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CN-117843442-B - Continuous separation method of o-chlorotoluene chlorination catalyst

CN117843442BCN 117843442 BCN117843442 BCN 117843442BCN-117843442-B

Abstract

The invention discloses a continuous separation method of o-chlorotoluene chloride solution and a catalyst, which adopts a continuous freezing treatment and filtering method, firstly freezes the chloride solution until most of the catalyst is separated out, then filters the separated catalyst to remove the separated catalyst, and then carries out cyclic evaporation treatment on filtrate until the catalyst content in the concentrated solution is 5-10wt%, and the concentrated solution is mixed with the frozen chloride solution suspension after cooling and is filtered again. The invention adopts a continuous freezing and filtering method, and utilizes the property that the temperature obviously influences the solubility of the catalyst in the chloridizing solution to separate most of the catalyst from the chloridizing solution, and the filtrate is evaporated to remove the residual catalyst which is not frozen and separated out, so as to realize the continuous separation of the insoluble solid catalyst and the o-chlorotoluene chloridizing solution. The method not only avoids the defect that a large amount of wastewater containing metal salt is generated in the process of removing the catalyst in the chloridizing liquid by the traditional water washing and alkali washing method, but also realizes the recycling and reutilization of the catalyst.

Inventors

  • QIAO XU
  • CHEN XIAN
  • Cui Maifen
  • TANG JIHAI
  • ZHOU ZHE
  • XU XIHUA
  • QI MIN

Assignees

  • 南京工业大学
  • 江苏集萃化工科技创新研究院有限公司

Dates

Publication Date
20260512
Application Date
20231114

Claims (9)

  1. 1. A continuous separation method of o-chlorotoluene chloride solution and a catalyst is characterized in that a continuous freezing treatment and filtering method is adopted, the chloride solution is frozen until most of the catalyst is separated out, the separated catalyst is removed through filtering, the filtrate is circularly evaporated until the catalyst content in the concentrated solution is 5-10wt%, the concentrated solution is cooled and then mixed with a frozen chloride solution suspension for filtering again, wherein the chloride solution is prepared by using o-chlorotoluene as a raw material and inorganic chloride as a catalyst, and the o-chlorotoluene and chlorine react under the action of the catalyst at the temperature of 40-60 ℃, and the catalyst is aluminum chloride, ferric chloride or zinc chloride.
  2. 2. The method for continuously separating the o-chlorotoluene chlorination catalyst according to claim 1, comprising the following steps: Step (1), freezing, namely continuously feeding the chloridizing solution into a freezer for freezing treatment to obtain chloridizing solution suspension containing solid catalyst particles; filtering, namely introducing the chloride suspension into a first filter to filter, removing precipitated catalyst, allowing filtrate to enter a filtrate tank, switching the chloride suspension into a second filter connected with the first filter in parallel for filtering when the filter cake capacity reaches the design value of the first filter, simultaneously back flushing the first filter by adopting the filtrate in the filtrate tank, switching the chloride suspension into the first filter for filtering after regeneration when the filter cake capacity reaches the design value of the second filter, and back flushing the second filter by adopting the filtrate in the filtrate tank; and (3) concentrating, namely, the filtrate obtained in the step (2) enters an evaporation kettle, evaporation treatment is carried out under a vacuum state, the evaporated gas phase material enters a rectification separation system, the material in the evaporation kettle is reboiled by a reboiler and then returns to the evaporation kettle, the concentration is circularly carried out until the content of the catalyst in the concentrated solution in the evaporation kettle is 5-10wt%, and the concentrated solution is cooled and then mixed with the chloridized solution suspension obtained by freezing treatment, and the concentrated and separated catalyst is separated.
  3. 3. The method for continuously separating o-chlorotoluene chlorination catalyst according to claim 1 or 2, wherein the freezing treatment temperature is 5-8 ℃.
  4. 4. The method for continuously separating the o-chlorotoluene chlorination catalyst according to claim 1 or 2, wherein the filtering temperature is 5-8 ℃.
  5. 5. The method for continuously separating o-chlorotoluene chloride catalyst according to claim 2, wherein the first filter and the second filter are membrane filters with average pore diameters of 0.1-0.5 μm.
  6. 6. The method for continuously separating an o-chlorotoluene chlorination catalyst according to claim 2, wherein the pressure of the back flushing is not more than 0.2MPa.
  7. 7. The continuous separation method of the o-chlorotoluene chlorination catalyst of claim 2, wherein the back flushing liquid enters a back flushing liquid clarifying tank for natural sedimentation to separate a filter cake, supernatant liquid and chlorinated liquid to be treated are mixed for freezing treatment again, and the separated filter cake is returned to a catalyst preparation system for recycling.
  8. 8. The continuous separation method of the o-chlorotoluene chlorination catalyst according to claim 1 or 2, wherein the evaporation treatment temperature is 100-180 ℃ and the vacuum degree is 95-98 kPa.
  9. 9. The continuous separation method of the o-chlorotoluene chlorination catalyst according to claim 1 or 2, wherein the weight ratio of the concentrated solution to the chlorinated solution suspension is 1:5-1:10.

Description

Continuous separation method of o-chlorotoluene chlorination catalyst Technical Field The invention relates to a separation method, in particular to a continuous separation method of an o-chlorotoluene chlorination catalyst, and especially relates to a method for continuously separating the catalyst from a chlorination solution for producing dichlorotoluene by catalytic chlorination of o-chlorotoluene. Background Both 2, 3-dichlorotoluene and 2, 6-dichlorotoluene are important intermediates for preparing products such as bactericides, pesticides, herbicides, preservatives, dyes, pigments, photosensitive materials and the like. The dichlorotoluene is usually obtained by reacting o-chlorotoluene serving as a raw material with chlorine under the action of a Lewis acid catalyst. The chlorinated products contain 2, 3-dichlorotoluene, 2, 4-dichlorotoluene, 2, 5-dichlorotoluene, 2, 6-dichlorotoluene and 3, 4-dichlorotoluene. Common lewis acid catalysts are inorganic chlorides such as aluminum chloride, ferric chloride, zinc chloride, etc., which have a certain solubility in aromatic hydrocarbons. When the chlorination reaction is completed, the chlorinated aromatic hydrocarbon product is required to be separated by adopting a rectification technology, the inorganic chloride can generate precipitation in the rectification process to cause a tower blocking effect, so that the production cannot be normally performed, and the inorganic chloride has strong acidity and can corrode tower equipment. Therefore, inorganic chlorides need to be removed before product rectification can be performed. The method for removing chloride usually uses the principle that inorganic chloride has large solubility in water, adopts a method of washing with water and then washing with alkali to remove the chloride, and aims to reduce the consumption of alkali, ensure that the alkali-washed chloride solution is neutral or slightly alkaline, but has the main defects that a large amount of acidic sewage containing organic aluminum chloride is generated in the water washing process, and simultaneously, the aluminum chloride is easy to hydrolyze and is completely destroyed in the water washing process to become aluminum hydroxide, so that the aluminum chloride cannot be recycled, the waste of resources is caused, the production cost is increased, and huge environmental protection pressure and catalyst cost are caused for enterprises, so that process innovation is needed. Disclosure of Invention The invention aims to solve the environmental protection problem of a large amount of sewage generated in the separation process of the catalyst in the o-chlorotoluene chloridizing solution, and provides a continuous separation method of the o-chlorotoluene chloridizing catalyst, which adopts a continuous freezing filtration method, and utilizes the property that the temperature obviously influences the solubility of the catalyst in the chloridizing solution, most of the catalyst is separated from the chloridizing liquid, the filtrate after most of the catalyst is separated is evaporated to remove the residual catalyst which is not frozen and separated out, so that the continuous separation of the insoluble solid catalyst and the o-chlorotoluene chloridizing liquid is realized, and the separated catalyst is recycled. The invention aims at realizing the following technical scheme: A method for continuously separating o-chlorotoluene chloride solution from catalyst includes such steps as freezing chloride solution until most catalyst is separated out, filtering to remove the separated catalyst, cyclic evaporating until the catalyst content in concentrated solution is 5-10 wt%, cooling, mixing with the suspension of frozen chloride solution, and filtering again. In particular to a continuous separation method of an o-chlorotoluene chlorination catalyst, which comprises the following steps: Step (1), freezing, namely continuously feeding the chloridizing solution into a freezer for freezing treatment to obtain chloridizing solution suspension containing solid catalyst particles; filtering, namely introducing the chloride suspension into a first filter to filter, removing precipitated catalyst, allowing filtrate to enter a filtrate tank, switching the chloride suspension into a second filter connected with the first filter in parallel for filtering when the filter cake capacity reaches the design value of the first filter, simultaneously back flushing the first filter by adopting the filtrate in the filtrate tank, switching the chloride suspension into the first filter for filtering after regeneration when the filter cake capacity reaches the design value of the second filter, and back flushing the second filter by adopting the filtrate in the filtrate tank; And (3) concentrating, namely, the filtrate obtained in the step (2) enters an evaporation kettle, evaporation treatment is carried out under a vacuum state, the evaporated gas phase material enters a rect