Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
10~;'6959
BACKGROUND
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Cyclopentadienyl maganese compounds are excellent
antiknocks in gasoline used to operate spark ignited internal
combustion engines. Use of such compounds as antiknocks is
described in U.S. 2,818,417 (Brown et al) issued December 31,
1957; U.S. 2,839,552 (Shapiro et al) issued June 17, 1958
and U.S. 3,127,351 (Brown et al~issued March 31, 1964. Not only
are these compounds effective antiknock agents, but it has also
been found that they do not adversely affect the activity of
;~ 10 catalysts used to decrease the amount of undesirable constituents
in engine exhaust gas. Under some operating conditions it has
been found that, although the manganese antiknocks do not
lessen the activity of the exhaust gas catalyst, they can inter-
act in some manner at the surface of the catalyst bed leading to
a reduction in the size of the openings into the bed thereby
causing an increase in exhaust back pressure. The present
invention provides a simple effective means of alleviating this
problem.
SUMMARY
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,~ 20 Broadly speaking, the present invention provides
a method of preventing the early plugging of an exhaust gas
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catalyst being used in an exhaust system of an internal
combustion engine at a location where the temperature of the
exhaust gas initially contacting the catalyst exceeds about
` 1000F. during normal engine cruise conditions, the catalyst
being used to lower the amount of undesirable constituents in
the exhaust gas from an internal combustion engine operating
on a liquid hydrocarbon fuel containing a cyclopentadienyl manganese
antiknock compound, the method comprising passing the
exhaust gas through a conduit section containing a sexies of
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baffles, each of the baffles having at least one large opening
through which exhaust gas can pass, the openings being arranged
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such that the openings in one baffle are not substantially
in.axial alignment with the openings in an adjacent baffle, the
space between each baffle being empty, the baffles forming an
unimpeded tortuous flow path, and then passing the exhaust gas
into a catalytic reactor containing the catalyst whereby the
exhaust gas passes through the catalyst, the baffles functioning
to inhibit the plugging of the catalyst by manganese
compounds in the exhaust gas.
The above method may be carried out in an exhaust
system for an internal combustion engine, the exhaust system
including a catalytic reactor at a location where inlet exhaust
temperature exceeds about 1000F. during normal engine cruise
conditions, the catalytic reactor being defined by a reactor
' housing having an inlet and an outlet and having a catalyst
. bed disposed between the inlet and the outlet, the space
;: between the inlet and the entry face of the catalyst form.ing an
expansion zone wherein the exhaust flow cross-section e.xpands
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from the cross-sectional area of the inlet to the surface area
of the entry face, the inlet being operatively connected by
exhaust conduit means to the exhaust outlet of the engine,
the catalyst comprising a catalytic metal supported on a honey-
. comb monolithic ceramic support which is prone to plugging when
'~ the engine is operated on gasoline containing a cyclopentadienyl
manganese antiknock, the improvement comprising a plurality of
transverse baffles located in the exhaust conduit means upstream ~.
from and proximate to the inlet, each of the baffles having at
least one large opening through.which exhaust gas can pass, the
openings being arxanged such that the openings in one baffle
are not substantially in axial alignment with the openings
30 in an adjacent baffle, the space between the baffles being empty,the baffles forming an unimpeded tortuous flow path and function-
: ing to inhibit the plugging of the catalyst by manganese
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compounds in the exhaust gas.
Furthermore, the present invention provides a
catalytic reactor resistant to plu~ging when used in the
exhaust system of an internal combustion engine operating on
gasoline containing a cyclopentadienyl manganese antiknock
; compound, the catalytic reactor comprising a reactor housing
having an inlet and an outlet and containing a catalyst bed
between the inlet and the outlet such that the exhaust gas
passes through the catalyst bed in passing from the inlet
to the outlet, the inlet having a cross-sectional area
substantially less than the area of the entry face of the
catalyst, the housing having an expansion zone between the
inlet and the entry face, the reactor including a conduit
section connected to the inlet extending away from the expansion
zone, the conduit section containing a plurality of transverse
baffles, each of the baffles having at least one large opening
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~ through which exhaust gas can pass, the openings being arranged
.. . .
such that the openings in one baffle are not substantially in
axial alignment with the openings in an adjacent baffle, the
space between each baffle being empty, the baffles forming an
; unimpeded tortuous flow path through the conduit section, the
~; baffles functioning to inhibit the plugging of the catalyst
bed by manganese compounds in the exhaust gas.
: DESCRIPTION OF l~HE DRAWINGS
Figure 1 is a longitudinal cross-section of a
catalytic exhaust reactor having a baffle unit connected to its
inlet.
Figure 2 is a plan view of each of the baffle disks
taken from the baffle unit of Figure 1.
Figure 3 is a plan vie~ of an optional set of baffle disks
suitable for use in the baffle unit of Figure 1.
Figure 4 is a plan view of another optional set of
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baffle disks suitable for use in the baffle unit of Figure 1.
: Figure 5 is a longitudinal cross-section of a
catalytic exhaust reactor having baffle disks located in its
inlet plenum.
Figure 6 is a plan view of the baffle disks taken from
the inlet plenum of Figure 5.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
j: A preferred embodiment of the invention is an exhaust
1 system for a spark ignited internal combustion engine comprising
; 10 a ca-talytic exhaust reactor connected to the exhaust outlet of
; the engine and including a plurality of baffles in the exhaust
~, flow path between the catalyst bed and the engine. The baffles
are arranged transverse to the direction of exhaust flow and
~' form a tortuous flow path.
The essential elements of such a system are shown
;. in Figure 1. Catalytic reactor 1 is formed by enlarged
~,' cylindrical-frustoconical housing 2 having inlet 3 and outlet
, 4. Located within housing 2 is catalyst bed 5 which, in this
embodiment, is
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a honeycomb alumina-magnesia-silica monolithic ceramic supported
platinum catalyst as described in U.S. Patent 3,441,381.
Connected to inlet 3 is baffle unit 6 comprising
tubular housing 7 containing baffle disks 9, 10, 11 and 12.
These disks can be welded to the inside of housing 7 or held
in place by any equivalent means. They are preferably but not
necessarily spaced about 1/4" - 2" apart, and more preferably
about 1/4" - 1/2" apart. Each baffle disk can be seen to
have openings of various shapes which when installed in
housing 7 are not in substantial alignment with the openings
in an adjacent disk and thus form a tortuous flow path through -
housing 7. In other words, when the exhaust gas passes
through an opening in the first element it encounters a sur-
face on the second element, causing it to abruptly change
lS directions and flow to openings in the second element. After
passing through openings in the second element, it again en-
counters a surface of the third element, again causing it
to change directions to seek the openings in the third
~ element, etc. As shown, disks 9, 10, 11 and 12 also contain
- 20 small perforations in their "non-opening" surface, which has
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been found to give good results.
Disk baffles 9A, lOA, llA and 12A of Figure 3, or
- 9B, lOB, llB and 12B of Figure 4, can optionally be substituted
for disks 9, 10, 11 and 12.
Baffle unit 6 is connected by pipe 15 to the ex-
haust outlet of an internal combustion engine (not shown) and
is adapted to conduct hot exhaust gas from the engine to baffle
unit 6 from which it proceeds directly into catalytic reactor 1.
In order to obtain rapid warm-up required for
catalyst activation, the catalytic reactor is preferably
located proximate
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to the engine exhaust outlet. In some embodiments catalytic
; reactor 1 is connected through baffle unit 6 directly to the
!~; engine exhaust manifold outlet. In fact, baffle unit 6 can be
constructed as part of the internal structure of the exhaust
~ manifold thereby permitting direct connection of catalytic
: reactor 1 to the manifold outlet.
; ` As mentioned above, the catalytic reactor is
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~ preferably, but not necessarily, proximate to the engine.
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~- By "proximate" is meant that it is close enough such that
- 10 the catalyst bed is rapidly heated to "light-off" or
activation temperature. The exhaust gas temperature required
~ to accomplish this is dependent upon the nature of the
; catalyst. Noble metal catalysts or those containing at leasi
some noble metal light-off at much lower exhaust temperatures,
e.g., 350-500F. However, in order to insure early light-off,
the catalytic reactor is preferably located such that the
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S, inlet exhaust temperature is above about 1000F., and more
;~ preferably above about 1400F., during normal engine cruise
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~, conditions. It is also under these conditions that the
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` 20 cyclopentadienyl manganese antiknocks are most likely to plug
the catalyst and, hence, it is under these preferred
conditions that the present invention is most useful.
- The exhaust system of this invention is useful in
both chemical oxidation and reduction applications of
:- catalytic exhaust reactors. When reduction of nitrogen oxides
is desired the engine is operated slightly rich ~e,g., below
14/1 air/fuel ratio) without employing air injection. When
oxidation of hydrocarbons and carbon monoxide is desired the
oxygen content of the exhaust gas is increased by either
- 30 operating lean (e.g., above 15/1 air/fuel ratio) or by
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injecting air into the exhaust gas, or both. The present
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` invention is most useful when used in exhaust gas oxidation.,`. , .
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applications,although it is by no means limited to this,
As stated above, the embodiment being discussed uses
a honeycomb monolithic ceramic supported platinum catalyst as
described in U.S. 3,441,381. These are made by coating a
corrugated ceramic structure such as described in U.S.
3,444,925 with a~ activated alumina (e g., gamma-alumina) and ;
a platlnum compound. The preferred ceramics are made accord-
ing to U.S. 3,444,925 using alumina-silica (e.g., mullite,
3Al203 2SiO2), magnesia-alumina-silica (e.g., cordierite,
2MgO 2A12O3-5SiO2), or mixtures thereof. Palladium can be
used in place of platinum, and since these elements generally
occur in nature together, it is sometimes preferred to use
mixtures of platinum and palladium.
The invention is not limited to honeycomb monolithic
ceramic supported platinum or palladium catalysts, Examples
of other catalytic metals include V, Cr, Mn, Fe, Co, Ni, Cu,
zn, Zr, Nb, I~, Ru~ Rh, Ag~ W~ Re, Os~ Ir~ Pb, Ba( and the like~
These are generally used in an oxide form. They may be used
individually or in various combinations such as Cu-Cr, Cu-Cr-V,
Cu-Pd, Mn-Pd, Ni-Cr, and the like. They may be supported on
the above monolithic ceramic support or on any other of
numerous well-known catalyst supports such as granular,
pelletized or extruded alumina, silica, silica-alumina,
` zirconia, magnesia, alumina-magnesia, and the like. Such
catalysts are disclosed in U,S. 3,540,838; 3,524,721;
3,447,893; 3,433,581; 3,428,573; 3,425,792; 3,374,183;
3,271,324; 3,224,981; 3,224,831 and 3,207,704.
In operation, exhaust gas from the engine is
conducted by pipe 15 to baffle unit 6 On passing through
housing 7 the exhaust gas encounters baffle disks 9, 10, ll
and 12. Openings in these disks are arranged such that
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the exhaust gas after passing through the openings in one disk
is forced to abruptly change direction prior to passing
th:rough an opening in a subsequent disk -- in other words, the
openings in the disks are arranged to form a tortuous path
through the baffle unit.
Other disks such as 9A-12A or 9B-12B can be used in
, ~ baffle unit 6 to form the tortuous path. The invention is not
limited to the precise shape of the disks as long as they are
arranged to form the required tortuous path.
: 10 . After passing through baffle unit 6, the exhaust
~ gas enters catalytic reactor 1 at inlet 3 and then enters
.- catalyst bed 5. After traversing catalyst bed 5 wherein the
amount of undesirable constituents are lowered, the exhaust
: gas leaves catalyst reactor 1 at outlet 4 and is conducted
; by exhaust pipe 8 to a suitable exhaust location,
In the embodiment of Figure 5 the baffle disks are
, located within the catalytic reactor. Catalytic reactor 20
is formed by reactor housing 21 having inlet 22 and outlet 23,
Located within housing 21 is catalyst bed 24 forming frusto-
~ 20 conical inlet plenum 25 between catalyst bed 24 and inlet 22,
. Baffle disks 26, 27, 28, 29 and 30 are positioned in plenum
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~:: 25 transverse to its longitudinal axis and are attached to the
~:- inside of housing 21 by any suitable means such as welding,
Baffle disks 27-30 have a multitude of small perforations,
Disks 26-30 have openings arranged such that the openings in
: one disk are for the most part not axially in line with the
: openings in the subsequent disk, Inlet 22 is connected by
:~ pipe 31 to the exhaust outlet of the engine (not shown) and
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~:. outlet 23 connects through pipe 32 to a suitable exhaust area~
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In operation, hot exhaust gas from the engine
passes through pipe 31 to inlet 22 and enters inlet plenum
25 where it encounters baffle disks 26-30. The great
majority of the exhaust gas passes through the large openings
in the baffle disks and is thus forced to follow a tortuous
path prior to reaching catalyst bed 24, The exhaust gas
then passes through cataly~t bed 24 and leaves catalytic
reactor 20 at outlet 23 from where it is conducted by pipe
32 to an exhaust area.
As stated previously, it is generally desirable to
have the catalytic reactor close to the engine to insure early
light-off. In one embodiment inlet 22 of catalytic reactor '
20 is connected directly to the outlet of the engine exhaust
manifold
It is not clear exactly how the invention functions
to reduce catalyst plugging by cyclopentadienyl manganese
antiknocks, but tests have been conducted which show that it
is highly effective in accomplishing this objective These
tests were made using a single cylinder 36 CID engine
operating on gasoline containing one gram of manganese per
gallon as methylcyclopentadienyl manganese tricarbonyl,
Air/fuel ratio was adjusted to approximately 16/1 to obtain
1.8 per cent oxygen in the exhaust. The engine was
continuously operated at wide open throttle and the exhaust
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gas conducted to a catalytic reactor of the type shown in
Figure 1 containing a honeycomb monolithic ceramic supported
platinum catalyst (Engelhard Industries, Inc., PTX-313)
The exhaust temperature at the catalyst inlet was about
1500F. in all tests. Exhaust back pressure was measured to
~` 30 determine degree of catalyst plugging. Initial back pressure
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was about 0.3 psig. An increase to 2 psig was considered a
plugged catalyst bed. Results obtained compared to a no
baffle control are shown in the following table.
Hours to Plu~ging
control 45
3 baffles in inlet plenuml 174
3 baffles ahead of inlet2 360
l. Similar to Figure 5
2. As in Figure l
As the results show, the present invention is highly
effective in alleviating the catalyst plugging problem
associated with use of exhaust gas catalysts in engines
operating on fuel containing a manganese antiknock.
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