuously adding a hydrochloric acid solution at a certain feeding rate, reacting and crystallizing to obtain a concentrated solution of benzoic acid, and discharging crystal mush in evaporative crystallization at a certain rate;
(3) and cooling, crystallizing and vacuum drying the discharged crystal slurry to obtain a benzoic acid crystal product.
2. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: in the reduced pressure evaporation process in the step (2), the reduced pressure evaporation temperature is controlled to be 75-80 ℃.
3. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the feeding speed of continuously adding the wastewater containing sodium benzoate into the evaporative crystallization is 80 ml/h-200 ml/h.
4. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the concentration of the hydrochloric acid is 5.6-6.6 mol/l.
5. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the reaction crystallization temperature was controlled at 80 ℃.
6. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the feeding speed of the hydrochloric acid is 50 ml/h-160 ml/h.
7. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the solid content of the crystal mush is kept to be 20-30 percent.
8. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the discharging speed of the crystal mush in the step (3) is 110-400 ml/h.
9. The method for recycling sodium benzoate-containing wastewater according to claim 1, which is characterized in that: the stirring speed in the cooling crystallization process is 250-400 rpm, and the temperature is controlled at 10-15 ℃.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202110228448.9A CN112851492A (en) | 2021-03-02 | 2021-03-02 | Method for recovering benzoic acid from sodium benzoate-containing wastewater |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202110228448.9A CN112851492A (en) | 2021-03-02 | 2021-03-02 | Method for recovering benzoic acid from sodium benzoate-containing wastewater |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114105754A (en) * | 2021-12-02 | 2022-03-01 | 湖北科林博伦新材料有限公司 | Organic sodium salt treatment process and device in toluene oxidation process |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101152969A (en) * | 2006-09-29 | 2008-04-02 | 中国石油化工股份有限公司 | Method of processing p-benzene dicarboxylic acid production wastewater |
| CN111689537A (en) * | 2020-05-18 | 2020-09-22 | 南京工业大学 | Method for treating sodium benzoate or halogenated sodium benzoate wastewater |
| CN111909018A (en) * | 2019-05-09 | 2020-11-10 | 聊城隆盛化工有限公司 | Process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater |
-
2021
- 2021-03-02 CN CN202110228448.9A patent/CN112851492A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101152969A (en) * | 2006-09-29 | 2008-04-02 | 中国石油化工股份有限公司 | Method of processing p-benzene dicarboxylic acid production wastewater |
| CN111909018A (en) * | 2019-05-09 | 2020-11-10 | 聊城隆盛化工有限公司 | Process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater |
| CN111689537A (en) * | 2020-05-18 | 2020-09-22 | 南京工业大学 | Method for treating sodium benzoate or halogenated sodium benzoate wastewater |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114105754A (en) * | 2021-12-02 | 2022-03-01 | 湖北科林博伦新材料有限公司 | Organic sodium salt treatment process and device in toluene oxidation process |
| CN114105754B (en) * | 2021-12-02 | 2024-02-27 | 湖北科林博伦新材料有限公司 | Organic sodium salt treatment process and device in toluene oxidation process |
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Application publication date: 20210528 |