NO147380B - PROCEDURE FOR THE PREPARATION OF 1,2-DICHLORETHANE BY ECYCLORATING ETHYLENE - Google Patents

Description

The invention relates to a method for the production of 1,2-dichloroethane by oxychlorination of ethylene in a fixed-bed catalytic process.

It is well known that hydrocarbons, e.g. ethylene, can be chlorinated by reaction with hydrogen chloride and gases containing elemental oxygen, especially air, in the presence of a catalyst at elevated temperatures and pressures. Such a process is generally termed an "oxychlorination" or a Deacon process and typically employs a catalyst comprising a chloride of a metal having at least two valences, generally on a porous refractory support. The most common catalyst for such processes comprises copper (II) chloride on a particulate material, e.g. activated alumina, silica, alumina/silica, infusoria etc. Activated alumina, in one or another of its various forms, is the most common carrier used. In addition, the catalyst may contain such additives as alkali metal chlorides, chlorides of rare earth metals and other metal compounds which help to accelerate the desired reaction and/or to inhibit side reactions. In particular, potassium chloride has been used as an additive to such a catalyst when it is desired to produce 1,2-dichloroethane from ethylene, as potassium chloride is known to suppress the formation of ethyl chloride. The amount of potassium chloride used is, however, kept low as it also tends to reduce the catalyst's activity towards the primary reaction.

When carrying out such a fixed-bed oxychlorination process, one of the things that must be taken care of is the regulation of the reaction temperature. The oxychlorination reaction itself is highly exothermic, and furthermore the regulation of the reaction temperature is hampered by the fact that the catalyst layer itself has low thermal conductivity. As a result of these two factors, there is a danger of the formation of unwanted extra-ordinarily high local temperature zones in the catalyst layer. Numerous remedies have been proposed in the prior art with the aim of preventing, or at least reducing to a minimum, the existence of such exceptionally high local temperatures. For example, it has been proposed to regulate the temperature by adjusting the ratio between the reaction partners; by diluting the feed with an inert gas or an excess of one or more reactant gases; by using a tubular reactor with controlled external cooling and/or tubes of varying diameters; by diluting the catalyst particles with inert particles; and by varying the particle size of the catalyst and/or inert particles.

Especially when the reaction is carried out in tubular reactors, it is known from the state of the art, e.g. as described in US patent 3,184,515, that the problem of undesirably high local temperatures does not exist throughout the reactor. This is a result of the nature of the oxychlorination reaction itself, which becomes progressively less vigorous in the direction of flow of the reaction mixture. At the inlet to the catalyst layer, the reaction progresses rapidly and strongly, and control of both the temperature and the localization of the hot spot (point of highest temperature) in the layer is important. However, as the reaction partners progress through the bed, the reaction becomes somewhat less vigorous as oxygen is consumed. This is especially the case when, as is known from the state of the art, the oxychlorination process is carried out in a series of two or more catalytic reactors where the total air (or oxygen) feed is split between the different reactors. Therefore, as the oxychlorination feed mixture reacts, oxygen is used up toward the outlet of each reactor, and the concern of a runaway reaction or excessively high local temperature in this zone is less than in the portion of the reactor closer to the inlet.

One solution that has been proposed to achieve acceptable conversions and selectivity to dichloroethane as well as to achieve reasonable control of the reaction temperatures and generation of high local temperatures is to dilute the catalyst with inert particles mixed into the catalyst particles. The inert particles can e.g. consist of silicon dioxide, aluminum oxide, graphite, glass beads, etc. In some processes, the ratios between catalyst and diluent in the oxychlorination reactor have been varied, on the inlet side of the reactor it is desirable to have a less concentrated catalyst due to the danger of reactions running

runaway/or high local temperatures. Further away from the inlet, as the reaction progresses and becomes less vigorous,

however, these dangers are not quite so prevalent, and it would actually be desirable to have a more highly active catalyst to continue to speed up the reaction as oxygen is consumed. Therefore, it is common, when using diluted catalysts,

dividing the layer into two or more zones, each zone containing a different ratio between catalyst and diluent, whereby the ratio between catalyst and diluent increases towards the outlet end of the reactor. E.g. US Patent 3,184,515 describes a process (Example 1) which uses a dilute catalyst whereby the reaction tube is divided into four zones, a first zone containing 7% by volume of catalyst and 93% by volume of graphite diluent, a second zone which contains catalyst/diluent in a volume % ratio of 15:85, a third zone containing a 40:60 mixture and a fourth zone containing 100% catalyst. In another variant, a fairly highly active catalyst can be placed just at the inlet to the reactor with the intention of initiating the reaction, immediately followed by a much less active catalyst to prevent the formation of hot spots in the adjacent reaction zone.

However, the use of a diluted catalyst as described in the preceding paragraphs has several disadvantages. Firstly, it requires charging the catalyst in several different reaction zones and thus the preparation of several catalyst/diluent mixtures with different ratios. Of greater concern, however, is the fact that the mixture of catalyst and diluent can result in an uneven mixture. There is therefore a probability of the formation of undesirably high local temperatures due to a concentration of catalyst particles in a particular section of the reaction zone if the mixing is not carried out to a sufficiently thorough degree. Additionally, in many cases the diluent particles are not of the same general size or shape as the catalyst particles. It is e.g. have been proposed to dilute cylindrical catalyst particles or spherical catalyst particles with diluent particles of a different shape or size. In such cases, the overall mixture does not provide a reasonably smooth surface to the reaction partners, and the pressure drop and/or pressure drops that occur during the reaction may be anything but beneficial. Even if the diluent particles have the same relative shape or size as the catalyst particles,

there is still the possibility that the diluent and catalyst will not be satisfactorily mixed and that hot spots may result, as well as the tedious matter of having to mix up different catalyst/diluent mixtures

for the different reaction zones.

Another solution that has been proposed is to provide a catalyst, either with or without diluent particles, where the particle size decreases from the inlet to the outlet. Such an idea

is described in US patent 3,699,178. However, such a practice, even if the catalyst is used without a diluent, requires careful preparation in order to ensure that the particle sizes are as desired, and it is necessary that it be prepared at least

two, and most likely three or four different catalysts, so that the goal of this idea can be reached. in the alternative embodiment of this idea, where the catalyst is mixed together with diluent particles, the disadvantages of using diluent particles are added to those of producing catalyst particles of different sizes.

It is an object of the present invention to provide an oxychlorination process for the production of 1,2-dichloro-

ethane from ethylene.

It is further an object of the invention to provide

an oxychlorination process for the production of 1,2-dichloroethane from ethylene whereby hot spot location and temperature can be easily controlled.

It is another object of the present invention to provide a method for the production of 1,2-dichloroethane by oxychlorination of ethylene at high hydrogen chloride conversion rates.

Another object of the present invention is to provide such a method by which a substantially uniform pressure drop can be maintained for a reasonably long time.

Another object of the present invention is to provide such a method in which selectivity when converting ethylene to 1,2-dichloroethane is acceptably high, and in which an excess of reaction partners such as ethylene and/or air can be kept to a minimum.

A further object of the present invention is to provide such a method which can be carried out at high current

ning rates of the reaction partners.

Another object of the present invention is to provide a method for the oxychlorination of ethylene which can be run using either air or oxygen as the oxygen-containing gas.

In short, the present invention aims to provide a new oxychlorination process which uses a catalyst comprising copper (II) chloride and potassium chloride on a support of spherically shaped activated alumina with a high surface area and with high structural integrity. The ethylene is converted to 1,2-dichloroethane at high rates with regard to conversion and selectivity with good hot spot control and very little increase in pressure drop over long periods of time using such a catalyst in a series of three reactors, in which the catalyst is used essentially without presence of an inert diluent, where the content and weight ratio between copper (II) chloride and potassium chloride in the catalyst is varied within each reactor. In each of the first two reactors, the catalyst bed is divided into two zones, with the catalyst in the zone closest to the inlet preferably having a somewhat lower content of copper (II) chloride and a higher weight ratio between potassium chloride and copper (II) chloride than the catalyst in the zone closest to the outlet.

More particularly, the invention includes a method for the production of 1,2-dichloroethane by oxychlorination of ethylene in a solid layer, using an oxygen-containing gas in the form of air or oxygen, characterized by the following steps: (a) reaction of ethylene, hydrogen chloride and a first portion of an oxygen-containing gas in a first reaction zone in contact with a first catalyst bed, which is substantially undiluted by catalytically inert particles, and comprising copper (II) chloride and potassium chloride on a support of spherical particles of activated alumina, the the first catalyst layer is divided into two parts in the direction of flow of the reaction partners through it, whereby the first part comprises between 4.5 and 75% of the layer, while the second part comprises between 25 and 55% of the layer, the first part comprises between 4.5 and 12 .5% by weight copper(II) chloride and between 1.5 and 7% by weight potassium chloride, in a weight ratio between copper(II) chloride and potassium chloride of between 1.5:1 and 4:1, while the other part comprises between 12 and 25% by weight copper(II) chloride and between 0.5 and 4% by weight potassium chloride, in a weight ratio between copper(II) chloride and potassium chloride of between 5:1 and 15:1; (b) reacting the product of step (a) and another portion of an oxygen-containing gas in another reaction zone in contact with another catalyst bed, which is substantially undiluted by means of catalytically inert particles, and comprising copper(II)- chloride and potassium chloride on a carrier of spherical particles of activated alumina, the second catalyst layer being divided into two parts in the direction of flow of the reaction partners through this, whereby the first part constitutes between 45 and 75% of the layer, while the second part constitutes between 25 and 55% of the layer, the first part of the layer comprising between 5.5 and 15% by weight of copper (II) chloride and between 1 and 5% by weight of potassium chloride, in a weight ratio between copper (II) chloride and potassium chloride of between 2 :1 and 6:1, while the second part of the layer comprises between 12 and 25% by weight copper(II) chloride and between 0.5 and 4% by weight potassium chloride, in a weight ratio between copper(II) chloride and potassium chloride of between 5 :1 and 15:1; and (c) marketing the product from step (b) and a third

part of an oxygen-containing gas in a third reaction zone in contact with a third catalyst layer, which is essentially undiluted by catalytically inert particles, and comprises between 12 and 25% by weight of copper (II) chloride and between 0.5 and 4% by weight of potassium chloride , on a support of spherical particles of activated alumina, in a weight ratio between copper (II) chloride and potassium chloride of between 5:1 and 15:1.

Step (b) includes the possible feature that some hydrogen chloride is first fed into step (b) and there is reacted with the oxygen-containing gas.

Step (c) includes the optional feature of bringing the hydrogen chloride into contact with a layer of spherical particles of activated alumina impregnated with sodium chloride or potassium chloride before bringing it into contact with the first catalyst layer, optionally combining the ethylene, the hydrogen chloride and the first part of the oxygen-containing gas and contacting the combined feed with a bed of spherical particles of activated alumina impregnated with sodium chloride or potassium chloride, preferably potassium chloride, before contacting the combined feed with the first catalyst bed.

The invention will now be described with reference to the drawing which shows an illustrative flow chart for carrying out the process and using the catalyst and the system as described here.

As can be seen from the drawing, the process is carried out in three reactors in series, denoted , and R^. Each of the reactors contains a catalyst layer, respectively 12, 14 and 16. The reactors are preferably tubular reactors, with tubes packed with the catalyst. In reactor R^, the catalyst layer is divided into two parts in the direction of flow of the reaction partners through it. The first part, at the inlet side of the reactor, comprises between approx. 45 and approx. 75%, preferably between 55 and 65%, of the length of the catalyst pipe and contains a catalyst that has between approx. 4.5 and approx. 12.5, preferably between 5 and 8, and most preferably between 5.5 and 6.5% by weight of copper(II) chloride, and between approx. 1.5 and approx. 7, preferably between 2.7 and 3.3% by weight of potassium chloride, whereby the weight ratio between copper (II) chloride and potassium chloride is between approx. 1.5:1 and 4:1, preferably between 1.5:1 and 3:1, and most preferably at approx. 2:1. The other half of the layer, at the outlet end of the reactor, comprises correspondingly between approx. 25 and approx. 55%, preferably between 35 and 45%, of the layer length and contains a catalyst which has between 12 and 25% by weight, preferably between 15 and 20% by weight, copper(II) chloride, between 0.5 and 4% by weight, preferably between . 1.5 and 3% by weight of potassium chloride, the weight ratio between copper (II) chloride and potassium chloride being between 5:1 and 15:1, preferably between . 5:1 and 12:1, most preferably approx. 10:1. Thus, the catalyst bed 12 in reactor R contains two types of catalysts: a first catalyst in the bed section towards the inlet, with a relatively lower activity in order to ensure that the reaction does not become uncontrollable in its early stages, and a second catalyst that has a higher copper (II) chloride content and therefore higher activity, in the reactor part towards the outlet, for the continuation of the reaction at the point where the reaction begins to lose power due to the consumption of oxygen. Reactor R2 contains catalyst layer 14 which is also divided into two parts. The first part of the catalyst layer, at the inlet side of the reactor, comprises between 45 and 75%, preferably between 55 and 65%, of the layer length, and the second part, towards the outlet end, comprises between 25 and 55%, preferably between 35 and 45 %, correspondingly, of the layer length. The catalyst in it

first part of layer 14 in reactor R may be somewhat stronger or more active than the catalyst in the first part of layer 12 in reactor , since the reaction has already progressed partially towards completion. In reactor R2, the catalyst in the first part of the layer contains between 5.5 and 15%, preferably between approx. 7.5 and . 12.5%, and most preferably between 9 and .11% by weight copper (II) chloride, and between 1 and 5, preferably between 1.5 and 3.5, and most preferably between 2.5 and

3.5% by weight of potassium chloride, the weight ratio between copper (II) chloride and potassium chloride being between 2:1 and 6:1, preferably between 3:1 and 4:1, most preferably 10:3 (3.3:1) . Similar to reactor R^, the second part of the catalyst mixture in reactor R2 contains a stronger catalyst, which has between

12 and 25% by weight, preferably between ■ 15 and 20% by weight, copper (II) chloride and between 0.5 and 4% by weight, preferably between 1.5 and 3% by weight potassium chloride, the weight ratio between copper (II) chloride and potassium chloride is between 5:1 and

15:1, preferably between ; 5:1 and 12:1, most preferably approx. 10:1. Similar to reactor R^, and since the reaction has lost intensity as the gases pass through the catalyst's nozzle, due to the consumption of oxygen, the danger of undesirably high local temperatures in the part of the bed closest to the outlet is much less than in the part that is close to the inlet, and therefore a more active catalyst can, and indeed should, be used to achieve the best conversions.

In both reactors R1 and R2, the weight ratio between potassium chloride and copper (II) chloride is preferably higher in the first part of the catalyst layer than in the second part.

When you get to reactor R^, the reaction has proceeded quite far towards completion, and there is much less danger of undesirably high local temperatures compared to reactors R^ and R^. Therefore, the entire layer in reactor R^ can consist of the more active catalyst used in the lower sections of layers 12 and 14, i.e. a catalyst containing between 12 and 25% by weight, preferably between 15 and 20% by weight copper(II) chloride, and between 0.5 and 4% by weight, preferably between 1.5 and 3% by weight, potassium chloride, whereby the weight ratio between copper(II) chloride and potassium chloride lies between . 5:1 and 15:1, preferably between , 5:1 and 12:1, most preferably approx. 10:1. It may also be possible to use such a catalyst in reactor R^ and/or the parts of the catalyst layers 12 and 16 which are closest to the outlet in reactors R1 and R2 with an even lower potassium chloride content and a higher weight ratio between copper (II) chloride and potassium chloride.

When carrying out the method according to the invention, hydrogen chloride gas is introduced through line 1 and is pre-heated in the pre-heater 22. The ethylene is introduced through line 2, is pre-heated in the pre-heater 21 and is combined with the hydrogen chloride feed in line 1. An oxygen-containing gas, which can be air, molecularly oxygen or oxygen-enriched air, is introduced through line 3 and divided into three parts in lines 3a, 3b and 3c respectively. The division can be in three equal or different parts. The part in line 3a is combined with the mixed hydrogen chloride/ethylene feed in line 1 and introduced into reactor R^ through line 4. The temperature in the mixed gas feed is generally approx. from 120-220°C, preferably approx. 135-180°C. The mixed feed passes through catalytic layer 12 which, as explained earlier, preferably consists of catalyst packed in tubes, and is drained from the reactor through line 5.

The products from reactor R^ in line 5 are combined with the second part of oxygen-containing gas in line 3b, introduced into reactor R2 via line 6 and brought into contact with catalyst in bed 14. Reaction products are removed via line 7, brought into contact with

a third part of oxygen-containing gas in line 3c and is introduced via line 8 into catalytic layer 16 in reactor R^. The reaction products are removed in line 9, preferably cooled in the heat exchanger 23 and condensed in the product cooler 24. The reaction products are recovered

in line 10 and consists primarily of 1,2-dichloroethane, with small amounts of ethyl chloride and other chlorinated hydrocarbons.

In general, the method is carried out at a total system pressure of between 2.1 and 7 kg/cm, preferably between 2.8 and

7.2 kg/cm 2. in order to maintain temperature regulation

in the reactors R^, R2 and R^, these reactors are preferably constructed as reactors which are provided with a jacket, the jacket surrounding the tubes or catalyst layers containing a heat exchange fluid, e.g. boiling water, steam or "Dowtherm". General perform-

es the reaction at temperatures between 180 and 340°C, preferably between 235 and 300°C. In the reactor, the hot spot temperature is generally kept below approx. 330°C, preferably below approx. 300°C. In reactor R2, the hot spot temperature is generally kept below 330°C and preferably also below 300°C, and in reactor R3 the hot spot temperature is generally kept below 320°C, preferably below 300°C. Another important factor is the regulation of the location of the hot spots in the reactors. In each reactor, the hot spot must be located towards the inlet end of the catalyst bed. In the reactors R^' and R2, the hot spot should actually be located towards the inlet side in the first, or less active, part of the layer. If the hot spot is found too far towards the outlet of the layer, this is an indication that the reaction is progressing too slowly in the layer, i.e. that the catalyst is not utilized efficiently, furthermore, if the hot spot occurs too far towards the outlet of the bed, a cumulative result can be produced with the stronger catalyst's reaction-enhancing effect in the other part of the bed, resulting in an undesirably high temperature level at this point.

The division of the oxygen-containing gas along the lines 3a, 3b and 3c can be carried out so that equal amounts enter all three reactors, or, if desired, the amount entering each reactor can be varied according to what is known in the art . A variation in the amount of this gas that is introduced into each reactor can affect the temperature and the location of the hot spot in the reactor.

For illustration purposes, the figure shows a system where all three reactors are of the downstream type. This means that the reaction partners are introduced at the top of the reactors, and the products are drained off at the bottom. However, the invention can be carried out either in downstream or upstream reactors, with suitable devices which hold the catalyst down, as used for upstream reactors. The construction of the reactors as alternatively downstream and upstream can reduce costs for pipelines, thus the reactors R1 and R^ could be upstream reactors and reactor R2 a downstream reactor. Conversely, the reactors R^ and R^ could be downstream and R2 upstream.

The hydrogen chloride feed need not be introduced all at once into the first reactor. A part of it can be separated and introduced into reactor R, together with the other part of the oxygen-containing gas.

In general, the method is carried out with an excess of both oxygen-containing gas and ethylene with respect to hydrogen chloride in order to ensure as complete a conversion of hydrogen chloride as possible. When air is used, it is desirable to maintain as low an excess of these reactants as possible so as to avoid handling large quantities of gas. In such a case, the ethylene surplus is kept at a maximum of approx. 35%, preferably between approx. 5 and approx. 20%, and the excess air is kept at a maximum of approx. 25%, preferably between approx. 5 and approx. 20%.

The invention is described here primarily in connection with one oxychlorination process where the oxygen-containing gas is air. However, the catalyst, the system and the process described here are also suitable for use in an operation where molecular oxygen or oxygen-enriched air is used. In one such process, described in US Patent 3,892,816, a large excess of ethylene with respect to the oxygen and hydrogen chloride is used to prevent overreaction and unusually high hot spots. The excess ethylene is preferably recovered from the reaction product and recycled to the oxychlorination reactors. thus, reducing the excess ethylene in such a process is not a goal.

If steel equipment is used in the hydrogen chloride flow circuit, small amounts of ferric chloride can be formed and these are introduced into the catalyst together with the feed stream. Corrosion of the oxygen-containing gas supply system can produce iron oxides which can be converted to ferric chloride by reaction with hydrogen chloride in the reactor. The catalyst may contain small amounts of iron as impurities. However, it has been found that additional ferric chloride, even in small amounts, tends to contaminate and deactivate a copper (II) chloride oxychlorination catalyst. In one embodiment of the invention, therefore, ferric chloride contamination of the catalyst is avoided, as shown in the concurrent application to Ramsey G. Campbell, entitled "Purification of Gas Streams Containing Ferric Chloride", Serial No. 595,464, filed July 14, 1975, at

passing either the hydrogen chloride stream or the mixed gas feed stream through a bed of activated alumina impregnated with

between approx. 5 and approx. 25, preferably between 10 and 20% by weight of sodium chloride or potassium chloride. The layer can be located in the hydrogen chloride line 1, either before or after the preheater 22, or in the combined feed line 4. Alternatively, it can be located inside the room 30 near the inlet. In a preferred embodiment, in which tubular reactors are used, the bed material can be charged in the parts of the tubes in reactor R^ which are located next to the inlet, in front of the copper (II) chloride catalyst in the direction of flow of the reaction partners and can be separated from the by a screen or the like in order to

prevent migration of removed ferric chloride into the copper (II) chloride catalyst. In a preferred embodiment, the aluminum oxide used is the same as that used as catalyst carrier.

It should be noted that the operation of each of the reactors R^ and R^ is only partially affected by the operation of the other. Therefore, should e.g. the localization or the temperature of the hot spot in one of the reactors R^ and R^ is temporarily outside the desired range, then the operation of the other reactor would not necessarily be adversely affected, or if it were, it could be possible to control the operation separately by adjustment of the cooling temperature, the distribution of air between the reactors, etc. Likewise, it is possible, although it is less preferred, to use the catalyst disclosed here, in the weight ratios and layer divisions disclosed herein, in one of the reactors R^ or R^, and another suitable, though probably less effective, catalyst in the other. Such an arrangement would not be expected to possess all the advantages of the present invention in terms of throughput, pressure drop, conversion, selectivity, etc., but may be necessary in the event of an emergency or temporary unavailability of catalyst.

To further illustrate the invention in its various embodiments and modifications, the following examples are presented.

The catalysts used in the following examples,

was produced as described in divisional application 77 1494.

The experimental data in the tables that follow were obtained

using catalysts as described in dept

no. 771494 in an apparatus which was arranged in a flow sequence as indicated in the figure. The three reactors, , R^ and R^ , each consisted of one nickel pipeline No. 40, with a length of 3.75 m and a diameter of 2.54 cm, provided with a jacket throughout its length with a 6.35 cm pipeline of steel No. 40, and arranged for downstream with respect to the reactants. The reaction heat was removed by reflux cooling of "Dowtherm" E in the annular space between the two pipelines. The hot spot temperature and location inside the catalytic bed in each reactor was measured using a movable thermo-element inside a 3.6 m long thermowell which was introduced at the bottom of each reactor.

As shown in the figure, hydrogen chloride was introduced into the system

in line 1 through a preheater 22. The ethylene was introduced into the system in line 2 through a preheater 21. Air was introduced into line 3 and split up into sublines 3a, 3b and 3c, the air in line 3a being introduced into reactor R^, the air in 3b in reactor R2 and the air in 3c in reactor R^. The mixed feed to reactor R^ after preheating was at a temperature of approx. 140 C. A 100% throughput basis was established as equivalent to a hydrochloride mass rate in the reactor of o 117.6 g -mol/h-in.<2>. The air and ethylene feed rates are expressed as percent excess based on hydrogen chloride, assuming a stoichiometric reaction

tion for the production of 1,2-dichloroethane.

The gas flowing out from reactor R^, after pressure reduction, was cooled in a water-cooled glass condenser which condensed all the unreacted hydrogen chloride as a water phase and the main amount of the produced 1,2-dichloroethane as a relatively pure (approx. 98 .5%) organic phase. The hydrochloride conversion was determined by titrating the aqueous phase with sodium hydroxide to obtain its hydrogen chloride concentration in weight percent.

The uncondensed gas from the water-cooled condenser was analyzed by gas chromatography. The analyzes were used to calculate the amount of ethylene oxidation and formation of ethyl chloride, both expressed as a percentage of the ethylene feed.

Table I illustrates conditions in one trial of the method according to the invention, in a preferred embodiment. The experiment, which continued for a total of 320 hours, was divided into two sections. In the first section, which took the first 298 hours, the equipment was operated with a throughput of 125% of hydrogen chloride and other reactants. In the last 22 hours, the equipment was operated by a through-

walking speed of 100%.

The catalysts used are shown in Table 1 as catalysts A, B and C. The desired weight percentages of copper (II) chloride and potassium chloride were:

(Table I shows the amounts found to be present after analysis of the catalysts. The amounts of copper(II) chloride and potassium chloride in catalyst C varied somewhat because catalysts from several different preparations were used.) In all three reactors, the catalyst bed length was 343 cm; the first (upper) part was 206 cm (60% of the layer length) and the second (lower) part 137 cm long, or 40% of the total layer length. Catalyst A was used in the first part of reactor R (layer 12); catalyst B was used in the first part of reactor R2 (layer 14); catalyst C was used in reactor R^ and the lower parts of reactors R^ and R,,.

During the first 60 hours of the experiment, various sources producing unstable data were corrected and stabilized. Likewise, the time from hours 265 to 298, which occurred between the two parts of the entire experiment, was occupied by restabilization of the pilot plant which followed a 1-month standstill between the parts of the experiment.

During operation, as can be seen from the following table, variations were made in the total excesses of pressure, air and ethylene in the system, and in the distribution of air between the three reactors, in order to determine the effect of these conditions on hydrogen chloride conversion, selectivity for the reaction to 1,2-dichloroethane, as well as hot spot temperature and location. The test data and results are given in the following table II.

Similar to Experiment No. 1 described above, several experiments were carried out which are indicated in Table III below as Experiments 2 to 9, where different combinations of catalyst mixtures and reaction conditions were used within the framework of the invention. In all cases, in the same way as in experiment No. 1, the catalyst bed was 343 cm long. In both R and R2, the first zone, at the upper end (inlet end) of the reactor occupied 206 cm, or 60% of the bed, while the second zone occupied 13 7 cm, or 40% of the entire bed length. The catalyst in reactor R^ was similar to that of Experiment No. 1. Cooling temperatures were maintained as in Experiment No. 1.

In all experiments 1 to 9 above, it can be seen that the use of the catalyst described, in the step patterns described, resulted in maintaining hot spot temperatures generally below approx. 340°C at throughputs as high as 125% of the intended throughput. The hot spots were in adjustable locations and in fact in many cases, as will be seen, they fell well below 300°C. Of equal importance is that the pressure drop remained practically constant throughout the reaction system, even in experiment no. 1, where the duration of the experiment was over 300 hours in total. Therefore, no pressure reduction was required to maintain hot-spot control, and the pressure drop did not increase over long test times due to catalyst destruction. Furthermore, even when operating at high throughput, the ethylene excess could be kept within reasonable limits without significantly affecting the hydrogen chloride conversion. As can be seen from the data in Tables II and III, it was entirely possible to work with an ethylene excess of approx. 10% while still achieving as much as 99+% hydrogen chloride conversion.

Furthermore, the catalyst in the step pattern described here has also proven suitable for operation with less than intended clearance. Thus, the catalyst and the system described here are versatile and can be used in a plant where the throughput can be variable, depending on such conditions as raw material supplies and market needs, over a range from substantially less than intended capacity to in all, significantly more than the intended capacity, without any replacement or modification being required.

Claims (2)

Process for the production of 1,2-dichloroethane by oxychlorination of ethylene in a solid layer, using an oxygen-containing gas in the form of air or oxygen, characterized by carrying out one or more of the following steps: (a) reacting ethylene, hydrogen chloride and a first portion of an oxygen-containing gas in a first reaction zone in contact with a first catalyst bed, which is substantially undiluted by catalytically inert particles, and comprising copper (II) chloride and potassium chloride on a support of spherical particles of activated aluminum oxide, the first catalyst layer being divided into two parts in the direction of flow of the reaction partners through it, whereby the first part constitutes between 45 and 75% of the layer, while the second part constitutes between 25 and 55% of the layer, the first part comprises between 4.5 and 12.5% by weight copper(II) chloride and between 1.5 and 7% by weight potassium chloride, in a weight ratio between copper(II) chloride and potassium chloride of between 1.5:1 and 4 :1, while the second part comprises between 12 and 25% by weight copper(II) chloride and between 0.5 and 4% by weight potassium chloride, in a weight ratio between copper(II) chloride and potassium chloride of between 5:1 and 15:1 ; (b) reacting the product of step (a) and another portion of an oxygen-containing gas in another reaction zone in contact with another catalyst bed, which is substantially undiluted by catalytically inert particles, and comprises copper (II) chloride and potassium chloride on a carrier of spherical particles of activated alumina, the second catalyst layer being divided into two parts in the direction of flow of the reaction partners through it, whereby the first part constitutes between 45 and 75% of the layer, while the second part constitutes between 25 and 55% of the layer , the first part of the layer comprising between 5.5 and 15% by weight of copper (II) chloride and between 1 and 5% by weight of potassium chloride, in a weight ratio between copper (II) chloride and potassium chloride of between 2:1 and 6:1 , while the second part of the layer comprises between 12 and 25% by weight copper(II) chloride and between 0.5 and 4% by weight potassium chloride, in a weight ratio between copper(II) chloride and potassium chloride of between 5:1 and 15:1 ; step (b) includes the possible feature that a portion of hydrogen chloride is first fed into step (b) and there is reacted with the oxygen-containing gas; and (c) reacting the product from step (b) and a third portion of an oxygen-containing gas in a third reaction zone in contact with a third catalyst bed, which is substantially undiluted by catalytically inert particles, and comprises between 12 and 25% by weight copper (II) chloride and between 0.5 and 4% by weight potassium chloride, on a carrier of spherical particles of activated aluminum oxide, in a weight ratio between copper (II) chloride and potassium chloride of between 5:1 and 15:1, as well as optionally bringing the hydrogen chloride into contact with a layer of spherical particles of activated aluminum oxide impregnated with sodium chloride or potassium chloride before contacting the first catalyst bed, optionally combining the ethylene, hydrogen chloride and the first portion of the oxygen-containing gas and contacting the combined feed with a bed of spherical particles of activated alumina impregnated with sodium chloride or potassium chloride, preferably potassium chloride, before contacting the combined feed with the first catalyst bed. 2. Method as stated in claim 1, characterized in that only step (a) is carried out.