Selective gas-phase catalytic fluorination of 1,1,2,3-tetrachloropropene to 2-chloro-3,3,3-trifluoropropene

Article abstract of DOI:10.1016/j.catcom.2014.02.013

For synthesis of 2,3,3,3-tetrafluoropropene, 2-chloro-3,3,3- trifluoropropene (HCFO-1233xf) is an essential intermediate. We here report the catalytic fluorination of 1,1,2,3-tetrachloropropene (4E) to 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) over fluorinated chromia catalyst modified by Y or La. A highly selective and stable catalyst was achieved over the La promoted fluorinated chromia, where almost 100% 4E conversion and HCFO-1233xf selectivity were obtained for a 96 h TOS. The results of preliminary characterization indicated that surface CrO_xF_y species and BET area of catalyst were related with the 4E fluorination activity.

Full text of DOI:10.1016/j.catcom.2014.02.013

Catalysis Communications 49 (2014) 73–77
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Catalysis Communications
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Short Communication
Selective gas-phase catalytic fluorination of 1,1,2,3-tetrachloropropene
to 2-chloro-3,3,3-trifluoropropene
⁎
Wei Mao, Bo Wang, Yangbo Ma, Wei Zhang, Yongmei Du, Yue Qin, Jianping Kang, Jian Lu
Department of Catalytic Technology, Xi'an Modern Chemistry Research Institute, Xi'an 710065, Shaanxi Province, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
For synthesis of 2,3,3,3-tetrafluoropropene, 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) is an essential inter-
mediate. We here report the catalytic fluorination of 1,1,2,3-tetrachloropropene (4E) to 2-chloro-3,3,3-
trifluoropropene (HCFO-1233xf) over fluorinated chromia catalyst modified by Y or La. A highly selective and sta-
ble catalyst was achieved over the La promoted fluorinated chromia, where almost 100% 4E conversion and
HCFO-1233xf selectivity were obtained for a 96 h TOS. The results of preliminary characterization indicated
that surface CrOxFy species and BET area of catalyst were related with the 4E fluorination activity.
© 2014 Elsevier B.V. All rights reserved.
Received 10 October 2013
Received in revised form 4 January 2014
Accepted 12 February 2014
Available online 19 February 2014
Keywords:
Catalytic fluorination
HF
Chromia
1,1,2,3-Tetrachloropropene
2-Chloro-3,3,3-trifluoropropene
1. Introduction
Although there is no open report on the synthesis of HFO-1234yf, re-
cent patents suggest a viable two-step fluorination process via the inter-
Global warming and depletion of the atmospheric ozone have
been the main environmental issues that threaten the sustainable
development of the world [1]. Being the most potent and main
greenhouse gases (GHG), hydrofluorocarbons (HFCs) such as 1,1,1,2,-
tetrafluoroethane (HFC-134a) with a global warming potential (GWP)
over 1400 are still used as refrigerants, foaming and cleaning agents
[2]. Thus, more stringent legislations have been putting on the emission
of potent GHGs, and this has prompted the research and development
of environmentally benign alternatives to HFCs [2b,3]. Among the
available choices, 2,3,3,3-tetrafluoropropene (HFO-1234yf) has
been proven one of the most promising alternatives to HFCs due to
its less impact on environment, i.e., GWP of 4 and zero ozone deple-
tion [3]. Thus, the environmentally benign process for the production
of HFO-1234yf becomes a recently important topic in the related do-
mains.
mediate of 2-chloro-3,3,3-trifluoropropene (HCFO-1233xf) [4]. Thus
the gas-phase catalytic fluorination of 1,1,2,3-tetrachloropropene (4E)
to HCFO-1233xf is a crucial step for the synthesis of HFO-1234yf. In
patent [4], the chromia was employed to catalyze this reaction, but
fast catalyst deactivation was observed. Then, organic amine molecules
like diisopropyl amine were added into the reaction material to im-
prove the lifespan of catalyst. Possibly, these organic bases can inhibit
the undesirable polymerization reaction and/or coking involving the
catalyst.
Generally, the Cr-based catalysts after pretreatment with fluorine
containing gases such as HF are active for the common gas-phase
fluorination reactions [5]. Moreover, the catalytic fluorination of
chloroethenes such as trichloroethylene has been quantitatively in-
vestigated [6], and the isolated CrF3, Cr(OH)xFy and CrOxFy (the Cr
with valent N +3) species are suggested to be possibly active phases
[7]. However, in comparison with chloroethenes, the increased
carbon-chain length and the carbon–carbon double bands make the
fluorination of 4E more complex. Further reaction paths are expected
to decrease the selectivity of the desired product. Carbon deposition
over the catalyst could be easily occurred, leading to rapid catalyst
deactivation. Thus, the design of a selective and stable catalyst for
the fluorination of 4E is challengeable.
cat:
→
CCl2 ¼ CCl−CH2Cl þ 3HF
4E
CF3−CCl ¼ CH2 þ 3HCl
HCFO‐1233xf
ð1Þ
ð2Þ
cat:
→
CF3−CCl ¼ CH2 þ HF
HCFO‐1233xf
CF3−CF ¼ CH2 þ HCl
HFO‐1234yf
Based on the coherent thoughts, the surface acidity of the Cr-based
catalyst must be regulated so that the 4E fluorination could be oc-
curred effectively and the coke deposition is greatly inhibited.
More importantly, we assume that the catalytic performance is dif-
ferent over aforementioned active Cr species, and modifying surface
⁎
Corresponding author. Tel./fax: +86 29 88291213.
E-mail address: lujian204@gmail.com (J. Lu).
http://dx.doi.org/10.1016/j.catcom.2014.02.013
1566-7367/© 2014 Elsevier B.V. All rights reserved.

74
W. Mao et al. / Catalysis Communications 49 (2014) 73–77
Cr species would affect significantly the catalyst behavior in this re-
action. Following these rules, La2O3 and Y2O3 were impregnated, re-
spectively, onto the prepared chromia, which were expected to
adjust the distribution of active Cr species as well as the surface acid-
ity. The main purpose of this work is to ascertain if these modified
chromia catalysts can achieve excellent performance in 4E fluorina-
tion without any organic additive. Then, for the first time, a highly
active and stable La promoted chromia catalyst was developed.
2.4. Characterization
The metal content in the sample was determined by X-ray fluo-
rescence (XRF) spectrometer (ELEMENTAR Vario ELIII) with the un-
certainty of 3%. Surface chemical compositions in the samples were
analyzed using an X-ray photoelectron spectrometer (XPS) (Thermo
Scientific K-Alpha) equipped with an Al monochromatic X-ray source
(Al Kα = 1486.6 eV) under room temperature in high vacuum (about
1 × 10−9 Pa). Curve fitting of the narrow-scan XPS spectra was carried
out with a mixed Gaussian–Lorentzian product function. Shirley back-
ground was subtracted from each spectrum before the curve fitting.
The position of C1s BE at 284.8 eV was used as an internal standard
for correcting any charge-induced peak shifts. Before the test, the pellet
type samples were outgassed for about 2 h at 423 K under a pressure of
1 × 10−6 Pa to minimize the surface contamination. Raman spectra
were obtained on a Renishaw Raman System 2000 with exciting wave-
length of 785 nm under ambient conditions. XRD patterns of the pre-
pared samples were collected with a Rigaku D/max-γA rotation
anode X-ray diffractometer (Cu Kα, λ = 0.15418 nm). The surface
area of the catalysts was measured using nitrogen adsorption at 77 K
and the Brunauer–Emmett–Teller (BET) method using a Micromeritics
ASAP2020 system. The temperature-programmed desorption of am-
monia (NH3-TPD) measurement was carried on an AutoChem II 2920
instrument (Micromeritics, USA) for comparing the acidity of various
samples. Prior to TPD studies, a sample of 50 mg was first pretreated
in pure He at 773 K for 60 min, then cooled to 393 K and saturated
at this temperature with anhydrous ammonia gas (10% in He) for
30 min. Weakly adsorbed NH3 was eliminated by treatment under
He at the same temperature for 60 min. The NH3-TPD profile was
recorded with a thermal conductivity detector with a heating rate
of 10 K min−1 from 393 to 673 K in a He flow.
2. Experimental
2.1. Preparation of catalysts
The pure chromium oxide was prepared by a precipitation method.
The detailed process was as follows: a solution of aqueous ammonia
(25 wt.%) was added into a stirring solution of chromium chloride
at a constant rate until a pH of 7.5 was reached. Then, the precipitate
obtained was filtered, washed with distilled water and dried at
120 °C for 12 h under nitrogen, followed by a calcination at 300 °C for
8 h in air. The resulting solid was powdered, mixed with 2% graphite
and formed into cylindrical pellets as the blank catalyst precursor. The
doped chromia catalysts were prepared by the incipient wetness im-
pregnation method. The prepared chromia powder was impregnated
by an aqueous solution of the corresponding La(NO3)3 or Y(NO3)3, sub-
sequently dried at 120 °C overnight, and finally calcined at 300 °C for 8
h under N2. The content of the metal salt in the solution was adjusted to
giving the final metal loading of 1 wt.%.
2.2. Catalyst activation
Prior to use, the fresh oxide sample was subject to a pre-fluorination
process so as to obtain an activity for the fluorination of 1,1,2,3-
tetrachloropropene. The pelletized catalyst precursor (60 mL) was
charged into a nickel tubular reactor with a diameter of 2.5 cm and
a length of 70 cm; it was heated at 200 °C for 8 h in N2 at a flow of
250 mL min−1, then activated with a mixture stream of HF and N2
(molar ratio of HF/N2 = 1:4) at 250–350 °C for 12 h. The fluorinated
chromia referred to F\Cr, and the fluorinated chromia promoted with
La2O3 and Y2O3 was denoted as La/F\Cr and Y/F\Cr, respectively.
3. Results and discussion
3.1. Fluorination of 4E over Cr-based catalysts
Fig. 1 displays the time-on-stream (TOS) results of 4E fluorination.
Each catalyst showed high initial activity (100% conv. for 4E) and se-
lectivity to HCFO-1233xf (N98%). However, only the La/F\Cr catalyst
sustained almost full 4E conversion and HCFO-1233xf selectivity
over a 96 h TOS. Conversely, above indexes decreased gradually
with time over the F\Cr catalyst, which were reduced by 12.4%
and 12.1%, respectively, after 96 h. The Y/F\Cr catalyst exhibited
the poorest stability in comparison with other catalysts, where the
4E conversion and HCFO-1233xf selectivity were reduced by 26%
and 32.2%, respectively, after reaction. These results clearly indicate
that the dopant La has positive promotional effect on the property
of fluorinated chromia, whereas the addition of Y exhibits negative
promotional effect. Thus, La2O3 is required to improve catalytic be-
havior of fluorinated chromia for the production of HCFO-1233xf.
On the other hand, introducing La or Y into chromia exhibited little
effect on the initial product distribution. Besides HCFO-1233xf,
the other minor components formed were 2,3-dichloro-3,3-
difluoropropene (HCFO-1232xe), 1,2-dichloro-3,3,3-trifluoropropene
(HCFO-1223xd), and 2,2,3-trichloro-1,1,1-trifluoropropane (HCFC-
233ab) with trace amounts of 2,3,3-trichloro-3-fluoropropene (HCFO-
1231xe), 2-chloro-1,1,1,2-tetrafluoropropane (HCFC-244bb), 2,3-
dichloro-1,1,1-trifluoropropane (HCFC-243db) and HFO-1234yf in
all the experiments. The total selectivity to byproducts was less
than 2% at the initial stage of reaction. However, it is worth noting
that the content of less fluorinated compounds HCFO-1232xe and
HCFO-1231xe increased gradually over time on the F\Cr and Y/F\Cr.
Especially the HCFO-1232xe selectivity, it reached to 10% and 28%, re-
spectively after 96 h TOS over the F\Cr and Y/F\Cr catalysts. At the
same time, the HCFO-1231xe selectivity reached to 2% and 3%, respec-
tively. Regardless of catalyst, the selectivity to other fluorinated
2.3. Catalytic fluorination
The fluorination reaction was carried out under atmospheric
pressure in the same reactor at 260 °C after the preliminary fluorina-
tion of catalyst. Flow rate of HF pre-heated in a chamber at 45 °C was
carefully controlled at 300 mL min−1 using a Sevenstar mass flow-
meter, and the CCl2 = CCl − CH2Cl feed was regulated at room temper-
ature with a liquid pump. The molar ratio of HF/CCl2 = CCl − CH2Cl was
fixed at 10:1 and the GHSV was 300 h−1. The product stream from the
reactor was scrubbed with H2O (50 °C), then passed through a drier (5
A zeolite) and finally to the GC. The organic reaction products were an-
alyzed by a gas chromatograph (Haixin GC-930) equipped with a flame
ionization detector (FID) and a DB-5 (30 m × 0.25 mm) capillary col-
umn. The relative composition of the products is based on peak areas
and therefore do not represent the absolute yields because of difference
in response factors. Moreover, GC–MS (Thermo Scientific ITQ 700) with
a DB-5MS capillary column was used for the identity of the organic
compounds formed during the reaction. The temperature for the gasifi-
cation compartment was maintained at 250 °C. The temperature con-
trol program was followed by maintaining at 40 °C for 3 min and then
increasing to 200 °C with an increment of 10 °C/min. The electron ener-
gy and the electron double voltage were set at 70 eV and 1200 V,
respectively.

W. Mao et al. / Catalysis Communications 49 (2014) 73–77
75
Hence, the transformation of 4E to HCFO-1231xe may run via the con-
secutive HF-addition followed by HCl elimination processes, although
the intermediate 1,1,2,3-tetrachloro-1-fluoropropane was not detected.
However, observing the molecular structure, the group CCl2F\ of HCFO-
1231xe can be hardly fluorinated to CClF2\ via the addition/elimination
process. The direct Cl against F exchange is more possible in the fluorina-
tion of HCFO-1231xe to HCFO-1232xe. Similar process may also occur in
the fluorination of HCFO-1232xe to HCFO-1233xf.
100
80
(a)
F-Cr
La/F-Cr
Y/F-Cr
60
3.2. Characterization of catalysts
40
To find out the reasons that affected the catalysts' behaviors, dif-
ferent Cr-based catalysts were characterized by XRD. As shown in
Fig. 2, all the samples exhibited only a broad diffuse peak with high
background intensities, indicating that typical amorphous structure
or microcrystalline phase was predominant in each fluorinated catalyst.
Indeed, the Cr species formed after treatment with HF were highly dis-
persed on the surface of catalyst in all the samples. The detailed molec-
ular structure of the Cr species was further probed by the Raman
spectroscopy (Fig. 3). For chromia, only a broad peak at 835 cm−1
was observed, which can be assigned to symmetrical stretching of mo-
nomeric chromate species (Cr6+) [7b]. This result indicates that the
chromium with oxidation state VI was present in the prepared chromia,
the molar ratio of Cr3+/Cr6+ was estimated to 3.2 according to the XPS
analysis. Previous studies have reported similar formation of oxidized
Cr-species (Cr N 3+) on the surface of chromia [7c–e]. After fluorina-
tion, above characteristic Raman band was also observed for the F\Cr
sample but clearly shifted (near 869 cm−1). Furthermore, two new
bands at 1319 and 1581 cm−1 appeared in the spectra of the F\Cr
sample, which can be assigned to stretching of the CrVIOxFy species
formed during the activation [7b]. The La/F\Cr sample showed the
same Raman bands of chromate and CrOxFy species as the F\Cr sample.
In contrast, only a Raman band of chromate species was observed for
the Y/F\Cr sample and the band of the CrOxFy species was not detected.
On the other hand, the peak intensity of chromate species was weak-
ened significantly for the fluorinated samples except the Y/F\Cr.
These Raman spectra results indicate that isolated chromate species
were transformed into CrOxFy species during the pre-fluorination for
the F\Cr and La/F\Cr samples, while for the Y/F\Cr sample this pro-
cess was not taken place.
12
24
36
48
60
72
84
96
Time on stream, h
100
80
(b)
F-Cr
La/F-Cr
Y/F-Cr
60
40
12
24
36
48
60
72
84
96
Time on stream, h
Fig. 1. Catalytic performances of various fluorinated Cr-based catalysts for 4E fluorination
with HF. (a) conversion of 4E vs. time on stream; (b) selectivity of HCFO-1233xf vs. time
on stream.
byproducts did not change significantly. Obviously, the greater catalyst
deactivation, the larger content of HCFO-1232xe and HCFO-1231xe.
Based on the information of product distribution, it is rational to
presume that HCFO-1232xe and HCFO-1231xe are the main interme-
diates during 4E fluorination. While we find it difficult to clarify
every intermediate in 4E fluorination at the moment, some specula-
tion on the reaction pathway can be obtained according to general
recognition for heterogeneous fluorination of chloroalkenes [7a,8].
Scheme 1 displays a simplified reaction pathway for fluorination of
4E to HCFO-1233xf. In general, a C\Cl bond at a double bonded carbon
is significantly stronger than that of a single bonded C-atom, indicating
that direct Cl/F exchange is difficult at the unsaturated C-atoms.
To reveal the upmost surface species, XPS was applied for different
fluorinated catalysts, and the results are given in Fig. 4. For the F\Cr
and La/F\Cr samples, the deconvolution of Cr2p3/2 gives three species
of Cr(OH)3 [Cr(I)], CrF3 [Cr(II)] and CrOxFy [Cr(III)] with the BE values
of 579, 581.8 and 584.6 eV, respectively [9]. Conversely, apart from the
Cr(OH)3 and CrF3 species, the deconvolution of Cr2p3/2 for the Y/F\Cr
sample gives a different species of Cr(OH)xFy with BE value of
583.4 eV [7d]. The XPS results confirm that different chromium species
La/F-Cr
Y/F-Cr
F-Cr
20
40
60
80
2
Scheme 1. Possible reaction paths for the fluorination of 4E catalyzed by Cr-based
catalysts.
Fig. 2. X-ray diffractograms for various fluorinated Cr-based catalysts.

76
W. Mao et al. / Catalysis Communications 49 (2014) 73–77
acid sites present on the surface of various catalysts. It can be observed
1319
869
1581
from Fig. 5 that a broad desorption profile in the range 120–400 °C ap-
pears in all the samples with one maximum peak around 200 °C. This
suggests that weak acid sites are predominant on the surface of pre-
pared Cr-based catalysts.
La/F-Cr
F-Cr
As mentioned above, catalytic activity over Cr-based catalyst is relat-
ed to the presence of chromium fluorides or oxyfluoride species after
the activation by HF. The XRD, Raman spectra and XPS results reveal
that both F\Cr and La/F\Cr catalysts contained isolated CrOxFy and
CrF3 species, while the Y/F\Cr catalyst contained isolated Cr(OH)xFy
and CrF3 species. Moreover, the quantitative XPS results show that a
higher CrOxFy content was obtained in the La/F\Cr than in the F\Cr.
Trunschke et al. have revealed that the addition of La can improve the
dispersion of surface chromium oxide species [10], while the monomer-
ic chromate species are easier fluorinated than the oligomeric chromate
species [7b]. Thus, our results suggested that the addition of La could
also favor the formation of active specie CrOxFy during the activation.
Luo et al. have reported that the Cr(OH)xFy species can be formed in
the Cr\Y catalyst [7d]. Our results are in good agreement with theirs.
Therefore, the role of different dopants can be ascribed to adjusting
the distribution of active Cr species on the catalyst. The difference of sur-
face CrOxFy content coincided exactly with the catalytic behaviors of
various catalysts, where the most active and stable catalyst for 4E fluo-
rination was the La/F\Cr with maximum CrOxFy species. Therefore, it
Y/F-Cr
chromia
1800
1500
1200
900
600
Raman shift, cm-1
Fig. 3. The Raman spectra of various fluorinated Cr-based catalysts.
were present on the fluorinated catalysts. The CrOxFy species were only
formed for the F\Cr and La/F\Cr samples. This is consistent with the
results of Raman spectra. Furthermore, the atom ratio of surface Cr(II)/
Cr(III) decreases from 3.9 to 3.5 after introducing La onto chromia, indi-
cating that more CrOxFy species were formed during the activation for
the La/F\Cr. The NH3-TPD is used for investigating the strength of
Cr 2 p3/2
579.1: Cr(OH)3
(a) La/F-Cr
581.9
Cr 2 p1/2
581.9: CrF3
584.6: CrOx F
y
584.6
579.1
600
595
590
585
580
575
Binding energy, eV
578.9: Cr(OH)3
581.7: CrF3
581.7
584.6
(b) F-Cr
584.6: CrOxFy
578.9
600
595
590
585
580
575
Binding energy, eV
578.7: Cr(OH)3
581.3: CrF3
(c) Y/F-Cr
581.3
583.4
583.4: Cr(OH)x F
y
578.6
595
590
585
580
575
Binding energy, eV
Fig. 4. The XPS spectra of Cr2p for various fluorinated Cr-based catalysts.

W. Mao et al. / Catalysis Communications 49 (2014) 73–77
77
4. Conclusion
In summary, gas-phase fluorination of 4E to HCFO-1233xf can be
performed on the fluorinated chromia using La as a promoter with a
highly catalytic activity and long lifetime, and a reasonable reaction
pathway was proposed. The characterization results revealed that ex-
cellent catalytic performance was relevant to the CrOxFy species and
large surface area of Cr-based catalyst. The addition of La can improve
the content of CrOxFy species on the fluorinated chromia. We anticipate
our discovery to be a starting point for developing effective chromia-
based catalysts for synthesis of the hydrofluoroolefin by heterogeneous
fluorination and will promote the commercialization of HFO-1234yf.
Y/F-Cr
La/F-Cr
F-Cr
400
150
200
250
300
350
Temperature, oC
Acknowledgment
We thank Prof. Dr. Zhongwen Liu for precious advices.
Fig. 5. The profiles for temperature-programmed desorption of ammonia on various fluo-
rinated Cr-based catalysts.
References
[1] J.M. Last, Annu. Rev. Public Health 14 (1993) 115–136.
[2] (a) K.P. Shine, W.T. Sturges, Science 315 (2007) 1804–1805;
(b) G.J.M. Velders, A.R. Ravishankara, M.K. Miller, M.J. Molina, J. Alcamo, J.S. Daniel,
D.W. Fahey, S.A. Montzka, S. Reimann, Science 335 (2012) 922–923.
[3] (a) S. Papasavva, D.J. Luecken, R.L. Waterland, K.N. Taddonio, S.O. Andersen, Envi-
ron. Sci. Technol. 43 (2009) 9252–9259;
(b) S. Papasavva, D.J. Luecken, R.L. Waterland, K.N. Taddonio, S.O. Andersen, Envi-
ron. Sci. Technol. 44 (2010) 343–348.
[4] (a) M.Y. Elsheikh, P. Bonnet, B.B Chen, US Patent 8076521 (2011)
(b) D. Deur-bert, L. Wendlinger, A. Pigamo, US Patent 8207383 (2012)
(c) D.C. Merkel, H.S. Tung, US Patent 8119845 (2012).
can be concluded that dispersed CrOxFy species are mainly responsible
for the fluorination of 4E to HCFO-1233xf. In addition, for gas-phase
fluorination, high surface area catalyst is crucial to achieve high activity
and long lifetime [6c]. Nevertheless the fluorination of metal oxides
leads generally to an important decline of the surface area. Following
the aborative pre-fluorination, the fluorinated chromia with
high surface area was obtained in this work, 96 m2 g−1 to F\Cr,
105.5 m2 g−1 to Y/F\Cr and 114.2 m2 g−1 to La/F\Cr, respectively.
These values are comparable to that reported for porous fluorinated
chromia (105.1 m2 g−1) [11]. Thus, the high activity and stability of
La/F\Cr can be also ascribed to its large surface area.
[5] (a) J. Barrault, S. Brunet, B. Requieme, M. Blanchard, Chem. Commun. (1993)
374–375;
(b) D.W. Bonniface, J.R. Fryer, P. Landon, J.D. Scott, W.D.S. Scott, M.J. Watson, G.
Webb, J.M. Winfield, Green Chem. (1999) 9–11;
(c) B. Adamczyk, O. Boese, N. Weiher, S.L.M. Schroeder, E. Kemnitz, J. Fluorine Chem.
101 (2000) 239–246.
[6] (a) L.E. Manzer, Science 249 (1990) 31–35;
(b) L.E. Manzer, V.N.M. RAO, Adv. Catal. 39 (1993) 329–350;
(c) L.E. Manzer, M.J. Nappa, Appl. Catal. A 221 (2001) 267–274.
[7] (a) A. Kohne, E. Kemnitz, J. Fluorine Chem. 75 (1995) 103–110;
(b) D.H. Cho, Y.G. Kim, M.J. Chung, J.S. Chung, Appl. Catal. B 18 (1998) 251–261;
(c) J.M. Rao, A. Sivaprasad, P.S. Rao, B. Narsaiah, S.N. Reddy, V. Vijayakumar, S.V.
Manorama, K.L. Krishna, K. Srinivas, K.R. Krishnan, S. Badrinarayanan, J. Catal.
184 (1999) 105–111;
Since the 4E conversion still achieved more than 70% after 96 h
TOS in all catalysts, this indicates that other active Cr species like
CrF3 and Cr(OH)xFy were also responsible for catalyst activity. But
the HCFO-1233xf selectivity declined remarkably over the F\Cr
and Y/F\Cr, indicating that 4E cannot be entirely fluorinated on
above active centers. It is well-known that the coke formation pri-
marily accounts for the catalyst deactivation in the fluorination ca-
talysis [6c,9a]. Based on the XPS analysis, the surface C content was
increased by 49%, 62% and 73% for La/F\Cr, F\Cr and Y/F\Cr, re-
spectively, after 4E fluorination. Thus, it is reasonable to infer that
the catalyst deactivation is related with carbon deposition in this re-
action. The HCFO-1233xf selectivity and 4E conversion could de-
crease gradually as the active Cr species like CrOxFy were reduced
by carbon deposition. The differences of active species and BET sur-
face make different activities and stabilities for various Cr-based cat-
alysts. The poor performance of Y/F\Cr can be due to the absence of
active specie CrOxFy.
(d) J. He, G.Q. Xie, J.Q. Lu, L. Qian, X.L. Zhang, P. Fang, Z.Y. Pu, M.F. Luo, J. Catal. 253
(2008) 1–10;
(e) S. Brunet, B. Requieme, E. Colnay, J. Barrault, M. Blanchard, Appl. Catal. B 5
(1995) 305–317.
[8] M. Bankhead, G.W. Watson, G.J. Hutchings, J. Scott, D.J. Willock, Appl. Catal. A 200
(2000) 263–274.
[9] (a) H. Lee, H.D. Jeong, Y.S. Chung, H.G. Lee, M.J. Chung, S. Kim, H.S. Kim, J. Catal. 169
(1997) 307–316;
(b) Y.S. Chung, H.J. Lee, H.D. Jeong, Y.K. Kim, H.G. Lee, H.S. Kim, S. Kim, J. Catal. 175
(1998) 220–225.
[10] A. Trunschke, D.L. Hoang, J. Radnik, H. Lieske, J. Catal. 191 (2000) 456–466.
[11] X.Q. Jia, H.D. Quan, M. Tamura, A. Sekiya, RSC Adv. 2 (2012) 6695–6700.