Rational construction of hierarchical SAPO-34 with enhanced MTO performance without an additional meso/macropore template

Abstract

A relatively facile strategy was rationally developed for the synthesis of hierarchical SAPO-34 using aluminum phosphate spheres as the nutrient and mesoporogen, without utilizing any additional meso/macropore-directing agents. The simple synthesis resulted in SAPO-34 (CHA) with classical rhombohedral morphology with dimensions between 2 and 3 μm and intracrystalline meso/macropores. It was demonstrated that the employment of spherical aluminum phosphate particles and the regulation of synthesis conditions to carry out the dissolution of aluminum phosphate spheres parallel to the crystallization process of the CHA phase were crucial factors leading to successful synthesis. The crystallization process of the hierarchical SAPO-34 was investigated and a possible crystallization model was proposed. The catalytic performances of the synthesized SAPO-34s in the MTO reaction were evaluated. The SAPO-34 with a hierarchical porous structure exhibited an improved catalytic lifespan and higher selectivity for light olefins. This work not only provides a new facile method to synthesize hierarchical SAPO-34 but also holds great promise for offering useful guidance for the synthesis of other aluminophosphate zeolites with hierarchical structures.