Mullite production by valorization of a hydrodesulphurization catalyst waste

Abstract The development of mullite‐based ceramic materials from the solid waste generated after the metal recovery process of spent catalyst waste originated in the petrochemical industry offers promising economic and environmental prospects. Mullite, an aluminosilicate with exceptional thermal and mechanical strength properties, is highly valued in various industrial applications. In this context, the present study aims at the formation of mullite from this amorphous catalyst waste with high alumina and silica content. The results indicate that above 1150°C, a solid‐state reaction develops between alumina and silica, leading to a product with high crystallinity and significant amounts of mullite and corundum. In terms of synthesis parameters, it has been experimentally determined that a temperature of 1200°C and a dwell time of 30 min are optimal to obtain 50 wt.% of mullite and 32 wt.% of corundum. The amorphous content and crystalline phases of the main thermal treatments were quantified using Rietveld refinement. Finally, the incorporation of amorphous silica significantly favors the formation of mullite, resulting in a product with a mullite content of 81% with an 18 wt.% of amorphous silica addition and promoting the formation of crystals with different morphologies.