SE174572C1 - - Google Patents

Description

Inventor: W J Read Priority begard iron 26 October 1956 oak 29 July 1957 (Great Britain) The present invention relates to a process and apparatus for the chlorination and / or bromination of normally gaseous olefins to olefin halides.

Patent 173001 discloses an improved continuous process for the chlorination and / or bromination of normally gaseous olefins by a reaction mainly in the aqueous phase, the halogen and olefin reagents being introduced into a reaction zone in the form of a vertical column internally provided with heat exchangers offering one large cooling surface per unit volume of free reactor space, so that olefin halide is formed near the cooling surface and flows downwards as a discontinuous water phase opposite to the ingressing olefin through a zone containing solid filler bodies and in which unreacted halogen is stripped from the product as In this process, the halogen is introduced directly into the reaction zone and the olefin is passed indirectly to the reaction zone up through the zone provided with filler bodies. However, experience has shown that the liquid dihalide stream formed as a product extending from the reaction zone to the reaction zone. with filling bodies f zone, contains a large amount of unreacted lost halogen despite the countercurrent operation a) that the reagents are mixed during turbulent flow and thus come into very intimate contact with each other and b) that unreacted halogen, which passes down through the reactor, is brought safely to contact with alit more unknown concentration of olefin, On the basis of the experience gained in the continuous countercurrent operation described above, it could be expected that for a given length of the reaction zone cocurrent contact between the olefin and the halogen would give much sarnre result an countercurrent contact. However, it has surprisingly been found that this is not the case and that a considerable exchange of the desired product can be obtained in relation to the size of the equipment used.

The present invention relates to a continuous process for the preparation of bromine and / or chlorine-containing dihalide from a normally gaseous olefin by reacting the olefin with halogen consisting of bromine or chlorine or mixtures therein, the halogen () or the olefin being continuously passed in cocurrent downstream through a vertically elongated reactor, which is internally provided with heat exchangers, which offer a large cooling area per unit volume of reactor vessels, heat being dissipated through the surface of the heat exchangers at a rate leading to continuous formation of liquid olefin halide near the cooling. Contact is made between olefin, halogen and formed dihalide, while it flows down as a discontinuous liquid phase over the surface of the heat exchangers, and a liquid stream containing formed dihalide is diverted from the lower part of the reactor, after which substantially halogen-free olefin halide is recovered.

The process according to the invention is suitably carried out in a reactor, in which the heat exchangers form a cooling part provided with filler bodies, which extends transversely over the reactor tube and picks up a considerable part of its height and is arranged to cause gas and liquid to flow into it. medstrom kings several winding paths distributed Over the reactor's cross section. The heat exchangers should generally have a construction which provides a large cooling surface and sorni at the same time creates turbulence in the downwardly directed liquid stream without the emergence of preferred rockers for the liquid down to the reactor rocks or through obstacle-free channels in the heat exchanger. A lamp heat exchanger is used, consisting of several flat, helically wound, tubular loops, the superimposed loops varying in relation to each other, so that annular channels through the heat exchangers are avoided. The outer edges of the individual loops are arranged at a distance from the reactor yags.

If the heat exchanger does not provide sufficiently turbulent mixing and even distribution of the liquid flow through the reactor, it may in some cases be convenient to arrange in the reactor, for example between individual Yarm exchangers. or several sections, which drew filled with filler bodies, such as Raschig rings, said that one. Mr. an intimate mixture of the individual liquid drums, which flow down through the reactor. However, such a section must allow co-current flow between the liquid and the gas without flooding or filling with liquid. Another solution, which can be applied in the place of or together with the arrangement of fitted sections, is to press in additional gas. one or more stables in the reactor cause fluid turbulence.

According to the present invention, it is essential to maintain a discontinuous water phase which flows downwards, suitably in a turbulent state over the surface of the heating shafts. The reactor should not at any time be filled with liquid either in the heat exchanger part or in the packed sections, asam anYanda.s. Such a discontinuous yatskef as Ran is easily maintained in the reaction zone. By appropriate control of the feed rate, the substances introduced into the reactor are obtained.

The process according to the invention is particularly suitable for bromination and / or chlorination of normal, gaseous olefins into dihalides while applying co-current surface. In practice, the halogen and the gaseous olefin can be introduced into the upper part of the vertical reactor above the lowest heat exchanger, next to which they react to form liquid dihalide, which flows from the heat exchanger to the water exchanger, which are arranged in the lower part of the reactor. The halogen and olefin are soluble in the dihalide, which serves as a solvent for carrying out the reaction in the liquid.

The product which emits from the lower part of the reactor may contain and often contains a certain amount. halogen and olefin which have not reacted, the reaction being effected by irradiation, for example with a mercury lamp, and / or by passing the product along a narrow tortuous path which causes turbulence, for example, a spiral tube and / or a terminating column,. containing filler bodies and through which the gas or liquid frail reactor is led up.t. In general, the liquid dihalide, which is discharged into the lower part of the reactor from Iran, contains less than 10% by weight of free halogen. If the halogen content were to be 10% or more, it would be convenient to provide a means for cooling the withdrawn product, for example by the application of a heat exchanger in the above-mentioned filling body provided with a final column. When the reaction is substantially complete, the liquid dihalide is separated in an apparatus for separating gas and liquid, after which the dihalide is further treated to give a product of the required purity.

The process is suitably carried out at a temperature above the 'freezing point of the halogen reagent or dihalide, depending on which am hogs', and below the boiling point of the dihalide formed as a product. In the production of olefin dibromides and olefin chlorombromides, the reaction temperature may be up to 140 DEG C., although the maximum temperature in the reaction zone may suitably be below 100 DEG C.. In the production of olefin dichloride slightly lower temperatures are preferred, for example 0 DEG-50 DEG C. or 75 DEG C. noclyandigt to carry out the reaction under negative pressure and it is suitably carried out at atmospheric pressure, although it can also take place at both negative and Oyer pressures. Furthermore, it is not necessary to observe a certain molar ratio between halogen and although the ratio usually amounts to 1.2: 1-1: 2. Technically, however, it is appropriate that anyanda substantially equimolar amounts of halogen and olefin, or some excess of olefin , which, however, should not exceed about 10%. The feed rates for olefin and halogen are, of course, dependent on. the desired reaction rate and the capacity of the reaction column.

The invention will be described in more detail in the following with reference to the accompanying drawing, which as an example shows an apparatus for producing lay ethylene dibromide. Fig. 1 is a flow chart schematically showing the construction of any other reactor column. Fig. 2 is a side view, partly in section, and on a larger scale, of a suitable type of glass heat exchanger for use in the reactor according to Fig. 1. Fig. 3 is a plan view of the heat exchanger according to Fig. 2.

As in Tram 1 of Fig. 1, the second reactor consists of a cylindrical glass column 1 provided with several glass firming exchangers 2, 3, 4, 5th 5 saint a zone 6 provided with filler bodies containing suitable filler bodies, such as Rasehig rings. The filling bodies. in zone 6 rest light on. a perforated plate (not shown) or some other suitable member which allows the liquid to tighten downwards is suitably distributed. Each heat exchanger 2-5 suitably consists of several, superficially arranged, series-connected helical loops, i.e. "Pancakes" - loops, which fill the main part of the cross-sectional area of the column 1, although at the same time they leave - 174 5123 paths for the liquid and the flow of gases down free. An inlet line 7 hr arranged in the upper dude of the column 1 for supply of liquid bromine Iran a, storage tank 8 under the influence, by weight, of the force. The inlet line 7 terminates in a distributor means 9, which is shown schematically 'and consists of four circuits arranged. Through another inlet line 10 at the upper dude of the column 1, gaseous ethylene is introduced. A common outlet 11 hr is arranged at the lower end of the column 1 for draining gas, and formed liquid ethylene dibromide. This outlet 11 stands through a helically wound glass tube 12 in connection with the lower spirit of a termination column 13 of glass inside, holding filling bodies 14, such as Raschig rings. An outlet 15 of the Iran end column is connected to a separator 16 with an outlet line 17 Mr gas, and an outlet line 18 for liquid-colored product. The line 1.8 is drawn to a 1-word container 19. The thermometer cable as shown is distributed along the column 1. To facilitate the substrate, the column 1 is challenged in several sections, which are separated by gaskets, suitably consisting of rings of asbestos material. with polytetrafluoro, ethylene, whereby, the surfaces which tata against the gasket aro 'especially slata, sa. 'that you get good sealing and leaching of bromine is prevented.

Figs. 2 and 3 show the preferred type of heat exchanger for use in the reactor of Fig. 1. This water exchanger consists of two sets 60 and 61 of eight helically wound, series-connected glass tube loops 62. The loops of the ram sets are provided with separate inlet tubes 63. , and 64 -for cooling water and a common outlet pipe 65. The heat exchanger dr enclosed in a. cylindrical gla, sheath 66, which forms one of the sections of which the reactor of Fig. 1 is constructed. The heat exchanger is supported on the jacket 66 by means of a Y-shaped gias element 67, the spirits of which are inserted into recesses 68 in the jacket. Each spiral loop varies Aro fOrstalida in relation to adjacent loops, sh that it forms several slins, grande paths for efficient co-current, contact melian gas and liquid. Furthermore, there is an annular space between the jacket and the loops to prevent the liquid, preferably, from flowing down the rocks of the reactor. It must be pointed out that in each part of the reactor column, which is filled by a water exchanger, the formed cooling surface should generally take at least about 33-49 dm2 and probably at least 66, dm2 per liter of reactor volume. If the area of the cooling surface is fed to the feed rate of halogen, this area for achieving best results should be at least about 1 dm2 and preferably 2 clm2, or more per mole of halogen, which is fed into the reactor per hour.

When the apparatus shown in Fig. 1 is inhaled, ethylene is introduced at a slight overpressure or at atm, a non-hazardous pressure through the passage 10, from which it flows medal through column -1. At the same time, liquid bromine at room temperature is introduced into the container 8 through the line 7 and the distributor means 9, while cooling water is passed through all the heat exchangers 2-5. The bromine which enters through the line 7 flows down on the surface of the cooling coils in the heat exchanger 2 and reacts with the ethylene during the formation of liquid ethylene dibromide. This reaction takes place partly homo, gent In the liquid phase, ie. a liquid phase consisting of ethylene dibromide and lost bromine, and ethylene, partly heterogeneous on the surface of the cooling coils, through which cold water is passed at a sufficient speed to absorb heat of reaction, et. A certain reaction takes place in the gas phase. Liquid dibromide, which is formed in the heat exchanger 2 ph surface of the cooling coils, flows downstream in gaseous ethylene stream as a discontinuous water phase to zone 6, in which the dibromide mixes, intimately due to the random formation of filler bodies, such as shiunda form several winding paths. The liquid, which emits from the lower spirit of the zone 6, continues to coexist in co-current with the gas. Further reaction takes place within the water exchanges 3-5, so that the liquid which reaches the column, even in the lower end, contains only a relatively small amount of unreacted bromine together with unreacted ethylene. The liquid corn flows out the lower dude of the Iran column 1 through the conduit 11, is then passed through a termination section, containing the helical loop 12 and the filled column 13, which has the task of providing an intimate turbulent mixture. the effluent from column 1 and thus to ensure the reaction to be completed. Both in the loop 12, and the column 13, gas containing bromine and usually also unreacted ethylene and some inert substances are added, which are added with the incoming ethylene, which are bitten in the liquid phase, whereupon the turbulence becomes violent, Better final treatment can be achieved by irradiating the sun-gun 12 ooh / or the column- 13 with, sunlight or any luminescent light source, such as a mercury, glare. The liquid and gas, coin avghr, from the byre spirit of the column 13, are led to the separator 16, frail which, free and gas is diverted through the line 17, melan liquid, the, elylendibromide is diverted through the line 18 to the storage tank 19. The outgoing gas can treated for recovery, g bromine, and optionally ethylene in the manner described in patent 173 001. The dibromide obtained as a product can be treated with water vapor and then neutralized, as described in the above-mentioned patent, which also applies to to procedures which can be easily adapted for manual or automatic control of the present procedure.

The process, which was described with reference to the drawing, is operated lampligert with 45 excess of ethylene to facilitate automatic control of the process, as described in the said patent. In this case, unreacted ethylene in the off-gas can be recovered by reaction with bromine outside the reactor. If. forfar pft this salt, infores a part I forvag formed ethendibromide together with it. input bromine. Maugden, this sat before ethylene dibromide should, however, be kept as low as possible, because the supply of dibromide together with ingende From can impair the quality of the formed product- Ethylene supply Bromine supply Coolant for the heat exchangers Temperature: thermometer thermometer T2 thermometer T3 Lower spirit of the column The maximum capacity of the system under these operating conditions is about 1 tonne of ethylene dibromide per day. If such a system is enlarged to work with a reaction column with an internal diameter of 304 mm, the capacity should be about 50-60 tons of dibromide per day, ie. approximately twice the capacity of the countercurrent system described in patent 173 001.

Operating conditions Essentially as above, this also applies to the reaction of propylene and butene with From and the reaction of ethylene, propylene and butene with equimolar liquid mixtures of chlorine and From to chloro bromides. If an olefin dichloride is desired, the only major change in the operating conditions is that it is appropriate to maintain lower temperatures in the reaction column, for example by using salt solution Time - 10 ° C to ° C as the coolant for the hydrogen exchangers. The cocurrent system described above is particularly suitable for the production of olefin dichlorides and chlorobromides, whereas in addition to the ratio at the countercurrent shift some special measures must be taken to prevent loss of evaporated chlorine from the upper spirit of the column.

Although the system shown in Fig. 1 has been found to work with many choices in practice, various modifications may be made. The section 6 provided with filler bodies can thus be omitted, in which case the column is required if necessary and additional heat exchangers are arranged at the lower end of the column. Furthermore, it may be appropriate to divide the feed into olefin and introduce a certain amount of ethylene at different locations between the upper, second and lower spirits of the reaction column. In this case, the olefin can be introduced tangentially so that turbulent flow is generated, and of course the capacity of the reaction column is fully utilized. If ethylene dibromide is introduced together with bromine, the molar ratio of dibromide to From should probably exceed 1: 1.

In Fig. 1 Or the apparatus is drawn substantially to scale. In the case of a glass column with an inside diameter of 76.2 mm, inside diameter in section 6: 38.1 mm, ailed heat exchanger is provided substantially constructed thereon in Fig. 2, and. 3 showed the set and containing Raschig rings of 6.4 mm in section 6 and the column had the following typical operating results obtained: 66 I / min at 0.35 atm and 20 ° C 2.9 mol / min with a hydrostatic pressure of 0, 5 at water at 20 ° C 90 ° C 100 ° C 85 ° C 35 ° C substantially 100% in the liquid phase flowing down the column. Furthermore, other mechanical aids can be used than filling bodies, for example inclined baffles to prevent leakage, efficient mixing and even distribution of the liquid over the whole cohort, provided that these aids do not entail too strong a restriction of the liquid flow with consequent flow.

Claims (12)

Patent claim: Process for the halogenation of normally gaseous olefins, according to patent 173 001, characterized in that the halogen and the olefin are introduced into an upper part of the reaction zone and are brought into contact in the co-stream in the presence of a large volume of liquid solvent, wherein atinone a stone proportion .of oak preferably alit the liquid solvent consists of in .situ formed product dihalide. Process according to claim 1, Uneeteeknet in that the heat exchangers form at least one filled cooling section, which extends transversely over the reaction zone and occupies a substantial vertical distance saint provides substantially vertical co-current flow of gas oak liquid, thereby along paths, which aro distributed Over the reactor cross-sectional area. Method according to claim 2, characterized in that - there are at least two. Filled cooling sections and between adjacent cooling sections at least one zone containing solid filling bodies () is arranged to provide mixing of individual streams, soul intrada clan. 4. A method according to the claim of the preceding patent claims, characterized in that the genide product is recovered without recirculation, thereof to the reactor. Process according to any one of the preceding patent claims, characterized in that the halogen Sr bromine. Process, according to claim 5, characterized in that the olefin is ethylene. Process, according to claim 5 or 6, wherein the reactor Wailes at an internal temperature in the range 19-100 ° C. And approximately equimolar amounts of halogen .00 hours of olefin are fed into the reactor. 7. A process according to any one of the preceding claims, which comprises a liquid and gas-containing stream containing a certain amount of unreacted halogen, and, olefin is taken from a lower part of the reactor and passed through a narrow tortuous path, which Sr. arranged to cause high degree of turbulence in the stream, or raised up through a column containing solid filler bodies, so that the free halogen in the stream is substantially completely eliminated by reaction with the olefin. 8. A process according to any one of the preceding claims, characterized in that the free halogen in the formed liquid dihalide, which is drained from the lower part of the reactor, contains a content of less than 10% by weight. 9. A process according to any one of the preceding claims, characterized in that the heat exchangers offer a heat exchange area of at least 0.1 dm2 per mole of halogen which is introduced into the reactor per hour. Modification of the apparatus for halogenating northern gaseous olefins according to patent 173 001 for carrying out the air process according to claim 1, comprising a thermoformed column with cooling devices, inlet devices for introducing olefin and halogen into an upper part of the column, outlet devices for as .fluidu.mproductstrom. from a lower part of the column and a device for separating gas and liquid, which is connected to the outlet devices, characterized in that the tubular column (1) is internally provided with, a plurality, separate tubular heat exchanger devices (2, 3, 4, 5) arranged it. one Over the other in the column and consisting in a substantial extent of transversely lying surfaces and forming a filled cooling section, which, extends transversely Over the column, but Sr at a distance Iran the cradle of the column, which heat exchanger devices extend vertically Over a considerable part of the column as well. achieve one. discontinuous liquid flow path down- dol column Over essentially the whole, its cross-sectional area. Apparatus, according to claim 11, characterized by the heat exchanger devices at least partially consisting of several one, one above the other arranged flat helically wound pipe loops (62) with the turns in adjacent loops formed in relation to the goods. Apparatus, according to patent claims 11 and 12, characterized in that between two adjacent heat exchanger devices (2, 3, 4, 5) a filled zone (6) is arranged containing small filling bodies, e.g. Rapid rings. Request publications; Patent Specification ter frail Schweiz 203 694; United Kingdom 557,720; Germany 692836; U. S. A. 1 402 337. Stockholm 1961. Kungl. Boktr. P. A. Norstedt & Soner. 610089 G EN ERALSTABENS L