We report on the occurrence of significant hysteresis effects in the high pressure CO hydrogenation over a potassium promoted Co/MnOx catalyst. Both the reaction rate and the selectivity to chain-lengthened paraffins and terminally functionalized products (aldehydes, alcohols, olefins) show bistability when varying the hydrogen/carbon monoxide partial pressures back and forth from overall reducing to carbonizing conditions. While the CO conversion and the selectivity to functionalized products follow clockwise hysteresis, the selectivity to paraffins shows counter-clockwise behavior. In-situ X-ray diffraction demonstrates the activity/selectivity bistability to be driven by a Co-Co2C phase transformation. The conclusions are supported by High Resolution Transmission Electron Microscopy which identifies, in addition to the Co-Co2C transformation, Mn5O8 layered topologies at low H2/CO partial pressure ratios and MnO at high such ratios.
Revised: January 28, 2021 |
Published: September 2, 2019
Citation
Xiang Y., L. Kovarik, and N. Kruse. 2019.Rate and selectivity hysteresis during the carbon monoxide hydrogenation over promoted Co/MnOx catalysts.Nature Communications 10, no. 1:Article No.3953.PNNL-SA-146618.doi:10.1038/s41467-019-11836-z