抄録
We have proposed selective reactions using catalyst particles covered with a permselective membrane. In this study, we have developed the coating method of silicalite-1 on spherical Pt/TiO2 particles (silicalite/Pt/TiO2). Silicalite-1 membranes were synthesized on spherical Pt/TiO2 particles with a diameter of 0.5 mm from an aqueous solution of fumed silica, tetrapropylammonium hydroxide (TPAOH) and ethanol under hydrothermal conditions. A two-step hydrothermal synthesis (method B) was performed as well as a conventional one-step synthesis (method A). The silicalite/Pt/TiO2 (B) particles were composed of a thinner silicalite layer with smaller crystals than the silicalite/Pt/TiO2 (A). Hydrogenation of a mixture of linear 1-hexene (1-Hex) and dibranched 3,3-dimethylbut-1-ene (3,3-DMB) was performed using a fixed-bed reactor with a continuous flow system. The composite silicalite-1/Pt/TiO2 (B) catalyst showed high 1-Hex/3,3-DMB hydrogenation selectivities of 20-35 at 323 K and 22-70 at 373 K due to the selective permeation of the reactant 1-Hex into Pt/TiO2 particles through the silicalite-1 layer. The conversions on the silicalite/Pt/TiO2 (B) were higher than those on the silicalite/Pt/TiO2 (A), suggesting that the effective membrane thickness of the silicalite layer prepared by the tow-step synthesis was thinner than those by the one-step synthesis. The high selectivity for the silicalite/Pt/TiO2 (B) indicates that the membrane quality was improved by the two-step synthesis. The feasibility of the application of catalyst particles coated with a permselective membrane to achieve reactant selectivities on a particle level has been demonstrated.
