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ZSM-5 zeolite; palygorskite; solvent-free synthesis.

Zeolites have extensively been applied in gas adsorption and separation, catalysis, and ion exchange thanks to their numerous interesting features. However, the synthesis of zeolites usually requires solvents, which often lead to water pollution, loss of silicon and aluminium components, and low synthesis efficiency. In this account, ZSM-5 zeolites were synthesized from natural clay palygorskite (PAL) by acid leaching, followed by thermal treatment under solvent-free conditions. The as-obtained ZSM-5 zeolites exhibited high crystallinity and mesoporous structure. The NMR spectra of ZSM-5 zeolites confirmed the presence of aluminium element derived from the acid-treated PAL (APAL) existed in zeolite framework. Thus, PAL was simultaneously employed as silica and aluminium sources for zeolite preparation. The Si/Al molar ratio of ZSM-5 zeolites could be adjusted by adding NaAlO$_2$, but against growth of ZSM-5 zeolites, resulting in formation of analcime. On the other hand, long thermal treatment for 72 h caused the dissolution of ZSM-5 zeolite crystals and formation of analcime. Overall, calcination could enhance the activity of APAL and crystallinity of ZSM-5zeolites, and solvent-free synthesis of zeolites from clay might efficiently reduce the cost of zeolites.

MEI WU¹ WENBIN JIANG¹ JINLONG JIANG¹ YUNQIN ZOU¹ PENGYU ZHANG¹ PING MAO¹ YING XU¹ YINGYING SHI¹

1. Key Laboratory for Palygorskite Science and Applied Technology of Jiangsu, National & Local Joint Engineering Research Center for Mineral Salt Deep Utilization, School of Chemical Engineering, Huaiyin Institute of Technology, Huaian 223003, Jiangsu Province, People’s Republic of China

Published

29 October 2020

Manuscript received

18 November 2019

Accepted

26 June 2020

Final version published online

29 October 2020