NOVELTY - Heterogeneous catalyzed gas phase oxidation of propane to acrolein and/or acrylic acid uses 2 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, such as for active materials and polymers.    ADVANTAGE - Acrolein and acrylic acid are normally manufactured from propylene, which is produced mainly as byproduct 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, for example in natural gas, but existing methods using propane involve several stages operating under different conditions and have various other drawbacks, such as poor selectivity. The present process avoids these difficulties.    DETAILED DESCRIPTION - Heterogeneous catalyzed gas phase oxidation of propane to acrolein and/or acrylic acid involves passing a mixture of propane, oxygen and optionally inert gas over a stationary catalyst bed at 300-500 degreesC.    Two consecutive, stationary beds of catalysts based on different multimetal oxides (A and B) are used and a starting gas mixture containing 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 materials of the catalyst beds are multimetal oxides of formula M1aMo1-bM2bOx (I) in bed A and multimetal oxides of formula Bia'Mob'X1c'X2d'X3e'X4f'X5g'X6h'Ox'(II) in bed B:    M1 = Co, Ni, Mg, Zn, Mn, Cu and/or Sn;    M2 = W, V, Te, Nb, P, Cr, Fe, Sb, Ce and/or La;    X1 = W, V and/or Te;    X2 = alkaline earth metal, Co, Ni, Zn, Mn, Cu, Cd, Sn and/or Hg;    X3 = Fe, Cr and/or Ce;    X4 = P, As, Sb and/or B;    X5 = alkali metal, Tl and/or Sn;    X6 = a rare earth metal, Ti, Zr, Nb, Ta, Re, Ru, Rh, Ag, Au, Al, Ga, In, Si, Ge, Th and/or 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.