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Патент USA US2406195

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Patented Aug. 20, 1946
2,406,195
UNITED STATES‘ PATENT‘ OFFICE
2,406,195
MANUFACTURE OF THE HIGHER
CHLORIDES OF METHANE
Oliver W; Cass,.Niagara Falls, N. Y., assignor ‘to
E. I. du Pont de Nemours & Company, Wilming
ton, Del‘., a corporation of Delaware
N'o Drawing. Application February 17, 1944,
Serial No. 522,799
2 Claims.
(Cl. 260—65'7')
2
This invention relates to a new and improved
process for preparing halogenated organic com
pounds. More particularly, it relates to a new
and improved method for preparing the higher
chlorides of methane, such as methylene chlo
ride, CI-IzC‘lz; chloroform, CHCl3-; and carbon
tetrachloride, CC14.
‘
In previous attempts to overcome this inherent
difficulty in the chlorination process, it has been
proposed to admix the entire reaction mixture
resulting from such a chlorination with an
amount of methanol essentially equivalent to the
hydrogen chloride content of the reaction mix
ture. The mixed gases were then passed through
My invention is primarily concerned with a'
a reaction chamber containing catalytic mate
new and improved procedure for the. chlorina
rial, for example alumina gel or fused zinc chlotion of methane, methyl chloride, or mixtures 10 ride, in whichv chamber a reaction between the
of these two compounds in varying, proportions,
whereby mixtures of the desired higher halide
derivatives of methane result. By the utiliza
vaporized methanol and hydrogen, chloride oc
curred, this reaction resulting in the formation
of further amounts of methyl chloride and water,
tion of my improved process for producing these
the latter being formed as a icy-product. In this
higher chlorides of methane, it is possible to 15 previously suggested processv the ?nal reaction
secure yields of chlorinated products that are
product was then separated into the following
much higher, from the viewpoint of the amount
constituents: (1.) the water, containing unre
of available chlorine utilized to form valuable
acted hydrogen chloride and methanol; (2): the
products, than previously possible.
higher halides of methane, including methylene
t is well understood in the art that the higher 20 chloride, chloroform, and carbon tetrachloride;
halides of methane, particularly methylene
chloride, chloroform, and carbon tetrachloride,
may be readily prepared by chlorinating meth
and (3) the methane or methyl chloride, or mix-- -
ture of the, two. In utilizing this process it. was
then necessary to dry both the higher halides
ane, a lower chlorinated methane halide such
of methane component, as well as the gaseous
as methyl chloride, or by the chlorination of 25 mixture of methane, methyl chloride, or, mixture
mixtures of these compounds.
This chlorina
tion. reaction has been carried out in a number
of ways, such as by reacting the starting mate
rials at an elevated temperature in the absence
of any catalytic or activating agent; by reacting
the starting materials at a moderately elevated
temperture in the presence of catalytic agents
possessing large surface areas such as activated
carbon; or by carrying out the reaction at still
lower temperatures in the presence of actinic
radiation as an activating agent. , Regardlessof
the particular procedure adopted, the funda
of methane and » methyl chloride.
The dried
higher halides of methane could then be Worked
up by known methods, While the gaseous mixture
was again recycled to the chlorination process.
By;utilizing this procedure it was possible to
recover at least a portion of the hydrogen chlo
ride formed as by-product in the substitution
chlorination reaction in the form of methyl chlo-_
ride, which could then be utilized in subsequent
chlorinations.
However, in the practical operation of such a
process, particularly on ‘the industrial scale, a
mental reaction involves a substitution of chlo
large number of dif?culties are encountered. .In
rine for hydrogen atoms in methane or methyl
the original chlorination reaction, especially
chloride with the formation of the higher chlo 40 when the chlorination is conducted, at relatively
rides of methane and the simultaneous 'pro
high temperatures, or With relatively high ratios
duction of hydrogen chloride as a by-product.
of chlorine to. the amount of the other reactants,
In practice the chlorination reaction is ordinarily
small quantities of carbon as'well as high boil
incomplete, as, in order to controlthe heat of the
ing condensation products are formed. These
reaction, only a portion of the starting mate 45 materials tend to accumulate upon or in the cat
rial, whether that material be methane, methyl
alyst mass which is utilized after the vaporized
methanol has been added to the reaction prod
uct in order to bring about reaction between the
methanol and the by-product hydrogen chloride
evident,,however, that an inherent defect in the
economical operation of this process by any of 50 to form further amounts of methyl chloride. As
the procedures speci?ed is the production of the
a consequence the catalyst mass becomes fouled
relatively worthless compound, hydrogen chlo
and rapidly loses its activity, necessitating fre
ride,» as a Icy-product, this product being produced
quent and uneconomical replacement of the cat
in amount equivalent to half of the chlorine sup
alyst body. Moreover, the hydrogen chloride is
plied to the process.
diluted by the entire reaction mixture so that it
chloride, or a mixture of the two, is chlorinated
per pass through the reaction system. It is
2,406,195
3
4
.
is impossible to secure even fairly complete uti
lization of the hydrogen chloride without in
.
ceiver is maintained at a temperature su?iciently
high to insure the removal of substantially all the
hydrogen chloride present, as well as a major
portion of the unreacted methyl chloride.
The condensation of the, major portion of
ther disadvantage, under the conditions main—
higher halides of methane at the top of the frac
tained in the reaction between the methanol
tionation column, and the separation out of the
and by-product hydrogen chloride, the higher
reaction product of substantially all the gaseous
halides of methane present, i. e. methylene chlo
constituents thereof, 1. e. the hydrogen chloride
ride, chloroform, and carbon tetrachloride, react‘
with the steam produced as by-product vin the“10 vand the'major portion of the methane or methyl
chloride,'I readily accomplish by maintaining a
hydrogen chloride-methanol reaction.” " The net‘
temperature gradient throughout the column.
effect is a decrease in the yield ofnthese higher
The actual temperature to which the top of the
halogenated methane derivatives, which, to some
column must be cooled in order to effect substan
extent, o?sets the advantages resulting from uti
tially complete removal of the higher chlorides
lizing the by-pro-duct hydrogen chloride to form
of methane will depend on the nature of the
further amounts of methyl chloride.
' '
chlorination. For example, if the reaction in-'
II have now found that the advantages incident
volves the chlorination of methyl chloride alone,
to the utilization of by-product hydrogen chloride
troducing economically excessive quantities of
methanol into the reaction mixture.
As a fur
wherein it is reacted with methanol to form fur
ther amounts of chlorinated products may be
retained, at the same ‘time avoiding the disad
with the use of some l‘to 3 mols chlorine per 5
vantages inherent in previously available proce-v
mols methyl chloride, temperatures of —18°. C.
to _—24° C. are suitable to, insure removal of 90-95
per cent of the higher halides of methane from
dures.
This is accomplished by a new and line
theoff-gas issuing from-the fractionating column.
proved process for handling the reaction products
of the chlorination system and for converting the
by—product hydrogen chloride by reaction with
On the other hand, if methane-methyl chloride
mixtures are being chlorinated, temperaturesiof
methanol to methyl chloride.
7
' ,
Accordingly, it is one object of my invention‘ to
provide an improved process for thepreparation
' of the 5 higher'chlorides of methane; namely, 30
methylene chloride, chloroform, and carbon tet
rachloride, which will‘ permit the utilization of
—50° to .-70°‘ C. may be required; or, if desired,
. the fractionation column may be operated under
pressure at somewhat higher temperatures.
' The actual temperature under any,v given set of.
conditions should be such that 90-95v per cent of
the higherhalides of methane are removed from
the o?-gas from thetop of the column.
‘At the bottom of 'the fractionation column a
temperature sufficient to ensure saparation of the
35 hydrogen chloride and av major portion of the
methyl chloride constituent is satisfactory, a
attempts to utilize the byeproduct hydrogen
temperature of approximately 40° to 50°. C., for
chloride. .Another object of my invention’ is‘ to
example, giving very e?icient results.
provide a new andimproved method for the man~
It is thus possible to withdraw from the're- '
ufacture of the higher halides of methane wherein
ceiver an anhydrous, essentially acid-free mix
the by-product hydrogen chloride is economically
ture of the higher halides of methane which,
f utilized to form valuable products in a cyclic proc
fromv that point on, may be handled in ordinary
ess under circumstances wherein fouling and in
steel equipment under substantially atmospheric
activation of the catalytic massis avoided. Still
pressure. At the sametime there is secured from
another object of my invention is the provision V
the top of the fractionation column a mixture
of a method wherein this by-product hydrogen
consisting essentially of hydrogen chloride to
chloride can‘ be utilized under circumstances
by-product ‘hydrogen chloride inthe formation
of furtheramountsof chlorinated hydrocarbon
without thedisadvantages incident to previous
' wherein dilution of the hydrogen chloride content
of the reaction mixture is avoided and objection
able side, reactions between the higher chlorinated
halides of methane and by-product steam do not "
occur. These and still other objects of my proc
ess will be apparent from the ensuing disclosure
of certain illustrative preferred embodiments
thereof.
In carrying out my improved procedure, meth
ane, methyl chloride,v or mixtures of these two
compounds in various proportions, are reacted
withchlorine in the usual manner, utilizing the
high temperature noncatalytic method, the mod
erately elevated temperature catalytic method, or. ‘
the reaction as carried out atrelatively low tem
peraturesrin the presence of actinic radiation.
The manner of carrying out all these‘ chlorina
tions isrfully understood in the’art, and'no de
tailed explanation thereof is necessary.’ The re
action gases coming from. the chlorination cham
her are, in accordance with my improved method,
passed directly into a fractionation column. At
gether with the unchlorinated starting materials,
whether those starting materials bef methane,
methyl chloride, or a mixture of the two. This
gaseous mixture from the top of the fractiona
tion column is then admixed with methanol in
quantity approximately equivalent to the hydro
gen chloride present therein, and thecombined
gaseous mixture then passed into a suitable re
action zone‘ where the methanol and hydrogen
chloride react to form methyl chloride and water.
The water, together withtraces of unreacted
methanol, may then be removed from the gas
stream by an appropriate means, the major por
tion of the unreacted hydrogen chloride beingrdis
‘solved therein and removed therewith. It is not,
however, necessary to remove the'unreacted hydrogen chloride. The gaseous mixture, now en
riched by the newly formed methyl chloride is
recycled to the chlorination unit.
'
'
i
It is apparent from the process as described
that each of the difficulties inherent in previous
attempts to utilize byejproduct hydrogen chloride
in the formation of further, amountsof. chlori
the top of this column the gas mixture is subjected
to a temperature low enough to cause condensa 70 nated products has been overcome by the scrub
tion of the major, portion of the desired product,
bing, action occurring in the fractionation'col
umn. The particles of free carbon present, to
the higher halides'of methane, present therein.
gether with highboiling condensation products
The condensate is allowed to ?ow back through
and tars, are scrubbed‘ from the mixture which, is
the column and iscollected in the receiver at
the base of the fractionation column. This re 75 to'be fed to the catalyst mass employed. inpthe
‘2,406,195
6
5
preparation of additional methyl chloride. As a
result the catalyst mass retains its activity in
de?nitely. Furthermore, a considerable concen
tration of the hydrogen chloride present in the
gaseous mixture has been effected by the removal
from the mixture of the higher halides of meth
ane, thus permitting greater utilization of the
by-product hydrogen chloride. It will also be
evident that the higher halides of methane are
never subjected to the action of steam at high
temperatures, and, as a result, they are not de
composed by reaction therewith, there being thus
obtained an improved yield of these higher hal
ides. Other and additional advantages reside in
the separation of these higher halides of meth
ane in a form in which they may be readily han
dled in steel equipment at atmospheric pressure,
due to the substantially complete removal there
from in the process of the hydrogen chloride and
low boiling raw materials, such as methane or
methyl chloride, initially present therein.
In the appendedclaims the term higher chlo
rides of methane is to be understood as includ
ing all chlorides of methane containing a per
remove high boiling products, carbon and tars
from said uncondensed portion while maintain
ing the hydrogen chloride and a major portion of
the methyl chloride in the gaseous phase; adding
methanol to said gaseous portion and passing
the resulting gaseous mixture in contact with a
catalytic mass promoting reaction between meth
anol and hydrogen chloride at an elevated tem
perature, thus forming methyl chloride and wa
ter; removing water and unreacted methanol
from the resulting gaseous reaction product; and
returning said puri?ed gaseous reaction product
to prepare further amounts of the chlorides of -
methane.
2. The process for preparing the chlorides of
methane which comprises reacting a material se
lected from the group which consists of methyl
chloride and mixtures of methane and methyl
chloride with chlorine; cooling the resultant gas
eous reaction product, condensing the higher
chlorides of methane, scrubbing the uncon
densed portion of said reaction product with the
condensed portion so as to substantially complete
1y remove high boiling products, carbon and tars;
centage of chlorine higher than that present in 1
separating out said condensed portion, high boil
methyl chloride.
ing products, carbon andvtars from said uncon
7
The above description is intended to be illus
trative only. Any modi?cations of or variations
therefrom which conform to the spirit of the in
vention are intended to be included within the
scope of the appended claims.
I claim:
1
1. The process of preparing the chlorides of
methane which comprises reacting a material se
‘lected from the group which consists of methyl ‘
densed portion while maintaining the hydrogen
chloride and a major portion of the methyl
chloride in the gaseous phase; adding methanol
to ‘said unco-ndensed portion and passing the re
sulting gaseous mixture in contact with a cata
lyst mass promoting reaction between methanol
and hydrogen chloride at an elevated tempera
ture, thus forming methyl chloride and water;
and removing water and unreacted methanol
from the ‘resulting gaseous product, and return- '
chloride and mixtures of methyl chloride and
ing the puri?ed gaseous reaction product to pre
methane with chlorine; cooling the resultant
pare further amounts of the chlorides of meth
gaseous reaction product, condensing the higher
chlorides of methane, scrubbing the uncondensed
portion of said reaction product with the con 40
OLIVER w. oAss,
densed portion so as to substantially completely
ane.
'
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