| 摘要 |
1277458 Microspherical alumino silicates ENGLEHARD MINERALS & CHEMICALS CORP 18 June 1969 [20 June 1968 25 March 1969] 30917/69 Heading B1E [Also in Division C1] A process for preparing an ion-exchanged synthetic crystalline faujasite comprises spray drying a slurry in water of hydrated (or a mixture of hydrated and calcined) kaolin clay to form microspheres, calcining the clay until the hydrated clay is dehydrated and the microspheres at least partially undergo the kaolin exotherm, suspending the microspheres at 65‹-130‹ F in an aqueous solution of an alkali metal hydroxide of, e.g. 12-22% concentration (w/w), agitating the microspheres in the solution at 150‹-200‹F until hydrated alkali metal faujasite crystals form in said microspheres and silica is leached therefrom, separating the microspheres from solution and then ion-exchanging them, e.g. with NH 4 <SP>+</SP> ions to reduce the alkali metal content thereof. Metakaolin in the form of microspheres may be incorporated into the alkali metal hydroxide solution in an amount of 1-20% by weight of the calcined kaolin. The hydrothermal treatment is preferably terminated after substantially the maximum amount of synthetic faujasite (preferably sodium zeolite Y) has crystallised, if the hydrothermal treatment is continued, zeolite B beings to crystallise (eventually all the crystalling constituent would be present as this). The products, catalysts for cracking hydrocarbons, in the form of attrition-resistant microspheres (100/325 mesh Tyler) containing ion-exchanged faujasite and an amorphous alumina-silica residue of alkali metal hydroxide-leached calcined kaolin clay (which has undergone the kaolin exotherm) analyze (on a volatile-free weight basis) as at least 90% SiO 2 with Al 2 O 3 (typically 30-50% SiO 2 and 50-65% Al 2 O 3 , in a SiO 2 /Al 2 O 3 molar ratio of 0.8-1.4:1; the Na 2 O constituent is typically less than 3%, and the faujasite constituent in the product (usually 1-70%) preferably has a SiO 2 /Al 2 O 3 molar ratio in excess of 4. |
