Note: Descriptions are shown in the official language in which they were submitted.
6 ~
The present invention relates to a process for producing
non-acqueous hydrogen peroxide solutions.
It is known that the water content of hydrogen peroxide
solutions causes pxoblems in many reactions, for example, in oxi-
dations or epoxidations (see, for example, Org. Reactions 7, 395
(1953).
Quite some time ago attempts were made to use correspon-
ding organic solutions instead of pure aqueous solutions of hydro-
gen peroxide.
However, difficulties were encountered in the production
of these solutions. Aqueous solutions of hydrogen peroxide were
usually used as the starting material for producing organic hydro-
- gen peroxide solutions and either they were only mixed with the
desired organic compound and subsequently dehydrated by distilla-
tion or the aqueous solutions were extracted with the organic
compound and, when required dehydrated.
In both cases orsanic solutions of hydrogen peroxide
were actually obtained but their water content always was at
approximatQly 1% by weight or higher (see, for example, German
20 Patents Nos. 2,038,319 and 2,038,320, US Patent No. 3 743 706 and
British Patent No. 931,11g).
According to the processes of the German Patent Nos.
2,038,319 and 2,038,320 attempts were made to remove the water
present in the organic solutions by distillation at reduced pres-
sure or followed by azeotropic distillation with an additional
entraining agent.
In the process of US Patent No. 3,743,706 the extracting
agent itself was to be used as the entraining agent. However,
details are lacking.
Also in British Patent No. 931,119 the participant in the
mixture was used for azeotropically distilling off the water. How-
ever, in the production of organic hydrogen peroxide solutions
~2~6~
from aqueous solutions a further s~bstantial disadvantage became
evident in addition to the frequently two high water content.
During the removal of the water at the pressures applied
in that case a specific percentage of hydrogen peroxide was en-
trained with the distillate; i.e., between 0.5 and 0.6% by weight
in the simulation test. Moreover, further losses due to decompo-
sition were incurred at the bottom.
In the processes of German Patents Nos. 2,038,319 and
2,038,320 organic phosphorus compounds and heterocylic nitrogen
compounds were us~d and in the processes of British Patent No.
931,119 and US Patent No. 3,743,706 aliphatic or cycloaliphatic
esters were used. While in US Patent No. 3,743,706 no data on
carrying out an azeotropic distillation are provided, in the pro-
cesses of the other three patents pressure far below 100 mbars.
are used (see the examples).
In fact in the two German patents a pressure range is
~uite generally mentioned; it was below 400 mbars. However in
the simulation of the process with triethyl phosphate and N-methyl
pyrrolidone at pressures of 400 and 100 m bars respectively hydro-
20 gen peroxide in amounts of 0.28 and 0.6% by weight and 0.26 and
0.8% by weight was found in the distillate, in both cases relative
to the distillate. Furthermore, an additional loss of hydrogen
peroxide was incurred, i.e., 7.5 and 4.1% by weight and 4.7 and
3.9~ by weight, relative to the hydrogen peroxide used. On adding
up the amount of hydrogen peroxide removed with the distillate and
the amount lost due to decomposition the total losses at a distilla-
tion at 400 and 100 m bars respectively were at least 7 to 8% by
weight of hydrogen peroxide used. However, when the distillation
is carried out at substantially lower pressures, i.e., far below
100 m bars, then it is clear tha-t substantially higher amounts of
hydrogen peroxide are in the distillate which can exceed one per-
cent by wei~ht, relative to the distillate. However, at these
-- 2
~2~t7~
pJeSsures which are assumed to be preferred the examples are
carried out (see loc. cit.).
According to the prior art i-t seemed, therefore, that
drying by distallation of organic hydrogen peroxide solutions
produced with a solvent whose own boiling point or the boiling
point of possible azeo-tropes is closed to or above the boiling
point of hydrogen peroxide necessarily results in substantial
losses of hydrogen peroxide when operating on a large industrial
scale.
However, not only was the loss of -the hydrogen per-
oxide a substantial disadvantage but the fact that the residues
from distillation were not anhydrous by any means was another
disadvantage.
Thus, for example, the phosphorus-organic solutions
had residual wa-ter contents of between 0.97 and 9.5% by weight.
However, -these solutions are not really suitable for, e.g.,
hydroxylation processes. Even in the only example of the German
Patent No. 2,038,320 the water con-tent was 11.4% by weight in
-the organic phase.
It has also been proposed to produce practically
anhydrous organic solutions of hydrogen peroxide by mixing them
with carboxylic acid in such a way that the aqueous hydrogen
peroxide solutions are brought into contact with a]kyl or
cycloalkyl esters of saturated aliphatic carboxylic esters
having a to-tal of 4 to 8 carbon atoms and forming azeotropes
with water and that -the azeo-tropic dehydra-tion is carried out at
pressures of between 160 and 1000 mbars, see applicant's German
Offlegungsschrift No. 3,225,307 published January 12, 1984.
~674~
Organic solutions of hydrogen peroxide whose water
content lies below 0.5% by weight are obtained in this manner.
Furthermore, practically no losses of hydrogen peroxide used are
incurrent in their produc-tion.
~lowever, this process is restricted to the carboxylic
- 3a -
.~
:~2~
esters mentioned above, but it would be desirable to also have a
process for producing similarly anhydrous .solutions of hydrogen
peroxide in higher boiling organic solvents.
It has now been found that anhydrous solutions of hydro-
gen peroxide in higher boiling organic solvents can be produced
practically without loss of hydrogen peroxide used by producing
solutions of hydrogen peroxide in higher boiling solvents having
a water content of up to 1~ by weight, preferably below 0.5% by
weight by mixing solutions of hydrogen peroxide in organic solv-
ents forming one or several azeotropes with water whose boilingpoints lie below the boiling point of hydrogen peroxide, relative
to standard pressure, with higher boiling organic solvents which
form no azeotropes with water or only azeotropes which boil close
to or above the boiling point of hydrogen peroxide, relative to
standard pressure, and that the starting solutions of hydrogen
peroxide in the solvents forming azeotropes with water whose
azeotrope boiling points lie below the boiling point of hydrogen
peroxide, relative to standard pressure, can also be formed while
directly mixing aqueous hydrogen peroxide solutions with those
azeotrope-forming solvents and the higher boiling solvents, where-
upon the entire solvent which forms azeotropes with water whose
azeotrope boiling lies below the boiling point of hydrogen perox-
ide distilled off and an anhydrous solution of hydrogen peroxide
in the corresponding higher boiling solvent is obtained.
By higher boiling organic solvents which form no azeo-
tropes with water or only azeotropes whose boiling points at
standard pressure are close to or above the boiling point of hydro-
gen peroxide are meant on the one hand phosphorus compounds having
the formula
~2~7~
Rl--(X)m~ (Z) p
( )n R2
wherein X, ~ and Z represent an 0-atom, or an N-(Cl-C8)-alkyl
group or an N-(C4-C7)-cycloalkyl group, n, m and p represent the
number 0 or 1 and Rl, R2 and R3 represent straight-chain or bran-
ched Cl-C~-alkyl or C4-C6-cycloalkyl radicals which can be sub-
stitu-ted, when required, by halogen, hydroxyl, Cl-C4-alkoxy, CN
or phenyl groups.
Primarily trialkyl phosphates with Cl-C8 groups, pre-
ferably triethyl phosphate, are suitable ~or producing the organic
solutions of hydrogen peroxide according to the present invention.
Even aromatie carboxylic esters having the structural
formula R
R2 ~ C00 Rl
wherein R represents the grouping CH3, C2H5, n-C3H7, i C3H7,
20 n-C4Hg, i-C4Cg, tert. C4Hg, see. C4Hg, R2 and R3 represent sub-
stituents whieh are inert with respect to hydrogen peroxide such
as H, Cl, F, alkyl such as Rl, CH30, C2H50, C00 R~R4=Rl) and R2
and R3 ean be in any position relative to C00 R grouping, are
excellently suitable for the present invention. Thus, particularly
phthalic esters, preferably phthalic diethyl ester, have been
found to be very favourable.
Furthermore, carboxylic amides or lactams having the
general formula (C 2)n
C~O
R
wherein R represents a straight-ehain or branched Cl-C4-alkyl
6~d9L~
radical which can be substituted when required by halogen, hydr-
oxyl or Cl-C3-alkyl radicals and n represents the number 2 to 5.
Very good results were attained here with N-alkyl pyrro-
lidones with Cl-C4-alkyl groups, particularly with N-methyl pyrr-
olidone.
It has also been found that tetra substituted ureas
having the following formula can be used:
R~ / R
N - C - N
R4/ \ R2
wherein Rl, R2, ~3 and R4 represent Cl-C6-alkyl groups, ureas in
which Rl, R2, R3 and R4 are identical to each other being prefer-
ably used.
Tetramethyl, tetraethyl and tetrabutyl ureas have been
found to be very good higher boiling solvents.
Hydrogen peroxide can be present in aqueous solutions of
any concentration. Solutions containing from 3 to 90~ by weight
of hydrogen peroxide, perferably from 30 to 85~ by weight, are
best suited.
Conventional stabilizers, for example, those mentioned
in ULLMANN, Enzyklopadie der technischen Chemie, Vol. 17, 4th
Edition, page 709, can be used as stabilizers for hydrogen perox-
ide.
Ethers such as dioxane, diisopropyl ether or methyl-tert.-
butyl ether as well as dichloro methane and C5-C8-aliphatic hdyro-
carbons are useful as organic solvents which form one or several
azeotropes with water whose boiling points are below the boiling
point of hydrogen peroxide at standard pressure.
However, preferred solvents of this type are alkyl or
cycloalkyl esters of satruated aliphatic carboxylic acids which
6 _
~6~
have a total of 4 to 8 carbon atoms, primarily acetic-n-propyl
ester or acetic-i-propyl ester or acetic ethyl ester and also
dichloro methane. The concentration of hydrogen peroxide in the
aliphatic carboxylic esters is, for example, 3 to 60~ by weight.
In these low-boiling solvents hydrogen peroxide can be used in
the dissolved form or, as described hereinbefore, the aqueous
hydrogen peroxide solution is mixed with the low-boiling solvent
and the high~boiling solvent, whereupon the azeotrope-forming low-
boiling solvent is distilled off toge-ther with the water.
When the hydrogen peroxide is used as a solution in the
low-boiling solvents described above, these solutions have a water
content of maximally 1~ by weight, preferably below 0.5~ by weight.
The lower hoiling solvent is distilled off together with
the possibly introduced water as the corresponding azeotrope at
a pressure from 50 to 1000 mbars.
In each case the pressures to be used especially in this
range vary with the higher boiling solvent applied.
The amount of the lower boiling solvent must be at least
so rated that the water introduced, when required, can be distilled
off as azeotrope with this solvent so that a solution of hydrogen
peroxide can be obtained in the higher boiling solvent containing
up to 1~ by weight, preferably below 0.5~ by weight of water.
This can easily be determined by a preliminary test.
Apart from using aqueous hydrogen peroxide solutions
this possibly present water can also be entrained by the higher
boiling solvent itself. Thus, when using organic hydrogen perox-
ide solutions the higher boiling solvent need not be anhydrous.
The advantage of the process according to the present invention
also lies in that the solutions according to the present invention,
in the case that their water content should have increased by de-
composition of the hydrogen peroxide can be azeotropically
dehydrated again by a correspondingly dosed addition of the lower
boiling sol~ent.
The hydrogen peroxide solution and the solvent are usu-
ally mixed in mixing kettles preferably provided with stirring
equipm~nt.
` The process according to the present invention can be
carried out in conventional evaporators and distilling apparatuses,
as for example, tower packing columns and tray columns.
Any material which is inert with respect to hydrogen
peroxide, as for example, glass, enamel, aluminium, passivated
refined steel, specific plastics, is a suitable material.
The advance in the art of the process according to the
present invention lies in the safety of obtaining hydrogen perox-
ide solutions in solvents which have higher boiling points than
those of hydrogen peroxide but have a wa-ter content of only up to
1~ by weight, preferably even below 0.5% by weight. Furthermore,
during the production of these solutions practically no loss of
hydrogen peroxide applied is incurred~
The advantages also are the decisive differences as com-
pared with the processes of DE-AS Nos. 2,462l957 and 2,462,900 in
which hydrogen peroxide is jointly distilled off with the phenols
or phenol ethers to be reacted from a mixture containing as the
third component a solvent for hydrogen peroxide which has a boil-
ing point higher than that of the phenol or phenol ethers. Accor-
ding to the examples and according to DE-AS No. 2,410,742 and
DE-AS No. 2,419,758 from which the above Auslegeschriften have
been divided, preferred third components are trioctyl phosphates.
It is not described how the hydrogen peroxide solutions
to be applied are produced in trioctyl phosphates. Therefore, it
must be assumed that these solutions were produced in a manner
3Q ana logous to that described in German Patent No. 20 38 319 and,
therefore, must have comparably high residual water contents. Of
course, this residual water also changes into the vapour phase.
-- 8 --
4~1~
Furthermore, the production of the anhydrous solutions
of hydrogen peroxide in phenols or phenol ethers according to
DE-AS Nos. 2,462,957 and 2,462,990 requires a high expenditure of
energy because of the total evaporation of the phenol component
together with the hydrogen peroxide.
At the same time safety problems are encountered due to
the common presence of hydorgen peroxide and of the organic compo-
nents in the vapour phase, quite apart from the losses of hydrogen
peroxide due to the distillation.
As compared therewith, the process according to the pre-
sent invention produces the anhydrous solutions which are obtained
as a bottom product and not as a top product without any lower
boiling entraining agent.
The present invention will be described by way of the
following Examples.
Example _
420O0 g of triethyl phosphate are added to 421 g of a
42.74% by weight solution of hydrogen peroxide in acetic-isopropyl
ester (= 179.9 g of H2O2) having a residual water content of 0.03
by weight. 240.3 g of acetic isopropyl ester having a content of
0.01% by weight of H2O2 are distilled off at a vacuum of between
250 and 350 mbars. The bottom temperature lies betwPen 75 and 77C
and the top temperature reaches a maximal value of 48C. At the
bottom there remains 600 g of a 29.91~ by weight anhydrous solution
of H2O2 in triethyl phosphate. A residual water content can no
longer be detected (smaller than 0.01~ by weight) as measured af~er
the production.
Example 2
400.0 g of phthalic diethyl ester are added to 250.0 g
of an anhydrous solution of H2O2 in acetic-isopropyl ester contain-
ing 44.10~ by weight of hydrogen peroxide and having a residual
water content of 0.03% by weight. 138.7 g of acetic-isopropyl
9 _
ester are distilled off via a column at a vacuum of 100 to 50 mbars.
I'he bottom temperature increases from an initial value of 55C to
73.5C. The top temperature reaches a maximal value of 29 C.
508.5 g of a 21.5% by weight anhydrous solution of hydrogen perox-
ide in phthalic diethyl ester remains at the bottom. A residual
water content can no longer be detected (lower than 0.01% by weight),
measured as in Example 1.
Example 3
350 g of N-methyl pyrro]idone-2 are added to 363.0 g of
anhydrous solution of H2O2 in acetic-isopropyl ester containing
42.74% by weight of and having a residual water content
of 0.03% by weight. 207.3 g of acetic-isopropyl ester are distil-
led off via a column at a vacuum of 400 to 350 mbars. The acetic-
isopropyl ester has an H2O2 content of 0.05% by weight.
The bottom temperature increases from an initial value
of 71 to 76C and the top temperature reaches a maximal value of
53C. 507.0 g of a 30.5% by weight solution of hydrogen peroxide
in N-methyl pyrrolidone remains at the bottom. A residual water
content is no longer detectable (lower than 0.01% by weight),
measured as in Example 1.
Example 4
250.0 g of acetic isopropyl ester and 257.0 g of a 70%
by weight aqueous H2O2 solution (corresponding to 179.9 g of H2O2)
are added to 420.0 g of N-methyl pyrrolidone-2. At a vacuum of
350 to 370 mbars and top temperatures of 52 to 56 C, 77.0 g of
H2O2 are distilled off via a water separator. The H2O2 content
of the distilled ~l2O is 0.05% by weight. The residual acetic-
isopropyl ester (249.6 g) is then distilled off at 200 to 250 mbars.
The H2O2 content of the ester is < 0.01% by weight. 608.0 g of a
30 29.6% by weight anhydrous solution of H2O2 in N-methyl pyrrolidone-
2 remains at the bottomO The residual water content is 0.01% by
weight, measured as in Example 1.
-- 10 --
67~
Example 5
395.0 g of a 45.6% by weight anhydrous solution of hyd-
rogen peroxide in acetic isopropyl ester (- 180.1 g of H2O2 (100%))
with a residual water content of 0.03~ by weight are added to 420.0
g of tetramethyl urea. At a pressure of 260-170 mbars 213.6 g
acetic-isopropyl ester are distilled off via a column. The acetic-
isopropyl ester has a hydrogen peroxide content of O.lg by weight.
The bottom temperature increases from an initial value
fo 68 C to 74C and the top temperature reaches a maximal value of
46C. 598.2 g of a 29.98~ by weight anhydrous solution of hydrogen
peroxide in tetramethyl urea remain at the bottom. A residual
water content is no longer detectable (lower than 0.01% by weight)
- measured as in Example 1.
o~arison Example for Example 5
449.7 g of a newly distilled tetramethyl urea are added
to a solution of 190.8 g of hydrogen peroxide in 84.8 g of water
(= a 69.22% by weight aqueous hydrogen peroxide solution). At a
vacuum of 65 to 25 mbars 104.03 g of a 15.3~ by weight aqueous
H2O2 solution (= 88.0 g of H2O) are distilled off via a column.
The bottom temperature increases from an initial value of 60C to
77.5C and the top temperature reaches a maximum value of 53C.
616.0 g of a 26.23% by weight solution of H~O2 in tetramethyl urea
are obtained as the residue.
(The comparison example was not produced by means of the
process accordiny to the present invention).
- 11
