Edge-hydroxylated Boron Nitride for Oxidative Dehydrogenation of Propane to Propylene

Article abstract of DOI:10.1002/cctc.201700004

Oxidative dehydrogenation of propane to olefins is a promising alternative route to industrialized direct dehydrogenation, but encounters the difficulty in selectivity control for olefins because of the overoxidation reactions that produce a substantial amount of undesired CO₂. Here we report edge-hydroxylated boron nitride, a metal-free catalyst, that efficiently catalyzed dehydrogenation of propane to propylene with superior selectivity (80.2 %) but with only negligible CO₂ formation (0.5 %) at a given propane conversion of 20.6 %. Remarkable stability was evidenced by the operation of a 300 h test with steady conversion and product selectivity. The active BNO^. site, generated dynamically through hydrogen abstraction of B?OH groups by molecular oxygen, triggered propane dehydrogenation by selectively breaking the C?H bond but simultaneously shut off the pathway of propylene overoxidation towards CO₂.

Full text of DOI:10.1002/cctc.201700004

Accepted Article
Title: Edge Hydroxylated Boron Nitride for Oxidative Dehydrogenation
of Propane to Propylene
Authors: Lei Shi, Dongqi Wang, Wei Song, Dan Shao, Wei-Ping
Zhang, and An-Hui Lu
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Edge Hydroxylated Boron Nitride for Oxidative Dehydrogenation
of Propane to Propylene
Lei Shi,[a] Dongqi Wang,[b] Wei Song,[a] Dan Shao,[a] Wei-Ping Zhang,[a] and An-Hui Lu*[a]
Abstract: Oxidative dehydrogenation of propane to olefins is a
promising alternative route to industrialized direct dehydrogenation,
but encounters the difficulty in selectivity control for olefins because
of the over-oxidation reactions that produce a substantial amount of
undesired CO2. Here we report edge hydroxylated boron nitride, a
metal-free catalyst, efficiently catalyzed dehydrogenation of propane
to propylene with a superior selectivity (80.2%) but with only
negligible CO2 formation (0.5%) at a given propane conversion of
20.6%. Remarkable stability was evidenced by the operation of a
300-hour test with steady conversion and product selectivity. The
active BNO site, generated dynamically through hydrogen
abstraction of B-OH groups by molecular oxygen, triggered propane
dehydrogenation by selectively breaking the C-H bond but
simultaneously shut off the pathway of propylene over-oxidation
towards CO2.
catalyst shall be highly selective for C-H bond cleavage but not
for C-C bond cleavage under the oxidative dehydrogenation
conditions. Unfortunately, development of such
selective catalyst is still challenging.
a highly
Quite recently, Hermans’s group reported that boron nitride
exhibited high selectivity to propylene (79%) and ethylene (12%)
at 14% conversion level in the ODH reaction of propane.[6]
Nevertheless, in view of activity, selectivity, and stability, there is
still room to improve. Moreover, for such a novel catalytic system,
the detailed structure characterization and its correlation with the
ODH reaction of propane remains to further be understood.
Independently, our group also found that boron nitride, after
steam hydroxylation at the edges, can efficiently catalyze the
ODH of propane. For example, our studies showed that boron
nitride offers high selectivity toward propylene (up to 80.2%) at
higher propane conversion (20.6%). At a 6.5% conversion level
of propane, boron nitride offered
a surprising propylene
selectivity as high as 97.4%. Furthermore, the emphasis of our
studies was placed in understanding the catalytic origin of boron
nitride in the ODH reaction of propane, i.e. our studies identified
that the B-OH groups at the edges of boron nitride selectively
activated the C-H bond in propane and simultaneously
suppressed the over-oxidation of propylene into CO2.
Introduction
Propylene, one of the most important light olefins in
petrochemical industry, is currently produced mainly through the
catalytic cracking of petroleum-derived hydrocarbons or the
multistage coal-based methanol-to-olefins process, both
involving extensive energy consumption and significant emission
of CO2.[1] Direct catalytic dehydrogenation of propane to
propylene has been developed as a more economical and
environmentally friendly route, and commercialized by UOP and
ABB Lummus in 1990s, using Pt- and CrOx-based catalysts,
respectively.[2] However, this process practically suffered from
the thermodynamic limitation in further prompting the reaction
efficiency and also the rapid catalyst deactivation by coking and
catalyst sintering that required a frequent regeneration of the
catalysts under harsh conditions.[3]
Results and Discussion
Oxidative dehydrogenation of propane
The boron nitride was first impregnated with 1 M sodium
nitrite aqueous solution, followed by a steam (5 vol % H2O/N2)
activation at 530 C for 3 hours; the resulting sample (BNOH)
was washed by aqueous ammonia and finally calcined at 500 °C
for 2 hours in air.
Oxidative dehydrogenation (ODH) of propane, catalyzed by
transition metal oxides and alkaline-earth metal oxychlorides,[4]
offers an attractive alternative with the prominent characters of
free coking of catalyst and non-equilibrium limit in propane
conversion, but the selectivity toward propylene is often lower
than the direct dehydrogenation route, primarily because of the
over-oxidation of the formed propylene to CO2 (1060%).[5]
Under the reaction conditions, the formed electron-rich
propylene reacted more easily with molecular oxygen over the
metal oxide catalysts, resulting in the cleavage the C-C bond
through a consecutive oxygen insertion and thus forming the
final product, CO2. From a chemical point of view, an ideal
The BNOH catalyst provided surprisingly high selectivity
toward propylene during the oxidative dehydrogenation of
propane at 530 C. The conversion of propane approached
-1
20.6%, equivalent to a reaction rate of 7.74 gC3H8 gcat h-1; the
product slate consisted of propylene, ethylene, methane, CO
and CO2. In particular, the selectivity was 80.2% for propylene
and only 0.5% for CO2 (Figure 1a). Taking the equally important
ethylene into account, the selectivity for light olefins (ethylene +
propylene, C2-3=) was up to 90.9%, which was much higher than
those obtained over the well-developed metal or metal oxide
catalysts at a comparable propane conversion level, as well as
carbon and carbonaceous materials.[4b, 5d, 5e, 7] More significantly,
the formation of CO2 (0.5%) was considerably lower than that
from the traditional ODH processes (1060% CO2),[5] clearly
showing the excellent performance of the current BNOH catalyst
in selective activation of the C-H bond in propane.
A control experiment with a feed gas of C3H6/O2/He showed
no measurable conversion of propylene (Supporting Information,
Figure S1), evidencing that the BNOH catalyst does not activate
the C-C bond of propylene and thus avoids its over-oxidation
under ODH conditions. The remarkable stability of the BNOH
catalyst in the ODH of propane was evidenced by the operation
[a]
Dr. L. Shi, W. Song, D. Shao, Prof. W.-P. Zhang, Prof. A.-H. Lu
State Key Laboratory of Fine Chemicals, School of Chemical
Engineering,
Dalian University of Technology
Dalian 116024, China
E-mail: anhuilu@dlut.edu.cn
[b]
Prof. D. Q. Wang
Center for Multi-Disciplinary Research
Institute of High Energy Physics, Chinese Academy of Sciences
Beijing 100049, China
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10.1002/cctc.201700004
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of a 300-hour test at 530 °C without obvious variations in the
conversion and product selectivity (Figure 1b), demonstrating
the potential for industrial application. Moreover, the selectivity
toward propylene can be further promoted by mediating the
reaction conditions. For example, propylene selectivity of 97.4%
(C2-3=: 99.1%) was obtained at 510 °C at a propane conversion
level of 6.5%; whilst it approached 59.8% (C2-3=: 76.3%) at
540 °C with a propane conversion level of 38.2% (Figure S2).
point 4) of the in-plane, primarily because of the local warp or
wrinkle at the edge,[9] and the B/N ratio (1.28, point 2) at the
edge was higher than that (0.95, point 4) of the in-plane (Figure
2b). XPS analysis identified that the surface concentrations of
boron and oxygen were 44.3% and 9.2% (Figure 2c),
respectively. There were two types of boron species (Figure 2c);
one was coordinated with nitrogen on the flat surface while the
other was bonded to oxygen at the edge.[10] The chemical
environment for the coordination between boron and oxygen
was further verified by two-dimensional (2D) 11B multiple-
quantum (MQ) MAS NMR spectrum of the BNOH catalyst
(Figure 2d). There were two types of boron-oxygen bonding at
26.0 and 24.4 ppm; the former represented the edge boron sites
bonded to two bridging oxygen atoms, while the latter
corresponded to B-OH bonding, which was identified by the
1
1
sharp H resonance at 1.2 ppm in the H MAS NMR spectrum
(Figure 2d, inset).
Figure 1. Oxidative dehydrogenation of propane over the BNOH catalyst.
Propane conversion and product selectivity (a), and long-term stability test (b).
Reaction conditions: temperature, 530 C; catalyst weight,100 mg; gas feed,
16.7 vol % C3H8, 25.1 vol % O2, and He balance; space velocity, 37.6 gC3H8
gcat-1 h-1.
Figure 2. Structural characterization of the BNOH catalyst. a) Aberration-
corrected TEM images along [001] direction and FFT image of the (i) area. b)
HAADF-STEM image (top left), boron and nitrogen K-edge EELS spectrum
(right), and B/N ratio (bottom left) calculated by EELS spectrum. c) B1s, N1s
and O1s XPS spectra. d) 2D 11B MQ MAS NMR and 1H MAS NMR (inset)
spectra as well as structural model (inset) of BNOH edge.
Structural characterization of the BNOH catalyst
In order to verify the origin of the unique selectivity of the
BNOH catalyst, detailed structural analyses were conducted.
The BNOH catalyst inherited a hexagonal layered structure of
boron nitride (Figure S3). Aberration-corrected transmission
electron microscopy (TEM) analyses identified the in-plane
lattice retained its hexagonal symmetry with a large number of
edges that were newly created during steam activation (Figure
2a, Figures S4 and S5). TEM images viewed along [001]
direction (Figure 2a and Figure S6) revealed that the most
frequently-exposed lateral termination facets were {1010}, {011
0}, and {1100}, suggesting that the terminated configuration had
zigzag edges.[8] Lattice relaxations and distortions occurred
exclusively at the edge of the layer (Figure 2a and Figure S7).
Boron K-edge electron energy loss spectroscopy (EELS)
analysis with a high-angle annular dark field (HAADF) STEM
mode (Figure 2b and Figure S8) showed that the edge
possessed a higher * to * ratio (1.27, point 2) than that (0.52,
Identification of active sites of BNOH catalyst
FT-IR analysis was carried out to identify the roles of the B-
O-B and B-OH groups under reaction conditions. The
characteristic band of hydroxyl stretching vibration was clearly
observed at ~3400 cm-1 (Figure 3a).[11] Upon exposure to C3H8
atmosphere at 530 C, the band position of the hydroxyl
stretches remained unchanged, and no propane conversion was
detected (Figure 3a). With the addition of molecular oxygen
(O2/C3H8/He), however, the absorption of hydroxyl vibrational
stretches gradually weakened (Figure 3a), accompanied with the
formation of propylene, indicating that the OH groups interacted
with molecular oxygen and incorporated into the reaction
network. The intensities of hydroxyl vibrational stretches were
fully recovered upon steam activation (Figure 3a and Figure S9),
suggesting that the OH groups could be readily regenerated.
-
-
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10.1002/cctc.201700004
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insert into the B-O-B bridges to recover the two adjacent B-OH
groups. The freshly formed H218O during the ODH will participate
in the reversible breakage of the B-O-B bridges, through which
the exchange between the gaseous 18O and the 16O at the
BNOH edge site will be fulfilled, and the edge B-OH sites can
remain at their active state (Figure S11).
Figure 4. Kinetic behaviours of propane ODH over the BNOH catalyst.
a) Arrhenius plots for the reaction rate (activation energy, Ea) of C3H8 (triangle
symbols) and O2 (circle symbols). Reaction rates of propane and oxygen were
measured in the range of 500 ~ 535 C with a feed gas of 16.7 vol %
C3H8/25.1 vol % O2/He at the space velocity of 75.2 gC3H8 gcat-1 h-1. b) Reaction
rates of C3H8, CH3CD2CH3, and C3D8 as function of reaction time in ODH of
propane. Reaction rates were measured at 530 C with a feed gas of 16.7
vol % C3H8 or CH3CD2CH3 or C3D8/25.1 vol %O2/He at the space velocity of
75.2 gC3H8 gcat-1 h-1. c) and d) Effect of partial pressure of propane and oxygen
on propane conversion in the ODH reaction over the BNOH catalyst. Reaction
conditions: catalyst weight, 100 mg; gas feed, 0 ~ 25.2 vol % C3H8, 0 ~ 25.2
vol % O2, and He balance; reaction temperature, 530 C; space velocity, 75.2
gC3H8 gcat-1 h-1; 0.1 MPa.
Figure 3. Identification of active sites of BNOH catalyst. a) FT-IR spectra of B-
OH vibration over the BNOH catalyst under C3H8, C3H8/O2/He and H2O/He
atmospheres at 530 C. b) Mass spectra of C3H6, H2O, HDO and D2O species
upon pulsing C3H8 and O2 onto the deuterated BNOH(D) catalyst at 530 C. c)
Mass spectra of C3H6, H216O and H218O species during pulsing C3H8 and 18O2
onto the BNOH catalyst at 530 C.
Kinetic behaviour of propane ODH over the BNOH catalyst
The kinetic characters of the ODH reaction of propane over
the BNOH catalyst nicely supported the conclusion from in situ
FT-IR and isotope-labelling experiments. Initially, the apparent
activation energies (Ea) of two reactants, propane and oxygen,
were obtained by evaluating the dependence of their converting
rates on the reaction temperature. It was found that the Ea of
propane conversion was 184 kJ mol-1, lower than that (~ 250 kJ
mol-1) reported by Hermans’s group.[6] In the current study, the
Ea (213 kJ mol-1) of oxygen activation was estimated to be
higher than that of propane conversion (Figure 4a). This means
that the cleavage of C-H bonds readily happens after oxygen
activation in the BNOH catalytic system for the ODH of propane.
This deduction was further verified by measuring the kinetic
isotope effects (KIEs) of C-H cleavage. The low KIEs for primary
Isotopic measurements further confirmed the catalytic role
of the B-OH groups. When C3H8 and O2 were pulsed into the
deuterated BNOH(D) catalyst at 530 C, both HDO and D2O
were formed immediately, and their amounts gradually
decreased during subsequent pulses (Figure 3b and Figure S10).
This indicated that the H/D atoms in the BNOH(D) catalyst were
abstracted during the reaction process. Meanwhile, the
neighboring oxygen atoms were also involved in the reaction
process. When the BNOH catalyst was exposed to a mixture of
18O2 and C3H8 (Figure 3c), both H216O and H218O were produced,
suggesting that the 16O atom in the B-OH groups participated in
the formation of H216O molecule. In subsequent pulses, the
amount of H218O continuously increased whilst the amount of
H216O decreased, further verifying the isotopic exchange
between 16O sites at the BNOH edge and gaseous 18O2.
hydrogen abstraction (k1,C-H/k1,C-D
= 1.4 using C3H8 and
CH3CD2CH3 as reactants) and secondary hydrogen abstraction
(k2,C-H/k2,C-D = 1.5 using CH3CD2CH3 and C3D8 as reactants) also
indicated that the cleavage of C-H bonds readily happened in
our BNOH catalytic system for propane ODH (Figure 4b),
supporting the deduction from activation energy measurements.
Density functional theory (DFT) calculations demonstrated
that two adjacent B-OH groups could dehydrate through the
transition state with a four-membered ring, leading to the
formation of B-O-B bridges. Reversibly, the gaseous H2O could
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temperature for 1 hour. The reaction mixture was C3H8/O2/He with a
molar ratio of 1/1.5/3.5 at atmospheric pressure. Flow rate was fixed at
192 mL min-1, and reaction temperature was varied in the range of
500550 C. Reactants and products were analyzed by an online gas
chromatograph (Techcomp, GC 7900). A GDX-102 and molecular sieve
5A column, connected to a TCD were used to analyze the O2, He, C3H8,
C3H6, C2H4, CH4, CO, and CO2.
Conversion was defined as the number of moles of carbon
converted divided by the number of moles of carbon present in the feed.
Selectivity was defined as the number of moles of carbon in the product
divided by the number of moles of carbon reacted. The carbon balance
was checked by comparing the number of moles of carbon in the outlet
stream to the number of moles of carbon in the feed. Under our typical
evaluating conditions, the carbon balance was within ±3%. In order to
account for the volume expansion in the reaction, helium was used as
the internal standard.
Moreover, the effect of reactant concentrations on the
reaction rate was measured to investigate the kinetic behaviors
(Figure 4c and 4d). Langmuir-type dependence on oxygen
concentration corresponds with a reaction mechanism that is
controlled by adsorption or activation of molecular oxygen on the
catalyst surface. First-order dependence on propane
concentration suggested that the propane reacted directly from
the gas-phase with the active oxygen species on the surface of
BNOH catalyst.[12]
Conclusions
We have demonstrated that boron nitride, upon steam
activation to generate B-OH groups at the edges, efficiently
catalyzed the oxidative dehydrogenation of propane with a
In kinetic analysis, reaction rates were measured in a packed-bed
single-pass
flow
microreactor
with
plug-flow
hydrodynamics. Experimental data of propane and oxygen conversion at
different temperature levels were used in order to obtain the apparent
activation energy. Effect of residence time on reaction rate and product
distribution was measured by varying reactant flow rates. Reaction rates
were extrapolated to zero residence time to obtain the kinetic information
in the initial reaction stage. Reaction orders of ethane and oxygen were
obtained by measuring the effect of reactant partial pressure on reaction
rates. Catalytic reaction was supposed to proceed under net kinetic
control.
superior selectivity toward propylene and
a significantly
minimized CO2 emission. The hydrogen abstraction of B-OH
groups by molecular oxygen dynamically generates the active
sites, which triggered propane dehydrogenation. This novel and
metal-free catalyst system not only opens up a new research
direction in selective activation of the C-H bond of alkanes, but
also serves as a highly potential catalyst for the industrial ODH
process.
Catalyst characterization.
Powder X-ray diffraction (XRD) measurements were made on a
Rigaku D/Max 2400 diffractometer using Cu Kα radiation (λ = 0.15406
nm). The powder catalyst was placed inside a quartz-glass sample
Experimental Section
holder
prior
to
testing.
Rietveld
refinements
of
PXRD
Catalyst preparation.
pattern were carried out with GSAS program.
The pristine boron nitride was synthesized using a high-temperature
solid-phase reaction, using boric acid (H3BO3) and melamine (C3H6N6)
together with urea (CO(NH2)2) as the boron and nitrogen sources,
respectively. The typical synthesis procedure is as follows: 1.856 g
H3BO3 and 0.755 g C3H6N6 were dissolved in 10 mL methanol, and then
0.269 g CO(NH2)2 was added into the solution. Subsequently, the
methanol was completely evaporated at 25 C under vigorous stirring
conditions. The resulting solid was then heated to 1500 C and
maintained at that temperature for 1 hour in a graphite boat (total length,
55 mm; width, 22 mm; height, 22 mm) in a quartz tube furnace under a
N2 flow of 80 mL/min. The product was washed using deionized water of
90 C for three times and filtered to remove excess boron oxide. The
white boron nitride had a specific surface area of 32 m2 g-1 and a pore
volume of 0.23 cm3 g-1.
High-resolution transmission electron microscope (TEM) images
were recorded on an aberration-corrected and monochromated FEI Titan
ETEM 80-300 microscope. The microscope was operated at an
accelerating voltage of 80 kV to limit structural damage to the sample.
High-angle annular dark field scanning transmission electron microscope
(HAADF-STEM) images and electron energy loss spectroscopy (EELS)
were taken on an aberration-corrected Nion Ultra STEM 100 at 100 kV
equipped with a Gatan Enfinium Spectrometer. The specimen was
prepared by ultrasonically dispersing the powder sample in ethanol and
droplets of the suspension were deposited onto a carbon-coated copper
grid.
Solid-state magic-angle-spinning nuclear magnetic resonance (MAS
NMR) spectra were recorded on an Agilent DD2-500 MHz spectrometer.
11B and 1H MAS NMR experiments were carried out at 160.3 MHz and
499.8 MHz, respectively, using a 4-mm MAS NMR probe with a spinning
rate of 10 kHz. 1H MAS NMR spectra were accumulated for 32 scans
with a 5 second recycle delay. The chemical shifts were referenced to
tetramethylsilane (TMS). Two-dimensional (2D) 11B multiple-quantum
(MQ) MAS NMR experiments were performed using a three-pulse
sequence incorporating a z-filter at a spinning speed of 10 kHz. A two-
dimensional Fourier transformation followed by a shearing transformation
gave a pure absorption mode 2D contour plot. The chemical shifts were
referenced to a 1 M H3BO3 aqueous solution at 19.6 ppm. Prior to testing,
the sample was dehydrated at 400 °C for 1 h at 10-4 Pa and then
transferred to a 4-mm MAS rotor in a home-made device without
exposure to air.
The as-prepared boron nitride was hydroxylated by a sodium-
assisted high-temperature steam activation process.[13]
A typical
procedure was as follows: 200 L of sodium nitrite solution (1 mol L-1)
was initially impregnated in 1.0 g boron nitride powder and then
maintained at 50 C for 6 hours, followed by calcination in air at 560 C
for 1 hour. After air-cooling to room temperature, the solid product was
transferred to a fixed bed reactor and then treated with 5 vol % H2O/N2 at
530 C for 3 hours. Sodium ions were further leached out with a reflux in
3 mol L-1 ammonia at 80 C for 3 times, followed extensive washing with
ultrapure water (40 times, 50 mL water each). The obtained powders
were treated in air at 500 C for 2 hours with a heating rate of 10 C min-1,
and the resultant sample was denoted as BNOH. The inductively coupled
plasma optical emission spectroscopy (ICP-OES) measurement showed
that the residual content of sodium was 0.18 wt%.
X-ray photoelectron spectroscopy (XPS) analysis was performed on
an Omicron Sphera II hemispherical electron energy analyzer with an in
situ reaction cell attached to the instrument. Monochromatic Al K X-ray
source (1486.6 eV, anode operating at 15 kV and 300W) was used as
incident radiation. The binding energy of the element was calibrated
Catalytic evaluation.
Catalytic reactions were carried out in
a packed-bed quartz
using an
measurements, all the samples were treated in-situ at 500 °C for 1 hour
N
1s photoelectron peak at 398.1 eV.[10,14] Before the
microreactor (I.D. = 6 mm). Prior to testing, the catalyst was heated to
560 C at a rate of 10 C min-1 in 20 vol % O2/N2 and maintained at this
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10.1002/cctc.201700004
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under an Ar stream (32 mL min-1) and then moved to the measured
chamber under vacuum conditions.
Acknowledgements
ICP-OES measurments were conducted to monitor the sodium
content in the hydroxylation process. The samples were dissloved in
We thank Dr. Yan Zhou (Dalian Institute of Chemical Physics,
Chinese Academy of Sciences) for assistance on TEM
measurements, Prof. Mingshu Chen (Xiamen University, China)
for his assistance on XPS measurements, and Prof. Wenjie
Shen (Dalian Institute of Chemical Physics, Chinese Academy of
Sciences) for the valuable discussions. This work was financially
supported by National Natural Science Foundation of China
(21225312, U1462120, 21473206, and 21373035) and Cheung
Kong Scholars Programme of China (T2015036). A Chinese
patent and an international patent application under the Patent
Cooperation Treaty are pending.
a
mixture of HNO3 and HF under microwave-assisted heating
conditions.
Nitrogen adsorption-desorption isotherms were measured with a
Micromeritics TriStar 3000 adsorption analyzer. Before the
measurements, the sample was degassed at 200 °C for 4 hours. The
specific surface area was calculated from the adsorption data in the
relative pressure range from 0.05 to 0.3 using the Brunauer-Emmett-
Teller (BET) method.
In situ infrared spectroscopy.
In situ Fourier transform infrared spectra (FT-IR) were recorded
under reaction condition on a Nicolet 6700 FT-IR spectrometer equipped
with mercury cadmium telluride (MCT) detector. The BNOH catalyst of
~25 mg was compressed as a thin disk ( = 1.2 cm), and placed in a
Keywords: boron nitride • edge hydroxylation • propane •
quartz transmission cell equipped with CaF2 windows and
a
oxidative dehydrogenation • active site
thermocouple mount that allowed direct measurement of the surface
temperature. Spectra were averaged over 512 scans in the range
4004000 cm-1 with a 2 cm-1 resolution. Prior to collecting spectra,
catalysts were pretreated for 1 hour at 530 C in helium (40 mL min-1).
The gas composition at the reactor outlet during in situ FT-IR
experiments was controlled by online mass spectrometry (MS, Pfeiffer,
OminStarTM). The propane and oxygen conversions were calculated from
the inlet and outlet concentration of these components. The following
mass-to-charge (m/z) signals were analyzed: 29 (C3H8), 32 (O2), 41
(C3H6, C3H8), 44 (C3H8, CO2), and 18 (H2O). A rehydroxylation of the
used catalysts was made with a 4 vol % H2O/He stream.
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Metal-free
catalysis:
edge
L. Shi, D. Wang, W. Song, D. Shao, W.-
P. Zhang, A.-H. Lu*
hydroxylated boron nitride shows
superior selectivity for the oxidative
dehydrogenation of propane to
propylene with only negligible CO2
formation. The active BNO site,
Edge Hydroxylated Boron Nitride for
Oxidative
Dehydrogenation
of
Propane to Propylene
generated
dynamically
through
hydrogen abstraction of B-OH groups
by molecular oxygen, triggered
propane
selectively breaking the C-H bond but
simultaneously avoided further
propylene oxidation towards CO2.
dehydrogenation
by
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