Combined Operando X‐ray Diffraction/Raman Spectroscopy of Catalytic Solids in the Laboratory: The Co/TiO₂ Fischer–Tropsch Synthesis Catalyst Showcase

Abstract

A novel laboratory setup for combined operando X‐ray diffraction and Raman spectroscopy of catalytic solids with online product analysis by gas chromatography is presented. The setup can be used with a laboratory‐based X‐ray source, which results in important advantages in terms of time‐on‐stream that can be measured, compared to synchrotron‐based experiments. The data quality was much improved by the use of a relatively high‐energy MoKα radiation instead of the more conventional CuKα radiation. We have applied the instrument to study the long‐term deactivation of Co/TiO2 Fischer–Tropsch synthesis (FTS) catalysts. No sign of Co sintering or bulk oxidation was found during the experiments. However, part of the metallic Co was converted into cobalt carbide (Co2C), at elevated pressure (10 bar). Furthermore, graphitic‐like coke species are clearly formed during FTS at atmospheric pressure, whereas at elevated pressure fluorescence hampered the interpretation of the measured Raman spectra.

In‐situ X‐Ray Absorption Near Edge Structure Spectroscopy of a Solid Catalyst using a Laboratory‐Based Set‐up

“…This instrument provides the opportunity to carry out unique experiments, which are complimentary to the research performed at synchrotron radiation facilities. [16] Furthermore, during FTS at different conditions (pressure and H 2 /CO ratio) no cobalt re-oxidation was observed, which is in line with earlier reports [35][36][37] from our research group, confirming that oxidation of the cobalt is not a main deactivation route for FTS, leaving sintering and coke formation as main reasons for the detrimental activity over time for Cobased FTS catalyst. Such experiments are difficult to perform at synchrotrons due to the limited time available during granted beamtimes.…”

Cobalt‐Iron‐Manganese Catalysts for the Conversion of End‐of‐Life‐Tire‐Derived Syngas into Light Terminal Olefins

“…As soon as the catalyst is heated in a stream of H 2 and He, reduced phases are observed. After the reduction at a constant temperature of 400 °C, the majority of both Co (59 %) and Fe atoms (70 %) are then reduced to their metallic state, probably forming an alloy, which could be confirmed by operando XRD measurements (Figure S 11 ), making use of a laboratory set‐up developed recently in our laboratory . In both cases, little change is seen between the two datasets recorded at different times during the reduction indicating that the process was complete after the first spectrum was recorded.…”

In Situ Diffraction of Fischer–Tropsch Catalysts: Cobalt Reduction and Carbide Formation

“…Very few,h owever,h ave elaborated on this discovery to provide greater understanding of CO reduction of the cobalt oxide phase, [11] the effect of CO partial pressures for carbidization and linked this with FT testing. The report by the Weckhuyseng roup has also shown an ovel approacht oi nsituX RD and cobalt carbidef ormation, [12] in which they monitora nd track the reduction of cobalt oxide with hydrogen, and follow up with CO treatments to show carbidef ormation and decomposition. In this work, they were ablet ot rack cobalt oxide reduction with hydrogen before doing FT and observing Co 2 Cf ormation.Asubsequent test was completed with CO feed to study the formation of cobalt carbide and the complete transition to hcp phase cobalt upon af urther hydrogen reduction.A lthoughC Oo r syngas hasb een demonstrated previously, [13] it is not ar oute that has received significant investigation.…”