| 摘要 |
<p>Hydroxylamine salts are made by reducing nitrate ion or nitrogen monoxide with hydrogen in an acid medium in the presence of a noble metal catalyst. The catalyst mass is sepd. from the reaction mixt. and at least part of it is reused after first removing silicate and/or silicon dioxide by treating the catalyst mass with an aq. soln. of fluorosilicic acid at pH 1.5-4.5. Removal of the silicate or silicon dioxide deposits from the catalyst gives improved filterability of the catalyst from the reaction medium by preventing build up of silicate and silica deposits on the catalyst, which cause increasing filtration resistance. In an example, a palladium-platinum catalyst on active carbon carrier, activated with germanium oxide, was used for prodn. of hydroxylamine phosphate in the known way. After separation, the catalyst contained 4.9 wt.% SiO2. The catalyst was cleaned by treatment at 60 degrees C with an aq. soln. of fluorosilicic acid and ammonium fluoride at pH 3.7.</p> |
