Combustion synthesized nickel-cobalt catalyst deactivation by coking during ethanol decomposition reaction

Abstract

In this work, we report the catalytic dehydrogenation of ethanol over porous cobalt oxide and nickel-cobalt bimetal oxide (NiCoO2). Catalyst deactivation and the nature of carbon formation on these two catalysts are studied in detail to correlate the active phase with carbon formation. In-situ FTIR analysis was conducted between 50°C to 400°C on Co3O4 and NiCoO2 catalysts to understand the reaction mechanism and product selectivity. Addition of Ni improves the activity for ethanol decomposition by achieving complete ethanol conversion at 350°C as compared to 420°C for cobalt alone. The crystallinity, morphology and particle analysis of the spent catalyst after reaction was identified using XRD, SEM and TEM respectively. The XRD shows a phase change of porous NiCoO2 to NiCo alloy, whereas SEM indicates the presence of fibrous structure on the surface with 91.7 % of carbon while keeping 1:1 ratio of Ni and Co after the reaction. The detailed analysis of carbon structure using HRTEM-STEM (Fig. 1) shows simultaneous growth of carbon nanofibers (CNFs) and multiwalled carbon nanotubes (MWCNTs) that were favored by larger and smaller crystallites respectively.