Turning Waste into Value: Potassium-Promoted Red Mud as an Effective Catalyst for the Hydrogenation of CO2

Article abstract of DOI:10.1002/cssc.202000242

Since 1887, red mud has been an unavoidable waste derived from the production of alumina in the Bayer process. Because of its high alkalinity and metal loading, red mud disposal and storage constitute a significant environmental risk. With worldwide storage capacity reaching its limits and no alternatives to the Bayer Process, the development of methods for the valorization of red mud is a must. In this study, red mud is converted into an efficient catalyst for the valorization of CO₂. By simple potassium promotion, 45 % conversion of CO₂ with a light olefin (C₂–C₄) selectivity of 36 % is achieved at 375 °C, 30 bar, and 9600 mL g^?1 h^?1, matching the performance of some of the best catalysts reported to date.

Full text of DOI:10.1002/cssc.202000242

Chemistry–Sustainability–Energy–Materials
Accepted Article
Title: Turning waste into value: potassium-promoted Red Mud as an
effective catalyst for the hydrogenation of CO2
Authors: Artem Russikikh, Genrikh Shterk, Bandar Solami, Bandar
Fadhel, Adrian Ramirez, and Jorge Gascon
This manuscript has been accepted after peer review and appears as an
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To be cited as: ChemSusChem 10.1002/cssc.202000242
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0
1/2020

ChemSusChem
10.1002/cssc.202000242
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Turning waste into value: potassium-promoted Red Mud as an
effective catalyst for the hydrogenation of CO
2
a
a
b
b
a
Artem Russkikh , Genrikh Shterk , Bandar H. Al-Solami , Bandar A. Fadhel , Adrian Ramirez , and
Jorge Gascon*,a
Abstract: Since 1887 Red Mud is an unavoidable waste derived from
the production of alumina in the Bayer process. Because of its high
alkalinity and metal loading, Red Mud disposal and storage constitute
an important environmental risk. With worldwide storage capacity
reaching its limits and no alternatives to the Bayer Process, the
development of methods for the valorization of Red Mud is a must.
Here, we demonstrate that Red Mud can be turned into an efficient
with renewable hydrogen,[10] could present a turning point as two
wastes (CO and Red Mud) could be valorized at the same time
making use of renewable energy. Mostly two different
thermocatalytic routes have been proposed to convert CO into
highly demanded products[11-13]: (i) it can be hydrogenated into
methanol that can be further converted to olefins or aromatics
over a zeolite in a bifunctional configuration,[14, 15] or, (ii) it can be
converted over an Fe catalyst via reverse water gas shift (RWGS)
2
2
catalyst for the valorization of CO
2
. By a simple potassium promotion,
4
5% conversion of CO with a light olefin (C
2
2
-C ) selectivity of 36%
4
2
to CO and H which will be further converted into a variety of
-
1
-1
has been achieved at 375 ºC, 30 bar and at 9600 mL·g ·h , matching
the performance of some of the best catalysts reported to date.
hydrocarbons following a typical Fischer-Tropsch synthesis (FTS)
mechanism.[15] The main advantage of the Fe route is the low
undesired CO selectivity coupled with the large range of
hydrocarbons.[16] Catalysts promoted with potassium which
increase selectivity to light olefins are especially interesting.[
Moreover, light olefins market is expected to reach 475.8 million
USD at the end of 2027, with an annual growth rate of 5.85%.[
Here, we demonstrate that, via potassium promotion, Red Mud
17]
Introduction
18]
With the constant world population growth (expected to reach 8.6
[
1]
billion in 2030, 9.8 billion in 2050 and 11.2 billion in 2100 ), waste
management has become one of the biggest challenges of our
society. The storage of industrial hazardous wastes is considered
particularly challenging by the scientific community. Among them,
Red Mud is one of the most critical, being already the cause of
severe ecological accidents.[2] This waste is generated during
alumina production in the Bayer process, responsible for more
than 95% of all alumina produced in the world. In this process, for
one ton of aluminum oxide produced 0.3 to 2.5 tons of residues
are co-generated.[3] As a consequence, 155 million tons of Red
Mud are being created annually[4] with worldwide storage capacity
already exceeded over 3.5 billion tons in 2014.[5] The typical
disposal and storage methods for Red Mud are marine, lagooning,
dry stacking and dry cake disposal.[6] However, Red Mud
solutions are highly alkaline (pH range from 10 to 13), have a
considerable metal content and, therefore, the potential leach into
the soil represents a real danger for our environment.[7]
can be turned into an efficient catalyst for the valorization of CO
4
achieving a 45% conversion of CO with a light olefin (C -C )
selectivity of 36% at 375 ºC, 30 bar and at 9600 mL·g ·h ,
matching the performance of some of the best catalysts reported
to date.
2
2
2
-1 -1
Results and Discussion
Red Mud characterization
We first performed X-ray Fluorescence (XRF) analysis to
investigate the elemental composition of our Red Mud sample, as
the composition can vary depending on the country of origin.[
Our results show that the Red Mud employed in this study
contains 14.3% of Na, 15.0% of Al, 15.5% of Si, 0.8% of S, 0.1%
of K, 2.1% of Ca, 3.6% of Ti and 6.4% of Fe. However, analysis
of different areas shows a great heterogeneity within the sample
9]
Nevertheless, the presence of different metals in Red Mud could
potentially allow its use as a catalyst. In this line of research
(
spectra of 4 different measurements can be found in
[
8,
several attempts have been made by the scientific community,
supplementary information, Figure S1), being in range with the
reported typical compositions.[4] The high iron content confirms
that, indeed, Red Mud can be a real catalyst candidate for the
9
]
but still no real application of Red Mud has been found. Among
all possible applications, CO valorization, only when carried out
2
hydrogenation of CO
2
. Additionally, the presence of Na and traces
of K can be beneficial for olefin production.[ Moreover, Ti can
19]
[
a]
A. Russkikh, G. Shterk, A. Ramirez, J. Gascon.
KAUST Catalysis Center (KCC), Advanced Catalytic Materials.
King Abdullah University of Science and Technology (KAUST).
Thuwal 23955, Saudi Arabia.
E-mail: jorge.gascon@kaust.edu.sa
Bandar H. Al-Solami, Bandar A. Fadhel.
potentially improve catalytic performance of Fe in the FTS
synthesis.[20] Finally, the high content of Al in the sample shows
the limitation of the Bayer process, with almost 17% of aluminum
left unrefined.
[
b]
Carbon Management Research Division, Research & Development
Center. Saudi Aramco, Dhahran, Saudi Arabia.
Scanning Electron Microscopy (SEM) revealed highly roughened
particles of 50 to 200 µm in size (see Figure S2). The elemental
distribution of these particles shows certain agreement with the
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ChemSusChem
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XRF characterization, pointing out again the heterogeneity of the
sample (see Table S1). A better picture of the Red Mud
composition can be observed by performing elemental mappings
(
see Figure 1), where several segregated phases can be
distinguished: one containing Na, Si and Al, one containing Fe
and one containing Ti. Oxygen is well distributed across whole
particle. In accordance with the EDS-SEM data, X-ray Diffraction
Spectroscopy (XRD) revealed several crystalline phases:
Gibbsite (Al(OH) ), Perovskite (CaTiO ), Hematite (Fe O ) and
3 3 2 3
Cancrinite (hydrate of carbonate and silicate of sodium, calcium
and aluminum) (see Figure 2).
Figure 2. XRD spectra of Red Mud and simulated diffractograms of Gibbsite,
Perovskite, Hematite and Cancrinite (PDF 04-011-1369, PDF 04-007-5451,
PDF 01-089-0596 and PDF 01-075-8617 correspondingly).
Red Mud as catalyst for the hydrogenation of CO
2
The catalytic performance of Red Mud and Red Mud promoted
with K can be found on Figure 3. We can observe that, as
expected from the above characterization, the unpromoted Red
Mud is active in the hydrogenation of CO
2
at all the temperatures
studied (see Figure 3a), specially at relatively high temperatures:
-1
-1
under the studied reaction conditions (30 bar, 9600 mL·g ·h )
raising the reaction temperature from 325 to 375 °C increased the
2 2 4
conversion of CO from 25% to 42% and the selectivity to C -C
olefins from 4% to 15%. This performance was stable during for
at least 50 h.
As it is already known for this reaction, promotion with K
drastically enhances the selectivity to olefins (see Figure 3b) by
favoring CO
2
adsorption and decreasing the hydrogenation
strength of Fe.[
23]
After promotion, selectivity to light olefins
increases up to 36% at 350 °C and even higher conversions are
achieved (up to 45% at 375 °C) while catalyst stability remains
unchanged. The selectivity to CO for the unpromoted Red Mud
decreases with increasing the reactor temperature (from 30% at
325°C to 16% at 375 °C, see Figure S6). On the other hand, for
the K promoted samples, similar values are obtained regardless
of the temperature (circa 20-25%). This behavior is in line with our
previous observations[23]: when K promoted, temperature has little
effect in the overall CO selectivity.
Figure 1. Elemental EDS-SEM mapping of a Red Mud particle.
Transmission Electron Microscopy (TEM) showed the presence
of particles with different sizes from around 10 to 80 nm and
agglomerates with sizes from 500 nm to several µm (see Figure
S4). Nitrogen physisorption at 77 K of Red Mud revealed a type
V isotherm with H3 hysteresis[21] (see Figure S5). The BET area
We further evaluated the effect of K loading (see Figure 3c). After
2
8 hours on stream, at nearly isoconversion, selectivity to C
olefins increases from 15% for the unpromoted sample to 22%,
0% and 36% for samples containing 0.5, 1.0 and 2.0 wt % K
2 4
-C
3
correspondingly. In addition, increasing the K content also leads
to an increase of the formation of higher hydrocarbons (C5+). This
phenomena is also observed by the increasing of alpha from 0.42
to 0.57 (see Figure S7).[ Again, this behavior is in line with our
previous observations[23]: increasing the K content will lead to a
decrease in the hydrogenation activity of Fe and therefore to the
preference formation of olefins that may re-adsorb and allow
2
-1
of the Red Mud studied was 12 m ·g , in line with other Red Mud
measurements.[22]
24]
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ChemSusChem
10.1002/cssc.202000242
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further chain growth.[25] The detailed product distribution of the K
promoted and unpromoted samples can be found on Figure 3d.
Finally, we also investigated the effect of the type of K precursor
the performance of both precursors is very similar, with K
showing a slightly better C -C olefins selectivity at the same
conversion level (see Figure S8).
2 3
CO
2
4
2 3
by comparing KOH and K CO as its source. Our data show that
Figure 3. Catalytic results of Red Mud and K promoted Red Mud in the hydrogenation of CO
and 375 °C for Red Mud; b) CO conversion and selectivity to C -C olefins at 325 °C, 350 °C and 375 °C for Red Mud promoted with 2 wt % of K from K
Product distribution for Red Mud and Red Mud promoted with K from K CO after 28 h TOS; d) Detailed product distribution of the Red Mud and Red Mud promoted
with 2 wt % of K from K CO after 25 h TOS. Reaction conditions: 350 °C, 30 bar, CO
2
. a) CO
2
conversion and selectivity to C
2
-C
4
olefins at 325 °C, 350 °C
2
2
4
2
CO ; c)
3
2
3
2
3
2 2
:H .
=1:3, and 9600 mL·g−1·h
−1
XRD after reaction revealed that iron partially reduces under
reaction conditions (from FeIII to Fe , see Figure 4a). This
reduction is accompanied with decreasing of peak intensities
related to Hematite and increasing the ones related to Magnetite.
If we look in detail at the 30 to 50 2θ degree region, we can
observe that iron carbide is formed during the reaction[26] (see
Figure 4b). Finally, no significant differences were found in the
phase distribution by comparing spectra of samples with and
without K promotion. Comparison of XPS spectra before and after
reaction points out the same direction (see Figure 4c): the content
of iron carbide increases after reaction for both samples. In
addition, Red Mud samples contain a variety of different iron
Fe[27-30] (Table S3). Similarly to the XRD, K promotion does not
change the distribution of iron species according to XPS.Similarly
to the XRD, K promotion does not change the distribution of iron
species according to XPS.
TGA-MS analysis of the spent and fresh catalyst samples is
shown in Figure S9. Comparison among catalysts before and
after reaction reveals differences that are associated to the
chemical change in the structure of the catalyst upon reaction
conditions and that discard the formation of coke, that would
II
2 2
normally be identified by an overlap between H O and CO (18
and 44 mass-to-charge ratio). For fresh samples, evolution of
water is obvious between 200 and 500°C and can be attributed to
the decomposition of Gibbsite[31], phase absent after reaction, as
3 2 3 2 4
compounds, such as Fe C, Fe O , FeO, K FeO , and metallic
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ChemSusChem
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observed by XRD analysis. In case of the fresh promoted Red
these iron oxides are the active species for the RWGS reaction.[24]
Furthermore, these oxides are reactants for the carbide formation,
which is the selective phase for the hydrocarbon synthesis via FT.
Mud, evolution of CO
decomposition of KHCO
together with the absence of considerable amounts of H
2
and H
2
O at 120°C is associated with the
in spent samples,
O is
3
. The evolution of CO
2
2
Next, the basicity and CO
catalysts was studied by CO
of promoted and unpromoted Red Mud revealed that potassium
incorporation leads to an increase of the CO
adsorbed[23] (see
2
adsorption behavior of the different
associated to the oxidation of iron carbide, which is more
abundant in case of promoted samples.
Following, TPR was performed on Red Mud and 2 wt % with K
promoted Red Mud (see Figure S10). Several differences could
be observed upon comparing both samples: (i) peaks below
2
and H TPD. As expected, CO TPD
2
2
2
Figure S11). The two peaks observed can be attributed to
moderately (200-500 °C) and strong basic sites (500-800 °C).[
It is worth noting that the unprompted Red Mud shows already the
presence of basic sites derived from the presence of Na and Ca
37]
1
20 °C for
K
promoted sample, which arise from the
decomposition of KHCO
3
that starts at 67 °C[ ; (ii) peaks in the
32]
region from ~370 °C to ~730 °С, which come from the reduction
of iron species: reduction of Hematite (Fe ) into Magnetite
Fe ) at 420 °C (vs. 450 °C for the promoted sample), broad
reduction of Magnetite to iron monoxide from 510 °C to 720 °C
2
in the material. The H TPD showed two main peaks at around
2
O
3
430°C and 490°C[38] with a noticeable signal decrease for the K
promoted sample. These results are in line with our previous
(
3 4
O
2
observations of potassium promotion reducing H .
adsorption[23]
(
vs. from 530 °C to 730 °C for the promoted sample); after that,
Altogether, we can conclude that during reaction the selective
carbide phase formation takes place and that, in line with previous
works, the main K role is likely to be that of an electronic
the reduction to metallic Fe at 750 °C.[33-35] In line with the
literature, the addition of K shifts reduction temperature of iron
oxide species to higher temperatures.[36] Unlike the metallic phase, modulator.
Figure 4. Characterization of Red Mud and Red Mud promoted with 2% of K after reaction at 350 °C, 30 bar and 50 hours TOS a) XRD results of iron containing
phases of samples before and after catalytic reaction (PDF 01-089-0596, PDF 04-012-7038, PDF 04-014-4562 diffractograms were used for Hematite, Magnetite
and iron carbide phases correspondingly); b) 30 to 50 2θ degree region of samples before and after catalytic reaction; c) XPS analysis results of samples before
and after catalytic reaction.
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Last but not least, if we compare the data reported in this work
with the state of the art iron-based catalysts published for this
application[23, 26, 39-54] (see Table S4), we can observe that Red
Spectroscopy (EDS) analysis was done by using a TEAM™ EDS analysis
system provided by EDAX® at 20 or 30 kV and 3.2 or 13 nA current.
Distance between beam gun and sample was 10 mm. Samples’ drift was
less than 2% during EDS sessions. Dead time was in the 30-40% range.
Mud outperforms most of them and only our recent Fe MOF-
mediated catalyst[23] displays a higher space time yield into olefins
X-ray Diffraction Spectroscopy (XRD) was performed on a Brucker® D8
Advance. The source of X-ray radiation was CuKα and the analysis was
performed in a 2θ range from 10 to 80°. X-ray voltage was set to 40 kV,
current was 40 mA. The crystalline phase was identified by comparison
with Powder Diffraction File™ (PDF®), from the International Center for
Diffraction Data. Elimination of fluorescence and Kβ radiation was done by
using a LYNXEYE XE-T detector.
-1
(
31.8 vs. 16.6 mmolC2-C4=·gcat-1·hour ). Furthermore, we
compared the Red Mud sample with commercially available iron
III) oxide (see experimental section and Table S5). Our results
(
show that both catalysts display similar performance, although
Red Mud sample is slightly superior. Nevertheless, this simple
catalyst made by commercial iron oxide is still superior to most of
catalysts of Table S4. These critical observations highlight the
importance of rational design when developing complex (and
expensive) supported CO to olefins catalysts: iron waste or even
2
plain iron oxide are likely to be superior by just a simple potassium
promotion.
Transmission Electron Microscopy (TEM) was conducted on a FEI®
Tecnai Twin microscope in the bright field mode. Prior to study, samples
were grinded and sonicated in ethanol, then 2 µL of its solution was put on
the carbon film (Electron Microscopy Sciences®, Prod. FCF400-CU).
Filament voltage was set to 120 kV.
Nitrogen physisorption at 77 K study was conducted on a Micrometrics®
ASAP 2420 analysis system. Samples were degassed to 67 Pa at 1330
Pa·s-1 rate, then hold for 60 min. Following, a temperature ramp was
Conclusions
performed at 10 °C·min-1 rate until 300 °C, then held for 12 h. The N
In summary, Red Mud seems a very promising candidate for the
2
0
-1
adsorption isotherm was measured between p·(p ) ꢀ=ꢀ0.01–0.95. BET
conversion of CO
2
to olefins. By a simple potassium promotion,
5% conversion of CO with a light olefin (C -C ) selectivity of
6% has been achieved at 375 ºC, 30 bar and at 9600 mL·g ·h ,
0
surface area was calculated between p to p ꢀratio inꢀ0.05−0.30 range.
4
3
2
2
4
-1
-1
Catalytic tests were conducted in a 16 channel Flowrence® Avantium
setup. The reactors are standard steel with an inner diameter of 2.3 mm.
Typically, 50 mg of catalyst were placed per reactor. The reaction feed had
matching the performance of some of the best catalysts reported
to date. We hope that these results will motivate the scientific
community to take a step further in the valorization of industrial
waste in catalytic applications.
7
2 2
2% of H , 24% of CO and 4% of He as a standard. The ratio between
-1 -1
gas flow and mass of catalyst was maintained at 9600 mL·g ·h per
channel. One of the 16th channels was used without catalyst as a blank.
The reaction was studied at 325 °C, 350 °C and 375 °C, while the pressure
was maintained at 30 bar. Prior to feeding the reaction mixture all samples
Experimental Section
were pretreated in situ with a pure H
and 3 bar. After that, the tubes were pressurized using a membrane-based
pressure controller. CO conversion (X, %), selectivity (S, %), and space
2
atmosphere for 4 hours at 350 °C
Red Mud was kindly provided by Saudi Aramco. Samples with 0.5, 1.0, 2.0
wt % of K were prepared by suspension in K
2
2 3
CO (Aldrich, 99.9%) or KOH
-
1
-1
time yields (STY, mmol·gcat ·h ) were calculated using the following
formulas:
(Aldrich, 99.9%) solutions. The amount of added water was minimal for
making a suspension of Red Mud. In a typical synthesis, 170 mg of Red
Mud and the appropriate amount of K precursor were mixed in 0.7 mL of
ꢁ(퐻푒
)∙ꢁꢂꢁꢃ
ꢄ푅
ꢅ
푏푙푎푛푘
푋(퐶푂 ) = ꢀ1 −
ꢅꢆ ∙ 100
2
2
deionized H O in a 25 mL round-bottom flask. Then, the flask with the
ꢁ(퐻푒푅)∙ꢁꢂꢁꢃꢄ푏푙푎푛푘
solution was connected to a rotatory evaporator at 90 rpm rate under 200
mbar pressure and 70 °C for 60 minutes. After evaporation, samples were
dried in the oven using a heating rate of 5 °C·min-1 until 100 °C and held
at this temperature for 12 h. Iron (III) oxide nanopowder (<50 nm particle
size, Aldrich) was used for comparison purposes. K promotion was done
in a similar way as in the Red Mud samples.
ꢇ∙ꢁ(ꢁ푛)
푆(퐶 ) =
∙ 100
ꢇ
∑
푥ꢂꢇ∙ꢁ(ꢁ푛)ꢅ
ꢈ(ꢁꢃꢄ)∙ꢉ(ꢁ푛)∙ꢉ푉∙ꢊ.24
ꢋ
푆푇푌(퐶 ) =
∙
ꢇ
22.4
ꢋꢊꢊꢊꢊ
where C(Heblank), C(CO2R), C(He
R
), C(CO2blank) are the concentrations of
in the outlet of the reactor, He in the outlet
in the blank one determined by GC analysis
) is the concentration of the product with n carbon atoms
in the reactor outlet determined by GC analysis, x is the total number of all
the He in the blank reactor, CO
of the reactor and CO
respectively; C(C
2
X-ray Fluorescence (XRF) analysis was performed on a Horiba® XGT-
2
7
200. The X-ray tube is equipped with a Rh target, voltage was set at 30
kV, no X-ray filter was used, and analysis preset time was 400 s. Before
measurement, samples were placed on double-sided tape
NICETACK™, Prod. No NW-15) and then put into the chamber, which
n
-
1
-1
a
analyzed products; SV is the space velocity calculated in mL·gcat ·h ,
and 0.24 is the CO molar concentration in the blank reactor. Gas
(
2
was then degassed. An average of four measurements per sample were
taken.
Chromatograph is an Agilent 7890B with two sample loops. One sample
loop goes to Thermal Conductivity Detector (TCD) channel with 2 Haysep
2 4
pre-column and MS5A, where He, H , CH and CO are separated. Another
sample loop goes to an Innowax pre-column (5m, 0.20MM OD, 0.4 uM
film), first 0.5 min of the method the gases coming from pre-column are
sent to Gaspro column (Gaspro 30M, 0.32 MM OD) followed by Flame
Ionization Detector (FID). Gaspro column separates C -C , parafins and
1 8
olefins. After 0.5 min, valve is switched and gases are sent to Innowax
column (45 m, 0.2 MM OD, 0.4 uM) followed by FID. Innowax separates
Scanning Electron Microscopy (SEM) was performed on a FEI® Teneo VS
microscope in the optiplan mode using the Everhart-Thornley detector.
Samples were placed on a double-sided carbon tape (PELCO Tabs™,
Prod. No 16084-1) on the aluminum stub prior to SEM characterization.
No additional coating was applied. Distance between beam gun and
sample was maintained at 10 mm. Accelerating voltage and beam current
were set to 5 kV and 50 pA correspondingly. Energy-Dispersive X-ray
9
oxygenates, larger paraffins and olefins (>C ) and aromatics BTX and C9+
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ChemSusChem
10.1002/cssc.202000242
FULL PAPER
aromatics. The front FID also has the possibility for CO and CO
measurement after CO and CO is converted to CH with a Ni based
2 4
methanizer. The error found in carbon balance was smaller than 2.5%.
Oxygenates selectivity was lower than 0.5% in all samples.
2
[3]
[4]
International Aluminium Institute, European Aluminium Association,
2015, p. 31.
International Aluminium Institute, European Aluminium Association,
2018, p. 56.
[
5]
S. Xue, F. Zhu, X. Kong, C. Wu, L. Huang, N. Huang, W. Hartley, Environ.
Sci. Pollut. Res. 2016, 23, 1120-1132.
The surface chemical composition of the powder samples was analyzed
using high resolution X-ray Photoelectron Spectroscopy (XPS) on a Kratos
Axis Ultra DLD spectrometer equipped with a monochromatic AlKα X-ray
source (hν=1486.71 eV) operating at 150 W, under ultra-high vacuum
[
[
6]
7]
G. Power, M. Gräfe, C. Klauber, Hydrometallurgy 2011, 108, 33-45.
S. Ruyters, J. Mertens, E. Vassilieva, B. Dehandschutter, A. Poffijn, E.
Smolders, Environ. Sci. Technol. 2011, 45, 1616-1622.
B. Qiu, N. Deng, Y. Zhang, H. Wan, Asia-Pac. J. Chem. Eng. 2018, 13,
e2150.
~10−9 mbar). Measurements were taken in hybrid mode using
[8]
(
electrostatic lenses, and the take-off angle was 0°. All spectra were
recorded using an aperture slot of 300×700 μm. The survey and high-
resolution spectra were collected at fixed analyzer pass energies of 160
eV and 20 eV respectively. For charge neutralization source of the low
energy electrons was applied. As a reference for spectrum calibration, the
C1s peak with binding energy 285.0 eV was used. The data was analyzed
using commercially available software, CasaXPS v.2.3.19.
[
[
[
9]
S. Sushil, V. S. Batra, Appl. Catal., B 2008, 81, 64-77.
10] G. Glenk, S. Reichelstein, Nat. Energy 2019, 4, 216-222.
11] H. Yang, C. Zhang, P. Gao, H. Wang, X. Li, L. Zhong, W. Wei, Y. Sun,
Catal. Sci. Technol. 2017, 7, 4580-4598.
[
12] A. Álvarez, A. Bansode, A. Urakawa, A. V. Bavykina, T. A. Wezendonk,
M. Makkee, J. Gascon, F. Kapteijn, Chem. Rev. 2017, 117, 9804-9838.
13] C. F. Shih, T. Zhang, J. Li, C. Bai, Joule 2018, 2, 1925-1949.
14] Z. Ma, M. D. Porosoff, ACS Catal. 2019, 9, 2639-2656.
[
[
[
Thermal Gravimetric Analysis (TGA) coupled with Mass Spectroscopy
15] A. Dokania, A. Ramirez, A. Bavykina, J. Gascon, ACS Energy Lett. 2019,
(MS) was performed on Mettler Toledo® TGA/DSC 1 STARe System and
4, 167-176.
ThermoStar™ GSD 320 T3 correspondingly. 10 mg of sample were placed
into 70 µL alumina crucible. Then, sample was heated in 30 mL·min-1 flow
of air with 10°C·min-1 rate from 40°С to 800°C. The gases were analyzed
on the Faraday detector in Multiple Ion Detection mode.
[16]
T. Riedel, H. Schulz, G. Schaub, K.-W. Jun, J.-S. Hwang, K.-W. Lee, Top.
Catal. 2003, 26, 41-54.
[
[
[
17] D. L. King, J. B. Peri, J. Catal. 1983, 79, 164-175.
18] Kenneth Research, (Ed.: D. Dooley), 2019.
19] H. Yang, C. Zhang, P. Gao, H. Wang, X. Li, L. Zhong, W. Wei, Y. Sun,
Catalysis Science & Technology 2017, 7, 4580-4598.
Temperature-Programmed Reduction (TPR) was performed on
a
Micrometrics® Autochem 2920 setup. 50 mg of sample were placed in the
U-shaped quartz reactor between two layers of quartzwool. Following, 50
mL·min-1 of He flow were introduced for 15 min. Then, flow was changed
[
[
20] V. P. Santos, L. Borges, S. Sartipi, B. Van der Linden, A. I. Dugulan, A.
Chojecki, T. Davidian, M. Ruitenbeek, G. R. Meima, F. Kapteijn, M.
Makkee, J. Gascon, Appl. Catal., A 2017, 533, 38-48.
to 50 mL·min-1 of 10% H
°C·min-1 temperature rate until 800 °C. Analysis of exhaust gases was
performed on a TCD.
in Ar. Sample was afterwards heated with
2
21] M. Thommes, K. Kaneko, V. Neimark Alexander, P. Olivier James, F.
Rodriguez-Reinoso, J. Rouquerol, S. W. Sing Kenneth, in Pure Appl.
Chem., Vol. 87, 2015, p. 1051.
5
[
[
22] M. Gräfe, C. Klauber, Hydrometallurgy 2011, 108, 46-59.
23] A. Ramirez, L. Gevers, A. Bavykina, S. Ould-Chikh, J. Gascon, ACS
Catal. 2018, 8, 9174-9182.
Temperature-Programmed Desorption (TPD) of
H
2
and CO
2
was
performed on Altamira Instruments® AMI-200 IP setup. 200 mg of sample
were placed in the U-shaped quartz reactor between two layers of
quartzwool. First, 40 mL·min-1 of Ar flow were introduced for 5 min.
[
[
24] G. P. Van Der Laan, A. A. C. M. Beenackers, Catal. Rev.: Sci. Eng. 1999,
41, 255-318.
Following, flow was changed to 32 mL·min-1 of pure H
Next, sample was heated with 5 °C·min-1 rate until 350 °C, and held at this
temperature 4 hours under the H flow. Afterwards, the sampled was
cooled down in 40 mL·min-1 of Ar to 50 °C and held at this temperature for
hours. For adsorption of CO or H or 25%
40 mL·min-1 flow of pure H
CO in He were introduced into the reactor at 50 °C for 2 hours. Then, 40
for 20 minutes.
2
25] V. P. Santos, T. A. Wezendonk, J. J. D. Jaén, A. I. Dugulan, M. A.
Nasalevich, H.-U. Islam, A. Chojecki, S. Sartipi, X. Sun, A. A. Hakeem,
A. C. J. Koeken, M. Ruitenbeek, T. Davidian, G. R. Meima, G. Sankar, F.
Kapteijn, M. Makkee, J. Gascon, Nat. Commun. 2015, 6, 6451.
2
2
2
2
2
[
26] A. Ramirez, S. Ould-Chikh, L. Gevers, A. D. Chowdhury, E. Abou-Hamad,
A. Aguilar-Tapia, J.-L. Hazemann, N. Wehbe, A. J. Al Abdulghani, S. M.
Kozlov, L. Cavallo, J. Gascon, ChemCatChem 2019, 11, 2879-2886.
27] C. Myers, H. Franzen, J. Anderegg, Inorg. Chem. 1985, 24, 1822-1824.
28] I. N. Shabanova, V. A. Trapeznikov, J. Electron Spectrosc. Relat.
Phenom. 1975, 6, 297-307.
2
-
1
mL·min of Ar flow were fed for 60 minutes at to get rid of unadsorbed
species. Finally, desorption was studied with 5 °C·min-1 heating rate until
[
[
800 °C. Analysis of gases was performed on a TCD with Ar using as a
reference gas.
[
[
29] N. S. McIntyre, D. G. Zetaruk, Anal. Chem. 1977, 49, 1521-1529.
30] H. Konno, M. Nagayama, J. Electron Spectrosc. Relat. Phenom. 1980,
1
8, 341-343.
31] J. T. Kloprogge, H. D. Ruan, R. L. Frost, J. Mater. Sci. 2002, 37, 1121-
129.
Acknowledgements
[
[
[
1
Funding for this work was provided by King Abdullah University of
Science and Technology (KAUST).
32] M. Hartman, K. Svoboda, B. Čech, M. Pohořelý, M. Šyc, Ind. Eng. Chem.
Res. 2019, 58, 2868-2881.
33] R. C. C. Costa, F. C. C. Moura, P. E. F. Oliveira, F. Magalhães, J. D.
Ardisson, R. M. Lago, Chemosphere 2010, 78, 1116-1120.
34] S. F. Kurtoğlu, A. Uzun, Sci. Rep. 2016, 6, 32279.
Keywords: Heterogeneous catalysis • Waste chemistry • Red
[
[
[
2
Mud • CO conversion • Olefins
35] S. Ordóñez, H. Sastre, F. V. Dıe
36] S. C. Ndlela, B. H. J. I. Shanks, e. c. research, Ind. Eng. Chem. Res.
003, 42, 2112-2121.
́
z, Appl. Catal., B 2001, 29, 263-273.
[
[
1]
2]
United Nations, Vol. Volume I: Comprehensive Tables, New York, 2017,
p. 346.
2
[
[
37] W. Cai, Q. Chen, F. Wang, Z. Li, H. Yu, S. Zhang, L. Cui, C. Li, Catal.
Lett. 2019, 149, 2508-2518.
D. Winkler, A. Bidló, B. Bolodár-Varga, Á. Erdő, A. Horváth, Sci. Total
Environ. 2018, 644, 1292-1303.
38] L. Huazhang, L. Caibo, L. Xiaonian, C. Yaqing, Ind. Eng. Chem. Res.
2003, 42, 1347-1349.
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.202000242
FULL PAPER
[
[
[
39] F. Ding, A. Zhang, M. Liu, Y. Zuo, K. Li, X. Guo, C. Song, Ind. Eng. Chem.
Res. 2014, 53, 17563-17569.
40] S. Hu, M. Liu, F. Ding, C. Song, G. Zhang, X. Guo, J. CO
2
Util. 2016, 15,
89-95.
41] C. G. Visconti, M. Martinelli, L. Falbo, A. Infantes-Molina, L. Lietti, P.
Forzatti, G. Iaquaniello, E. Palo, B. Picutti, F. Brignoli, Appl. Catal., B
2017, 200, 530-542.
[
[
[
[
42] S.-S. Nam, S.-J. Lee, H. Kim, K.-W. Jun, M.-J. Choi, K.-W. Lee, Energy
Convers. Manage. 1997, 38, S397-S402.
43] M. Albrecht, U. Rodemerck, M. Schneider, M. Bröring, D. Baabe, E. V.
Kondratenko, Appl. Catal., B 2017, 204, 119-126.
44] J. Liu, A. Zhang, M. Liu, S. Hu, F. Ding, C. Song, X. Guo, J. CO
017, 21, 100-107.
45] J. Liu, Y. Sun, X. Jiang, A. Zhang, C. Song, X. Guo, J. CO
5, 120-127.
2
Util.
2
2
Util. 2018,
2
[
[
46] Z. You, W. Deng, Q. Zhang, Y. Wang, Chin. J. Catal. 2013, 34, 956-963.
47] Y. H. Choi, Y. J. Jang, H. Park, W. Y. Kim, Y. H. Lee, S. H. Choi, J. S.
Lee, Appl. Catal., B 2017, 202, 605-610.
[
[
48] P. H. Choi, K.-W. Jun, S.-J. Lee, M.-J. Choi, K.-W. Lee, Catal. Lett. 1996,
40, 115-118.
49] L. M. Chew, P. Kangvansura, H. Ruland, H. J. Schulte, C. Somsen, W.
Xia, G. Eggeler, A. Worayingyong, M. Muhler, Appl. Catal., A 2014, 482,
1
63-170.
50] S.-S. Nam, H. Kim, G. Kishan, M.-J. Choi, K.-W. Lee, Appl. Catal., A
999, 179, 155-163.
51] J. Wei, J. Sun, Z. Wen, C. Fang, Q. Ge, H. Xu, Catal. Sci. Technol. 2016,
, 4786-4793.
52] W. Wang, X. Jiang, X. Wang, C. Song, Ind. Eng. Chem. Res. 2018, 57,
535-4542.
[
[
[
[
1
6
4
53] T. Numpilai, N. Chanlek, Y. Poo-Arporn, S. Wannapaiboon, C. K. Cheng,
N. Siri-Nguan, T. Sornchamni, P. Kongkachuichay, M. Chareonpanich,
G. Rupprechter, J. Limtrakul, T. Witoon, Appl. Surf. Sci. 2019, 483, 581-
592.
[
[
[
54] J. Liu, A. Zhang, X. Jiang, G. Zhang, Y. Sun, M. Liu, F. Ding, C. Song, X.
Guo, Ind. Eng. Chem. Res. 2019, 58, 4017-4023.
55] I. T. Burke, W. M. Mayes, C. L. Peacock, A. P. Brown, A. P. Jarvis, K.
Gruiz, Environ. Sci. Technol. 2012, 46, 3085-3092.
56] J. F. Moulder, J. Chastain, Handbook of X-ray Photoelectron
Spectroscopy: A Reference Book of Standard Spectra for Identification
and Interpretation of XPS Data, Physical Electronics Division, Perkin-
Elmer Corporation, 1992.
This article is protected by copyright. All rights reserved.

ChemSusChem
10.1002/cssc.202000242
FULL PAPER
Table of Contents
FULL PAPER
Red Mud can be turned into an
efficient catalyst for the valorization of
Artem Russkikh, Genrikh Shterk, Bandar
H. Al-Solami, Bandar A. Fadhel, Adrian
Ramirez, and Jorge Gascon*
CO
potassium promotion, high selectivity
to C -C olefins can be achieved at
2
into hydrocarbons. By a simple
Page No. – Page No.
2
4
high conversion levels. With a stable
catalyst operation, red mud matches
the performance of some of the best
catalysts reported to date.
Turning waste into value: potassium-
promoted Red Mud as an effective
catalyst for the valorization of CO
2
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