A–14
16023463
©2006 Maytag Services
Care and Cleaning
(cont’d)
CATALYST DEACTIVATION & POISONING AGENTS
The following partial list of poisoning agents and inhibitors have been found to have a detrimental effect on the
activity of the noble metal catalyst. Optimum life and performance of the catalyst requires that exposure to these
substances must be avoided.
SUBSTANCE
EFFECT
REMEDIAL ACTION
1.
Coating Agents
a. rust
b. dirt
c. inorganic oxides
Covers catalyst active site.
Non-phosphate detergent
washing usually effective for
removal.
2.
Coating Agents - "Glass" Forming
Materials
a. organic silicates (esters)
b. silicones
Covers catalyst active site.
Replacement usually
required. Non-phosphate
detergent washing may be
effective.
3.
Poisons
a. heavy metals (such as
mercury, lead, zinc, tin,
arsenic, antimony, etc.)
b. phosphorus.
Permanent catalyst deactivation
None, replace with new
catalyst.
4.
Sulfides
Permanent catalyst deactivation
None, replace with new
catalyst.
5.
Halogens
a. fluorine
b. chlorine
c. bromine
d. iodine
e. halogenated hydrocarbons
Low concentration exposure -
Occupies active site resulting in
inhibition of oxidation reaction. High
concentration exposure – Chemical
reaction with washcoat components to
resulting in permanent deactivation.
Activity usually returns if low
concentration source is
eliminated. High
concentration exposure will
require replacement with new
catalyst.
6.
Organic Droplets and Aerosols
a. Covers active site
b. Possible cause of catalyst hot spot
Thermal cleaning in clean air
at temperatures 200°F hotter
than normal operating point
or chemical washing with a
strong alkaline solution.
