Note: Descriptions are shown in the official language in which they were submitted.
1 2Z4793
Prior Art
The invention relates to a process for the preparation of
alkylene carbonates by the reaction of the corresponding alkylene
oxide with carbon dioxide. Such reactions are well known in the
art. Alkylene carbonates are useful as solvents or as a source of
the corresponding glycols. They are of particular interest as
int~rmediates in the process of converting ethylene oxide into
ethylene glycol ~hile avoiding the inefficiency associated with
tne conventional nydration process.
~ everal processes have been disclosed for a single ste~
hydration of al~ylene oxides to glycols in the presence of a
catalyst and carbon dioxide. Such processes are said to make
possible the reduction in the amount of water used. The removal
of excess water is a major expense in the conventional hydration
process, The carbon dioxide is not consumed in the process, but
i ~t has been sugge~ted that the hydration proceeds via the alkylene
carbonate as an intermediate compound.
U.S. 3,922,314 discloses a process for the hydration of
ethylene oxide to ethylene glycol which uses no catalyst, but
operates with an aqueous ethylene oxide solution containing at
least 8 wt% ethylene oxide and at least 0.1 wt % carbon dioxide.
A catalytic process is described in Britisn patent
1,177,877 (or U.S. 3,629,343). ~l~ylene oxides are hydrated to
the glycols at temperatures of 80-22CC and pressures of 10-180
atmospheres in the presence of a halide catalyst. Preferr~d are
alkali metal or quaternary ammonium halides, particularly bromides
and iodides. Alkali metal hydroxides, carbonates, or bicarbonates
were said to be beneficial.
~1~
lZZ4793
A similar process is discusse~ in U.S. 4,160,116 where
quaternary phosphonium halides, preferably the iodides and
bromides were used to catalyze the nydration of alkylene oxides in
the presence of carbon dioxide. The temperature is 50-200C and
'Ithe pressure 3-50 kg/cm2.
Still ar.other such process is disclosed in published
Japanese patent application 81-45426, in which molybdenum and/or
tungsten compounds are combined with known catalysts such as
alkali metal halides, quaternary ammonium or phosphonium salts,
organic halides, and organic amines. The reactlon is stated to '~e
carried out at 20-250C and 0-30 kg/cm2 gaug~.
The formation of alkylene carbonates, as opposed to the
hydration of alkylene oxides to glycols, takes place in the prior
art to be ~iscussed with no water present. Catalysts and reaction
conditions similar to those described above for the hydration of
alkylene oxides have been disclosed to be useful.
In U.S. 2,667,497 magnesium or calcium halides were used
at 150-250C and 500-2000 psi to produce al~ylene carbonates from
the corresponding oxides.
U.S. 2,766,258 discloses the use of quaternary am~lonium
hydroxides, carbonates, and bicarbonat2s to catalyze the reaction
of al~ylene oxides with carbon dioxide. The reaction was carried
out at temperatures between 100-225C and pressures of 300-500
ps lg .
The quaternary ammonium hali~es were use~ ~y the
patentees in U.S. 2,773,070 at temperatures of 100-225C and
pressures greater than 800 psi.
Amines were the catalyst used for the reaction by the
patentees in U.S. 2,773,881. The reaction was carried out at
100-~00C and more than 500 psi.
122~793
Three patents lssued to the same assignee, i.e. U.S.
2,994,705; 2,994,704; and 2,993,908 disclose substantially the
same conditions, 93-260C and 8-212 ks/cm2 gauqe, with organic
phosphonium halides, organic sulfonium halides, and urea nydro-
halides given as catalysts for the preparation of alkylene car-
bonates from the corresponding oxirane compo~nd.
Hydrazine or a halide salt thereof was used to catalyze
th~ reaction by the patentees in U..S. 3,S35,341 at temperatures ol
100-250C. An anion exchange resin containing quaternary ammonium
groups was disclo~ed in U.C. 4,233,221 as useful for vapor-phase
r~action.
~ rganic antimony nalides were s~own in published Japanes~
pat~nt application 80-122,776 to make possible the formation of
alkylene carbonates, at room temperature to 120C, in a water-fre~
mixture. The time required in the single example carried out at
room.temperature was about 5 days, a generally impractical period
of time.
I have now discov~re(3 that the reaction of alkylene
oxides to the corresponding carbonates can be carried out with
known catalysts at lower temperatures than 'neretofore used in the
art. Further, the reaction is operable even in the presence of
substantial amounts of water. The hydrolysis of the carbonates to
glycols can be minimized and the principal product is tne
carbonate, as will be seen in tne following discussion.
Summary of the Disclosure
Alkylene oxides may be reacted with carbon dioxide to
form alkylene carbonates in the presence of a catalytic amount of
~7~24793
suitable catalysts at relatively low temperatures in the range of
about 20-90C and in the presence of water. Preferably the tem-
perature will be about 30-70C. The pre~sure at which the reac-
tion is carried out is in the range of about 25-200 kg/cm2
I gauge, and may be autogenerated. The mol ratio of carbon dioxide
~o ~lkylene oxide is in the range of 1/l-lOO/l and preferably
about 2/1-10/1. Suitable catalysts inclu~e a member or members of
the group consisting of quaternary organic ammonium and phospho- I
nium hali~es, organic sulfoniu~ halides, and organic antimony
halide~i~ particularly methyl triphenyl phosphonium iodide,
tetra-ethyl ammonium bromide, an~ tétr~phenyl antimony bromide.
The corresponding carbox~ylates may also be used. The quantity of
catalyst used is generally within tne range of 0.01 to 0.15 mols
per mol of alkylene oxide, preferably 0.02 to 0.10.
Contrary to previous expectations, water ~ay be present
in substantial amounts, even exceeding those used in prior art
hydration processes, but without formation of significant amounts
of glycol. Useful mol ratios of water to al~ylene oxide are
0.1/1-20/1. With certain catalysts, the effect of water actually
is to improve the selectivity of the conversion of the oxirane to
the carbonate.
In another embodiment, the invention comprises a process
for reacting alKylene oxides with carbon dioxide to form alkylene
carbonates at relatively low temperatures in tne range of about
20-90C in the presence of at least one catalyst selected ~rom the
group consisting of quarternary organic ammonium and phosphonium
halides and carboxylates and organic sulfonlum halides and carbox-
¦ ylates. Such catalysts have hitherto been employed at operatingtemQeratures higher than those now found to be useable.
lZZ4793
f DESCRIPTION OF THE PREFERRED EMBODIMENTS
Heretofore, those familiar with the reaction of al~ylene
oxides with carbon dioxide to form alkylene car~onates have
carried out the reaction at temperatures generally in the range of
100-300C, particularly about 150-225C. Although it was not
generally discussed in detail, it will be seen from prior art
di~closures that tne reaction was carried out in the practical
ab~er.ce sf water. For Example, in U.S. 4,233,221 the reactants
w~re ~ried by condensation of water after compression so that the
;moisture level of the reactan~ gases "as quite low, estimated to
; be about 0.2 mol percent. Since the hydrolysis of carbonates was
known to take place at elevated temperatures and with catalysts
ialso useful for the direct hydrolysis of alkylene oxides to
glycols, it seems probable that prior workers in the art avoided
w~ter if only the carbonate was to be produced. ~therwise,
hydrolysis to the glycol could be expected.
~, Surprisingly, I have found that when the reaction of
alkylene oxides with carbon dioxide is undertaken at temperatures
substantially lower than taught by the prior art, that the pre-
sence of water can be not only tolerated, but actually may be
beneficial in some instances. Alkylene carbonates can be prepared
with minimal losses by hydrolysis to the glycols. This process is
particularly useful when applied to a stream combining c~rbon
dioxide, ethylene oxide, and water obtained by extraction of
ethylene oxide from a dilute aqueous solution witn near-critical
or supercritical carbon dioxide.
~ he reaction may be carrie~ out at temperatures in the
range of about 20-90 C, preferably 25-80C, especially 30-70C.
lZ2~793
Although lowering tlle tem~erature woul~ be expected to increase
the reaction time, nevertheless reasonable periods in tne general
range of 2-~ hours i~ay be achieved by properly selecting the
amount and type of catalyst and the other reaction conditions. Inl
j one embodiment, the temperature used is established by the ambient¦
conditions available for cooling the feed mixture and thus would
be in the range of about 20-30C.
,~ Pressure i~ not an especially critical variable in the
reaction. Typically, it will be in the range of about 25-200
kg/cm2 gauge and if the temperature is sufficiently low, will
be autog~nerated and thus established by the feed composition and
the temperature at which the reaction is carried out.
The molar ratio o carbon dioxide to alkylene carbonate
may range from 1/1 to 100/1. Usually a ratio greater than 1/1
would be selected, preferably 2/1 to 10/1. Where the process of
i¦ the invention i8 associated with the extraction of alkylene oxide
by (near) super-critical carbon dioxide the ratio may be
; ~0/1-60/1, with satisfactory results obtained.
It is of particular importance that water does not appear
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to hydrolyze alkylene carbonates to the alycols to a significant
extent under conditions found suitable Eor the process of the in-
vention. At higner temperatures, the amount of glycols produced
would be expected to increase until eventually the process would
no longer produce carbonates, but glycols, instead as disclosed in
the patents mentioned earlier. No limit has been established on
the amount of water which can be tolerated, in fact, amounts well
in excess of those useful for the direct hydration of alkylene
oxides to glycols have been demonstrated, as will be seen in
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1~24q93
subsequent examples. Remarkably, it has been discovered that the
presence of water may have a beneflcial effect on the selectivity
of the reaction to produce carbonate, c~ntrary to what might be
expected. This effect may be more pronounced in association with
certain catalysts, particularly those in whicn the bond between
the halide atom and the rest of tne molecule is ionic, rather than
covalent in nature.
The catalysts found useful in the process of the inven-
tion include rnany of those known in tne art, hut used now under
significantly altered conditions. Broad classes of compounds
which may be useful include one or more members of the group
consisting of organic quaternary ammonium or phosphonium halides,,
organic sulfonium halides, and organic antimony halides. The
corresponding carboxylates also may be used. Examples of com-
pounds which may be employed are the following ammonium compoundsr
tetraethyl ammonium bromide, and tetra ethyl ammonium iodide.
Specific phosphonium compounds include methyl triphenyl phos- ,
phonium iodide and methyl triphenyl phosphonium bromide. Sulfonium
compounds may include trimethyl sulfonium, iodide and trimethyl
sulfonium bromide. Antimony compounds have been found ~uite
effective when no water is present, but appear to be adversely
affected when water is included. Typical compounds are
tetraphenyl antimony bromide and triphenyl antimony dichloride.
Particularly preferred catalysts when water is present are methyl
triphenyl phosphonium iodide and tetraethyl ammonium bromide. ~f
the halides, bromides and iodides are preferred.
The amount of catalyst will be similar to that used in
other processes, about 0.01-0.15 mols of the catalyst per mol of
~22~793
alkylene oxide may be used, preferably 0.02-0.1 mols per mol,
although larger or smaller amounts are not intended to be
excluded.
While other workers in tne field have indicated that
relatively high temperatures of 100~C or preferably more would be
used either to for~ alkylene carbonates when no water was present,
or alkylene glycols when water was available to hydrolyze alkylene~
oxi~s, it ha8 been found that by carrying out the reaction at low
temperature~ in the range of about 20-90C, preferably 30-70C,
one can produce alkyl~ne carbonates and even in the presence of
wa~er.
The reaction to form carbonates may be carried out in the
pre~ence of substantial amounts of water. At higner temperatures
typical o~ the prior art, glycols would be expected when water is
present and, in fact, this is the basis for several processes as
previously di~cussed. As will be ~een, by operating at relatively¦
low temperatures, it is possible to minimize hydrolysis and to
for~ carbonates instead.
Example 1
A sample of the catalyst being tested is introduced to a
130 cc bomb produced by the Parr Instrument Company. Samples of
ethylene oxide and carbon dioxide are c'narged at -78C by immers-
ing the bomb in a dry-ice/ acetone batn. The bomb is then closed
and placed in a 36C bath so that the internal temperature of the
bomb is increased to 3nc and the reaction proceeds. Agitation is
via a magnetically driven disk. After a suitable period of time,,
the bomb is removed from the bath and the contents analyzed. The
results of a number of such tests are shown in Table A below.
~Z2~L~793
Table A
milli- Max. I
Feed, mols Pressure EC**
Test Catalyst, sath Time, kg/cm2 EO* Sel. i
No. EO* CO2 gms*** ~C hrs gau~e Conv._%
1 13.6 681 a 0.1456 36 19.5 28.1 51.7
2 13.6 681 b 0.4385 36 19.5 29.5 55 16
3 18.2 681 c 0.3654 32 19.5 1~.3 94 8~.2
~ 15.9 681 d 0.3064 37 18.5 15.5 37.7
,; 5 18.2 1022 e 0.3881 38 19.5 30.6 51.1 ----
6 22.7 1022 f 0.2406 38 19.5 7~.1 77.9 50.4
It has been discovered that water may be present without
formation o significant amounts of glycols, provided that the
temperature is sufficiently low. Surprisingly, it has been found
l that water has a beneficial effect on the selectivity to the
!I carbonate with some catalysts, while with others the selectivity
,appears to, be suppressed.
* EO = ethylene oxide
** ~C = ethylene carbonate
*** a = trimethyl sulfonium iodide
b - methyl triphenyl pho~phonium iodide
c = tetraphenyl antimony bromide
i d = triphenyl antimony dichloride
! e = methyl triphenyl phospnonium bromide
f = tetraethyl ammonium bromide
Example 2
Effect of Water on Catalysts
The procedure of Example 1 is followed except that vary-
ing amounts of water are introduced to the Parr bomb, with the
following results.
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12;~4793
Table B
milli- Max.
Feed, mols Pres. EO EC
Test Catalyst, Bath Time, kg/cm2 Conv. Sel.
~Jo. EO C02 H20 gms* C hrs ~auge %
7 19.3 1022 -~ c 0.5507 3319.5 27.8 91.1 88.5
8 18.2 1022 lO c 0.546~ 3419.5 27.4 95.6 47.1
9 20.4 1022 S b 0.4380 37 21 44.3 86 35
20.4 1022 20 b 0.4227 37 21 42.5 92 47.4
11 20.4 1022 40 b 0.4319 37 21 43.2 93 63
12 22.7 1022 80 b 0.4365 37 21 41.1 83.8 76
The data of Table B show that the presence of water
appears to 'nave no recognizable effect on the overall conversion
of ethylene oxide, the selectivity to ethylene carbonate is
reduced when catalyst "c" is used, while when catalyst "b" is
employed the selectivity to ethylene carbonate is surprisingly
improved. Catalyst "c" would be more suitable for a reaction
system in which the amount of water present is not large. Note
that the ratio of water to ethylene oxide is abQut 0.55/1 compared~
to the theoretical ratio of 1/1 for the hydrolysis reaction.
Catalyst "b" appears less effective when no water is present (see
test 2) but its performance is enchanced when water is used. Note
that the ratios for this catalyst shown réach nearly 4/1 water/~O
* c = tetraphenyl antimony bromide
b = methyl triphenyl phosphonium iodide
Although the process of the invention is particularly
useful in connection with the formation of ethylene carbonate, it
is more widely ap licaole to other oxirane compounds, as will oe
seen in the following example.
Il l
~224793
Example 3
A sample of the catalyst being tested and water (if
used) is introduced to a 130 cc Parr bomb. Samples of propylene
oxide and carbon dioxide are charged at -78C by irnmersing the
bomb in a dry-ice/acetone bath. The bomb is then closed and
,I placed in a 36C bath so that the internal temperature of the bomb
l i~ increased to 30C and the reaction proceeds. After a suitable
,I period of time, the bomb ie removed from the bath and the contents
analyzed. The results of a number of such tests are shown in
Table C below.
Il Table C
'j milli- Max.
Feed, mols Pres. PO PC**
Test Catalyst, Bath Time, kg/cm2 Conv. Sel.
No ~ PO* C02 H20 gms*** C hrs ~auge ~ %
' 13 20.3 1022 -- a 0.5511 35 21 42.6 96.2 90.3
f; 14 20.6 1022 -- b 0.4385 36 21 34<2 60.2 25.4
ii 15 20.2 1022 -- c 0.2401 36 21 56.1 85.0 58.3
'! 16 20.4 10225 b 0.43~2 36 21 47.3 88.2 34.6
17 20.6 102220 b 0.4378 36 21 52.8 89.7 56.4
! 18 20.1 1~22~0 b 0.4386 36 21 54.2 87.4 68.3
19 20.4 102280 b 0.4391 36 21 62.1 91.4 82.3
~'' ' ',
* PO = pro~ylene oxide ~ I
I ** PC = propylene carbonate
*** a = tetraphenyl antimony bromide
b = methyl tripnenyl phosphonium iodide
c = tetraethyl ~mnonium bromide
I
; Example_4
The experimental procedure of Example 3 was followed with¦
1,2-butylene oxide charged in lieu of propylene oxi~e. The
results of a number of such ~ests are shown in Table D below.
. ' ,
., ,
.~ i
., i
~ZZ4793
Table D
milli- Max.
Feed, mols Pres. BO BC**
Test Catalyst, Batn Time, kg/cm2 Conv. Sel.
No . BO* C02 ~20 qms*** C hrs gauge ~ %
20.4 1022 -- a 0.5513 36 21 44.8 92.1 87.6
21 20.7 1022 -- ~ 0.4378 36 21 47.2 58.3 22.6
22 20.1 1022 -- d 0.2436 36 21 42.6 82.0 53.2
23 20.1 10225 b 0.4386 36 21 51.8 8~.2 40.5
24 20.8 102220 b 0.4392 36 21 43.8 91.4 59.8
20.2 102240 b 0.4369 36 21 56.2 93.4 72.8
26 20.6 102280 b 0.4381 36 21 53.6 90.8 84.3
,
¦ * BO ~ 1,2-butylene oxide
** BC ~ 1,2-butylene carbonate
l *** a 3 tetraphenyl antimony bromide
I b ~ methyl triphenyl phosphonium iodide
l c - tetraethyl ammonium bromide
Example 5
A sample of the catalyst being tested, along with H2O
and solvents (when ui~ed) is introduced to a 300 cc electrically
heated stainless steel autoclave equipped with impeller agitation
produced by Autoclave Engineers, Inc. Samples of ethylene oxide
~¦and carbon dioxide are charged at -78C while the autoclave is
immersed in a dry-ice/acetone bath. The autoclave is then closed
and heated to the desired re~ction temperature. After a suitable
period of time, the autoclave is cooled and the contents analyzed.l
The results of a number of such tests are shown in Table E below. !
Table E
milli- Max.
Feed, mols Pres. EO EC****
; Test Catalyst, Bath Time, kg/cm2 Conv. Sel.
I No. EO* CO2 H2O THF** gms*** C hrs gauge % %
27 347 1590 346 1262 a 20.0 60 452.0 95.6 97.0
28 695 2794 695 -- a 20.0 60 6104.8 95.8 90.5
' 29 1157 2113 583 -- a 20.0 50 657.7 98.2 95.5
30 349 1590 350 1263 a 20.0 70 257.3 99.5 96.0
,1
* EO = ethylene oxide
** THF = tetrahydrofuran
*** a = methyl triphenyl phospnonium iodide
**** EC - ethylene carbonate
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i 1216 - 13 -
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