| 摘要 |
1,177,169. Aluminosilicates. ENGELHARD MINERALS & CHEMICALS CORP. 19 Sept., 1967 [21 Sept., 1966], No. 42712/67. Heading C1A. A crystalline aluminosilicate of the fun jasite structure having an SiO2/Al2O3 mole ratio of at least 4:1, advantageously 4À8:1, is prepared by (a) acidifying a sodium silicate solution to a pH below 10 to produce a silica hydrogel, (b) removing the acid anions from the hydrogel, (c) mixing the silica hydrogel obtained in step (b) with sodium aluminate and, if desired, sodium hydroxide, to form a mixture having Na2O/SiO2, SiO2/AlO3 and H2O/Na2O mole ratios of 0À3 to 0À6:1, 8 to 30:1, and 25 to 80:1 respectively, (d) ageing the mixture at 10‹ to 50‹ C. for 10 to 100 hr., and (e) heating the mixture to 85‹ to 110‹ C. at which temperature it is aged to crystallize the aluminosilicate. The acid anion may be removed from the hydrogel by water washing, e.g. when HCl is used as the acid, followed if necessary by removal of excess water, or by decomposition of the acid anion by calcination at 400-600‹ C., e.g. when nitric, formic or acetic acid are used, followed by rehydration of the gel. The silica hydrogel combined with the sodium aluminate often has a water content of 40 to 95% by wt. A mineral acid, e.g. HCl, is used to acidify the sodium silicate and sodium hydroxide is added along with a sodium aluminate solution to the hydrogel produced, after the latter has been water washed, to provide a mixture having mole ratios 1 Al2O3/8À5 SiO2/3À3 Na2O/159 H2O. The mixture is aged at 30‹ C. for 24 hrs., and heated at 95‹ C. for 40 hrs. to crystallize the aluminosilicate. In Example (5), HNO3 is used to precipitate the silica gel, which is heated at 500‹ C. to decompose nitrate ion. The product is then rehydrated in water. The products may be base-exchanged with, e.g. Li, K, H, Ag, NH4, Mg, Ca, Zn, Ba, Mn and Al ions. |
