HYDROGENATION OF 1,3-BUTADIENE ON PLATINUM SURFACES OF DIFFERENT STRUCTURES

1,3-butadiene hydrogenation is studied on platinum foil and Pt(111), P t(100), Pt(755) single-crystal surfaces at 300-375 K. The results are compared with the data of alkene hydrogenation reactions. Similar to t he hydrogenation kinetics of butenes, 1,3-butadiene hydrogenation exhi bits near zeroth-order dependence on hydrocarbon and near first-order dependence on hydrogen pressure. With the same hydrocarbon (3.5-70 Tor r) and hydrogen (14-140 Torr) pressure, the rate of 1,3-butadiene hydr ogenation is one order of magnitude lower than for the rates for n-but enes. The hydrogenation products include l-butene, trans- and cis-2-bu tene, and n-butane. The reaction selectivity is independent of reactan t mixture and platinum surface structure, but changes slightly as a fu nction of reaction temperature. The butene product distribution is det ermined by surface reaction kinetics. While 1-butene is thermodynamica lly less stable than trans- and cis-2-butene, it is the major butene p roduct in 1,3-butadiene hydrogenation.