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O
O
O
O
O
HO
OH
HO
O
OH
O
HO
OH
HO
OH
Wheat bran, xylan
+ H
+
Hydrogenolysis
O
HO
D
-xylose
OH
HO
OH
-3 H
2
O
O
O
Furfural
FIGURE 18.8
Conversion of xylan into furfural via xylose.
The direct processing of cellulose is hampered by solubility issues; cellulose is not
soluble in aqueous mixtures, and efficient separation of LA and gVL from these
mixtures requires special solvents. Interestingly, the combination of hydrolysis and
hydrogenation seems to overcome some of these challenges. Integrated biorefinery
approaches using the formed formic acid as hydrogen source for gVL production,
combined with recycling of H
2
SO
4
streams, have been proposed, and these seem
to overcome some of the major disadvantages of cellulose processing, namely,
low yields and the production of sulfuric acid (needed as catalyst) as waste.
These integrated solutions are definitely needed in order to make the production of
these C5 platformmolecules acceptable both from a green chemistry and an economic
standpoint.
Several LA derivatives, such as gVL and its hydrogenated analogue MeTHF, have
been considered as fuel candidates. However, Shell researchers reported that the fuel
blending properties of these compounds are poor and instead proposed VA derivatives
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