Method for producing acetic acid

1. A process for preparing acetic acid comprising oxidizing ethane with molecular oxygen in a fluidized bed of catalyst particles, wherein the particle diameter of at least 70% of the catalyst particles used is less than or equal to 80 μm, the density of the catalyst particles used in the fluidized-bed reactor is from 500 kg/m 3 to 6,000 kg/m 3 , the fluidized bed index is greater than or equal to 1 and the gas volume flow is selected so that the bubble diameter of the reaction gas mixture fed in in the fluidized-bed reactor is less than 12 cm.

2. A process as claimed in claim 1 , wherein the gas volume flow is set so that the bubble diameter of the reaction gas mixture fed in is less than 5 cm.

3. A process as claimed in claim 1 wherein the particle diameter of from 10% to 60% of the catalyst particles is less than 60 μm.

4. A process as claimed in claim 1 wherein from 20 to 50% of the particles have a diameter of less than 40 μm.

5. A process as claimed in claim 1 wherein the catalyst particles are within a particle diameter range from 10 μm to 40 μm.

6. A process as claimed in claim 1 wherein the fluidized bed index is in the range of from 1 to 10.

7. A process as claimed in claim 1 wherein the catalyst used has the formula (I),

Mo a Pd b X c Y d   (I)

wherein

X is at least one element selected from the group consisting of Cr, Mn, Nb, Ta, B, Ti, V, Te, Re and W,

Y is at least one element selected from the group consisting of B, Al, Ga, In, Pt, Zn, Cd, Bi, Ce, Co, Rh, Ir, Cu, Ag, Au, Fe, Ru, Cs, Mg, Ca, Sr, Ba, Li, K, Na, Rb, Be, Nb, Zr, Hf, Ni, P, Pb, Sb, Si, Sn, TI and U and the indices a, b, c and d are the gram atom ratios of the corresponding elements, where, based on a=1, b is from 0.000 1 to 0.01, c is from 0.1 to 1 and d is from 0 to 1, where X and/or Y may represent a plurality of elements.

8. A process as claimed in claim 1 wherein the catalyst is selected from the group consisting of

Mo 1.0 Pd 0.0005 V 0.25 NB 0.12 ,

Mo 1.00 Pd 0.0005 V 0.45 Nb 0.03 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.0005 V 0.45 Nb 0.03 Sb 0.01 Ca 0.01 K 0.015 ,

Mo 1.00 Pd 0.00075 V 0.45 Nb 0.03 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.00075 V 0.55 Nb 0.03 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.00075 V 0.04 Nb 0.06 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.0008 V 0.55 Nb 0.06 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.00085 V 0.55 Nb 0.06 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.00075 V 0.55 Nb 0.09 Sb 0.01 Ca 0.01 ,

Mo 1.00 Pd 0.0008 V 0.50 Nb 0.15 Te 0.01 Ca 0.01 and

Mo 1.00 Pd 0.00075 V 0.50 Nb 0.09 W 0.01 Pd 0.0003 .

9. A process as claimed in claim 1 wherein the reaction is carried out at a temperature from 100 to 500° C.

10. A process as claimed in claim 1 wherein the reaction is carried out at a reactor pressure in the range from 1 to 50 bar.

11. A process as claimed in claim 1 wherein not only ethane and molecular oxygen but also an inert gas, carbon dioxide and/or water vapor are present in the reaction gas mixture.

12. A process as claimed in claim 1 wherein the fluidized-bed reactor has a plurality of reaction stages or reaction zones.

13. A process as claimed in claim 12 wherein one or more reactants or water are fed into various zones or stages of a single-stage or multistage reactor.