Roles of alkaline-earth metals and electron density of Al3+ in octanol dehydration for linear alpha-olefin production

Abstract

Linear alpha-olefins (LAOs), containing a terminal double bond at their carbon chain, are widely used as raw materials in the production of polyolefins, lubricants, alcohol-based detergents, and alpha-olefin sulfonates. One common method for synthesizing LAOs is alcohol dehydration, for example, conversion of 1-octanol to 1-octene. However, this reaction often produces double-bond isomers, increasing production costs due to the need for further purification. Therefore, catalysts that enhance alcohol dehydration while minimizing isomer formation are needed. This study proposes alkaline-earth metal (AEM)-impregnated Al₂O₃ catalysts to improve 1-octene purity. Our approach focuses on understanding how AEM impregnation alters the electron density of Al₂O₃ and, consequently, affects the catalytic activity. Among the catalysts tested, Ba-impregnated Al₂O₃ demonstrated the highest 1-octene purity, which is attributed to the increased electron density at Al³⁺ sites, facilitated by active electron transfer from the AEM to Al³⁺. Density functional theory calculations further reveal that this electron density increase reduces the energy of 1-octene re-adsorption, limiting its subsequent isomerization. These results highlight the relationship between the electronic modulation of the Al³⁺ active site and reaction mechanism, which can contribute to the development of more efficient catalysts in the petrochemical industry.