Synthesis of Pd particle-deposited microporous silica membranes via a vacuum-impregnation method and their gas permeation behavior

Abstract

Pd particle-deposited microporous silica membranes were synthesized to improve hydrogen permselectivity of the microporous silica membrane and to overcome high cost of palladium and crack formation through hydrogen embrittlement. Pd particles below 400 nm in diameter were readily deposited on the microporous silica membrane via a vacuum-impregnation method by using a Pd(C 3H 5)(C 5H 5) precursor. After deposition of Pd particles on the microporous silica membrane, hydrogen permselectivity over nitrogen considerably increased from 11–28 to 30–115 in a permeation temperature range of 25–350 °C due to plugging membrane defects and hydrogen adsorption diffusion through the interface between the Pd and silica layer. The activation energy of the Pd-deposited silica membrane (6.32 kJ mol −1) was higher than that of the microporous silica membrane (4.22 kJ mol −1). In addition, the Pd-particle deposition led to an increase in the permselectivity of He and CO 2 with little chemical affinity for the Pd particles, which indicates that Pd-particle deposition gives the effect of plugging defects such as pinholes or cracks, which could be formed during the membrane preparation. Therefore it is demonstrated that Pd-particle deposition on the silica membrane is effective for induction of the hydrogen adsorption diffusion and plugging membrane defects.