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Physical Chemistry Chemical Physics
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DOI: 10.1039/C6CP06864B
Journal Name
ARTICLE
Photoassist-phosphorylated TiO2 as a catalyst for direct formation
of 5-(hydroxymethyl)furfural from glucose
Masashi Hattori,a Keigo Kamataa and Michikazu Hara⋆ab
Received 00th January 20xx,
Accepted 00th January 20xx
Photo-assisted phosphorylation of anatase TiO2 catalyst was examined to improve its catalytic performance for the direct
production of 5-(hydroxymethyl)furfural (HMF), a versatile chemical platform, from glucose. In phosphorylation based on
simple esterification between phosphoric acid and surface OH groups on anatase TiO2 with water-tolerant Lewis acid sites,
DOI: 10.1039/x0xx00000x
2
the density of phosphates immobilized on TiO2 is limited to 2 phosphates nm– , which limits selective HMF production.
Phosphorylation of the TiO2 surface under fluorescent light irradiation increases the surface phosphate density to 50%,
which is higher than the conventional limit, thus preventing the adsorption of hydrophilic glucose molecules on TiO2 and
resulting in more selective HMF production over photoassist-phosphorylated TiO2.
water, and the immobilization of phosphate species on Nb2O5
and TiO2 largely improves selective HMF production from
glucose.8,9 In particular, phosphateꢀimmobilized TiO2 (PꢀTiO2)
1. Introduction
Biomass conversion has been extensively investigated to provide a
renewable feedstock for the production of useful chemicals and
fuels. 5ꢀ(hydroxymethyl)furfural (HMF) is an attractive intermediate
for such a biomassꢀderived chemical platform because it can be
further converted into various polymers, such as polyesters,
polyamides and polyurethanes.1–3 HMF is currently produced by the
acidꢀcatalyzed dehydration of fructose obtained by the enzymatic
isomerization of glucose,4 whereas the direct production of HMF
from glucose would provide larger amounts of this versatile
intermediate with much lower energy consumption. However, direct
HMF production from glucose has not yet been commercialized,
because there is no practical process to selectively produce HMF
from concentrated glucose solutions with low energy consumption.
Zhao et al. first demonstrated an HMF yield of 70% in an
ionic liquid system using a CrCl2 catalyst, homogeneous Lewis
acid catalyst, where isomerization of glucose into fructose and
subsequent dehydration of fructose into HMF proceed in the
system.5 Davis et al. also succeeded in direct HMF production
from glucose in a biphasic reaction system composed of a
waterꢀinsoluble organic extraction phase and an aqueous phase
with Snꢀincorporated beta zeolite and HCl, a homogeneous
Brønsted acid.6,7 Snꢀincorporated beta zeolite as a Lewis acid
catalyst isomerizes glucose, and the resulting fructose is
dehydrated into HMF by HCl.7 We have reported that MOx
unsaturated coordination spheres, Lewis acid sites, on group 4
and 5 oxides such as Nb2O5 and TiO2 are workable even in
acts as a highly efficient heterogeneous catalyst for HMF
formation in biphasic reaction systems.10,11 Dutta et al. reported
that porous titanium and tin phosphates exhibit high catalytic
performance for HMF production from glucose and fructose,
due to the enhancement of surface acidity by surface
phosphorylation.12,13 On the other hand, there is no significant
difference in acidity and acid site density between bare TiO2
and PꢀTiO2: the catalysis of PꢀTiO2 cannot be simply explained
by acidity and acid site density.9,11 Through a detailed
experiment using deuterated glucose molecules, we have
determined that glucose is not converted into HMF on the
catalyst by isomerization and subsequent dehydration but only
by dehydration through 3ꢀdeoxyglucosone, a highly reactive
intermediate.11 While an increase in surface immobilized
phosphate species (TiꢀOꢀPO(OH)2) that are formed by
esterification between phosphoric acid and surface terminal OH
groups on TiO2 improves the HMF selectivity, the role of the
phosphate species has not been clarified. In addition, the
density of surface OH groups on TiO2 is limited, so that the
amount of phosphate species immobilized on TiO2 through
esterification is also restricted, which limits further
improvement of the HMF selectivity for the catalyst. Here, we
report the photoꢀassisted phosphorylation of anatase TiO2 to
prepare a catalyst for efficient HMF production. TiO2 is known
to exhibit superꢀhydrophilicity during and after UV light
irradiation due to excess formation of surface OH groups under
light irradiation.14,15 The esterification of phosphoric acid and
OH groups on such TiO2 would increase the density of surface
phosphate species, thereby enhancing the catalytic
performance.
2. Methods
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 1
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