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Comparison of different kinetic models for NO X storage on a lean NO X trap
Author(s) -
Watling Timothy C.,
Bolton Paul D.,
Swallow Daniel
Publication year - 2014
Publication title -
the canadian journal of chemical engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.404
H-Index - 67
eISSN - 1939-019X
pISSN - 0008-4034
DOI - 10.1002/cjce.22015
Subject(s) - trap (plumbing) , kinetic energy , kinetics , thermodynamics , function (biology) , atmospheric temperature range , chemistry , range (aeronautics) , materials science , analytical chemistry (journal) , physics , chromatography , meteorology , quantum mechanics , evolutionary biology , composite material , biology
The kinetics of NO X storage on a lean NO X trap (LNT) were studied using NO X breakthrough curves measured with a laboratory reactor. A much wider range of temperatures (125–450°C) was used than in most studies to facilitate discrimination between potential models. The breakthrough curves were run until the LNT was saturated to (i) enable NO oxidation to NO 2 to be studied in the absence of NO X storage, (ii) to enable the effective NO X capacity as a function of temperature to be determined, and (iii) to provide a more demanding test for potential models. Breakthrough curves for 125 and 450°C were very similar, while curves at intermediate temperatures initially followed that for 125°C before breaking away from this curve at a point that became earlier with increasing temperature. Thus, the breakthrough curves have a temperature independent initial portion, followed by a temperature dependant portion. This was explained by there being two types of site: fast sites and slow sites. Fast sites are responsible for the initial part of the curve; both the rate of storage on these sites and the available capacity are independent of temperature. The rate of storage on slow sites, on the other hand, is temperature dependant, as is the available storage capacity. Slow sites are more abundant than fast sites. The performance of three NO X storage models for these sites was compared. The amount of NO X stored as a function of temperature was bell‐shaped. The models naturally predicted that storage was limited by kinetics at lower temperatures and nitrate stability at higher temperatures.