Method for production of 1,2-dichloroethane with nitrogen addition

FIELD: organic chemistry.

SUBSTANCE: 1,2-dichloroethane is obtained by liquid phase ethylene chlorination with discharging of reaction heat due to operation medium boiling. In claimed process nitrogen is added to chlorine and ethylene reagents. Ratio of chlorine volume consumption to nitrogen volume consumption is maintained as 1:1. Reaction is carried out at temperature lower than 1,2-dichloroethane boiling point, and discharging of reaction heat is carried out by evaporative cooling of operation medium in nitrogen.

EFFECT: process of increased selectivity; decreased yield of by-products.

1 tbl, 5 dwg

 

The technical field to which the invention relates.

The invention relates to a method for producing 1,2-dichloroethane by the method of high-temperature liquid-phase chlorination of ethylene to remove the heat of reaction due to the evaporation of the working medium at boiling.

The level of technology.

The most intimate of ways to obtain 1,2-dichloroethane are high-temperature and low-temperature liquid-phase chlorination of ethylene [1].

High temperature process is performed at a temperature equal to the boiling temperature of the working environment (83,5-110°depending on the pressure). Reactor high-temperature process is a bubbling gas-lift column 1 with internal circulation tube 4 (Fig 1). The working environment is liquid 1,2-dichloroethane. The catalyst is FeCl3, which is located in the reactor in dissolved form. To obtain a solution of chlorine gas through the distributor 2 is fed in the lower part of the annular space. The reaction is carried out upstream when entering into the reactor in gaseous ethylene through the distributor 3. Due to the difference of density in the circulation pipe and the annular space occurs the liquid circulation. In the upper part of the reactor are perforated plates 6, designed to intensify peremeshivanija part of the reactor plays the role of a separator for separating liquid droplets from the steam. The reaction products are discharged in the form of vapor to the stage rectification through the nozzle in the lid of the reactor. Due to the low volatility of the catalyst remains in the reactor. To maintain the liquid level in the lower part of the reactor is introduced 1,2-dichloroethane.

An important advantage of the high-temperature process compared to low temperature is efficiency: heat is consumed for evaporation and distillation products, waste no water, the catalyst consumption is minimal.

The disadvantage of the high-temperature process is the low selectivity (98,0-98,7%), associated with an increased rate of adverse reactions with increasing temperature. By-products - trichloroethane, trichlorethylene and other higher chlorinated ethane is formed in the reactor as a result of substitution reactions of chlorination. The rate of adverse reactions decreases with decreasing temperature [2]. In the formation of 1 mol of 1,2-dichloroethane is allocated an amount of heat sufficient to evaporate 6 moles of 1,2-dichloroethane.

The low-temperature process (figure 2) is performed in a bubble column 1, connected at the top and bottom with an external shell and tube heat exchanger 5. The working environment in the reactor is the product of the reaction, 1,2-dichloroethane in the liquid state. Chlorine is introduced into the lower part of the column through the dispenser 2. Above image is vasica chlorine solution through the dispenser 3 is introduced ethylene. Due to the difference of density in the refrigerator and column raises the circulation of the working environment with upward flow in the column. The temperature in the reactor is 65°C. the Removal of the synthesized product by gravity flow through the overflow. The separation of product from catalyst is carried out at the stage of purification. The catalyst after the cleanup phase and not subject to regeneration. The products of the process from the stage of purification act of rectification.

The advantage of the low-temperature process is the high selectivity (99,6%), owing to the slowdown of adverse reactions substitution chlorination at lower temperature. The disadvantages of the low-temperature process include high consumption of wastewater at the stage of purification of the product from the catalyst, significant consumption of catalyst per unit of production, high energy costs for cooling the reaction mass and irrational use of the heat of reaction.

Disclosure of the invention.

The objective of the invention is to develop a new method for the production of 1,2-dichloroethane by means of liquid-phase chlorination of ethylene with the addition of the reagents nitrogen. Invited to lead the process of liquid-phase chlorination of ethylene at a temperature below the boiling point of dichloromethane by adding in entering the reactor raw materials (ethylene and chlorine) nitrogen. The warmth Boo who should be drained when not boiling, as the high-temperature method, and due to the evaporation of 1,2-dichloroethane in nitrogen. At the exit of the reactor nitrogen saturated vapor 1,2-dichloroethane. The more nitrogen flow, the less the temperature of the working environment (figure 3). The graph (figure 3) based on material and thermal balances of the reactor. By reducing the temperature output of by-products is reduced. Due to the decrease of the yield of by-products increases the selectivity of the process.

The invention can be obtained the following results:

1. Adding nitrogen to chlorine leads to a decrease in the concentration of chlorine in the gas phase. In the result, decreases the equilibrium concentration of chlorine in the liquid in accordance with Henry's law [3]:

where x*- equilibrium gas concentration in solution (mol. share); yA- the chlorine concentration in the gas (mol. share); m is the constant phase equilibrium.

By reducing the concentration of chloride in 1,2-dichloroethane will decrease the rate of adverse reactions. It follows from the work [5], which shows that the decrease in the concentration of dissolved chlorine in the liquid leads to a decrease in the rate of formation of by-products in accordance with the equation:

where W is the rate of adverse reactions; k is the reaction rate constant; [C2H42] is the concentration of chlorine in the liquid.

2. Supplied additional gaseous nitrogen improves the mixing of the working environment, eliminating stagnant zones. In [4] it is shown that the coefficients of the mixing apparatus with bubbling layer increases with increasing gas flow.

3. The temperature in the reactor is maintained below the boiling point, this leads to a decrease in the rate of adverse reactions. The dependence of the rate of adverse reactions on temperature is given in [6]:

where W is the rate of adverse reactions, c-1; R - universal gas constant, j/(KMOL·K); T is the temperature of the reaction mixture, To; [C2H4Cl2] is the concentration of 1,2-dichloroethane in the liquid. The increase in the rate of adverse reactions with increasing temperature has been veried in [2].

Thus, adding the reagents of nitrogen are created more favorable conditions for the process.

A brief description of the drawings.

List of figures:

figure 1 - bubbling gas-lift reactor high-temperature liquid-phase chlorination of ethylene;

figure 2 - bubble reactor low-temperature chlorination of ethylene;

figure 3 - dependence of the temperature of the working medium from the flow of nitrogen at a flow rate of chlorine 3000 m3/h at normal is s;

4 is a bubbling gas-lift reactor liquid-phase chlorination of ethylene with the addition of the reagents nitrogen;

5 - industrial bubble reactor.

In figures 1 and 2 describe the analogues of the invention. In fig.z graphically presents the dependence of the temperature of the working environment from the consumption of nitrogen added to the reagents. Figure 4 describes the reactor, which can be implemented in the invention. Figure 5 is an industrial reactor, which was tested a new method for producing 1,2-dichloroethane.

The implementation of the invention.

The invention is carried out in a bubbling reactor liquid-phase chlorination of ethylene. Working environment temperature in the reactor is maintained within 78-83°when the pressure in the upper part of the reactor 1 at. Bubble reactor for the production of 1,2-dichloroethane by means of liquid-phase chlorination of ethylene with the addition of the reagents nitrogen (figure 4) is as follows. Gaseous chlorine with nitrogen through the dispenser 2 is fed in the lower part of the annular space. The reaction is carried out upstream when entering into the reactor in gaseous ethylene / nitrogen through the distributor 3. Due to the difference of density in the circulation pipe and the annular space occurs the liquid circulation. In the upper part of the reactor are perforated container is CI 6, designed for intensive mixing. The upper part of the reactor plays the role of a separator for separating liquid droplets from the steam. In a gas-liquid separator 7 separates the nitrogen from the liquid product. Part of the condensed 1,2-dichloroethane to maintain the level of liquid is delivered by a pump 9 into the lower part of the reactor, and the other part in the form of the finished product is discharged into collection vessels. Nitrogen from a gas-liquid separator 7 compressor 8 is fed into the line chlorine and ethylene.

The results of industrial tests of the method for producing 1,2-dichloroethane by adding reagents nitrogen

The high selectivity of the new method of producing 1,2-dichloroethane was confirmed by testing in an industrial reactor (JSC SayanskKhimPlast, Sayansk) with an estimated capacity chlorine 300 m3/am Reactor is a bubbling gas-lift column 1 with a diameter of 1.4 m with internal circulation tube 4 with an outer diameter of 219 mm and a height of 9600 mm (figure 5). Throughout the height of the column there are five perforated plates at a distance of 1000 mm from each other with a hole diameter of 12 mm

The test consisted in the following. The reactor was filled 1,2-dichloroethane, and then through the distribution unit 2 was applied chlorine with nitrogen, 3 - ethylene. Moreover, the attitude about the roadways to the consumption of chlorine by volume of nitrogen was maintained at 1:1. Then after the reactor is at steady state were measured temperatures at the top and bottom of the reactor was controlled by the flow rate of chlorine, ethylene and nitrogen. The main operational parameters are given in table. 1.

Table 1
The modes of industrial tests of the new method
No. modeChlorine consumption,The consumption of ethylene,Nitrogen flow,TCf(in the upper part of the reactor),EDC, wt.% (at the outlet of the condenser)
m3/hm3/hm3/h°
12402502407799,94
22042102107699,93
3235,22452407799,94
423024524077of 99.96
5243,62452507799,92
6235,2240240 7699,92
7239,424024076at 99.95

Working environment temperature in the reactor was 76-77°when the pressure in the top of the reactor 1 at, which is below the boiling point of 1,2-dichloroethane (83,5°). The warmth was given due to the evaporation of 1,2-dichloroethane in nitrogen. Boiling in the reactor was not.

To determine the selectivity of the process was carried out analyses of samples of liquid 1,2-dichloroethane at the outlet of the condenser 5, the composition of the product was determined by gas-liquid chromatography. The results in table 1.

Tests showed that the selectivity of the process for producing 1,2-dichloroethane by adding reagents nitrogen amounted to more than 99.9% (table 1). To map the selectivity of the process without adding nitrogen in the same reactor with a capacity of 300 m3/h was 98%. High selectivity is obtained when the ratio of the flow rate of chlorine to nitrogen flow of 1:1. Thus, a new method for producing 1,2-dichloroethane allows you to increase the selectivity of the process with 98% to 99,90-of 99.97% compared to the high-temperature method, to reduce the output of by-products.

Sources of information

1. Lebedev N.N. Chemistry and technology of basic organic and petrochemical synthesis. Ed. 2nd Per. M.: Chemistry, 1975 - 736 S.

2. Avetyan MG, Sonin EV, is aidman O.A. and other study of the process of direct chlorination of ethylene in an industrial environment. // Chemical engineering, 1991, No. 12, s-713.

3. Ramm, V.M. gas Absorption. Ed. M.: Chemistry, 1966.

4. Dillman CENTURIES, Eisenbud could BE ON the coefficient of longitudinal mixing in bubble flow reactor columns. // Chemical industry, 1962, No. 8, s.

5. Rozhkov V., zeidman O.A., Sonin EV, krištáľ NF, Avetyan MG, Traeger Y.A., V. Kharitonov, Passes A.F., Mubarak RG Patterns of liquid-phase chlorination of ethylene. // Chem. prom. 1991. No. 7. S.

6. Rozhkov V., zeidman O.A., Sonin EV, Avetyan MG, krištáľ NF, Traeger Y.A., Kharitonov V. Liquid-phase chlorination of 1,2-dichloroethane in the presence of ferric chloride. // Chem. prom. 1991. No. 5. Pp.261.

Method for producing 1,2-dichloroethane by means of liquid-phase chlorination of ethylene to remove the heat of reaction by boiling working medium, characterized in that the reagents chlorine and ethylene is added to the nitrogen, and the ratio of the volumetric flow of chlorine to the volumetric flow rate of nitrogen is maintained at 1:1, and the process occurs at a temperature below the boiling point of 1,2-dichloroethane, and the exhaust heat of reaction is due to evaporative cooling of the working medium in nitrogen.



 

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