IDENTIFICATION BY DIFFUSE REFLECTANCE AND EXAFS OF THE CHANGES IN COORDINATION OF NAY ENTRAPPED PD(NH3)X2+ ION DURING CALCINATION

The coordination chemistry of Pd(NH3)x2+ ions in zeolite NaY after calcination has been identified by u.v.-VIS diffuse reflectance (d.r.s.) and EXAFS spectroscopies. Pd(NH3)42+ ions remain intact in NaY supercages after calcination in 1 atm of O2 at Tc = 150°C; they show a characteristic absorption maximum at 33.5 × 103 cm-1. Roughly 50% of the ammine ligands are known to be destroyed by calcination at 250°C; EXAFS and d.r.s. both show that Pd ions are coordinated to oxygen and nitrogen. Calcination at 500°C leads to bare Pd2+ ions coordinated to four Oz ions; the EXAFS data indicate coexistence of Pd2+ in two locations; sodalite cages and hexagonal prisms. © 1990.