This master thesis reviews the current research based on hierarchical zeolite and Pulsed-field gradient nuclear magnetic resonance (PFG NMR) as a diffusion measurement method, compares other characterisation methods and predicts the advantages of combining this technique. Hierarchical zeolites are widely used in fluid catalytic cracking (FCC) processes to solve carbon deposition and increase the reaction rate. While retaining its inherent zeolite properties, the combination with mesopores can enhance molecular transfer efficiency within the zeolite. The ultra-stable Y (USY) hierarchical zeolite was produced to introduce mesopores in the commercial dealuminated zeolites through alkaline solutions in the presence of cetyltrimethylammonium bromide (CTAB). In addition, after NH4Cl ion exchange, select molecules for diffusion test, and apply PFG NMR to characterise the diffusion properties of samples. The zeolite samples will be characterised by a series of analytical techniques, hoping to prove the properties of the particles' internal pore structure. It is expected that the obtained satisfied zeolite has improved mass transfer efficiency, and at the same time, the internal pore connectivity is higher, while the relative crystallinity is reduced. This characterisation method has potential applications for laboratory-level material industrialisation prediction.