Production of olefins from ethanol by Fe-supported zeolite catalysts

Abstract

Ethanol conversion to C₃₊ olefins over Fe/H-ZSM-5 catalysts was investigated. Fe is a non-toxic and cheap metal. C₃₊ olefins are useful not only as fuels but also chemicals. Fe catalysts are fully effective even in the presence of water in EtOH. Therefore, there is no need to remove water from water-containing ethanol, such as bio-ethanol. The initial selectivity of C₃₊ olefins was not affected by the kind of Fe source and calcination temperature significantly, except in the case of iron phosphate used as the iron source, which showed low C₃₊ olefins selectivity. In general, the selectivity of C₃₊ olefins was slightly decreased with time-on-stream. As causes of catalytic deactivation, carbon deposition on the catalyst and framework collapse of the zeolite support can be considered. However, in the cases of Fe₂(SO₄)₃- and FeCl₃-derived catalysts, calcined at 700 °C, the decrease in C₃₊ olefins selectivity could be suppressed. In general, selectivity of aromatics was decreased and selectivity of ethylene was increased with time-on-stream. Used catalyst can be regenerated by air treatment at 500 °C, but the degree of regeneration was dependent on the kind of iron starting materials and the calcination temperature. An FeCl₃-based catalyst, calcined at 700 °C, and catalysts calcined at 900 °C (irrespective of iron source) can be almost completely regenerated, while Fe(NO₃)₃- or Fe₂(SO₄)₃-based catalyst, calcined at 700 °C, cannot be completely regenerated by this treatment.