SYNTHESIS AND CHARACTERIZATION OF ZEOLITE MCM- 22 WITH HIERARCHICAL PORES

• Main Author: Nur Chasanah, Siti
• Format: Theses
• Language: Indonesia
• Subjects: Kimia
• Online Access: https://digilib.itb.ac.id/gdl/view/62592
• Institution: Institut Teknologi Bandung

Zeolite MCM-22 is an aluminosilicate material that has MWW framework structure. This zeolite can be synthesized using Organic Structure Directing Agent (OSDA) of Hexamethylene Imine (HMI). MCM-22 zeolite has 3-dimensional structure formed by calcination process of the MCM-22 precursor. The calcination process causes OSDA to decompose so that the silanol group in the precursor can be condensed. Zeolite MCM-22 can be synthesized under two conditions, namely static conditions and tumbling conditions (rotating autoclave). Under static conditions, the synthesis of MCM-22 requires greater amounts of Na2O than the tumbling conditions. The amount of Na2O affects the silica dissolution process. The synthesis of MCM-22 zeolite under static conditions could produce zeolite with high crystallinity but requires large amounts of Na2O and long synthesis time. In order to produce MCM-22 zeolite with high crystallinity and relatively shorter synthesis time, the MCM-22 zeolite synthesis was carried out at a higher temperature. The resulting MCM-22 zeolite has a micro pore size of 0.71 nm consisting of 12 rings (12 MR). Ring 12 is easier to form mesopores by desilication using a mixture of NaOH-surfactants than smaller rings. So that MCM-22 needs to be desilicated with a mixture of NaOH-surfactant in order to produce intracrystalline mesopores. Analysis related to crystal phase, morphology, and pores were characterized by XRD, SEM and TEM. Based on the results of the analysis, it is known that MCM- 22 zeolite can be synthesized under static conditions with Si/Al ratio of 15 at 170oC for five days. Produced MCM-22(P) precursor which still contains OSDA and MCM-22 zeolite which is the calcined zeolite of MCM-22(P). This synthesis resulted in a mixture of MCM-22 zeolite and ZSM-5 zeolite with a crystallinity of 87.63%. The synthesis of MCM-22 zeolite with a temperature of more than 150? can produce an impurity phase in the form of MFI type zeolite. Zeolite ZSM-5 (MFI) and zeolite MCM-22 (MWW) have the same Composite Building Units (CBU), namely mel. This allows the formation of the ZSM-5 impurity phase on the MCM- 22 zeolite. The precursor MCM-22(P) and zeolite MCM-22 have a platelet-like morphology with a diameter of 4-5 m and a thickness of 0.5-1 m. Formation of intracrystalline mesoporous MCM-22 can be done by desilication. Desilication was carried out on precursor MCM-22(P) and zeolite MCM-22 using NaOH and a mixture of CTABr-NaOH. The desilication process on the MCM-22(P) precursor was carried out using 0.1-1 M NaOH. The higher the concentration of NaOH that used the ZSM-5 phase decreased. This is because OSDA, only protects the MCM- 22 crystal. Desilication of MCM-22(P) precursor with NaOH and a mixture of CTABr/NaOH resulted in mesoporous with crystallinity reduction 15-16%. The formation of mesopores was confirmed from the TEM image, namely the presence of intracrystalline mesopores. The desilication process on MCM-22 zeolite was carried out using 0.1-0.5 M NaOH. The higher the concentration of NaOH used, the lower the MCM-22 phase. This is because MCM-22 has a lower framework density (FD) value than ZSM-5. MCM-22 is less stable than ZSM-5 so it is easily desilicated by NaOH. Desilication with NaOH resulted in mesoporous intracrystalline with a significant decrease in crystallinity. The decrease in crystallinity is up to 35%. Meanwhile, desilication using mixture of CTABr/NaOH resulted in mesoporous intracrystalline without significant decrease in crystallinity. Decrease in its’s crystallinity by 19%. The addition of surfactant during the desilication process can form mesopores while protecting the MCM-22 crystals. In addition to the formation of mesopores, desilication using a mixture of CTABr/NaOH can induce a phase change from ZSM-5 (MFI) to EU-1 (EUO). ZSM- 5 has a higher framework density (FD) value than EU-1, but has the same CBU, cas. This allows for a phase change from ZSM-5 to EU-1.