Liquid Phase Fischer-Tropsch Synthesis on Iron Ultrafine Particle Catalysts.

Abstract

For the purpose of developing the catalysts for the liquid phase Fischer-Tropsch (FT) synthesis, fundamental studies of catalysis by ultrafine particles (UFP) of Fe were carried out using a slurry bed reactor. The UFP of Fe were prepared by two different methods: Gas evaporation (GE) method and liquid phase reduction (LR) method.A good catalytic performance of UFP of Fe prepared by the GE method was attained by proper physical and chemical pretreatments. The activity was found to be highly enhanced by ultrasonic irradiation of the catalyst suspension. This provides a general technique effective for use of UFP catalysts in liquid phase reactions. The activity was also found to increase by preoxidizing treatment. The enhanced catalytic activity is discussed in relation to sintering of the catalyst under the reaction conditions.Chemical modification of the surface of Fe UFP was also found to be effective to enhance the catalytic activity and shift the selectivity toward a specified product. The Fe UFP catalyst prepared by the LR method showed an excellently hiuh activity when promoted by both K and Cu. In addition. this catalyst was extremely selective for production of liquid fuels, even at a reaction temperature of 300°C, which is higher than ordinary FT synthesis temperatures. Another chemical modification was used to promote Fe UFP prepared by the GE method with Mn. The catalysts thus obtained were highly selective for olefin production, particularly for lower olefins.