Automotive catalyst analysis

The characterization of fresh and used automotive catalysts, which includes the examination of poisons accumulated in the catalysts, uses a variety of modem analytical techniques. The two principal tools, besides conventional chemical methods, are atomic absorption and, most important, X-ray fluorescence (XRF). The latter technique has been refined and adapted for the analysis of automotive catalysts to permit rapid and accurate determination of all constituents, including the inadvertent contaminants. An example of a simultaneous XRF analysis of... 

The future work on the poisoning of automotive catalysts will have to deal, primarily, with the specific interaction of particular poisons with the active components. The present trend toward more complex catalytic systems, containing several active components, will make the task still more difficult. One could foresee the use of modem, more sophisticated methods of surface analysis for studying the interactions between poison and active components. 

Another example of the analytical utility of the sample compaction methodology for GD-MS is work by Wayne [44] that used a Kratos double-focusing analyzer for the analysis of precious metals deposited on cordierite supports (i.e., automotive catalysts). Spectral interferences from TaO species on the target palladium, rhodium, and platinum analytes made aluminum a better choice as the matrix element. Because the Kratos instrument does not have cryogenic cooling... 

Ludke C and Hoeemann E (1996) Analysis of particulates in automotive catalyst exhausts by ETV-ICPMS. Fresenius J Anal Chem 355 261-263. 

Modeling of Poisoning by Organo Phosphorous Compounds. - Hegedus and Cavendish have proposed a mathematical model for phosphorus poisoned automotive catalysts. Using electron microprobe analysis they observed four different zones in a partially deactivated pellet. The schematic representation of the cross section of this pellet is shown in Figure 18. 

In the present study, the method developed by Komai et. al. has been modified slightly and used to characterize the noble metal particle sizes of commercial Pt/Rh and Pd/Rh three-way automotive catalysts (TWC). Good agreement was obtained with x-ray diffraction particle size analysis of the same catalysts, indicating general utility of the CO methanation technique for rapidly determining the particle sizes of both fi-esh and aged automotive catalysts. 

Transient Reaction Analysis OF AN Automotive Catalyst ON A Millisecond Time Scale... 

Some required specifications for our transient reaction analysis of automotive catalysts are shown below. 

Iransient Reaction Analysis ot an Automotive Catalyst on a Millisecond 1 ime. .. 201... 

Oukaci R, Blackmond DG, Goodwin JG, Jr, Gallaher G, Steady-state isotopic transient kinetic analysis investigation of CO-O2 and GO-NO reaction over a commercial automotive catalyst, in Silver RG, Sawyer JE, Summers JG (eds.). Catalytic Control of Air Pollution Mobile and Stationary Sources, Washington, DG, 1992. 

Several other successful applications of SIMS in catalyst characterization have been described in the literature [14, 15]. Of particular note are the extensive studies of Vickerman et al. [21] on automotive exhaust catalysts, a SIMS analysis of catalyst coatings in microreactors by Gnaser et al. [22], imaging studies which reveal the lateral distributions of elements [23, 24], and an excellent study on the reactive species present on a supported catalyst during reaction. These will be discussed in a little more detail in the following paragraphs. 

ICP-MS is useful for analysis of catalysts from two perspectives The composition of the catalysts must be carefully controlled, particularly because the active elements are often expensive. The catalysts are often finely distributed in a substrate material so their concentration in the bulk material may be quite low. Second, catalysts, particularly those used in automotive catalytic converters, can be a significant source of platinum group elements in the environment. Re and Pt have been measured in catalysts by ICP-MS [193], Procedures for the analysis of used catalytic converter materials by ICP-MS have been reported [355]. Accurate measurements are essential for many of these applications so isotope dilution-based concentration calibration is commonly used. 

In this section we will discuss an example of recent laboratory work on the impact of sulfur on palladium catalysts formulations compared to other noble metal formulations. The laboratory studies discussed here have been performed using an apparatus which simulates the exhaust gas generated from a vehicle under several operating modes. The simulated exhaust gas is then heated to a controlled level and directed to a sample core taken from a commercial automotive converter. Quantitative analysis of pollutant and other gas species (CO, HC, NOx, COj and Oj) is performed using gas bench analyzers prior to and following the catalyst sample to determine the conversion efficiency for HC, CO and NOx. 

PERIODIC OPERATION EFFECTS ON AUTOMOTIVE NOBLE METAL CATALYSTS — REACTION ANALYSIS OF BINARY GAS SYSTEMS —... 

Periodic Operation Effects on Automotive Noble Metal Catalysts. Reaction Analysis of Binary Gas Systems",... 

Shinjoh, H., H. Muraki and Y. Fujitani, 1987, Periodic operation effects on automotive noble metal catalysts Reaction analysis of binary gas systems, in Catalysis and Automotive Pollution Control, eds A. Crucg and A. Frennet (Elsevier, Amsterdam) pp. 187-197. 

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