Date of Award

1984

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemical Engineering

Abstract

The catalytic properties of Ru and Fe-Ru bimetallics supported on Y-Zeolite were determined for the CO hydrogenation reaction. The results, based on the reaction at 523 K and an H(,2):CO ratio of 3:1, revealed that the addition of Fe to Ru effectively reduces the number of both H(,2) and CO active sites as determined by chemisorption experiments. Based on H(,2) chemisorption, the dispersion (number of active sites per total number of metal atoms) decreased from 0.59 with no Fe present to 0.02 with 5.9% Fe. This phenomenon was substantiated by the ESCA analysis which indicated totally reduced Ru metal particles in both Ru and Fe-Ru bimetals, however iron oxides could not be reduced to their metallic state. The addition of Fe also influences the product distribution. An increase in Fe content reduces the amount of methane while increasing the amount of long chain hydrocarbons. Furthermore the product distribution follows the Schultz-Flory distribution. This observation is probably due to surface H(,2) deficiency encouraging chain propagation instead of chain termination. The rate determining step is the hydrogenation of surface methylene species. The infrared analysis of CO adsorption on Ru catalyst at 373 K indicates 3 types of adsorption: bridge adsorption at 1950 cm('-1), linear adsorption at 2046 cm('-1), and multiple adsorption at 2089, 2102, 2137, and 2157 cm('-1). However under methanation reaction conditions at 523 K, it was found that the surface of the catalyst was saturated by linearly adsorbed CO around 2000 cm('-1). The infrared experiments as well as the isotopic dilution experiment point to surface segregation where Ru and Fe do not enter into a solid solution. Finally, the addition of Fe to Ru catalysts produces neither a geometrical nor an electrical effect on Ru atoms.

Pages

179

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