Untangling the active sites in the exposed crystal facet of zirconium oxide for selective hydrogenation of bioaldehydes

Article abstract of DOI:10.1039/d0cy01259a

The present study reports the influence of the crystal phase, facets, and active sites of zirconium oxide (ZrO2) on the conversion of bio-aldehydes to their corresponding alcohols in isopropanol under mild reaction conditions. Various ZrO2-based catalysts, having different compositions of monoclinic and tetragonal crystal phases, are successfully prepared in the presence of a base via a solvothermal process. From the detailed characterization through XRD, TEM, CO2-TPD, XPS, AES, BET and poisoning studies, M-ZrO2-U-N, synthesized using zirconium oxynitrate and urea as a precursor and precipitant, respectively, in water, possesses a 100% monoclinic crystal phase with a maximum amount of exposed (-111) facets and surface oxygen concentration along with the highest number of basic sites. The catalytic study on the transformation of furfural (FFA) into furfuryl alcohol (FOH) reveals that M-ZrO2-U-N exhibits the best efficiency with a nearly quantitative yield of FOH. On the other hand, T-ZrO2-U-N, synthesized using zirconium oxynitrate and urea as a precursor and precipitant, respectively, in methanol, is found to have a 94.4% tetragonal phase and a 2.2-fold lower number of basic sites in comparison with M-ZrO2-U-N. The catalytic result with T-ZrO2-U-N displays the lowest activity in terms of the FOH yield (8.1%). According to the comparative and systematic catalytic studies with the various ZrO2 catalysts having different amounts of tetragonal and monoclinic phases, the ZrO2 catalyst having a more monoclinic phase with more exposed (-111) facets, basic sites, surface oxygen species and surface area is found to be crucial for the FFA conversion to FOH with high selectivity. M-ZrO2-U-N is found to be stable and recyclable and also shows excellent activity towards the transformation of other bio-aldehydes and ketones into their corresponding alcohols. This journal is

Full text of DOI:10.1039/d0cy01259a

View Article Online
View Journal
Catalysis
Science &
Technology
Accepted Manuscript
This article can be cited before page numbers have been issued, to do this please use: S. Kumar, M. M.
Devi, S. Kansal and S. Saravanamurugan, Catal. Sci. Technol., 2020, DOI: 10.1039/D0CY01259A.
Volume
Number
7
2
This is an Accepted Manuscript, which has been through the
Royal Society of Chemistry peer review process and has been
accepted for publication.
21
January 2017
Pages 313-534
Catalysis
Science &
Technology
rsc.li/catalysis
Accepted Manuscripts are published online shortly after acceptance,
before technical editing, formatting and proof reading. Using this free
service, authors can make their results available to the community, in
citable form, before we publish the edited article. We will replace this
Accepted Manuscript with the edited and formatted Advance Article as
soon as it is available.
You can find more information about Accepted Manuscripts in the
Information for Authors.
Please note that technical editing may introduce minor changes to the
text and/or graphics, which may alter content. The journal’s standard
Terms & Conditions and the Ethical guidelines still apply. In no event
shall the Royal Society of Chemistry be held responsible for any errors
or omissions in this Accepted Manuscript or any consequences arising
from the use of any information it contains.
ISSN 2044-4761
PAPER
Chaoqiu Chen, Yong Qin et al.
Highly dispersed Pt nanoparticles supported on carbon
nanotubes produced by atomic layer deposition for hydrogen
generation from hydrolysis of ammonia borane
rsc.li/catalysis

Page 1 of 11
CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
View Article Online
DOI: 10.1039/D0CY01259A
ARTICLE
Untangling the Active Sites in Exposed Crystal Facet of Zirconium
Oxide for Selective Hydrogenation of Bioaldehydes
Sahil Kumara, Mayanglambam Manolata Devia, Sushil Kumar Kansalb, Shunmugavel
Saravanamurugan*
Received 00th January 20xx,
Accepted 00th January 20xx
a
DOI: 10.1039/x0xx00000x
The present study reports the influence of crystal phase, facets, and the active sites of zirconium oxide (ZrO
conversion of bio-aldehydes to corresponding alcohols in isopropanol under mild reaction condition. Various ZrO
catalysts, having a different composition of monoclinic and tetragonal crystal phases, are successfully prepared in the
presence of a base via the solvothermal process. From the detailed characterizations through XRD, TEM, CO -TPD, XPS, AES,
BET and poisoning studies, M-ZrO -U-N, synthesized using zirconium oxynitrate and urea as precursor and precipitant,
2
) on the
2
-based
2
2
respectively, in water, possesses 100% monoclinic crystal phase with a maximum amount of exposed (-111) facet and surface
oxygen concentration along with the highest number of basic sites. The catalytic study on the transformation of furfural
(
FFA) to furfuryl alcohol (FOH) reveals that M-ZrO
On the other hand, T-ZrO -U-N, synthesized using zirconium oxynitrate and urea as precursor and precipitant, respectively,
in methanol, is found to have 94.4% tetragonal phase and 2.2-fold lower basic sites in comparison with that of M-ZrO -U-N.
The catalytic result with T-ZrO -U-N displays the lowest activity in terms of FOH yield (8.1%). According to comparative and
systematic catalytic studies with the various ZrO catalysts having a different amount of tetragonal and monoclinic phases,
the ZrO having more monoclinic phase with more exposed (-111) facet, basic sites, surface oxygen species and surface area
is found to be crucial for the FFA conversion to FOH with high selectivity. M-ZrO -U-N is found to be stable, recyclable and
also shows excellent activity towards the transformation of other bio-aldehydes and ketones to their corresponding alcohols.
2
-U-N exhibits the best efficiency with a nearly quantitative yield of FOH.
2
2
2
2
2
2
2
Keywords: Furfural, Hydrogenation, Furfuryl alcohol, ZrO , Monoclinic, Crystal phase and facet, Basic sites
and 5-hydroxymethylfurfural (HMF).FFA is regarded as one of the top
value-added chemicals, which can be used as a starting substrate for
producing a broad spectrum of chemicals like, e.g., alcohols,
hydrocarbons and biofuels [4]. However, the catalytically selective
transformation of such molecules having multi-functionalities to
target products under benign reaction conditions is still a challenge.
Thus, the catalysts having a unique activity to selectively produce the
target product by preventing the formation of undesired products
has significantly become appealing [5]. In connection with this, the
selective hydrogenation of FFA to furfuryl alcohol (FOH) is considered
to be one of the important transformations as FOH has extensive
applications in foundry resins, synthetic fibres, lubricants and other
1
. Introduction
Societal needs of energy, fuels and chemicals have been continuously
fulfilled by the outputs based on fossil resources. However, the
anticipation of diminishing the confined resources of fossils in the
future accentuates the essential need for sustainable resources [1].
With regard to this, terrestrial lignocellulosic biomass is deemed as
an alternative sustainable resource with high abundant in nature as
a source of carbon, which can potentially replace the chemicals
derived from fossil resources. The oxygen-rich lignocellulosic
biomass with intertwined structure can be transformed to high-value
chemicals through various processes, such as dehydration,
hydrogenation and hydrodeoxygenation [2]. Of which,
hydrogenation process is one of the most useful transformations for
producing several benchmark chemicals with a wide range of
applications including pharmaceuticals, agrochemicals and fine
chemicals [3]. Most platform chemicals derived from biomass
contain more than one unsaturated functional group, especially
aromatic compounds having carbonyl groups such as furfural (FFA)
fine chemicals (Scheme 1) [6].
Fragrances
Fine chemicals
O
OH
O
O
Biomass/
Hemicellulose
Foundry resins
Synthetic fibres
Furfural
Furfuryl alcohol
Lubricants
a. Laboratory of bioproduct chemistry, Center of Innovative and Applied
Scheme 1. Hydrogenation of furfural to furfuryl alcohol and its
applications.
Bioprocessing, Sector-81 (Knowledge City), Mohali
India.Email:saravana@ciab.res.in
- 140 306, Punjab,
b.
Dr. S. S. Bhatnagar University Institute of Chemical Engineering and Technology,
Panjab University, Chandigarh, 160 014, India.
Please do not adjust margins

CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Page 2 of 11
ARTICLE
Journal Name
Importantly, 62.0% total annual production of FFA is being converted FOH (98.0%) [33]. FDCA-based zirconium hybrid pVrieewpaArreticdle Obnylinae
into FOH every year to meet the demands in the polymer industry hydrothermal treatment was also applied foDrOFIF: A10h.1y0d3r9o/Dge0nCaYt0i1o2n59tAo
[
7]. Copper chromite catalyst is currently being used for commercial FOH (96.0%) [34]. High loading of zirconium carbonate as catalyst
production of FOH from FFA in the liquid phase reaction; however, was also studied, achieving 99% FOH from FFA [35]. The use of these
the toxicity and lower stability associated with chromium metal organic molecules for generating active sites has a complicated
makes this catalyst system perilous to the environment [8]. To synthetic procedure and no high thermal stability. In this context,
overcome these significant drawbacks, various noble and non-noble Zhang et al. prepared amorphous zirconium hydroxide by using
metal-based catalysts based on Ir, Pd, Pt, Ru, Cu and Ni have been ammonia as a precipitating agent and tested for FFA hydrogenation
explored, yielding 90.0 – 99.0% of FOH [9-15]. In addition to this, to FOH (98%) under relatively high temperature (170 °C) at 10 bar of
some bimetallic catalysts, such as Cu-MgO, Pt-Sn, Ni-Sn, Ru-Sn, Pt-Co nitrogen pressure [36]. The XRD results showed that zirconium
and Pd-Ru were also reported for the conversion of FFA to FOH under hydroxide possessed an amorphous structure, suggesting the
high hydrogen pressure reaction condition, achieving very high requirement of highly stable, crystalline material. Li et al. found a
selectivity of FOH [16-21]. However, the studies mentioned above single-phase monoclinic, and tetragonal zirconium oxide prepared
also have drawbacks such as performing reactions at relatively high using a hydrothermal and solvothermal treatment in water and
temperature, pressure, the requirement of a highly sophisticated methanol as solvent, respectively [37]. This pioneering work
instrument(s), accumulation/sintering of particles and leaching of provoked us to explore the role of crystal phase and exposed facet of
metal(s), thus decreasing the activity and stability of the catalyst(s) ZrO
2
on the hydrogenation of FFA to FOH in isopropanol.
in the subsequent runs.
Here, we report the synthesis of a series of ZrO possessing various
2
Hydrosilane-mediated hydrogenation of FFA was also studied over composition of monoclinic and tetragonal phases in methanol/water
Pd/C under very mild conditions, yielding excellent FOH selectivity by the solvothermal approach in the presence of a base as
(>99%) [22], but the separation of the product after the reaction is a precipitant. All the synthesized catalysts were characterized with
challenging task. Catalytic transfer hydrogenation (CTH) is an XRD, Raman, HRTEM, CO -TPD, XPS, AES, and BET and investigated
2
alternative approach in which organic compounds, such as formic for the catalytic transformation of FFA to FOH under identical
acid and isopropanol, were employed as in situ H-donor [23]. In line reaction conditions in isopropanol. The optimisation of various
with this, Ahn et al. performed FFA hydrogenation with Rh/ED-KIT-6 reaction parameters, kinetic study and recyclability of the best
using formic acid as H-donor in isopropanol, affording 98.0% yield of performing catalyst (M-ZrO
FOH [8]. Instead of using organic acid, alcohols are preferred for CTH the present study focuses on exploring the role of crystal phase, and
reaction as they play a dual role as solvent and H-donor. CTH reaction facet, active site and surface oxygen concentration of ZrO on the
2
-U-N) were also performed. Moreover,
2
generally involves through Meerwein-Ponndorf-Verley (MPV) yield of FOH as no report related to these aspects have been
reduction mechanism, in which the carbonyl group of the compound disclosed so far to the best of our knowledge.
gets reduced to the respective alcohol [24]. Marchi et al. reported
FFA hydrogenation with Cu-Mg-Al (40 wt. % Cu) as a catalyst in
isopropanol at 150 °C, giving a quantitative yield of FOH [25].
2
. Results and Discussion
Although a quantitative yield FOH obtained, the catalytic system was 2.1 Catalytic Activities of ZrO
2
found unappealing due to a high content of copper loading. Al-Zr@Fe
The synthesized ZrO
transformation of FFA to FOH in isopropanol at 110 ºC and the results
are summarised in Table 1. ZrO , synthesized by using zirconium
oxychloride and zirconium oxynitrate as precursors and urea as a
precipitant in water (designated as M-ZrO -U-C and M-ZrO -U-N),
2
catalysts were employed for the
and commercial NiO were also reported for the conversion of FFA to
FOH in isopropanol at 170-180 °C, achieving 90.4 and 94.0% of FOH,
respectively [26, 27]. Hydrotalcite derived mixed oxide catalyst have
also been employed as catalysts for the transformation of FFA,
2
2
2
attaining a high selectivity (97.0%) at 110 ºC, 30 bar H
2
pressure [28].
showed excellent activity, giving maximum yield of 85.5 and 89.8%
FOH, respectively (Table 1, entry 1 and 3). On the other hand, the
Co -Al over hydrotalcite supported catalyst also offered FOH
3
O
4
2 3
O
selectivity of 92% at 180 ºC [29]. In a nutshell, the studies above
related to FFA hydrogenation indicate the uses of harsh reaction
conditions along with toxic metal(s) such as chromium and precious
metal(s) as catalysts, showing the inevitability for designing robust
catalyst.
similarly prepared ZrO
ZrO -U-C and T-ZrO -U-N) (Table 1, entry 2 and 4) exhibited inferior
catalytic activity, affording 34.2 and 8.1% FOH, respectively. For
comparison, the catalytic activity of the commercially available ZrO
ZrO -C) prepared by simply calcination of zirconium oxide at 400 ºC
2
in methanol instead of water as a solvent (T-
2
2
2
(
2
Catalysts containing metal oxides/metal hydroxides without other was also employed as catalysts. The obtained results revealed that
auxiliary metal(s) have also been recently reported for the ZrO -C gave a negligible yield of FOH (<1.0%) along with difurfuryl
upgradation of biomass-derived substrates [30, 31]. Among the ether as a major product, confirmed by GC-MS (Table 1, entry 5).
reported various metal oxides, ZrO is found to be promising due to From Table 1, one can understand that ZrO synthesised with two
its tuneable acidic and basic properties along with high hydrothermal different precursors in the presence of urea as precipitant in water
stability [32]. In connection with this, the organophosphate group displayed an excellent catalytic activity than other ZrO catalysts,
incorporated in ZrO and nanohybrid ZrO were reported for the intriguing to get a deeper understanding into to the physicochemical
2
2
2
2
2
2
transformation of FFA to FOH in isopropanol. The role of properties of the ZrO
2
materials.
incorporating organophosphate group was to introduce bifunctional
acidic and basic sites in ZrO , resulting in a near-quantitative yield of
2
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 3 of 11
CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Journal Name
ARTICLE
Table 1: Screening of various ZrO
hydrogenation in isopropanol.
2
catalysts for furfural The amount of monoclinic was found to be only 5.6% (Table S1).
View Article Online
DOI: 10.1039/D0CY01259A
2
From these observations, one can understand that M-ZrO -U-N
exclusively composed of pure monoclinic phase exhibited the best
FOH
Sel.
FFA Conv. FOH Yield
%) (%)
catalytic efficiency (89.8% FOH). Whereas T-ZrO -U-N having
2
Entry
Catalyst
(
composed of tetragonal (94.4%) and monoclinic (5.6%) phase
displayed a minimal catalytic activity (8.1% FOH), substantiating the
(%)
1
2
3
4
5
M-ZrO
2
-U-C
-U-C
-U-N
-U-N
-C
92.0
44.7
92.4
22.2
10.9
85.5
92.9
76.5
97.1
36.4
6.6
prominent catalytic role of the monoclinic phase in ZrO
reaction condition. The XRD patterns and the composition of
tetragonal and monoclinic phases of other ZrO catalysts are shown
2
under given
T-ZrO
2
34.2
89.8
8.1
M-ZrO
2
2
T-ZrO
ZrO
2
in Figure S1 and Table S1, respectively. The detailed XRD analysis
revealed a similar trend in terms of catalytic activity that the higher
2
0.72
Reaction Conditions: 1 mmol FFA, 80 mg Catalyst, 4 mL Isopropanol, the fraction of monoclinic phase composition, the higher the yield of
10 °C, 6 h.
FOH. However, M-ZrO -U-C and M-ZrO -U-N, having the same
1
2
2
content of monoclinic phase (100%), showed FOH selectivity of 92.9
and 97.1, respectively (Table 1 and S1). This discrepancy in the
2
.2 Influence of crystal phase on the catalytic
activity
catalytic activity of M-ZrO
based on the relative ratio of crystal facets between (- 111) and (111).
M-ZrO -U-N possessed a ratio of 1.51 while M-ZrO -U-C had a slightly
2 2
-U-C and M-ZrO -U-N could be explained
XRD Analysis: In order to understand the diverse activities of the
ZrO
were analysed with X-ray diffractometer. The characteristic XRD
patterns of the most and least efficient catalysts (M-ZrO -U-N and T-
ZrO -U-N) are shown in Figure 1. The XRD pattern of M-ZrO -U-N
exhibited peaks corresponding to the crystal facets of (110), (-111),
111), (200), (-112) and (211) of the monoclinic phase of ZrO
according to JCPDS no. 00-037-1484. No other peak corresponding
to any unreacted reagents was observed, inferring that M-ZrO -U-N
is purely composed of monoclinic ZrO . Whereas, the XRD pattern of
T-ZrO -U-N displayed diffraction peaks at 2θ of 30.2, 35.3, 50.3, 59.7
and 73.9, which can be indexed to the corresponding crystal facets
of (111), (200), (220), (311) and (400) of tetragonal phase of ZrO
2 2
catalysts, the crystal phases and purity of all the ZrO catalysts
2
2
lower ratio of 1.44 respectively, inferring that (-111) crystal facet
might have played a significant role in enhancing the yield of FOH
2
2
2
[
38] (Table S2).
(
2
Raman Analysis: To further substantiate the presence of monoclinic
and tetragonal phases in ZrO catalysts, M-ZrO -U-N and T-ZrO -U-N
2
2
2
2
2
were analysed with complementary technique Raman spectroscopy,
and the obtained Raman spectra are shown in Figure S2. The Raman
2
spectrum of M-ZrO
06, 341, 382, 479, 540, 559 and 618 cm , which could be ascribed
to the monoclinic phase of ZrO [37]. Likewise, T-ZrO -U-N displayed
peaks at 222, 274, 327, 382, 462, 475, 556, 621, and 644 cm . Of
2
-U-N showed characteristic peaks at 182, 222,
2
-1
3
(JCPDS # 00-017-0923). On careful observation, the maximum
2
2
2
intensity of (111) peak of T-ZrO -U-N does not seem to be
-1
symmetrical in shape; thus, the peak was deconvoluted and is shown
in an inset in Figure 1. The deconvoluted pattern showed two peaks
corresponding to a minor and major peak of (-111) plane of
monoclinic and (111) plane of tetragonal ZrO
that T-ZrO -U-N catalyst composed of both monoclinic as well as
tetragonal phases.
-1
which, the peaks at 274, 327, 462, 475, 556, 621, and 644 cm can
be assigned to the tetragonal phase of ZrO ; however, the peaks at
22 and 382 cm belonged to the monoclinic phase as in agreement
with the previous report [37]. Thus, the Raman spectroscopic studies
also confirmed that M-ZrO -U-N has purely monoclinic phase
whereas T-ZrO -U-N has both tetragonal and monoclinic phases, as
2
-1
2
2
, respectively, implying
2
2
2
in line with the results obtained from XRD analysis.

Tetragonal ZrO
Monoclinic ZrO
T-ZrO2-U-N
Peak1
Peak2
Tetragonal
111)
2
2
600
400
200
0
(

PeakSum
2.3 Role of exposed facet and active sites in the
catalyst
Monoclinic
-111)
(
Microscopic Analysis: To shed light on the role of crystal facet and
26
27 28 29 30 31 32 33
 (degree)
particle size, low and high-resolution TEM images for M-ZrO
and T-ZrO -U-N nanoparticles were carefully captured and are shown
in Figure 2. The TEM image of M-ZrO -U-N (Figure 2a) displayed an
2
-U-N
2
2
2
M-ZrO -U-N
2
average particle size of 10±5 nm, which is in good agreement with
T-ZrO -U-N
the particle size obtained from XRD by using the Scherrer equation
2
(
Table S1). The d-spacing values of M-ZrO
measured through the HRTEM image (Figure 2b) and estimated to be
.28, 0.31, and 0.36 nm, which corresponds to the crystal facets of
111), (-111) and (110) of monoclinic ZrO phase, respectively.
2
-U-N nanoparticles were
0
(
20
30
40
50
 (degree)
60
70
80
2
2
Moreover, the analysis of Fast Fourier transform (FFT) pattern (inset
in Figure 2b) obtained from the marked area confirmed the presence
Figure 1. X-ray diffraction patterns of M-ZrO
The inset shows deconvoluted (111) peak of T-ZrO
2
2
-U-N and T-ZrO -U-N.
2
-U-N.
of (110), (111) and (-111) crystal facets in the M-ZrO
2
-U-N
nanoparticles, implying that the nanoparticles are composed of
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Page 4 of 11
ARTICLE
Journal Name
View Article Online
DOI: 10.1039/D0CY01259A
(a)
(c)
Figure
resolution
2. Low and high-
TEM images of (a, b)
M-ZrO
U-N
2
-U-
N, and (c, d) T-ZrO
nanoparticles
2
-
purely
Entry
Catalyst
Additive
FFA
Conv.
(%)
86.8
8.3
FOH
Yield (%)
monoclinic ZrO
ZrO -U-N nanoparticles was found to be 20 nm (Figure 2c). The
HRTEM image of T-ZrO -U-N nanoparticles showed lattice fringes
2
phase. Similarly, the average particle size of the T-
2
a
b
2
1
2
M-ZrO -U-N
2
Pyridine
2-
Nitrobenzoic
acid
Pyridine
2-
Nitrobenzoic
acid
73.8
1.4
having d-spacing values of 0.18, 0.29, 0.31 and 0.36 nm (Figure 2d).
According to the database of powder diffraction patterns (JCPDS# 00-
M-ZrO -U-N
2
0
2
17-0923), the pure tetragonal phase of ZrO can have a maximum
3c
-
-
0
12.4
0
0
d-spacing value of 0.29 nm, corresponding to (111) plane. Therefore,
the observed d-spacing value of 0.18 and 0.29 nm can be attributed
d
4
to the (220) and (111) crystal facets of tetragonal ZrO
and 0.36 nm correspond to the (-111) and (110) of monoclinic ZrO
JCPDS # 00-037-1484), respectively. These observations were
2
whereas 0.31
2
Reaction conditions: 1 mmol FFA, 80 mg M-ZrO
isopropanol, 110 °C, 6 h. a80 mg pyridine added; 80 mg 2-
nitrobenzoic acid added. The reaction was performed with 80 mg
of pyridine or 2-nitrobenzoic acid in the absence of a catalyst.
2
-U-N catalyst, 4 ml
(
b
further confirmed with the FFT patterns obtained from the marked
areas of the HRTEM image (Figure 2d). The analysis of the FFT pattern
obtained from the marked area (inset on the upper-right side of
Figure 2d) displayed the diffraction pattern corresponding to
c,d
tetragonal ZrO
side of Figure 2d) showed both tetragonal and monoclinic ZrO
Hence, the detailed TEM analysis corroborates the presence of
entirely monoclinic phase in M-ZrO -U-N, whereas T-ZrO -U-N
possess a combination of both monoclinic and tetragonal phase in
nanoparticles, as consistent with the XRD and Raman results.
2
whereas that of marked area (inset on the upper-left
the respective basic and acidic sites of catalyst during the reaction,
and the results are summarized in Table 2. It has been previously
2
.
4
+
2-
reported that Zr and O ions of ZrO
acidic sites and strong basic sites, respectively [39]. M-ZrO
a very good yield of FOH (73.8%) at a conversion of 86.8% FFA (Table
, entry 1) when adding pyridine, which selectively passivates acidic
2
contribute to weaker Lewis
2
2
2
-U-N gave
2
Poisoning Studies: To get a deeper insight into the role of active sites
2
in M-ZrO -U-N, systematic experiments were performed by adding
an acid (2-nitrobenzoic acid) or a base (pyridine) additive to poison
Table 2: Influence of acid and base additives on the yield of FOH.
(b)
(
a)
Weak
Medium Strong
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
T-ZrO -U-N
2
Please do not adjust margins

Page 5 of 11
CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Journal Name
ARTICLE
View Article Online
DOI: 10.1039/D0CY01259A
Figure 3. (a) CO
2
-TPD profile, (b, c) Zr3d and O1s XPS spectra and (d) AES spectra of M-ZrO
2
-U-N and T-ZrO
2
-U-N.
-U-N [40]. The
basic sites have been divided into three kinds such as weak, medium
medium and strong basic sites in total than T-ZrO
2
sites during the reaction, thus making basic sites freely available for
catalysing the reaction. On the other hand, no significant yield of FOH
1.4%) with 8.0% conversion of FFA (Table 2, entry 2) was obtained
with M-ZrO -U-N when adding 2-nitrobenzoic acid, which selectively
prevents the basic sites, thus enabling acidic sites unhampered for
catalysing the reaction. When using pyridine and 2-nitrobenzoic acid
as catalyst separately in the absence of M-ZrO -U-N, no FOH was
2
formed, indicating no catalytic role of these additives on FOH
formation. These experimental results demonstrated that basic sites
[
40]
and strong based on previously reported articles . It has been
generally considered that desorption temperature below 200 C
belongs to the weak basic sites and above 200 C regarded as
(
2
medium and strong basic sites. Furthermore, M-ZrO
.4-times higher medium sites than T-ZrO -U-N. The results obtained
from CO -TPD analysis indicate that medium and strong basic sites
present in M-ZrO -U-N played a crucial role in catalysing the
transformation of FFA to FOH (89.8%) with a selectivity of 97.1%
Table 1, entry 3). On the other hand, T-ZrO -U-N yielded only 8.1%
FOH with a selectivity of 36.4% (Table 1, entry 4). Similarly, the CO
TPD profiles of other catalysts (M-ZrO -U-C, T-ZrO -U-C and ZrO -C)
2
-U-N possessed
4
2
2
2
(
2
in M-ZrO
FOH in isopropanol (Table 2, entry 3 and 4).
CO -TPD Analysis: To corroborate further the role of basic sites, M-
ZrO -U-N and T-ZrO -U-N were subjected to CO -temperature
programmed desorption (CO -TPD) analysis and the corresponding
profiles are given in Figure 3a. M-ZrO -U-N possessed total basic sites
of 521 µmol/g, which is more than 2.2-fold higher than that obtained
for T-ZrO -U-N (238 µmol/g). Moreover, the weak (50-200 ºC),
medium (200-350 ºC) and strong (350-750 ºC) basic sites were also
quantified and found that M-ZrO -U-N contained 2-fold higher
2
-U-N virtually uniquely participated in catalysing FFA to
2
-
2
2
2
2
and their weak, medium and strong basic sites are presented in
Figure S3 and Table S3, respectively. Moreover, the strong basic sites
2
2
2
2
peak appeared at 650 C for M-ZrO
contributed to the active basic sites compared to the peak appeared
at 600 C in the case of T-ZrO -U-N, which showed an inferior activity
Figure 3a). Concurrently, T-ZrO -U-N possessed a very low ratio of (-
11/111) facet (Table S2)and exhibited a poor activity, even though,
-U-N displayed a major peak around 600 C. Furthermore, the
peak appeared at 600 C for strong basic sites from T-ZrO -U-N might
have originated from (111) facet of ZrO , which could be less active
for this hydrogenation reaction. Similarly, M-ZrO -U-C also displayed
2
-U-N might have predominantly
2
2
2
(
1
2
2
T-ZrO
2
2
2
2
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Page 6 of 11
ARTICLE
Journal Name
a peak around 650 C and showed comparable catalytic activity to M- sites than that of T-ZrO
ZrO -U-N (Table 1 and Figure S3), implying that strong basic sites TPD results.
might have originated from (-111) facet of ZrO . These results further
manifest that the higher the medium and strong basic sites in total,
the higher the conversion to FOH.
View Article Online
2 2
-U-N, which is in good agreement with CO -
DOI: 10.1039/D0CY01259A
2
2
Plausible reaction mechanism: On the basis of the results obtained
from various characterizations through XRD, TEM, CO -TPD, XPS and
AES, and the poisoning studies, one can understand that M-ZrO -U-
2
2
XPS Analysis: To get more insight with regard to the chemical states N having purely monoclinic crystal phase with highest basic sites
as well as the acidic and basic sites, M-ZrO -U-N and T-ZrO -U-N were among employed catalysts played a crucial role in the transformation
subjected to X-ray photoelectron spectroscopy (XPS) analysis, and of FFA to FOH reaction. The following plausible reaction mechanisms
the corresponding spectra are shown in Figure 3b and c. The XPS (pathway 1 and 2) for the transformation of FFA to FOH with M-ZrO
spectrum of M-ZrO -U-N (Figure 3b) showed two peaks at 181.8 and U-N are proposed and shown in Figure 4. The mechanism of pathway
84.2 eV, which can be assigned to the respective Zr 3d5/2 and Zr 1 proceeds through three key steps viz., i) interaction between
d3/2 lines. These lines indicate the presence of Zr4+ species, isopropanol and the basic sites (O of ZrO
) of M-ZrO -U-N to form
-U-N is composed of ZrO [36]. Similarly, the XPS four-membered cyclic intermediate state [46], ii) FFA interaction
-U-N (Figure 3b) also indicates the presence of Zr
species; however, the peak positions of Zr 3d5/2 (182.0 eV) and Zr membered cyclic intermediate thereby hydride transfer takes place
d3/2 (184.4) lines slightly shifted towards higher binding energy and iii) finally desorption of FOH from the surface of M-ZrO -U-N,
values in comparison to that of M-ZrO -U-N (181.8 and 184.2 eV), resulting in the regeneration of M-ZrO -U-N for next catalytic cycle
inferring that T-ZrO -U-N possibly contained more Lewis acidic sites [47]. In case of pathway 2, when adding 2-nitrobenzoic acid as an
41]. In other words, M-ZrO -U-N possesses more basic sites, which additive to passivate the basic sites of M-ZrO -U-N by absorbing a
is consistent with the results obtained from CO -TPD. Concomitantly, proton from the acid additive, the initial adsorption of isopropanol
O1s spectra of both M-ZrO -U-N and T-ZrO -U-N were also obtained on the basic sites of M-ZrO -U-N was hampered, forming negligible
2
2
2
-
2
1
3
2
2
implying that M-ZrO
spectrum of T-ZrO
2
2
4
+
2
2
with acidic sites (Zr) of M-ZrO -U-N, consequently, forming six-
3
2
2
2
2
[
2
2
2
2
2
2
through XPS analysis to find out the chemical states of oxygen amount of FOH (pathway 2, Figure 4) (entry 2, Table 2). From the
species and found to be not symmetrical in shape. Thus, the peaks above mechanistic pathway, one could understand that the
were deconvoluted and are shown in Figure 3c. The spectra of both adsorption of isopropanol over the basic sites of M-ZrO
M-ZrO -U-N and T-ZrO -U-N exhibit two peaks at 529.7 and 531.2 eV, crucial step.
which can be attributed to the lattice (Olatt) and adsorbed oxygen
ads), respectively [42]. In order to calculate the surface oxygen
concentration, the relative ratio of Oads/Olatt was calculated based on
the area under the peak. The calculated Oads/Olatt in M-ZrO -U-N was
found to be 32% whereas 40 % for that of T-ZrO -U-N. On the other
way around, M-ZrO -U-N contains 68% of lattice oxygen species
which is 8% higher than that of T-ZrO -U-N, indicating that M-ZrO
2
-U-N was the
2
2
O
(O
N+
O-
OH
2
O
2
2
2
2
-
O
Zr OH
4
U-N have relatively more exposed lattice oxygen species which
contributes to the basic sites [43].
O
OH
OH
OH
O
Zr
O
AES Analysis: To further quantify and substantiate the surface
2 2
oxygen concentration, M-ZrO -U-N and T-ZrO -U-N were carefully
H
analyzed through Auger electron spectroscopy (AES) and the
corresponding spectra are shown in Figure 3d. Four similar
characteristic peaks at 90, 141, 149 and 511 eV were observed for M-
O
O
O
O
H
H
3
Zr
O
O
Zr
O
2
ZrO -U-N, which can be assigned to Zr(MNN)metal, Zr(MNV)oxide,
1
Zr(MNV)metal and O(KLL), respectively, according to the reported
literature [44, 45]. Similarly, very slightly lowered kinetic energy
values were observed for T-ZrO -U-N (Figure 3d). The surface oxygen
2
concentration (Co) of each catalyst was calculated based on the
equation given below, employing the peak intensities of
Zr(MNV)metal and O(KLL) [44].
H
O
O
O
O
O
O
H
O
Zr
O
2
Io / So
Co 
I /Sj
j
j
where I
j
and S
j
represent the intensities and sensitivity factors of the
th
j peak, respectively. The sensitivity factor of 0.5 and 0.22 for O (KLL)
and Zr(MNV)metal peaks were employed for the calculation
according to reported literature [44]. The calculated Co of M-ZrO
N and T-ZrO -U-N was found to be 89 and 73%, respectively,
suggesting that M-ZrO -U-N has a relatively larger number of basic
2
-U-
2
2
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 7 of 11
CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Journal Name
ARTICLE
Figure 4. Plausible mechanistic pathways for the conversion of FFA monoclinic crystal phase of M-ZrO
2
-U-N has 27-fold higher catalytic
View Article Online
DOI: 10.1039/D0CY01259A
to FOH with M-ZrO
additive.
2 2
-U-N in the absence and presence of the acid activity than that of the tetragonal crystal phase of T-ZrO -U-N.
The initial rate of all the catalysts based on their surface area was
also calculated and are presented in Table 3. M-ZrO -U-N possessed
a higher initial rate of 69.6 µmolm h than that of all the other
catalyst (Table 1 and 3). Moreover, M-ZrO -U-N has a higher surface
area and pore volume, which could contribute to the reaction on
catalysts, it is very enhancing the yield of FOH. Unpromisingly, the ZrO -C showed
imperative to compare the relative catalytic activities at a similar negligible activity in terms of FOH yield (2.2%) with an initial rate of
2
-2 -1
2
2
.4 Activity of various ZrO at similar conversion
2
To determine the real activity of various ZrO
2
2
-2 -1
conversion of FFA under identical reaction conditions. With regard to 0.03 µmolm h even after a prolonged reaction time of 96 h (entry
this, the experiments were performed to obtain a conversion range 5, Table 3). with M-ZrO
2
-U-N (Table 3).
of 30-50% of FFA, and the results are presented in Table 3. The
2
Similarly, the results obtained with other catalysts (M-ZrO -U-C and
T-ZrO -U-C) showed moderate activities in comparison that M-ZrO -
2 2
2
reaction with M-ZrO -U-N afforded 33.4 % conversion of FFA with
FOH selectivity of 94.9% after 30 min of reaction time (Table 3, entry
U-N. Overall, it can be concluded showed a highest catalytic activity
in terms of FOH yield with the highest selectivity, owing to the
prominent role of (-111) crystal facet possessing a maximum number
of basic sites with a substantial amount of exposed lattice oxygen
species along with high surface area and pore volume.
3
4
), whereas T-ZrO
0.7% conversion with FOH yield of only 26.7% (Table 3, entry 4).
-U-N and T-ZrO -U-N
were also calculated based on total basic sites obtained from CO
2
-U-N required 24 h of reaction time to achieve
Moreover, turn over frequency (TOF) of M-ZrO
2
2
2
-
-1
TPD and found to be 15.1 and 0.57 h , respectively, manifesting that
2
Table 3: The activity of different ZrO catalysts similar conversion
Entry
Catalyst
FOH
Yield
Sel.a
%]
Time
[h]
Surface
Area
Pore
Volume
Total Basic
Sites
Initial Rateb
TOFc
-2 -1
-1
[
[µmolm h ]
[h ]
2
-1
3
-1
[µmolg-1]
[
%]
[m g ]
106.9
70.4
[cm g ]
0.23
1
2
3
4
5
M-ZrO
T-ZrO -U-C
M-ZrO -U-N
T-ZrO -U-N
ZrO -C
2
-U-C
17.8
36.6
31.7
26.7
2.2
43.9
74.5
94.9
65.6
10.5
0.5
4
433
41.6
16.2
69.6
2.8
10.2
3.6
2
0.04
311
2
0.5
24
96
113.9
49.3
0.26
524
15.1
0.57
0.15
2
0.04
241
2
25.6
0.03
19
0.11
a
b
Reaction conditions: 1 mmol FFA, 80 mg catalyst, 4 ml isopropanol, 110 °C, Selectivity= yield/conversion, Initial rate= (FOH mol)/ (BET
c
surface area* catalyst weight time*time), TOF= (FOH mol)/ (basic sites*catalyst weight*time)
untreated M-ZrO
during the reaction. In a similar fashion, the stability of FOH was also
studied in isopropanol in the presence of M-ZrO -U-N at 110 ºC for 6
h and the obtained results based on Gas Chromatography (GC)
analysis revealed that there was no significant degradation of FOH,
implying that the final product FOH during the reaction was also very
stable.
2
-U-N, indicating that the catalyst was quite stable
2
.5 Influence of other reaction parameters on the
yield of FOH
2
The influence of reaction parameters such as temperature, time and
catalyst loading was also optimised with the best efficient catalyst
2
(M-ZrO -U-N), and the results are shown in Figure S4. The results
revealed that as the reaction temperature increases from 75 to 125
ºC, the conversion of FFA and the yield of FOH increases from 53.6 to
9
9% and 35.2 to 99%, respectively (Figure S4a). In the cases of
2
.6. Kinetic study and hydrogenation of other bio-
reaction time and catalyst loading, a similar trend of increase in both
the conversion of FFA and formation of FOH was observed with
longer reaction time (Figure S4b) and higher amount of catalyst
based substrates
The kinetic study of catalyst for the transformation of FFA to FOH was
also performed with M-ZrO -U-N at various temperature (348 to 398
2
2
loading (Figure S4c). The stability of M-ZrO -U-N was also studied by
K) and time (30 to 360 min), and the results are shown in Table S4
and Figure S5. According to the previous study, the transformation
of FFA to FOH follows the first-order rate-law, that is, –ln(1-x)=kt,
where x, k and t are the FFA conversion, rate constant and reaction
time, respectively [33]. Therefore, the rate constant (k) of each
treating the catalyst with isopropanol as a solvent in ace pressure
tube at 110 ºC for 24 h, followed by drying at 80 ºC and tested its
activity towards the conversion of FFA to FOH in fresh isopropanol at
1
10 °C for 6 h. The obtained result revealed that the catalytic activity
of treated M-ZrO U-N remained unchanged in comparison with the
2
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Page 8 of 11
ARTICLE
Journal Name
reaction at a different time and temperature was calculated by The recyclability of M-ZrO
plotting the graphs of -ln (1-x) vs t and the obtained results are studied at lower conversion (<30.0%) in isoprDopOaI:n1o0l.1f0o3r9f/oDu0rCrYu0n1s2a5n9Ad
summarised in Table S4. Further, the activation energy was also the results are shown in Figure 5. After each run, the spent M-ZrO
calculated using the Arrhenius equation and found to be 49 kJ/mol-1 U-N was employed after recovering by washing with ethanol and
Table S5), which is 1.2 to 1.3 times lower than that of previously acetone and dried at 80 ºC overnight followed by calcination at 400
reported catalysts (ZrPN, ZrO and Zr-beta) [33,48]. These results ºC for 6 h in air. After the first run, 25.0% of FOH with 26.7%
demonstrate that M-ZrO -U-N showed an excellent catalytic activity conversion of FFA was obtained. The activity of recovered M-ZrO -U-
2
-U-N for the conversion FFA to FOH was
View Article Online
2
-
(
2
2
2
among all the reported catalysts, owing to the presence of pre- N was slightly lost in the second run, yielding 21.0% FOH, suggesting
dominantly exposed (-111) crystal facet having a large number of that organic moieties might have strongly adsorbed on the active
basic sites along with high surface area and pore volume, which sites. After the third run, no significant loss in activity was found and
facilitated the facile adsorption of FFA followed by hydrogenation to maintained the yield of FOH about 18.0%. Furthermore, the
FOH in isopropanol.
comparison of the XRD pattern (Figure S6) obtained from the
recovered after the fourth run and the fresh M-ZrO -U-N revealed
2
2
The activity of M-ZrO -U-N was extrapolated for hydrogenation of
that the crystal structure or composition remains unchanged.
However, the ratio of exposed surface facet between (-111) to (111)
was found to be 1.34, which is slightly lower than that of fresh
catalyst (1.51), confirming the active participation of (-111) facet in
the reaction. The slight decrease in the activity of M-ZrO -U-N during
2
the subsequent reactions of recyclability test was due to a slight loss
in the amount of exposed (-111) facet.
other bio-based carbonyl compounds (5-methylfurfural, benzalde-
hyde, anisoldehyde, p-tolualdehyde, veratraldehyde and cyclohexa-
none) under similar reaction conditions, and the results are present-
ed in Table 4. The yields of corresponding alcohols were obtained
between 77.0 and 100% at reaction condition of 110 ºC for 6-10 h
depending on the reactivity of the substrate. High conversion of
these aldehydes and ketone to the corresponding alcohols with the
2
better yields were achieved with M-ZrO -U-N at a relatively lower
temperature as compared to the reported zirconium nanohybrid
catalyst [33]. For example, with zirconium nanohybrid, benzaldehyde
conversion to benzyl alcohol required a reaction temperature of 160
°
C temperature for 6 h, whereas M-ZrO
2
-U-N needed relatively a low
-U-N possesses
temperature (110 °C), demonstrating that M-ZrO
2
active basic sites in (-111) crystal facet, which could efficiently
catalyze the reaction at a relatively lower temperature.
Table 4: Hydrogenation of various bio-based carbonyl compounds
2
with M-ZrO -U-N.
O
M-ZrO2-U-N
OH
R'
Figure 5. Recyclability of M-ZrO
FOH. Reaction conditions: M-ZrO
isopropanol to furfural ratio = 32.7, 110 °C, 30 min.
2
-U-N for the conversion of FFA to
R
R'
R
2
-U-N to furfural ratio = 1.20,
Iso-propanol
O
OH
OH
3
. Conclusions
5
-methylfurfuryl alcohol
Benzylalcohol
Y=>99% (9h)
Y=97% (6h)
In summary, we have demonstrated the successful preparation of
various ZrO based catalysts for the transformation of FFA to FOH in
isopropanol. Among all the catalyst, M-ZrO -U-N showed an
excellent activity with a maximum yield of FOH ( 99.9 %). Based on
the detailed analysis of XRD and TEM, it was revealed that M-ZrO
U-N possesses purely monoclinic phase while the least active
catalyst, T-ZrO -U-N (8.1% FOH) has predominantly tetragonal phase
along with minimal amount of monoclinic phase, inferring that the
monoclinic phase of M-ZrO -U-N is responsible for the efficient
transformation of FFA to FOH. Among the synthesized catalysts, two
catalysts (M-ZrO -U-N and M-ZrO -U-C) exhibit purely monoclinic
phase, however, M-ZrO -U-N displayed the best catalytic activity in
terms of product formation and selectivity, owing to the presence of
more exposed (-111) crystal facet in comparison to that of M-ZrO
2
O
2
OH
OH
(
4-methoxyphenyl)methanol
p-tolylmethanol
Y=99% (9h)
2
-
Y=99.9% (9h)
2
O
OH
OH
O
2
Veratrole alcohol
Y=77% (9h)
Cyclohexanol
Y=98% (6h)
2
2
Reaction conditions: 1 mmol substrate, 80 mg M-ZrO
isopropanol, 110 °C.
2
-U-N, 4 ml
2
2
-
2
.7 Recyclability of M-ZrO -U-N
U-C. Insight studies related to the poisoning of acidic and basic sites
2
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 9 of 11
CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Journal Name
ARTICLE
2
present in the monoclinic phase of M-ZrO -U-N with pyridine or 2-
nitrobenzoic acid additives during the reaction untangled that basic
sites in the catalyst play a critical role on the yield of FOH. Moreover,
4
.3 Characterisation Techniques
View Article Online
DOI: 10.1039/D0CY01259A
The phase identification and purity of all the catalysts were
determined in the 2θ range of 20-80º at a scan rate of 2º/min through
powder X-ray diffractometer (PANalytical Xpert Pro. equipped with
x’Celerator solid-state detector at the operating parameter of the 45
kV, 40 mA, with target Cu-Kα (λ= 1.54056 Å). The Raman spectra
CO
highest basic sites and exposed surface oxygen concentration in M-
ZrO -U-N among all the catalysts. In addition to the monoclinic
phase, surface oxygen species and basic sites, the higher surface area
and pore volume of M-ZrO -U-N also contributed to the reaction on
enhancing the yield of FOH. The kinetic studies also revealed that M-
2
-TPD, XPS and AES analysis also confirmed the presence of the
2
-
1
were recorded in the range of 100-1500 cm using Raman
spectroscopy (BWTEK Inc.) at an excitation wavelength of 532 nm.
2
The average particle size and lattice spacing of the catalysts; M-ZrO
U-N and T-ZrO -U-N were examined through transmission electron
microscopy (TEM, FEI Tecnai) at operating voltage of 200 keV. The
chemical states and the surface oxygen concentration of M-ZrO -U-
N and T-ZrO -U-N were also measured through X-ray photoelectron
and Auger electron spectroscopy (PHI 5000 versa Prob II, FEI Inc.) in
a binding or kinetic energy range of 0 to 1200 eV with
monochromatic X-ray source of AI Kα. The instrument was priory
calibrated with C1s at a binding energy of 284.6 eV. The number of
2
-
-1
2
ZrO -U-N requires low activation barrier of 49.0 kJmol for the FFA
2
conversion reaction in comparison with that of the previously
reported zirconium-based catalysts, which could be due to the
2
presence of active basic sites on the exposed (-111) facet of M-ZrO
2
-
2
U-N. M-ZrO -U-N was possible to reuse at least for three times with
2
a minimal loss of activity, and could efficiently convert other bio-
based aldehydes and ketone in excellent yields (77-99.9%), paving
the way for transforming a wide range of biomass based carbonyl
compounds to their corresponding alcohols.
basic sites in all the catalysts was also determined by CO
2
-
temperature programmed desorption (CO -TPD) (BELCAT II version
2
p0.5.1.10) equipped with TCD detector. 50mg of the catalyst was
taken in a quartz tube and heated from room temperature to 500 ºC
within 60 min of time under He gas flow of 50ml/min and continue
degassed for another 50 min at the same condition. Then, the tube
4
. Experimental
4
.1 Chemicals
Furfural, furfuryl alcohol, naphthalene, zirconium oxynitrate hydrate,
zirconium oxychloride octahydrate, 5-methyl furfural,
containing catalyst was cooled down to 50 ºC and performed CO
adsorption study under the gas of 5% CO -He at a flow rate of 50
ml/min. Subsequently, the catalyst was flushed with He gas at a flow
rate of 50 ml/min to remove physisorbed CO . Finally, desorption
2
2
cyclohexanone, benzaldehyde, p-touladehyde, anisalde-hyde,
veratraldehyde, veratryl alcohol, 5-methyl-2-furyl methanol, benzyl
alcohol, cyclohexanol, pyridine and 2-nitrobenzoic acid were
purchased from Sigma Aldrich. Urea and Isopropanol were bought
from TCI chemicals respectively. All the chemicals are of analytical
grade and used without any further treatment or purification.
2
studies were carried out at a temperature range of 50-750 ºC at the
ramp rate of 10 ºC/min. The surface areas and pore volumes of all
the catalysts were determined from N -sorption measurement at
2
liquid nitrogen temperature through BET and t-plot methods,
respectively, using a Quantachrome Nova 2000e/Micromeritics ASAP
4
.2 Catalyst preparation
2
6
020 physisorption analyzer. Each sample was degassed at 150 º for
h under vacuum prior to the analysis.
All the ZrO
2
based catalysts were prepared by slightly modifying the
procedure available in the previous report [37]. In a typical synthesis,
0
.4 mol of zirconium precursor (zirconium oxynitrate/zirconium 4.4 Catalytic reactions
oxychloride) and 2 mol of the precipitating agent (urea) were
dissolved in 30 mL of solvent (methanol/distilled water). The solution
was then transferred to Teflon lined autoclave of 100 ml capacity and
placed in an oven at 140 °C for 20 h after completely sealed. After
each reaction, the autoclave was naturally cooled down to room
temperature and each catalyst was thoroughly washed with distilled
water and methanol and dried at 100 °C. Subsequently, each catalyst
was calcined at 400 °C for 4 h with a ramp rate of 2°C/min in
atmospheric air to obtain the final catalyst for the reactions. For the
All the reactions were performed in a 15 ml ace pressure tube. In a
typical reaction, 1mmol of FFA, 4 ml of isopropanol, 80 mg of catalyst
and 15 mg of Naphtalene was taken in ace pressure tube and after
tightly closed the pressure tube, it was dipped into a preheated
silicon oil bath, which is already placed on a magnetic stirrer with a
heating plate. The internal reaction temperature was measured
using an ace pressure tube attached with a plunger valve and
thermowell. After the completion of each reaction, the pressure tube
was cooled down to room temperature naturally. An aliquot of each
reaction mixture was withdrawn and filtered off using 0.2µm nylon
syringe filter and analysed using Agilent 7890B gas chromatogram,
equipped with flame ionization detector (FID) and DB-5 MS column
2 2
catalysts; T-ZrO -U-N and T-ZrO -U-C, zirconium oxynitrate and
zirconium oxychloride were used as respective Zr precursors while
methanol and urea were utilized as a solvent and precipitating agent.
On the other hand, M-ZrO
using zirconium oxynitrate and zirconium oxychloride as their
respective Zr precursors with water and urea. ZrO -C was derived
from commercialized ZrO (obtained from Sigma-Aldrich) by
2 2
-U-N and M-ZrO -U-C were also prepared
(30m×0.32×0.25µm). The conversion of FFA and yield of FOH were
quantified by making a series of individual standards along with
naphthalene as an internal standard.
2
2
calcining at 400 °C for 4 h with a ramp rate of 2 °C/min and
atmospheric condition.
Conflicts of interest
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins

CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Page 10 of 11
ARTICLE
Journal Name
The authors declare no competing financial interest.
14. S. Sitthisa, D. E. Resasco, Catal. Lett. 2011, 141, 784-791.
View Article Online
1
5. S. Tian, W. Gong, W. Chen, N. Lin, Y. Zhu,DQO.IF: e10n.g10, 3Q9./XDu0,CQY0. 1F2u5,9CA.
Chen, J. Luo, W. Yan, H. Zhao, D. Wang, Y. Li, ACS Catal., 2019, 9,
5
1
2
1
223-5230.
6. M. Ghashghaee, S. Sadjadi, S. Shirvani, V. Farzaneh, Catal. Lett.
017, 2, 318-327.
7. A. Driscoll, T. Curtin, W. Y. Hernandez, P. V. D. Voort, J. J. Leahy,
Acknowledgements
We gratefully thank the Department of Biotechnology (DBT),
New Delhi, India, for the financial support and infrastructural
facilities provided at CIAB. SK gratefully thanks CIAB/DBT for
providing financial support through Senior Research Fellowship
and Panjab University for PhD registration. We also
acknowledge the National Agri-Food Biotechnology Institute for
kindly permitting us to use GC. We thank SKK for allowing us to
use BET surface area analyzer available at his laboratory at
Panjab University.
Org. Process Res. Dev. 2016, 20, 1917-1929.
8. S. Rodiansono, T. Khairi, N. I. Hara, S. Shimazu, Catal. Sci.
Technol., 2012, 2, 2139-2145.
1
1
5
2
2
9. J. J. Musci, A. B. Merlo, M. L. Casella, Catal. Today 2017, 296, 43-
0.
0. M. G. Dohade, P. L. Dhepe, Green Chem. 2017, 19, 1144-1154.
1. O. F. Aldosari, S. Iqbal, P. J. Miedziak, G. L. Brett, D. R. Jones, X.
Liu, J. K. Edwards, D. J. Morgan, D. K. Knight, G. J. Hutchings, Catal.
Sci. Technol. 2016, 6, 234-242.
References
2
2. H. Li, W. Zhao, S. Saravanamurugan, W. Dai, J. He, S. Meier, S.
Yang, A. Riisager, Communications Chemistry., 2018, 32.
3. A. Boddien, B. Loges, F. Gartner, C. Torberg, K. Fumino, H. Junge,
R. Ludwing, M. Beller, J. Am. Chem. Soc. 2010, 132, 8924-8934.
1
2
2
. (a) A. Corma, S. Iborra, A. Veltey, Chem. Rev. 2007, 107, 2411-
502. (b) P. Gallezot, Chem. Soc. Rev. 2012, 41, 1538-1558.
. (a) A. Sheldon, Green Chem. 2014, 16, 950-963. (b) M. Chatterjee,
2
T. Ishizaka, H. Kawanami, Green Chem. 2018, 20, 2345. (c) A. J.
Ragauskas, C. K. Williams, H. B. Davison, G. Britovsek, J. Cairney, C.
A. Eckert, W. J. F. Jr, J. P. Hallett, D. J. Leak, C. L. Liotta, J. R. Mielenz,
R. Murphy, R. Templer, T. Tschaplinski, Science 2006, 311, 484-489.
2
2
2
2
2
2
2
2
2
4. M. Chia, J. A. Dumesic, Chem. Commun. 2011, 47, 12233-12235.
5. M. M. Villaverde, T. F. Garetto, A. J. Marchi, Catal. Commun.
015, 58, 6-10.
6. J. He, H. Li, A. Riisager, S. Yang, ChemCatChem 2018, 10, 430-438.
7. J. He, L. Schill, S. Yang, A. Riisager, ACS Sustainable Chem. Eng.
018, 6, 17220-17229.
8. X. Meng, Y. Yang, L. Chen, M. Xu, X. Zhang, M. Wei, ACS Catal.
019, 9, 4226-4235.
9. R. Ramos, A. F. Peixoto, B. I. Arias-Serrano, O. S. G. P. Soares, M.
(d) M. S. Holm, S. Saravanamurugan, E. Taarning, Science 2010, 328,
6
3
1
02-605.
. (a) W. R. Brode, R. W. V. Dolah, Ind. Eng. Chem. 1947, 39, 1157-
160. (b) I. Mcmanus, H. Daly, J. M. Thompson, E. Connor, C.
Hardacre, S. K. Wilkinson, N. S. Bonab, J. T. Dam, M. J. H. Simmons,
E. H. Stitt, C. D. Agostino, J. Mcgregor, L. F. Gladdan, J. J. Delgado, J.
Catal. 2015, 330, 344-353. (c) R. L. Augustine, Catal. Today 1997, 37,
F. R. Perira, D. Kubicka, C. Freire, ChemCatChem. 2019
0. H. Li, A. Riisager, S. Saravanamurugan, A. Pandey, R. S. Sangwan,
S. Yang, R. Luque, ACS Catal. 2018, 148-187.
3
4
4
19-440.
. (a) D. Lei, K. Yu, M. R. Li, Y. Wang, Q. Wang, T. Liu, P. Liu, L. L. Lou,
3
7
3
5
3
1. H. Li, S. Yang, S. Saravanamurugan, A. Riisager, ACS Catal. 2017,
, 3010-3029.
2. G. D. Wilk, R. M. Wallace, J. M. Anthony, J. Appl. Phys. 2001, 89,
243-5275.
G. Wang, S. Liu, ACS Catal. 2017, 7, 421-432. (b) G. S. Zhang, M. M.
Zhu, Q. Zhang, Y. M. Liu, H. Y. He, Y. Cao, Green Chem. 2016, 18, 2155-
2
5
1
2
164.
. (a) A. Marimuthu, J. Zhang, S. Linic, Science 2013, 339, 1590-
593. (b) X. Liu, X. Ye, F. Bures, H. Liu, Z. Jiang, Angew. Chem. Int. Ed.
015, 54, 11443-11447. (c) R. H. Tunuguntla, R. Y. Henley, Y. C. Yao,
3. H. Li, J. He, A. Riisager, S. Saravanamurugan, B. Song, S. Yang, ACS
Catal. 2016, 6, 7722-7727.
4. H. Li. X. Liu, T. Yang, W. Zhao, S. Saravanamurugan, S. Yang,
ChemSusChem 2017, 10, 1761-1770.
5. M. Ma, P. Hou, J. Cao, H. Liu, X. Yan, X. Xy, H. Yue, G. Tian, S. Feng,
Green Chem. 2019, 21, 5969-5979.
3
T. A. Pham, M. Wanunu, A. Noy, Science 2017, 357, 792-796.
. (a) M. M. Villaverde, N. M. Bertero, T. F. Garetto, A. J. Marchi,
Catal. Today. 2013, 213, 87-92.
6
3
7
2
8
4
9
1
. K. Yan, G. Wu, T. Lafleur, C. Jarvis, RENEW. SUST. ENERG. REV.
014, 38, 663-676.
. C. K. P. Neeli, Y. M. Chung, W. S. Ahn, ChemCatChem 2017, 9,
570-4579.
. P. Puthiaraj, K. Kim, W. S. Ahn, Catal. Today. 2019, 324, 49-58.
0. C. R. Baria, M. Isaacs, K. Wilson, A. G. Ruiz, I. R. Ramos, Appl.
3
6
3
8
3
3
2
4
6. J. Zhang, K. Dong, W. Luo, H. Guan, ACS Omega 2018, 3, 6206-
216.
7. W. Li, H. Huang, H. Li, W. Zhang, H. Liu, Langmuir 2008, 24, 8358-
366.
8. A. Kushwaha, M. Aslam, J. APPL. PHYS. 2012, 112, 54316.
9. S. Kouva, K. Honkala, L. Lefferts, J. Kanervo, Catal. Sci. Technol.
015, 5, 3473.
Catal. A. 2018, 563, 177-184.
1
2
1
2
1
1. X. Liu, B. Zhang, B. Fei, X. Chen, J. Zhang, X. Mu, Faraday Discuss.
017, 202, 79-98.
2. X. Chen, L. Zhang, B. Zhang, X. Guo, X. Mu, Sci. Rep. 2016, 6,
8558.
0. (a) S. Han, D. Zhao, T. Otroshchenko, H. Lund, U. Bentrup, V. A.
Kondratenko, N. Rockstroh, S. Bartling, D. E. Doronkin, J. D.
Grunwaldt, U. Rodemerck, D. Linke, M. Gao, G. Jiang and E. V.
Kondratenko. ACS Catal. 2020, 10, 8933-8949. (b) J. Ren, C. Mebrahtu
and R. Palkovits. Catal. Sci. Technol. 2020, 10, 1902-1913. (c) Y. Liu,
3. J. Chen, F. Lu, J. Zhang, W. Yu, F. Wang, J. Gao, J. Xu,
ChemCatChem 2013, 5, 2822-2826.
2
| J. Name., 2012, 00, 1-3
This journal is © The Royal Society of Chemistry 20xx
Please do not adjust margins

Page 11 of 11
CP al et aa lsy es i ds oS c ni eo nt c ae d &j uTs et c mh na or gl oi ng sy
Journal Name
ARTICLE
Y. Wu, Z. Akhtamberdinova, X. Chen, G. Jiang and D. Liu.
View Article Online
ChemCatChem, 2018, 10, 4689-4698.
DOI: 10.1039/D0CY01259A
4
1
4
1. H. J. M. Bosman, A. P. Pijpers, A. W. M. A. Jaspers, J. Catal. 1996,
61, 551-559.
2. M. Zhang, J. Zhang, Y. Wu, J. Pan, Q. Zhang, Y. Tan, Y. Han, Appl.
Catal. B: Environ. 2019, 244, 427-437.
4
4
2
4
4
3. K. Pokrovski, T. K. Jung, A. T. Bell, Langmuir 2001, 17, 4297-4303.
4. Y. Nishino, A. R. Krauss, Y. Lin, D. M. Gruen, J. Nucl. Mater. 1996,
28, 346-353.
5. T. Tanabe, M. Tanaka, S. Imoto, Surf. Sci. 1987, 187, 499-510.
6. A. Segawa, K. Taniya, Y. Ichihashi, S. Nishiyama, N. Yoshida, N.
Okamoto, Ind. Eng. Chem. Res. 2018, 57, 70-78.
4
2
4
7. M. Boronat, A. Corma, M. Renz, J. Phys. Chem. B 2006, 110,
1168-21174
8. M. Koehle, R. F. Lobo, Catal. Sci. Technol. 2016, 6, 3018-3026.
Table of Contents (TOC)
(-111) facet
>
Basic sites

OH
M-ZrO2
O
O
O
Isopropanol
Furfuryl alcohol
Y = 100%
Furfural
T-ZrO2

(111) facet
< Basic sites
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins