27
7.5 TCR Cracking
Ex situ and in situ catalytic pyrolysis (Fig. 11) are used to upgrade and develop the
properties of the bio-oil. In comparison with the in situ process, ex situ technology
is more efficient in eliminating oxygen from the pyrolysis bio-oil due to the lower
homogeneity of the applied catalyst [157]. Additionally, the ex situ process has a
higher selectivity and flexibility to produce more specific compounds, because the
catalyst is placed in an external reactor, and thus the final products can be easily
produced [169]. However, the main inconveniences of this route are the quick catalyst deactivation and the high cost of the technology, particularly for industrial
units [170].
During the in situ process (Fig. 11), the catalyst is introduced into the reactor to
favour thermal cracking reactions and to convert heavy components present in the
bio-oil to lighter ones [171]. However, a higher cracking rate requires more catalyst,
and a consequence is the extra production of coke [167]. In situ pyrolysis can
improve the formation of aromatics and low molecular weight compounds in the
bio-oil [169]. However, this integrated catalytic system is limited and less flexible
owing to the use of a single reactor operating at the same parameters for the pyrolytic and catalytic reactions [172]. The main challenge of in situ catalytic pyrolysis
is to find a robust, active and stable catalyst that is easy to regenerate and can resist
the reactor’s mechanical environment and enhance the quality of the bio-oil by
reducing its oxygen and coke content [173].
TCR technology is able to minimize some negative aspects of the current in situ
and ex situ catalytic routes such as coke formation, limitation/flexibility of the process, selection of a proper catalyst and the economic viability for larger plants. The
biomass conversion occurs in the intermediate pyrolysis reactor, and then vapours
undergo the catalytic treatment in a different reactor (called the reforming unit). The
catalyst is the biochar generated in the previous step (auger intermediate pyrolysis
Biomass
feedstock
Pyrolysis
Vapour
phase
catalysis
Upgraded
bio-oil
Ex-situ catalyst
TCR or
catalytic
pyrolysis
In-situ catalyst
Biochar
Fig. 11 In situ and ex situ catalytic pyrolysis. (Reproduced with permission from [174], Copyright
© 2017, Elsevier)
Thermochemical Conversion of Biomass and Upgrading of Bio-Products to Produce…
7.5 TCR Cracking
Ex situ and in situ catalytic pyrolysis (Fig. 11) are used to upgrade and develop the
properties of the bio-oil. In comparison with the in situ process, ex situ technology
is more efficient in eliminating oxygen from the pyrolysis bio-oil due to the lower
homogeneity of the applied catalyst [157]. Additionally, the ex situ process has a
higher selectivity and flexibility to produce more specific compounds, because the
catalyst is placed in an external reactor, and thus the final products can be easily
produced [169]. However, the main inconveniences of this route are the quick catalyst deactivation and the high cost of the technology, particularly for industrial
units [170].
During the in situ process (Fig. 11), the catalyst is introduced into the reactor to
favour thermal cracking reactions and to convert heavy components present in the
bio-oil to lighter ones [171]. However, a higher cracking rate requires more catalyst,
and a consequence is the extra production of coke [167]. In situ pyrolysis can
improve the formation of aromatics and low molecular weight compounds in the
bio-oil [169]. However, this integrated catalytic system is limited and less flexible
owing to the use of a single reactor operating at the same parameters for the pyrolytic and catalytic reactions [172]. The main challenge of in situ catalytic pyrolysis
is to find a robust, active and stable catalyst that is easy to regenerate and can resist
the reactor’s mechanical environment and enhance the quality of the bio-oil by
reducing its oxygen and coke content [173].
TCR technology is able to minimize some negative aspects of the current in situ
and ex situ catalytic routes such as coke formation, limitation/flexibility of the process, selection of a proper catalyst and the economic viability for larger plants. The
biomass conversion occurs in the intermediate pyrolysis reactor, and then vapours
undergo the catalytic treatment in a different reactor (called the reforming unit). The
catalyst is the biochar generated in the previous step (auger intermediate pyrolysis
Biomass
feedstock
Pyrolysis
Vapour
phase
catalysis
Upgraded
bio-oil
Ex-situ catalyst
TCR or
catalytic
pyrolysis
In-situ catalyst
Biochar
Fig. 11 In situ and ex situ catalytic pyrolysis. (Reproduced with permission from [174], Copyright
© 2017, Elsevier)
Thermochemical Conversion of Biomass and Upgrading of Bio-Products to Produce…