The ternary systems Al–Ga–Pd and Ga–Sb–Pd. Search for new catalytic materials

Abstract

The phase relations in the Pd-rich region (≥ 50 at.% Pd) of the ternary systems AlGa -Pd at 600°C and Ga-Sb-Pd at 500°C have been investigated by means of X-ray powder diffraction and EDX analysis. Four continuous substitutional solid solutions were found in the AlGa -Pd system: Al 1-x Ga x Pd (FeSi-type structure, space group P2 1 3, Pearson symbol cP8), (Al 1-x Ga x) 3 Pd 5 (Rh 5 Ge 3-type structure, space group Pbam, Pearson symbol oP16), Al 1-x Ga x Pd 2 (Co 2 Si-type structure, space group Pnma, Pearson symbol oP12), (Al 1-x Ga x) 2 Pd 5 (Pd 5 Ga 2-type structure, space group Pnma, Pearson symbol oP28). In the Pd-rich part of the Ga-Sb-Pd system, three new ternary phases were revealed: Ga 1-x Sb x Pd 2 (Fe 2 P-type structure, space group P-62m, Pearson symbol hP9) and two tetragonal phases with approximate compositions close to Ga 0.5 Sb 0.5 Pd 3 , one of which crystallizes with Pt 3 Ga-type structure (space group P4/mbm, Pearson symbol tP16). The existence of the previously reported phase Ga 4.5 Sb 4.5 Pd 25 was confirmed. The isothermal sections were constructed for the Pd-rich regions of both systems. The catalytic properties of the sample Ga 28.3 Sb 5 Pd 66.7 were investigated for semi-hydrogenation of acetylene.