초록

In a process for heterogeneously catalyzed gas-phase oxidation, a reaction gas starting mixture comprising propane, molecular oxygen and, if desired, inert gas is passed at from 300 to 500° C. over a fixed-bed catalyst.

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1. A process for the heterogeneously catalyzed gas-phase oxidation of propane to acrolein and/or acrylic acid, in which a reaction gas starting mixture comprising propane, molecular oxygen and, if desired, inert gas is passed at from 300 to 500° C. over a fixed-bed catalyst which comprises two catal

1. A process for the heterogeneously catalyzed gas-phase oxidation of propane to acrolein and/or acrylic acid, in which a reaction gas starting mixture comprising propane, molecular oxygen and, if desired, inert gas is passed at from 300 to 500° C. over a fixed-bed catalyst which comprises two catalyst beds A and B arranged spatially in succession, with the proviso that the active composition of bed A is at least one multimetal oxide of the formula I Ma1Mo1-bMb2Ox (I), where M1=Co, Ni, Mg, Zn, Mn and/or Cu, M2=W, V, Te, Nb, P, Cr, Fe, Sb, Ce, Sn and/or La, a=0.5-1.5, b=0-0.5 x=a number which is determined by the valence and amount of the elements different from oxygen in I, and the active composition of bed B is at least one multimetal oxide of the formula II Bia,Mob,X1c,X2d,X3e,X4f,X5g,X6h,Ox, (II), where 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=rare earth metal, Ti, Zr, Nb, Ta, Re, Ru, Rh, Ag, Au, Al, Ga, In, Si, Ge, Th and/or U, a'=0.01-8, b'=0.1-30, c'=0-20, d'=0-20, e'=0-20, f'=0-6, g'=0-4, h'=0-15, x'=a number which is determined by the valence and amount of the elements different from oxygen in II, wherein the reaction gas starting mixture comprises ≥50% by volume of propane, ≥15% by volume of O2and from 0 to 35% by volume of inert gas and flows through the catalyst beds A and B in the order first A, then B. 2. A process as claimed in claim 1, wherein the temperature is from 325 to 450° C. 3. A process as claimed in claim 1, wherein the temperature is from 350 to 420° C. 4. A process as claimed in claim 1, wherein the reaction gas starting mixture comprises ≥60% by volume of propane. 5. A process as claimed in claim 1, wherein the reaction gas starting mixture comprises ≥70% by volume of propane. 6. A process as claimed in claim 1, wherein the reaction gas starting mixture comprises ≥20% by volume of O2. 7. A process as claimed in claim 1 which is carried out continuously. 8. A process as claimed in claim 1, wherein the molar ratio of propane to molecular oxygen in the reaction gas starting mixture is 1 bar. 11. The process of claim 1, wherein M1is Co, Ni, and/or Mg and M2is Sn, W, P, Sb, and/or Cr. 12. The process of claim 1, wherein M1is Co and/or Ni and M2is W, Sn, and/or Sb. 13. The process of claim 1, wherein X1is W, X2is Co, Ni, and/or Zn, X3is Fe, X4is P and/or Sb, X5is K and/or Na. 14. The process of claim 1, wherein X6is Si, Zr, Al, Nb, Ag, and/or Ti. 15. The process of claim 1, wherein X6is Si. 16. The process of claim 1, wherein e' is 0.5-10. 17. The process of claim 1, wherein X6is Si and e' is 0.5-10.