Expanding the Synthesis Field of High‐Silica Zeolites. (15th July 2020)

• Record Type: Journal Article
• Authors: Shi, Diandian; Haw, Kok‐Giap; Kouvatas, Cassandre; Tang, Lingxue; Zhang, Yiying; Fang, Qianrong; Qiu, Shilun; Valtchev, Valentin
• Is Part Of: Angewandte Chemie. Volume 132:Number 44(2020)
• Page Start: 19744
• Page End: 19749
• Publication Date: 2020-07-15
• Subjects: acidic media -- crystallization -- MFI-type -- zeolites; Chemistry -- Periodicals; 540
• DOI: 10.1002/ange.202007514
• Languages: English
• ISSNs: 0044-8249

Abstract

Abstract: Aluminosilicate zeolites are synthesized under hydrothermal conditions in a basic/alkaline medium in the pH range between 9 and 14. The synthesis of MFI‐type zeolite in an acidic medium is presented. The critical parameter determining the zeolite formation in an acidic medium was found to be the isoelectric point (IEP) of gel particles. MFI‐type zeolite was synthesized above the isoelectric point of the employed silica source, where the silica species exhibit a negative charge and the paradigm of zeolite formation based on the electrostatic interaction with the positively charged template is retained. No zeolite formation is observed below the isoelectric point of silica. The impact of aluminum on the zeolite formation is also studied. The results of this study will serve to extend the synthesis field of high silica zeolites to the acidic medium and thus open new opportunities to control the zeolite properties. Abstract : Zeolite synthesis in an acidic medium is investigated. The isoelectric point (IEP) of the silica source is found to be the critical factor controlling the zeolite formation under acidic conditions. The zeolite crystalizes solely at a pH above the IEP when the silica particles are negatively charged.