Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGRO~ND OF THE INVENTION
Field of the Invention
This application relates to the oxidation of ethylene
and is more particularly concerned with the preparation of
ethylene oxide by using thallic alkanoates.
Prior Art Statement
The preparation of certain selected epoxides by the oxida-
tion of the corresponding olefin with thallic acetate is described
by W. Kruse et al., J. Org. Chem. 36 1154 (1971). In this reaction,
epoxides of isobutylene and propylene were obtained, but only
traces of epoxides were detected when ethylene and cis- and trans-
2-butene were treated. U.S. Patent 3,641,067, (issued in 1972 to
W. M. Kruse) also describes the preparation of the epoxides of
propylene and isobutylene by means of lower alkyl thallic carboxy-
lates but makes no reference to ethylene oxide. Kruse describes
the use of pressures up to 30 psi in connection with the prepara-
tion of epoxides from propylene and isobutylene.
In the application of William F. Brill, "Preparation of
Epoxides," Canadian Serial No. 275,420 a process is described
for preparing epoxides from the corresponding olefins by means
of an aryl thallic
.
~ .
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r
c~rboxyl~tc in the prescnce oE an Inert polar Gr~anic solvent and in the
presence of t~later. While the aryl tllalllc carL)oxylate ls employed alone or
ln combination with a thallic alkanoate, the ratio of aryl and non-aryl carboxy-
late is required to be at least 1:1. Apparently,because of inefficient agitation,
ethylene oxide is obtained in very low yieids (Example 6: 7.2% yield, based .
on thallic acetate reacted) when ethy].ene is reacted with thallic acetate in
the rotated apparatus therein described, pressured to 100 pslg with ethylene.
SUMMARY OF THE INVENTION
_ _
According to the process of the present invention, ethylene oxide
is produced by ccntacting ethylene with a thallic alkanoate in the presence
of a turbulently agitated liquid medium containing water and an alkanoic acid,
and optionally containing an inert organic solvent, in a reaction zone having
an ethylene partial pressure of at least 50 psig.
DETAII.ED DESCRIPTTON OF THE INVENTION .
- It has now been discovered that when ethylene is oxidized to
produce the corresponding ethylene oxide by means of a thallic alkanoate in
the presence of an alkanoic acid and in the presence of water, and preferably
also in the presence of an inert organic solvent, significant quantities of
ethylene oxice can be produced if the ethylene partial pressure in the reaction
zone ls at least 50 psig and if the reaction medium is sufficlently agitated to
provide a substantially turbulent liquid reactlon medium.
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As indicatcd above, the etllylene partial pressure in the reaction
zone should l~e at least 50 psig. t preferably at least 100 psig. and most
preferably at least 200 psig. I-t is not critical for the ethylene partial pressure
in the reaction zone to be maintained at a constant value throughout the
reaction, and the pressure may be allowed to vary, as for example due to the
reaction of ~aseous ethylene. The ethylene can be used in pure form or it
can be diluted with an inert gas, e.g., nitrogen, argon, helium or the like,
if desired. The presence of a diluent will, of course, make it necessary to
use a i~.igher to.al pressure to provide the equivalent ethylene pressure,
¦Ordinarily, there is no advantage in em?loying total pressures greater than
~ SOG~ psig .
¦¦ Tne thallic alkanoates wh~ch are suitably used in accordance with
¦Ithis invention !nClude th~ thallic salts of alkanoic acids containing 1 to 20
¦!carbon atoms, which may be uns.lbstituted or may ~ie substituted with non-
.eactive substituents such as halogen, alkoxy, alkyl, and the like. Thus,
examples of such allcanoic acids include formic acid, acetic acid, propionic
acid, butyric acid, isobutyric acid, valeric acid, pivalic acid, octanoic acid,
dodecanoic acid, tri~luoroacetic acid, and the like.
Each thallic alkanoate can be used as the sole thallic carboxylate
or it can be used in admixture with other thallic alkanoates of the type specified,
Preferably, howe~rer, only one thallic alkanoate is used and most preferably,
the thallic alkanoate is thallic acetate, thallic propionate or thallic ~sobutyrate.
It will, of course, be understood that the thallic alkanoates can have other
thallic salts mixed with them (such as the aryl thalllc carboxylates described
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by W. Brill in Serial No. 275,420 referred to above), but -the
alkanoates are preferably the sole thallic salts and in any
case they represent more than 50 mol percent of total organic
thallic salts present.
The epoxidation is carried out in the presence of an
alkanoic acid and water and optionally, but preferably, in the
presence of an inert organic solvent, which may be polar or non~
polar, preferably polar, this mixture being referred to as the
reaction medium. The alkanoic acid can be any of the acids re-
ferred to above, i.e., alkanoic acids containing 1 to 20 carbon
atoms which may be substituted with non-reactive substituents.
Typical non-polar solvents include carbon tetrachloride and
hydrocarbons such as heptane. Typical polar organic solvents
include ethers such as tetrahydrofuran and p-dioxane, alcohols
such as t-butyl alcohol, amides such as dimethyl formamide and
, dimethyl acetamide, ketones such as acetone, methyl ethyl Xetone
and diethyl ketone, polar chlorinated hydrocarbons such as
chloroform, as well as dimethyl sulfoxide, and the liXe, ethers
of d ethylene glycol and triethylene glycol and ether alcohols
such as diethylene glycol, ethylene glycol monomethyl ether,
ethylene glycol monoethyl ether, ethylene glycol dimethyl ether,
ethylene glycol diethyl ether, diethylene glycol monomethyl ether,
diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl
ether and diethylene glycol diethyl ether, glycol esters such
as ethylene glycol monoacetate, ethylene glycol diacetate, di-
ethylene glycol monoacetate or diethylene glycol diacetate, and
the corresponding ethers and esters or propylene glycol, butylene
glycol, and the like. The alkanoic acid component of the reaction
medium can also, of course, function as a solvent. It will be
understood that the solvents mentioned above are merely representa-
tive of suitable solvents.
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The amount of water will generally ranse from about 0.1 to /0
volume percent of the reaction medium but preferably is at least 3 volume
percent, and a particularly advanta~eous quantity is S-S~ volume percent, and
most preferably is from about 9 to 26 volume percent. The amount of reaction
medium is freel~ variable. Most suitably, however, enough is used to dis-
solve tne thallic alkanoate and to provide a molar ratio of water to thallic
alkancc;te of at least 1:1, preferably at least 2:1, The alkanoic acid is suit-
ably OI at least about 1 volume percent of the .otal reaction medium. The
thallic alkanoate is typically employed in a concentration in the reaction
medium of at least 0. osM and preferably above 0. lM.
The reac~ion can be carried out at any convenient temperature, e.g. ,
oC, room temperature, or above, but for best results, from the standpoint of
reaction rate, it is adva;ltageous to heat the reachon mixture moderately, e.g~, ¦
to temperatures of 25 to 150C, preferably 30 to 80C, but higher tempera-
tures c~.n be used if desired .
The reaction is suitably carried out in any vessel into which the
solvent-water mixture and the thallic alkanoate can be charged, which
will withstand sufficient pressure to provide the desired ethylene pressure
and in which the desired substantially turbulent agitation of the liquid reaction
medium can be induced. The reaction vessel is provided with a suitable inlet
tube for loading the ethylene from its source Into the liquid reaction mixture in
the reactor or the reaction mixture can be pressured with ethylene to the
desired pressure before introduction into the vess01. The reaction can be
carried out batchwise or it can be mn continuously.
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To achieve the significant ethylene oxide quantities
of the process of the present in~ention, the liquid reaction medi-
um should be agitated so as to provide substantially turbulent
mixing conditions therein and to avoid completely laminar flow.
Such turbulent agitation can be accomplished by conventional means
which will, of course, vary depending on the configuration and
size of the reactor, the volume of the liquid reaction medium and
other factors. Thus, a backmixed reactor can be provided with
any of the conventional stirring means, including but not limited
to blades, impellers, turbines, paddles, propellers, and the like,
and can be unbaffled or baffled. Alternatively, as in a tubular
reactor, the liquid medium can be passed through the reactor at
such a rate, relative to the reactor volume, as will result in tur-
bulence within the liquid. Likewise, the liquid reaction medium
can be turbulently agitated by passing gases therethrough, employ-
ing conventional gas-liquid contacting apparatus and techniques,
e.g., using such devices as open-ended pipes, perforated plates,
and ring- or cross-style perforated pipe spargers. Suitable gases
will, of course, include gaseous ethylene, inert gases and mix-
tures thereof.
The degree of agitation necessary to induce "turbulent
agitation" in a given reaction will be obvious to one skilled in
the art. Thus, in a stirred vessel, turbulent agitation can be
defined by Reynold's Numbers in excess of about 20, preferably in
excess of 100, more preferably in excess of 300 and most preferably
in excess of 1,000, which value may be calculated by the well-known
expression (I):
NR = D2N ~ (I)
wherein NR is the Reynold's Number; D is the diameter of the im-
peller; N is the rotational speed of the impeller; ~ is the density
of the liquid; andf~ is the viscosity of the liquid; all in con-
sistent units. See Mixing Theory and Practice, vol. 1, pg. 122
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(V. W. Uhl and J. s. Gray, eds. 1966) Likewise, fluid flowing
through a tubular reactor will be turbulently agitated when the
liquid is characterized by a Reynold~s Number in excess of 1,000,
preferably greater than 1,500 and most preferably at least 2, ono,
as can be calculated by the well~known expression (II):
NR = dv ~ (II)
e ~
wherein NR is the Reynold's number; d is the inside diameter of
the tubular reactor; v is the velocity of the liquid; ~ is the
density of the liquid; and ~ is the viscosity of the liquid,
all in consistent units. Chemical Engineers' Handbook, page 5-21
et seq. (J. H. Perry, ed.) (Fifth Edition 1973). Further, the
liquid medium can generally be turbulently agitated by gas sparg-
ing techniques using superficial gas velocities sufficient to
provide orifice Reynold's Numbers in excess of 50, preferably in
~` excess of 1,000, more preferably in excess of 10,000, and most
preferably in excess of 30,000, as defined by the equation (III):
N' = ~ (III)
wherein N'R is the orifice Reynold's Number, L is the orifice
e
diameter, V is the superficial gas velocity through the orifice,
~ is the density of the gas, ~is the gas viscosity. Chemical
Engineers' Handbook, supra at page 5-13.
The product ethylene oxide can be readily recovered
from the reaction mixture by distillation. Acetaldehyde will
normally be formed as a minor by-product and can be separa-ted from
the ethylene oxide in conventional manner, e.g., by distillation.
Simila ly, the thallium sal-ts can also be recovered from the
reaction mixture by distilling off the more volatile components.
; In the course of the reaction, at least some of the thallic ion
is reduced to the thallous state. If desired, the thallous ion
can be reoxidized to the thallic state in any convenient manner
to permit the formation of further quantities of thallic alkanoate.
For example, the thallous salt can be oxidized with molecular
oxygen in the presence of Group VIII noble metals as catalysts
to produce the corresponding thallic carboxyla-te.
The invention will be more fully understood by
reference to the ollowing specific examples, but i-t is to be
understood that these examples are given solely for illustrative
purposes and are not intended to be limitative of the invention.
In the examples, the determination of ethylene oxide and acetalde-
hyde was effected by gas chromatography.
EXAMPLE 1
- A mixture of 18 volume percent isobutyric acid, 10
volume percent water, and 72 volume percent tetrahydrofuran
containing a 0.1 molar concentration of thallic acetate, is
charged into a stirred pressure vessel provided with a 7/8 inch-
diameter, Teflon coated, magnetic stirring disk and the vessel
is pressured with 500 psig ethylene at room temperature (25%).
The vessel is then heated for 15 minutes at 80C with continuous
stirring at an average impeller rotational speed of about 500
revolutions per minute employing a magnetic stirrer, thereby
providing a turbulently agitated liquid medium having a
Reynold's Number of about 10,000. Gas chromatographic analysis
of the effluent shows it to contain ethylene oxide in an amount
corresponding to a yield of 39% based on the thallic salt
charged, along with a minor amount of acetaldehyde, the ethylene
oxide and the acetaldehyde being present in the molar ratio of
10 . 9 : 1 .
_g _
EXAMPLE 2
Example 1 is repeated except that the reaction is carried
out at 100C. The effluent is found to contain ethylene oxide in
40c yield, the ethylene oxide to acetaldehyde molar ration being
8.8:1.
EXAMPLE 3
Example 2 is repeated except that the reaction is carried
out at 60C and the reaction time is 30 minutes. The effluent is
found to contain ethylene oxide in 39% yield, the ethylene oxide
to acetaldehyde molar ratio being 10:1.
1 0 -
~.~ I .
EXA M PL T~ .~
ExaMple 2 is repeated except that the reaction is carried out at 40C
for 3 hours. The effluent is found to contaln ethylene ocide in 57% yield, the
ethylene oxide to acetaldehyde molar ratio being 7.9
EXA~IPLE 5
Example 2 is asain repeated except that the reaction }s carried out at
40C for 5 hours, and the concentration of thallic salt is 0.5~ The effluent
¦ is Iound to contain ethylene oxide in 50% yleld, the ethylene oxide to
¦ acetaldehyde molar ratio being 8 . 9 :1 .
EXAMPLE 6
Example 5 is repeated except that the reaction is carried out at 40C
for 3 hours. he efIluent is found to contain ethylene oxide in 38~/o yield, the
etnylene oxide to acetaldehyde molar ratio being 6.9:1.
. '.
EXAMPLE ? :.
.
Example 6 is repeated except that the ethylene pressure is 350 psig.
The effluent is found to contain ethylene oxide in 32% yield, the ethylene
oxide to acetaldehyde molar ratio being 6. 2:1.
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EXA M PL E 8
Example 6 ls repeated exce2t that the temperature is 60C, the
ethylene pressure is 800 psig, and the reaction is carried out for 1 hour. The
effluent is found to contain ethylene oxiàe in 38% yield, the ethylene oxide
to acetaldehyde molar ratio being 7. 7:1 .
E.YAMPLE 9
Example 2 is repeated once again except that the tetrahydrofuran
is substituted by an equal volume quantity of ethylene glycol diacetate. The
e.~luent is found to contain ethylene oxide in 39% yield, the ethylene oxide to
acetaldehyce molar ratio being 7 . 2 :1 . .
¦ ` E~AMPLE 10
The pressure vessel is charged with a mixture of 18 volume percent
isobutryi_ acid, 10 volume percent water, and 72 volume percent triglyme
containing a 0.1 molar concentration of thallic acetate and the vessel is
pressured with 500 psig ethylene at room temperature (25C). The vessel is
then heated for 30 minutes at 60C with continuous stirring. Gas chromato-
graphic analysis of the effluent shows lt to contain ethylene oxide in an amo.~nt
corresponding to a yield of 41% based on the thallic salt charged, the ethylene
oxide to acetaldehyde molar ratio being~ 8. 9:1 . Triglyme is the dimethyl ether
of triethylene ~lycol~
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EX.'~ M l'L E U
Example 10 is rcpeated except that the reaction is carried out at 25C
for 10 hours. The effluent is found to contain ethylena oxide ln 69% yield, the .
ethylene oxide to acetaldehyde molar ratio being 12 1.
EXAMPLE 12
Example 10 is repeated except tha~ the trislyme is replaced with an
¦ equal volume of acetone. The ef~luent is found to contain ethylene oxide in
36% yield the ethylene oxide to acetaldehyde molar ratio being 6.5:1.
'.' I
EXAMPLE~3
Ex2mple 10 is again repeated except that the trigiyme is replaced by an
equal ~tolume of methyl ethyl ketone. The effluent is found to contain ethylene
oxide in 26Yo yield, the ethylene oxide to acetaldehyde molar ratio being 6.6:1.
EXAMPLE 14
~ . !
Again Example 10 is repeated except that the triglyme is replaced by
an equal ~olume of methyl isobutyl ketone. The effluent is found to contain
ethylene oxide in 31% yield, the ethylene oxide to acetaldehyde molar ratio
being 5.6:1. -
EXAMPLE 15
Example 10 is repeated except that the reaction is carried out for onehour. The efflu~ent ls found to contain ethylene oxide ln 51% yield, the ethylene
oxide to acetaldehyde molar ratio being 11.9:1.
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E~M rI~
Example 15 is repea~ed e~ccept tilat the reaction is carried out at 25C
and the reaction time is 10 hours. The effluent is found to contain ethylene
oxide in 55% yield, the etnylene oxide to acetaldehyde molar ratio being 11.8:1.
EXAMPI.F 17
T press ~re vessel is chargcd with a mLxture of lS volume porcert
propionic acid~ lO volume perc2nt water, and 75 volume percent tertiary butyl
alcohol, contain~ng a 0.1 molar concentration of thallic acetate and the vessel
is 3ressured ~ith ~00 psig ethvlene at room temperature (25C). The vessel
is then hea~ed for 30 minutes at 60QC with continuous stirring as in E~xample 1.Gas chromatogranilic analysis of the effluent shows it to contain ethylene oxidein an amount corresponding to a yield of 4'1% based on the tnallic salt charged,the etnylene oxide to acetaldehyde molar ratio being 10 1.
EXAMPLE 18
Example 17 is again repeated except that the reaction medium compris~ s
10 volume percent propionic acid, 18 volume percent water and 72 volume per-
cent tetrahydrofuran and the reaction time is 30 minutes. The effluent is found
to contain ethylene oxide in 41% yield, the ethylene oxide to acetaldehyde
molar ratio being 10 . 2:1 . .
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LX~ M l~L ~: 1 9
Example 10 is repeated except that the acld is acetic acid and the
reaction meclium com?rises 10 volume percent acetic acid, 9 volume percent
water and 81 volume percent tetrahydrofuran. The effluent is found to contain
etnylene oxide in 35% yield, the ethylene oxide to acetaldehyde molar ratio
being 6.1:1.
EXAMPLE 2 0
Example 19 is repeated except that the ethylene pressure is reduced to
20~ ~sig ar.d the reaction time is exter.ded to one hour. The effluent is found
to co?.tain ethylene oxide in 34% yield, the ethylene oxide to acetaldehyde
molar ratio being 7.2:1.
E,~MPLEI , . '
The pressure vessel is charged with a hlixture of 10 volume percent
acetic acid, 9 volume percent water, and 81 volume percent tetrahydrofuran
containing a 0.1 molar concentration of thallic acetate and 0. 025M concentra-
tion of thallous acetate and the vessel is pressured with 200 ~sig ethylene at
room temperature (25C). The vessel is then heated for 30 minutes at 60C
with continuous sl:irrin~ as ln Example 1. Gas chromatographic analysis of
the effluent shows it to contain ethylene oxide in an amount corresponding to
a yield of 29% based on the thallic salt charged, the ethylene oxide to acetal~
dehyde molar ratio being 8.3:1.
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E`~ M l'L 1: 2 2
Into the stirred pressure vessel of Exarnple 1 is char~ed a mixture of
70 volume percent isobut~ric acià and 30 volume percent water containing a
0.1 molar concentration of thallic acetate. T'ne vessel is pressured ~ith 500
psig ethylene at room temperature (25C) and is then heated for 30 minutes at
60C with con~inuous stirring as in Example 1. Gas chromatographic analysis
of the ef~luent shows it to contain ethylene o:~ifie in an amount corresponding
to a yield of 42% based on the thallic salt charged, and to contain acet-
aldehyde in an ethylene oxide to acetaldehyde molar ratio of 4.7:1.
EXAMPLE 23
Exa;nple 22 is repeated except t~.at the charge to the pressure 'vessel
is a mixture of ao volume percent isobutyric acid and 10 volume percent water
contair~;ng a 0.1 molar concentration of thallic acetate and the pressurecl. . '
vessel is heated for 30 minutes at 40 C. The effluent is found to contain
ethylene oxide in a 39~ yield, the ethylene oxide to acetaldehyde molar ratio
beirlg 4.3:1.
EXAMPLE 24-26 .
The procedure of Example 1 is repeated except that the liquid medium
is continuously stirred at an impeller speed sufficient to provide a Reynold' s
Number of 20, 1,000 or 5,000. Data thereby obtained are set forth in Table 1. .
I . ' .
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¦~ T/~13LB 1
. Product Yield*(%)
Exa mple Reynold' s Ethylene ~cet-
No. Number Oxide alde'nvde
24 20 30 4
1,000 37 5 .
26 5,000 3~ 5
*Based on thallic ace;ate charged.
EXAMPLE 27 29
The procedure of Example 1 is repeated except that the pressure A
vesse! is pressured with either 50,60 or 100 psig ethylene at room temperature
¦ (25C`. Data thereby obtained is icet forth ln TabIe 2. . '
.
TABLE 2
P~oduct Yie!d ( '''~) *_
Exa!nple Ethylene Ethylen~ Acet-
No. Pressure (~siq~ Oxide aldehys~e
27 50 13 2.4
28 60 18 4.8 .
`i` 29 100 23 4.0 .
,'
*Based on thallic acetate charged;
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It will be obvio~ls tl~a~ various chan~es dnd modltications may be
made without departing from the invention and it is intended, therefore, that
all matter contained in the foregoing description shall be interpreted as
illustrative only and not as limitative of the invention.
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