By the Wacker process

Alternatively, the intermediate acetaldehyde (qv) for this process was obtained from ethylene by the Wacker process (9). A small amount of -butyl alcohol is produced in the United States by the Ziegler-Natta chain growth reaction from ethylene [74-85-1] (10). 

Acetaldehyde [75-07-0] can be obtained by the Wacker process, ia which a homogeneous CuC —PdCl system is used for the oxidation. 

Production of acetaldehyde from ethylene by the Wacker process using PdCl2 and CuCl2 as catalysts. 

Production of Acetaldehyde from Ethylene by the Wacker Process... 

Nucleophilic attack by water on coordinated ethylene, as shown by Reaction 2.12, is the key step in the manufacture of acetaldehyde by the Wacker process (see Chapter 8). In Reaction 2.13 the high oxidation state of titanium makes the coordinated oxygen atom sufficiently electrophilic for it to be attacked by an alkene. As we will see in Chapter 8, this reaction is the basis for the homogeneous catalytic epoxidation of alkenes, using organic hydroperoxides as the oxygen atom donors. 

Conversion of ethylene to acetaldehyde with a soluble palladium complex was one of the early applications of homogeneous catalysis. Traditionally, acetaldehyde was manufactured either by the hydration of acetylene or by the oxidation of ethanol. As most of the acetic acid manufacturing processes were based on acetaldehyde oxidation, the easy conversion of ethylene to acetaldehyde by the Wacker process was historically a significant discovery. With the... 

Chlorination of Acetylene. Tetrachloroethane. The production of tetra-chloroethane by the addition chlorination of acetylene is probably best carried out by the Wacker process. Here a large body of the final product, tetrachloroethane, is used as a diluent for the reacting gases anhydrous ferric chloride is the catalyst, and the reaction is carried out under reduced pressures. The principal facilities (Fig. 6-13) are a tetrachloroethane generator which comprises a dephlegmator superimposed on the reactor (chlorinator) and a chlorine absorption tower that is integrated with a cooling system. 

The conversion of ethanol to acetaldehyde can be effected by dehydrogenation over copper at 250-300°C or by (partially) oxidative dehydrogenation over silver at 450-500°C. However, this route was largely superseded by the Wacker process for the direct oxidation of ethylene in aqueous solutions of Pd/Cu chlorides. Rhone-Poulenc and BP have also patented potential processes for the homologation of methanol to acetaldehyde ... 

The production of another important chemical and polymer intermediate, acetic acid, was revolutionized by the Wacker process that was introduced in 1960. It was a simple, high yield process for converting ethylene to acetaldehyde, which replaced the older process based on ethanol and acetylene. In the Wacker reaction, the palladium catalyst is reduced and then reoxidized. Ethylene reacts with water and palladium chloride to produce acetaldehyde and palladium metal. The palladium metal is reoxidized by reaction with cupric chloride, which is regenerated by reaction with o gen and hydrochloric acid. In 1968, BASF commercialized an acetic acid process based on the reaction of carbon monoxide and methanol, using carbonyl cobalt promoted with an iodide ion (74). Two years later, however, Monsanto scored a major success with its rhodium salt catalyst with methyl iodide promoter. Developed by James F. Roth, this new catalyst allowed operation at much milder conditions (180°C, 30-40 atm) and demonstrated high selectivity for acetic acid (75). 

Fig. 4. The coupled reactions involved in catalytic oxidation of alkenes by the Wacker process.

The Wacker oxidation was discovered by Smidt and co-workers at Consortium fiir Electrochemie (a subsidiary of Wacker Chemie and Farbwerken Bayer). It is actually a combination of known reactions and thus not a catalytic reaction in the strictest sense (Scheme 1). The first and most basic reaction, the oxidation of ethene in aqueous solution was first discovered by Phillips in 9AP The precipitation of palladium metal from a palladium(II) chloride solution was used as a test for olefins. However, it was the discovery by Smidt and co-workers that the Pd(0) formed could be regenerated by cupric chloride that made the reaction a commercial success. The final step, the oxidation of CuCl to CuCl2 is one of the fastest reactions in inorganic chemistry, The three reactions add up to the simple air oxidation of ethene to ethanal. At one point over two billion pounds a year of ethanal was produced by the Wacker process. Presently, the Monsanto acetic acid process has largely replaced the Wacker procednre.t" ... 

Scheme 6.8. An abbreviated cartoon depiction of what might be occurring in the oxidative conversion of ethene (CH2=CH2) to acetaldehyde (CH3CH=0) by the Wacker Process. Unspecified ligands to Pd might include H2O, Cl, and H.

It is used as a catalyst for synthesizing ketene in the production of acetic anhydride by the Wacker process. 

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