Highly Selective Catalytic Dechlorination of Dichloromethane to Chloromethane over Al?Ti Mixed Oxide Catalysts

The European Society Journal for Catalysis

Supported by

Accepted Article

Title: Highly Selective Catalytic Dechlorination of Dichloromethane to

Chloromethane over Al-Ti Mixed Oxide Catalysts

Authors: Wongeun Yoon, Seungjun Lee, Yuseong Noh, Seongmin

Park, Youngmin Kim, Hyung Ju Kim, Ho-Jeong Chae, and

Won Bae Kim

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: ChemCatChem 10.1002/cctc.202000879

Link to VoR: https://doi.org/10.1002/cctc.202000879

0

1/2020

ChemCatChem

10.1002/cctc.202000879

Highly Selective Catalytic Dechlorination of Dichloromethane

to Chloromethane over Al-Ti Mixed Oxide Catalysts

a

b

Wongeun Yoon, Seungjun Lee, Dr. Yuseong Noh, Seongmin Park, Dr. Youngmin Kim,

b

a

Dr. Hyung Ju Kim, Dr. Ho-Jeong Chae, and Prof. Dr. Won Bae Kim*

^aDepartment of Chemical Engineering, Pohang University of Science and Technology (POSTECH), 77

Cheongam-Ro, Nam-gu, Pohang, Gyeongbuk 37673, Republic of Korea

^bCarbon Resources Institute, Korea Research Institute of Chemical Technology (KRICT), 141 Gajeong-

ro, Yuseong-gu, Daejeon 34114, Republic of Korea

CORRESPONDING AUTHOR FOOTNOTE

Prof. Dr. Won Bae Kim

Tel.: +82-54-279-2397 / Fax: +82-54-279-5528

E-mail: kimwb@postech.ac.kr

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10.1002/cctc.202000879

ABSTRACT

In this paper, a series of Al-Ti mixed oxides with different Al/Ti ratios are prepared by a simple sol-

gel method and they are used as active catalysts for selective dechlorination of dichloromethane to

chloromethane. The Al-Ti mixed oxide catalyst with the same molar ratio of Al and Ti shows the highest

activity in dechlorination of dichloromethane. The strong and abundant Lewis acid sites in the Al-Ti

mixed oxides formed along with Al-O-Ti bondings are responsible for the high catalytic activity toward

the selective dechlorination reaction in this work. From a kinetic study, the activation energy of this

-

1

reaction over the optimum Al-Ti mixed oxide catalyst appears to be 59.4 kJ mol based on Langmuir-

Hinshelwood model. The improved catalytic performance suggests that the Al-Ti mixed oxide could be

used as the effective catalyst for the highly selective dechlorination of dichloromethane to chloromethane.

2

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1

. INTRODUCTION

Chloromethane (CH

3

Cl) has been regarded as a substitute for naphtha as a raw material for light

olefins^[¹^-⁵^]and used as methylating or chlorinating agent to produce methyl cellulose, silicones and rubber.

[

6,7]

This compound has often been synthesized from chlorination of methane as the following reaction

1).^[⁷^]

(

CH

4

3

2

+ Cl

2

→ CH

3

Cl + HCl

(1)

(2)

(3)

(4)

Cl + Cl

2

→ CH

2

Cl

2

3

+ HCl

Cl

2

+ Cl → CHCl

2

CHCl

3

+ Cl

2

→ CCl + HCl

4

However, by-products from several series reactions, which are multi-chlorinated methane compounds

such as dichloromethane (CH Cl ), chloroform (CHCl ), tetrachloromethane (CCl ), are generally

2

3

4

produced during the chlorination of methane (reactions (2)-(4)). These are also recognized as chlorinated

volatile organic compounds (CVOCs), which are very harmful to the environment and human body, thus

its exposure should be suppressed. The oxidative decomposition of CVOCs by reacting them with

dioxygen can convert CVOCs to harmless substances such as carbon dioxide, in which a number of

efficient catalysts have been studied for the catalytic oxidation of CVOCs, including zeolites,^[⁸^-¹⁰^]

perovskites,^[¹¹^-¹⁴^]noble metals^[¹⁵^-¹⁹^]and metal oxides.^[²⁰^-²⁹^]The complete oxidation of CVOCs to CO

2

would be efficient approach to solve the environmental problems of CVOCs, but another potential way

to convert the CVOCs into value-added intermediates could be considered. Selective partial

dechlorination of multi-chlorinated methane compounds to convert to a mono-chlorinated methane, i.e.,

chloromethane (CM), is desired since the CM can be used as extractant, refrigerant or chemical

intermediate for the production of value-added products. By converting the by-products formed through

the reactions (2)-(4) to CM, the overall efficiency of selective methane chlorination reaction to produce

CM could be increased, but the research for the selective conversion process of the multi-chlorinated

3

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10.1002/cctc.202000879

methanes to the CM has not received much attention yet. Among these by-products, dichloromethane

DCM) accounts for the largest proportion as the by-products formed from the typical methane

(

chlorination reaction, so the partial and selective dechlorination of DCM to CM can be a promising

strategy for improving the overall efficiency of the selective methane chlorination.^[³^]

Dechlorination of DCM follows a disproportionation reaction, in which two dichloromethane

molecules are simultaneously oxidized and reduced. During the selective catalytic dechlorination of DCM

in the presence of steam, the desired products of CM together with carbon monoxide and hydrochloric

acid are produced according to the reaction (5).^[¹⁹^]

2CH

2

Cl

2

+ H

2

O → CO + CH

3

Cl + 3HCl

(5)

O ^[

19]

and TiO

[30,31]

were reported to show catalytic activity

The conventional metal oxides such as Al

2

3

2

for this reaction since Lewis acidity is beneficial to the formation of intermediates^[²¹^]and the surface

hydroxyl groups in these metal oxides could react with DCM to produce CM.^[¹⁹^]However, low overall

efficiencies over the conventional Al

2

O

3

and TiO catalysts should be significantly improved to develop

2

a practical catalytic process for the selective dechlorination to chloromethane.

Mixed metal oxides have been widely used in various fields such as organic reaction, chemical

synthesis, petroleum industry and environmental chemistry, since the improved catalytic activity can be

expected through the acid-base and redox properties of mixed metal oxides.^[³²^]In this research, we have

developed highly efficient Al-Ti mixed oxides for the selective dechlorination of DCM to CM. The Al-

Ti mixed oxides with different Al contents were synthesized by a simple sol-gel method, and these oxide

catalysts were characterized by X-ray diffraction (XRD), temperature-programmed desorption (TPD), H

2

-

temperature-programmed reduction (H -TPR), Fourier-transform infrared spectroscopy (FT-IR),

2

thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near

edge structure (XANES) analyses to identify the active catalytic species and investigate the relationship

between the dechlorination activity of DCM to CM and the specific catalyst properties.

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2

. EXPERIMENTAL

.1. Catalysts preparation

Sol-gel method was used to synthesize a series of mixed oxides with different Al/Ti molar ratios

using the pre-calculated amounts of corresponding metal alkoxide precursors.^[³³^,³⁴^]Aluminum-tri-sec-

butoxide (97 %, Sigma Aldrich) and 3.1 mL of acetylacetone (≥ 99 %, Sigma Aldrich) were dissolved in

115 mL of 2-propanol (99.5 %, Sigma Aldrich) with vigorous stirring at room temperature for 30 min.

Then, titanium (IV) isopropoxide (97 %, Sigma Aldrich) was added to the solution containing aluminum

precursor under a continuous stirring for 30 min. Subsequently, 5 mL of 0.5 M nitric acid was added to

the solution. The resultant was aged at room temperature for 2 days. The Al-Ti mixed oxides were

obtained after calcination treatment at 600 °C for 5 h. Total moles of metals in the mixed oxides were

fixed to 0.127 mol. The Al-Ti mixed oxides were denoted as Al

ratio of Al/Ti.

m

Ti

n

x

O , where m/n represents the molar

2

.2. Catalysts characterization

The crystal structures of prepared catalysts were examined by XRD analysis (Ultima IV, Rigaku),

as scanned with an X-ray source of Cu-K radiation in the 2θ range of 10° to 80°. The Brunauer-Emmett-

Teller method was used to characterize the surface areas by using N adsorption-desorption at the liquid

2

nitrogen temperature (ASPS 2010 BET/Porosimeter, Micromeritics). The FT-IR (Nicolet iS50 FT-IR,

ThermoFisher) of pyridine adsorption was carried out to investigate the acid sites of catalyst with a diffuse

reflectance (DRIFT) cell. After pretreatment at 300 °C for 30 min, pyridine adsorption was carried out at

5

0 °C and FT-IR spectra were obtained at 100 °C. The FT-IR spectra of the Al-Ti mixed oxides were

normalized at the similar intensity. The acidity of mixed metal oxides was characterized by NH -TPD

BELCAT-II, MicrotracBEL). Prior to the measurement, the catalysts were pretreated at 300 °C for 30

min at He atmosphere. For the NH adsorption on the catalyst, the sample was exposed to NH gas at

00 °C for 1 h and purged for 1 h at 100 °C to remove physisorbed NH molecules in He atmosphere.

3

(

3

1

3

NH

3

desorbed from the catalyst was analyzed while raising the temperature from 100 °C to 700 °C at a

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10.1002/cctc.202000879

-

1

heating rate of 10 °C min . The reducibility of Al-Ti mixed oxides was characterized by H

2

-TPR

gas while raising the temperature from

00 °C to 900 °C at a heating rate of 5 °C min , and the amount of H consumed by the reduction of the

(

BELCAT-II, MicrotracBEL). The catalyst was reacted with H

2

-1

1

2

catalyst was monitored with a thermal conductivity detector (TCD). The coke content deposited in the

used catalysts was estimated by TGA (SDT Q600, TA instruments) in an O atmosphere while raising the

2

-1

temperature from 100 °C to 700 °C at a heating rate of 10 °C min . The XPS (K-ALPHA, ThermoFisher)

was carried out in order to obtain the information of oxidation states of the surface elements. The XANES

spectra of Ti K-edge were obtained on the Pohang Accelerator Laboratory (PLS-II).

2

.3. Catalytic activity tests and kinetic studies

To evaluate the catalytic dechlorination activity, the reaction tests were performed over a catalytic

fixed-bed flow reactor as schematized in Figure S1. To investigate possible effects of the mass transfer

limitation during the dechlorination of DCM, gas hourly space velocity (GHSV) was varied from 40,000

to 120,000 mL gcat h^-¹, while the other parameters kept constant such as the total flow rate of 100 mL

-1

min , concentrations of DCM and steam to 2,500 ppm and 2 %, respectively. In this study, the rates of

reaction were normalized by several specific quantities of catalysts such as weight, surface area, and

surface site. For the kinetic measurements, most experiments were carried out by controlling GHSV and

DCM concentration in order for the conversion to be small enough to satisfy a differential reactor

condition. In this condition, the mass-normalized reaction rates appeared to be invariant even with

changes of GHSV, as shown in Fig. S2. The reaction condition for the kinetic measurements of DCM

dechlorination over the Al-Ti mixed oxide catalysts, therefore, could be assumed to be essentially in the

kinetic regime that is free from the mass transfer resistances in this study. In the typical reaction condition,

the prepared catalyst was charged with an amount of 0.1 g into the fixed bed reactor. Water and DCM

were vaporized through two corresponding saturators and each gas was fed into the reactor after being

thoroughly mixed in a mixer by carrier gas of He. The feed composition was controlled with a gas mixture

of 2,500 ppm DCM and 2 % steam, and GHSV was fixed at 60,000 mL gcat h^-¹with a total flow of 100

-1

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10.1002/cctc.202000879

-1

mL min . To measure the catalytic activity, the reactor temperature was fixed at 80 °C for 1 h to reach

-1

the adsorption-desorption equilibrium and heated at a rate of 1 °C min . The dechlorination reaction was

carried out from 100 to 400 °C in an atmospheric pressure. To prevent corrosion of analysis equipment,

HCl formed in the products was removed using a water trap. The products were analyzed using an on-line

gas chromatography (GC, 5890B-5977B, Agilent) equipped with a flame ionization detector (FID). DCM

conversion and CM selectivity were calculated according to the following equations, where n represents

number of moles of the corresponding molecules. In the reaction (5), two DCM molecules are consumed

while one CM is produced. Due to the difference of stoichiometry coefficient between DCM and CM, the

maximum value of CM yield obtainable is 50 %. Considering the stoichiometry of the reaction in this

study, the obtained CM yield was multiplied by 2 folds.

^ꢀ^ꢁꢂꢃ,ꢄꢅ

ꢆꢀ_ꢁ_ꢂ_ꢃ_,_ꢇ_ꢈ_ꢉ

DCM conversion =

^ꢀ^ꢁꢂꢃ,ꢄꢅ

^ꢊ^ꢀꢂꢃ,ꢇꢈꢉ

CM yield =

^ꢀ^ꢁꢂꢃ,ꢄꢅ

The turnover frequency (TOF) values of dechlorination reaction of DCM were calculated according to

the following equation, where rCM represents rate of formation of CM per a gram of the catalyst, and Xacid

site is mole number of acid site per a gram of the catalyst.

^ꢋꢂꢃ

TOF =

^ꢌꢍꢎꢄꢏ ꢐꢄꢉꢑ

To obtain kinetic parameters for the dechlorination reaction over the prepared catalysts, the reaction

was conducted under different reaction temperatures of 280, 290, 300, 310 and 320 °C. The concentration

of DCM was varied between 2,500 to 10,000 ppm to examine the concentration effect on the kinetics.

The steam concentration was also controlled between 2.0 to 6.5 % with a balance gas of He for a total

flow rate of 100 mL min . The GHSV was set to 60,000 mL gcat h^-¹to establish the differential reactor

-

1

-1

condition which is used to determine the rate of reaction while taking advantage of being able to perform

7

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10.1002/cctc.202000879

kinetic studies based on the concentration of the products. The apparent activation energy was calculated

by using a power law model and Arrhenius equation according to the following equations.^[³⁵^]

ꢕ

ꢍ

ꢆ

ꢜ

ꢛ

ꢚ

ꢖꢗ

r_ꢒꢓ Aꢔ ꢘ ꢘ

ꢙ

,

where r

c

is the reaction rate, A is the pre-exponential term, E is the activation energy, R is the gas

a



constant, T is the reaction temperature, C

a

and C

b

are the concentrations of the reactant a and b,  and 

are the partial orders of reaction for a and b. Langmuir-Hinshelwood and Eley-Rideal kinetic models were

utilized for the kinetic parameters analysis in this study.

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3

. RESULTS AND DISCUSSION

.1. Characterization of Al-Ti mixed oxide catalysts

Chemical compositions, BET surface areas, and average pore sizes of the Al-Ti mixed oxides are

2

-1

summarized in Table 1. The surface area for the AlO without Ti was 332.0 m g which is slightly smaller

x

2

-1

2

-1

than that of Al

4

1

Ti O

x

(393.8 m g ), but larger than that of Al

1

Ti

1

O (278.5 m g ). As the Al/Ti was

x

2

-1

decreased to 0.25, the surface area of the Al-Ti oxide was substantially decreased to 84.1 m g . The

average pore sizes of Al-Ti mixed oxide appeared to show negligible differences between the samples,

showing in the range of 72-74 nm. The Ti/(Al+Ti) values in the surface of Al-Ti mixed oxides calculated

based on the XPS measurements seemed to be somehow different as compared with the nominal ratio of

Ti and Al that was used for the synthesis step. These results might be attributed to the formation of TiO

agglomerates,^[³⁶^]which can be confirmed by the following XRD results.

x

Table 1. Chemical composition, BET surface area and average pore size of the Al

m

Ti

n

x

O (m/n = molar

ratio of Al/Ti) catalysts.

BET

Average

_A_l_/_T_i_[a]

Ti/(Al+Ti) ^[^a^]Ti/(Al+Ti) ^[^b^]

surface area

pore size

Catalysts

2

-1

(

m g )

332.0

393.8

278.5

84.1

(nm)

AlO

x

-

0.00

0.20

0.50

0.80

1.00

0.00

0.15

0.42

0.64

1.00

71.1

73.2

Al

4

1

Ti

1

O

x

4.00

1.00

0.25

0.00

1

4

74.4

72.1

TiO

x

4.1

n.d. ^[^c^]

[a]

[b]

[c]

Theoretical values.

Estimated values by XPS analysis.

Not detected.

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Fig. 1 shows the XRD patterns for Al-Ti mixed oxides of Al

with the single metal oxides of AlO and TiO . The XRD patterns reveal that the AlO

and the TiO represents combined phase of both anatase and rutile TiO structures. The coexistence of

both TiO phases is probably due to the calcination temperature insufficient to completely change from

anatase to rutile phase. In the case of Al Ti mixed oxide, however, a single phase of the anatase

structure was evolved. The XRD patterns of Al Ti and Al Ti reveal negligible crystalline peaks,

indicating the amorphous phase. It can be expected that a strong interaction between the Ti and Al, which

4

Ti

1

O

x

, Al

1

Ti

1

O

x

and Al

1

Ti

4

O

x

together

x

has γ-Al

2

O

3

phase

x

2

1

4

O

x

4

1

O

x

1

O

x

could decrease the surface mobility of the TiO

2

domains and restrain the crystallization and growth of

crystal structure, is present in the Al-Ti mixed oxides at a high Al/Ti ratio.^[³⁴^]

Figure 1. XRD patterns of the Al

TiO2, □: γ-Al

m

Ti

n

x

O (m/n = molar ratio of Al/Ti) catalysts. ●: rutile TiO2, ▽: anatase

2

3

O .

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The type of acid site of Al-Ti mixed oxide catalysts was investigated by pyridine-FT-IR method (Fig.

-1

2

). Four peaks appeared in the wavenumber range of 1400 to 1700 cm in the Al-containing samples. The

-1

peaks around 1450 and 1600 cm correspond to strong Lewis acid sites, and the peak at 1575 cm to a

-1

[37]

weak Lewis acid site and 1492 cm to Brønsted and Lewis acid sites. Since all the peaks in the spectra

could represent the presences of the Lewis acid sites, it seems that the Lewis acid sites are dominant in

the Al-Ti mixed oxide catalysts prepared in this study.

Figure 2. Pyridine FT-IR spectra of the Al

m

Ti

n

x

O (m/n = molar ratio of Al/Ti) catalysts. SL: Strong Lewis

acid sites, WL: Weak Lewis acid sites, B: Brønsted acid sites.

To further investigate the acidity of the catalysts, NH

temperature and amount of desorbed NH are summarized in Table 2. Al-containing oxides of AlO

Al Ti , Al Ti , Al Ti revealed apparently broad NH desorption peak which could be

3

-TPD was performed (Fig. 3). The desorption

3

x

,

4

1

O

x

1

O

x

1

4

O

x

3

deconvoluted into at least two peaks: one at the low temperatures of 220-240 °C (peak 1) and the other at

the high temperatures of 320-340 °C (peak 2). The former peak 1 corresponds to a relatively weak Lewis

acid site and the latter peak 2 to a strong Lewis acid site, which are also observed in the previous pyridine

11

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10.1002/cctc.202000879

FT-IR results. As the content of Ti in the catalysts is increased, both the strong and weak Lewis acid sites

seem to shift to higher temperatures, except the TiO without containing Al, which showed no adsorption

and desorption of NH in the temperature range tested in this work. The shift of NH desorption peaks

could represent that the strength of both strong and weak Lewis acidity would be enhanced by addition of

Ti, and the Al Ti sample revealed the strongest acidic property among the prepared catalysts. The total

peak area, which could be associated with the amount of acid sites, is higher over Al-Ti mixed oxides

than AlO except Al Ti which exhibits a relatively low BET surface area. The RHL, which is the ratio

of NH desorption area at high temperature to low temperature, could give information on the relative

x

3

1

O

x

1

4

O

x

3

ratio of strong to weak acid sites in the samples. As the content of Ti species in the mixed oxide was

increased, the RHL appeared to be also increased. A relatively higher RHL value may be associated with

the interaction between Al and Ti species in the mixed oxides and strong acid sites are dependent on the

amount of Ti species. This correlation between the acidity and Ti content of Al-Ti mixed oxide catalysts

could be related to the charge imbalance caused by formation of Al-O-Ti bonds, from mixing of Al and

Ti with different coordination number.^[³⁸^]Based on the acidity of Al-Ti mixed oxide catalysts, density of

acid sites on the catalyst surface, which is amount of acid sites normalized to the BET surface area, can

be obtained and summarized in Table 2. The density of acid sites showed similar values for the AlO

Al Ti and the highest value was observed for the Al Ti catalyst.

x

and

4

1

O

x

1

4

O

x

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Figure 3. NH

3

-TPD patterns of the Al

m

Ti

n

x

O (m/n = molar ratio of Al/Ti) catalysts.

Table 2. NH

3

-TPD data for acidity distribution of the Al

m

Ti

n

O

x

(m/n = molar ratio of Al/Ti) catalysts.

Temperature of

desorption (°C)

Acidity distribution

Density of acid sites

-1

-2

(mol-NH

3

g

cat

)

(mol-NH

3

m )

Catalysts

[a]

Low

High

Total

Low

High

R

HL

Total Low

High

AlO

x

227

228

319

323

345

n.d.

472

577

516

171

n.d.

187

232

188

46

285

345

328

125

n.d.

1.53

1.48

1.74

2.69

n.d.

1.42 0.56

1.46 0.59

1.85 0.67

2.03 0.55

n.d. n.d.

0.86

0.87

1.18

1.48

n.d.

Al

4

1

Ti

1

O

x

1

4

236

235

TiO

x

n.d. ^[^b^]

n.d.

[

a]

b]

Ratio of NH

3

desorption area at high temperature to that of desorption area at low temperature.

[

Not detected.

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The chemical states of Al and Ti species on the surface of mixed oxides were investigated by XPS

Fig. 4 and Table 3). Fig. 4a and 4b show that the core level binding energies of Al 2p and Ti 2p appeared

(

to decrease to lower energies with the increase of Ti addition in the Al-Ti mixed oxides. This binding

energy decrease could be attributed to an interaction between Ti and Al elements with formation of

adsorbed oxygen species.^[³⁹^]In Fig. 5, the Al

Ti

O

represents the largest peak intensity in the H -TPR

1

x

2

profiles among the tested catalysts, indicating that most abundant formation of the adsorbed oxygen

occurs,^[⁴⁰^]which could also give rise to the lowest binding energies in the Al 2p and Ti 2p XPS spectra.

Both of XPS and H

maximize the interaction between Ti and Al species as compared with the other Al-Ti mixed oxides. Fig.

c shows the O 1s spectra of the samples. The single metal oxides of AlO and TiO revealed one broad

2

-TPR results imply that the Al

1

Ti

1

O sample with the same ratio of Al and Ti could

x

4

x

O 1s peak which could be deconvoluted into two peaks: one at the high binding energy and the other at

-

the low binding energy. The former peak corresponds to OH impurities and the latter peak to Al-O and

Ti-O. The XPS O 1s peak of Al-Ti mixed oxides could be also deconvoluted into two peaks: one at the

high binding energy corresponding to Al-O and the other at the low binding energy which corresponds to

Ti-O. Comparing the shift of peaks in the Al-Ti mixed oxides, Al-O showed the same trend as Al 2p, but

Ti-O showed different trend from the case with Ti 2p. The Al

1

Ti

1

O revealed the relatively increased

x

binding energy of Ti-O species, which is probably due to the effect of adsorbed O species on the mixed

oxide surface.^[⁴¹^]

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Figure 4. XPS spectra of the Al

m

Ti

n

O

x

(m/n = molar ratio of Al/Ti) catalysts over the regions of (a) Al

2p, (b) Ti 2p, and (c) O 1s.

15

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10.1002/cctc.202000879

Table 3. XPS binding energy values for the Al

m

Ti

n

x

O (m/n = molar ratio of Al/Ti) catalysts.

Binding energy, eV

Catalysts

Al 2p

Al-O

74.6

74.5

74.2

74.5

-

Ti 2p2/3

Ti-O

-

O 1s

Ti-O

-

Al-O

531.2

531.6

531.2

531.5

-

OH impurities

AlO

x

532.5

Al

4

1

Ti

1

O

x

458.8

458.7

458.9

530.4

530.2

529.9

530.1

-

1

4

-

TiO

x

532.0

Figure 5. H

2

-TPR profiles of the Al

m

Ti

n

x

O (m/n = molar ratio of Al/Ti) catalysts.

16

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The XANES analysis was used to identify and relatively quantify the Al-O-Ti bondings in the

samples (Fig. 6). For the pre-edge fitting of XANES, Ti K-edge XANES spectra of Al-Ti mixed oxide

were obtained together with TiO

2

as reference of Ti-O-Ti (TOT) bonding. TiO has octahedral Ti (IV)

2

coordination which is represented by three weak peaks in the pre-edge region, as an indication of TOT

bondings. While tetrahedral Ti (IV) is indicated by a single strong peak in the pre-edge region.^[⁴²^]In

Figure 6, some mixed oxides displayed apparently one strong peak over the samples with the least Ti

contents in the Al-Ti mixed oxide catalysts, implying that the tetrahedral coordination of Ti is

predominant in these mixed oxide samples. AlO

x

in a structure of Al

2

O

3

has both tetrahedrally and

octahedrally coordinated Al cations and vacancies.^[⁴³^]In the mixed oxides, tetrahedrally coordinated Ti is

expected to spread evenly across the tetrahedral sites of Al

Therefore, in this work, TiO and Al Ti samples were used as the references for the bonding states of

octahedral TOT and tetrahedral AOT, respectively. Al Ti is a mixed oxide with a minimum amount

2

O

3

to form Al-O-Ti (AOT) bondings.

2

6

1

O

x

6

1

O

x

of Ti content tested here, so it is assumed that AOT is predominant with least TOT. Linear combination

fittings for the pre-edge of XANES were carried out to estimate relative composition of Ti species in

forms of AOT and TOT in the samples, as demonstrated in Figure S3, and the results were summarized

in Table 4. The fraction of AOT appeared to monotonically decrease with increasing Ti content. However,

considering the relative amount of surface AOT that is normalized by amount of Ti on the surface of

catalysts, the Al

1

Ti

1

O sample shows the most abundant AOT bonding on the surface (9.82 %). The

x

formation of AOT could lead to a charge imbalance,^[⁴⁴^]which in turn affecting the acidity of the mixed

oxides.

17

ChemCatChem

10.1002/cctc.202000879

Figure 6. Ti K-edge XANES spectra of Al

m

Ti

n

x

O (m/n = molar ratio of Al/Ti) catalysts

Table 4. Weight ratio from pre-edge fitting in the Al

m

Ti

n

O

x

(m/n = molar ratio of Al/Ti) catalysts.

Surface atomic percent of Ti ^[^a^]

%)

Relative composition of Ti species

estimated by pre-edge fitting

(

Catalysts

AOT

TOT

AOT

TOT

Al

6

4

1

Ti

1

4

O

x

1.00

0.93

0.74

0.16

-

0.07

0.26

0.84

1.00

4.83

9.82

2.94

-

0.36

3.45

15.41

-

TiO

x

[a]

Normalized surface composition of Ti species by surface atomic ratio estimated by XPS analysis.

18

ChemCatChem

10.1002/cctc.202000879

3

.2. Selective dechlorination of DCM to CM

Catalytic activities of the prepared Al-Ti mixed oxide catalysts were evaluated for the selective

dechlorination reaction of DCM to CM over a typical continuous flow fixed-bed catalytic reactor (Fig.

S1). A differential reactor was used to determine the rate of reaction as a function of either concentration

or partial pressure of reactants, in which the reactor used a small amount of catalyst, thus mass and heat

transfer limitations could be avoided. These negligible resistances in the mass transfer were further

confirmed by separate experiments as demonstrated in Figure S2. To satisfy low DCM conversion in

-1

activity test, the GHSV and concentrations of DCM and H

and 2 %, respectively. The conversion of DCM was also maintained to be small under 10 % in most

experiments. The TiO showed negligible DCM conversion with least CM yield, suggesting that the

2

O were set to 60,000 mL gcat h^-¹, 2,500 ppm

x

catalytic activity could be attributed to the presence of Al species in the mixed oxides (Fig. S4). Arrhenius

plots of turnover frequencies for DCM dechlorination over the Al-Ti mixed oxide catalysts were displayed

with apparent activation energies in Figure 7a.

The Lewis acid sites are assumed to be the active sites of dechloriantion of DCM because Leiws acid

sites are consumed during the reaction,^[¹⁹^]and intermediates are formed on them.^[²¹^]The TOF of

dechlorination over Al-Ti mixed oxide catalysts was calculated as the formation rate of CM per acid site

as summarized in Table 5. By comparing with the TOF values under the mentioned reaction conditions,

-

4

-1

the order of the selective catalytic dechlorination reaction is as follow: Al

1

Ti

1

O

x

(1.63×10 sec )

(7.21×10 sec ). When Al-Ti mixed

oxides were used as catalysts, the dechlorination of DCM was significantly enhanced and the Al Ti

catalyst showed the best activity profile for formation of CM (Fig. 7a). The apparent activation energy

-4

-1

-5

-1

-5

-1

>

Al

1

Ti

4

O

x

(1.60×10 sec ) >AlO

x

(8.89×10 sec ) >Al

4

Ti

1

O

x

1

O

x

-1

obtained was 100.9, 115.6, 124.5 and 143.4 kJ mol for the Al

1

Ti O

x

, Al

1

4

Ti O

x

, AlO

x

, Al

4

Ti

1

x

O and

catalysts, respectively.

19

ChemCatChem

10.1002/cctc.202000879

Figure 7. (a) Arrhenius plots of turnover frequencies over the Al-Ti mixed oxide catalysts. Reaction

-

1

conditions: [CH

over the Al-Ti mixed oxide catalysts for the dechlorination of DCM: plots for (b) conversion of DCM; (c)

yield of CM as a function of reaction temperature. Reaction conditions: [CH Cl ] = 5,000 ppm, [H O] =

2

Cl

2

] = 2,500 ppm, [H

2

O] = 2 %, GHSV = 60,000 mL gcat h^-¹

.

Catalytic performance

2

%, GHSV = 10,000 mL gcat h^-¹

-

1

5

.

To obtain high DCM conversion and CM yield, catalyst activity tests were carried out under low

GHSV conditions. The feed composition was controlled to 5,000 ppm DCM and 5 % steam, and GHSV

-

1

-1

was fixed at 10,000 mL gcat h with a total flow of 100 mL min . The Al

1

Ti

1

x

O catalyst also showed the

20

ChemCatChem

10.1002/cctc.202000879

best activity profile for DCM conversion in this reaction condition as shown in Fig. 7b, reaching almost

00 % conversion with the highest yield at the significantly lower temperature. The yields of CM over

the synthesized catalysts were also plotted with respect to the reaction temperature as shown in Fig. 7c.

The AlO alone without Ti exhibited the relatively lower yield of CM than the Al-Ti mixed oxide catalysts

over the temperature range tested. The Al Ti catalyst exhibited the highest yield of CM among the

tested catalysts below the reaction temperature of 340 °C, reaching to ca. 85.3 %, which is at least two

times greater than that of AlO

The catalytic activity values are summarized in Table 5, in which the Al

most effective among the Al-Ti mixed oxide catalysts tested here. The Al

1

x

1

O

x

.

1

Ti

1

O

x

catalyst appears to be

catalyst exhibits the

1

Ti

1

O

x

highest specific rate and TOF value with a low apparent activation energy compared to the other catalysts

in the kinetic regime, and also shows the high CM yield under low GHSV conditions. By combining the

previous NH -TPD results and these dechlorination activity tests, it can be found that the stronger and

3

more Lewis acid sites, the greater the DCM conversion and CM yield were obtained under the reaction

conditions in this work. The presence of Lewis acid sites could facilitate the generation of methoxy species

which is an intermediate during the dechlorination reaction of DCM.^[²¹^]Therefore, the Al-Ti mixed oxide

catalysts, revealing the improved acidity by generation of AOT bonding, can provide high CM yield for

the dechlorination of DCM. The decreased yield of CH

3

Cl above 340 °C can be accompanied by the

decreased CH Cl selectivity. At high temperatures, hemiacetal and formate species, which are

3

intermediates of the dechlorination of dichloromethane, could be decomposed, leading to decrease of the

.^[²⁶^]

CH

3

Cl yield along with increased formations of CO and CO

2

The Al

1

Ti

4

O exhibits a high TOF, but it has relatively small acid sites from the small BET surface

x

area, resulted in a low CM yield at a low GHSV condition. The density of acid sites over Al-Ti mixed

oxide catalysts showed similar tendency with variation of TOF. In the proposed mechanism,^[²¹^]three

adjacent active sites participate in the dechlorination of dichloromethane. Therefore, it is expected that

not only the strength of the acid sites, but also the density of acid sites will have a significant effect on the

21

ChemCatChem

10.1002/cctc.202000879

activity of catalysts. Therefore the Al

1

Ti

1

O

x

catalyst with the strongest Lewis acid sites and highest

density of acid sites would be the most suitable catalyst in this reaction.

Table 5. Catalytic activity of the Al

Ti

m n

O

x

(m/n = molar ratio of Al/Ti) catalysts.

Rate ^[

a]

TOF

[b]

Activation energy

[c]

Catalysts

T

Y50

-1

(

molCM

g

cat sec )

(sec )

(kJ mol )

AlO

x

4.20×10^-⁸

4.16×10^-⁸

8.39×10^-⁸

2.73×10^-⁸

n.d. ^[^d^]

8.89×10^-⁵

7.21×10^-⁵

1.63×10^-⁴

1.60×10^-⁴

n.d.

124.5

115.6

100.9

143.4

n.d.

347

300

293

323

n.d.

Al

4

1

Ti

1

O

x

1

4

TiO

x

[a]

Normalized by mass of catalyst. Reaction conditions: DCM (2,500 ppm), H O (2 %), total flow rate

2

100 mL min ), GHSV (60,000 mL gcat h^-¹), Temperature (300 °C)

-

1

-1

(

[

b]

Normalized by the number of acid sites. Reaction conditions: DCM (2,500 ppm), H O (2 %), total

2

flow rate (100 mL min ), GHSV (60,000 mL gcat h^-¹), Temperature (300 °C)

-

1

-1

[c]

Temperature of 50 % yield of CM. Reaction conditions: DCM (5,000 ppm), H O (5 %), total flow

2

-1

-1 -1

rate (100 mL min ), GHSV (10,000 mL gcat h )

[

d]

Not detected.

Stability tests for the dechlorination of DCM on the Al

1

Ti

1

O

x

were performed at 340 °C and compared

Ti catalyst represents

with the well-known catalyst of AlO

x

(Fig. 8). The results showed that the Al

1

O

x

the relatively more stable conversion and yield profiles for the tested time. It is known that the deactivation

process during the dechlorination reaction could be involved with coke deposition and chlorination of

catalyst.^[¹⁸^]To examine the deactivation characteristics of catalysts, the XPS and TGA analyses were

further carried out. The atomic population on the catalysts surface and coke content comparison between

the fresh and used catalysts are summarized in Table S1. It was confirmed that the deposition of both

species of C and Cl occurred during the dechlorination of DCM, and when Al

1

Ti

1

x

O was used under the

22

ChemCatChem

10.1002/cctc.202000879

same reaction conditions, the amounts of deposited elements (C and Cl) on the catalyst surface were

relatively high. TGA analysis was performed on the used catalysts after the stability test (Fig. S5). The

coke contents in the used catalysts were 10.1 wt% and 8.1 wt% for Al

Normalized coke content, which is considered by the extent of total reacted amount of DCM during the

dechlorination reaction, however, showed that the Al Ti has the better tolerance against coke

deposition than that of AlO . It was shown that 9.1 mmol of coke was deposited on the AlO during 1

mole of DCM was reacted, while 5.8 mmol of coke was deposited on Al Ti at the same condition (See

Table S1). Therefore, it can be concluded that the Al Ti is the more effective and stable catalysts for

the dechlorination of DCM in this reaction condition.

1

Ti

1

O

x

and AlO

x

, respectively.

1

O

x

1

O

x

1

O

x

Figure 8. Stability test for the dechlorination of DCM over the catalysts: plots for (a) conversion of DCM;

b) yield of CM as a function of reaction time on stream.

(

23

ChemCatChem

10.1002/cctc.202000879

3

.3. Kinetics investigation of Al-Ti mixed oxide catalyst on DCM dechlorination

The kinetic parameters for the dechlorination reaction of DCM with the Al Ti

1

O

x

, which showed the

highest catalytic activity among the Al-Ti mixed metal oxide catalysts, have been investigated at various

concentrations of DCM and H O over different temperatures. Also in this experiment, the GHSV was set

2

to 60,000 mL gcat h^-¹to satisfy the required reaction conditions for a differential reactor. The

concentrations of DCM and steam were varied from 2,500 to 10,000 ppm and from 2.0 % to 6.5 %,

respectively, at five different temperatures of 280, 290, 300, 310, and 320 °C. Feed stream was balanced

-1

with He to be a total flow rate of 100 mL min .

Fig. 9 shows the effects of DCM and H O concentrations on the rate of reaction, which were obtained

at 300 °C with the catalysts of Al Ti and the AlO . The rate of reaction was increased with increasing

DCM concentration, while H O concentration revealed a negative effect on the reaction rate. Considering

2

1

O

x

2

the results, it is expected that the competitive adsorption of two molecules could take place on the catalyst

surface which is in a well agreement with the previous work.^[²³^]It was reported that H

2

O can be adsorbed

on catalyst surface dissociatively.^[¹⁸^]Based on the experimental results, a kinetic model was derived using

the Langmuir-Hinshelwood rate expressions with two assumptions that a rate determining step is surface

reaction and H O is adsorbed dissociatively. The rate equation of dechlorination could be first

2

hypothesized based on the assumed kinetic model as follows:

ꢤ

ꢡ

ꢞꢟ_ꢁ_ꢂ_ꢃ

ꢟ

ꢣ

ꢠ ꢢ ꢁꢂꢃ

ꢡ

ꢠ ꢢ

ꢡ

ꢝ ꢓ

ꢤ

ꢡ

ꢨ^ꢡ

ꢥꢦꢧꢟ_ꢁ

ꢣ

ꢧꢟ

ꢣ

ꢂꢃ ꢁꢂꢃ

ꢠ ꢢ

ꢡ

ꢠ ꢢ

ꢡ

ꢰ_ꢙ

ꢩ ꢓ ꢪ_ꢋ_ꢫ_ꢙ_ꢒ_ꢬ_ꢭ_ꢮ_ꢀexpꢥꢯ

ꢳ_ꢴ_ꢵ_ꢶꢓ ꢪ_ꢴ_ꢵ_ꢶexpꢥꢯ

ꢨ

ꢱꢲ

∆

^ꢷꢴ_ꢵ_ꢶ

ꢨ

ꢱꢲ

∆

ꢷ

ꢸ_ꢡꢹ

ꢳ_ꢸ_ꢡ_ꢹꢓ ꢪ expꢥꢯ

ꢨ

ꢸ ꢹ

ꢡ

ꢱꢲ

24

ChemCatChem

10.1002/cctc.202000879

ꢩ is reaction rate constant of dechlorination reaction of DCM when the surface reaction is a rate

determining step, ꢳ_ꢴ_ꢵ_ꢶand ꢳ are adsorption-desorption equilibrium constants of DCM and H O,

and

2

ꢸ ꢹ

ꢡ

respectively. ꢪ and ꢰ are pre-exponential factor and activation energy, respectively. ∆ꢷ

ꢙ

ꢴꢵꢶ

∆

ꢷ_ꢸ_ꢡ_ꢹare enthalpy changes of adsorption of DCM and H

2

O, respectively. ꢺ_ꢴ_ꢵ_ꢶand ꢺ

are partial

ꢸ ꢹ

ꢡ

pressures of DCM and H O, respectively. ꢳ_ꢴ_ꢵ_ꢶ, which is a relatively small value, was multiplied by rate

2

constant k to facilitate the calculation convergence and ꢩ ∙ ꢳ_ꢴ_ꢵ_ꢶwas expressed as ꢩ′. ꢰ ′, which is the

ꢙ

activation energy of ꢩ′, is strictly ꢰ ꢻ ∆ꢷ_ꢴ_ꢵ_ꢶ, however, ∆ꢷ_ꢴ_ꢵ_ꢶis also ignored and activation energy

ꢙ

of overall reaction is assumed to be ꢰ ′. In the denominator of rate expression, ꢳ

was ignored as a

ꢙ

ꢴꢵꢶ

lower value than ꢳ_ꢸ_ꢡ_ꢹ. Accordingly, the kinetic expressions can be simplified like:

ꢰ ′

ꢙ

ꢩ′ ꢓ ꢪ_ꢋ_ꢫ_ꢙ_ꢒ_ꢬ_ꢭ_ꢮ_ꢀꢪ_ꢴ_ꢵ_ꢶexpꢥꢯ

ꢨ

ꢱꢲ

ꢼ

ꢰ ꢓ ꢰ ꢻ ∆ꢷ

ꢙ

ꢴꢵꢶ

ꢤ

ꢡ

ꢞ^ꢽꢟ

ꢣ

ꢠ ꢢ ꢁꢂꢃ

ꢡ

ꢠ ꢢ

ꢡ

ꢝ ꢓ

ꢤ

ꢡ

ꢥꢦꢧꢟ

ꢣ

ꢨ^ꢡ

ꢠ ꢢ

ꢡ

ꢠ ꢢ

ꢡ

For an accurate regression convergence, the kinetic study of dechlorination of DCM was carried out at

80, 290, 310 and 320 °C (Fig. S6-S7). In the regression analysis for the kinetic parameter analysis, 80

experimental results were used for each catalyst of AlO and Al Ti . To support the validity for this

rate expression, a number of additional models that are plausible for the surface reaction mechanisms

were employed and tested for the dechlorination of DCM to CM over the Al Ti , as summarized in

Table S2. Models 1 and 2 are obtained from the Langmuir-Hinshelwood model but with a difference in

the adsorption step of H O, which assume dissociative and non-dissociative adsorption of H O,

2

x

1

O

x

1

O

x

2

respectively. The Eley-Rideal model is also used and simulated with two cases, in models 3 and 4. By

performing non-linear regression analysis, six rate expressions were resulted with positive values of

parameters, however, among them only two rate expressions showed reliably high correlation value (R²

>

0.95). One is Langmuir-Hinshelwood expression with assumptions that water adsorbs dissociatively on

25

ChemCatChem

10.1002/cctc.202000879

the catalyst and surface reaction is the rate determining step, and the other is also Langmuir-Hinshelwood

expression, but with assumptions that non-dissociative adsorption of H O occurs and adsorption of DCM

2

is the rate determining step. Since the dissociative adsorption of H

2

O is generally involved in this reaction

mechanism,^[¹⁸^]rate parameters obtained using the Langmuir-Hinshelwood expression under the condition

with dissociative adsorption of H

in this work. The rate parameters of this model with AlO

Table 6. Based on the ꢳ_ꢸ_ꢡ_ꢹ, the absolute value of heat of adsorption was 91.5 kJ mol for the AlO

2

O and surface reaction as the rate-determining step could be rationalized

x

and Al Ti were obtained as summarized in

1

O

x

-1

x

which

(80.0 kJ mol ). The higher absolute value of heat of adsorption, the greater the

energy released when the water molecule is adsorbed. Therefore, the AlO adsorbs H O more easily than

the Al Ti Ox. However, more importantly, the activation energy of ꢩ′ based on this reaction model over

the Al Ti

-1

is higher than Al

1

Ti

1

O

x

2

1

-1

1

O

x

catalyst was 59.4 kJ mol , which is significantly lower by at least 8 % than that of AlO

x

-1

(

64.4 kJ mol ), indicating that the developed Al-Ti mixed oxide is an effective catalyst on the selective

dechlorination reaction of DCM to CM.

26

ChemCatChem

10.1002/cctc.202000879

Figure 9. Reaction rate at various concentration of (a, c) H

2

O and (b, d) DCM with the Al

1

Ti

1

O

x

and AlO

x

catalysts at the reaction temperature of 300 °C.

Table 6. Kinetic parameters of AlO

x

and Al

1

Ti

1

O

x

catalysts calculated by Langmuir Hinshelwood model.

ꢩ^ꢼ

^ꢳꢸꢡꢹ

ꢰ_ꢙ

(kJ mol )

∆ꢷ_ꢸ_ꢡ_ꢹ

(kJ mol )

Catalysts

ꢤ

ꢡ

-2

-1

_m_b_a_rꢆ

(

mol m sec mbar )

(

)

7

745

11000

ꢲ

ꢆꢊ

ꢨ 6.81 ꢾ 10^ꢆ^ꢦ^ꢿexpꢥ

AlO

x

7.05 ꢾ 10 expꢥꢯ

ꢨ

64.4

-91.5

ꢲ

7

146

ꢲ

9619

ꢆꢊ

ꢆꣂ

Al

1

Ti O

x

4.00 ꢾ 10 exp ꣀꢯ

ꣁ

3.27 ꢾ 10 expꢥ

ꢨ

59.4

-80.0

ꢲ

27

ChemCatChem

10.1002/cctc.202000879

4

. CONCLUSIONS

Al-Ti mixed metal oxide catalysts were prepared by sol-gel method and followed by calcination at

600 °C, and they were used as active catalysts for the selective dechlorination of DCM to CM. The

Al

1

Ti

1

O catalyst exhibited the highly active dechlorination performance of DCM where the increased

x

strength and amount of Lewis acid sites that were generated on the Al-Ti mixed oxide surface are

responsible for the relatively high activity. A charge imbalance produced by formations of Al-O-Ti bonds

in the Al-Ti mixed oxide could lead to the increased amount and strength of Lewis acid sites. The mass-

normalized activity of dechlorination reaction was highest over the Al

1

Ti O

x

among the synthesized

catalysts in the kinetic regime. The apparent activation energy of dechlorination reaction over the

-1

-

Al

1

Ti

1

O

x

(59.4 kJ mol ) based on Langmuir-Hinshelwood model could be reduced by at least 5.0 kJ mol

1

-1

compared with the AlO

x

(64.4 kJ mol ). Therefore, the DCM dechlorination over the Al

1

Ti

1

x

O catalyst

could increase the efficiency of DCM dechlorination reaction with the highly improved catalytic activity.

ACKNOWLEDGEMENTS

This research was supported by C1 Gas Refinery Program through the National Research Foundation of

Korea (NRF) funded by the Ministry of Science and ICT (No. 2016M3D3A1A01913567) and also by

Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by

the Ministry of Science and ICT (NRF-2019R1A2C2088174).

28

ChemCatChem

10.1002/cctc.202000879

REFERENCES

[

1] G. Centi, K. Barbera, S, Perathoner, N. K. Gupta, E. E. Ember, J. A. Lercher, ChemCatChem 2015,

, 3036-3046.

7

[

2] Q. Liua, D. Wena, Y. Yanga, Z. Fei, Z. Zhanga, X. Chena, J. Tanga, M. Cuia, X. Qiao, Appl. Surf.

Sci. 2018, 435, 945-952.

[3] V. B. Rozanov, Y. A. Treger, Kinet. Catal. 2010, 51, 635-643.

[4] S. G. Podkolzin, E. E. Stangland, M. E. Jones, E. Peringer, J. A. Lercher, J. Am. Chem. Soc. 2007,

129, 2569-2576.

[5] R. Horn, R. Schlogl, Catal. Lett. 2015, 145, 23-29.

[6] S. A. Schmidt, N. Kumar, B. Zhang, K. Eranen, D. Y. Murzin, T. Salmi, Ind. Eng. Chem. Res. 2012,

5

1, 4545-4555.

7] Y. Kim, J. Kim, H. W. Kim, T.-W. Kim, H. J. Kim, H. Chang, M. B. Park, H.-J. Chae, ACS Catal.

019, 9, 9398-9410.

8] R. López-Fonseca, J. I. Gutiérrez-Ortiz, M. A. Gutiérrez-Ortiz, J. R. González-Velasco, J. Catal.

002, 209, 145-150.

[

2

[

9] M. H. Nilsen, S. Svelle, S. Aravinthan, U. Olsbye, Appl. Catal. A 2009, 367, 23-31.

10] R. López-Fonseca, A. Aranzabal, P. Steltenpohl, J.I. Gutiérrez-Ortiz, J.R. González-Velasco, Catal.

Today 2000, 62, 367-377.

[

11] J. Lou, C. Hung, B. Yang, J. Air Waste Manage. Assoc. 2004, 54, 727-740.

12] C. Zhang, C. Wang, W. Zhan, Y. Guo, Y. Guo, G. Lu, A. Baylet, A. Giroir-Fendler, Appl. Catal. B

[

2

013, 129, 509-516.

13] S.-X. Chen, Y. Wang, A.-P. Jia, H.-H. Liu, M.-F. Luo, J.-Q. Lu, Appl. Surf. Sci. 2014, 307, 178-

88.

14] C. Zhang, C. Wang, W. Hua, Y. Guo, G. Lu, S. Gil, A. Giroir-Fendler, Appl. Catal. B 2016, 186,

73-183.

[

1

15] X. Liu, L. Chena, T. Zhu, R. Ning, J. Hazard. Mater. 2019, 363, 90-98.

29

Article Doi

Highly Selective Catalytic Dechlorination of Dichloromethane to Chloromethane over Al?Ti Mixed Oxide Catalysts

DOI: 10.1002/cctc.202000879

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Article abstract of DOI:10.1002/cctc.202000879

Full text of DOI:10.1002/cctc.202000879

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