Environmental Engineering Reference
In-Depth Information
OH
OH
HO
H
O
OH
H
O
O
Isomerizatio n
-3 H 2 O
H
OH
O
HO
H
HO
OH
H
HO
H
OH
H
H
HO
Glucose
Fructose
Hydroxymethylfurfural (HMF)
FIGURE 18.5 Glucose to fructose to HMF.
O
Dimethylfuran (DMF)
O
O
O
-HCOOH
+ 2 H 2 O
-H 2 O + 3 H 2
HO
O
HO
OH
O
O
OH
Levulinic acid
-H 2 O + 1.5 O 2
O
Furan dicarboxylic acid
O
Hydroxymethyl-
furfural (HMF)
-H 2 O + ROH
Acetone
-H 2 O
O
OR
O
OH
O
O
DMF ethers
Aldol condensates
FIGURE 18.6 HMF as platform chemical; regarding the DMF ethers, MMF is the product
when R = Me, and EMF is the product when R = Et.
The dehydration principle is a chemical process for which many additives and
(acidic) catalysts have been probed to increase the selectivity. Direct conversion of
glucose generally results in low conversions and selectivities. Yields for the produc-
tion of HMF from glucose using mineral or organic acids of up to 45% have been
reported (Rosatella et al., 2011). Generally, biphasic systems are applied, which
diminish the subsequent hydration of HMF to LA (see Section 18.4.3). The greenness
of this process is highly questionable, according to its E-factor: yields of 45%, accom-
panied by the formation of many by-products, cannot form the basis for a sustainable
process. Therefore, significant technological progress is needed for scale-up.
HMF has been proposed as a starting material for the production of fuel additives,
notably 2,5-dimethylfuran (DMF), DMF ethers, and aldol condensates. DMF is not
soluble in water and can be used as blender in transportation fuels. Aldol condensates
can act as precursors for diesel- and kerosene-type fuels. HMF has also been proposed
as platform chemical for the production of polymers. In this case, furan dicarboxylic
acids are the desired polymer building blocks. An overview of the major outlets of
HMF is presented in Figure 18.6. We call this kind of technology platform technol-
ogy. An alternative is not to produce HMF itself but the corresponding more stable
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