US2899370A - Photochemical chlorination process - Google Patents

Photochemical chlorination process Download PDF

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US2899370A
US2899370A US2899370DA US2899370A US 2899370 A US2899370 A US 2899370A US 2899370D A US2899370D A US 2899370DA US 2899370 A US2899370 A US 2899370A
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liquid
chlorine
reaction zone
polychlorohydrocarbon
chlorination
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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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  • This invention relates to a process for the chlorination of aliphatic and alicyclic hydrocarbons. More particularly, this invention relates to a continuous process for the photochemical chlorination of aliphatic and alicyclic hydrocarbons and partially chlorinated hydrocarbon derivatives thereof, containing three to eight carbon atoms in the molecule.
  • the poresize of the difiusers normallyused is about -20 microns, andpores of this size are readily pluggedby trace contaminants entrained in the gases.
  • gaseous feeds require the use of an elaborate vaporization system operating under pressure to force the starting material through the small pores ofthe difiuser.
  • bubbles of gaseous reactants may coalesce and form explosive mixtures.
  • the principal object-of this invention is to provide a newcontinuous process for the photochemical chlorination of aliphatic and'alicyclic hydrocarbons and partially chlorinated hydrocarbon derivatives thereof, wherein increasedoverall' efficiency and economy are realized from improved operating conditions.
  • Anotherobject ofthis invention is to provide a safe and economical i process which employs" liquid chlorine and liquid hydrocarbon or partially chlorinated hydrocarbons as reactants-which avoids the wasteful procedure of firstvaporizingythe reactions external to the reactor andin effect recondensing them in the chlorinator.
  • Another object of this invention is to provide a contiI-iuous process for photochemical chlorination wherein the mechanical difliculties of the prior art are substantially reduced.
  • Still another object of this invention is to provide a process wherein the danger of explosion in using liquid reactants is even less than the danger involved in using gaseous reactants wherein the gaseous reactants may coalesce to form explosive mixtures.
  • Figure 1 is a diagrammatic flow sheet showing the separate injection of the reactants into a circulating stream and is one method which may be employed in the performance of this process.
  • Figure 2 is a diagrammatic flow sheet showing a modification of the process of this invention wherein the reactants are injected into separate circulating streams.
  • Liquid chlorine 1 and liquid hydrocarbon starting material 2 are separately injected through nozzles into a circulating stream 3 of liquid polychlorohydrocarb'on having a specific gravity between about 1.3 and about 1.8.
  • the external stream is circula-ted through the system by means of-pumps 4.
  • the temperature of the reaction medium in the photochemical clorinator 5 is maintained between about 25 degrees and about degrees centigrade by means of an external heat exchanger 6.
  • a portion of the polychlorohydrocar hon is withdrawn in the product withdrawal zone 7 to a product recovery zone 8 wherein the desired product is obtained.
  • Efiluent gases, such as chlorine and hydrogen chloride are removed from the chlorinator and vented 9 to a recovery system.
  • the photochemical energy is supplied from a mercury vapor lamp suspended in a light well 10.
  • Liquid chlorine 1 and liquid hydrocarbon starting material 2 are injected through nozzles into separate circulating streams 3 of liquid polychlorohydrocarbon having a specific gravity between about 1.3 and about 1.8.
  • Thestreams are circulated through'the system by means of pumps 4.
  • the temperature of the reaction medium in the photochemical chlorinator 5 is maintained between about 25 degrees and 150 degrees Centigrade by means of external heat exchangers 6.
  • a portion of the polychlorohydrocarbon is withdrawn in a product withdrawal zone 7, to a product recovery zone 8 wherein the desired product is obtained.
  • the photochemicalenergy is'supplied from a mercury-vapor lamp suspended in a light-well 10.
  • Example 1 The chlorination apparatus employed to obtain the data of the following example consisted of an eight-inch diameter nickel pipe, seventy inches long, fitted with a jacketed light well assembly which consisted of a two inch diameter Pyrex pipe mounted inside a four-inch diameter Pyrex pipe and supported on the vertical axis of the chlorinator. A 3,000 watt Westinghouse BH-9 mercury vapor lamp suspended in the light well was used to furnish the photochemical energy for this experiment.
  • the chlorinator had a conical bottom section, six and one half inches long, wherein the circulating liquid streams entered the chlorinator through a one-inch nickel pipe. A drain valve was provided at the bottom.
  • a two-inch diameter liquid overflow at the top of the chlorinator provided a liquid depth of fifty-six and one-half inches in the straight section giving a net liquid volume of eight and eight-tenths gallons. Exit gases were withdrawn through a one-inch diameter nickel pipe mounted nine inches above the liquid overflow. A thermometer well extend- 'ed into the body of the chlorinator for measuring the liquid temperature.
  • the chlorine to pentane mole ratio was kept between 9.0 and 9.5 to 1.
  • the temperature of the reaction medium was maintained between about 83 degrees and about 88 degrees centigrade.
  • the average temperature drop through the heat exchanger was degrees centigrade.
  • 95 percent of the chlorine feed was in solution in the stream entering the reactor.
  • the hydrogen chloride/ chlorine gas stream leaving the reactor contained about 27 percent chlorine.
  • Approximately 80.5 pounds per hour of chlorine was reacted.
  • a product having a specific gravity of 1.621 at 20 degrees centigrade corresponding to an average composition of C Cl -H was recovered.
  • Example 2 The chlorination apparatus employed to obtain the data of the following example consisted of a thirty-eight inch length of two-inch diameter Pyrex pipe which was illuminated externally by 6 l00 watt AH-4 lamps distributed spirally at uniform intervals (6 inches) along the reaction zone to furnish photochemical energy for the experiments. A drain valve was provided at the bottom of the chlorinator. A one-inch diameter liquid overflow was provided at the top of the chlorinator and gave a net liquid volume of 037 gallon. Exit gases were withdrawn through a one-inch diameter Pyrex pipe mounted above the liquid overflow. A thermometer well extended into the body of the chlorinator for measuring the liquid temperature.
  • the mole ratio of chlorine to hydrocarbon starting material is maintained between about 3 to 1 and about 12 to 1.
  • the circulating stream is passed through an irradiated reaction zone to effect the chlorination of the hydrocarbon in a reaction medium of liquid polychlorohydrocarbon.
  • the reaction is catalyzed by exposing the main liquid body of polychlorohydrocarbons to the action of actinic light having a wave length from about 3,000 to about 5,000 A.
  • the temperature of the liquid body of polychlorohydrocarbon employed as a reaction medium for the chlorination is maintained between about 25 degrees and about 150 degrees centigrade and preferably between about 50 degrees and about degrees centigrade by means of external heat exchangers located in the circulating stream.
  • a portion of the liquid polychlorohydrocarbon stream leaving the reaction zone is withdrawn continuously to maintain a constant liquid volume in the reaction system.
  • the liquid reactants are separately injected. through nozzles into the circulating stream of liquid polychlorohydrocarbon at any point that would permit dissolving the reactants externally so that reactants enter the chlorination zone as a homogeneous solution. Addition of the reactants precedent to the product withdrawal zone would provide a product recovery problem.
  • the reactants are liquid, any method. for adding liquid material is satisfactory.
  • a preferred embodiment is that shown in the drawings wherein the liquid chlorine and liquid hydrocarbon starting materials are injected into separate circulating streams of liquid polychlorohydrocarbons at a fiow point precedent to the pumps to reduce the possibility of forming explosive mixtures should any part of the system fail to operate properly. As stated, this procedure is particularly applicable to hydrocarbons containing three to eight carbon atoms in the molecule. Since the C-3 hydrocarbons have the lowest boiling points, any procedure applicable to these compounds can be used for the higher-boiling members of the series.
  • the photochemical chlorinator contains liquid polychlorohydrocarbons having a specific gravity between about 1.3 and about 1.8 as the coolant and diluent for the chlorination of hydrocarbons.
  • the reaction is catalyzed by exposing the liquid body of polychlorohydrocarbons containing the dissolved reactants to the action of actinic light having a wavelength from about 3,000 to about 5,000 A.
  • the temperature of the reaction medium is maintained between about 25 degrees and about degrees centigrade and preferably betweenabout 50 degrees. and about 125 degrees centigrade by removing the heat of reaction and the heat of the mercury arc lamps by circulating the polychlorohydrocarbons through ex-
  • the heat load is reduced by about 25 percent by. using liquid feed instead of gaseous :2; feed.
  • the flow rate of the circulating stream of liquid polychlorohydrocarbons having a specific gravity between about 1.3 and about 1L8 is maintained-by pumping means, such as a'centrifugal' pump, and is dependent upon-the available heat'ex'ch'anger capacity and the chlorine feed rate required for the desired production. It is assumed that all heat of reaction is removed in the heat exchanger, as is consistent with sound design principles. The economics of heat exchanger capacity dictate the maximum flow rate While the minimum flow rate is dictated by the chlorine feed rate required. In the process of this invention at least 90 percent and preferably substantially all of the chlorine should be in solution on entrance to the chlorinator. Therefore, a minimum ratio must be maintained between the rate of circulation of the polychlorohydrocarbon and the chlorine feed flow rate to maintain the desired solubility. This minimum ratio is dependent upon the chlorination temperature.
  • the table illustrates that at a circulating rate of 22,500 pounds per hour of polychloropentane, in order to keep 90% of the chlorine in solution, the minimum chlorine feed rates are 281 and 141 pounds per hours at 75 degrees and 95 degrees centigrade, respectively.
  • the preferred ratio of the polychloropropane circulating rate to the chlorine feed rate is 340, which is somewhat higher than the 210 ratio which is the minimum ratio for polychloropentane under substantially the same reaction conditions.
  • reaction between chlorine and a hydrocarbon is especially sensitive to certain impurities. Therefore, the starting materials should be free from harmful inhibitors or materials which may delay or slow down the reaction between the hydrocarbon and the chlorine. Presence of reaction inhibitors such as free oxygen or oxygenated organic compounds in the system will inhibit chlorination and they should be eliminated before starting chlorination.
  • An operational hazard arises from the possibility of accumulating an explosive mixture of chlorine and the hydrocarbon vapor.
  • explosive mixtures of gaseous chlorine and hydrocarbon may be present.
  • An excellent control procedure is provided in a circulating system by measurement of the concentration of chlorine in the streams entering and leaving 6 r the chlorinator, since chlorine consumptioniis also a meets-'1 ure of the amount of hydrocarbon which is reacted;
  • a continuous process for the photochemical chl'ori nationof aliphatic and alicyclic hydrocarbons and partially chlorinated hydrocarbon derivatives thereof,', con taining three to eight carbon atoms in the molecule inclu sive, which comprises: maintaining a circulating stream of liquid polychlorohydrocarbon in communication with a reaction zone containing the main body of liquid polychlorohydrocarbon said stream being external to said reaction zone; separately injecting the reactants consisting of liquid chlorine and liquid hydrocarbon into said externally circulating stream of liquid polychlorohydrocarbon, maintaining the chlorine feed rate and the chlorinator temperature such that percent of the reactants entering said reaction zone are in the liquid phase; passing the mixture so produced through an irradiated reaction zone to effect chlorination of the organic feed; withdrawing a portion of said externally circulating stream leaving the reaction zone and recovering said portion as a product.
  • a process according to claim 1 wherein the body of liquid polychlorohydrocarbon maintained as a reaction medium has a specific gravity between about 1.3 and 1.8.
  • liquid hydrocarbon starting material is liquid propane and partially chlorinated hydrocarbon derivatives thereof.
  • liquid hydrocarbon starting material is liquid pentane and partially chlorinated hydrocarbon derivatives thereof.
  • a continuous process for the photochemical chlori-- nation of aliphatic and alicyclic hydrocarbons, and par-- tially chlorinated hydrocarbon derivatives thereof, con-- taining three to eight carbon atoms in the molecule in-- elusive which comprises: maintaining separate circulating; streams of liquid polychlorohydrocarbon in communication with a reaction zone containing the main body of' liquid polychlorohydrocarbon said stream being external to said reaction zone; separately injecting the reactantsconsisting of liquid chlorine and liquid hydrocarbons intosaid separate externally circulating streams of liquid polychlorohydrocarbons; maintaining the chlorine feed rates and the chlorinator temperature such that 90 percent of the reactants entering said reaction zone are in the liquid phase; passing the mixture so produced through an irradiated reaction zone to effect chlorination of the organicfeed; withdrawing a portion from said externally circulating streams leaving the reaction zone to a product recov-- ery zone, passing the remaining portions of the circulating. streams through heat exchangers to maintain the temperature
  • a continuous process for the photochemical chlorin-- ation of aliphatic and alicyclic hydrocarbons, and par-- tially chlorinated hydrocarbon derivatives thereof, containing three to eight carbon atoms in the molecule inclusive which comprises: maintaining separate circulating streams of liquid, polychlorohydrocarbon in communication with a reaction zone containing the main body of liquid polychlorohydrocarbon said streams being external to said reaction zone; separately injectingthe reactants consisting of liquid chlorine and liquid hydrocarbons into .said separate externally circulating streams of liquid polychlorohydrocarbon so that the reactants entering said reaction zone are substantially in solution; passing the mixture so produced through an irradiated reaction zone to effect chlorination of the organic feed; withdrawing a portion from a circulating stream leaving the reaction zone to a 5 and about 150 degrees ce nt igradc.

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  • Physical Or Chemical Processes And Apparatus (AREA)
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Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3145155A (en) * 1962-05-24 1964-08-18 Dow Chemical Co Hydrobromination of ethylene
US3320144A (en) * 1962-08-30 1967-05-16 Dow Chemical Co Manufacture of ethyl bromide
US3405046A (en) * 1964-11-03 1968-10-08 Knapsack Ag Process for the manufacture of 2, 2, 3-trichlorobutane
US3453339A (en) * 1967-05-11 1969-07-01 Chevron Res 1-haloalkyl substituted aromatic hydrocarbons and process for their production
US3528900A (en) * 1966-05-31 1970-09-15 Hooker Chemical Corp Photochlorination process
US4978435A (en) * 1987-08-27 1990-12-18 Atochem Free chlorine removal process

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2473161A (en) * 1945-09-26 1949-06-14 Purdue Research Foundation Propane chlorination
US2473162A (en) * 1945-12-20 1949-06-14 Purdue Research Foundation Liquid phase chlorination
US2571901A (en) * 1945-12-12 1951-10-16 Niagara Alkali Company Chlorinating process
US2744862A (en) * 1951-04-27 1956-05-08 Olin Mathieson Production of benzene hexachloride

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2473161A (en) * 1945-09-26 1949-06-14 Purdue Research Foundation Propane chlorination
US2571901A (en) * 1945-12-12 1951-10-16 Niagara Alkali Company Chlorinating process
US2473162A (en) * 1945-12-20 1949-06-14 Purdue Research Foundation Liquid phase chlorination
US2744862A (en) * 1951-04-27 1956-05-08 Olin Mathieson Production of benzene hexachloride

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3145155A (en) * 1962-05-24 1964-08-18 Dow Chemical Co Hydrobromination of ethylene
US3320144A (en) * 1962-08-30 1967-05-16 Dow Chemical Co Manufacture of ethyl bromide
US3405046A (en) * 1964-11-03 1968-10-08 Knapsack Ag Process for the manufacture of 2, 2, 3-trichlorobutane
US3528900A (en) * 1966-05-31 1970-09-15 Hooker Chemical Corp Photochlorination process
US3453339A (en) * 1967-05-11 1969-07-01 Chevron Res 1-haloalkyl substituted aromatic hydrocarbons and process for their production
US4978435A (en) * 1987-08-27 1990-12-18 Atochem Free chlorine removal process

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