Small‐Crystal SAPO‐34 Preparation by Regulating Precursor Mixing Temperature for Methanol‐to‐Olefins Conversion

ABSTRACT

Small‐crystal SAPO‐34 zeolites provide substantial benefits for methanol‐to‐olefins (MTO) conversion, yet their industrial synthesis still struggles with achieving crystal size control through a straightforward method. In this work, a hydrothermal method was used to prepare a series of pure‐phase SAPO‐34 zeolites with varying crystal sizes by precisely regulating the mixing temperature of the synthetic precursor slurry. The nucleation and growth mechanisms of small‐crystal SAPO‐34 mediated by mixing temperature were systematically investigated, revealing a transformation from classical single‐crystal oriented growth to non‐classical polycrystalline nucleation‐aggregation growth. A moderate acid system, dominated by Si(4Al) species, is established in the as‐prepared small‐crystal zeolite. The mesoporous structure was also simultaneously enhanced. A comparison between nanoscale and conventional micrometer‐sized SAPO‐34 was made in the MTO reaction. The nanoscale version outperformed its counterpart, as evidenced by a longer catalytic lifetime (105–189 min) and a higher combined selectivity for ethylene and propylene (82.8%–85.1%).