Transformation of iron based catalysts (γ-FeOOH α-FeOOH and natural pyrite) to pyrrhotite (Fe1-xS) was investigated in relation to the catalytic activ-ity in the initial stage of direct liquefaction of brown coal.
XRD analysis indicated that γ-FeOOH could be completely transformed to pyrrho-tite with smaller crystallite size at 250°C, while only a part of pyrite converted at 350°C with a large crystal growth of pyrrhotite. It was found that remarkable hydrogen con-sumption was observed on the heating to 450°C during the liquefaction of Yallourn coal with γ-FeOOH compared to pyrite catalyst. Results from the analysis in the products suggested that gaseous hydrogen could be activated on Fe1-xS surface, followed by trans-fer to radical fragments produced through the thermal decomposition of coal.
It was ascertained that γ-FeOOH had a excellent catalytic activity for hydrogen transfer to radical fragments in the initial stage during the liquefaction of brown coal be-cause of its lower transformation temperature to fine crystallite size pyrrhotite with high surface area, resulted in the higher oil yield with lower hydrogen consumption due to the less formation of hydrocarbon gases.
