| 摘要 |
Siliceous zeolite catalysts comprising zeolitic mono- and/or divalent metal cations and a non-zeolitic Group VIII noble metal hydrogenating component supported thereon, which catalysts have undergone damage by thermal and/or hydrothermal stresses resulting in a maldistribution of the metal components, are rejuvenated in activity by a first treatment with a volumetric excess of aqueous ammonium hydroxide, followed by a second treatment with an extractive proportion of an aqueous ammonium salt solution. The combined treatments have a twofold effect of bringing about a desirable redistribution of the Group VIII noble metal, and of exchanging out at least a portion of undesired zeolitic mono- and/or divalent metal ions. A highly advantageous procedure for carrying out the rejuvenation involves simply neutralizing the ammonium hydroxide-catalyst mixture from the first treatment with a suitable acid to give the ammonium salt desired for the second treatment.
|
