Identification of fibre mats in
Catalytic converters are manufactured in all shapes and sizes,
with the primary aim of reducing the volatile organic compounds
(VOCs), carbon monoxide and nitrous oxides emitted from vehicle
exhaust gas. Some catalytic converters and diesel particulate
filters are known to contain supporting insulation mats made from
refractory ceramic fibres (RCF).
RCF is classified as a Category 1B carcinogen and end of life
catalytic converters should therefore be treated as hazardous
waste. RCF are also covered by the Registration, Evaluation,
Authorisation, restriction of Chemicals regulations (REACH 2006)
and Classification, Labelling and Packaging of substances (CLP
2009). This means that suppliers and users must be aware that
products contain RCF when selling on or sending for re-cycling.
Appropriate packaging and labelling must also be used.
However, catalytic converters are also manufactured with
poly-crystalline wools (PCW) or alkali earth wools (AEW), neither
of which is classified as a carcinogen. PCWs and AEWs are visually
very similar in appearance to RCF's and it is therefore impossible
to differentiate between these fibre types by visual
The catalytic converter manufacturers and suppliers will
typically replace the existing stock of new customers with their
own products. As a result large numbers of RCF containing
converters are either sent for recycling (extraction of precious
metals) or sold on to third parties.
The morphology and chemistry of RCF and PCW's are very similar
and therefore can be difficult to differentiate. The chemistry of
AEW is sufficiently different to RCF and PCW to allow easy
How We Can Help
Using transmission electron microscopy (TEM) and energy
dispersive X-ray analysis (EDX), we can use morphology and
elemental composition to differentiate between RCFs and AEWs.
Electron diffraction (ED) can then be used to determine
crystallinity and differentiate between RCFs and PCWs.
TEM image of RCF fibres and
EDX spectrum from RCF fibre
Above ED pattern from PCW showing concentric ring pattern
Right-hand Image shows a cross-section of a catalytic converter
(left) and a close up of the recyclable honeycomb structure (right)
which contains the precious metals. The recyclable part is
shown in yellow in the cross-section, surrounded by the white fibre
matting which may contain F's.
The identification of fibre type within catalytic converter
fibre mats will identify which contain RCF and which contain
unregulated PCW and AEW. This allows provide significant cost
savings by identifying which converters require segregation and
special treatment due to the presence of RCFs and which do not.
Worker health is also protected by preventing accidental exposure
to RCF during disposal and recycling.
HSL is UKAS accredited (ISO 17025) for the identification of
inorganic fibres by TEM/EDX.