Novel Silicoaluminophosphate Molecular Sieves with CHA/GME Intergrowth Structures: Synthesis, Structural Elucidation and Catalytic Application

Two novel SAPO molecular sieves, detonated as DNL-8 and DNL-9, were synthesized by an aminothermal co-templating strategy. This approach employed diisopropanolamine (DIPA) as both the solvent and the primary organic structure-directing agent (OSDA), with benzyltrimethylammonium chloride (BTACl) or trimethylamine (TMA) serving as a co-OSDA. 13C MAS NMR results demonstrate that the organics occluded in the crystals are the combination of TMA & DIPA for both samples. Three-dimensional (3D) rotation electron diffraction (RED) was used to elucidate their structures, revealing that both the DNL-8 and DNL-9 are the intergrowth of CHA/GME framework. In combination with the simulated XRD patterns of the intergrowths, the GME/CHA ratio is estimated to be 80%GME/20%CHA for DNL-8 and 20%GME/80%CHA for DNL-9. Interestingly, DNL-9 exhibits remarkable catalytic performance in the methanol amination reaction with a super-high selectivity of monomethylamine (MMA) plus dimethylamine (DMA) (~ 96 wt%), suggesting its potential application for the synthesis of MMA and DMA.