TITLE: Role of catalyst activation on the activity and attrition of precipitated iron Fischer-Tropsch catalysts.

AUTHOR: A. K. Datye;   M. D. Shroff;   M. S. Harrington;   K. E. Coulter; A. G. Sault.

INST.  AUTHOR: Sandia National Labs., Albuquerque, NM.

SPONSOR: Department of Energy, Washington, DC.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  1995,  6p.

NTIS ORDER NO.: DE96010927INW

NOTES: International natural gas conversion symposium (4th), Kruger National Park (South Africa), 19-23 Nov 1995. Sponsored by Department of Energy, Washington, DC.

ABSTRACT:

The results of this work indicate that magnetite is not catalytically active for Fischer-Tropsch Synthesis (FTS) in precipitated, unsupported iron catalysts, but the formation of the carbide phase is necessary to obtain FTS activity. The transformation of magnetite to carbide, though essential to obtain FTS activity, also causes the catalyst to break down.  This can lead to severe problems during operation in a commercial slurry phase reactor. The results presented here imply that activation and attrition are simultaneous and complementary processes. In another study, we show that the catalyst can also under go attrition on a micron scale which is caused by lack of strength of the forces binding the catalyst primary particles in the agglomerates. Both these processes can make wax separation and product recovery extremely difficult. In this study, we have also shown that H(sub 2) reduction of this catalyst to metallic iron is detrimental to subsequent catalyst activity and causes a loss of surface area due to sintering of the iron crystallites. Reduction to metallic Fe also causes impurities such as S to segregate to the surface causing a complete loss of FTS activity. It has been shown that even submonolayer amounts of S can cause a dramatic decrease in FTS activity, hence reduction to metallic Fe should be avoided during activation of these catalysts. We have shown, however, that a mild H(sub 2) reduction to magnetite does not lead to S segregation to the surface, and is therefore acceptable.

REPORT  NUMBER: CONF-9511172-2

CONTRACT  NUMBER: AC04-94AL85000