Zeolite Catalysts with Tunable Hierarchy Factor by Pore-Growth Moderators

Authors

  • Javier Pérez-Ramírez,

    Corresponding author
    1. Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16, Tarragona, 43007 (Spain)
    2. Catalan Institution for Research and Advanced Studies (ICREA) Passeig Lluís Companys 23, Barcelona, 08010 (Spain)
    • Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16, Tarragona, 43007 (Spain).
    Search for more papers by this author
  • Danny Verboekend,

    1. Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16, Tarragona, 43007 (Spain)
    Search for more papers by this author
  • Adriana Bonilla,

    1. Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16, Tarragona, 43007 (Spain)
    Search for more papers by this author
  • Sònia Abelló

    1. Institute of Chemical Research of Catalonia (ICIQ) Avinguda Països Catalans 16, Tarragona, 43007 (Spain)
    Search for more papers by this author

Abstract

The design of hierarchical zeolite catalysts is attempted through the maximization of the hierarchy factor (HF); that is, by enhancing the mesopore surface area without severe penalization of the micropore volume. For this purpose, a novel desilication variant involving NaOH treatment of ZSM-5 in the presence of quaternary ammonium cations is developed. The organic cation (TPA+ or TBA+) acts as a pore-growth moderator in the crystal by OH-assisted silicon extraction, largely protecting the zeolite crystal during the demetallation process. The protective effect is not seen when using cations that are able to enter the micropores, such as TMA+ Engineering the pore structure at the micro- and mesolevel is essential to optimize transport properties and catalytic performance, as demonstrated in the benzene alkylation with ethylene, a representative mass-transfer limited reaction. The hierarchy factor is an appropriate tool to classify hierarchically structured materials. The latter point is of wide interest to the scientific community as it not only embraces mesoporous zeolites obtained by desilication methods but it also enables to quantitatively compare and correlate various materials obtained by different synthetic methodologies.

Ancillary