Method for isolation of fine dispersed, gummy and high boiling by-products from dichloroethane pyrolysis reaction gases from vinylchloride production

FIELD: chemical technology, in particular method for vinylchloride production.

SUBSTANCE: claimed method includes fast gas cooling in quenching column followed by separation of pyrolysis products. Quenching and separation are carried out by barbotage through the layer of liquid concentrated by-products of these gases in quenching column cube. Then steam/gas mixture is brought into contact with returning condensate in regular filling layer of rectification tower with simultaneous purification of steam/gas mixture in rectification zone upstream. Liquid concentrated by-products are additionally rectified in vacuum with isolating and recovery of products having boiling point higher than the same for dichloroethane and distillate recycling. Method of present invention also makes it possible to produce perchloroethylene and tricloroethylene.

EFFECT: vinylchloride of high quality; reduced effort and energy consumption.

2 tbl, 4 dwg, 2 ex

 

The invention relates to the technology of basic organic synthesis and can be used in the allocation of finely dispersed solid, resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride used to produce polymeric materials, in particular PVC skin.

A known method of separation of finely dispersed resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride having a temperature of 440-520°and pressure 10-28 ATM, by rapid cooling in the quenching column with subsequent separation of the products of pyrolysis of dichloroethane (patent DE 3147310, C 07 C 21/06, 18.01.90).

Quenching of the reaction gases by this method (figure 1) is conducted at a temperature 105-200°in column 1, acting on the principle of capacitor mixing by spraying chilled circulating pump 4 hardening liquid 2, which is formed by condensation of the reaction gases. Next part 7a condensed in the condenser 6 of the reaction products are returned to the column 1, and the remaining part 7b together with gaseous products 8 and hardening the liquid is subjected to distillation in a system of distillation columns, providing for the allocation in the form of distillate initially, hydrogen chloride, and then blame the chloride, next "boiling" by-products of pyrolysis and, finally, unreacted dichloroethane, returned to the pyrolysis, which is released together with "high-boiling by-products". The Department returned to the pyrolysis of dichloroethane from "high-boiling" by-products is carried out in conjunction with selection of the "high-boiling" by-products of direct dichloroethane, synthesized from ethylene and chlorine by original distillation of pure dichloromethane and then the residual dichloroethane from distillation products.

This classical scheme of hardening by cooling and separation of the reaction products by successive selection of light components has a number of serious drawbacks:

- heavy-duty system rectification, including the column quenching of the reaction gases, due to the presence in the bottom hardening liquid of high viscosity products and solid resinous particles. This forces the user to install on the lines of still liquids special filters 3 for the separation of these impurities. Simultaneously, the presence of such impurities in the distillation of liquids distillation columns helps to reduce the duration of pre-owned boilers between cleanings;

- presence in the flowsheet column hardening of the circulation pump and having a large circulation flow strongly pitched fluid;

-residual rectification dichloroethane after the selection is returned to the pyrolysis of dichloroethane may not be used for processing in other target products and must be destroyed. The result is permanently lost valuable products, such as higher chlorethane.

The closest analogue of the present invention (the prototype) is a method of separation of finely dispersed solid, resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride, which consists in the following (patent RU 2153486 C 07 C 7/09, 7/11, 17/25, 21/06).

The reaction gases (temperature 440-520° (C) the coil of the furnace pyrolysis of dichloroethane (figure 2) served in the cube hardening of the column 1 through the bubbler in a layer of concentrated liquid by-products at the temperature of boiling 120-200°C. the resulting gas-vapor mixture passes through capleton and mass transfer 19 20 plates of a distillation zone hardening of the column 1 and is in the form released from the high-boiling components of the gas mixture 3 in the refrigerator 4. The condensate part of this gas mixture are returned to the quenching column 1 in the form of phlegmy 5A and part in the form of distillate 5B together with the unfused flux 6 serves to further separate.

Taken from the bubble layer, the liquid 2 is served in the evaporator circuit, which includes a capacity of 7, a device for forced circulation 8 and the evaporator 9. Gas-vapor mixture from the evaporator served in the distillation column 11 capacily the ohms 12, the capacitor 13 and the reflux tank 14 for discharge from her target dichloroethane in the form of distillate, part of which is returned to distillation column 11 in the form of phlegmy by a pump 15, and a part goes into the quenching column 1 by a pump 16. CBM product 18 from the column 11 together with concentrated products osmola 17 is removed from the system.

However, the method has some significant drawbacks:

distillation column 11 operates under atmospheric pressure, which causes a high boiling point in the evaporator and, as a consequence, the resinification products and the formation of solid deposits on the heating surfaces;

- high (about 20 wt.%) the concentration of dichloromethane in the waste sent for recycling;

- the presence of the evaporator, including the capacity of 7, a device for forced circulation 8 and the evaporator 9 makes the site more separation of liquid by-products are cumbersome and bulky.

The invention consists in that in the method of separation of finely dispersed solid, resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride by rapid cooling in the quenching column and the subsequent separation of pyrolysis products by ozonation them through the layer of liquid skoncentrirovat the different by-products of these gases in the cube quenching column with subsequent contact of the gas mixture with return condensation of these gases in a distillation zone, providing a cleaning gas mixture from the high-boiling products, output products and their additional distillation with the selection and output of the process of finely dispersed solid resin particles and the products boiling above dichloroethane, and the return of the distillate in the process, additional rectification carried out under vacuum in a distillation column equipped with a regular nozzle and high speed evaporator with the withdrawal of finely dispersed solid resin particles and the high-boiling by-products with kubovy the remainder of the column.

When carrying out the invention is achieved by the following technical result:

- decrease to ~5 wt.% loss of dichloroethane by reducing its content in the waste sent for recycling by reducing the boiling temperature and elimination of polymerization processes in the evaporator of the column additional rectification;

- ensures the development of high quality;

- the conditions for a possible skilled use of polyvinyl chloride fraction2formed during the synthesis of dichloroethane, for example, to obtain perchloroethylene, trichloroethylene, etc.;

- ensures that the concentration of coke, tar and high-boiling by-products of the reaction of pyrolysis of dichloroethane and their removal from the gas-vapor separation system is Messi with kubovy the remainder of the column additional rectification;

- reduced size and metal installation by eliminating the evaporator and the fluid directly into the distillation column.

The presence of one new distinctive characteristic compared to the prototype determines whether the claimed technical solution the criterion of “novelty”.

Conform to the technical solutions to the criterion of “inventive step” is due to the appearance of the essential features of a new technical result, which consists in reducing the loss of dichloroethane in the waste sent for recycling, by lowering the boiling point and removing the polymerization processes in the evaporator of the column additional rectification. Figure 3 shows the dependence of the boiling point of waste sent for recycling, the pressure at different concentrations of dichloroethane. It is seen that at a pressure of P=1 at boiling point of the mixture with a concentration of dichloroethane X=20 wt.% (dashed line corresponding to the columns work the prototype) is ~120°C. If lower the pressure to P=0.1 at a mix with a lower concentration of dichloroethane X=5 wt.% will have a boiling temperature t=105°With (curve 1). Hence the conclusion that without exceeding the permissible temperature, it is possible to reduce the loss of dichloroethane waste more than three times.

The administration is giving process of rectification in the column under vacuum reduces the boiling point of the mixture in the evaporator and to take on the disposal of a mixture with a higher content of high-boiling impurities. This, in turn, leads to reduction of dichloroethane waste. Figure 3 (curve 4) shows the dependence of the boiling point of the liquid content of high-boiling impurities at a pressure in the cube columns of P=0.5 ATM. It is seen that the boiling point 113°corresponds to the concentration of high-boiling impurities 90 wt.% and, accordingly, the concentration of dichloroethane less than 3 wt.%.

List of figures in the drawings:

Figure 1 - scheme of the method of separation of finely dispersed resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride by similar, patent DE 3147310.

Figure 2 - scheme of the method of separation of finely dispersed resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride by the prototype.

Figure 3 - dependence of the boiling point of waste sent for recycling, the pressure at different concentrations of dichloroethane.

4 is a diagram of the proposed method of selection of finely dispersed resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride.

The method is as follows. The reaction gases (temperature 440-520° (C) the coil of the furnace pyrolysis of dichloroethane served in the cube hardening of the column 1 through the bubbler in the layer of liquid concentrated on the internal products at the temperature of boiling 120-200°C. the resulting gas-vapor mixture passes through the layer of regular packing 2 distillation zone hardening of the column 1 and is in the form released from the high-boiling components of the gas mixture 3 in the fridge 4.

The condensate part of this gas mixture is returned to the column 1 in the form of phlegmy 5A and part in the form of distillate 5B together with neskondensirovannyh flow 6 serves to further separate.

Finely dispersed solid, resinous products from the reaction pyrolysis gases are trapped in the bubble layer hardening of the column. Taken from the bubble layer, the liquid 7 in conjunction with tankodesantniki resinous products is served through the reducing valve 8 in the middle part of the distillation column 9, provided with a regular showerhead 10 and 11, a high-speed evaporator 12, operating with circulationin pump 13, a capacitor 14 and the reflux tank 15. The vacuum in the column 9 is created by the condensation of vapors and supported by the vacuum pump 16. Part of the condensate from the tank 15 is returned by the pump 17 in column 9 in the form of phlegmy 18a and part 186 by the pump 19 is directed into the quenching column 1.

CBM product from the column 9 in conjunction with the fine resinous products 20 are removed from the system for recycling.

Use regular packing and SK the speed of the evaporator, working in conjunction with the circulation pump makes distillation column 9 is insensitive to the presence in the liquid finely dispersed solid substances, which are displayed together with concentrated high-boiling components. The composition of the material flows is presented in table 1.

Table 1
The approximate composition of the flows in the circuit (figure 4)
  The concentration of components, wt. -%
№ p/pThe components of the mixtureThe sinThread 3 (a pair of quenching column)Thread 7 (the liquid from the quench column)Thread 20 (waste from the vacuum distillation column)
1Hydrogen chloride18,1418.28--
2Acetone0,040,04--
3The vinyl chloride30,9531,0--
41,1-Dichloroethane0,150,15--
5Carbon tetrachloride 0,05--
6Benzene0,720,70--
71,2-Dichloroethane49,5849,7689,05,0
8Trichloroethylene0,150,024,338,9
91,1,2-Trichloroethane0,010,020,32,7
10M-Dichlorobenzene0,060,021,715,4
11Tetrachlorethylene0,150,024,238,0
12Fine solid products+-++

Example 1 of the method.

From bubble layer fluid in the number of 1600 kg/h is fed into the middle portion of the vacuum distillation column 9, provided with a regular showerhead and irrigated from above phlegm in the amount of 1450 kg/h. To prevent polymerization of the separation products in a high-speed evaporator, the temperature should be about 120°C.

When carrying out the process at atmospheric pressure the boiling point 10° With has a mixture containing dichloroethane 20 wt.% (figure 3, point a). The pressure drop in the column to 0.4 ATA provides for allowable temperature 120°boiling with a mixture of dichloroethane 5 wt.% (figure 3, point b). This leads to the reduction of losses of dichloroethane with high-boiling waste by 44 kg/h and reduce waste sent for disposal by 16% (see table).

The number of dichloroethane in the waste sent for recycling, kg/h
Table 2
№ p/pThe name of the indicator and its dimensionValue
prototypethe proposed method
1The amount of fluid taken from columns 1, kg/h16001600
2The concentration of dichloromethane in the fluid taken from columns 1,% mass.8686
3The boiling point of the mixture in the evaporators, °120120
4The concentration of dichloromethane in the waste sent for recycling, % of the mass.205
5The quantity of waste sent for recycling, kg/h280236
65612
7Reduction of losses of dichloroethane in comparison with the prototype, kg/h-44

Example 2 of the method.

In contrast to the conditions of example 1, the pressure in the vacuum column 9 is reduced to 0.1 at. This reduces the boiling temperature with a mixture of dichloroethane 5 wt.% to 105°C. the Lower boiling point 120°C to 105°With (figure 3, point C) will slow down the processes of polymerization products division in the circuit evaporators and, therefore, reduce the pollution of surface heating during operation.

This performance installation will remain the same as in example 1.

The method of separation of finely dispersed solid, resinous and high-boiling by-products from the reaction gases of the pyrolysis of dichloroethane in the production of vinyl chloride by rapid cooling in the quenching column and the subsequent separation of pyrolysis products by ozonation them through the layer of concentrated liquid by-products of these gases in the cube quenching column with subsequent contact of the gas mixture with return condensation of these gases in a distillation zone, providing a cleaning gas mixture from the high okiyama products the output of by-products and their additional distillation with the selection and output of the process of finely dispersed solid resin particles and the products boiling above dichloroethane, and the return of the distillate in the process, characterized in that the additional rectification carried out under vacuum in a distillation column equipped with a regular nozzle and high speed evaporator with the conclusion of finely dispersed solid resin particles of the high-boiling by-products with kubovy the remainder of the column.



 

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FIELD: petroleum chemistry, chemical technology.

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EFFECT: improved separating method.

2 dwg, 6 tbl

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FIELD: chemical industry, in particular method for production of value monomer such as vinylchloride.

SUBSTANCE: claimed method includes passing of reaction mixture containing dichloroethane vapor trough catalytic layer providing dehydrochlorination of dichloroethane to vinylchloride. Catalyst has active centers having in IR-spectra of adsorbed ammonia absorption band with wave numbers in region of ν = 1410-1440 cm-1, and contains one platinum group metal as active component, and glass-fiber carrier. Carrier has in NMR29Si-specrum lines with chemical shifts of -100±3 ppm (Q3-line) and -110±3 ppm (Q4-line) in integral intensity ratio Q3/Q4 from 0.7 to 1.2; in IR-specrum it has absorption band of hydroxyls with wave number of ν = 3620-3650 cm-1 and half-width of 65-75 cm-1, and has density, measured by BET-method using argon thermal desorption, SAr = 0.5-30 m2/g, and specific surface, measured by alkali titration, SNa = 10-250 m2/g in ratio of SAr/SNa = 5-30.

EFFECT: method with high conversion ratio and selectivity.

3 cl, 2 ex

FIELD: chemical industry, in particular method for production of value products from lower alkanes.

SUBSTANCE: claimed method includes passing of gaseous reaction mixture containing at least one lower alkane and elementary chlorine through catalytic layer. Used catalyst represents geometrically structured system comprising microfiber with diameter of 5-20 mum. Catalyst has active centers having in IR-spectra of adsorbed ammonia absorption band with wave numbers in region of ν = 1410-1440 cm-1, and contains one platinum group metal as active component, and glass-fiber carrier. Carrier has in NMR29Si-specrum lines with chemical shifts of -100±3 ppm (Q3-line) and -110±3 ppm (Q4-line) in integral intensity ratio Q3/Q4 from 0.7 to 1.2; in IR-specrum it has absorption band of hydroxyls with wave number of ν = 3620-3650 cm-1 and half-width of 65-75 cm-1, and has density, measured by BET-method using argon thermal desorption, SAr = 0.5-30 m2/g, and specific surface, measured by alkali titration, SNa = 10-250 m2/g in ratio of SAr/SNa = 5-30.

EFFECT: method of increased yield.

3 cl, 4 ex

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