w .lm H A L E E A L
1,951,280
Cwmc exmA'rIoN 017' ALcoHoLs To FORM ALIPHATIC Actus ‘
Filed Oct. 3. 1931
VêcaaM/‘Da/MP
"
Aq
1
1,951,280
Patented Mar. 13, 1934
UNITED STATES
PATENT
OFFICE
y
‘
1,951,280
CYCLIC OXIDATION OF ALCOHOLS TO
FORM ALIPHATIC ACIDS
William J. Hale, Midland, Mich., and William l S.
Haldeman, Monmouth, Ill.
Application October 3, 1931, Serial No. 566,802 ’
(Cl. 260-116)
tity of said oxidizing agent available to the other
The present invention concerns an improved
involved.
method for preparing an aliphatic acid whereby reactants
We have now found that 'hydrogen may be
an aliphatic alcohol is dehydrogenated to form present in materially lower concentration than
the corresponding aldehyde and the latter is oxi
9 Claims.
5 dized to form the ldesired acid, said reactions be
that produced through dehydrogenating alcohol 65
ing conducted conjointly and in such a way as to
avoid the presence of hydrogen in high concen
according to the method described in co-pending
application, Serial No. 284,271, and still substan
tially prevent the undesirable decomposition ot
tration during the period in which said reactions the acid product, and that we can remove a large
,
portion of the hydrogen by-product, substantially 70
10
In the drawing, the iigure is a diagram as it is formed and as the nearly pure element,
matic illustration of one form of apparatus for thereby making possible the production of nearly
carrying out the method.
pure hydrogen as a by-product and the produc
In our co-pending application, Serial No. tion of the desired acid in a yield appreciably
284,271, iiled June 9, 1928, we have described a- higher than is possible when such acid is pre 75
process whereby a gaseous mixture comprising an
15 aqueous alcohol and its corresponding aldehyde pared from the corresponding alcohol according
is passed, at a temperature between 150 and 350 to procedure described -in our aforementioned co
application.
degrees C., first into contact with a catalyst ca pending
To the accomplishment of the'foregoing and
pable of promoting the dehydrogenation of alco
ends, the invention, then, consists in an
‘20 hol to form an vadditional quantity of such alde related
improved method for oxidizing a lower primary
hyde and then passing the mixed gases (now con aliphatic alcohol to the corresponding acid, of
occur.
taining hydrogen) at the aforementioned temper
ature into contact with an agent capable of oxi
dizing part of the aldehyde to the corresponding
acid and part of the hydrogen to water. The acid
25 so produced is removed from the mixed products
through fractional condensation and the remain
ing gaseous mixture is returned to the system for
re-employment.
which an illustrative form is hereinafter de
scribed, but it will be understood that this illus
tration sets forth in detail merely one mode of 85
carrying out the invention, and that the invention
may be practiced in other manners. Such a lower
In the above mentioned co
pending application, it is pointed out that the
30 presence of the hydrogen produced during the
step of dehydrogenating alcohol is advantageous
in that it Vinhibits greatly the tendency of the
acid product to split out carbon dioxide under
35 conditions maintained during the reaction period,
and thereby reduces considerably the loss of ma
terials through such decomposition.
In producing an acid according to the pro
cedure such as described in our co-pending ap
primary aliphatic alcohol, according to the
present invention, is characterized in that it may
be evaporated below 350° C., so that the procedure 90
occurs in the vapor.
In operating according to our improved mode
of procedure,-a lower primary alcohol which may
or may not contain up to about 30 per cent by
weight of water and/ or the aldehyde correspond 95
ing to that obtainable through oxidation of the
alcohol, is passed into a tube having walls per
meable to hydrogen and presenting both a catalyst
capable of promoting the dehydrogenation of
alcohol as for example copper, silver, gold and/ or
40 plîcation, at least two of the reactions involved mercury or oxides thereof which are hereinafterA
are of the reversible type, viz:
denominated “dehydrogenating catalysts”; and
an agent capable of oxidizing an aldehyde to the
corresponding acid as for example oxide of silver,
copper, or a near noble metal, or mixtures thereof. 105
45 While it is true that the presence of hydrogen The tube is maintained at any temperature be
protects the acid product against decomposition, tween 150 and 350 degrees C., but preferably at
yet, from the above equations it may readily be a temperature between 250 and 320 degrees C.,
seen that the presence of hydrogen, in excess of during passage of gases therethrough. The above
that quantity required to ensure the aforemen mentioned tube itself may be made of a material 110
50 tioned protective action, is disadvantageous both such as palladium, platinum, nickel, wrought iron,
in that its presence inhibits the dehydrogena
tion of alcohol to form the intermediate aldehyde
product and in that said hydrogen tends to re
duce the desired acid product back to the inter
55 mediate aldehyde stage. The presence of hydro
gen in excess of the amount required for success
ful operation is further disadvantageous in that
hydrogen tends to reduce the oxidizing agent em
ployed for the conversion of aldelulde to acid and
60 thereby quickly and materially lessens the quan
or various alloys, or of aluminum oxide, silli
manite, or partially fused earthy materials in
general, the only practical restriction with re
spect to the composition of such tube being that 115
the walls of the same must be permeable to hydro
gen but practically impermeable to all other com
ponents of the reaction mixture under the condi
tions at which the reaction is carried out.
In practicing our invention, we prefer to em
2
1,951,280
ploy a double-tubular reactor, i. e., a reactor com
prising a small tube inside of a larger one. The
After continued operation with a given reactor
in the above describedV manner, the metal oxide,
outer of these tubes presents a surface practically employed
as an agent for oxidizing vthe aldehyde
impermeable to hydrogen, as for example, glass;
GR copper, brass, high chromium steel, enameled to its corresponding acid, becomes largely reduced
to thefree metal and must beY reconverted to the 80
steel, etc.; and the inner tubes present a surface metal
oxide before continuing the acid forming
and composition relatively permeable to hydrogen operations.
This may be accomplished readily
as set forth above. The space betweenthe inner
and outer tubes of the reactor is filled with a metal
10 oxide or an inert substance carrying the same.
by passing a current of air through the reaction
chamber at atemperature which will permit oxi
During operation, the desiredlgaseous reactants dation of the metal.Y For instance, when copper
is the metalïconcerned, it may be reconverted to 85
its oxide by passing air over the granules of the
metal at 27Q to 320 degrees C. and the copper
oxide formed under?such conditions is an espe
cially active'oxidizing agent for the conversion of 90
time maintained within the inner tube so as Yto aldehydes to acids. It is desirable in certain in~
facilitate witliglrawal of hydrogen from the re stances
to mix the entering vapors with inert
action mixture substantiallyYV as it is formed. gases such
as nitrogen.
When operating according to'the procedure de
The following examples describe two of the
'20 scribed above, in an initial phase, the gaseous
alcohol iirst comes into contact with, for example, various ways in which the principle of our inven 95
copper oxide at a temperature between 150 and tion may be employed. It is to be understood,
350 degrees C; The copper oxide is reduced, at however, that such examples are purely illustra
the point of contactn with alcohol, to the free tive and are not to be construed as a limitation
25 metal, and hydrogen is split from the alcohol to onY the invention. In descríbingrthe examples,
formY water, the alcohol itself being thereby con reference will be ?made to the apparatus dia 100
grammatically illustrated in the accompanying
verted to the corresponding aldehyde. The drawing.
'
metallic copper, formed during the ñrst few
Example 1
minutes or initial phase of operation, is in itself
30 an excellent dehydrogenating catalyst and pro
A slender sillimanite thimble A was inserted, 105
motes the splitting of free hydrogen from the
fresh quantities of alcohol passed into the ap to a depth of about 20 inches, into an ordinary
paratus. 'I‘he hydrogen, as it is split from the glass combustion tube B, about 36 inches in
alcohol, passes to a large extent, from the re length and 0.75 inch in diameter. The annular
35 action mixture through the wall of the inner tube space within the combustion tube and about the
of the reactor substantially as it is formed. The inserted thimble was ñlled with granulated cop 110
aldehyde, formed through such dehydrogenation per oxide C, the open end of the sillimanite thim
ble was connected with a vacuum pump D, and
of alcohol, comes nite immediate contact with the
combustion tube itself was fitted with con
fresh quantities of copper oxide and is to a large
40 extent oxidized by the latter to the corresponding nections E which would permit the~ passage of
aliphatic acid which passes from the annular gases through the combustion tube and about the 115 y
space of the reactor intermixed with some alde porous thimble. The combustion tube was then
hyde and very small portions of hydrogen and un heated by a suitable heating unit F to about 310
degrees C., the sillimanite thimble was evacuated
reacted alcohol, as well as with any inert gaseous
45 materials which may have been employed along by means of the continuously operating pump,
and the vapor from 85 per cent ethyl alcohol
with the reactants themselves. The reacted was passed, at the rate of about 110 gms. of 85 per ' 120
mixture, after passing from the reactor, is cent alcohol vapor in 20 to 30 minutes, through
dephlegmated so as to separate the acid product
therefrom and the remaining gaseous mixture the annular space filled with copper oxide. It
is replenished with alcohol vapor and returned to was observed that this oxide was reduced to me
the reactor for reeemployment. Through operat tallic copper at the end of the tube at which the 125
ing in this cyclic manner, nearly all of the alcohol alcohol vapors were admitted into the reactor
is eventually converted to the corresponding acid and that, as the operation was continued, such
and nearly pure hydrogen is obtained as a by= transformation of copper oxide to the free metal
are passed, preferably under super-atmospheric
pressure, into and through the annular space be
tween the inner and outer tubes of the reactor,
15 anda sub-atmospheric pressure is at'the saine
55 product.
extended itself gradually throughout the length
In operating according to the above described of the tube. The vapors issuing from the reac 130
procedure, we prefer to control the relative rates tion chamber were passed through a dephlegma
tor G and dephlegmated so as to separate most
of the acetic acid produced, and the gaseous mix
through the reactor, and at which hydrogen is
60 withdrawn from the reaction mixture, so that ture remaining after such separation was re
with additional vapor from 85 per cent`
the mixture at all times contains sufficient hydro plenished
ethyl
alcohol
and was again passed through the 135
gen to substantially prevent decomposition of
annular
reaction
chamber. By continuously op
the acid produced. The exact quant-ity of hy
at which the gaseous reactants are passed
drogen required for such purpose is dependent erating our cyclic process over a period of about
seven hours (with intermittent interruptions for
the regeneration of copper oxide through passing
which are the rate at which gaseous reactants
140
are passed through the reactor, and the exact air at 270 to 320 degrees C., instead of the alco
holic
mixture,
through
the
annular
reaction
temperature at which said reactor is maintained
during such passage. We have found, however, chamber), we obtained a 75 to 80 per cent solu
tion of acetic acid 'in quantity representing a
that under convenient operating conditions, the yield
of approximately 93 per cent of that the 145
quantity of hydrogen in the mixed gaseous prod
oretically
obtainable from the quantity of alco
ucts which issue from the reactor need not exceed
employed, and approximately 65 per cent of
5 per cent of the total volume of the mixture to hol
afford the acid product almost complete protec the hydrogen theoretically liberated through de
65 upon a number of factors, important among
75 tion against decomposition.
hydrogenation of the quantity of alcohol. The
hydrogen recovered was about 90 per cent pure. 150
3
1,951,280
Along with the above-mentioned desirable prod
stead of those explained, without departing from
the scope of the appended claims, provided the
ucts we obtained a small amount of ethyl acetate, step or steps stated by any of the following claims
and small amounts of carbon dioxide, and both or the equivalent of such stated step or steps be
saturated and unsaturated hydrocarbons.
employed.
Example 2
We claim:
1. A cyclic method of converting a lowerpri->
Through operating in a manner similar to that mary aliphatic alcohol to the corresponding ali
described in Example 1, a vaporized normal propyl phatic acid which comprises passing the alcohol
alcohol solution of 85 per cent concentration was in vapor form, at a temperature between 150
10 found to give normal propionic acid of about the and 350 degrees C., over a dehydrogenating cat
same concentration. The optimum temperature alyst to form the corresponding aldehyde and
for the dehydrogenation of normal propyl alcohol free hydrogen, bringing the reaction mixture
was found to be 10 to 15 degrees higher than that into contact with a material permeable to, hy
desirable for ethyl alcohol. The proportion of drogen -whereby to separate part of the hydro
15 propyl aldehyde to the propionic acid product was gen from the reaction mixture substantially as
approximately 1 to 4, and such aldehyde and it is formed, contacting the aldehyde-containing
other incandescent vapors, asin Example 1, were vapors, at a temperature between 150 and 350
returned to the system along with incoming va degrees C., with a readily reducible metal oxide 95
pors of fresh normal propyl alcohol. The over so as to oxidize such aldehyde to the correspond
20 all yield of- normal propionic acid from normal ing aliphatic acid and a portion of the free hy
propyl alcohol-amounted, on an average, to ap
proximately 91 per cent of theoretical. The pro
duction of carbondioxide and hydrocarbon gases
did not exceed 4 per cent of theoretical.
In operating accord’ng to the manner described
25
in Example 1, we find that the water content of
drogen to water, separating said acid from the
mixed products, replenishing the remaining
mixed products with a fresh quantityof vapor
of the said alcohol, and recycling the resultant 100
mixture through the steps described above.
2. A cyclic method of converting a lower pri
the mixed intermediate materials gradually tends mary aliphatic alcohol to the corresponding ali
to build up, and that after seven hours of such phatic acid which comprises passing the vapor
cyclic operation it becomes advisable to remove ized alcohol, at a temperature between 150 and 105
most of such water from said intermediate prod 350 degrees C., over a readily reducible metal
ucts before continuing operations. Th’s may be oxide, to form the aldehyde corresponding to the
done through fractional distillation, drying with alcohol, water, free hydrogen, and free metal
a suitable agent, etc.
Also, we find it advanta
from the metal oxide bringing the reaction mix
geous to employ a highly cooled by-pass H through ture into contact with a material permeable to 110
hydrogen whereby to separate part of the hy
35 which nitrogen (which has entered during re
generation, or which is being introduced as inert drogen from the reaction mixture substantially
gas), may escape from the vaporized intermedi as it is formed, contacting the aldehyde-contain
ate products before recycling the latter through ing vapors immediately as said aldehyde is formed
the system. Such by-pass is suitably attached to with additional metal oxide at a temperature 115
40 _ the top of a vertical condenser and consists of a
between 150 and 350 degrees C. so as to oxidize
-iiap-valve which will permit gas to escape slowly said aldehyde to the corresponding aliphatic acid,
from the system but will not permit admittance separating the acid from the mixed products, re
plenishing the remaining mixed products with a
of air to the same.
The princ'ple of our invention may be employed fresh quantity of vapor of the said alcohol, and 120
45 in ways other than those previously mentioned. recycling the resultant mixture through the steps
We may, for instance, employ a triple tube re
described above.
3. A cyclic method of converting a lower pri
actor, that is, a reactor having a relatively large
impervious outer tube with a smaller intermedi mary aliphatic alcohol to the corresponding ali
phatic acid which comprises passing the vapor 125
ate one inside, and a still smaller inner tube With
50 in the intermediate tube. The intermediate tube ized alcohol, at a. rate such that hydrogen is re
mentioned has Walls porous to hydrogen but not tained in the mixed reaction products and at a
to the other materials employed or formed dur-` temperature between 250 and 320 degrees C., over
ing the reaction; the inner tube has Walls im copper oxide and copper to form the aldehyde
pervious to hydrogen and the annular space be corresponding to the alcohol employed, water, free 130
55 tween the inner and intermediate tubes is filled hydrogen, and free copper. bringing the reaction
with metal oxide (e. g. copper oxide) and consti mixture into -contact with a material permeable
tutes the reaction chamber. Through the inner to hydrogen whereby to separate part of the hy
tube is circulated a liquid maintained at any tem drogen from the reactionl mixture substantially
perature desired. Gaseous hydrogen is With as it is formed, contacting the aldehyde-con 135
taining vapors immediately as said aldehyde is
60 drawn from the annular space between the out
er and intermediate tubes by a suction pump. By formed with ladditional copper oxide at a tem
employing such apparatus, excellent temperature perature between 250 and 320 degrees C. whereby
control may be maintained with very little heat to oxidize said aldehyde to the corresponding ali
loss. Again, a battery of reactors may be con phatic acid and a portion of the hydrogen to 140
65 nected to a single dephlegmator and a single water, separating the acid from the mixed prod
source of alcohol vapor, with control valves at the ucts, replenishing the remaining mixed products
inlets and outlets, so that the production of acid with a fresh quantity of vapor of the said alco
may proceed in one or more tubes while regen
hol, recycling the resultant mixture through the
eration of the oxidiz'ng agent is occurring in steps described above, and interrupting the re 145
other tubes. The control valves may be arranged cycling from time to time and passing air through
so as to alternately pass air and the desired re
the mass of copper and copper oxide at a tem
action mixture through the various reaction perature of approximately 270 degrees C., where
chambers as required for most eiiicient operation. by to regenerate the copper oxide.
_
It is obvious that other modes of applying the
4. A cyclic method of converting ethyl alco 150
principle of our invention may be employed in
4
1,951,280
hol to acetic acid which comprises passing the
vaporized alcohol, at a rate such that hydrogen at a rate such that hydrogen is retained in the
is retained in the mixed reaction products and mixed reaction products and at a temperature be
at a temperature between 150 and 350 degrees C., tween 250 and 320 degrees C., over copper oxide
over copper oxide and copper to form acetalde
to form propionic aldehyde, water, free hydrogen,
hyde, Water, free hydrogen, and free copper, and free copper, bringing the reaction mixture î
bringing the reaction mixture into contact with into contact with a material permeable to hydro
a material permeable to hydrogen whereby to gen whereby to separate part of the hydrogen
separate part of the hydrogen from the reaction from the reaction mixture substantially as it is
“10 mixture substantially as it is formed, contacting formed,^contacting the aldehyde-containing va.
the aldehyde-containing vapor immediately as pors immediately as said aldehyde is formed and l 85
said aldehyde is formed and at a temperature at a temperature between 250 and 320 degrees C.,
between 150 and 350 degrees C., with additional with additional copper oxide, whereby to oxidìze
copper oxide whereby to oxidize said aldehyde to said aldehyde to propionic acid, separating the
acetic acid, and a portion of the free hydrogen. acid from the mixed reaction products, replen
to water, separating the acid from the mixed re ishing the remaining mixed products with a fresh
action products, replenishing the remaining quantity of vapor of propyl alcohol, recycling the
mixed products with a fresh quantity of ethyl resultant mixture through the steps described
alcohol vapor, and recycling the resultant mix above, and interrupting the recycling from time
to time and passing air through the mass of cop
20 ture through the steps described above.
and copper oxide at a temperature of 270 to '
5. A cyclic method of converting ethyl alco per
320 degrees C., whereby to regenerate the copper 95
hol to acetic acid which comprises passing the oxide.
vaporized alcohol along with water vapor in a
proportion not exceeding 30 per cent by weight,
25 at a rate such that hydrogen is retained in the
mixed reaction products and at a temperature
between 250 and 320 degrees C., over copper oxide,
whereby to form free copper and a reaction mix
ture containing acetaldehyde, water and free hy
80 drogen, bringing the reaction mixture into con
tact with a material permeable to hydrogen
whereby to separate part of the hydrogen from
the reaction mixture substantially as it is formed,
contacting the aldehyde-containing vapors im
mediately as said aldehyde is formed and at a
8. In a cyclic method of converting a lower
primary aliphatic alcohol to the corresponding
aliphatic acid, the steps which consist in passing 100
a gaseous mixture containing the alcohol and the
corresponding aliphatic aldehyde first over me
tallic copper at a temperature between 150 and
350 degrees C., whereby hydrogen is split from
the alcohol and an additional quantity of the 105
said aldehyde is formed thereby, bringing the
reaction mixture into contact with a material
permeable -to hydrogen whereby to separate part
of the oxygen from the reaction mixture sub
temperature between 250 and 320 degrees C., with stantially as it is formed, then passing the alde 110
additional copper oxide whereby to oxidize said hyde-containing vapors over copper oxide at the
aldehyde to acetic acid and a portion of the r`e said temperature andî immediately as such alde
maining hydrogen to water, separating the acid hyde is being formed whereby part of said alde
from the mixed reaction products, replenishing hyde is oxidized by the copper oxide to the cor
the remaining mixed products with a fresh quan responding aliphatic acid, separating the acid 115
tity of vapor of ethyl alcohol; recycling the re from the mixed reaction products, replenishing
sultant mixture through the steps described the remaining mixed products with a fresh quan
above; and interrupting the recycling from time tity of vapor of the said alcohol, and recycling
45 to time and passing air through the mass of cop the resultant mixture through the steps described
per and copper oxide at a temperature of 270 above.
120
9. In a cyclic method of converting a lower
to 320 degrees C., whereby to regenerate the cop
per oxide.
primary aliphatic alcohol to the corresponding
6. A cyclic method of converting propyl alcohol aliphatic acid, the steps which consist in passing
to propionic acid, which comprises passing the a gaseous mixture containing the alcohol and the
vaporized alcohol, at a rate such that hydrogen corresponding aliphatic aldehyde, at a rate such 125
is retained in the mixed reaction products and that hydrogen is retained in the mixed reaction
at a temperature between 150 and 350 degrees products, first over metallic copper at a temper
C., over copper oxide to form propionic aldehyde, ature between 250 and 320 degrees C., whereby
water, hydrogen, and some free copper, bringing hydrogen is split from the alcohol and an addi
the reaction mixture into contact with a material tional quantity of the said aldehyde is formed, 130
permeable to hydrogen whereby to separate part bringing the reaction mixture into contact with
of the hydrogen from the reaction mixture sub a material permeable to hydrogen whereby tosep
stantially as it is formed, contacting the alde arate part of the hydrogen from the reaction mix
60 hyde-containing vapors immediately as said a1 ture substantially as it is formed, then passing
dehyde is formed and at a temperature between the aldehyde-containing vapors over copper oxide i135
150 and 350 degrees C., with additional copper at the aforementioned temperature and immedi
oxide whereby to oxidize said aldehyde to acetic ately as such aldehyde is being formed whereby
acid, separating the latter from the mixed reac part of said aldehyde is oxidized by the copper
65
tion products, replenishing the remaining mixed oxide to the corresponding aliphatic acid, sep
products with a fresh quantity of vapor of propyl arating the acid from the mixed reaction prod L40
alcohol, and recycling the resultant mixture ucts, replenishing the remaining mixed prod
ucts with a fresh quantity of vapor of the said
through the steps described above.
7. A cyclic method of vconverting propyl alcohol alcohol, and recycling the resultant mixture
70 to propionic acid which comprises passing the through the steps described above.
vaporized alcohol along with water vapor in a
proportion not exceeding 30v per cent by weight,
WILLIAM J. HALE.
145
WILLIAM S. HALDEMAN.
u
150
CERTIFICATE oF CORRECTION.
Patent No. 1,951, 280'.
March 13, 1934,
WILLIAM J. HALE, ET LAL.
lt is hereby certified that error appears in the printed specification of the
above numbered patent requiring correction as follows: Page 4, line 109, claim
8, for "oxygen" read hydrogen; and that the said Letters Patent should be read
with this correction therein that the same may confonn to the record of the case
in the Patent ûffice.
'
Signed and sealedv this 15th day of May, A. D. i934.
Bryan M. Battey
(Seal)
y
v
Acting Commissioner of Patents.