Note: Descriptions are shown in the official language in which they were submitted.
li3~B42
BACKGROUND OF THE INVENTION
The present invention refers to a process for the
preparation of epoxides (oxiranes) by reacting compounds con-
taining one or more olefinic double bonds with peracetic acid.
Heretofore, epoxidation with per acids has been carried out in
such a way, that the per compound, which had been prepared
first, was freed from reducing and decomposing substances, such
as aldehydes and traces of heavy metals, by distillation, and
finally reacted with the olefinic compound (cf. Ullman, Encyclo-
pedie der Technischen Chemie, 4th Edition, vol. 10, p. 563 ff,
publishing house Chemie, Weinheim/Bergstr., 1975). Such a pro-
cess has the disadvantage that purification of the per acid is
subject to a danger of explosion. It is not possible to do
without the purification of the peracetic acid, which is pre-
pared through oxidation of acetaldehyde with oxygen, because the
unconverted acetaldehyde is converted with the peracetic acid
to acetic acid through a redox reaction.
Thus an object of the present invention is to provide
a process by which the dangerous distillation to obtain pure
peracetic acid is not needed.
SUMMARY OF THE INVENTION
There has now been discovered a process for the
preparation of an epoxide from an olefin which has a boiling
point above 40C at 1 to 40 bar, comprising oxidizing acetalde-
hyde with oxygen in the presence of an organic solvent, which
boils below the boiling point of said olefin, and a heavy metal
oxidation catalyst to form a peracetic acid containing reac-
tion mixture, containing acetaldehyde, peracetic acid, said
catalyst and said organic solvent and subsequently epoxidizing
the olefin by contacting said olefin with the peracetic acid
containing reaction mixture, said mixture being at a tempera-
ture of from -10 to +10C prior to said contacting, in the
presence of a complexing agent for the
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catalyst, at a temperature from about 50 to about 150C, at a
pressure from about 1 to about 15 bar, while simultaneously dis-
~tilling off unreacted acetaldehyde, solvent, and acetic acid by-
product, by pa~sing an inert yas through the reaction mixture.
DESCRIPTION OF THE PREFERRED E~!BODIMENTS
In the process of the present invention it is, of
course, possible to vary the particular epoxidation conditions
and thus epoxidation may be effected at any pressure from about 1
to about 15 bar. Also, any typical epoxidation catalyst may be
employed. Likewise, the olefin may be brought into contact with
¦the peracetic acid reaction mixture in the form of the pure olefin
~or in the form of a solution of the olefin in an organic solvent.
IObviously, the oxygen may be introduced as pure oxygen or in the
¦form of an oxygen containing gas, such as air.
According to a preferred version of the process pursuant
to the invention, the peracetic acid reaction mixture is cooled to
-10 to +10C, the complexing agent and, if necessary, the epoxi-
dation catalyst added to the peracetic acid reaction mixture, or
to the olefin or olefin solution, and the peracetic acid reaction ¦
mixture is gradually added to the olefin, or olefin solution,
kept under epoxidation conditions.
According to another preferred version of the process
pursuant to the invention, the olefin, or olefin solution and, at
the same time, the peracetic acid reaction mixture are continu-
ously metered into a reactor kept at epoxidation conditions; unre-
¦ acted acetaldehyde, solvent and, paxtly, acetic acid are continu-
ously distilled off, by passing an inert gas through; and the
¦liquid reaction mixture containing the epoxy is continuously with-
¦drawn from the reactor sump.
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The first stage of the process, i.e. oxida~ion of
the acetaldehyde with oxygen or gases containing oxygen, such
as air, to peracetic acid, is carried out pursuant to known
proc~sses, in which the-acetaldehyde diluted with a solvent is
reacted with oxygen or air. In this connection, reference is
made to D. Swern, Chemical Reviews, vol. 45 (1949), pp. 5 to 8.
In industry, preference is given to performing the reaction
in the presence of a catalyst. In this respect, reference is
e.g. made to German published patent application 1,165,009.
Suitable catalysts are, for example, FeC13,
Fe(~03)2, Co(~O3)2, Co(CH3C00)2 and molybdenum acetonyl-
acetonate. With respect to conversion rate and selectivity,
there is practically no difference between the iron and cobalt
salts. The selectivity in the formation of peracetic acid is
more than 90% and the aldehyde conversion rate is about 60%.
The catalyst is employed in customary quantities, for example,
in quantities from about 0.001 to about 0.01 percent, by
weight, referred to the acetaldehyde. Oxidation is carried
out at any customary temperature, such as from about O to
about 30C, preferably between about 0 and about 20C.
Customarily, the reaction periods are from about 30 to about
120 minutes.
Solvents used in the oxidation of the acetal-
dehyde may be, for example, acetone, acetic ester, chloro-
benzene, methylethyl ketone, acetic acid, or methylene
chloride, preferably, acetone or acetic ester. The quantity
of solvent is chosen in such a way, that the concentration of
acetaldehyde in the oxidation mixture is within a range of
about 5 to about ~0 percent, preferably within a range from
about 10 to about 20 percent.
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¦ It is an essential point of the invention, that the
reaction mixture obtained in the oxidation of~the acetaldehyde is
not processed to separate the pure peracetic acid, but the olefin
is reacted with the reaction mixture containing acetaldehyde,
solvent and catalyst. During this time, most of the organic sol-
vent, as ~ell as part of the formed acetic acid and the unreacted
acetaldehyde are distilled off with the addition of an inert gas.
Of course, this is possible only if, under the conditions of
epoxidation, the boiling points of the inert organic solvents and
10 ¦ the acetaldehyde are lower than the boiling point of the olefin
¦used for epoxidation. Consequently, the process pursuant to the
invention is only suitable for the conversion of such olefins,
the boiling point of which, under the epoxidation conditions to
be considered here, is higher than the boiling point of the
acetaldehyde. Selection of a suitable organic solvent depends of
course upon the boiling point of the olefin to be subjected to
epoxidation, i.e. under the epoxidation conditions, the boiling
point of the organic solvent has to be lower than the hoiling
point of the olefin.
Olefins which may be epoxidized according to the processj
puxsuant to the invention are, for example, normal and iso-alkenes,
substituted alkenes,~oe~st,abu~nesaturated fatty acids and polyolefins`
with double bonds in middle and/or terminal position. The follow-
ing may be mentioned as examples of such alkenes:
Hexene-l, octene-l, decene-l, undecene-l, dodecene-l,
octadecene-l, polycyclopentadiene, polybutadiene-1,2
and!or polybutadiene-1,4, allyl chloride, propylene
trimer, linseed oil and oleic acid.
~11 these olefins possess boiling points that are
higher than the boiling point of acetaldehyde. Examples of
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i
olefins that cannot be converted accorclin~ to the process pursuant,
to the invention because their boiling points are lower than the
boiling point of acetaldehyde are ethene, propene and the butenes.l
Epoxidation is typically carried out at temperatures in !
a range from about 50 to about 150C~ preferably from about 80 to
about 110C, and at pressure of up to about 15 bar. Epoxidation
is performed under pressure when a comparatively low-boiling sol-
vent is used, which is necessary when the olefinic compound to be
subjected to epoxidation also has a relatively low boiling point. !
Suitable solvents are, for example, acetone, acetic
ester, methylene chloride, methyl chloride, chlorobenzene and
methylethyl ketone. For reasons of economy ald processing tech-
nology, the same solvent is used for epoxidation, as in the oxida-
tion of the acetaldehyde, preferably acetone or acetic ester.
The followiny table shows by way of an example some of
the possible and expedient process parameters:
Alkene Temperature Pressure Solvent
(C) (bar)
_ I
hexene-l 90 - 100 12 methylene chloride
octene-l 90 - 100 3 acetone
decene-l 90 - lO0 1 acetic ester
polybutadiene-1.290 - l00 l acetic ester
polybutadiene-1.490 - 100 1 acetic ester
octadecene-l 90 - 100 1 acetic ester
25 undecene-l 90 - lO0 1 acetic ester
propylene trimer90 - lO0 1 acetic ester
oleic acid 90 - lO0 l acetic ester
linseed oil 90 - 100 1 acetic ester
allyl chloride90 - lO0 15 methylene chloride
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For purposes of the formation of complex compounds with
the heavy metal catalysts present from the oxidation of the alde-
hyde to per acid, as well as to prevent decomposition of the per
acid through a wall reaction with meta]lic materials (see M. Andoh
let al., Nippon Ragaku Kai Shi (1975), No. 8, 1383), a complexing
agent is used in the epoxidation stage. Suitable complexing
agents are, for example, polyphosphoric acid, pyromellitic acid
and pyridinecarboxylic acids.
If desired, one of the customary epoxidation catalysts
can be used during epoxidation. Among those which are useful are
sulfuric acid, trifluoroacetic acid, tungstic and molybdic acid,
alkanesul~onic acids, cation exchange resins and zinc phosphate.
The compounds polyphosphoric acid and pyromellitic acid, effective
as complexing agents, also exert a catal~tic influence on epoxi-
dation.
The epoxidation catalysts, or complexing agents, aretypically used in quantities o ahout 0.01 to about 1 percent, by
weight, preferably in quantities of about 0.1 to about 0.3 percent,
by weight, Leferred to the per acid. Preferably, use is made of
polyphosphoric acid or pyromellitic acid as complexing agent in
epoxidation and as epoxidation catalyst, or of sulfuric acid as
epoxidation catalyst and ofla pyridinecarboxylic acid as com- !
plexing agent.
In contrast to the known process, the catalyst used in
the oxidation of the acetaldehyde remains in the reaction mixture. !
It influences the progress of epoxidation to a decisive extent.
It has, for example, been found, that some of the catalysts used
in the oxidation of acetaldehyde exert a negative influence on
selectivity during e~oxidation. This is, for example, the case
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with feriferous an organic catalysts and can be explained as
follows: as is known, an intermediary, dicyclic,addition
complex is formed during epoxidation (see Bartlett, Rec. Chem.
Proc., 11, 51, (1960)).
¦¦ + ¦ C - R ~ C - R~
C H ..., 0 H------0
As was shown by our investigations, this addition complex can
break down in two directions and into different reaction
products:
r~o~--.C~
a. b.
C H0 C H0
¦ / 0+ ~ C - R ¦l + 0 + C - R ~ -
Path a. ch?racterizes normal decomposition to the epoxide,
path b. is strongly catalysed, for example, by heavy metal
ions, thus the decline in selectivity is only in part due to a
direct decomposition of the per acid since, in the absence of
olefinic double bonds, due to the presence of heavy metal
ions, it breaks down more slowly under the same reaction con-
ditions. merefore, metals present in the form of inorganic
salts during the oxidation of the acetaldehyde have to be
rendered harmless by precipitation or complex formation. Among
others, the compounds mentioned above are suitable for that
purpose.
Compared with the known process, the process
pursuant to the invention has the advantage, that distillation
of the
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'peracetic acid, which is subject to explosion hazards, as well as
the processing steps connecte~ therewith, are eliminated. In
addition, in the process pursuant to the invention, the concentra-
tion of peracetic acid in the epoxidation reaction mixture can
always be kcpt low, but reaction with the olefinic com~ound will
nevertheless proceed rapidly. Since, in the process pursuant to
the invention, unreacted acetaldehyde is largely distilled off,
there is practically no reaction of this compound with the per-
acetic acid. This fact, as well as the simultaneous distilling
¦off of the solvents re~uired for oxidation, but harmful for
epoxidation, leads to a very high selectivity for the epoxy com-
¦pounds.
¦ The following nonlimiting examples further demonstrate
¦the present invention.
15 ¦ Example I
¦ A reactor of enamelled steel and e~uipped with a coolingjacket, a gas supply and a gas discharge line, as well as a mag-
netic stirrer, was charged with 200 g acetaldehyde and 1800 g
ethyl acetate, to which 0~01~ by weight, referred to the acetalde-
hyde, of FeC13 was added as catalyst. For 2 hours, 1 normalliter/hr. of oxygen was introduced into the mixture cooled to
~10C, under a pressure of albout 4 bar.
Analysis of the reaction mixture showed an aldehyde
conversion rate of 63% and a peracetic acid selectivity of 97%.
The reaction mixture was used in the epoxidation described in the
following without any further processing.
For epoxidation of decene-l, 100 g of this material were
placed in a pipe reactor (bubble column) and heated to 100C by
means of jacket heating. After that, nitrogen was conducted
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through the decene-l at a flow speed of 20 lit. per hour. In
the following, 285 g of the reaction mixture containing per-
acetic acid and prepared in the manner described above were
cooled to 0C, mixed with polyphosphoric acid and fed into the
heated reactor within 15 minutes. Continuing the bubbling
through of nitrogen, the reaction was continued for another 5
minutes; the preponderant part of the low-boiling components
was distilled off and condensed in a cooler. In addition to
acetic ester, acetic acid and acetaldehyde, the distillate
still contained 29% of the charged peracetic acid.
An epoxydecane solution free from peracetic acid
was withdrawn from the sump of the reactor and the solvent
distilled off. Referred to the decene-L, the reaction con-
version was 33%, referred to the peracetic acid it was 71%.
Referred to the epoxydecane, the selectivity was 98%, while
referred to the peracetic acid it was 92%.
ExamPle II
A pipe reactor was used for the continuous pre-
paration of epoxyoctadecane. The interior of that reactor was
equipped with a steam-heated, coiled spiral tube provided with
a supply tube and a gas discharge tube at the upper end, and a
gas supply tube at the lower end, while the exterior was equipped
with a coil, a gas supply tube at the lower end and a gas dis-
charge tube at the upper end, with the lower discharge tube of
the inner spiral tube ending in the lower part, and the upper
gas discharge tube of the inner spiral tube ending in the upper
part of the external part of the reactor. 1540 g/hr. of a
liquid reaction mixture cooled to 0C and consisting of 765 g
octadecene-l and a reaction mixture containing peracetic acid
mixed with polyphosphoric acid as
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described in ~xample I, were metered into the upper supply tube
llf the ir~ner spiral coil. The reaction mixture containing per-
¦¦acetic acid consi'sted of 115 g peracetic acid; 40.4 g acetalde-
!I hyde, 2.~3 g acetic acid, 98~ g acetic ester, 0.1 ~ FeC13 and
j 0.35 g polyphosphoric acid.
The reaction mixture went from top to bottom in the
team-heated spiral coil. It fillefl its volume to a~out 20%. A
stream of inert gas was introduced at the lower end of the spiral
coil, in a counter-current with the reaction mixture. On this
o !j occasion, the biggest part of the low-boiling components (acetic
¦ester, acetic acid, acetaldehyde ana unreacted peracetic acid)
~¦evaporated and, going through the upper gas supply tube, reached
llthe upper space of the external part of the re~ctor, which func-
¦!tions asvapor space of the after-reaction zone. The epoxydecane
1l solution free from peracetic acid went through the lower discharge
tube of the spiral coil to the lower part of the external part of
the reactor, which functions as after-reaction space. Inert gas
was supplied in this part of the reactor as well. There, the
Iremainder of the low-boiling components evaporated, and, together
with the low-boiling components evaporated in the spiral coil, was
withdrawn at the upper end of the external part of the reactor via
a cooler and ~ed to a condenser. The epoxydecane solution was
¦withdrawn from the after-reaction space and then processed hy
means of distillation. I
The conversion, referred to the octadecene-l, was 42~, ¦
referred to the peracetic acid it was 92%. The selectivity re-
l ferred to the epoxyoctadecane was 97%, referred to the per acid
I it was 90~.
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