In-situ hydrogenation of furfural conversion to furfuryl alcohol via aqueous-phase reforming of methanol

Article abstract of DOI:10.1016/j.apcata.2019.05.031

It is a promising pathway to reduce the dependence on fossil fuels and obtain the bio-fuels or chemicals production from biomass derivatives. The conversion from furfural (FFR) to furfuryl alcohol (FFA) is an important industrial technology using the liquid-phase hydrogenation method with external hydrogen gas. However, the natural environment is threatened by the security of external hydrogen gas, toxicant catalyst, and the high energy consumption. Recently, in-situ hydrogenation is a novel method to converse FFR to FFA at mild reaction conditions to replace the dangerous external hydrogen gas. In this paper, we reported an efficient in-situ hydrogenation method via aqueous-phase reforming of methanol using Pt loading MgTiO₃ (perovskite-type material) at mild conditions. Pt nanoparticles were high dispersion on the nano-MgTiO₃-450 surface, and CH₃OH and H₂O were reformed to produce hydrogen gas on the catalyst surface through the action of Pt nanoparticles. A part of active hydrogen could be involved in the reduction of Pt²⁺ to Pt⁰, resulting in the perfect recyclability of the Pt@MT-450 catalyst. The other part of active hydrogen were participated in the hydrogenation of FFR conversion to FFA under the interaction of Pt and Mg elements. The in-situ hydrogenation of FFR to FFA using Pt@MT-450 is an effectively pathway to reduce the reaction conditions than that with external hydrogen gas.

Full text of DOI:10.1016/j.apcata.2019.05.031

Accepted Manuscript
Title: In-situ hydrogenation of furfural conversion to furfuryl
alcohol via aqueous-phase reforming of methanol
Authors: Shiqiu Zhang, Xue Yang, Kui Zheng, Ruihao Xiao,
Qidong Hou, Bangjun Liu, Meiting Ju, Le Liu
PII:
S0926-860X(19)30244-3
DOI:
Reference:
https://doi.org/10.1016/j.apcata.2019.05.031
APCATA 17097
To appear in:
Applied Catalysis A: General
Received date:
Revised date:
Accepted date:
2 March 2019
24 May 2019
27 May 2019
Please cite this article as: Zhang S, Yang X, Zheng K, Xiao R, Hou Q, Liu
B, Ju M, Liu L, In-situ hydrogenation of furfural conversion to furfuryl alcohol
via aqueous-phase reforming of methanol, Applied Catalysis A, General (2019),
https://doi.org/10.1016/j.apcata.2019.05.031
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

In-situ hydrogenation of furfural conversion to furfuryl alcohol
via aqueous-phase reforming of methanol
Shiqiu Zhang1, Xue Yang1, Kui Zheng2, Ruihao Xiao3, Qidong Hou1, Bangjun Liu3, Meiting
Ju1, *, Le Liu1, *
1. College of Environmental Science and Engineering, Nankai University, Jinnan District,
Tianjin, 300350, RP China
2. Analytical and Testing Center, Southwest University of Science and Technology, Mianyang,
621010, Sichuan, RP China
3. School of Materials Science and Engineering, Northeastern University, Shengyang, 110819,
Liaoning, RP China
4. Department of Environmental Analytical Chemistry, Institute of Atmospheric and
Environmental Sciences, J. W. Goethe University, Frankfurt am Main, Germany
*Corresponding author: Email: nkujumeiting@sohu.com (Meiting Ju), Tel: +86 13820988813; Email:
tjliule@126..com (Le Liu), Tel: +86 13672031215
Address: College of Environmental Science and Engineering, Nankai University, 38 Tongyan Road, Tianjin
300350, China.
Graphical abstract
1

Highlights



The hydrogenation of FFR to FFA via APR of CH3OH using Pt@MT-450 catalyst.
Perfect conversion, selectivity, and recyclability of the catalyst.
The safe, mild condition without external hydrogen gas
Abstract:
It is a promising pathway to reduce the dependence on fossil fuels and obtain the
bio-fuels or chemicals production from biomass derivatives. The conversion from
furfural (FFR) to furfuryl alcohol (FFA) is an important industrial technology using
the liquid-phase hydrogenation method with external hydrogen gas. However, the
natural environment is threatened by the security of external hydrogen gas, toxicant
catalyst, and the high energy consumption. Recently, in-situ hydrogenation is a novel
method to converse FFR to FFA at mild reaction conditions to replace the dangerous
external hydrogen gas. In this paper, we reported an efficient in-situ hydrogenation
method via aqueous-phase reforming of methanol using Pt loading MgTiO3
(perovskite-type material) at mild conditions. Pt nanoparticles were high dispersion
on the nano-MgTiO3-450 surface, and CH3OH and H2O were reformed to produce
hydrogen gas on the catalyst surface through the action of Pt nanoparticles. A part of
active hydrogen could be involved in the reduction of Pt2+ to Pt0, resulting in the
perfect recyclability of the Pt@MT-450 catalyst. The other part of active hydrogen
2

were participated in the hydrogenation of FFR conversion to FFA under the
interaction of Pt and Mg elements. The in-situ hydrogenation of FFR to FFA using
Pt@MT-450 is an effectively pathway to reduce the reaction conditions than that with
external hydrogen gas.
Keywords: Furfural; Furfuryl alcohol; Aqueous-phase reforming; Alcohols; Mild
condition
1. Introduction
As the depletion of fossil resource and growing environmental deterioration,
biomass resource has received increased attentions in various industries. The
productions of bio-fuels or added-value chemicals obtained from sustainable biomass
resources are a promising pathway to reduce the dependence on fossil fuels and
decrease the emission of greenhouse gas [1-3]. In particular, furfuryl alcohol (FFA)
has been the primarily chemical intermediate as the starting for the production of
chemical products, such as vitamin C, lysine, plasticizer, dispersing agent, lubricant,
resins etc. [1, 4-6]. The annual production of FFA exceeds 2.8×105 t/Y, and
approximately 60% of FFA are produced by the catalytic hydrogenation of furfural
(FFR), which is one of the main products derived from lignocellulosic biomass [7, 8].
However, the hydrogenation of FFR conversion to FFA is a complex chemical
reaction with lots of undesirable products. The potential reaction pathways for the
hydrogenation of FFR [9, 10] are displayed in Figure 1. FFA produced by the
hydrogenation of C=O is in competition with tetrahydrofurfural (THFR) obtained by
the hydrogenation of ring. The other by-products accompanied by the hydrogenation
of FFR are 2-methylfuran (2-MF, hydrogenolysis of C=O), 2-methyltetrahydrofuran
(2-MTHF, hydrogenolysis followed by hydrogenation). Additionally, the formation of
furan and butanol are produced by the decarbonylation reaction under the same
conditions of the hydrogenation of FFR. Therefore, a variety of undesired substances
could be produced via the saturation of different functional groups, and all these
competing reactions make it difficult to enhance the selectivity of the target product
3

(FFA). Therefore, the core challenge of hydrogenation of FFR conversion to FFA is to
avoid the side reactions and control the hydrogenation extent.
Figure 1 Reaction pathways of the hydrogenation of FFR
Industrially, there are two strategies to produce FFA via the hydrogenation of
FFR [5, 11, 12]: gas-phase hydrogenation and liquid-phase hydrogenation.
Considering gas-phase hydrogenation, the energy consumption of FFR evaporation is
high, and the selectivity or conversion of FFA are low [13, 14]. Compared with
gas-phase hydrogenation, liquid-phase hydrogenation is an effective technology with
preferable selectivity [16, 17], and molecular hydrogen gas is regarded as one of the
most popular raw materials in conventional liquid-phase hydrogenation. However, the
application of expensive external hydrogen gas presents several issues, such as the
potential safety issues regarding hydrogen transportation, storage, and handling [5, 9].
Furthermore, the conventional liquid-phase hydrogenation would accompany by the
huge energy consumption with high temperature and pressure, and the catalysts (such
as Cr-species) are high toxicity and unfriendly to environment. In order to realize the
green hydrogenation, the technique for FFR hydrogenation to FFA using environment
friendly catalysts and solvents without external hydrogen gas at mild conditions is
required. In recent years, catalytic transfer hydrogenation (CTH), referring to the
addition of hydrogen to a molecule from a non-H2 hydrogen donor, has been proposed
as an attractive way to hydrogenate organic molecules including biomass-derived
compounds [18-20]. In-situ hydrogenation, one of the catalytic transfer hydrogenation,
is a novel method to upgrade the complex chemicals [16, 21]. The literatures release
4

that conversion efficiency of in-situ hydrogenation using activity hydrogen from
aqueous-phase reforming (APR) is higher than the conventional liquid-phase
hydrogenation using external hydrogen gas as the hydrogen donors [21, 22]. This
method does not employ the hazardous pressurized hydrogen gas, catalysts and
solvents, and it could reduce the cost of expensive transportation and storage of
external gaseous hydrogen at mild conditions. In the reaction, catalysts, hydrogen
donors, and solvents would affect the efficiency of upgrading and the product
distributions. Several researches reporting the hydrogenation in organic components
(alcohols or formic acid) have been published, while the hydrogenation proceed in
water is still quite challenging. The researches about the catalysts about
aqueous-phase reforming are noble metal loaded materials and non-noble materials,
including Au, Pt, Pd, Ni, Mo, Ce, Mg etc. [23, 24], and the support materials are
usually activated carbon, metallic oxide, alloy, polyethersulfone (PES) and perovskite
type materials etc. [23, 25, 26]. While the research about the coupling of APR and
hydrogenation is less in publication and need further investigation.
In this paper, we investigated the in-situ hydrogenation of furfural conversion to
furfuryl alcohol via aqueous phase reforming of alcohols using homemade MgTiO3
support material with noble metals loading at mild conditions. The alcohols contained
methanol, ethylenglycol, and glycerol, and the noble metals were Au, Pt, and Pd.
Effect of the other parameters on the hydrogenation process was also investigated to
optimize the experimental conditions, including reaction temperature, reaction time,
reaction pressure, and component proportion. Additionally, the commercial Pd/C
catalyst and recyclability of the excellently catalyst were also performed. Moreover,
in order to better understanding the mechanism of the in-situ hydrogenation catalysis,
the aqueous-phase reforming of methanol and water to produce hydrogen gas and the
hydrogenation of FFR conversion to FFA with external hydrogen gas were also
investigated. The morphology properties were characterized by scanning electron
microscope (SEM), energy dispersive X-ray spectroscopy (EDX), transmission
electron microscope (TEM) and high angle angular dark field-scanning transmission
electron microscopy (HAADF-STEM). The structures and chemical states of the
5

catalyst were analyzed by thermogravimetric analysis (TG-DSC),
H2-temperature-programmed reduction (H2-TPR), O2-temperature-programmed
desorption (O2-TPD), H2-temperature-programmed desorption (NH3-TPD), X-ray
diffraction (XRD), nitrogen adsorption-desorption isotherms, Fourier transform
infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS).
2. Materials and methods
2.1 Reagents
Furfural (C5H4O2, GC: 99.5%) and furfuryl alcohol (C5H6O2, GC: 98%) were
purchased from Aladdin Chemistry Co. Ltd. Methanol (CH4O, HPLC: 99.9%), ethyl
alcohol (C2H5O, GC: 99.9%), ethylenglycol (C2H6O2, GC: 99.9%) and glycerol
(C3H8O3, GC: 99.9%) were purchased from Tianjin Kemiou Chemical Reagent Co.,
Ltd. Tetrabutyl titanate (C16H36O4Ti, AR: 99.9%) and Mg(NO3)2·6H2O (AR: 99.9%)
were purchased from Sinopharm Chemical Reagent. Commercial catalyst (Pd/C, Pd:
1.0 wt%) was purchased from Aladdin Chemistry Co. Ltd. HAuCl4·6H2O,
H2PtCl6·6H2O and Na2PdCl4 were all analytically pure and purchased from Tianjin
Kemiou Chemical Reagent Co., Ltd. The water used for all the experiments was
deionized water with a resistivity of 18.25 MΩ·cm.
2.2 Catalysts preparation
2.2.1 MgTiO3 support
The details of the MgTiO3 support materials preparation were as follows.
Solution-A: 0.01 mol·L-1 of C16H36O4Ti was dissolved in the absolute ethyl alcohol
with vigorously stirring. Solution-B: 0.01 mol·L-1 of Mg(NO3)2·6H2O was dissolved
in 100 mL of ethyl alcohol aqueous solution (Vethyl alcohol:Vwater=1:1). Then the
isopyknic Solution-B was injected in Solution-A dropwise (5 mL·min-1) with
vigorously stirring for 4 h. Next, the suspension was crystallized under vacuum
condition at 318 K for 12 h, then it was filtrated, washed and dried at 393 K for 12 h.
Finally, the powder was calcination in muffle at 723 K, 823 K and 923 K for 3 h
respectively, denoted as MgTiO3-450, MgTiO3-550 and MgTiO3-650. So the MgTiO3
support materials were obtained.
6

2.2.2 Noble metal loading
An appropriate amounts of HAuCl4·4H2O, H2PtCl6·6H2O and Na2PdCl4 were
loaded onto the homemade MgTiO3 support materials surfaces respectively, using the
wetness impregnation method [16, 27]. Firstly, the MgTiO3 support materials were
added into the aqueous solution of H2AuCl6·6H2O, H2PtCl6·6H2O or H2PdCl6·6H2O.
Secondly, the mixture was adjusted to pH=9.5 using 30% ammonium hydroxide.
Thirdly, the suspensions were ultrasonic dispersion vigorously for 4 h, dried under
vacuum condition at 353 K for 12 h (denoted as Au/Pt/Pd powders), and the Au/Pt/Pd
powders were calcination at 623 K, denoted as Calcination sample. Lastly, the
Calcination samples were reduced with Ar/H2 (VAr:VH2=90:10), which the reduction
temperature program heated the sample to 623 K at a rate of 5 K·min−1 and held it for
1 h. The catalyst samples were denoted as Au/Pt/Pd@MT-450, Au/Pt/Pd@MT-550
and Au/Pt/Pd@MT-650. Hence, the noble metal (0.5 wt%) loaded catalysts were
prepared.
2.3 Experimental procedure
2.3.1 In-situ hydrogenation
The in-situ hydrogenation catalysis experiments were carried out via the
aqueous-phase reforming of alcohols for hydrogenation of FFR conversion to FFA.
Deionized water, alcohols, furfural and catalyst were added into a 10 mL autoclave,
which the proportions (mass ratio) of water, alcohols, and FFR were 1:49:1, 10:40:1,
20:30:1, 25:25:1, 30:20:1, 40:10:1, and 49:1:1 with the fixed volume of 6 mL. The
ratios of furfural/catalyst mass proportion were also tested. The alcohols contained
methanol, ethylenglycol and glycerol, and the air in the autoclave was removed with
N2 flow before heating. Then the autoclave was heated at a rate of 3 K·min-1 with a
stirring rate of 500 rpm. The desired reaction temperature was between 373 K and 453
K (20 K interval), and remained for a set time period. The effect of initial pressure
also performed with argon gas (0-5 MPa, 1 MPa interval). In addition, 0 MPa referred
to the approximate 0 MPa, which the autoclave was purged by extremely low N2 gas
flow for 5 min, and then closed the air inlet valve and the air outlet valve. After the
reaction, the autoclave was cooled rapidly in a water bath to room temperature. The
7

mixture was removed from the autoclave and filtered through a 0.45-μm membrane
filter. Then the products were obtained in high purity by distillation of the filtrate
under vacuum at 333 K to recover the alcohols and water. The recovered alcohols and
water could be used in subsequently hydrogenation tests. Furthermore, the tests
without catalysts were also executed at the same conditions. The hydrogenation
products were analyzed by Shimadzu GC-14A gas chromatography equipped with a
Flame Ionization Detector and a capillary column (CP-Wax 52CB).
2.3.2 Controlled experiment
The controlled experiments were carried out to investigate the mechanism of the
in-situ hydrogenation of FFR conversion to FFA. The test was broken into two parts.
The first part was to execute the aqueous-phase reforming of CH3OH and H2O using
the Pt@MT-450 catalyst at the same conditions of the in-situ hydrogenation test. The
sealed autoclave was purged using N2 (10 vol% Ar, internal standard) three times.
After the reactions, the gas phase was analyzed using Agilent 7820 gas
chromatograph with a thermal conductivity detector (TCD). The second part was to
set up the traditional hydrogenation of FFR to FFA with external hydrogen gas. The
reaction step was the same as the Section 2.3.1 without methanol.
3. Results and discussion
3.1 Parameters affecting
Figure 2a & Figure S1(a-c) show the conversion and selectivity of FFR
hydrogenation to FFA using different solvents and catalysts. As shown in the results,
MgTiO3-450 support material exhibits the higher catalytic activity than the other
support materials, and Pt loaded MgTiO3-450 (Pt@MT-450) releases the best catalytic
activity than Ag or Pd loaded MgTiO3 materials in different solvents system.
Pt@MT-450 also shows the higher catalytic activity than the commercial catalyst
(Pd/C). While the hydrogenation of FFR to FFA without catalyst is approximately
equal to zero, and the conversion and selectivity of FFR hydrogenation to FFA are
lowest using water as the single solvent. Methanol with water displays the better
catalytic efficiency than ethylenglycol or glycerol with water, indicating that the more
8

complex structures of alcohols lead to the lower catalytic activity. Hence, the suitable
solvent is methanol with water. Figure 2b shows the effect of the components
proportion on the hydrogenation of FFR. It is evident that the suitable components
proportion is 30:20:1 for water:methanol:FFR. Figure S1 (d-e) show the conversion
and selectivity of FFR hydrogenation to FFA at different reaction temperature and
reaction time. As shown in Figure S1d, the conversion of FFR increases with the
reaction temperature increasing, while the selectivity of the target product increases
before 393 K and then decreases. Figure S1e shows that the conversion of FFR
increases before 1.0 h and then it remains a constant, while the selectivity increases
before 1.0 h and then decreases obviously. The decreased selectivity could be caused
by the condensation reaction or the depth hydrogenation. Hence, the suitable reaction
temperature is 393 K and the suitable reaction time is 1.0 h. The effect of the initial
pressure is shown in Figure 2c. From the results, it indicates that the initial pressure
could affect the conversion and the selectivity of FFR hydrogenation to FFA distinctly.
With the initial pressure increasing, both the conversion and the selectivity increase.
The suitable initial pressure is 0.5 MPa, and the conversion of FFR is about 88% and
the selectivity is near 95%. In order to further enhance the conversion of FFR, the
catalyst dosage was also investigated (Fig. S1f). As shown in the figure, it could be
known that the higher catalyst dosage, the higher conversion of FFR. The suitable
dosage was 10:1 for furfural:catalyst mass ratio with the conversion of 97.1% and the
selectivity of 96.3%. The recyclability of the Pt@MT-450 catalyst is shown in Figure
2d. From the results, it is evident that the conversion and selectivity of FFR
hydrogenation to FFA also maintain the high level after six times recycled. Compared
to the published articles [9, 28], the catalytic activity of aqueous-phase reforming of
methanol technology using Pt@MT-450 catalyst is superior than the other
technologies and catalysts.
9

10

Fig.2 Parameters affecting the in-situ hydrogenation of FFR
(a: Conversion and selectivity of the FFR hydrogenation to FFA using different catalysts and
solvents, Condition: 393 K, 1 h, 0 MPa, 10:40:1:0.02 (water:alcohols:FFR:catalyst); b: effect of
the components proportion, Condition: 393 K, 1 h, 0 MPa, CH3OH+H2O, Pt@MT-450; c: effect of
the initial pressure, Condition: 393 K, 2 h, 30:20:1:0.02 (water:alcohols:FFR:catalyst),
CH3OH+H2O, Pt@MT-450; d: recyclability of the catalyst, Condition: 393 K, 1 h, 0.5 MPa,
30:20:1:0.1 (water:alcohols:FFR:catalyst), CH3OH+H2O, Pt@MT-450)
11

3.2 Contrast test
The results of the aqueous-phase reforming of CH3OH to produce molecular
hydrogen gas are listed in Table 1. From the results, the hydrogen gas could be
produced via methanol reforming over the Pt loaded MgTiO3-450 catalyst. While the
hydrogen gas could not be detected by MgTiO3-450 support material without Pt
loading, indicating that Pt element performed the important role in hydrogen gas
production. On the other hand, the production amount of hydrogen gas by
Pt@MT-450 increases with the initial pressures increase. Considering the TOF value,
the Pt@MT-450 value increased with initial pressures, and the TOF value under 1.0
MPa is about 1085. In addition, the other gases has been listed in Table S1. According
to the results, it could be observed that there is a slight amounts of CO production.
Table 1 The results of the in-situ aqueous-phase reforming of CH3OH*
H2 production ratea
TOFb
Initial pressure
(p0, MPa)
MT-450
Pt@ MT-450
MT-450
Pt@ MT-450
573
0
-
-
-
34.1
51.7
64.6
-
-
-
0.5
1.0
869
1085
* Time: 1.0 h, Temperature: 393 K, FFR:Catalyst=10:1
a: μmol H2 per gram catalyst per hour
b: the turnover frequency (mol H2 per mol Pt over 1 hour)
The results of GC-MS analysis via the traditional hydrogenation of FFR with
external hydrogen gas are listed in Table 2. The conversion using traditional
hydrogenation with external hydrogen gas performs an obviously decrease than that
using the in-situ hydrogenation method at the same conditions. The conversion
increases with the initial pressure increase, and the conversion is only 81.38% under
the initial pressure of 1.0 MPa, and there is also a significant reduction on the
selectivity of FFR hydrogenation to FFA. The results of GC-MS indicate that the
products contain the furfuryl alcohol, 2-methylfuran, furan, tetrahydrofurfuryl alcohol,
and even 2-methyltetrahydrofuran. Therefore, the efficiency of the traditional
hydrogenation with external hydrogen using the Pt@MT-450 as the catalyst is lower
than that of the in-situ hydrogenation at the same conditions.
Table 2 GC-MS analysis of the traditional hydrogenation with external hydrogen gas*
12

Initial pressure (p0, MPa)
Yield (%)
0
0.5
1.0
Furfuryl alcohol
2-methylfuran
Furan
70.7
10.3
13.4
3.8
72.9
9.3
75.5
7.7
10.9
5.2
8.9
Tetrahydrofurfuryl
2-methyltetrahydrofuran
Conversion
6.2
1.8
1.7
1.6
35.7
68.2
81.4
*Catalyst: Pt@MT-450, Time: 1.0 h, Temperature: 393 K
3.3 Catalyst Characterization
3.3.1 Morphology properties
SEM & EDX analysis. Figure S2 shows the SEM images and EDX spectra of
Pt@MT-450 catalyst. As shown in Figure S2a & S2b, the results release that there is
no specific morphology and particle size, and it could be observed as the nearly
spherical structure with nanoscale particles size. The elemental mapping results of the
catalyst (Figure S2c & Figure S2d) show a homogeneous distribution of Mg element,
Ti element, and Pt element on the Pt@MT-450 surface.
TEM analysis. The morphology and the particles size distribution of Pt
nanoparticles on the Pt@MT-450 catalyst are characterized and examined by TEM.
From Figure 3a, the MgTiO3-450 support material has the polygonal crystalline shape
which is consistent with the results of SEM, and the average particles size of the
support material is about 20-40 nm. As shown in Figure 3b & 3c, it shows that the
high dispersion Pt nanoparticles could be easily obtained via incipient wetness
impregnation method. Moreover, the average size of the Pt nanoparticles is about 2.2
nm in the visible range. The HAADF-TEM images (Figure 3d & 3e) indicate that the
brighter particles could be the Pt nanoparticles and homogeneous dispersion on the
MgTiO3-450 support material. Figure 3f displays the particles distribution of the Pt
nanoparticles, indicating that the Pt nanoparticles in mean size of about 2-3 nm.
13

Fig. 3 TEM images (a-c), HAADF-TEM images (d-e), and the Pt nanoparticles distribution of the
Pt@MT-450 catalyst
3.3.2 Physicochemical properties
The physicochemical properties of the Calcination sample, Fresh catalyst,
Recycled catalyst, APR catalyst, TH catalyst (Pt@MT-450-450 used in traditional
hydrogenation with external hydrogen gas), and Support material are summarized in
Table S2. The presence of Pt, Ti and Mg elements in all the catalysts are determined
by ICP-AES. The Pt and Mg mass ratios in Support material are 0% and 20.62%,
closed to theoretical content of MgTiO3. Compared to the Support material, the
Recycled catalyst has the lowest Mg content which may be dissolved in the solvent,
and it has no significantly change in the other catalysts. The Pt element also has no
significantly change except for the Recycled catalyst, which could be related to the
separation of small amount of Pt nanoparticles from the support material surface after
reaction. The surface specific areas (SSA) of the support material is 132.73 m2·g-1,
while after loading the Pt nanoparticles, the SSA of the Fresh catalyst increases to
144.15 m2·g-1. As depicted in Figure S3, the catalyst performs the isotherms with
characteristics of type III patterns, and the H4 type isotherm of the catalyst reflects the
slot hole, which might be resulted from the plate particle accumulation. After
hydrogenation reaction, the SSA of the Recycled catalyst is lower than the Fresh
14

catalyst.
DSC-TG analysis. As shown in Figure S4, it reveals the weight loss of the Pt
powder during the measurement under air flow condition. The material is stable, and
the maximum weight loss is only 0.7960% at approximately 653 K which may be
mainly caused by the dissociation of chloroplatinic acid. Then it increase about
0.1592% from 653 K to 923 K may be caused by the oxidation of Pt element. Hence
this Pt powder is suitable for calcination at 673 K and the dissociation of
chloroplatinic acid is conducive to the reduction of the oxidation platinum.
FT-IR analysis. Figure S5 shows the FT-IR spectra of the Support material,
Fresh catalyst, Recycled catalyst, APR catalyst, and TH catalyst. It shows that the
bands near 570 and 445 cm-1 are attributed to the characteristic peak of the MgTiO3
support material (Ti−O stretching and Ti−O−Ti bridge stretching modes) [29]. As
compared to the Fresh catalyst, the characteristic peaks of the other catalysts barely
change. However, the other new bands on the Recycled catalyst, APR catalyst and TH
catalyst may be assigned to the characteristic peaks of FFR or FFA.
XRD analysis. Figure 4 shows the X-ray diffraction patterns of the Fresh
catalyst, Recycled catalyst and Support material. It reveals that the MgTiO3-450
support material is matched well with the pattern of standard diffraction peaks of
geikielite (pdf = No. 06-0494). Compared to the Support material, the Fresh catalyst
also is matched well with the pattern of platinum (pdf = No. 04-0802, 2θ=39.5, 46.6
and 67.3 represent the {1,1,0}, {2,0,0} and {2,2,0}). Moreover, it also shows that the
peak intensity of the Recycled catalyst releases an obviously decrease, indicating that
the crystallinity of the MgTiO3-450 support changed during the catalysis recycled.
Moreover, the characteristic peaks of Pt are barely to find in the Recycled catalyst,
and it indicates that the Pt particle reacted in the hydrogenation process or separated
from the catalyst surface, resulting a low activity.
15

Fig.4 X-ray diffraction patterns of the Fresh catalyst, Recycled catalyst and Support material
H2-TPR analysis. The H2-TPR profiles of the Calcination sample, Fresh catalyst,
Recycled catalyst, APR catalyst, TH catalyst, and Support material are plotted in
Figure S6. All the materials show two or three reduction peaks except for Fresh
catalyst (only one peak). Regarding the Fresh catalyst, the only reduction peak could
be attributed to the partial reduction of Ti4+ to Ti3+ [30, 31]. There is no other
reduction peak because that the sample has been reduced under H2 flow under 623 K.
For the rest of samples, the peak at about 607 K could be assigned to the reduction of
high valence Pt to zero valence Pt. The normal Pt reduction temperature is more than
623 K, while the lower reduction temperature of the catalyst implies that a smaller
size and higher dispersion of Pt nanoparticles on the MgTiO3-450 support material
[32]. The reduction peak at about 473 K could be attributed to reduction of removing
physically adsorbed oxygen and/or the ordinarily chemically oxygen on the sample
surfaces [33]. Table 3 shows the H2 consumption calculated through quantitative
integration of the corresponding TPR peaks. There is on obviously change of the
consumption of Ti4+ reduction peak for all samples, and the H2 consumption amount
of Ti4+ reduction to Ti3+ for each sample is about 0.35 mmol·g-1. Moreover, the
consumptions of Pt reduction peaks for Recycled catalyst, APR catalyst, and TH
16

catalyst show a significantly decrease than the Calcination sample (the order:
Calcination sample > Recycled catalyst > TH catalyst > APR catalyst). The H2
consumption amount of the Pt reduction peak on Support material sample was not
detected, indicating that no other elements on the sample could be reduced at the same
temperature.
O2-TPD analysis. As shown in Figure S7, the oxygen desorption profiles
exhibit three regions from 373 to 600 K (Region I), from 673 to 900 K (Region II),
and from 900 to 1123 K (Region III), respectively. The desorbed oxygen in Region I
could be ascribed to the surface adsorbed molecular oxygen and/or oxygen species
migrating via surface oxygen vacancies [22]. For the Region II, it could be ascribed to
the oxygen species migrating from the subsurface of Pt particles or the interface
between the Pt particles and the support material [34, 35]. Peaks at about 1023 K in
the Region III for all the catalysts could be linked to lattice oxygen, whose migration
and desorption should be achieved at even high temperature [35]. Table 3 also
summarizes the desorbed oxygen amounts based on the quantitative integration of
O2-TPD profiles. The lowest desorption amount of Support material and Calcination
sample in Region I was detected, which could be associated to the lowest oxygen
mobility or the minimum amount of surface oxygen species. The phenomenon could
be related to lack of surface oxygen vacancies. While the desorption amount of Fresh
catalyst in Region I is higher than Recycled, APR, and TH catalyst samples,
indicating that the oxygen vacancies decrease on the catalysts after reaction and lead
to a decrease in catalysis hydrogenation. For the Region II, there was no signal on
Support sample surface, while it was detected the highest amount on the Fresh
catalyst surface. For the Region III, it should be noted that all the catalysts exhibited
the high amount of desorbed oxygen (centered at 1023 K), indicating that the lattice
oxygen over MgTiO3 could be released. According to the literatures [36], the higher
content of oxygen vacancies and oxygen species on the catalyst surface, the higher
catalytic activity.
NH3-TPD analysis. NH3 is often selected as the probe molecule to test the
acidity of the catalyst, which could influence the catalytic activity for hydrogenation.
17

NH3-TPD is measured to determine acid strength and amounts of acid sites.
According to the results (Fig. S7 and Tab. 3), the NH3-TPD profiles could be divided
into three regions: i) the low temperature region from 373 to 573 K corresponds to
weak-strength acid sites, ii) the middle temperature region from 573 to 773 K
corresponds to moderate acid sites iii) the peak appearing at temperatures higher than
923 K assigns to the strong acid sites [22, 37]. All the samples present the Region I,
and Region II do not appear in Calcination sample and Support material. For Region
III, the Fresh catalyst is observed the highest intensity. After the reaction, both the
intensities of moderate and strong acid sites decrease. The strong acid sites are benefit
for the C=O adsorption on the catalyst, leading to the high selectivity [38].
Table 3 H2 consumption and amounts of desorbed NH3 and O2 over catalysts Calcination sample,
Recycled catalyst, APR catalyst, TH catalyst, and Support material, respectively.
H2 consumption
(mmol·g-1)
Desorbed O2
(mmol·g-1)
Desorbed NH3
(mmol·g-1)
Sample
O
Pt
Ti
I
II
0.0015 0.0031 0.0214 0.0138
0.0075 0.0105 0.0252 0.0171 0.0042
0.0045 0.0027 0.0243 0.0113 0.0035
III
Weak
Moderate Strong
Calcination sample 0.5162
Fresh catalyst
Recycled catalyst 0.1348
2.1866
-
0.3520
0.3504
0.3512
0.3503
0.3569
0.3584
-
0.0006
0.0087
0.0067
0.0072
0.0070
0.0047
-
1.0732
0.4313
0.5211
-
APR catalyst
TH catalyst
0.0603
0.0582
0.0037 0.0023 0.0235 0.0134 0.0041
0.0032 0.0016 0.0241 0.0138 0.0039
Support material 0.2216
0.0013
-
0.0189 0.0143
-
XPS analysis. XPS measurement is carried out to evaluate the composition and
valence states of Ti element, Mg element, and Pt element on the catalyst surface. As
illustrated in Figure S8a, two intensive photoelectron peaks appearing in 458.4 eV
and 464.2 eV are attribution to Ti 2p3/2 and Ti 2p1/2 [9, 29], and the bending energies
of Ti elements on the Fresh catalyst, Recycled catalyst, APR catalyst and TH catalyst
surfaces demonstrate that there are no significant change. Hence, it is evident that Ti
element may be not involved in the hydrogenation reaction. Figure S8b shows that
the bending energy of Mg 2p on the Fresh catalysis surface is 1303.5 eV, while it
shifts to 1304.8 eV on the Recycled catalysis surface and 1305.4 eV on the TH
catalysis surface, indicating that the Mg element may take participation in the in-situ
hydrogenation catalysis and the traditional hydrogenation catalysis. The changed
18

bending energy of Mg elements may provide energy for the hydrogenation catalysis
[9]. However, the bending energy of Mg 2p on the APR catalyst surface is unchanged,
indicating that the Mg element may not serve the aqueous-phase reforming of CH3OH
reaction. As indicated in Figure 5, the bending energy of Pt 4f performs the change on
the Fresh catalyst, Recycled catalyst, APR catalyst and TH catalyst surfaces. In
Figure 5a, the Pt element on the Fresh catalyst reveals that there is only the single
valence (metallic Pt0, Pt 4f 7/2: 70.2 eV; Pt 4f 5/2: 73.8 eV), which is consistent with
the result of H2-TPR. [39, 40]. However, Pt element on the Recycled catalyst surface
(Figure 5b) shows a positive shift and a new Pt valence compared to the Fresh
catalyst (Pt2+, Pt 4f 7/2: 71.4 eV; Pt 4f 5/2: 75.6 eV) [40, 41], indicating that Pt
elements are involved in the in-situ hydrogenation catalysis reaction. Moreover, the Pt
element on the APR catalyst surface and the TH catalyst surface (Fig. 5c & 5d) also
performs the similar positive shift and the new Pt valence peaks. The Pt2+ species may
originate from surface layer formation of Pt-O bonds [41]. The atom ratio of Pt2+
calculated by the XPS results is about 38.73%, 15.62% and 29.78% in the total Pt
atoms on the surfaces of Recycled catalyst, APR catalyst and TH catalyst respectively.
It is speculated that the Pt element is involved in the aqueous-phase reforming of
CH3OH reaction and the hydrogenation catalysis of FFR to FFA. In summary, the
Pt2+content on the Recycled catalyst surface is higher than that on the APR catalyst
surface or TH catalyst surface, while it is lower than the sum of Pt2+content on the
APR catalyst and TH catalyst, indicating that the Pt2+ may be reduced by the high
activity hydrogen obtained by the aqueous-phase reforming of CH3OH.
19

Fig.5 High-resolution XPS patterns of Pt 4f on the surfaces of Fresh catalyst (a), Recycled
catalyst (b), APR catalyst (c), and TH catalyst (d)
During the in-situ hydrogenation of FFR conversion to FFA via aqueous-phase
reforming of CH3OH, the proposed catalysis model is illustrated in Figure 6.
According to the morphology properties tests (TEM and SEM), Pt nanoparticles are
high dispersion on the MgTiO3-450 support nanoparticles. As the nanomaterial offers
the large specific surface area, both the reactant and products could be accelerated.
According to the results of contrast test, CH3OH and H2O could be reformed on the
catalyst surface and H2, CO2, CO and trace CH4 are produced. Based on XPS analysis,
Pt element performs the main role of the active site. Then the hydrogenation of FFR
conversion to FFA would be occurred on the catalyst surface. During the reaction, the
C=O bands are selectively hydrogenation to the C-OH bands from by the attack of the
activity hydrogen gas on the surface of the catalyst with the strong acid sites. Once
FFA is formed on the Pt@MT-450 surface, it leaves quickly and then the new FFR
molecule replaces the FFA molecule. CO is toxic to Pt active site, while the yield of
CO is few. The presence of methanol and low reaction temperature could reduce the
production of carbon deposition. According to the XPS analysis and H2-TPR, we
20

speculated that a part of active hydrogen may be involved in the process of Pt2+
reduction to Pt0 [42]. All of the reasons result in the perfect recyclability of this
catalyst. Furthermore, the better dispersibility of nanomaterial in water favored for the
hydrogenation reaction. These properties are all contributed to the significant
improvement of catalytic activity of Pt@MT-450 nanoparticles catalyst.
Fig. 6 Proposed catalysis model of in situ hydrogenation of FFR to FFA via APR of CH3OH
4. Conclusion
A novel method for the hydrogenation catalysis of FFR to FFA was proposed
using Pt@MT-450 as the catalyst via in-situ hydrogenation method. Methanol and
water could be reformed on the catalyst surface by the action of the Pt nanoparticles.
The hydrogenation of FFR was occurred on the catalyst surface with the synergistic
effect of Pt nanoparticles and Mg elements. The hydrogen gas obtained by the
methanol reforming could not only hydrogenate the FFR conversion to FFA but also
reduce the oxidation Pt to Pt0 which could improve the recyclability of the
Pt@MT-450 catalyst. The results revealed that the conversion was about 97% and the
selectivity was about 96% at the mild conditions (393 K, 0.5 MPa).
Acknowledgement
This study was supported by the National Natural Science Foundation of China
(51708301), National Natural Science Foundation of China (21878163), Natural
21

Science Foundation of Tianjin, China (17JCZDJC39500), 2017 Science and
Technology Demonstration Project of Industrial Integration and Development, Tianjin,
China-Demonstration of Organic Fertilizer Production technology based on straw
carbonization, and 2017 Jinnan District Science and Technology Project of Tianjin,
China (20171505). We acknowledge critical and quantity of testing work supported
by Beijing Zhongkebaice Technology Service Co., Ltd. The authors appreciate the
financial support and thank the editor and reviewers for their very useful suggestions
and comments.
Author Contributions: Shiqiu Zhang, Meiting Ju, and Le Liu conceived and
designed the experiments; Shiqiu Zhang, Xue Yang and Qidong Hou performed the
experiments; Shiqiu Zhang, Ruihao Xiao, and Bangjun Liu analyzed the data; Kui
Zheng, Meiting Ju, and Le Liu contributed reagents/materials/analysis tools; Shiqiu
Zhang wrote the paper.
22

References
[1] B.M. Reddy, G.K. Reddy, K.N. Rao, A. Khan, I. Ganesh, J. Mol. Catal. A-Chem. 265 (2007)
276-282.
[2] J.P. Stanford, M.C. Soto, P.H. Pfromm, M. Rezac, Catal. Today 268 (2016) 19-28.
[3] H. Li, X. Chen, J. Ren, Biotechnol. Biofuels. 8 (2015) 127.
[4] A. Corma, S. Iborra, A. Velty, Chem. Rev. 107 (2007) 2411–2502.
[5] B.M. Nagaraja, A.H. Padmasri, B.D. Raju, K.S. Rao, J. Mol. Catal. A-Chem. 265 (2007)
90-97.
[6] K. Yan, C. Jarvis, T. Lafleur, Y. Qiao, X. Xie, RSC Adv. 3 (2013) 25865-25871.
[7] C.Z. Li, X.C. Zhao, A.Q. Wang, G.W. Huber, T. Zhang, Chem. Rev. 115 (2015) 11559-11624.
[8] D. Santos, U.F. Silva, F.A. Duarte, Ultrason. Sonochem. 40 (2018) 81-88.
[9] X. Chen, L. Zhang, B. Zhang, Sci. Rep. 6 (2016) 28558.
[10] V.V. Pushkarev, N. Musselwhite, K. An, Nano Let. 12 (2012) 5196-5201.
[11] J. Wu, Y.M. Shen, C.H. Liu, H. Wang, C. Geng, Z. Zhang, Catal. Commun. 6 (2005)
633-637.
[12] R.V. Sharma, U. Das, R. Sammynaiken, A.K. Dalai, J. Mol. Catal. A.-Chem. 454 (2013)
127-136.
[13] J.P. Lange, H.E. Van, B.J. Van, R. Price, Chemsuschem 5 (2012) 150-166.
[14] J. Dai, X. Fu, L. Zhu, L. Tang, X. Guo, C. Hu, Chemcatchem 8 (2016) 1379-1385.
[15] F. Wang, Z.H. Zhang, ACS Sustain. Chem. Eng. 5 (2016) 942-947.
[16] L.L. Lin, W. Zhou, R. Gao, S. Yao, X. Zhang, W. Xu, S. Zheng, Z. Jiang, Q. Yu, Y.W. Li, C.
Shi, X.D. Wen, D. Ma, Nature, 544 (2017) 80-83.
[17] M. Nielsen, E. Alberico, W. Baumann, H.J. Drexler, H. Junge, S. Gladiali, M. Beller, Nature,
495 (2013) 85-89.
[18] S.Q. Zhang, X. Yang, L. Liu, M.T. Ju, K. Zheng, Materials 11 (2018) 299.
[19] C. Gunanathan, D. Milstein, Chem. Rev. 46 (2015) 12024–12087.
[20] I. Gandarias, J. Requies, P.L. Arias, U. Armbruster, A. Martin, J. Catal. 290 (2012) 79-89.
[21] J. Mao, D. Jiang, Z. Fang, X. Wu, J. Ni, X. Li, Catal. Commun. 90 (2017) 47-50.
[22] Z. Zhang, Q. Yang, H. Chen, K. Chen, X. Lu, K.O. Ping, Green Chem. 20 (2017) 197.
[23] A.B. Merlo, V. Vetere, J.F. Ruggera, M.L. Casella, Catal. Commun. 10 (2009) 1665-1669.
[24] Z. Strassberger, M. Mooijman, E. Ruijter, A.H. Alberts, C. Graaff, R.V. Orru, G. Rothenberg,
Appl. Organomet. Chem. 24 (2010) 142–146.
[25] S.Q. Wei, J.H. Cui, J. Wang, S. Zhuo, W. Yi, L. Wang, Particuology 9 (2011) 69-74.
[26] C.P. Jiménez-Gómez, J.A. Cecilia, I. Márquez-Rodríguez, R. Moreno-Tost, P.
Maireles-Torres, Catal. Today 279 (2017) 327-338.
[27] L. Liu, X. Yang, Q.D. Hou, S.Q. Zhang, M.T. Ju, J. Clean, Prod. 187 (2018) 380-389.
[28] G. Bagnato, A. Figoli, C. Ursino, F. Galiano, A. Sanna, J. Mater. Chem. A. 6 (2018) 4955.
[29] W.Q. Wang, Y.G. Zhu, S.Q. Zhang, J. Deng, Y. Huang, W. Yan, Minerals 7 (2017) 134.
[30] S. Cimino, S. Colonna, D. Rossi, M. Faticanti, L. Lisi, I. Pettiti, J. Catal. 205 (2012) 309-317.
[31] A. Machocki, T. Ioannides, B. Stasinska, W. Gac, G. Avgouropoulos, D. Delimaris, J. Catal.
227 (2004) 282-296.
[32] X. Song, Q. Guan, Z. Cheng, W. Li, Appl. Catal. B Environ. 227 (2018) 13-23.
[33] L. Wang, H.K. Xie, X.D. Wang, G. Zhang, G. Lu, Chinese J. Catal. 35 (2017) 1406-1412.
[34] T. Nitadori, M. Misono, J. Catal. 93 (1985) 459-466.
23

[35] B.P. Barbero, J.A. Gamboa, L.E. Cadús, Appl. Catal. B Environ. 65 (2006) 21-30.
[36] Z.P. Hao, D.Y. Cheng, Y. Guo, Y. Liang, Appl. Catal. B Environ. 33 (2001) 217-222.
[37] A. Aranzabal, M. Romero-Sáez, U. Elizundia, J.R. González-Velasco, J.A. González-Marcos,
J. Catal. 296 (2012) 165-174.
[38] A. Fatima, M. Candida, T. Raymonde, J. Catal. 235 (2005) 1-9.
[39] J.H. Kim, S.M. Choi, S.H. Nam, M.H. Seo, S.H. Choi, W.B. Kim, Appl. Catal. B Environ. 82
(2008) 89–102.
[40] A.I. Frenkel, C.W. Hills, R.G. Nuzzo, J. Phys. Chem. B 105 (2001) 12689–12703.
[41] G. Neri, C. Milone, S. Galvagno, A.P.J. Pijpers, J. Schwank, Appl. Catal. A-Gen. 227(2):
105–115.
[42] L. Zhou, H. Gu, X. Yan, Catal. Lett. 132: 16-21.
24