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Two series of Rh/spinel catalysts supported on alumina were prepared. In the first series, magnesium, nickel, and aluminum nitrates were co-impregnated over γ-alumina beads (200 m² g⁻¹), dried, and further calcined at 1000 °C to obtain Mg_xNi_1−xAl₂O₄/Al₂O₃ supports (≈100 m² g⁻¹), where x ranged from 0 to 1. These supports were impregnated with aqueous solutions of Rh nitrate to obtain 0.1–0.2 wt% Rh catalysts. We prepared the second series by coating alumina beads with Mg acetate. The support was dried and calcined at 1000 °C. The MgAl₂O₄ spinel was formed by solid–solid reaction between magnesia and alumina. MgAl₂O₄ was impregnated with different Rh precursor salts (nitrate, chloride, acetate) to obtain 0.2–0.8 wt% Rh loading. Supports and catalysts were characterized by BET area, pore volume, XRD, TEM and SEM, CO₂ chemisorption (basicity), and dimethyl-3,3-but-1-ene …