Environmental Engineering Reference
In-Depth Information
(>250°C, 50 bar H
2
) have been used for the conversion of sorbitol to alkanes and
various oxygenates (alcohols, aldehydes and ketones), but poor selectivity, high
energy demands and the use of platinum group catalysts are required [68].
Although cellulose and hemicellulose are separated from the lignocellulose
matrix prior to use in most of the examples above, cellulosic biomass can be
converted into platform molecules directly. This approach can substantially reduce
costs by removing the need for saccharification or solubilisation pretreatments
[69]. The term lignocellulose is often used to describe biomass left as a waste
from agricultural or industrial processes; examples of common lignocellulosic
biomass include corn stover, wheat straw, olive pomace, sugarcane bagasse and
sawdust. Since the majority of waste biomass is in the form of lignocellulose, the
development of technologies for the conversion of lignocellulose into platform
molecules is a major objective of the bio-based economy. The Biofine Process is
one such example where lignocellulose can be processed directly, converting the
constituent cellulose and hemicellulose into levulinic acid, furfural and formic
acid (Figure 4.5). Using dilute sulphuric acid in a two-stage reaction at temperatures
from 190 to 220°C with short reaction times (seconds to minutes), cellulose is
converted into HMF and this in turn converts into levulinic acid with formic acid
produced as by-product. The furfural product is a result of the dehydration of the
xylose units of hemicellulose. Residual degraded lignin along with humic material
is left as a solid char that is currently burnt for energy recovery. The levulinic acid,
furfural and formic acid are all useful platform molecules, with a diverse range of
chemical and material derivatives possible from each. In nearly all instances
Biofine process
dilute H
2
SO
4
, > 200 °C
OH
O
O
HO
O
OH
Lignocellulose
O
HO
OH
O
HO
Levulinic acid
OH
O
Cellulose
O
OH
H
OH
HO
Hemicellulose
Formic acid
O
OH
HO
Lignin
O
Furfural
Char (degraded
lignin and humics)
Figure 4.5
The Biofine Process for the conversion of lignocellulose to levulinic acid, formic
acid, furfural and lignin-derived char.
