Project Details
Projekt Print View

Topotactic transformation of naturally occurring layer silicates into porous framework silicates

Applicant Dr. Bernd Marler
Subject Area Mineralogy, Petrology and Geochemistry
Term from 2019 to 2023
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 416605983
 
Final Report Year 2024

Final Report Abstract

The joint research project of Ruhr-University Bochum and Waseda University Tokyo aimed to investigate the topotactic transformation of naturally occurring layer silicates into porous framework silicates. The project has been sectioned into a series of five steps, each building on the findings of the previous step. The first step includes the structural characterization of naturally occurring hydrous layer silicates (HLS) magadiite and kenyaite. The structures of the sodium layer silicates were successfully solved after characterising the silicates by a combination of powder X-Ray and electron diffraction techniques, spectroscopic methods and model building. The aim of the second step was to investigate the condensation of natural magadiite to form a structurally ordered silica zeolite of high density (RWZ-1) by exchanging the sodium for hydrogen , refluxing in N-methylformamide (NMF) and finally heating the material. During the third step, two crystalline silicic acids (CSAs), Hydrated H-Apophyllite and H-Carletonite, have been obtained from natural layer silicates (apophyllite and carletonite) by acid leaching. The CSAs which were characterised in detail were sufficiently ordered to analyze their structures. The crystal structure of silhydrite, the only natural silicic acid, remains – while showing similarities to magadiite – unsolved due to the severe structural disorder. Leaching experiments on the mineral gillespite acting as a precursor material were conducted to obtain another silicic acid, but led to a highly disordered H-gillespite material. The fourth step entails attempts to apply the condensation technique of the 3rd step to other silicates, such as H-carletonite and kenyaite. In a fifth step, emphasis is laid on the synthesis of an Interlayer Expanded Zeolite (IEZ) in a single-step-synthesis (RUB-5 and RUB-11), in contrast to the multi-step synthesis of the well established interlayer expansion and subsequent pillaring and condensation. In a profitable side step, SiO2 polymorphs keatite, RUB-11 and silica-sodalite have been investigated in order to determine the thermal expansion with special attention to a material with possibly zero volumetric thermal expansion.

Publications

 
 

Additional Information

Textvergrößerung und Kontrastanpassung