MXPA00005367A - Method for producing 1,2-dichloroethane by oxychlorination - Google Patents

Abstract

The invention relates to a method for producing 1,2-dichloroethane from ethene, hydrogen chloride and oxygen or a gas containing oxygen on a fluidized bed catalyst containing copper. According to the invention, the catalyst is retained in the reactor by fine filtration, which simplifies the method considerably.

Description

PROCESS FOR THE PREPARATION OF 1,2-DICHLOROETHANE BY OXYCOLORATION Under "oxychlorination" is meant the transformation of an alkene - in this case ethylene - with hydrogen chloride and oxygen or an oxygen-containing gas such as air, with formation of a chlorinated saturated alkane - in this case 1,2-dichloroethane, hereinafter referred to as "DCE". The reaction takes place according to the equation C2H4 + 2HCl + 1? Oz «• CI-CH2-CH2-CI + H2O. The by-product water of the reaction can therefore form, with the starting material, unreacted hydrogen chloride, the corrosive hydrochloric acid, so that materials which are suitably resistant - and therefore expensive - have to be used for the apparatuses. In one embodiment of this process, which is frequently used on a large industrial scale, a turbulent bed is used as a catalyst, in which the catalyst consists essentially of copper chloride on an aluminum oxide support. In conventional industrial processes, the turbulent agitated catalyst is separated in the upper part of the oxychlorination reactor by several cyclones interspersed one after the other and thereby retained for the most part in the reactor. However, in this case a small proportion passes with the residual gas in the reaction and thus ends up in the DCE treatment, where it has to be separated.

DE-A-41 32 030 discloses a process for removing the abrasion residue from the catalyst, which is produced in the reaction zone during the preparation of DCE according to the oxychlorination process and is evacuated from the reaction zone. with the gross gaseous DCE stream, which is characterized in that the abrasion residue of the evacuated catalyst is separated from the gross gaseous DCE stream in a purification zone operating in dry conditions. Preferred embodiments of this process are characterized in that the abrasion residue of the catalyst is separated in a fine dust separator or in an electrofilter as a purification zone, because the fine dust separator is provided with sleeve filters, which are cleaned with compressed recycle gas, because the abrasion residue of the precipitated catalyst in the purification zone is released from adsorbed reaction products in a desorption zone disposed downstream, because the desorption zone is operated at a temperature of 50 to 350 ° C, particularly 150 to 180 ° C, by gasification or at low pressure, because air, nitrogen or recycle gas are used for the gasification, and because the abrasion residue of the catalyst is treated in the desorption zone for 0.5 to 5 hours. hours, preferably 1 to 2 hours, at elevated temperature. With this process it is avoided that, by removing the water formed from the washing water used in the treatment, a residual water contaminated with heavy metal and inorganic sludge is formed. However, the proportion of fines of the separated catalyst has to be rejected and evacuated in an appropriate manner. DE-A-195 46 068 relates to a process for reducing the consumption of catalyst and doped catalyst residues in the preparation of DCE according to the oxychlorination process on a turbulent bed catalyst containing copper in a reaction zone. , in which the abrasion residue of the catalyst is separated from the gross gaseous DCE stream in a separation zone operating under dry conditions, which is characterized in that the abrasion residue of the catalyst is classified and certain granulometric fractions are carried again to the reaction zone. Preferred embodiments of this process consist in that the abrasion residue of the catalyst is classified into a fraction of thicknesses and a fraction of fines, because the fraction of coarse corresponds to a granulometry > 5 μm and the fraction of fines to a granulometry < 5 μm, because the coarse fraction is returned to the reaction zone, because the fines fraction is subjected to thermal after-treatment at 300 to 800 ° C, preferably 600 to 800 ° C, because the post-treated waste gases are introduced into a combustion furnace, because the combustion furnace operates at a temperature above 900 ° C, preferably above 1000 ° C, because they are recovered from the fraction of fine copper and / or aluminum, because the fines fraction is deposited in a controlled manner and because the dioxins and / or furans are separated from the abrasion residue of the catalyst. With this process, the disadvantages of the process are therefore solved according to DE-A-41 32 030, but with the cost of a considerable expense in equipment and work in its operation and entertainment. It is common to both known processes that the separation of the proportions of catalyst fines removed is carried out in a separate area of the reactor. It has now been found that the evacuation of the catalyst from the reactor can even be avoided when the catalyst is almost completely retained in the upper part of the reactor by a very fine filtration. The invention therefore relates to a process for the preparation of DCE by oxychlorination, in which in a turbulent bed of a copper-containing catalyst ethylene with hydrogen chloride and oxygen or an oxygen-containing gas are reacted; in which the reaction gas leaving the reactor is released from the catalyst in the reactor by a very fine filtration and this is thus retained in the reactor. By "very fine filtration" is meant a process that realizes the retention of the proportion of fines of the oxychlorination catalyst. While conventional cyclones hitherto allowed a proportion of fines of less than about 10 μm to fall into the product stream, according to the invention, particles of sizes less than about 1 μm are retained, that is practically all of the catalyst. Surprisingly, it has also been found that, according to the invention, the separation of the proportion of coarse particles from the catalyst can be suppressed by cyclones. Therefore, the proportion of coarse and the fine proportion of the catalyst in a single step is retained by the very fine filtration. This brings with it a series of advantages: By eliminating the cyclones, not only the cost of the apparatuses and the complicated entertainment of these hardly accessible components are avoided, but the height of construction of the reactors can also be significantly reduced. In this way, the reactor is considerably cheaper and the requirement for space in the installation and therefore the construction cost is naturally reduced as well. In comparison, the installations required for the very fine filtration - known per se - are easy to install in a satisfactorily accessible manner in the upper part of the reactor, for example in appropriate supports in each case, which allow a simple entertainment or a rapid change of the filtration apparatus with only brief interruptions of the operation. In addition, a construction of this type allows individual devices to be taken out of service during the course of the operation. For example, filtering plugs of materials suitable for the preparation of DCE are suitable, for example, metals, alloys, glass or ceramic, preferably with porous metal filtering plugs, sufficiently resistant to corrosion such as sintered metal powders or metallic fabrics or non-woven wire materials made of stainless steel or highly corrosion-resistant alloys, such as those commercially available under the designations © INCONEL (brand name of Inco Ltd, nickel-chromium alloy), © MONEL (brand name) Inco Ltd, nickel-copper alloy), © HASTELLOY (nickel alloy), and porous ceramic materials.

Additionally, fabric filters made of plastic materials that are sufficiently heat-resistant, particularly fluorinated, such as polytetrafluoroethylene, for example sleeve filters or cartridges, are useful. All very fine filters that retain particles of approximately 1 μm and above are suitable, and therefore preferably allow only particles smaller than about 0.8 μm, particularly less than about 0.5 μm or even less than 0.2 μm to pass through. The separation of the catalyst filter cakes formed in the filtration materials is carried out - as usual - advantageously by means of countercurrent gas lines, preferably reaction gases (raw materials), inert gases or gas returned to the cycle (gas recycle), for example in pulses, preferably at regular intervals of time, or as soon as a predetermined thickness of the filter cake has been formed and / or a corresponding pressure loss has been reached. It is extremely surprising that with this simple arrangement of the very fine filter in the reactor even an evacuation of the catalyst can be reliably avoided and the cost of recovery and treatment necessary so far, which was always linked to losses, can be suppressed. Additionally, even the abrasion caused by the catalyst in the parts of the installation until the elimination of the proportion of fines is avoided. Due to the turbulent agitation of the catalyst, the granulometric spectrum moves with time to smaller particles. Since this process is linked to an increase in the active surface, this is linked to an increase in the activity of the catalyst. In case this is undesirable or is required only after a longer operation, the undesirable fine proportion can be easily separated by a brief interruption of the process. The disadvantages that occur in the known processes with the continuous evacuation of the proportion of fines do not therefore arise in this case. A process for the treatment of 1,2-dichloroethane from oxychlorination has already been proposed, characterized in that the gaseous products from the oxychlorination reactor are released from the entrained catalyst, and then the acidic components are separated in a washing zone. with an alkaline washing solution (German Patent Application 197 03 857.3, dated 03.02.1997). Preferred embodiments of this process are characterized in that the alkaline washing solution is passed in countercurrent and because between the removal of the catalyst and the washing zone a partial stream of the gaseous products bifurcates and is analytically investigated. A device for carrying out the known process has also been proposed, which is characterized by an oxychlorination reactor, a gas evacuation pipe, which is carried through a catalyst separator to a washing zone, in which the constituents acids are separated with an alkaline washing solution. Additionally, a bifurcation pipe between the catalyst separation and the washing zone is advantageously provided for the analytical monitoring of the reaction. A process has also been proposed for the preparation of 1,2-dichloroethane from ethylene, hydrogen chloride and oxygen or an oxygen-containing gas, in which unreacted hydrogen chloride from the reaction mixture is washed with water, a parameter is determined in the wash water and this is used for the at least partial neutralization of hydrogen chloride, which is characterized in that the parameter is additionally used for the regulation of the amount of hydrogen chloride used. Advantageously, in this case the electrical conductivity is determined as a parameter, the wash water is conducted to the cycle and / or the conductivity in the outlet wash water and in addition in the inlet wash water is measured (German Patent Application 196 31 382.1, dated 02.08.1996).

This process can also be advantageously combined with the process according to the invention, optionally also in combination with the process proposed in German Patent Application 197 03 857.3. Otherwise, the oxychlorination process is carried out in a manner known per se: The temperatures in the reaction zone of the reactor reach 200 to 270 ° C, preferably 215 to 230 ° C and in particular 220 to 225 ° C. The pressures are between 2.5-105 and 5-105 Pas, preferably between 3-105 and 4-105 Pas, and particularly between 3.4-105 and 3.5-105 Pas (overpressure in all cases). By mole of ethylene, up to 1.92 mol of hydrogen chloride and up to 0.53 mol of oxygen are used, and it is sought - in a manner known per se - that ethylene or oxygen first comes into contact with the catalyst, before The same substance can be combined with the other substance which is a part of the reaction (for example, WO-A-96/26003) or, in a known manner, the explosive gas mixtures are avoided. The treatment of the reaction gas is also carried out in a conventional manner. In this regard reference can be made to the documents mentioned at the beginning. In the following example, the invention is further illustrated with the aid of FIG. 1.

EXAMPLE 5910 m3N / h of hydrogen chloride with a temperature of 150 ° C and 1600 m3N / h of oxygen are heated to 110 ° C, and are introduced together through line 1 into reactor 2. 3000 m3N / h of ethylene are heated together with the recycle gas at 150 ° C and are fed to reactor 2 through line 3. In reactor 2 there are 40 t of turbulent bed catalyst (aluminum oxide with a copper content of 4% by weight) with the following granulometric distribution: The heat of reaction is eliminated by a cycle of hot water with obtaining steam. The reaction gas passes through after the turbulent bed exit for the precipitation of the entrained catalyst particles the very fine filter 4 in the upper part of the reactor, in which the catalyst is almost completely deposited. The reaction gas released from the catalyst at the temperature of 210 ° C is led through line 5 to the quench column 6, in which the production water is condensed and fed through line 7 to the sewage treatment. The copper content in quench water is < 0.05 mg / l. The overhead stream, consisting essentially of DCE and recycle gas, is fed via line 8 to the DCE treatment. The very fine filter 4 is cleaned, under conditions of controlled differential pressure, by way of the pipe 9 with nitrogen, which is heated in the preheater 10 to 180 ° C. The product retained is > 99.99%

Claims (3)

NOVELTY OF THE INVENTION CLAIMS

1. - Process for the preparation of 1,2-dichloroethane by transformation of ethylene with hydrogen chloride and oxygen or an oxygen-containing gas on a turbulent copper-containing catalyst, characterized in that all of the particles in the reactor are retained by filtration. catalyst up to a size of 1 μm.

2. Process according to claim 1, characterized in that the filtration is carried out by means of filtering spark plugs, sleeve filters or cartridge filters.

3. Process according to claim 2, characterized in that sintered metal or ceramic filtering plugs are used.