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Патент USA US2407921

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Patented Sept. 17, 1946
2,407,920 ‘
UNITED STATES PATENT OFFICE
PROCESS OF PRODUCING PENTA
’
.
‘ERYTHRITOL
Richard F. B‘. Cox, Wilmin§ton,.Del;,‘ assignbr to
Hercules Powder Company, Wilmington, Del., ‘a
corporation of Delaware
No Drawing. Application geptember 25,1942,
Serial No. 459,707
‘8 Claims. (01. atria-Z)
1
t
This invention relates ‘to an improved process
2
formic ester characterized by the. abilityvto pro
for the preparation of pentaerythritol. More
particularly, it is concerned with an improved
duce a ternary azeotropic composition with the
alcohol and water, said azeotropic composition
having .a boiling point of not more than 99* C.,
method for recovering pentaerythritol from the
crude reaction mixture of acetaldehyde and 5 while the reaction mixture is maintained at a
'
formaldehyde.
temperature of ‘from about 60° C. to about 99° C.
and the formic ‘ester is removed.
Pentaerythritol has been prepared according to
different procedures described in the art by the
Now, having indicated in a ‘general way the
nature and purpose of the invention, the fol
in the presence of an alkaline catalyst. Consid 10 lowing examples will illustrate the invention but
erable dif?culty has been experiencedfin obtain
‘are not ‘to be construed as limiting the same.
ing‘ maximum yields of pentaerythritol due in
In the examples, ‘the ingredients are in parts by
part to the exacting’ conditions under which the
weight unless otherwise indicated.
condensation of acetaldehyde with formaldehyde
reaction ‘must be cbnductedand in part to the
formation of ‘by-products ‘during the recovery of 15
the pentaerythritol from the reaction mixture.
Various methods havebeen described for the re
moval of the metal ion from the catalyst which
is ‘present asa lformate. ‘For example, calcium
_
Example 1
>To '90 parts of ‘formalin (35%‘ formaldehyde)
and 200 parts of water were added simultaneous
131 11 parts acetaldehyde and ‘9.5 parts calcium
‘hydroxide. The reaction was carried ‘out at a
has been‘precipitated as the sulfate or oxalate in 20 v'teinper'atu‘re between 18° C. and 41° C. for a pe
such ‘a manner that formic ‘acid has remained in
riod of six hours. ‘After the reaction was com
plete, the ‘condensate was acidi?ed with carbon
‘erythrito-l?-Lformic acid solution, it has been gen
dioxide and ?ltered ‘to remove excess lime and
eral to___¢oneentrate and crystallize the penta
material, The filtrate was then con
erythritol. In carrying out this concentration, 25 insoluble
centrated ‘in vacuo and crystallized alternately
however, nonécrys‘talliz‘able ‘syrups have resulted
with removal ‘of thefcry‘stals in 5 crops. Alcohol
due tothe formation of formic esters by reaction
"was then added to the ?ltrate to precipitaterthe
the reaction mixture. In Working up the penta
between the p'entaerythritol and the formic acid,
alcohol-‘insoluble ‘pent'aerythritOLcaIcium
thus reducing the yield of ‘crystalline penta
erythritol,
‘
i
_
‘
I
new,
‘accordance with this invention, a
method‘ has been ‘found‘of ‘recovering high yields
of pentaerythritol from the crude ‘penta‘erythri
for- v
mate crystallizable material from‘ the alcohol
30 sol'uble no'n‘écrys‘tall'i‘ne syrups. The pentaeryth
ritolj-c’alcium
'form‘ate
crystalline
material
amounting to 46 ‘parts was removed by ?ltra
tion
and then dissolved ‘in 100 parts of water and
tol reaction mixture resulting from the conden
sation of acetaldehyde with formaldehyde in the 35 acidi?ed with 25 parts or 50% ‘sulfuric acid. The
precipitated 'calc'ium'sulfate was removed by lil
presence of an alkaline catalyst. The improved
tration
and was given a “displacement wash with
method involves removing the formic acid from
water.
The solution amounting to 150 parts and
the hot reaction ‘mixture by converting the formic
containing penta'erythritol and formic acid was
acid ‘into a formic ester ‘characterized by the
then ‘heated ‘to 95° C‘. while hot ‘ethanol vapors
ability to produce ‘a ternary ‘az‘eotropic composi 40 were
‘passed through the ‘solution to carry off the
one with the alcohol used to‘ form the ester and
formic acid ‘as the, volatile ethyl ester, having a
‘water, ‘s‘a'id azeotropic composition having a boil
boiling point of 54° 'C. The ‘distillates were ‘col
mg ‘paint erect more than 99° c.“ In general, a
lected and analyzed for ‘formic ester by saponi?
vaporized monohydric alcohol is distilled into the
hot reaction ‘mixture containing‘ pentaerythritol
solution leaving behindaj‘solution of pen'taeryth
‘and formic acid and‘the ester distill'slout of the
45
ritol {from which the pentaery‘thritol can ‘be iso
lated by"cjry‘stalli‘zation,v evaporation, or by spray
vdrying.
Thus, in carrying out the process of
‘producing 'p‘enta'erythritol involving condensa
tion 'of 'aceta'ldehyde with (formaldehyde in the
icf an alkaline catalyst; acidi?cation of
the reaction mixture, and ‘removal of the metal
ion of the ‘catalyst, the reaction mixture is treat 55
"ed with “a monohyd'ric alcohol which forms a
cation ‘and calculated 'as formic acid.
sults were as follows:
Fraction
‘
The re
‘
Weight
130
108
170
192
176
‘
geégé‘fi
5. O2
1. 45
.34
. 19 i
.07
168
.
192
. 03
The ‘aqueous solution thus freedof formic ‘acid
2,407,920
3
was concentrated in vacuo and crystallized al
ternately with removal of pentaerythritol, each
crop of pentaerythritol being given a displace
ment wash _withswater~ The las,_t_._of the penta
erythritol was removed from 'the ‘mother liquor
by precipitation with alcohol. The total penta
' erythritol amounted to 28 parts by weight, or an '
80% yield based on the acetaldehyde.
4
crude pentaerythritol solution is shown. How
ever, any other method of carrying out the con
densation may be employed.
It is preferred,
however, to :use a method which will direct the
reaction to the formation of pentaerythritol and
keep side're'a'ctions at an absolute minimum. The
timeand temperature of the reaction may vary
according to known ranges. The condensate
. may be acidi?ed with any mineral acid as a sul
' To 175 parts of formalin (35% formaldehyde) ,
and 370 parts of water were‘ added simultaneous‘
furic or hydrochloric acid by any of the means
known to the art. Generally, the metal ion of
"the catalyst may be removed before removal of
ly 22 parts of acetaldehyde and 20 parts calcium
the formic esters, but, if desired, the formic ‘es
Example 2
'
'
' .7
hydroxide. The reaction was carried out under"
the same reaction conditions as in Fxample_.-1.v
After the reaction was complete, the solution was '
acidified with 47 parts of 50% sulfuric acid. Cal- ‘
cium sulfate was removed by ?ltration and given
a displacement wash with hot water. The ?l
trate and Wash water were freed of the last of
1the calcium by the addition of oxalic, acid and
; ?ltered.
'
The reaction mixture containing pentaeryth
ters may be ?rst removed from the condensate.
The‘metal ion of the catalyst may be removed in
- various ways. For example, if calcium hydroxide
is used» as the catalyst, the calcium may be pre
cipitated from the reaction mixture as calcium
sulfate. The, formic acid is removed from the
reaction mixture as the formic ester character
ized, by the ability to produce a ternary azeo
tropic composition having a boiling point of not
more than 99° C. with the alcohol used to form
ritol and formic acid was heated to 90° 'C. while . ‘the ester and water, for example, by distilling
hot methanol vapors were passed through the 25 Vapors of a monohydric alcohol into the reaction
mixture while the reaction mixture is main~
solution to carry off the formic acid as the vola
‘tained at a temperature of from about 60° C. to
tile methyl formate having a boiling point of
about 99° C. _ If desired, however, the monohy
32° C, , This was continued until 100 parts meth
dric alcohol may be added as a liquid. The proc
anol had been distilled through the solution. The
solution of pentaerythritol freed of formic acid 30 ess _is usually continued until 90-100% of the
formic acid is removed from the reaction mixture.
was then concentrated in vacuo and the penta
If desired, however, it may be discontinued be—
erythritol was crystallized. After removal of
fore this amount of formic acid has been re
- the first crop of pentaerythritol, the solution was
moved. The reaction mixture thus freed from
concentrated to get further crops. The last of
formic acid may be concentrated according to
the pentaerythritol was obtained by adding a1
the method shown in Example 1 or other known
_ cohol in which the pentaerythritol was insoluble
methods and the crystalline pentaerythritol re
and the non-crystalline syrups were soluble. The
covered.
total yield of pentaerythritol thus obtained
When pentaerythritol is isolated by concentra
‘_ amounted to 54 parts, or an 80% yield based on
tion of the acidi?ed condensate of acetaldehyde
s the acetaldehyde.
'
The normal formaldehyde-acetaldehyde ra
' tio which may be used in carrying out the proc
' ess of this invention may be from about 2.5 to l
to about 6 to 1 and preferably from about 4 to 1,.
to‘ about 5 to 1. A preferred ratio of alkaline con- '
' tent is from about 1.0 to about 1.2 equivalents
. and formaldehyde, the large amounts ofv formic
acid set free react during the concentration to
, esterify the pentaerythritol and to catalyze reac
tion between aldehydes and pentaerythritol. By
gthe process of removing the formic acid from the
, reaction mixture in the form of its ester by treat
ing the reactionrmixture with a monohydric alco
l per mol of acetaldehyde although more alkaline
, hol, while the reaction mixture is maintained at
I catalyst may be used if desired. '
a temperature of from about 60° C. to about 99°
0., a convenient and efficient method is provid
_In carrying out the process of this invention,
calcium hydroxide is preferred as the alkaline‘
; catalyst, However, otherv alkaline catalysts such
as sodium hydroxide, potassium hydroxide; bar
ed of preventing side reactions with pentaeryth
ritol and a materially increased yield of penta
erythritol is thus obtained.
What I claim and desire to protect by Letters
ium hydroxide, magnesium hydroxide, strontium
hydroxide, and the like may be used.
In the examples, methanol and ethanol vapors
were used as the monohydric alcohols. However,
monohydric alcohols may be used that will ‘con
Vert the formic acid into a formic ester charac
terized by the ability to produce a ternary azeo
tropic composition with the alcohol and water,
said azeotropic composition having a boiling
point of not more than 99° C., such as n-propyl,
isopropyl, n-butyl,
isobutyl,
tertiary
butyl,
n-amyl, iso-amyl and the like.
The amount of such monohydric alcohols may
vary, but generally speaking an amount should
be used adequate to esterify all of the formic acid
Patent is:
adding an acidic precipitant for the metal ion
of the alkaline material thereby freeing formic
acid, removing the metal ion of the alkaline ma
terial, treating the remaining mixture compris
ing pentaerythritol and formic acid with metha
,-nol to convert the formic acid present into
methyl formate, distilling off said methyl for
.mate while maintaining the temperature of the
mixture at from about 60° C. to about 99°C., and
.recovering pentaerythritol from the residue.
present in the reaction mixture, as well as to
2. A process for making pentaerythritol com
form a ternary azeotropic composition with for- .
‘mic ester and water.
,
1. A process for making pentaerythritol com
prising condensing acetaldehyde and formalde
hyde in the presence of an alkaline material,
prising condensing acetaldehyde and formalde
70
hyde in the presence of an alkaline material, add
The temperatureof the reaction mixture dur
ing the esteri?cation and removal of the formic
esters may vary from about 60° C. to about 99° C.
but is preferably from about 80° C. to about 99° C.
In the examples, a' method of preparing the 75
ing an acidic precipitant for the metal ion of the
alkaline material thereby freeing formic acid,
removing the metal ion'of the alkaline material,
treating the remaining mixture comprising pen
2,407,920
5
6
taerythritol and formic acid with ethanol to con
vert the formic acid present into ethyl formate,
6. A process for making pentaerythritol com
distilling off said ethyl formate while ‘maintain
ing the temperature of the mixture at from about
60° C. to about 99° 0., and recovering penta
erythritol from the residue.
3. A process for making pentaerythritol com
prising condensing acetaldehyde and formalde
hyde in the presence of an alkaline material, add_
ing an acidic precipitant for the metal ion of the
alkaline material thereby freeing formic acid,
removing the metal ion of the alkaline material,
treating the remainingr mixture comprising pen
prising condensing acetaldehyde and formalde
hyde in the presence of an alkaline material,
adding an acidic precipitant for the metal ion of
the alkaline material thereby freeing formic
acid, removing the metal ion of the alkaline ma
terial, treating the remaining mixture compris
ing pentaerythritol and formic acid with a mono
hydric alcohol, which will form a ternary azeo
tropic composition having a boiling point of not
more than 99° C. of such monohydric alcohol, the
formic ester thereof and water, to convert the
formic acid into the ester, distilling off said for
taerythritol and formic acid with isopropanol to
mic ester while maintaining the temperature of
convertthe formic acid present into isopropyl 15 the mixture at from about 60° C. to about 99° C.,
formate, distilling off said isopropyl formate
and recovering pentaerythritol from the residue.
while maintaining the temperature of the mix
7. A process for making pentaerythritol com
ture at from about 60° C. to about 99° C., and re
prising condensing acetaldehyde and formalde
covering pentaerythritol from the residue.
hyde ‘in the presence of an alkaline material,
4. A process for making pentaerythritol com 20 adding an acidic precipitant for the metal ion of
prising the condensation of acetaldehyde and
the alkaline material thereby freeing formic acid,
formaldehyde in the presence of an alkaline ma
removing the metal ion of the alkaline material,
terial, adding an acidic precipitant for the metal
treating the remaining mixture comprising pen
ion of the alkaline material thereby freeing for
taerythritol and formic acid with a monohydric
mic acid, removing the metal ion of the alkaline 25 alcohol, which will form a ternary azeotropic
material, heating the remaining mixture com
composition having a boiling point of not more
prising pentaerythritol and formic acid to a ‘tem
than 99° C. of such monohydric alcohol, the for
perature of from about 60° C. to about 99° C.,pass
mic ester thereof and water, to convert the for
ing vapors of a monohydric alcohol, which will
mic acid into the ester, distilling off said formic
form a ternary azeotropic composition having a 30 ester while maintaining the temperature of the
boiling point of not more than 99° C. of such mono
mixture at from about 80° C. to about 99° C. and
hydric alcohol, the formic ester thereof and wa
recovering pentaerythritol from the residue.
ter, through the mixture to convert the formic
8. A process for making pentaery'thritobcom
acid into the ester, distilling off said formic ester
prising condensing acetaldehyde and formalde
While maintaining the temperature of the mix 35 hyde in the presence of an alkaline material,
ture at from about 60° C. to about 99° C’., and
adding an acidic precipitant for the metal ion
recovering pentaerythritol from the residue.
of the alkaline material thereby freeing formic
5. A process for making pentaerythritol com
acid, removing the metal ion of the alkaline ma
prising condensing acetaldehyde and formalde
terial, treating the remaining mixture compris
hyde in the presence of an alkaline material, 40 ing pentaerythritol and ‘formic acid with vapors
adding an acidic precipitant for the metal ion of
of a monohydric alcohol, which will form a ter
the alkaline material thereby freeing formic acid,
nary azeotropic composition having a boiling
treating the resulting mixture with a monohy
dric alcohol, which will form a ternary azeotropic
point of not more than 99° C. of such monohy
composition having a boiling point of not more _
than 99° C. of such monohydric alcohol, the for
mic ester thereof and water, to convert the for
mic acid into the ester, distilling off said formic
ester while maintaining the temperature of the
mixture at from about 60° C. to about 99° C., and
recovering pentaerythritol from the residue.
dric alcohol, the formic ester thereof and water,
to convert the formic acid into the ester, distil
ling off said formic ester while maintaining the
temperature of the mixture at from about 60° C.
to about 99° C., and recovering pentaerythritol
from the residue.
RICHARD F. B. COX.
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