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Method capable of recycling acids for preparing 2,5-dichloronitrobenzene (DCNB) through continuous nitration

A technology of dichloronitrobenzene and p-dichlorobenzene, which is applied in the field of continuous nitration to prepare 2,5-dichloronitrobenzene, can solve the problems that waste acid cannot be used mechanically, product quality and yield fluctuations, etc., and achieve large production capacity , stable product quality and yield, and the effect of reducing environmental pressure

Active Publication Date: 2015-05-27
JIANGSU YANGNONG CHEM GROUP +2
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0007] The present invention aims at the disadvantages of the existing process of preparing 2,5-DCNB by nitration of p-dichlorobenzene, which is produced in a batch manner, waste acid cannot be used mechanically, product quality and yield fluctuate, etc., and provides a process for preparing 2,5-DCNB by continuous nitration Scheme, the heat released during the reaction is removed through the heat exchange medium to ensure stable temperature control in the process, and at the same time realize the recycling of waste acid through a series of post-treatment procedures

Method used

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  • Method capable of recycling acids for preparing 2,5-dichloronitrobenzene (DCNB) through continuous nitration
  • Method capable of recycling acids for preparing 2,5-dichloronitrobenzene (DCNB) through continuous nitration
  • Method capable of recycling acids for preparing 2,5-dichloronitrobenzene (DCNB) through continuous nitration

Examples

Experimental program
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Effect test

Embodiment 1

[0022] Add 535.16g of 90% sulfuric acid to a 1000ml glass reactor, control the stirring speed, slowly add 288.18g of 98% nitric acid dropwise to prepare a mixed acid, and control the temperature during the dropping of nitric acid to ≤40°C. The weight ratio of sulfuric acid: nitric acid: water in the mixed acid is 58.5:34.3 : 7.2.

[0023] Continuous nitration uses three glass reactors with volumes of 1000ml, 500ml, and 500ml in series, and the effective volume of each kettle is 500ml, 248ml, and 248ml, totaling 996ml. During the process, the D.V.S value is controlled to be 3.5, the nitric acid ratio is 1.03, the temperature of the first-stage reactor is 56-60°C, the residence time is about 3h, the temperature of the second-stage reactor is 60-65°C, the residence time is about 1.5h, and the temperature of the third-stage reactor is 65-70°C The time is about 1.5h. Start feeding to the first-stage reactor, the feed rate of p-dichlorobenzene is 86.68ml / h, and the feed rate of mix...

Embodiment 2

[0028] In Example 1, 4 times of recovering 90% sulfuric acid were used mechanically, and a certain amount of 90% sulfuric acid was added to reach 624.36g, and 262.58g of 98% nitric acid was added dropwise to prepare a mixed acid in which the sulfuric acid: nitric acid: water weight ratio was 63.4:29.0:7.6. Control D.V.S value 4.0 in the process, nitric acid ratio 1.01, p-dichlorobenzene feed rate 80.55ml / h, mixed acid feed rate 85.45ml / h, other conditions are the same as embodiment 1, spent acid is applied mechanically 4 batches under this scheme. The experimental results are shown in Table 1.

Embodiment 3

[0030] In Example 2, 8 times of recovery of 90% sulfuric acid were applied mechanically, and a certain amount of 90% sulfuric acid was added to reach 716.34g, and 238.78g of 98% nitric acid was added dropwise to prepare a mixed acid in which the weight ratio of sulfuric acid: nitric acid: water was 67.5:24.5:8.0. Control D.V.S value 4.5 in the process, nitric acid ratio 1.00, p-dichlorobenzene feed rate 73.98ml / h, mixed acid feed rate 92.02ml / h, other conditions are the same as embodiment 1, waste acid is applied mechanically 4 batches under this scheme. The experimental results are shown in Table 1.

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Abstract

The invention relates to a production method for preparing 2,5-dichloronitrobenzene (DCNB) through continuous nitration, which particularly realizes the recycling of waste acids in the preparing process. The invention provides a technological program capable of recycling acids for preparing 2,5-dichloronitrobenzene (DCNB) through the continuous nitration, which is characterized in that sulfuric acid and nitric acid are prepared into a mixed acid, the mixed acid and paradichlorobenzene are simultaneously fed into a three-stages kettle (ring) type continuous reactor to carry out nitration reaction, a nitration reaction solution discharged form the third-stage kettle (ring) type continuous reactor is stood for layering so as to obtain a nitrifying oil layer and a nitrifying waste acid, and the nitrifying oil layer is subjected to alkali cleaning, water washing and light component removal so as to obtain a 2,5-DCNB finished product; paradichlorobenzene is added into the nitrifying waste acid to extract organic matters in the acid layer, residual HNO3 in the acid layer is consumed, after the extraction is completed, the obtained product is layered so as to obtain an extraction oil layer and an extracted residual waste acid, the extraction oil layer is used for next-batch nitrification, the extracted residual waste acid after being concentrated and nitric acid are prepared into the waste acid for next-batch nitrification, a small amount of emulsion layer is produced in the process of recycling, and the emulsion layer after being combined with the nitrifying oil layer is subjected to alkali cleaning and water washing.

Description

technical field [0001] The invention relates to a production process for preparing 2,5-dichloronitrobenzene through continuous nitration, especially to realize recovery and utilization of waste acid in the process. Background technique [0002] 2,5-Dichloronitrobenzene (2,5-DCNB for short) is mainly used to prepare 2,5-dichloroaniline, red-based 3GL, scarlet-based RC, etc. It is also a nitrogen fertilizer synergist, which has the effect of nitrogen fixation and fertilizer preservation . At present, the main process route of industrial production is to prepare 2,5-DCNB by using p-dichlorobenzene as raw material, preparing mixed acid nitration with nitric acid and concentrated sulfuric acid, alkali washing, water washing, and light removal. [0003] This method adopts the batch method to produce 2,5-DCNB, which has the disadvantages of large investment in production equipment, low production capacity, cumbersome procedures, and high operating intensity. Changing to continuous...

Claims

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Application Information

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IPC IPC(8): C07C205/12C07C201/08
Inventor 杨树斌徐林赵开荣沈杰王丹袁源赵洁缪荣荣
Owner JIANGSU YANGNONG CHEM GROUP
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