The promoting effect of halogen ions on selective hydrogenation of (E)-2-butenal to (E)-2-buten-1-ol over alumina-supported cobalt catalyst

The promoting effects of halogen ions (Cl−, Br−, I−) on catalytic activity and selectivity in the hydrogenation of (E)-2-butenal to form (E)-2-buten-1-ol were investigated using alumina-supported cobalt catalyst in a liquid phase. The addition of Cl− or Br− to the reaction media greatly promoted the formation of (E)-2-buten-1-ol and simultaneously suppressed the formation of butanal, whereas the addition of I− prevented CC bond hydrogenation. The promoting effects increased with increasing electronegativity of the halogen atoms. The rate ratio of CO bond hydrogenation to CC bond hydrogenation was increased eightfold when Cl− was used under optimum conditions.