Acetic acid reforming over Rh supported on La₂O ₃/CeO₂-ZrO₂: Catalytic performance and reaction pathway analysis

Reforming of acetic acid was investigated on Rh supported on CeO ₂-ZrO₂ modified with 3 wt % La. The active catalyst converted acetic acid to H₂-rich gas and hardly formed coke. The low rate of coke formation is concluded to be related to the presence of redox-active oxygen limiting the concentration of coke precursors. Temperature-programmed ¹⁸O₂ isotope exchange measurements showed that the La₂O₃ and Rh enhanced the mobility of lattice oxygen compared with that of the parent CeO₂-ZrO₂. Ketonization and decarboxylation of acetic acid are the dominating reactions over the latter up to 600 C, whereas above 600 C, steam reforming and water gas shift also contribute. Over 0.5 wt % Rh on La₂O₃/CeO ₂-ZrO₂, reforming and water gas shift reactions dominate, even below 300 C, producing mostly H₂ and CO₂. Using isotope labeling, it is shown that acetic acid adsorbs dissociatively on Rh, forming acetates, which sequentially decarboxylate and form surface methyl groups. The latter are in turn converted to CO, CO₂, and H ₂.