1-Octanol dehydration to linear α-olefins over γ-Al2O3 catalyst: Kinetic, mechanistic insights and integrated reaction-separation process design

Different from the dehydration of ethanol, the catalytic dehydration of long-chain fatty alcohols to linear α-olefins with the low selectivity arises from a complex reaction network, particularly the secondary isomerization to internal olefins. This study aimed to elucidate the fundamental mechanisms governing selectivity in the catalytic dehydration of n-octanol to 1-octene over conventional γ-Al 2 O 3 catalysts. The combination of kinetic analysis, in situ infrared spectroscopy, and density functional theory (DFT) calculations, we demonstrated that the reaction primarily proceeded via a dioctyl ether intermediate, which rapidly decomposed into olefin and alcohol. In contrast, the isomerization of 1-octene followed a water-assisted re-adsorption and hydration pathway: 1-octene re-adsorbed onto surface acid sites, hydrated to form 2-octanol, and subsequently underwent secondary dehydration, preferentially yielding internal olefins in accordance with Saytzeff's rule. Based on these mechanistic insights, an integrated reaction-separation process was designed using Aspen Plus simulation. Employing a dual-column distillation scheme with heat integration, the process achieved a 1-octene product purity exceeding 98% with ~5.9% lower overall energy consumption. This work provided systematic insights and a feasible strategy, that bridges molecular-scale mechanisms with process engineering, facilitating the highly selective production of α-olefins from biomass-derived long-chain alcohols.