FI66829C - FOERFARANDE FOER FRAMSTAELLNING AV VINYLKLORIDMONOMER SAMT KATALYT FOER UTFOERANDE AV FOERFARANDET - Google Patents

Description

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(32) (33) (31) PyrJ «** r> M * r <frterttn 19.10.77 2A.05.78 USA (US) 843721, 9089 *» 6 (71) The B.F. Goodrich Company, 500 South Main Street, Akron, Ohio AA318, USA (72) Michael Francis Lemanski, Euclid, Ohio, Frederick Carl Leitert, North Madison, Ohio, Carl George Vinson Jr., Mentor, Ohio, USA ) (7 * 0 Berggren Oy Ab (5 * 0 Process for the preparation of vinyl chloride monomer and catalyst for carrying out the process - Förfarande för framstä11 Ning av vinylkloridmonomer samt katalyt för utförande av förfarandet

Vinyl chloride or monochloroethylene (CH2 = CHCl) has been known since the beginning of the nineteenth century. With the growth of polyvinyl chloride polymers (PVC), vinyl chloride has become more commonly used as the basic starting material, called vinyl chloride monomer (VCM), and has become a very important product of commercial importance. In 1976, nearly 2.5 billion kg of PVC was produced in the United States alone.

VCM has been commercially synthesized by various combinations of processes and procedures, but these generally occur in one of two main ways: 1) acetochlorination of acetylene or 2) oxyhydrochlorination of ethylene (OHC) and / or chlorination to 1,2-dichloroethane (EDC) followed by a pyrolysis reaction. in which dichloroethane is pyrolyzed to VCM and hydrogen chloride. Unless the context clearly indicates otherwise, the terms chlorination, chlorination, oxychlorination and / or oxyhydrochlorination reaction, etc. are to be understood as meaning any of the various procedures for preparing EDC from ethylene.

Although the hydrochlorination of acetylene is clearly an easier and straighter way chemically, acetylene is a significantly more expensive hydrocarbon 2 66829 than ethylene. On the other hand, the economic advantage of ethylene is counterbalanced in part by a more complex series of required reactions and also by the energy imbalance that is characteristic of these reactions when carried out separately.

The ethylene route first involves an exothermic chlorination reaction, most often followed by an endothermic pyrolysis reaction. With respect to the total thermal calories produced, the heat generated by such an OHC reaction is 2-3 times greater than the heat input required for the pyrolysis reaction. Nevertheless, it has hitherto been impossible in a commercial operation to carry out the pyrolysis reaction using only the heat obtained from the OHC reaction, since the OHC reaction is usually carried out at a temperature of about 200 ° C lower than the pyrolysis reaction. Essentially, while the amount of heat generated may be sufficient, it is not of sufficient "quality" heat (i.e., a sufficiently high temperature) and the supply of additional energy has hitherto generally been required for the pyrolysis reaction.

It is, of course, clear that the ideal solution would be a process in which the heat generated in the chlorination reactions would be of sufficient quality as well as quantity to carry out the pyrolysis reaction; such as lowering the temperature at which the pyrolysis reaction can be performed and / or raising the temperature of the chlorination reaction while maintaining substantially the same efficiency in the conversion of ethylene to VCM.

Although such a process is referred to herein as an "adiabatic process", it is clear that it does not require thermal equilibrium, but only the elimination of the need for an independent supply of any substantially higher temperature heat.

In the most desirable form, such an adiabatic process would compromise the chlorination of ethylene to dichloroethane in an exothermic OHC reaction that would provide heat for substantially simultaneous, highly VCM-selective in situ pyrolysis of dichloroethane to VCM and hydrogen chloride. Since the HCl by-product of the pyrolysis reaction could be used in situ for the OHC reaction, such a process would not only eliminate the need to recover the heat output of the chlorination reaction and the need to transfer this heat to the pyrolysis reactor, but would substantially eliminate or reduce the need to recover, purify and recycle most hydrogen chloride by-product.

Il 3 66829 The "simultaneous reaction" process is in fact described in English Patent 1,159,296. However, the special catalyst used in the description of this English patent is not very highly selective for VCM and the resulting low overall ethylene yield to VCM significantly impairs commercialization. . In addition, this process requires that significant volumes of hydrogen chloride be fed to the reaction, making it necessary to recover and recycle this feedstock at considerable operating costs.

A process with a more desirable VCM yield from ethylene is described in U.S. Patent 3,291,846, in which a gaseous mixture of ethylene, chlorine and ethylene dichloride is fed at 450-550 ° C to a first reactor (fluidized bed containing only sand) to form a product containing VCM. , HCl 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 a second reactor where it is catalytically oxyhydrochlorinated to a mixture of ethylene chloride and chlorinated by-products, the ethylene chloride is purified, in particular of oxygen, and returned to the first reactor. Essentially, this process involves a stoichiometric excess of ethylene at a non-catalytic vapor phase chlorination temperature above that at which EDC would normally be pyrolyzed to VCM and where the reaction equilibrium is further directed toward VCM production using a feed stream with a carbon to chlorine ratio of greater than 2.

As with most non-catalytic reactions that produce a reactive intermediate, this process can be expected to produce large amounts of by-product chlorohydrocarbons.

The detailed steps of a balanced process involve much more than simply achieving energy balance or eliminating the need for an independent heat supply to the pyrolysis reaction. It should also provide a high degree of selectivity for VCM while minimizing by-products by shifting the reaction equilibrium either out of this production or into a form where they can be recycled back to the original reactor.

For example, since the energy production of the OHC reaction is about twice the energy input required for the pyrolysis reaction, the most desirable supply to the reactor is not just a source of oxygen and chlorine plus ethylene, but a source of oxygen and chlorine plus a mixture of ethylene and EDC. This provides not only energy balance but also material balance so that HCl, ethylene, oxygen and non-pyrolyzed EDC can be recycled back to the original reactor either directly or after a separate OHC reaction where HCl and ethylene are converted to EDC.

There are a large number of catalytic oxyhydrochlorination processes well known to those skilled in the art, most often using copper chloride (alone or with a modifier) impregnated with alumina, silica or other support. While this is perhaps the most widely used catalyst for oxyhydrochlorination, other chlorides such as iron chlorides have been used. A wide variety of materials have been used with copper chloride to modify the properties of one or more catalysts. Potassium chloride is probably the most commonly used modification material, usually added to reduce evaporation losses of copper chloride, although other alkali metal chlorides have been used in a similar manner.

For example, the catalyst used in the aforementioned English Patent 1,159,296 was copper chloride and potassium chloride with diatomaceous earth support. As mentioned above, the selectivity for VCM shown by this catalyst is low. In addition, although the catalyst was reported to be suitable for use in either solid or fluidized bed reactors, the patent specification indicates that only a solid bed reactor could provide operation under adiabatic conditions.

In the drawings, Figure I is a schematic representation of a conventional method for preparing VCM by oxychlorination of ethylene to EDC, which is then pyrolyzed to VCM and HCl. Figure II is a schematic representation of one of the preferred embodiments of the method of the present invention.

According to the present invention, there is provided a continuous process for synthesizing VCM from ethylene, an oxygen source and a chlorine source by oxyhydrochlorination of ethylene to EDC and substantially simultaneous pyrolysis of EDC to in situ VCM and hydrogen chloride to a first loaded with a catalyst containing about 0.01-6% by weight of a salt of a metal selected from the group consisting of rhodium and platinum, about 0.01-15% by weight of a salt of a metal selected from the group consisting of , comprising iron and copper, and about 1.0 to 25% by weight of a zinc salt impregnated with a support selected from the group consisting of alumina, titanium dioxide, zirconia, silica and silica-alumina, said percentages being expressed as each. the metal content of the component based on the total weight of the catalyst, and then the VCM gas is removed a mixture of feed materials, end products and by-products, the reactions being carried out at a pressure of about 0-1 MPa with a contact time of about 2-60 seconds and a temperature of about 325-450 ° C, which temperature is maintained substantially free of any other independent thermal energy. the need for a feed other than that which may be required to initiate a continuous process and / or to preheat the reagents.

The invention also provides a novel catalyst for the preparation of VCM, characterized in that it contains about 0.01 to 6% by weight of a salt of a metal selected from the group consisting of rhodium and platinum, about 0.01 -15% by weight of a salt of a metal selected from the group consisting of iron and copper and about 1.0-25% by weight of a salt of zinc, the catalyst being impregnated with a support selected from the group consisting of alumina, titanium dioxide, zirconia, silica and silica-alumina, the percentages of which indicate the metal content of each component, calculated on the total weight of the catalyst.

This catalyst can be used in a solid or fluidized bed reactor to prepare vinyl chloride adiabatically from a feed stream containing ethylene, a source of chlorine and a source of elemental oxygen. The feed stream may optionally contain ethylene dichloride.

L ___ 66829 6 In the adiabatic process of the present invention, the reactor is maintained at a pressure of about 0-100 kPa and a temperature of about 325-450 ° C for a contact time of about 2-60 seconds.

The final vinyl chloride product can be separated and recovered by any conventional means well known to those skilled in the art. The effluent from the reactor, in particular the commercial reactor, also contains by-products of the mixture together with VCM, including unreacted dichloroethane, air or oxygen, carbon oxides, chlorine or hydrogen chloride and more chlorinated chloroethanes and chloroethylenes. The non-pyrolyzed EDC can, of course, be recycled back to the first reactor feed or separately pyrolyzed to VCM in a conventional pyrolysis furnace. Ethylene can also be oxychlorinated to EDC or chlorinated with liquid or gaseous chlorine to produce EDC for use as feed to the first reactor. This EDC is usually in addition to the source of chlorine in the feed stream to the first reactor, but since the EDC produces hydrogen chloride in situ in the pyrolysis reaction, it can in fact be used as the sole source of chlorine to the first reactor. More chlorinated chloroethanes and chloroethylenes can be further processed to produce commercially important products, e.g., perchlorethylene, trichlorethylene, etc.

The preferred catalyst of this invention contains (calculated as a metal content) about 0.03-2.0% by weight of rhodium chloride, 0.02-10% of ferric chloride and 2.2 to about 15% of zinc chloride impregnated on a suitable support or support. The preferred catalyst of this invention may also contain about 0-3.0% by weight of lithium chloride. The preferred support for the present invention is a high purity alumina support having a surface area of about 0.1-10.0 m / g and containing about 0.2-1.0% by weight of sodium oxide.

Figure I is a schematic representation of a conventional process for preparing VCM in which ethylene is converted to EDC either by reaction with chlorine and / or oxychlorination with chlorine or hydrogen chloride, with exhaust gases passed through a purifier to separate EDC, which is then passed to a pyrolysis reactor where VC is pyrolyzed. and HCl and the pyrolysis reactor exhaust is passed to a second purifier where the VCM is separated from the HCl and the VCM is recovered by a large number of means well known to those skilled in the art and the HCl is recycled back to the oxychlorination reactor.

The energy balance for a typical process, such as the process in Figure I, would be approximately as follows: 66829 7

Energy balance (Kcal / mol) A. 1/2 (C2H4 + Cl2 - * C2H4Cl2) ΔΗ = -22 B. 1/2 (C2H4 + HCl + 1/2 02 —► C2H4Cl2 + H2O) ΔΗ = -29 C. 1 / 40 (C2H4 + 2.75 02 —y 1.5 CO2 + 0.5 CO + 2H2O) ΔΗ = -6 D. C2H4Cl2 -> C2H3Cl + HCl ΔΗ = +17

In view of the above, it is found that although this conventional process produces 57 kilocalories per gram mole (kcal / mol) in exothermic reactions, and requires only a 17 kcal / mol heat input for the pyrolysis reaction, this 17 kcal / mol must be fed independently at high temperature. as heat and the product 57 kcal / mol can be used, if at all, only for secondary applications such as steam production and / or EDO purification.

Figure II shows a preferred embodiment of the process of the present invention in which ethylene, air, HCl and EDC are fed to a first reactor maintained at a temperature of about 350 ° C and an overpressure of about 0-310 kPa and in which ethylene is oxychlorinated To EDC, which alone and / or with the EDC in the feed stream is pyrolyzed simultaneously to VCM. The exhaust gases are quenched to cool and remove HCl (recycled back to the first reactor) and the quench gases are fed to the first separator at a suitable temperature where ethylene is removed from the top of the separator as a gas and VCM and other chlorinated hydrocarbons are removed as a liquid from the chlorinated hydrocarbons to a suitable collection device, while the EDC is then removed from the other chlorinated hydrocarbons in a third separation device for recycling back to the first reactor. The unreacted ethylene from the first separator is fed to a direct chlorination reactor together with a suitable chlorine source and converted to EDC, which is then fed to the first reactor.

The following examples are intended to be illustrative, but not limiting, of the novel catalyst and process of this invention.

__ - r: 8 66829

Example 1

The catalyst was prepared by impregnating alumina granules (4.8 mm 2 diameter, 2.6 m / g surface area) with an aqueous solution containing FeCl 2 .4H 2 O, RhCl 3 * 3H 2 O, ZnCl 2 and LiCl. After filtration, drying and calcination at 400 ° C for 8 hours, the metal content of the catalyst was 1.3% by weight of Fe, 0.054% by weight of Rh, 3.3% by weight of Zn and 0.37% by weight of

Li.

The catalyst was charged to a 31.5 mm outer diameter tubular quartz reactor, heated to 350 ° C and a gas mixture containing 16.7 mol% HCl, 16.7 mol% C 2 H 4 16.7 mol% 1,2-dichloroethane, 16.7 mol -% nitrogen and 33.3 mol% air, was passed through at a volume flow rate of 750 cm 3 / min, without operating overpressure and with a contact time of 7.5 seconds. Exhaust gas analysis by gas chromatography ("GC analysis" based on carbonaceous products gave the following results:

Compound Mol-% COx 6.55 C2H3Cl 38.86 c- and t-C2H2Cl2 1.30 1,2-C2H4Cl2 24.92 C2H4 28.37

Example 2

Example 1 was repeated except that the operating temperature was raised to 400 ° C. GC analysis based on carbonaceous products gave the following:

Compound Mol-% CO 8.81 C2H3Cl 40.39 1.1- C2H2C12 0.15 c- and t-C2H2Cl2 1/91 1.2- C2H4Cl2 10.25 C2HCl3 0.70 C2C14 0.48 C2H4 37.31 66829 9

Example 3 The same support and impregnation procedure as in Example 1 were used to obtain a catalyst preparation containing 1.2% by weight of Fe, 0.044% by weight of Rh, 2.7% by weight of Zn and 0.32% by weight of Li. The same operating conditions were used except that the operating overpressure was 310 kPa and the 3 flow rate was 3000 cm / min. GC analysis of carbon-containing products showed the following:

Compound Mol-% 00χ 10.15 C2H3Cl 25.97 c- and t-C2H2Cl2 0.84 1.2- C2H4Cl2 28.12 C2C14 0.31 C2H4 34.61

Example 4

The catalyst was prepared by impregnating a fluidized alumina support (physical properties similar to Example 1) to give final metal concentrations of 1.5 wt% Fe, 0.074 wt% Rh; 3.4 wt% Zn and 0.4 wt% Li.

The catalyst was charged to a quartz tubular fluidized bed reactor maintained at 350 ° C. The same molar ratio of gas as in Example 3 was used at a volume flow rate of 800 cm / min, corresponding to a contact time of 8 seconds, without operating overpressure. GC analysis of the carbonaceous effluent from the reactor gave the following:

Compound Mol-% CO 7.54 x C2H3Cl 39.60 c- and t-C2H2Cl2 0.98 1.2- C2H4Cl2 26.76 C2H4 25.12

Example 5

Example 4 was repeated except that a volume flow rate of 1280 cm-3 min corresponding to a contact time of 5 seconds was used. Subsequent GC analysis based on carbonaceous products was as follows: Γ - 10 66829

Compound Mol-% 00χ 4.92 C2H3Cl 28.49 c- and t-C2H2Cl2 0.15 1.2- C2H4Cl2 36.17 C2H4 30.27

Example 6 3

Example 4 was repeated except that a volume flow rate of 640 cm / min was used, corresponding to a contact time of 10 seconds. The GC analysis was as follows:

Compound Mol-% C0v 7.98 Λ C2H3Cl 43.71 c- and t-C2H2Cl2 0.61 1.2- C2H4Cl2 19.46 C2H4 28.24

Example 7

Example 4 was repeated again except that the following gas molar ratio was used: 20 mol% C 2 H 4, 20 mol% ethylene dichloride, 20 mol% nitrogen and 40 mol% air (no HCl). The GC analysis was as follows:

Compound Mol-% CO 3.05

X

C2H3Cl 30.83 1.2- C2H4Cl2 33.27 C H. 32.85 2 4

Example 8 2

Impregnation was performed on a small area (1 m / g) alumina support so that the final metal concentrations were 1.2 wt% Fe, 0.049 wt% Rh, 3.0 wt% Zn and 0.34 wt% Li. The operating conditions were the same as in Example 4 except that the molar ratios of the gas were: 25 mol% C 2 H 4, 25 mol% HCl, 25 mol% N 2 and 25 mol% air (no 1,3-dichloroethane). GC analysis gave the following: 66829 11

Compound Mol-% 00χ 5.68 C2H3Cl 15.62 c- and t-C2H2Cl2 0.50 1.2- C2H4Cl2 1.25 c2hci3 0.11 C2H4 75.84

Example 9

The catalyst was prepared by impregnating a low surface area fluidizable alumina support with a solution of CuCl 2 * 2H 2 O, RhCl 3 * 3H 2 O, ZnCl 2 and LiCl. The composition of the obtained catalyst corresponded to 1.7% by weight of Cu, 0.084% by weight of Rh, 4.0% by weight of Zn and 0.43% by weight of Li. The operating conditions were identical to those used in Example 4. GC analysis of the carbonaceous effluent gave the following:

Compound Mol-% C0x 7.16 C2H3Cl 1.90 c- and t-C2H2Cl2 0.84 1.2- C2H4Cl2 28.48 C2H3Cl3 0.19 C2HCl15 0.18 C2H4 21.25

Example 10

A solution containing FeCl 2 * 4H 2 O, H 2 PtCl 2 · 6H 2 O, ZnCl 2 and LiCl was used to impregnate a small surface area of fluidizable alumina support. The composition of the obtained catalyst after calcination at 400 ° C corresponded to 1.8% by weight of Fe, 0.17% by weight of Pt, 4.0% by weight of Zn and 0.56% by weight of Li. The operating conditions were identical to those used in Example 4. The GC analysis of the carbonaceous effluent was as follows: f 66829 12

Compound Mol-% COx 5.16 C2H3Cl1 37.72 1.1- C2H2C12 0.16 c- and t-C2H2Cl2 0.92 1.2- C2H4Cl2 25.14 C2H3Cl3 0.33 C2H4 30.57

An additional set of experiments was performed in the same manner. In the first of these, one or more catalyst components were omitted, and the data obtained in this series of experiments are shown in Table I. In the second series of experiments, the concentration of individual catalyst components was varied, resulting in the results shown in Table II.

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Oi CO 1-3 66829 15 Examining these tables, in particular Table I, it should be noted that the percentage yield of VCM, carbon oxides and other chlorohydrocarbons has been calculated on the basis of the actually converted ethylene. Thus, the results presented in these tables must take into account not only the VCM yield but also the ethylene conversion percentage. For example, in the third run shown in Table I, 45% of the ethylene converted was VCM, a seemingly acceptable result, however, only 12.8% of the ethylene was converted.

Table I clearly confirms the criticality of iron (or copper), rhodium, and zinc as essential components of the catalyst. In the first five runs described in Table I, one or more of these essential components were omitted and in most cases the VCM yield was too low to be acceptable and in all cases the ethylene conversion percentage was too low to be acceptable. The last two runs of Table I were performed under catalyst conditions within the scope of this invention, and with respect to these two runs, it should be noted that both ethylene conversion and VCM yield were substantially higher. These two runs also clearly confirm that while lithium is a desirable optional component of the catalyst system (which can substantially extend the useful life of the catalyst), it is clearly not a necessary component of the catalyst.

In the second set of experiments, all the necessary components of the catalyst were present, but the concentration of these components was varied. The results in Table II clearly confirm that a catalyst containing at least 0.03% rhodium or platinum, at least 0.02% iron or copper, and at least about 2.2% zinc, i.e., a catalyst that falls within the scope of the predefined catalyst of this invention , provides satisfactory ethylene conversions and VCM yields.

A further series of experiments were performed in which the composition of the catalyst was kept unchanged and the operating conditions were varied. The results of these experiments are shown in Table III, which clearly shows that the catalyst of the present invention can be used at varying temperatures and pressures and in either fixed or fluidized bed reactors. Other operating variables such as contact time (and / or volume flow rate) and feed molar ratio were examined in Examples 1-10.

66829 16

Examining the results in Table III again, it should be noted that the composition of the catalyst was not changed, only the operating conditions were varied. The special catalyst composition used in this particular series of experiments tended to produce higher VCM yields, but lower ethylene conversions and higher amounts of oxide when the temperature and / or pressure was raised. It is expected that any given catalyst composition will have a set of optimal operating conditions and / or that there will be small differences in the optimal catalyst composition for each given set of operating conditions.

Table III

The effect of activity variables on activity

Variables Temperature Pressure Reactor kPa design Temperature (° C) 350 400 2415 350

Pressure kPa O O 310 O

Reactor structure solid solid solid fluidized bed

Reaction products:% VCM 56.8 69.9 43.0 55.7% DCEs 1.9 3.3 1.4 1.4% EDC 36.5 17.8 46.6 37.6

Other 0 1.4 0.5 O

C2H4 conversion% 41.3 21.6 27.1 47.8 C2H4 selectivity:% Chlorohydrocarbons 95.2 92.4 91.5 94.7% Carbon oxides 4.8 7.6 8.5 5.3

Catalyst composition Feed molar ratio% Fe Ρύ 1% (HCl: C2H4: EDC: air: N2) I Rh fa 0.05% = 1: 1: 1: 2: 1% Zn 1¾ 3%% Li 0.3%

Carrier:

Low surface area alumina 66829 17

The choice of the particular catalyst composition and operating conditions may also be influenced by external factors, such as economic conditions. For example, if there is significant use for ethylene chloride and all other uses for non-convertible ethylene are lacking, the run shown in Table II would be attractive. On the other hand, if a significant excess of EDC and several other processes in which unconverted ethylene might be used were already at hand, a second run at a higher temperature in Table III would be desirable.

In other words, the examples in Tables II and III show that by varying the composition and / or operating conditions of the catalyst it is possible to control not only the conversion of ethylene and its co-reagents and the yield of VCM, but also at least to some extent. It will also be appreciated that the choice of the optimal set of catalyst composition and / or operating conditions will depend not only on the novel catalyst and process of this invention, but also on other factors that are completely external to the catalyst and / or process. In addition, the optimum process variable for a given starting catalyst composition changes when the catalyst composition changes during use, e.g. due to evaporation losses.

In commercial OHC reactors, evaporation losses of 10% or more per year are not uncommon and a "make-up catalyst" is added from time to time to compensate for these losses. It is also expected that the use of the catalyst of this invention in a commercial reactor over a long period of time would also result in a gradual evaporation loss of iron and copper chloride. The evaporation loss would be expected to vary according to the reaction conditions, especially the temperature.

For example, it has been calculated that even if only about 0.5% of the copper chloride> evaporates in use during the year at temperatures of about 340-350 ° C, at temperatures of 420 ° C losses of 3-6% or more could occur. Therefore, the amount of catalyst, and in particular the ratio of rhodium, zinc and lithium chloride to copper or iron chloride in the make-up catalyst, may need to be adjusted to a significantly higher iron or copper chloride level so that when the make-up catalyst is added to the reactor and mixed with the catalyst already present. the total atomic ratio is adjusted to approximately the atomic ratio of the fresh catalyst salts initially charged to the reactor.

18 66829

Although it is possible to accurately estimate the evaporation losses of the metal chloride by calculating based on the reaction conditions, it is clearly advisable to adjust the ratios of the metals in the make-up catalyst using actual quantitative data. This information can be obtained directly from the analysis of batch samples of the catalyst bed 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 of this invention to operate effectively at or below 350 ° C is, of course, a significant advantage in substantially reducing the volatility of the catalyst components. However, further improvement can be achieved by adding about 0.01-3% by weight of lithium. Alkali metal chlorides, especially potassium chloride and some alkaline earth metal chlorides, have long been known to be used as catalyst modifiers to reduce the volatility of oxyhydrochlorination catalysts. Surprisingly, in the context of the catalyst of this invention, only lithium appears to have some use as a catalyst modifier.

This was clearly demonstrated in a series of lifetime trials. In a blind or standard experiment, a catalyst within the scope of this invention containing 0.05% rhodium, 0.6% iron and 2.7% zinc was found to have a useful life of approximately 1 month before a sharp decrease in VCM yield and percentage of converted ethylene and a significant percentage of carbon oxides. growth. The addition of 0.3% lithium chloride to this catalyst system significantly extended the life of the catalyst.

In similar experiments, neither calcium chloride nor rhodium chloride varnish appeared to have a significant effect on the useful life of the catalyst; while sodium chloride, cesium chloride, barium chloride, and magnesium chloride significantly shortened the useful life of the catalyst, usually less than about 1 week. Attempts to replace lithium chloride with potassium chloride resulted in a catalyst that had too little activity to be accepted even when fresh, so that, in fact, this catalyst did not have any useful life. Although sodium is not a suitable lithium substitute as a modification metal in the catalyst preparation of this invention, alumina supports with about 0.2-1.0% sodium oxide do 66829 19 do prove to have an optimization advantage.

Again, although optimum results appear to be obtained using a catalyst containing rhodium, iron, zinc, and lithium with a low surface area alumina support containing a small amount of sodium oxide, the optimum is for percent ethylene conversion and VCM yield. As mentioned above, this may not always be the case and when there is an alternative use for unconverted ethylene and more EDC or other chlorohydrocarbon by-products are desired, the reaction equilibrium can be shifted in this direction either by adjusting operating conditions and / or adjusting catalyst composition. In such a case, control of the catalyst composition could involve the use of replacement materials.

For example, it has been found that ferric chloride can be replaced by copper chloride. Replacement of rhodium with iridium or cerium has generally been a less desirable substitution and has generally led to a decrease in ethylene conversion rate, a decrease in VCM selectivity, and a higher concentration of chlorohydrocarbon by-products.

Although we refuse to accept any theory that could explain the operation of the catalyst or process of this invention, it would appear that iron and copper chloride and possibly rhodium chloride act as a highly selective oxyhydrochlorination catalyst system, while zinc chloride possibly acts as a dehydrochlorination-ED catalyst: , respectively.

On the other hand, it is impossible to even theorize the current kinetics of the reaction equilibrium in the reactor; i.e., how much, if any, of the VCM is from pyrolysis of the EDC in the feed stream compared to the EDC formed in situ by oxyhydrochlorination of ethylene in the feed stream. However, it is clear that the catalyst of this invention is likely to produce at least some VCM by simultaneous oxyhydrochlorination and pyrolysis. This is clearly confirmed in Example 8, where the feed stream consisted only of ethylene, oxygen, and hydrogen chloride, i.e., where the change from the previous examples was the exclusion of EDC from the feed stream.

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Claims (15)

A continuous process for synthesizing VCM from ethylene, an oxygen source and a chlorine source by oxyhydrochlorination of ethylene to EDC and substantially simultaneous pyrolysis of EDC in situ to VCM and hydrogen chloride, characterized in that ethylene, an oxygen source and a chlorine source are fed to the first reactor, contains about 0.01-6% by weight of a salt of a metal selected from the group consisting of rhodium and platinum, about 0.01-15% by weight of a salt of a metal selected from the group consisting of iron and copper , and about 1.0 to 25% by weight of a zinc salt saturated with a support selected from the group consisting of alumina, titanium dioxide, zirconia, silica, and silica-alumina, said percentages being expressed as the total metal content of each component based on the total weight of the catalyst, and then removing the VCM from the mixture of gaseous feedstocks, end products and by-products the reactions are carried out at a pressure of about 0-1 MPa for a contact time of about 2-60 seconds and at a temperature of about 325-450 ° C, which temperature is maintained substantially free of the need for any independent supply of thermal energy other than that required. may be required to initiate a continuous process and / or preheat the reagents. Process according to Claim 1, characterized in that the feed to the first reactor also contains EDC. Process according to Claim 2, characterized in that ethylene, an oxygen source, EDC and a chlorine source are fed to a first reactor charged with a catalyst containing about 0.03-2% by weight of rhodium salt, about 0.02- 10% by weight of an iron salt and about 2.2-15% by weight of a zinc salt, the catalyst being impregnated in a high-purity 2 alumina support having a surface area of about 0.1-10.0 m / g and containing n 0.2 to 1.0% by weight of sodium oxide, the percentages of which indicate the metal content of each component, based on the total weight of the catalyst. 66829 Process according to Claim 1, characterized in that the feed to the first reactor contains EDC as the sole source of chlorine. Process according to Claim 4, characterized in that ethylene, an oxygen source and EDC are fed to a first reactor charged with a catalyst containing about 0.03 to 2% by weight of rhodium salt, about 0.02 to 10% by weight. -% iron salt and about 2.2-15% by weight of zinc salt, the catalyst being impregnated with a high-purity alumina support having a surface area of about 0.1-10.0 m / g and containing approx. 0.2 to 1.0% by weight of sodium oxide, which percentages indicate the metal content of each component based on the total weight of the catalyst. Process according to any one of the preceding claims, characterized in that any unreacted ethylene from the first reactor is fed to a second reactor in which the unreacted ethylene is converted into EDC. Process according to any one of claims 1 to 5, characterized in that the first reactor is a fluidized bed reactor. Process according to any one of Claims 1 to 5, characterized in that the first reactor is a fixed-bed reactor. Catalyst for the preparation of VCM according to any one of claims 1 to 8, characterized in that it contains about 0.01 to 6% by weight of a salt of a metal selected from the group consisting of rhodium and platinum, about 0, 01-15% by weight of a salt of a metal selected from the group consisting of iron and copper and about 1.0-25% by weight of a salt of zinc, the catalyst being impregnated with a support selected from the group consisting of alumina, titanium dioxide , zirconia, silica and silica-alumina, the percentages of which indicate the metal content of each component, calculated on the total weight of the catalyst 22 66829. Catalyst according to Claim 9, characterized in that the salts are salts of rhodium, iron and zinc. Catalyst according to Claim 9, characterized in that the catalyst contains about 0 to 3% by weight of lithium salt. Catalyst according to Claim 9, characterized in that the support is high-purity alumina with a surface area of about 0.1 to 10.0 m / g and containing about 0.2 to 1.0% by weight. sodium oxide. Catalyst according to Claim 9, characterized in that it contains about 0.03 to 2.0% by weight of rhodium salt, about 0.02 to 10% by weight of iron salt and about 2.2 to 15% by weight of iron salt. % zinc salt. Catalyst according to Claim 13, characterized in that the catalyst contains about 0 to 3% by weight of lithium salt. Catalyst according to Claim 13, characterized in that the support is high-purity alumina with a surface area of about 0.1 to 10.0 m / g and containing about 0.2 to 1.0% sodium oxide.