Hydrogenation of 1, 3-Butadiene on Supported and Unsupported Metals

This reaction has been examined in great depth on a number of supported and unsupported metals in various laboratories, and extensive use of deuterium for isotopic labelling has led to very detailed mechanistic schemes. In this section we focus on the products formed with hydrogen, and the effect of catalyst composition and structure thereon studies bearing directly on detailed mechanism are deferred to the next section. 

We come now to the matter of the relative amounts of the butene isomers formed, expressed as i, Szi and Sei- Except for the base metals of Groups 8 to 10, where special factors apply, it is fairly easy to quote typical values for each metal, because in general they were only weakly dependent on temperature (unless 

TABLE 8.6. Hydrogenation of 1,3-Butadiene Product Selectivities for Various Forms 

Note The above results have been obtained at various H2/butadiene ratios and d rees of conversion, but neither has 

Although it may seem at first sight that the values of the selectivities are almost random, closer inspection reveals some important regularities. (1) The Z-2-butene selectivity is almost always the smallest in the case of palladium at about room temperature (under which conditions the j8-hydride phase may be formed) it is 5% or less. (2) 1-Butene is almost always the major product, and with copper, manganese and cobalt (Type A) it is more than 85%. Only with zirconium, and with iron, cobalt and nickel as Type B, is -2-butene formed as major product. (3) Except for the base metals of Groups 8 to 10, product distributions under comparable conditions show little significant dependence on physical form, as befits a structure-insensitive reaction. 

---