Abstract
The influence of potassium species on a Co based Fischer-Tropsch catalyst was investigated using an aerosol
deposition technique. This way of poisoning the catalyst was chosen to simulate the actual potassium behaviour
during the biomass to liquid (BTL) process utilizing gasification followed by fuel synthesis. A reference catalyst
was poisoned with three levels of potassium and the samples were characterized and tested for the Fischer-
Tropsch reaction under industrially relevant conditions. None of the conventional characterization techniques
applied (H2 Chemisorption, BET, TPR) divulged any difference between poisoned and unpoisoned samples,
whereas the activity measurements showed a dramatic drop in activity following potassium deposition. The
results are compared to previous results where incipient wetness impregnation was used as the method of potassium
deposition. The effect of potassium is quite similar in the two cases, indicating that irrespective of how
potassium is introduced it will end up in the same form and on the same location on the active surface. This
indicates that potassium is mobile under FTS conditions, and that potassium species are able to migrate to sites
of particular relevance for the FT reaction.
deposition technique. This way of poisoning the catalyst was chosen to simulate the actual potassium behaviour
during the biomass to liquid (BTL) process utilizing gasification followed by fuel synthesis. A reference catalyst
was poisoned with three levels of potassium and the samples were characterized and tested for the Fischer-
Tropsch reaction under industrially relevant conditions. None of the conventional characterization techniques
applied (H2 Chemisorption, BET, TPR) divulged any difference between poisoned and unpoisoned samples,
whereas the activity measurements showed a dramatic drop in activity following potassium deposition. The
results are compared to previous results where incipient wetness impregnation was used as the method of potassium
deposition. The effect of potassium is quite similar in the two cases, indicating that irrespective of how
potassium is introduced it will end up in the same form and on the same location on the active surface. This
indicates that potassium is mobile under FTS conditions, and that potassium species are able to migrate to sites
of particular relevance for the FT reaction.
