WO2022155779A1

WO2022155779A1 - Preparation process for epichlorohydrin

Info

Publication number: WO2022155779A1
Application number: PCT/CN2021/072661
Authority: WO
Inventors: 李朝波; 刘庆德; 齐运峰; 陈晓荣; 刘霞; 谭明奇; 王志雪
Original assignee: 汇智工程科技股份有限公司
Priority date: 2021-01-19
Filing date: 2021-01-19
Publication date: 2022-07-28

Abstract

A preparation process for epichlorohydrin. The process involves the following steps: (1) a chlorination reaction, wherein glycerol and hydrogen chloride gas are transported to a reaction kettle for a chlorination reaction; and (2) a cyclization reaction, wherein the product obtained from step (1) and a liquid alkali are mixed in a tube mixer for a preliminary cyclization reaction, and then delivered to a cyclization tower to complete the cyclization reaction and to obtain the product. The chromaticity (Pt-Co number) of epichlorohydrin produced by the present method is less than or equal to 20, the water content is less than or equal to 0.060%, and the epichlorohydrin content is greater than or equal to 99.80%.

Description

Preparation technology of epichlorohydrin

technical field

The invention relates to the technical field of epichlorohydrin production, in particular to a preparation process of epichlorohydrin.

Background technique

Epichlorohydrin is an important organic chemical intermediate and fine chemical with a wide range of uses. The production capacity has exceeded 2.2 million t/a.

At present, the commonly used epichlorohydrin preparation technology has the following two kinds:

1. High temperature chlorination of propylene

The existing problems are: (1) there are many reaction by-products, the conversion rate of raw materials is low, and the consumption quota is high;

(2) The equipment is seriously corroded, the energy consumption is high, and the sewage discharge is large.

Second, the propylene acetate method

The existing problems are: (1) there are many reaction steps, and the process route is long and complicated; (2) there is acetic acid in the system, and stainless steel equipment is used; (3) the oxidation reactor is large in size, difficult to overhaul, and the catalyst is expensive and cannot be regenerated; (4) ) In the reaction, chlorine gas is added, and the circulating gas is compressed, and attention must be paid to the safety and reliability of the propenyl alcohol unit against the explosion of the mixed gas.

SUMMARY OF THE INVENTION

The technical problem to be solved by the present invention is: to overcome the deficiencies of the prior art, a preparation process of epichlorohydrin is provided, the chromaticity (platinum-cobalt number) of the epichlorohydrin produced is less than or equal to 20, and the moisture content is less than or equal to 0.060%. , Epichlorohydrin content ≥ 99.80%.

The technical scheme of the present invention is:

The preparation technology of epichlorohydrin, comprises the following steps:

(1) chlorination reaction: glycerol and hydrogen chloride gas are transported to the reactor to carry out chlorination reaction;

(2) cyclization reaction: the product obtained in step (1) and liquid caustic soda are first mixed in a pipeline mixer to carry out a preliminary cyclization reaction, and the product after the reaction is transported to a cyclization tower to complete the cyclization reaction, Generate epichlorohydrin.

Preferably, before the product obtained in step (1) is subjected to the cyclization reaction, it is first transported to the first rectification tower for rectification, and the rectification temperature is 100-140° C. The cooler and the secondary cooler are condensed and transported to the crude dichloropropanol tank; a part of the material in the crude dichloropropanol tank is refluxed to the top of the first rectifying tower, and a part is transported to the crude dichloropropanol transfer tank; The heavy components at the bottom of a rectifying tower are returned to the reactor and continue to participate in the chlorination reaction.

Preferably, in step (1), after the excess hydrogen chloride gas in the chlorination reaction and the water generated by the reaction are condensed by the initial evaporation condenser, gas-liquid separation is carried out through the chlorination gas-liquid separation tank, and the separated liquid is transported to the initial stage. In the steam storage tank, the separated hydrogen chloride gas is returned to the reactor to continue to participate in the chlorination reaction.

Preferably, the material in the primary steam storage tank is transported to the dichloropropanol separation tower, and after the hydrogen chloride gas is removed, the primary steam at the bottom of the tower is transported to the primary steam transfer tank.

Preferably, the materials in the crude dichloropropanol transfer tank and the primary steam transfer tank are transported to the dichloropropanol mixing tank for mixing, and then transported to the pipeline mixer to participate in the cyclization reaction.

Preferably, the tail gas of the reactor, the tail gas of the crude dichloropropanol tank and the tail gas of the primary steam storage tank are transported to the tail gas water absorption tower, and the concentrated hydrochloric acid produced after countercurrent contact with the dilute hydrochloric acid is transported to the water absorption circulation tank, and then from the water absorption circulation tank It is transported to the hydrochloric acid storage tank; the tail gas absorbed by the dilute hydrochloric acid in the tail gas water absorption tower is transported to the alkali absorption tower, and the solution generated after countercurrent contact with the dilute alkali is transported to the alkali absorption circulation tank, and then transported from the alkali absorption circulation tank to the circulation tank. Chemical wastewater treatment plant.

Preferably, in step (1), the chlorination reaction temperature is 90-120° C., and the reaction pressure is 0.05-0.3 MPa.

Preferably, in step (1), glycerol and hydrogen chloride gas are sequentially transported to the first reactor, the second reactor and the third reactor for chlorination reaction.

Preferably, in step (2), before the liquid caustic soda is transported to the pipeline mixer, it is heated to 50-60° C. in a liquid caustic heater.

Preferably, in step (2), the gas product generated at the top of the cyclization tower is transported to the cyclization tower condenser to be condensed to below 40 ° C, and then transported to the cyclization tower reflux tank; the water in the upper layer of the cyclization tower reflux tank The layer is returned to the top of the cyclization tower, and the oil layer in the lower layer is transported to the crude epichlorohydrin buffer tank.

Preferably, the material in the crude epichlorohydrin buffer tank is transported to the preliminary distillation tower, and the crude epichlorohydrin at the bottom of the preliminary distillation tower is cooled to 60-80°C by the preliminary distillation tower tower kettle liquid cooler; The low boilers at the top are cooled by the top cooler of the initial distillation column and then transported to the reflux tank of the preliminary distillation column. The organic layer was refluxed to the initial distillation column.

Preferably, the crude epichlorohydrin at the bottom of the preliminary distillation column is cooled and transported to the second distillation column, and the dichloropropanol at the bottom of the second distillation column is transported to the primary distillation medium-turning tank; the top of the second distillation column After the epichlorohydrin is condensed to below 40 ℃ by the condenser at the top of the rectification tower, it is transported to the reflux tank of the rectification column. A part of the material in the reflux tank of the rectification column is refluxed to the top of the second rectification column, and part of it is transported to the reflux tank of the rectification column. The epichlorohydrin intermediate tank is transported to the epichlorohydrin storage tank after passing the sampling test.

Compared with the prior art, the present invention has the following beneficial effects:

The invention adopts the glycerol method to produce epichlorohydrin, gets rid of dependence on petroleum resources as raw materials, not only saves a lot of petroleum resources, but also reduces environmental pollution. Compared with the propylene method, the generation of three wastes is greatly reduced, and the amount of wastewater produced is only 1/5-6/1 of the propylene method. Compared with the propylene method, the annual COD emission reduction is about 13kg/t epichlorohydrin, and the annual standard coal saving is about 256kg/t. tEpichlorohydrin. In recent years, the high oil price has driven the price of downstream propylene, and glycerol is a by-product of biodiesel production. With the rise of global biodiesel, the price of glycerol has dropped year by year, and the glycerol method has obvious advantages over the propylene method in terms of production cost. Advantage. In addition, in terms of equipment investment, the production of epichlorohydrin by the glycerol method is only one-third of the propylene method. The process of the invention makes full use of the biological resources of crops, which facilitates the recycling of resources and the sustainable development of economy. And the chromaticity (platinum-cobalt number) of epichlorohydrin produced by the process of the invention is less than or equal to 20, the moisture content is less than or equal to 0.060%, and the content of epichlorohydrin is greater than or equal to 99.80%.

Description of drawings

Fig. 1 is the process flow diagram of the chlorination reaction unit of the present invention.

Fig. 2 is the process flow diagram of the primary distillation unit of the present invention.

Figure 3 is a process flow diagram of the primary vapor degassing unit of the present invention.

Fig. 4 is the process flow diagram of the dichloropropanol mixing unit of the present invention.

Figure 5 is a process flow diagram of the tail gas absorption unit of the present invention.

Figure 6 is a process flow diagram of the cyclization reaction unit of the present invention.

Figure 7 is a process flow diagram of the fore distillation unit of the present invention.

Figure 8 is a process flow diagram of the secondary rectification unit of the present invention.

Detailed ways

As shown in Figures 1-8, the present invention provides a preparation process of epichlorohydrin, comprising the following steps:

(1) Chlorination reaction unit

The glycerin enters the first reaction kettle, is pumped into the second reaction kettle, and then is pumped into the third reaction kettle; the hydrogen chloride gas is distributed through the HCl distribution table and then introduced into the three reaction kettles for further chlorination reaction. The temperature is 90-120°C, and the reaction pressure is 0.05-0.3MPa.

The chlorination reaction equation is as follows:

_CH2CHCH2 (OH ₎₃ ₊ _HCl = _CH2CHCH2 (OH)2Cl ₊ _H2O

_CH2CHCH2 ₍ OH) _2Cl ₊ HCl= _{CH2CHCH2OHCl2} ₊ _H2O .

Excessive HCl gas in the chlorination reaction and the water generated by the reaction are condensed by the primary evaporation condenser, and then gas-liquid separation is carried out in the chlorination gas-liquid separation tank. The separated liquid (mainly water, HCl, dichloropropanol and a small amount of monochloropropanediol) is controlled by the liquid level of the primary steam receiver, and the primary steam delivery pump is transported to the primary steam storage tank, and enters the primary steam degassing unit; The separated HCl gas enters the second reaction kettle, and the glycerin in the second reaction kettle is used to absorb excess HCl gas to continue participating in the chlorination reaction, and the absorbed HCl tail gas enters the tail gas absorption unit.

(2) Primary rectification unit

The fully reacted material in the third reaction kettle is pumped into the first rectification tower, the first rectification tower is evacuated by a vacuum pump, the bottom of the first rectification tower is heated by the reboiler of the first rectification tower, and the temperature is controlled at 100-140℃. The incoming materials are subjected to negative pressure rectification, and light components such as HCl, water, and dichloropropanol (DCH) enter the primary cooler and the secondary cooler for condensation. The condensed materials enter the crude dichloropropanol tank, and a part of Backflow to the top of the first rectifying tower, and a part is pumped to the thick dichloropropanol transfer tank; the heavy components such as catalyst, tar, unreacted glycerin at the bottom of the first rectifying tower are pumped to the reactor to continue Involved in the chlorination reaction.

(3) Primary steam degassing unit

In step (1), the first steam in the first steam material storage tank (mainly water, HCl, DCH and a trace amount of monochloropropanediol) enters the dichlorohydrin separation tower from the upper part of the tower, and is heated by the circulation of the reboiler. The HCl is removed by the method, and the primary steam after removing HCl is controlled at the liquid level at the bottom of the column, and is transported to the primary steam transfer tank by a pump.

(4) Dichloropropanol mixing unit

In the step (3), the first distillation thing of the transfer tank in the first distillation is transported to the thick dichlorohydrin transfer tank of step (2) with pump flow control, and the thick DCH in the thick dichlorohydrin transfer tank is transferred with thick dichlorohydrin Pump flow control to the dichloropropanol mixing tank. The primary distillation product after rectification and crude DCH are mixed to a specified concentration in a dichloropropanol mixing tank and then transported to a pipeline mixer by a dichloropropanol feed pump to participate in the cyclization reaction. The flow rate of the primary steam and crude DCH entering the dichloropropanol mixing tank is adjusted to ensure the concentration of the two mixed.

(5) Exhaust gas absorption unit

From the reactor tail gas of step (1), the first steam storage tank tail gas and the thick dichloropropanol tank of step (2), the HCl tail gas enters the tail gas water absorption tower from the bottom of the tower, and is in countercurrent contact with the dilute hydrochloric acid sprayed at the top of the tower, After HCl and dilute hydrochloric acid form concentrated hydrochloric acid, the liquid level control at the bottom of the tower enters the water absorption circulation tank; the concentrated hydrochloric acid in the water absorption circulation tank is pumped to the hydrochloric acid storage tank. The absorbed tail gas enters the alkali absorption tower from the lower part of the tower, and is in countercurrent contact with the dilute liquid alkali sprayed at the top of the tower. HCl and the dilute liquid alkali generate sodium chloride aqueous solution at the bottom of the tower. After reaching a certain concentration, it is pumped to the cyclization wastewater treatment device.

(6) Cyclization reaction unit

The liquid caustic soda is transported to the liquid caustic heater by the liquid caustic pump flow control for heat exchange. The liquid alkali solution is preheated to 50-60° C. and then enters the pipeline mixer through flow control, and is mixed with the mixed solution from the dichloropropanol mixing tank in step (4). Most of the reactions are carried out during mixing, and the mixed reaction enters the cyclization tower, where the reaction of remaining DCH and liquid alkali to generate epichlorohydrin (ECH) is completed in the cyclization tower. Liquid caustic soda and DCH solution adopt flow proportional control.

The cyclization reaction equation is as follows:

The ECH generated by the cyclization tower is steamed from the top of the tower, condensed to below 40°C with circulating water through the cyclization tower condenser, and the condensate enters the cyclization tower reflux tank. The condensate is divided into a water layer and an oil layer in the reflux tank of the cyclization tower. The upper water layer is returned to the top of the cyclization tower after being controlled by the pump liquid level. Propane buffer tank.

The ring tower is evacuated by a vacuum pump. In order to suppress the production of glycerol, the generated ECH must be quickly rectified from the top of the ring tower with steam, and the steam enters directly from the bottom of the tower. The cyclization wastewater is sent from the bottom of the cyclization tower to the bottom of the cyclization tower with a pump to adjust the liquid level at the bottom of the tower, and then sent to the flash tank. It is sent to the cyclization wastewater storage tank. Before the cyclization wastewater storage tank, a certain amount of tail gas waste acid is added through the regulating valve, and it is adjusted and processed by an online pH meter, and the specified pH value is adjusted and sent to the sewage workshop.

(7) Preliminary distillation unit

The crude ECH in the crude epichlorohydrin buffer tank is sent to the preliminary distillation column to separate low boiler water through the flow control of the preliminary distillation column feed pump. The crude ECH obtained from the bottom of the preliminary distillation tower is transported by the bottom pump of the preliminary distillation tower, and cooled to 60-80 ℃ by circulating water through the liquid cooler of the preliminary distillation tower tower. After metering, it enters the rectification tower. The low boiler obtained at the top of the preliminary distillation tower is condensed to below 40°C with circulating water through the top of the preliminary distillation tower cooler, and enters the preliminary distillation tower reflux tank, where the water layer and the organic layer are separated. The upper layer is the water layer, overflows into the vacuum sealing tank, and is pumped to the loop tower reflux tank of step (6) with ECH; the organic layer of the lower layer is controlled by the preliminary distillation column reflux tank liquid level through the preliminary distillation column reflux pump and After the flow detection, it is returned to the initial distillation column as the reflux of the initial distillation column.

(8) Secondary rectification unit

The ECH obtained at the bottom of the preliminary distillation column enters the second distillation column, and the high boilers therein are separated. In the second rectifying column, the DCH separated from the column bottom is transported by a pump, and is sent to the initial distillation transfer tank of step (3) after adjusting the liquid level at the column bottom and detecting the flow rate. The rectified ECH obtained at the top of the second rectification tower is cooled to below 40°C by circulating water through the rectification tower overhead condenser, and enters the rectification tower reflux tank. A part of the rectified ECH in the rectification tower reflux tank is passed through the rectification reflux pump. The flow is adjusted and returned to the top of the second rectifying tower; the other part is adjusted by the liquid level of the rectifying tower, and the flow is measured into the epichlorohydrin intermediate tank. The chloropropane feed pump is transported to the epichlorohydrin storage tank.

The chromaticity (platinum-cobalt number) of epichlorohydrin produced by the process of the invention is less than or equal to 20, the moisture content is less than or equal to 0.060%, and the content of epichlorohydrin is greater than or equal to 99.80%.

Claims

The preparation technology of epichlorohydrin, is characterized in that, comprises the following steps:

(1) chlorination reaction: glycerol and hydrogen chloride gas are transported to the reactor to carry out chlorination reaction;

(2) cyclization reaction: the product obtained in step (1) and liquid caustic soda are first mixed in a pipeline mixer to carry out a preliminary cyclization reaction, and the product after the reaction is transported to a cyclization tower to complete the cyclization reaction, Generate epichlorohydrin.
The preparation technique of epichlorohydrin as claimed in claim 1, is characterized in that, before the product obtained in step (1) is carried out cyclization reaction, it is first transported to the first rectifying tower for rectification, and the rectification temperature is 100-140℃, the light components from the rectification are condensed by the primary cooler and the secondary cooler successively and then transported to the crude dichloropropanol tank; a part of the material in the crude dichloropropanol tank is refluxed to the first rectification At the top of the tower, a part is transported to the crude dichloropropanol transfer tank; the heavy components at the bottom of the first rectification tower are returned to the reactor to continue to participate in the chlorination reaction.
The preparation technique of epichlorohydrin as claimed in claim 2, it is characterized in that, in step (1), after the excessive hydrogen chloride gas in the chlorination reaction and the water that the reaction generates are condensed by the initial evaporation condenser, then chlorinated The gas-liquid separation tank conducts gas-liquid separation, the separated liquid is transported to the primary steam storage tank, and the separated hydrogen chloride gas is returned to the reactor to continue participating in the chlorination reaction.
The preparation technology of epichlorohydrin as claimed in claim 3, it is characterized in that, the material in the primary steam storage tank is transported to the dichlorohydrin separation tower, after removing the hydrogen chloride gas therein, the primary steam at the bottom of the tower Then it is transported to the primary steam transfer tank.
The preparation technology of epichlorohydrin as claimed in claim 4, it is characterized in that, after the material in the thick dichlorohydrin transfer tank and the initial steaming medium transfer tank is transported to the dichlorohydrin mixing tank for mixing, and then transported to the pipeline for mixing Participate in the cyclization reaction.
The preparation technology of epichlorohydrin according to any one of claims 3-5, it is characterised in that the tail gas of the reactor, the tail gas of the thick dichloropropanol tank and the tail gas of the primary steam storage tank are transported to the tail gas water absorption tower, and the The concentrated hydrochloric acid produced after the countercurrent contact with hydrochloric acid is transported to the water absorption circulation tank, and then transported from the water absorption circulation tank to the hydrochloric acid storage tank; the tail gas absorbed by the dilute hydrochloric acid in the tail gas water absorption tower is transported to the alkali absorption tower, and countercurrent with the dilute liquid alkali The solution generated after the contact is transported to the alkali absorption circulation tank, and then transported from the alkali absorption circulation tank to the cyclization wastewater treatment device.
The preparation process of epichlorohydrin according to any one of claims 1-5, characterized in that, in step (1), the chlorination reaction temperature is 90-120° C., and the reaction pressure is 0.05-0.3 MPa.
The preparation technique of epichlorohydrin according to any one of claims 1-5, wherein in step (1), glycerol and hydrogen chloride gas are sequentially transported to the first reaction kettle, the second reaction kettle and the third reaction kettle The chlorination reaction is carried out in the kettle.
The preparation technology of epichlorohydrin according to any one of claims 1-5, it is characterized in that, in step (2), before the liquid caustic soda is transported to the pipeline mixer, it is first heated to 50-50 in the liquid caustic heater 60°C.
The preparation technology of epichlorohydrin according to any one of claims 1-5, it is characterized in that, in step (2), the gas product that the cyclization tower tower top produces is transported to the cyclization tower condenser to be condensed to 40 Below ℃, it is transported to the reflux tank of the cyclization tower; the water layer of the upper layer of the reflux tank of the cyclization tower is returned to the top of the cyclization tower, and the oil layer of the lower layer is transported to the crude epichlorohydrin buffer tank.
The preparation technology of epichlorohydrin as claimed in claim 10, is characterized in that, the material in the crude epichlorohydrin buffer tank is transported to the preliminary distillation column, and the crude epichlorohydrin at the bottom of the preliminary distillation column is passed through the preliminary distillation column. The tower kettle liquid cooler is cooled to 60-80 °C; the low boilers at the top of the preliminary distillation tower are cooled by the preliminary distillation tower top cooler and then sent to the preliminary distillation tower reflux tank, and the water in the upper and middle layers of the preliminary distillation tower reflux tank is sent to After vacuum sealing the tank, it is transported to the reflux tank of the cyclization tower, and the organic layer of the lower layer is refluxed to the initial distillation tower.
The preparation technique of epichlorohydrin as claimed in claim 11, is characterized in that, the thick epichlorohydrin at the bottom of the first distillation tower is cooled and transported to the second rectifying tower, and the dichloride at the bottom of the second rectifying tower is cooled. The propanol is transported to the primary steam transfer tank; the epichlorohydrin at the top of the second rectification tower is condensed to below 40°C by the condenser at the top of the rectification tower, and then transported to the reflux tank of the rectification tower and the reflux tank of the rectification tower A part of the material is refluxed to the top of the second rectification tower, and a part is transported to the middle tank of epichlorohydrin, which is transported to the epichlorohydrin storage tank after passing the sampling test.