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Патент USA US2117463

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Patented May 17, 1938
2,117,463
UNITED STATES PATENT OFFICE
2,117,463
METHOD OF PRODUCING ISOPULEGOL
Charles 0. Terwilliger, Birmingham, Ala., as
signor, by mesne assignments, to Theodore
Swann, Birmingham, Ala.
No Drawing. Application September 28, 1936,
'
Serial No. 102,981
12 Claims.
(Cl. 260-153)
This invention relates to the conversion of
citronellal to isopulegol, and has for its‘ principal
object the provision of such a process which shall
be simple and easily carried out and whereby
5 satisfactory yields may be obtained.
Citronellal obtained by fractional distillation
of citronella oil is generally reported in the literature as a mixture of aldehydes (Simonsen, “The
Terpenes”, 1931 Ed), represented by the for10 mulae
E30
(I)
peated the work of Kuwata and have found that
only a small percentage of the theoretical yield
of isopulegol may be thus obtained. Similar re
sults were observed when ferric oxide, kaolin, and
ordinary red clay were employed as catalysts.
5
In my investigation of the problem, I have
found that a siliceous earth containing certain
metallic impurities, particularly a small amount
of the oxide of iron, acts as a catalyst to bring
about the reaction sought, to the exclusion of 10
undesired side reactions. In particular, diatoma
\CZOH_CH2_CH2__OH_CHPCH0
HaO/
CH3
oeous earth having a formula approximating,
Per cent
15 and
SiOz __________________________________ __ 92.30 15
H;C\
(
A1203 _________________________________ __ , 3.90
\ C—~CH—CH——CH
II
)
2
2
’_
H“)
20
F6203 _________________________________ __
CH—~CH—CHO
’
CH3
Isopulegol is a substance obtained from Formula II.
.
1.40
0.15
T102 _________________________________ __
Formula I apparently does not enter
.
.
CaO- and MgO _________________________ __
0.90
Total alkali as Na?o ------------------- --
0-80 20
.
a
.
if properly t1 eated, as hereinafter set forth, and
$3153;riggti?géoypfalgggroflilzallgogtgzrkggg?
added to citronellal in ?nely divided form, the
ucts
citronellal being heated to the proper temperature
’ t 11131 e U ps P
(in) Menthol
This
’ crys 3‘ n
‘
'
"
'
25 menthol is optically active, having a speci?c
.
D
o
.
laevo rotatlon of —-45
to --55
(Nan line).
and agitated during the reaction, will produce ap
.
.
.
25
proximately 901% of the theoretically possible
yield of isopulegoll
Isopulegol has not been found to occur in nature,
_
.
but he‘? hfeletofo're been. proquced m the labor?"
toty prmclpatly by hea’tmg cltronenal “(1th acetlc
30 gggag ggiltlglsin?glélggngo 11358331120115 (£321,321
’
.
.
.
'
.
‘
’
upon hydrolysis ylelds lsopulegol' The yields by
Th
.
sults are obtained if a small amount of carbon be 30
mixed
with
the
earth
before
calcining.
After
calcining, the earth is ground until in a ?nely
this method are very low, due to the predomi-
nance of side reactions producing heavier cyclic
35 compounds‘
In 1931’ Kuwa'ta reported (‘1' SOP‘ Chem‘ Ind‘
.
e d1atomaceous earth should be calcined be
fore use in a suitable furnace, preferably at a
temperature of from 17000 to 1750“ F. Better re
.
.
.
.
‘
‘
gilded form’ and Screened’ when It 15 leady for
'I:he diatomaceous earth which I have found 35
best suited for my purpose is found in the Cali
Jg‘pa’n 34’ 7043). that up‘)? h'ea‘tmg cltrotlenal
fornia and Florida deposits, though it is to be
223:) nJzggilriseeda$3)fiazlhi‘c‘gollin15832525211332;
understood that my invention is not limited to the
.
40 numbe?dof 13926311081 gogggung? I532 aghzf)
were 1 en 1 e ’
1
‘
an
0
.
'
use of earth from those particular deposits.
It
should be used when freshly calcined, as I have 40
found that upon long exposure to the atmosphere,
'
'
l
'
‘h’
h
.
.
.
gggugtnogelgggag?gglby21712156211555?gflgtr?leif
its catalytic properties are greatly weakened and
lal with acetic acid or acetic anhydride, it is still
sometimes _completely lost.
,
45 too low a yield to serve as a means for a commenial source of menthoL
The dimculty of the problem has‘ been to ?nd
In Farrymg out my lmpmvedprocess,
add
the diatomaceous earth to the citronellal in an 45
amount equal to from 2% to 5% of the weight
a Vehicle to bring about the conversion to 150.
pulegol, without at the same time causing the for50 mation of undesired compounds. Of the many
reactions which may occur, it is necessary for a
commercially feasible process, that the conversion
to isopulegol take place in preference to other
of the citronellal. The mixture is‘ heated to a
temperature of from 130° to 135° C- and agitated
until the reaction is complete. The reaction is 50
exothermic, and while it is necessary to heat the
mixture to start the reaction, it may be necessary
to employ some cooling means in order to prevent
ossible reactions.
In my investigation of the problem, I have re-
the temperature from going too high. The tem
perature should not be allowed to exceed 140° C., 55
55
2.
2,117,463
or otherwise an excess of undesirable side reac
tions occur.
10
15
20
25
30
6. A method of converting citronellal to iso
pulegol which comprises heating citronellal with
Agitation of the mixture is preferably accom - calcined diatomaceous earth to a temperature of
plished by passing a gas through the mixture from 130° to 140° C., and stirring the mixture
while the reaction is going on. With freshly while the reaction is going on.
calcined diatomaceous earth a stream of air may
7. A method of converting citronellal to iso
be employed with good results. If the earth has pulegol which comprises heating citronellal with
partially lost its catalytic power, a stream of CO2 calcined diatomaceous earth to a temperature of
gas appears to produce the best results.
from 130° to 140° C., and stirring the mixture by
The reaction should go to completion in from passing a stream of gas therethrough while the
three to twelve hours time, depending upon the reaction is going on.
“activity”, amount, and degree of dispersion of
8. A method of converting citronellal to iso
the catalyst. The reaction may be considered as pulegol which comprises heating citronellal with
complete when the refractive index, at 20° C., is from 2 to 5% of its weight of ?nely ground cal
from 1.4721 to 1.4728. Also, it may be determined cined diatomaceous earth, maintaining the mix 15
by ascertaining the aldehyde content of the mix
ture at a temperature of from 130° to 140° C.
ture, which should be reduced to around 2% or while the reaction is going on, meanwhile agi
less.
After the reaction is complete, the resulting. tating the mixture to maintain the diatomaceous
20
mixture is hydrogenated by known methods, earth in suspension therein.
9. A method of converting citronellal to iso
whereupon the isopulegol produces menthol which
may be separated and re?ned by methods which pulegol which comprises heating citronellal with
from 2 to 5% of its weight of ?nely ground cal
form no part of my present invention.
While I have shown my invention in but one cined diatomaceous earth, maintaining the mix
form, it will be obvious to those skilled in the ture at a temperature of from 130° to 140° C. 25
art that it is not so limited, but is susceptible of while the reaction is going on, meanwhile agi
tating the mixture to maintain the diatomaceous
various changes and modi?cations, without de
parting from the spirit thereof, and I desire, earth in suspension therein, and continuing the
therefore, that only such limitations shall be treatment until the mixture has a refractive in
placed thereupon as are imposed by the prior art dex at 20° C. of 1.4721 to 1.4728.
10. A method of converting citronellal to iso~
or as are speci?cally set forth in the appended
pulegol which comprises heating citronellal with
claims.
I
from 2 to 5% of its weight of ?nely ground cal
WhatI claim is:
cined diatomaceous earth, maintaining the mix
1. A method of converting citronellal to iso
35 pulegol which comprises heating with agitation
citronellal and a diatomaceous earth catalyst
containing metallic impurities up to‘ 8%.
2. A method of converting citronellal to iso
pulegol which comprises adding to citronellal a
diatomaceous earth containing iron oxide as an
impurity in ?nely divided form, heating the mix
ture to around 135° C., and agitating to main
tain the diatomaceous earth in suspension while
the reaction is going on.
I
3. A method of converting citronellal to iso
pulegol which comprises introducing into the
citronellal with agitation ?nely divided diatoma
ceous earth, and maintaining the temperature
around 135° C. while the reaction is proceeding.
4. A method of converting citronellal to iso-'
50
45
pulegol which comprises introducing into the
citronellal with agitation ?nely divided calcined
diatomaceous earth, heating the mixture to start
the reaction, and maintaining the temperature
55 of the mixture to an upper limit of 140° C. as the
reaction proceeds.
_,
5. A method of converting citronellal to iso
ture at a temperature of from 130° to 140° C. 35
while the reaction is going on, meanwhile agi
tating the mixture by passing a stream of carbon
dioxide therethrough to maintain the diatoma
ceous earth in suspension therein, and continuing
the treatment until the mixture has a refractive 40
index at 20° C. of 1.4721 to 1.4728.
11. The method of converting citronellal to iso
pulegol which comprises calcining diatomaceous
earth having’ a silica content of around 92%, in
the presence of carbon, grinding the calcined 45
earth, adding the thus treated earth to citron
ellal, and heating and agitating the mixture
while the reaction is going on.
12. The method vof converting citronellal to
isopulegol which comprises calcining diatoma 50
ceous earth having a silica content of around
92%, in the presence of carbon, grinding the
calcined earth, adding the thus treated earth to
citronellal, maintaining the temperature of the
mixture at from 130° to 140° C., and agitating 55
the same while the reaction is going on to main
tain the diatomaceous earth in suspension.
pulegol which comprises heating citronellal with
calcined diatomaceous earth to a temperature of
from 130° to 140° C.
CHARLES O. TERWILLIGER.
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