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Last update: 2010-02-01

XRF Analysis of Catalyst 
Overview of Samples

Applications
Automotive Exhaust Catalyst
Catalytic Converter Samples
Organic Samples with Catalyst Residues

At this moment we do not have results obtained with UniQuant 4.
The results shown below have been obtained with UniQuant 1 or 2.
   

Automotive Exhaust Catalyst

Material base: Corderite (ceramic string)
Layer (Al Ce Zr) by slurry washing, then Pt Rh added
Ground sample as loose powder on supporting film and analysed
by XRF + UniQuant 1 in Sweden, June 1991.
No standards have been used.
       UniQuant1    Production Target
       ---------    -----------------
Pt       0.27        0.237 ± 0.004 
Rh       0.059       0.047 ± 0.002 
Pd      <0.01        0.02  ± 0.02
Al2O3   45.7        42.8   ± 0.4 
CeO2     7.5         7.6   ± 0.2 
ZrO2     0.34        0.25  ± 0.01
SiO2    33.0        35.9   ± 0.4 
MgO     10.5        10.0   ± 0.1 
Fe2O3    0.54        0.45  ± 0.02 
TiO2     0.46        0.51  ± 0.02 
Cl       0.30        0.23  ± 0.01 
Na2O     0.12        0.2   ± 0.1 
CaO      0.075       0.088 ± 0.002 
CdO      0.043  
K2O      0.033       0.04  ± 0.01 
Sb2O3    0.023 
SO3     <0.01        0.00  ± 0.01 
Cr2O3   <0.01        0.02  ± 0.02 
MnO     <0.01        0.02  ± 0.02 
NiO     <0.01        0.02  ± 0.02 
ZnO     <0.01        0.00  ± 0.01 
BaO     <0.01        0.05  ± 0.01 
La2O3   <0.01        0.02  ± 0.01 
Pb      <0.01        0.000 ± 0.001

Elements in bold (Pt, Rh, Al2O3, CeO2 and ZrO2) are on the outside of the corderite,
which is the reason why the UniQuant values are somewhat too high. This can be
corrected only by adapting Kappa's to this type of sample.


Overview



Catalytic Converter Samples

Analysis by XRF + UniQuant1 in Italy, May 1991.
Calibration did not include any special standards.
                          DIFFERENCES
       Specified          UniQuant-Specified 
       Range %C            Low       High
       ---------------     ----------------
Pt     0.158 ... 0.237     -0.016   +0.015
Rh     0.033 ... 0.057     -0.007   +0.002
Ce     2.38  ... 6.23      -0.55    -0.08
La     0.043 ... 0.205     -0.021   +0.024
Matrix:
SiO2     about 30
Al2O3    about 47
MgO      about 9

Note:
The error range of Ce, -0.55 to -0.08, may be due to a systematic error that is
easily overcome by a refinement of the instrumental sensitivity, Kappa, for
the XRF line with which Cerium is measured.


Overview



Organic Samples with Catalyst Residues

Twelve samples, labelled D1..D4, E1..E4 and F1..F4, were submitted by Welcome Research,
UK, for standardless XRF analysis by UniQuant 2.The samples are loose powders of cellulose.
For each sample, the Pd concentration is specified in ppm (range 89 to 915 ppm).

Sample Presentation

A 'de KAT' cup with a 6 mm polypropylene bottom is used for measuring loose powder.
The sample is put on the film and slightly presses to have a top surface that is parallel to the film.
The net mass that 'sits' over the 24 mm ø viewed area is determined as well as the height
(thickness) of the sample since both are required by UniQuant. The spectrometer uses Helium
(instead of vacuum) to avoid powder spilling.

Measurements

Each sample has been measured by the full analytical program as prescribed by the UniQuant
method. The total spectrometer time then is 15 minutes per sample. The full (comprehensive)
program is to determine the concentrations of 72 elements (UniQuant 2). For routine analysis,
one could make a sub set analytical program with fewer analytical lines while spending more
time at lines (elements) of direct interest. In the case of the submitted samples, the spectrometer
time may be reduced to say 5 minutes whilst spending much more time at elements like Pd.
PdKa was here measured for 10 seconds, all other (102) lines at 6 or 10 seconds.

Evaluation by UniQuant

Results are sensitive to the exact nature of the 'unknown Rest'. We have assumed that
the 'Unknown Rest' is Cellulose in the form of C6H10O5, of which UniQuant is to determine the
concentration. If the molecular formula is not quite correct, this may cause errors in the results for
the lighter elements in the order of 10 to 20 % relative. UniQuant has not used any special standards.
For example, for Pd the instrument has merely been calibrated by a 100% Pd metal sample.
Not any adaptations have been made for fitting the data.

Results for Pd
All Concentrations are in [mg/kg]

Sample     Pd       Pd     Estim.    %Rel. 
       specified UniQuant1 Max.Err.  diff.
  D1       96       97      10       +3     Light grey 
  D2      216      180      20      -17     Light grey 
  D3      403      370      30       -8     Light grey 
  D4      739      680      60       -9     Light grey
  E1       77       76       9      -13     Medium grey 
  E2      206      140      10      -32     Medium grey 
  E3      391      300      30      -23     Medium grey 
  E4      861      640      50      -25     Medium grey
  F1      105       89      10      -10     Darker grey 
  F2      193      180      20       -7     Darker grey 
  F3      376      360      30       -4     Darker grey 
  F4      915      900      70       -3     Darker grey

Because the UniQuant results for samples E1..E4 have a larger bias with respect to the specified
values, we suspect that the organic material for these samples is different from those in
the D and F series. This would also explain the difference in the grey colour shades between
the three groups of samples. The estimated maximum UniQuant errors do not include errors
caused by inaccurate specification of the nature (composition) of the 'Rest'. Accurate specification
would eliminate such source of error. It would have been easy to adapt the calibration of UniQuant
to compensate for the average bias. We did not do that in order to show UniQuant's performance
on the basis of a one-off calibration that is universally used for any type of sample (steel, soil, ash,
plastic, oil, etc.).

Overview

 

 
   


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