SYNTHESIS OF HIERARCHICALLY POROUS NANOZEOLITE ZSM-5 VIA TOP-DOWN METHOD

• Main Author: RIZKI SUPRIYANTI ( NIM : 20513305 ), TENTY
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/24504
• Institution: Institut Teknologi Bandung

Hierarchical porous zeolite is a solution for world catalysts problems, particularly in petrochemical industry. This catalyst can increase molecules diffusion, yield product and selectivity that not shown by conventional zeolite used as catalyst. Generally, hierarchical porous zeolite could be synthesized by two methods, that are bottom-up and top-down method. The first method is bottom-up, where zeolite synthesized from amorf silica and alumina precursors with addition of mesoporogens that are soft and hard template. That method are industrially less favorable due to relatively long reaction time. The second method is top-down method, which is modify a commercial ZSM-5 zeolite crystal. Top-down method is divided to two techniques. The first technique is dessilication and dealumination, while the second one is milling technique followed with recystallization. Milling technique could creates ZSM-5 zeolite crystal size in nanometer scale, however it decrease the zeolite crystallinity and significantly alternate the Si/Al ratio, which the outer part of zeolite become amorphous while recrystallization could convert back the amorphous phase to crystalline phase without alternate the Si/Al ratio and milled crystal size. In this study, a micelle surfactant Cetyltrimethylammonium bromide (CTAB) was added as directing agent of mesoporous creation in zeolite. Planetary ball milling was used to prepare nanozeolite from conventional zeolite with three variations of reaction time such as 0.5, 1 and 3 hours. According to SEM photograph, the milling process reduce the ZSM-5 zeolite crystal size. According to X-Ray diffractograms, characteristic peak of ZSM-5 zeolite still existed after 0.5, 1 and 3 hours of milling at 2&#61553; angle range 7.5-8.5o and 22.5-25o. Furthermore, recrystallization without CTAB addition and with CTAB addition of 0.03 and 0,07 moles generates product differences which has hierarchical porous and one which do not, where the recrystallization process without CTAB exhibit higher peak intensity than recrystallization with 0.03 and 0.07 moles of CTAB. Based on low angle X-ray diffractograms, sample that recrystallized with CTAB addition shows a peak at 2&#61553; angle 0.5o which suggest that order interlattice reflection was occured, while recrystallization without CTAB did not exhibit any peaks at those region. This can explain that CTAB addition could direct mesoporous generation in nanozeolites. FTIR characterization shows a peak at wavenumber 550cm-1 which is corresponding with pentasyl group of ZSM-5 zeolite was decreased. Meanwhile, that peak reappeared after recrystallization without CTAB and with CTAB addition of 0.03 and 0,07 moles, which is indicating that the pentasyl group of ZSM-5 have been regenerated. Hierarchical porous ZSM-5 nanozeolite have been successfully synthesized by top-down method with CTAB addition at recrystallization process. <br />