Oxidative Cracking of n-Butane over Various Silica Packings

摘要

In order to study the difference between catalytic and non-catalytic oxidative cracking of n-butane, the oxidative cracking over various silica was investigated in the temperature range of 600-700 deg C. The reactions were conducted with molecular oxygen, nitrogen, and n-butane using a fixed bed reactor loaded with various silica packings. Homogeneous radical reaction in the gas phase proceeded farther in an empty silica tube reactor and the highest conversion on n-butane was attained. With the loading of various silica packings, the conversion of n-butane was lowered; however, the conversion obtained using amorphous silica was quite different from that obtained using crystalline silica such as quartz and or silicalite. The radical reaction was not suppressed so much by amorphous silica packing as by crystalline silica packing, and the n-butane conversion was as high as that in the empty tube reactor without silica packing. it was considered that the surfac eOH groups on the amorphous silica are involved in the radical chain reactions of the oxidative cracking. Ethylene, propylene, and butenes were obtained as major products and the selectivity of light olefins was high (700 deg C, about 75% at 45% conversion) compared with that obtained using other oxides.