CIEC Catalysis -- Ethanoic Acid

The simplification of the production plant reduces the cost of new ethanoic acid plants by 30%. There are substantial benefits to be gained by the Cativa process with plants that operate with higher productivity and reduced environmental impact with reduced costs.

Question

Click to refer back to the diagram of the Monsanto process plant.

Compare the two and identify differences which make the Cativa process more advantageous.

Answer

One distillation column less (removal of water)

The final distillation column is smaller (fewer high boiling impuriries need removal).

There is no need for a motor to mix the contents in the reaction vessel

No need to vent gases from the reaction vessel because CO₂ and _H2 not being produced. Unlike rhodium, iridium does not catalyse this side reaction.

Advantages of the Cativa process.

Iridium is much cheaper than rhodium
Less iridium is needed because it is so stable that all the catalyst is recycled in the plant
The reaction is faster and the quantities of by-products are much lower, reducing the purification costs. For example steam is used to heat the distillation columns and there is a 30% saving of steam over the Monsanto process
Some conversion of CO to CO₂ still occurs but at a much lower rate.
CO utilisation is increased from about 85% to over 94%
Overall the Cativa process releases about 30% less CO₂ per tonne of product than does the rhodium process.