Industrial RuO₂‐Based Deacon Catalysts: Carrier Stabilization and Active Phase Content Optimization

RuO 2 /SnO 2 –Al 2 O 3 has been recently reported as an industrial catalyst for Cl 2 production through HCl oxidation. The stabilizing role of the alumina binder in the material, essential for its durable performance, is elucidated here. Al 2 O 3 prevents chlorination of the SnO 2 carrier under relevant reaction conditions, whereas, in its absence, SnO 2 losses exceed 80 wt % in very short times owing to volatilization as SnCl 4 . Characterization by using X‐ray diffraction, temperature‐programmed reduction with hydrogen, and high‐resolution TEM indicates expansion of the cassiterite cell in the SnO 2 –Al 2 O 3 composite with respect to pure SnO 2 , which suggests the insertion of certain Al species upon mechanochemical and thermal activation of the oxide mixture. 27 Al magic‐angle spinning NMR and X‐ray photoelectron spectroscopy studies reveal that the pentahedrally coordinated Al 3+ cations interact with SnO 2 , generating an electron‐depleted region near the surface of SnO 2 particles. This induces some acidic character in cassiterite, which possibly makes it inert toward HCl. Besides this electronic effect, the presence of thin porous amorphous alumina films, partly covering the SnO 2 surface, can offer additional geometric protection of the support. Mechanical mixing followed by calcination is essential to attain stabilization, and maximized effects are achieved with a high‐surface area alumina. Other oxides such as SiO 2 are ineffective in preventing tin losses during HCl oxidation. The practical implications of these findings are very important. The metal loading (fourfold decrease) and, thus, the cost of the catalyst can be significantly lowered without compromising its long‐term stability.