Effects of yttrium-doping on the performance of Cr2O3 catalysts for vapor phase fluorination of 1,1,2,3-tetrachloropropene

Article abstract of DOI:10.1016/j.jfluchem.2014.07.030

The synthesis of 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) from 1,1,2,3-tetrachloropropene was performed over a series of Y₂O ₃-Cr₂O₃(F) catalysts and the effect of yttrium-doping on the performance of Cr₂O₃ catalysts was investigated. Various characterization results showed that the addition of yttrium in the Cr₂O₃ led to the formation of high valent Cr species in the samples, which could be consequently converted to catalytically active CrO_xF_y species during the pre-fluorination process. Although the Cr₂O₃ catalyst with or without yttrium-doping showed very high 1,1,2,3-tetrachloropropene conversion in long term reaction, the addition of yttrium in the Cr ₂O₃ helped to maintain the high selectivity to HCFC-1233xf, with the highest selectivity (97%) obtained on a 1 mol% yttrium-doped Cr₂O₃ after 100 h reaction. X-ray photon spectroscopy results on the spent Cr₂O₃(F) and 1Y ₂O₃-Cr₂O₃(F) catalysts indicated that the content of the active CrO_xF_y species declined after 70 h reaction, which was responsible for the loss of selectivity (from 97% to 88%), while it remained almost unchanged on the spent 1Y₂O ₃-Cr₂O₃(F) catalyst.

Full text of DOI:10.1016/j.jfluchem.2014.07.030

Journal of Fluorine Chemistry 166 (2014) 78–83
Contents lists available at ScienceDirect
Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Effects of yttrium-doping on the performance of Cr2O3 catalysts for
vapor phase fluorination of 1,1,2,3-tetrachloropropene
Fang Wang, Jing-Lian Fan, Yang Zhao, Wen-Xia Zhang, Yan Liang, Ji-Qing Lu,
*
Meng-Fei Luo, Yue-Juan Wang
Key Laboratory of the Ministry of Education for Advanced Catalysis Materials, Institute of Physical Chemistry, Zhejiang Normal University, Jinhua 321004, China
A R T I C L E I N F O
A B S T R A C T
Article history:
The synthesis of 2-chloro-3,3,3-trifluoropropene (HCFC-1233xf) from 1,1,2,3-tetrachloropropene was
performed over a series of Y2O3-Cr2O3(F) catalysts and the effect of yttrium-doping on the performance
of Cr2O3 catalysts was investigated. Various characterization results showed that the addition of yttrium
in the Cr2O3 led to the formation of high valent Cr species in the samples, which could be consequently
converted to catalytically active CrOxFy species during the pre-fluorination process. Although the Cr2O3
catalyst with or without yttrium-doping showed very high 1,1,2,3-tetrachloropropene conversion in
long term reaction, the addition of yttrium in the Cr2O3 helped to maintain the high selectivity to HCFC-
1233xf, with the highest selectivity (97%) obtained on a 1 mol% yttrium-doped Cr2O3 after 100 h
reaction. X-ray photon spectroscopy results on the spent Cr2O3(F) and 1Y2O3-Cr2O3(F) catalysts indicated
that the content of the active CrOxFy species declined after 70 h reaction, which was responsible for the
loss of selectivity (from 97% to 88%), while it remained almost unchanged on the spent 1Y2O3-Cr2O3(F)
catalyst.
Received 6 June 2014
Received in revised form 9 July 2014
Accepted 31 July 2014
Available online 7 August 2014
Keywords:
Y2O3-Cr2O3(F)
Fluorination
1,1,2,3-Tetrachloropropene
2-Chloro-3,3,3-trifluoropropene
CrOxFy
ß 2014 Elsevier B.V. All rights reserved.
1. Introduction
As HCFC-1233xf can be used as raw material or intermediate to
synthesize HFC-1234yf, the synthesis of HCFC-1233xf plays an
2,3,3,3-Tetrafluoropropene (HFC-1234yf) is considered as a
promising candidate for the replacement of 1,1,1,2-tetrafluor-
oethane (HFC-134a) and maybe become the new generation of
refrigerant [1–3], due to its excellent environment parameters
(GWP = 4, ODP = 0). It can also be used in heat transfer medium,
polymerization media, foaming agents, blowing agents, buffing
abrasive agents, displacement drying agents, gaseous dielectrics,
sterilant carriers, particulate removal fluids, and power cycle
working fluids [4,5].
One of the effective routes to synthesize HFC-1234yf is as
follows, 1,1,2,3-tetrachloropropene is fluorinated to synthesis
HFC-1234yf via intermediate 2-chloro-3,3,3-trifluoropropene
(HCFC-1233xf) [6,7].
extremely important role.
Cr-based catalysts have been widely applied in vapor phase
fluorination reaction. Extensive investigations were carried out
and some general concepts have been recognized. One is the
importance of the presence of high valent Cr species (such as Cr (VI)
and Cr (V)). Cho et al. [8] found that amorphous Cr (VI) with higher
dispersion was more advantage for fluorination reaction than the
crystalline Cr2O3. Brunet et al. [9] investigated that the effects of
activation temperature and activation atmosphere (N2, H2 or air) of
Cr2O3 catalyst on the synthesis of 1,1,1,2-tetrafluoroethane (HFC-
134a) from 2-chloro-1,1,1-trifluoroethane (HCFC-133a). They
concluded that Cr species of reversible oxidation state are the
active sites of reaction. Another key issue is the catalytically active
sites in the Cr-based catalysts. It has been recognized that CrOxFy
species formed during the pre-fluorination or reaction process play
an essential role in the reaction. Adamczyk et al. [10] compared the
fluorination of HCFC-133a and dismutation of dichlorodifluoro-
methane (CFC-12) over CrOxFy, CrF3 and Cr2O3 catalysts and found
that the CrOxFy catalyst showed the highest activity. Also, Chung et
al. [11] found that a CrF3ꢀ4H2O catalyst after calcination contained
more CrOxFy species compared to the uncalcined one, which
resulted in the relatively easier formation of labile fluorine on the
HF
HF
CCl2¼CClCH2Cl!CF3CCl¼CH2C!at:CF3CF¼CH2
Cat:
*
Corresponding author. Tel.: +86 0579 82282954; fax: +86 0579 82282595.
E-mail address: znuwyj@zjnu.cn (Y.-J. Wang).
http://dx.doi.org/10.1016/j.jfluchem.2014.07.030
0022-1139/ß 2014 Elsevier B.V. All rights reserved.

F. Wang et al. / Journal of Fluorine Chemistry 166 (2014) 78–83
79
catalyst surface via the interaction between the antibonding
orbitals of HF with the valence band of CrOxFy species. Their X-ray
photon spectroscopy results also showed that the catalyst with
different valent Cr species made density of states near the Fermi
level increase in the catalyst. The presence of such CrOxFy species
in the Cr-based catalysts is also important for the selectivity to the
desired products. Cheng et al. [12] prepared a series of Cr-based
catalysts for the fluorination of perchloroethylene (PCE) to
synthesize 2,2-dichloro-1,1,1-trifluoroethane (HCFC-123), 1-
chloro-1,2,2,2-tetrafluoroethane (HCFC-124) and pentafluor-
oethane (HFC-125). They found that the enhanced selectivities
to HCFC-123, HCFC-124 and HFC-125 are due to the formation of
CrOxFy species generated during the pre-fluorination. It should be
noted that the generation of the active CrOxFy species could be
approached by the addition of other metals in the Cr-based
catalysts. For example, Lee et al. [13] found that MgF2/Cr2O3
catalyst was more active than Cr2O3 catalyst for the synthesis of
HFC-134a from HCFC-133a, which is related to MgCrOxFy species
generated through the reaction of CrF3 and MgF2.
Fig. 2. Raman spectra of (a) fresh Y2O3-Cr2O3, (b) pre-fluorinated Y2O3-Cr2O3 and (c)
spent Y2O3-Cr2O3 catalysts. Top to bottom (A–D): 10Y2O3-Cr2O3, 5Y2O3-Cr2O3,
1Y2O3-Cr2O3, and Cr2O3.
It can be seen that the active CrOxFy species are extremely
important for the fluorination reaction over the Cr-based catalysts.
Thus, the generation of such CrOxFy species becomes the focus of
future research. In this paper, a series of Y2O3-Cr2O3(F) catalysts
were prepared and tested for vapor phase fluorination of 1,1,2,3-
tetrachloropropene. The effect of yttrium-doping on the catalyst
properties and the catalytic behaviors was also studied.
atmosphere. This observation is consistent with the results
reported in literatures [10,14]. In contrast, Y2O3 could be easily
fluorinated to YF3 [15]. However, no distinct diffraction peaks of
YF3 in Y2O3-Cr2O3(F) catalysts could be observed, probably due to
the fact that the formed YF3 is in very low content or highly
dispersed.
2. Results and discussion
Fig. 2 shows Raman spectra of the fresh Y2O3-Cr2O3 and pre-
fluorinated Y2O3-Cr2O3 catalysts. For the as-prepared Y2O3-Cr2O3
catalysts (Fig. 2a), four Raman bands at 303, 350, 553 and
613 cmꢁ1 are observed, all these Raman bands are attributed to
Cr2O3 species [16]. Besides, two weak Raman bands at 862 cmꢁ1
and 1000 cmꢁ1 are assigned to Cr2O5 [17,18] and CrO3 [19–21],
respectively. For the pre-fluorinated Y2O3-Cr2O3 catalysts (Fig. 2b),
four Raman bands at 303, 350, 553 and 613 cmꢁ1 are also observed.
But two weak Raman bands at 862 cmꢁ1 and 1000 cmꢁ1
corresponding to Cr2O5 and CrO3 species disappear, indicating
that these high valent Cr species could be easily fluorinated [22].
Note that species such as Cr2O5 and CrO3 are not detected in the
XRD patterns, implying that the contents of such species in the
catalyst might be too low to be detected, while Raman
spectroscopy has much higher sensitivity for these species.
Table 1 lists the relative molar contents of chromium, yttrium
and fluorine elements in Y2O3-Cr2O3(F) catalysts measured by XRF.
From Table 1, it can be seen that the contents of yttrium and
2.1. Phase analysis of catalysts
The surface areas of the pre-fluorinated catalysts are essentially
the same (42–30 m2 gꢁ1), and the surface area slightly decreases
with increasing Y2O3 content in the catalyst.
Fig. 1 shows the XRD patterns of the Y2O3-Cr2O3 and the Y2O3-
Cr2O3(F) catalysts. As shown in Fig. 1a, diffraction peaks due to
crystalline Cr2O3 are clearly observed in all the Y2O3-Cr2O3
catalysts. However, no diffraction peak related to yttrium species
(such as: Y2O3, YCrO4, YCrO3) could be detected, suggesting the
yttrium species might be highly dispersed. Also, with increasing
yttrium content in the catalyst, the diffraction peaks of Cr2O3
become more intense, indicating that the addition of yttrium
promotes the growth of Cr2O3 crystallites. After pre-fluorination,
no obvious changes are found for the Y2O3-Cr2O3(F) catalysts
(Fig. 1b) compared with the Y2O3-Cr2O3 catalysts, which implies
that crystalline Cr2O3 is difficult to be fluorinated in HF
Fig. 1. XRD patterns of (a) Y2O3-Cr2O3 and (b) Y2O3-Cr2O3(F) catalysts.

80
F. Wang et al. / Journal of Fluorine Chemistry 166 (2014) 78–83
Table 1
Relative molar contents of chromium, yttrium and fluorine elements in the Y2O3-
Cr2O3(F) catalysts.
Catalyst
Relative molar content (mol%)
D
Fa (mol%)
Cr
Y
F
Cr2O3(F)
94.2
92.0
75.4
61.8
–
5.8
7.3
5.8
5.2
1Y2O3-Cr2O3(F)
5Y2O3-Cr2O3(F)
10Y2O3-Cr2O3(F)
0.7
4.0
6.7
17.6
31.5
5.6
11.4
a
DF = F ꢁ 3Y.
fluorine elements increase with increasing yttrium-doping con-
tent, which is because of the fact that yttrium element is easily
fluorinated to produce YF3. Furthermore, assuming that all the
yttrium elements exist in the form of YF3 after pre-fluorination, the
rest of fluorine elements (
as CrF3 or CrOxFy [23]. By calculation, the contents of rest fluorine
F) are 5.8, 5.2, 5.6 and 11.4 mol% in the Cr2O3(F), 1Y2O3-Cr2O3(F),
DF) should be related to Cr species such
(
D
5Y2O3-Cr2O3(F) and 10Y2O3-Cr2O3(F) catalysts, respectively. These
values suggest that the high valent Cr species in the catalysts are
about 5 mol% (except format 10Y2O3-Cr2O3(F)), and such a low
content of Cr species might not be detected by XRD (Fig. 1). In
addition, these essentially constant values also reflect the fact that
the yttrium-doping hardly changes the high valent Cr species in the
catalysts.
Fig. 4. Cr 2p XPS spectra of Y2O3-Cr2O3(F) catalysts.
of Y2O3-Cr2O3 catalysts. The average valences of Cr are 3.07, 3.08,
3.11 and 3.15 in the Cr2O3, 1Y2O3-Cr2O3, 5Y2O3-Cr2O3 and 10Y2O3-
Cr2O3 catalysts, respectively. This slightly higher average valences
of Cr (3.07–3.15) compared to the nominal value (3 in Cr2O3)
clearly indicate the presence of high valent Cr species (e.g. Cr (V) or
Cr (VI)), which is consistent with the Raman results (Fig. 2). As
these high valent Cr species are easily fluorinated to CrF3 or CrOxFy
2.2. Valence of Cr in Y2O3-Cr2O3 catalysts
Fig. 3 shows the H2-TPR profiles of the Y2O3-Cr2O3 catalysts. For
the Cr2O3 catalyst, only one reduction peak at 295 8C is observed.
Considering that crystalline Cr2O3 is not reduced below 800 8C in
H2 atmosphere, the reduction peak of the catalyst is probably
attributed to the reducible CrOx (x > 1.5) species [12,24,25]. For the
Y2O3-Cr2O3 catalysts, the reduction peaks at 295 8C are also
attributed to the easily reducible CrOx (x > 1.5). With increasing
yttrium-doping content in the catalyst, the reduction peak
gradually shifts to high temperature but the peak area increases.
The calculated H2 consumptions of Cr2O3, 1Y2O3-Cr2O3, 5Y2O3-
Cr2O3 and 10Y2O3-Cr2O3 catalysts are 0.26, 0.28, 0.39 and
0.50 mmol gꢁ1, respectively. Considering that Y2O3 cannot be
reduced under the experimental condition, the average valence of
Cr is calculated according to the amount of hydrogen consumption
[10,24,26], the content of fluorine element related to Cr (
gradually increases in Y2O3-Cr2O3 (F) catalysts.
DF)
2.3. XPS analysis
Fig. 4 shows the XPS spectra of the Cr 2p level for Y2O3-Cr2O3(F)
catalysts. The broad peak of Cr 2p3/2 could be deconvoluted to three
peaks. The peak with binding energy of 578.8 eV is assigned to
CrOxFy [27], the other peaks are consistent with published XPS
spectra for oxides or the hydroxide of Cr (III) [28–31]. The
hydroxide of Cr (III) could be that Cr (III) oxides reacts with
hydroxyl or water because the spent samples were exposed in air
before the XPS test [31]. These results indicate that surface Cr
species in Y2O3-Cr2O3(F) catalysts are a mixture of Cr2O3, Cr(OH)3
and CrOxFy. The surface CrOxFy content is calculated by the peak
area of CrOxFy divided by the total peak area of Cr species. The
calculated values are 41.5, 44.0, 46.8 and 51.5% for the Cr2O3(F),
1Y2O3-Cr2O3(F), 5Y2O3-Cr2O3(F) and 10Y2O3-Cr2O3(F) catalysts,
respectively. It suggests that nearly half of the Cr species are in the
form of CrOxFy on the catalyst surface. Note that these values are
much higher than those calculated in Table 1, suggesting a surface
enrichment of such CrOxFy on the catalyst surface. Also, with the
addition of yttrium, a shift toward higher binding energy of the
CrOxFy peak is observed, which can be attributed to the increase of
average valence of Cr species. The content of CrOxFy (44.0%) on the
1Y2O3-Cr2O3(F) catalyst surface is slightly higher than that (41.5%)
on the Cr2O3(F) catalyst surface. However, with the content of
doped yttrium further increases, the content of CrOxFy species
increases. This suggests that the content of doped yttrium has
effects on the content of CrOxFy species and average valence of Cr
species in Y2O3-Cr2O3(F) catalysts.
2.4. Reaction performance of Y2O3-Cr2O3(F) catalysts
Table 2 shows the catalytic behaviors of the Y2O3-Cr2O3(F)
catalysts for fluorination of 1,1,2,3-tetrachloropropene at 280 8C.
The data were obtained after 10 h reaction. As can be seen in
Fig. 3. H2-TPR profiles of Cr2O3 and Y2O3-Cr2O3 catalysts.

F. Wang et al. / Journal of Fluorine Chemistry 166 (2014) 78–83
81
Table 2
Catalytic results obtained over Y2O3-Cr2O3(F) catalystsa.
Catalyst
Conversion (%)
Selectivity (%)
HCFC-1233xf
CClF5CClCH2Cl
CF25CClCH2Cl
Cr2O3(F)
99.0
99.5
99.6
99.6
97.5
98.1
96.2
94.1
2.5
1.9
2.4
3.2
0
1Y2O3-Cr2O3(F)
5Y2O3-Cr2O3(F)
10Y2O3-Cr2O3(F)
0
1.4
2.7
a
Reaction temperature: 280 8C, data obtained after 10 h reaction.
Fig. 5. Catalytic properties of the Cr2O3(F) and the 1Y2O3-Cr2O3(F) catalysts.
Table 2, the conversion of 1,1,2,3-tetrachloropropene is over 99%
for all the catalysts, and the selectivity to the main product HCFC-
1233xf is generally high (>94%). The by-products are
CClF55CClCH2Cl and CF255CClCH2Cl.
the reaction, it seems that the formation of carbon does not affect
the reactivity.
In order to investigate the structural changes of the catalysts
after reaction, characterizations of the spent samples were
conducted. Fig. 6 shows the XRD patterns of the spent Cr2O3(F)
and 1Y2O3-Cr2O3(F) catalysts after 70 h reaction. It is found that the
features of these two spent samples are identical to the fresh ones,
implying that there are few changes in the catalyst structures. Also,
XPS analyses of the spent samples were performed, as shown in
Since the stability of the catalyst is crucial in practical
application, long term reactions were also conducted over two
representative catalysts Cr2O3(F) and the 1Y2O3-Cr2O3(F) at a
reaction temperature of 280 8C, as shown in Fig. 5. It is found that
for these two catalysts, the conversions remained constant (>99%)
during the 70 or 100 h testing, indicating that both catalysts are
stable. However, differences in the catalytic behaviors are also
observed. The selectivity to the HCFC-1233xf remains almost
constant during 100 h reaction (about 97%) for the 1Y2O3-Cr2O3(F)
catalyst, while for the Cr2O3(F) catalyst the selectivity gradually
declined from 97% to 88% after 70 h reaction. The by-products
detected are CClF55CClCH2Cl and CF255CClCH2Cl. Such a difference
suggests that the addition of yttrium in the Cr2O3 is beneficial to
the promotion of selectivity, while the yield of HCFC-1233xf
declined on the Cr2O3(F) catalyst.
First of all, surface areas of the spent Cr2O3(F) and 1Y2O3-
Cr2O3(F) catalysts were analyzed, which are 39 and 35 m2 gꢁ1
,
respectively. These values are similar to those of the fresh catalysts
(42 m2 gꢁ1 for the fresh Cr2O3(F) and 37 m2 gꢁ1 for the fresh
1Y2O3-Cr2O3(F)), indicating the surface area does not change much
after reaction.
It has been well recognized that coke deposition on the Cr-
based catalysts during Cl-F exchange reactions is a main reason
for catalyst deactivation [14]. Therefore, Raman spectra of the
spent Cr2O3(F) and 1Y2O3-Cr2O3(F) catalysts were recorded, as
shown in Fig. 2c. For the spent catalysts, the features are similar
to those of the pre-fluorinated Y2O3-Cr2O3 catalysts, except that
strong Raman bands at 1397 and 1603 cmꢁ1 assigned to carbon
[32] are observed. The presence of such species suggests the
deposition of carbon on the catalyst surface during the reaction;
however, since the catalysts remain the same activities during
Fig. 6. XRD patterns of the spent Cr2O3(F) and 1Y2O3-Cr2O3(F) catalysts after 70 h
reaction.

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F. Wang et al. / Journal of Fluorine Chemistry 166 (2014) 78–83
stirring until a precipitated slurry was obtained. The resulting
slurry was dried at 120 8C overnight. Finally, it was calcined at
600 8C for 4 h in N2 to obtain the xY2O3-Cr2O3 catalysts, where x
(x = 0, 1, 5 or 10%) refers to the molar percent of Y in the xY2O3-
Cr2O3 catalysts.
4.3. Catalyst characterizations
X-ray diffraction (XRD) patterns were recorded using
PANalytic X’Pert PW3040 diffractiometer with Cu K radiation
= 0.1542 nm) operated at 40 kV and 40 mA. The patterns were
collected in a 2 range from 10 to 908, with a scanning step of
0.158 sꢁ1
a
a
(
l
u
.
Raman spectra were collected by a Renishaw RM1000 confocal
microprobe under ambient conditions. The wavelength of the
excitation laser was 514 nm. The scanning range was 200–
2000 cmꢁ1
.
Fig. 7. Cr 2p XPS spectra of the spent Cr2O3(F) and Y2O3-Cr2O3(F) catalysts after 70 h
reaction.
X-ray photonelectron spectroscopy (XPS) experiment were
carried out on a VGESCALAB MK2 system with Al-K radiation
a
Fig. 7. The spent samples also contain three main peaks at 578.8,
576.8 and 576.0 eV assigning to CrOxFy, Cr2O3 and Cr(OH)3,
respectively. The surface contents of different Cr species were
calculated. The contents of CrOxFy, Cr2O3 and Cr(OH)3 in the fresh
1Y2O3-Cr2O3(F) are 44.0, 42.8, 13.2%, respectively. For the spent
1Y2O3-Cr2O3(F), the contents of CrOxFy, Cr2O3 and Cr(OH)3 are 42.0,
48.9, 9.1%, respectively. The contents of CrOxFy, Cr2O3 and Cr(OH)3
in the fresh Cr2O3(F) are 41.5, 46.7, 11.8%, respectively. For the
spent Cr2O3(F), the contents of CrOxFy, Cr2O3 and Cr(OH)3 are 37.5,
53.0, 9.5%, respectively. The differences in the contents of Cr
species (particularly the CrOxFy) suggest changes in the catalyst
surface properties after/during the reaction, because the 1,1,2,3-
tetrachloropropene molecules are reducing agents. Moreover, it is
well known that the presence of CrOxFy species is important to the
catalytic performance (both activity and selectivity) [10–12], and
the loss of selectivity to HCFC-1233xf in these two catalysts is due
to the decline of CrOxFy species, particularly for the Cr2O3(F)
sample.
(hv = 1486.6 eV). Binding energies were calibrated by using the
contaminant carbon (C1s = 284.6 eV).
The contents of Cr and yttrium in the catalysts were measured
by an ARL ADV ANT’X Intelli Power 4200 X-ray fluorometer. The
data were obtained using the UNIQUANT quantitative analysis
software.
4.4. Catalytic performance test
Before the reaction, pre-fluorination was carried out in order to
activate the catalyst. The pre-fluorination of the oxide sample
(Y2O3-Cr2O3) was carried out in a fixed bed reactor (10 mm
(i.d.) ꢂ 300 mm), equipped with an electric heater. 3 ml of Y2O3-
Cr2O3 was loaded into the reactor and dried at 300 8C for 1 h in N2
with a flow rate of 30 ml minꢁ1. Then the N2 flow was stopped and
mixture of HF (40 ml minꢁ1) and N2 (10 ml minꢁ1) was introduced
at 260 8C for 1 h and subsequently at 400 8C for 3 h. The xY2O3-
Cr2O3 catalysts after the activation process (pre-fluorination) were
denoted as xY2O3-Cr2O3(F). After the catalyst activation, a mixture
of HF and 1,1,2,3-tetrachloropropene (CCl255CClCH2Cl) with a
molar ratio of HF/CCl255CClCH2Cl = 15 was introduced. The contact
time is 8.4 s. The products were analyzed by a gas chromatograph
mass spectrometer (GCMS-QP2010s) equipped with a HP GS-
GASPRO capillary column (60 m ꢂ 0.32 mm).
3. Conclusions
This work demonstrates the promoting effect of yttrium in the
Cr2O3 catalysts for vapor-phase fluorination of 1,1,2,3-tetrachlor-
opropene to synthesize HCFC-1233xf. It is found that the addition
of yttrium in the Cr2O3 catalyst efficiently improves the selectivity
of the catalyst, particularly when proper amount of yttrium (about
1%) was added. The highest selectivity to HCFC-1233xf is about 97%
after 100 h reaction.
Acknowledgement
This work was supported by the National Natural Science
Foundation of China (No. 21373186).
4. Experimental
4.1. Experiment reagent
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