U.S. patent application number 12/315645 was filed with the patent office on 2009-04-16 for method of treating atmospheric pollutants.
This patent application is currently assigned to Johnson Matthey Public Limited Company. Invention is credited to Martyn Vincent Twigg.
Application Number | 20090098034 12/315645 |
Document ID | / |
Family ID | 9914635 |
Filed Date | 2009-04-16 |
United States Patent
Application |
20090098034 |
Kind Code |
A1 |
Twigg; Martyn Vincent |
April 16, 2009 |
Method of treating atmospheric pollutants
Abstract
A method of reducing at least one atmospheric oxidising
pollutant, such as ozone, with a reducing agent comprises
contacting the reducing agent with the at least one atmospheric
oxidising pollutant, wherein the reducing agent comprises a
precious metal-free trap material, such as a zeolite, including at
least one trapped atmospheric reducing pollutant, e.g. a
hydrocarbon, whereby as the at least one atmospheric oxidising
pollutant is reduced the at least one trapped atmospheric reducing
pollutant is oxidised.
Inventors: |
Twigg; Martyn Vincent;
(Cambridge, GB) |
Correspondence
Address: |
RATNERPRESTIA
P.O. BOX 980
VALLEY FORGE
PA
19482
US
|
Assignee: |
Johnson Matthey Public Limited
Company
London
GB
|
Family ID: |
9914635 |
Appl. No.: |
12/315645 |
Filed: |
December 5, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10478037 |
May 12, 2004 |
7488456 |
|
|
PCT/GB02/02139 |
May 15, 2002 |
|
|
|
12315645 |
|
|
|
|
Current U.S.
Class: |
423/219 ;
423/210; 423/215.5; 423/235; 423/242.1; 423/245.1; 423/246 |
Current CPC
Class: |
B01D 53/60 20130101;
B01J 37/0246 20130101; B01J 37/0225 20130101; B01J 23/70 20130101;
Y02C 20/20 20130101; B01D 53/8675 20130101; B01D 53/8653 20130101;
B01J 23/80 20130101; B01D 53/66 20130101 |
Class at
Publication: |
423/219 ;
423/210; 423/245.1; 423/235; 423/242.1; 423/215.5; 423/246 |
International
Class: |
B01D 53/46 20060101
B01D053/46; B01D 53/54 20060101 B01D053/54; B01D 53/48 20060101
B01D053/48; B01D 53/50 20060101 B01D053/50; B01D 53/62 20060101
B01D053/62; B01D 53/56 20060101 B01D053/56; B01D 53/72 20060101
B01D053/72 |
Foreign Application Data
Date |
Code |
Application Number |
May 15, 2001 |
GB |
0111801.7 |
Claims
1. A method of treating atmospheric pollutants comprising
atmospheric oxidising pollutants and atmospheric reducing
pollutants, which method comprises: contacting a first reducing
agent with the at least one atmospheric oxidising pollutant wherein
the first reducing agent comprises a precious metal-free trap
material including at least one trapped atmospheric reducing
pollutant; and contacting the gas leaving the trap material with at
least one second agent for reducing at least one atmospheric
oxidising pollutant, whereby as the at least one atmospheric
oxidising pollutant is reduced, the at least one trapped
atmospheric reducing pollutant is oxidised.
2. A method according to claim 1, wherein the at least one
atmospheric reducing pollutant is selected from the group
consisting of an aliphatic or cyclic hydrocarbon, an alkane, a
paraffin, an olefin, an alkene, an alkyne, a dialkene, a conjugated
unsaturated hydrocarbons, a diene, a carboxylic acid, a peroxy
acid, a sulfonic acid, a partially oxygenated hydrocarbon, an
aldehyde, a conjugated aldehyde, a ketone, an ether, an alcohol, an
ester, an amide, an ammonium compounds, an aromatic hydrocarbon,
and a cycloparaffin.
3. A method according to claim 1, wherein the first reducing agent
is capable of reducing at least one atmospheric oxidising pollutant
from between ambient temperature and 110.degree. C.
4. A method according to claim 1, wherein the at least one
atmospheric oxidising pollutant is selected from the group
consisting of ozone (O.sub.3), nitrogen dioxide (NO.sub.2),
dinitrogen tetroxide (N.sub.2O.sub.4) and sulfur trioxide
(SO.sub.3).
5. A method according to claim 2, wherein the atmospheric reducing
pollutant comprises one or more nitrogen-, sulfur-, oxygen- or
phosphorus-atoms.
6. A method according to claim 2, wherein the atmospheric reducing
pollutant further comprises carbon monoxide, sulphur dioxide, or a
soot or a particulate matter component.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/478,037, filed May 12, 2004, which is a
U.S. National Phase application of PCT International Application
No. PCT/GB02/02139, filed May 15, 2002, and claims priority of
British Patent Application No. 0111801.7, filed May 15, 2001, all
of which are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a method of reducing at
least one atmospheric oxidising pollutant, such as ozone (O.sub.3)
or nitrogen dioxide (NO.sub.2), with a reducing agent and to an
apparatus for treating at least one atmospheric oxidising pollutant
and at least one atmospheric reducing pollutant, e.g. a
hydrocarbon.
BACKGROUND OF THE INVENTION
[0003] Ground-level O.sub.3, a component of smog, is created from
the reaction of nitrogen oxides (NOx) and hydrocarbons (HC), from
vehicle and industrial emissions. Aldehydes, organic species having
a relatively high Maximum Incremental Reactivity adjustment factor
(MIR) also known as carter factors (as defined by "Californian
Non-methane organic gases test procedures", The California
Environmental Protection Agency Air Resource Board dated Aug. 5,
1999), are also produced. Part of this reaction is catalysed by
sunlight and can be represented by two equations:
O.sub.2+RCH.sub.2CH.sub.3+NO.fwdarw.RCH.sub.2CHO+NO.sub.2; (i)
and
NO.sub.2+O.sub.2.fwdarw..sup.hvO.sub.3+NO. (ii)
Smog can cause asthma and respiratory ailments and is a particular
problem in the southern California basin, Los Angeles and Houston,
Tex. in the USA.
[0004] In WO 96/22146, Engelhard describes the concept of coating
an atmosphere-contacting surface of a vehicle with a composition
for treating one or more atmospheric pollutant, such as O.sub.3
alone, O.sub.3 and carbon monoxide (CO) or O.sub.3, CO and HC. The
surface is preferably that of a heat exchanger, such as a radiator
or air conditioner condenser, located within the vehicle's engine
compartment. As the vehicle is propelled through the atmosphere,
pollutants suspended in the atmosphere contact the composition and,
depending on the formulation of the composition, it catalyses the
reduction of the atmospheric oxidising pollutant O.sub.3 to oxygen,
and/or the oxidation of the atmospheric reducing pollutant carbon
monoxide to carbon dioxide and/or of HC to water and carbon
dioxide.
[0005] By "atmospheric oxidising pollutant" herein, we mean an
atmospheric pollutant that has the potential to oxidise other
atmospheric pollutants in a redox reaction. Examples of atmospheric
oxidising pollutants are O.sub.3, NO.sub.2, nitrogen tetroxide
(N.sub.2O.sub.4) and sulfur trioxide (SO.sub.3).
[0006] By "atmospheric reducing pollutant" herein, we mean an
atmospheric pollutant that has the potential to reduce other
atmospheric pollutants in a redox reaction. Non-limiting examples
of atmospheric reducing pollutants are hydrocarbons including
aliphatic hydrocarbons, e.g. alkanes, and cyclic hydrocarbons;
paraffins; olefins, alkenes and alkynes; dialkenes including
conjugated unsaturated hydrocarbons; carboxylic, peroxy or sulfonic
acids; partially oxygenated hydrocarbons including aldehydes,
conjugated aldehydes, ketones, ethers, alcohols and esters; amides;
ammonium compounds; aromatic hydrocarbons and cycloparaffins; any
of the above including one or more nitrogen-, sulphur-, oxygen- or
phosphorus-atoms; CO; sulphur dioxide and soot or particulate
matter components exhausted from, e.g. a power plant (as defined
hereinbelow).
[0007] Engelhard markets a vehicle radiator having a catalytic
coating for reducing O.sub.3 under the trade name PremAir.RTM..
Details of PremAir.RTM. can also be found on Engelhard's website at
www.Engelhard.com/premair. It is also described in its WO 96/22146.
We understand that the active material on the marketed radiators is
a manganese-based component, cryptomelane
(KMn.sub.8O.sub.16.xH.sub.2O, structurally related to
.alpha.-MnO.sub.2). Coated radiators have been fitted on certain
Volvo production passenger vehicles, e.g. the S80 luxury sedan in
USA and throughout Europe.
[0008] At page 12, lines 16-24 of WO 96/22146, it is stated:
"adsorption compositions can also be used to adsorb pollutants such
as hydrocarbons and/or particulate matter for later oxidation or
subsequent removal. Useful and preferred adsorption compositions
include zeolites, other molecular sieves, carbon . . . Hydrocarbons
and particulate matter can be adsorbed from 0.degree. C. to
110.degree. C. and subsequently treated by desorption followed by
catalytic reaction or incineration." Further details of "adsorption
compositions" are given at page 48, lines 13-37. There is no
Example in WO 96/22146 showing the ability of precious metal-free
adsorption compositions to treat a synthetic gas mixture including
both O.sub.3 and hydrocarbons without involving the destruction of
the adsorption component itself.
SUMMARY OF THE INVENTION
[0009] We have now found that a precious-metal free trap material
including at least one trapped atmospheric reducing pollutant can
reduce at least one atmospheric oxidising pollutant. Consequently,
the at least one trapped atmospheric reducing pollutant itself is
oxidised.
[0010] According to one aspect of the present invention, there is
provided a method of reducing at least one atmospheric oxidising
pollutant with a reducing agent, which method comprises contacting
the reducing agent with the at least one atmospheric oxidising
pollutant, wherein the reducing agent comprises a precious
metal-free trap material including at least one trapped atmospheric
reducing pollutant, whereby as the at least one atmospheric
oxidising pollutant is reduced the at least one trapped atmospheric
reducing pollutant is oxidised.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] In order that the invention may be more fully understood,
the invention will now be described by reference to the following
illustrative Examples and by reference to the accompanying
drawings, in which:
[0012] FIG. 1 is a schematic drawing showing three arrangements
according to a preferred embodiment of the apparatus according to
the present invention; and
[0013] FIG. 2 is a graph showing the amount of O.sub.3 detected in
the exhaust gas against time.
DETAILED DESCRIPTION OF THE INVENTION
[0014] The Penguin Dictionary of Chemistry, second edition (1990),
Ed. D.W.A. Sharp defines a "catalyst" as "A substance which when
added to a reaction mixture changes the rate of attainment of
equilibrium in the system formally without itself undergoing a
permanent change." It will be appreciated that the combination of a
trap material and at least one trapped atmospheric reducing
pollutant is not a "catalyst" as such since in reducing at least
one atmospheric oxidising pollutant, the at least one trapped
atmospheric reducing pollutant itself is oxidised. This mechanism
also differs from that described by Engelhard above in that the
combination of the at least one trapped atmospheric reducing
pollutant and the trap material causes both the reduction of the at
least one atmospheric oxidising pollutant and the oxidation of the
at least one trapped atmospheric reducing pollutant, whereas,
according to Engelhard, the HC is first desorbed before it is
oxidised.
[0015] By "precious-metal free" we mean the absence of a
catalytically active amount of a precious metal such as gold,
silver or any platinum group metal, e.g. platinum, palladium or
rhodium.
[0016] By "trapped", we mean adsorbed or absorbed including the
physical interaction of a trapped species with a trap material such
as by covalent bonding and ionic bonding and electrostatic bonding,
such as by van der Waals' forces or hydrogen bonding.
[0017] Due to the nature of the trap material, e.g. the presence of
"acidic" sites in certain zeolites, reactions of and between
trapped species can be promoted in situ usually resulting in the
formation of less volatile species, non-limiting examples of
reactions which include aldol condensation, oligomerisation and
partial fragmentation, e.g. of saturated HC, polymerisation and
coking. The term "trapped atmospheric reducing species" etc. is
intended to embrace trapped species and products of the in situ
reaction of trapped species.
[0018] One application for our observation is in treating
atmospheric O.sub.3 and HC contacted by a vehicle, although
non-mobile applications are equally viable, as will be explained
below.
[0019] Carbon is described in WO 96/22146 both as an alternative
pollutant treating catalyst composition (see page 44, first
paragraph, and patch #8 and #12 in Example 3 on pages 51-55) and an
adsorption component (see page 48, lines 25-30). Whilst it is
possible that the carbon may adsorb HC, we believe that any O.sub.3
contacting the HC adsorbed on the carbon will result in the
destruction of the carbon catalyst/adsorber itself according to the
equation C+HC+O.sub.3.fwdarw.CO.sub.2+H.sub.2O. This is in contrast
to the method of the present invention in which the trap material,
e.g. zeolite, is substantially inert.
[0020] An important feature of the present invention is that the
atmospheric reducing pollutant is trapped to react with the
atmospheric oxidising pollutant and not merely trapped to release
for reaction elsewhere, e.g. gas phase oxidation. It is also a
preferred feature of the method that the trap material is such that
the residence time of the atmospheric reducing pollutant on the
trap material is increased. This enables the nature of the trap
material to be "tuned" to trap particular atmospheric reducing
pollutants.
[0021] For the purposes of the present invention, "atmosphere" as
defined herein is the mass of air surrounding the earth, and
"atmospheric pollutant" etc. should be interpreted accordingly. For
the avoidance of doubt, the atmosphere is not comprised of any
atmospheric oxidising pollutant present in a gas exhausted from an
engine unless and until the gas exits to atmosphere an exhaust
system carrying it.
[0022] An advantage of the present invention is that one
atmospheric pollutant is used to destroy another with the result
that both atmospheric pollutants are converted to less polluting
species.
[0023] Moreover, the invention provides the advantage that the
atmospheric reducing pollutants that are more reactive, i.e. ones
that are more likely to react according to equation (i) above, are
selectively treated. More reactive atmospheric reducing pollutants
have relatively high MIR adjustment factors in the Table at
Appendix 1 of "Californian Non-methane organic gases test
procedures", The California Environmental Protection Agency Air
Resource Board dated Aug. 5, 1999, incorporated herein by
reference. Thus the more reactive species such as 1,3 butadiene,
1,2 propadiene, ethene and alkyl-substituted benzenes and
formaldehyde have relatively high MIR adjustment factors.
Generally, the more reactive the atmospheric reducing pollutant,
the more likely it is to be trapped on the trap material and
oxidised to CO.sub.2, H.sub.2O and/or an atmospheric reducing
pollutant having a lower MIR adjustment factor by combustion with
the O.sub.3.
[0024] In a preferred embodiment, the method of the invention
provides a further step of contacting the gas leaving the trap
material with at least one agent for reducing at least one
atmospheric oxidising pollutant. This additional step ensures that
when there is insufficient trapped atmospheric reducing pollutant
to reduce the at least one atmospheric oxidising pollutant, the
efficiency of the method according to this embodiment to reduce the
at least one atmospheric oxidising pollutant, e.g. O.sub.3, is
maintained.
[0025] According to a further aspect, the invention provides an
apparatus for treating at least one atmospheric oxidising pollutant
and at least one atmospheric reducing pollutant, which apparatus
comprises an atmosphere contacting surface, a precious metal-free
trap material supported on the surface, which trap material is
capable of trapping at least one atmospheric reducing pollutant,
and means for causing movement of the surface relative to the
atmosphere for contacting the supported trap material with at least
one atmospheric oxidising pollutant and at least one atmospheric
reducing pollutant, whereby the at least one atmospheric oxidising
pollutant is reduced by a combination of the trap material and the
at least one trapped atmospheric reducing pollutant, which at least
one trapped atmospheric reducing pollutant is consequently
oxidised.
[0026] For the avoidance of doubt, the surface can be a stationary
part in a moving air stream or a moving part in a still atmosphere,
provided that in either case a movement causing means causes the
movement of air relative to the surface.
[0027] An advantage of this aspect of the present invention is that
no expensive precious metal catalytic material is required in
addition to the trap material and trapped atmospheric reducing
component to treat the at least one atmospheric oxidising
component. Thus, the present invention renders possible the
treatment of, for example, O.sub.3 and HC without using expensive
catalyst materials such as platinum group metals, e.g.
platinum.
[0028] The trap material can be any material that traps at least
one atmospheric reducing pollutant. Examples of trap materials
include high surface area inorganic species such as zeolites, other
molecular sieves, crystalline silicates, crystalline
silicate-containing species, aluminas, silicas, (optionally
amorphous) aluminosilicates, layered clays and aluminium
phosphates. Where the trap material is zeolite, we prefer
beta-zeolite or zeolite Y and most preferably ZSM-5, optionally
metal-substituted, so long as the metal substituted zeolite does
not decompose O.sub.3 per se, e.g. the zeolite is not transition
metal substituted.
[0029] The percent conversion of atmospheric oxidising and reducing
pollutants depends on the temperature and space velocity of the
atmospheric air relative to the atmosphere-contacting surface and
the temperature of the atmosphere contacting surface. An advantage
of the present invention is that relatively large volumes of
atmospheric air can be treated at relatively low temperatures. An
indication of the amount of air being treated as it passes the trap
material is commonly referred to as the space velocity. This is
measured as the volume of air per hour which passes across the
volume of the trap material and is measured in e.g. litres per hour
of air divided by the litres of trap material. That is, the units
are reciprocal hours. Space velocities encountered by a radiator
mounted in an engine compartment at typical driving speeds of up to
100 mph can range from 0 to 1,000,000 hr.sup.-1, e.g. 300,000 to
650,000 hr.sup.-1 or 400,000 to 500,000 hr.sup.-1.
[0030] In a preferred embodiment, the means for causing movement of
the surface relative to the atmosphere is a power plant. The power
plant can be a motor fuelled by gasoline or diesel or alternative
fuels such as liquid petroleum gas, natural gas, methanol, ethanol
or methane or mixtures of any two or more thereof. Alternatively,
the power plant can be an electric cell, a solar cell or a
hydrocarbon or hydrogen-powered fuel cell.
[0031] Preferably the support surface is on or in a vehicle, and
the movement-causing means is a power plant as described above. The
vehicle can be a car, van, truck, bus, lorry, aeroplane, boat,
ship, airship or train, for example. A particularly preferred
application is for use in heavy-duty diesel vehicles, i.e. vans,
trucks, buses or lorries, as defined by the relevant European
legislation.
[0032] The atmosphere-contacting surface can be any suitable
surface that encounters and contacts the atmosphere, most
preferably, at relatively large flow rates as the vehicle moves
through the atmosphere. The support surface is preferably located
at or towards the leading end of the vehicle so that air will
contact the surface as the vehicle is propelled through it.
Suitable support locations are fan blades, wind deflectors, wing
mirror backs or radiator grills and the like. Alternative locations
for supporting the trap material are given in WO 96/22146 and are
incorporated herein by reference.
[0033] In a most preferred embodiment the apparatus comprises a
heat exchange device such as a radiator, an air conditioner
condenser, an air charge cooler (intercooler or aftercooler), an
engine oil cooler, a transmission oil cooler or a power steering
oil cooler. This feature has the advantage that the heat exchange
device reaches above ambient temperatures, such as up to
140.degree. C., e.g. 40.degree. C. to 110.degree. C., at which, for
example, O.sub.3 reduction can occur more favourably. A further
advantage of using heat exchangers as the support surface for the
trap material is that in order to transfer heat efficiently they
have a relatively large surface area comprising fins or plates
extending from the outer surface of a housing or conduit for
carrying a fluid to be cooled. A higher surface area support
surface provides for a greater level of contact between the trap
material and the atmosphere.
[0034] By "ambient" herein we mean the temperature and conditions,
e.g. humidity, of the atmosphere.
[0035] In a particularly preferred embodiment, the apparatus
comprises a radiator and/or air conditioning condenser which is
housed within a compartment of a vehicle also including the power
plant, e.g. an air-cooled engine. This provides the advantage that
the radiator and/or condenser is exposed to ambient atmospheric air
as the vehicle is propelled through the atmosphere whilst being
protected by the radiator grill from damage by particulates, e.g.
grit or stones, and from the impact of flies. For mid- and
rear-engine vehicles, air intakes and conduits can be arranged to
carry atmospheric air to and from the supported trap material. A
further advantage of locating the radiator and/or condenser in the
engine compartment is that exposure to corrosion-causing agents
such as moist air, salt and/or grit is reduced and hence so too is
the rate of any corrosion. Whilst the radiator and/or condenser can
be formed of any material, it is usually a metal or an alloy. Most
preferably, the heat exchanger is aluminium or an alloy containing
aluminium. Hereinafter "aluminium" will be used to refer to
aluminium and alloys of aluminium.
[0036] Another advantage of using a heat exchanger, such as a
radiator, as the support surface for the trap material is that the
radiator is releasably attached to a vehicle, typically in the
engine compartment of the vehicle. This enables coated radiators
and other heat exchangers to be retrofitted to the vehicle, e.g.
during normal servicing of the vehicle, thereby to improve the
pollutant treating ability of the vehicle.
[0037] Alternatively the apparatus can be non-mobile, and the
surface is associated with the movement-causing means to provide
the required relative movement between the surface and the
atmosphere. For example, the surface can be one or more blades for
causing movement of air. In one embodiment the blades are fan
blades for cooling a stationary power plant such as for powering an
air conditioning unit or advertising hoarding. In another
embodiment the blade is a fan or turbine blade for drawing air into
the air conditioning system of a building.
[0038] In addition to or instead of the support surface being on a
fan or turbine blade, the surface can be the internal surfaces of
pipes, tubes or other conduits for carrying atmospheric air, e.g.
in an air conditioning system for a vehicle or a building and
condenser elements in air conditioning units as long as the
movement of the air is caused by a movement causing means.
[0039] In another preferred embodiment, the apparatus further
comprises at least one agent for reducing at least one atmospheric
oxidising pollutant. The or each reducing agent can be supported on
the same or a different surface from the trap material. For
example, the at least one agent can be in a separate layer under
the trap material. However, we prefer that the at least one
reducing agent is supported on a surface within the apparatus
separate from the surface supporting the trap material. In any
event, the arrangement must be such that the at least one reducing
agent is contacted by gas leaving the trap material. In a
particularly preferred arrangement, the apparatus is mounted in the
engine compartment of a vehicle and comprises an upstream condenser
or radiator supporting the trap material and a downstream radiator
or condenser supporting the at least one reducing agent.
[0040] The at least one reducing agent can be any agent that is
capable of reducing atmospheric oxidising pollutants. In particular
the at least one reducing agent can be any catalyst described in WO
96/22146 for this purpose, such as a manganese-based reducing
agent, e.g. MnO.sub.2 or cryptomelane. Moreover, it can include one
or more precious metals, such as platinum group metals. However, we
presently prefer to use one or more reducing agents described in
our application entitled "Agents for reducing atmospheric oxidising
pollutants" with the same filing date as the present application.
Suitable reducing agents include at least one transition element
and/or one or more compounds including at least one transition
element wherein the standard electrode potential of the redox
reaction including the transition element and an ionic species of
the transition element or between the ionic species of the
transition element present in the or each compound and a further
ionic species of the transition element is less than +1.0 volt.
[0041] Preferably, the transition element is copper, iron or zinc
or a mixture of any two or more thereof. The or each compound
including one or more transition element can be any suitable
compound such as an oxide, carbonate, nitrate or hydroxide, but is
preferably an oxide. In some circumstances, it is preferable to
reduce the transition element in a transition element-including
compound if in the reduced form the reducing agent is more active
in its intended use. Compounds including transition elements prior
to reduction can be referred to as `precursor`. For example, in a
preferred embodiment the reducing agent is CuO/ZnO//Al.sub.2O.sub.3
is the precursor and the active form of the reducing agent is
obtained by reducing the CuO to give Cu/ZnO//Al.sub.2O.sub.3. The
reduced form of a transition element can be stabilised with
suitable stabilisers as appropriate.
[0042] If supported, the transition element or transition element
compound is preferably supported on a high surface area oxide
selected from alumina, ceria, silica, titania, zirconia, a mixture
or a mixed oxide of any two or more thereof.
[0043] According to preferred embodiments, the active form of the
reducing agent is copper (II) oxide per se, a mixture of reduced
copper (II) oxide and zinc oxide on an alumina support or iron
oxide on a mixed alumina/ceria support.
[0044] Methods of manufacturing copper (II) oxide, copper (II)
oxide and zinc oxide on Al.sub.2O.sub.3 or iron oxide on a mixed
alumina/ceria support are known to a person skilled in the art or
can be deduced by reasonable experimentation, e.g. by
co-precipitation of the or each transition element component and/or
support. For example, in a CuO/ZnO//Al.sub.2O.sub.3 reducing agent
the Cu and Zn can be co-precipitated and the already formed
Al.sub.2O.sub.3 added thereto. Specific details of the
manufacturing processes will not be given here.
[0045] The CuO/ZnO//Al.sub.2O.sub.3 reducing agent composition can
be any suitable for the intended e.g. CuO30:ZnO60:Al.sub.2O.sub.3
10 or CuO60:ZnO30:Al.sub.2O.sub.3 10. Commercially available forms
of these compositions are available from ICI as ICI 52-1 and ICI
51-2 respectively. Commercially available CuO/ZnO//Al.sub.2O.sub.3
is sold as pellets, which can be ground to the required particle
size.
[0046] The trap material and, where present, the or each reducing
agent can be applied to the support surface in a formulation
including suitable binders, stabilisers, age resistors,
dispersants, water resistance agents, adhesive improvement agents
etc. known to persons skilled in the art. Binders include polymeric
binders which can be thermosetting or thermoplastic polymeric
binders and are listed in WO 96/22146, incorporated herein by
reference. However, we most prefer to use water soluble binders,
particularly organic binders including vinyl and acrylic water
soluble binders e.g. PVA, cellulosic binders including ether or
ester or semi-synthetic cellulosic binders, preferably
hydroxypropyl- or methyl cellulose or mixtures of any two or more
of the above mentioned binders, e.g. a mixture of PVA and
hydroxypropyl cellulose. The preferred binders are described in our
co-pending application entitled "Compositions including agents for
reducing atmospheric oxidising pollutants" filed on the same date
as the present application.
[0047] An important advantage of the compositions including the
preferred binders is that the compositions can be cured at
relatively low temperatures, e.g. .ltoreq.90.degree. C., compared
with compositions including Engelhard's preferred binders. In
particular, this feature enables the preparation of a radiator core
fitted with its plastic tanks in a continuous process, i.e. without
having first to prepare a coated core and then fit the plastic
tanks thereto. However, with compositions requiring higher curing
temperatures, the coated radiator core must be prepared before
assembling the tanks to prevent heat damage to the tanks during
curing. Thus, not only is there an economic advantage in that the
energy required to cure the composition is reduced, but the process
of radiator manufacture is simplified.
[0048] Referring to FIG. 1, 2 is a composition comprising
beta-zeolite, and 4 is a composition including a mixture of
"reduced" copper (II) oxide and zinc oxide on an Al.sub.2O.sub.3
support (Cu/ZnO//Al.sub.2O.sub.3) for reducing at least one
atmospheric oxidising pollutant, such as O.sub.3. In FIG. 1A,
composition 2 is supported on an aluminium alloy air conditioning
condenser 6 and composition 4 is supported on an aluminium alloy
radiator 8. Both the condenser 6 and the radiator 8 are mounted in
the engine compartment (not shown) of a motor vehicle in such a way
that the condenser 6 is forward of the radiator 8. The arrangement
is such that when the motor vehicle is travelling in its forward
direction, substantially all the atmospheric air (represented by
the arrow) entering the engine compartment that contacts the
condenser 6 and the supported composition 2 thereon also passes
over the downstream radiator 8 and the supported composition 4. In
other words, atmospheric air contacts the zeolite first before the
at least one reducing agent.
[0049] FIG. 1B shows an alternative arrangement of an aluminium
alloy radiator 10 coated with composition 2 on its upstream half
and with composition 4 on its downstream half. Once again, it will
be seen that this configuration maintains the requirement for the
atmospheric air first contacting the zeolite before the at least
one reducing agent.
[0050] FIG. 1C shows a further embodiment wherein an aluminium
alloy radiator 12 is coated with a first layer of composition 4
over which composition 2 is coated. Here atmospheric air will
contact the zeolite first before contacting the at least one
reducing agent.
EXAMPLE 1
[0051] To test the concept of reducing O.sub.3 using a HC trapped
on a trap material, we investigated the reaction of O.sub.3 with a
selection of trapped HC at room temperature. A test rig comprising
an upstream O.sub.3 generator, a stainless steel tube including
metal mesh to pack a reactor bed material therebetween and a
downstream O.sub.3 detector was set up in a fume cupboard. O.sub.3
was generated and mixed with air before passing through the reactor
bed material comprising 1 inch (2.54 cm) of H--Y zeolite (Si:Al
ratio 200:1) on which was adsorbed HC. The HC tested were an alkane
(heptane), an alkene (cyclohexene), an alcohol (propan-1-ol), an
aromatic HC (toluene), an aldehyde (formaldehyde), a ketone
(acetone) and two ethers (diethyl ether and t-butyl methyl ether).
The exhaust gas from the reactor bed was passed through an O.sub.3
detector (measured in 5 ppm units) before being vented. An inlet
O.sub.3 concentration of .about.200 ppm at a space velocity (GHSV)
of .about.1000/hr was used. Whilst higher space velocities would be
observed at, e.g. the surface of a vehicle radiator in use, and
atmospheric O.sub.3 concentrations are present in the parts per
billion range, the results were useful to compare directly the
potential of each HC material tested to reduce O.sub.3.
[0052] Referring to FIG. 2, when the reactor bed was packed with
zeolite only or zeolite and adsorbed water, the O.sub.3 quickly
passed through the reactor bed and reached its maximum value,
indicating that no O.sub.3 decomposition had occurred.
[0053] For all of the HC tested, there was a delay before O.sub.3
reached the detector compared to the zeolite only sample and the
outlet O.sub.3 concentrations were lower than the inlet O.sub.3
concentrations throughout the duration of the tests. Accordingly,
there is clear evidence that O.sub.3 reacts with trapped HC at room
temperature. The greatest O.sub.3 removal was observed with
cyclohexene, with significant removal also occurring with diethyl
ether and toluene. This could offer an additional advantage; such
species have a higher propensity to form 03 in the atmosphere than
saturated alkanes. See the table of MIR adjustment factors in the
Table at Appendix 1 of "Californian Non-methane organic gases test
procedures", The California Environmental Protection Agency Air
Resource Board dated Aug. 5, 1999, incorporated herein by
reference.
EXAMPLE 2
[0054] There is now described a composition including a beta
zeolite trap component for application to an aluminium radiator
substrate.
[0055] Beta zeolite was mixed with an aqueous solution of
hydroxypropyl cellulose binder, Klucel.TM., to a concentration of
10% wt/wt. The coating was applied to each side of a Visteon
aluminium radiator of 20 mm thickness using a compressed air spray
gun and then cured at up to 90.degree. C.
* * * * *
References