Correlating the degree of metal–promoter interaction to ethanol selectivity over MnRh/CNTs CO hydrogenation catalysts

•CNT supported rhodium catalysts with variable amounts of Mn promoter were synthesized and evaluated for CO hydrogenation.•The active phase of the promoter is identified by XANES and EELS as MnO.•The enhancement in the degree of metal–promoter interaction leads to an increase in the ethanol selectivity.

Multi-walled carbon nanotubes (MCNTs) were used as a support for Rh-based catalysts for high pressure (20 bar) CO hydrogenation. 3 wt% Rh/CNTs catalysts were loaded with 1 wt% and 2 wt% Mn promoter, respectively, in order to study the effect of metal–promoter interactions for ethanol synthesis. Both STEM and EXAFS results showed ∼1 nm Rh particles in promoted as well as the unpromoted catalysts, STEM and EELS results verified the enhanced metal–promoter interaction when the amount of Mn promoter increased from 1 wt% to 2 wt%. The enhancement in the degree of metal–promoter interaction leads to an increase in the ethanol selectivity. Moreover, due to the nature of CNTs (low Z number), the Mn–Rh interactions could be observed at atomic resolution during the STEM–EELS characterization, and the promoter phase is confirmed as Mn(II) oxide by XANES and EELS.

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