| 简介 |
Agglomerated zeolite adsorbents comprising a barium X zeolite powder and an inert binder have a Dubinin volume of at least 0.245 cm 3>/g and a mechanical strength (Shell SMS1471-74) of at least 2 MPa. The zeolite powder has a crystal diameter of 1.6 mu m or less and a silicon/aluminum ratio of 1.15-1.5, where at least 90% of the cation exchange sites are occupied by barium ions or by barium and potassium ions, provided that no more than 1/3 of these sites are occupied by potassium ions. Independent claims are also included for : (1) process (P1) for producing adsorbents as above by agglomerating an X zeolite powder with a binder comprising at least 80 wt.% zeolitizable clay and a silica source, drying and calcining the agglomerates, zeolitizing the binder with an alkali solution, substituting at least 90% of the exchange sites with barium, washing and drying the product, optionally substituting up to 33% of the exchange sites with potassium, and washing, drying and activating the product, where potassium exchange can be effected before or after barium exchange; (2) process (P2) for recovering p-xylene from C 8aromatic fractions in the liquid or gas phase by adsorption on an adsorbent as above in the presence of a desorbent. |
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