Note: Descriptions are shown in the official language in which they were submitted.
62
PREPARATION OF ETHYLIDENE DIACE~ATE A~D ET~YL AC~TATE
This in~ention relates to a novel process for the
preparation of ethylidene diacetate and ethyl acetate by
hydrogenating acetic anhydride. The invention also relates to
a novel process for hydrogenating mixtures of acetic anhydride
and ethylidene diacetate to obtain ethyl acetate.
An economically advantageous process for the prepar-
ation of acetic anhydride by the carbonylation of methyl acetate
has been reported in the patent literature. See, for example,
Belgian Patent 819,~55, British Published Patent Application
2,013,184, ~apanese Published Patent Applications 75-47921 and
75-47922 and U.S. Patents 3,927,078 and 4,046,807. Not only is
acetic anhydride itself an important chemical, for example as
an acetylating agent in the manufacture of cellulose acetate
and other esters, but it can be converted to ethylidene diacetate
and ethyl acetate. The ethylidene diacetate can be converted
to vinyl acetate which, along with ethyl acetate, are derived
primarily from petroleum. ~ery little prior art exists con-
cerning the hydrogenation of acetic anhydride. The hydrogen-
ation of acetic anhydride to ethylidene diacetate and acetic
acid with a catalyst consisting of a Group VIII noble metal and
a biphyllic ligand selected from the group consisting of trihy-
- drocarbyl phosphines, arsines, and stibines is disclosed in U.S.
Patent 3,579,566. With these catalysts the reaction rate was
slow. Depending upon the reaction conditions and catalyst
used, ethyl acetate and acetic acid were produced, along with
the desired ethylidene diacetate product. The co-production of
:;
6;~
acetic anhydride and ethylidene diacetate hy the carbonylation
of methyl acetate in the presence of hydrogen, a Group VIII
noble metal catalyst and methyl iodide is disclosed in Belgian
Patent 839,321. The preparation of ethylidene diacetate from
acetic anhydride using a supported palladium catalyst in the
presence of a strong acid, i.e., HCl, HF, or methane ~ulfonic
acid, is disclosed in Belgian Patent 879,178. ~hen HCl was the
acid used, large amounts of l-chloroethylacetate were produced
along with the desired ethylidene diacetate and acetic acid
products. The hydrogenation of acetic anhydride to ethyl
acetate with Ru(X2)~PR3)3 cataly~t where X is a halogen or lower
alkyl and PR3 is an alkyl or aryl phosphine is described in
U. S. Patent 3,9579827. Ber., $3B, 796 (1930) discloses the
hydrogenation of acetic anhydride to ethyl acetate with a
palladium black catalyst. Addition of HCl promoted the hydrogena-
tion reaction. - -
The process of this invention comprises hydrogenating
at elevated pre~sure and temperature acetic anhydride in thepresence of a catalytic amount of a homogeneous ruthenium
compound, methyl iodide and, optionally, lithium iodide.
Depending upon how much methyl iodide and lithium iodide are
employed, the process can be utilized to produce all or essen-
tially all ethylidene diacetate, all or essentially all ethyl
acetate or a mixture of the two in good to excellent space-time
yields. The process also can be used to convert mixtures of
acetic anhydride and ethylidene diacetate, resulting from the
carbonylation of methyl acetate in the presence of hydrogen, to
ethyl acetate. The feed to the hydrogenation reactor can, if
desired, contain, in addition to acetic anhydride and/or ethylidene
diacetate, an inert solvent such au acetic acid.
The reactions involved in the process are:
6~
Ethylidene ~ Acetic
Diacetate Acid
~2 /
2 Acetic
Anhydride
2 ~
Ethyl + 2 Acetic
Acetate Acid
Ethylidene ~ Ethyl ~ Acetic
Diacetate Acetate Acid
The co-product acetic acid may be converted to methyl acetate
and u~ed in the production of acetic anhydride.
The concentration of the ruthenium can be varied
substantially depending on such factors as the temperature and
presuure employed, the space-time yield desired, etc. Generally,
ruthenium (as Ru) concentrations in the range of about 100 to
2500 ppm, hased on the acetic anhydride and/or ethylidene
diacetate fed, will give good results when using appropriate
pressures and temperatures. Ruthenium concentrations (same
basis) of about 500 to 1000 ppm will most often be used. The
particular ruthenium compound charged to the hydrogenation
reactor is not critical 80 long as it is soluble in the reaction
mediu~ or results in the formation of a soluble forM of ruthenium,
i.e. a homogeneous catalyst. ~xamples of suitahle ruthenium
compounds include ruthenium chloride, ruthenium acetate, ruthenium
iodide~ etc.
The hydrvgenation-effective temperature and pressures
employed in the process of this invention also can be varied
substantially. Not only are temperature and pressure inter-
dependent with re~pect to reaction rate but each also is de-
pendent upon catalyut concentrations. Temperatures in the range
of about 125 to 250C. may he us~d although at the higher
~emperatures tar formation may be a problem, especially in
continuous operations. The preferred temperatures ar~ from
8~2
about 160 to 210C., especially 185 to 210~C. Pressures (total
reaction pressure) in the range of about 250 to 2500 psig may be
used, although pressures of about 500 to 2200 psig, especially
about 1000 to 2000 psig, are preferred.
The amount of methyl iodide employed de ~nds on the
particular product or co-products that are desired, the tempera-
ture and, to a lesser degree, the pressure employed in the
hydrogenation proce6s. When it is desired to hydrogenate acetic
anhydride to essentially all ethylidene diacetate, the amount of
methyl iodide employed should be in the range of about 3 to 15
~eight percent based on the acetic anhydride fed. The use of
methyl iodide alone in the lower part of the range generally
will require the use of higher temperatures, e.g. 200C. or
above. The presence of lith;um iodide in a concentration of
15 about 0.3 to 200, prçferably 0.5 to 1.5, weight percent based on
the weight of the acetic anhydride, usually improves the rate of
ethylidene diacetate formation depending on temperature. The
lithium iodide may be fed as such or it may be generated in the
reaction mixture from other lithium compounds such as lithium
hydroxide, lithium carbonate or lithium acetate.
In hydrogenating acetic anhydride or a mixture of acetic
anhydride and ethylidene diacetate to essentially all ethyl
scetate the amount of methyl iodide fed should be less than
about 1.5 weight percent and under most ccnditions less than
about 1 weight percent based on the weight of the reactant(s),
i.e., acetic anhydride and, when present ethylidene diacetate.
The lower limit on the methyl iodide is about 0.25 weight percent.
To obtain good reaction rates for the production of ethyl acetate,
very little, e.g. less than about 0.1 weight percent of lithium
iodide and preferably no lithium iodide is present. When it is
desired to produce significant amounts of ethylidene diacetate
and ethyl acetate, e.g. in weight ratios of or between about 2:1
to 1:2, the amount of methyl iodide normally charged is about
7.5 to 25 weight percent while the amount of lithium iodide
should be in the range of about 0.5 to 1.5 weight percent.
6~ .
The amounts of methyl iodide and lithiu~ iodide that
may be used to convert mixtures of acetic anhydride and
ethylidene diacetate to essentially all ethyl acetate can be
varied considerably depending on such variables as the amounts
of each reactant in the mixture, the temperature employed and
the hydrogen pressure. Generally, for mixtures of acetic
anhydride and ethylidene diacetate in a weight ratio of about
3:1 to 1:3, the amount of methyl iodide fed should be in the
range of about 0.25 to 5 weight percent based on the weight of
the reactants. In hydrogenating the mixture to essentially all
ethyl acetate, very little, and preferably no, lithium needs to
be present.
The process of the invention may be carried out as a
batch operation or, more suitably, as a continuous process
wherein acetic anhydride and/or ethylidene diacetate are
continuously fed to a hydrogenation reactor and reaction mixture
containing the desired product or produc~:s is continuously
removed. Vnreacted materials and co-product acetic acid may be
removed from the reactor take-off, Eor e~cample, in a distilla-
tion train, and recycled, along with any catalyst and iodides
present9 to the reactor.
The process of the invention is further illustrated by
the following examples.
EXAMPLE~ 1-25
Acetic anhydride (100 g.) was hydrogenated for 30
minutes in the presence of ruthenium charged as 0.25 g.
ruthenium chloride using different temperatures and total
autoclave pressures and varying amounts of methyl iodide and
lithium iodide. The acetic anhydride, ruthenium chloride,
methyl iodide and lithium iodide (when used) were loaded into a
300 ml. Hastelloy (trademark) B autoclave designed to operate in
a rocking mode. The autoclave was purged with 100 psig hydrogen
gas pressure at room temperature and then the gas was vented.
The autoclave internal pressure was increased to 10 psig ~y
adding hydrogen gas at room temperature. The autoclave was
sealed and heated
,~
6Z
and rocked until reaction temperature was xeached, at which
time additional hydrogen gas was added to increase the auto-
cla~e internal pressure to the predetermined ~alue. The time
at which the autoclave internal pressure reached the pre-
determined value was taken as the start of the 30-minute re-
action time. Reactor pressure was maintained at the preset
value during the experiment by adding hydrogen gas at the
same rate at which it was consumed by the reactants. When the
predetermined reaction time was completed the autoclave was
cooled by a stream of cold air. After the gas was ~ented from
th,e autocla,~e the xeaCtiQ~ pxoduct wa,s a,~a,lyzed by ~as
chromatographic methods.
Table 1 shows th,e temperature (C.) a~,d pressure
(psig) used, the amounts of methyl and ~ithium iodide (CH3I,
LiI, g.) charged, the amounts (in moles) of ethyl a,cetate (EA),
acetic acid (HOAc) and ethylidene diacetate (EDA) produced, the
amount of acetic anhydride (Ac20, in moles) recovered and the
space-time yields (STY, in gramstliter hour) for ethylidene
diacetate and ethyl acetate.
~J'
.~
z
~ ~D O ~ O ~ C~ O ~ r~ U~ o ~ _ ~ ~ rJ ~
~ ~ o ' ` ~ ~ ~ 0 OD ~
W U~ V ~ ~ -- _ ~ ~ o
O _ O _ `D ~ ~ O
o ~ o o ~ o o _ o C`~ o ~ o o ~ _ ~
o o o o o o o o o o o o o o o o
o~ ~ ~ ~ _ ~ 00, C~ ~ ~D ~ ~D 0~ 0 --
o _ ~ ~ o~ ~ ~ C~ o e~ o U~ ~ ~
-- I O I I O O O O ~` ~ ~ ~ ~ ~D 1` ~ C`l ~ O
~: o o ooooooooooooooo
~ o ~ ~ c~
~1 ~ C~ O ~D O _ ~ I~ ~ D ~ O O ~D ~ ~D U~
O ~ o e~ ^ ~ ~ _ O ~ _ ~
~: o____I_o_--~ooooooooooo
cr~ ~ o o o _ ~ ~ _ I~ ~ c~ OD 00 ~ CO
U~ r~ 00 ~ ~ ~ ~ U~ O _ O _ O _ O _ O _
¢ I ~I ~') ~ ~ ~ t`) ~ t`~ O O O I O O O O O O O
~-I~:1 OOOOOOOOOOO OOOOOO-O
E~ ~ o o o
~U~OOOOOOOOOOOOOOO
~ IOOOO__~
',~ I I I I I I I I I I I I I I I _ _ O O _ O
h
OOOOOOOOOOOOOOOOOOOO
~O OOOOOOOOOOOOOOOOOOOO
:~ U~ O O O O O U~ O O O O O O O o O o
~ I 8 $ o o o u~
e _ ~ O _ ~ O
X _I _ _ _ _ _ _ _ _ _I C~
z
co o U~ o a
~ u~ ~ ~
E~ o ~ _ co u~
u~ u~ r~ _
u~
~ r~
c~ - ~ o - -
. . . .
o o o o o
.
o~ l o ~ ~ ~o o
c)
c o o o o o
cJ
¢ ~ ~ ~
~: o o o o o
. _ O O `D a~
~ ~ o o o - -
c ~ o o o o o
o
~ o o o o o
~ :~
E~
~ ~ o o o
~ o o o o ~
o~ o o o o o
:~ o c: o o o
`l ~ ~ c`l ~
~ u~ o o
~ o o ~
E~ ~ c~
~ I
~ ~ c`~
EXAMPLE 26
Ethylidene diacetate (100 g.) was hydrogenated at
190C. for 1 hour at a total autoclave pressure of 1000 psig in
the presence of 0.25 g. ruthenium chloride and 9.0 g. methyl
iodide according to the procedure employed in the previous
examples. Ethyl acetate (0.578 moles) was recovered in a
theoretical yield of about 85~ and a space-time yield of about
500 g./l.-hr.
EXAMPLES 27-35
A mixture of acetic anhydride and ethylidene diacetate
(50 g. of each) was hydrogenated in the presence of ruthenium
charged as 0.25 ruthenium chloride using different temperatures
and pressures and varying amounts of methyl iodide. No lithium
iodide was used in these runs. The acetic anhydride, ethylidene
diacetate, ruthenium chloride and methyl iodide were loaded into
a 300 ml. Hastelloy (trademark) B autoclave designed to operate
in a rocking mode. The autoclave was purged with hydrogen at
room temperature and then a predetermined amount of hydrogen was
added. The autoclave was sealed and heated and rocked until a
predetermined temperature was reached and then held at that
temperature for 30 minutes. No additional hydrogen was added
during the reaction period. When the 30~minute reaction time
was completed the autoclave was cooled by a stream of cold air.
After the gas was vented from the autoclave the reaction product
was analyzed by gas chromatographic methods.
Table II shows the temperature (C.) used, the amounts
of hydrogen (H2, moles) and methyl iodide (CH3I, g.)
charged, the amounts (in moles) of ethyl acetate (EA) and acetic
acid (HOAc) produced, the amount (in moles) of acetic anhydride
(Ac2O) and ethylidene diacetate (EDA) produced, the amount
recovered and the percent yield and space-time yield (STY, in
grams/liter-hour) for ethyl acetate produced.
L ,l ~ . ~,,, I
I
-- 10 --
~ D ~~ _0
¢ E~ ~ o~ ~ _ ~D C`l 1~ `D a~
~o ~ I ~ ~ -- ~ ~ o _ oo ~,
C~ I~ ~ _ ~D ~ O ~ U~ ~D
I ~ ~ ~o o
Q Oc~ ~ 7 o ~ _
~:1
O O ~ O O O O O
~ O ~ -- -- o C`~ _ o _
¢ O O O oO ~:) O o C~
~U~ o1~ oU~ o
¢ ~ _r~ ~ ~ ~I` ~ ~
t~. . . . . . . . . ..
~ ::: O O O o _ O o_l o
E~ ~
U~ ~ O
¢ ~ O----~~ o ~ ~ _
1~3 O O O O O O O o o
o r~ ~ ~ I~ I~ ~ r~ ~
~ ~ _ o o ~ o -~ o
Z ~ O --I O ~ O --~ ~ O
.
~ U~ o o o o o o o o
e ,~ ~ ~ O ~
X ~ ~ ~ ~ r~ ~ ~ ~ ~
~ lthough the invention has been descrihed in con-
siderable detail with particular reference to certain preferred
embodiments thereof, variations and modifications can be effected
within the spirit and scope of the invenLion.
