EPA/AA/CTAB/88-12
Technical Report
Evaluation Of A Resistively Heated Metal Monolith
Catalytic Converter On A Gasoline-Fueled Vehicle
by
Gregory K. Piotrowski
December 1988
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, Michigan 48105
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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY
ANN ARBOR. MICHIGAN 48105
OFFICE OF
AIR AND RADIATION
MEMORANDUM
SUBJECT: Exemption From Peer and Administrative Review
FROM :
TO:
Karl E. Hellman, Chief
Control Technology and Applications Branch
Charles L. Gray, Jr., Director
Emission Control Technology Division
The attached report entitled "Evaluation of a Resistively
Heated Metal Monolith Catalytic Converter On A Gasoline-Fueled
Vehicle," (EPA/AA/CTAB/88-12) concerns an emissions testing
program conducted on a gasoline-fueled Volkswagen Golf
vehicle. The emissions control technology tested was a
resistively heated metal monolith catalytic converter provided
by Camet, a subsidiary of W. R. Grace. The vehicle was
evaluated at two different test cell temperatures, 72-74°F and
20°F.
Since this report is concerned only with the presentation
of data and its analysis and does not involve matters of policy
or regulations, your concurrence is requested to waive
administrative review according to the policy outlined in your
directive of April 22, 1982.
Concurrence:
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 1
III. Catalytic Converter Description 2
IV. Vehicle Description 2
V. Test Facilities and Analytical Methods 3
VI. Test Procedure 3
VII. Discussion 4
A. Testing At 72-74°F Conditions 4
B. 20°F Ambient Temperature Testing 10
VIII.Highlights From Testing 14 -
IX. Acknowledgments 14
X. References 16
APPENDIX A - Camet Resistively Heated Catalytic Converter
Specifications and Power Requirements . . . A-l
APPENDIX B - Test Vehicle Specifications B-l
APPENDIX C - Average Mass of Emissions - Bag 3 of the
FTP Cycle - 72-74°F Ambient Condition
Testing C-l
APPENDIX D - Individual FTP Results - 72-74°F Conditions . D-l
APPENDIX E - Individual Test Results - Lower Ambient
Temperature Evaluation E-l
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I. Summary
A prototype metal monolith catalytic converter, which may
be resistively heated, was emission tested on a gasoline-fueled
vehicle. The vehicle was tested at 72-74°F ambient test cell
conditions and -at 20°F ambient "cold-room" conditions.
The testing reported here was conducted over the Federal
test procedure (FTP) cycle.[1] The most efficient resistive
heating/excess air addition strategy tested at 72-74°F ambient
conditions is given below:
Bag 1: Preheat the catalyst for 20 seconds prior to cold
start and heat for 20 seconds following cold start. Bottled
air at 2.0 standard cubic feet per minute (SCFM) was added
ahead of the catalyst at cold start until the cessation of
resistive heating (the last 20 seconds).
Bag 2: No resistive heating or excess air addition
employed.
Bag 3: Preheat the catalyst for 10 seconds prior to hot
start and heat for 15 seconds following hot start. Bottled air
at 2.0 SCFM was added at hot start until the cessation of
resistive heating (the last 15 seconds).
Hydrocarbons (HC) and carbon monoxide (CO) were reduced to
0.043 and 0.57 grams per mile respectively with this strategy.
No weighted FTP benefits for HC and CO were noted at 20°F
ambient conditions with the heating/air addition strategies
employed.
II. Introduction
The major portion of HC and CO emissions measured from a
catalyst-equipped gasoline-fueled vehicle over the FTP cycle
are generated during cold start and warmup of the catalyst.
These emissions are difficult to control because engine-out
emissions are high and catalytic converters have low conversion
efficiency during their warm-up phase of operation.
A resistively heated metal monolith catalyst has been
evaluated by EPA on a methanol-fueled vehicle. Results from
this previous testing indicated the feasibility of the concept
of a resistively heated metal monolith substrate as a quick
light-off catalyst support.[2] This catalytic converter, when
tested as a three-way catalyst without resistive heating,
controlled emissions over the Federal test procedure (FTP) to
levels previously obtained by ceramic substrate converters
coated with noble metal catalyst formulations. Resistively
heating the catalyst substantially lowered HC and formaldehyde
(HCHO) emission levels compared to those from the unheated
tests.
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The purpose of the testing reported on here was to
evaluate this resistively heated catalyst technology on a
gasoline-fueled vehicle. In order to facilitate qualitative
comparisons in emissions results with the levels measured with
the methanol vehicle, a gasoline-fueled Volkswagen Golf with a
similar fuel injection system was a desirable choice as the
test vehicle, and such a vehicle was loaned to EPA by
Volkswagen for this test program.
We were interested in two separate ambient temperature
ranges for this testing: 1) 72-74°F, and 2) 20°F. The first
range refers to our usual laboratory test cell temperatures,
within the boundaries (68-86°F) required for constant volume
sampler (CVS) dilution air by the FTP.[3] The 20°F conditions
were of interest because other researchers [4,5] have reported
that HC and CO emissions rise as the ambient temperatures at
which gasoline-fueled vehicles operate at are reduced.
The first part of this evaluation, referred to in the
Discussion as "Testing at 72-74°F Conditions" was conducted in
a chassis dynamometer test cell at those ambient temperatures.
This testing was conducted over the FTP cycle. The second part
of the Discussion refers to testing conducted in a temperature
controlled chamber which housed a chassis dynamometer. Test
cell temperatures could be varied over the range 20-70°F; 20°F
was chosen for this cold temperature evaluation because it was
the temperature at which many other test programs have been run.
Ill. Catalytic Converter Description
The catalytic converter evaluated here was a dual-bed
configuration consisting of an unheated metal monolith catalyst
and a smaller resistively heated metal monolith catalyst. This
is the same converter that was evaluated on a methanol-fueled
vehicle in [2].
The dimensions of the converter are similar to those of
typical underfloor catalysts on late model compact
automobiles. The amperage draw was comparable to that required
by an automotive starter motor cranking in cold weather.
Detailed specifications are provided in Appendix A.
IV. Vehicle Description
The test vehicle was a 1987 Volkswagen Golf 4-door sedan,
equipped with automatic transmission, continuous fuel injection
(Bosch CIS) and radial tires. The 1.78-liter engine had a
rated maximum power output of 85 horsepower at 5250 rpm. The
vehicle was tested at 2,500 Ibs inertia weight and 7.7 actual
dynamometer horsepower.
A more detailed description of the vehicle is provided in
Appendix B.
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V. Test Facilities and Analytical Methods
Emissions testing at 72-74°F conditions 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 CVS 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 chemilumines-
cent NOx analyzer. Methane was measured with a Bendix Model
8205 methane analyzer.
Exhaust formaldehyde was measured using a dinitrophenyl
hydrazine (DNPH) technique.[6] 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.
Exhaust HC emissions at 20°F ambient conditions were
measured with a Beckman Model 400 FID. CO was measured with a
Horiba Model AIA 23 infrared detector, while NOx emissions at
20°F were determined by chemiluminescent technique using a
Beckman Model 951A NOx analyzer.
VI. Test Procedure
The gasoline-fueled vehicle evaluation of this catalyst
technology was conducted in two phases:
1. An evaluation at 72-74°F ambient conditions, and
2. Testing at 20°F ambient conditions.
The first phase of this evaluation was conducted to
determine the catalysts' effectiveness at reducing pollutants
in vehicle exhaust at 72-74°F ambient conditions. Of special
interest was the determination of the catalysts' ability to
oxidize HC and CO emissions. Although HCHO emissions from
light-duty gasoline-fueled vehicles are not currently
regulated, they were measured during this testing to determine
if this catalyst reduced emissions below stock catalyst levels.
Testing during this phase was conducted over the FTP
cycle. Of particular interest was the difference in HC and CO
emission levels between the first and third bag portions
(initial and final 505 seconds of the Urban Dynamometer Driving
Schedule). These portions involve similar driving conditions;
the first bag begins with a cold start however, compared to a
hot start beginning the third bag. We wished to know if the
resistively heated catalyst could lower Bag 1 emissions to Bag
3 levels by bringing the catalyst to light-off conditions prior
to cold start.
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A tap was placed in the exhaust line approximately eight
inches upstream from the catalytic converter for the
introduction of bottled air. Admission of air ahead of the
catalyst simulates oxidation catalyst conditions over
timeframes of interest. Controlling air pressure at the gas
bottle regulator allowed the variation of airflow through the
catalyst.
The second phase of this evaluation was conducted to
determine the effectiveness of this catalyst system at a lower
ambient temperature, 20°F. This testing was also conducted
over the FTP cycle.
VII. Discussion
A. Testing At 72-74°F Conditions
The initial evaluation of the resistively heated converter
was conducted over the FTP. cycle only. The test cell
temperature varied between 72° and 74°F during this testing.
The test vehicle was originally eguipped with a stock
underfloor noble metal monolith catalyst. The car was tested
twice in this configuration; this is referred to below as stock
catalyst testing. This catalyst was removed and replaced with
a straight exhaust pipe; testing in this configuration is
referred to below as baseline testing.
The Camet resistively heated metal monolith was evaluated
in the same underfloor location that the stock catalyst
occupied in the exhaust stream.
Two conditions were varied during the evaluation of the
heated converter: the amount of time that resistive heating
was applied to the catalyst and the amount of air flowed over
the catalyst during heating.
The electrical circuit consisted of a 12-volt battery
power source, a starter switch and relay, on/off power
indicator, heavy gauge copper wiring and the catalytic
converter. Resistive heating was confined to the
cold-start/hot-start portions (Bags 1 and 3) of the FTP. The
following scheme had been developed during the methanol-fueled
vehicle evaluation of this technology:
1. Heating for 10 seconds prior to cold start and 20
seconds following cold start during the Bag 1; and
2. Heating for 5 seconds prior to and 15 seconds
following the hot start in Bag 3.
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This strategy was chosen with a 10-second cold start
preheat time to achieve timing that might be customer
acceptable. The first diesel engines had glow plug preheat
times of up to one minute. As they were improved, this time
was reduced to 10 seconds or less. Since this time seemed to
be acceptable to customers, it was chosen as a maximum
preheating time for this test phase. This strategy was used
during this gasoline-fueled vehicle testing; this scheme is
referred to below as the 10/20, 5/15 heating scheme. A
modification to the scheme also used was a 20-second
preheat/20-second heating after cold start (Bag 1) and
10-second preheat/15-second heating after hot start (Bag 3).
The amount of air flowed over the catalyst during catalyst
heating/vehicle operation was also varied. A tap into the
exhaust stream was made approximately eight inches upstream of
the converter for the introduction of bottled air. When used,
bottled air was flowed over the catalyst only when the vehicle
engine was operated and resistive heating was simultaneously
applied to the catalyst. Air was not admitted prior to cold or
hot start. The air pressures referred to in the discussion
correspond to pressures at the secondary regulator on the gas
bottle. A relationship between air flow rate and regulator
pressure is given below.
30 psi: 2.4 SCFM
20 psi: 2.0 SCFM
12 psi: 1.0 SCFM
6 psi: 0.2 SCFM
A summary of the data from this phase of the evaluation is
presented below in tabular and graphical form. Table 1
presents emission levels in grams (milligrams for HCHO) over
Bag 1 of the FTP for the various catalyst configurations
tested. Bag 3 results can be found in Appendix C. Table 2
presents weighted FTP averages for these emissions categories.
Figures 1 and 2 present a summary of HC and CO bag data in
grams for some catalyst configurations tested, while Figure 3
presents weighted FTP averages.
The levels in Table 2 are below the current light-duty
gasoline vehicle standards for HC, CO and NOx. HCHO efficiency
over the FTP was 88 percent with this catalyst. The stock
catalyst is a good benchmark; the resistively heated metal
monolith converter would have to reduce pollutant emissions to
very low levels in order to compare favorably with this
catalyst.
The configuration labeled Camet no-heat/no-air in Tables l
and 2 is the metal monolith tested without heating in the
three-way mode. HC and CO levels over the FTP were low for
this configuration, lower even than those from the stock
catalyst. NOx was substantially higher, yet lower than the
level of the 1 gram per mile current vehicle standard. This
could be due to the difference in the active catalysts used
between the stock and Camet converters, rather than physical or
volume differences between the substrates.
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Table 1
Average Mass of Emissions
Bag 1 of FTP Cycle, 72-74°F Testing
Baseline (no catalyst)
Stock catalyst
Camet no heat/ no
Camet heat 10/20,
Camet no heat, 30
Camet heat 10/20,
Camet heat 10/20,
Camet heat 20/20,
Camet heat 20/20,
Duration
Lyst)
air
no air
psi air
6 psi air
12 psi air
12 psi air
20 psi air
30 psi air
HC
(g)
5.33
1.09
0.92
0.85
0.87
0.66
0.65
0.48
0.42
0.52
NMHC*
(q)
5.01
0.93
0.81
0.75
0.77
0.57
0.55
0.37
0.33
N/A
CO
(q)
88.36
20.01
16.08
16.07
16.09
12.07
10.91
9.15
7.95
7.58
C02
(q)
1296.
1437.
1335.
1342.
1335.
1318.
1331.
1321.
1316.
1318.
NOx
(q)
14.14
1.32
2.34
1.82
2.22
2.30
2.06
1.95
1.90
2.01
Aldy
(mg)
165.
17.
11.
7.
14.
9.
13.
6.
N/A
7.
N/A Not available
* Non-methane hydrocarbons.
FIGURE 1
HC. CO, BAG 1 OF FTP
CATALYST CONFIGURATION
BASELINE
STOCK
•NO HEAT. NO AIR
•20/20. 20 PSI AIR
CAMET CATALYST
I HC. QRAM9 %g& CO, GRAMS
86.C
20 40 80 80 100
HC, CO. GRAMS
FIGURE 2
HC, CO, BAG 1 OF FTP
INCREASED HEATING, AIR FLOW SCHEMES
HEAT/AIR
•I HC. QRAMS ^\ CO, QRAM8 I
0.86
^^•^^^^^^^f^^^^f^^^^yf^^^^^^ 16.07
0.66
'^^^^^f^^^^^^^^'^^ 12.07
0.66
^^ff-^^^^^^f^^^^^'^^ 10.91
0.48
^^^$$>^^^^^^^ 9.15
0.42
^&^&%3£
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Table 2
Emission Levels Over the FTP Cycle, 72-74°F Testing
Catalyst Configuration
Baseline (no catalyst)
Stock catalyst
Camet no heat, no air
Camet heat 10/20 Bag 1,
5/15 Bag 3, no air
Camet no heat 30 psi air
Camet heat 10/20 Bag 1,
5/15 Bag 3, 6 psi air
Camet heat 10/20 Bag 1,
5/15 Bag 3, 12 psi air
Camet heat 20/20 Bag 1,
10/15 Bag 3, 12 psi air
Camet heat 20/20 Bag 1,
10/15 Bag 3, 20 psi air
Camet heat 20/20 Bag 1,
10/15 Bag 3, 30 psi air .
N/A Not available.
HC NMHC CO C02 NOx Aldy.
(q/mi) (q/mi) (q/mi) (q/mi) (q/mi) (mq/mi)
1.030 0.99 12.33 348. 3.48 41.
0.100 0.08 1.63 376. 0.20 5.
0.077 0.063 1.06 354. 0.72. 1.
0.071 0.058 1.08 356. 0.63 2.
0.071 0.055 1.04 355. 0.70 N/A
0.058 0.044 0.83 349. 0.77 2.
0.057 0.043 0.76 351. 0.67 4.
0.048 0.033 0.65 346. 0.66 1.
0.043 0.029 0.57 343. 0.67 2.
0.049 N/A 0.56 346. 0.66 1.
FIGURE 3
HC. CO, FTP CYCLE
CATALYST CONFIGURATION
STOCK
•NO HEAT/NO AIR ILf^L^
•10/20, 6/15, NO AIR |
•NO HEAT, 30 PSI
•10/20, 5/15, 12 PSI
•20/20, 10/16,20 PSI
I HC. QMS/Ml EM3 CO, QMS/Ml I
•CAM6T CATALYST
0.6 1 1.6
HC. CO, GRAMS/MILE
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The Camet catalyst was tested with two variable
conditions: 1) air flow over the catalyst during resistive
heating (oxidation catalyst simulation), and 2) variations in
heating times during Bags 1 and 3 of the FTP. In Tables 1 and
2 the heating times mentioned refer to preheating before and
heating after start. Addition of air is denoted by the
secondary regulator pressure given in units of psi. Air was
added only from the time of engine start to the end of
resistive heating.
The Camet catalyst was tested without resistive heating
but with the addition of air during Bags 1 and 3. Air was
added for 20 seconds following engine start during Bag 1 and
for 15 seconds following engine start in Bag 3. The catalyst
was also tested with resistive heating but without the addition
of air.
Emission levels from each of these two configurations were
generally only slightly lower than those from the unheated/no
air added configuration over Bag 1. In addition, emission
levels from each pollutant category were similar for both
configurations over the FTP. HC, CO and NOx emissions were
also very similar between the unheated/no air added
configuration and the two configurations mentioned above. -It
appears that resistive heating or the addition of air did not
provide a substantial emission reduction benefit when employed
as separate strategies.
The simultaneous addition of air and resistive heating was
then evaluated as an operating strategy. This mode involved
10/20-Bag 1 and 5/15-Bag 3 heat times as well as the addition
of air at 6 psi. The result was a substantial decrease in Bag
1 HC and CO levels, to 0.66 and 12.07 grams, respectively.
This corresponds to a 40 percent increase in HC and CO
efficiency from stock catalyst Bag 1 levels. Weighted FTP
efficiency increases of 42 and 50 percent respectively over
stock catalyst HC and CO levels were obtained with this
heat/air added strategy. NOx levels changed little from those
measured from Camet catalyst testing without heating or the
addition of air; adding heat and air did not provide a NOx
benefit.
The next strategy evaluated was increasing the air flow
over the catalyst while keeping the same heating scheme (to 12
psi air). This did not result in substantial emissions
reduction. HC and CO levels over the FTP were very similar to
those obtained with the previous heating/air addition
configuration. NOx over the FTP dropped to 0.67 grams per
mile; this was essentially the same level as the Camet
converter no heat/no air configuration level of 0.72 grams per
mile.
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Increasing the catalyst preheat times to 20 seconds in Bag
1 and 10 seconds in Bag 3 (air added at 12 psi) reduced FTP HC
and CO emissions to 0.048 grams per mile and 0.65 grams per
mile, respectively. This represented 52 percent and 60 percent
decreases in HC and CO respectively from stock catalyst levels,
a considerable improvement. NOx was measured at 0.66 grams per
mile, essentially unchanged from the 0.67 grams per mile
obtained with the 10/20, 5/15, 12 psi resistive heating/air
addition scheme testing.
A further decrease in HC and CO emissions was obtained by
using a 20/20 Bag 1, 10/15 Bag 3 heating scheme, and increasing
the air flowrate over the catalyst to 20 psi. HC emissions
were reduced to an average 0.043 grams per mile over the FTP,
the lowest levels measured during this evaluation. CO was
reduced to 0.57 grams per mile over the FTP. NOx was unchanged
from the 0.67 grams per mile measured during the previous
resistive heating/air scheme testing.
The secondary regulator was then opened to maximum
pressure, 30 psi, during the heat-on/engine-operating portions
of Bags 1 and 3. HC level increased slightly from tHe
immediate previous configuration to 0.049 grams per mile over
the FTP. CO levels remained approximately at the same level
from the previous mode, 0.56 grams per mile over the FTP. This
was the first time during the variation of either heating
scheme or air flow over the catalyst that HC or CO levels had
increased after heating or air flow had been increased.
Previous evaluation of this technology on a methanol-fueled
vehicle [2] suggested that increased heating time in Bag 1 may
not increase catalyst midbed temperature substantially from
temperatures caused by a 20/20 heating scheme. The first part
of the evaluation was ended with the heating/air-flow scheme of
20/20 Bag 1 heating, 10/15 Bag 3 heating, 20 psi air, selected
as the overall most effective scheme of those tested.
Formaldehyde levels were also measured during this
testing. The stock catalyst lowered FTP formaldehyde levels to
5 milligrams per mile; the Garnet catalyst reduced this further
to approximately 1-2 milligrams per mile. Levels lower than
this are difficult to precisely ascertain, given the accuracy
of our current formaldehyde measuring system. Resistive
heating and the addition of air did not appear to lower
formaldehyde below this 1-2 milligrams per mile level.
Figures 1 and 2 graphically depict the ability of the
catalyst configurations tested to oxidize the pollutants of
greatest interest here, HC and CO. Figure 1 presents HC and CO
in grams over Bag l of the FTP for four catalyst
configurations. The stock catalyst reduces HC and CO levels
substantially while the Garnet catalyst in the no-heat/no-air
mode provides a slight improvement over stock catalyst levels.
The most efficient heating/air-addition scheme for Bag 1 HC and
CO with the Garnet catalyst is also depicted. • This particular
scheme had HC and CO efficiencies of 61 and 60 percent
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respectively over Bag l levels obtained with the stock
catalyst, a substantial improvement.
Figure 2 shows the decrease in HC and CO Bag l emission
levels with increasing heating/air-addition schemes. A 50
percent increase in HC and CO efficiency over no-heat/no-air
Garnet operation was provided by the 20/20 Bag 1 heating, 20 psi
air addition scheme.
Figure 3 depicts HC and CO levels in grams per mile over
the FTP for several configurations tested. Stock catalyst as
well as heat/no air and no-heat/air Camet configuration HC and
CO levels are included. Results from two other Camet
configurations representing increased resistive heating and air
addition are also included. The trend toward increasing HC and
CO efficiencies over the FTP with increased resistive
heating/air addition in Bag l is evident here.
B. 20°F Ambient Temperature Testing
The second phase of this evaluation of the resistively
heated metal monolith technology involved testing at lower
ambient temperature conditions. 20°F was chosen for this
temperature as it was the lowest temperature to which our cold
test cell could be reliably lowered to and maintained.
This testing was conducted over the FTP cycle. The
vehicle was driven over the LA-4 prep cycle prior to testing
and soaked overnight outside of the laboratory. Overnight soak
temperatures ranged between 30°-40°F. Prior to testing the
vehicle was placed in the cold test cell and force-cooled to
20 °F. Coolant and oil sump temperatures were monitored to
determine 20°F vehicle engine temperature.
The catalyst was evaluated in four different operating
modes. First, the converter was tested in an ordinary
three-way catalyst configuration; no resistive heating was
applied nor was extra air added in front of the catalyst during
this testing. The catalyst was then resistively heated during
Bags 1 and 3 without additional air. The catalyst was
preheated for 10 seconds prior to cold start in Bag 1;
resistive heating continued for 30 seconds following cold
start. No resistive heating was applied during Bag 2.
Resistive heating was applied for 5 seconds prior to hot start
in Bag 3; heating continued for 20 seconds following hot start.
Two different resistive heating/oxidation catalyst
simulation strategies were evaluated. The first strategy
involved the same heating scheme as given above; air at 30 psi
was added in front of the catalyst during the simultaneous
resistive heating/engine running portions of Bags 1 and 3. The
second strategy involved increasing the post-start resistive
heating period in Bag 1 to 50 seconds. Air at 30 psi was added
during the resistive heating/engine running portions of Bags 1
and 3.
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Emission results from the Bag 1 and 3 portions of this
testing are given in grams in Tables 3 and 4, while Table 5
presents weighted emission level averages over the FTP.
The effect, of the difference in catalyst light-off times
between Bags 1 and 3 for a typical three-way catalyst at 20°F
is underscored by the no heat/no air configuration test results
in Tables 3 and 4. HC emissions during Bag 1 were roughly 30
times higher than levels under hot start Bag 3 conditions. CO
level differences were even more profound; Bag 1 CO levels were
approximately 100 times greater than those from Bag 3. A
comparison of Bag 3 HC and CO levels from Table C-l in Appendix
C (72-74°F testing) and Table 4 (20°F) indicate that the
catalyst was operating with similar efficiencies over this
portion of the FTP under those widely different ambient
temperature conditions. Clearly, a strategy to substantially
lower FTP emissions of HC and CO at 20°F ambient conditions
would have to lower these emissions during cold start and
catalyst warm up.
Heating the catalyst without the addition of bottled air
did not lower emissions of HC and CO over the FTP at 20°F. The
catalyst was preheated for 10 seconds prior to engine start and
for 30 seconds following start during Bag 1. Table 3 shows
that average HC and CO emissions over Bag 1 were not reduced by
resistive heating. NOx levels over Bag 1 were relatively
unaffected by the resistive heating. Bag 3 HC and CO emission
levels were unaffected by resistive heating. Weighted FTP
average emissions for HC and CO were also unchanged or slightly
higher than those from no heat/no air mode testing. Though
only a very minimum number of tests were conducted, resistive
heating during an early part of Bag 1 without the addition of
excess air appeared to provide very little emissions benefit
over the no heat/no air configuration.
The use of resistive heating and the simultaneous addition
of excess air appeared to cause a slight reduction in emissions
of HC and CO. When air at 30 psi (2.4 SCFM) was added during
catalyst heating/engine operation HC and CO levels fell to 7.81
and 175.6 grams, respectively, over Bag 1; this compares to
8.58 and 190.5 grams, respectively, for the no heat/no air
configuration. This represents an almost 9 percent increase in
both HC and CO efficiency over Bag 1. Weighted FTP
efficiencies increased by over 7 percent for both HC and CO
through the use of this heating/air addition strategy.
Increasing the amount of time the catalyst was resistively
heated during Bag l while adding air at 30 psi during the
simultaneous heating/engine running period was then evaluated.
The Bag 1 preheat time was kept at 10 seconds; the time that
the catalyst was resistively heated after cold start was
increased to 50 seconds, an increase from the 30 second heating
time of the previous configuration.
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Table 3
Average Mass of Emissions
20 °F Testing, Bag 1 of FTP Cycle
Camet Configuration
No heat, no air
Heat 10/30, no air
Heat 10/30, 30 psi air
Heat 10/50, 30 psi air
Bag 3
20
Camet Configuration
No heat, no air
Heat 10/30, no air
Heat 10/30, 30 psi air
HC CO
(g) (q)
8.58 190.5
8.89 191.7
7.81 175.6
8.73 192.2
Table 4
of FTP Cycle
°F Testing
HC CO
(q) (q)
0.26 1.8
0.29 1.8
0.26 1.7
Table 5
C02
(g)
1370.
1340.
1375.
1350.
C02
(g)
1166.
1149.
1140.
NOx
(q)
1.15
1.18
1.80
1.70
NOx
(g)
1.73
2.37
2.28
Emission Levels Over the FTP Cycle
20
Camet Configuration
No heat, no air
Heat 10/30 Bag 1,
°F Testing
HC CO
(g/mi) (g/mi)
0.525 11.19
0.574 11.31
C02
( q/mi )
351.
351.
NOx
(g/mi)
0.47
0.73
5/20 Bag 3, no air
Heat 10/30 Bag 1,
5/20 Bag 3, 30 psi air
Heat 10/50 Bag 1,
5/20 Bag 3, 30 psi air
0.487
0.540
10.36
11.37
355.
344.
0.69
0.75
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-13-
The increased heating did not lower HC and CO emissions
below levels from the previously tested configuration. HC and
CO weighted FTP average emissions were essentially unchanged
from levels with the Camet catalyst in the no heat/no air
mode. HC and CO emissions over Bags 1 and 3 were also
unchanged from levels measured with the no heat/no air
configuration.
CO by percent in undiluted exhaust (ahead of the CVS) was
continuously monitored during the Bag 1 portion of the tests,
which utilized the 10/50 heating scheme and addition of air
over the catalyst at 30 psi. CO was measured at 9 percent of
undiluted exhaust .during the 3 minutes of Bag 1 at 20°F ambient
conditions. CO concentration dropped to approximately 6
percent during the period of 180 to 240 seconds into a test;
after approximately 4 minutes of engine operation, CO levels
dropped sharply to stable value much less than 1 percent. The
level did not change after that time.
We also attempted to- measure midbed catalyst gas
temperature during this testing. The thermocouples used
invariably made contact with the resistively heated walls
shortly after commencing the test; the data collected was very
unreliable as a result.
The amount of power necessary to bring a stream of raw
exhaust from an engine soaked and operated at 20°F conditions
to catalyst-active temperature shortly after cold start has
been calculated to be possibly greater than 10,000 watts.[7]
The Camet catalyst is capable of delivering approximately 2200
watts in its present configuration. A rather large shortfall
between power required and power supplied, at these ambient
conditions, is obvious.
A refinement of the catalyst heating scheme/excess air
addition scheme may be required in order to obtain substantial
HC and CO emissions reduction at 20°F ambient conditions. HC
and CO levels were substantially reduced by catalyst resistive
heating/air addition from no heat/no air catalyst configuration
levels at 72-74°F conditions. At 20°F, however, the resistive
heating may not transfer sufficient heat quickly enough to
bring boundary layer gases to catalyst active temperatures.
This resistive heating may be wasted by heating exhaust gas to
catalyst inactive temperatures during the relatively short
residence time in the converter. The warmed, but yet
chemically unconverted exhaust gas may have been passed to the
atmosphere in its unconverted state during the approximately 50
seconds of resistive heating following cold start.
The CO data collected during this testing suggests that CO
levels remain very high for the first 4 minutes of Bag 1 at
20°F ambient conditions. Any reduction of CO levels during
this 4 minute period could substantially reduce weighted FTP CO
emissions. More carefully controlled testing may determine the
-------
-14-
catalyst temperature at which resistive heating and the
addition of excess air would provide optimum HC and CO
emissions benefit, given the present resistive heating hardware
and a similar sized catalyst. Resistive heating would be
catalyst gas temperature controlled; heating may not commence
prior to vehicle start, as was the case in the evaluation
reported on here.
Another variable not addressed here was the location of
the catalyst in the exhaust stream. The present evaluation
used an underfloor catalyst location; catalyst performance at
20 °F ambient conditions might have been better if it was
located closer to the engine.
VIII.Highlights From Testing
The Garnet catalyst-equipped vehicle in the no-heat/no-air
mode had lower HC and CO emission levels over the FTP than the
stock catalyst that the vehicle was originally equipped with.
NOx levels over the FTP were higher than stock catalyst levels;
this may be due to the difference in the composition of the
actual noble metals used between these two catalytic
converters, however.
Resistively heating the Camet catalyst without the
addition of excess air did not substantially lower HC and CO
below no-heat/no-air catalyst levels. Addition of air in the
absence of resistive heating also did not lower HC and CO
emissions below no-heat/no-air configuration levels.
The simultaneous use of resistive heating and the addition
of excess air in front of the catalyst caused a decrease in HC
and CO from the no-heat/no-air strategy test. HC and CO were
reduced to 0.043 and 0.57 grams per mile respectively, with the
most efficient strategy tested. This strategy consisted of
preheating the catalyst for 20 seconds prior to Bag l cold
start and heating for 20 seconds following cold start;
preheating for 10 seconds prior to hot start and heating for 15
seconds following hot start in Bag 3. Air at 20 psi (2.0 SCFM)
was added in front of the catalyst during resistive-heating/
engine-running conditions. Emissions benefits from resistively
heating the catalyst and two resistive heating/excess air
addition strategies were not observed at 20°F ambient
c ond i t i ons, however.
IX. Acknowledgements
The catalyst used in this test program was supplied by
Camet, located in Hiram. OH. Camet is a manufacturer and sales
agent for W. R. Grace and Company. The test vehicle used in
this program was supplied by Volkswagen of America.
-------
-15-
The author thanks Ernestine Bulifant, Robert Moss, and
Stephen Halfyard of the Test and Evaluation Branch (TEB),
Emission Control Technology Division (ECTD), who conducted the
driving cycle tests at 72 °F and prepared the formaldehyde
samples for analysis. The author also recognizes the efforts
of James Garvey and Rodney Branham, also of TEB, who conducted
the driving cycle tests at 20°F. The efforts of Jennifer Criss
and Marilyn Alff of the Control Technology and Applications
Branch (CTAB), ECTD, who typed this report are also greatly
appreciated.
-------
-16-
X. References
1. 1975 Federal Test Procedure, Code of Federal
Regulations, Title 40, Part 86, Appendix I(a), Urban
Dynamometer Driving Schedule.
2. "Evaluation Of A Resistively Heated Metal Monolith
Catalytic Converter On An M100 Neat Methanol-Fueled Vehicle,"
Piotrowski, G. K., and D. M. Blair, EPA/AA/CTAB/88-09, August,
1988.
3. "Emission Regulations for 1977 and Later Model Year
New Light-Duty Vehicles and New Light-Duty Trucks; Test
Procedures," Code of Federal Regulations, Title 40, Part 86,
Subpart B.
4. "Vehicle Emissions - Summer to Winter," Ashby, H.
A., R. C. Stahman, B. H. Eccleston, and R. W. Hurn, SAE Paper
741053, 1974.
5. "Impact of Low Ambient Temperature on 3-Way Catalyst
Car Emissions," Braddock, J. N., SAE Paper 810280, 1981.
6. "Formaldehyde Measurement In Vehicle Exhaust a>t
MVEL, Memorandum, Gilkey, R. L., OAR, OMS, EOD, Ann Arbor, MI,
1981.
7. "Energy Requirements to Bring Low Temperature
Exhaust To Catalyst Light-Off Conditions," Memorandum,
Piotrowski, G. K., OAR, OMS, ECTD, Ann Arbor, MI, December 1988.
-------
A-l
APPENDIX A
CAMET RESISTIVELY HEATED CATALYTIC CONVERTER
SPECIFICATIONS AND POWER REQUIREMENTS
Construction
Dual-bed element composed of
two metal monolith catalysts,
a smaller resistively
heatable one and a larger one
with no provisions for
resistive heating
Catalyst material/loadings Proprietary
Shape
Rectangular
Overall outer dimensions
(excluding mounting flanges)
10-3/4" x 4-1/4" x 2-3/4"
Length: flange to flange
14-3/4"
Heated brick dimensions
3" x 4-1/4" x 2-3/4" (approx)
Unheated brick dimensions
4" x 4-1/4" x 2-3/4" (approx)
Power supply
12-volt automotive battery
Power delivered
300-400 amps at 10-11 volts
Heatup time to 600°F
with no gas flow through
the converter
Less than 20 seconds from 70°F
-------
B-l
APPENDIX B
TEST VEHICLE SPECIFICATIONS
Vehicle Type
1987 Volkswagen Golf
Fuel
Indolene clear
Engine:
Displacement
Bore
Stroke
Compression ratio
Maximum output SAE net
1.78 liter
8.10 cm
8.64 cm
9.0 to 1
85 hp at 5250 rpm
Fuel System
Continuous injection system
(fuel injection) with Lambda
feedback control, electric
fuel pump
Transmission:
Type
Torque converter stall
torque ratio
Hydrodynamic torque converter
and planetary gearing with
three forward and one reverse
gear
2.50
Torque converter stall speed 2400-2600 rpm
Gear ratios;
1
2
3
Axle
2.71
1.50
1.00
3.41
Curb weight
2340 Ibs
Equivalent test weight
2500 Ibs
-------
APPENDIX C
AVERAGE MASS OF EMISSIONS -
BAG 3 OF FTP CYCLE
72-74°F AMBIENT CONDITION TESTING
-------
01
Table C-l
Average Mass of Emissions
Bag 3 of FTP Cycle 72-74T Testing
Catalyst Configuration
Baseline (no catalyst)
Stock
Camet
Camet
Camet
Camet
Camet
Camet
Camet
Camet
catalyst
no heat, no air
heat 5/15, no air
no heat, 30 psi air
heat 5/15, 6 psi air
heat 5/15, 12 psi air
heat 10/15, 12 psi air
heat 10/15, 20 psi air
heat 10/15, 30 psi air
HC
Jg)
3
0
0
0
0
0
0
0
0
0
.34
.35
.21
.19
.18
.17
.17
.16
.16
.15
NMHC
(g)
3
0
0
0
0
0
0
0
0
.20
.25
.16
.14
.12
.12
.12
.11
.11
N/A
CO
_(_q)
34
4
1
1
1
1
1
1
1
1
.09
.67
.64
.87
.42
.71
.69
.49
.50
.50
C02
(q)
1131.
1280.
1171.
1181.
1184.
1160.
1162.
1144.
1146.
1149.
NOx
(q)
14
0
2
1
2
2
2
1
2
1
.96
.82
.00
.18
.04
.39
.00
.99
.01
.98
Aldy.
(mg)
134.
12.
3.
6.
6.
8.
9.
5.
N/A
3.
N/A Not available.
-------
APPENDIX D
INDIVIDUAL FTP RESULTS -
72-74°F AMBIENT CONDITION TESTING
-------
Test Number/Type
885190/baseline (no catalyst)
890124/baseline (no catalyst)
884951/stock catalyst
884952/stock catalyst
885191/Camet, no heat, no air
885546/Camet, no heat, no air
885192/Camet, heat
10/20 Bag 1, 5/15 Bag 3,
no air
885193/Camet, heat
10/20 Bag 1, 5/15 Bag 3,
no air
885245/Camet, heat
10/20 Bag 1, 5/15 Bag 3,
no air
890787/Camet, heat
10/20 Bag 1. 5/15 Bag 3,
no air
890969/Camet, heat
10/20 Bag 1, 5/15 Bag 3,
no air
885349/Camet, heat 10/20
Bag 1, 5/15 Bag 3, 6 psi air
885350/Camet, heat
10/20 Bag 1, 5/15 Bag 3,
6 psi air
885351/Camet, heat
10/20 Bag 1, 5/15 Bag 3,
12 psi air
D-l
Table D-l
Individual FTP Test Results
VW Golf Vehicle
HC NMHC CO C02 NOx Aldy.
(g/mi) (q/mi) (g/mi) (q/mi) (q/mi) (mq/tni)
1.02 0.98 10.65 346. 3.73 42.0
1.05 1.00 14.02 349. 3.23 39.7
0.10 0.08 1.63 377. 0.20 4.3
0.10 0.08 1.62 374. 0.19 5.5
0.087 0.073 1.12 357. 0.68 1.4
0.067 0.052 1.00 350. 0.76 1.2
0.070 0.057 0.99 349. 0.81 1.6
0.082 0.068 1.17 358. 0.61 1.3
0.063 0.051 1.02 355. 0.53 1.4
0.070 0.056 1.11 354. 0.61 2.3
0.071 0.056 1.13 365. 0.57 2.6
0.060 0.045 0.82 348. 0.86 2.1
0.056 0.042 0.84 349. 0.69 1.4
0.057 0.043 0.76 351. 0.67 3.8
-------
D-2
Table D-l (cont'd)
Individual FTP Test Results
VW Golf Vehicle
Test Number/Type
885389/Camet, heat
20/20 Bag 1, 10/15 Bag 3,
12 psi air
885400/Camet, heat
20/20 Bag 1, 10/15 Bag 3,
12 psi air
885401/Camet, heat
20/20 Bag 1, 10/15 Bag 3,
20 psi air
885402/Camet, heat
20/20 Bag 1, 10/15 Bag 3,
30 psi air
885403/Camet, no heat,
30 psi air
885545/Camet, no heat,
30 psi air
HC NMHC CO C02 NOx Aldy.
(g/mi) (g/mi) (g/mi) (g/mi) (g/mi) (mg/mi)
0.049 0.034 0.63 346. 0.66 1.3
0.047 0.032 0.66 347. 0.66 N/A
0.043 0.029 0.57 343. 0.67 1.6
0.049 NA 0.56 346. 0.66 1.1
0.071 0.056 1.07 354. 0.71 2.2
0.071 0.055 1.00 356. 0.68 1.3
-------
APPENDIX E
INDIVIDUAL FTP RESULTS -
LOWER AMBIENT TEMPERATURE EVALUATION
-------
E-l
Table E-l
Individual FTP Test Results
Garnet Catalyst - 20°F Ambient Conditions
HC CO C02 NOx
Test Number/Type (g/mi) (g/mi) (g/mi) (g/mi)
890125, no heat, no air 0.525 11.19 351. 0.47
890126, Heat 0.576 11.56 352. 0.63
10/30 Bag 1, 5/20 Bag 3,
no air
890127, Heat 0.572 11.05 349. 0.83
10/30 Bag 1, 5/20 Bag 3,
no air
890128, Heat 0.478 10.62 355. 0.74
10/30 Bag 1, 5/20 Bag 3,
30 psi air
890636, Heat 0.495 10.09 355. 0.64'
10/30 Bag 1, 5/20 Bag 3,
30 psi air
890781, Heat 0.527 10.80 337. 0.73
10/50 Bag 1, 5/20 Bag 3,
30 psi air
890782, Heat 0.552 11.86 350. 0.76
10/50 Bag 1, 5/20 Bag 3,
30 psi heat
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