Trimethylsilyl functionalization of alumina (γ-AlO) increases activity for 1,2-propanediol dehydration

γ-Al 2 O 3 was functionalized with trimethylsilyl (TMS) and evaluated as a catalyst for 1,2-propanediol dehydration. TMS-coated catalysts demonstrated a ∼50% activity increase compared with the native uncoated alumina catalyst. Results from kinetic studies indicated similar activation barriers, rate laws, and deactivation profiles for uncoated and coated catalysts, suggesting that the increased rate of dehydration was not caused by an alternative mechanism, but rather by an increase in the effective number of active sites available on the TMS-functionalized surface. However, the apparent concentration of acid and base sites on the coated catalyst measured by base/acid adsorption decreased when compared with the native catalyst. Temperature programmed reaction spectroscopy (TPRS) studies suggested that binding of 1,2-propanediol on the coated catalysts was much weaker than on the native catalyst, with a desorption energy similar to that of 2-propanol. When the monofunctional alcohols 1-propanol and 2-propanol were used as reactants, the TMS coating decreased the catalyst activity, suggesting that the coating served mainly to favour binding of diols in a monodentate configuration that is invoked in the E2-like concerted dehydration mechanism. Trimethylsilyl prevents strong binding of 1,2-propanediol and increases dehydration activity on γ-Al 2 O 3 .