Sustainable catalysts for methanol carbonylation

Article abstract of DOI:10.1039/c3gc00024a

Methanol carbonylation is the most important process for manufacturing C2 molecules from methanol. The present industrial carbonylation has been proven to be the most successful process on economical grounds. However, there is a request to develop more sustainable and 'green' processes to overcome the inherent drawbacks. Well-designed cross-linked copolymers were prepared and used as support for the simultaneous immobilization of rhodium and iodide species. The resulting catalyst was proven to be highly active in CH₃I-free methanol carbonylation and methyl acetate was the main product. Approximately 90% of methanol was converted after a two-hour reaction time at 120 °C under a CO pressure of 3.0 MPa. The immobilization strategy of the active species works efficiently and the present methanol carbonylation catalyst shows good recyclability. After regenerating the catalyst twice over a fifteen-batches test, the catalyst keeps an acceptable activity. The process based on the present catalyst is evidently a promising sustainable methanol carbonylation.

Full text of DOI:10.1039/c3gc00024a

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Sustainable catalysts for methanol carbonylation
Fengbo Li,*a Bingfeng Chen,a,b Zhijun Huang,a Tao Lu,a,b Yin Yuana,b and
Cite this: DOI: 10.1039/c3gc00024a
Guoqing Yuan*a
Methanol carbonylation is the most important process for manufacturing C2 molecules from methanol.
The present industrial carbonylation has been proven to be the most successful process on economical
grounds. However, there is a request to develop more sustainable and ‘green’ processes to overcome the
inherent drawbacks. Well-designed cross-linked copolymers were prepared and used as support for the
simultaneous immobilization of rhodium and iodide species. The resulting catalyst was proven to be
highly active in CH3I-free methanol carbonylation and methyl acetate was the main product. Approxi-
mately 90% of methanol was converted after a two-hour reaction time at 120 °C under a CO pressure of
3.0 MPa. The immobilization strategy of the active species works efficiently and the present methanol
carbonylation catalyst shows good recyclability. After regenerating the catalyst twice over a fifteen-
batches test, the catalyst keeps an acceptable activity. The process based on the present catalyst is
evidently a promising sustainable methanol carbonylation.
Received 4th January 2013,
Accepted 26th March 2013
DOI: 10.1039/c3gc00024a
www.rsc.org/greenchem
improvement. Iodide is employed as the main cocatalyst for
both the rhodium and iridium catalysts. Expensive materials
Introduction
The homogeneous carbonylation of methanol is one of the are required to construct equipment to resist the corrosion of
major industrial applications of homogeneous catalysis.1 Its HI. Halide-free methanol carbonylation processes may lead to
products, methyl acetate and acetic acid, are important ali- a considerable decrease in plant construction costs. In the
phatic intermediates which are used for the manufacture of present homogeneous processes, the product separation and
many industrially significant secondary products such as catalyst recycling are carried out through continuous distilla-
acetate esters, acetate salts, chloroacetic acids, acetic anhy- tion columns and catalyst recycling stream systems. A hetero-
dride and ketene. In the late 1950s, Reppe and coworkers at geneous catalyst, which has competitive activity and selectivity
BASF developed and commercialized a cobalt iodide-based with the existing homogeneous catalysts, could overcome the
methanol carbonylation process under relatively high reaction engineering concerns about product–catalyst separation which
temperatures and pressures.2 A more efficient iodide-promoted hamper homogeneous processes. Various solid supports,
rhodium complex catalyst was discovered by Paulik and Roth including carbon materials, inorganic oxides, zeolites and
at Mosanto3 and this process has become the main technology polymeric materials, have been employed to immobilize
for methanol carbonylation with the licensed operation of BP expensive rhodium catalysts for liquid or vapor phase hetero-
Chemicals and Hoechst-Celanese. In the early 1990s, BP geneous methanol carbonylation.5 It was revealed that the
Chemicals developed and commercialized an iridium-complex ionic attachment strategy was the most efficient supporting
catalyst as the Cativa™ process.4 In China, the catalysts of our model for rhodium catalysts.6 In 1998, Chiyoda and UOP
research group have been commercialized in Jiangsu (1.2 × 106 claimed the commercialization of heterogeneous methanol
tonnes per annum) and Henan (0.6 × 106 tonnes per annum). carbonylation as Acetica™ process, which is based on the
Homogeneous methanol carbonylation has been intensively support of polyvinylpyridine resin.7 Our research group has
investigated and numerous reviews cover this subject.5
reported many results of heterogeneous methanol carbonyl-
Although the present industrial processes have excellent ation and a pilot system was built up.8 In all heterogeneous pro-
catalytic activity and selectivity, there is plenty of room for cesses, iodide cocatalyst must be added to the reactant stream
and then separated from the catalytic system with the product.
The problems with recycling the iodide cocatalyst actually
limit the scale of heterogeneous methanol carbonylation.
Some efforts have been made to address these issues, such as
aBeijing National Laboratory of Molecular Science, Laboratory of New Materials,
Institute of Chemistry, Chinese Academy of Sciences, Beijing, 100190, P. R. China.
E-mail: lifb@iccas.ac.cn, yuangq@iccas.ac.cn; Fax: +(86)-10-62559373;
the development of halide-free dimethyl ether carbonylation,
methylformate isomerization and oxidative carbonylation of
Tel: +(86)-10-62634920
bUniversity of Chinese Academy of Sciences, Beijing, 100049, P. R. China
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methane or ethane. However, their activity cannot compete
with iodide-cocatalyzed rhodium catalysts.
Catalysis plays a critical role in promoting the sustainability
and eco-efficiency of methanol carbonylation processes. The
sustainability of chemical processes, as promoted by the Euro-
pean Technology Platform on Sustainable Chemistry (ETP
SusChem),9 is relevant to process intensification. A core tech-
nology of process intensification is utilised to develop new cata-
lysts, which allow improvements in yields/productivity and
abate process costs through longer catalyst life, milder reaction
conditions, and reduction of separation and environmental
costs.10,11 In this work, sustainable methanol carbonylation
was achieved by the simultaneous immobilization of rhodium
and iodide species over well-designed cross-linked copolymeric
materials. In the catalytic cycle, the terminal groups of copoly-
meric supports are involved as cocatalysts. The immobilization
strategy works effectively and very low rhodium and iodide
concentrations are observed in the product stream. The cata-
lyst shows good recyclability. After the fifteen-run test, no sig-
nificant loss of catalytic activity was observed. This process is
evidently a promising sustainable methanol carbonylation.
Fig. 1 (a) A selected catalyst particle. (b) EMPA image of the dispersion of Rh
species over the copolymeric support. (c) TEM image of Rh nanoparticles over
the copolymeric support. (d) XPS peaks of Rh species over the copolymeric
support.
Results and discussion
Heterogenizing Rh and iodide species over cross-linked
polymeric materials
background noise in Fig. 1b. The bright points are Rh-
enriched spots. The TEM image (Fig. 1c) demonstrates that Rh
nanoparticles are kept in a monodispersed state. Their size
distribution is in the range of 1–3 nm. Fig. 1d shows the XPS
peaks of Rh nanoparticles. The binding energy of Rh 3d5/2 is
307.5 eV, which is attributed to zero-valent Rh species.
Rh catalytic species and the iodide cocatalyst were simul-
taneously immobilized over cross-linked polymeric supports
through the route in Scheme 1. Porous cross-linked macromole-
cular architectures were synthesized by controlled polymeriz-
ation. Approximately 30% of pyridine groups were methylated.
Rh species and iodide ions were immobilized through strong
ion-pair interactions and the steric effect of cross-linked poly-
meric architectures. Supported Rh species were converted to
zero-valent metal nanoparticles. The dispersion state of Rh
nanoparticles was characterized by EMPA. Fig. 1a shows the
selected sample and Fig. 1b is the dispersion of Rh nanoparti-
cles over copolymeric supports. There is some negligible
Cross-linked polymeric supports contain functional groups
that act as promoters or anchoring sites for catalysts. Hetero-
genizing the homogeneous methanol carbonylation catalyst by
immobilization over these functional groups is the key to
developing chemically homogeneous but physically hetero-
geneous catalysts. Fitting of C 1s envelope in the XPS spectrum
of the cross-linked polymeric support resulted in the identifi-
cation of four chemical states of carbon. Peaks at the higher
binding energy of 287.4 eV and 288.5 eV are attributed to
methylated pyridine groups and methyl carboxylate groups
(Fig. 2a). Fitting of N 1s resulted in the identification of two
chemical states of nitrogen: one with a binding energy of 399.7 eV
with an atomic concentration of 34.6% and another at 398.6 eV
with an atomic concentration of 65.4% (Fig. 2b). The peak at
the higher binding energy is attributed to the methylated pyri-
dine groups, which are anchoring sites for active Rh species.
Other pyridine groups are base sites for adsorbing HI. Methyl
carboxylate groups are cocatalysts for converting methanol to
methyl iodide, which is the rate-determining step in the cata-
lytic cycle of methanol carbonylation (Scheme 1).
Catalytic activity and mechanistic aspects of methanol
carbonylation over copolymeric catalysts
Methanol carbonylation to give acetic acid involves formal
Scheme 1 Schematic illustration of the preparation procedure of cross-linked
copolymer supported Rh nanoparticles and iodide species.
insertion of carbon monoxide into the C–O bond of methanol.
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Fig. 3 Methanol carbonylation over the copolymeric catalyst.
acetate and acetic acid. After 180 min under 3.0 MPa CO with
a continuous feeding flow, the methanol conversion reached
approximately 90% (Fig. 3). Methyl acetate was the main
carbonylation product. The yield to acetic acid was approxi-
mately 10%. This methanol carbonylation process proceeded
without the addition of iodide promoters (methyl iodide or HI).
A model reaction was performed to investigate the involve-
ment of the functional polymeric catalyst in the methanol
carbonylation. The catalyst (0.5 g) was suspended in 20 ml
reaction medium of 1,2-dichlorobenzene–water (v/v 5 : 1). The
reaction was performed under typical conditions. Acetic acid
was detected after the reaction. The amount of acetic acid in
the resulted mixture is a function of the load of iodide promo-
ters over the cross-linked polymeric architectures (Fig. 4a). The
methyl acetate groups of the copolymeric chains were con-
verted to methyl iodide (Scheme 2). The carbonylation over Rh
sites and the subsequent hydrolysis led to the formation of
acetic acid. The presence of iodide promoter over the copoly-
meric is the key to activating the methyl acetate to form more
active methyl iodide. As revealed by Fig. 4a, the conversion of
methyl acetate is determined by the load of iodide promoters,
which is represented by the XPS intensity ratio of I 3d peak to
N 1s peak. The calculated maximum amount of acetic acid was
Fig. 2 (a) Fitting of C 1s envelope in the XPS spectrum of the copolymeric
support. (b) Fitting of N 1s envelope in the XPS spectrum of the copolymeric
support.
Scheme 2 Proposed catalytic cycle of methanol carbonylation over the copoly-
meric catalyst.
The Rh catalyst does not activate methanol directly. More derived from the proportion of methacrylate ester monomer in
active methyl substrates must be generated in situ as the reac- the copolymeric chains on the supposition that methyl acetate
tants. Under the typical industrial conditions, methyl iodide is groups were totally converted. The production of acetic acid in
added as a cocatalyst and the iodide promoter is recycled in the methanol-free medium proved that methyl acetate groups
the form of HI to convert methanol into methyl iodide. In a and iodide promoters over the copolymeric chains were
working catalytic system, the reaction medium is acetic acid involved in the catalytic cycle as shown in Scheme 2.
and methanol is converted into methyl acetate. Methyl acetate
Methanol from the reaction medium was activated to
is activated to form methyl iodide with the aid of the iodide methyl iodide with the aid of methyl acetate groups and iodide
promoter. As shown in Scheme 2, side-groups (methyl acetate) promoters over the copolymeric chains. Methanol was
and anchored iodide promoters over the cross-linked poly- smoothly carbonylated according to the mechanism depicted
meric architectures facilitate the catalytic cycle of converting in Scheme 2. The load of iodide promoters over the cross-
methanol to methyl iodide. The methyl iodide undergoes linked copolymeric architectures directly affects the reaction
carbonylation by the Rh catalyst to give acetyl iodide, which is rate of methanol activation, which is the rate-determining step
rapidly hydrolyzed or alcoholyzed to acetic acid or acetate of methanol carbonylation. Fig. 4b shows that the TOF of
ester. The activity of the polymeric catalyst was tested by methanol carbonylation increases sharply with the increase of
directly suspending it in pure methanol under carbon mono- the iodide promoter load. The presence of methyl acetate side-
xide (3.0 MPa). Methanol was gradually converted into methyl groups was indispensable to methanol activation. Model
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Fig. 5 (a) The TOF of methanol carbonylation as a function of the surface area
of the copolymeric support. (b) The influence of adding LiI into the methanol
carbonylation mixture.
pyridine lowers the local concentration of iodide promoters
over the copolymeric architectures, and then leads to the loss
of catalytic activity.
Porosity of the copolymeric support is another important
factor in controlling the mass transfer of methanol activation.
The surface area of the copolymeric support was adjusted by
controlling the addition of pore templates during the synthetic
procedure. Fig. 5a shows the TOF of methanol carbonylation
as a function of the surface area of the copolymeric support.
The increase in the surface area markedly improves the cata-
lytic activity in methanol carbonylation. When the surface area
reaches 70 m2 g−1, the TOF of methanol carbonylation exhibits
little fluctuating.
Fig. 4 (a) Experimental results about the involvement of methyl acetate
groups over copolymeric chains in the carbonylation process. (b) The relationship
between methanol carbonylation activity and the load of iodide promoters over
the copolymeric support. (c) The relationship between methanol carbonylation
activity and the proportion of methacrylate ester monomer in the copolymeric
chain.
As exemplified by the Celanese Acid Optimization (AO Plus)
technology,12 lithium iodide was implemented to increase the
catalysts with various proportions of methacrylate ester productivity
of
rhodium-complex-catalyzed
methanol
monomer in the copolymeric chains were investigated to carbonylation at very low water concentrations. It has been
address this relationship. As shown in Fig. 4c, when methacry- found that lithium iodide promotes the activation of methyl
late ester monomer is replaced with styrene, the copolymeric acetate to methyl iodide13 and the subsequent oxidative
support of vinyl pyridine–styrene exhibits low catalytic activity. addition of methyl iodide to rhodium catalysts.14 In this work,
There is an optimum proportion of methacrylate ester the promoting effect of lithium iodide was investigated under
monomer in the copolymeric chains. Methanol carbonylation different concentrations in the reaction solution. As shown in
exhibits the highest TOF at the proportion of approximately Fig. 5b, the addition of lithium iodide exercised very little
18 mol% under typical reaction conditions. When the pro- influence upon the conversion of methanol. However, the
portion reaches 25 mol%, a sharp decrease in the TOF value is selectivity toward acetic acid increased with the concentration
observed. The resulting decrease in the proportion of vinyl of lithium iodide.
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Fig. 7 The leaching amount of rhodium species and iodide promoters in the
reaction solution after each test batch of the first five-run test depicted in Fig. 6.
Fig. 6 The recyclability of the cross-linked copolymer supported catalyst.
Recyclability and stability of the catalyst
The recyclability of the cross-linked copolymer supported cata-
lyst was explored through a five-run recycling test. Product–
catalyst separation was carried out through a simple filtration.
In the subsequent batch test, a continuous filter was used to
separate the catalyst. The catalyst was recycled into the auto-
clave with the methanol feedstock stream. The catalyst exhi-
bited an approximately 25% loss of activity after the fifth test
(Fig. 6). The used catalyst can be regenerated by impregnation
in a diluted methanol solution of HI. The surplus iodide ions
were washed out with methanol until there were no iodide
ions in the cleaning fluid. In the second five-run consecutive
test, a similar downward tendency in catalytic activity was
observed. The catalyst was regenerated twice and fifteen
batches of activity tests were performed to investigate its recycl-
Scheme 3 The catalytic cycle of rhodium-complex-catalyzed homogeneous
methanol carbonylation.
ability and stability, as shown in Fig. 6. It was found that the (32 ppb) due to loosely anchored rhodium species. However,
gradual leaching of iodide promoters from the copolymeric the value in the subsequent batch test is approximately 10 ppb,
architectures directly led to the downward tendency in the cata- which is negligible and acceptable in a practical operation.
lytic activity during each five-run consecutive test. The metha- A cumulative effect is observed after the second regeneration
nol activation over the copolymeric chains is attributed to the and ten-batch tests.
leaching of iodide promoters, as revealed by Scheme 2.
As shown by the catalytic cycle of rhodium-complex-cata-
However, a simple regeneration process can mitigate this lyzed methanol carbonylation (Scheme 3), rhodium species are
problem. Another inevitable problem is rhodium leaching heavily involved in several key steps. Transfer between the sup-
caused by the formation of carbonyl complexes over the ported catalyst and the reaction solution is inevitable, which is
rhodium nanoparticle surface during the methanol carbony- attributed to the leaching of active metal species. For sup-
lation. After the second regeneration, the reactivated catalyst ported rhodium catalysts (complexes or nanoparticles), the
retained approximately 80% of the catalytic activity of the fresh leaching of rhodium from the reaction flow is a serious
one (Fig. 6). This decrease is attributed to rhodium leaching.
problem.15 However, well-designed support structures and
The leaching degree of rhodium species and iodide promo- attachment strategies can efficiently immobilize the active
ters was measured by determining their concentrations in the centers and then greatly mitigate leaching during the catalytic
reaction solution after each test batch. Fig. 7 shows the conversion.16 In this work, the leaching of rhodium was con-
measurement results of the first five-run test depicted in trolled to a negligible scale (Fig. 7). The concentration of leach-
Fig. 6. The concentration of iodide is in the range 50 ppm to ing rhodium in the reaction solution is approximately 10 ppb.
60 ppm, which is approximately 5000 times higher than that There are two main mechanisms for confining the irreversible
of rhodium. The iodide leaching is low and occurs in manage- transfer of rhodium species: the anchoring and trapping of
able proportions. It exerts only a small influence on a single highly ionized cross-linked copolymeric architectures and the
batch test, but the cumulative effects lead to a visible loss in compatible coexistence of iodide promoters with rhodium cata-
the catalytic activity after the five-run overall test. The level of lysts over the copolymeric supports (Scheme 1). The pyridine
rhodium leaching is relatively high in the incipient batch groups were methylated or acidified to give cationic sites,
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The 3d5/2 peak at 307.5 eV was attributed to zero-valent
rhodium nanoparticles. Another 3d5/2 peak at 308.4 eV was
indexed to a rhodium carbonyl intermediate ([Rh(CO)xI2]−,
Scheme 3),17 which is trapped by cationic sites over copoly-
meric architectures or over the surface layer of the rhodium
nanoparticles. Although this rhodium carbonyl intermediate is
dissolvable and transferable, highly ionized cross-linked co-
polymeric architectures efficiently confine its mobility.
Conclusions
In summary, we have developed an immobilization strategy to
simultaneously anchor Rh and iodide species. Well-designed
cross-linked copolymers contain functional groups that act as
promoters or anchoring sites to heterogenizing homogeneous
methanol carbonylation catalyst. Side-groups (methyl acetate)
and anchored iodide promoters over the cross-linked poly-
meric architectures facilitate the catalytic cycle of converting
methanol to methyl iodide. Approximately 90% of methanol
were converted to methyl acetate and acetic acid after two-hour
reaction at 120 °C under CO pressure of 3.0 MPa. The copoly-
meric catalyst exhibits good recyclability being regenerated
twice over a fifteen batch test and could be harnessed as a pro-
totype for developing sustainable methanol carbonylation.
Experimental
Preparation of cross-linked polymeric support
Solution A: sodium sulfate (48 g) was dissolved in deionized
water (480 ml), and then bentonite (10 g) was added and dis-
persed with rapid stirring. Solution B: an organic mixture of
purified monomers (2-vinylpyridine: 30 g, methacrylate ester:
26 g), cross-linker (DVB: 5.0 g), radical initiator (AVBN: 1.0 g),
pore templates (isoamyl alcohol: 6.0 g, diethyl phthalate:
6.0 g), solvents (o-xylene: 15.0 g, cyclohexane: 30.0 g).
Solution A was heated to 65 °C and stirred at the speed of
300 r min−1. Solution B was added to solution A over 15 min.
The mixture was stirred for 1 h and stored at 75 °C for 24 h.
The copolymeric particles were filtered and washed with
boiling water for three times to remove bentonite. The dry
copolymeric materials were extracted in an acetone stream for
30 h.
Purified copolymeric supports (2.0 g) were suspended in
toluene (30 ml). The mixture was sealed in a 100 ml autoclave
with a magnetic stirrer and flushed with argon for three times.
MeI (0.26 ml) was injected and the autoclave was heated to
90 °C for 3 h under stirring. After the autoclave was cooled to
room temperature, the copolymeric supports were filtered and
dried under vacuum.
Fig. 8 (a) TEM image of the dispersion state of Rh nanoparticles over the copo-
lymeric support after the recycling test. (b) Rh XPS peaks of the fresh catalyst
and the used one.
which could anchor and trap anionic rhodium carbonyl com-
plexes from the catalytic cycle. The coexistence of iodide pro-
moters with rhodium species facilitate completing the entire
carbonylation cycle over the copolymeric architectures, and
greatly mitigate the rhodium leaching during mass transfer
between the catalysts and the reaction solution. The dispersion
of rhodium nanoparticles of the used catalyst after ten batches
of activity tests (regenerated twice, as shown in Fig. 6) was
characterized by TEM (Fig. 8a). Compared with the fresh cata-
lyst (Fig. 1c), rhodium nanoparticles were redispersed. Some
nanoparticles exhibited a poorly-defined physical shape and a
marked growth in their size. It was clearly revealed that the
rhodium species transfer among the nanoparticles in a certain
form of rhodium carbonyl intermediate. The rhodium chemi-
cal states of the used catalyst were detected by XPS (Fig. 8b).
Fitting of the Rh 3d envelope resulted in the identification of
two chemical states of rhodium: one with a binding energy of
Immobilization of Rh and iodide species over the copolymeric
support
307.5 eV (3d5/2) with an atomic concentration of 56.2% and (NH4)2RhCl5 (34. 85 mg) was dissolved in methanol (30 ml)
another at 308.4 eV with an atomic concentration of 43.8%. and methylated copolymeric support (1.0 g) was added. The
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mixture was stirred for 45 min and the color of the methanol
solution disappeared. The solid materials were filtered and
Acknowledgements
washed with deionized water (10 ml) and methanol (10 ml). This work was financially supported by the National Natural
The washing operation was repeated for three times. The Sciences Foundation of China (no. 21101161, 21174148).
resulting solid was suspended in methanol and NaBH4
(5.5 mg) in water (2 ml) was added under stirring. The solid
materials turned light gray. After filtration and washing, the
solid materials were dried under vacuum for 3 h. The Rh load
Notes and references
was 1.0 wt%.
1 A. Haynes, Adv. Catal., 2010, 53, 1.
Before the catalyst test, the catalyst was loaded with HI
through direct suspension in a HI methanol solution. The
iodide amount was controlled by the concentration of HI in
solution. The resulted materials were washed with deionized
water until no iodide anion was detected in the eluent through
silver cation test. After being washed with methanol and
diethyl ether sequentially, the catalyst was dried under
vacuum.
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Characterization methods
X-ray photoelectron spectroscopy (XPS) was performed over a
VG ESCA-Lab200I-XL instrument. All peak positions in XPS
experiments were calibrated by the binding energy of C 1s as
reference of 284.6 eV. An Eclipse V2.1 data analysis software
supplied by the VG ESCA-Lab200I-XL instrument manufacturer
was applied for the manipulation of the acquired spectra.
Transmission electron microscopy (TEM) was performed on a
JEOL 2010 TEM with an accelerating voltage of 200 kV. Elec-
tron Probe Microanalysis (EPMA) (carried out on EPMA1600,
SHIMADZU) was used to characterize the dispersion state of
rhodium nanoparticles. The rhodium concentrations in the
reaction mixture were determined by ICP-OES using a Perkin
Elmer Optima instrument. The ionic iodide content in the
reaction mixture was determined by a 797 VA Computrace
polarograph manufactured by Metrohm, the detection limit of
which was 0.1 ppb. Trace methyl iodide (CH3I) in the reaction
mixture was measured by a chromatograph with an ECD detec-
tor and backflushing technique. Nitrogen-adsorption isother-
mal and textural properties of the as-synthesized materials
were determined by using liquid nitrogen over a Quanta-
chrome Autosorb Automated Gas Sorption System (Quanta-
chrome Corporation).
The products were analyzed by GC and GC-MS. GC was
carried out over GC-2014 (SHIMADZU) with a high temperature
capillary column (MXT-1, 30 m, 0.25 mm ID) and a FID detec-
tor. GC-MS was carried out over GCT Premier/Waters with
capillary column (DB-5MS/J&W Scientific, 30 m, 0.25 mm ID).
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istry, http://www.suschem.org (accessed in 2009).
Test of the catalytic activity for methanol carbonylation
The catalyst tests were carried out in a 50 ml Hastelloy auto-
clave. Typical reaction conditions: the catalyst; 0.2 g, methanol;
10 ml, reaction temperature; 120 °C, CO pressure; 3.0 MPa,
reaction time; 180 min. Product–catalyst separation was
carried out through simple filtration in the five-run recyclabi-
lity test. In consecutive batch tests, a continuous filter was 10 C. Gabriele and P. Siglinda,in Sustainable Industrial
applied to separate the catalyst. The catalyst was recycled into
the autoclave with the methanol feedstock stream.
Processes, ed. C. Fabrizio, C. Gabriele, P. Siglinda and
T. Ferruccio, Wiley-VCH, Weinheim, 2009, pp. 1–72.
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11 M. Duncan, in Heterogenized Homogeneous Catalysts for 15 W. O. Haag and D. D. Whitehurst, German Patent, 1800371,
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