Berlin 2018 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Aktualisierungen | Downloads | Hilfe

O: Fachverband Oberflächenphysik

O 7: Heterogeneous Catalysis: Experiment

O 7.10: Vortrag

Montag, 12. März 2018, 12:45–13:00, MA 141

High-pressure STM study of the low-temperature Fischer Tropsch synthesis on Co(0001) — •Bernhard Böller, Katharina Durner, and Joost Wintterlin — Ludwig-Maximilians-Universität, Munich

We report an operando high-pressure STM study of a Co(0001) single crystal model catalyst, performed under several 100 mbar of syngas (2 : 1 mixtures of H2 and CO) at 493 K. Under these conditions, ethane and propane can be detected as products, in addition to methane, which is in contrast to previous experiments performed at 10 mbar and at higher H2-to-CO ratios that only gave methane. The experiments thus represent a critical step toward the actual Fischer Tropsch synthesis of higher hydrocarbons. Massive problems had to be solved with respect to gas cleanliness, in particular from sulfur compounds and Ni(CO)4 that decomposed on the sample surface to give sulfur and nickel. These contaminants led to strong effects on the surface that can misleadingly indicate morphology changes induced by the reaction conditions. However, after extensive experimental measures the surface could be kept free from S and Ni on the timescale of hours. Also the amounts of surface carbon and oxygen, as measured by ex situ XPS, were low. Under these conditions, atomically resolved STM data showed no significant changes of the surface morphology, except for an enhanced mobility of steps, in contradiction to established models of the low-temperature Fischer Tropsch synthesis.