A heterogeneous catalytic reaction involves a catalyst in a different phase than the reactants. Combustion of coal is a homogeneous gas-phase reaction (fuel + O₂ → CO₂) without a solid catalyst. Haber's process (N₂ + H₂ → NH₃, Fe catalyst), Ostwald's process (NH₃ → NO, Pt-Rh catalyst), and hydrogenation of oils (H₂ + oil → fat, Ni catalyst) all use solid catalysts with gaseous/liquid reactants, making them heterogeneous.

Final answer: Combustion of coal