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Патент USA US2121954

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Patented June 28, 1938_
[UNITED STATES PATENT OFFICE
2,121,951
METHOD OF DEHYDRATING ‘AQUEOUS
ALCOHOLS
George Lewis Cunningham, Niagara Falls, N. Y.,
. assignor to The Mathieson Alkali Works, Inc.,
vNew York, N. Y., a corporation of Virginia
No Drawing. '
ApplicationlDecember 29, 1936
Serial No. 118,083
'
9 Claims. (Cl. 260-156)
My invention, when operated in its simplest
This invention relates to an‘ improved process
for the production of anhydrous or absolute al
cohols from hydrous mixtures of such alcohols.
More particularly it relates to a simple and ?ex
ible method for the dehydration of hydrous alco
form, involves reacting an aqueous alcohol with -
an alkali metal amalgam in the presence of elec
trically conducting but non-amalgamating con
tact electrodes in contact with the amalgam and
the alcohol. The use of such contact electrodes
in the formation of lower alcoholates is claimed.
hols whose boiling point at atmospheric pressure
does not exceed about 125°C.
1
A wide variety of methods have been proposed in my copending application‘serial No; 65,491,
which have been used with varying degrees of .. ?led February 24, 1935. These electrodes may
success in the past for the preparation of an: be. used with advantage in the present instance, .
hydrous alcohols.‘ Many of these methods have since they cause the amalgam to react with‘ the‘
involved the use of hygroscopic saltsor salts water‘to form‘ the corresponding alkali metal hy-'
which readily formedhydrates such as, for ex
droxide prior to reaction with the alcohol. For ,
Yl'io
various reasons it is advantageous to use amal
ample, CaClz or CaSOr or NazSOr. 'The use of
14.5 .
gams containing less than 1% of the alkali metal.
While such amalgams will react with the water
scopic salts has also been proposed. . The use of
these agents has been unsatisfactory commercial- _' in the aqueous alcohol before reacting with the‘;
glycerol alone or in combination‘ ‘with hygro
ly. due to a variety of causes. ‘For example CaClz
alcohol, the speed and efficiency of the reaction‘ ‘ i
unites chemically with alcohol torform addition, is materially increased by operation in the pres
20. compounds. The recovery of‘ the dehydrating
ence of the contact electrodes mentioned above.
ingredients is frequently involved and expensive, The reaction is vcontinued until the number of
20; 1
necessitating an extensive outlay for‘equipment. , alkali metal atoms in solution is slightly in ex
cess of the number of water molecules originally
These operations are-cumbersome and commer
Reagents such as metallic
present in the aqueous alcohol used, that is a
calcium, aluminum or magnesium have beenused
cially unsatisfactory.
with some success but have not been practical .
molar quantity o?alkali metal as amalgam not
less than the molar quantity'of water present is
commercially.
reacted with‘the aqueous alcohol.
,
1
The distillation method has been mcresuc
cessful than any of the foregoing examples. This
30! involves conducting a distillationiof an‘ aqueous
alcohol solution of an alkali in the presence of
a' liquid which yields an azeotropic mixture.
This method permits‘ considerable economy of
operation, but its maximum e?iciency is reached
-.only on very large scale operations where con
tinuous operation and close control can be eco-'
nomically
-
4-50’
applied.
'
- ’
~
‘
The standard of excellence for manyyears for
the removal of the last traces of H20 fromhy
drous alcohols has been metallic sodium. This is
7 used successfully in the laboratory but certain
economic and chemical dif?culties have made its _
commercial use on a large scale inexpedient.
The alcohol ,
solution is then separated from the amalgam
layer; heated, and distilled to recover as a dis
tillate the pure anhydrous alcohol in nearly 100%
yield. The following example will serve to illus
trate this method of operation:
Example I
I
-‘ >
-
‘
'
"
.
250 parts (by weight) of aqueous ethyl alcohol
3 5 Z.
containing 6.5 parts H2O are treated with .3%
' sodium amalgam, using a carbon contact elec-'
trode, until 10 parts of sodium have reacted. The
solution is separated from the amalgam and 240'
parts of anhydrous alcohol are distilled there 40.“,
I from.
~ The residue from the distillation in the above
example‘ is largely NaOH. This may be returned
These difficulties include such considerations as toan electrolytic cell to produce more sodium
'Ihigh cost of metallic Na and the dif?culties of amalgam, thus making ‘the process cyclic and 451,,
’
.
shipping and‘ handling it, and the production vof more economical.
According to a further embodiment of my in
hydrogen and heat when used with hydrous al
vention, aqueous alcohols containing not more
cohols thus introducing aserious ?re and ex
than four carbon atoms'may be completely de
plosion hazard.
without reacting the entire aqueous so-'
.501 According to one embodiment of the present hydrated
lution with the amalgam. In this method of
. invention, I have provided a process which pos
' sesses‘ all the advantages of the use of metallic
Na but does not possess the attendant disad
vantages. Large quantities of absolute alcohol
.5101 j including methyl, ethyl and isopropyl are used in
industrial processes‘ where even the presence or
a trace of water renders the alcohol un?t for use.
I The process of the present invention affords a
commercially satisfactory method of producing
1 such alcohols.
operation a certain fraction of the alcohol to be '
' dehydrated is treated according to the method
describedabove with the exception that the re
action is caused to proceed further, by reaction. 55
of additional alkali metal, so that in addition to
the hydroxide produced by reaction with the
water present there is also produced a quantity
of the corresponding alkali metal alcoholate.
The quantity. of alcoholate so produced should
2
2,121,954
be su?icient to react with the entire amount of
water present in the remainder of the aqueous
alcohol. 'I'his‘treated fraction of the alcohol is
such as graphite or castiron, until the solution
contains upwards of 14% of sodium methylate.
An appropriate amount of this alcoholic solution
is added to aqueous tertiary amyl alcohol. The
solution mixture is heated, anhydrous methyl al
then mixed with the remainder, the mixture
heated and the entire quantity of anhydrous al
cohol recovered from this mixture by distillation. cohol distilling 01f ?rst, followed by the desired
The general reaction involved in the second step anhydrous tertiary amyl alcohol, and leaving
behind solid sodium hydroxide. A more detailed
of this mode of operation may be typi?ed as fol
lows:
10
C2I-I5ONa+H2O:C2H5OH+NaOI-I
example will serve to- illustrate further the opera
tion‘ according to this embodiment of my inven
tion:
Example III
10
Following is an illustrative example of the oper
ation of my invention according to this embodi
250‘ parts of anhydrous methyl alcohol are re
ment.
" acted with 0.7 %_ sodium amalgam in the presence
Example II
15
15
250 parts of anhydrous methyl alcohol are of a castiron grid until 15 parts of sodium have
reacted.
The
alcohol
solution
is
separated
from
reacted with .l% sodium amalgam using a steel the amalgam and added to 1000 parts of aqueous
alloy contact electrode until 15 parts of sodium
have reacted. The methyl alcohol solution of
20 sodium methylate so produced is separated and
1000 parts of hydrous methyl alcohol containing
11.5 parts of H20 are added to the separated al
cohol solution.‘ The resulting alcohol solution is
distilled to recover as distillate 1238.5 parts of
257 absolute methyl alcohol. 26 parts of sodium hy
droxide is left in the still. This is returned to
the amalgam cell to produce more sodium amal
gam, 250 parts of the anhydrous alcohol is
passed through the alcoholate cell and the cycle
30' is repeated.
It will be apparent that, in practicing the pres
ent invention, the above-described two-step proc
ess can beinitiated by using a small fraction of
the anhydrous alcohol to prepare the alcoholate
351 which in the second step reacts with the H20 of
the aqueous alcohol to be dehydrated. In this
case also the alkali residue may be returned in a
cyclic operation to produce more fresh amalgam.
Alkali metal amalgams react with alcohols with
decreasing energy and rapidity as the number of
‘ carbon atoms in the molecule increases, as the
concentration of amalgam is decreased, and as the
temperature is lowered. For various reasons,
chemical and economic, therefore, it is not ex
pedient. to- react alcohols containing more than
four carbon atoms’ with alkali metal. amalgams.
A further embodiment of the present invention
overcomes this di?iculty. According to this modi
?cation, aqueous alcohols containing four or
more carbon atoms may readily be dehydrated.
50
This is accomplished by a two-step process in
which a lower alcohol, either hydrous or anhy
drous having a fewer number of carbon atoms, but
not more than four, is reacted with an alkali
metal amalgam in the presence of a suitable con
tact electrode as described above to produce an
alcoholic solution of the corresponding alcoholate.
This solution is separated from the amalgam and
an appropriate amount is added to the aqueous
60 higher alcohol to be dehydrated. An amount of
the alcoholate should be added such that there
will be present one molecule of alcoholate for
each molecule of water in the aqueous higher a1
cohol. The mixture is heated and the lower an
65. hydrous alcohol distilled off ?rst. On further dis
tillation the higher alcohol comes off leaving be
hind a residue of NaOI-I. In commercial prac
tice, this sodium hydroxide residue may then be
returned to the amalgam cell as described above,
70 and the lower anhydrous alcohol which’ distills
o? ?rst may be recycled to the original reaction
vessel in order‘ to produce more of the alcoholate
of‘ the lower alcohol. For example, methyl al
cohol may be reacted with ‘sodiumvv amalgam in
the presence of‘ some suitable contact electrode.
tertiary butyl alcohol containing 11.5 parts of
H20. The reaction mixture is distilled. Anhy
drous methyl alcohol distills off ?rst, followed by
the desired anhydrous tertiary butyl alcohol,
leaving 26 parts of sodium hydroxide in the still.
It will be understood from the foregoing that
the various butyl alcohols may be dehydrated by
the described methods involving the direct action 25
of the amalgam which includes the use of ' a por
tion of sodium butylate in butyl. alcohol to de—
hydrate a larger portion of aqueous butyl alco
hol; and also by the use of the alcoholate of a
lower alcoholate as presentedv in Example III
above. I In general the lower reaction rate in
volved when the butyl alcohols are employed,
causes the last described procedure as exempli
?ed in Example ‘III to be used with better ad~
vantage with butyl alcohols.
35
. The alcohols which may be successfully dehy
drated by my invention are those the boiling
points of which at normal atmospheric pressure
are not higher than about 125° C. One known
method for the preparation of the alcoholates of 4.0
the higher alcohols is to react the anhydrous al
cohol with an alkali metal hydroxide, and then
to distill off the water formed in the reaction.
The typical reaction involved may be expressed
45
as follows: '
where R represents the residue of mono or poly
hydric alcohol and M represents an alkali or al
kaline earth metal. In such operations, however, 50
the “R” grouping must be relatively large and the
boiling point of the alcohol ROI-I high in order
to permit the H20 to be distilled from the mixture
without any of the alcohol.
In the process of
the present invention the formation of alcoholate 55
by this reaction is avoided, and the ROH is dis
tilled away from the MOI-I without reacting with
it to form the corresponding alcoholate and water.
It has been found that alcohols whose boiling
point is not higher than about 125° C. may be so 60
distilled away from the hydroxide formed by the
reaction between the alcoholate and water. Thus,
the butyl alcohols and certain of the amyl alco
hols, such as for example tertiary amyl alcohol
(B; P. 102° C.) or methyl-propyl carbinol, a sec
65.
ondary amyl alcohol (B. P. 119° C.) may be suc
cessfully dehydrated by my process described
above and illustrated in Ex. III. My invention,
on the other hand, is not applicable to normal
primary amyl alcohol (B. P. 138° C.) .
I claim:
1. The method of dehydrating aqueous alco
hols, wherein an aqueous alcohol is reacted with
a molar quantity of alkali metal amalgam not
less than the molar quantity of H20 ‘originally
70
3
2,121,954
present in the aqueous alcohol, said reaction
6. The method of dehydrating aqueous alco
being conducted in the presence of an electrically
hols containing not more than four carbon atoms,
conducting but non-amalgamating electrode in , wherein an aqueous alcohol containing not more
contact with the amalgam and the alcohol,
separating the alcoholic solution from the amal
than four carbon atoms is reacted with a molar.
quantity of alkali metal amalgam not less than
gam, heating the mixture, and‘ recoveringv the the molar quantity of H20 originally present in
‘thus formed anhydrous alcohol ‘by distillation. the aqueous alcohol,- said reaction being con
ducted in the presence of an electrically conduct
2. The methodof dehydrating aqueous alco
10
hols containing not more than four carbon . ing but non-amalgamating electrode in contact.
atoms, wherein an aqueous alcohol containing with the amalgam and the alcohol, separating 10
not more than four carbon atoms is reactedwith the alcoholic solution from the amalgam, heating
a molar quantity of ' alkali metal amalgam in
' excess ofthat necessary to react with the water
the mixture, recovering the thus formed anhy
drous alcohol by distillation, and returning the
present, said reaction being conducted in the alkali metal hydroxide residue to an electrolytic
presence of an electrically ‘conducting but non
cell for further production of the alkali metal
,
amalgamating electrode. in contact with the amalgam.
7. The method of dehydrating aqueous alco
amalgam and the alcohol, separating the alco- '
holic solution of the thus formed alkali metal hols containing not more than four carbon atoms,
hydroxide and alkali metal alcoholate, causing wherein an aqueous alcohol containing not more
20 said solution. to react with another portion of than four carbon ‘atoms is reacted with a molar 20
the aqueous alcohol containing not more than quantityof alkali metal amalgam in excess of
four carbon atoms, heating the mixture, and that necessary to react with the water present,
recovering the thus formed anhydrous alcohol
said reaction being conducted in the presence of ,
by distillation.
an electrically conducting but non-amalgamating
'
3. The methodof dehydrating aqueous alco-,
hols containing not more than four carbon
. atoms, wherein an'anhydrous alcohol having not
more thanv four carbon atoms is reacted with an
alkali metal amalgam in the‘ presence of an
30
electrically conducting but non-amalgamating
electrode in contact with the amalgam and the
alcohol, separating the alcoholic solution of the
thus formed alcoholate, reacting it with the
aqueous alcohol containing not more than four
35
carbon atoms, heating the mixture, and recov
ering the thus formed anhydrous alcohol by dis
. tillation.
'
4. The method of dehydrating aqueous alco
hols containing not less than four carbon atoms
whose boiling point is less‘than about 125° (3.,
wherein an aqueous alcohol having not more
than four carbon'atoms is reacted with a molar
quantity of alkali metal amalgam in excess of
that necessary to react with the water present,
said
being conducted in the presence
45 of anreaction
electrically conducting but non-amal
gamating electrode in contact with the amalgam
‘and the alcoholito' form the corresponding alkali
metal alcoholate, separating the alcoholic solu
of the thus formed alcoholate, reacting it
50 tionv
with the aqueous alcohol to be dehydrated which
electrode in contact with the amalgam ‘and the 25
alcohol, separating the alcoholic solution of the,
thus formed alkali metal hydroxide and alkali
metal alcoholate, causing said solution to react
with another portion of the aqueous alcohol con
taining not more than four carbon atoms, heat» 30
‘ing the mixture, recovering the thus formed an—
hydrous alcohol by distillation, and returning
the alkali metal hydroxide residue to an electro
lytic cell for, further production of the alkali
metal
amalgam.
.
'
.
8. The method of dehydrating aqueous alco
hols containing not more than four carbon atoms,
wherein ananhydrous alcohol having not more
than four carbon atoms is reacted with an alkali
metal amalgam in the presence of an electrically 40
conducting but non-amalgamating electrode in
contact with the amalgam and the alcohol, sepa
rating the ‘alcoholic solution of the thus formed
alcoholate, reacting it with the aqueous alcohol
containing not more than four carbon atoms,
45
heating the mixture, recovering the thus formed ‘
anhydrous alcohol by distillation, and returning
the alkali metal hydroxide residue to an electro
lytic cell for further production of the alkali 50
metal amalgam.
‘
' contains not less than four carbon atoms, heating
9. The method of dehydrating aqueous alco
the mixture,'recovering the alcohol having not 1 hols containing not less than four carbon atoms
more than four carbon atoms by distillation, and whose boiling point is less than about 125° CL, ' V
recovering the desired anhydrous alcohol con
wherein an anhydrous alcohol containing not
55 taining not less than four carbon atoms by fur
ther distillation.
.
5. The method of dehydrating aqueous alco
hols containing not less than four carbon‘ atoms
whose boiling point is less than about 125° 0.,
j 60
wherein an anhydrous alcohol containing not
more than four carbon atoms is reacted with 'an
alkali metal amalgam inthe presence of .an elec
_ trically conducting but non-amalgamating elec
trode in'contact with‘ the amalgam and the alco
holv to form the corresponding alkali metal al
coholate, separating the alcoholic solution of the
thus formed‘ alcoholate, reacting it with the
75
more than four carbon atoms is reacted with an ‘
alkali metal amalgam in the presence of an elec
trically conducting but non-amalgamating elec
trode in contact with the amalgam and the alco
hol to form the corresponding alkali metal al
coholate,.separating the alcoholic solution of the
thus formed alcoholate, reacting it with the
aqueous alcohol to be dehydrated which contains
not less than four carbon-atoms, heating the 65
mixture, recovering the alcohol'having not more
than four carbon atoms by distillation, returning
said alcohol to further react with the alkali metal
aqueous alcohol to be dehydrated which contains
amalgam, recovering the desired anhydrous al
‘not less than four carbon atoms, heatingthemix
ture, recovering the alcohol having not more-than
four carbon atoms by distillation,,and recover
ing the desired anhydrous alcohol containing not
less than four carbon atomsby further distil
cohol containing not less than four carbon atoms
lation.
>
,
'
by further distillation, ‘and returning the alkali
metal hydroxide residue to an electrolytic cell
for further production of the alkali metal
amalgam.
‘
GEORGE LEWIS CUNNINGHAM.
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