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Comparative catalytic performance of PGM-nanoparticle-doped alumina Xerogels and aerogels for potential application in automotive pollution mitigation.

Authors :
Bruno, Bradford A.
Anderson, Ann M.
Hoffman, Anna
Carroll, Mary K.
Source :
Journal of Non-Crystalline Solids. Jul2024, Vol. 636, pN.PAG-N.PAG. 1p.
Publication Year :
2024

Abstract

• Compares alumina aerogel vs xerogel Pd and Rh catalysts under identical conditions. • Catalyst performance tests representative of use in automotive three-way catalysts. • Aerogel and xerogel catalysts characterized via: TEM, XRD, BET and BJH analysis. The structural (low density, high porosity), thermal (low thermal conductivity, high temperature stability), and chemical (high degree of tailorability) properties of aerogels make them attractive in a range of applications, including catalysis. The automotive industry relies on three-way-catalysts (TWCs) for automotive pollution mitigation, and TWCs in turn depend heavily on the use of platinum group metals (PGMs). Reduction of the use of PGMs in TWCs would be advantageous. To investigate the effect of aerogel structure and processing on three-way catalytic performance we prepared alumina wet gels doped with ca. 15 nm rhodium and palladium nanoparticles and dried them (1) supercritically to form aerogels and (2) under ambient conditions to form xerogels. Nanoparticle concentration was adjusted to ensure that both forms of the catalyst (aerogel and xerogel) had the same volumetric concentration of PGM after calcination to 800°C. Powder x-ray diffraction and transmission electron microscopy (TEM) confirmed the presence of PGMs. TEM images showed PGM particle agglomeration on the order of 40 to 200 nm in both the aerogel and xerogel materials. Gas adsorption analysis indicated that the aerogels have a surface area of 460 m2/g with most pores in the 2- to 100-nm range, whereas the xerogel surface area was 170 m2/g with a narrow pore distribution around 10 nm. Catalytic performance tests under a range of simulated automotive operating conditions show that, in all cases, the aerogels outperformed the xerogels. The aerogel light-off temperatures (the temperature at which a 50 % conversion is achieved) were 45 to 120 °C lower for the conversion of HCs, 25 to 55 °C lower for the conversion of CO and 40 to 145 °C lower for the conversion of NO. This study provides direct evidence that aerogel processing of catalysts provides catalytic performance benefits separate from the underlying chemistry of the catalysts. TEM/EDX showing palladium nanoparticles in a Pd/Al 2 O 3 aerogel sample [Display omitted] [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
00223093
Volume :
636
Database :
Academic Search Index
Journal :
Journal of Non-Crystalline Solids
Publication Type :
Academic Journal
Accession number :
177513095
Full Text :
https://doi.org/10.1016/j.jnoncrysol.2024.122994