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224 Lignocellulosic Biomass to Liquid Biofuels

Table 7.2 Effects of alkali promoters on catalytic behaviors of Fe-based
Fischer Tropsch (FT) catalysts.
Promoter Possible functions References

[67,70,71]
Mn Decreases deactivation by forming minor Fe [70,72]
carbide species by the formation of mixed
oxides with iron
Enhances CO conversions that increase the
selectivity of C 2 C 4
Increases dispersion and increases selectivity
to lower alkenes
Mg Improves the FT synthesis process, while [55,67,73,74]
reduces WGS reaction
Enhances the production of olefins
Changes the selectivity for production of
gasoline
Cu or Ru Enhances the reduction and carburization of [50,75]
iron
Increases the selectivity to heavier
hydrocarbons and the fraction of olefins in
lighter hydrocarbons, possibly by
enhancing the basicity together with alkali
metal ions
Promotes CO hydrogenation and WGS
activity
Promotes the Fe-catalyzed FT reaction by a
combination of enhanced structural
integrity and catalytic properties
1
K and alkali Enhance the syngas conversion to light
metal ions olefins and improved olefins selectivity
Improve the activity of Fe in FT synthesis
and enhance WGS reaction
Enhance the olefin/paraffin ratio in C 2 C 4
hydrocarbons
Increase the selectivity to C 51 hydrocarbons
and decreased CH 4 production
Increase surface basicity that enhances olefin
production
Reduce rapid catalyst deactivation
WGS, Water gas shift.