PROCEDURE FOR SYNTHESIS OF CRYSTALLINE MICROPOROUS SILICO-ALUMINO-PHOSPHATES

Procédé amélioré de production de catalyseurs de silico-alumino-phosphates servant à transformer du méthanol en oléfines légères telles que de l'éthylène et du propylène (réaction M-O). Ce procédé amélioré de synthèse peut être utilisé pour contrôler la composition chimique des silico-alumino-phosphates, plus particulièrement leur teneur en silicium. Plus spécifiquement on a découvert que les catalyseurs pouvant être synthétisés sont plus stables à la désactivation par encrassement provoqué par des dépôts de composés carbonifères. Cette caractéristique est très importante dans la conception d'un procédé de transformation de méthanol en oléfines fondé sur les silico-alumino-phosphates de synthèse. PCT No. PCT/NO92/00193 Sec. 371 Date Aug. 25, 1994 Sec. 102(e) Date Aug. 25, 1994 PCT Filed Dec. 9, 1992 PCT Pub. No. WO93/13013 PCT Pub. Date Jul. 8, 1993A process for producing crystalline microporous silico-alumino-phosphates with controlled Si content from a mixture of reactive sources of SiO2, Al2O3 and P2O5 and an organic template material, by combining at least a portion of the Al source and the P source in the absence of the Si source, mixing the resulting mixture with any remaining Al source, the Si source and the organic template material to obtain a gel, and heating the gel to obtain crystallization, wherein the Al and Si sources in the reaction mixture are mixed in the same mole ratios as in the crystalline microporous silica-alumino-phosphate to be produced, the P source is added in stoichiometric excess and hydrochloric acid is added at the same time as the P source, in a quantity such that the ratio of silica to hydrochloric acid in the gel is kept between 0.3 and 3. The invention also provides a crystalline microporous silico-alumino-phosphate produced by the process, and the use of such silico-alumino-phosphate as a catalyst for producing olefins from methanol.