Ethanol Dehydrogenation to Acetaldehyde over Co@N-Doped Carbon

Abstract

Cobalt and nitrogen co-doped carbon materials (Co@CN) have recently attracted significant attention as highly efficient noble-metal-free catalysts exhibiting a large application range. In a similar research interest, and taking into account the ever-increasing importance of bioethanol as a renewable raw material, here, we report the results on ethanol dehydrogenation to acetaldehyde over Co@NC catalysts. The catalyst samples were synthesized by a variety of affordable techniques, ensuring generation of various types of Co species incorporated in carbon, such as subnanosized cobalt sites and nano-sized particles of metallic cobalt and cobalt oxides. The catalytic activity was tested under both oxidative and non-oxidative gas-phase conditions at 200–450 °C using a fixed-bed flow reactor. The non-oxidative conditions proved to be much more preferable for the target reaction, competing, however, with ethanol dehydration to ethylene. Under specified reaction conditions, ethanol conversion achieved a level of 66% with 84% selectivity to acetaldehyde at 400 °C. The presence of molecular oxygen in the feed led mainly to deep oxidation of ethanol to COx, giving acetaldehyde in a comparatively low yield. The potential contribution of carbon itself and supported cobalt forms to the observed reaction pathways is discussed.

Literature review: state-of-the-art hydrogen storage technologies and Liquid Organic Hydrogen Carrier (LOHC) development

“…Other active metals such as Ru and other PGM [405,406], Ag [407], Au [408], and Co [409] were tested with less success. Selectivity was usually an issue for PGM catalysts due to their higher tendency to promote condensation and dehydration reactions [405,406].…”

“…Finally, while early attempts with Co catalysts mainly induced the reforming of the carrier [413], recent advances proposed Co supported on N-doped carbon catalysts, with an EtOH conversion of 66% and a selectivity of 84% to ACE at 400 °C. Nonetheless, the dehydration to ethylene was also observed as a competing reaction attributed to the presence of oxidized Co species formed during the reaction [409].…”

Heterogeneous Catalysis for Carbon Dioxide Mediated Hydrogen Storage Technology Based on Formic Acid

“…Very recently, an inexpensive and simple method for forming single atom site was declared by Koltunov and coworkers. [ 138 ] That is, Co@NC SAC could be synthesized via simply grinding and pyrolyzing the mixture of Co(II) salt, commercial carbon, and nitrogenous precursor. Although small amount of Co NPs presented on Co@NC, they contributed no activity (similar to Beller's observation), interestingly, the performance (147 mL H 2 g −1 h −1 ) was attributed to the atomic Co or CoN x site.…”