The catalytic activity of partially reduced Pt/MoO
3 for alkane isomerization was investigated. The surface area of Pt/MoO
3 was markedly enlarged by H
2 reduction to a maximum after reduction at 673 K for 12 h. Enlargement of the surface area was caused by formation of pores with diameters of 0.6-3 nm. The catalytic activity of partially reduced Pt/MoO
3 for heptane isomerization increased with reduction temperature, and reached a maximum at 723 K. The catalytic activity for 2-propanol dehydration was very similar to that of heptane isomerization. The isomerization and dehydration activities of partially reduced Pt/Na-MoO
3 rapidly decreased with increasing content of Na. In contrast, the hydrogenation of cyclohexene was promoted on catalysts containing Na. The isomerization and dehydration activities were related to the number of acid sites, determined by NH
3-TPD. Therefore, the isomerization activity of partially reduced Pt/MoO
3 depends on the activity as an acid catalyst. H
2 reduction at 673 K enlarged the surface areas of H
1.55MoO
3 and Pt/MoO
3, but not the surface area of MoO
3. H
1.55MoO
3 and Pt/MoO
3 reduced at 673 K had comparable activity for pentane isomerization, and were much more active than MoO
3 reduced at 673 K, even after considering the differences in surface areas. Molybdenum oxyhydride, MoO
xH
y, was formed after the decomposition of hydrogen molybdenum bronze in the reduction of H
1.55MoO
3 and Pt/MoO
3. On the other hand, MoO
3 was reduced to MoO
2 without the formation of hydrogen bronze. These results show that surface area and isomerization activity were improved by the formation of MoO
xH
y from H
xMoO
3.
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