On the successful pelletization of a fragile mesoporous material and its mechanical stability mechanism

Abstract

Mechanical stability is a crucial property for the industrial implementation of heterogeneous catalysts and adsorbents. Both particle size and shape need to be investigated for each application where, typically, a compromise between mass transfer and pressure drop needs to be understood. In this study, we investigate the mechanical stability of a fragile mesostructured cellular foam material, formed of 3D aluminosilicate struts and porous cages, that are connected through windows. Successful pelletization was found at ca. 20 MPa, where the structural and textural properties are either unaltered or minimally modified. This condition is satisfactory for the final application of the pelletized material, though a lower-limit pressure could still be optimized. The use of higher pelletization pressures was observed to increase disorder in the systems. The structure contracts, the cage's size decreases markedly leading to more disordered wormhole-like pores. The decrease in cage/pore size seems to compensate for the structural densification, resulting in relatively constant BET areas. The pore volume's decrease is in agreement with the smaller cage sizes and densification. The damage and the mechanism causing this damage differ from that observed in conventional mesoporous materials. Besides the successful pelletization conditions and identification of damage mechanism, it is also noteworthy to highlight that values for BET area can be misleading when assessing mechanical stability; at high pressures, the BET areas remain fairly constant despite significant changes in pore size and structure are observed.