<p>This paper outlines the failure analysis investigation of fireclay refractory bricks used in a Catofin reactor. Several laboratory-based examinations were carried out to identify the failure mechanism and its correlation with the process conditions. The visual examination showed a black core in the center of the bricks, and most of the bricks exhibited singular cracks. Ceramographic analysis of the black core revealed grayish-black matter within the refractory pores. Additionally, micrographic analysis revealed that the cracks were straight and singular, following the path along the pores that were impregnated with deposits. X-ray diffraction and elemental mapping confirmed variations in mineral composition between the black core and outer rim of the refractory brick, with significant carbon content detected in the core. The findings indicate that the internal carbon deposition caused volume expansion, leading to surface cracking and reduced mechanical properties, notably in the modulus of rupture. The primary cause of the failure was related to the reduction of CO to carbon deposits, promoted by Fe₂O₃. To mitigate future failures, recommendations include selecting low-iron oxide refractory material, employing alternative binding agents, and optimizing process parameters to limit carbon activity.</p>