US1717136A - Chlorination - Google Patents

Description

-., museum 11, 1929.

UNITED STATES PATEN OFFICE.

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' I CHLOBINATIOR.

No Drawing.

My invention relates to chlorination and particularly to bringing together in the vapor phase'chlorine and a substance to be. chlorinated in such manner that explosion is 5 avoided. I v

In clorination there is great danger ofex-' f plosion when chlorine vapor is mixed-with a 4 perature if the pressure of the mixture is su'fiiciently high. Furthermore, a mixture having chlorine and hydrocarbon present in explosive proportions maybe safely handled and safe reaction between the substancescan be efv fected by merely heatin such mixture in the absenee of a flame or lig t that would initiate an explosion. It is therefore imperative to 9 avoid ignition in any part of such a mixture.

However, even though a mixture of chlorine and hydrocarbon is subject to such conditions I of temperature and pressure that spontaneous explosion thereof is not likely to or will not '25 occur, ignition may nevertheless occur at the point where the chlorine and h drocarbon vapors are brought together, un er those other wise safe temperatures and pressures, to produce the mixture. Moreover, ignition may occur at the point where the chlorine and hydrocarbon are brought together even though'the final mixture is not of explosive proportions under the existing temperature and pressure, although in such case explosion does not result'from such ignition. In other words, ignition may occur at the point of junction regardless of whether the resulting mixture is of explosive proportions at the existing temperature and pressure; Also,

there is little danger of ignition at the junction point when some substances are mixed with chlorine at atmospheric temperature but there is considerable danger of ignition at the junction point when the same substances are so mixed at higher temperatures.

Pentaneis an example of such a substance.

I have found that when hydrocarbons are I to be mixed with, chlorine in the vapor phase at a temperature at which the velocity of reaction between them is low, ignition at the junction point will not occur if that vapor into which the vapor is introduced is moving at sufiicient velocity with respect to the junction point. For example, ignition will not' occur if chlorine enters a stream of hydro- Appli'eat'ion fled February 4, 1927. Serial No. 165,876

carbon vapor that is moving at a velocity in excess of one-half of the velocity required for distinctly turbulent flow of the mixture, provldedjthe vapors are brought together at a temperature at which the velocity of the re- .action' between themis low. This'freedom "from danger of ignition exists re ardless of the proportions in which the ch orine and hydrocarbon arebrou ht-together and exist in thefinal mixture. ixtures consisting of chlorine and hydrocarbon in explosive proportions can not be kept standing althou h the constituents of such mixtures may be sa e 1y brought together by the practice of my invention. An 1mportantfeature of my discovery'resides in the fact that in making mixtures of chlorine and hydrocarbon vapors explosion due to'ignition at the junction point is avoided both where the final mixture 1s intendedto contain chlorine-and hydrocarbon in explosive proportion "and when explosive mixtures are accidentally produced during the making of mixtures that are intendedto be in non-explosive proportions.

The velocity at which the mixture will pass with turbulent flow through the conduit that carries it to the reactor, may be determined in various ways. A practical method of determining that velocltv consists in cooling the exterior of the con uit as by circulation of 35 water, placing a thermometer in the conduit with its bulb at the axis thereof, placing a second thermometer in the conduit with its bulb closely adjacent the wall. of the conduit, in-

creasing the velocity of flow until the two thermometers give substantially the same reading. So long as the flow is not rapid enough to produce turbulence the thermometer near the wall of the conduit will have a lower reading, but when the velocity of turbulent flowis reached the resulting agitation within the conduit will cause the two thermometers to have substantially the same reading. I -When the'chlorine is mixed with hydrocarbon by being introduced into the hydrocarbon vapor, ignition at the point of junction is avoided in the practice of my invention at temperatures at which ignition would otherwiseoccur even though, as is very apparent, mixtures ofall proportions occur in the zone. in which the substances come together and while they are becoming disseminated one within the other. i

In the chlorination of substances on a commercialscale, the chlorine vapor and the substance to be chlorinated are brought together and the resultingmixture is conducted to and introduced into a reactor ind-which the reaction is caused to occur at a rapid'rate by conditions imposed upon the mixture in the reactor, as by the application of heat, the

conditions being so maintained that a desired substitution of chlorine takes place'instead of an ignition. If conditions are such that the mixture is delivered to the reactor vwithout substantial chlorinating reaction in transit, thereto'therate of reaction in the mixture passing to the reactor may be said tobe low and practical handling of the mixture is possible without serious danger ofignition; and further references herein to a low rate ofreaction are intended to refer to such a safe rate'.

Thus, as a specific example of the application of my invention, it is possible to introduce chlorine into vpentane vapor to produce a mixture of even equal proportions. and

having a temperature of 90 C. without the occurrence of ignition at the point of junction provided the stream of pentane is moving in excess of one-half of the velocity required for distinctly turbulent flow of the mixture, 6. g., fifty feet per second, but ignition would occur at that temperature at the point of junction if the pentane were not moving with the necessary velocity even though the proportion of pentane to chlorine were as high as 5:1, and perhaps highen Conversely, if hydrocarbon vapor is introduced into a stream of chlorine vapor, the

vapor becomes less than fifty feet per second. The velocity at which the vapor must be moving in order to prevent, in accordance with my invention, an ignition at the junction point, depends upon the ratio of chlorine to hydrocarbo and upon the temperature of, the resultin mixture and that velocity must'be increased as thetempera' ture increases and as the proportions-of the mixture approach the Iproportions of the most explosive mixture.

peratures below 150 C.

In practice, however, it 'is advisable to maintain a higher velocity than is necessary for normal operation because accidental have found that the. velocity of reaction between vapors ofpenhugs and chlorine vapor is very low at temvariations of temperature and of proportions of the mixture might otherwise produce conditions requiring such higher velocity to certainly prevent ignition. The existence of a flame at the point where chlorine and the hydrocarbon mix causes explosionof explosive mixtures, or, if the mixture does not ex-' plode as a result of ignition, causes the production of products that are not desired, as described in Patent No. 1,286,353. In:-the

practice of this invention the existence of such a flame 1s prevented by maintaining such conditions with respect to the velocity of the vapors at the time they are brought together that such a flame cannot exist or form.

A further feature of my invention is the chlorination'of substances, and particularly saturated aliphatic hydrocarbons of three to six carbon atoms, by causing the initiation and completion of the chlorinating reaction to occur promptly after the chlorine and substance are brought into contact, and thereby preventing formation of some chloride before the mixture comes into the influence of the reacting'agent (heat or light) and the consequent formation of undesirable higher chlorides after the mixture comes into the influence thereof.

What I claim and desire to secure by Letters Patent is:

1'. In the chlorination of hydrocarbons that exist in vapor phase at temperatures at which their rate of reaction with chlorine is low, the step comprising introducing chlorine into the hydrocarbon vapor while maintaining the latter in motion at a velocity in excess of one-half of thatrequired for distinct turbulent flow ofthe mixture.

2. In chlorination of hydrocarbons wherein chlorine is introduced into the hydrocarbon, the step comprising maintaining the vapor of a hydrocarbon, that exists in vapor phase at a temperature at which its rate of reaction with chlorine is low, in motion at'a velocity sufliciently high to prevent persistence of ignition at the point of introduction ing at that point.

of the chlorine under the temperature existv3'. In chlorination of hydrocarbons, the I step com rising bringing together chlorine vapor and vapor of a hydrocarbon that exists'in vapor phase at a temperature at whlch its-rate of reaction with chlorine is low, by maintaining oneof the vapors in motion at a sufficient velocity, with respect to the point at which the vapors are brought togetheryt'o prevent persistence of ignition of the mixture at that point at the existing temperature while introducing the other vapor into the vapor that is in motion.

4. In chlorination of hydrocarbons, the step comprising bringing together chlorine vapor and vapor of a hydrocarbon that exists in vapor phase at a temperature at which its rate of reaction is low, by maintaining one of the vapors in motion at a velocity not less than fifty feet per second in a conduit not more than eight inches in diameter with respect to the point at which the vapors are brought together while introducing the other vapor into the vapor that is in motion.

5. In the chlorination of pentanes the step perature.

6. In thechlorination of pentanes the step comprising introducing chlorine vapor into pentane vapor while maintaining the pen tane vapor 1n motion at a velocity in excess of fifty feet per second in a conduit not more than eight inches in diameter with respect to the point at which the chlorine is introduced.

7 In the chlorination of pcntanes the step comprising introducing chlorine vapor into pentane vapor While maintaining thepentane vapor in motion at a sufficient velocity with respect to the point at which the chlorine is introduced to prevent persistence of ignition of the mixture while maintaining the temperature of the mixed vapors below 8. In the chlorination of pent-anes the step comprising introducing chlorine vapor into pentane vapor while maintaining the pentane vapor in motion at a velocityin excess of fifty feet per second in a conduit not more than eight inches in diameter with respect to the point at which the chlorine is introduced I while maintaining the temperature of the mixed vapors below 150 C.

9. In the chlorination of'hydrocarbons, the step comprising bringing together chlorine vapor and vapor of a hydrocarbon that exists in vapor phase at a temperature at which its rate of reaction with chlorine 1s low, by

maintaining one of the vapors in motion at a velocity in excess'of one-half of that required for distinct turbulent flow thereof, with respect to the point at which the vapors are brought together, while introducing the other'vapor into the vapor that is in motion.

10. In the chlorination of pentanes, the step comprlsmg bringing together chlorine taining one of the vapors in motion, with respect to the polnt at which the vapors are brought together, at a velocity in excess of vapor and vapor of the pentanes, by mainone-half of that required for distinct turbulent flow thereof while introducing the other vapor into the vapor that is in motion. In testimony whereof, I have signed my name to' this specification.

EUGENE ,E. AYRES, JR.