JPS5911567B2 - Method for oxychlorination of ethylene - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 1,2-dichloroethane (hereinafter abbreviated as EDC) by oxychlorinating ethylene.

More specifically, the present invention relates to a method for producing EDC by oxychlorinating ethylene with a catalyst using hydrogen chloride and molecular oxygen. The production of EDC by the oxychlorination reaction of ethylene proceeds according to the following formula, for example, in the presence of a copper catalyst.

C2H4+2HCl+1/202=C2H4C12
+H2O... (1) In general, in chemical reactions involving multiple reactive species, other reactive species are used in excess of the stoichiometric ratio to increase the reaction rate of one of them. What is necessary is shown by the theory of chemical equilibrium,
In the oxychlorination reaction of ethylene, in order to maximize the reaction rate of hydrogen chloride, excess ethylene, 2
5 It is effective to use oxygen.

When air is used as the oxygen source, the reaction product is diluted with nitrogen, and it is not economical to separate and recover unreacted ethylene.

On the other hand, ethylene is diluted with nitrogen without being separated and recovered.
Japan Patent No. 468415 discloses that the air is circulated to the reactor, but the partial pressure of each raw material component is further reduced by the newly charged nitrogen in the air, so it is theoretically possible to circulate the reactor. method, the reaction cannot be carried out on a steady basis and is not practicable. For this reason, when air is used as the oxygen source, the oxychlorination method must be carried out under pressure and without using a circulation system, which has the disadvantage of requiring expensive equipment.

On the other hand, regarding a method of circulating unreacted ethylene and oxygen using oxygen gas as an oxygen source, a description of such a method of circulating unreacted raw materials can be found in German Patent No. 430,539. It merely suggests the circulation of ethylene, and does not mention anything about the treatment of side reaction products such as carbon monoxide that accumulate.

Furthermore, in Japanese Patent Publication No. 33010 of 1972, a part of the by-product carbon monoxide is also changed into carbon dioxide at the same time by the oxychlorination reaction catalyst, and the carbon monoxide concentration in the system is maintained within an extremely desirable level. It is said that there is no gradual accumulation of carbon oxide. However, in reality, it is difficult to keep the amount of carbon monoxide constant, and in order to keep the concentration of carbon monoxide in the system within a certain level, it is necessary to reduce the amount of carbon monoxide that is produced as a by-product in the oxychlorination reaction. It is necessary to remove carbon oxide from the circulating gas, and at present, part of the circulating gas is released to maintain the amount of carbon monoxide within a certain range. On this point, P. R
each;HydrOcarbOnPrOcessin
There is also a description to the same effect in gp85, March, 1976. Naturally, when a portion of the circulating gas is discharged, there is an accompanying loss of ethylene and oxygen, and air pollution due to the discharged gas is also unavoidable. Furthermore, if the release of circulating gas is suppressed, the amount of non-reactive components in the gas supplied to the reactor increases, leading to a decrease in production capacity. Therefore, the present inventors conducted extensive studies with the aim of carrying out the oxychlorination reaction of ethylene using oxygen in a completely closed circulation system, and completed the present invention in which no part of the circulating gas is released at all.

That is, in a method for producing 1,2-dichloroethane by the oxychlorination reaction of ethylene, hydrogen chloride, and oxygen, a part of the carbon monoxide contained in the reaction product is removed from the reaction zone (oxychlorination reactor and its (Refers to attached equipment.)
The concentration of carbon monoxide contained in the reactor feed gas is brought within the desired level by converting it into carbon dioxide with a catalyst outside and removing it from the reaction system (refers to the oxychlorination reactor and the circulation gas flow path). We discovered the fact that it is possible to maintain ED by highly efficient and stable oxychlorination reaction of ethylene.
This led to the invention of a method for manufacturing C. In the method of the present invention, carbon monoxide can be removed at any point in the circulating gas system, but the reaction product EDC and the side reaction product carbon dioxide can be collected and removed. It is preferable to remove the unreacted component gas (recirculated gas) containing carbon monoxide in the flow path after the reaction.

This is because the amount of gas to be treated is the minimum and the carbon monoxide concentration is relatively high, so after recovering and removing EDC and carbon dioxide, the removal treatment is carried out in the flow path before being introduced into the reaction zone. This is because it is the most practical thing to do. The circulating gas after EDC and carbon dioxide removal is an unreacted gas containing carbon monoxide, and also contains ethylene, oxygen, and others.
Methods for removing carbon monoxide from a mixed gas containing ethylene, oxygen, and carbon monoxide as main components include a catalytic oxidation method using coexisting oxygen, and a catalytic reduction method using an adsorbent with the addition of hydrogen. Methods such as adsorption and removal of carbon monoxide and solution-based absorption and removal methods are conceivable, but methods other than the catalytic oxidation method are not practical because the removal equipment becomes complicated and operation costs are too high. In the oxidation of carbon monoxide using a catalyst, many effective catalysts have already been discovered, and the effective operating temperature as a catalyst is said to be from about -20 degrees Celsius to about 1000 degrees Celsius.

Therefore, as a catalyst for oxidizing carbon monoxide from the circulating gas of the ethylene oxychlorination reaction, any known catalyst may be used as long as it is effective at an appropriate oxidation reaction temperature. In detail, as already mentioned, unreacted ethylene is contained in the circulating gas, so it is preferable to carry out the reaction at a temperature at which ethylene does not change due to decomposition or oxidation.Practical catalytic reaction temperatures range from room temperature to 300°C. Degrees can be given. The carbon monoxide oxidation catalyst used in the method of the present invention includes cobalt oxide (), copper oxide (1),
Nickel oxide (), manganese oxide (), chromium oxide ()
, zinc dichromate, copper oxide (), trilead tetroxide, iron oxide (
), tin oxide (), zinc oxide, cerium oxide (), barium peroxide, titanium oxide (), thorium oxide, vanadium oxide (), alpha manganese monoxide (), aluminum oxide, and other oxides are preferred. Examples include oxides of copper, cobalt, manganese, and tin. The catalyst for carbon monoxide oxidation may be one or a mixture of two or more of the various metal oxides listed above, and if necessary, it may be supported on diatomaceous earth, asbestos, pumice, etc. as a carrier, or other compounds. It may be added.

The shape of the catalyst may be powder, granules, pellets, etc., and the size of the catalyst is not particularly limited. The apparatus for CO oxidation reaction is not particularly limited, and may be of any type, such as a fixed catalyst bed type or a catalyst fluidized bed type. Furthermore, the oxidation reaction of carbon monoxide is a considerably exothermic reaction with a heat of reaction of about 67 Kcal/MOle, and it is also possible to attach an effective temperature control method to the catalytic reaction apparatus.

Of course, if necessary, it is also possible to control the temperature of the gas supplied to the catalytic reaction device or to add oxygen to the supplied gas. Ethylene, oxygen, EDC, water vapor, carbon oxides, etc. are present in the circulating gas of the oxychlorination reaction, and the effects of these components on the catalyst are complex, but according to the method of the present invention, more than the necessary amount is present. Carbon monoxide can be converted to carbon dioxide and easily removed from the system by suitable means, such as alkaline scrubbing, anywhere in the circulation system.

The oxychlorination reaction process and operation according to the method of the present invention will be explained in detail with reference to the drawings.

In the drawing, 1 is an oxychlorination reactor, which is equipped with a built-in cooler for removing reaction heat using a heating medium and controlling the temperature, as well as various equipment necessary for the reactor, and is loaded with a copper-based catalyst. In the present invention, this part is abbreviated as the reaction zone) 2 is a gas-liquid countercurrent type gas cooler, into which high-temperature reaction product gas is charged from the bottom, and is mixed with the irrigation liquid whose main components are E'DC and dilute hydrochloric acid. Most of the crude EDC and water produced by the reaction during the flow contact are condensed, and the condensed liquid is continuously discharged from the conduit 4.

The remainder of the irrigation liquid is circulated and reused at the top of the gas cooler 2 after its sensible heat is removed by the cooler 3. The mixed gas containing unreacted ethylene, oxygen, carbon monoxide, carbon dioxide, etc. that has exited the top of the gas cooler 2 is charged to the bottom of the gas-liquid countercurrent gas scrubbing tower 5, and the dilute alkali gas that circulates within the tower is charged. Carbon dioxide is neutralized and removed by contact with the liquid.

The concentration of the circulating fluid is kept constant by the alkali added through the conduit 7, and the temperature of the fluid is kept constant by the cooler 6. If the liquid containing crude EDCl water and alkali carbonate, which is continuously discharged from the gas cooler and gas scrubbing tower conduits 4 and 8, is separated, washed, distilled, etc., high-purity ED can be obtained.
C can be obtained.

Note that the gas cooler 2, gas scrubbing tower 5, etc. may be replaced with other known devices that perform the intended functions. Ethylene and oxygen flowing out from the top of the gas scrubbing tower 5,
The circulating gas mainly composed of carbon monoxide passes through the conduit 9 and is pressurized by the proa 10, and a part of it is transferred to the oxidation reactor 16.
The oxidation catalyst oxidizes carbon monoxide to carbon dioxide.

The gas leaving the reactor 16 is again combined with the circulating gas and mixed with raw materials ethylene, hydrogen chloride, and oxygen, which are charged into the system in approximately stoichiometric ratios through conduits 11, 12, and 13, and then transferred to conduit 14. It is introduced into the reactor 1 through . Conduit 15 is used during transition periods, such as when changing process operating conditions.
This is a gas exhaust port that is used as an auxiliary to keep the reaction system steady. In the method of the present invention, the composition of the mixed gas supplied to the reactor 1 (the composition at the position of the conduit 14 in the drawing) varies depending on the reaction temperature, gas flow rate, and space velocity relative to the catalyst bed, but the molar ratio of ethylene 1.5-2.5: Hydrogen chloride 2
,00: 0.55 to 1.0 of oxygen, and preferably 0.5 to 3 of carbon monoxide to 2.00 of hydrogen chloride.
．． It is necessary to set the value between 0 and 0.

The lower limit for each is the minimum amount that allows the reaction to proceed smoothly, and the upper limit for ethylene is determined by the explosion limit for oxygen, which has a negative effect on the catalyst, while for carbon monoxide, it is determined by the economic capacity of the reactor. defined by. Therefore, it becomes necessary to remove a portion of the carbon monoxide that gradually accumulates in the reaction system that falls outside of the preferred range.

Therefore, a part of the circulating gas is taken out and supplied to the carbon monoxide oxidation catalytic reaction device 16 to convert the accumulated excess carbon monoxide into carbon dioxide, which is combined with the circulating gas and sent to the reactor 1. . In order to adjust the composition of the gas supplied to the reactor, the molar ratio can be controlled within a desired range by increasing or decreasing the load on the propeller 10 to change the amount of circulating gas. The presence of some carbon dioxide, water vapor, saturated hydrocarbons, chlorinated hydrocarbons, nitrogen, etc. in the feed gas in addition to those listed above does not interfere with operation of the process according to the method of the invention. The reaction temperature in the oxychlorination method using a copper-based catalyst is the normal oxychlorination temperature, that is, 1
80 to 300°C, preferably 200 to 260°C,
The pressure may be normal pressure or pressurized.

When the oxychlorination reaction of ethylene is carried out using a copper-based catalyst under the above-mentioned reaction conditions, hydrogen chloride easily exhibits a high reaction rate of 99% or more. According to the method of the present invention, by using the above-mentioned catalyst and carrying out the operation control operations detailed in the text, high-purity EDC can be produced in high yield while maintaining stable operating conditions, according to the process illustrated in the drawings. Therefore, its practical value is extremely large.

The effects of implementing the present invention are clear as shown in the examples. That is, in methods other than the present invention, in order to maintain a high reaction rate and maintain a constant carbon monoxide concentration in the reactor supply gas, it is necessary to release a part of the circulating gas.
It is impossible to continue the reaction with high yield and stability. Note that the reaction rate, selectivity, etc. below are based on the following calculations.

Examples will be described below, but the embodiments of the present invention are not limited thereto.

Example 1100.4 kg of cupric chloride (dihydrate) was
Dissolved in 740 kg of 5% (actual amount) hydrochloric acid and diluted with 26 kg of water.
801 and 45% by weight sodium hydroxide aqueous solution 711.2k9 and aluminum hydroxide 318.4k9.
After dissolving 12501? with water? ．． A gel-like precipitate was generated by mixing with a diluted solution.

After ripening the precipitate at room temperature, water was added to the cake obtained by filtration to make a slurry, spray-dried, and further washed with water.
C. for 3 hours to obtain a copper/alumina fluidized catalyst for oxychlorination. The copper content of the catalyst was 13.35% by weight, and the apparent bulk density was 0.83V/ml, and the average particle size was 60μ (microspherical). This catalyst 120kg has an inner diameter of 4001!1
1 height 300]! A reactor 1 having 1 reaction chamber was loaded. The flow rates, temperature and other reaction conditions and results when the reaction reached a steady state were as follows. The molar ratio of each component of the reactor feed gas passing through conduit 14 is ethylene 1.86
:Hydrogen chloride 2.00:Oxygen 0.84:-carbon oxide 0.9
0. At a reaction temperature of 240°C, the amount of raw materials charged to the process was ethylene 35.80 m1/hour (all flow rates were converted to standard conditions), hydrogen chloride 71.68 wI/hour, and oxygen 18.45 m1/hour.
It was m3/hour.

Component concentration in the circulating gas in conduit 9 (all percentages by volume)
) was 36.6% ethylene, 13.8% oxygen, 38.4% carbon monoxide, and 11.2% others, but in order to maintain steady operation, carbon monoxide was 0.69 m゜/hour. It was necessary to remove it. Commercially available carbon monoxide oxidation catalyst (composition: 53.3% by weight of zinc oxide, 26.7% by weight of copper dioxide, 20.0% by weight of alumina, tablet-shaped catalyst with a diameter of 61 tm and a height of 3 mm).

) 3 kg was loaded into a multi-tubular reactor 16 having 6 reaction tubes with a diameter of 25 m and a height of 1 m in a fixed bed manner, and 2.9 I/h of circulating gas was sucked into the reactor 16 using a blower. supplied. The temperature of the circulating gas supplied to the reactor 16 is 90°C, the temperature of the gas discharged from the reactor 16 is 110°C, the temperature of the heating medium supplied to the reactor jacket is 95°C, and the temperature of the gas discharged from the jacket is 95°C. The temperature of the heating medium was 100°C. The concentration of components in the circulating gas supplied to the reactor (both by volume %) is 36.6% ethylene, 13.8% oxygen, 38.4% carbon monoxide, and 11.2% other components. At outlet No. 16, ethylene was 41.6%, oxygen 2.0%, carbon monoxide 16.4%, and others 40.0%.

The results of the oxychlorination reaction after 700 hours of continuous operation were a reaction rate of 100% (based on raw material ethylene) or 99.6%.
(based on raw material hydrogen chloride), and the EDC selectivity was 99.1% (based on carbon) or 99.4% (based on chlorine).

The conversion of ethylene to carbon dioxide, that is, the combustion rate, was 0.58%, and there was no need to discharge circulating gas containing carbon monoxide to the outside of the circulation system. The obtained crude EDC had a yield of 157.3 ky/hour, and its composition was as follows.

EDC99. 15 mol% Ethyl chloride O.08″ trichloroethane 0.12 Water
0.55 Other 0.
10 Comparative Example 1 The same procedure as in Example 1 was carried out except that the circulating gas was not sucked into the carbon monoxide oxidation reactor 16.

To maintain steady operation, circulate gas 1. from the gas outlet 15.
It was necessary to discharge 80 m3/h.

The resulting loss of unreacted ethylene was 0.65 i/hour.

Example 2 Ultrafine particles with an average particle size of 60 μm were obtained by mechanically crushing a commercially available carbon monoxide oxidation catalyst (tablet-shaped catalyst with a composition of 22% by weight of copper dioxide and 78% by weight of manganese dioxide).
．． The same procedure as in Example 1 was carried out except that 30 kg was loaded into the reactor 16 in a fluidized bed manner.

The amount of circulating gas sucked by the proa and supplied to the reactor 16 is 2
．． It was 8m and 7 o'clock. The temperature of the circulating gas supplied to the reactor 16 is 90°C, the temperature of the gas discharged from the reactor 16 is 100°C, and the temperature of the heating medium supplied to the reactor 16 is 95°C.
℃, and the temperature of the heating medium discharged from the reactor 16 is 100℃.
It was warm at ℃. The component concentrations (both volume %) in the circulating gas supplied to the reactor 16 are 36.6% ethylene and 1% oxygen.
3.8%, carbon monoxide 38.4%, other 11.2%, and at the reactor 16 outlet, ethylene 41.8%, oxygen 1
．． 5%, carbon monoxide 15.3%, and other 41.4%. As a result of continuous operation for 240 hours, there was no need to discharge circulating gas containing carbon monoxide to the outside of the system.

[Brief explanation of the drawing]

The drawings are for explaining one embodiment of the ethylene oxychlorination method according to the present invention.

Claims (1)

[Claims] 1. In the oxychlorination reaction zone, 1.5 to 2.5 moles of ethylene and 0.55 to 1.5 moles of oxygen are added per 2.00 moles of hydrogen chloride.
In a method for producing 1,2-dichloroethane by an oxychlorination reaction of ethylene, hydrogen chloride, and oxygen by supplying a raw material gas at a ratio of 0 molar, the gas containing by-product carbon monoxide flowing out from the reaction zone is At least a portion of the carbon monoxide is oxidized in the presence of an oxidation catalyst to convert at least a portion of the carbon monoxide into carbon dioxide, and the converted carbon dioxide is selectively transferred to the reaction zone and the circulating gas stream. The circulating gas is removed from the reaction system consisting of a channel, and the circulating gas is circulated and supplied to the reaction zone while maintaining the concentration of carbon monoxide contained in the circulating gas within an allowable range. Method for oxychlorination of ethylene without emissions.