CA1120501A - Process for the production of hexachlorocyclopentadiene - Google Patents
Process for the production of hexachlorocyclopentadieneInfo
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- CA1120501A CA1120501A CA000306248A CA306248A CA1120501A CA 1120501 A CA1120501 A CA 1120501A CA 000306248 A CA000306248 A CA 000306248A CA 306248 A CA306248 A CA 306248A CA 1120501 A CA1120501 A CA 1120501A
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C23/00—Compounds containing at least one halogen atom bound to a ring other than a six-membered aromatic ring
- C07C23/02—Monocyclic halogenated hydrocarbons
- C07C23/08—Monocyclic halogenated hydrocarbons with a five-membered ring
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/013—Preparation of halogenated hydrocarbons by addition of halogens
- C07C17/04—Preparation of halogenated hydrocarbons by addition of halogens to unsaturated halogenated hydrocarbons
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C17/00—Preparation of halogenated hydrocarbons
- C07C17/093—Preparation of halogenated hydrocarbons by replacement by halogens
- C07C17/10—Preparation of halogenated hydrocarbons by replacement by halogens of hydrogen atoms
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Abstract
Case 3773 6/27/77 ASC/cil PROCESS FOR THE PRODUCTION OF
HEXACHLOROCYCLOPENTADIENE
ABSTRACT
A process for the production of hexachlorocyclopentadiene, an intermediate useful in the production of pesticides, comprises simultaneously introducing, in the vapor phase, chlorine and a polychlorinated cyclopentane of the formula C5H8-xCl2+x where x is 0 to 4, into a pool of molten salt comprising a mixture of copper chlorides, maintained at a temperature of about 250° to about 500°Celsius.
HEXACHLOROCYCLOPENTADIENE
ABSTRACT
A process for the production of hexachlorocyclopentadiene, an intermediate useful in the production of pesticides, comprises simultaneously introducing, in the vapor phase, chlorine and a polychlorinated cyclopentane of the formula C5H8-xCl2+x where x is 0 to 4, into a pool of molten salt comprising a mixture of copper chlorides, maintained at a temperature of about 250° to about 500°Celsius.
Description
BACKGROUND OF THE INVENTION
This invention relates to a process for the production of hexachlorocyclopentadiene.
The chemical literature is replete with processes for the preparation of chlorinated hydrocarbon compounds. Many of the known processes are used commercially for the preparation of specific chlorinated hydrocarbons. The development of a suitable process for the preparation of a particular chlorinated hydro-carbon depends on a variety of factors, including for example, 1~ the chemical and physical properties of available starting materials, the chemical and physical properties of the chlor-inated compound to be prepared, the economic factors relative to utilization of materials and energy involved in the process, and the environmental impact of the process. It is known, for example, 15 that hexachlorocyclopentadiene may be produced in low yields by the chlorination of cyclopentadiene at elevated temperatures using C12 as the chlorinating agent. However, at the high tem-peratures required for the reaction, cyclopentadiene exhibits a strong tendency to polymerize, resulting in the production of 20 dimeric and polymeric compounds as well as substankial amounts of other undesired side products, especially octachlorocyclo-pentene. To avoid the problem of polymerization, a process, disclosed in U. S. Patent 3,637,479, provides for a two stage chlorination wherein cyclopentad~ene is first reacted with 25 chlorine at lower temperatures such as below about 110 Celsiusg to form a poly chlorinated product having a composition approxi-mating tetrachlorocyclopentane, and then photo chlorinated to produce hexachlorocyclopentane. The product may then be sub-iected to catalytic vapor phase dehydrochlorination at elevated 30 temperatures to form hexachlorocyclopentadiene. In the vapor phase process about 20% excess of the stoichiometric amount of -," `~
chlorine is employed. Thus, this route of preparation involves three separate steps or stages each requiring substantially dif-ferent conditions.
A single s~age thermal chlorination process is disclosed in U.S. Patent 3,649,699. In accordance with the disclosure of that patent, normal penta~e and chlorine are reacted at 275 to 400 Celsius in the presence of a catalyst comprising alumina h~ving a low surface ~rea to produce hexachlorocyclopentadiene. In another single stage process disclosed in U.S. Patents 3,364,269 10 hexachlorocyclopentadiene is prepared by a single stage catalytic process employing a fluidi~ed bed of catalytically activated carbon.
It will be appreciated that although a variety of processes are known and used for the production of hexachlorocylcopentadiene, a need continues to ex;st for the development of a process pro-15 viding improvemen~s in efficiency of the utilization of reactantsand energy and the elimination or minimization of waste products.
Accordingly, it is an object of the present invention to provide a novel and improved process for the preparation of hexa-chlorocyclopentadiene from cyclopentadiene starting material. A
20 further object of the present invention is to provide a process for the production of hexachlorocyclopentadiene wherein the use of excess amounts of chlorine is avoided.
SUMMARY OF THE INVENTION
In accordance with this invention there is provided a process for the preparation of hexachlorocyclopentadiene comprising si-multaneously introducing, in the vapor phase, chlorine and a polychlorinated c~clopentane of the formula C5H8 xC12+x, where x is Q to 4, into a pool of molten salt comprising a mixture of copper chlorides, preferably maintained at a temperature of about 3Q 250 to about 500 and most preferably about 250 to about 350 Celsius.
" f~ ,, . ~
The polychlorinated cyclopentane and chlorine may be fed as separate streams into a reactor containing the molten salt. In a preferred form, the polychlorinated cyclopentane is vaporized, mixed with chlorine and the reactant mixture fed into a pool oF
molten copper chl~ride salts.
Typically, the vaporized mixture may be sparyed into the bottom of a bubble reactor containing the molten salt. To assure a uniform feed rate to the reactor, it is preferred to employ an inert gas, such as nitrogen or HCl in admixture with either of 10 the vaporized reactants or mixture thereof. The inert gas may be mixed with the gaseous reactants prior to entering the molten salt reactor. The amount of inert gas may vary considerably but is preferably in the range of about 10 to about 50 weight percent of the entire gaseous mixture. The rate of feed of the vaporized mixture, expressed as reciprocal space velocity may vary consider-ably, but will typically be in the range of about 2 to about 20 seconds. At low values of reciprocal space velocity, that is faster feed rate, complete conversion may be achieved. A~ higher values the formation of dimers or over-chlorinated products, such 20 as octachlorocyclopentene is likely to increase.
The molten salt mixture employed is a mixture of copper chlor-ides comprising cupric chloride, and cuprous chloride and a minor proportion of a metal salt melting point depressant which is sub-skantially non-volatile. Suitable melting point depressants are 25 salts, preferably chlorides, of a metal having only one positive valence state. Metal salts, known to be useful for this purpose, include for example the heavy metal chlorides of ~roups 1, II, III and IV of the Periodic Table, including for example, zinc chloride, silver chloride, thallium chloride and the like or 30 mixtures thereof. The preferred melting point depressants are the alkali metal chlorides, preferably potassium and/or lithium chloride. The amount of metal chloride melting point depressant present in the copper chloride mixture may vary considerably but should be an amount sufficient to lower the melting point of the copper chloride mixture to a temperature below the lowest process temperature contemplated and preferably to a mel~ing point below about 250 Celsius. The proportions of the components of the molten salt mixture may vary considerably. The preferred com-positions for this purpose are mixtures containing about 10 to about 40 percent and preferably about 10 to about 20 percent by weight of cupric chloride; about 30 to about 65 percent and pre~
10 ferably about 50 to about 60 percent by weight of cuprous chloridei :~
and about 20 to about 50 percent by weight of a melting point de~
pressant, preferably an alkali metal chloride, most prefer~bly, potassium chloride. In addition, copper oxychloride may be present in the molten salts, in amounts, for example of ~bout 15 0.5 to about 5.5 percent by weight.
Cyclopentadiene - a starting material for the formation of hexachlorocyclopentadiene in some processes of the prior art -is not employed directly in the molten salt chlorination of this invention since the required temperatures result in the formation 20 of undesired volatile chlorornethanes and polymeric materials.
However, cyclopentadiene may be chlorinated readily in a simple low temperature chlorination to ~form a polychlorinated cyclo-pentane having the approximate composition C5H8 xC12~x, where x is 0 to ~. The polychlorinated product formed in this manner is well-suited for chlorination in the hereinabove-described molten salt chlorination to prepare a hexachlorocyclopentadiene product.
Thus, a preferred embodiment of the present invention provides a two-stage chlorination process for the production of hexachloro-cyclopentadiene which comprises the steps of:
a) reacting chlorine with cyclopentadiene in the l~quid phase at a temperature of below 110C to produce a polychlorinated cyclopentane product having an approximate composition of 5~
C5H8 xC12+x, where x is O to ~;
b) heating the polychlorinated cyclopentane product to form vapors thereof;
c) feeding the vapors of polychlorinated cyclopentane to-gether with chlorine gas into a molten salt comprising a mixture of copper chlorides maintained at a temperature of about 250 to about S00Ci and d) recovering hexachlorocyclopentadiene therefrom.
In the first stage, that is the low temperature chlorination step, cyclopentadiene is reacted with chlorine at a temperature of about 0 to about 110 Celsius and preferably about 30 to about 80 Celsius. The chlorination is preferably carried out at atmos-pheric pressure although subatmospheric or super-atmospheric pres-sures may be employed iF desired.
Typically, in the low temperature liquid phase chlorination step chlorine gas and liquid cyclopentadiene are fed separately into a temperature-controlled reaction vessel, preferably at a molar ratio of about 2 to about ~ moles of chlorine gas per mole of cyclopenta-diene, and liquid polychlorocyclopentane having a composi~ion as 20 set forth hereinabove is withdrawn. The reaction may be efFected in the presence of an inert liquid diluent such as carbon tetra-chloride, or preferably a portion of the polychlorinated cyclo pentane product may be recirculated as a diluent for the process.
The composition oF the product, that iS9 the degree of chlorination 25 may be varied by varying the time of reaction and/or the proportion of chlorine reactant to cyclopentadiene reactant. The preparation of higher chlorinated cyclopentanes, such as C5H8 xC12~x, where x is greater than about 3, by low temperature chlorination is diffi-cult and becomes increasingly less efficient from the standpoint 30 of chlorine utilization due to the need of excess chlorine gas reactant. On the other hand, the molten salt chlorination of lower chlorinated cyclopentanes becomes increasingly less effi-cient, from the standpoint of chlorine utilization as the aforesaid ~lZ050~
value of x decreases, especially at values where x is less than about 2. Thus it is preferred to carry out the low temperature chlorination to a degree sufficient to provide a polychlorinated cyclopentane product having an approximate composition of C5H8 x~
C12+x, where x is about 0 to about 3, and most preferably about 1.5 to about 2.5, a product having an average composition approxi-mating that of tetrachlorocyclopentane and to utilize such poly-chlorinated cyclopentanes as reactants in the subsequent molten salt chlorination step to prepare hexachlorocyclopentadiene.
10 Polychlorinated cyclopentanes prepared in this manner by low temp-erature chlorination are generally a mixture of chlorinated cyclo-pentanes. Thus, a polychlorinated cyclopentane having a compo-sition of C5H8 xC12+x, where x is between 1.5 and about 2.5, will generally be a mixture wherein the predominant components are 15 C5H5C15, C5H6C14, and C5H7C13. Although the preferred starting material for the preparation of the polychlorinated cyclopentane by low temperature chlorination is cyclopentadiene, other five membered hydrocarbon ring compounds, in particular cyclopentene, may be employed.
In the molten salt chlorination, when a polychlorinated cyclopentane having a composition characterized by the formula C5H8 xC12+x. where x is about 1.5 to about 2.5 is employed, it has been found that hexachlorocyclopentadiene is advantageously produced with less than the stoichiometric amount of chlorine 25 gas reactant than is required for the chlorination and dehydro-chlorination reactions involved. During the reaction additional chlorine atoms are contributed by the conversion of cupric chloride to cuprous chloride in the molten salt. The depletion of the cupric chloride may be compensated for by replacement of 30 the molten salt or periodic additions of cupric chloride thereto.
Alternatively, when the cupric chloride component is depleted the molten salt may be regenerated by addition of chlorine values, O~
preferably utilizing waste chlorine values from the low temp-erature chlorination step.
The following specific examples are provided to further illuskrate this inven-tion and the manner in which it may be carried out. It will be understood that the specific details given in the examples have been chosen for purpose of illustration and are not to be construed as a limitation of the invention. In the examples, unless otherwise indicated, all parts and percentages are by weight and all temperatures are in degrees Celsius.
EXAMPLE I
A) Low temperature chlorination of cyclopentadiene Six hundred parts of cyclopentadiene and 1930 parts of chlorine gas were fed continuously in separate streams over a period of six hours into a reactor containing a pool of about 300 parts of a poly-chlorinated cyclopentane having an average composition approximately corresponding to tetrachlorocyclopentane. The reactor contents were continuously circulated through an external cooler to maintain a reactor temperature of about 40C. The chlorine feed was main-tained at about 50% excess of the stoichiometric amount. A polychlorinated 20 cyclopentane product having an approximate average composition of C5H6 16C13 ~4 was conkinuously wi-thdrawn from the bot-tom of -the reactor.
B) Molten salt chlo nation of polychlorinated cyclopentane Polychlorinated cyclopentane, prepared as in I-A, above, having an approximate average composition of C5~l6 16C13 84 was heated to about 300C and the resultant vapors mixed with chlorine gas and nitrogen in a proportion of about 1.42 par-ts of polychlor-inated cyclopentane to about 1.5 parts of chlorine gas (about 77 percent of the stoichiometric amount of chlorine required for the production of hexachlorocyclopentadiene) and 0.05 parts of nitrogen.
The mixture was continuously bubbled over a period of ~ hours into ~ - , a molten salt pool comprising 300 parts of a mixture of 15l CuC12, 60% CuCl, and 25% KCl. The molten salt w~s maintained at a tem-perature of about 350C and the reactant mixture was allowed to bubble through the molten salt with an approximate reciprocal space velocity of about 11 seconds. Product vapors were withdrawn, condensed, and analyzed using gas chromatographic techniques, every 15 minutes for the first two hours and every 30 minutes there~fter for the total 4 hour reaction period. The product thus obtained was found to contain greater than 94% hexachlorocyclopentadiene, 10 the remainder being primarily octachlorocyclopentene.
A) Low temperature chlorination Dichlorocyclopentane was prepared by low temperature chlori-nation reaction of cyclopentene with approximately stoichiometric 15 amoun~s of chlorine. Cyclopentene vapor and chlorine were fed simultaneously (feed rates about 2 mls/minute and 1.6 g/minute, respectively) into the upper portion of a tubular reactor packed with 0.5 inch Berl saddles. The reactor was maintained at a tem-perature of about 35C by external cooling and the dichlorocyclo-20 pen~ane produced was continuously condensed and collected inquantitive amounts at the bottom of the reactor. Analysis o~ the dichlorocyclopentane product indicated a chlorine content of 55.4 weight percent (~heoretical value, approximately 51 weight percent).
B) Molten salt chlorination A reactor containing about 300 parts of a mixture of 15%
CuC12, 60% CuCl and 25% KCl was heated to about 280C and chlorine gas was fed into the molten salt, to saturate the salt with chlorine.
Dichlorocyclopentane~ prepared as in Example 2A, was heated to about 170C and the resultant vapors continuously mixed with chlorine gas 30 and nitrogen and ~he mixture continuously-fed into -the molten salt in a manner similar to that of Example lB. The process was con-tinued over a period of about 4 hours during which the molten salt ~24~5~
was maintained a~ a temper~ture about 280C. The reactants were mixed and fed into the molten salt at an initial rate of about 4.5 parts/minute of dichlorocyclopentane to about 0.25 parts/minute of chlorjne and the quantities gradually increased to the final rate of about 7.0 parts/minute of dichlorocyclopentane to about 5.0 parts/
minute of chlorine. The product vapors were continuously withdrawn, condensed and analyzed using gas chromatographic techniques. Init-ially the product obtained represented approximately 75% conversion of the dichlorocyclopentane to hexachlorocyclopentadiene. When the 10 chlorine feed rate WAS increased to approximately double the stoichio-metric amount, a conversion of about 96% to hexachlorocyclopentadiene and octachlurocyclopentene was achieved.
Molten salt chlorination of hexachlorocyclopentane Hexachlorocyclopentane was continuously mixed with chlorine gas and minor proportions of nitrogen and the vapor mixture fed into a reactor containing a pool of 300 parts of chlorides (15%
Cu~12, 6q% CuCl, and 25% KCl) following the general procedure oF
Example lB. During the reaction, the temperature of the molten 20 salt was maintained at between about 310 and 375C. The reaction was run over a period of 4 hours and 34 minutes, with an average feed rate of about l.l9 parts/minute of hexachlorocyclopentane to about 0.4 parts/minute of chlorine yas. The proportions of hexachlorocyclopentane and chlorine reactants was varied during 25 the reaction period. Ini-tially, chlorine was added -to the mixture at a rate equivalent to about 36 percent of the stoichiometric amount required for complete conversion of hexachlorocyclopentane to hexachlorocyclopentadiene. At this proportion, product analy-sis indicated 91.8% hexachlorocyclopentadiene and minor amounts 30 of hexachlorocyclopentanone and octachlorocyclopentene. When the chlorine feed rate was increased to about ~6% of the stoichiometric amount, the product analysis indicated greater than 98% hexachloro-cyclopentadiene with very minor amounts of hexachlorocyclopentanone s~
and octachlorocyclopentene. Similar r~sults, i.e. 98% hexachloro-cyclopentadiene, were achieived when the chlorine feed rate was ~urther increased to 45 to 52% of the stoichiometric amount.
In a number of experiments utilizing different polychlor-inated cyclopentane starting materials, it was found that for a given molten salt composition, the chlorine efficiency, that is, the percent of chlorine, based on the stoichiometric amount, varied inversely with the chlorine content of the polychlorinated cyclopentane. Thus, when the starting material for the molten 10 salt chlorination step was dichlorocyclopentane, essentially quantitative conversion to hexachlorocyclopentadiene required about double the stoichiometric amount of chlorine gas reactant required for the chlorination and dehydrochlorination reaction.
When the starting m~terial composition was approximately that 15 of tetrachlorocyclopentane, essentially quantitative conversion to hexachlorocyclopentadiene required about 75% of the stoichio-metric amount of chlorine gas reactant. About 50% of the stoichio-metric amount of chlorine gas reactant was required for essentially quantitative conversion of hexachlorocyclopentane to hexachloro-20 cyclopentadiene.
This invention relates to a process for the production of hexachlorocyclopentadiene.
The chemical literature is replete with processes for the preparation of chlorinated hydrocarbon compounds. Many of the known processes are used commercially for the preparation of specific chlorinated hydrocarbons. The development of a suitable process for the preparation of a particular chlorinated hydro-carbon depends on a variety of factors, including for example, 1~ the chemical and physical properties of available starting materials, the chemical and physical properties of the chlor-inated compound to be prepared, the economic factors relative to utilization of materials and energy involved in the process, and the environmental impact of the process. It is known, for example, 15 that hexachlorocyclopentadiene may be produced in low yields by the chlorination of cyclopentadiene at elevated temperatures using C12 as the chlorinating agent. However, at the high tem-peratures required for the reaction, cyclopentadiene exhibits a strong tendency to polymerize, resulting in the production of 20 dimeric and polymeric compounds as well as substankial amounts of other undesired side products, especially octachlorocyclo-pentene. To avoid the problem of polymerization, a process, disclosed in U. S. Patent 3,637,479, provides for a two stage chlorination wherein cyclopentad~ene is first reacted with 25 chlorine at lower temperatures such as below about 110 Celsiusg to form a poly chlorinated product having a composition approxi-mating tetrachlorocyclopentane, and then photo chlorinated to produce hexachlorocyclopentane. The product may then be sub-iected to catalytic vapor phase dehydrochlorination at elevated 30 temperatures to form hexachlorocyclopentadiene. In the vapor phase process about 20% excess of the stoichiometric amount of -," `~
chlorine is employed. Thus, this route of preparation involves three separate steps or stages each requiring substantially dif-ferent conditions.
A single s~age thermal chlorination process is disclosed in U.S. Patent 3,649,699. In accordance with the disclosure of that patent, normal penta~e and chlorine are reacted at 275 to 400 Celsius in the presence of a catalyst comprising alumina h~ving a low surface ~rea to produce hexachlorocyclopentadiene. In another single stage process disclosed in U.S. Patents 3,364,269 10 hexachlorocyclopentadiene is prepared by a single stage catalytic process employing a fluidi~ed bed of catalytically activated carbon.
It will be appreciated that although a variety of processes are known and used for the production of hexachlorocylcopentadiene, a need continues to ex;st for the development of a process pro-15 viding improvemen~s in efficiency of the utilization of reactantsand energy and the elimination or minimization of waste products.
Accordingly, it is an object of the present invention to provide a novel and improved process for the preparation of hexa-chlorocyclopentadiene from cyclopentadiene starting material. A
20 further object of the present invention is to provide a process for the production of hexachlorocyclopentadiene wherein the use of excess amounts of chlorine is avoided.
SUMMARY OF THE INVENTION
In accordance with this invention there is provided a process for the preparation of hexachlorocyclopentadiene comprising si-multaneously introducing, in the vapor phase, chlorine and a polychlorinated c~clopentane of the formula C5H8 xC12+x, where x is Q to 4, into a pool of molten salt comprising a mixture of copper chlorides, preferably maintained at a temperature of about 3Q 250 to about 500 and most preferably about 250 to about 350 Celsius.
" f~ ,, . ~
The polychlorinated cyclopentane and chlorine may be fed as separate streams into a reactor containing the molten salt. In a preferred form, the polychlorinated cyclopentane is vaporized, mixed with chlorine and the reactant mixture fed into a pool oF
molten copper chl~ride salts.
Typically, the vaporized mixture may be sparyed into the bottom of a bubble reactor containing the molten salt. To assure a uniform feed rate to the reactor, it is preferred to employ an inert gas, such as nitrogen or HCl in admixture with either of 10 the vaporized reactants or mixture thereof. The inert gas may be mixed with the gaseous reactants prior to entering the molten salt reactor. The amount of inert gas may vary considerably but is preferably in the range of about 10 to about 50 weight percent of the entire gaseous mixture. The rate of feed of the vaporized mixture, expressed as reciprocal space velocity may vary consider-ably, but will typically be in the range of about 2 to about 20 seconds. At low values of reciprocal space velocity, that is faster feed rate, complete conversion may be achieved. A~ higher values the formation of dimers or over-chlorinated products, such 20 as octachlorocyclopentene is likely to increase.
The molten salt mixture employed is a mixture of copper chlor-ides comprising cupric chloride, and cuprous chloride and a minor proportion of a metal salt melting point depressant which is sub-skantially non-volatile. Suitable melting point depressants are 25 salts, preferably chlorides, of a metal having only one positive valence state. Metal salts, known to be useful for this purpose, include for example the heavy metal chlorides of ~roups 1, II, III and IV of the Periodic Table, including for example, zinc chloride, silver chloride, thallium chloride and the like or 30 mixtures thereof. The preferred melting point depressants are the alkali metal chlorides, preferably potassium and/or lithium chloride. The amount of metal chloride melting point depressant present in the copper chloride mixture may vary considerably but should be an amount sufficient to lower the melting point of the copper chloride mixture to a temperature below the lowest process temperature contemplated and preferably to a mel~ing point below about 250 Celsius. The proportions of the components of the molten salt mixture may vary considerably. The preferred com-positions for this purpose are mixtures containing about 10 to about 40 percent and preferably about 10 to about 20 percent by weight of cupric chloride; about 30 to about 65 percent and pre~
10 ferably about 50 to about 60 percent by weight of cuprous chloridei :~
and about 20 to about 50 percent by weight of a melting point de~
pressant, preferably an alkali metal chloride, most prefer~bly, potassium chloride. In addition, copper oxychloride may be present in the molten salts, in amounts, for example of ~bout 15 0.5 to about 5.5 percent by weight.
Cyclopentadiene - a starting material for the formation of hexachlorocyclopentadiene in some processes of the prior art -is not employed directly in the molten salt chlorination of this invention since the required temperatures result in the formation 20 of undesired volatile chlorornethanes and polymeric materials.
However, cyclopentadiene may be chlorinated readily in a simple low temperature chlorination to ~form a polychlorinated cyclo-pentane having the approximate composition C5H8 xC12~x, where x is 0 to ~. The polychlorinated product formed in this manner is well-suited for chlorination in the hereinabove-described molten salt chlorination to prepare a hexachlorocyclopentadiene product.
Thus, a preferred embodiment of the present invention provides a two-stage chlorination process for the production of hexachloro-cyclopentadiene which comprises the steps of:
a) reacting chlorine with cyclopentadiene in the l~quid phase at a temperature of below 110C to produce a polychlorinated cyclopentane product having an approximate composition of 5~
C5H8 xC12+x, where x is O to ~;
b) heating the polychlorinated cyclopentane product to form vapors thereof;
c) feeding the vapors of polychlorinated cyclopentane to-gether with chlorine gas into a molten salt comprising a mixture of copper chlorides maintained at a temperature of about 250 to about S00Ci and d) recovering hexachlorocyclopentadiene therefrom.
In the first stage, that is the low temperature chlorination step, cyclopentadiene is reacted with chlorine at a temperature of about 0 to about 110 Celsius and preferably about 30 to about 80 Celsius. The chlorination is preferably carried out at atmos-pheric pressure although subatmospheric or super-atmospheric pres-sures may be employed iF desired.
Typically, in the low temperature liquid phase chlorination step chlorine gas and liquid cyclopentadiene are fed separately into a temperature-controlled reaction vessel, preferably at a molar ratio of about 2 to about ~ moles of chlorine gas per mole of cyclopenta-diene, and liquid polychlorocyclopentane having a composi~ion as 20 set forth hereinabove is withdrawn. The reaction may be efFected in the presence of an inert liquid diluent such as carbon tetra-chloride, or preferably a portion of the polychlorinated cyclo pentane product may be recirculated as a diluent for the process.
The composition oF the product, that iS9 the degree of chlorination 25 may be varied by varying the time of reaction and/or the proportion of chlorine reactant to cyclopentadiene reactant. The preparation of higher chlorinated cyclopentanes, such as C5H8 xC12~x, where x is greater than about 3, by low temperature chlorination is diffi-cult and becomes increasingly less efficient from the standpoint 30 of chlorine utilization due to the need of excess chlorine gas reactant. On the other hand, the molten salt chlorination of lower chlorinated cyclopentanes becomes increasingly less effi-cient, from the standpoint of chlorine utilization as the aforesaid ~lZ050~
value of x decreases, especially at values where x is less than about 2. Thus it is preferred to carry out the low temperature chlorination to a degree sufficient to provide a polychlorinated cyclopentane product having an approximate composition of C5H8 x~
C12+x, where x is about 0 to about 3, and most preferably about 1.5 to about 2.5, a product having an average composition approxi-mating that of tetrachlorocyclopentane and to utilize such poly-chlorinated cyclopentanes as reactants in the subsequent molten salt chlorination step to prepare hexachlorocyclopentadiene.
10 Polychlorinated cyclopentanes prepared in this manner by low temp-erature chlorination are generally a mixture of chlorinated cyclo-pentanes. Thus, a polychlorinated cyclopentane having a compo-sition of C5H8 xC12+x, where x is between 1.5 and about 2.5, will generally be a mixture wherein the predominant components are 15 C5H5C15, C5H6C14, and C5H7C13. Although the preferred starting material for the preparation of the polychlorinated cyclopentane by low temperature chlorination is cyclopentadiene, other five membered hydrocarbon ring compounds, in particular cyclopentene, may be employed.
In the molten salt chlorination, when a polychlorinated cyclopentane having a composition characterized by the formula C5H8 xC12+x. where x is about 1.5 to about 2.5 is employed, it has been found that hexachlorocyclopentadiene is advantageously produced with less than the stoichiometric amount of chlorine 25 gas reactant than is required for the chlorination and dehydro-chlorination reactions involved. During the reaction additional chlorine atoms are contributed by the conversion of cupric chloride to cuprous chloride in the molten salt. The depletion of the cupric chloride may be compensated for by replacement of 30 the molten salt or periodic additions of cupric chloride thereto.
Alternatively, when the cupric chloride component is depleted the molten salt may be regenerated by addition of chlorine values, O~
preferably utilizing waste chlorine values from the low temp-erature chlorination step.
The following specific examples are provided to further illuskrate this inven-tion and the manner in which it may be carried out. It will be understood that the specific details given in the examples have been chosen for purpose of illustration and are not to be construed as a limitation of the invention. In the examples, unless otherwise indicated, all parts and percentages are by weight and all temperatures are in degrees Celsius.
EXAMPLE I
A) Low temperature chlorination of cyclopentadiene Six hundred parts of cyclopentadiene and 1930 parts of chlorine gas were fed continuously in separate streams over a period of six hours into a reactor containing a pool of about 300 parts of a poly-chlorinated cyclopentane having an average composition approximately corresponding to tetrachlorocyclopentane. The reactor contents were continuously circulated through an external cooler to maintain a reactor temperature of about 40C. The chlorine feed was main-tained at about 50% excess of the stoichiometric amount. A polychlorinated 20 cyclopentane product having an approximate average composition of C5H6 16C13 ~4 was conkinuously wi-thdrawn from the bot-tom of -the reactor.
B) Molten salt chlo nation of polychlorinated cyclopentane Polychlorinated cyclopentane, prepared as in I-A, above, having an approximate average composition of C5~l6 16C13 84 was heated to about 300C and the resultant vapors mixed with chlorine gas and nitrogen in a proportion of about 1.42 par-ts of polychlor-inated cyclopentane to about 1.5 parts of chlorine gas (about 77 percent of the stoichiometric amount of chlorine required for the production of hexachlorocyclopentadiene) and 0.05 parts of nitrogen.
The mixture was continuously bubbled over a period of ~ hours into ~ - , a molten salt pool comprising 300 parts of a mixture of 15l CuC12, 60% CuCl, and 25% KCl. The molten salt w~s maintained at a tem-perature of about 350C and the reactant mixture was allowed to bubble through the molten salt with an approximate reciprocal space velocity of about 11 seconds. Product vapors were withdrawn, condensed, and analyzed using gas chromatographic techniques, every 15 minutes for the first two hours and every 30 minutes there~fter for the total 4 hour reaction period. The product thus obtained was found to contain greater than 94% hexachlorocyclopentadiene, 10 the remainder being primarily octachlorocyclopentene.
A) Low temperature chlorination Dichlorocyclopentane was prepared by low temperature chlori-nation reaction of cyclopentene with approximately stoichiometric 15 amoun~s of chlorine. Cyclopentene vapor and chlorine were fed simultaneously (feed rates about 2 mls/minute and 1.6 g/minute, respectively) into the upper portion of a tubular reactor packed with 0.5 inch Berl saddles. The reactor was maintained at a tem-perature of about 35C by external cooling and the dichlorocyclo-20 pen~ane produced was continuously condensed and collected inquantitive amounts at the bottom of the reactor. Analysis o~ the dichlorocyclopentane product indicated a chlorine content of 55.4 weight percent (~heoretical value, approximately 51 weight percent).
B) Molten salt chlorination A reactor containing about 300 parts of a mixture of 15%
CuC12, 60% CuCl and 25% KCl was heated to about 280C and chlorine gas was fed into the molten salt, to saturate the salt with chlorine.
Dichlorocyclopentane~ prepared as in Example 2A, was heated to about 170C and the resultant vapors continuously mixed with chlorine gas 30 and nitrogen and ~he mixture continuously-fed into -the molten salt in a manner similar to that of Example lB. The process was con-tinued over a period of about 4 hours during which the molten salt ~24~5~
was maintained a~ a temper~ture about 280C. The reactants were mixed and fed into the molten salt at an initial rate of about 4.5 parts/minute of dichlorocyclopentane to about 0.25 parts/minute of chlorjne and the quantities gradually increased to the final rate of about 7.0 parts/minute of dichlorocyclopentane to about 5.0 parts/
minute of chlorine. The product vapors were continuously withdrawn, condensed and analyzed using gas chromatographic techniques. Init-ially the product obtained represented approximately 75% conversion of the dichlorocyclopentane to hexachlorocyclopentadiene. When the 10 chlorine feed rate WAS increased to approximately double the stoichio-metric amount, a conversion of about 96% to hexachlorocyclopentadiene and octachlurocyclopentene was achieved.
Molten salt chlorination of hexachlorocyclopentane Hexachlorocyclopentane was continuously mixed with chlorine gas and minor proportions of nitrogen and the vapor mixture fed into a reactor containing a pool of 300 parts of chlorides (15%
Cu~12, 6q% CuCl, and 25% KCl) following the general procedure oF
Example lB. During the reaction, the temperature of the molten 20 salt was maintained at between about 310 and 375C. The reaction was run over a period of 4 hours and 34 minutes, with an average feed rate of about l.l9 parts/minute of hexachlorocyclopentane to about 0.4 parts/minute of chlorine yas. The proportions of hexachlorocyclopentane and chlorine reactants was varied during 25 the reaction period. Ini-tially, chlorine was added -to the mixture at a rate equivalent to about 36 percent of the stoichiometric amount required for complete conversion of hexachlorocyclopentane to hexachlorocyclopentadiene. At this proportion, product analy-sis indicated 91.8% hexachlorocyclopentadiene and minor amounts 30 of hexachlorocyclopentanone and octachlorocyclopentene. When the chlorine feed rate was increased to about ~6% of the stoichiometric amount, the product analysis indicated greater than 98% hexachloro-cyclopentadiene with very minor amounts of hexachlorocyclopentanone s~
and octachlorocyclopentene. Similar r~sults, i.e. 98% hexachloro-cyclopentadiene, were achieived when the chlorine feed rate was ~urther increased to 45 to 52% of the stoichiometric amount.
In a number of experiments utilizing different polychlor-inated cyclopentane starting materials, it was found that for a given molten salt composition, the chlorine efficiency, that is, the percent of chlorine, based on the stoichiometric amount, varied inversely with the chlorine content of the polychlorinated cyclopentane. Thus, when the starting material for the molten 10 salt chlorination step was dichlorocyclopentane, essentially quantitative conversion to hexachlorocyclopentadiene required about double the stoichiometric amount of chlorine gas reactant required for the chlorination and dehydrochlorination reaction.
When the starting m~terial composition was approximately that 15 of tetrachlorocyclopentane, essentially quantitative conversion to hexachlorocyclopentadiene required about 75% of the stoichio-metric amount of chlorine gas reactant. About 50% of the stoichio-metric amount of chlorine gas reactant was required for essentially quantitative conversion of hexachlorocyclopentane to hexachloro-20 cyclopentadiene.
Claims (20)
-
- THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
- PRIVILEGE IS CLAIMED IS DEFINED AS FOLLOWS:
- A process for the production of hexachlorocyclopentadiene which comprises introducing, in the vapor phase, chlorine and a polychlorinated cyclopentane of the formula C5H8-xC12+x, where x is 0 to 4, into a pool of molten salt comprising a mixture of copper chlorides, maintained at a temperature of about 250° to about 500° Celsius.
- A process according to Claim 1 wherein the molten salt comprises, in weight percent, about 10 to about 40 percent cupric chloride, about 30 to about 65 percent cuprous chloride, and about 20 to about 50 percent of an alkali metal chloride.
- A process according to Claim 2 wherein the alkali metal chloride is potassium chloride.
- A process according to Claim 1 wherein the polychlorinated cyclopentane is characterized by the formula C5H8-xC12+x, where x is about 0 to about 3.
- A process according to Claim 4 wherein the chlorine and the polychlorinated cyclopentane are combined to form a reactant mixture prior to introduction into the molten salt.
- A process according to Claim 5 wherein the reactant mixture comprises about 10 to about 50 percent by weight of an inert gas.
- A process according to Claim 6 wherein the inert gas is nitrogen.
- A process according to Claim 7 wherein the molten salt comprises, in weight percent, about 10 to about 40 percent cupric chloride, about 30 to about 65 percent cuprous chloride, and about 20 to about 50 percent of an alkali metal chloride.
- A process according to Claim 8 wherein the alkali metal chloride is potassium chloride.
- A process according to Claim 9 wherein the polychlorinated cyclopentane is characterized by the formula C5H8-xCl2+x, where x is about 1.5 to about 2.5.
- A process according to Claim 9 wherein the amount of chlorine present in the reactant mixture is less than the stoichiometric amount required for the conversion of the polychlorinated cyclo-pentane to hexachlorocyclopentadiene.
- A process according to Claim 1 wherein the polychlorinated cyclopentane is a mixture of polychlorinated cyclopentanes having an average composition characterized by the formula C5H8-xCl2+x, where x is about 0 to about 3, produced by reacting chlorine with a five-membered hydrocarbon ring compound at a temperature of below about 110° Celsius.
- A process according to Claim 12 wherein the five membered hydrocarbon ring compound is cyclopentadiene.
- A process for the production of hexachlorocyclopentadiene which comprises the steps of a) reacting chlorine with cyclopentadiene at a temperature of below about 110°C. to produce a polychlorinated cyclopentane product having a composition characterized by the formula
- C5H8-xCl2+x, where x is about 1.5 to about 2.5, b) heating the polychlorinated cyclopentane product to form vapors thereof;
c) introducing the vapors of polychlorinated cyclopentane together with chlorine gas in the presence of a molten salt com-prising a mixture of copper chlorides maintained at a temperature of about 250° to about 500°C.; and d) recovering hexachlorocyclopentadiene therefrom. - A process according to Claim 14 wherein the molten salt comprises, in weight percent, about 10 to about 40 percent cupric chloride, about 30 to about 65 percent cuprous chloride, and about
- 20 to about 50 percent of an alkali metal chloride.
A process according to Claim 15 wherein the alkali metal chloride is potassium chloride.
A process according to Claim 16 wherein the amount of chlorine gas introduced into the molten salt is less than the stoichiometric amount required for the conversion of the polychlorinated cyclo-pentane to hexachlorocyclopentadiene.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US81301377A | 1977-07-05 | 1977-07-05 | |
| US813,013 | 1977-07-05 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1120501A true CA1120501A (en) | 1982-03-23 |
Family
ID=25211217
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000306248A Expired CA1120501A (en) | 1977-07-05 | 1978-06-27 | Process for the production of hexachlorocyclopentadiene |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5414940A (en) |
| BE (1) | BE868778A (en) |
| CA (1) | CA1120501A (en) |
| DE (1) | DE2829473A1 (en) |
| FR (1) | FR2396734A1 (en) |
| IL (1) | IL55071A (en) |
| IT (1) | IT1097481B (en) |
| NL (1) | NL7807301A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105884569A (en) * | 2016-04-22 | 2016-08-24 | 北京宇极科技发展有限公司 | 1,2-dichlorohexafluorocyclopentene preparation method |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| BE542596A (en) * | ||||
| BE506748A (en) * | 1957-07-22 | |||
| FR1347854A (en) * | 1962-11-21 | 1964-01-04 | Velsicol Chemical Corp | Process for the production of hexachlorocyclopentadiene |
| DE2062773A1 (en) * | 1970-12-19 | 1972-06-22 | Farbwerke Hoechst AG, vormals Meister Lucius & Brüning, 6000 Frankfurt | Process for the production of polychlorocyclopentane and hexachlorocyclopentadiene |
| US4036897A (en) * | 1976-08-04 | 1977-07-19 | The Lummus Company | Production of hexachlorocyclopentadiene |
-
1978
- 1978-06-27 CA CA000306248A patent/CA1120501A/en not_active Expired
- 1978-07-03 FR FR7819763A patent/FR2396734A1/en not_active Withdrawn
- 1978-07-04 IL IL55071A patent/IL55071A/en unknown
- 1978-07-04 JP JP8140278A patent/JPS5414940A/en active Pending
- 1978-07-05 DE DE19782829473 patent/DE2829473A1/en not_active Withdrawn
- 1978-07-05 IT IT25355/78A patent/IT1097481B/en active
- 1978-07-05 NL NL7807301A patent/NL7807301A/en not_active Application Discontinuation
- 1978-07-05 BE BE189105A patent/BE868778A/en unknown
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105884569A (en) * | 2016-04-22 | 2016-08-24 | 北京宇极科技发展有限公司 | 1,2-dichlorohexafluorocyclopentene preparation method |
Also Published As
| Publication number | Publication date |
|---|---|
| IL55071A0 (en) | 1978-09-29 |
| BE868778A (en) | 1979-01-05 |
| JPS5414940A (en) | 1979-02-03 |
| IL55071A (en) | 1981-07-31 |
| FR2396734A1 (en) | 1979-02-02 |
| NL7807301A (en) | 1979-01-09 |
| IT7825355A0 (en) | 1978-07-05 |
| IT1097481B (en) | 1985-08-31 |
| DE2829473A1 (en) | 1979-01-18 |
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