(5a) Microkinetic Investigation of the Transient CO2 Methanation on Ni Catalysts in a Berty Reactor | AIChE

(5a) Microkinetic Investigation of the Transient CO2 Methanation on Ni Catalysts in a Berty Reactor


Kreitz, B. - Presenter, Brown University
Turek, T., Clausthal University of Technology
Goldsmith, C. F., Brown University
Dynamic operation of reactors becomes increasingly important to couple fluctuating renewable energy with chemical reactions, such as the production of CH4 from CO2 via power-to-gas technology. Consequently, microkinetics are required that can accurately quantify transient phenomena to design efficient and safe reactors. This study combines transient methanation experiments with automated mechanism generation considering DFT-based uncertainties to develop a microkinetic model for the transient CO2 methanation.

Experiments were performed with a Ni/SiO2 catalyst in a Berty reactor, which can be modeled as an ideal CSTR using the Cantera framework. Periodic concentration forcing was applied to the system by alternating between H2 and CO2. 5000 microkinetic models for the CO2 methanation on Ni(111) were taken from a previous study [1] that embedded the Reaction Mechanism Generator into a global uncertainty assessment (GUA) considering DFT-based uncertainties [1]. Adsorbate-adsorbate interactions were included in the model.

The experiment in Figure 1a shows a build-up behavior after the feed is initially switched from H2 to CO2, which converges to a limit cycle and ends with a small overshot for CH4 after the last change to H2. Moreover, the CO profile shows a doubling in the frequency response. These complex phenomena can be investigated and understood through microkinetic modeling. The GUA creates a broad spread of possible results considering the uncertainty in the DFT-derived databases, as seen in Figures 1b, c. A feasible set of energetic parameters can be identified from this set of mechanisms, which is in quantitative agreement with all experiments as displayed for CH4 and CO. The identified best match microkinetic model provides insights into the CO2 methanation mechanism under transient conditions, which can be used to screen for optimal reactor operation conditions and process intensification through a forced periodic operation.

[1] Kreitz, B., et al. JACS Au. DOI: 10.1021/jacsau.1c00276