CHEMSUSCHEM
COMMUNICATIONS
DOI: 10.1002/cssc.201301270
Biphasic Catalytic Conversion of Fructose by Continuous
Hydrogenation of HMF over a Hydrophobic Ruthenium
Catalyst
Yanliang Yang,[a, b] Zhongtian Du,[a] Jiping Ma,[a] Fang Lu,[a] Junjie Zhang,[a, b] and Jie Xu*[a]
The production of chemicals directly from sugars is an impor-
tant step in biomass conversion. Herein, tetrahydro-2,5-furandi-
methanol (THFDM), obtained from fructose, is formed by using
a combination of acid and hydrophobic Ru/SiO2 in a water/cy-
clohexane biphasic system. Two key factors enable the high se-
lectivity towards THFDM: modifying the hydrogenation catalyst
so that it has hydrophobic properties, and the continuous hy-
drogenation of generated 5-(hydroxymethyl)furfural in the cy-
clohexane phase. Moreover, the selectivity towards THFDM is
found to depend strongly on the acid catalyst used.
We postulate that the key for this one-step process is the
separation of sugar and hydrogenation catalyst, to prevent hy-
drogenation of the sugar. Herein, we use a biphasic system to
achieve this goal (Scheme 1). The dehydration of fructose to
Diminishing fossil resources are driving chemists to find ways
to make full use of renewable biomass for the production of
fuels and chemicals.[1,2] 5-(Hydroxymethyl)furfural (HMF), ob-
tained from the dehydration of sugars, is viewed as one of the
most important platform compounds.[3] Converting HMF into
valuable chemicals by means of oxidation, hydrogenation, and
etherification is a subject of growing interest.[4–6] Among these
chemicals, especially tetrahydro-2,5-furandimethanol (THFDM),
derived from the hydrogenation of HMF, is a valuable molecule
that can be used as solvent or monomer.[7] Recent research has
revealed that THFDM can be converted to 1,6-hexanediol, an
important monomer in the plastics industry, in very high
yield.[2c,8]
Scheme 1. Conversion of fructose into THFDM in a water/cyclohexane bi-
phasic system.
HMF was catalyzed by Amberlyst-15 in the aqueous phase. The
generated HMF was then hydrogenated to THFDM over hydro-
phobic Ru/SiO2-TM (Ru/SiO2 modified by trimethylchlorosilane)
in the organic phase. This strategy avoids the hydrogenation
of fructose to mannitol and sorbitol under H2. Simultaneously,
the rehydration of HMF to levulinic acid (LA), occurring in
water in the presence of acid, can also be avoided. Moreover,
the low concentration of HMF can be maintained by continu-
ous hydrogenation of the generated HMF, thus decreasing the
degradation reaction. Thereby the selective direct transforma-
tion of fructose into THFDM is realized.
Previous studies have reported the hydrogenation of HMF
to THFDM over Ni, Cu, Pt, Pd, or Ru, Ni–Pd bimetallic cata-
lysts.[9] Considering that HMF is not stable and not easy to be
separated, purified, or stored, it is desirable to directly obtain
THFDM from sugars via one-pot, one-step dehydration and hy-
drogenation processes. However, this is challenging because
the sugars could be hydrogenated to sugar alcohols before
they dehydrate to HMF. As far as we are aware, so far no
report has described the direct conversion of sugars to
THFDM.
The key to this strategy is the design of a hydrophobic hy-
drogenation catalyst. Therefore, we began our study with the
preparation of a hydrophobic hydrogenation catalyst of Ru/
SiO2-TM according to our previous work.[10] Direct introduction
of Ru nanoparticles onto the surface of hydrophobic SiO2 is
not easy When the H2 reduction method is employed, elevated
.
temperatures that can destroy the hydrophobic components
of organic groups are inevitable. As for the chemical reduction
method, the hydrophobic surface of SiO2 prevents close con-
tact with the ruthenium precursor of RuCl3. As a result the
ruthenium cannot be successfully loaded onto the surface of
SiO2. Based on the above considerations, we first prepared hy-
drophilic Ru/SiO2 using an impregnation method, and then
modified it with trimethylchlorosilane (TMCS) using a post-
grafting method.
[a] Y. Yang, Dr. Z. Du, Dr. J. Ma, Dr. F. Lu, J. Zhang, Prof. Dr. J. Xu
Dalian National Laboratory for Clean Energy
State Key Laboratory of Catalysis
Dalian Institute of Chemical Physics, Chinese Academy of Sciences
457 Zhongshan Road, Dalian 116023 (PR China)
Fax: (+86)411-84379245
[b] Y. Yang, J. Zhang
The crystalline Ru/SiO2 phase was examined by X-ray
powder diffraction (XRD). The XRD pattern showed six peaks at
2q=388, 428, 448, 588, 698, and 788, which can be assigned to
(100), (002), (101), (102), (110), and (103) diffractions of Ru, re-
University of Chinese Academy of Sciences
Beijing 100039 (PR China)
Supporting Information for this article is available on the WWW under
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ChemSusChem 2014, 7, 1352 – 1356 1352