COMPARISON OF PD(NH3)(4)(2+) DECOMPOSITION AND PD2+ REDUCTION IN ZEOLITES NAY, NAX AND CSX

The decomposition of Pd(NH3)(4)(2+) and further reduction to Pd-0 in P d6.4NaY and three zeolites differing in alkalimetal cation or Pd loadi ng (Pd(2.9)NaX, Pd(7.4)NaX and Pd(8.2)CsX) are investigated by TPO, TP R and UV-VIS-NIR spectroscopy. With regard to the temperature, the ord er for the decomposition of the ammine complex is PdCsX < PdNaX < PdNa Y and that for the reduction of bare Pd2+ ions located in the same typ e of cage within the zeolites is PdCsX < PdNaX approximate to PdNaY. T hese orders depend an the stabilization of the various intermediate Pd complexes. It is shown that NaX favours the location of Pd2+ ions in the inner sites (i.e. sodalite and hexagonal prism). Parameters import ant for the various locations of Pd complexes are discussed in terms o f the zeolite basicity and steric hindrance for migration of Pd(NH3)(x )(2+) complexes or Pd2+ ions in the inner cavities.