Gold catalysts vinyl chloride

Gold(III) was identified as the most active catalyst for that process in 1985, when Hutchings recognized that the efficiency in catalyzing the hydrochlorination of ethyne to vinyl chloride (a very important industrial process that previously used mercury salts as catalysts) correlated with the standard reduction potential of the supported metal cation. That meant that the metal could be found as a transient species in the reaction [10]. 

In this chapter there are collected short accounts of a number of reactions that do not fit easily into the previous chapters. Section 13.2 deals with the synthesis of vinyl chloride, a reaction of interest because its discovery signalled the resurgence of interest in what gold could do as a catalyst. It is also effective in the formation of C-C bonds (Section 13.3). The reactions mentioned in the other sections serve to demonstrate vividly the versatility of gold in catalysis. 

The first examples of hydration of alkynes catalyzed by gold salts were reported in 1976 by Thomas." Later, Utimoto found that the reaction could be carried out with lower amounts of catalyst." Tanaka and coworkers reported a general hydration of alkynes using cationic Au(I) complexes generated in situ by protonolysis of [AuMe(PPh3)] as depicted in equations (2) and (3). Markovnikov-type addition is observed in all cases. Other complexes of Au(I) and Au(III) have proved to be effective in this reaction. The somewhat related gold-catalyzed addition of HCl to alkynes is an industrial process for the generation of vinyl chloride. " ... 

Consequently, gold on carbon has considerable potential as a commercial catalyst for the manufacture of vinyl chloride (see Sect. 6.5.2). 

Gold catalysts supported on activated carbon were found to be about three times more active than commercial mercuric chloride catalysts for vinyl chloride production and to deactivate much less rapidly than other supported metal catalysts. Deactivation can be minimised if high loadings of gold are used [18,248,249], Also, Au catalysts can be reactivated by treatment offline with HCl or CD, and by co-feeding NO with the reactants from the start of the reaction, deactivation could be virtually eliminated [259]. Gold is thus the catalyst of choice for this reaction [6,7,18,213,248,249,258,259],... 

---