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Oxidation of Methylidene Groups to Carbonyl Groups

Oxidation of Methylidene Groups to Carbonyl Groups: Industrial Application:

The Wacker process is used in industry to manufacture acetone from ethylene and acetaldehyde from propylene.

Continuous manufacture of acetaldehyde is accomplished by passing a gaseous mixture of ethylene and oxygen at 90-95°C through an aqueous solution of 1.78 g palladium(II) chloride, 150 g copper(II) chloride and 24 g copper(II) acetate per liter contained in a packed-column reactor. To reduce the danger of an explosion, the gaseous mixture consists of 84% ethylene and 16% oxygen. A stream of unreacted gas is used to remove the mixture of acetaldehyde and steam from the reactor. Condensation yields 90% or more of the desired product and small amounts of chloracetaldehyde as side product.

Using the same process, acetone can be manufactured in 92 - 94% yield by air oxidation of propylene at 110-120°C and 10-14 bar in the presence of an aqueous solution of palladium(II) chloride and copper(II) chloride. Today, acetone is produced mostly from petrochemicals.

Manufacture of actone from propylene by direct air oxidation

  1. Oxidation reactor (solution of catalysts reacts with atmospheric oxygen, unreacted air is removed)
  2. Reaction vessel (propenyl reacts at 110 - 120°C , 10-14 bar)
  3. Depressurizing column (using a valve to depressurize the reaction mixture, refilling spent volume of catalyst-solution with water, steam distilling and condensing of products)
  4. Low-temperature distillation column (distillation and subsequent condensation of propylaldehyde ( Tvap,k 49°C ) takes place in this column)
  5. High-temperature distillation column (distillation and subsequent condensation of acetone ( Tvap,k 56°C ) takes place in this column, waste water is purified and reused )

Manufacture of other carbonyl compounds (e.g. butanone) on an industrial scale is carried out in a series of steps involving reaction of 80% sulfuric acid with the alkene, hydrolysis of the sulfuric acid ester and catalytical dehydrogenation of the alcohol.

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