Porosity and Structure of Hierarchically Porous Ni/Al2O3 Catalysts for CO2 Methanation

Sebastian Weber, Ken L. Abel, Ronny T. Zimmermann, Xiaohui Huang, Jens Bremer, Liisa K. Rihko-Struckmann, Darren Batey, Silvia Cipiccia, Juliane Titus, David Poppitz, Christian Kübel, Kai Sundmacher, Roger Gläser, Thomas L. Sheppard - Karlsruhe Institute of Technology (KIT) / Universität Leipzig / Otto-von-Guericke University Magdeburg / Technische Universität Darmstadt / Max Planck Institute Magdeburg / Diamond Light Source

Carbon dioxide emissions must be reduced significantly to limit the negative consequences of climate change. For this reason, fossil fuels must be replaced by renewable energy sources. However, wind and solar energy, for example, are sporadic sources and, thus, not inevitably available when needed. This results in periods of energy surplus and shortage, which are not necessarily predictable. Hence, energy storage concepts are required to compensate for these fluctuations, thereby retaining energy during surplus periods and supplying it during shortages. In regions with existing natural gas infrastructure, the Power-to-Methane concept is a promising option [1,2,3]. This can be performed through conversion of CO2 and H2 to CH4, in a process called CO2 methanation.

CO2 methanation is often performed on Ni/Al2O3 catalysts, which can suffer from mass transport limitations and, therefore, decreased efficiency. Here we show the application of a hierarchically porous Ni/Al2O3 catalyst for methanation of CO2. The material has a well-defined and connected meso- and macropore structure with a total porosity of 78%. The pore structure was thoroughly studied with conventional methods, i.e., N2 sorption, Hg porosimetry, and He pycnometry, and advanced imaging techniques, i.e., electron tomography and ptychographic X-ray computed tomography. Tomography can quantify the pore system in a manner that is not possible using conventional porosimetry.

How Amira-Avizo Software is used

Porosity Analysis. The separated pores, total pore and material labels for both the ET and PXCT volumes were quantitatively analyzed to retrieve porosity descriptors for the Ni/Al2O3-h catalyst. From the label analysis using Avizo we retrieved information such as volume and surface area for the material and total pore labels, as well as the equivalent pore diameter deq for each individual pore label, for the PXCT and ET volumes, respectively.