Effect of Pd loading on the catalytic properties of molybdenum oxides for the isomerization of heptane

The catalytic properties of MoO3 with and without Pd for the isomerization of heptane have been investigated at 523 K under atmospheric pressure. The isomerization activity of Pd/MoO3 increased with the period of H-2. reduction at 623 K, and became almost constant after 36 h reduction. This behavior was almost the same as that of MoO3, although the reducibility of MoO3 was markedly improved in the presence of Pd. The reduced Pd/MoO3 was al,out 2.5 times as active as the MoO3. The mixture of MoO3 and Pd/SiO2 exhibited a similar catalytic performance to Pd/MoO3, indicating the important role of hydrogen spillover. H-2 reduction was found to increase the surface area of MoO3, especially in the presence of Pd. The isomerization activity of reduced Pd/MoO3 was dependent on the amount of Pd loading up to 0.01 mol%. We conclude from these results that the high isomerization activity of Pd/MoO3 can be attributed to its large surface area as well as to the promotion of dehydrogenation-hydrogenation steps by Pd. (C) 1999 Elsevier Science B.V. All rights reserved.