NO151891B - PROCEDURE FOR THE PREPARATION OF VINYL CHLORIDE MONOMES BY OXYCHLORATION AND / OR CHLORATION OF ETHYLENE FOLLOWED BY PYROLYSE OF 1,2-DICHLORETHANE - Google Patents

Description

Vinyl chloride or monochloroethylene (CH2 = CHC1) has been known since the early nineteenth century. With the development of polyvinyl chloride polymers (PVC), vinyl chloride as the basic "starting" material became more commonly referred to as vinyl chloride monomer (VCM), and it has become a product of very great commercial importance. During 1976, nearly 2.5 billion kg of PVC was produced in the United States alone.

VCM has been synthetically produced on a technical scale using various combinations of processes and methods, but these can generally be grouped into one of two main groups: 1) hydrochlorination of acetylene or 2) oxyhydrochlorination (OHC) and/or chlorination of ethylene to 1 ,2-dichloroethane (EDC) followed by a pyrolysis reaction where the dichloroethane is pyrolyzed to VCM and hydrogen chloride. With the exception of if the textual context clearly suggests otherwise, the terms chlorination, oxychlorination and/or oxyhydrochlorination reaction etc. as used herein shall be intended to denote any of the various methods for producing vinyl chloride from ethylene.

Although hydrochlorination of acetylene is of course the easiest and most chemically direct method, acetylene is a hydrocarbon that is considerably more expensive than ethylene. On the other hand, the economic advantage of ethylene as a starting material is partially offset by the more complex series of reactions that are necessary and also by the energy imbalance that results from these reactions when carried out separately.

The ethylene method first involves an exothermic chlorination re-

action which is most frequently followed by an endothermic pyrolysis reaction. Expressed in terms of the total amount of heat calories generated, the heat developed in such an OHC reaction is 2-3 times greater than the heat input required for the pyrolysis reaction. Despite

for this reason, it has so far been impossible when operating on a technical scale to carry out the pyrolysis reaction using only the heat from the OHC reaction because this is usually carried out at a temperature which is approx. 200°C lower than the temperature of the pyrolysis reactor. Although the amount of heat developed may be sufficient, in reality it is not of a sufficient "quality" (ie of a sufficiently high temperature) and therefore additional energy input has usually been required for the pyrolysis reaction.

It is of course clear that the ideal solution would

be a process where the heat developed by the chlorination reaction or reactions would have a sufficient quality and also a sufficient quantity that the pyrolysis reaction could thereby be carried out, such as by lowering the temperature at which the pyrolysis reaction can be carried out and/or by increase the chlorination reactor temperature, while essentially maintaining the same conversion yield of ethylene to VCM. Although such a process will hereafter be termed an "adiabatic process", it will be clear that this does not require heat balance, but simply removal

of the need for a substantial, independent supply of heat of a higher temperature.

In its most desired form, such an adiabatic process would comprise the chlorination of ethylene to dichloroethane by an exothermic OHC reaction which would provide heat for an essentially simultaneous in situ pyrolysis of the dichloroethane to VCM and hydrogen chloride with high selectivity to form VCM. Since the HCl by-product of the pyrolysis reaction could be consumed in situ for the OHC reaction, such a process would not only remove the need to collect the heat generated by the chlorination reaction and the need to transfer this heat to a pyrolysis reactor, but it would also remove or substantially reducing the need to recover, purify and recycle most of the hydrogen chloride by-product.

A "simultaneous reaction" process is actually described in British Patent No. 1159296. However, the particular catalyst used according to this British patent is not highly selective for the formation of VCM, and overall low percentage yields of ethylene to VCM were obtained down - strongly emphasizes the potential commercial importance of this process. In addition, this process requires that large volumes of hydrogen chloride must be added to the reaction, and this makes it necessary to recover and recycle this raw material with significant operating costs.

A process that gives a better yield of ethylene to VCM is described in US patent no. 3291846, where a gaseous mixture of ethylene, chlorine and ethylene dichloride at a temperature of 450-550°C is fed to a first reactor (with a fluidized bed which containing only sand) to form a product containing VCM, HC1 and unreacted ethylene from which the VCM is removed, leaving only hydrogen chloride and ethylene to which oxygen is then added. The mixture of ethylene, oxygen and hydrogen chloride is then fed to another reactor in which the mixture is catalytically oxyhydrochlorinated to a mixture of ethylene dichloride and chlorinated by-products, and the ethylene dichloride is purified, especially for oxygen, and recycled to the first reactor. This process actually involves a non-catalytic vapor phase chlorination of a stoichiometric excess of ethylene at a temperature higher than the temperature at which EDC would normally be pyrolyzed to VCM, and in which the reaction equilibrium further tends towards the production of VCM by the use of a feed - flow in which the ratio between carbon and chlorine is over 2:1. As is the case for most non-catalytic reactions that produce a reactive intermediate, this process can be expected to produce larger amounts of chlorohydrocarbon by-products.

The detailed steps for a balanced process involve far more than simply achieving an energy balance or removing the need for an independent heat input to the pyrolysis reaction.

Such a balanced process must also provide a high selectivity for the formation of VCM, while the formation of by-products must be a minimum, by changing the reaction equilibrium either so that it tends away from this production or so that a process is obtained where the by-products can be recycled to the original reactor.

Then e.g. the energy generation in the OHC reaction is approx. 2

times the required energy input for the pyrolysis reaction,

will the most desired feed material to the reactor not only be a starting material for oxygen and chlorine, plus ethylene,

with a starting material of oxygen and chlorine, plus a mixture of ethylene and EDC. This not only achieves an energy balance, but also that the materials are balanced by the fact that HCl, ethylene, oxygen and unpyrolyzed EDC can be recycled to the original reactor either directly or after a separate OHC reaction where HCl and ethylene are converted to EDC.

There are a number of different catalytic oxyhydrochlorination processes which are well known to those skilled in the art and where divalent copper chloride is most often used (alone or together with a modifier) which is impregnated on an aluminum oxide, silicon dioxide or other carrier material. Although this is possibly the most widely used catalyst for oxyhydrochlorination, other chlorides, including ferric chlorides, have been used. A number of different materials have been used in conjunction with the copper divalent chloride to change one or more of the catalyst's properties. Potassium chloride is possibly the most frequently used modifying material and is added as a rule to reduce the evaporation losses of divalent copper chloride, although other alkali chlorides have been used in a similar way.

In e.g. the above-mentioned British Patent No. 1159296 used the catalyst copper chloride and potassium chloride on a support material of diatomaceous earth. As noted above, this catalyst's selectivity to VCM was low. Moreover, it is stated in the patent, although the catalyst was reported to be suitable for use in both fixed bed reactors and fluidized bed reactors, that only the fixed bed reactor could provide a process under adiabatic conditions.

The present invention relates to a process for the continuous production of vinyl chloride monomer from ethylene, oxygen and chlorine, where ethylene, a source of oxygen,

a source of chlorine and/or 1,2-dichloroethane is supplied

to a primary reactor containing a catalyst containing a salt of iron or copper impregnated on a support material of aluminum oxide, titanium dioxide, zirconium dioxide, silicon dioxide or silicon dioxide-aluminum oxide, the reaction being carried out at a temperature of 325-450°C to oxyhydrochlorinate the ethylene to 1,2-dichloroethane while the 1,2-dichloroethane is essentially simultaneously pyrolyzed in situ to vinyl chloride monomer and hydrogen chloride,

after which the vinyl chloride monomer is removed from the mixture of gaseous feed material, end products and by-products, and the method is characterized by the use of a catalyst containing 0.01-6% by weight of a salt of rhodium or platinum, 0.01-15% by weight of a salt of iron or copper, 1.0-25% by weight of a salt of zinc and optionally up to 3% by weight of a lithium salt, impregnated on the support material, the percentages expressing the metal content in each component as a function of the total weight of the catalyst, and that the reaction is carried out at a pressure from atmospheric pressure (101 kPa) to 1033 kPa in a contact time of 2-60 seconds and at a reaction temperature of 325-450°C.

The final vinyl chloride product can be separated and recovered by any conventional means well known to those skilled in the art. The product from the reactor, especially a commercial reactor, will also contain a mixture of by-products together with VCM, including unreacted ethylene, unpyrolyzed dichloroethane, air or oxygen, carbon oxides, chlorine or hydrogen chloride and with highly chlorinated chloroethanes and chloroethylenes. The unpyrolyzed EDC

can of course be recycled to the original feed stream for the reactor or pyrolyzed separately to VCM in a normal pyrolysis furnace. In addition, the ethylene can be oxychlorinated to EDC or chlorinated with liquid or gaseous chlorine to produce EDC for use as feed material for the original reactor. Such an EDC is usually present in the feed stream to the original reactor in addition to the chlorine output material, but as it forms hydrogen chloride in situ during the pyrolysis reaction, EDC can in reality be used as the only chlorine output material for the original reactor. The higher chlorinated chloroethanes and chloroethylenes can be processed further to produce products of commercial importance, e.g. perchlorethylene or trichlorethylene etc.

It is preferred according to the invention to use a catalyst which comprises (based on the metal content) 0.03-2.0% by weight rhodium chloride, 0.02-10% by weight iron chloride and 2.2-15% by weight zinc chloride impregnated on a suitable substrate material or carrier material. The preferred catalyst used can also contain up to 3.0% by weight of a lithium salt, preferably lithium chloride. The preferred support material is a high-purity aluminum oxide support material with a surface area of 0.1-10.0 m/g and containing 0.2-1.0 by weight of sodium oxide. Furthermore, it is preferred to carry out the reaction at a pressure of from 101 kPa to 411 kPa.

Although the preferred catalyst is defined and discussed in terms of the chlorides of rhodium, iron, zinc and lithium, it will of course be understood by those skilled in the art that other suitable salts of these metals can be used in the preparation of the catalyst, either before it is filled into the OHC reactor and /or in situ followed by the addition of a chlorine feedstock to the reactor.

In the drawing, Fig. 1 is a flow chart for the usual process for the production of VCM by oxychlorination of ethylene to EDC which is then pyrolysed to VCM and HC1. Fig. 2 is a flowchart for one of the preferred embodiments of the method according to the invention.

Fig. 1 shows a flow chart for a common process for the production of VCM, where ethylene is converted to EDC either by reaction with chlorine and/or oxychlorination with chlorine or hydrogen chloride, the exhaust gases being led through a cleaning device to separate the EDC formed which is then transferred to a pyrolysis reactor, in which the EDC is pyrolyzed to VCM and HC1, the waste gases from the pyrolysis reactor being transferred to another purification device, in which the VCM formed is separated from the HC1 formed, and the VCM formed is collected on any of the large number various ways well known to those skilled in the art, while the HC1 formed is recycled to the oxychlorination reactor.

The energy balance for a typical process as shown in Fig. 1 will be approximately as follows:

An examination of the above equations will show that while such a common process develops 57 kilocalories per gram-molecule (kcal/mol) in the exothermic reactions and only requires a heat supply of 17 kcal/mol for the pyrolysis reaction, these 17 kcal/mol must be supplied independently as high temperature heat, and the developed 57 kcal/mol can be used, if at all, only for low-priority applications, such as for the production of steam and/or purification of EDC.

Fig. 2 shows one of the preferred embodiments of the present method, where ethylene, air, HC1 and EDC are supplied to a primary reactor which is kept at a temperature of approx. 350°C and a pressure of loi - 411 kPa, in which the ethylene is oxyhydrochlorinated to EDC which alone and/or together with EDC in the feed stream is simultaneously pyrolysed to VCM. The exhaust gases are quenched to cool the gases and remove the formed HC1 (for recycling to the primary reactor), the gases from the quench being transferred to a first separation device at a suitable temperature, in which the ethylene is removed at the top of the separation device in the form of a gas, while the VCM and other chlorinated hydrocarbons are removed as a liquid via the bottom of the separator and transferred to another separator, where the VCM is volatilized from the remaining chlorinated hydrocarbons and into a suitable collection device, while the EDC is then removed from the other chlorinated hydrocarbons in a third separation device for recycling to the primary reactor. The unreacted ethylene from the first separation device is fed to a reactor for direct chlorination together with a suitable starting material for chlorine and converted to EDC which is then fed to the primary reactor.

Example 1

The catalyst was prepared by impregnating aluminum oxide pellets (diameter 4.76 mm, surface area 2.6 m 2 /g) with an aqueous solution containing FeCl 2 • 4H 2 O, RhCl.j*3H 2 O, ZnCl 2 ; and LiCl. After filtering, drying and calcining for 8 hours at 400°C, the metal content of the catalyst was 1.3 wt% Fe, 0.054 wt% Rh, 3.3 wt% Zn and 0.37 wt% Li. The catalyst was charged into a quartz tube reactor with an outside diameter of 3.18 cm and heated to 350°C, and a gas mixture containing 16.7 mol% HCl, 16.7 mol% C^jH^, 16 .7 mol% 1,2-dichloroethane, 16.7 mol% nitrogen and 33.3 mol% air were passed through the reactor at a volume rate of 750 cm^/min at a working pressure of 101 kPa and a contact time of 7.5; seconds. An analysis of the exhaust gas using gas chromatography ("GK analysis") based on carbonaceous products gave the following results: ;;Example 2 ;Example 1 was repeated, but with the change that the working temperature was increased to 400°C. GK analysis based on carbonaceous products gave the following results: ;Example 3 ;The same carrier material and the same impregnation method as in example 1 were used to obtain a catalyst containing 1.2 wt% Fe, 0.044 wt% Rh, 2, 7 wt% Zn and 0.32 wt% Li. The same working conditions were used, but with the change that the working pressure was 411 kPa and the volume velocity ;3000 cm 3/min. A GK analysis of the carbonaceous products gave the following results: ;;Example 4 ;The catalyst was prepared by impregnating a fluidized aluminum oxide carrier material (with physical properties similar to those described in example 1), so that the final concentrations of metals were 1.5 wt% Fe, 0.074 wt% Rh, 3.4 wt% Zn and 0.4 wt% Li. The catalyst was filled in a quartz tube reactor with a fluidized bed which was maintained at a temperature of 350°C. The same mole-gas ratio as in example 1 was used at a volume velocity of 800 cm 3 /min, corresponding to a contact time of 8 seconds, at a working pressure of 101 kPa. A GK analysis of the carbonaceous effluent from the reactor gave the following results: ;Example 5 ;Example 4 was repeated, but with the change that a volume rate of 1280 cm 3 /min corresponding to a contact time of 5 seconds was used. The subsequent GK analysis based on carbonaceous products gave the following results: Example 6 Example 4 was repeated, but with the change that a volume velocity of 640 cm 3 /min corresponding to a contact time of 10 seconds was used. The GK analysis gave the following results: ;;Example 7 ;Example 4 was again repeated, but with the change that the following mole-gas ratios were used: 20 mol% C^H^, 20 mol% ethylene dichloride, 20 mol% nitrogen and 40 mol% air (no HC1). The GK analysis gave the following results: ;Example 8 ;A low surface area aluminum carrier material ;(1 m 2 /g) was impregnated Blik that the final concentrations of metals were 1.2 wt% Fe, 0.049 wt% Rh, 3.0 wt% Zn and 0.34 wt% Li. The working conditions were the same as in Example 4, but with the change that the molar gas ratios were as follows: 25 mol% C2H4, 25 mol% HC1, 25 mol% N2 and 25 mol% air (no 1,2-dichloroethane). The GK analysis gave the following results: ;;Example 9 ;The catalyst was prepared by impregnating a low surface area fluidizable alumina support material with a solution containing CuCl2*2H20, RhCl3»3H20, ZnCl2 and LiCl. The composition of the obtained catalyst corresponded to 1.7 wt% Cu, 0.084 wt% Rh, 4.0 wt% Zn and 0.43 wt% Li. The working conditions were the same as those used in example 4. The GK analysis of the carbonaceous effluent gave the following results:

Example 10

A solution containing FeCl 2 -4H 2 O, I^PtClg-6H 2 O, ZnCl 2 and LiCl was used to impregnate a low surface area fluidizable Al 0 0 3 material. It obtained

catalyst's composition after calcination at 400°C corresponded to 1.8 wt% Fe, 0.17 wt% Pt, 4.0 wt% Zn and 0.56 wt% Li. The working conditions were the same as those used in the example

4. GK analysis of the carbonaceous effluent gave the following results: Further series of experiments were carried out in a similar manner. By it in the first of these, one or more of the catalyst components were omitted, and the data obtained in this series of experiments are reproduced in table I. In the second series of experiments, the concentration of the individual catalyst components was varied, and the data obtained for this series of experiments are reproduced in table II.

Upon examination of these tables, especially Table I, it should be noted that the percentage yields of VCM, carbon oxides and other chlorohydrocarbons are calculated on the basis of the ethylene actually converted. For the results described in these tables, it is thus necessary to take into account not only the stated data regarding the yield of VCM, but also the percentage ethylene conversion. By e.g. in the third run shown in Table I, 45% of the converted ethylene was converted to VCM which is apparently an acceptable result. However, only 12.8% of the ethylene was converted.

Table I clearly establishes the criticality of the iron (or copper), rhodium and zinc components for the catalyst. In the first five experiments listed in Table I, one or more of these essential components were omitted, and in most cases the yield of VCM was unacceptably low, and in each case the percentage conversion of ethylene was unacceptably low. The last two experiments according to Table I were carried out according to

invention, and as regards these two experiments, it will appear that both the ethylene conversion and the VCM yield were significantly higher. In these two experiments, it is thus clearly established that although lithium is a desired optional component for the catalyst system (which can greatly extend the catalyst's lifetime), it is not an essential component for the catalyst.

In the second series of experiments, all the essential components for the catalyst system were present, but the concentration of these components was varied.

From the data in Table II, it is clearly established that a catalyst containing at least 0.03% rhodium or platinum, at least 0.02% iron or copper and at least 2.2% zinc,

will give satisfactory ethylene conversions and VCM yields.

A further series of experiments was carried out where the catalyst composition was kept constant, while the working conditions were varied. The data from these experiments are reproduced in Table III, and these clearly suggest that "the method according to the invention can be carried out at a number of different temperatures and pressures and both in fixed bed reactors and fluidized bed reactors. Other working variables, such as contact time (and/or volume rate) and moltil -conducting conditions were investigated in the execution of examples 1-10.

When evaluating the data according to Table III, it should again be noted that the composition of the catalyst was not varied, but only the working conditions. In this particular series of experiments, the particular catalyst composition used tended to give higher VCM yields, but lower ethylene conversions and higher oxides, when the temperature and/or pressure was increased. It can be expected that any given catalyst composition will have a range of optimum working conditions and/or that for any given range of working conditions there will be small differences in the optimum catalyst composition.

The choice of a particular catalyst composition and of particular working conditions can also be influenced by external considerations, such as economic conditions. If e.g. there is a significant use for ethylene dichloride, while there is no other use for the converted ethylene, the first attempt described in Table III would be attractive. If, on the other hand, there is already a significant excess of EDC and several other processes where unconverted ethylene can be used, the higher temperature in the second experiment would

according to table III be desired.

In other words, it is clear from the examples and from the tables

I and III that by varying the catalyst's composition and/or the working conditions, it is possible to regulate not only the conversion of ethylene and core actants and the yield of VCM, but also, at least to a certain extent, the conversion of by-products in the off-gas from the reactor. It is also clear that the choice of an optimal catalyst composition and/or an optimal set of working conditions is not only a function of the catalyst and of the present method, but also of other factors that fall completely outside the catalyst and/or process itself. Moreover, even for a given starting catalyst composition, the optimal process variable will change as the catalyst composition changes during use, e.g. due to evaporation losses.

In commercial OHC reactors, evaporation losses of 10%

or above per years not uncommon, and "top-up catalyst" is added from time to time to replace these losses. It may

it is also expected that the catalyst used in the present method in a commercial reactor for a longer period of time will also experience a gradual evaporation loss of iron or copper chloride. Fordam<p>ninasta It is expected to vary according to the reaction conditions, especially the temperature.

It has thus been calculated that while only approx. 0.5% of the bivalent copper chloride will evaporate during one year of use at temperatures of 340-350°C, losses of 3-6% or more could occur at temperatures of 420°C. For this reason, the composition of the catalyst, especially the ratio of rhodium, zinc and lithium chloride to copper or iron chloride in the make-up catalyst, may have to be adjusted to a significantly higher iron or copper chloride content, so that when the make-up catalyst is added to the reactor and mixed with the already catalyst present, the overall atomic ratio between metals in the catalyst will be regulated approximately to the ratio between the fresh catalyst salts that were originally introduced into the reactor.

Although it is possible to obtain a close approximation of a metal chloride evaporation loss by calculation based on reaction conditions,

it is clearly preferred to regulate the metal ratios in the make-up catalyst based on real quantitative data.

These data can be obtained directly from an analysis of periodic

taken samples from the catalyst layer or indirectly from any of a number of sources, such as monitoring the iron or copper content of the aqueous condensate from the reactors etc.

The ability of the catalyst used to work effectively

at a temperature of 350°C or lower is of course a significant advantage in that the volatility of the catalyst components is thereby considerably reduced. However, a further improvement can be obtained by adding 0.01-3% by weight of lithium. Alkali chlorides, especially potassium chloride, and certain alkaline earth chlorides have long been recognized as useful as catalyst modifiers to reduce the volatility of oxyhydrochlorination catalysts. In connection with the catalyst used according to the invention, it has surprisingly been found that only lithium appears to have any useful application as catalyst modifier.

This was clearly established by means of a series of experiments for

to investigate the lifetime of the catalyst. During the control examination, a catalyst showed . which contained 0.05%

rhodium, 0.6% iron and 2.7% zinc, said to have a useful life of approx. 1 month before a sharp drop occurred in the yield of VCM and the percentage of ethylene conversion and also a significant increase in the percentage of carbon oxides. An addition of 0.3% lithium chloride to this catalyst system significantly increased the lifetime of the catalyst.

In similar experiments, neither calcium chloride nor rubidium chloride seemed to have any significant effect on the catalyst's useful life, while sodium chloride, cesium chloride, barium chloride and magnesium chloride all greatly reduced the catalyst's useful life, usually to a period of less than approx. 1 week. Attempts to replace the lithium chloride with potassium chloride resulted in a catalyst with unacceptably low activity even when newly made, so that this catalyst effectively had no useful live charge whatsoever. Although sodium is not a suitable substitute for lithium as a modifying metal for the catalyst, aluminum oxide support materials appear

with 0.2-1.0% sodium oxide to have an optimization advantage.

Although optimum results appear to be obtained using a catalyst containing rhodium, iron, zinc and lithium on a low surface area alumina support material containing a small amount of sodium oxide, the optimum results are in relation to the percentage ethylene conversion and the VCM yield . As indicated above, this does not always have to be the case, and if there is an alternative use of the unconverted ethylene and a desire to produce additional EDC or other chlorohydrocarbon by-products, the reaction equilibrium can be changed in this direction either by regulating the working conditions and/or by regulate the composition of the catalyst.

In such a case, a regulation of the catalyst's composition may also include the use of substitute materials.

It has thus already been stated that e.g. ferric chloride can be replaced by copper chloride. Replacement of rhodium with iridium or cerium has generally been a less desirable replacement and has generally resulted in a decrease in percent ethylene conversion, a decrease in VCM selectivity, and a higher concentration of chlorohydrocarbon by-products.

Although it is not desired here to be bound by any theory to explain the effect of the catalyst used in the process according to the invention, it appears that "the iron or copper chloride and possibly also the rhodium chloride act as a highly selective oxyhydrochlorination catalyst system, while the zinc chloride presumably acts as a dehydrochlorination catalyst that promotes the pyrolysis of EDC to VCM.

On the other hand, it is impossible to even speculate about the particular kinetic conditions for the reaction equilibrium in the reactor, i.e. how much, if any, of the VCM formed is from pyrolysis of EDC in the feed stream, as opposed to EDC formed in situ by oxyhydrochlorination of the ethylene in the feed stream. However, it is clear that the catalyst used presumably leads to the production of at least some VCM by simultaneous oxyhydrochlorination and pyrolysis. This is clearly established in example 8, where the supply stream consisted only of ethylene, oxygen and hydrogen chloride, i.e. where the difference compared to the previous examples was the omission of EDC from the supply stream.

Because of the above, it will be clear to those skilled in the art that a number of changes and substitutions can be made to the composition of the catalyst used and/or to the steps and working conditions of the present process.

The catalyst used in the execution of the present method is the subject of divisional patent application no. 842758.

Claims (2)

1. Process for continuous production of vinyl chloride monomer from ethylene, oxygen and chlorine, where ethylene, a source of oxygen, a source of chlorine and/ or 1,2-dichloroethane is fed to a primary reactor containing a catalyst containing a salt of iron or copper impregnated on a support material of aluminum oxide, titanium dioxide, zirconium dioxide, silicon dioxide or silicon dioxide-aluminum oxide, the reaction being carried out at a temperature of 325-450 °C to oxyhydrochlorinate the ethylene to 1,2-dichloroethane while the 1,2-dichloroethane is essentially simultaneously pyrolyzed in situ to vinyl chloride monomer and hydrogen chloride, after which the vinyl chloride monomer is removed from the mixture of gaseous feed material, end products and by-products, characterized by that a catalyst is used which contains 0.01-6% by weight of a salt of rhodium or platinum, 0.01-15% by weight of a salt of iron or copper, 1.0-25% by weight of a salt of zinc and optionally up to 3% by weight of a lithium salt, impregnated on the carrier material, the percentages expressing the metal content in each component as a function of the total weight of the catalyst, and that the reaction carries out es at a pressure from atmospheric pressure (101 kPa) to 1033 kPa in a contact time of 2-60 seconds and at a reaction temperature of 325-450°C. 2. Method according to claim 1, characterized in that a catalyst is used which contains 0.03-2% by weight of a salt of rhodium, 0.02-10% by weight of a salt of iron and 2.2-15% by weight of a salt of zinc, impregnated on a support material of high-purity aluminum oxide with a surface area of 0.1-10.0 m 2 /g and containing 0.2-1.0% by weight sodium oxide, and that the reaction is carried out at a pressure from 101 kPa to 411 kPa.