Surface characterisation of carbon monoxide hydrogenation catalysts under reducing conditions, using X-ray photoelectron spectroscopy and auger electron spectroscopy

Abstract Promoted, fused iron catalysts, active for CO hydrogenation have been monitored by electron spectroscopy during reduction in 1 bar flowing hydrogen, using an integrated reaction cell/surface analysis system. XPS chemical shift data clearly reveal the extent of reduction and show that it is virtually complete after 6 h reaction at the highest temperature employed (673 K). Apart from reduction, hydrogen also causes segregation of many promoters to the surface with the following order of mobilities: K>Ca≅Si>Mg≅A1. Due to this segregation, surface oxide remains the dominant species, even after reduction, with a comparatively low level of metallic iron. The presence of bulk carbon in the catalyst was also indicated.