Synthesis, characterization, and catalytic use of acicular iron particles

The synthesis of granular iron particles via hydrotriorganoborate reduction of FeCl₃ has been reported previously by several research groups. Notably, during the course of studying some of the reaction parameters involved in FeCl₃ reduction, we discovered the experimental conditions necessary to synthesize acicular iron particles, at low temperature and low pressure, in the absence of a constraining medium. Specifically, the effects of the reaction temperature, the stirring rate, and the FeCl₃ solution dropping rate on the size and morphology of the iron particles were examined. Under optimal conditions acicular iron particles were produced having diameters of ∼300 nm, lengths on the order of tens to hundreds of micrometers, and surface areas of approximately 20 m²/g. Both the acicular and the granular iron particles were found to be active catalysts for the formation of carbon nanofibers from the reaction of carbon monoxide and hydrogen gases. The graphitic natures of the carbon nanofibers formed from either acicular or granular iron catalysts were characterized by HRTEM and XRD. Also, while both types of iron catalysts produced straight carbon nanofiber morphologies, the granular iron catalysts also formed carbon nanofibers with spiral gross morphologies. Finally, the diameters of the carbon nanofibers were comparable to the diameters of the acicular or granular iron catalysts.