DE2849469A1 - METHOD FOR PRODUCING VINYLIDEN CHLORIDE - Google Patents

Description

1,1,2-trichloroethane can be dehydrochlorinated in the vapor phase a reaction product is formed, which is mainly vinylidene chloride and a mixture of cis and trans-1,2-dichloroethylene isomers. Vinylidene chloride can either be polyvinylidene chloride be polymerized or it can be catalytically hydrochlorinated, with methyl chloroform arises. Since the 1,2-dichloroethylene isomers of essential are lower, there is a desire to increase the proportion of vinylidene chloride in the reaction product raise.

In the dehydrochlorination of 1,1,2-trichloroethane in The vapor phase can increase the selectivity in the direction of the formation of vinylidene chloride and also the ratio of vinylidene chloride to the 1,2-dichloroethylene isomers are improved by the fact that the reaction in Carries out the presence of a suitable catalyst. This is described, for example, in US Pat. No. 3,870,762 and also forms the subject of the previous US filings with the file numbers 754 564 and 852 897.

For example, it has been observed that the vapor phase dehydrochlorination of essentially 100% 1,1,2-trichloroethane at atmospheric pressure and a temperature of 450 ^° C. in the absence of any catalyst results in the formation of about 34 to 36% vinylidene chloride at a ratio of Vinylidene

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chloride to the 1,2-dichloroethylene isomers of about 0.5: 1 to 0.6: 1 leads.

However, if 1,1,2-trichloroethane under the same reaction conditions in the presence of certain catalysts, such as cesium chloride, on a silica gel is dehydrochlorinated with a large surface, it was observed that the proportion of vinylidene chloride to about 57.4% at a ratio of vinylidene chloride to the 1,2-dichloroethylene isomers up to about 1.5: 1 increases.

Although the selection of the catalyst and the reaction conditions increase the yield and the selectivity for the formation of vinylidene chloride, it was found that the selectivity for the formation of vinylidene chloride in the dehydrochlorination of 1,1,2-trichloroethane in the vapor phase and in the presence of Catalysts decreases to the extent that the pressure of 1,1,2-trichlorethylene in the starting gas increases, the reaction temperature being kept constant. This decrease in the catalytic selectivity in the direction of the formation of vinylidene chloride with the increase in the pressure of 1,1,2-trichloroethane is disadvantageous if it is desired to carry out the vapor phase conversion at elevated pressure, in particular at a pressure of 4.0 atmospheres or higher .

It has now been found that the selectivity in the direction of the formation of vinylidene chloride in the cat-

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lytic dehydrochlorination of 1,1,2-trichloroethane can be increased in the vapor phase.

The invention therefore provides a process for the preparation of vinylidene chloride by catalytic Dehydrochlorination of 1,1,2-trichloroethane in the vapor phase, in which a gaseous mixture of 1,1,2-rrichloroethane and a non-reactive one Diluent with a catalyst under conditions for vapor phase dehydrochlorination is brought into contact, this method being characterized in that this gaseous mixture at a temperature of at least 375 ° C and a total pressure of at least 3.5 atmospheres is brought into contact with the catalyst and the partial pressure of 1,1,2-trichloroethane is adjusted in the gas mixture so that it does not exceed 3.0 atmospheres.

It was observed that in the catalytic vapor phase dehydrochlorination of 1,1,2-trichloroethane the catalytic selectivity in the direction of the formation of Vinylidene chloride decreases with increasing pressure of 1,1,2-trichloroethane, the catalytic selectivity decreases with increasing pressure of 1,1,2-trichloroethane to a point at which apparently the catalytic Activity ceases even though the reaction is carried out in the presence of a catalyst. In in such a case the selectivity of the reaction and the product distribution are essentially the same

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as when carrying out the reaction in the absence of a catalyst.

The invention consequently makes it possible to carry out the catalytic vapor phase dehydrochlorination at a high total pressure perform, with the catalytic selectivity in the direction of the formation of vinylidene chloride through Control of the partial pressure of 1,1,2-trichloroethane in the gaseous starting materials is maintained.

In the invention, the vapor phase dehydrochlorination of 1,1,2-trichloroethane is carried out at a total pressure of at least about 3.5 atmospheres and a partial pressure of 1,1,2-trichloroethane in the gaseous mixture of the starting materials of no higher than about 3.0 atmospheres. Although there is no particular upper limit of the invention for total pressure can be a total pressure of well above about 5.0 atmospheres be disadvantageous from the economic point of view because of the dilution effect. The vapor phase reaction will therefore typically at a total pressure between about 3.5 and 5.0 atmospheres, preferably 3.7 and 4.4 Atmospheres carried out. "Atmosphere" is always understood here to mean the physical atmosphere (atm).

With regard to the lower limit of the partial pressure of 1,1,2-trichloroethane in the gas mixture, it is preferred this partial pressure above atmospheric pressure but not above about 3.0 atmospheres, preferably not to be maintained above about 2.0 atmospheres. The partial pressure of 1,1,2-trichloroethane in

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however, the gas mixture can also be below atmospheric pressure. For example, dehydrochlorination was carried out using nitrogen gas as a diluent with 1,1,2-trichloroethane. The gaseous mixture of nitrogen and 1,1,2-trichloroethane had a total pressure of 3.86 atmospheres and a partial pressure of 1,1,2-trichloroethane of 0.03 atmospheres. This mixture was brought into contact with a cesium chloride catalyst at a temperature of 450 ^° C. and vinylidene chloride was obtained with a selectivity of 76.2%. This experiment shows that the selectivity for vinylidene chloride would approach 100% if the partial pressure of 1,1,2-trichloroethane were kept sufficiently below atmospheric pressure. Because of the dilution effect, however, it would probably be uneconomical to operate the process with a partial pressure of 1,1,2-trichloroethane below atmospheric pressure even at relatively moderate total pressures.

The partial pressure of 1,1,2-trichloroethane in the gaseous Mixing can be done by regulating the molar ratio from 1,1,2-trichloroethane to the non-reactive Diluents can be adjusted. For example, if the dehydrochlorination is within the preferred range of the total pressure, i.e. between about 3.5 and 5.0 atmospheres, the molar ratio is from 1,1,2-trichloroethane to the non-reactive diluent preferably in the range of about 1: 1 to about 1: 3.

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The diluent can be any gas or liquid which can be used under the dehydrochlorination conditions is vaporizable, these substances essentially with both 1,1,2-trichloroethane and with the reaction products should not react under the reaction conditions. The diluent should can preferably also be easily separated from the reaction product. Examples of suitable diluent gases are ethylene, acetylene and inert gases such as nitrogen. Examples of suitable dilution fluids are cyclohexane and perchlorethylene.

The catalytic dehydrochlorination of 1,1,2-trichloroethane in the vapor phase can be carried out within a wide temperature range, temperatures of at least about 375 ^° C., preferably between about 400 and 500 ^° C., being used as a rule. Although temperatures can be used below 375 ° C and above 500 ⁰ C, require low temperatures for too long reaction times and excessively high temperatures may lead to decomposition of the product. The reaction time, that is to say the residence time of the gaseous mixture in the reactor, usually does not exceed two minutes and is typically not greater than about 10 seconds.

Any known dehydrochlorination catalyst, which is selective for the formation of vinylidene chloride can be used. One of those The catalyst is described, for example, in US Pat. No. 3,870,762. A particularly preferred catalog

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lysator contains a Caesiurahalogenid, in particular one Cesium chloride, these catalysts as a carrier for the active substance usually a silica gel with a large surface included. A detailed description of such a catalyst is in the US application, Serial number 744 564 available. Another preferred catalyst contains cesium nitrate on a silica gel with a large surface. A detailed description of this catalyst can be found in the US application, Serial Number 856 897. With regard to the catalysts, reference is made to the entire contents of this patent specification and of the two patent applications are referred to.

In a typical implementation of the invention, a gaseous mixture of 1,1,2-trichloroethane and a non-reactive diluent at a molar ratio of 1,1,2-trichloroethane to diluent of about 1: 1 to about 1: 3 is continuously added a total pressure between about 3.5 and 5.0 atmospheres in a reactor, where it ^{is brought into contact with a catalyst at a temperature between 400 and 500 0} C for a sufficient time for the satisfactory conversion of the 1,1,2-trichloroethane . The residence time of the gaseous mixture in the reactor is typically no longer than 10 seconds. The catalyst can be used in a conventional manner, for example in the form of a fixed bed or a fluidized bed. The gaseous reaction mixture is collected on leaving the reactor and worked up in the usual way.

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The invention is explained in more detail in the following examples.

Examples 1 to 4

For all these experiments, a vertical tubular reactor with a length of 70 cm and an inner Diameter of 2.54 cm made of a commercially available nickel alloy (Inconel ^ S / 600) is used. With the Reactor tube was connected at a right angle and at its upper end a preheater that was one length 30.5 cm and an inner diameter of 2.54 cm and made of a nickel tube. The reactor was charged with catalyst to a depth of about 25.4 cm. The catalyst bed was from a disk of porous silicon carbide carried about six inches from the lower end of the reactor tube was removed.

On those parts of the reactor tube which contained the catalyst, heat was applied via a 30.5 cm long heating jacket put on. The preheater was heated by resistance heating, including the preheater pipe wrapped with a layer of glass fabric and a commercially available heating wire (nichrome 22) was.

The catalyst used in Examples 1 to 4 consisted of silica gel impregnated with cesium chloride with a cesium chloride content of about 10% by weight,

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based on the total weight of the catalyst. This catalyst is the subject of the aforementioned U.S. Application 744 564. The catalyst is prepared by the silica gel is pre-saturated with water vapor at a temperature below 5O ⁰ C, after which it is impregnated with an aqueous solution of cesium chloride and is dried.

The temperatures of the reactor and the preheater were adjusted to 450 or 150 C and it was liquid 1,1,2-trichloroethane in the preheater initiated where it was vaporized. The vaporized 1,1,2-trichloroethane was passed through the catalyst bed led down and the escaping vapor stream was collected and analyzed * 1,1,2-trichloroethane was introduced at such a rate that a contact time between steam and catalyst from about 7 to 10 seconds was observed.

Four tests were carried out at different pressures of 1.0, 2.56, 4.06 and 10.52 atmospheres. The test conditions and the results of these tests 1 to 4 are summarized in Table I.

Example 5

The same procedure was used as in the previous examples, but was used as a catalyst Cesium nitrate on a silica gel with a large surface area with a cesium nitrate content of about 10% by weight., based on the weight of the catalyst.

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The catalyst was prepared in a manner similar to the previous examples. That with steam Presaturated silica gel was impregnated with an aqueous solution of cesium nitrate and the impregnated Product was dried. This catalyst and its manufacturing process is more detailed in that already mentioned U.S. application 852,897.

From the information in Table I it can be seen for experiments 1 to 4 that with the increase in the vapor pressure of 1,1,2-trichloroethane, both the catalytic selectivity in the direction of the formation of vinylidene chloride and the ratio of vinylidene chloride to 1,2- Decrease dichloroethylene isomers. It was found that when the dehydrοChlorierung at 450 ⁰ G in the presence of a cesium chloride catalyst at a pressure of 1,1,2-trichloroethane of higher than about 3.72 atmospheres, the catalytic effect disappears and the selectivity in the direction of formation of vinylidene chloride is essentially that which is achieved in the absence of a catalyst under equilibrium conditions at 450 ^° C., that is to say about 34 to 36%.

In experiment 5, the dehydrochlorination was carried out in the presence of cesium nitrate at a pressure of 1,1,2-trichloroethane of 4.06 atmospheres, with a catalytic selectivity of vinylidene chloride of 41 and a ratio of vinylidene chloride to 1,2-dichloroethylene isomers of 0.72 was obtained. It turns out that a slightly higher pressure of 1,1,2-trichloroethane

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until the catalytic effect disappears can be tolerated if the reaction with cesium nitrate takes place is catalyzed with cesium chloride.

As a result, depending on the catalyst used and the reaction conditions, the pressure of the 1,1,2-trichloroethane, in which the selectivity to the formation of vinylidene chloride disappears, fluctuate somewhat, but this limit can be adjusted for a given catalyst and given reaction conditions can easily be determined by simple experiments.

In any case, however, satisfactory results are achieved with the invention, that is to say the catalytic results Selectivity to the formation of vinylidene chloride is kept at a sufficiently high level when the total pressure is maintained at 3.5 atmospheres or higher and the 1,1,2-trichloroethane with a suitable diluent is mixed so that the partial pressure of the 1,1,2-trichloroethane in the mixture is not higher is than about 3.0, and preferably no greater than 2.0 atmospheres.

Example 6

The procedure of Examples 1 to 4 was repeated with the exception that the evaporated 1,1,2-trichloroethane was diluted with nitrogen in the ratio of 2.57 moles of nitrogen per mole of 1,1,2-trichloroethane

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28A9469

and that the gaseous mixture is introduced into the reactor under a total pressure of 3.86 atmospheres became. The experimental conditions and the results are shown in Table II.

Examples 7 to 9

The procedure of Examples 1 to 4 was repeated with the exception that the evaporated 1,1,2-trichloroethane with ethylene gas in the molar ratios of Ethylene was diluted to 1,1,2-trichloroethane as follows:

Experiment No. 7 1: 1
Experiment No. 8 1.1: 1
Trial No. 9 1.7: 1

The gaseous mixture of Runs 7 through 9 was fed to the reactor under a total pressure of 4.12 respectively 4.12 and 4.40 atmospheres. Because of the summary of the test conditions and the results reference is made to Table II.

Example 10

The general procedure of Examples 1 to 4 was followed, but the 1,1,2-trichloroethane was used mixed with cyclohexane in a ratio of 3 moles of cyclohexane to 1 mole of 1,1,2-trichloroethane and the mixture was evaporated and fed to the reactor under a total pressure of 4.06 atmospheres.

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- '16 -

These results are also shown in Table II.

From the information in Table II it can be seen that the vapor phase reaction was carried out at a high total pressure as long as the partial pressure of 1,1,2 · trichloroethane in the gaseous mixture is sufficient is low. For example, in experiment no. 6, a gaseous mixture of nitrogen and 1,1,2-trichloroethane was used dehydrochlorinated at a total pressure of 3.66 atmospheres, the partial pressure of 1,1,2-trichloroethane in the gaseous mixture was 1.08 atmospheres. In this experiment, the catalytic Selectivity for vinylidene chloride and the ratio of vinylidene chloride to 1,2-dichloroethylene isomers comparable to that of experiment no. 1, with the 1,1,2-trichloroethane alone at atmospheric Pressure has been dehydrochlorinated.

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TABLE I.

CATALYTIC VAPOR DEHYDROCHLORATION OF

1,1,2-TRICHLORETHANE AT VARIOUS PRESSURES

Experiment No. 12 3 4 5

Reaction temperature 450 450 450 450 446 ^{0 C}

TCÄ pressure, atm 1.00 2.56 4.06 10.52 4.06

Catalyst CsCl CsCl CsCl CsCl CsNO.

Contact time, sec 10 10 7 8 10

TCÄ conversion, % 98 56 78 67 95

VDC selectivity,% 57.4 41.0 34.4 34.4 41.0

c-1.2 selectivity,% 21.0 26.4 31.5 33.0 31.3

t-1.2 selectivity,% 17.4 23.3 24.8 28.9 25.7

Ratio VDC / c-, 1.50 0.82 0.61 0.56 0.72 t-1.2

Yield VDC / 56 23 27 23 39 passage,%

TCÄ = 1,1,2-trichloroethane

VDC = vinylidene chloride

t-1,2 = trans-l ^ -dichlorethylene

c-1,2 = cis-l ^ -dichlorethylene

CsCl - 10% cesium chloride on silica gel with

large surface

CsNO ₃ β 10% cesium nitrate on silica gel with a large surface

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TABLE II

CATALYTIC VAPOR DEHYDROCHLORATION OF 1,1,2-TRICHLORETHANE, WITH ADDED MISCELLANEOUS NON-REACTIVE THINNERS

Attempt no. 6th 7th 8th 9 10 Reaction temperature,
⁰ C 450 451 441 459 456 Total pressure, atm 3.86 4.12 4.12 4.40 4.06 Partial pressure of
TCÄ, atm 1.08 2.06 1.97 1.63 1.02 catalyst CsCl CsNO ₃ CsCl CsCl CsCl Diluents ^N 2 C ₂ H ₂ C ₂ H ₂ C ₂ H ₂ ^G 6 ^H 12 Contact time, sec 9 9 9 11 10 TCÄ conversion. % 91 99 99 95 88

VDC selectivity, % 56.1 47.1 38.5 44.5 43.5 c-1.2 selectivity,% 21.9 22.6 31.9 23.6 21.3 t-1.2 selectivity,% 20.1 27.0 26.0 26.8 26.3 Ratio VDC / 1.33 0.9 0.7 0.9 0.9 c-, t-1.2

Yield VDC / 51.1 46.6 38.1 42.3 38.3 pass,%

TCÄ = 1,1,2-trichloroethane

VDC = vinylidene chloride

t-1,2 = »trans-1,2-dichloroethylene

c-1,2 = cis-l ^ -dichlorethylene

N ₂ = nitrogen

C ₂ H ₂ = ethylene

CgH, - = "cyclohexane

CsCl = 10% cesium chloride on silica gel with a large surface

CsNO ₃ = * 10% cesium leakage on SLLLkageL mLt

Claims (10)

Dr. Michael Hann (1180) H / Ha / W Patent Attorney Ludwigstrasse 67 Giessen PPG Industries, Inc., Pittsburgh, Pa., USA METHOD FOR THE PRODUCTION OF VINYLIDEN CHLORIDE Priority: November 18, 1977 / USA / Ser. No. 852 October 5, 1978 / USA / Ser. No. 948 claims: 1.1 Process for the production of vinylidene chloride by catalytic dehydrochlorination of 1,1,2-trichloroethane in the vapor phase, in which a gaseous mixture of 1,1,2-trichloroethane and a non-reactive diluent in contact with a catalyst under conditions for vapor phase dehydrochlorination is brought characterized in that this gaseous mixture is ^{brought into contact with the catalyst at a temperature of at least 375 0} C and a total pressure of at least 3.5 atmospheres and the partial pressure of the 1,1,2-trichloroethane in the gas mixture is set so that it does not exceed 3.0 atmospheres. 909821/0584 2. The method according to claim 1, characterized in that the vapor phase dehydrochlorination of 1,1,2-trichloroethane is carried out at a temperature between 400 and 500 ^° C. 3. The method according to claim 1, characterized in that the vapor phase dehydrochlorination at a total pressure of 3.5 to 5.0 atmospheres and the molar ratio from 1,1,2-trichloroethane to non-reactive Diluent in the gaseous mixture is 1: 1 to 1: 3. 4. The method according to claim 3, characterized in that the vapor phase dehydrochlorination at at a total pressure of 4.0 to 4.4 atmospheres. 5. The method according to claim 1, characterized in that the diluent is at ambient temperature and atmospheric pressure is a gas. 6. The method according to claim 5, characterized in that the diluent is ethylene or nitrogen is. 909821/0584 7. The method according to claim 1, characterized in that the diluent is at ambient temperature and atmospheric pressure is a liquid which is under the dehydrochlorination conditions is vaporizable. 8. The method according to claim 7, characterized in that the diluent is cyclohexane. 9. The method according to claim 1, characterized in that the catalyst is a cesium halide or Is cesium nitrate. 10. The method according to claim 9, d ad characterized by that the cesium halide is cesium chloride. 909821/058 *