Synthesis of alcohols from CO and H 2 on a Fe/A1 20 3 catalyst at 8-30 bars pressure

Abstract

We have investigated the effect of the temperature and pressure on the activity and selectivity in the production of alcohols and hydrocarbons from CO/H 2 on supported iron catalysts. The tests were performed in a differential microreactor in the 8-30 bars range and between 200 and 275°. The results show that pressure increases the rate of production of hydrocarbons and alcohols. At low temperatures (200-225°), a high methanol selectivity is observed, up to 40%. Homologous linear alcohols are also obtained and their yield is increased upon raising the reaction temperature. However the alcohol-selectivity diminishes on account of a higher conversion into hydrocarbons. The influence of temperature upon the relative hydrocarbon and alcohol formation as well as the Schulz-Flory distributions suggest that a comlmon precursor exists between hydrocarbons and higher alcohols (C 3-C 11). Furthermore, the enhancement of the production of n pentanol-1 by adding n-butene-1 to the H 2/CO mixture indicates that CO insertion in a metal-alkyl like bond must occur during the synthesis, and probably constitutes the reaction pathway to alcohols. That supposes the existence of a molecularly adsorbed CO which supposedly is stable at the prevailing pressures. The presence of adsorbed CO also explains the observed methanol selectivity.