POTENTIAL OF DIFFUSIONLESS INTERZEOLITE TRANSFORMATION OF FAU-CHA USING ORGANICCONFINED TECHNIQUE

• Main Author: Hutami Wahyudi, Dian
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/75490
• Institution: Institut Teknologi Bandung

Zeolites are crystalline alumina-silica microporous materials that have been widely used as catalysts, adsorbents, and ion exchangers. One of the development methods for synthesizing zeolites is through interzeolite transformation strategies. Interzeolite transformation can be achieved through a diffusionless conversion, in which the parent zeolite endures rearrangement or reconstruction to form the target zeolite. The transformation of zeolite FAU to CHA has also been reported to occur through a dissolution and recrystallization process. The hypothesis in this study is the interzeolite transformation from FAU to CHA can also occur through diffusionless conversion. Diffusionless conversion can be carried out by applying organic-confined techniques to the parent zeolite. In this approach, organic compounds are added to FAU zeolite and act as stabilizers for maintaining the crystallinity of the structure while inhibiting the dissolution of the zeolite during the interzeolite transformation. To prove the hypothesis, FAU zeolite which has been inserted with organic compounds transformed into target zeolite under hydrothermal conditions at 100 °C and 150 °C for 4 days. The zeolite products are characterized using XRD (X-Ray Diffraction), SEM (Scanning Electron Microscope), and EDS (Energy Dispersive X-Ray Spectroscopy). Based on the analysis results, FAU zeolite has been successfully synthesized and gives a flowerlike morphology. Protonated FAU zeolite using NH4NO3 shows the same morphology as FAU before protonation but suffers some destruction due to the dissolution of Al in the FAU framework. The organic-confined technique is applied using four different organic compounds, two of them (TMAdaOH and BTMAOH) are specific organic structure directing agents (OSDAs) to the formation of CHA zeolite, while the other two organic compounds (TEAOH and TPAOH) are specific OSDAs to the formation of BEA and ZSM-5 zeolites. The organic compounds incorporated into the HFAU framework do not break the HFAU framework, as evidenced by the preserved FAU crystal topology. HFAU zeolite which is inserted with organic compounds is transformed at 100 °C for 4 days using K+ ions. The transformation of HFAU with 4 different organic compounds gives the CHA framework topology. SEM analysis also shows similar morphologies as the aggregated material for all transformation products. Transformations are also carried out at 150 °C, but the resulting zeolites do not exhibit specific structures based on the organic compounds. Although using different organic compounds and higher transformation temperatures, the products still maintain the same crystal topology as CHA zeolite. In this study, it can be concluded that the organic compounds do not act as structure-directing agents but rather as structure stabilizers for the FAU framework. This is consistent with the hypothesis that the organic compounds within the FAU framework will maintain the stability of the FAU framework during the transformation. FAU zeolite does not endure a dissolution process but rather undergoes reconstruction or rearrangement with the assistance of organic compounds. This is supported by the similarity in CBU between FAU and CHA zeolites which strongly indicates the occurrence of diffusionless interzeolite transformation. This research provides insights into the role of organic compounds inserted into the FAU zeolite framework in maintaining the stability of the FAU zeolite structure during the transformation.