Abstract
ZSM-5 zeolite was synthesis under hydrothermal conditions at 175oC. The synthesis parameters have been investigated to find optimum synthesis method. Firstly, the crystallization time has been investigated to find the optimum crystallization time. Also, the ageing time was studied. The morphology, structure, and composition of the synthesized ZSM-5 zeolite were characterized using scanning electron microscopy (SEM), pH meter, viscometer, and X-ray powder diffraction (XRD). The bulk Si/Al ratio of ZSM-5 zeolite was in the range of 9.5—11.7. The synthesized ZSM-5 zeolite with appropriate ageing time could adjust crystal size and degree of the crystallinity. The crystal size of ZSM-5 zeolite obtained at an ageing time of 24 h was around 2.0 μm. The suitable aging time was 24 h, and the relative crystallinity of ZSM-5 zeolite could reach up to 100% after crystallization for 48 h at 175oC
Highlights
The ZSM-5 is a member of MFI zeolite pentasil family that consists of ten membered rings with a medium pore zeolite of 5.4–5.6 Å, Catlow, 1992
There was no effect of the crystallization time on purity of ZSM-5 phase ; the crystalline phase is hardly distinguished within twelve hours
The Si/Al bulk ratio was increased from 9.25 at 4 h to 10.77 at 16 h dropped to 10.27 at 24 h and remained constant with further prolonging of the time to 32 h. These results are in good agreement with a previous work with zeolite Y, Alrubaye, 2016, which showed the crystal size was the minimum at long ageing time due to the formation of proper precursors which accelerate the nucleation toward zeolite
Summary
The ZSM-5 is a member of MFI zeolite pentasil family that consists of ten membered rings with a medium pore zeolite of 5.4–5.6 Å, Catlow, 1992. Ageing time applied is to homogenize the amorphous aluminosilicate gel prior to the crystallization process at 25oC or slightly higher temperature, which is lower than the crystallization temperature, ALRubaye, 2013. The synthesis parameters have great effect on zeolite properties; these parameters such as ageing time, crystallization time, and crystallization temperature etc., are found to have influence on crystal size, Si/Al ratio, and degree of crystallinity. Therefor, the zeolite crystal size reduction has a huge impact on the activity and catalytic properties such as, catalyst selectivity, Abrishamkar, et al, 2010. Therefor, tailoring the size of the ZSM-5 crystal depends on the selectivity and activity of the catalyst and in which process it will be used is crucial, Xue, et al, 2012. The second method is including the post-synthesis modification of synthesis zeolite that is known as “Top-down “,Valtchev, et al, 2013
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