Environmental Engineering Reference
In-Depth Information
hydration. Several routes may be considered for the production of acrylates from
biomass and a few of these are shown in FigureĀ 4.11. The ethanol needed for the
esterification is simply produced from fermentation of glucose, and this ethanol
can also be used to form ethene needed for the metathesis in the fumaric acid
route. Glucose is also needed as the feedstock for fermentation and can be used to
produce (1) lactic acid and 3HP, giving acrylic acid via dehydration; or (2) fumaric
acid giving acrylic acid via ethenolysis. As described later in Section4.8.4,
glycerol can also be used for acrylic acid formation via dehydration to acrolein
and oxidation to acrylic acid.
The example of acrylic acid above is one of a bio-based 'drop-in replacement'
for a former fossil-derived equivalent, that is, a chemical of the exact same
structure but produced from a biomass feedstock as opposed to being
petroleum-derived. These drop-in replacements are of particular interest to the
chemical industry as the downstream technologies, facilities and markets are
already established. An alternative to drop-in replacements would be to move to
new materials and products (e.g. poly(ethylenefuranoate) replacing PET). It is
likely that some new products, different from those derived from base chemicals,
will become preferable in the bio-based chemical industry either as a result of
superior properties or more favourable economics. The limitation of this
approach is the time and money required to establish the supply chain,
manufacturing capacity, potential infrastructure changes, regulatory approval
and consumer acceptance of a new chemical, material or product. As the bio-
based economy matures, the most likely outcome is a combination of bio-based
drop-in replacements for current fossil-derived consumer products and the
gradual introduction of new products. Both consumer demand for greener prod-
ucts and government legislation and incentives could increase the rate of uptake
of bio-based products, but is unlikely to result in a preference for novel materi-
als over drop-in replacements in the short term.
The comparison of wt% oxygen and wt% hydrogen for base chemicals and
platform molecules (Figure 4.12) also highlights another valuable characteristic
of certain platform molecules: a similarity in functionality to fossil-derived base
chemicals. Both terpenes and fatty acids/esters occupy an area of the plot
(FigureĀ 4.12) populated by the fossil base chemicals, and clearly these two classes
of platform molecule are of importance if the user seeks applications where a lack
of heteroatoms is important (e.g. hydrophobic head of a surfactant or water-
repelling polymers).
As demonstrated in the list of platform molecules (Table 4.5), many of the
chemicals derived from biomass contain chiral centres and are usually, as a result
of their natural origin, enantiopure. This is obviously advantageous in circum-
stances where the user wishes to target a specific stereoisomer product; indeed,
levoglucosenone and proline are both often used in synthesis to target specific
isomers of a given product. Examples also exist where several stereoisomers are
potentially derivable from bio-based feedstocks, resulting in some interesting
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