Efficient removal of tar from gas fraction resulting from thermo-chemical conversion of biomass using coal fly ash–based catalysts

A requirement for the development of a viable biomass conversion technology for clean energy production is the efficient cleaning of the gas fraction. The aim of this work was to use fly ash (AF) to develop cheap and efficient catalysts in removing tar. FA was separated in two fraction, oxide fly ash (OFA) and unburned carbon (UCFA) and both were used for catalysts preparing. The toluene was used as a tar model and a fixed-bed reactor for testing. The calcined oxide fly ash (COFA) showed a steady decrease in catalytic activity, the removal efficiency was reduced by 13.52% after 3 h. Reduced catalyst (RCOFA) and activated and reduced catalyst (AROFA) showed a higher activity than COFA catalyst and were able to maintain their performance. The RCOFA catalytic activity decreased suddenly when the steam was present, and tar removal efficiency descended to 57.32% after only 3 h and to 49.03% after 5hrs, respectively. Results showed that the catalysts obtaining by mixing RCOFA/AROFA with UCFA led to high effective toluene conversion in a reforming environment, over 90% and their catalytic activity remained constant after 12 h, because the unburned carbon presence kept the iron in its reduced form, much more catalytically active.