NOVELTY - A novel method of producing acrolein and/or acrylic acid by heterogeneous catalyzed gas phase oxidation of propane, by using two consecutive, stationary beds of catalysts based on different multimetal oxides, and a starting gas mixture containing at least 50 vol.% propane, at least 15 vol.% oxygen and 0 - 35 vol.% inert gas.    USE - Acrolein and acrylic acid are valuable intermediates, e.g. for active materials and polymers.    ADVANTAGE - Acrolein and acrylic acid are normally manufactured from propene, which is produced mainly as by-product in the manufacture of ethylene from naphtha by steam cracking but is a valuable raw material, e.g. for polypropylene manufacture. Propane is readily available, e.g. in natural gas, but existing methods using propane involve several stages operating under different conditions and have various other drawbacks, e.g. poor selectivity. The present process avoids the difficulties.    DETAILED DESCRIPTION - A mixture of propane, oxygen and optionally inert gas is passed over two stationary catalyst beds at 300 - 500degreesC. The beds are based on different multimetal oxides (A and B) are used. The starting gas mixture contains at least 50 vol.% propane, at least 15 vol.% oxygen and 0 - 35 vol.% inert gas is passed through the catalyst bed A and then B. The active material of the catalyst beds is multimetal oxide(s) of formula (I) in bed A and multimetal oxide(s) of formula (II) in bed B;    M1aMo1-bM2bOx (I)    Bia'Mob'X1c'X2d'X3e'X4f'X5g'X6h'Ox' (II)    M1 = cobalt (Co), nickel (Ni), magnesium (Mg), zinc (Zn), manganese (Mn), copper (Cu) and/or tin (Sn);    M2 = tungsten (W), vanadium (V), tellurium (Te), niobium (Nb), phosphorus (P), chromium (Cr), iron (Fe), antimony (Sb), cerium (Ce) and/or lanthanum (La);    X1 = W, V and/or Te;    X2 = alkaline earth metal, Co, Ni, Zn, Mn, Cu, cadmium (Cd), Sn and/or mercury (Hg);    X3 = Fe, Cr and/or Ce;    X4 = P, arsenic (As), Sb and/or boron (B);    X5 = alkali metal, thallium (Tl) and/or Sn; X6 = a rare earth metal, titanium (Ti), zirconium (Zr), Nb, tantalum (Ta), rhenium (Re), ruthenium (Ru), rhodium (Rh), silver (Ag), gold (Au), aluminum (Al), gallium (In), silicon (Si), germanium (Ge), thorium (Th) and/or uranium (U);    a = 0.5 - 1.5;    b = 0 - 0.5;    a' = 0.01 - 8;    b' = 0.1 - 30;    c' = 0.1 - 20;    d', e' = 0 - 20;    f' = 0 - 6;    g' = 0 - 4;    h' = 0 - 15;    x, x' = a number, depending on the valency and content of elements other than oxygen.