Wacker single-stage process

Acetic acid is manufactured by three processes acetaldehyde oxidation, //-butane oxidation, and methanol carbonylation.Ethylene is the exclusive organic raw material for making acetaldehyde, 70 percent of which is further oxidized to acetic acid or acetic anhydride. The single-stage (Wacker) process for making acetaldehyde involves cupric chloride and a small amount of palladium chloride in aqueous solution as a catalyst. 

FIGURE 1 Acetaldehyde manufacture by the single-stage (Wacker) process. 

The liquid-phase oxidation of ethylene to acetaldehyde was pioneered by the Consortium fiir Elektrochemische Industrie G.m.b.H. Industrially, the single-stage process was developed mainly by Farbwerke Hoechst A. G. and the two-stage process by Wacker Chemie G.m.b.H. itself. Both processes are licensed by Aldehyd G.m.b.H., jointly owned by Wacker Chemie G.m.b.H. and Farbwerke Hoechst G.m.b.H. The basic patents of these two companies on the Wacker process are listed in Table IV. In addition to these patents, which have given Wacker Chemie G.m.b.H. and Farbwerke Hoechst a dominant role in this field, other companies hold some patents in this area (Table X). How many of the patents listed in Tables IX and X are commercially important cannot be judged, based on the open literature alone. 

The commercial Wacker process for the manufacture of acetaldehyde operates in a single-stage... 

The single-stage process was developed by a research group of Hoechst AG (also see [36]). At the time, Hoechst AG owned 50% of the shares of Wacker Chemie. Via the board, they learned at an early time about Wacker s activity on ethylene oxidation and began research on this field. Later on, both companies cooperated and combined their results. 

The two-stage process has been developed by the research group of Wacker s Consortium fiir elektrochemische Industrie. While this group worked on the development of a single-stage process, Wacker had to realize that at the time and the site of the scheduled first commercial plant, oxygen was not available at a reasonable price. So, Wacker was forced to develop another version using air as the oxidant. 

Acetaldehyde may be prepared from ethylene via the Wacker process, and then oxidized as above. In more recent times, a cheaper, single-stage conversion of ethylene to acetic acid was commercialized by chemical company Showa Denko, which opened an ethylene oxidation plant in Oita, Japan, in 1997. The process is catalysed by a palladium metal catalyst supported on a heteropoly acid such as tungstosilicic acid. It is thought to be competitive with methanol carbonylation for smaller plants (100-250 kt/a), depending on the local price of ethylene. 

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