Method for producing 1,2-dichloroethane

 

(57) Abstract:

The invention relates to chemical technology and can be used for the production of dichloroethane (E) by direct chlorination of ethylene. The objective of the invention is to minimize the amount of harmful high-boiling compounds per unit produced D. the Proposed method is carried out in a reactor having two communicated with each other on the top and bottom of the vertical columns of the reaction column 1 and the circulating column 2 filled with liquid L and forming a vertical closed circulation loop. In zone 5 column 1 is injected with a specified flow rate of chlorine and ethylene in the gaseous state, liquid return lines and through consumption booster creates an active circulation of the liquid L on the vertical closed loop reactor. Circulation of the liquid L through the zone 5 is carried out with a flow rate of not less calculated based on the proposed, taking into account the specified flow rate of chlorine, thermal effect of the reaction of chlorination of ethylene, the heat capacity of the liquid L, the difference of boiling points D at a pressure level selection vapors D. (zone 8) and at the level of the upper boundary of zone 5, where the reaction occurs. This ensures uniform dissolution and smecheriile proceeds in the liquid phase D, and the process of boiling the D zone starts above 5 reactions. 3 Il.

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

The known method for producing 1,2-dichloroethane, protected by the patent of Germany N 3146246 (M CL C 07 C 19/045, 1983), according to which the method is carried out in a small two-loop reactor column type by direct chlorination of ethylene in the reaction zone, filled with liquid dichloroethane containing conventional catalyst for the activation of chlorine and inhibitor adverse reactions. In the upward flow of liquid dichloroethane, circulating by the difference in densities of the layers is heated, boiling and chilled dichloroethane, enter equimolar amount of chlorine and ethylene in the gaseous state, which, as the dissolution in the liquid dichloroethane enter into chemical interaction with each other. When this occurs, a large amount of heat. The temperature in the reaction zone is 75-200oC, a pressure of 0.1-0.15 MPa. Performed an excerpt of the mixture in the reactor length from 1 to 15 hours reaction Heat is removed mainly by means of the shell-and-tube heat the material of the heat of reaction is removed by evaporation boiling synthesized dichloroethane and due to the selection of dichloroethane vapor from the separation zone (zone of reduced pressure), located in the upper extended part of the column upstream of the second loop circulation circuit. From the heat exchanger and downstream of the second loop of the primary circuit liquid dichloroethane having a reduced temperature, is returned to the bottom of the column of the upward stream and then into the reaction zone to reduce the temperature of dichloroethane in it. The temperature difference between the top and bottom of the reaction zone is 20-30oC. Circulation dichloroethane through the reaction zone is small in the amount of consumption, the consumption of circulating dichloroethane through the reaction zone is not associated in magnitude with the flow fed to the reactor chlorine.

The method has the following disadvantages: complexity, high cost, large metal structure four-column reactor that implements the method and require the use of two-loop circulation system using a special heat exchanger-refrigerator, for which at small charges of circulating dichloroethane requires a large heat exchange surface, and therefore the application of this method on an industrial scale is very difficult; high operating costs due to the need for the very useful and cost control reactor according to the method because of the need to automatically maintain the level of liquid dichloroethane in three zones of the reactor: in the area of stay (excerpts), located in the upper part of the column upstream of the first loop circulation circuit, in the upper part of the column downstream of the same loop and in the area of low pressure, located in the upper part of the column downstream of the second loop circulation circuit.

The known method for producing 1,2-dichloroethane by and.c. USSR N 787079 (M CL 01 J 19/00, publ. in BI, N 46 15.12.80 g), which is carried out in small laboratory column reactor with external circulation pipe has a built-in heat exchanger-refrigerator, by direct chlorination of ethylene in the liquid dichloroethane with the catalyst in the liquid phase and inhibitor adverse reactions substitution of chlorine in the gas-vapor phase. When entering gaseous chlorine and ethylene in the liquid dichloroethane processes of their dissolution and mixing, chemical interaction of dissolved chlorine with ethylene in the reaction zone with the release of a large amount of heat, most of which is removed by the entry of a liquid dichloroethane reduced in the heat exchanger temperature and the remainder of the heat is removed by taking vapors of the boiling dichloroethane, and also due to the natural heat transfer through the walls of the re is m The resulting liquid dichloroethane divert through the nozzle located in the upper part of the reaction column. Circulation of liquid dichloroethane in a closed circulation loop reactor is due to the difference in the densities of boiling and liquid dichloroethane and has a small intensity due to the small and unregulated flow of circulating dichloroethane, passing through the reaction zone.

The disadvantages of this method are the following: the need for continuous tahaliyani liquid dichloroethane, circulating through the reaction zone to reduce the temperature of dichloroethane it requires mandatory use of heat exchanger-refrigerator, which complicates the design of the reactor affects the hydrodynamic conditions of his work, which leads to deterioration of the selectivity of the process and reduction of the degree of conversion of ethylene; this leads to an increase of metal and energy costs and, in addition, to increase operating expenses for the repair of the heat exchanger, which can often fail due to exposure to aggressive environment, namely hydrochloric acid, which is formed by the interaction of hydrogen chloride contained in clubmania when it is a minor defect or damage; low consumption of dichloroethane, circulating through the reaction zone, and the lack of a quantitative relationship between the flow rate introduced into the reaction zone of chlorine and the flow rate of the circulating dichloroethane lead to uneven distribution of chlorine in the cross section upstream of dichloroethane and its uneven use in the reaction zone; this leads to the emergence in the reaction zone of local areas with high concentration of chlorine, and, therefore, increased temperature dichloroethane, increasing the rate of formation of harmful high-boiling compounds. The result of uneven use of chlorine in the reaction zone may be moving molecules of free chlorine in the area of the boil dichloroethane, where temperature increases, and this accelerates the reaction of formation of high-boiling compounds.

Known industrial method for producing 1,2-dichloroethane implemented at JSC "Sayanskhimprom" in the column type reactor with internal circulation pipe (type reactors R-401 displacement of 160 m3). The process is conducted by direct chlorination of ethylene in the liquid dichloroethane circulating due to the difference of the densities of the layers of the liquid (in the circulation pipe) and boiling dichloroethane is evident and the circulation pipe. The consumption of circulating through the reaction zone dichloroethane is not greater than 0.25-0.4 kg/s (800-1200 kg/h) and is not associated quantitatively with a flow rate introduced into the reaction zone of chlorine, that is, with the load of the reactor by chlorine. The known method includes putting into circulation of gaseous chlorine and ethylene, input return liquid dichloroethane, conducting processes of dissolution and mixing of chlorine and ethylene in the liquid dichloroethane, their chemical interactions in the reaction zone, located in the lower part of the upward flow of dichloroethane. The chemical interaction of dissolved chlorine with dissolved ethylene is secreted a significant amount of heat, which is given by evaporation synthesized and incremental (return) of dichloroethane and selection of dichloroethane vapor, as well as due to natural cooling of dichloroethane through the walls of the reactor. However, due to insufficient intensity of the heat sink temperature dichloroethane in the reaction zone decreases slightly higher than the temperature of its boiling point. As a result, the chemical interaction of chlorine and ethylene occurs in the boiling dichloroethane almost the entire height of the reaction zone in liquid and vapor-gas phase, i.e., this process takes place is within a higher temperature, than liquid dichloroethane. For this reason, in the reaction zone simultaneously with the process of synthesizing 1,2-dichloroethane processes of synthesizing high-boiling compounds, including highly environmentally harmful, such as, for example, dichloromethane, the reaction rate of synthesis which increases sharply at high temperatures (>115-119oC). To ensure full use of chlorine in the known method serves in the reaction zone, the excess amount of ethylene, which exceeds the stoichiometric chlorine consumption by 20-30% vapor Pressure dichloroethane above the surface separation is from 0.02 to 0.12 MPa (0.2 to 1.2 kg/cm2).

Thus, the known method of producing 1,2-dichloroethane, taken as a prototype, identified the following main disadvantages:

1. Intensive education in the reaction zone increased amount of environmentally harmful by-products of the reaction of the high-boiling compounds and particularly trichloroethane (up to 1-3% of the yield of 1,2-dichloroethane, i.e., up to 10-30 kg/t). The cause of their formation is not sufficiently active heat removal in the reaction zone, due to the low flow intensity circulation dichloroethane through the reaction zone, a small temperature difference, Dania chlorine and ethylene in the cross section of the ascending flow reaction medium. In this regard, the heating temperature dichloroethane rises above its boiling point, which causes it to boil almost the entire height of the reaction zone to the formation of a vapor-gas phase, in which the process of synthesis of dichloroethane in turn leads to elevated temperature in the vapor-gas phase, exceeding the boiling temperature of dichloroethane, resulting in a vapour-gas phase dramatically increases the reaction rate of synthesis of high-boiling compounds.

2. Education increased amount of high-boiling compounds reduces economic indicators known way due to the necessary costs of disposal and reduce the degree of conversion of chlorine, part of which is spent on the synthesis of high-boiling compounds.

3. The feed in the reaction zone of a large number of excess ethylene, part of which is spent on the formation of harmful compounds, reduces the efficiency of this method due to the increased consumption of ethylene or additional costs for its disposal, for example, dharitvena.

The objective of the proposed method for producing 1,2-dichloroethane is to reduce the number (share) of the resulting high-boiling compounds per unit proizvodimoe is in the area of chemical interaction of chlorine and ethylene (reaction zone) are excluded boil dichloroethane, which is achieved by increasing the intensity of heat-extraction from the reaction zone.

The invention consists in that in the method for producing 1,2-dichloroethane by direct chlorination of ethylene in the liquid dichloroethane circulating in the vertical closed circuit including the input in the circulation loop of gaseous chlorine and ethylene, return liquid dichloroethane, selection of dichloroethane vapor, as well as the processes of dissolution and mixing of chlorine and ethylene in the liquid dichloroethane, their chemical interactions in the reaction zone, boiling dichloroethane, separation of vapors, according to the invention the circulation of liquid dichloroethane through the reaction zone is performed with a flow rate of not less calculated based on

< / BR>
where Gg.minthe minimum value of the flow rate of the liquid dichloroethane, circulating through the reaction zone, kg/s;

Gholdemgiven chlorine consumption, entered for the chlorination of ethylene (load on chlorine), kg/s;

qpthermal effect of the reaction of chlorination of ethylene (referred to 1 kg of unreacted chlorine), j/kg;

WITHddeploymnet-level selection of dichloroethane vapor, the hail.

tK. D.(P5) boiling point dichloroethane at a pressure at the level of the upper boundary of the reaction zone, hail.

In Fig. 1 schematically shows a two-column reactor, which implements the proposed method, the direction of circulation of the liquid in the closed circuit and the location of technological zones; Fig. 2 the graph of the functional dependence of the boiling point of 1,2-dichloroethane from changes in pressure; Fig. 3A is a graph of pressure along the height of the reactor in an upward flow of the circulation dichloroethane; Fig. 3b is a graph of the boiling point of dichloromethane and the actual temperature in the technological areas upstream and downstream flows of dichloroethane at various flow rates through the reaction zone.

The proposed method of producing 1,2-dichloroethane is carried out in a reactor containing communicated with each other on the top and bottom of the two vertical columns of the reaction column 1 of the upward flow and circulation column 2 downstream of dichloroethane. In the lower part of the reactor is set the pump flow rate, representing the screw 3 axial pump with drive 4 of its rotation. To ensure optimalnoga 1 and 2, pre-calculate the minimum value of the flow rate of the liquid dichloroethane through the zone 5 of the reaction according to the following dependence:

< / BR>
where GD. minthe minimum value of the flow rate of dichloroethane, circulating through the reaction zone 5, kg/s;

Gholdemgiven chlorine consumption, entered for the chlorination of ethylene (load on chlorine), kg/s;

qpthermal effect of the reaction of chlorination of ethylene (referred to 1 kg of unreacted chlorine), j/kg;

WITHdheat capacity of liquid dichloroethane, j/(kg deg.);

tK. D.(P8) boiling point dichloroethane at a pressure level selection of dichloroethane vapor, hail.

tK. D.(P5) boiling point dichloroethane at a pressure at the level of the upper boundary of the reaction zone, hail.

Columns 1 and 2 of the reactor is filled with liquid dichloroethane to ensure the flow of liquid dichloroethane from the reaction column 1 in the circulation column 2. The inclusion of the actuator 4 is put into rotation of the screw 3 axial pump and set this frequency of its rotation, which provides active circulation of dichloroethane in a closed circulation loop with a flow rate of not less calculated values for the relationship. her part of the column 2 at column 1, in which is formed an upward flow of liquid dichloroethane. Accordingly, in column 2 is formed downward flow dichloroethane (Fig. 1). In the lower part of the column 1 through the glands and dispersing device (not shown) is injected in a gaseous form of chlorine and ethylene. The point of introduction of chlorine is below the level of the input ethylene. The input of chlorine produced with a flow rate set according to the relationship. Simultaneously with chlorine in the upward flow of dichloroethane is served in a small amount (0.5 to 2.5 percent) gaseous oxygen or air as an inhibitor adverse reactions occurring in the gas-vapor phase. Increased consumption of liquid dichloroethane promotes intense turbulence in the liquid dichloroethane in zone 5 of the reaction, therefore the injected chlorine and ethylene rapidly and vigorously mixed with liquid dichloroethane and evenly distributed over the cross section upstream of dichloroethane. When this happens fast dissolution in the liquid dichloroethane, and the reduction of its temperature (Fig. 3b, curve 10 in places input return dichloroethane, chlorine and ethylene). As the dissolution of ethylene in zone 5 shall enter into a chemical reaction with the dissolved chlorine, that is, the reaction occurs direct chlorination of ethylene in the PoE is spent on heating the liquid dichloroethane, circulating through the zone 5 (Fig. 3b, curve 10 in zone 5 reactions). As in the synthesis of one mole of dichloroethane is allocated the same amount of heat, which is enough to evaporate six moles of liquid dichloroethane (one mole synthesized dichloroethane and five moles extension), in the lower part of the reactor continuously introducing a stream of incremental (return) of liquid ethylene dichloride in the amount compensative selected number of dichloroethane vapor. Incremental and recirculating dichloride are mixed in the lower part of the reactor and the mixture is fed by the screw 3 in zone 5 with an estimated flow rate according to the relationship. Active circulation dichloroethane through zone 5, where there is intense heat, provides appropriate about the intensity of the heat from this area, so the temperature of dichloroethane in zone 5 does not reach the temperature of its boiling point and is not more than 110oC. Therefore, the reaction of synthesis of 1,2-dichloroethane is performed from beginning to end in the liquid phase without vaporization. As duct liquid dichloroethane through zone 5 is carried out with a flow rate proportional to the flow rate of the introduced chlorine, the process of chemical interaction with ethylene entire quantity of explosives is in the liquid dichloroethane order of magnitude higher than the reaction rate of synthesis of high-boiling compounds, therefore, in zone 5, the formation of only 1,2-dichloroethane, and the probability of synthesizing high-boiling compounds is minimized. According to this dependence, the chemical interaction of chlorine and ethylene ends at the upper boundary of zone 5 and the upward flow of dichloroethane is fed in above the zone 6, where the hydrostatic pressure is lower than in zone 5. As part of the upward flow of dichloroethane, arriving in zone 6, contains the actual 1,2-dichloroethane, some amount of excess ethylene, approximately 2-4% in relation to the number of ethylene, which entered into reaction with chlorine, and a certain amount of oxygen. When receiving a flow of heated dichloroethane in zone 6 is gradually boil, as its equilibrium temperature by reducing the hydrostatic pressure is reduced accordingly (Fig. 3A and 3b, curve 10 in zone 6). Boiling dichloroethane is accompanied by release of vapor and a gradual decrease in his temperature as the expenditure of heat of reaction on the transition dichloroethane from liquid state to vapor. Upon receipt of the boiling dichloroethane in the upper part of the column 1, i.e., in zone 7, where the hydrostatic galleriesasian separation zone 8, where is produced from the selection for further processing. Here occurs the separation of the excess ethylene and oxygen in the air and made their removal from the reactor together with the pairs of dichloroethane, the boiling point of which at the level of selection of the vapors is reduced in accordance with reduction in pressure in the upper part of the reactor (Fig. 3b, curve 10 at the level of selection of dichloroethane vapor). A significant part of the heat of reaction is carried away in the selection of vapor, so there is a further decrease in the temperature of dichloroethane, downdraft comes from zone 7 zone 9 circulation column 2, where the reduction of its temperature continues due to heat loss to the walls of the column 2 (3b, curve 11 in height zone 9 downstream). In the lower part of the reactor downward flow of circulating dichloroethane and the return flow of dichloromethane is mixed and the mixture is again served with the estimated flow rate in zone 5 of the reaction column 1. Next, the process of circulation of dichloroethane in a closed circulation loop is repeated. In Fig. 3b shows that reducing consumption of dichloroethane through zone 5 (curve 12) below the calculated values, the conditions for the synthesis of harmful high-boiling compounds, as timemessage interaction of chlorine and ethylene will occur in the vapor-gas phase. The nature of changes in the boiling point of dichloroethane from changes in the pressure of the working medium in the height of the reactor in column 1 is reflected by using the curve 13. When the flow rate increases dichloroethane through zone 5 to the value in excess of its estimated value (curve 14 in zone 5), there is an additional temperature reduction dichloroethane due to more intense heat of the reaction, however, increases the energy consumption for an increase in the frequency of rotation of the screw 3. Thus, the position of the curve 10 with respect to the curves 12, 13 and 14 in the zone 5 of the mechanism shown in Fig. 3b, confirm that only when the estimated value of consumption of dichloroethane, which is determined according to the above dependency is ensured sufficiently intensive and economical Teplodar from zone 5 reactions, excluding lash dichloroethane in it and how would bias the zone 6 boiling dichloroethane above zone 5.

The proposed method allows comparison with the prototype to reduce the amount of harmful high-boiling compounds such as trichloroethane, for example: to significantly reduce the amount of feed in zone 5 response of excess ethylene (30-50%); to increase the yield of 1,2-dichloroethane 1.2 1.5 percent; to reduce overall Energotech">

The proposed method is tested on simulated environment in the experimental reactor with transparent walls in laboratory conditions. Studies have confirmed the possibility of avoiding boiling of the medium in the reaction zone with an estimated value of its flow through the reaction zone.

Method for producing 1,2-dichloroethane by direct chlorination of ethylene in the liquid dichloroethane circulating in the vertical closed circuit including the input in the circulation loop of gaseous chlorine and ethylene, return liquid dichloroethane, selection of dichloroethane vapor, as well as the dissolution and mixing of the chlorine and ethylene in the liquid dichloroethane, their chemical interactions in the reaction zone, boiling dichloroethane, separation of vapor, characterized in that the circulation of liquid dichloroethane through the reaction zone is performed with a flow rate of not less calculated based on

< / BR>
where GD. minthe minimum value of the flow rate of the liquid dichloroethane, circulating through the reaction zone, kg/s;

Gholdemgiven chlorine consumption, entered for the chlorination of ethylene (load on chlorine), kg/s;

qpthermal effect of the reaction of chlorination of ethylene (referred to 1 kg reacted perature boiling dichloroethane at a pressure level selection of dichloroethane vapor, the hail.

tK. D.(P5- the boiling point of dichloroethane at a pressure at the level of the upper boundary of the reaction zone, deg.

 

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