A novel preparation method for porous noble metal ceramic catalytic membranes

Adsorption at liquid/solid interface has been explored to prepare catalytic ally 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 ca n 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(lll)) as a function of pH on gamma-Al2O3 particles was studi ed. Thus the noble metal complexes which can significantly adsorb in the ab ove pH range were found. Using the complexes, the noble metal ion modified boehmite sols were synthesized. Then by the set-gel process, the porous nob le metal/ceramic cataytic membranes were prepared. The membranes were furth er characterized by N-2 adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and SEM-WDX (wave dispersion of X-ray). The H-2 and N-2 permeation through these membranes at elevated temperatures was also measured. Based on the above experiments, the novel t echnique can produce the mesoporous catalytically active ceramic membranes without any defects and with a uniform dispersion of the active materials i n the coating. (C) 1999 Kluwer Academic Publishers.