Distributions of HF Co-impregnated rhodium, platinum and palladium in alumina honeycomb supports

Abstract

The co-impregnation of Rh, Pt, and Pd with hydrofluoric acid (HF) into 1.2 mm thick γ-alumina monolith walls has been investigated. Quantitative electron probe microanalysis (EPMA) results are presented which reveal the effect of co-impregnation with HF on the resulting internal catalyst distribution. Co-impregnation of RhCl 3 (H 2O) x with HF produced samples with inner shells (egg-whites) of Rh. Co-impregnation of PtCl 4 with HF produced samples with both inner shells (egg-whites) and inner cores (egg-yolks), of platinum. The co-impregnation of Pd(NO 3) 2(H 2O) x with HF yielded catalysts with uniform outer shells, (egg-shells), of palladium. Also, two approaches for the correction of atomic number, absorption, and fluorescence effects in the X-ray emission spectroscopy (XES) data taken in EPMA were compared for these catalyst systems. The atomic number correction, Z, was found to be the dominant term and to depend significantly upon its method of calculation. Total metal loadings obtained by integrating quantitative EPMA profiles were in close agreement with bulk chemical analyses.