TITLE: Sulfur Poisoning of Catalysts. Quarterly Progress Report, 1 July--30 September 1976.

AUTHOR: W. E. Isakson;   K. M. Sancier;   H. Wise;   B. J. Wood.

INST.  AUTHOR: Stanford Research Inst., Menlo Park, Calif.

SPONSOR: Energy Research and Development Administration.

LANGUAGE: English

PUB.  TYPE: Technical Report

PUB.  COUNTRY: United States

SOURCE: Energy Research and Development Administration [ERDA],  1 Nov 76, 68p.

ABSTRACT:

This study concerns the deactivation of catalysts used to produce fuels from CO and H sub 2 O. The first phase of this research emphasized S poisoning of methanol-synthesis catalysts. During this reporting period an examination has been started of the role of C in Fischer-Tropsch catalysts. A discussion is presented of surface sulfidation and segregation with methanol-synthesis catalysts and the kinetics of C formation on Fischer-Tropsch catalysts. The thermodynamics and surface structures of S chemisorbed on transition metals are reviewed in the Appendix. Several iron-based Fisher-Tropsch catalysts were examined during reduction and carburization by thermogravimetric (TGA) and thermomagnetic (TMA) analyses. Catalyst B6 was reduced in H sub 2 and carburized in H sub 2 /CO = 3 at atmospheric pressure. The results indicate that the fresh catalyst contains 77 wt% gamma -Fe sub 3 O sub 4 , the remainder is alpha -Fe, promoters, and possibly, some carbidic compounds. Carburization carried out under temperature programming conditions in the range of 175 to 324 exp 0 C results in the formation of Hagg carbide, Fe sub 2 C, as the only ferromagnetic phase. Carburizations performed isothermally indicate the formation of: Hagg carbide at 300 and 224 exp 0 C, a mixture of Hagg and hexagonal Fe sub 2 C at 250 exp 0 C, and hexagonal Fe sub 2 C at 200 exp 0 C. Formation of a precursor carbide is suggested during early stages of carburization at 324 exp 0 C. The TGA results indicate the existence of two successive diffusion-limited carburization rates. From the temperature dependence of these two rates processes, the isothermal work of diffusion was calculated to be 9.5 and 6.5 kcal mol exp -1 . (ERA citation 02:024152)

CONTRACT  NUMBER: EY-76-C-02-0060