Exploring Organic Structure-directing Agents Used for SAPO-34 to Synthesize SSZ-13

The aluminosilicate zeolite SSZ-13 and zeolitic silicoaluminophosphate molecular sieve (SAPO MS) SAPO-34 have been widely used in commercialized catalytic applications, such as the methanol-to-olefins (MTO) process and the selective catalytic reduction of NOx with NH3 (NH3-SCR). Nowadays, a variety of commercialized organic structure-directing agents (OSDAs) have been utilized for preparing SAPO-34, while the OSDAs for synthesizing SSZ-13 still mainly relies on the classical N, N, N-trimethyladamantammonium hydroxide (TMAdaOH) . Therefore, it is of great significance to seek for the suitable OSDAs, which can direct the synthesis of SSZ-13 with higher cost performance and appliable high silicon-to-alumina ratio (SAR). Herein, three OSDAs used for preparing SAPO-34 [diisopropylamine (DIPA) , dipropylamine (DPA) and n-butylamine (nBA)]were successfully employed for synthesizing SSZ-13 by partial replacing the expensive TMAdaOH with or without the assistance of seeds. Systemic investigation focused on SSZ-13 preparation was explored by powder X-ray diffraction (PXRD) and solid-state nuclear magnetic resonance (ss-NMR) analyses. As a result, the as-synthesized SSZ-13 zeolites possess a tunable range of SARs (11.22) and Cu-SSZ-13 catalysts show excellent NH3-SCR performance compared with commercialized ones. The crystallization mechanism of SSZ-13 synthesized by DIPA and TMAdaOH were also studied and the addition of DIPA would accelerate the crystallization process, improve the yields, and prevent the formation of amorphous phase. The work presented here might provide new insights for identifying more efficient and commercialized OSDAs for preparing SSZ-13 with tailored properties.

Automated summary

The aluminosilicate zeolite SSZ-13 and zeolitic silicoaluminophosphate molecular sieve SAPO-34 are widely used in commercial catalytic applications. Finding suitable OSDAs is important for directing the synthesis of SSZ-13 with specific properties. By using different OSDAs, SSZ-13 molecular sieves with different SARs can be obtained. This work provides new insights for identifying more efficient and commercialized OSDAs for preparing tailored SSZ-13 with specific properties.