Volcano-shaped relation between heats of oxide formation of metals and coal-liquefaction activities of liquid-metal catalysts

Plots of coal-liquefaction activities of molten Zn, Cd, Ga, In, Tl, Bi, Sn, and Pb against the heats of oxide formation of these metals exhibited a volcano-shaped relationship which suggests that the interactions between the atoms of the catalyst metal and the oxygen atoms which link the structural units of coal are one of the important factors which determine coal-liquefaction activity.