Reaction probe study of the dual surface structure of graphite-supported FeRh catalysts

Abstract

As part of a continuing effort to characterize the structure of base-metal noble-metal bimetallic catalyst particles the catalytic chemistry of graphite-supported iron-rhodium particles was tested after two different pretreatments. Specifically, the activity of the catalyst for 1-butene isomerization/ hydrogenation was tested after oxidation and (i) low-temperature (375 K) hydrogen reduction and (ii) high-temperature (675 K) reduction. It was found that the catalytic chemistry of these two reduced surface states was entirely different. After the low-temperature reduction the chemistry was very much like that of rhodium. After high-temperature reduction the surface had activity similar to that of rhodium, but, like iron, selectively isomerized rather than hydrogenated the 1-butene. These results could be readily explained on the basis of an earlier model which suggests that following low-temperature reduction the surface consists of “zones” of zero-valent iron and zones of zero-valent rhodium, and after high-temperature reduction the surface is a true iron-rhodium alloy.