A novel preparation method for porous noble metal/ceramic catalytic membranes

Abstract

Adsorption at liquid/solid interface has been explored to prepare catalytically active ceramic membranes. Boehmite sol maintains its dynamic stability in the pH range of 3.5–4. Adsorption of metal salt on the sol particles can only be performed in the above pH range, but the adsorption can still be optimized by proper choice of ligand. Therefore, the effect of the ligands (NH3, Cl−, EDTA) on the adsorption of the noble metal ions (Pd(II), Pt(II), Pt(IV) and Rh(III)) as a function of pH on γ-Al2O3 particles was studied. Thus the noble metal complexes which can significantly adsorb in the above pH range were found. Using the complexes, the noble metal ion modified boehmite sols were synthesized. Then by the sol-gel process, the porous noble metal/ceramic cataytic membranes were prepared. The membranes were further characterized by N2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and SEM-WDX (wave dispersion of X-ray). The H2 and N2 permeation through these membranes at elevated temperatures was also measured. Based on the above experiments, the novel technique can produce the mesoporous catalytically active ceramic membranes without any defects and with a uniform dispersion of the active materials in the coating.