Relationship between single and bulk mechanical properties for zeolite ZSM5 spray-dried particles

In this work the typical mechanical properties for the catalyst support material, ZSM5 zeolite particles, have been measured in order to relate the bulk behaviour of the powder material to the single particles mechanical properties. Particle shape and size distribution of the powders were determined by laser diffraction and Scanning Electron Microscopy (SEM) confirmed the spherical shape of the spray dried particles. The excellent flowability of the material was assessed by typical methods such as the Hausner ratio and the Carr’s index. This was confirmed by bulk measurements of particle-particle internal friction parameter and flow function using a Schulze shear cell, which also illustrated the poor compressibility of the material. A single particle compression technique was used for characterising individual particle mechanical properties such as reduced elastic modulus and strength by applying the Hertz contact mechanic theory. Furthermore, nanoindentation was employed to measure particle surface mechanical properties such as hardness and elastic modulus. The latter two methods gave different mechanical properties in terms of reduced elastic modulus showing the mechanical non-homogeneity between the surface of the particle and the entire particle. Finally, particle bulk compression was used to show the influence of single particle mechanical properties on bulk compression behaviour and the Adams model was shown to be suitable for describing the bulk compression. The predicted Adams model parameter, apparent strength for the single particles was in good agreement with the single particle strength determined by single particle compression test. This work illustrates the importance of a comprehensive understanding of particles properties in order to predict or understand the bulk behaviour of powder material during a specific process such as powder compaction.