Catalytic transformation of ethanol to methane and butene over NiO NPs supported over mesoporous SBA-15

Article abstract of DOI:10.1016/j.mcat.2020.111381

Hexagonally ordered mesoporous silica material SBA-15 with thick pore wall is an ideal catalytic support for immobilizing reactive tiny metal oxide nanoparticles (NPs) due to its large pore size, high specific surface area, excellent feasibility for the i

Full text of DOI:10.1016/j.mcat.2020.111381

Molecular Catalysis 502 (2021) 111381
Contents lists available at ScienceDirect
Molecular Catalysis
journal homepage: www.journals.elsevier.com/molecular-catalysis
Catalytic transformation of ethanol to methane and butene over NiO NPs
supported over mesoporous SBA-15
Sauvik Chatterjeea, Kushanava Bhadurib, Arindam Modaka, Manickam Selvarajc,
,
,
Rajaram Bald, Biswajit Chowdhuryb *, Asim Bhaumika *
a School of Materials Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata, 700 032, India
b Department of Chemistry, Indian Institute of Technology (ISM), Dhanbad, Dhanbad 826004, Jharkhand, India
c Department of Chemistry, Faculty of Science, King Khalid University, Abha 61413, Saudi Arabia
d Nanocatalysis Area, Light Stock Processing Division, CSIR-Indian Institute of Petroleum, Dehradun 248005, Uttarakhand, India
A R T I C L E I N F O
A B S T R A C T
Keywords:
Hexagonally ordered mesoporous silica material SBA-15 with thick pore wall is an ideal catalytic support for
immobilizing reactive tiny metal oxide nanoparticles (NPs) due to its large pore size, high specific surface area,
excellent feasibility for the immobilization of NPs and robust nature of the mesoporous framework. NiO@SBA-15
nanocomposite material has been synthesised through non-ionic surfactant assisted hydrothermal synthesis of
SBA-15 followed by calcination, functionalization and impregnation. The material has been thoroughly char-
acterized by using powder XRD, N2 sorption, XPS and NH3-TPD. NiO@SBA-15 with ca. 13 % Ni(II) loading
displayed specific surface area of 409 m2 gꢀ 1 and weak surface acidity. NiO@SBA-15 showed good catalytic
Mesoporous SBA-15
Immobilization of NiO NPs
Dehydrogenation of ethanol
Hydrocarbon fuels
Hydrogen production
̊
activity for conversion of ethanol to hydrocarbon fuels, specifically C1 and C4 hydrocarbons at 300 C together
with the production of hydrogen in almost stoichiometric amount. Further increase in the reaction temperature
favoured cracking to yield methane as the major product. Supported NiO NPs acts as efficient catalytic centre for
the conversion of ethanol to hydrocarbon fuels, which is an alternate to fossil fuel. Catalytic process is envi-
ronment friendly and sustainable as the feedstock ethanol can be easily obtained from biomass resources.
Introduction
synthesis of hydrocarbon fuels [3,9]. This will also be an additional
relief in the context of fast diminishing fossil fuels. Moreover, hydrogen
In the backdrop of global energy scenario, conversion of biomass
derived abundant resources like ethanol to hydrocarbon fuels is
becoming increasingly demanding in the field of energy research [1].
Ethanol derived from natural sources like sugarcane [2] is an excellent
platform chemical for various value added chemicals such as iso-
propanol, ethylene, 1,3-butadiene, 2-butene, acetaldehyde and many
more [3]. However, ethanol can be used only as an additive to gasoline
for achieving high torque and output power in comparison to gasoline
alone engine. It suffers from the major disadvantage of low net calorific
value [4]. Often it can be considered as a replacement of fossil fuel as a
gasoline component [5–8]. However, direct utilization of ethanol as fuel
is not feasible in existing motorization technique [5,7]. Hence, one step
up-gradation can be considered as a good attempt to convert the large
volume of ethanol supply chain into fuel with low carbon count. In this
viewpoint a new approach of research has been conducted to boost up
the valuation of ethanol by using it as a starting material for direct
is also produced as one of the major products in the ethanol dehydro-
genation process. Hydrogen is recognized as an alternative energy car-
rier for attaining a low carbon economy and excellent sustainability in
the supply of energy [10,11]. However, hydrogen is mostly produced via
biomass gasification or methane reforming [12], which are energy
consuming and involved complex catalytic processes. Hence, in this
scenario H2 production via ethanol transformation can make a credible
alternative as it is produced from biomass fermentation [13] without
applying any additional energy. In this way abundant biomass can be
efficiently utilized, which in return make the hydrogen production much
cheaper. This altogether fulfils the idea of integrated refining of biomass
for sustainable energy [14–16].
Porous inorganic nanomaterials have long been considered as
attractive heterogeneous catalyst because of their high specific surface
area, tuneable porosity and ease of stabilization of the metal/metal
oxide NPs at its pore surface [17–20]. Amongst them mesoporous silica
* Corresponding authors.
E-mail addresses: biswajit72@iitism.ac.in (B. Chowdhury), msab@iacs.res.in (A. Bhaumik).
https://doi.org/10.1016/j.mcat.2020.111381
Received 16 September 2020; Received in revised form 23 December 2020; Accepted 24 December 2020
Available online 18 January 2021
2468-8231/© 2021 Elsevier B.V. All rights reserved.

S. Chatterjee et al.
Molecular Catalysis 502 (2021) 111381
has been intensively studied as support for designing reactive hetero-
geneous catalysts [21–27]. Owing to very high BET surface area the
2D-hexagonal mesoporous silica materials are often used as support for
surface functionalization as well as immobilizing active catalytic sites.
Large mesopores of the functionalized SBA-15 is found to be very effi-
cient for loading of metal and metal oxide NPs [28–31]. This in turn
could facilitate the catalytic activity by easy diffusion of reactant and
products along the pore channels. For achieving high conversion in
ethanol to gasoline, H-ZSM-5 has been employed as catalyst under
fixed-bed reaction conditions [32–34]. On the other hand enhancement
of the catalytic activity of ZSM-5 in the conversion of ethanol to ethylene
and subsequent higher hydrocarbons has been the underway for several
decades [35,36]. The acid site of ZSM-5 catalyses the poly-alkylation
and cracking to produce C3+ hydrocarbons and olefins. The hydrocar-
bon efficiency can be enhanced by increasing the metallic sites in the
zeolitic support [37]. While the acidic site of the H-ZSM-5 enhances the
protonation of the alcohol and subsequent dehydration, metal centre
present in the framework act as a dehydrogenating cum coupling agent
to form higher olefins. Hence by eliminating acidic centre from the
support the olefin pool may be enhanced. Thus, SBA-15 with very mild
acidity [38] is quite good support for the metal oxides to convert ethanol
into a hydrocarbon pool having high fuel efficiency.
modification. In case of NiO@SBA-15 (100), (110) and (200) peaks are
recorded at 1.01, 1.71 and 1.96 degrees of 2Θ. For pure silica SBA-15
material the peaks appeared at 0.96, 1.63 and 1.88 degrees of 2Θ
respectively. This result agrees well with 2D-hexagonally ordered
SBA-15 material (Fig. 1B, right) [40,41]. The shift in the peak positions
indicated the decrease in d-spacing upon functionalization and NiO
loading. The Scherrer’s equation has been employed to estimate the
average particle size of the NiO nanoparticles. The average particle size
NiO NPs by using this method was found to be ca. 5.2 nm.
Surface area analysis
To understand the porosity and BET surface area of NiO@SBA-15 the
N2 adsorption-desorption analysis has been performed at 77 K. The N2
sorption isotherms shown in Fig. 2 displayed a typical type IV isotherm
together with a H1 type hysteresis loop indicative of presence of large
mesopore, characteristics of SBA-15 type framework [42]. Significant
drop in BET surface area was observed when SBA-15 was first func-
tionalized with APTES followed by loading of NiO. In the case of SBA-15
the observed specific surface area was 872 m2 gꢀ 1, whereas in case of
NiO@SBA-15 the same was found to be 409 m2 gꢀ 1. The pore size dis-
tribution shown in the inset of Fig. 2 suggested the presence of broad
mesopore with peak pore width of 6.5–7.2 along with some micropore of
ca. 1.1 nm size in the NiO@SBA-15 sample. The mesopore size corre-
sponds to the 2D-hexagonal mesophase of SBA-15 framework, whereas
the micropore contribution could be attributed to some porosity in the
amorphous pore wall.
Here we have supported NiO NPs over functionalized 2D-hexagonal
mesoporous SBA-15 material followed by calcination in air to obtained
NiO@SBA-15 material. NiO@SBA-15 acts as an efficient catalyst for the
dehydrogenation of ethanol to a mixture of methane and butane iso-
mers. NiO@SBA-15 has been synthesized by surface modification of
SBA-15 followed by immobilization of Ni(II) at its surface and calcina-
tion (Scheme 1). NiO@SBA-15 showed good catalytic activity for con-
version of ethanol to a mixture of hydrocarbons, specifically C1 and C4
X-ray photoelectron spectroscopic analysis
̊
hydrocarbons at mere 300 C reaction temperature under fixed-bed re-
X-ray photoelectron spectroscopic analysis have been carried out for
NiO@SBA-15 to understand the oxidation state of Ni present in the
material after calcination. Peaks observed at 104 and 533 eV could be
assigned due to the binding energies of the Si 2p (Fig. 3A) and O 1s
(Fig. 3B) electrons present in the mesoporous silica framework [43]. The
binding energy for Ni 2p3/2 state was found to be at 857 eV with its
satellite peak at 863 eV, which confirms that the Ni present in material is
exclusively in +2 oxidation state (Fig. 3C) [44]. XPS spectra has been
quantitatively analysed and it suggested loading of Ni in the material
was 13.67 wt%. High loading of Ni in NiO@SBA-15 nanocatalyst in turn
is helpful for carrying out the catalytic reaction under fixed-bed reaction
conditions.
action conditions. Further increase in the reaction temperature favoured
cracking to yield CH4 as major product.
Results and discussion
Powder XRD analysis
The mesophase of NiO@SBA-15 has been characterized through the
powder XRD analysis (Fig. 1). The PXRD data for SBA-15 showed only
broad hump at 24◦ 2Θ region (Fig. 1B, left) due to amorphous thick silica
pore wall. After the loading of NiO NPs we got additional peaks at 37, 43
and 63◦ 2Θ, which suggested the presence of (111), (200) and (220)
planes for NiO nanoparticles as per the JCPDS card No. 47-1049
(Fig. 1A) [39]. To understand the periodicity of the material small
angle PXRD pattern has been recorded. There we observe consecutive
shift in peaks towards lower 2Θ value upon each step of surface
Morphological study
To understand the morphological features scanning electron micro-
scopic and transmission electron microscopic images were recorded. The
Scheme 1. Schematic synthesis pathway for NiO@SBA-15.
2

S. Chatterjee et al.
Molecular Catalysis 502 (2021) 111381
Fig. 1. Wide angle (left) and small angle (right) PXRD for NiO@SBA-15 (A) and pure silica SBA-15 (B).
ca. 7 nm in NiO@SBA-15. It is pertinent to mention that functionaliza-
tion with 3-aminopropyl groups provides specific metal binding sites at
the mesopore surface, so that the Ni(II) ions can evenly dispersed across
the support. This helps in the formation of very small dimension NiO
nanoparticle upon calcination. TEM images and elemental mapping data
suggested that NiO NPs are well dispersed throughout the NiO@SBA-15
material and NiO NPs are located both inside the pore channel as well as
outside the pores.
Surface acidity measurement
To understand the surface acidity, temperature programmed
desorption of ammonia experiment has been carried out from 298 to
1073 K for NiO@SBA-15 material. It is observed that the sharp peak at
lower temperature range 313ꢀ 498 K is (12.4 mL/g or 0.5549 mmol/g
Fig. 5) and this could be attributed to the weak acid sites present in the
material. On the other hand, two broad peaks in the temperature range
512ꢀ 1073 K is observed. These broad peaks are deconvoluted to un-
derstand the contribution of each peaks. These high temperature NH3
desorption peaks could be attributed to the presence of the medium and
strong acidic sites. It is seen that the peak appeared in the temperature
range 512ꢀ 783 K corresponds to moderate acidity with acidity of 0.475
mmol/g and the one observed in the temperature range 793ꢀ 1073 K
could be assigned due to strong acidity with total concentration of
0.55089 mmol/g. In Fig. 5b we have shown the strengths of different
acid sites through bar diagram.
Fig. 2. N2 adsorption-desorption isotherm for SBA-15 (A) and NiO@SBA-15(B);
Pore size distribution for SBA-15(A) and NiO@SBA-15(B) in the inset.
SEM images reveal the materials are arranged like the fish gill like
orderly array (Fig. 4a). Elemental mapping images showed the NiO
nanoparticles are distributed uniformly (Fig. 4b, c and d). The high
resolution SEM image (Figure S1) shows the presence of periodic
channels which was also confirmed from the HR TEM image (Fig. 4e, f).
This HR TEM image of NiO@SBA-15 suggested the tiny NiO nano-
particles of dimension ca. 5ꢀ 6 nm are uniformly distributed throughout
the material. Further, the HR TEM images confirmed the pore width of
Catalytic activity
Catalytic transformation of ethanol has been carried out over
NiO@SBA-15 in the temperature range 300ꢀ 400 ◦C. In Table 1 we have
Fig. 3. Short range XPS scan of NiO@SBA-15 for the Si (A), O (B), Ni (C).
3

S. Chatterjee et al.
Molecular Catalysis 502 (2021) 111381
Fig. 4. FE-SEM image of NiO@SBA-15 (a), its elemental mapping for Ni (b), Si (c), O (d); and HR TEM images (e,f) at different magnifications.
summarized the yields of different products over NiO@SBA-15 catalyst
at different temperatures. At 300 ◦C the ethanol conversion was rather
low but formation of methane and butene occurs predominantly along
with ethylene, diethyl ether and trace amount of other hydrocarbons.
Further we could detect small amount of benzene also at 300 ◦C.
However, with increase in temperature to 350 ◦C we can see the ethanol
conversion increases considerably and further at 400 ◦C a near complete
conversion of ethanol was observed. Among the hydrocarbons high
amount of CH4 was observed at higher temperature and selectivity to
this leads to reduced coke deposition on the catalyst surface.1 It is
interesting to note that substantial amount of hydrogen was detected in
all temperatures. The production of hydrogen can be explained mainly
on the basis of cracking and ethanol steam reforming (ESR) at high
temperatures. Further, high yield of methane could be attributed to the
methanation of ESR product (Eqs. (1)–(5)) [45].
C2H5OH →C2H4 + H2O
(2)
(3)
(4)
(5)
C2H5OH + 3H2O →2CO2 + 6H2
CO + 3H2 → CH4 + H2O
CO2 + 4H2 → CH4 + 2H2O
–
C2-C4 were found in trace amount (Fig. 6). At higher temperature C
C
bond breaking occurs by the following step at the NiO@SBA-15 surface
(Eq. (1)).
C2H5OH →CH4 + CO+ H2
(1)
During regeneration more methane was formed along with
hydrogen, which indicated more decomposition/cracking of ethanol
(Table S1). However, among the lower hydrocarbon products C4 frac-
tions were obtained predominantly compare to C1-C3 fractions (Fig. 6).
At low temperature it was previously observed that comparatively
large amount of high molecular weight hydrocarbons are formed, which
could diffuse through the mesoporous pore channels of the catalyst and
4

S. Chatterjee et al.
Molecular Catalysis 502 (2021) 111381
Fig. 5. NH3-TPD profile (a) and amount of NH3 (mL/g) desorbed (b) over NiO@SBA-15.
Table 1
Optimization of NiO@SBA-15 catalyst at different temperatures for the transformation of ethanol.
Temp. (◦C)
TOS (h)
Ethanol Conv.%
Selectivity (%)
Carbon Balance (%)
H2
CH4
C2H4
C2H6
C3H6
C3H8
C4H8
DEE
C6H6
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
39.4
28.1
30.3
29.8
33.3
30.3
24.8
26.3
80.2
85.6
80.9
85.6
77.2
77.9
87.4
82.8
99
8.7
0.3
0.4
0.3
0.3
0.3
0.3
0.4
0.3
1.1
0.6
0.6
0.4
0.6
0.5
0.4
0.4
0.2
0.2
0.2
0.2
0.1
0.1
0.1
0
0
0.7
0.9
0.7
0.7
0.5
0.7
0.9
0.8
0.5
0.3
0.3
0.3
0.3
0.3
0
8
0.3
0.5
0.4
0.4
0.4
0.4
0.5
0.4
0.7
0.5
0.5
0.4
0.5
0.5
0.4
0.5
0.5
0.5
0.4
0.4
0.3
0.3
0.3
trace
21.1
29.6
22.8
21.6
18.4
20.3
24.4
22.5
81.6
70.2
77.0
67.2
76.5
77.2
69.5
80.7
87.0
69.1
76.6
81.7
73.7
73.3
71.8
71.5
82.5
79.2
79.4
75.6
78.7
84.0
82.3
82.8
72.9
80.3
71.8
81.7
83.0
73.1
84.1
94.0
70.6
79.3
84.6
76.0
75.9
74.1
13
0
0
10.1
8.2
7.9
6.9
7.6
8.9
8.4
1.8
0.9
0.9
0.6
0.8
0.8
0.4
0.5
0.3
0.2
0.3
0.4
0.3
0.2
0.2
trace
10.9
11
0
0
trace
0
0
trace
300
9.5
0
0
trace
10.5
12.6
11.7
45.9
42.4
46.9
42.7
48.5
49.9
45.4
52.8
60.9
46
0
0
trace
0
0
trace
0
0
trace
0
1.3
1.2
1.3
1.2
1.3
1.4
1.2
1.4
2.2
1.4
1.5
1.6
1.3
1.3
1.3
2.5
1.2
1.6
0.7
0.8
0.7
0.3
0.4
0.6
0.3
0.3
0.4
0.2
0.2
0.2
0
0
0
350
400
0
0
0
0
0
0.5
0.2
0.3
0.4
0.2
0
0
98.9
98.4
96.6
98.3
97.9
98.1
0
51.8
54.9
50.1
50.2
49.2
0
0
0
0
0
0
Mechanistic pathway of ethanol transformation
reaction over HZSM-5 and concluded that at temperature above 300 ◦C
ethanol gets into a hydrocarbon pool mechanism, which associates
continuous ethylation and results higher hydrocarbon compounds with
water. After that these higher hydrocarbons gets involved in complex
secondary reaction mechanisms like oligomerisation, cracking, isomer-
isation, dehydrocyclization to ultimately end up as a hydrocarbon
mixture containing olefins, aromatics, paraffin, naphthene etc. [1]. Van
der Borght et al. carried out ETH reaction over metal modified ZSM-5
and proposed that ethylene can oligomerize to form higher hydrocar-
bons which can be cracked or subjected to H-transfer to ultimately form
aromatics and paraffin. This direct ethanol to ethylene dehydration
The ethanol to hydrocarbon conversion is quite complex and mainly
based upon the understanding of methanol to hydrocarbon reaction.
Different mechanistic investigations have been carried out over modi-
fied ZSM-5, SAPO, supported metal oxide etc. for both methanol to
hydrocarbon (MTH) and ethanol to hydrocarbon (ETH) reactions [46].
Although there still lies some uncertainty regarding the actual reaction
pathway but it is clear that both the reactions pass through the so-called
hydrocarbon pool (HCP) mechanism. The hydrocarbon pool mechanism
was originally proposed by Dahl and Kolboe using isotope labelling
experiment for methanol reaction over H-SAPO-34 catalyst [47]. Also
the subsequent investigation by Johansson et al. it was concluded that
both methanol to gasoline (MTG) and ethanol to gasoline (ETG) result in
same product distribution [48] as they mostly branch from similar
mechanism. Further, computational investigations mainly suggested the
HCP mechanism [49]. Accordingly there is no direct path from ethanol
to detected products through C2 entities but rather the zeolite with the
entrapped HCP combined acts as an inorganic/organic scaffold for the
formation of product by continuous rearrangement, addition and
cracking of the HCP molecules. Ramasamy et al. performed ETH
–
knocks out the requirement for an indirect C C coupling route like the
hydrocarbon pool mechanism [2]. In the ethanol to hydrocarbon con-
version over metal supported alumina an alternative mechanism for the
growth of hydrocarbon over MxOy nanoparticle (M = Re, W, Ta) has
been proposed. Here the condensation reaction between ethanol and its
intermediate reaction products predominantly yield C3H6, C4H8 and
C6H12 alkenes. In case of Pt and Pd reductive dehydration occurs as a
result of surface ethane condensation [3]. In case of supported metal
oxides like NiO/MCM-41 ethylene is generated by dehydration of
ethanol and then ethylene dimerization, isomerisation and metathesis
5

S. Chatterjee et al.
Molecular Catalysis 502 (2021) 111381
Comparison with other reported catalysts
Ethanol conversion to hydrocarbons has been carried out over
different catalytic systems, which mainly includes zeolites/modified
zeolites and mixed metal oxides. Madeira et al. performed ethanol to
hydrocarbon reaction over HZSM-5 catalyst at 350 ◦C temperature with
a total pressure of 30 bar. They mainly obtained C3+ hydrocarbons in
high selectivity and high conversion of ethanol [53]. Gayubo et al.
carried out ethanol transformation to olefins on a Ni-ZSM-5 catalyst and
also studied is deactivation [54]. They could achieve high selectivity for
C3-C4 hydrocarbons at 400ꢀ 500 ◦C temperature and 1 atm pressure with
high conversion of ethanol. Iwamoto et al. reported complete ethanol
conversion on Ni/MCM-41 catalyst with nearly 30 % selectivity for
propylene at 400 ◦C with total pressure of 5.6 kPa [50]. Nikolaev et al.
carried out conversion of ethanol to C3+ hydrocarbons over M/Al2O3 (M
= NiO, Au, NiO/Au) catalysts at 350 ◦C temperature [3]. In case of the
NiO cluster, it resulted a selectivity of 12.73 %, whereas for the mixed
NiO/Au particles the selectivity increased up to 34.19 %. Ramasamy
et al. carried out ethanol conversion over HZSM-5 catalyst at 300ꢀ 400
◦C at 300 psig and achieved compete ethanol conversion with high
selectivity towards higher hydrocarbons [1]. In the investigation by
Vander Brought et al., they prepared Ni, Ga, Fe modified ZSM-5 for
ethanol to hydrocarbon reaction [2]. In terms of products they obtained
light olefins, paraffins, aromatics and C5+ hydrocarbons at 350 ◦C
temperature and 101 kPa total pressure over catalysts with low metal
content. For most of the aforementioned catalytic systems for the
ethanol to hydrocarbon reaction require high pressure conditions,
where no pressure condition is needed for our synthesized NiO@SBA-15.
On the other hand, though our higher hydrocarbon yield is low but there
is substantial amount of hydrogen production which is impressive. Thus,
our catalytic data suggested that NiO@SBA-15 is an efficient catalyst for
the synthesis of renewable energy compounds from ethanol.
Experimental section
Fig. 6. Selectivity of reaction products for the dehydrogenation of ethanol over
NiO@SBA-15 at 300 ◦C (top) and at 400 ◦C (bottom).
Synthesis of NiO@SBA-15
Pure silica SBA-15 have been synthesized by using triblock copol-
ymer P123 as structure directing agent [39]. Then SBA-15 was surface
modified with 3-aminopropyltriethoxysilane (APTES) to get F-SBA-15.
1.0 g SBA-15 was dispersed in 25 mL dry dichloromethane (DCM) and
0.728 g APTES was added to it followed by continuous stirring for 24 h.
The reaction mixture was then filtered and washed with plenty of DCM
and ethanol to obtain F-SBA-15. 1.0 g F-SBA-15 was then dispersed in 20
mL water and 0.324 g Ni(NO3)2 in 5 mL water was added to it. 1.0 mL
NH2-NH2 was added dropwise for 10 min to the mixture and stirred for 4
reactions follows [50]. Dehydration and isomerization takes place on
the acidic silica support. On the other hand dimerization and metathesis
takes place on the Ni site [51,52]. After considering all the possible
mechanistic ways and the product distribution we can suggest a possible
reaction pathway for ethanol to C3-C4 hydrocarbons over acidic
NiO@SBA-15 catalyst as shown in Scheme 2.
Scheme 2. The schematic reaction pathway for the synthesis of hydrocarbons from ethanol.
6

S. Chatterjee et al.
Molecular Catalysis 502 (2021) 111381
h. The mixture was then filtered and washed with plenty of water to
obtain Ni(II)@F-SBA-15. Then this Ni(II)@F-SBA-15 was calcined under
air flow at 550 ⁰C for 4 h to obtain NiO@SBA-15. Here during the
catalyst synthesis NH2NH2 was used for successful binding of Ni(II) sites
over the functionalized SBA-15. When we have carried out the immo-
bilization in the absence of NH2NH2, loading of Ni(II) at the mesopore
surface was very poor.
supported over 2D hexagonal mesoporous silica may open new oppor-
tunities for the utilization of supported 3d-transition metal oxides for the
production of sustainable energy sources.
CRediT authorship contribution statement
Sauvik Chatterjee: Methodology, Data curation, Formal analysis,
Writing - original draft. Kushanava Bhaduri: Methodology, Data
curation, Formal analysis, Writing - original draft. Arindam Modak:
Data curation, Formal analysis. Manickam Selvaraj: Data curation,
Formal analysis. Rajaram Bal: Data curation, Formal analysis. Biswajit
Chowdhury: Supervision, Funding acquisition, Writing - original draft,
Writing - review & editing. Asim Bhaumik: Supervision, Funding
acquisition, Writing - original draft, Writing - review & editing.
Characterizations
Powder X-ray diffraction (PXRD) patterns were recorded by using a
PANalytical X’Pert PRO diffractometer with Cu Kα (λ =0.15406 nm)
radiation. The PXRD data in small angle was taken by using Bruker D-8
Advance diffractometer operated at 40 mA current using Cu K
α (λ
=0.15406 nm) radiation and 40 kV voltage. We have calculated the
particle size of the nanoparticles from powder X-ray diffraction FWHM
data by using Scherrer’s equation (D = 0.89 λ / β cos Θ), where D is the
Declaration of Competing Interest
There are no conflicts to declare.
Acknowledgements
mean size of the crystalline domain, λ is the Cu Kα (λ =0.15406 nm)
radiation and β is the line broadening at half maxima intensity after
subtracting the instrumental line broadening. Quantachrome
A
Autosorb-iQ system was used to do N2 sorption analysis at liquid N2
temperature 77 K. The samples were degassed at 150 ◦C under vacuum
prior to the experiment. The non-local density function theory (NLDFT)
method was used to obtain the average pore size distribution. The NH3-
TPD measurement was carried out on a ChemiSorb 2750 instrument
(Micromeritics, USA) using thermal conductivity detector. 100 mg ma-
terial was activated under helium (99.999 %) gas flow at 623 K for 1 h
and NH3 was adsorbed at room temperature by flowing NH3/He (10 %)
at a rate of 25 mL/min before conducting the experiment. The TPD
profile was recorded in the range of 310ꢀ 1073 K under the flow of He
(99.999 %).
SC wishes to acknowledge DST, New Delhi, India for INSPIRE-SRF.
The authors extend their appreciation to the Deanship of Scientific
Research at King Khalid University for funding this study through the
Small Research Group Project under grant number R.G.P. 306/1442. BC
and AB wish to thank Indo-German Science & Technology Centre
(IGSTC), New Delhi for an international collaboration project grant
(CO2BioFeed). Authors would like to acknowledge Anirudha Singha for
his help in product analysis.
Appendix A. Supplementary data
Catalytic study
Supplementary material related to this article can be found, in the
online version, at doi:https://doi.org/10.1016/j.mcat.2020.111381.
The catalytic reactions were carried out in a fixed bed tubular quartz
reactor (9 mm i.d.) under atmospheric pressure using 200 mg of catalyst.
The reaction temperature, measured by a thermocouple placed near the
catalyst bed, was between 573 and 673 K. The catalyst bed was kept
between a pair of glass wool block. Before the catalytic evaluation, the
catalyst bed was preheated to eliminate water and other adsorbed spe-
cies, using a N2 flow (30 mL minꢀ 1) at 723 K for 1 h (ramping rate: 5 K
minꢀ 1). When the catalyst bed was cooled down to reaction tempera-
ture, a 99.9 % ethanol was fed (through a pre-heater with temperature
473 K) at the top of the reactor with a syringe pump and mixed with a N2
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