The fast pyrolysis of biomass in the absence of oxygen has
the potential to contribute to the world’s need for liquid fuels
and, ultimately, for chemicals production. However, the feed
complexity and variability makes it difficult to define standard
processes. Bio-oil production within the context of biorefineries
is likely to be of greater value than self-standing bio-oil plants,
much like the manner in which petroleum refinery economics
is dependent on the formation of heavy oils, lubricants, fuel
oils, gasoline, kerosene, waxes, and such chemicals as the BTX
fraction, ethylene, propylene, etc. Therefore, we envision
pyrolysis processes in which biomass alone, or biomass cofeeds
with waxes, petroleum residues, waste plastics, oxidized oils,
and/or municipal wastes, can be varied and adapted to produce
liquid fuels or gases of designed compositions to supply energy
for transportation, heating, or electricity generation. We believe
synergies with biodiesel production will exist in such refineries
where the glycerin byproduct is fed into bio-oil production and
is balanced by higher-percentage carbon co-feeds (such as waste
plastics or tires).
The use of raw biomass as a source of chemicals production
should become more attractive within the biorefinery concept.
The current situation resembles the early days of the development
of a chemicals industry from coal and coke or the later
development of the early petrochemical industry. A huge amount
of research and process development will be required. However,
this will occur when, and if, either the economic incentive
beckons or climate change regulations push us in this direction.
Chemical and engineering knowledge is now far more advanced,
so technical advances will occur more rapidly when economics
dictate a change.
Major technical opportunities exist to develop catalytic
biomass pyrolysis processes and subsequent catalytic transformation
of the bio-oils and gases produced. This area is certainly
understudied and in its infancy. The applications of novel solidfeed mixtures for pyrolysis, catalysts, co-gas feeds, and related
approaches have not been explored very much. These topics
are open for development.
Adapting innovative chemical thinking should lead to major
advances. For example, Dumesic239 estimated that alkanes that
were generated from corn would generate 2.2 times more energy
than that required to generate these alkanes, if the water removal
step can be eliminated. Dumesic239 then went on to combine
hydrogen generation from sorbitol with sorbitol hydrogenation
to make hexane as one example. Also, cellulose was transformed
by dehydration, aldol condensations, and hydrogenation to make
longer-chain alkanes at 250-265 °C in a four-phase reactor
system, using a Pt/SiO2-Al2O3 catalyst. Processes such as this