Kinetics and mechanisms of alcohol dehydration pathways on alumina materials

Abstract

The steady state rates of ethene and diethyl ether formation in parallel ethanol dehydration reactions at 573 and 623 K are mechanistically and kinetically described by the same rate expression on different alumina materials (α-, γ-, and η-Al₂O₃), implying that alumina materials have similar surface sites under reaction environments. In situ chemical titration using pyridine as a titrant elucidates similar site densities (∼0.12 sites nm⁻² and ∼0.07 sites nm⁻² for ethene formation and ∼0.14 sites nm⁻² and ∼0.09 sites nm⁻² for diethyl ether formation on γ- and η-Al₂O₃, respectively) on γ- and η-Al₂O₃ indicating that similar surface features exist on both γ- and η-Al₂O₃. Pyridine-ethanol co-feed experiments show that pyridine inhibited the formation of ethene to a greater extent than diethyl ether suggesting that the two parallel dehydration reactions are not catalyzed by a common active site.