Effect of water properties on selectivity for 1-octene and 2-octanol reaction systems in sub- and supercritical water using a TiO2 catalyst

Abstract The effect of water properties on solid acid catalysis using TiO 2 as the catalyst in sub- and supercritical water was elucidated using the reactions of 1-octene and 2-octanol as models. Kinetic data for these reactions at 290–410 °C and 25 MPa were analyzed, and relationships between reaction selectivities and water properties were evaluated quantitatively. The cis / trans selectivity for 2-octene produced in reactions of both 1-octene and 2-octanol drastically increased at around the critical temperature of water, and was quantitatively explained using the model of acid catalysis in sub- and supercritical water derived from kinetic analyses. The hydration selectivity of 1-octene conversion had a local maximum at around 330 °C, which was explained by considering the change in reactivity of water as a reactant caused by changes in both water density and the degree of hydrogen bonding.