The synthesis of SAPO-34 zeolite for an improved MTO performance: tuning the particle size and an insight into the formation mechanism

• Published in: Inorganic chemistry frontiers Vol. 8; no. 9; pp. 2315 - 2322
• Main Authors: Zhou, Yida, Shi, Huaizhong, Wang, Bolun, Chen, Guangrui, Yi, Jian, Li, Jiyang
• Format: Journal Article
• Language: English
• Published: London Royal Society of Chemistry 07.05.2021
• Subjects: Alkenes; Aluminum phosphate; Catalytic converters; Chemical synthesis; Crystallization; Inorganic chemistry; NMR; Nuclear magnetic resonance; Particle size; Plates; Polyethylene glycol; Selectivity; Silicon; Trimethylamine; Zeolites
• ISSN: 2052-1553; 2052-1545; 2052-1553
• DOI: 10.1039/d1qi00016k

Traditional SAPO-34 zeolites synthesized using trimethylamine (TEA) as organic templates have relatively large particle size and limited MTO performance. In this work, SAPO-34 plates have been successfully synthesized using TEA as templates with the presence of polyethylene glycol (PEG) as an assisted template. Two-step crystallization is utilized in the concentrated gel system to control the particle size in the range of 0.9-1.2 μm. The MTO catalysis shows that the as-synthesized SAPO-34 plates exhibit enhanced catalytic performance. At 99% conversion, it has a catalytic lifetime (326 min) that is eight times longer than that of the conventional sample and 80% selectivity for light olefins. Moreover, the NMR study reveals the distinct crystallization process of SAPO-34 in two gel systems. Different from silicon being the activated species and the crystal center in a normal gel system, the aluminophosphate framework is first generated and then silicon gradually enters to replace Al or P in the concentrated gel system. Effect of gel systems, additives and crystallization conditions on the size of SAPO-34 and the MTO performance has been studied.