Synthesis and characterization of nanocrystalline Zeolite Socony Mobil-5 using some Ghanaian clays as the starting raw materials By Benjamin Kwadzo Kokloku (B.

Abstract

Zeolites are aluminosilicate crystals having a porous structure and are useful as catalysts, adsorbents, and ion exchange materials. The synthesis of zeolites using clay minerals is a promising approach because it utilizes inexpensive and widely available starting materials. However, clays originate from different sources and the parameters of synthesis vary depending on the environment and nature of the clay. Therefore, the process requires suitable pre-treatment of the raw clay and the optimization of the synthesis parameters to ensure that the synthesized zeolite has the desired properties. In this work, a protocol to be used in the synthesis of ZSM-5 zeolite using Anfoega, Mfensi, Teleku-Bokazo, and Tetebu clays was developed. These clays serve as silica and alumina sources. The raw clays were first calcined, followed by acid leaching to dealuminate the calcined samples to increase the SiO2/Al2O3 molar ratio while removing impurities, and finally hydrothermal zeolitization. From the results obtained, acquiring the ZSM-5 phase in the final product depended greatly on the pre-treatment technique applied to the raw clay. ZSM-5 zeolite was effectively synthesized from all four clay sources at a crystallization temperature and crystallization period of 190 °C and 24 h, respectively. The relative crystallinity and crystallite sizes of the ZSM-5 phase were calculated to be 41.23% and 36.08 nm, 32.02% and 35.53 nm, 35.37% and 34.75 nm, and 54.43% and 29.74 nm for Anfoega, Mfensi, Teleku-Bokazo, and Tetegu clays respectively. The synthesis conditions of the ZSM-5 zeolite using Tetegu clay were further investigated in more detail and the parameters were optimized. Hence, for the Tetegu clay, the effects of key synthesis parameters, i.e., temperature, time, aging conditions, and reactant molar ratios were investigated. The optimal production conditions of nano-crystallite ZSM-5 zeolite using the Tetegu clay were found to be a molar ratio of SiO2/Al2O3 = 51.97, NaOH/SiO2 = 0.032, TPABr/SiO2 = 0.072, H2O/SiO2 = 25; crystallization temperature = 190 °C; crystallization time = 24 h, with aging at room temperature (without stirring) for 24 h. This study has established the viability of clay samples obtained from Anfoega, Mfensi, Teleku-Bokazo, and Tetegu as starting materials for the production of ZSM-5 zeolite, and the appropriate optimal production conditions were established for Tetegu clay.