Note: Descriptions are shown in the official language in which they were submitted.
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PROCESS FOR CARBONYLATION OF ALIPHATIC ALCOHOLS AND/OR
REACTIVE DERIVATIVES THEREOF.
=
BACKGROUND OF THE INVENTION
[0001] This invention relates to a process for the selective production of
lower aliphatic
carboxylic acids and/or their corresponding esters by the carbonylation of the
corresponding
lower aliphatic alcohol and/or ester or ether derivatives thereof, and, in
particularto the
selective production of acetic acid and/or methyl acetate by the carbonylation
of methanol
and/or ester or ether derivatives thereof. This invention also relates to an
improved process
for the production of methyl acetate from dimethyl ether, and more generally
to the
production of alkyl esters of aliphatic carboxylic acids, by the carbonylation
of alkyl ethers.
In another aspect this invention relates to the production of lower aliphatic
carboxylic acids
by first producing an alkyl ester from a lower alkyl ether, followed by
hydrolysis of the ester
to the acid. An example of this is the production of acetic acid by
carbonylation of dimethyl
ether, to form methyl acetate, followed by hydrolysis of the ester to produce
acetic acid.
[0002] The most widely used industrial process for production of acetic acid
is the
carbonylation of methanol, which is described generally in British patents
1,185,453 and
1,277,242 and U.S. patent 3,689,533, for instance. In that type of process,
methanol is
reacted with carbon monoxide or a carbon monoxide- containing gas in the
presence of a
rhodium- or iridium-containing catalyst, in the additional presence of a
halogen (usually
iodine)-containing promoter. Though widely used, nonetheless these processes
require the
use of expensive corrosion-resistant alloys due to the presence of iodide and
result in
production of low levels of iodine-containing byproducts that are difficult to
remove from the
acetic acid by conventional distillation. Some non-halide based catalyst
systems have been
investigated for this reaction, but none have been commercialized, primarily
due to issues
with catalyst lifetime and selectivity.
[0003] A number of patents describe processes in which methanol or a mixture
of methanol
and dimethyl ether is carbonylated in the presence of a catalyst. Typically
the products are a
mixture of acetic acid and methyl acetate, sometimes also including acetic
anhydride. In
those patents it is disclosed that one of the reactions that may occur is the
carbonylation of
dimethyl ether to form methyl acetate.
- 1 -
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[0004] EP-A- 0 596 632 discloses the preparation of an aliphatic carboxylic
acid by
contacting an aliphatic alcohol or a reactive derivative thereof with carbon
monoxide in the
presence of a copper, nickel, iridium, rhodium or cobalt loaded mordenite
zeolite catalyst at
high temperatures and pressures.
[0005] WO 2005/105720 discloses a process for the preparation of an aliphatic
carboxylic
acid, ester or anhydride thereof by contacting an aliphatic alcohol and/or a
reactive derivative
thereof with carbon monoxide in the presence of a copper, nickel, iridium,
rhodium or cobalt
loaded mordenite catalyst which has as framework elements, silicon, aluminium
and also one
or more of gallium, boron and iron.
=
[0006] US 6,387,842 discloses processes and catalysts for converting an
alcohol, ether and/or
ether alcohol feedstock to oxygenated products by reaction with carbon
monoxide in the
presence of a catalyst comprising a solid super acid, clay, zeolite or
molecular sieve under
conditions of temperature and pressure.
[0007] Cheung et al (Angew. Chem. Int. Ed 2006, 45, (10), 1617) carried out
carbonylation
of dimethyl ether with the zeolites mordenite, ferrierite and also with the
zeolites ZSM-5,
BEA and USY. These latter three zeolite types do not contain 8-member ring
channels.
BRIEF SUMMARY OF THE INVENTION
[0008] This invention comprises a process for the selective production of a C1-
C3 aliphatic
carboxylic acid such as acetic acid and/or the corresponding C1-C3 ester, such
as methyl
acetate by carbonylating the corresponding C1-C3 aliphatic alcohol, such as
methanol and/or
an ester or ether derivative thereof, such as dimethyl ether with carbon
monoxide in the
presence of a catalyst comprising a zeolite, having at least one 8-member ring
channel, said
8-member ring channel being interconnected with a channel defined by a ring
with greater
than or equal to 8 members, said 8-member ring having a window size of at
least 2.5
Angstroms x at least 3.6 Angstroms and at least one Bronsted acid site and
wherein the
zeolite has a silica : X203 ratio of at least 5, wherein X is selected from
aluminium, boron,
iron, gallium and mixtures thereof, with the proviso that the zeolite is not
mordenite or
ferrierite.
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[0009] .This invention also comprises a process for producing a product
comprising a Ci-C3
alkyl ester of a C1-C3 aliphatic carboxylic acid, such as methyl acetate
comprising
carbonylating a C1-C3 alkyl ether, such as dimethyl ether with carbon monoxide
under
substantially anhydrous conditions in the presence of a catalyst comprising a
zeolite having at
least one 8-member ring channel, said 8-member ring channel being
interconnected with a
channel defined by a ring with greater than or equal to 8 members, said 8-
member ring
having a window size of at least 2.5 Angstroms x at least 3.6 Angstroms and at
least one
BrOnsted acid site and wherein the zeolite has a silica: X203 ratio of at
least 5, wherein X is
selected from aluminium, boron, iron, gallium and mixtures thereof, with the
proviso that the
zeolite is not mordenite or ferrierite.
DETAILED DESCRIPTION OF THE INVENTION
[0010] This invention comprises a process for the selective production of a C1-
C3 aliphatic
carboxylic acid such as acetic acid and/or the corresponding ester, such as
methyl acetate by
carbonylating the corresponding C1-C3 aliphatic alcohol, such as methanol
and/or an ester or
ether derivative thereof, such as dimethyl ether with carbon monoxide in the
presence of a
catalyst comprising a zeolite having at least one 8-member ring channel, said
8-member ring
channel being interconnected with a channel defined by a ring with greater
than or equal to 8
members, said 8-member ring having a window size of at least 2.5 Angstroms x
at least 3.6
Angstroms and at least one Bronsted acid site and wherein the zeolite has a
silica : X203 ratio
of at least 5, wherein X is selected from aluminium, boron, iron, gallium and
mixtures
thereof, with the proviso that the zeolite is not mordenite or fenierite.
[0011] This invention also comprises a process for producing a product
comprising a C1-C3
alkyl ester of a C1-C3 aliphatic carboxylic acid, such as methyl acetate
comprising
carbonylating a C1-C3 alkyl ether, such as dimethyl ether with carbon monoxide
under
substantially anhydrous conditions in the presence of a catalyst comprising a
zeolite having at
least one 8-member ring channel, said 8-member ring channel being
interconnected with a
channel defined by a ring with greater than or equal to 8 members, said 8-
member ring
) having a window size of at least 2.5 Angstroms x at least 3.6 Angstroms
and at least one
BrOnsted acid site and wherein the zeolite has a silica: X203 ratio of at
least 5, wherein X is
selected from aluminium, boron, iron, gallium and mixtures thereof, with the
proviso that the
zeolite is not mordenite or ferrierite.
=
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[00121 In one aspect of the invention, one component of the feed to the
process may be a C1-
C3 aliphatic alcohol. The process is particularly applicable to alcohols such
as methanol,
ethanol and n-propanol. A preferred alcohol is methanol. Reactive derivatives
of the alcohol
which may be used as an alternative to, or in addition to the alcohol, include
esters of the
alcohol and ether derivatives of a C1-C3 alcohol. Suitable reactive
derivatives of methanol
include methyl acetate and dimethyl ether. A mixture of the alcohol and a
reactive derivative
thereof may also be employed, such as a mixture of methanol and methyl
acetate.
[0013] Where an alcohol is used as the feed to the process, the product will
be dependent
upon the degree of conversion of the alcohol. If the conversion is 100% then
the product will
be the corresponding carboxylic acid. Thus where methanol is the alcohol feed,
the product
will comprise acetic acid. If the conversion is less than 100%, the alcohol
will be converted to
a mixture of the corresponding carboxylic acid and carboxylic acid ester. If
the ester
employed as the feed, is a symmetrical ester, for example, methyl acetate, the
main product
of the carbonylation process will be the corresponding carboxylic acid (in
this case, acetic
acid). If the ester is asymmetrical, then the product will comprise a mixture
of carboxylic
acids formed from each of the alkyl groups of the ester.
[0014] In a further aspect of the invention, one component of the feed to the
process
comprises a C1-C3 alkyl ether, that is, a compound having the formula
R1-0-R2
in which R1 and R2 are independently C1-C3 alkyl groups. The total number of
carbon atoms
in groups R1 and R2, if R1 and R2 are alkyl groups, is from 2 to 6.
Preferably, R1 and R2 are
straight-chain alkyl groups, most preferably straight-chain alkyl groups
having from 1 to 3
carbon atoms each, such as methyl, ethyl and n-propyl.
[0015] If the ether is a symmetrical ether, for example, dimethyl ether, the
main product will
be the corresponding alkyl ester of an aliphatic acid (in this case, methyl
acetate). If the ether
is asymmetrical, the product will comprise one or both of the two possible
carboxylic acid
I esters, depending on which of the two C-0 bonds is cleaved in the
reaction. For example, if
the feed is methyl ethyl ether (R1 = methyl; R2 ethyl), then the product will
comprise ethyl
acetate and/or methyl propionate.
=
= 4=
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[0016] A second component of the process is a feed comprising carbon monoxide.
The feed
may comprise substantially pure carbon monoxide (CO), for example, carbon
monoxide
typically provided by suppliers of industrial gases, or the feed may contain
impurities that do
not interfere with the conversion of the alkyl ether to the desired ester,
such as hydrogen,
nitrogen, helium, argon, methane and/or carbon dioxide. For example, the feed
may
comprise CO that is typically made commercially by removing hydrogen from
synthesis gas
via a cryogenic separation and/or use of a membrane.
[0017] The carbon monoxide feed may contain substantial amounts of hydrogen.
For
example, the feed may be what is commonly known as synthesis gas, i.e. any of
a number of
gaseous mixtures that are used for synthesizing a variety of organic or
inorganic compounds,
and particularly for ammonia synthesis. Synthesis gas typically results from
reacting carbon-
rich substances with steam (in a process known as steam reforming) or with
steam and
oxygen (a partial oxidation process). These gases contain mainly carbon
monoxide and
hydrogen, and may also contain smaller quantities of carbon dioxide and
nitrogen. Suitably,
the ratio of carbon monoxide : hydrogen may be in the range 1 : 3 to 15: 1 on
a molar basis,
such as 1: 1 to 10: 1. The ability to use synthesis gas provides another
advantage over
processes for producing acetic acid from methanol, namely the option of using
a less
expensive carbon monoxide feed. In methanol-to-acetic acid processes, the
inclusion of
hydrogen in the feed can result in production of unwanted hydrogenation.
[0018] The catalyst for use in the process of the invention is a zeolite,
excluding mordenite
and ferrierite. Zeolites, both natural and synthetic are microporous
crystalline aluminosilicate
materials having a definite crystalline structure as determined by X-ray
diffraction. The
chemical composition of zeolites can vary widely but they typically consist of
Si02 in which
some of the Si atoms may be replaced by tetravalent atoms such as Ti or Ge, by
trivalent
atoms such as Al, B, Ga, Fe or by bivalent atoms such as Be, or by a
combination thereof. A
zeolite is comprised of a system of channels which may be interconnected with
other channel
systems or cavities such as side-pockets or cages. The channel systems are
uniform in size
1 within a specific zeolite and may be three-dimensional but are not
necessarily so and may be
two-dimensional or one-dimensional. The channel systems of a zeolite are
typically accessed
via 12-member rings, 10-member rings or 8 member rings. The zeolites for use
in the present
invention contain at least one channel which is defined by an 8-member ring.
Preferred
zeolites are those which, do not have side-pockets or cages within the zeolite
structure. The
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Atlas of Zeolite Framework Types (C. Baerlocher, W. M. Meier, D. H. Olson, 5th
ed. Elsevier,
Amsterdam, 2001) in conjunction with the web-based version (http://www.iza-
structure.org/databases/) is a compendium of topological and structural
details about zeolite
frameworks, including the types of ring structures present in the zeolite and
the dimensions of
the channels defined by each ring type. For the purposes of the present
invention, the term
'zeolite' also includes materials having a zeolite-type structure such as
delaminated porous
crystalline oxide materials and pillared layered oxide materials such as ITQ-
36.
[0019] The process of the present invention employs a zeolite having at least
one channel
defined by an 8-member ring of tetrahedrally co-ordinated atoms (tetrahedra)
with a window
size having a minimum dimension of 2.5 Angstroms x 3.6 Angstroms. The 8-member
ring
channel is interconnected with at least one channel defined by a ring with
equal to or greater
than 8 members, such as 10 and/or 12 members. The interconnected 8-, 10, and
12- member
ring channels provide access to BrOnsted acid sites contained in the 8-member
ring channels
to enable the carbonylation of the C1-C3 alcohol or derivative thereof, such
as methanol and
dimethyl ether to proceed at acceptable rates.
[0020] The zeolite for use in the present invention may consist of
interconnected channels
defined solely by 8-member rings, such as zeolites of framework type CHA, for
example,
chabazite and framework type ITE,' for example ITQ-3. Preferably, however, the
zeolite has
at least one channel formed by an 8-member ring and at least one
interconnecting channel
defined by a ring with greater than 8 members, such as a 10, and/or 12 member
ring. Non-
limiting examples of zeolites having 8- member ring channels and
interconnecting larger ring
channel systems include zeolites of framework type OFF, for example,
offretite, GME, for
example Gmelinite, MFS, such as ZSM-57, EON such as ECR-1 and ETR such as ECR-
34.
Preferably, the zeolites for use in the process of the present invention have
at least one 8-
member ring channel interconnected with at least one 12-member ring channel,
such as those
of framework type OFF and G1V1E, for example, offretite and gmelinite.
[0021] However, the mere presence of an interconnected 8-member ring channel
in a zeolite
is not sufficient to develop an effective carbonylation process. The window
size of the
channel systems also has to be controlled such that the reactant molecules can
diffuse freely
in and out of the zeolite framework. It has now been found that effective
carbonylation can be
achieved if the aperture (pore width) of an 8-member ring channel of the
zeolite has a
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minimum dimension of 2.5 x 3.6 Angstroms. Channel dimensions of zeolite
framework
types may be found, for example, in the Atlas of Zeolite Framework Types. In
addition, M.D.
Foster, I. Rivin, M.M.J. Treacy and 0. Delgado Friedrichs in "A geometric
solution to the
largest-free-sphere problem in zeolite frameworks" Microporous and Mesoporous
Materials
90 (2006) 32-38, have used Delaunay triangulation methods applied to known
zeolite
frameworks and have tabulated the largest free-sphere diameters for diffusion
along the three
principal crystallographic directions for the 165 zeolite frameworks that are
currently listed in
the Atlas of Zeolite Framework Types. Ring window sizes may be modified by
suitable
atomic substitutions that change bond lengths and bond angles of the
tetrahedrally co-
ordinated atoms and the bridging oxygens.
[0022] A partial listing of zeolite framework types having at least one
interconnected 8
member ring channel of minimum dimension of 2.5 x 3.6 Angstroms taken from The
Atlas of
Zeolite Framework Types is given below:
MOR Mordenite 12 (6.5 x 7.0A) 8 (3.4 x 4.8A) 8 (2.6 x
5.7A)
OFF Offretite 12 (6.7 x 6.8A) 8 (3.6 x 4.9A)
FER Ferrierite 10 (4.2 x 5.4A) 8 (3.5 x 4.8A)
CHA Chabazite 8 (3.8 x 3.8A)
1TE ITQ3 8 (3.8 x 4.3A) 8 (2.7 x 5.8A)
GME Gmelinite 12 (7.0 x 7.0A) 8 (3.6 x 3.9A)
ETR ECR-34 18 (10.1A) 8 (2.5 x 6.0A)
MFS ZSM-57 10 (5.1 x 5.4A) 8 (3.3 x 4.8A)
EON ECR-1 12 (6.7 x 6.8A) 8 (3.4 x 4.9A) 8 (2.9 x
2.9A)
[0023] Zeolites are available from commercial sources. Alternatively they may
be
synthesized using known techniques. In general, synthetic zeolites are
prepared from aqueous
reaction mixtures comprising sources of appropriate oxides. Organic directing
agents may
also be included in the reaction mixture for the purpose of influencing the
production of a
zeolite having the desired structure. After the components of the reaction
mixture are
properly mixed with one another, the reaction mixture is subjected to
appropriate
crystallization conditions. After crystallization of the reaction mixture is
complete, the
crystalline product may be recovered from the remainder of the reaction
mixture. Such
recovery may involve filtering the crystals, washing with water followed by a
calcination
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treatment at high temperature. The synthesis of zeolites is described in
numerous references.
For example, zeolite Y and its synthesis is described in US 3,130,007, zeolite
ZSM-23 is
described in US 4,076,842 and J.Phys. Chem. B, 109, 652-661 (2005), Zones,
S.I. Darton,
R.J., Morris, R and Hwany, S-J; ECR-18 is described in Microporous Mesoporous
Mat., 28,
233-239 (1999), Vaughan D.E.W. & Strohmaier, K.G.; Theta-1 is described in
Nature, 312,
533-534 (1984). Barn, S.A.I., Smith W.G., White, D and Young, D.; Mazzite is
described in
Microporous Mesoporous Mat., 63, 33-42 (2003), Martucci, A, Alberti, A, Guzmar-
Castillo,
M.D., Di Renzo, F and Fajula, F.; Zeolite L is described in Microporous
Mesoporous Mat.,
76, 81-99 (2004), Bhat, S.D., Niphadkair, P.S., Gaydharker, T.R., Awate, S.V.,
Belhekar,
A.A. and Joshi, P.N and also in J. Ind. Eng. Chem. Vol. 10, No. 4 (2004), 636-
644, Ko Y.S,
Ahn W.S and offretite is described in Zeolites 255-264, Vol. 7, 1987 Howden
M.G.
[0024] The zeolite catalyst for use in the process of the present invention is
used in the acid
form, generally referred to as the 'H' form of the zeolite, for example, FE-
offretite. Other
forms of the zeolite, such as the NH4 form can be converted to the H-form, for
example, by
calcining the NH4 form at elevated temperature. The acid form of a zeolite
will possess
BrOnsted acid (H+) sites which are distributed among the various channel
systems in the
zeolite. For example, H-offretite has 11+ sites located in the 12 member ring
channels and in
the 8 member ring channels. The number or concentration of 1-1+ species
residing in any
particular channel system can be determined by known techniques such.as infra-
red NMR
spectroscopic techniques. Quantification of Bronsted acidity by FTIR and NNIR
spectroscopy is described, for example, in Makarova; M.A., Wilson, A.E., van
Liemt, B.J.,
Mesters, C. de Winter, A.W., Williams, C. Journal of Catalysis 1997, 172, (1),
170. The two
types of channels in H-offretite (defined by 12 member rings and 8 member
rings) give rise to
at least two bands associated with the hydroxyl region of H-offretite, one
corresponding to
vibration into the larger pores and the other, at a lower frequency, vibrating
into the smaller
pores. Work by the present inventors has shown that there is a correlation
between the
number of II+ sites located in an 8-member ring channel and the carbonylation
rate whereas
no such correlation has been observed for 12-member ring channels. It has been
found that
carbonylation rates increase in parallel with the number of El+ sites within 8
member ring
channels. In contrast, no correlation is evident with the number of 11+ sites
within 12 member
ring channels. The number of Er sites within 8-member ring channels can be
controlled by
replacement of the 11 with metal cations such as Na + or Co2 using known ion-
exchange
techniques.
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=
[0025] The chemical composition of a zeolite may be expressed as involving the
molar
relationship:
Si02 : X203
wherein X is a trivalent element, such as aluminium, boron, iron and/or
gallium, preferably
aluminium. The Si02: X203 ratio of a given zeolite is often variable. For
example, it is
known that offretite can be synthesized with Si02: A1203 ratios of 6 to 90 or
greater, zeolite
Y, from about 1 to about 6, chabazite from about 2 to 2000 and gmelinite may
be synthesised
with Si02 : A1203 ratios of greater than 4. In general, the upper limit of the
Si02 : X203 ratio
is unbounded, for example, the zeolite ZSM-5. The zeolites for use in the
present invention
have a Si02 : X203 molar ratio of at least 5, preferably in the range 7 to 40,
such as 10 to 30.
Suitably, the Si02 : X203 molar ratio is less than or equal to 100. Particular
Si02: X203 ratios
can be obtained for many zeolites by dealumination (where X is Al), by
standard techniques
using high temperature steam treatment or acid washing.
[0026] Depending on the nature of the feed, water may be generated in-situ.
For example,
where an alcohol is used as the feed, water is generated by the dimerisation
of the alcohol to
an ether, Water may also be generated by the estenification of the alcohol
with the carboxylic
acid product. Water may be fed separately or together with the alcohol or
ester feed
component or a mixture thereof. The water may be present in liquid or vapour
form. Where,
the process of the present invention is carried out under hydrous conditions
and the feed is an
aliphatic alcohol or an aliphatic ester, the carbonylation reaction products
will be the
corresponding carboxylic acid and/or ester. For example, where the feed is
methanol or
methyl acetate, the reaction products will be acetic acid and/or methyl
acetate. Where the
feed is a C1-C3 alkyl ether, such as dimethyl ether the carbonylation reaction
is preferably
carried out under substantially anhydrous conditions. In the substantial
absence of water, the
carbonylation of dimethyl ether is selective to methyl acetate product.
=
[0027] Where the reaction is to be conducted substantially in the absence of
water, the
catalyst and preferably, the feed components should be dried before beginning
the operation,
for example, by preheating to 400- 500 C.
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[0028] In general, where the feed is an ether, such as dimethyl ether, the
process is run at
temperatures at or below about 250 C, that is, at temperatures of from about
100 to about 250
C, preferably from about 150 to about 180 C . Where the feed is an alcohol or
an ester, such
as methanol or methyl acetate, the process is run at temperatures above 250 C,
that is, at
temperatures of from about 250 to about 400 C, preferably from about 275 to
about 350 C .
[0029] Typical total operating pressures are from about 1 bar to about 100
bar, preferably
with carbon monoxide pressures greater than 10 bar and reactant pressures
below 5 bar.
[0030] The process may be run as either a continuous or a batch process, with
continuous
processes typically preferred. 'Essentially, the process is a gas-phase
operation, with reactants
being introduced in either liquid or gaseous phase and products withdrawn as
gases. As
desired, the reaction products may subsequently be cooled and condensed. The
catalyst may
be used as convenient, in either a fixed bed or a fluidized bed. In operating
the process,
unreacted starting materials may be recovered and recycled to the reactor.
Where the product
is methyl acetate it may be recovered and sold as such, or may be forwarded to
other
chemical process units as desired. If desired, the entire reaction product may
be sent to a
chemical process unit for conversion of the methyl acetate or acetic acid and
optionally other
components to other useful products.
[0031] In one preferred embodiment of the invention, where methyl acetate is a
product, it
may be recovered from the reaction products and contacted with water to form
acetic acid via
hydrolysis reactions. Alternatively, the entire product may be passed to a
hydrolysis step,
and acetic acid separated thereafter. The hydrolysis step may be carried out
in the presence
of an acid catalyst, and may take the form of a reactive distillation process,
well known in the
art.
=
[0032] After separation, any alcohols produced in the reaction may be sent to
a dehydration
reactor to produce an ether, which can be separated from water and recycled to
the
carbonylation unit as fresh feed for the carbonylation reactor.
[0033] In another embodiment, the hydrolysis of an ester product to alcohol
and carboxylic
acid is performed by injecting water at one or more points in the catalyst
bed, once a
significant amount of ester has been produced by carbonylation. Injection of
water in this
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manner essentially stops the conversion of, for example, dimethyl ether to
methyl acetate, and
removes the requirement for a separate hydrolysis reactor.
[0034] The following examples are presented as illustrative of the invention.
However, they
are not meant to limit the scope of this invention
General Procedures
1) Catalyst Preparation
[0035] A catalyst sample in the ammonium or acid form was compacted at 12
tonnes in a 33
TM
mm die set using a Speedo' Press, then crushed and sieved to a particle size
fraction of 212 to
335 microns. The catalyst (typically 1g) was then calcined to convert the
N114+ form to 11+
form in a muffle oven (oven-volume = 30L) under a static atmosphere of air.
The temperature
was increased from room temperature to 450 C at a ramp rate of 5 C/mm and
then held at
this temperature for 12 hours. Details of the zeolites are given in Table 1
below.
Table 1
Zeolite precursor Silica/Alumina Channel Structure
Molar Ratio
NH4-0ffretite-10 10 8 (3.6 x 4.9A)
12 (6.7 x 6.8A)
=
NH4-Chabazite 7.3 8 (3.8 x 3.8A)
NH4-ZSM-23 85 10(4.5 x 5.2A)
NH4- ECR-18 7.8 8 (3.6 x 3.6A)
8 (3.6 x 3.6A)
NH4-Theta-1 70 10 (4.6 x 5.7A)
NH4- Zeolite "A 1.2 8 (4.1 x 4.1A)
=
(Grace Davison)
NH4-Zeolite L 14 12 (7.1 x 7.1A)
H-Mazzite 7.7 8 (3.1 x 3.1A)
12 (7.4 x 7.4A)
N114-BETA-18 18 12 (6.6 x 6.7A)
(ZeolystTM International) 12 (5.6 x 5.6A)
The sodium form of zeolite A was converted to the NH4+form by stirring 1 gram
of material
in a 10 ml solution of 1 molar ammonium nitrate for three hours and then
filtering off the
solution. This was repeated three times and the solid dried at 100 C in air
before pressing
and sieving. The N1L4+ exchanged NaA was not calcined prior to use.
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Dimethvl Ether Carbonvlation Reaction
[0036] Dimethyl ether carbonylation reactions were carried out in a pressure
flow reactor unit
consisting of 60 identical parallel isothermal co-current tubular reactors.
Into each tube 50
micro litres of catalyst was loaded onto a metal sinter having a pore size of
20 micrometers.
All catalyst samples were heated at a ramp rate of 5 C/ min. to 100 C under
N2 at
atmospheric pressure at a flow rate of 3.33 ml] hour, and held at this
temperature for 1 hour.
The reactor was then pressurised to 70 barg with N2and the system held at this
condition for
1. hour. The nitrogen gas feed was then changed to a mixture comprising 64
mole % carbon
monoxide, 16 mole % hydrogen and 20 mole % nitrogen at a gas flow rate of 3.33
ml/ hour,
and the system were heated at a ramp rate 3 C/ min. to a temperature of 300
C. The system
was then held at this condition for 3 hours. After this the temperature was
reduced to 180 C
and allowed to stabilise for 10 minutes. At this point catalyst activation is
considered
complete and the gas feed was changed to a mixture comprising 64 mole % carbon
monoxide, 16 mole % hydrogen, 15 mole % nitrogen and 5 mole % dimethyl ether
at a gas
flow rate of 3.33 ml/ hour. The reaction was allowed to continue for 27.8
hours after which
the temperature was increased to 250 C. The exit stream from the reactor was
passed to a
TM
Varian 4900 micro gas chrornatograph with three columns (Molecular Sieve 5A,
Porapake Q
TM
and CP-Wax-52) each column being equipped with a thermal conductivity
detector; and an
Interscience Trace gas chromatograph having two columns (CP-Sil 5 and CP-Wax
52) each
equipped with a flame ionization detector. The results of the carbonylation
reactions are
given in Table 2.
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CA 02671361 2009-06-02
WO 2008/073096 PCT/US2006/047718
Table 2
Example Catalyst Reaction Time on STYmeoAc
temperature Stream /hrs grlh-1
1 C
1. NI-14-Offretite-i0 180
19.6 55
2. _ 250 48.8
21
3. NH4-Chabazite 180 19.7
13
4. 250 49.0 0
5. NH4-ZSM-23 180 21.2
1
6. 250 50.4 4
7. NH4-ECR-18 180 16.0
25
8. 250 50.8 1
9. NH4-Theta-1 180 17.3
0
10. 250 52.1 1
11. Na-Zeolite A 180 21.4
0
12. 250 50.6 0
13. NH4-Zeolite L 180 20.3
0
14. 250 49.5 0
15. H-Mazzite 180 20.7
1.
16. 250 49.9 6
17. NH4-BETA-18 180 16.2 1
18. 250 51.0 2
[0037] In the above experiments, the offretite, chabazite, and ECR-18 zeolites
have a silica:
alumina molar ratio of at least 5, an 8-member ring channel of window size of
at least 2.5
Angstroms x at least 3.6 Angstroms and at least one Bronsted acid site,
and.the 8-member
ring channel is interconnected with a channel defined by a ring with greater
than or equal to 8
members. These experiments demonstrate that significant carbonylation activity
may be
achieved by these zeolites. However, in the carbonylation reactions employing
the zeolites,
ZSM-23, Theta-1, Zeolite-A, Zeolite-L, Mazzite and Beta-18, little, if any
carbonylation
activity was found to occur. ZSM-23,and Theta-1 possess 10-member ring
channels only and
do not have 8-member ring channels; Beta-18 and Zeolite-L have 12-member ring
channels
only and does not have 8-member ring channels; the Zeolite-A has 8- member
ring channels
but its silica/alumina ratio is below 5; Mazzite has both 8- and 12-member
ring channels but
the 8-member ring channels do not intersect with either 8-member ring channels
or 12-
member ring channels. =
General Procedures B
[0038] To investigate the catalytic activity of zeolites for non-iodide
carbonylation of
methanol to acetic acid the zeolites can be tested in a pressure flow reactor
in accordance
13
CA 02671361 2013-09-18
30109-195
with the following procedure. Zeolite pellets of size 500-1000um are loaded
into a pressure
flow reactor. A catalyst pre-bed is also employed to ensure efficient
mixing/heating of the
reactants. The pre-bed is gamma-alumina which allows methanol to form a
methanol/dimethylether/water equilibrium. The catalysts are activated under
flowing nitrogen
(100cm3/min) at 350 C for 16hrs and then reduced under carbon monoxide
(200cm3/min) at
.350 C for 2 hours. The system is then pressurised up to 30barg using a back
pressure
regulator. The flow rate of the carbon monoxide is adjusted to
400cm3/min(GHSV=2200)
and methanol is fed to the reactor via a pump (rate+0.15m1imin). The liquid
products and
unconverted reactants are collected in a cooled trap, while gaseous products
and un-reacted
feeds are sampled downstream by an online gas chromatograph. The reaction is
sampled at
frequent intervals and the liquid products analysed off line using gas-
chromatography. Using
zeolite H-Offretite (silica: alumina molar ratio of 10) as the catalyst in the
above described
carbonylation of methanol, it would be expected that significant amounts of
both methyl
acetate and acetic acid would be seen in the liquid products. Similarly, if
zeolite H-Gmelinitc
(silica: alumina molar ratio of 8) was employed as the catalyst in the above
described
carbonylation of methanol, it would be expected that significant amounts of
both methyl
acetate and acetic acid would be seen in the liquid products. Both offretite
and gmelinite
zeolites have 8-member ring channels intersecting with 12-member ring
channels. In
comparison, it would be expected that if zeolite H-ZSM-5 (silica: alumina
ratio of 23; 10-
member ring channels only) or zeolite H-Y (silica: alumina ratio of 12; 12-
member ring
channels only) were employed as the catalyst, only trace amounts of acetic
acid would be
seen in the liquid product.
[0039] Although the foregoing invention has been described in some detail by
way of illustration and
example for purposes of clarity of understanding, it will be readily apparent
to those of ordinary skill
in the art in light of the teachings of this invention that certain changes
and modifications may be made
thereto without departing from the scope of the appended claims.
14
