Transient adsorption studies of automotive hydrocarbon traps

Abstract

A chromatographic adsorption unit was designed and built to study the adsorption of alkanes in zeolites for the hydrocarbon trap systems in three‐way catalysts, to assist in the selection of optimal materials for this application. The experimental apparatus used a zeolite bed in place of the column in an ordinary gas chromatograph and could be accurately modeled to determine the adsorption equilibrium constants for simple alkanes in MFI zeolites. The adsorption of iso‐pentane was studied in BEA zeolites with varying Si/Al2 ratios, before and after ex situ zeolite aging simulating engine exhaust, and in the presence of water vapor. The elution times were shown to depend directly on the zeolite adsorption capacity. The primary effect of water was to decrease the iso‐pentane adsorption capacity by partial filling of the zeolite pores through adsorption of water at acid sites. Some implications of this work for choosing the best materials for hydrocarbon trapping are discussed. © 2014 American Institute of Chemical Engineers AIChE J, 60: 2875–2881, 2014

Coupled NO and C3H6 Trapping, Release and Conversion on Pd/BEA: Evaluation of the Lean Hydrocarbon NOx Trap

“…The NO x trapping efficiency decreases from 21.1% in the absence of H 2 O to 4.8% in its presence (Table S2, Figure a), while the C 3 H 6 trapping efficiency decreases from 59 to 20% (Table S3, Figure b). Zeolites with sufficiently low SAR effectively adsorb water in the form of H 3 O + on protonated sites (), so these findings are expected. − …”

Zeolite Beta Doped with La, Fe, and Pd as a Hydrocarbon Trap

“…Propene-TPD experiments performed in wet conditions (5% H 2 O) were conducted; however, the results did not indicate any propene storage. This is most likely due to the competition of water and propene for the hydrophilic sites in the zeolite structure [22,32].…”

Enhanced Adsorption Properties of Ag-Loaded β-Zeolite towards Toluene

“…Zeolites, having unique physicochemical properties, are widely applied as catalysts and sorbents [11]. Appropriate thermal stability of this class of materials makes it possible to consider them as a perspective system to solve 'cold start' problem [3,4,12]. Adsorption properties and overall effectiveness regarding to hydrocarbons trapping are affected by such key parameters as acidity of the zeolite, nature of the promotors used, and tolerance of zeolite towards water vapors [3,6,13,14].…”