Method for producing 1,2-dichloroethane

 

(57) Abstract:

The invention relates to the production of dichloroethane by direct chlorination of ethylene in the liquid dichloroethane. Obtaining 1,2-dichloroethane is carried out in a vertical two-column reactor with gas lift circulation dichloroethane in the vertical circuit, which is injected chlorine and ethylene. At the outlet of the reaction zone in the first column with plates create a local hydraulic resistance to movement of the upward flow of dichloroethane and reduce the pressure of the upward flow at the local hydraulic resistance to a value close to the vapour pressure of dichloroethane in place of the output from the reactor. In the zone of boiling point above the reaction zone, to form probabally the flow regime upstream of dichloroethane. Boil dichloroethane in the reaction zone exclude by maintaining the pressure created by the column of liquid dichloroethane in the second column, and also by creating the appropriate value of the hydraulic resistance. The vapor content of the liquid-vapor mixture in the boiling zone at paracetalmol mode of its flow reaches 0,8 - 0,95. This significantly increases the driving force of processador from the reaction zone, to increase productivity and produce high-quality final product. 2 C. p. F.-ly, 2 Il.

The invention relates to chemical technology and can be used, in particular, in the production of dichloroethane by direct chlorination of ethylene in the liquid dichloroethane.

The known method for producing 1,2-dichloroethane, protected by the RF patent N 2074849 (IPC C 07 C 19/045, 17/02. Bull. N 7, 1997), which is carried out in a reactor having two communicated with each other on the top and bottom of the vertical columns filled with liquid dichloroethane. These columns form a vertical closed circulating circuit in which through the use of the pump flow and also due to the gas-lift effect is circulated dichloroethane in the form of a downward flow of the more dense (degassed liquid and the upward flow of liquid having a lower density in areas of absorption of chlorine and reaction, as well as in zones of boiling and separation. Circulation of liquid dichloroethane through the reaction zone is performed with a flow rate of not less calculated by proposed in the known method dependencies between the parameters of the consumption process components and parameters characterizing thermal effect, heat capacity of the s reaction. This flow provides the necessary Teplodar from the reaction zone, so that no Pets boiling dichloroethane in the reaction zone and the process of boiling begins slightly above the reaction zone, where there is a zone of boiling. Thus the boiling zone is entirely within the upward flow of the circulation loop as part of the separation zone. The known method also includes the input gaseous source component reaction of chlorine and ethylene in the lower part of the upward flow of the circulation loop, the input return liquid dichloroethane, chlorination of ethylene in the medium circulating liquid dichloroethane with the formation of the synthesized dichloroethane, boil synthesized and circulating dichloroethane in the zone of boiling with the heat of reaction for the formation of vapours, the separation of the steam and liquid phases of dichloroethane, the output of dichloroethane vapor.

The known method has the following disadvantages:

1. Requires additional energy to provide a design flow of liquid dichloroethane through the reaction zone due to the need to use booster liquid dichloroethane, and additional efforts for its maintenance and repair.

The known method for producing 1,2-dichloroethane, protected by a U.S. patent N 4347391 (IPC C 07 C 17/02, 1982), according to which the process lead by the direct chlorination of ethylene in the liquid dichloroethane. The known method includes providing gas lift circulation of liquid dichloroethane closed by vertical fluid circulation loop reactor having two communicated between a vertical column with ascending and descending flows circulating dichloro Lorena above the reaction zone in the upper connecting the extended portion of the reactor, filled with liquid dichloroethane. This area is located above the boiling upward flow and is not part of their volume in a closed circulation loop. In addition, the upward flow between the boiling zone and the reaction zone there is a significant height and volume of the drop zone with liquid dichloroethane, providing the necessary hydrostatic pressure in the reaction zone to prevent premature boiling of dichloroethane. The temperature of dichloroethane in the reaction zone is maintained lower than the equilibrium temperature of its boiling point in the reaction zone at a pressure in the reaction zone, the value of which is higher than the value of the pressure in the boiling zone. The method also includes putting into circulation of the gaseous components of the reaction of chlorine and ethylene and their subsequent reaction and the formation of crude dichloroethane, transition crude synthesized in a mixture of dichloroethane with circulating liquid dichloroethane through the intermediate zone from the reaction zone into the zone of boiling. In the area of the boil there is a gradual boil this mixture with a gradual increase in the intensity of evaporation as it moves into the upper liquid dichloroethane, filling the extended portion of the reactor. In the zone of boiling puoi and liquid phases of dichloroethane at the top level of the liquid dichloroethane, fill the extended portion of the reactor, where the temperature decrease of dichloroethane.

The known method compared to the offer at similar settings on the height and diameter of the reactor has the following disadvantages.

1. The relatively lower performance on synthesized dichloroethane while ensuring the same quality of process synthesis in the reaction zone. This disadvantage is due to the relatively smaller flow rate of the circulating liquid dichloroethane through the reaction zone in an upward flow circulation circuit in a known way. The reason for the relatively smaller flow circulation in the known method is less driving force of the circulation process, the value of which is determined less by the difference in densities between the gas-liquid mixture in the zone of absorption of the upward flow, and the monolithic column liquid dichloroethane, in the downward flow of the circulation loop. Since the area of the boil in a known way outside of the upward flow, that is outside the scope of the circulation loop, it has no significant impact on the magnitude of the driving force of the circulation process, despite mengshu the th column of liquid dichloroethane to create additional hydrostatic pressure in the reaction zone in order to prevent boiling in her dichloroethane further reduces the magnitude of the driving force of the circulation, increasing the average density of the medium in the upstream dichloroethane.

2. The relatively low quality of the synthesis process, i.e. it reduced selectivity requires additional purification (distillation) of the synthesized dichloroethane. The main reason for the decrease in selectivity of this method is the lack of difference between the equilibrium pressure and the actual temperature at the end of the reaction zone, which is also due to the relatively lower flow rate circulating through the reaction zone of the flow, due to the small difference between the average densities in the upward and downward flows of dichloroethane in the circuit.

The objective of the proposed method for producing 1,2-dichloroethane is the possibility of improving its performance on synthesized dichloroethane with its high quality, as well as increase its efficiency.

The technical result of the invention is expressed in the increase of the driving force of the process of circulation of liquid dichloroethane in the circuit due to a sharp increase in the difference of the densities of circulating media in descending and ascending flows of dichloroethane.

The invention consists in that the ethane, including the provision of gas lift circulation dichloroethane in the vertical circuit with a downward and upward flows of dichloroethane, maintaining a temperature of dichloroethane in the reaction zone is less than the equilibrium temperature of its boiling point at a pressure in the reaction zone, with the location of the zone of boiling dichloroethane above the reaction zone, putting into circulation of the gaseous starting components of the reaction of chlorine and ethylene, input return liquid dichloroethane, education in the reaction zone of the synthesized dichloroethane, boil dichloroethane in the zone of boiling with the heat of reaction for the formation of vapours, the separation of the steam and liquid phases of dichloroethane, the output of dichloroethane vapor, according to the invention the area of the boil dichloroethane are placed in the upstream vertical circulation circuit, at the output from the reaction zone in the circuit creates a local hydraulic resistance to movement of the upward flow of dichloroethane and reduce the pressure of the upward flow at the local hydraulic resistance to a value close to the vapour pressure of dichloroethane in place of their output, and form in the zone of boiling probabally the flow regime upstream dichloro the e local hydraulic resistance can be suitably changed in inverse proportion, that is, when the increased costs of chlorine and ethylene is local hydraulic resistance and consequently reduced, and cost reduction of chlorine and ethylene is local hydraulic resistance increase accordingly.

The steam concentration in the zone of boiling can be 0,8-0,95.

In Fig. 1 schematically shows a two-column reactor, which implements the proposed method, Fig. 2 is a graph of the variation of pressure with altitude operating reactor in an upward flow of dichloroethane.

The proposed method of producing 1,2-dichloroethane is carried out in the reactor (Fig. 1) containing communicated with each other on the top and bottom of the two vertical columns of the reaction column 1 with upward flow and circulation column 2 downdraft dichloroethane, which form the vertical circulation loop. To start the reactor columns 1 and 2 is filled with liquid dichloroethane to a certain level by entering the return liquid dichloroethane in column 2. The level of dichloroethane in column 2 is supported such that the hydrostatic pressure during startup of the reactor provided an exception to the boil dichloroethane in the reaction zone. In the liquid dichloroethane the PPA of the main reaction, and inhibitor adverse reactions. In the lower part of the column 1 in the zone of absorption and reaction through the dispersing device is injected gaseous components of the reaction of chlorine and ethylene, respectively, with the required flow rate. Simultaneously with the introduction of chlorine in the column 1 is served in a small amount of gaseous oxygen or air as an inhibitor adverse reactions occurring in the gas-vapor phase. Dissolved in the liquid dichloroethane chlorine from the absorption rises in the reaction zone due to the lower density of the upper layers of dichloroethane, where rise the gaseous components of the reaction. In the reaction zone dispersed and partially dissolved in dichloroethane ethylene is mixed with the dissolved in dichloroethane chlorine and enters with him into a chemical reaction, which is synthesized 1,2-dichloroethane. The reaction of chlorine with ethylene occurs with the release of a large amount of heat that is spent on heating the liquid dichloroethane. Heated in the reaction zone to a temperature close to the boiling temperature of the mixture is formed (synthesized) and return dichloroethane with upward flow rises from the reaction zone into the zone of boiling. The output of the upward flow from the reaction zone create mestecko resistance reduces the pressure upstream of dichloroethane to the value close to the vapour pressure of dichloroethane in the upper part of the column 1, in the place of their withdrawal from the reactor. To create a local hydraulic resistance can be used, for example, plate 4, installed at the outlet of the reaction zone, the resistance value of which is calculated in accordance with the value of the cost of chlorine and ethylene. After reaching the reactor operating mode lash dichloroethane in the reaction zone is prevented by maintaining it appropriate pressure, which is ensured by the design height of the column of liquid dichloroethane in the downward flow of the column 2 and the corresponding value of the hydraulic resistance of the plates 4. The moment you pass through the holes of the plates 4, the pressure upstream of dichloroethane decreases sharply to a value of 6 (see Fig. 2) close to the vapour pressure of dichloroethane in place of the output from the reactor. Due to a sharp drop in pressure on the plate 4, there is intense boiling of liquid dichloroethane received in the boiling zone of the reaction zone, with the formation of large amounts of vapor. Due to the high intensity of vaporization at the boiling zone, the volume of the vapor phase it increases rapidly, making the cut is th the flow regime of the liquid-vapor mixture enters probabaly over the entire height of the boiling zone. To ensure reliable formation in the zone of boiling prokopenkovo flow regime upstream of dichloroethane changing costs of chlorine and ethylene introduced into the circulation loop, the value of the local hydraulic resistance change accordingly inversely proportional, that is, when the increased costs of chlorine and ethylene is local hydraulic resistance and consequently reduced, and cost reduction of chlorine and ethylene is local hydraulic resistance correspondingly increases. The vapor content of the liquid-vapor mixture in the boiling zone at paracetalmol mode of its flow reaches 0.6-0.95, and in the optimal mode - 0,8-0,95.

The main volume of the boiling zone at paracetalmol mode current environment is in the vapor phase, so the density of this medium in 8-16-fold lower compared with the density of the liquid-vapor mixture, boiling at bubble mode of its course, when the largest volume of the boiling zone is a liquid phase. Due to the significant decrease in the density of the medium in the zone of boiling compared to high density monolithic fluid in the downward flow column 2, are provided with high values of the driving force of proIT intensive Teplodar from the reaction zone, to support in this area is relatively low values of the actual temperature, which in turn significantly improves the performance of the proposed method for synthesizing 1,2-dichloroethane and provide a high selectivity of the synthesis.

More intensive Teplodar occurs in the zone of boiling due to intensive evaporation, due to a sharp decrease in the pressure at the inlet zone of the boil. The upward flow paracetalmol mixture in which the vapor phase has a higher speed than the drops of liquid dichloroethane, is in the zone of separation. In the separator 3 is the process of separating the steam and liquid phases dichloroethane using droplet separator 5, which reflects the flow of liquid droplets and directs it to the lower part of the separator 3, where the cooled liquid dichloroethane flows in the downward flow of the circulation loop of the column 2. Vapor phase dichloroethane is removed from the reactor in the upper part of the separator 3. Due to the constant feeding of return liquid dichloroethane upper level of liquid dichloroethane in the downward flow column 2 is supported at such a height at which the reaction zone, create the necessary working pressure, through the cat who nd it boil in this area.

The proposed method provides the possibility of significantly increasing the flow of liquid dichloroethane through the reaction zone, which can further reduce the value of the actual temperature in the reaction zone and on its output and to improve the performance of the process on the synthesized 1,2-dichloroethane even at a lower hydrostatic pressure in the reaction zone.

The low value of the actual temperature in the reaction zone provides the opportunity of increasing the positive difference between the equilibrium boiling point of dichloroethane at the end of the reaction zone and the actual temperature at the end of the reaction zone. This increase is the difference between the equilibrium temperature of ebullition of dichloroethane at a pressure supported at the end of the reaction zone, and the actual temperature of dichloroethane at the end of the reaction zone, as well as reducing the absolute temperature of dichloroethane at the end of the reaction zone contributes to a further reduction in the intensity of synthesis of harmful products of side reactions and, therefore, allows to obtain a synthesized dichloroethane higher purity (content of 1,2-dichloroethane over 99.6 percent) and send it to the pyrolysis synthesis of vinyl chloride), bypassing the stage of purification in rectify is the task of improving the performance of the synthesized pure 1,2-dichloroethane, the quality of which exceeds 99.6% of and approaches to 99.9%.

The proposed method does not require additional energy costs in the intensification of the circulation process and allows you to have high performance at a lower height settings and the volume of the circulation loop.

1. Method for producing 1,2-dichloroethane by direct chlorination of ethylene in the liquid medium circulating dichloroethane, including the provision of gas lift circulation dichloroethane in the vertical circuit with a downward and upward flows, maintaining a temperature of dichloroethane in the reaction zone is less than the equilibrium temperature of its boiling point at a pressure in the reaction zone, with the location of the zone of boiling dichloroethane above the reaction zone, putting into circulation of the gaseous starting components of the reaction of chlorine and ethylene, input return liquid dichloroethane, education in the reaction zone of the synthesized dichloroethane, boil dichloroethane in the zone of boiling with the heat of reaction for the formation of vapours, the separation of the steam and liquid phases of dichloroethane, the output of dichloroethane vapor, characterized in that the zone of boiling dichloroethane are placed in the upstream vertical circulation account the movement of the upward flow of dichloroethane and reduce the pressure of the upward flow at the local hydraulic resistance to the value close to the vapour pressure of dichloroethane in place of their output, and form in the zone of boiling probabally the flow regime upstream of dichloroethane.

2. The method according to p. 1, characterized in that when you change the value of the cost of chlorine and ethylene introduced into the circulation loop, the value of the local hydraulic resistance change accordingly inversely proportional, i.e., with increasing costs of chlorine and ethylene is local hydraulic resistance and consequently reduced, and cost reduction of chlorine and ethylene is local hydraulic resistance increase accordingly.

3. The method according to PP.1 and 2, characterized in that the steam concentration in the boiling zone is 0,8 - 0,95.

 

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EFFECT: reduced expenses due to using production waste.

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