| 摘要 |
1,223,731. Purification of molecular sieves. W. R. GRACE & CO. 26 July, 1968 [18 Aug., 1967], No. 35907/68. Heading C1A. Precipitated compounds are washed from a calcined cation exchanged zeolite by slurrying with sufficient of an acid solution having a pH of 3.5 to 5.5 that the pH of the slurry is maintained between 3À5 and 5.5, maintaining the slurry for at least 5 minutes at a temperature of 125‹ to 200‹ F., and filtering the slurry to recover the zeolite. The zeolite may then be further washed with acid solution of pH 3À5 to 5.5, filtered, washed with water and dried. The zeolites may be rare earth metal exchanged, and the rare earth materials washed from the zeolite may be recovered and recycled for use as exchange material. The acid solution used may contain acids only, e.g. hydrochloric, sulphuric or nitric acids, acids with buffering agents, e.g. ammonium sulphate, chloride or acetate, or acidic salts only, e.g. ammonium sulphate, chloride or acetate. Further acid solution may be added to the slurry to maintain the pH within the required range. The zeolite may be finally dried by heating at 250‹ F.
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