Coke formation is a complex topic on the surface of catalyst, in particular for ICCU-DRM. This topic is relatively new, and could mainly gain insights from conventional DRM. Coke can be produced from the disassociation of CO2 or CH4. The following content provides some insights, and is copied from this reference (DOI: 10.1126/sciadv.aav5077).
“the CaL methane reforming process proposed is faced with the issue of carbon deposition, which is revealed to be a result of the thermodynamic and kinetic differences between the reverse Boudouard and CH4 dissociation reactions in this study. There was more carbon deposited in the material with a higher Ni/(Ca + Ni) molar ratio (fig. S8). However, the type of the deposited carbon remained unchanged. The formation of filamentous carbon around Ni nanoparticles was observed in the transmission electron microscopy (TEM) images of spent sorbent-catalysts (fig. S9, A and B), and the presence of two carbon species was confirmed in the Raman spectra of spent sorbent-catalysts (fig. S9C). They were the species at G band (~1580 cm−1) and D band (~1330 cm−1), which are related to the graphitic carbon and its defective structures, respectively (46). Therefore, from the perspective of material design, the CaO-Ni bifunctional sorbent-catalyst developed in this study has room to be improved in terms of the carbon-resistant ability, which could be achieved by manipulating the particle size of metallic Ni (47) and/or using the bimetallic Ni-based catalysts (48).”
