Raney promoting elements

The coupling reaction proceeds better when a rigorously degassed Raney nickel catalyst is used, but a nickel catalyst prepared by a much simplifled procedure (Note 9) is also effective. The coupling may also be promoted by other elements, including copper and palladium. 

The term major active component may be used to describe the active component, the proportion of which greatly exceeds that of the others. Secondary components added on purpose may be described as additives, whereas the term impurities should be reserved for trace amounts of other elements, over which the investigator (manufacturer) has little control. The use of the word promoter implies that the additive improves some particular property of the catalysts, and it is desirable to indicate this property when known (e.g. activity, selectivity, textural properties, resistance to sintering). The term modifier is used sometimes in this context, but is not recommended. The term modifier is used in a special and proper sense in the context of asymmetric hydrogenation when, for example, Raney nickel is modified by optically active tartaric acid in order to impart the property of asymmetry to hydrogenation reactions over the catalyst. 

In the 1970s, a catalyst system promoted by metallic potassium [73, 74] was studied. The ammonia synthesis rates at 80 kPa and 588 K over transition metals supported on active carbon and promoted by metallic potassium are given in Fig. 3.2 [69]. The activity of isotopic equilibration of N2 over the same series of catalysts at 30 kPa of N2 and at 588 K are shown in Fig. 3.3 [75]. The same reaction over Raney metals are also shown in this figure [76]. In these cases ruthenium is the most active metal. There is a common belief that Fe, Ru and Os are the most active elements in ammonia synthesis, ammonia decompo-... 

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