| 摘要 |
<p>PROBLEM TO BE SOLVED: To drastically reduce an oxygen concentration to a specific value or below by thermally decomposing a palladium intermediate product to form metal palladium and heat treating this metal palladium in a vacuum. SOLUTION: Silver electrolysis anode slime formed by recovering crude silver from copper electrolysis anode slime by electrolytic refining is subjected to a wet process treatment or reduction treatment, by which a dichlorodiamine palladium complex is collected. This complex is subjected to dehydrating and drying to obtain a porous sponge palladium complex salt (intermediate). When this complex salt is fired at 700 to 1,000 deg.C, the complex salt is decomposed and the sponge palladium is obtained. The oxygen concentration of the fired sponge palladium is about 0.2 to 2%. This metal (sponge) palladium is heat treated in the vacuum. The heat treatment is executed for >=10 minutes at >=500 deg.C and the melting point of the palladium or below. The vacuum degree is preferably <=0.1 Torr. As a result, the oxygen concentration may be reduced to <=100 ppm which is the purity required as a catalyst for engines.</p> |
