CO Hydrogenation on Cobalt‐Based Catalysts: Tin Poisoning Unravels CO in Hollow Sites as a Main Surface Intermediate

Abstract

Site poisoning is a powerful method to unravel the nature of active sites or reaction intermediates. The nature of the intermediates involved in the hydrogenation of CO was unraveled by poisoning alumina-supported cobalt catalysts with various concentrations of tin. The rate of formation of the main reaction products (methane and propylene) was found to be proportional to the concentration of multi-bonded CO, likely located in hollow sites. The specific rate of decomposition of these species was sufficient to account for the formation of the main products. These hollow-CO are proposed to be main reaction intermediates in the hydrogenation of CO under the reaction conditions used here, while linear CO are mostly spectators.

A flexible cell for in situ combined XAS–DRIFTS–MS experiments

“…In contrast, metallic tin present in Co 1-x Sn x phases, with x ( 1, prevails as the majority species at higher Sn loadings. These observations are consistent with earlier results showing that the sample with the highest amount of Sn was the most deactivated, since the active phase for syngas conversion to hydrocarbon is metallic cobalt (Paredes-Nunez et al, 2018).…”

“…The cell is based on the previous version (Agostini et al, 2018) developed on beamline ID24 at the ESRF. This previous version of the cell [shown schematically in Fig.…”

“…10 presents a comparison for the IR data collected in a commercial SpectraTech reaction cell (Paredes-Nunez et al, 2018) and the data collected over the cell developed here. A detailed description of the band assignment obtained over these materials is reported elsewhere (Paredes-Nunez et al, 2018). Note that the X-ray fluorescence detector was partly in the path of the IR beam.…”

“…Recently, Agostini et al (2018) presented a new design overcoming some limitations of the previous versions. In particular, measurements at high temperatures (up to 600 C) and with a small dead volume became possible in transmission mode.…”

“…Thus, to overcome these limitations we have improved the design of this cell (Agostini et al, 2018) to perform coupled experiments using XAS, DRIFTS and MS, particularly on highly dilute materials and/or heavy matrices where XAS measurements in fluorescence mode are necessary.…”