CO + H Sub 2 Reaction over Nitrogen-Modified Iron Catalysts. Quarterly Technical Progress Report, April 1-September 30, 1985

摘要

A 4.5 wt % supported on Carbolac - 1 catalyst was prepared by incipient wetness and characterized by in-situ Moessbauer spectroscopy. The reduced catalyst exhibited superparamagnetic iron at RT as well as extreme sensitivity to oxygen. Both of these results are indicative of small (approx.20A), very highly dispersed iron crystallites. After nitriding to xi-Fe sub 2 N followed by Fischer-Tropsch synthesis (with 3:1 H sub 2 /CO at 250 exp 0 C) for 20 hrs, the sample was re-reduced in H sub 2 for 8 hrs at 400 exp 0 C. The re-reduced spectrum showed that approx.84% of the iron appeared to be bulk-like, indicating that the reaction environment can induce iron migration on the catalyst. Computer simulation of the decomposition of a gamma -Fe sub 4 N catalyst in hydrogen at 523 K indicates that the observed ammonia evaluation curve can be modeled by a two step process. The model incorporates a conversion from a homogeneous mixture of nitrogen in the core into a surface nitrogen species, which is subsequently hydrogenated to ammonia. The model demonstrates that competition between this nitrogen surface species and adsorbed hydrogen for the available surface sites can account for the maximum in the observed NH sub 3 evoluation rate. Other models incorporating shrinking core distribution of nitrogen in the core failed to fit the experimental results. (ERA citation 11:007069)