Highly efficient Mg(OH)Cl/SiO2 catalysts for selective dehydrochlorination of 1,1,2-trichloroethane

Article abstract of DOI:10.1016/j.apcata.2015.09.024

A series of Mg catalysts supported on SiO₂ were prepared by an incipient wetness impregnation method and tested for gas phase dehydrochlorination of 1,1,2-trichloroethane. It was found that these catalysts were very active and selective for the reaction. The catalytic performance depended on the Mg loading rather than the Mg precursors as the catalysts using Mg(NO₃)₂·6H₂O and MgCl₂·6H₂O as the precursors showed the similar performance. A catalyst containing 10 wt.% of Mg showed the best performance with a steady state TCE conversion of 92% and cis-dichloroethene selectivity of 91%. Moreover, characterizations of the catalysts revealed the formation of Cl-containing Mg species on the surface during the reaction. The analyses of the compositions of the stable catalysts under working conditions indicated a Cl/Mg ratio of 1, suggesting that Mg(OH)Cl could be the active sites for the reaction.

Full text of DOI:10.1016/j.apcata.2015.09.024

Applied Catalysis A: General 508 (2015) 10–15
Contents lists available at ScienceDirect
Applied Catalysis A: General
journal homepage: www.elsevier.com/locate/apcata
Highly efficient Mg(OH)Cl/SiO2 catalysts for selective
dehydrochlorination of 1,1,2-trichloroethane
Cen Tanga, Yanxia Jina, Jiqing Lua, Xiaonian Lib, Guanqun Xiea,b,∗, Mengfei Luoa,∗
a Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004,
PR China
b Industrial Catalysis Institute, Zhejiang University of Technology, Hangzhou 310014, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 7 July 2015
Received in revised form
18 September 2015
Accepted 19 September 2015
Available online 25 September 2015
A series of Mg catalysts supported on SiO2 were prepared by an incipient wetness impregnation method
and tested for gas phase dehydrochlorination of 1,1,2-trichloroethane. It was found that these catalysts
were very active and selective for the reaction. The catalytic performance depended on the Mg loading
rather than the Mg precursors as the catalysts using Mg(NO3)2·6H2O and MgCl2·6H2O as the precursors
showed the similar performance. A catalyst containing 10 wt.% of Mg showed the best performance with a
steady state TCE conversion of 92% and cis-dichloroethene selectivity of 91%. Moreover, characterizations
of the catalysts revealed the formation of Cl-containing Mg species on the surface during the reaction.
The analyses of the compositions of the stable catalysts under working conditions indicated a Cl/Mg ratio
of 1, suggesting that Mg(OH)Cl could be the active sites for the reaction.
Keywords:
Dehydrochlorination
1,1,2-Trichloroethane
cis-1,2-Dichloroethene
Mg(OH)Cl
© 2015 Elsevier B.V. All rights reserved.
Heterogeneous catalysis
1. Introduction
a conversion of 90% and a selectivity of 90% in the first pulse at
250 ◦C. Moreover, the hydroxyl groups on the silica surface were
Chlorinated hydrocarbons such as 1,1,2-trichloroethane (TCE)
have been widespread in the environment by extensive application
as degreasing agents [1]. However, the emission of these com-
pounds is detrimental to the environment, which causes acid rain,
ozone layer depletion and greenhouse effects [2–4]. Thus, the treat-
ment of chlorinated hydrocarbons becomes a very important issue.
One approach is the decomposition of these compounds, including
direct incineration [5], catalytic combustion [6,7], biodegradation
[8,9] and photo-catalytic decomposition [10,11]. Another approach
is the conversion of these compounds to other valuable chemicals,
including catalytic hydrodechlorination [12,13] and dehydrochlo-
rination [14].
The dehydrochlorination of TCE leads to three main products:
vinylidene chloride (VDC) [15], cis-1,2-dichloroethene (cis-DCE)
[16–19] and trans-1,2-dichloroethene (trans-DCE) [14]. The main
researches in the dehydrochlorination of TCE focus on the pro-
duction of VDC from TCE [20–22]. For example, the catalytic
dehydrochlorination of TCE into VDC was investigated over CsCl
catalysts supported on silica gels using a pulse technique [23], with
assumed to accelerate the elimination of hydrogen chloride.
However, there are few reports on the direct dehydrochlorina-
tion of TCE to cis-DCE. The wide applications of cis-DCE include
fungicides, anesthetics and frozen agents. Cis-DCE also could be
used as solvents for paint, resin, wax, rubber and acetate fibers.
The production of cis-DCE could be achieved through reductive
dechlorination of tetrachloroethene by a thermophilic anaerobic
enrichment culture [24], the photo initiated chlorination of C2H2 in
N2 [25], and aqueous-phase reductive dechlorination (hydrogenol-
ysis) of trichlorothylene [26]. Unfortunately, the resulting products
in these processes generally contain a mixture of both cis-DCE and
trans-DCE [25–28] and the selectivity to cis-DCE is quite low [26].
Therefore, highly efficient catalyst system for the synthesis of
cis-DCE is desirable. MgO supported on SiO2 are typically used as
Ziegler–Natta catalysts [29–31], which are the best candidates for
the low pressure production of linear low-density polyethylene
and ethylene co-polymers from the gas phase. In the current work,
Mg(OH)Cl/SiO2 catalysts were used for dehydrochlorination of TCE.
It is interesting that these catalysts are very active and selective for
the production of cis-DCE. Moreover, the possible active sites of the
catalysts have been investigated.
∗
Corresponding authors. Fax: +86 579 82282595.
E-mail addresses: gqxie@zjnu.edu.cn (G. Xie), mengfeiluo@zjnu.cn (M. Luo).
http://dx.doi.org/10.1016/j.apcata.2015.09.024
0926-860X/© 2015 Elsevier B.V. All rights reserved.

C. Tang et al. / Applied Catalysis A: General 508 (2015) 10–15
11
2. Experimental
Mg(NO3)2
MgO
2.1. Catalyst preparation
A series of Mg(N)/SiO2 catalysts with different Mg loadings
were prepared using an incipient wetness method. In a typical
preparation, the SiO2 support (SBET = 378.8 m2 g−1) was added to
an appropriate amount of aqueous solution of Mg(NO3)2·6H2O
(Aladdin, 99 %), and the mixture was sonicated for 30 min at room
temperature by a commercial ultrasonic cleaner (Branson, 1510R-
MT, 70 W, 42 kHz). Then the mixture was kept for 6 h at room
temperature. Finally, it was mildly evaporated at 90 ◦C to com-
pletely remove water, and then dried at 120 ◦C overnight. The
resulting solid was pretreated under a N2 flow (30 ml min−1) at dif-
ferent temperatures (300–500 ◦C) for 1.5 h. The obtained catalysts
were designated as xMg(N)/SiO2−y, with x and y refer to the weight
percent of Mg and pretreatment temperature, respectively. A refer-
ence catalyst 10Mg(Cl)/SiO2−300 with a precursor of MgCl2·6H2O
was also prepared in a similar manner.
20Mg(N)/SiO2-300
10Mg(N)/SiO2-300
6Mg(N)/SiO2-300
2Mg(N)/SiO2-300
1Mg(N)/SiO2-300
SiO2
10 20 30 40 50 60 70 80
2 Theta / o
2.2. Catalyst characterization
Fig. 1. XRD patterns of Mg(N)/SiO2 catalysts with different Mg loadings.
Actual contents of Mg and Cl in the catalysts were determined by
X-ray fluorescence (XRF) analysis, on a Shimadzu XRF-1800 spec-
trometer. The Qual-Quantitative analysis automatically executed a
quantitative analysis in the FP method after the qualitative analy-
sis of a sample of unknown composition. The X-ray generator was
operated at 40 kV and 70 mA, while the step angle and speed were
0.1◦ and 8◦ min−1, respectively.
equipped with a FID detector. The carbon balance was calculated
to be 5%.
3. Results and discussion
The BET surface areas of the catalysts were measured by N2
adsorption at liquid-nitrogen temperature (77 K), using a surface
area analyzer (Quantachrome Autosorb-1). The catalysts were pre-
treated at 120 ◦C for 6 h in vacuum.
Table 1 summarizes the physical properties of the Mg catalysts.
It is found that the actual content of Mg is very close to the cor-
responding nominal value, suggesting that there is no loss of Mg
in the preparation process. The surface area of the Mg catalyst
gradually declines with Mg loading. The 20Mg(N)/SiO2−300 cat-
alyst has the lowest surface area (32.7 m−2 g−1), probably due to
the blockage of internal pores of SiO2 by the Mg species. Fig. 1
presents the XRD patterns of the Mg catalysts with different Mg
loadings. Only one broad diffraction peak centered at about 2ꢀ of
22.3◦ could be observed for the catalyst with Mg content lower
than 10 wt.%, which is attributed to the amorphous SiO2 support.
No diffraction of Mg species could be detected, probably due to
the high dispersion of these species on the surface. When the Mg
loading is 20 wt.%, the diffraction peaks due to MgO (PDF 30-0794)
and Mg(NO3)2 (PDF 19-0765) emerge. The formation of MgO is a
result of the thermal decomposition of Mg(NO3)2 (2 Mg(NO3)2 → 2
MgO + 4 NO2 + O2). Thus, it could be concluded that the fresh cata-
lyst (N2-pretreated) contains MgO and Mg(NO3)2. This conclusion
is supported by TG-DTA curves of the un-pretreated 10Mg(N)/SiO2
catalyst (Fig. 2). The first major weight loss of the sample ranges
from 99 to 330 ◦C, and the DTA curve gives two characteristic
peaks at 133 and 264 ◦C, which are due to the gradual removal of
crystal water in Mg(NO3)2· 6H2O molecule [32]. Besides, the ther-
mal decomposition of Mg(NO3)2 starts from 330 ◦C and completes
at 483 ◦C to form MgO. The weight loss at these stages is about
55.4% of the total weight, which is consistent with the theoretical
value (54.5%,(2 Mg(NO3)2·6H2O → 2 MgO + 4 NO2 + O2 + 12H2O)). It
is worth noting that the thermal decomposition of Mg(NO3)2·6H2O
is not completed at low calcination temperatures (i.e. 300 ◦C), as
the XRD results reveal the presence of both MgO and Mg(NO3)2,
particularly at high Mg loadings (e.g. 20Mg(N)/SiO2). The influence
of Mg loadings on the catalytic performance is shown in Fig. 3.
It can be seen that the conversion of TCE first increases and then
decreases with the Mg loading, and the highest conversion (92%)
is obtained on the 10Mg(N)/SiO2−300 catalyst. Also, it seems that
there is an induction period for the TCE conversion, which gradu-
ally increases in the first 2 h reaction and gradually reaches a steady
X-ray diffraction (XRD) patterns were recorded with a PANalyt-
ical XꢀPert PRO MPD powder diffractometer using Cu K␣ radiation.
The working voltage was 40 kV and the working current was 40 mA.
The patterns were collected in a 2ꢀ range from 10 to 80◦, with a
scanning speed of 0.15◦ s−1
.
High-resolution transmission electron microscopy (HRTEM)
was performed on a JEM-2100F microscopy with a field emissive
gun, operated at 200 kV and with a point resolution of 0.24 nm.
Thermogravimetric analysis (TG-DTA) was conducted on a NET-
ZSCH STA 449C thermal graphic analyzer. N2 was used as the carrier
gas (30 ml min−1, atmospheric). The heating rate was 10 ◦C min−1
.
Fourier transform infrared (FTIR) spectra of the samples were
recorded on a NEXUS670 spectrometer equipped with a MCT detec-
tor in the range of 400–4000 cm−1 using KBr pellets. All obtained
spectra were auto-baseline corrected.
2.3. Activity test
Catalytic dehydrochlorination of TCE was carried out in a con-
ventional fixed-bed reactor (i.d. = 8 mm). 0.3 g of the catalyst was
diluted into a volume of 0.6 ml with a small amount of quartz
sand and loaded in the reactor. A thermalcouple was placed in
the middle of the catalyst bed to monitor the actual reaction
temperature. Before reaction, the catalyst was heated from room
temperature to desired temperature (300 - 500 ◦C) at a heating
rate of 5 ◦C min−1 in N2 (30 ml min−1) and kept for 90 min at the
desired temperature, and then was cooled to the reaction temper-
ature of 300 ◦C. The reactant flow was generated by flowing N2
through a bubbler containing liquid TCE (TCE content = 4.6 vol.%,
N2 flow rate = 30 ml min−1, GHSV = 1000 h−1). The reactant flow
was introduced to the catalyst bed consisting of the Mg catalysts.
The concentrations of TCE and other organic products during the
reaction were analyzed by an Agilent 6850 gas chromatograph

12
C. Tang et al. / Applied Catalysis A: General 508 (2015) 10–15
Table 1
Physical properties of the Mg catalysts.
Catalyst
Mgloading/% Mg/(Mg + SiO2)
Surface area/m2 g−1
Cl/Mg molar ratioa
Nominal
Actual
1Mg(N)/SiO2-300
2Mg(N)/SiO2-300
6Mg(N)/SiO2-300
10Mg(N)/SiO2-300
20Mg(N)/SiO2-300
10Mg(Cl)/SiO2-300
1.1
2.3
6.0
10.0
20.0
10.0
1.0
2.4
6.0
10.1
19.4
10.2
295.6
263.9
238.0
175.3
32.7
n.d.
0.9
0.9
1.1
n.d.
0.9
176.3
n.d.: not detected
a
: measured on the spent sample after 4 h reaction.
100
80
60
40
20
10Mg(N)/SiO2-300
10Mg(N)/SiO2-400
10Mg(N)/SiO2-450
10Mg(N)/SiO2-500
0
0
1
2
3
4
100
80
60
40
20
0
Fig. 2. TG–DTA curves of non-pretreated 10 Mg(N)/SiO2 catalyst.
100
b)
0
1
2
3
4
80
Reaction time / h
60
40
20
1Mg(N)/SiO2-300
2Mg(N)/SiO2-300
6Mg(N)/SiO2-300
10Mg(N)/SiO2-300
20Mg(N)/SiO2-300
Fig. 4. Effect of pretreatment temperature on the dehydrochlorination of TCE over
10Mg(N)/SiO2 catalysts. Reaction temperature = 300 ◦C.
state. Fig. 3b illustrates the selectivity of cis-DCE with different
Mg contents. In addition to the main product of cis-DCE, some by-
products such as VDC and trans-DCE are also detected. It is found
that the selectivity of cis-DCE first increases then decreases with
increasing Mg content, with the highest selectivity (91%) obtained
on the 10Mg(N)/SiO2−300 catalyst. As the Mg contents in the cata-
lysts are different, a comparison of specific reaction rates based on
Mg loading may reflect more relevant information of the reactiv-
0
0
1
2
3
4
100
a)
80
60
40
20
0
ity. The specific reaction rates are 2.6 × 10−5, 3.1 × 10−5, 2.3 × 10−5
,
1.7 × 10−5 and 7.2 × 10−6 molTCE gMg s−1 for the 1Mg(N)/SiO2-
300, 2Mg(N)/SiO2-300, 6Mg(N)/SiO2-300, 10Mg(N)/SiO2-300 and
20Mg(N)/SiO2-300 catalysts, respectively. It is noticed that the cal-
culated specific rates are close for the catalysts with Mg loadings
less than 10 wt.%, while for the 20Mg(N)/SiO2-300 catalyst the rate
is much lower. This is an implication that the Mg species may highly
dispersed at low Mg contents (e.g. less than 10 wt.%) but they might
aggregate at high Mg content (e.g. 20 wt.%) and the lesser activity
of 20 Mg(N)/SiO2-300 catalyst should also be due to the presence
of Mg(NO3)2 particles, which are consistent with the XRD results
(Fig. 1).
0
1
2
3
4
Reaction time / h
Fig. 3. Effect of Mg loadings on the dehydrochlorination of TCE over Mg(N)/SiO2-300
catalysts. Reaction temperature = 300 ◦C.
Fig.
4
demonstrates the effect of pretreatment tem-
perature on the performance of the Mg catalysts. It is

C. Tang et al. / Applied Catalysis A: General 508 (2015) 10–15
13
Fig. 5. TEM images of 10Mg(N)/SiO2 catalysts pretreated at different temperatures: (a) 400 ◦C (10Mg(N)/SiO2-400); (b) 500 ◦C (10Mg(N)/SiO2-500).
2.0
1.5
1.0
0.5
0.0
100
80
60
40
20
0
Conversion of TCE
selectivity to cis-DCE
0
1
2
3
4
5
6
7
8
0
2
4
6
8
10 12 14 16 18 20
Reaction time / h
Reaction time / h
Fig. 6. Stability of 10Mg(N)/SiO2-300 catalyst for the dehydrochlorination of TCE.
Fig. 7. Molar ratio of Cl/Mg of 10Mg(N)/SiO2-300 catalyst during the dehydrochlo-
Reaction temperature = 300 ◦C.
rination reaction. Reaction temperature = 300 ◦C.
revealed that the overall activities follow the order of
10Mg(N)/SiO2−300 > 10 Mg(N)/SiO2−400>10 Mg(N)/SiO2−450 >
10 Mg(N)/SiO2-500, which implies that high pretreatment tem-
perature is detrimental to the activity of the Mg catalysts. While
the selectivity to cis-DCE (about 85–90%) merely changes upon
the pretreatment temperature. Fig. 5 shows the TEM images of the
Mg samples. The 10Mg(N)/SiO2-400 catalyst shows no obvious
MgO particles (Fig. 5a), while the 10 Mg(N)/SiO2-500 sample
(Fig. 5b) shows distinct MgO entity by measuring the D-space
distance of the particle. Therefore, the decline of the activity on
the high-temperature pretreated sample (e.g. 10Mg(N)/SiO2-500)
is probably due to the aggregation of MgO particles during the
thermal treatment.
Furthermore, the stability of the Mg catalysts was also tested,
as shown in Fig. 6. The 10Mg(N)/SiO2-300 catalyst is quite sta-
ble during 18 h reaction, without obvious loss of activity during
the reaction process. Also, the Mg content in the spent catalyst is
9.5 wt.%, which indicates that there is no loss of Mg species during
the reaction.
the resulting products contain both main products of cis-DCE and
trans-DCE. Also, De Journett et al. [26] reported aqueous-phase
reductive dechlorination of trichloroethylene using a complicated
Ti(III) citrate mediated by 5,10,15,20-tetrakis-(4-carboxyphenyl)
porphyrin cobalt (II), in which the yield of cis-DCE was about 53%.
Therefore, the catalyst system employed in the current work has
several advantages such as simple preparation, high yield of cis-DCE
(83.7%).
It is worthwhile to explore the nature of the active sites on
the catalysts. Considering that HCl could be produced during the
reaction which would further react with Mg compounds to form
Cl-containing species such as MgCl2, it is possible that these Cl-
containing Mg species play an important role in the reaction.
Therefore, the contents of Cl in the different reaction stages were
measured by XRF, as shown in Fig. 7. The detection of the Cl contents
in different reaction stages were conducted by stopping the reac-
tion at desired reaction time and taking the catalyst out from the
reactor for the measurement. It is clear that the Cl content in the cat-
alyst gradually increases with reaction time. The Cl/Mg molar ratio
reaches a steady value (about 1.1) after 4 h reaction. This change
is consistent with the observed catalytic performance (Fig. 3), in
which an induction period was found in the first 3 h reaction for
The catalysts in the current work show superior performance
to those reported in literature. For example, Zhu and Yarwood
[25] reported photo initiated chlorination of C2H2 in N2, in which

14
C. Tang et al. / Applied Catalysis A: General 508 (2015) 10–15
100
80
10Mg(Cl)/SiO2-300
10Mg(N)/SiO2-300
60
40
20
0
0
1
2
3
4
5
100
80
60
40
20
0
10Mg(Cl)/SiO2-300
10Mg(N)/SiO2-300
Fig. 9. TG-DTA curves of pure MgCl2.6H2O.
Stage 1: from 25 to 115 ◦C
xMgCl2·6H2O + yMgCl2·4H2O → (x + y)MgCl2·4H2O + 2xH2O
0
1
2
3
4
5
(x + y) = 1
Reaction time / h
Stage 2: from 115 to 160 ◦C
Fig. 8. Effect of different precursors on the dehydrochlorination of TCE over
10Mg/SiO2-300 catalysts. Reaction temperature = 300 ◦C.
MgCl2·4H2O → MgCl2·2H2O + 2H2O
Stage 3: from 160 to 190 ◦C
MgCl2·2H2O → MgCl2·H2O + H2O
Stage 4: from 190 to 235 ◦C
the 10Mg(N)/SiO2-300 catalyst. This observation is a strong indica-
tion that the formed Cl-containing Mg species might be the active
sites of the reaction. Moreover, judging from the ratio of Cl and Mg
(about 1.1) in the spent catalyst, the possible formula of the Mg-Cl
species is Mg(OH)Cl.
MgCl2·H2O → aMgCl2·nH2O + bMg(OH)Cl + bHCl + (1–an-b)H2O
In addition, element analyses of spent catalysts with different
loadings also indicate that the Cl/Mg ratios are close to 1 (Table 1)
after steady state (about 4 h reaction), further implying the forma-
tion of Mg(OH)Cl.
According to the XRD and TG-DTA results (Figs. 1 and 2), the
fresh catalyst pretreated at low temperature contains both MgO
and Mg(NO3)2. Such Mg species could react with HCl in situ pro-
duced during the dehydrochlorination of TCE, and would further
form Cl-containing specie as Mg(OH)Cl according to the XRF results
(Fig. 7). The possible path of the Mg(OH)Cl formation would be as
follows:
4 < n < 1; a + b = 1
Stage 5: from 235 to 415 ◦C
Mg(OH)Cl → MgO + HCl
This above analysis suggests that the formation of Mg(OH)Cl
through the decomposition of MgCl2·6H2O could occur at
the temperature below 300 ◦C (stage 4). As the Mg catalyst
(10Mg(Cl)/SiO2-300) using MgCl2·6H2O as the precursor was pre-
treated and reacted at 300 ◦C in the dehydrochlorination of TCE, it
could be concluded that Mg(OH)Cl forms in this catalyst. In addi-
tion, the presence of such Mg(OH)Cl species is also evidenced by the
element analysis of the spent 10Mg(Cl)/SiO2-300 (Table 1), which
shows a Cl/Mg ratio of 0.93. Therefore, it could be concluded that the
active sites in the 10Mg(Cl)/SiO2-300 catalyst for the dehydrochlo-
rination of TCE are Mg(OH)Cl.
MgO + HCl → Mg(OH)Cl.
(1)
(2)
Mg(NO3)2·H2O + HCl → Mg(OH)Cl + 2HNO3.
To further investigate the nature of the active sites in the
10 Mg(N)/SiO2-300 catalyst, a reference catalyst (10Mg(Cl)/SiO2-
300) using MgCl2·6H2O as the precursor was also tested for this
reaction and the results are shown in Fig. 8. It is found that
the catalysts prepared using Mg(NO3)2·6H2O and MgCl2·6H2O as
the precursors almost show identical behaviors, except that the
10Mg(N)/SiO2-300 catalyst shows an induction period while the
10Mg(Cl)/SiO2-300 catalyst quickly reaches a steady state. These
results imply that the active sites in the two types of Mg catalysts
are the same regardless of the Mg precursors.
As the catalysts prepared using Mg(NO3)2·6H2O and
MgCl2·6H2O as the precursors almost show identical behav-
iors (Fig. 8), the active sites in 10Mg(N)/SiO2-300 catalyst and
10Mg(Cl)/SiO2-300 catalyst should be the same (e.g. Mg(OH)Cl),
which is formed through the reaction with HCl in situ produced
during the dehydrochlorination of TCE.
The surface features of the catalysts were investigated by
infrared spectroscopy, as shown in Fig. 10. For all the catalysts, a
broad band at 3420 cm−1, a sharp band at 1633 cm−1 and a broad
band at 1094 cm−1 are observed, which could be assigned to the
stretching vibration, bending vibration of the hydroxyl group and
To investigate the active sites on 10Mg(Cl)/SiO2-300 catalyst,
thermal decomposition of the pure MgCl2·6H2O was conducted, as
shown in Fig. 9. The decomposition of the MgCl2·6H2O involves five
stages as follows [33,34]:
asymmetric vibration of Si
O Si in the SiO2 support, respectively
[35]. For the fresh 10Mg(N)/SiO2-300 catalyst, a sharp band at
1378 cm−1 is observed, which is characteristic of MgO oxide [36].

C. Tang et al. / Applied Catalysis A: General 508 (2015) 10–15
15
element compositions of the spent catalysts revealed the forma-
tion of Cl-containing Mg species with a Cl/Mg molar ratio of about
1, implying that Mg(OH)Cl could be the active sites for the reaction.
Acknowledgments
10Mg(Cl)/SiO2-300
spent
This work is financially supported by National Natural Science
Foundation of China (Grant No. 21476207), and the open research
fund of top key discipline of chemistry in Zhejiang provincial col-
leges (Zhejiang Normal University Grant No. ZJHX201413).
10Mg(Cl)/SiO2-300
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The assignment of this band was confirmed by the observation
of the same band on a supported MgO/SiO2 sample, suggesting
the presence of MgO in the 10Mg(N)/SiO2-300 catalyst. After reac-
tion, the spectrum of the spent 10Mg(N)/SiO2-300 catalyst do not
change much compared to the fresh one, except for the disappear-
ance of the band at 1378 cm−1, implying the transformation of MgO
species during the reaction. Interestingly, the features of the spent
10Mg(N)/SiO2-300 are almost identical to those of the fresh and
spent 10Mg(Cl)/SiO2-300 catalysts, suggesting the same surface
species on these catalysts. Unfortunately, the direct detection of
the surface Mg(OH)Cl compound could not be reached because the
main band of Mg(OH)Cl located at 3500 cm−1 [37] is likely over-
lapped by the hydroxyl group of SiO2 in this region. Nevertheless,
since the presence of Mg(OH)Cl on the 10Mg(Cl)/SiO2-300 is readily
evidenced (Fig. 9), the same spectra of the spent 10Mg(N)/SiO2-300
and 10Mg(Cl)/SiO2-300 (either fresh and spent) lead to a reason-
able conclusion that Mg(OH)Cl species are also present on the spent
10Mg(N)/SiO2-300.
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4. Conclusions
In this work, gas phase dehydrochlorination of TCE to cis-
DCE was performed on Mg species supported on SiO2 using
Mg(NO3)2·6H2O as the precursor. It was found that these Mg cat-
alysts had excellent performance, with a TCE of conversion (92%)
and a cis-DCE selectivity of 91% obtained on the 10Mg(N)/SiO2-300
catalyst. This catalyst had the similar performance as the cata-
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these two catalysts had same active sites. Further analyses of the
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