CN111909018A - Process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater - Google Patents

Abstract

The invention relates to the technical field of p-chlorobenzaldehyde production, in particular to a process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from sodium p-chlorobenzoate wastewater, which comprises the following steps: (1) and (3) extraction: temporarily storing the p-chlorobenzoic sodium formate wastewater in a storage tank, calculating the required dichloromethane according to the capacity of the storage tank, adding dichloromethane, starting a pump to circulate, standing for two hours, then beginning to divide the wastewater into an upper layer and a lower layer, and removing dichloromethane and p-chlorobenzaldehyde from the lower layer in a distillation kettle; (2) and (3) oxidation: heating the upper layer aqueous solution in the step (1) with sodium hydroxide to 125 ℃, stirring, precipitating to obtain upper layer clear liquid and lower layer precipitate, and performing suction filtration on the lower layer precipitate to obtain sodium chloride; the supernatant in the step (2) is sent to an acidification kettle and is dripped with hydrochloric acid, and the dripping of hydrochloric acid is divided into three stages; (4) centrifuging (5) and drying. The technical scheme provided by the invention has the beneficial effects that: the process route is simple and reliable, and no dangerous process is available; low cost, and can realize the continuity and industrialization of sewage treatment.

Description

Process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater

Technical Field

The invention relates to the technical field of p-chlorobenzaldehyde production, in particular to a process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from sodium p-chlorobenzoate wastewater.

Background

The method has the defects that the investment is too much, 1 cubic unit of exchange resin needs about 5 to 6 ten thousand yuan of RMB, the annual capacity of 1500 tons of people is like that the method needs about 10 to 15 cubic units, the method is easy to saturate, methanol is needed for resolution and then is steamed after the saturation, the process is complex, the methanol has the dangerous characteristics of flammability and explosiveness, and new pollutants can be generated in the evaporation process. So that it is not easy to be used in industrialization.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from sodium p-chlorobenzoate wastewater, which has low cost and can realize sewage treatment continuity and industrialization.

The technical scheme of the invention is as follows:

a process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater comprises the following specific steps:

(1) and (3) extraction: temporarily storing the p-chlorobenzoic sodium formate wastewater in a storage tank, calculating the required dichloromethane according to the capacity of the storage tank, adding dichloromethane, starting a pump to circulate, standing for two hours, then beginning to divide the wastewater into an upper layer and a lower layer, and removing dichloromethane and p-chlorobenzaldehyde from the lower layer in a distillation kettle;

(2) and (3) oxidation: heating the upper layer aqueous solution in the step (1) with sodium hydroxide to 125 ℃, stirring, precipitating to obtain upper layer clear liquid and lower layer precipitate, and performing suction filtration on the lower layer precipitate to obtain sodium chloride;

(3) and (3) removing the supernatant in the step (2) into an acidification kettle, dropwise adding hydrochloric acid, heating and stirring, wherein the dropwise adding hydrochloric acid is divided into three stages:

A. firstly, dripping hydrochloric acid into sodium chlorobenzoate to neutrality, wherein the speed at the moment is firstly to ensure that the temperature in the reaction kettle is not lower than 95 ℃, and simultaneously to ensure that the materials in the reaction kettle are not flushed;

B. secondly, in a neutral stage, when the liquid enters the neutral stage, the dripping speed must be slow, the nucleation quantity of p-chlorobenzoic acid crystals in the liquid is controlled to be small, if the dripping is too fast, the nucleation quantity is too large, and the finished product particles are too fine, so that the centrifugation, washing, drying and quality are not facilitated;

C. in the acid stage, when the crystallization speed is increased in the acid stage, the temperature is ensured to be not lower than 95 ℃, and at the moment, the temperature is high, the crystallization particles are large, so that the centrifugation and washing are facilitated; when the pH value reaches 3, stopping dripping, cooling to 50-60 ℃, preparing to discharge materials, and controlling the whole crystallization process to be 12 hours;

(4) centrifuging: putting the materials into a centrifuge, and controlling the moisture in wet products within 20% to facilitate drying;

(5) drying: and transferring the wet product into a vacuum double-cone kettle, and drying until the wet product is not scalded in a vacuum exhaust tube to ensure that the finished product is loose and has no caking.

The technical scheme provided by the invention has the beneficial effects that:

the process route is simple and reliable, and no dangerous process is available; the cost is low, and the continuity and industrialization of sewage treatment can be realized; the technology solves the problem of treating the wastewater containing the p-chlorobenzoic acid sodium as hazardous waste, greatly improves the economic benefit, and can sell the p-chlorobenzoic acid as a byproduct and bring considerable income.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in further detail with reference to specific examples.

A process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater comprises the following specific steps:

(1) and (3) extraction: temporarily storing the p-chlorobenzoic sodium formate wastewater in a storage tank, calculating a required solvent according to the capacity of the storage tank, adding dichloromethane, starting a pump to circulate, standing for two hours, then beginning to divide the wastewater into an upper layer and a lower layer, and removing dichloromethane and p-chlorobenzaldehyde from the lower layer in a distillation kettle;

(2) and (3) oxidation: heating the upper layer aqueous solution in the step (1) with sodium hydroxide to 125 ℃, stirring, precipitating to obtain upper layer clear liquid and lower layer precipitate, and performing suction filtration on the lower layer precipitate to obtain sodium chloride;

(3) and (3) removing the supernatant in the step (2) into an acidification kettle, dropwise adding hydrochloric acid, heating and stirring, wherein the dropwise adding hydrochloric acid is divided into three stages:

A. firstly, dripping hydrochloric acid into sodium chlorobenzoate to neutrality, wherein the speed at the moment is firstly to ensure that the temperature in the reaction kettle is not lower than 95 ℃, and simultaneously to ensure that the materials in the reaction kettle are not flushed;

B. secondly, in a neutral stage, when the liquid enters the neutral stage, the dripping speed must be slow, the nucleation quantity of p-chlorobenzoic acid crystals in the liquid is controlled to be small, if the dripping is too fast, the nucleation quantity is too large, and the finished product particles are too fine, so that the centrifugation, washing, drying and quality are not facilitated;

C. in the acid stage, when the crystallization speed is increased in the acid stage, the temperature is ensured to be not lower than 95 ℃, and at the moment, the temperature is high, the crystallization particles are large, so that the centrifugation and washing are facilitated; when the pH value reaches 3, stopping dripping, cooling to 50-60 ℃, preparing to discharge materials, and controlling the whole crystallization process to be 12 hours;

(4) centrifuging: putting the materials into a centrifuge, and controlling the moisture in wet products within 20% to facilitate drying;

(5) drying: and transferring the wet product into a vacuum double-cone kettle, and drying until the wet product is not scalded in a vacuum exhaust tube to ensure that the finished product is loose and has no caking.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.

Claims (1)

1. A process for extracting p-chlorobenzaldehyde and p-chlorobenzoic acid from p-chlorobenzoic acid sodium wastewater is characterized by comprising the following specific steps:

(1) and (3) extraction: temporarily storing the p-chlorobenzoic sodium formate wastewater in a storage tank, calculating the required dichloromethane according to the capacity of the storage tank, adding dichloromethane, starting a pump to circulate, standing for two hours, then beginning to divide the wastewater into an upper layer and a lower layer, and removing dichloromethane and p-chlorobenzaldehyde from the lower layer in a distillation kettle;

(2) and (3) oxidation: heating the upper layer aqueous solution in the step (1) with sodium hydroxide to 125 ℃, stirring, precipitating to obtain upper layer clear liquid and lower layer precipitate, and performing suction filtration on the lower layer precipitate to obtain sodium chloride;

(3) and (3) removing the supernatant in the step (2) into an acidification kettle, dropwise adding hydrochloric acid, heating and stirring, wherein the dropwise adding hydrochloric acid is divided into three stages:

A. firstly, dripping hydrochloric acid into sodium chlorobenzoate to neutrality, wherein the speed at the moment is firstly to ensure that the temperature in the reaction kettle is not lower than 95 ℃, and simultaneously to ensure that the materials in the reaction kettle are not flushed;

B. secondly, in a neutral stage, when the liquid enters the neutral stage, the dripping speed must be slow, the nucleation quantity of p-chlorobenzoic acid crystals in the liquid is controlled to be small, if the dripping is too fast, the nucleation quantity is too large, and the finished product particles are too fine, so that the centrifugation, washing, drying and quality are not facilitated;

C. in the acid stage, when the crystallization speed is increased in the acid stage, the temperature is ensured to be not lower than 95 ℃, and at the moment, the temperature is high, the crystallization particles are large, so that the centrifugation and washing are facilitated; when the pH value reaches 3, stopping dripping, cooling to 50-60 ℃, preparing to discharge materials, and controlling the whole crystallization process to be 12 hours;

(4) centrifuging: putting the materials into a centrifuge, and controlling the moisture in wet products within 20% to facilitate drying;

(5) drying: and transferring the wet product into a vacuum double-cone kettle, and drying until the wet product is not scalded in a vacuum exhaust tube to ensure that the finished product is loose and has no caking.