Method for producing 1,2-dichloroethane

 

(57) Abstract:

The invention relates to the production of 1,2-dichloroethane by direct chlorination of ethylene in the liquid dichloroethane. 1,2-dichloroethane get in the reactor with a vertical casing and the Central reaction tube, which provide gas lift circulation flow of liquid dichloroethane in the vertical circuit with its calculated level of consumption, excluding lash dichlorethane in the reaction zone. Enter the gaseous chlorine and ethylene in the reactor is carried out through the distribution nozzle installed in the reaction tube. Previously, at least one gaseous reagent is dispersed in the liquid dichloroethane using the ejector through a nozzle which is injected or chlorine, or ethylene. Liquid dichloroethane served in the receiving chamber of the ejector with a flow rate of 0.01 to 0.2 from the calculated flow rate of the liquid circulating dichloroethane. The technical result is an increase in the yield of the final product by increasing the selectivity of conversion of the reactants. 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 Hai 7, 10.03.97 year), according to which the dichloroethane is produced by the direct chlorination of ethylene in the liquid medium circulating dichloroethane. The known method includes providing forced circulation of dichloroethane in the vertical circuit with a downward and upward flow of liquid dichloroethane, bubbling putting into circulation the original gaseous components of the reaction of chlorine and ethylene with their distribution in the flow of liquid circulating dichloroethane and mixing them with the liquid circulating dichloroethane, enter in the circulation loop return liquid dichloroethane, synthesizing dichloroethane in the reaction zone, the heat of reaction in the zone of boiling dichloroethane, the separation of the steam and liquid phases of dichloroethane with the withdrawal of vapors. This forced circulation of liquid dichloroethane through the reaction zone is performed with the estimated expense, excluding lash dichloroethane it, why support him no less calculated by mathematical relationships, including the flow of chlorine, thermal effect of the reaction of chlorination, heat capacity of liquid dichloroethane, boiling point dichloroethane at a higher pressure at the top level of the reaction zone and the temperature of cipea in excessive quantities.

The estimated minimum value of the flow rate of the circulating dichloroethane though and prevents boiling of liquid dichloroethane in the reaction zone, however, requires additional energy costs in the operation of the pump flow rate to ensure a sufficiently intense circulation of dichloroethane through the reaction zone.

The known method has other, more significant drawbacks. The main ones are incomplete conversion of ethylene (no more than 90-95%) and the impossibility of increasing the selectivity of the reaction of chlorine and ethylene component in a known way 98-99% as chlorine and ethylene. One of the reasons for the incomplete conversion of ethylene is its inability to rapid dissolution (absorption) in the liquid dichloroethane, and another reason for incomplete conversion of ethylene is because when bubbling input gaseous ethylene in poorly turbulizing the flow of circulating liquid dichloroethane formed a large number of large bubbles of ethylene, drastically reducing the flow velocity, as processes of gas absorption and chemisorption processes that leads to breakthrough not had time to absorb and react with the chlorine to form large bubbles of ethylene through the reaction zone in the zone o guys dispersion of ethylene with his bubbling input causing a significant reduction in total and the specific surface area of contact of phases in the system of gas - liquid, and therefore, decrease the speed of the process of chemisorption of chlorine solution in the liquid dichloroethane. Studies show that the share of small bubbles of the gas phase when it is bubbling input is not more than 33% of the total surface of contact of phases in the system of gas-liquid. With increasing gas flow rate, the share of large gas bubbles increases. The decrease in General and the specific surface area of contact of phases with low ability to ethylene absorption leads to an increase in the total time of the chemical interaction of chlorine and ethylene, and therefore, requires an increase in the volume and height of the reaction zone, leading in turn to increasing the yield of by-products in the reaction zone. The presence of large bubbles of ethylene in the reaction volume creates conditions for the emergence of local areas of high temperature, which has accelerated sharply adverse reactions and increases the yield of by-products. All of these reasons, reducing the selectivity of the known method for ethylene, lead to reduced yield of the target product - 1,2-dichlorethane, to the necessity of increasing the share of excess ethylene at its input s no way to increase the selectivity for chlorine because of the same above reasons. That is, the increase in reaction time between ethylene and chlorine, which has a higher absorption rate in dichloroethane, leads to the fact that chlorine has time to react not only with the absorbed ethylene, but also with liquid circulating dichloroethane to form with him by-products, mainly - trichloroethane, which also reduces the yield of the target product.

The known method for producing 1,2-dichloroethane by RF patent 2106907 (IPC 01 J 19/24, publ. in BI 8, 20.03.98 year), according to which the 1,2-dichloroethane produced by direct chlorination of ethylene in the liquid dichloroethane. The known method includes providing gas lift circulation flow of liquid dichloroethane in the vertical circuit with an estimated consumption, excluding lash dichloroethane in the reaction zone, enter through the ring bubbler or through the nozzle, or through a nozzle of the ejector in the circulation loop of the original gaseous components of the reaction of chlorine and ethylene and mixing them with upward flow of liquid circulating dichloroethane, input return liquid dichloroethane in the circulation loop, the synthesis of dichloroethane in the reaction zone, the heat of reaction in the zone of boiling dichloroethane, the separation of the steam and liquid phases of dichlorethane exercise in excessive quantities.

In the known method the input and distribution of gaseous components of chlorine and ethylene is carried out with the aid of a ring of bubblers, nozzles and ejectors, and he characterized the main disadvantages of the above-described analog, so as not ensured sufficiently fine dispersion of the introduced gas phase, and therefore not the task of the increase in General and the specific surface area of contact of phases in the system "gas - liquid". Cause insufficient dispersion of the gas phase in this case are as follows. It is known that the degree of dispersion of the gas phase introduced into the liquid phase, directly depends on the degree of turbulence of the liquid phase. In a known way in a cocurrent enter the gas phase through a conventional nozzle directly into the fluid flow circulating with a high consumption cannot be achieved the maximum dispersion of the gas phase, as a jet of gas in a flooded state flowing from the nozzle, produces a liquid weak turbulent effects. The gas phase in this case is divided mainly into large bubbles and a relatively small number of small bubbles, so the resulting gas-liquid mixture has a relatively small overall and specific pea, when according to a known method in the mixing chamber is forcibly given to the liquid circulating dichloroethane with full circulation flow, which is more than 20 times exceeds the capabilities of the ejector for ejection of the liquid phase stream of gas, also not achieved sufficient dispersion of the gaseous component of the reaction in the liquid dichloroethane due to the lack of vacuum between the nozzle and the mixing chamber.

It is known that the degree of dispersion of the gas phase is higher, the higher the degree of turbulence of the liquid phase into which is fed a stream of the gas phase. In turn, the degree of turbulence of the liquid phase in this case is higher, the higher the degree of dilution that occurs between the ejector nozzle and the mixing chamber. According to research by the maximum degree of turbulence of the flow of the liquid phase generated by the energy of the jet of gas supplied to the nozzle of the ejector, is achieved only in the case when the ejector creates maximum suction and it works in the mode of ejection. When this liquid phase enters the ejector with the same flow rate, with which he is able to draw due to the vacuum generated between the nozzle and the mixing chamber of the jet energy of the gas phase.

Due to the specified known method does not allow to increase the conversion rate of ethylene and does not provide increased selectivity as ethylene and chlorine due to the lack of opportunities to increase General and specific surface area of contact of phases between the gaseous components of the reaction and liquid circulating dichloroethane due to low degree of dispersion of the gas phase chlorine and ethylene. Therefore, the known method does not allow to increase the yield of the target product is 1,2-dichloroethane in view of the increased output pomocnych economic efficiency of the production of dichloroethane.

The task of the invention is to increase the conversion of ethylene and increase the selectivity of the process for producing 1,2-dichloroethane as chlorine and ethylene, the improvement of the economic efficiency of the method by increasing the yield of the target product is 1,2-dichloroethane by reducing output products without increasing energy costs.

The technical result of the invention is expressed in the increase of General and specific surface area of contact of phases in the system of gas - liquid in the zone of absorption and reaction due to the maximum use of the kinetic energy of a jet of gas phase introduced into the liquid dichloroethane, which allows significant acceleration of the process of chemical interaction between the source of gaseous components of the reaction of chlorine and ethylene and helps to reduce the volume and height zones of absorption and reaction.

The invention consists in that in the method for producing 1,2-dichloroethane by direct chlorination of ethylene in the liquid dichloroethane, including the circulating flow of liquid dichloroethane in the vertical circuit with an estimated consumption, excluding lash dichloroethane in the reaction zone, enter in Circulo circulating dichloroethane, enter return liquid dichloroethane in the circulation loop, the synthesis of dichloroethane in the reaction zone, the heat of reaction in the zone of boiling dichloroethane, the separation of the steam and liquid phases of dichloroethane with the withdrawal of vapors, according to the invention before entering into the circulation path at least one source of a gaseous component reactions of its pre-dispersed in a liquid dichloroethane using the ejector through a nozzle which enter the appropriate source of gaseous component reactions, and liquid dichloroethane served in the receiving chamber of the ejector with a flow rate of 0.01 to 0.2 from the calculated flow rate of the liquid circulating dichloroethane.

The invention is illustrated by drawings, where Fig.1 shows a diagram of the reactor that implements the proposed method, with deployme distributors and ejecting the dispersion of chlorine and ethylene, and Fig.2 is a graph of the specific surface area of contact of phases in gas-liquid mixture, depending on the flow of liquid dichloroethane fed to the ejector at a constant flow rate of gas supplied through the nozzle of the ejector.

The proposed method of producing 1,2-dichloroethane is carried out in a reactor with jet wooram on its axis placed the reaction tube 2. The upper and lower part of the tube 2 is in communication with the internal volume of the housing 1. In the absorption zone, located in the lower part of the tube 2, a nozzle 3 for input of chlorine gas at the boundary zones of absorption and reaction set the nozzle 4 to the input of gaseous ethylene. The nozzles 3 and 4 are connected respectively to the nozzles 5 and 6, to the input ends of which are coaxially attached ejectors with mixing chambers 7 and 8 and nozzles 9 and 10. To the nozzle 9 of the ejector is connected a pipe for feeding gaseous chlorine into the reactor, and to the nozzle 10 of the ejector pipe for supplying gaseous ethylene (not shown).

In the receiving chamber ejectors provides for the supply of liquid dichloroethane from the reactor through pipes 11 and 12, provided with regulating valves 13 and 14. In the lower part of the reactor enter return liquid dichloromethane with the addition of the catalyst for the main reaction and inhibitor adverse reactions in liquid medium (for example, trivalent ferric chloride). The filling of the reactor leads to the desired level determined by the load on chlorine. Gaseous components of the reaction of chlorine and ethylene is introduced into the reactor, respectively, through the nozzle 9 and 10 ejectors at open valves 13 and 14 and through raspredeliteli the amount of gaseous oxygen or air as an inhibitor adverse reactions, flowing in the gas-vapor phase. During steady state operation of the reactor in it due to gas generated vertical circulation with upward flow of liquid circulating dichloroethane in the reaction pipe 2 and a downward flow of liquid circulating dichloroethane in the housing 1 with an estimated consumption, circulation, eliminating lash dichloroethane in the reaction zone at the proper pressure it generated an estimated height of the column of liquid dichloroethane, circulating in a downward flow.

With the help of the valves 13 and 14 to regulate the flow of liquid dichloroethane fed to the receiving chamber ejectors, to ensure their effective operation of ejection, that is, suction liquid dichloroethane in the mixing chamber ejectors due to the vacuum generated by the kinetic energy of the jet of gaseous chlorine or ethylene. The most effective ejectors operate at a flow rate of liquid dichloroethane as low as 0.01 to 0.2 from the calculated flow rate of liquid dichloroethane circulating in the vertical circuit of the reactor. When the specified mode of operation of the ejectors is the most intensive process of dispersion of the gaseous components of the reaction in their cameradude in nozzle 9 and 10 with a high consumption of gaseous chlorine and ethylene, streams which have a high energy level, create turbulence liquid dichloroethane, suction through the pipes 11 and 12 of the mixing chamber 7, and 8 with a relatively small consumption of 0.01 to 0.2 from the calculated flow rate of the liquid circulating dichloroethane. In the mixing chambers 7 and 8 is formed local turbulent field with high specific density dissaperance of energy in it, through which a gas jet of chlorine and ethylene are broken into very small gas bubbles form in the liquid dichloroethane finely dispersed mixture. Formed in the mixing chambers 7 and 8 of finely dispersed mixture is fed through the nozzles 5 and 6 in the distribution nozzles 3 and 4, respectively, and introduced into the upward flow of liquid dichloroethane circulating in the reaction pipe 2 with a high flow rate, which excludes its boiling in the reaction zone. This fine mixture of gaseous chlorine and liquid dichloroethane is introduced into the absorption zone, where due to the high value of General and specific surface area of contact of phases in two-phase dispersed system "chlorine - liquid dichloroethane" gaseous chlorine is rapidly and completely dissolved in an upward flow of liquid circulating dichloroethane and evenly smesi Idaho dichloroethane is introduced through a distribution nozzle 4 directly into the reaction zone of the tube 2, where ethylene is also dissolves quickly in an upward flow of liquid circulating dichloroethane and simultaneously enters into a chemical reaction with dissolved chlorine due to the high value of General and specific surface area of contact of phases in two-phase dispersed system "ethylene - liquid dichloroethane".

Chemical reaction interaction of chlorine and ethylene, which is synthesized 1,2-dichloroethane, runs at high speed, as occurs completely in the liquid phase. Due to its high speed, the chemical interaction of chlorine and ethylene is completed at a small distance from the reaction zone, and therefore its volume is dramatically reduced. As a result, virtually eliminated the occurrence of side reactions, because they don't "have time" to occur, significantly increases the selectivity of the process as chlorine (99.9%), and ethylene (99.9%). Practically no mass "breakthrough" large bubbles of gaseous ethylene due to a very small amount of finely dispersed mixture of ethylene and liquid dichloroethane, which ensures a significant increase in the conversion of ethylene (up to 98%). However, there is an excessive amount of heat to heat the mixture synthesization intense heat, which is provided with calculated flow upward flow of liquid dichloroethane, circulating through the reaction zone, and maintaining the appropriate calculation of hydrostatic pressure in the reaction zone. A mixture of synthesized and circulating liquid dichloroethane upward flow rises from the reaction zone into the zone of boiling tube 2, i.e. in an area with a lower hydrostatic pressure, where the boiling dichloroethane with the formation of its vapor-liquid mixture. The process of evaporation intensified with the rise of the liquid-vapor mixture through the pipe 2. This results in intense heat of the reaction. In the area of the housing 1 above the pipe 2, and ends the process of evaporation and separation of the steam and liquid phases of dichloroethane. A pair of dichloroethane are derived from the upper part of the housing 1 through the corresponding nozzle, and liquid dichloroethane, chuckling over the upper edge of the tube 2 is returned to the downward flow of liquid dichloroethane circulating in the annular space enclosed between the walls of the casing 1 and the pipe 2. Then liquid dichloroethane is fed into the lower part of the reaction tube 2 through gas lift circulation created by the difference in densities paragidm the space between the walls of the casing 1 and the pipe 2. At the conclusion of dichloroethane vapor from the reactor, the quantity of liquid dichloroethane in it decreases. So his number is constantly compensate by feeding liquid return dichloroethane. Thanks to the upper level of liquid dichloroethane in a downward vertical flow circulation circuit is maintained at a certain estimated the altitude at which the reaction zone is generated pressure rating, providing the necessary equilibrium temperature dichloroethane, excluding its boiling within the specified range.

The proposed method is compared with the prototype allows to solve the problem of increasing the conversion of ethylene (up to 98%), increasing the selectivity of the process for producing 1,2-dichloroethane as chlorine (99.9%), and ethylene (99.9%), therefore, provides a significant reduction in output as low-boiling and high-boiling by-products and in this way allows you to increase the yield of the target product is 1,2-dichloroethane. The result is the increase of economic efficiency of the proposed method, as it requires no additional energy costs in the production of fine-dispersed gas-liquid mixture of the original gaseous components of the reaction and the Tana by direct chlorination of ethylene in the liquid dichloroethane, includes a circulating flow of liquid dichloroethane in the vertical circuit with an estimated consumption, excluding lash dichloroethane in the reaction zone, putting into circulation the original gaseous components of the reaction of chlorine and ethylene and mixing them with the liquid flow circulating dichloroethane, input return liquid dichloroethane in the circulation loop, the synthesis of dichloroethane in the reaction zone, the heat of reaction in the zone of boiling dichloroethane, the separation of the steam and liquid phases of dichloroethane with the withdrawal of vapors, characterized in that before putting into circulation, at least one source of a gaseous component reactions of its pre-dispersed in a liquid dichloroethane using the ejector through a nozzle which enter the appropriate source of gaseous component reactions, and liquid dichloroethane served in the receiving chamber of the ejector with a flow rate of 0.01 to 0.2 from the calculated flow rate of the liquid circulating dichloroethane, and injected into the circulation loop at least one source of a gaseous component of the reaction in the form of finely dispersed mixture with liquid dichloroethane formed in the mixing chamber of the ejector.

 

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