Micro/meso/macroporous (hierarchical) zeolites show remarkable catalytic performance for reactions involving bulky reactants. However, quantitative assessment of the microstructural characteristics contributing to the observed performance remains elusive. Here, structure–activity relationships are established for a set of micro/mesoporous self-pillared pentasil (SPP) zeolites using two parallel liquid-phase reactions (benzyl alcohol alkylation and self-etherification) based on analysis of mass transport and reaction kinetics. A reaction–diffusion mathematical model is developed that quantitatively assigns the catalytic contributions of the external surface and micropores of SPP zeolites for these reactions. In addition, the effect of the zeolite external surface structure on the corresponding catalytic activity is quantitatively assessed by comparing SPP zeolites (with MFI structure) with MCM-22 (with MWW structure). This work demonstrates that reaction–diffusion modeling allows quantitative description of the catalytic performance of hierarchical zeolites and provides a model reaction to assess nm-sized characteristic diffusion lengths in MFI.
Bibliographical noteFunding Information:
This work was supported by the Petroleum Institute of Abu Dhabi, part of Khalifa University of Science and Technology and as part of the Catalysis Center for Energy Innovation, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award DE-SC0001004. Portions of this work were conducted at the University of Minnesota Characterization Facility. Partial support for FTIR measurement was provided by the National Creative Research Initiative Program (2012R1A3A2048833) through the National Research Foundation of Korea. D. L. thanks for the support from the National Science Foundation (CBET-1264599).
© 2018 American Institute of Chemical Engineers
- hierarchical zeolites
- liquid-phase alkylation and etherification
- reaction–diffusion modeling
- surface topology