Oxidative cracking of eta-butane over various silica packings

In order to study the difference between catalytic and non-catalytic oxidat ive cracking of n-butane, the oxidative cracking over various silica was in vestigated in the temperature range of 600-700 degrees C. The reactions wer e 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 of n-butane was attained. With the loading of various si lica packings, the conversion of n-butane was lowered; however, the convers ion obtained using amorphous silica was quite different from that obtained using crystalline silica such as quartz sand or silicalite. The radical rea ction was not suppressed so much by amorphous silica packing as by crystall ine 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 surfa ce OH groups on the amorphous silica are involved in the radical chain reac tions of the oxidative cracking. Ethylene, propylene, and butenes were obta ined as major products and the selectivity of light olefins was high (700 d egrees C, about 75% at 45% conversion) compared with that obtained using ot her oxides.