Enhanced hydrocarbon trapping over ZSM-5 array-structure integrated on cordierite

Junfei  Weng, Department of Materials Science and Engineering & Institute of Materials Science, University of Connecticut

Enhanced hydrocarbon trapping over ZSM-5 array-structure integrated on cordierite

Junfei Weng, Jie Chen, Wenxiang Tang, Avinash M. Dongare, Pu-Xian Gao*

Department of Materials Science and Engineering & Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269-3136, USA

Abstract

Zeolites have been considered as a potential candidate for the low temperature hydrocarbon traps and passive NOx adsorber for emission control1-2. Generally, zeolite powders were loaded on the honeycomb cordierite substrate by washcoat. However, the washcoat method always caused transportation limit because of powders accumulation in the corner, as well as the hindrance of catalytic active sites3. Unlike the washcoat condition, array ensembles of one-dimensional (1D) nanostructures on the cordierite showed advantages of stronger gas-solid phase interaction, larger surface area and enhanced  stability and materials utilization efficiency4.

In this work, a layer of ZSM-5 array-structure was grown vertically on the cordierite by a secondary-growth method. Compared to the traditional dense ZSM-5 film, ZSM-5 array structure showed higher specific surface area, especially surface area from mesopores created by the interspacing between arrays. Thus, the ZSM-5 array structure could serve as a potential support for loading metal oxides. In addition, ZSM-5 array structure showed higher proportion of c-orientation, which exposed more channels along a- and b- orientation and promoted the mass transportation of reactant molecules. Furthermore, first-principles Density Functional Theory (DFT) calculations are performed to investigate the Al substitution site preference on the MFI framework, as well as the adsorption energetics of the reactant molecules.

Key words:

ZSM-5 array structure, hydrocarbon trapping, DFT

References

  1. Kim, H.; Jang, E.; Jeong, Y.; Kim, J.; Kang, C. Y.; Kim, C. H.; Baik, H.; Lee, K.-Y.; Choi, J., On the synthesis of a hierarchically-structured ZSM-5 zeolite and the effect of its physicochemical properties with Cu impregnation on cold-start hydrocarbon trap performance. Catalysis Today 2018.
  2. Westermann, A.; Azambre, B.; Finqueneisel, G.; Da Costa, P.; Can, F., Evolution of unburnt hydrocarbons under “cold-start” conditions from adsorption/desorption to conversion: On the screening of zeolitic materials. Applied Catalysis B: Environmental 2014, 158-159, 48-59.
  3. Ren, Z.; Guo, Y.; Liu, C. H.; Gao, P. X., Hierarchically nanostructured materials for sustainable environmental applications. Frontiers in chemistry 2013, 1, 18.

  4. Weng, J.; Lu, X.; Gao, P.-X., Nano-Array Integrated Structured Catalysts: A New Paradigm upon Conventional Wash-Coated Monolithic Catalysts? Catalysts 2017, 7 (9), 253.