DOI: 10.1002/cssc.201100489
The Production of 5-Hydroxymethylfurfural from Fructose in Isopropyl
Alcohol: A Green and Efficient System
Linke Lai and Yugen Zhang*[a]
Fossil fuels are still the primary carbon feedstock for a wide va-
riety of commodity and specialty chemicals, as well as thermal
energy and transportation fuels. However, after one century of
heavy industrial consumption hydrocarbon reserves are dimin-
ishing and concerns regarding their future scarcity of are well-
new system avoids the use of large volumes of organic solvent
and has a minimal environmental impact. It enables a simple
production and isolation of HMF, and offers a new opportunity
for a large-scale economically viable process.
Our reasoning for using an alcohol as solvent for the trans-
formation of sugars into HMF was two-fold: Firstly, alcohols are
environmentally friendly, cost efficient, and easy-to-use reac-
tion media. Their capacity to dissolve sugars is also high. Sec-
ondly, alcohols may further react with HMF to form HMF
ethers, which could prevent decomposition or oligomerization
of HMF (Scheme 1). Thus, methanol was first tested as a
medium for the transformation of fructose to HMF, with HCl as
founded. Biomass-derived carbohydrates are
a promising
carbon-based alternative, both as energy source and as sus-
tainable feedstock for chemicals.[1,2] Recently much effort has
been devoted to the conversion of biomass into 5-hydroxyme-
thylfurfural (HMF), a versatile and key intermediate in the bio-
fuel and petrochemical industries.[3,4] However, the large-scale
application of biomass-sourced HMF is still limited due to
some critical challenges, such as costs, supply, and
the environmental impact of industrial activity. Low
efficiency in synthesis and high solubility in water
pose difficulties in HMF mass production processes,
especially for isolation and purification.[5] In most re-
ported methods for the transformation of biomass or
derivatives into HMF, the HMF is obtained in solution
and the yield is reported by using HPLC or GC. How-
ever, developing efficient separation methods is very
important in order to make the industrial-scale pro-
duction of HMF economically viable.
Scheme 1. Equilibria between HMF and its alcohol derivatives.
Reaction media used for the synthesis of HMF from biomass
include water,[6] polar organic solvents such as dimethyl sulfox-
ide (DMSO) or dimethylformamide (DMF),[7] ionic liquids,[8] or
mixtures.[9] HMF can be isolated by extraction with various or-
ganic solvents, such as methyl isobutyl ketone (MIBK),[9a,b] di-
chloromethane (DCM),[9c] ethyl acetate,[10] tetrahydrofuran
(THF),[10] diethyl ether,[11] and acetone.[6c] Due to the high polari-
ty of HMF, its isolation typically requires multiple runs of vigo-
rous extraction processes. In this context, aqueous–organic
and ionic liquid–organic biphasic solvent systems are great im-
provements;[9,10] however, they still suffer from inefficient ex-
traction. The use of large volumes of organic solvent is costly
and has negative impacts on the environment.[12] Other chal-
lenges faced by biphasic systems are complex plant designs
and the difficulty of recycling the reaction system (e.g., ionic
liquids and catalyst).
catalyst. Fructose (0.45 g) and HCl (12.5m aqueous solution,
10 mol%) were added into methanol (5 mL). The mixture was
stirred at 808C for 8 h. NMR analysis showed that products A–
D in Scheme 1 were formed in a ratio of 1:3:4:17 (Table 1,
entry 8). The formation of products B, C, and D was not sur-
prising because the reaction conditions are suitable for acetali-
zation and ether formation. However, the total yield of furfural
products was only 25%. With these results in hand, other alco-
hols were also tested. In ethanol (entry 8), only HMF (A) and
ether (B) were produced in yields of 24% and 14%, respective-
ly. When isopropyl alcohol and tert-butanol were used as sol-
vent, HMF was produced as sole furfural product in yields of
67% and 62%, respectively. The high selectivity towards HMF
in isopropyl alcohol and tert-butanol is likely due to their bulki-
ness. Mixed solvents of methanol and isopropyl alcohol im-
proved neither the selectivity nor the yield of the reaction
(Supporting Information, Table S1). These results suggest that
isopropyl alcohol could be a suitable solvent for the dehydra-
tion of fructose to HMF.
In an effort to develop an economically viable HMF synthesis
process, we disclose herein an isopropyl alcohol-mediated re-
action system for the production of HMF from fructose.[13] The
A time-dependent analysis indicated that the reaction in iso-
propyl alcohol generally proceeded fast in the first few hours
and then slowly ran to completion (Figure 1). The reaction con-
ditions were then further optimized. The reaction was found to
quickly reach a yield of more than 82% at 1208C (less than
1 h). The yield slowly decreased after 4 h, possibly due to the
HMF decomposition/oligomerization. At 1008C, it took 3 h to
reach a yield of 82%. A yield of 85% was achieved in 5–6 h
[a] L. Lai, Dr. Y. Zhang
Institute of Bioengineering and Nanotechnology
31 Biopolis Way, The Nanos
Singapore 138669 (Singapore)
Fax: (+65)6478-9020
Supporting Information for this article is available on the WWW under
ChemSusChem 2011, 4, 1745 – 1748
ꢀ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1745