Study on the active phase formation of Pd-Zn/Sibunit catalysts during the thermal treatment in hydrogen

In the present research, the process of the formation of the active components of Pd-Zn catalysts supported on carbonaceous material Sibunit prepared by the joint impregnation (Pd:Zn = 1) is studied. It was shown by means of TPR and EXAFS techniques that the interaction between palladium and zinc begins already at T > 200 °C. During the reduction in hydrogen at temperatures of 200-300 °C the surface of particles being formed is enriched with oxidized zinc. In the temperature range of 400-500 °C zinc is completely reduced, and the crystal lattice of a substitutional solid solution based on fcc lattice of palladium is restructured in tetragonal lattice of PdZn. However, an increase of the calcination temperature in H₂ atmosphere (500 °C) significantly rises up the probability of partial destruction of bimetallic phase due to the partial migration of zinc atoms from the surface into the bulk of particles.