CN108997124B - Method for recovering nitrobenzene from nitrobenzene tar - Google Patents
Method for recovering nitrobenzene from nitrobenzene tar Download PDFInfo
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- CN108997124B CN108997124B CN201710419323.8A CN201710419323A CN108997124B CN 108997124 B CN108997124 B CN 108997124B CN 201710419323 A CN201710419323 A CN 201710419323A CN 108997124 B CN108997124 B CN 108997124B
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- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
- C07C201/06—Preparation of nitro compounds
- C07C201/16—Separation; Purification; Stabilisation; Use of additives
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Abstract
The invention discloses a method for recovering nitrobenzene from nitrobenzene tar. The method adopts alkali washing, water washing and adsorption separation to reduce the content of nitrophenol and sodium salt thereof in the nitrobenzene tar to below 10mg/kg, and then carries out rectification to recover nitrobenzene. The invention has the characteristics of mature treatment technology, safety, reliability and high nitrobenzene recovery rate, and has good economic benefit and social benefit.
Description
Technical Field
The invention relates to a method for recycling nitrobenzene tar, in particular to a method for reducing the content of nitrophenol and phenate thereof by alkali washing, water washing and adsorption separation and then recycling nitrobenzene from the nitrobenzene tar.
Background
Nitrobenzene is an important chemical raw material and intermediate, is mainly used for producing aniline and dye, and is also used in industries such as various medicines, pesticides and dye intermediates.
At present, the industrial nitrobenzene production process mainly comprises unit processes of benzene nitration, neutralization washing, rectification and the like, in the nitrobenzene rectification process, impurities (mainly nitrophenol and phenolate thereof) generated by nitration side reaction have high explosion risk and are easily accumulated on heated parts such as a rectification tower kettle, a reboiler and the like, and measures such as regularly cleaning the reboiler and extracting residual liquid in the rectification tower kettle and the like are adopted in the production to improve the safety of the refining process.
The residual liquid in the rectifying tower is commonly called tar, wherein the content of nitrobenzene in the tar is 70-95%, the content of dinitrogen is 3-25%, and the content of polynitrogen, nitrophenol and phenate thereof is about 1-5%. Because the cumulative content of the nitrophenol in the tar is high, the nitrobenzene is directly distilled and extracted, so that the safety risk exists, and the nitrobenzene tar is generally taken as solid waste and sent out to a solid waste treatment enterprise for treatment.
Patent CN201510307834.1 proposes a method for reducing the content of sodium salt in crude nitrobenzene, after nitration reaction, washing acid nitrobenzene which is a nitration product of mixed acid with water to remove part of waste acid, then neutralizing the acid nitrobenzene with sodium hydroxide, recycling part of alkali liquor in the neutralization process, improving the water-oil ratio in the alkali washing process, and improving the alkali washing effect; and then washing the crude nitrobenzene subjected to alkali washing, wherein in the washing process, part of wastewater is recycled, the water-oil ratio in the washing process is improved, the washing effect is improved, and sodium salt in the crude nitrobenzene is dissolved into a water phase, so that the aims of reducing the content of sodium salt in the crude nitrobenzene, reducing alkali consumption and improving system safety are fulfilled.
Patent CN201210330413.7 proposes a nitrobenzene washing and separating system. After the nitration reaction is finished, the nitration product and the waste acid enter a nitration separator for separation, the separated organic phase enters a neutralization washer and a water washing washer for alkali washing and water washing, the obtained organic phase enters a coalescence separator for further removing sodium salt and phenolate in the organic phase, and then the subsequent treatment is carried out. The coalescence separator mainly adopts a static separator such as a fiber filter element separator, a plate separator or a combined separator.
The above patents all mention the method of reducing the content of phenate and sodium salt in crude nitrobenzene, but only the treatment of crude nitrobenzene is limited, and the method of recycling nitrobenzene tar is not involved, and the phenate and sodium salt have high accumulated content in nitrobenzene tar, and high boiling substances such as dinitro and the like are much, so that the phenate and sodium salt cannot be recycled according to the treatment process of crude nitrobenzene.
Disclosure of Invention
Aiming at the characteristics that the content of nitrophenol and phenolate in the prior nitrobenzene tar is high, potential safety hazard exists for rectifying and recovering nitrobenzene in the nitrobenzene tar, and resource waste exists when the nitrobenzene tar is directly treated as solid waste, the invention adopts a neutralization method to neutralize the nitrophenol in the tar and alkali to generate nitrophenolate, and the nitrophenol sodium salt is easily dissolved in water and is removed in the water phase by washing, thereby reducing the content of the nitrophenol and the phenolate in the tar and realizing the purpose of safely recovering the nitrobenzene in the nitrobenzene tar.
Aims to provide a method for reducing the content of nitrophenol and phenate in nitrobenzene tar and then realizing the recovery of nitrobenzene.
The technical scheme adopted by the invention is as follows: the process of recovering nitrobenzene from nitrobenzene tar includes the steps of alkali washing, water washing and adsorption separation of nitrobenzene tar to lower the content of nitrophenol and sodium salt in nitrobenzene tar to below 10mg/kg, and rectifying to recover nitrobenzene. Wherein, the adsorption separation adopts the mixing of a hydrophilic adsorbent and the oil phase after water washing, thereby improving the removal rate of the nitrophenol and the sodium salt thereof.
The hydrophilic adsorbent is silica gel adsorbent or synthetic zeolite molecular sieve adsorbent.
The alkaline washing process adopts NaOH solution with the mass content of 0.001% -30%.
In the alkali washing and water washing processes, the nitrobenzene tar, the alkali liquor and the water are mixed by adopting a kettle type stirring or static mixer.
The alkaline washing temperature is 10-80 ℃.
The water washing temperature is 10-80 ℃.
The rectification may be operated batchwise or continuously.
Compared with the prior art, the invention has the characteristics that: (1) the content of nitrophenol and sodium salt thereof in the treated nitrobenzene tar is reduced to below 10mg/kg, and the nitrobenzene in the tar can be safely and stably refined and extracted; (2) the recovery process is simple and strong in operability; (3) the recovery rate of nitrobenzene reaches more than 95 percent.
Detailed Description
The following examples further illustrate the essential features and the significant effects of the present invention, but do not limit the contents of the present invention.
Example 1
Mixing and alkaline washing nitrobenzene tar and 0.05 percent NaOH solution according to the volume ratio of 1:1 by a static mixer, wherein the alkaline washing temperature is 20 ℃, performing oil-water separation after alkaline washing, separating out a water phase and an oil phase, mixing and washing the oil phase and the water according to the volume ratio of 1:1 by the static mixer, performing oil-water separation after water washing, separating out the water phase and the oil phase, and allowing the oil phase to pass through the static mixer with the specific surface area of 600m2The spherical silica gel adsorbent adsorbs and removes trace moisture, and the oil phase after adsorption and separation is subjected to batch rectification to recover nitrobenzene.
After adsorption and separation, the content of nitrophenol and sodium salt thereof in the oil phase is 9.3mg/kg, and the recovery rate of nitrobenzene is 95.5 percent.
Example 2
Mixing and alkali washing nitrobenzene tar and 1% NaOH solution according to the volume ratio of 1:1 by a static mixer, carrying out oil-water separation after the alkali washing at the temperature of 80 ℃, separating out a water phase and an oil phase, mixing and washing the oil phase and the water by the static mixer according to the volume ratio of 1:1, carrying out oil-water separation after the water washing at the temperature of 80 ℃, separating out the water phase and the oil phase, adsorbing and removing trace water from the oil phase by a mesoporous zeolite molecular sieve adsorbent, and carrying out batch rectification on the oil phase after the adsorption and separation to recover nitrobenzene.
After adsorption and separation, the content of nitrophenol and sodium salt thereof in the oil phase is 5.1mg/kg, and the recovery rate of nitrobenzene is 97.2 percent.
Example 3
Stirring and mixing alkaline washing nitrobenzene tar and 10% NaOH solution in a kettle manner according to the volume ratio of 10:1, wherein the alkaline washing temperature is 65 ℃, carrying out oil-water separation after alkaline washing, separating out a water phase and an oil phase, stirring and mixing the oil phase and the water in a kettle manner according to the volume ratio of 1:1, washing with water at the temperature of 65 ℃, carrying out oil-water separation after washing with water, separating out the water phase and the oil phase, and allowing the oil phase to pass through the water phase with the specific surface area of 600m2The spherical silica gel adsorbent absorbs and removes trace moisture, and the oil phase after absorption and separation is continuously rectified to recover nitrobenzene.
After adsorption and separation, the content of nitrophenol and sodium salt thereof in the oil phase is 7.7mg/kg, and the recovery rate of nitrobenzene is 96.3 percent.
Example 4
Mixing alkaline washing nitrobenzene tar and 0.1% NaOH solution in a kettle type stirring manner according to the volume ratio of 2:1, wherein the alkaline washing temperature is 80 ℃, carrying out oil-water separation after alkaline washing, separating out a water phase and an oil phase, carrying out oil-water separation after oil phase and water are mixed and washed in a kettle type stirring manner according to the volume ratio of 1:1, wherein the water washing temperature is 50 ℃, carrying out oil-water separation after water washing, separating out the water phase and the oil phase, adsorbing and removing trace moisture from the oil phase through a mesoporous zeolite molecular sieve adsorbent, and carrying out batch rectification on the oil phase after adsorption and separation to recover nitrobenzene.
After adsorption and separation, the content of nitrophenol and sodium salt thereof in the oil phase is 7.8mg/kg, and the recovery rate of nitrobenzene is 97.0 percent.
Example 5
Mixing and alkali washing nitrobenzene tar and 1% NaOH solution according to the volume ratio of 5:1 by a static mixer, wherein the alkali washing temperature is 30 ℃, performing oil-water separation after the alkali washing, separating out a water phase and an oil phase, mixing and water washing the oil phase and the water according to the volume ratio of 1:1 by the static mixer, performing oil-water separation after the water washing temperature is 30 ℃, separating out the water phase and the oil phase, and allowing the oil phase to pass through the static mixer with the specific surface area of 600m2The spherical silica gel adsorbent adsorbs and removes trace moisture, and the oil phase after adsorption and separation is subjected to batch rectification to recover nitrobenzene.
After adsorption and separation, the content of nitrophenol and sodium salt thereof in the oil phase is 4.5mg/kg, and the recovery rate of nitrobenzene is 98.5 percent.
Claims (7)
1. A method for recovering nitrobenzene from nitrobenzene tar is characterized in that the method comprises the steps of respectively carrying out alkali washing, water washing and adsorption separation on the nitrobenzene tar to reduce the content of nitrophenol and sodium salt thereof in the nitrobenzene tar to below 10mg/kg, then carrying out rectification to recover nitrobenzene, wherein hydrophilic adsorbent is adopted for adsorption separation and mixed with oil phase after water washing, so that the removal rate of the nitrophenol and the sodium salt thereof is improved.
2. The method of claim 1, wherein the hydrophilic adsorbent is silica gel adsorbent or synthetic zeolite molecular sieve adsorbent.
3. The method for recovering nitrobenzene from nitrobenzene tar according to claim 1, wherein the caustic wash process employs NaOH solution in an amount of 0.001% to 30% by mass.
4. The method for recovering nitrobenzene from nitrobenzene tar according to claim 1, wherein the nitrobenzene tar is mixed with the alkali liquor and water in the alkali wash and water wash process using a tank stirrer or static mixer.
5. The method for recovering nitrobenzene from nitrobenzene tar according to claim 1, wherein the caustic wash temperature is 10 to 80 ℃.
6. The method for recovering nitrobenzene from nitrobenzene tar according to claim 1, wherein the washing temperature is 10 to 80 ℃.
7. The method of claim 1, wherein said distillation is a batch or continuous operation.
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102020567A (en) * | 2009-09-11 | 2011-04-20 | 上海安赐机械设备有限公司 | Method and device for refining coarse nitrobenzene |
| CN102212025A (en) * | 2011-04-11 | 2011-10-12 | 中国石油化工股份有限公司 | Method for improving rectification yield of nitrated product |
| CN203222565U (en) * | 2013-04-26 | 2013-10-02 | 沧州丰源环保科技有限公司 | Nitrobenzene rectification residue recycling system |
| CN103664629A (en) * | 2012-09-10 | 2014-03-26 | 中国石油化工股份有限公司 | Nitrobenzene washing and separating system |
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- 2017-06-06 CN CN201710419323.8A patent/CN108997124B/en active Active
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102020567A (en) * | 2009-09-11 | 2011-04-20 | 上海安赐机械设备有限公司 | Method and device for refining coarse nitrobenzene |
| CN102212025A (en) * | 2011-04-11 | 2011-10-12 | 中国石油化工股份有限公司 | Method for improving rectification yield of nitrated product |
| CN103664629A (en) * | 2012-09-10 | 2014-03-26 | 中国石油化工股份有限公司 | Nitrobenzene washing and separating system |
| CN203222565U (en) * | 2013-04-26 | 2013-10-02 | 沧州丰源环保科技有限公司 | Nitrobenzene rectification residue recycling system |
Non-Patent Citations (3)
| Title |
|---|
| 硝基苯生产的安全技术分析;徐益;《化学工业与工程技术》;20020530;第23卷(第2期);第45-48页 * |
| 硝基苯精制再沸器爆炸事故的探讨;李卫明;《化学工业与工程技术》;20070828;第28卷(第4期);第55页1.2.1和第57页3.2.2 * |
| 苯硝化生产硝基苯工艺危险性分析及爆炸事故热安全研究;王犇;《中国博士学位论文全文数据库 工程科技I辑》;20120715(第7期);第B026-5页 * |
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Address after: Liuhe District of Nanjing City, Jiangsu province 210048 geguan Road No. 699 Patentee after: China Petroleum & Chemical Corp. Patentee after: SINOPEC NANJING CHEMICAL RESEARCH INSTITUTE Co.,Ltd. Address before: Liuhe District of Nanjing City, Jiangsu province 210048 geguan Road No. 699 Patentee before: China Petroleum & Chemical Corp. Patentee before: Nanhua Group Research Institute |