Temperaturowo programowane metody w badaniach katalizatorów nośnikowych zawieraja̧cych pallad

Catalysts prepared from (a) 3% and (b) 1.5% Pd/C (Siberian active C, ∼390 m²/g, impregnated with PdCl₂): (a) 4.3, 5.2, 6.4% (redox method) and 6.5% (capillary impregnation) Pd_xAu_(100-x)/C (x = 80, 70, 60, 60), (b) 2.2, 3.2 (co-impregnation with aq. NH₄AuCl₄), and 2.7% (redox) (x = 80, 60, 70 atom %), resp., and activated 3 h in H₂ at 400°C, were studied by chemisorption of H₂, temperature-programmed hydride decomposition (TPHD), and X-ray diffraction (XRD). Both TPHD (20-120°C) and XRD showed in series a and b the degree of alloying to be higher (though not ideal) in the redox-method than in the impregnation-method catalysts, thereby instrumental in preparing high-selectivity hydrodechlorination (of freons) catalysts. Two more catalysts, 0.3 and 2.77% Pd/γ-Al₂O₃, (A) heated 8°C/min in 10% H₂/He up to 300°C, and/or (B) heated 0.5 h in O₂ at 300°C, washed with He at 300°C, reduced with H₂17 h/600°C, and washed with He 1 h/600°C, were studied in thermal desorption of pyridine. Treatment B resulted in ∼50 and ∼30% more pyridine desorbed from catalysts A, B, and carrier γ-Al₂O₃, resp., presumably on account of the stronger acid sites generated. Unlike from γ-Al₂O₃, desorption from the A and B at >400°C gave plenty of H₂ owing to decomposition of pyridine to an extent apparently related to the Pd%. 33 refs.