Structural and transport properties of newly synthesized ZSM-5 sourcing silica from coconut shell ash
Aparna Sarker, Abu Sufian Rabbi, Nasrin Akter Nadi, Abul Kalam Md. Lutfor Rahman, Aurélien Momin, Khondoker Shahin Ahmed, Hasina Akhter Simol
Abstract
• Utilization of extracted silica from waste coconut shell in the synthesis of pure ZSM5. • The lower SiO 2 /Al 2 O 3 ratio (17.84) was obtained from WDXRF. • The dielectric constant decreased with the increase of frequency. • The presence of polaron hopping conduction mechanism was confirmed from electric modulus results. ZSM-5 is a crucial catalyst in industrial chemistry and petrochemical processing, distinguished by its unique structural and chemical properties. The cost of its production is heavily influenced by the expense of silica-alumina sources, which are the primary precursors for the formation of the zeolitic network. This study introduces a pioneering approach to synthesize the valuable zeolite ZSM-5 using waste coconut shell ash (CSA), a readily available and cost-effective alternative natural source of silica. High-purity amorphous silicon dioxide (SiO 2 ) was successfully extracted from discarded coconut shells, as confirmed by X-ray diffraction (XRD) analysis, providing an eco-friendly approach to the production of this valuable material. The optimal preparation conditions for ZSM-5 were found to be 150 °C and 60 h, yielding the ZSM-5 zeolite from extracted silica. The XRD pattern revealed the presence of a pure crystalline MFI phase in the ZSM-5, and the FTIR findings corroborated its pentasil structure. Microscopic images (SEM and TEM) confirmed that the zeolite was polycrystalline, with agglomerated rod-shaped particles. The WDXRF data revealed a low SiO 2 /Al 2 O 3 ratio of 17.84. Electrical characterization showed that the dielectric constant decreased with increasing frequency. Complex impedance spectroscopy enabled the distinction between grain and grain boundary contributions to total resistance, and the electric modulus indicated a hopping conduction mechanism. This study demonstrated the potential of a new ZSM-5 using CSA as the source of silica for various catalytic applications.