EPA/AA/CTAB/91-04
Technical Report
Evaluation Of A Kemira Oy
Resistively Heated Catalyst
On A Methanol-Fueled Vehicle
by
Gregory K. Piotrowski
Ronald M. Schaefer
September 1991
NOTICE
Technical Reports, do not necessarily represent final EPA
decisions or positions. They are intended to present technical
analysis of issues using data which are currently available. The
purpose in the release of such reports is to facilitate the
exchange of technical information and to inform the public of
technical developments which may form the basis for a final EPA
decision, position or regulatory action.
U. S. Environmental Protection Agency
Office of Air and Radiation
Office of Mobile Sources
Emission Control Technology Division
Control Technology and Applications Branch
2565 Plymouth Road
Ann Arbor, MI 48105
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\ UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
3
_T ANN ARBOR. MICHIGAN 48105
SEP 25 1991
OFFICE OF
AIR AND RADIATION
MEMORANDUM
SUBJECT: Exemption From Peer and Administrative Review
FROM: Karl H. Hellman, Chief
Control Technology and Applications Branch
TO: Charles L. Gray, Jr., Director
Emission Control Technology Division
The attached report entitled "Evaluation Of A Kemira Oy
Resistively Heated Catalyst On A Methanol-Fueled Vehicle"
(EPA/AA/CTAB/91-04) describes the evaluation of resistively heated
catalyst system on a methanol-fueled vehicle. A compact
resistively heated metal monolith converter was used to reduce
emission levels of unburned fuel, carbon monoxide, and formaldehyde
over the Bag 1 portion of the Federal test procedure driving cycle.
This catalyst system was evaluated with and without secondary air
assistance.
•
Since this report is concerned only with the presentation of
data and its analysis and does not involve matters of policy or
regulation, your concurrence is requested to waive administrative
review according to the policy outlined in your directive of April
22, 1982.
Concurrence: foJ* r^y Date:
Charles L. Gray, Jr./^Dir., ECTD
Nonconcurrence: ' Date:.
Charles L. Gray, Jr., Dir., ECTD
cc: E. Burger, ECTD
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Table of Contents
Page
Number
I. Summary 1
II. Introduction 2
III. Description of Catalytic Converter Technology 3
IV. Description of Test Vehicle 5
V. Test Facilities and Analytical Methods 5
VI. Test Procedures 5
VII. Discussion of Test Results 7
A. EHC Without Resistive Heat/Air Assist 7
B. EHC With Resistive Heating Only 9
C. EHC With Resistive Heat/Air Assist 13
D. EHC With Main Catalyst Testing 17
VIII.Evaluation Highlights 23
IX. Future Efforts 24
X. Acknowledgments 24
XI. References 25
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I. Summary
A fresh resistively heated catalytic converter was furnished
by Kemira Oy to the U.S. Environmental Protection Agency (EPA) for
evaluation on a methanol-fueled vehicle. This converter substrate
was constructed from metallic foil and was considerably smaller in
volume than three-way catalysts found on most late model U.S.
automobiles. The Kemira Oy converter is referred to hereafter as
an electrically heated catalyst (EHC).
The EHC was evaluated in four separate modes. First, this
catalyst was placed on an M100 (neat methanol) fueled vehicle and
emission tested without resistive heating or catalyst air assist.
The EHC was then tested using resistive heating, but with no air
assist provided during the period of heating. A catalyst operating
mode utilizing both resistive heating and air assist was evaluated
next. Finally, a larger catalyzed ceramic monolith was added
behind the EHC as a main catalyst. This two-catalyst system was
then evaluated, with resistive heating and catalyst air assist
applied to the upstream EHC.
The testing described here utilized M100 neat methanol fuel
and was conducted over the Federal test procedure (FTP) CVS-75 test
cycle. Catalyst resistive heating and air assist were limited to
portions of the initial cold start Bag 1 phase (first 505 seconds)
of the FTP. The emissions of primary interest during this
evaluation were methanol (unburned fuel), formaldehyde, and carbon
monoxide (CO). Details of the test procedure are discussed later
in a separate section of this report.
Resistively heating the EHC in the absence of catalyst air
assist provided a very limited reduction in emission levels. The
only substantial reduction occurred when the Bag 1 emissions of
methanol were reduced to 3.06 grams, from 6.22 grams with the
unassisted (no resistive heat/no air addition applied) catalyst.
A combination of EHC resistive heating and air assist however,
provided substantial reductions in emission levels of unburned fuel
and CO. Bag 1 emissions of methanol were reduced to 1.81 grams, a
reduction of over 70 percent from unassisted catalyst levels. CO
emissions were also reduced over 60 percent from unassisted
catalyst levels through this combination of EHC heating/air assist.
The two-catalyst system mentioned above, using resistive
heating/air assist of the EHC, provided the lowest emissions of all
catalyst configurations tested. Methanol and formaldehyde
emissions were reduced to 0.09 grams and 11 milligrams respectively
over Bag 1 with the two-catalyst system. These low Bag 1 emission
levels contributed substantially to the calculated emission rate of
0.02 grams per mile of organic material hydrocarbon equivalents
(OMHCE) over the FTP. Weighted average formaldehyde emissions over
the FTP were less than 2 milligrams per mile, well below the State
of California standard of 15 milligrams per mile. The very low Bag
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1 levels of methanol and formaldehyde, with the two-catalyst system
here, represent conversion efficiencies of greater than 99 percent
from baseline (no catalyst) levels from the test vehicle.
CO emissions over Bag 1 were reduced more than 96 percent from
no catalyst levels using the two-catalyst system. This efficiency
was reflected in FTP weighted average CO emissions, where the two-
catalyst system also provided 96 percent conversion efficiency from
no catalyst levels. NOx emissions, however, were relatively
unaffected by changes in catalyst configuration here. Even the use
of catalyst air assist (restricted to 100 seconds following cold
start in Bag 1) did not greatly affect NOx levels. A slight
decrease in Bag 1 emissions of NOx was noted with the two-catalyst
system, compared with the other catalyst configurations evaluated.
II. Introduction
HC and CO emissions from the cold start portion of Bag 1
represent the greatest portion of these emissions over the Federal
Test Procedure (FTP) from today's catalyst-equipped gasoline
vehicles. [1] The same is true for emissions of unburned fuel
(methanol), CO and formaldehyde for vehicles fueled on M100 neat
methanol.[2,3] Recent enactment of new clean air legislation in
the United States has also refocused attention on regional problems
of excess CO emissions from motor vehicles operated at low ambient
temperature conditions.[4]
One strategy to decrease cold start emissions utilizes a
resistively heated catalyst to shorten the time to light-off, or
the time at which the converter becomes catalytically active.
Excess emissions of unburned fuel and CO occur during engine
warmup, when the engine is operated slightly rich of normal
operating conditions to improve driveability. It is during this
period of excess emissions that conventional three-way exhaust
catalysts are not yet active, because of insufficient warming from
the relatively cool exhaust gases. Resistive heating can bring the
catalyst to active temperature (approximately 350°C for
conventional catalysts) quickly, seconds after the engine is
started during FTP testing at 75°F. The decrease in catalyst
light-off time, coupled with secondary air addition to assist
oxidation, can provide a flexible solution to this problem.
EPA has evaluated several resistively heated metal monolith
converters in efforts to reduce Bag 1 emissions of unburned fuel
and CO.[5,6,7,8,9] These efforts have involved the use of
converter substrates of different volumes and several different
active catalyst formulations. These catalysts were all low mileage
and relatively efficient at low mileage. All of the resistively
heated metal monolith converters evaluated and reported on to date
by EPA were supplied by Camet Co., a subsidiary of W. R. Grace.
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-3-
One of the reasons that EPA conducts and publishes the results
from emission control technology evaluations is to spur further
interest in new technologies by automakers and industry hardware
suppliers. Interest in resistively heated catalyst technology for
mobile sources has continued to grow, and several industry sources
have agreed to provide EPA with samples of their catalysts for
evaluation. One of these catalyst suppliers, Kemira Oy, recently
furnished EPA with a heated catalyst for evaluation on a methanol-
fueled vehicle. A preliminary evaluation of this low-mileage
converter was conducted; results from this testing are presented
below. More testing, however, will be necessary in order to refine
the catalyst heating and air addition strategies.
Ill. Description Of Catalytic Converter Technology
The resistively heated catalytic converter consists of a
folded metal foil which has been washcoated and catalyzed with a
5:1 platinum/rhodium mixture. The converter is described below; a
more complete description was provided by the manufacturer, Kemira
Oy, in an earlier paper of the Society of Automotive Engineers.[10]
The foil used for the substrate consisted of Aluchrom ISE with
a thickness of 0.044 mm. While the foil can be folded and rolled
to cell densities of 200-800 cells/square inch (cpsi), an
intermediate density of 500 cpsi was utilized here. A round,
rather than oval, substrate shape was utilized. Unlike the
catalysts described in the earlier paper by Kemira Oy,[10] a wool
insulation was added between the shell and the rolled foil for the
catalyst described here.
A 12-volt DC automotive battery was used to supply the energy
for resistively heating the converter. Resistance across the can
electrical connection posts was measured at 0.2 ohms. The
application of 12 volts from the fully charged battery caused a
current of approximately 350 amps at start in the circuit (the
other circuit components were #6 gauge copper cables six feet in
length and #00 gauge copper cables nine feet in length). This
measured current decreased to approximately 230 amps after 40
seconds of resistive heating.
Table 1 below presents specifications of the resistively
heated catalytic converter evaluated here. A picture of the
converter is presented here as Figure 1.
A catalyzed ceramic monolithic substrate provided by Engelhard
Industries was installed in back of the EHC during the latter part
of this evaluation. This ceramic monolith functioned as a main
catalyst in the two-catalyst system referred to later. This
substrate was cylindrical in shape, 4.0 inches in diameter and 6.0
inches in length. The monolith contained 400 cells per square inch
and was catalyzed with platinum only, at a loading of 50 grams per
cubic feet.
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Table 1
Specifications Of Kemira Oy Resistivelv Heated Catalyst
Specification
Substrate Diameter
Length
Volume
Cells Per Square Inch
Geometric Surface Area
Cross Section
Active Catalyst
Weight of Substrate (Average)
Total Weight (Average)
Shell Material
Dimension
68.5 mm
50 mm
0.184 dm3
500
0.6 m2
36.9 cm2
0.26 grams total
1.41 g/dm3 (40 g/ft3)
5:1 Platinum/Rhodium
235 grams
1065 grams
Thermax (AISI 409)
Figure 1
Main Catalyst Left, EHC Right
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IV. Description Of Test Vehicle
The test vehicle was a 1981 Volkswagen Rabbit 4-door sedan,
equipped with automatic transmission, air conditioning, and radial
tires. The 1.6-liter engine had a rated maximum power output of 88
horsepower at 5,600 rpm, when using neat methanol fuel. The
vehicle was tested at 2,500 Ibs inertia weight and 7.7 actual
dynamometer horsepower. This vehicle was loaned to the U.S. EPA by
Volkswagen of America.
A detailed description of the vehicle and special methanol
modifications were provided in an earlier report.[5]
V. Test Facilities And Analytical Methods
Emissions testing at EPA was conducted on a Clayton Model ECE-
50 double-roll chassis dynamometer, using a direct-drive variable
inertia flywheel unit and road load power control unit. The Philco
Ford constant volume sampler has a nominal capacity of 350 CFM.
Exhaust HC emissions were measured with a Beckman Model 400 flame
ionization detector (FID). CO was measured using a Bendix Model
8501-5CA infrared CO analyzer. NOx emissions were determined by a
Beckman Model 951A chemiluminescent NOx analyzer.
Exhaust formaldehyde was measured using a dinitrophenyl-
hydrazine (DNPH) technique.[11,12] Exhaust carbonyls including
formaldehyde are reacted with DNPH solution forming hydrazine
derivatives; these derivatives are separated from the DNPH solution
by means of high performance liquid chromatography (HPLC), and
quantization is accomplished by spectrophotometric analysis of the
LC effluent stream.
The procedure developed for methanol sampling and presently
in-use employs water-filled impingers through which are pumped a
sample of the dilute exhaust or evaporative emissions. The
methanol in the sample gas dissolves in water. After the sampling
period is complete, the solution in the impingers is analyzed using
gas chromatographic (GC) analysis.[13]
VI. Test Procedures
The goal of this test program was a brief evaluation of the
Kemira Oy resistively heated catalyst on a methanol-fueled vehicle.
The test procedures were similar to those used in the evaluation of
a resistively heated Camet compact EHC in June 1991. These
procedures were used for two reasons. First, the Kemira Oy and
Camet converters had total displacements that were similar in
volume, and both made use of typical three-way (platinum:rhodium)
catalyst formulations. Second, a comparison of the performance of
the two heated catalyst systems was facilitated because the same
test vehicle/procedures were used. Further testing of the Kemira
Oy catalyst will be conducted to determine the most efficient
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resistive heating/air addition convention for the reduction of Bag
1 emissions of unburned fuel, CO, and formaldehyde.
The testing commented on here was conducted in several phases.
Each succeeding phase used an additional assist which.was intended
to further lower pollutant emission levels. The Bag 1 emissions of
particular interest were unburned fuel (methanol), CO, and
formaldehyde.
Several baseline emission tests were first conducted.
Baseline here refers to emission tests over the FTP cycle with a
straight pipe inserted in place of the underfloor catalyst. After
these tests, the straight pipe was removed and the fresh Kemira Oy
EHC was placed in exhaust underfloor, approximately 2\ feet
downstream of the ends of the exhaust manifold runners.
Several emission tests were conducted over the FTP without
catalyst heating or air assist. This testing provided a reference
for determining the improvement in emission level reduction
provided by catalyst resistive heating and/or air assist.
Resistive heating over selected initial portions of Bag 1 of
the FTP was then used to shorten catalyst light-off time. The
first scheme, 0/20, denotes a 20-second period of heating following
cold start in Bag 1. The first number, or numerator in these
fractions, refers to the time of resistive catalyst preheating
before start in Bag 1. Several tests were also conducted using a
0/40 convention. In both of these cases, catalyst heating
commenced upon cold start; no preheating was involved.
CTAB asked the catalyst manufacturer (Kemira Oy) to permit a
short period of catalyst preheating prior to cold start in Bag 1.
This was to enable the catalyst to reach light-off temperature
prior to start. One possible drawback to this technique may be
heightened durability concerns, however. Kemira Oy responded by
stating that a short 10-20 second resistive heating period prior to
start would probably give better emission test results.[14]
The catalyst was then tested several times over the FTP using
a 15/40 second heating scheme. The 15-second preheat period was
the same length as that used during a recent evaluation of a
similarly sized resistively heated Camet catalyst. A limited
performance comparison between these two catalysts was enhanced by
this choice of heating schedule here. This schedule, however, is
probably not optimized for the Kemira Oy catalyst. More testing
will be necessary to determine an optimized resistive heating
scheme. Kemira Oy has used 120 seconds of resistive heating
following start in Bag 1 during some of their developmental
work.[14]
Following this heated catalyst-only testing, air was added in
front of the catalyst to assist the oxidation reactions. The air
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was added from a shop air line during the period of resistive
heating following start in Bag i. The air assist was used for a
limited period of time only, however. It was assumed that limiting
air addition to this period would minimize any undesired effect on
the ability of the three-way catalyst to convert NOx emissions.
A gas rotameter was inserted in the shop air line to the
vehicle to measure excess air flowrate to the catalyst. This meter
also provided an indication of the effect of exhaust backpressure
on air flowrate. A bypass valve in the air line controlled excess
air flow to an average 5.0 ft3/minute over the period of air
addition.
The converter was tested over a 15/40 second heating cycle
with air addition occurring during a 100 second period following
cold start. Following this testing, the EHC was replaced by the
main catalyst, and several emission tests were conducted using this
ceramic monolith and catalyst air assist. The EHC was then placed
into the exhaust again, upstream of the main catalyst (MC). This
two-catalyst system was emission tested with resistive heating and
catalyst air assist applied to the upstream EHC.
VII. Discussion Of Test Results
A. EHC Without Resistive Heat/Air Assist
This evaluation was divided into four separate phases. First,
the EHC was emission tested over the FTP to determine its
efficiency without resistive heating or air assist. This testing
is described here, in Section A of the Discussion Of Test Results.
The next section describes the performance of the catalyst when it
was resistively heated. The final sections of the Discussion
describe the emissions performance when air assist was provided to
the resistively heated catalyst alone, and with the MC.
The first 505 seconds of Bag 1 of the FTP cycle includes the
initial minutes of the test during which the engine and catalytic
converter warm to relatively steady-state temperatures. This warm-
up period is important to the emissions process for two reasons.
First, current automotive engines operate over relatively richer
air/fuel ranges during cold start and warm-up. This is done to
ensure that sufficient fuel is vaporized for starting and smooth
performance after start. This richer operation causes excess
emissions of unburned fuel and CO over levels occurring after the
warmed engine begins operating at a leaner setting. Second, the
catalyst is ineffective until its surface temperature has reached
light-off, or catalytically active temperature. The resistively
heated catalyst is designed to minimize this time period.
The emissions of primary interest here are those related to
the warm-up period after start. Emissions of unburned fuel
(methanol) are related to the larger guantities of fuel inducted,
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poorer vaporization and mixing, and colder combustion chamber
conditions at cold start. CO and formaldehyde emissions are
important as products of partial combustion or intermediates,
production of which are enhanced at the relatively richer-
conditions.
Bag 1 emission levels are presented in grams over the Bag 1
test segment, except for formaldehyde, which is given in milligrams
over Bag l. Composite FTP emissions are given in grams per mile
except for formaldehyde levels, which are presented in milligrams
per mile.
Table 2 presents the results from emissions testing with the
catalyst in the unheated mode, and no air assist provided. The
category referred to as baseline describes testing with a straight
pipe, rather than a catalytic converter present in the exhaust.
The catalyst was reasonably effective in the no-heat/no-air mode,
in spite of its smaller volume. Emissions of unburned fuel were
reduced by more than 50 percent from baseline levels, as were CO
emissions. Bag 1 NOx emissions were also substantially reduced, as
were aldehyde emissions. This approximately 75 percent reduction
in aldehyde emissions, however, is not sufficient to bring aldehyde
levels under the 15 mg/mile limit mandated in the State of
California.
Table 2
No Resistive Heat, No Air Assist
Baa 1 Of FTP Cycle
NMHC HC CH3OH HCHO OMHCE CO NOx
Category g g g mg g g g
Baseline
No Heat/No Air
0.13
0.13
5.16
2.20
15.28
6.22
1983
521
7.71
3.11
35.9
16.5
6.1
3.6
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
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The roughly 50 percent improvement in most Bag 1 emissions is
complimented by increases in efficiency in the other portions of
the test cycle. These improvements are evident in the composite
FTP results given in Table 3. For example, emissions of unburned
fuel decreased almost 80 percent over the entire FTP through the
use of the unheated catalyst. Emissions of formaldehyde over the
FTP were very high though, at an average 85 mg/mile. This level of
emissions far exceeds the California standard; the active catalyst
would have to be altered or supplemented by another converter to be
a practical methanol vehicle emission control technology.
Table 3
No Resistive Heat, No Air Assist
FTP Composite Emission Levels
Category
NMHC HC CH3OH HCHO OMHCE CO NOx
g/mi g/mi g/mi mg/mi g/mi g/mi g/mi
Baseline
No Heat/No Air
0.02
0.03
0.91
0.22
2.71
0.57
480
85
1.43
0.33
8.1
1.8
1.3
0.8
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
B- EHC With Resistive Heating Only
The EHC was next tested using three separate resistive heating
schemes. No air assist was provided to the catalyst during this
testing.
The three heating1 schemes evaluated here utilized resistive
heating only during the Bag 1 phase of the FTP. Heating was
limited to Bag 1 primarily because of the influence of cold start
emissions on the weighted FTP, but also to limit deep drains on the
storage battery power source. Limiting the number of deep
discharge episodes in practice could significantly extend the
useful life of the power source.
Figure 2 presents the results from methanol sampling over the
Bag 1 phase of the FTP. Emissions are given in grams/Bag l. The
numerator in the description of the catalyst heating refers to the
number of seconds of resistive heating applied to the catalyst
before start in Bag 1. The denominator refers to the number of
seconds of resistive heating applied following the Bag 1 cold
start.
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Figure 2
Resistive Heat/No Air Assist, EHC Only
Methanol Emissions, Bag 1 Of FTP
EHC Resistive Heat Configuration
Baseline
No Heat/No Air
0/20-
0/40
15/40
0 5 10 15 20
Exhaust Methanol (grams)
• Heat 0 Seconds Prior To Start,
20 Seconds Following Start
Methanol emissions decreased slightly with the application of
resistive heating after start in Bag 1. The usefulness of this
heating may be questioned, however, as the extension of heating
time to 40 seconds did not result in lower emissions of unburned
fuel. A significant decrease in emissions occurred when a short
period of resistive heating preceded Bag 1 cold start. The 3.06
grams of methanol measured with the 15/40 heating convention
represents a 50 percent reduction in emissions from unheated
catalyst levels.
Emissions of formaldehyde over Bag 1 are presented in Figure
3. Resistive heating appeared ineffective as an emissions
reduction strategy. Extending the time of resistive heating
following cold start did not decrease formaldehyde emissions, and
preheating the catalyst for 15 seconds prior to start appeared to
have no effect on emissions. Another three-way resistively heated
catalyst recently evaluated [9] reduced Bag l formaldehyde
approximately 20 percent from unheated catalyst levels, on this
methanol-fueled vehicle. No noticeable decrease in formaldehyde
levels occurred with resistive heating of the catalyst evaluated
here, however.
Figure 4 presents CO emission levels over Bag 1. As in the
case of formaldehyde, CO emissions did not decrease with resistive
heating. CO indeed substantially increased, as the length of
resistive heating time following cold start was increased to 40
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Figure 3
Resistive Heat/No Air Assist, EHC Only
Formaldehyde Emissions, Bag 1 of FTP
EHC Resistive Heat Configuration
Baseline
No Heat/No Air
0/20-
0/40
15/40
* Heat 0 Seconds Prior To Start,
20 Seconds Following Start
0 500 1000 1500 2000 2500
Exhaust Formaldehyde (milligrams)
Figure 4
Resistive Heat/No Air Assist, EHC Only
Carbon Monoxide Emissions, Bag 1 of FTP
EHC Resistive Heat Configuration
Baseline
No HeatXNo Air
0/20-
0/40
15/40
16.5
19.4
23.2
18.4
35.9
0 10 20 30 40 50
Exhaust Carbon Monoxide (grams)
• Heat 0 Seconds Prior To Start,
20 Seconds Following Start
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seconds. Resistively heating the catalyst prior to cold start gave
the lowest CO emissions of the heated configurations evaluated,
18.4 grains CO over Bag 1. Even this lower level of emissions,
however, exceeded the rate of CO emissions with the unheated
catalyst.
These higher levels of CO may have resulted from catalyst
temperatures still too low to promote the oxidation reaction or
comparatively rich conditions in the converter. Additional testing
with catalyst air assist, described later in this report, was
conducted to improve the converter efficiency with respect to CO
conversion.
A summary of emissions over the Bag 1 phase with the heated
catalyst is provided in Table 4. Calculated OMHCE emissions,
closely related to measured unburned fuel emissions, significantly
decreased as catalyst heating was increased to the 15/40
configuration. NOx emissions were not significantly impacted by
the various catalyst heating schemes.
Table 4
Resistive Heating Applied, No Air Assist
Baa 1 Of FTP Cycle
NMHC HC CH3OH HCHO OMHCE CO NOx
Category g g g mg g g g
Baseline
No Heat/No Air
0/20 Heat
0/40 Heat
15/40 Heat
0.13
0.13
0.10
0.09
0.03
5.16
2.20
1.94
2.10
1.05
15.28
6.22
5.45
5.95
3.06
1983
521
512
555
520
7.71
3.11
2.76
3.00
1.62
35.9
16.5
19.4
23.2
18.4
6. 1
3.6
3.6
3.5
3.4
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
Table 5 presents weighted emission levels over the FTP cycle.
Generally, the changes in Bag 1 emissions brought about by catalyst
heating are reflected in the weighted FTP levels. For example, the
insignificant changes in Bag 1 formaldehyde levels contributed to
very similar weighted cycle averages for all of the heating
conventions evaluated. Average weighted CO for the 0/40 heated
catalyst testing was substantially increased above emission rates
from no resistive heat/no air assist mode catalyst testing.
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-13-
Table 5
Resistive Heating Applied, No Air Assist
FTP Composite Emission Levels
Category
NMHC HC CH3OH HCHO OMHCE CO NOx
g/mi g/mi g/nti mg/mi g/mi g/mi g/mi
Baseline
No Heat/No Air
0/20 Heat
0/40 Heat
15/40 Heat
0.02
0.03
0.02
0.02
0.01
0.91
0.22
0.21
0.23
0.15
2.71
0.57
0.57
0.61
0.43
480
85
88
98 •
92
1.43
0.33
0.31
0.34
0.24
8.1
1.8
1.9
2.5
1.7
1.3
0.8
0.8
0.8
0.8
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
While this catalyst-equipped vehicle appears to meet current
Federal emission standards for light-duty vehicles at low mileage,
the high formaldehyde emission rates are a serious concern. The
EHC in its tested configuration would have to be supplemented with
additional formaldehyde emission control technologies for the
entire system to be considered practical.
C.
EHC With Resistive Heat/Air Assist
Catalyst efficiency with respect to oxidation reactions may be
severely limited at cold start due to the lack of sufficient oxygen
in the exhaust to bring the desired reactions to completion. The
testing described in this section made use of catalyst air assist
to promote the desired oxidation reactions.
Other EPA work with methanol-fueled vehicles has indicated
that air assist to conventional three-way catalysts can cause a
significant increase in the production of NOx and formaldehyde
emissions.[9,15] In order to minimize the formation of these
pollutants and also limit the cooling effect of the added air on
the resistively heated substrate, air assist only occurred during
the initial portion of Bag 1. The period of air addition was
restricted to the first 100 seconds of vehicle operation following
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cold start for the testing described here. Restricting the period
of air assist in this manner has been shown to substantially limit
the production of excess NOx emissions from methanol vehicles.[9]
Air was added from a shop air hose, rather than from a belt or
electrically driven air pump. A regulator was placed in the air
line to decrease the air flowrate to approximately 5.0 cubic feet
per minute. An airflow meter was also added to determine the
effect of changes in exhaust flowrate on the flow of air assist to
the catalyst. The air addition began at key-on and continued for
a period of 100 seconds.
Figure 5 presents the results of this testing for methanol
emissions over Bag 1. Some previously presented data is also
included for comparison. Baseline methanol emissions of 15.28
grams over Bag 1 were reduced to 6.22 grams with the Kemira Oy
catalyst unassisted by resistive heating/air addition. The use of
15/40 resistive heating resulted in a roughly 50 percent decrease
in emissions from unassisted catalyst levels, to 3.06 grams. The
use of air assist for 100 seconds after cold start increased
methanol conversion efficiency by only 10 percent, however, from
unassisted catalyst levels.
Figure 5
Resistive Heat/Air Assist, EHC Only
Methanol Emissions, Bag 1 Of FTP
EHC Heat/Air Configuration
Baseline
No Heat/No Air
No Heat. 100 Sec Air
15/40 Heat Only
15/40 Heat, 100 Air*
15.28
1.81
0 5 10 15 20
Exhaust Methanol (grams)
* Heat 15 Seconds Prior To/40 Seconds
Following Start, 100 Seconds Air
Addition Following Start
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-15-
A combination of catalyst resistive heating and air assist
provided a greater reduction in Bag l emissions of methanol than
either assist by itself. 15/40 catalyst heating was combined with
air addition for 100 seconds following cold start to reduce
methanol emissions to 1.81 grams. This level of emissions
represented a substantial decrease, greater than 70 percent, from
unassisted catalyst levels.
An improvement in formaldehyde emissions over Bag l was not
noted when catalyst air addition was utilized (Figure 6) . In the
absence of resistive heating, the use of air addition under the
previously described convention increased the emissions of
formaldehyde substantially, more than 50 percent above unassisted
catalyst levels. Adding resistive heating decreased the
formaldehyde emissions rate, though it still exceeded formaldehyde
emissions from unassisted catalyst operation. The 620 milligrams
of formaldehyde emitted with the heated/air assisted catalyst
represented an increase of almost 20 percent over levels from the
unassisted catalyst.
Figure Q
Resistive Heat/Air Assist, EHC Only
Formaldehyde Emissions, Bag 1 Of FTP
EHC Heat/Air Configuration
Baseline
No Heat/No Air
100 Sec Air Only
15/40 Heat Only
15/40 Heat, 100 Air*
0 500 1000 1500 2000 2500
Exhaust Formaldehyde (milligrams)
* Heat 15 Seconds Prior To/40 Seconds
Following Start, 100 Seconds Air
Addition Following Start
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-16-
Figure 7 presents Bag 1 CO emissions results. As previously
noted, resistive heating alone did not reduce CO emissions below
levels with the unassisted catalyst. The use of air assist alone,
however, decreased CO emissions almost 30 percent from unassisted
catalyst levels. Adding 15/40 resistive heating to the air assist
strategy further decreased Bag 1 CO emissions to 6.5 grams. This
lower level represents an increase in efficiency greater than 60
percent from unassisted catalyst levels. This degree of
improvement in CO efficiency with catalyst resistive heating/air
assist has been noted in previous EPA catalyst technology
evaluations.[7,9]
Figure 7
Resistive Heat/Air Assist, EHC Only
Carbon Monoxide Emissions, Bag 1 Of FTP
EHC Heat/Air Configuration
Baseline
No Heat/No Air
100 Sec Air Only
15/40 Heat Only
15/40 Heat, 100 Air*
35.9
16.5
11.6
18.4
0 10 20 30 40 50
Exhaust Carbon Monoxide (grams)
* Heat 15 Seconds Prior To/40 Seconds
Following Start, 100 Seconds Air
Addition Following Start
Table 6 is a summary of Bag 1 emissions from air assisted
catalyst testing. Most of the emission levels there have been
discussed above; it should be noted that OMHCE decreased
approximately 30 percent from heated catalyst levels when catalyst
air assist was also used. The 40 percent decrease in methanol
emissions noted when air assist was provided to the heated catalyst
was partially offset by the increase in formaldehyde emissions.
NOx emissions did not change with resistive heating/air assist
restricted to the cold start portion of Bag 1.
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-17-
Table 6
Catalyst Resistive Heating/Air Assist
Bag 1 Of FTP Cvcle .
NMHC HC CH3OH HCHO OMHCE CO NOx
Category g g g mg g g g
Baseline
No Heat/No Air
100 Sec Air
Only
15/40 Heat Only
15/40 Heat, 100
Sec Air
0.13
0.13
0.16
0.03
0.02
5.16
2.20
2.04
1.05
0.65
15.28
6.22
5.61
3.06
1.81
1983
521
798
520
620
7.71
3.11
3.01
1.62
1.14
35.9
16.5
11.6
18.4
6.5
6.1
3.6
3.7
3.4
3.5
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
Table 7 details the impact of changes in Bag 1 emission levels
on weighted FTP emissions. Though the FTP averages generally
follow the direction of changes in Bag l emissions caused by the
different catalyst conventions, the changes may not be directly
translated in magnitude. For example, the decrease in Bag 1 CO
levels when the resistively heated catalyst was assisted with air
addition was substantial, approximately 65 percent below heated
catalyst only levels. The difference in CO emission rates over the
FTP between these two catalyst configurations is only 12 percent,
however. A difference between these incremental changes should be
expected because of the weighting of Bag 2 and 3 emissions (no
catalyst assists) in the FTP averages. However, Bag 2 and 3 CO
emissions from the heated/air assisted catalyst testing were
actually substantially higher than Bag 2 and 3 emissions from the
heated catalyst only testing. This was an unexpected result; the
cause of these differences later in the test were not investigated
at this time, as they were outside the area of immediate concern of
this testing (Bag 1 cold start emissions).
D. EHC With Main Catalyst Testing
One obvious method of improving the performance of this
compact EHC is to supplement it with a larger, non-resistively
heated main catalyst. The smaller EHC may be more easily located
close to the engine, near the exhaust manifold. A larger main
catalyst might be mounted in a more accessible underfloor location
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-18-
Table 7
Catalyst Resistive Heating/Air Assist
FTP Composite Emission Levels
Category
NMHC HC CH3OH HCHO OMHCE CO NOx
g/mi g/mi g/mi mg/mi g/mi g/mi g/mi
Baseline
No Heat/No Air
100 Sec Air
Only
15/40 Heat Only
15/40 Heat, 100
Sec Air
0.02
0.03
0.02
0.01
0.01
0.91
0.22
0.24
0.15
0.15
2.71
0.57
0.63
0.43
0.39
480
85
125
92
104
1.43
0.33
0.36
0.24
0.24
8.1
1.8
2.3
1.7
1.5
1.3
0.8
0.8
0.8
0.8
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
downstream of the EHC. Here, a catalyzed ceramic monolith,
described earlier in Section III, was installed immediately behind
the Kemira Oy EHC, underfloor. This ceramic monolith is referred
to hereafter as the main catalyst (MC). Because of its location
downstream, but close to the EHC, the MC may have received a light-
off assist due to the catalytic activity/resistive heating of the
EHC. Also, the use of air assist to the EHC will affect the
performance of the downstream MC.
Figure 8 summarizes Bag 1 methanol emissions testing of this
two-catalyst system. Air was added in front of the EHC for 100
seconds after cold start. The platinum main catalyst, with air
assist, had Bag 1 unburned fuel emissions nearly three times higher
than the most efficient EHC configuration separately tested. When
used as part of a two-catalyst emission control system with the
EHC, however, extremely low Bag 1 emissions of methanol were noted.
Bag 3 methanol emissions, an average of 0.25 grams, were even
higher than Bag 1 emissions (the EHC was not resistively heated nor
was catalyst air assist used during Bag 3). The 0.09 grams of
methanol measured with the two-catalyst system represents a greater
than 99 percent methanol conversion efficiency from baseline (no
catalyst) levels.
A summary of Bag 1 formaldehyde emissions results is given in
Figure 9. The air assisted main catalyst substantially decreased
formaldehyde below levels from the most efficient EHC
configuration. As in the case of the conversion of methanol, the
heated/air assisted two-catalyst system reduced formaldehyde
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-19-
Figure 8
EHC And Main Catalyst Testing
Methanol Emissions, Bag 1 Of FTP
EHC Heat/Air Configuration
Baseline ™
EHC. No Heat/Air
EHC, With Heat/Air
MC Only, 100 Sec Air
6.22
1.81
5.24
EHC+MC, Heat/Air- 0.09
15.28
0 5 10 15
Exhaust Methanol (grams)
* Heat 15 Seconds Prior To/40 Seconds
Following Start, 100 Seconds Air
Addition Following Start
20
Figure 9
EHC And Main Catalyst Testing
Formaldehyde Emissions, Bag 1 Of FTP
EHC Heat/Air Configuration
Baseline
EHC, No Heat/Air
EHC, With Heat/Air
MC Only, 100 Sec Air m 107
EHC+MC, Heat/Air«
11
0 500 1000 1500 2000 2500
Exhaust Formaldehyde (milligrams)
- Heat 15 Seconds Prior To/40 Seconds
Following Start, 100 Seconds Air
Addition Following Start
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-20-
emissions to levels far below the lowest noted with the EHC alone.
An average of only 11 milligrams of formaldehyde was noted over Bag
1 with the two-catalyst system, an efficiency in excess of 99
percent from no catalyst levels.
The compact EHC alone, with catalyst heat/air assist, was
substantially more efficient for the conversion of CO than the MC
with air assist (Figure 10) . However, the use of the MC in
conjunction with the assisted EHC provided the lowest CO levels of
any catalyst configuration tested. The two-catalyst system reduced
CO emissions almost 80 percent from levels with the most efficient
EHC configuration. The low 1.4 grams of CO over Bag 1 obtained
with the two-catalyst system represents an efficiency of 96 percent
from no catalyst levels.
Figure 10
EHC And Main Catalyst Testing
Carbon Monoxide Emissions, Bag 1 Of FTP
EHC Heat/Air Configuration
Baseline
EHC, No Heat/Air
EHC, With Heat/Air
MC Only, 100 Sec Air
EHC+MC, Heat/Air*
35.9
16.5
6.5
9.8
1.4
0 10 20 30 40 50
Exhaust Carbon Monoxide (grams)
* Heat 15 Seconds Prior To/40 Seconds
Following Start, 100 Seconds Air
Addition Following Start
Table 8 contains a summary of Bag 1 emissions from testing the
two-catalyst system. The substantial decrease in measured
emissions of methanol and formaldehyde is evident in the very low
calculated OMHCE emissions. NOx emissions were relatively
unaffected by either catalyst assist or the use of the MC behind
the resistively heated EHC.
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-21-
Table 8
EHC and Main Catalyst Testing
Bag 1 of FTP Cycle
Category
NMHC HC CH3OH HCHO OMHCE CO NOx
mg
Baseline
QLOC Only, No
Heat/No Air
QLOC Only,
15/40 Heat, 100
Sec Air
Main Cat Only,
100 Sec Air
QLOC and Main
Cat, 15/40
Heat, 100 Sec
Air
0.13
0.13
0.02
0.08
0.01
5.16
2.20
0.65
1.84
0.05
15.28
6.22
1.81
5.24
0.09
1983
521
620
107
11
7.71
3.11
1.14
2.45
0.07
35.9
16.5
6.5
9.8
1.4
6.1
3.6
3.5
3.5
3.2
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
Very low emissions over the weighted FTP resulted from the use
of the two-catalyst system (and the EHC provided with resistive
heating/air assist). Bag 2 and 3 emission levels are not commented
upon here, as the purpose of this testing was to evaluate the
improvement in Bag 1 emissions of unburned fuel, formaldehyde, and
CO with the heated/air assisted EHC. It should be noted, however,
that the two-catalyst system was extremely efficient at converting
emissions of methanol, formaldehyde, and CO over Bags 2 and 3, even
without catalyst resistive heating/air assist applied to the EHC in
Bag 3. These emission level improvements, though not as great in
magnitude as the improvements noted above in Bag 1, are also
reflected in the FTP composite averages (Table 9).
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-22-
Table 9
EHC and Main Catalyst Testing
FTP Composite Emission Levels
Category
NMHC HC CH3OH HCHO OMHCE CO NOx
g/mi g/mi g/mi mg/mi g/mi g/mi g/mi
Baseline
QLOC Only, No
Heat/No Air
QLOC Only,
15/40 Heat, 100
Sec Air
Main Cat Only,
100 Sec Air
QLOC and Main
Cat, 15/40
Heat, 100 Sec
Air
0.12
0.03
0.01
**
**
0.91
0.22
0.15
0.11
0.02
2.71
0.57
0.39
0.31
0.04
480
85
104
7
2
1.43
0.33
0.24
0.15
0.02
8.1
1.8
1.5
0.6
0.3
1.3
0.8
0.8
0.8
0.7
Gasoline-fueled vehicle measurement procedure with a propane-
calibrated FID.
Less than 0.005 measured.
Non-methane HC emissions with the two-catalyst system were low
enough to be considered negligible over the weighted FTP. OMHCE
emissions at low mileage were below Ultra Low Emission Vehicle
standards, as considered by the State of California. Very little
CO was produced (0.3 grams per mile) over the FTP with the two-
catalyst system. Methanol emissions over the FTP were reduced more
than 98 percent when the two-catalyst system was used. NOx
emissions were not adversely impacted by the use of the additional
MC; a very small improvement in Bag 1 NOx emissions is manifest in
a slightly lower weighted FTP value.
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-23-
VIII. Evaluation Highlights
1. Resistive heating, in the absence of catalyst air assist,
provided little reduction in most Bag 1 emission levels when the
EHC was tested without a main catalyst in the exhaust. Bag 1
emissions of methanol were reduced to 3.06 grams when the EHC was
resistively heated, from 6.22 grams with no catalyst resistive
heating.
2. Catalyst air assist was provided for 100 seconds
following start in Bag 1, and the catalyst was resistively heated
using the 15/40 convention described earlier. This combination of
catalyst heating/air assist decreased methanol emissions over Bag
1 to 1.81 grams, down from 6.22 grams with the no heat/no air EHC
configuration. CO emissions over Bag 1 also decreased
substantially, below air assisted catalyst levels, when a
combination of catalyst resistive heating/air assist was used.
Formaldehyde emissions, however, increased almost 20 percent above
unassisted catalyst levels when the EHC was provided with 15/40
resistive heating and catalyst air assist.
3. A two-catalyst system, incorporating the EHC and a
catalyzed ceramic monolith main catalyst, was evaluated. Resistive
heating, using the 15/40 convention, and 100 seconds of air assist
following cold start in Bag 1 were used with the EHC during this
testing. The two-catalyst system produced the lowest Bag 1
emissions of unburned fuel, formaldehyde, and CO of the catalyst
configurations tested. The platinum-catalyzed main catalyst, with
air addition, was more efficient than the compact EHC without
heat/air assist. When combined into a two-catalyst system located
underfloor, these catalysts provided extremely low Bag 1 emissions
of all measured pollutants with the exception of NOx.
Methanol and formaldehyde emissions were reduced to 0.09 grams
and 11 milligrams respectively over Bag 1 with the two-catalyst
system. The low Bag 1 emissions contributed substantially to the
calculated emission rate of 0.02 grams per mile of OMHCE over the
FTP. Weighted average formaldehyde emissions over the FTP were
less than 2 milligrams per mile, well below the California standard
of 15 milligrams per mile for alcohol-fueled vehicles. The very
low Bag 1 levels of methanol and formaldehyde, with the two-
catalyst system here, represent conversion efficiencies of greater
than 99 percent from baseline (no catalyst) levels from the test
vehicle.
CO emissions over Bag 1 were reduced greater than 96 percent
from no catalyst levels using the two-catalyst system. This
efficiency was reflected in FTP weighted average CO emissions,
where the two-catalyst system also provided a 96 percent conversion
efficiency from no catalyst levels. NOx emissions, however, were
relatively unaffected by changes in catalyst configuration here.
Even the use of catalyst air assist (restricted to 100 seconds
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-24-
following cold start in Bag 1) did not greatly affect NOx levels.
A slight decrease in Bag 1 emissions of NOx was noted with the two-
catalyst system, compared with the other catalyst configurations
tested.
IX. Future Efforts
The evaluation of the EHC discussed here did not determine an
optimized resistive heating/air assist strategy. In addition, some
EHC operating strategies, such as no resistive heat/air assist in
the two-catalyst configuration mentioned previously, were not
evaluated. To ensure a more accurate accounting of the
contribution of the components of resistive heating and air assist
to catalyst efficiency, it is necessary to supplement the testing
discussed here. Additional testing will be conducted to better
determine the EHC's ability to reduce emission levels of unburned
fuel, CO, and formaldehyde.
Future efforts will be made to quantify the relationship
between catalyst heating/air addition and real time emission rates
of individual pollutants. These efforts will be concerned only
with the period of time during which resistive heating and/or air
addition is occurring.
A Horiba modal analysis system has been installed at the EPA
Motor Vehicle Emission Laboratory; this analyzer will be used to
map the effects of changes in catalyst resistive heating/air
addition on emissions. While it is not possible to obtain methanol
or formaldehyde analysis, CO, NOx, and FID-measured hydrocarbons
emission levels will be determined.
X. Acknowledgments
The resistively heated catalyst evaluated in this test program
was supplied by Kemira Oy, located in Finland. The platinum-coated
ceramic monolith used here as a main catalyst was supplied by the
Specialty Chemicals Division of the Engelhard Corporation. The
methanol-fueled test vehicle was supplied by Volkswagen of America.
The authors appreciate the efforts of James Garvey, Steven
Halfyard, Robert Moss, Rodney Branham, and Ray Ouillette of the
Test and Evaluation Branch, ECTD, who conducted the driving cycle
test and prepared the methanol and formaldehyde samples for
analysis. The authors also appreciate the efforts of Jennifer
Criss of CTAB, ECTD, for word processing and editing support.
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-25-
XI. References
1. "New Potential Exhaust Gas Aftertreatment Technologies
for 'Clean Car1 Legislation," SAE Paper 910840, Gottberg, I., et
al., February 1991.
2. "Resistive Materials Applied To Quick Light-Off
Catalysts," SAE Paper 890799, Hellman, Karl H. , et al., March 1989.
3. "Recent Results From Prototype Vehicle And Emission
Control Technology Evaluation Using Methanol Fuel," SAE Paper
901112, Hellman, Karl H., and G. K. Piotrowski, May 1990.
4. U.S. Code. 7401, Sec. 202(j), as amended by PL 101-549,
November 15, 1990.
5. "Evaluation of A Resistively Heated Metal Monolith
Catalytic Converter On A M100 Neat Methanol-Fueled Vehicle,"
EPA/AA/CTAB/88-08, Blair, D. M. , and G. K. Piotrowski, August 1988.
6. "Evaluation Of A Resistively Heated Metal Monolith
Catalytic Converter On A Gasoline-Fueled Vehicle," EPA/AA/CTAB/88-
12, Piotrowski, Gregory K., December 1988.
7. "A Resistively Heated Catalytic Converter With Air
Injection For Oxidation Of Carbon Monoxide And Hydrocarbons At
Reduced Ambient Temperatures," EPA/AA/CTAB/89-06, Piotrowski,
Gregory K., September 1989.
8. "Evaluation of Resistively Heated Metal Monolith
Catalytic Converters On An M100 Neat Methanol-Fueled Vehicle, Part
II," EPA/AA/CTAB/89-09, Piotrowski, Gregory K., December 1989.
9. "Evaluation of Camet Resistively Heated Metal Monolith
Catalytic Converters On An M100 Neat Methanol-Fueled Vehicle, Part
III," EPA/AA/CTAB/91-03,Piotrowski, Gregory K. and R. M. Schaefer,
July 1991.
10. "How To Achieve Optimum Physical Properties In The Metal
Catalyst," SAE Paper 910614, Lylykangas, R. and P. Lappi, February
1991.
11. Formaldehyde Measurement In Vehicle Exhaust At MVEL,
Memorandum, Gilkey, R. L., OAR, QMS, EOD, Ann Arbor, MI, 1981.
12. "Formaldehyde Sampling From Automobile Exhaust: A
Hardware Approach," EPA/AA/TEB/88-01, Pidgeon, W., July 1988.
13. "Sample Preparation Techniques For Evaluating Methanol
and Formaldehyde Emissions From Methanol-Fueled Vehicles and
Engines," EPA/AA/TEB/88-02, Pidgeon, W., and M. Reed, September
1988.
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-26-
14. Private Communication, Kemira Oy to U.S. EPA, July 29,
1991.
15. "Catalysts For Methanol Vehicles," SAE Paper 872052,
Piotrowski, G. K. and J. D. Murrell, November 1987.
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