INVESTIGATING THE EFFECT OF BICYCLIC DIQUATERNARY AMMONIUM COMPOUND AS STRUCTURE- DIRECTING AGENT IN THE CRYSTALLIZATION MFI ZEOLITE

• Main Author: Lestari, Widia
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/32306
• Institution: Institut Teknologi Bandung

The great interest on zeolite minerals lies on the application as catalysis, ion exchanger and molecule filters. One of zeolite application being developed is the role of zeolite as catalyst. The pores on zeolite surface leads to a high selectivity heterogenous catalyst. The search of large porous crystalline catalyst for processing large molecules such as vacuum gas oil is continued. For this specific reason, the pore of zeolite is designed using large structure-directing agent (SDA). Common linear quaternary ammonium SDA is modified into cyclic quaternary ammonium molecule and cyclic diquaternary ammonium molecule. The use of cyclic compound is meant to obtain new type of zeolite with large pore size whereas the use of long diquaternary ammonium molecule has the objective to alter the crystal morphology. Here, we have successfully synthesized newly type of bicyclic diquaternary ammonium cations to be tested as SDA for zeolite synthesis. SDA made by reacting piperidine with 1,4-dibromobutane and sodium hidroxide with molar composition of 1:1:2 through a SN2 reaction mechanism in a 12 hours reflux process. To obtained product of ammonium salt solid was separated from the solvent through evaporation. The compound shows molecular structure of piperidine – C4 - piperidine after an evaluation from solution-state NMR spectroscopy and mass spectroscopy. Consequently, the SDA is mixed in the aluminosilicate gel under molar composition of Si/Al = 22.7 , H2O/Si = 20, NaOH/Si = 0.3 , SDA/Si = 0,19 and hydrothermally treated at 150°C for 5 days. The synthesized zeolite was calcined at 550°C for 8 hours to discard the organic molecules. The crystallization leads to the formation composites of MOR and MFI zeolite. In the absence of SDA, the aluminosilicate gel treated under similar conditions resulted in MFI zeolite. SEM analysis was completed on MOR zeolite sample synthesized using piperidine-C4-piperidine compound, showing the existence of prismatic and spherical crystals, while MFI zeolite sample showing a hexagonal prismatic crystals. The formation of composites is due to the bulkiness of this newly-type of SDA molecule that only fit to be positioned in the straight channel but not to the perpendicular sinusoidal channel in MFI framework. This causes one dimensionality preference that MOR zeolite is one of the options.