Flame spray-synthesized Pt-Co/TiO2 catalysts for the selective hydrogenation of furfural to furfuryl alcohol

Article abstract of DOI:10.1016/j.catcom.2020.106246

Flame spray-synthesized Pt/TiO₂ and PtCo/TiO₂ catalysts with 0.7 wt% Pt and 0–0.4 wt% Co were studied in the hydrogenation of furfural to furfuryl alcohol (FA) at 50 °C and 2 MPa H₂. Particle formation under high temperatu

Full text of DOI:10.1016/j.catcom.2020.106246

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Flame spray-synthesized Pt-Co/TiO2 catalysts for the selective
hydrogenation of furfural to furfuryl alcohol
Weerachon
Tolek,
Kitima
Khruechao,
Boontida
Pongthawornsakun, Okorn Mekasuwandumrong, Francisco José
Cadete Santos Aires, Patcharaporn Weerachawanasak, Joongjai
Panpranot
PII:
S1566-7367(20)30322-8
DOI:
https://doi.org/10.1016/j.catcom.2020.106246
CATCOM 106246
Reference:
To appear in:
Catalysis Communications
Received date:
Revised date:
Accepted date:
30 April 2020
29 October 2020
17 November 2020
Please cite this article as: W. Tolek, K. Khruechao, B. Pongthawornsakun, et al., Flame
spray-synthesized Pt-Co/TiO2 catalysts for the selective hydrogenation of furfural to
furfuryl alcohol, Catalysis Communications (2020), https://doi.org/10.1016/
j.catcom.2020.106246
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Flame spray-synthesized Pt-Co/TiO catalysts for the selective hydrogenation of furfural to furfuryl alcohol
2
a
a
a
b
Weerachon Tolek , Kitima Khruechao , Boontida Pongthawornsakun , Okorn Mekasuwandumrong Francisco José Cadete Santos
c,d
e
a,*
Aires, , Patcharaporn Weerachawanasak , and Joongjai Panpranot joongjai.p@chula.ac.th
a
Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering,
Chulalongkorn University, Bangkok 10330, Thailand
b
Department of Chemical Engineering, Faculty of Engineering and Industrial Technology, Silpakorn University, Nakorn Pathom 73000, Thailand
c
Université de Lyon, Université Claude Bernard Lyon 1, CNRS - UMR 5256, IRCELYON
2, Avenue Albert Einstein, 69626-Villeurbanne Cedex, France
d
Laboratory for Catalytic Research, National Research Tomsk State University
36 Lenin Avenue, Tomsk 634050, Russian Federation
e
Department of Chemistry, Faculty of Science, King Mongkut's Institute of Technology Ladkrabang Bangkok, 10520 Thailand
*
Corresponding author.
Abstract
Flame spray-synthesized Pt/TiO and PtCo/TiO catalysts with 0.7 wt% Pt and 0-0.4 wt% Co were studied in the
2
2
o
hydrogenation of furfural to furfuryl alcohol (FA) at 50 C and 2 MPa H . Particle formation under high temperature flame facilitated
2
high Pt dispersion and formation of Pt-TiO interface sites, which were beneficial for furfural conversion to FA. Modifying with Co
x
accelerated rutile phase TiO formation, which strongly diminished hydrogenation activity on the (FSP)-PtCo/TiO . On the other
2
2
1

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hand, (I)-PtCo/TiO prepared by conventional impregnation, anatase phase TiO was preserved (> 85%) and both furfural conversion
2
2
and FA selectivity increased upon increasing Co loading.
Keywords: selective hydrogenation; furfural; furfuryl alcohol; Pt/TiO ; flame spray pyrolysis; Co addition
2
1
. Introduction
Furfural, obtained via acid-catalyzed dehydration of pentose such as xylose and arabinose or via fast pyrolysis of biomass, is
one of the most promising biomass-derived platforms as a building block in the bio-refinery approach [1, 2]. Selective hydrogenation
of furfural has gained much attention for the production of furfuryl alcohol (FA), an important intermediate for the manufacturing of
lysine, ascorbic acid (vitamin C), plasticizers, dispersing agent, and lubricants and is mainly used in the manufacture of resins,
synthetic fibers, and agrochemicals [3]. In furan industrial process, copper chromite has traditionally been used as the catalyst for
hydrogenation of furfural to FA [2, 3]. However, concern of the environmental toxic impact due to the chromium presence in the
catalysts led to the development of chromium free catalysts.
Platinum-based catalysts are known as highly efficient catalysts used in the hydrogenation of furfural to FA because of their
ability to hydrogenate the C=O under mild conditions [3-5]. Pt nanoparticles in the range of 3-7 nm were found to favor the
hydrogenation of furfural to FA whereas Pt particle size less than 3 nm promoted the decarbonylation of furfural to furan [3, 6].
However, modification of Pt catalysts by alloying [7, 8], adding promoters [7, 9], and by using strong metal-support interaction to
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induce electronic effects [8, 10] show significant impact on both activity and selectivity towards FA of the catalysts in furfural
hydrogenation. For examples, The metal-support interaction on Pt/TiO induced hydrogen spillover, leading to the formation of
2
furfuryl-oxy intermediate on the titania support [11, 12]. Synergetic effect between Pt and Co on carbon obtained by co-impregnation
was reported to be beneficial in furfural hydrogenation and product selectivity can be adjusted depending on the weight ratio of Pt and
Co [13, 14].
In this study, monometallic Pt/TiO and bimetallic Pt-Co/TiO were prepared by flame spray pyrolysis (FSP) and studied in the
2
2
liquid-phase selective hydrogenation of furfural to FA under mild conditions. The characteristics of Pt-Co/TiO formed by one-step
2
FSP were quite different from those obtained by co-impregnation as illustrated by various characterization techniques such as CO
pulse chemisorption, H -temperature-programmed reduction (H -TPR), transmission electron spectroscopy (TEM), and Fourier
2
2
transform infrared (FTIR) spectroscopy of adsorbed CO. A structural-activity relationship of these FSP-PtCo/TiO catalysts was
2
proposed.
2
2
. Experimental
.1 Catalyst preparation
The Pt/TiO (0.7 wt% Pt) and Pt-Co/TiO (0.7 wt% Pt and 0-0.4 wt.% Co) catalysts were prepared by FSP method according
2
2
to the procedure described in Ref. [15] using platinum (II) acetylacetonate (Pt(C H O ) , 99.99%, Aldrich), cobalt naphthenate
5
7
2 2
(
CoC H O , 6 wt% in mineral spirits, Aldrich), and titanium (IV) butoxide (Ti(OCH CH CH CH ) , 97%, Aldrich) as Pt, Co, and
22 14 4 2 2 2 3 4
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TiO precursors, respectively. The catalysts prepared by FSP are denoted as (F) Pt/TiO and (F) Pt-Co/TiO , respectively. The TiO
2
2
2
2
supported Pt and PtCo catalysts were also prepared by incipient wetness impregnation using platinum (II) acetylacetonate
Pt(C H O ) , 99.99%, Aldrich), cobalt naphthenate (CoC H O , 6 wt% in mineral spirits, Aldrich) as Pt and Co precursors and P-25
(
5
7
2 2
22 14
4
TiO as the support. The catalysts were dried in an oven at 100°C overnight, and calcined in air at 500°C for 2 h. The impregnated
2
catalysts are denoted as (I) Pt/TiO and (I) Pt-Co/TiO , respectively.
2
2
2
.2 Catalyst characterization
The XRD patterns were recorded using a Bruker D8 Advance X-ray diffractometer with Ni-filter CuK radiation. The actual
α
amount of Pt and Co loadings in the samples were analyzed by AAS. The N physisorption was conducted by using a Micrometrics
2
ASAP 2020 instrument with the Brunauer–Emmett–Teller (BET) method. The TEM observations were performed with a JEOL JEM
2
010 transmission electron microscope operated at 200kV and equipped with LaB thermoionic electron-gun, an UHR pole piece
6
(point resolution 0.196 nm) and a Pentafet Link-INCA EDX spectrometer (Oxford Instruments). The percentages of Pt dispersion
were measured by CO pulse chemisorption using a Micromeritics ChemiSorb 2750 equipped with ChemiSoft TPx software. Prior to
3
chemisorption, the catalyst was reduced with hydrogen (25 cm /min) at 500 °C for 2 h and then cooled down to the room temperature
3
under helium flow (25 cm /min). The H -TPR was carried out on a Micromeritics ChemiSorb 2750 with ChemiSoft TPx software.
2
3
The sample was pretreated at 150 °C under N flow (25 cm /min) for 1 h. The FT-IR spectra of adsorbed CO were collected using
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-1
FTIR-620 spectrometer (JASCO) with a MCT detector at a wavenumber resolution of 2 cm . The sample was heated to 300°C and
reduced by H for 30 min.
2
2
.3 Catalytic reaction study
Prior to the reaction test, the catalyst was reduced with hydrogen (25 cm /min) at 500 °C for 2 h. Approximately 0.05 g of
3
3
catalyst was dispersed into the reactant mixture of 50 µL furfural (99%, Aldrich) and 10.0 mL methanol (98%, Aldrich) in 100 cm
stainless steel autoclave reactor (JASCO, Tokyo, Japan). The selective hydrogenation reaction was carried out at temperature of 50 °C
and H pressure of 2 MPa for 2 h. After that, the liquid product was collected and analyzed by a gas chromatography equipped with a
2
flame ionization detector (FID) and Rtx-5 capillary column.
3
. Results and discussion
Based on the XRD patterns of the Pt/TiO and Pt-Co/TiO catalysts (Fig.1), the crystalline phases of TiO consisting of anatase
2
2
2
phase at 2θ=25° (major), 37°, 48°, 55°, 56°, 62°, 71°, and 75° and rutile phase at 2θ = 28° (major), 36°, 42°, and 57° [16] were
observed. The characteristic peaks for Pt metal/Pt oxides and Co metal/Co oxides could not be detected due probably to the low
amount of metal (Pt and Co) loading and/or high dispersion of these metals on the TiO support. As shown in Table 1, the TiO
2
2
anatase phase composition of (I) Pt/TiO (85.8%) was slightly lower than that of (F) PT/TiO (89.6%). Adding Co by different
2
2
methods led to different effects on the TiO phase composition. When Co was co-impregnated with 0.7 wt% Pt on the TiO support,
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the anatase phase composition increased from 85.8 to 90.5% with increasing Co loading from 0.04 to 0.2 wt%. Because the ionic
2
+
4+
2+
radius of Co (0.075 nm) is not much different from Ti (0.061 nm), it has been postulated that Co ions could enter into TiO
2
anatase structure and inhibit the phase transformation from anatase to rutile [17]. Upon substitutional dopants, the level of oxygen
vacancies decreased, inhibiting the rutile phase transformation [18, 19]. On the contrary, the TiO anatase phase composition of the
2
FSP-derived bimetallic Pt-Co catalysts was significantly decreased to ~70% comparing to the monometallic (F) PT/TiO . The ionic
2
4
+
4+
substitution of Ti with metal cationic ions could occur during the particle formation step during FSP. The replacement of Ti with
2
+
metal cationic ions having lower valences such as Co would generate more oxygen vacancies, promoting phase transformation from
anatase to rutile along the flame. Simultaneous formation of TiO support and Co metal by using polymeric precursor [20] or by sol-
2
gel technique [21] also showed similar effect of TiO phase transformation as in the FSP method. The average crystallite size of
2
anatase phase TiO for the (F) PT/TiO remained unaltered at 12 nm upon Co loading by FSP method whereas those obtained by co-
2
2
impregnation led to a slight increase of anatase phase TiO crystallite size from 12 to 16 nm.
2
2
The BET surface areas of the Pt-based catalysts prepared by impregnation were in the range of 52 - 60 m /g, and were slightly
2
larger than those prepared by FSP (43 - 50 m /g). Regardless of the preparation method used, Co addition as a second metal led to the
increment of the BET surface area. For a similar amount of metal loading, Pt dispersion of the Pt-based catalysts prepared by
impregnation was higher than that prepared by FSP. During FSP synthesis, suppression of CO chemisorption on surface Pt sites may
be due to partial coverage of metal surface by the support matrix [22, 23]. However, addition of Co as a second metal resulted in
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higher Pt dispersion regardless of the preparation method used. The interaction between Pt and Co was reported to compensate the
electron deficiency of Pt sites by d-electron rehybridization, thus enhancing the adsorption ability of CO [24].
The H -TPR profiles of the catalysts are shown in Fig. 2. All the synthesized Pt-based catalysts showed three major reduction
2
o
0
peaks at 94 - 105 C, 313 - 380°C, and 509 - 687°C, which were attributed to the reduction of PtO particles to metallic Pt particles,
x
the reduction of Pt species interacting with the TiO support in the form of Pt-TiO interface sites, and the reduction of surface
2
x
capping oxygen of TiO support, respectively [25]. It is obviously seen that the reduction peak of the Pt-TiO interface sites for the (F)
2
x
Pt/TiO catalyst shifted towards higher temperature and became broader compared to the (I) Pt/TiO , indicating the stronger metal-
2
2
support interaction induced by FSP method. For both cases, Co addition as a second metal in the Pt-based catalysts further shifted the
reduction temperature of the Pt-TiO species, due probably to the Pt-Co interaction and/or the migration of Co particles onto the Pt
x
surface (decoration effect) [26]. Moreover, the reduction of surface capping oxygen of TiO drastically shifted from 545°C for the
2
monometallic (I) Pt/TiO to 615 - 687°C for the bimetallic (I) Pt-Co/TiO while those of the FSP made catalysts remained unchanged
2
2
o
at 510 C. On the other hand, for bimetallic Pt-Co/TiO , the Pt-TiO reduction peak of (I) Pt-Co/TiO were located at higher
2
x
2
temperatures compared to (F) Pt-Co/TiO , which could be attributed to stronger metal-support interaction upon Co addition on the
2
impregnated catalysts. As a consequence, the (I) Pt-0.2Co/TiO showed higher conversion and selectivity of FA compared to (F) Pt-
2
0
.2Co/TiO , which was consistent with the metal-support interaction from H -TPR. Nevertheless, it can be suggested that Co addition
2 2
on FSP-made catalyst was not necessary for improvement of the interaction between metals and support in order to enhance the
selectivity to FA.
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As observed from the TEM images (Fig. 3), the monometallic (I) Pt/TiO catalyst was significantly composed of very small
2
and narrowly distributed nanoparticles (≤ 2 nm). Very rarely large (10 – 100 nm) Pt particles could be observed. (F) Pt/TiO catalyst
2
showed three types of nanoparticle sizes. First, a collection of very small nanoparticle (≤ 2 nm) similar to the one found on (I) Pt/TiO2,
then a collection of nanoparticles between 3 and 10 nm, and finally some very large spherical nanoparticles with sizes of several tens
to several hundreds nm. It is suggested that (I) Pt/TiO essentially showed very small Pt nanoparticle sizes (≤ 2 nm) and the selectivity
2
of FA was significant lower than the (F) Pt/TiO . The selectivity of FA may depend on the Pt particle size. It has been report that Pt
2
nanoparticles of sizes less than 2 nm supported on the silica are highly selective toward decarbonylation of furfural to main product of
furan over vapor phase furfural hydrogenation [6].
Concerning the Co addition as a second metal, (I) Pt-0.2Co/TiO was essentially consisted of very small nanoparticles as (I)
2
Pt/TiO . The average particle size of these nanoparticles slightly increased with the addition of Co (1.7 nm for (I) Pt-0.2Co/TiO and
2
2
1
.3 nm for (I) Pt/TiO ) and the particle size distribution was substantially broader. There are also very rare of larger particles. The (F)
2
Pt-0.2Co/TiO catalyst also showed characteristics similar to those of (F) Pt/TiO . Two types of nanoparticles and some large
2
2
spherical ones. The smaller nanoparticles also slightly increase in size of 1.9 nm for (F) Pt-0.2Co/TiO compared to 1.5 nm for (F)
2
Pt/TiO . The intermediate nanoparticles were not vary too much in size (6.8 nm for (F) Pt-0.2Co/TiO compared to 6.2 nm for (F)
2
2
Pt/TiO ). The large spherical particles have several hundreds nm. The larger spherical particles that originated by FSP method were
2
much larger than the size of the grains of titania and thus their interaction was poor, resulting to reduce the catalytic activity. The IR
-1
spectra of adsorbed CO on the different catalysts reduced at 500°C are shown in Fig. 4. The bands at 2188 - 2185 cm represented to
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4
+
-1
CO formed with Ti cations on the surface [27]. The band at 2086 - 2078 cm was assigned to CO linearly adsorbed on low -
0
0
-1
coordination Pt (Pt -CO) or Co (Co -CO) atoms on edge sites, while the band at 1850 cm was assigned to CO bridged between two
0
0
Pt metal atoms (Pt -CO-Pt ). It has been reported that linear-type adsorbed CO dominated on small Pt particles while bridge-type
0
adsorbed CO formed mainly on larger Pt particles [28, 29]. The ratio of Pt on linearly CO adsorbed (Pt -CO) to bridged CO adsorbed
0
0
(
Pt -CO-Pt ) atom was high due to the presence of very small Pt particles size (≤ 2 nm), which was consistent with the average particle
0
size observed from TEM and further increase selectivity of FA with the Co addition. The Pt -CO band center of (F) Pt/TiO shifted to
2
0
lower frequency with lower intensity compared to (I) Pt/TiO . The lower shift and increase in intensity of the Pt -CO band were also
2
observed in bimetallic (F) Pt-0.2Co/TiO compared to (I) Pt-0.2Co/TiO .
2
2
3
.2 Catalytic reaction study
In this study, FA was the only desired product being formed and 2-furaldehyde dimethyl acetal was the solvent product (SP)
which can be generated upon furfural acetalization when using methanol as the solvent [3] in the presence of metal catalysts. The
catalytic performances of all the Pt-based catalysts in the liquid-phase selective hydrogenation of furfural to FA are summarized in
Table 2. The furfural conversion and selectivity to FA over (I) Pt/TiO catalyst were 84.6% and 71.5%, respectively. Modification of
2
(
I) Pt/TiO by Co addition, furfural conversion and selectivity to FA increased with increasing Co loading up to 0.2 wt% in which
2
furfural was fully converted within 2 h of reaction time and high selectivity to FA up to 97.5% was achieved. Improvement in furfural
conversion upon Co addition by co-impregnation was correlated with high Pt dispersion and high TiO anatase phase composition.
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The subsurface oxygen vacancies on the reduced anatase TiO -supported metal catalysts were found to be favorable adsorption sites
2
for H atoms [30]. On the other hand, the hydrogen would weakly interact with the rutile TiO -supported ones [31]. In addition,
2
increase in the selectivity to FA could be attributed to the formation of Pt-TiO interface sites, in which oxygen atom in the C=O
x
group of furfural could be coordinated via a lone pair of electrons, promoting the selective activation of carbonyl bonds in furfural
[
32]. In the perspective of electronic effect, the stronger interaction between Pt and TiO support indicated more electron transfer from
2
support to metals, thus leading to the formation of electron-rich metal particles. The electronegativity of metal catalysts has been
reported to affect the C=O activation in furfural hydrogenation [32]. Stronger electronegativity of metal particles (or electron-rich
metals) could activate the C=O bond towards the furfural hydrogenation to FA. Similar results have been reported over Cu/TiO -SiO ,
2
2
Au/Al O , Fe-promoted Ni-B amorphous alloy catalyst, Au/ZrO , and Au/TiO .
2
3
2
2
Furfural conversion of the monometallic (F) Pt/TiO was not much different from the (I) Pt/TiO catalyst but the selectivity to
2
2
FA was found to be largely improved. This improvement was attributed to the stronger metal-support interaction upon FSP. However,
Co addition upon FSP slightly improved the selectivity to FA but decreased furfural conversion. It is suggested that the presence of
higher rutile TiO phase diminish the furfural conversion despite its high Pt dispersion based on CO chemisorption ability.
2
Nevertheless, it could be said that Co addition into the Pt-based catalysts upon FSP was unnecessary for modification of the
interaction between metals and support in order to enhance the selectivity to FA. Comparing the bimetallic Pt-0.2Co/TiO catalysts
2
prepared by impregnation and flame spray pyrolysis, the (I) Pt-0.2Co/TiO catalyst showed higher furfural conversion and selectivity
2
to FA than the (F) Pt-0.2Co/TiO catalyst because of higher Pt dispersion, TiO anatase phase composition, and the strong interaction
2
2
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between metals and support. Among all Pt-based catalysts in this study, the (I) Pt-0.2Co/TiO exhibited the highest FA yield at 97.5%.
2
st
nd
The activity of 1 cycle and 2 cycle for (F) Pt-0.2Co/TiO catalyst were 71.1% and 67.4%, respectively. It can be observed that the
2
nd
activity decreased by 5.2% after 2 reaction. Table 3 shows a comparison between the Pt-based catalysts in this study and those
reported in the literature. It is notable that one of the best results with furfural conversion (100%) and FA selectivity (95.7%) could be
obtained over 2 wt% Pt-1 wt% Re/TiO -ZrO [10], however more severe conditions (130℃, 5 MPa of H ) and long reaction time (8
2
2
2
h) were used in the presence of ethanol as a solvent. The catalysts in the present studies achieved similar conversion/selectivity under
milder reaction conditions.
4
. Conclusions
While Co addition via co-impregnation on Pt/TiO catalysts improved both furfural conversion and selectivity to FA due to
2
higher TiO anatase phase composition, high Pt dispersion, and stronger interaction between metals and support, formation of Pt-
2
Co/TiO by one-step FSP resulted in a decreased furfural conversion despite its high Pt dispersion due to the acceleration of rutile
2
phase transformation of the TiO . However, a largely improvement of FA selectivity on the FSP-made catalysts was attributed to the
2
stronger metal-support interaction upon FSP as revealed by the higher reduction temperature of the Pt-TiO interface sites. Thus,
x
modification of the Pt/TiO by Co addition was unnecessary for catalyst improvement when using the FSP Pt/TiO catalysts.
2
2
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Acknowledgments
The financial supports from the Rachadapisek Sompote Endowment Fund for the Postdoctoral Fellowship, Chulalongkorn
University for W.T. and the Thailand Science Research and Innovation for the Basic Research grant BRG6180001, IRN62W0001, and
CAT-REAC Industrial Project RDG6250033 are gratefully acknowledged. The authors also would like to thank the Research Team
Promotion grant from the National Research Council of Thailand (NRCT).
Declaration of interests
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the
work reported in this paper.
The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Credit Author Statement
Weerachon Tolek: Conducting a research and investigation process, specifically performing the experiments, or data/evidence
collection, Writing first draft
Kitima Khruechao: Conducting a research and investigation process, specifically performing the experiments, or data/evidence
collection
Boontida Pongthawornsakun: Data analyzing and discussion
Okorn Mekasuwandumrong: Data analyzing and discussion
Francisco José Cadete Santos Aires: Data analyzing and discussion
1
2

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Patcharaporn Weerachawanasak: Conducting a research and investigation process, specifically performing the experiments, or
data/evidence collection
Joongjai Panpranot: Acquisition of the financial support for the project leading to this publication, Reviewing and Editing
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Table 1. Metal loading, XRD analysis, N physisorption properties and Pt dispersion results of the Pt-based catalysts.
2
a
b
Metal loadings
Phase composition N physisorption results
2
Crystallite
size of
Pt
Average
pore
diameter
d
BET
Pore
dispersion
(%)
Pt
Co
Anatase Rutile
c
Catalyst
anatase
surface areas
c
volume
b
(
wt.%) (wt.%)
(%)
(%)
2
3
TiO (nm)
2
(
m /g)
(cm /g)
(nm)
(
(
(
(
(
(
I) Pt/TiO2
0.73
-
12
14
14
16
12
12
12
85.8
88.1
89.7
90.5
89.6
82.4
69.0
14.2
11.9
10.3
9.5
52.2
59.3
59.5
60.0
42.6
44.5
49.8
16.5
18.7
18.8
25.1
14.0
10.7
10.6
0.28
0.34
0.35
0.44
0.12
0.11
0.10
23.4
26.8
32.2
35.0
19.2
20.1
42.4
I) Pt-0.04Co/TiO2 0.70
I) Pt-0.1Co/TiO2 0.67
I) Pt-0.2Co/TiO2 0.66
0.04
0.11
0.22
-
F) Pt/TiO2
0.66
10.4
17.6
31.0
F) Pt-0.2Co/TiO2 0.65
0.20
(F) Pt-0.4Co/TiO2 0.74
a
0.48
Determined by atomic absorption spectroscopy
Base on XRD results
Determined from the Barret-Joyner-Halenda (BJH) desorption method
Based on CO-chemisorption
b
c
d
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Table 2. Catalytic performances for all Pt-based catalysts in the liquid-phase selective
hydrogenation of furfural to furfuryl alcohol under mild reaction conditions.
Selectivity (%)
Catalyst
Conversion (%)
Furfuryl alcohol
Solvent product
(
(
(
(
(
(
(
I) Pt/TiO2
84.6
85.8
86.4
100
83.4
71.1
68.3
71.5
88.9
93.5
97.5
95.1
95.5
97.2
28.5
11.1
6.5
2.5
4.9
I) Pt-0.04Co/TiO2
I) Pt-0.1Co/TiO2
I) Pt-0.2Co/TiO2
F) Pt/TiO2
F) Pt-0.2Co/TiO2
F) Pt-0.4Co/TiO2
4.5
2.8
Reaction: 50 µL furfural in 10 ml methanol at 50 ºC with 50 mg catalyst under 20 bar H for 120 min
2
Solvent product: 2-furaldehyde dimethyl acetal
Table 3. Comparison between the synthesized Pt-based catalysts in this work and others
Results
Reaction
time (h)
FA
selectivity
No. Catalysts
Reaction conditions
Ref.
Conversion
%)
(
(%)
This
work
1
2
(I) Pt-0.2Co/TiO2 50℃, 2 MPa of H2
2
8
100
100
97.5
95.7
Pt-Re/TiO -ZrO
130℃, 5 MPa of H2
50℃, ambient of H2
[10]
[3]
2
2
Pt/ɣ-Al O
80
79
77
99
97
98
2
3
3
4
Pt/MgO
7
Pt/CeO2
Cu-Pt/SiO2
Pt/SiO2
15.3
12.5
90.5
55.8
[9]
250℃, 0.7 MPa of H2 1.5
5
6
Pt/Al O
25℃, 6 MPa of H2
100℃, 2 MPa of H2
1
5
65.6
31
99.7
29
[1]
[2]
2
3
Pt/SiO2
Fig. 1. XRD patterns of the Pt-based catalysts prepared by impregnation and flame spray
pyrolysis.
Fig. 2. H -TPR profiles of (a) (I) Pt/TiO , (b) (I) Pt-0.04Co/TiO , (c) (I) Pt-0.1Co/TiO , (d) (I)
2
2
2
2
Pt-0.2Co/TiO , (e) (F) Pt/TiO , (f) (F) Pt-0.2Co/TiO and (e) Pt-0.4Co/TiO catalysts.
2
2
2
2
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Fig. 3. TEM micrographs and particle size distribution of (a) (I) Pt/TiO , (b) (I) Pt-0.2Co/TiO ,
2
2
(
c) (F) Pt/TiO and (d) (F) Pt-0.2Co/TiO catalysts.
2 2
Fig. 4. IR spectra of CO adsorbed on (a) (I) Pt/TiO , (b) (I) Pt-0.2Co/TiO , (c) (F) Pt/TiO and
2
2
2
(
d) (F) Pt-0.2Co/TiO catalysts.
2
Graphical abstract
Highlights





Flame spray-synthesized Pt/TiO and PtCo/TiO with 0.7 wt% Pt and 0-0.4 wt% Co
2
2
Appropriate uniform Pt particle size 3.1-3.5 nm with strong Pt-TiO interface sites
x
High furfuryl alcohol selectivity (> 95%) with and without Co addition
Co adding during FSP accelerated rutile TiO , leading to low catalyst activity
2
Opposite trend observed on co-impregnated PtCo, performance improved by adding Co
1
7