Specific zone within 8-membered ring channel as catalytic center for carbonylation of dimethyl ether and methanol over FER zeolite

Accepted Manuscript Title: Specific Zone within 8-Membered Ring Channel as Catalytic Center for Carbonylation of Dimethyl Ether and Methanol over FER Zeolite Authors: Pei Feng, Guanqun Zhang, Xiaofang Chen, Kailu Zang, Xiujie Li, Longya Xu PII: DOI: Reference:

S0926-860X(18)30137-6 https://doi.org/10.1016/j.apcata.2018.03.018 APCATA 16592

To appear in:

Applied Catalysis A: General

Received date: Revised date: Accepted date:

5-1-2018 19-3-2018 20-3-2018

Please cite this article as: Feng P, Zhang G, Chen X, Zang K, Li X, Xu L, Specific Zone within 8-Membered Ring Channel as Catalytic Center for Carbonylation of Dimethyl Ether and Methanol over FER Zeolite, Applied Catalysis A, General (2010), https://doi.org/10.1016/j.apcata.2018.03.018 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Specific Zone within 8-Membered Ring Channel as Catalytic Center for Carbonylation of Dimethyl Ether and Methanol over FER Zeolite

a

IP T

Pei Fenga, d, Guanqun Zhangb, Xiaofang Chena*, Kailu Zanga, d, Xiujie Lic and Longya Xuc State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics,

b c

SC R

Chinese Academy of Sciences, Dalian 116023, China

School of Physical Science and Technology, ShanghaiTech University, Shanghai 201210, China Dalian National Laboratory for Clean Energy, Dalian Institute of Chemical Physics, Chinese

University of Chinese Academy of Sciences, Beijing 100049, China

N

d

U

Academy of Sciences, Dalian 116023, China

CC E

PT

ED

M

A

* Corresponding author. E-mail address: [email protected]; Tel: +86-411-8437 9385

A

Graphical abstract

Highlights 1. For the first time the mechanism of dimethyl ether and methanol carbonylation over FER zeolite was investigated using DFT method. 1

2. Surface methoxy groups from methanol/DME interacting with Brønsted acid sites of zeolite preferentially form within the 8MR and 10MR channels of FER. 3. CO attack on surface methoxy groups occurs selectively in the 6MR zone of 8MR

IP T

channel of FER zeolite.

Abstract

SC R

The DFT investigation of methanol and dimethyl ether (DME) carbonylation at different sites of FER zeolite is carried out in an attempt to explore whether some specific acid sites are present to selectively catalyze the desired reaction. It is shown that the surface methoxy groups (SMG),

U

generated by the reaction of methanol or DME with the Brønsted acid sites of zeolites, preferentially

N

forms in the 8-membered ring (8MR) and 10-membered ring (10MR) channels. Further study of the

A

CO attack on the SMG shows that, the carbonylation reaction occurs selectively at the 6MR zone of 8MR channel of FER zeolites. This result not only provides a theoretical perspective for the

M

experimentally observed higher carbonylation reactivity of SMG located inside the 8MR channels,

ED

but also makes the location of the reaction more accurate.

1. Introduction

PT

Key Words: Dimethyl ether; FER zeolite; Carbonylation; DFT

Introduction of CO into organic substrates can produce carbonyl-containing compounds, which are

CC E

widely employed in chemical industry to produce various useful chemicals[1-4]. Among these carbonylation reactions, the carbonylation of methanol or dimethyl ether (DME) with CO attracts particular attention for its application in producing industrially important acetic acid and methyl

A

acetate[5-8]. Traditional catalysts of dimethyl ether (DME) carbonylation are usually homogenous catalysts like halide complex or Rh/Ir organometallic complexes, such catalysts are intoxicated to human health and hazardous to environment[9]. In 2006, Iglesia[10] reported the DME carbonylation catalyzed by various acidic zeolites, and acid MOR and FER zeolite show excellent carbonylation activity and selectivity to methyl acetate. Compared with the halide complex or organometallic catalysts, acidic zeolites exhibit high activity even at relatively low reaction temperatures 2

(423-463K), and they can be easily separated from the liquid-state reactant and product. Zeolites are microporous aluminosilicates of ordered arrangement of channels and/or cavities. Different zeolites have various types of channel/cavity systems, and adjustment of the Si/Al ratios of the zeolite can change the acidity of the zeolites (since the framework Al3+ of zeolite generates Brønsted acid sites). Consequently, the diversity of the pore size, shape and channel connectivity, together with adjustable acidity make zeolite widely used catalysts in various catalytic reactions[11-14]. In methanol or DME

IP T

carbonylation with CO, the MOR-type zeolite, which contains the intersected 12 membered-ring (12MR) channel and 8MR channel, exhibits highest activity and methyl acetate selectivity among a

SC R

series of acidic zeolites; while the FER-type zeolite, which contains the intersected 10MR-8MR channel, exhibits slightly lower activity, while other zeolites that contain no 8MR channels, such as MFI-, BEA- or FAU-type zeolites, exhibits much lower activities.

U

The successful applications of the aluminosilicate MOR zeolites in methanol and DME

N

carbonylation reactions have prompted researchers to investigate the catalytic mechanism within

A

these zeolites. In 2007, Iglesia[15] studied the IR spectra of various MOR zeolites, and concluded that the C-C bond formation from CO and chemisorbed methyl groups occurs selectively within

M

8MR channels, and related this site specificity to the paramount catalytic activity of MOR zeolite. In

ED

2008 Boronat[8] employed quantum-chemical methods to investigate the carbonylation in MOR, and discovered that the Brønsted acid sites on T3-O33 site of the 8MR channel is energetically and sterically favorable for the interaction between surface methoxy group with CO, the author believed

PT

that this specific site results in the high carbonylation selectivity of MOR zeolites. In contrast to the enormous investigations on the mechanism of MOR-catalyzed carbonylation[8,

CC E

16, 17], the study on the mechanism of FER-catalyzed carbonylation reaction is quite rare. In 2011 Roman-Leshkov synthesized a series of FER zeolites of different acid distributions, and tested their catalytic properties in DME-CO carbonylation[18]. The results show a clear dependence between the

A

DME carbonylation rates with the acid site number within the 8MR channels of FER zeolites, which implies that the acid sites within 8MR are the most active catalytic centers of FER zeolites. Although MOR and FER zeolites are both catalytically active in methanol and DME carbonylation and possess 8MR channel, the 8MR of MOR zeolite has an ellipse shape with the pore size of 5.7*2.6 Å, while the 8MR of FER zeolite has a near-circle shape with the pore size of 4.6*3.5 Å. The different 8MR shapes and sizes cause the different distribution of Brønsted acid sites[19], and thus lead to different 3

catalytic behavior of FER from MOR. Here we present a DFT study to investigate the preferential sites of the surface methoxy groups (SMG) formed on Brønsted acid sites, and the competitive interaction of CO, methanol, water and DME with SMG. We have discovered that the T2-O5 and T4-O7 sites of the 8MR of FER are energetically favorable for the interaction between surface methoxy group with CO.

IP T

2. Computational Details

The structure of FER was obtained using the data from Internal Zeolite Associates (IZA)[20], with

SC R

the maximum symmetric space group being Immm and the crystallographic parameters being a = 19.018, b = 14.303 and c = 7.541 Å, respectively. The all-silica framework of FER zeolite is composed of 4- and 5-membered rings that link in various sequences to form large 10MR channels

U

(with the pore opening of 5.4 Å × 4.2 Å) along the [001] direction, which intersect the 8MR channel

N

(with the pore opening of 4.8 Å × 3.5 Å) along the [010] direction[21, 22]. Four types of crystallographically unequivalent sites (denoted as T1, T2, T3 and T4, respectively) exist in FER

A

structure, which were occupied by either Si or Al atoms. Among these atoms, T1, T2 sites are located

M

in the intersection between 10MR and 8MR channels, T3 sites are located in the 10MR channel, and T4 are inside the FER 8MR channel (see Fig. 1).

ED

In this work, a cluster model involving 346 atoms including 104T was selected to represent the FER zeolite, which was cut out from the periodic all-silica FER structure (Fig. 2). This cluster model

PT

included both the intersecting 8MR and 10MR channels. The single Al substitution FER structure was obtained by the replacement of one Si atom at a specified T sites by one Al atom, and a methoxy

CC E

group was set to form on each of the 4 different O atoms bonded to Al atom. All the possible orientations of the methoxy groups that are formed on the different O atoms in FER were obtained through optimization process and was listed in Table 1. It is noteworthy that T2-O6a and T2-O6b

A

represents 2 types of orientations of methoxy groups on the O6 atoms bonded to T2 sites (details of the two structures were shown in Fig. S1). It should be noticed that in our previous research about the siting of protons in FER zeolites, a total of 14 configurations (including site and orientation) were obtained by calculation; specifically, protons at the T1-O1 site can have 2 distinct orientations, while when the protons are replaced by larger, steric SMG, only one possible configuration can be obtained from optimization(i.e., in the intersection of 8MR and 10MR channels). A similar case is T2-O6 site 4

where 2 possible configurations can also be obtained. For the rest of the sites, only one possible orientation of SMG can be obtained. Therefore, there are 13 possible SMG configurations recorded in this manuscript[23]. The dangling Si atoms are terminated by hydrogen along the bond direction of the next lattice oxygen atoms with the distance of 1.47 Å. The reaction of 104 T model was optimized employing the 2-layer scheme ONIOM[24, 25] in the Gaussian 09 computer program[26] with different processing approaches for different cluster regions. The inner region, which has an

IP T

intimate relationship to catalytic reactions, is treated at high-level with the density functional theory method for accuracy, while the peripheral region away from the active center is treated at low-level

SC R

with the semi-empirical calculation method for efficiency. The atoms in high-level region were represented with ball, while the atoms in low-level with stick in Fig. 2. All the high-layer atoms were relaxed to be optimized, while the low-layer fixed in their crystallographic sites to retain the zeolite

U

structure. All the calculation used density functional theory (DFT) with the B3LYP functional with

CC E

PT

ED

M

A

N

6-31G(d,p)[27] for high-level region and am1[28, 29] for low-level region.

A

Fig. 1. The T sites and the corresponding oxygens site of the FER framework viewed from [001] (a) and [010] (b) directions. Gray area represents 6MR zone of 8MR channel.

5

IP T

SC R

Fig. 2. The 2-layer FER zeolite cluster model, the atoms in high-level region were represented with ball, while the atoms in low-level with stick.

3. Results and Discussion

U

3.1 Formation of the methoxy group

N

We selected from the whole 13 crystallographically independent T sites of FER zeolite, and

A

obtained a total of 13 T-O configurations as depicted in Fig. 1 and the orientations of the methyl

M

groups formed on the different O atoms are listed in Table 1. Table 1. Orientations of the methyl groups formed on the different O atoms on the surface of FER zeolites. Site on

T1-O1

Intersection of 8MR and 10MR

T1-O2

Intersection of 8MR and 10MR

T1-O3

Intersection of 8MR and 10MR

T3-O1

Intersection of 8MR and 10MR

T2-O2

10MR

T2-O6b

10MR

T2-O5

6MR zone of 8MR channela

T2-O6a

6MR zone of 8MR channel

T4-O5

6MR zone of 8MR channel

T4-O7

6MR zone of 8MR channel

T1-O4

8MR cageb

T3-O7

8MR cage

T3-O8

8MR cage

A

CC E

PT

ED

configuration

a

See the gray area in the Fig. 1.

b

Description of the cage see Fig. S2.

According to Boronat[8, 16], the initially chemisorbed methanol (or DME) molecule on the acid 6

sites of the MOR or FER zeolites would form cationic CH3OH2+ (or CH3OCH4+), which would subsequently decompose into a water (or methanol) molecule and a methoxy group, so the author started with the adsorbed methoxy groups on FER zeolite. We intended to compare the formation preference of SMG at different sites in FER, so to make calculation process simpler we also only considered the stability of the resultant materials of surface methoxy and water (or methanol if DME

this ability was defined as in the following equation: ΔEmethanol/DME= (ESMG+ Ewater/methanol)- (Eacid + Emethanol/DME)

IP T

as the reactant), in respect to the initial Brønsted acid sites and methanol or DME. More specifically,

SC R

ΔE stands for the reaction energy of the formation of methoxy group on FER surface, and was to used represent the stability of the stability of formed methoxy groups[8]. While ESMG, Ewater, Eacid, Emethanol and EDME stand for the formation enthalpies of the SMG, water molecules, acid sites of

U

zeolite, methanol and DME molecules, respectively.

N

Table 2. Calculated reaction energies (kJ/mol) for the process Z-H + CH3OH /DME→ Z-CH3 + H2O/CH3OH and optimized values of the r(OFER-CSMG), which is the C-O distance(Å) of the SMG of FER zeolite.

CC E

PT

ED

M

A

Configuration r(OFER-CSMG) ΔEmethanol 24.32 T1-O1 1.47478 39.22 T1-O2 1.48430 39.39 T1-O3 1.48669 212.65 T1-O4 1.43647 25.46 T2-O2 1.47990 52.63 T2-O5 1.49460 83.49 T2-O6a 1.49609 43.98 T2-O6b 1.48089 10.75 T3-O1 1.47468 64.94 T3-O7 1.43784 50.05 T3-O8 1.43858 58.54 T4-O5 1.49690 52.43 T4-O7 1.51264

ΔEDME 34.53 49.43 49.60 222.86 35.67 62.84 93.71 54.19 20.96 75.15 60.26 68.75 62.64

A

Table 2 listed the calculated reaction energies and lengths of the C-O bond of the SMG. A

general observation is that for FER model clusters, the SMG formation is an endothermic process, which is in line with the case of the SMG formation over H-MOR zeolites[8]. Generally in which site, the reaction energies between FER with methanol are always ~10kJ/mol lower than that between FER with DME. Moreover, in terms of SMG formation from methanol, the T3-O1 site (at the intersection of 8MR and 10MR) is thermodynamically most favorable, followed by T1-O1 (at the 7

intersection of 8MR and 10MR) and T2-O2 (at the 10MR channel); on contrary, the T1-O4 site (at the 8MR cage) is significantly not favorable. This result shows that SMG, the important intermediate for carbonylation process, preferentially forms at insides the 10MR and 8MR channels, but seldom at

A

N

U

SC R

IP T

the 8MR cage of the zeolites.

M

Fig. 3. Correlation between ΔEmethanol with the r(OFER-CSMG) bond length.

The correlation between the ΔEmethanol with the r(OFER-CSMG) bond length is depicted in Fig. 3.

ED

Aside from the abnormally high ΔEmethanol of T1-O4, the ΔEmethanol for most T1 and T2 sites generally increases with the r(OFER-CSMG) bond length, i.e., the shorter the bond length, the more stable the

PT

SMG. However, for T3 and T4 sites, there is no clear correlation between the ΔEmethanol with the

CC E

r(OFER-CSMG) bond length.

3.2 Attack of CO, H2O, CH3OH and DME on the SMG The key step in the carbonylation process is the attack of CO molecule on SMG to form the acetyl intermediate, which readily reacts with methanol or DME to produce corresponding acetic

A

acid or methyl acetate[30, 31]. The process of CO attack on SMG has been recognized as the rate-determining step in the mechanism of methanol/DME carbonylation reaction[32]. In reaction conditions, however, the formed SMG are not only open to CO attack, but also are vulnerable to be attacked by other nucleophilic molecules like H2O, CH3OH, or DME[33]. In the latter cases, other

8

reaction pathways such than carbonylation are present, and ultimately yield different products (see Equation 1-4). [SiO(CH3 )Al] + CO→ [SiOAl] - + CH3CO+

(1)

[SiO(CH 3 )Al] + H2 O →[SiOAl] - + CH 3 OH2 +

(2)

[SiO(CH 3 )Al] + CH 3 OH →[SiOAl] - + (CH 3 ) 2 OH+

(3)

[SiO(CH3 )Al] + CH3 OCH3 →[SiOAl] - + (CH 3 )3 O+

(4)

IP T

For carbonylation pathway, a bond is formed between the CSMG with the CCO via a OFER-CSMG-CCO transition state; while for other possible reaction pathways, the bond emerges

SC R

between the CSMG with the O atom of the nucleophilic molecules via the OFER-CSMG-OM (M=H2O, CH3OH, DME) transition states, producing and CH3OH, DME and hydrocarbons as final product, respectively[16, 34]. It is noteworthy that the hydrocarbons, formed by reaction between SMG with

U

DME, that may undergo further reaction for coke formation and deactivates the catalyst[8].

H2O r(CSMG-CCO)

r(OFER-CSMG)

T1-O1

2.033

1.870

2.167

T1-O2

2.049

2.008

T1-O3

2.070

T1-O4

CH3OH

DME

r(OFER-CSMG)

r(CSMG-O)

r(OFER-CSMG)

r(CSMG-O)

1.856

2.0615

1.869

2.023

1.890

2.042

1.965

1.985

1.991

1.986

2.026

1.951

2.133

1.940

2.057

1.955

1.995

1.982

2.186

2.224

2.109

2.109

2.093

2.122

2.169

2.239

T2-O2

2.064

1.935

2.106

1.909

2.021

1.936

2.016

1.951

T2-O5

2.070

2.042

2.101

2.026

2.024

2.061

1.958

2.038

T2-O6a

2.059

2.070

1.910

2.064

1.954

2.053

1.953

2.072

T2-O6b

2.037

1.975

2.013

1.971

1.984

2.018

1.962

1.923

T3-O1

2.043

1.889

2.152

1.858

2.066

1.895

1.979

1.836

T3-O7

2.131

1.981

2.138

1.928

2.130

1.942

2.103

1.923

T3-O8

2.096

1.922

2.198

1.836

2.108

1.886

2.127

1.881

T4-O5

2.091

2.057

2.084

2.016

2.003

2.028

1.964

2.066

T4-O7

2.088

2.117

2.055

2.111

1.982

2.102

1.970

2.110

ED

PT

CC E

A

r(CSMG-O)

M

r(OFER-CSMG)

A

CO

Configuration

N

Table 3. Optimized values of the distances (Å) in the transition states for the attack of CO, H2O, CH3OH, and DME on different SMG of FER

Break down of original bond and the formation of new bond would concomitantly occur during the attack of nucleophilic molecules of CO, H2O, methanol and DME on SME[17, 35]. To further probe the effect of the attacking molecules on the SMG, the bonding angle and bonding length of the 9

OFER-CSMG-attacking molecules were systematically investigated. The result of the calculated angles of the possible OFER-CSMG-CCO and the OFER-CSMG-OM (M=H2O, CH3OH, DME) transition states shows that, generally for all types of attacking atoms, the angles of both OFER-CSMG-CCO and the OFER-CSMG-OM transition states are, in most cases, around 180o, which is an indication that these transition states have quasi-linear geometries (see Table S1). The lengths of r(OFER-CSMG) and r(CSMG-CCO/OM) bonds of the transition states from the attack of CO, H2O, CH3OH, and DME on

IP T

different FER model clusters were shown in Table 3. For most transition states, the r(OFER-CSMG) bond is longer than the r(CSMG-CCO) bond or r(CSMG-OM) bond. This result exhibits that in these

SC R

cases, SMG is closer to the attacking nucleophilic molecules than to the O atom of zeolite framework, suggesting at these sites the SMG are, to a large extent, activated by the attacking molecules, forming a strong bonding with CO or other nucleophilic molecules. Theoretical research by Boronat

U

on MOR zeolite also reveals that, the cationic CH3+ fragment is in general slightly closer to the

N

attacking molecules of CO, H2O and CH3OH than to the framework O atoms[8]. Nevertheless, in

A

present work 3 types of T sites, T1-O4, T2-O6a and T4-O7, have remarkably shorter r(OFER-CSMG) bond than r(CSMG-CCO) bond or r(CSMG-OM) bond. It is noteworthy that these three sites are all within

M

the 8MR channels (T1-O4 in the 8MR cage, while T2-O6a and T4-O7 at the 6MR zone of 8MR

A

CC E

PT

ED

channel).

10

Fig. 4. Calculated activation energies (kJ/mol) for the reactions of CO, H2O, CH3OH, and DME with SMG at different sites of FER zeolite.

To compare the pathway selectivity, the activation energies of the OFER-CSMG-CCO and the OFER-CSMG-OM transition states are calculated and shown in Fig. 4 and detailed values in Table S2. From Fig. 4, we can see that the activation energies of the attack of CO (for carbonylation), H2O, DME (for hydrocarbon formation, the side reaction) and CH3OH on SMG are highly dependent on

IP T

the sites. In FER zeolite CO always has remarkably higher activation energy than H 2O, DME and CH3OH at all Brønsted acid sites (except for T2-O5 sites), the activation energies of the attack of

SC R

H2O, CH3OH, and DME at SMG are 20-50 kJ/mol lower than CO attack; interestingly, Corma’s research[8] on methanol and DME carbonylation over MOR also reveals the generally higher activation energies of CO than of H2O, DME and CH3OH with the SMG (with only one exception of

U

T3-O33 sites). The generally higher activation energy of CO than of DME suggest the higher energy barrier of carbonylation than hydrocarbon formation.

N

Additionally, it can be seen that in FER the CO attack at SMG has considerably lower activation

A

energies at the T4-O7 site than at any other sites, which is followed by T2-O5, T4-O5 and T2-O6a

M

sites. It is noteworthy that, these three sites are all located in the 6MR zone of 8MR channel (see Table 1). Our work shows that the carbonylation reaction do not happen at random sites in 8MR

ED

channels, but rather selectively at T4-O7, T2-O5, T4-O5 and T2-O6a sites at the 6MR zone of 8MR channel, which indicates that the FER-catalyzed carbonylation process is thermodynamically favored

PT

at the 6MR zone of 8MR channel of the zeolite. Although there are also several other T sites located in the 8MR channel, activation energies of CO attack on SMG at these sites are significantly higher,

CC E

and some (for instance T3 sites) are even higher than that at the SMG in 10MR channels. The geometry of these transition states is depicted in Fig. 5. Our previous study on the adsorption behavior of DME and CO on FER zeolite reveals that CO and DME molecules are preferentially

A

located in the 6MR zone of 8MR channel[36]. The selective adsorption may contribute to the high carbonylation selectivity of FER in reaction conditions.

11

12

A ED

PT

CC E

IP T

SC R

U

N

A

M

Fig. 5. The [001] and [010] views of the optimized FER structures containing the transition state for the attack of CO on the methoxy group at T2-O5 site (a, b), T2-O6a site (c, d) , T4-O5 site (e, f) and T4-O7 site (g,h).

Also activation energy plot suggest that T4-O7, T2-O5, T4-O5 and T2-O6a sites are thermodynamically favored for carbonylation, further investigation precludes T2-O6a and T4-O5 sites as the candidate active sites for carbonylation. Although the T2-O6a has quite low CO activation energy, this site requires a very high energy for SMG formation, resulting in a quite high

IP T

total energy for CO Attack, so T2-O6a is not a good active site. Also, T4-O5 is also not a good choice because it is much more preferential to DME than to CO as compared to many other sites.

SC R

Generally, only T4-O7 and T2-O5 require total energy for CO activation less than 106 kJ/mol, making them suitable site for reaction to happen. 3.3 FER v.s. MOR in carbonylation pathway

U

Besides the generally high activation energy required for carbonylation in both MOR (140~180

N

kJ/mol)[8] and FER (80~170 kJ/mol), comparison between the activation plot of FER with MOR also reveals some difference: the SMG formation over MOR zeolite (0.8~35 kJ/mol) is significantly

A

more favored than over FER zeolite (8~90 kJ/mol), which probably explains the lower activity of

M

FER than MOR in carbonylation. In MOR, the activation energies for carbonylation at T3-O31 and T3-O33 sites are comparable or lower than the activation energies for hydrocarbon formation, which

ED

indicates that at these two sites the carbonylation reaction are advantageous over hydrocarbon formation. In comparison, in FER no sites have lower or even comparable activation energies for

PT

carbonylation compared with those for hydrocarbon formation, indicating that carbonylation over FER is not so energetically favored as that over MOR and may explain the experimentally lower

CC E

carbonylation selectivity of FER than that of MOR[30]. In spite of that, in FER two sites, T4-O7 and T2-O5, have remarkably lower activation energies for carbonylation than other sites, indicating that the carbonylation is more thermodynamically favored at these two sites. Generally, for FER the

A

reaction of CO with SMG, the rate-determined step in methanol and DME carbonylation, is faster in the 6MR zone (T4-O7 and T2-O5 sites) of the 8MR channel than in 10-MR channel or other sites. In MOR, except for the carbonylation-preferred sites of T3-O31 and T3-O33, the activation energies of water are always smaller than CO but larger than CH3OH and DME, however, in FER the activation energies of water seem to be highly dependent on the Brønsted acid sites, and no clear energies sequence of H2O, DME and CH3OH can be observed; particularly, at the 13

carbonylation-preferred sites of T2-O5, the activation energy for carbonylation is comparable with that for water attack. According to Iglesia[32], the water may adsorb competitively with CH3OH or DME at the CO-SMG intermediate and/or cause parallel methanol dehydration, thus decrease the carbonylation reaction rate. In MOR, the water attack is always more favorable than carbonylation or hydrocarbon formation regardless of the Brønsted acid sites, which may be the main reason of the slow CH3OH carbonylation rate over MOR; however, in FER the T2-O5 sites are carbonylation are

IP T

almost equally energetically favored, suggesting that the decreased reaction rate by the presence of water would be much less over FER than over MOR.

SC R

Besides the energetic concern, the different shapes of the 8MR channel openings may also influence the carbonylation selectivity[37-39]. The circle-shape 8MR opening of FER is not likely to sterically favor the formation of SMG-CO intermediate as the ellipse-shape of 8MR opening of

U

MOR does. However, the 10MR channel of FER can suppress the possible carbohydrate reaction and

N

subsequent coke formation more effectively than the 12MR of MOR zeolite, which results in the

A

longer catalyst life of FER[30, 40].

M

4. Conclusions

To sum up, we employed quantum-chemical method to explore the active sites that can

ED

selectively catalyze carbonylation methanol and dimethyl ether over aluminosilicate FER zeolites. The first finding is that the SMG preferentially forms in the 8MR and 10MR channels. Moreover,

PT

calculation results show that, carbonylation reaction occurs preferentially at the T4-O7 and T2-O5 sites at the 6MR zone of 8MR channel of FER zeolites. This result provides a theoretical perspective

CC E

for the experimentally observed higher carbonylation reactivity of methoxy groups located inside the 8MR channels.

A

Acknowledgement

We sincerely express our thanks to the supercomputer center of Virtual Laboratory of

Computational Chemistry, Computer Network Information Center, Chinese Academy of Science for the computational resources. This research was supported by DICP DMTO201601, the National Natural Science Foundation of China (Grant No. 21376235), the National Basic Research Program of China (Grant No. NKBRSF2013CB834604), and the Ministry of Science and Technology of 14

China (Grant 2017YFA0204800).

References [1] X. Li, X. Liu, S. Liu, S. Xie, X. Zhu, F. Chen, L. Xu, RSC Advances 3 (2013) 16549-16557. [2] V. Hosseinpour, M. Kazemeini, A. Mohammadrezaee, Applied Catalysis A: General 394 (2011) 166-175. [3] S. Yacob, B.A. Kilos, D.G. Barton, J.M. Notestein, Applied Catalysis A: General 520 (2016) 122-131. [4] F.E. Celik, T.-J. Kim, A.T. Bell, Journal of Catalysis 270 (2010) 185-195. [5] D.B. Rasmussen, J.M. Christensen, B. Temel, F. Studt, P.G. Moses, J. Rossmeisl, A. Riisager, A.D. Jensen, Angewandte

IP T

Chemie-International Edition 54 (2015) 7261-7264.

[6] H. Zhou, W. Zhu, L. Shi, H. Liu, S. Liu, S. Xu, Y. Ni, Y. Liu, L. Li, Z. Liu, Catalysis Science & Technology 5 (2015) 1961-1968.

SC R

[7] Z. Martinez-Ramirez, G.A. Flores-Escamilla, G.S. Berumen-España, S.A. Jimenez-Lam, B.E. Handy, M.G. Cardenas-Galindo, A.G. Sarmiento-Lopez, J.C. Fierro-Gonzalez, Applied Catalysis A: General 502 (2015) 254-261. [8] M. Boronat, C. Martinez-Sanchez, D. Law, A. Corma, Journal of the American Chemical Society 130 (2008) 16316-16323.

[9] M.V. Luzgin, M.S. Kazantsev, G.G. Volkova, W. Wang, A.G. Stepanov, Journal of Catalysis 277 (2011) 72-79.

U

[10] P. Cheung, A. Bhan, G.J. Sunley, E. Iglesia, Angewandte Chemie International Edition 45 (2006) 1617-1620. [11] T. De Baerdemaeker, B. Yilmaz, U. Müller, M. Feyen, F.-S. Xiao, W. Zhang, T. Tatsumi, H. Gies, X. Bao, D. De Vos,

N

Journal of Catalysis 308 (2013) 73-81.

A

[12] Z. Chen, B. Holmberg, W. Li, X. Wang, W. Deng, R. Munoz, Y. Yan, Chemistry of Materials 18 (2006) 5669-5675. [13] C. Chen, Q. Wu, F. Chen, L. Zhang, S. Pan, C. Bian, X. Zheng, X. Meng, F.-S. Xiao, Journal of Materials Chemistry A 3

M

(2015) 5556-5562.

[14] A. Corma, L.T. Nemeth, M. Renz, S. Valencia, Nature 412 (2001) 423-425. [15] A. Bhan, A.D. Allian, G.J. Sunley, D.J. Law, E. Iglesia, Journal of the American Chemical Society 129 (2007)

ED

4919-4924.

[16] M. Boronat, C. Martinez, A. Corma, Physical Chemistry Chemical Physics 13 (2011) 2603-2612. [17] T. Blasco, M. Boronat, P. Concepción, A. Corma, D. Law, J.A. Vidal-Moya, Angewandte Chemie International Edition

PT

46 (2007) 3938-3941.

[18] Y. Román-Leshkov, M. Moliner, M.E. Davis, The Journal of Physical Chemistry C 115 (2011) 1096-1102. [19] J. Dĕdeček, Z. Sobalík, B. Wichterlová, Catalysis Reviews: Science and Engineering 54 (2012) 135-223.

CC E

[20] http://asia.iza-structure.org/IZA-SC/framework.php?STC=FER. [21] Z. Zhao, W. Zhang, P. Ren, X. Han, U. Müller, B. Yilmaz, M. Feyen, H. Gies, F.S. Xiao, D.D. Vos, Chemistry of Materials 25 (2013) 840-847.

[22] K. Jíša, J. Nováková, M. Schwarze, A. Vondrová, S. Sklenák, Z. Sobalik, Journal of Catalysis 262 (2009) 27-34. [23] P. Feng, X.-F. Chen, X.-J. Li, D. Zhao, S.-J. Xie, L.-Y. Xu, G.-Z. He, Microporous and Mesoporous Materials 239 (2017)

A

354-362.

[24] S. Humbel, S. Sieber, K. Morokuma, The Journal of chemical physics 105 (1996) 1959-1967. [25] M. Svensson, S. Humbel, R.D.J. Froese, T. Matsubara, S. Sieber, K. Morokuma, The Journal of Physical Chemistry 100 (1996) 19357-19363. [26] M. J. Frisch, e. al.;, Gaussian 09, Revision D.01, Inc., Wallingford CT.

(2013).

[27] P.C. Hariharan, J.A. Pople, Theoretica Chimica Acta 28 (1973) 213-222. [28] A. Pinisakul, C. Kritayakornupong, V. Ruangpornvisuti, Journal of Molecular Modeling 14 (2008) 1035-1041. [29] E. Anders, R. Koch, P. Freunscht, J. Comput. Chem. 14 (1993) 1301-1312. 15

[30] D.B. Rasmussen, J.M. Christensen, B. Temel, F. Studt, P.G. Moses, J. Rossmeisl, A. Riisager, A.D. Jensen, Catalysis Science & Technology 7 (2017) 1141-1152. [31] T. He, P. Ren, X. Liu, S. Xu, X. Han, X. Bao, Chemical Communications 51 (2015) 16868-16870. [32] P. Cheung, A. Bhan, G. Sunley, D. Law, E. Iglesia, Journal of Catalysis 245 (2007) 110-123. [33] Y. Jiang, M. Hunger, W. Wang, Journal of the American Chemical Society 128 (2006) 11679-11692. [34] E. Catizzone, A. Aloise, M. Migliori, G. Giordano, Journal of Energy Chemistry 26 (2017) 406-415. [35] A.D. Chowdhury, K. Houben, G.T. Whiting, M. Mokhtar, A.M. Asiri, S.A. Al-Thabaiti, S.N. Basahel, M. Baldus, B.M. Weckhuysen, Angewandte Chemie International Edition 55 (2016) 15840-15845. [37] A.J. Jones, E. Iglesia, ACS Catalysis 5 (2015) 5741-5755.

IP T

[36] P. Feng, G. Zhang, K. Zang, X. Li, L. Xu, X. Chen, Chemical Physics Letters 684 (2017) 279-284. [38] Y. Chu, B. Han, A. Zheng, F. Deng, The Journal of Physical Chemistry C 116 (2012) 12687-12695. [39] A. Zheng, S. Li, S.-B. Liu, F. Deng, Accounts of Chemical Research 49 (2016) 655-663.

A

CC E

PT

ED

M

A

N

U

SC R

[40] J. Liu, H. Xue, X. Huang, Y. Li, W. Shen, Catal Lett 139 (2010) 33-37.

16