Properties and product selectivities of iron ultrafine particles as a catalyst for liquid phase hydrogenation of carbon monoxide

Abstract

The catalytic activity of ultrafine particles (UFP) of iron was shown to be greater for liquid phase Fischer-Tropsch synthesis than that of a precipitated iron catalyst. This difference in activity was interpreted as being caused by the different nature of surface structure between these two types of catalyst, whether porous or not. A colloidal solution of potassium could effectively modify the nonporous surface of iron UFP. Deactivation of the UFP catalyst caused by oxidation of iron was suppressed by addition of potassium. The carbon number distributions obtained over the iron UFP catalyst unpromoted and promoted by various kinds of alkali metals were simulated by a superposition of two Flory type distributions or a dual-site model. It is ascertained that the surfaces of unpromoted and alkali-promoted UFP catalysts possess two kinds of sites which exhibit different chain growth probabilities.