EP1360163A2

EP1360163A2 - Direct condensation

Info

Publication number: EP1360163A2
Application number: EP02704714A
Authority: EP
Inventors: Peter Kammerhofer; Ingolf Mielke; Horst Ertl; Dieter Jaculi; Manfred Stöger
Original assignee: Vinnolit Technologie GmbH and Co KG
Current assignee: Vinnolit Technologie GmbH and Co KG
Priority date: 2001-02-13
Filing date: 2002-02-13
Publication date: 2003-11-12
Also published as: WO2002064534A2; NO20024877L; ZA200207916B; US20030176748A1; CN1297525C; CA2404562A1; RU2233828C2; HUP0302927A2; HUP0302927A3; PL368224A1; CN1457331A; DE10107091A1; WO2002064534A3; NO20024877D0

Abstract

The invention relates to a method for producing 1,2-dichloroethane, by reacting ethene with hydrogen chloride and a gas containing oxygen in an oxochlorination reactor to produce a reaction gas. According to said method, the reaction gas is condensed after filtration without prior quenching.

Description

direct condensation

The present invention relates to a process for producing 1,2-dichloroethane (EDC) by reacting ethene with hydrogen chloride and an oxygen-containing gas in an oxychlorination reactor, whereby a reaction gas is formed.

Oxychlorination means the reaction of an alkene - here ethene - with hydrogen chloride and oxygen or an oxygen-containing gas such as air, with the formation of a saturated chlorinated alkane - here 1,2-dichloroethane, hereinafter also referred to as “EDC”. The reaction takes place here according to the equation

C ₂ H ₄ + 2HC1 + ^ 0 ₂ → C1-CH ₂ -CH ₂ -C1 + H ₂ 0.

However, the reaction by-product water of this reaction can form the very strongly corrosive hydrochloric acid with unreacted starting material hydrogen chloride, so that when such a process is carried out, correspondingly resistant - and therefore expensive - materials have to be used for the apparatus for carrying out the process.

On a large industrial scale, this process is often carried out in a fluidized bed, the catalyst e.g. B. consists essentially of copper chloride on an alumina support. From German published patent application DE 41 32 030 a method for removing the catalyst abrasion is known which is carried out of the reaction zone with the raw EDC gas stream. The catalyst abrasion is separated from the raw EDC gas stream in a dry operated cleaning zone. Preferred embodiments of this method are characterized in that the catalyst abrasion is separated off on a dust separator or in an electrostatic filter as a cleaning zone, the dust separator being able to be equipped with bag filters which are cleaned with compressed cycle gas. After the catalyst abrasion has been separated off, the gas stream is cooled with water and condensed, ie quenched.

It is also possible to remove adsorbed reaction products from the catalyst abrasion deposited in the cleaning zone in a downstream desorption zone. The desorption zone can be operated at a temperature of 50 to 350.degree. C., preferably 150 to 180.degree. C., by gassing or under reduced pressure and air, nitrogen or circulating gas (circulating gas for fluidizing the catalyst) can be used for the gassing and Catalyst attrition are treated for 0.5 to 5 hours, preferably for 1 to 2 hours at elevated temperature in the desorption zone.

With such a process it is avoided that during the discharge of the water formed and of the washing water used in the workup, waste water contaminated with heavy metal and inorganic sludge is formed.

DE 195 46 068 AI relates to a method for reducing the catalyst consumption and contaminated catalyst waste in the production of EDC using the oxychlorination process. In this process, the catalyst abrasion is separated from the raw EDC gas stream in a dry operated separation zone. The catalyst abrasion is classified and certain grain fractions are returned to the reaction zone. In this process, too, the gas stream is cooled with water and condensed after the catalyst abrasion has been separated off.

DE-A-197 53 165 discloses a process for producing EDC by oxychlorination, the reaction gas in the reactor being freed from catalyst by very fine filtration and thus being retained in the reactor. The reaction gas freed from the catalyst is then passed into a quench column and condensed in a known manner.

Furthermore, it is known from the prior art (Ullmann's Encyclopedia of Industria Chemistry, Vol. A6, 1986, p. 269), the hot reaction gases from a fluidized bed reactor which, in addition to EDC and water, also contain unreacted HCl gas without quenching with an aqueous solution without further treatment. In this process, catalyst deposits which have not separated out and unreacted hydrogen chloride from the oxychlorination of ethene are washed out. Both external water and water which is formed during the reaction, so-called reaction water, can be used as the washing liquid. EDC is distilled off together with water from the quench and condensed.

All known processes of the prior art with fluidized bed technology have the disadvantage that the polychlorinated dibenzo-p-dioxins / furans (PCDD / PCDF) formed during the reaction into those during the quenching used aqueous quench solution. This must be removed and further processed, which is complex and very expensive due to the fact that the quench solution is loaded with PCDD / PCDF.

Furthermore, the thermal energy of the hot process gases (= reaction gases) cannot be used in a quench.

It is therefore an object of the present invention to provide a method and a device for producing 1,2-dichloroethane in which the polychlorinated dibenzo-p-dioxins / furans formed in the reaction do not get into an aqueous phase, but remain in the organic phase ,

It is a further object of the present invention to provide a corresponding method and a corresponding device in which the thermal energy of the hot process gases can be used.

These objects are achieved by providing a method and a device of the type mentioned in the introduction, in which the reaction gas formed in the oxychlorination is condensed after filtration without quenching. The process step of quenching in the fluidized bed process which has always been necessary in the prior art is thus eliminated. The method and the device are therefore simpler and therefore also less expensive.

With such a method and such a device, it is therefore not necessary to provide a so-called quench tower, which saves space and investment costs. Furthermore, in the method and the device according to the invention, no PCDD / PCDF get into the aqueous phase, so that the time-consuming and expensive workup is eliminated. Rather, the polychlorinated dibenzo-p-dioxins / furans (PCDD / PCDF) are separated from the other components and then, for example, are incinerated with the other high-boiling components of the process.

Because no quenching is carried out in a method according to the invention or in the device, it is possible according to a preferred embodiment of the present invention that the thermal energy of the hot reaction gases is used. It is preferably used to generate water vapor or to preheat the cycle gas / ethylene stream to the reactor, e.g. in a heat exchanger. The rest of the heat (evaporation enthalpy of EDC and water) is preferably given off in a further heat exchanger to a cooling medium such as cooling water. The steam can, for example, continue to be used in an existing EDC / VC system (e.g. pulling up various product streams or heating distillation columns). This leads to energy savings and thus to a reduction in costs.

A conventional reactor can be used as the oxychlorination reactor. Fluidized bed reactors in particular have proven themselves in practice for oxychlorination. During the reaction, reaction gases are formed, which mainly contain 1,2-dichloroethane, but also water, hydrogen chloride, PCDD / PCDF and catalyst abrasion. They can also contain unreacted ethene and chlorine. A catalyst is preferably used for the oxychlorination step, with CuCl ₂ or FeCl ₃ catalysts having proven to be particularly suitable.

In particular, CuCl ₂ , which is applied to a carrier, has proven itself as a catalyst. Suitable carriers are, for example, silicon dioxide, diatomaceous earth, fuller's earth, clay and aluminum oxide, with γ-aluminum oxide being preferably used.

The process conditions, in particular the oxychlorination step, can preferably be carried out in accordance with the process conditions described in German Patent Specification 1,518,931 and German Patent 1,468,489, the disclosure of which is hereby incorporated by reference into the present description.

The fact that the reaction gases are filtered after the oxychlorination, preferably through a fine filter, almost no z. B. with PCDD / PCDF contaminated catalyst in the aqueous phase, but remains in the filter. Ultra-fine filtration is understood to mean a process which causes the fine fraction of the oxychlorination catalyst to be retained. The fine fraction has an average particle size of at least 1 μm. For example, the filtration can be carried out as described in PCT application PCT / EP98 / 07444. The disclosure of this document is hereby incorporated by reference into the present description.

It can be provided that the filtration takes place outside the oxychlorination reactor. This version is particularly advantageous when existing systems are to be retrofitted. In the case of new plants, however, it is generally preferred if the filtration takes place inside the oxychlorination reactor.

The filtration can be carried out according to the invention by means of filter candles, bag filters and / or cartridge filters. Such filters are described for example in DE 197 53 165 AI and are manufactured in particular by Pall, Micropul, Fluiddynamics etc.

After filtering the reaction gas, the reaction gas is cooled - without quenching - in which, for example, the recycle gas to the reactor is mixed with ethylene mixture and / or water vapor is generated, which is fed into the system steam network and can be used to heat columns and preheaters. The reaction gas is partially condensed in a second heat exchanger and the heat is preferably given off to a cooling medium again without quenching - for example in a heat exchanger. The liquid phase is separated from the cycle gas in a separator and fed to further processing. This workup is described in more detail in the attached copy of DE 100 59 299.5. The EDC / water mixture, ie the organic and aqueous phase, are expanded into a container, with the major part of the carbon dioxide escaping from the EDC / water. The water is then fed to a wastewater treatment, the EDC is fed into a downstream apparatus and the chloral and / or chloral hydrate contained therein is destroyed by treatment with an aqueous alkaline solution. The EDC is separated from the aqueous phase in a decanter. The alkaline aqueous phase from the decanter is also fed to a wastewater treatment.

The EDC from the decanter is fed to a distillation, for example in a so-called dewatering and low boiler column and a high boiler column. Such columns are known in EDC / VC plants. Low or high boilers or corresponding components are liquids with a lower or higher boiling point than EDC. The polychlorinated dibenzo-p-dioxins / furans are discharged in the described embodiment of the invention in the high boiler column together with the other high boilers of the process and then z. B. incinerated.

In a further preferred embodiment of the present invention, at least one of the educt streams hydrogen chloride and oxygen-containing gas is introduced via feed lines which have porous, gas-permeable moldings. According to the invention, oxygen-containing gases can e.g. B. be air, oxygen and gas mixtures containing oxygen. It can be introduced directly into the fluidized bed of the oxychlorination reactor. Examples of such porous, gas-permeable moldings are those produced by Pall, Fluid Dynamics, Krebsöge, etc.

According to a further preferred embodiment, the ethene and / or the cycle gas are introduced into the oxychlorination reactor via a base which has porous gas-permeable material. Examples of such porous gas-permeable materials are VA steel alloys, highly corrosion-resistant alloys, INCONEL®, MONEL®, HASTELLOY® and ceramic materials. Both the oxygen-containing gas on the one hand and the ethene on the other hand are preferably fed into the catalyst fluidized bed in finely divided form, as described, for example, in DE 199 03 335 A1.

The feed lines can be configured in the manner described in DE 199 03 335 AI, which is included here with reference to the description.

The process according to the invention is preferably carried out in a device for producing 1,2-dichloroethane by reacting ethene with hydrogen chloride and an oxygen-containing gas. This preferred device has an oxychlorination reactor, a filter, a condenser and a 1, 2-dichloroethane distillation device and is characterized in that a water vapor generator but no quench column are also provided.

The filter, which should be a fine filter, can be formed from filter candles, bag filters and / or cartridge filters.

If filter candles are used, they should be made of materials suitable for EDC production. These are, for example, metals, alloys, glass and / or ceramics. The filter candles preferably have sintered metal and / or ceramic.

Furthermore, fabric filters made of sufficiently temperature-resistant, in particular fluorinated plastics such as Polytetrafluoroethylene in the form of bag filters or cartridges can be used.

It has further been shown that the distillation device is preferably designed such that it has a dewatering and low-boiling column and a high-boiling column.

In order to obtain products that are as pure as possible, the steam generator / educt preheater made of carbon steel and the condenser on their product side should contain a nickel-containing material such as a nickel alloy, such as. B. HASTELLOY® from Haynes International, Inc. or tantalum.

In addition, it would also be possible for the steam generator and the condenser to have graphitic material on their product side, e.g. Have NS2 or NS3 from SIGRI.

In particular, in order to be able to carry out a process as described in more detail above, the device should preferably have feeds for hydrogen chloride and oxygen-containing gas, which lead directly into the fluidized bed of the oxychlorination reactor.

These feeds can contain porous, gas-permeable moldings.

It is also particularly expedient if the ethene and the circulating gas stream are passed into the oxychlorination reactor via a base which is made of porous, gas-permeable material or is provided with moldings made of porous, gas-permeable material. Further advantages and developments of the invention result from the patent claims, the drawing and the following description, in which exemplary embodiments of the invention are described in detail with reference to the drawing.

1 shows a device according to the invention for carrying out a method according to the invention according to a first preferred embodiment of the present invention;

2 shows an apparatus according to the invention for carrying out a method according to the invention in accordance with a second preferred embodiment of the present invention;

3 shows a device according to the invention for carrying out a method according to the invention in accordance with a third preferred embodiment of the present invention.

In Fig. 1 is an apparatus for performing a method for producing 1, 2-dichloroethane by reacting ethene with hydrogen chloride and oxygen or an oxygen-containing gas in an oxychlorination reactor to form a reaction gas. Direct condensation with educt preheating is described. The filter 5 is arranged outside the fluidized bed reactor 4.

A reactor 4, preferably a fluidized bed reactor, can be seen in FIG. Two lines 1 and 3 lead through these, through which the process gases are introduced. Hydrogen chloride and oxygen are via line 1 and Ethylene and cycle gas are fed to reactor 4 via line 3. Line 3 has a heat exchanger 6, in which the waste heat from the reaction gases emerging from the reactor is used to preheat the ethylene (or also called “ethene” gas) and / or the circulating gas. Ethylene is fed to the system via the feed line 2. The reactor The filter 5, through which the hot reaction gases emerging from the reactor are freed of solids, is connected downstream of 4. The reaction gases are cooled in the heat exchanger 6 before they are introduced into the condenser 7, the waste heat of which can also be used again via a heat exchanger ,

When leaving the condenser 7, the reaction gas is still at a temperature of approximately 60 ° C. At this temperature, the mixture, which comprises an organic phase containing the 1,2-dichloroethane and an aqueous phase, is introduced into the separating device 8.

From this separating device 8, the liquid mixture containing the product from an organic and aqueous phase is separated via line 12 from the gaseous phase, which is further used as circulating gas via heat exchanger 9 and circulating gas compressor 10. An exhaust pipe 11 is provided upstream of the cycle gas compressor 10.

According to the preferred embodiment shown in FIG. 1, the reaction gas is filtered after emerging from the fluidized bed reactor and then condensed without prior quenching.

2 is another preferred one

Embodiment of the present invention shown. It the same reference numerals are used for components corresponding to FIG. 1.

FIG. 2 shows a comparable block diagram of a system in which, instead of or in addition to the process gas preheating in the heat exchanger 6, the waste heat of the reaction gases is used by generating steam in the heat exchanger 6A.

Finally, FIG. 3 shows a reactor 4 with an internal filter 5, so that the hot reaction gases are still filtered in the reactor 4 and, as a result of the filtration, as little heat as possible before the reaction gases are introduced into a heat exchanger 6 which is used for preheating the process gases and / or Generation of steam, especially used to generate water vapor, is lost. The rest of the system is unchanged from that shown in FIGS. 1 and 2.

example

An oxychlorination reactor with a fluidized bed is used for the preparation of 1,2-dichloroethane, CuCl _{2 being} used as the catalyst. The oxychlorination is carried out as follows:

5910 Nm ³ / h of hydrogen chloride at a temperature of 150 ° C and 1600 Nm ³ / h of oxygen, heated to 110 ° C, are fed via line 1 directly into the fluidized bed (40 t of catalyst; aluminum oxide with a copper content of 4% by weight ) of the reactor 4 via feed lines 1, 3, the porous gas-permeable molded body, for example made of sintered chromium-nickel steel from Pall. included, initiated. The ethene (3000 Nm ³ / h) and the circulating gas stream are introduced via a base of the oxychlorination reactor 4, the base being made of porous gas-permeable material. After oxychlorination, the hot (200-250 ° C) reaction gas, consisting of EDC, H ₂ 0, C0 ₂ , CO, nitrogen, C ₂ H ₄ , HC1 and 0 ₂ , flows through after leaving the fluidized bed to separate entrained catalyst particles, here CuCl ₂ , in the upper part of the oxychlorination reactor 4 a fine filter 5 in which the catalyst is separated.

The reactor head gas, which is approx. 200 to 250 ° C., is cooled in a suitable device in a tube bundle heat exchanger made of carbon steel to approx. 140 ° C. The energy released is used to produce water vapor. The water vapor is fed into the plant steam network and further used for the distillation of the EDC in the high boiler or low boiler columns.

The steam thus produced with a temperature of 135 ° C and a pressure of 3 bar is consumed in the distillation column of the existing EDC / VC system (high boiler or low boiler column).

In a further cooling phase, the reactor head gas is further cooled to about 60 ° C. using a tube bundle heat exchanger made of an acid-resistant material, for example graphite NS1 from Sigri, and the EDC and water produced are condensed from the circulating gas stream. The energy dissipated is released to the cooling water.

The steam generator 6A is a horizontal tube bundle heat exchanger, in which the OC process gas through the tubes passed and the water vapor is released into an expanded jacket space via a pressure control valve in the system steam network.

The capacitor 7 is made on the product side from graphite WS2 from Sigri, so that no further contamination of the reaction gas occurs. The condensed product stream is now fed to the EDC distillation, in which the PCDD / PCDFs are separated by distillation together with the so-called high boilers and then burned.

The PCDD / PCDF 's contained in EDC raw gas are discharged via the bottom of the low boiler column to the high boiler column. In the high-boiling column, these high-boiling components are discharged through the bottom into the vacuum column, from where they are burned with the high-boiling residues in the thermal residue combustion at 1200 ° C.

Claims

Expectations

1. A process for the preparation of 1, 2-dichloroethane by reacting ethene with hydrogen chloride and oxygen or an oxygen-containing gas in an oxychlorination reactor to form a reaction gas, characterized in that the reaction gas is filtered and then condensed without quenching.

2. The method according to claim 1, characterized in that thermal energy of the reaction gas in particular for

Generation of steam is used and / or that thermal energy for cross-heat exchange (heating) of various product streams (preferably cycle gas) is used.

3. The method according to claim 1 or 2, characterized in that the oxychlorination reactor comprises a fluidized bed reactor (4).

4. The method according to any one of claims 1 to 3, characterized in that the filtration takes place within the oxychlorination reactor.

5. The method according to any one of claims 1 to 3, characterized in that the filtration takes place outside the oxychlorination reactor.

6. The method according to any one of the preceding claims, characterized in that the filtration is carried out by means of filter candles, bag filters and / or cartridge filters.

7. The method according to any one of the preceding claims, characterized in that after the condensation, the 1, 2-dichloroethane-containing phase is decanted from the water phase and fed to a 1,2-dichloroethane distillation.

8. The method according to claim 7, characterized in that the 1, 2-dichloroethane distillation is carried out first in a dewatering and low boiler column and then in a high boiler column.

9. The method according to claim 8, characterized in that polychlorinated dibenzo-p-dioxins / furans are separated in the high boiler / vacuum column.

10. The method according to any one of the preceding claims, characterized in that hydrogen chloride, ethene, cycle gas and / or the oxygen-containing gas are introduced through porous, gas-permeable moldings into the oxychlorination reactor.

11. Device for the preparation of 1, 2-dichloroethane by reacting ethene with hydrogen chloride and an oxygen-containing gas, in particular for use in a method according to one of the preceding claims, with an oxychlorination reactor, a filter, a condenser and a 1, 2- Dichloroethane distillation device, characterized in that that a water vapor generator (6A) or educt preheater (6) and a condenser (7) operated with cooling water and no quench column are also provided.

12. The apparatus according to claim 11, characterized in that the filter (5) comprises filter candles, a hose and / or cartridge filter.

13. The apparatus according to claim 12, characterized in that the filter candles have sintered metal and / or ceramic.

14. Device according to one of claims 11 to 13, characterized in that the distillation device has a dewatering and low boiler column and a high boiler column.

15. Device according to one of claims 11 to 14, characterized in that the capacitor (7) on its product side has a nickel-containing material such as a nickel alloy.

16. The device according to one of claims 11 to 15, characterized in that the capacitor (7) has graphitic material on its product side.

17. The device according to one of claims 11 to 16, characterized in that the oxychlorination reactor is a fluidized bed reactor (4).

18. The apparatus according to claim 17, characterized in that the feeds (1) for hydrogen chloride and oxygen-containing gas lead directly into a fluidized bed of the fluidized bed reactor (4).

19. The apparatus according to claim 18, characterized in that the feeds (1) are formed from porous, gas-permeable moldings.

20. Device according to one of claims 11 to 19, characterized in that the circulating gas and / or the ethene is passed through a porous, gas-permeable material having bottom in the oxychlorination reactor.