CARBON DEPOSITION ON IRON-NICKEL ALLOY PARTICLES

A combination of flow reactor studies and electron microscopy techniqu es have been used to investigate the manner by which the composition o f iron-nickel alloy particles influence the growth characteristics of carbon deposits formed during the decomposition of ethane at temperatu res over the range 815 to 865 degrees C. Major differences in the sele ctivity patterns of alloys were evident with the amount of catalytical ly produced solid carbon being significantly higher on a Fe-Ni (5:5) p owder than on a Fe-Ni (8:2) sample. Examination of the deposit reveale d the existence of two types of structures, carbon nanofibers and a gr aphite shell-like material, both of which contained associated metal p articles. The latter structures appeared to predominate at the higher temperature and were most abundant on the Fe-Ni (5:5) particles. A dra matic change in catalyst activity and selectivity was found when 50 pp m H2S was added to the ethane feed. Analysis of the gas phase product distribution showed that the behavior of the two alloy powders was alm ost identical. On the other hand, the yields of solid carbon were gene rally higher on the iron-rich sample and tended to consist of the shel l-like form on both alloys when sulfur species were present in the rea ctant.