Effect of hydrogen on n-butane isomerization over Pt/SO₄^2--ZrO₂ and Pt/SiO₂ + SO₄^2--ZrO₂

The effect of hydrogen on n-butane isomerization over Pt/SO₄^2--ZrO₂ and Pt/SiO₂ + SO₄^2--ZrO₂ hybrid (physical mixture of Pt/SiO₂ and SO₄^2--ZrO₂) was dependent on reaction conditions (temperature, hydrogen partial pressure). At high reaction temperature under low hydrogen pressure, the reaction order with respect to hydrogen was close to zero, but at low reaction temperature under higher hydrogen pressure, that of hydrogen was negative (-0.5 approx. -1.0). The inhibition effect of hydrogen on the activity may be caused by the hydride formed by the hydrogen spillover phenomenon. It was found that C₄ olefins and C₈ hydrocarbon were not reaction intermediates, and the reaction mechanism of n-butane isomerization is a mono-molecular mechanism. The reaction parameters were similar on Pt/SO₄^2--ZrO₂ and on Pt/SiO₂ + SO₄^2--ZrO₂ catalysts. This suggested that the hydrogen effect is universal on the catalyst surface and that the proximity of Pt and acid site is not so important.