TITLE: Nanoscale attrition during activation of precipitated iron Fischer-Tropsch catalysts: Implications for catalyst design.

AUTHOR: A. K. Datye;   M. D. Shroff;   Y. Jin;   R. P. Brooks;   J. A. Wilder.

INST.  AUTHOR: Sandia National Labs., Albuquerque, NM;   New Mexico Univ., Albuquerque, NM.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Department of Energy [DE],  1996,  10p.

NTIS ORDER NO.: DE96010918INW

NOTES: International congress on catalysis, Baltimore, MD (United States), 11 Jun 1996. Sponsored by Department of Energy, Washington, DC.

ABSTRACT:

This work has shown that the kaolin binder that has been used in commercial Fischer-Tropsch Synthesis catalysts doe not offer any significant attrition resistance. This is due in part to its morphology (plate-like) and to its particle size being much greater than the primary crystallite size of the iron oxide catalyst. From a microscopic examination of these catalysts, it appears that if the nanoscale attrition of the iron catalyst is to be avoided, the iron must be well dispersed on the binder, and the binder must provide an interlocking microstructure that provides strength and stability to the 30-70 (mu)m agglomerates. The study of Fe/SiO(sub 2) catalysts has shown that co-precipitation of the iron and silica leads to formation of an amorphous glassy phase which is difficult to reduce even at 723K. On the other hand, when the iron was precipitated on a preformed silica, 25-40% of the iron could be reduced and carbided. The supported iron catalyst, after reduction, formed 15-20 nm iron carbide particles that look very similar to those on the unsupported catalyst. The major difference is these nanometer sized particles are anchored on a support and therefore would not be expected to breakup further and contribute to the fines generated as catalyst attrition proceeds. However, since only a fraction of the silica-supported iron can be reduced to the active carbide phase, our present efforts are devoted to moderating the Fe/SiO(sub 2) interaction by introducing an interfacial oxide phase. We are also studying the role of added Cu on the ease of reducibility of Fe/SiO(sub 2). The implication of this work is that other binder materials should be explored that have a morphology that can strengthen the agglomerates and minimize the Fe-SiO(sub 2) interfacial reactions. This work is presently underway in our laboratory.

REPORT  NUMBER: CONF-9606217-1

CONTRACT  NUMBER: FG22-95PC95210;   AC04-94AL85000