| 摘要 |
A process for making a zeolite having a pore size of 4A by progressively adding, under agitation, a solution of sodium silicate in which the molar ratio Na2O : SiO2 ranges from 0.5 : 1 to 10 : 1 and the molar ratio of H2O : Na2O ranges from 5 : 1 to 50 : 1, to a solution of sodium aluminate in which the molar ratio Na2O : Al2O3 ranges from 1.2 : 1 to 2 : 1 and the molar ratio H2O : Na2O ranges from 20 : 1 to 50 : 1, the molar ratio of H2O : Na2O of each solution being such that during the precipitation the concentration of Na2O in the liquid phase is constant, the alumina present in the precipitate representing not more than 80% of the quantity present in the original aluminate solution and then converting the precipitate to a zeolite by known methods. The precipitation is carried out at 60-90 DEG C. and an ageing time of 1-3 hours is used at these temperatures. The zeolite has a crystal unit size of at least 1m and the porosity in pores of size greater than 5</>rA is less than 1 c.c. of benzene per 100 grams of zeolite.
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