Direct Conversion of Syngas into Methyl Acetate, Ethanol, and Ethylene by Relay Catalysis via the Intermediate Dimethyl Ether

Article abstract of DOI:10.1002/anie.201807113

Selective conversion of syngas (CO/H₂) into C₂₊ oxygenates is a highly attractive but challenging target. Herein, we report the direct conversion of syngas into methyl acetate (MA) by relay catalysis. MA can be formed at a lower temperature (ca. 473 K) using Cu-Zn-Al oxide/H-ZSM-5 and zeolite mordenite (H-MOR) catalysts separated by quartz wool (denoted as Cu-Zn-Al/H-ZSM-5|H-MOR) and also at higher temperatures (603–643 K) without significant deactivation using spinel-structured ZnAl₂O₄|H-MOR. The selectivity of MA and acetic acid (AA) reaches 87 % at a CO conversion of 11 % at 643 K. Dimethyl ether (DME) is the key intermediate and the carbonylation of DME results in MA with high selectivity. We found that the relay catalysis using ZnAl₂O₄|H-MOR|ZnAl₂O₄ gives ethanol as the major product, while ethylene is formed with a layer-by-layer ZnAl₂O₄|H-MOR|ZnAl₂O₄|H-MOR combination. Close proximity between ZnAl₂O₄ and H-MOR increases ethylene selectivity to 65 %.

Full text of DOI:10.1002/anie.201807113

A Journal of the Gesellschaft Deutscher Chemiker
Angewandte
Chemie
International Edition
www.angewandte.org
Accepted Article
Title: Direct Conversion of Syngas into Methyl Acetate, Ethanol and
Ethylene by Relay Catalysis via Dimethyl Ether Intermediate
Authors: Ye Wang, Wei Zhou, Jincan Kang, Kang Cheng, Shun He,
Jiaqing Shi, Cheng Zhou, Qinghong Zhang, Junchao Chen,
Luming Peng, and Mingshu Chen
This manuscript has been accepted after peer review and appears as an
Accepted Article online prior to editing, proofing, and formal publication
of the final Version of Record (VoR). This work is currently citable by
using the Digital Object Identifier (DOI) given below. The VoR will be
published online in Early View as soon as possible and may be different
to this Accepted Article as a result of editing. Readers should obtain
the VoR from the journal website shown below when it is published
to ensure accuracy of information. The authors are responsible for the
content of this Accepted Article.
To be cited as: Angew. Chem. Int. Ed. 10.1002/anie.201807113
Angew. Chem. 10.1002/ange.201807113
Link to VoR: http://dx.doi.org/10.1002/anie.201807113
http://dx.doi.org/10.1002/ange.201807113

10.1002/anie.201807113
Angewandte Chemie International Edition
COMMUNICATION
Direct Conversion of Syngas into Methyl Acetate, Ethanol and
Ethylene by Relay Catalysis via Dimethyl Ether Intermediate
Wei Zhou†,[a] Jincan Kang†,[a] Kang Cheng†,[a] Shun He,[a] Jiaqing Shi,[a] Cheng Zhou,[a] Qinghong
Zhang,*[a] Junchao Chen,[b] Luming Peng,[b] Mingshu Chen,[a] and Ye Wang*[a]
Abstract: Selective conversion of syngas (CO/H2) into C2+
oxygenates is a highly attractive but challenging target. Here, we
report the direct conversion of syngas into methyl acetate (MA) by
relay catalysis. MA can not only be formed at a lower temperature
(~473 K) using Cu-Zn-Al oxide/H-ZSM-5 and zeolite mordenite (H-
MOR) catalysts separated by quartz wool (denoted as Cu-Zn-Al/H-
ZSM-5│H-MOR) but also at higher temperatures (603-643 K)
without significant deactivation using spinel-structured ZnAl2O4│H-
MOR. The selectivity of MA and acetic acid (AA) reaches 87% at a
CO conversion of 11% at 643 K. Dimethyl ether (DME) is the key
intermediate and the carbonylation of DME results in MA with high
selectivity. We further discovered that the relay catalysis using
ZnAl2O4│H-MOR│ZnAl2O4 offers ethanol as the major product, while
oxygenates from syngas is an atom-efficient route because of
the incorporation of oxygen atoms into target products. Modified
Rh and bimetallic (e.g., Cu-Co) catalysts containing both CO
dissociation and non-dissociation active sites have typically
been investigated for the conversion of syngas to C2+
oxygenates, but the selectivity of C2+ oxygenates is low (usually
< 60%).[6] The product distribution in C2+ oxygenates is also
broad over most catalysts. The development of new methods for
direct conversion of syngas into C2+ oxygenates with high
selectivity is very attractive but challenging.
Here, we report
a highly selective synthesis of C2+
oxygenates from syngas in one reactor via relay catalysis. Our
previous studies demonstrated that the design of bifunctional
catalysts containing syngas-to-methanol component (Zn-Zr
oxide) and methanol-to-olefins (MTO) or methanol-to-aromatics
(MTA) component (zeolite SAPO-34 or ZSM-5) led to successful
conversion of syngas into lower olefins or aromatics with 70-
80% selectivity.[4a,4c,5a] Besides the MTO and MTA reactions,
methanol can undergo C-C coupling via carbonylation with CO.
Zeolite mordenite (H-MOR) catalyzes the carbonylation of
methanol or dimethyl ether (DME) into acetic acid (AA) or methyl
acetate (MA) at ~473 K.[7] The presence of H2 may exert a
positive effect on DME carbonylation.[7d] Thus, it would be
promising to realize the direct transformation of syngas into AA
ethylene
is
formed
with
a
layer-by-layer
ZnAl2O4│H-
MOR│ZnAl2O4│H-MOR combination. The increase in the proximity
between ZnAl2O4 and H-MOR increases ethylene selectivity to 65%.
Syngas (CO/H2), which can be produced from a variety of
carbon resources including natural/shale gas, coal, biomass and
even CO2, has attracted much attention as a key platform for the
synthesis of liquid fuels and chemicals.[1] Catalytic conversion of
syngas into C2+ compounds via controlled C-C coupling is the
core of syngas chemistry. Fischer-Tropsch (FT) synthesis is a
classic process for syngas conversions involving C-C coupling,
but the product distribution is broad because the C-C coupling
on FT catalyst surfaces is generally uncontrollable.[2] Significant
advances have recently been achieved in selective syntheses of
liquid fuels,[3] lower olefins,[4] and aromatics[5] from syngas by
or
MA
by
integrating
syngas-to-methanol/DME
and
methanol/DME-to-AA/MA. To the best of our knowledge, so far
there has been no success in the direct conversion of syngas
into AA/MA using the reaction-coupling strategy.
We performed syngas conversions using several
combinations of catalysts with different functions in one reactor
at 473 K. As expected, the Cu-Zn-Al oxide provided CH3OH with
high selectivity (Figure 1a). The Cu-Zn-Al/H-ZSM-5 catalyst,
prepared by mixing Cu-Zn-Al oxide and H-ZSM-5 powders,
showed a DME selectivity of 93% (Figure 1b), confirming that H-
ZSM-5 functioned for the dehydration of CH3OH to DME.[8] The
combination of Cu-Zn-Al oxide and H-MOR separated by thin
quartz wool (denoted as Cu-Zn-Al│H-MOR, Figure S1 in the
Supporting Information) catalyzed the formation of DME at the
initial stage (Figure 1c). The selectivity of DME decreased and
that of MA increased with time on stream, and the selectivities of
DME and MA became stable at ~40% and ~50%, respectively,
after ~6 h of reaction. Significantly higher MA selectivity could be
obtained by using the Cu-Zn-Al/H-ZSM-5│H-MOR combination
(Figure S1d and Figure 1d). The selectivity of DME became
negligibly small, and the sum of MA and AA selectivities reached
97% (MA selectivity, 84%) with a CO conversion of 4.5% after 4
h. At a lower weight ratio of H-MOR to Cu-Zn-Al/H-ZSM-5
(0.25:1), a part of DME still remained (Table S1). The increase
in the weight ratio of H-MOR to Cu-Zn-Al/H-ZSM-5 to ≥ 0.5:1
increased (MA + AA) selectivity to ≥ 95%. CO conversion was
slightly enhanced at the same time. Therefore, we succeeded in
converting syngas into MA and AA with high selectivity by a
relay catalysis via DME intermediate.
implementing
bifunctional catalysts.
On the other hand, the selective conversion of syngas into
C2+ oxygenates still remains challenging. C2+ oxygenates such
as ethanol, acetic acid and methyl acetate are important bulk
chemicals having numerous applications. The synthesis of C2+
a
reaction-coupling strategy and designing
[*]
W. Zhou,[†] Dr. J. Kang,[†] Dr. K. Cheng,[†] S. He, J. Shi, C. Zhou,
Prof. Dr. Q. Zhang, Prof. Dr. M. Chen, Prof. Dr. Y. Wang
State Key Laboratory of Physical Chemistry of Solid Surfaces,
Collaborative Innovation Center of Chemistry for Energy Materials,
National Engineering Laboratory for Green Chemical Productions of
Alcohols, Ethers and Esters, College of Chemistry and Chemical
Engineering
Xiamen University
Xiamen 361005 (China)
E-mail: zhangqh@xmu.edu.cn
wangye@xmu.edu.cn
J. Chen, Prof. Dr. L. Peng
Key Lab of Mesoscopic Chemistry, School of Chemistry and
Chemical Engineering
Nanjing University
Nanjing 210023 (China)
[†]
These authors contributed equally.
Supporting information for this article is given via a link at the end of
the document.
This article is protected by copyright. All rights reserved.

10.1002/anie.201807113
Angewandte Chemie International Edition
COMMUNICATION
dehydration of CH3OH to DME, could also be replaced by other
types of zeolites such as H-SAPO-34 and H-β without
significantly changing the (MA + AA) selectivity except for H-
MOR (Table S5). On the other hand, the use of other types of
zeolites to replace H-MOR in the Cu-Zn-Al/H-ZSM-5│H-MOR
combination remarkably decreased the (MA + AA) selectivity,
and part of DME remained unconverted (Table 1). Hydrocarbons
were formed with higher selectivity when other zeolites was
used. The (MA + AA) selectivity decreased in the following
sequence: Cu-Zn-Al/H-ZSM-5│H-MOR > Cu-Zn-Al/H-ZSM-5│H-
ZSM-35
> Cu-Zn-Al/H-ZSM-5│H-β > Cu-Zn-Al/H-ZSM-5│H-
ZSM-5 > Cu-Zn-Al/H-ZSM-5│SAPO-34. This agrees with the
fact that H-MOR is the most efficient catalyst for DME
carbonylation.[7] Zeolite H-ZSM-35, which has FER topology with
eight-membered ring (8-MR) channels similar to H-MOR,[9]
demonstrated
a
relatively better MA selectivity. These
observations confirm the essential role of H-MOR and provide
further evidence that MA and AA are formed via carbonylation of
DME intermediate.
It is noteworthy that MA and AA could not be obtained by
using the composite catalyst prepared by directly mixing Cu-Zn-
Al/ZSM-5 with H-MOR particles. Instead, ethane was formed
with a very high selectivity (90%) (Table 1). C2H6 was also the
major product over the Cu-Zn-Al/H-MOR catalyst or using the
Cu-Zn-Al/H-MOR│H-MOR combination (Table S5), which
contained Cu-Zn-Al oxide and H-MOR in direct contact. The Cu-
Zn-Al oxide in close contact with H-MOR might catalyze the
hydrogenation of MA and AA formed on H-MOR as well as the
resulting intermediates, finally leading to C2H6.
The selectivity of (MA + AA) declined and that of DME went
up after 25 h of reaction at 473 K for the Cu-Zn-Al/H-ZSM-5│H-
MOR combination, probably due to the deactivation of H-MOR
(Figure S3a). The coke deposition is known to occur facilely in
12-MR channels, which hinders DME to reach the active site for
carbonylation in 8-MR channels of H-MOR.[10] The poisoning or
removal of acid sites in 12-MR channels can enhance catalyst
Figure 1. Catalytic performances and reaction pathways for syngas
conversions at 473 K. a) Cu-Zn-Al oxide. b) Cu-Zn-Al/H-ZSM-5. c) Cu-Zn-
Al│H-MOR. d) Cu-Zn-Al/H-ZSM-5│H-MOR. e) Scheme for MA formation.
Reaction conditions: H2/CO = 1; P = 3 MPa; F = 25 mL min-1; weights of Cu-
Zn-Al, H-ZSM-5, H-MOR = 0.33, 0.17, 0.50 g.
Water is expected to be formed during the conversion of
syngas to DME on Cu-Zn-Al/H-ZSM-5 and may hinder the
subsequent carbonylation of DME on H-MOR.[7a] Although H2O
was formed with a considerable rate when the Cu-Zn-Al│H-
ZSM-5 or Cu-Zn-Al│H-MOR was employed for syngas
conversion, the Cu-Zn-Al/H-ZSM-5 composite exhibited
a
significantly lower H2O formation rate (Table S2). Instead, the
selectivity of CO2 became higher, indicating the occurrence of
water-gas shift (WGS) reaction, i.e., CO + H2O → CO2 + H2, due
to the catalytic function of Cu-Zn-Al oxide (Figure 1e). The Cu-
Zn-Al/H-ZSM-5│H-MOR combination showed significantly higher
(MA + AA) selectivity than the Cu-Zn-
Table 1. Catalytic performances of combinations of Cu-Zn-Al/H-ZSM-5 and different types of zeolites for
direct conversion of syngas.[a]
Al│H-MOR and Cu-Zn-Al│H-ZSM-5│H-
MOR combinations (Table S2). Thus,
the direct contact of Cu-Zn-Al oxide and
H-ZSM-5 can elegantly remove most of
the H2O via the WGS reaction, favoring
the subsequent carbonylation of DME.
Our studies further suggest that the
Catalyst
T [K]
CO
CO2
Selectivity[b] [%]
conv.
[%]
select.
[%]
CH3OH
3.1
DME
88
MA
3.2
14
21
33
84
83
85
0
AA
0
HC[c]
5.9
Cu-Zn-Al/H-ZSM-5│SAPO-34
Cu-Zn-Al/H-ZSM-5│H-ZSM-5
Cu-Zn-Al/H-ZSM-5│H-β
473
473
473
473
473
483
493
473
3.3
3.2
3.5
3.7
4.5
7.5
10
29
28
28
28
22
21
21
47
5.1
68
1.6
1.4
0.6
13
14
12
0
11
remaining
water
with
a
low
concentration may cause AA formation
in our system (Table S3 and Figure S2),
while almost no AA is formed in DME
carbonylation over H-MOR.[7a,7d] The
WGS reaction also enabled the use of
syngas with a lower H2/CO ratio. A high
(MA + AA) selectivity was obtained at a
H2/CO ratio of 0.5:1, although CO
conversion became slightly lower
(Table S4). Higher H2/CO ratios favored
CO conversion but was unbeneficial to
(MA + AA) selectivity.
7.5
43
27
Cu-Zn-Al/H-ZSM-5│H-ZSM-35
Cu-Zn-Al/H-ZSM-5│H-MOR
Cu-Zn-Al/H-ZSM-5│H-MOR[d]
Cu-Zn-Al/H-ZSM-5│H-MOR[d]
Cu-Zn-Al/H-ZSM-5/H-MOR[e]
4.0
56
6.1
0.3
0.8
2.5
0.6
7.2
2.1
0.1
0.9
0.1
2.3
4.1
1.3
92(90)[f]
[a] Reaction conditions: weights of Cu-Zn-Al, H-ZSM-5 and H-MOR = 0.33, 0.17 and 0.50 g; H2/CO = 1; P =
3 MPa; F = 25 mL min-1; time on stream, 5 h. [b] The selectivity was calculated on a molar carbon basis.
Carbon balances were all 95-99%. [c] Hydrocarbons. [d] H-MOR-steam used. [e] Mixture of Cu-Zn-Al/H-
ZSM-5 and H-MOR particles. [f] The number in parenthesis denotes C2H6 selectivity.
H-ZSM-5, which functioned for the
This article is protected by copyright. All rights reserved.

10.1002/anie.201807113
Angewandte Chemie International Edition
COMMUNICATION
stability.[11] We performed selective removal of framework Al in
thermodynamic limitations at higher temperatures (Figure S7).
Moreover, as expected, the increase in the weight ratio of H-
MOR to Zn-Al oxide in the Zn-Al│H-MOR decreased the
selectivity of DME and increased that of (MA +AA). The (MA +
AA) selectivity exceeded 85% at a weight ratio of H-MOR to Zn-
Al oxide of ≥ 2:1 (Table S8). Similar to the Cu-Zn-Al/H-ZSM-
5│H-MOR system, the Zn-Al│H-MOR can also be applied to the
conversion of syngas with different H2/CO ratios (Table S9).
Our characterizations revealed that ZnAl2O4 compound with
spinel structure was formed for the Zn-Al oxide (Figure S8) and
the mean size of ZnAl2O4 particles was 6.2 nm (Figure S9). The
Zn-Al oxide possessed stronger Lewis acidity than Zn-Zr and
Zn-Ga oxides (Figures S10 and S11). The stronger acidity may
accelerate the dehydration of CH3OH to DME on ZnAl2O4 at 643
K (Table S7). The conversions of methanol and DME on H-MOR
under syngas atmosphere at 643 K showed different product
distributions. MA was selectively formed from DME, whereas
hydrocarbons were the major products from CH3OH (Table S10).
These results demonstrate that H-MOR catalyzes the
carbonylation of DME to MA efficiently at 643 K, whereas the
conversion of CH3OH at 643 K mainly results in hydrocarbons.
The carbonylation of DME by H-MOR is generally performed
at 423-473 K.[7] Almost no report has been devoted to DME
carbonylation over H-MOR at > 600 K. We found that unlike the
12-MR channels by
a
high-temperature steam-treatment
method.[11] Characterizations for the obtained sample (denoted
as H-MOR-steam) confirmed that the Brønsted acid sites in 12-
MR channels were mostly removed (Figures S4-S6 and Table
S6). The Cu-Zn-Al/H-ZSM-5│H-MOR-steam became more
stable, and no significant decreases in both CO conversion and
(MA + AA) selectivity were observed in 100 h (Figure S3a).
To increase CO conversion is another important target. We
found that CO conversion for the Cu-Zn-Al/H-ZSM-5│H-MOR-
steam combination could be increased from 4.5% to 10% by
raising reaction temperature from 473 to 493 K, while the
selectivity of (MA + AA) was kept at >95% (Table 1). However,
the catalyst deactivation became significant even using H-MOR-
steam at higher temperatures (Figure S3b and S3c).[12] The
selectivity of (MA + AA) decreased to ~60% and that of DME
increased to ~30% after 25 h of reaction at 493 K for the Cu-Zn-
Al/H-ZSM-5│H-MOR-steam (Figure S3c).
We discovered that MA and AA could be formed from
syngas without significant deactivation at significantly higher
temperatures (603-643 K) using the combination of metal oxide
and H-MOR. The Cu-Zn-Al oxide is unsuitable for high-
temperature conversion of syngas to oxygenates. We observed
the formation of CH4 and C2+ hydrocarbons as major products
using Cu-Zn-Al oxide and Cu-Zn-Al│H-MOR at 643 K (Table S7). Cu-Zn-Al/H-ZSM-5│H-MOR at 473
K
(Figure S3a), the
The (MA + AA) selectivity was low by combining H-MOR with
Zn-Zr or Zn-Ga oxide, which alone mainly catalyzed the
formation of CH3OH from syngas (Table S7). On the other hand,
MA and AA were formed with high selectivity using a Zn-Al│H-
MOR combination. The Zn-Al oxide catalyzed the conversion of
ZnAl2O4│H-MOR exhibited a long induction period in syngas
conversion at 643 K (Figure 3a). CH4 and C2+ hydrocarbons
were mainly formed at the initial stage, and their selectivities
decreased with time on stream in the initial 10 h. The (MA + AA)
selectivity increased and reached ~85% with an 11% CO
syngas to DME with selectivity of ~85% at 603-643 K (Figure 2a). conversion after 10 h. No significant deactivation was observed
The integration of Zn-Al oxide with H-MOR produced (MA + AA)
with selectivity of >85% at 603-643 K and a CO conversion of
11% was attained at 643 K (Figure 2b). A further higher
temperature increased the selectivity of CH4 and C2+
hydrocarbons. The decrease in CO conversion should arise from
in ~70 h. The induction period became significantly shorter by
using H-MOR-steam, in which Brønsted acid sites in 12-MR
channels were mostly removed (Figure 3b), or almost
disappeared by pretreating H-MOR with DME at 643 K for 5 h
(Figure 3c). Thus, the conversion of DME intermediate in 12-MR
channels may be responsible for the formation of hydrocarbons
in the induction period. The removal of the acid sites in 12-MR
channels by steam pretreatment or by poisoning these sites with
coke deposition (DME pretreatment) led to steady-state activity.
It is of interest that, unlike the reaction with the Cu-Zn-Al/H-ZSM-
5│H-MOR at 493 K, where the quick deactivation occurred due
to the coke deposition in 12-MR channels of H-MOR (Figure
S3c), the carbonylation of DME still proceeds efficiently after the
induction period with the ZnAl2O4│H-MOR at 643 K (Figure 3).
Our NH3-temperature-programmed desorption studies revealed
that approximately half of the strong acid sites remained in the
H-MOR after the induction period at 643 K (Figure S12), which
corresponded to the strong acid sites in 8-MR channels (Table
S6). On the other hand, almost all the strong acid sites in H-
MOR in the Cu-Zn-Al/H-ZSM-5│H-MOR were poisoned after 15
h of reaction at 493 K (Figure S12).
Figure 2. Syngas conversions at high temperatures. a) Zn-Al oxide. b) Zn-
Al│H-MOR. Reaction conditions: H2/CO = 1; P = 3 MPa; F = 25 mL min-1; time
on stream, 20 h; weights of Zn-Al and H-MOR = 0.33 and 0.67 g.
This article is protected by copyright. All rights reserved.

10.1002/anie.201807113
Angewandte Chemie International Edition
COMMUNICATION
Figure 4. Effect of arrangements of ZnAl2O4 and H-MOR on catalytic
conversion of syngas. a) ZnAl2O4. b) ZnAl2O4│H-MOR. c) ZnAl2O4│H-
MOR│ZnAl2O4. d) ZnAl2O4│H-MOR│ZnAl2O4│H-MOR. e) Mixture of ZnAl2O4
and H-MOR granules with sizes of 250-600 μm. f) Mixture of ZnAl2O4 particles
with sizes of 4-9 nm and H-MOR particles with sizes of 0.3-1 μm. Reaction
conditions: H2/CO = 1; P = 3 MPa; F = 25 mL min-1; time on stream, 20 h; total
weights of ZnAl2O4 and H-MOR = 0.33 and 0.67 g.
A further increase in the proximity to nano-scale did not
significantly change CO conversion and C2H4 selectivity (Figure
4f). It is of high significance that the use of two components, i.e.,
ZnAl2O4 and H-MOR, with different arrangements can result in
different products by relay catalysis.
In conclusion, we have presented a new strategy for
selective conversion of syngas into C2+ oxygenates by designing
combinations of catalysts with different functions for relay
catalysis. The selectivity of (MA + AA) reaches ~95% at CO
conversion of 4.5% at 473 K by using a combination of Cu-Zn-
Al/H-ZSM-5 and H-MOR. No significant deactivation is observed
in 100 h by removing acid sites in 12-MR channels of H-MOR.
MA and AA can be synthesized at 603-643 K without significant
deactivation by using a combination of spinel-structured ZnAl2O4
and H-MOR. The selectivity of (MA + AA) is ~85% at CO
conversion of 11% at 643 K. DME is the key intermediate and
the precise C-C coupling via DME carbonylation results in highly
selective formation of MA and AA at both lower and higher
temperatures. We have further succeeded in direct conversion
of syngas into ethanol and ethylene by using ZnAl2O4 and H-
MOR combinations with different arrangements. The
ZnAl2O4│H-MOR│ZnAl2O4 provides ethanol with a selectivity of
52%, whereas the ZnAl2O4│H-MOR│ZnAl2O4│H-MOR offers
ethylene. The increase in the proximity between ZnAl2O4 and H-
MOR increases ethylene selectivity to 65%.
Figure 3. Changes of catalytic behaviors for syngas conversion with time on
stream. a) ZnAl2O4│H-MOR. b) ZnAl2O4│H-MOR-steam. c) ZnAl2O4│DME-
pretreated H-MOR. Reaction conditions: H2/CO = 1; T = 643 K; P = 3 MPa; F =
25 mL min-1; weights of ZnAl2O4 and H-MOR (H-MOR-steam or DME-
pretreated H-MOR) = 0.33 and 0.67 g.
We demonstrate that syngas can further be transformed into
ethanol in one reactor by relay catalysis via DME and MA
intermediates. Figure 4 shows the major products obtained from
syngas at 603 K by using different spatial arrangements of
ZnAl2O4 and H-MOR catalysts. The ZnAl2O4│H-MOR│ZnAl2O4
combination with a sandwich configuration offers C2H5OH as the
major product (Figure 4c). At ~6% CO conversion, C2H5OH
selectivity reached 52%, which is better than most of those
reported for the direct conversion of syngas.[6] This result
suggests that the ZnAl2O4 in the downstream of ZnAl2O4│H-
MOR functions for the hydrogenation of MA and AA into C2H5OH
and CH3OH. Considering the selectivities of MA and AA from the
ZnAl2O4│H-MOR, the maximum C2H5OH selectivity is 64%.
CH3OH and C2+ hydrocarbons were formed as the major by-
products (Figure S13a).
Furthermore, we found that ethylene was formed by using a
layer-by-layer ZnAl2O4│H-MOR│ZnAl2O4│H-MOR combination Acknowledgements
(Figure 4d). The selectivity of C2H4 was ~50%, which was almost
the same with that of C2H5OH in Figure 4c. Thus, H-MOR in the
downstream of ZnAl2O4│H-MOR│ZnAl2O4 catalyzed the
dehydration of ethanol. The increase in the proximity between
ZnAl2O4 and H-MOR by mixing ZnAl2O4 and H-MOR granules
with sizes of 250-600 μm increased C2H4 selectivity to 65% with
a CO conversion of 10% (Figure 4e). C3 and C4 olefins as well
as C2-C4 paraffins were the major by-products (Figure S13b).
This work was supported by the National Key Research and
Development Program of Ministry of Science and Technology
(2017YFB0602201) and the National Natural Science
Foundation of China (Nos. 91545203, 21433008, 21503174,
21403177 and 21673188).
This article is protected by copyright. All rights reserved.

10.1002/anie.201807113
Angewandte Chemie International Edition
COMMUNICATION
Conflict of interest
The authors declare no conflict of interest.
Keywords: C2+ oxygenates • C-C coupling • heterogeneous
catalysis • relay catalysis • zeolites
[1]
a) H. M. T. Galvis, J. H. Bitter, C. B. Khare, M. Ruitenbeek, A. I.
Dugulan, K. P. de Jong, Science 2012, 335, 835-838; b) F. Jiao, J. Li, X.
Pan, J. Xiao, H. Li, H. Ma, M. Wei, Y. Pan, Z. Zhou, M. Li, S. Miao, J.
Li, Y. Zhu, D. Xiao, T. He, J. Yang, F. Qi, Q. Fu, X. Bao, Science 2016,
351, 1065-1068; c) L. Zhong, F. Yu, Y. An, Y. Zhao, Y. Sun, Z. Li, T. Lin,
Y. Lin, X. Qi, Y. Dai, L. Gu, J. Hu, S. Jin, Q. Shen, H. Wang, Nature
2016, 538, 84-87.
[2]
[3]
K. Cheng, J. Kang, D. L. King, V. Subramanian, C. Zhou, Q. Zhang, Y.
Wang, Adv. Catal. 2017, 60, 125-208.
a) J. Bao, J. He, Y. Zhang, Y. Yoneyama, N. Tsubaki, Angew. Chem.
Int. Ed. 2008, 47, 353-356; b) J. Kang, K. Cheng, L. Zhang, Q. Zhang, J.
Ding, W. Hua, Y. Lou, Q. Zhai, Y. Wang, Angew. Chem. Int. Ed. 2011,
50, 5200-5203; c) X. Peng, K. Cheng, J. Kang, B. Gu, X. Yu, Q. Zhang,
Y. Wang, Angew. Chem. Int. Ed. 2015, 54, 4553-4556; d) N.
Duyckaerts, M. Bartsch, I. T. Trotuş, N. Pfänder, A. Lorke, F. Schüth, G.
Prieto, Angew. Chem. Int. Ed. 2017, 56, 11480-11484.
[4]
[5]
a) K. Cheng, B. Gu, X. Liu, J. Kang, Q. Zhang, Y. Wang, Angew. Chem.
Int. Ed. 2016, 55, 4725-4728; b) F. Jiao, X. Liu, K. Gong, Y. Chen, G. Li,
X. Bao, Angew. Chem. Int. Ed. 2018, 57, 4692-4696; c) X. Liu, W. Zhou,
Y. Yang, K. Cheng, J. Kang, L. Zhang, G. Zhang, X. Min, Q. Zhang, Y.
Wang, Chem. Sci. 2018, 9, 4708-4718; d) J. Su, D. Wang, Y. Wang, H.
Zhou, C. Liu, S. Liu, C. Wang, W. Yang, Z. Xie, M. He, ChemCatChem
2018, 10, 1536-1541.
a) K. Cheng, W. Zhou, J. Kang, S. He, S. Shi, Q. Zhang, Y. Pan, W.
Wen, Y. Wang, Chem 2017, 3, 334-347; b) B. Zhao, P. Zhai, P. Wang,
J. Li, T. Li, M. Peng, M. Zhao, G. Hu, Y. Yang, Y. W. Li, Q. Zhang, W.
Fan, D. Ma, Chem 2017, 3, 232-333; c) P. Zhang, L. Tan, G. Yang, N.
Tsubaki, Chem. Sci. 2017, 8, 7941-7946; d) J. L. Weber, I. Dugulan, P.
E. de Jongh, K. P. de Jong, ChemCatChem 2018, 10, 1107-1112.
a) J. J. Spivey, A. Egbebi, Chem. Soc. Rev. 2007, 36, 1514-1528; b) G.
Prieto, S. Beijer, M. L. Smith. M. He, Y. Au, Z. Wang, D. A. Bruce, K. P.
de Jong, J. J. Spivey, P. E. de Jongh, Angew. Chem. Int. Ed. 2014, 53,
6397-6401; c) H. T. Luk, C. Mondelli, D. C. Ferré, J. A. Stewart, J.
Pérez-Ramírez, Chem. Soc. Rev. 2017, 46, 1358-1426.
[6]
[7]
a) P. Cheung, A. Bhan, G. J. Sunley, E. Iglesia, Angew. Chem. Int. Ed.
2006, 45, 1617-1620; b) M. Boronat, C. Martínez-Sánchez, D. Law, A.
Corma, J. Am. Chem. Soc. 2008, 130, 16316-16323; c) Y. Ni, L. Shi, H.
Liu, W. Zhang, Y. Liu, W. Zhu, Z. Liu, Catal. Sci. Technol. 2017, 7,
4818-4822; d) H. Xue, X. Huang, E. Ditzel, E. Zhan, M. Ma, W. Shen,
Ind. Eng. Chem. Res. 2013, 52, 11510-11515.
[8]
[9]
G. Yang, N. Tsubaki, J. Shamoto, Y. Yoneyama, Y. Zhang, J. Am.
Chem. Soc. 2010, 132, 8129-8136.
X. Li, X. Liu, S. Liu, S. Xie, X. Zhu, F. Chen, L. Xu, RSC Adv. 2013, 3,
16549-16557.
[10] T. He, X. Liu, S. Xu, X. Han, X. Pan, G. Hou, X. Bao, J. Phys. Chem C
2016, 12, 22526-22531.
[11] H. Xue, X. Huang, E. Zhan, M. Ma, W. Shen, Catal. Commun. 2013, 37,
75-79.
[12] Z. Cheng, S. Huang, Y. Li, J. Lv, K. Cai, X. Ma, Ind. Eng. Chem. Res.
2017, 56, 13618-13627.
This article is protected by copyright. All rights reserved.

10.1002/anie.201807113
Angewandte Chemie International Edition
COMMUNICATION
Entry for the Table of Contents
COMMUNICATION
Relay catalysis using combinations of
catalysts with different functions is an
effective strategy for the conversion of
syngas to C2+ oxygenates. Using a
combination of Cu-Zn-Al/H-ZSM-5 or
ZnAl2O4 and H-MOR, we succeeded
in synthesizing methyl acetate and
acetic acid from syngas with
W. Zhou, J. Kang, K. Cheng, S. He, J.
Shi, C. Zhou, Q. Zhang,* J. Chen, L.
Peng, M. Chen, Y. Wang*
Page No. – Page No.
Direct Conversion of Syngas into
Methyl Acetate, Ethanol and Ethylene
by Relay Catalysis via Dimethyl Ether
Intermediate
selectivity of 87-97%. Ethanol and
ethylene can be obtained by using
layer-by-layer ZnAl2O4│H-
MOR│ZnAl2O4 and ZnAl2O4│H-
MOR│ZnAl2O4│H-MOR combinations.
This article is protected by copyright. All rights reserved.