Microscopic characterization of changes in the structure of KCo/CeO₂ catalyst used in the steam reforming of ethanol

The cobalt catalyst with a support of CeO₂ and potassium promoted (KCo/CeO₂) was prepared by an impregnation method and used in the steam reforming of ethanol (SRE). The catalyst was characterized in its initial oxide form and after its work in the SRE by electron microscopy and EDS methods. Microscopic characterization of the catalyst allowed for identification of the active phase (in Co₃O₄ form) and the CeO₂ support phase (O-terminated), existing in the fresh catalyst, and also the active phase (at various forms, Co and CoO), support phase as well as various carbonaceous phases in the used catalyst. STEM-EDS studies allowed to determine the distribution of constituent elements in the catalyst before reaction and besides of them - also carbon deposit after the SRE. Microscopic studies of used catalyst proved that it was largely covered with carbonaceous deposit which was the main reason of deactivation of the catalyst. Carbon deposit growing during the reaction causes destruction of the support and the active phase into smaller particles which are sunked in the carbonaceous structures. - Highlights: • CeO₂ and K promoter do not prevent cobalt catalyst from carbon formation in the SRE. • Carbon deposit was present in three forms: fibrous, encapsulates, partly surrounding. • Two types of carbon deposit structures: amorphous and hexagonal graphite were found. • Metallic cobalt and ceria support crystallites are present with K in fibrous carbon. • Cobalt active phase is present under SRE conditions as metallic Co and CoO.