Pt-KL zeolite catalysts of different preparation: Part I. Catalyst characterization

0.8% Pt on KL zeolite was prepared by reduction with H₂ and NaBH₄. Transmission electron microscopy and X-ray diffraction were used for characterization of morphology of the metal particles; acidity of the zeolite framework was measured with IR spectra of adsorbed pyridine. Reduction by NaBHP₄ produced rather large, needle-like Pt crystallites on the outer surface of zeolite grains which contained very little acidity. Subsequent hydrogen treatment brought about their severe sintering; at the same time, small crystallites appeared. A bimodal distribution was seen when the catalyst was reduced with hydrogen; this sample exhibited appreciable acidity. X-ray diffraction data showed the presence of Pt particles above noise level in the case of borohydride-reduced catalyst only, in agreement with EM data.