Use of catalyst and method of removing aldehydes

Abstract

A method of removing one or more aldehydes from a carrier fluid comprising ambient air, the method comprises contacting the carrier fluid comprising one or more aldehydes with a catalyst comprising ma

Description

BACKGROUND

[0001] The present disclosure relates to the removal of aldehydes from a fluid.

[0002] The present disclosure concerns the removal of aldehydes from a fluid. More particularly, but not exclusively, this disclosure concerns a method of removing one or more aldehydes from a fluid, such as a gas. The disclosure also concerns use of one or both of manganese IV oxide and cryptomelane to remove one or more aldehydes from a fluid, such as a gas.

[0003] In many countries, there are strict limits on the levels of certain airborne contaminants, such as volatile organic compounds (VOCs). Filters are often used to remove such compounds, and those filters may comprise a catalyst that facilitates the destruction of such compounds. An important category of such VOCs is aldehydes. Aldehydes are highly flammable and can cause eye, skin and respiratory irritation, and the removal of aldehydes from ambient air is desirable.

[0004] The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved method of removing one or more aldehydes from a fluid, such as a gas. SUMMARY The invention is defined in the appended claims.

[0005] According to a first aspect, a method of removing one or more aldehydes from a carrier fluid, the method comprising: contacting the carrier fluid comprising one or more aldehydes with a catalyst comprising manganese IV oxide and / or cryptomelane.

[0006] It has been discovered that, surprisingly, cryptomelane and manganese IV oxide are effective at removing aldehydes, particularly aldehydes with more than one carbon 04 04 25 atom, from a carrier fluid. Those skilled in the art will realise that the removal of one or more aldehydes comprises destruction of one or more aldehydes. In this connection, the catalyst catalyses the oxidation of one of more aldehydes, optionally to produce water and carbon dioxide.

[0007] The carrier fluid typically comprises an oxidant, such as oxygen. The catalyst catalyses the oxidation of one or more aldehydes.

[0008] As mentioned above, cryptomelane and manganese IV oxide have proved to be particularly effective at removing longer chain aldehydes from a carrier fluid. In this connection, the one or more aldehydes optionally comprises at least one aldehyde comprising at least two carbon atoms, optionally at least one aldehyde comprising at least three carbon atoms and optionally at least one aldehyde comprising at least four carbon atoms (such as butanal or crotanaldehyde). The applicant has surprisingly discovered that manganese IV oxide and cryptomelane are both effective at removing longer-chain aldehydes from a fluid stream.

[0009] The one or more aldehydes optionally comprises at least one aldehyde comprising up to six carbon atoms, optionally at least one aldehyde comprising up to 5 carbon atoms and optionally at least one aldehyde comprising up to 4 carbon atoms.

[0010] Optionally, the one or more aldehydes comprises no aldehydes comprising more than ten carbon atoms, optionally no aldehydes comprising more than eight carbon atoms, optionally no aldehydes comprising more than six carbon atoms and optionally no aldehydes comprising more than five carbon atoms.

[0011] The manganese IV oxide and / or cryptomelane may be supported i.e. the catalyst may comprise a support and the manganese IV oxide and / or cryptomelane.

[0012] The term “support” refers to a material (e.g., a metal, semi-metal, semi-metal oxide, metal oxide, polymeric, ceramic, foam) onto or into which the manganese IV oxide and / or cryptomelane is located. The support may comprise a foam, for example. The support may comprise a metal support. The support may be a filter. The support may, for example, be an air filter, such as an air filter for a vehicle or a domestic air treatment device, such as a domestic air conditioning device. 04 04 25

[0013] The catalyst may comprise at least 10wt% support, optionally at least 20wt% support and optionally at least 30wt% support. The catalyst may comprise up to 90wt% support, optionally up to 80wt% support and optionally up to 70wt% support.

[0014] The catalyst may comprise at least 2wt% manganese IV oxide and / or cryptomelane, optionally at least 5wt% manganese IV oxide and / or cryptomelane, optionally at least 10wt% manganese IV oxide and / or cryptomelane, optionally at least 15wt% manganese IV oxide and / or cryptomelane and optionally at least manganese IV oxide and / or cryptomelane. The catalyst may comprise up to 100wt% manganese IV oxide and / or cryptomelane, optionally up to 90wt% manganese IV oxide and / or cryptomelane, optionally up to 75wt% manganese IV oxide and / or cryptomelane, optionally up to 60wt% manganese IV oxide and / or cryptomelane, optionally up to 50wt% manganese IV oxide and / or cryptomelane, optionally up to 40wt% manganese IV oxide and / or cryptomelane, optionally up to 30wt% manganese IV oxide and / or cryptomelane and optionally up to 20wt% manganese IV oxide and / or cryptomelane.

[0015] The catalyst may comprise from 2wt% to 30wt% manganese IV oxide and / or cryptomelane and optionally from 5wt% to 20wt% manganese IV oxide and / or cryptomelane.

[0016] The catalyst may comprise a binder. The binder may comprise alumina or a polymer, for example. The catalyst may comprise up to 60wt% binder, optionally up to 50wt% binder, optionally up to 40wt% binder and optionally up to 30wt% binder.

[0017] The manganese IV oxide and / or cryptomelane may optionally be unsupported.

[0018] The catalyst may comprise one or more catalytic additives. For example, the catalyst may comprise one or both of potassium and calcium.

[0019] The catalyst may be substantially free of catalytic additives.

[0020] The carrier fluid is preferably a gas, and preferably comprises air. As mentioned above, the catalyst catalyses the oxidation of one or more aldehydes, and air provides oxygen for the oxidation of one or more aldehydes. The carrier fluid optionally consists essentially of air. The carrier fluid optionally comprises, and optionally consists essentially of, ambient air, such as interior (indoor) ambient air or exterior (outdoor) ambient air. 04 04 25

[0021] The catalyst may, for example, be acidic or basic. The catalyst may have been treated with an acid or a base.

[0022] It has been discovered that, surprisingly, manganese IV oxide and cryptomelane are effective at removing aldehydes from a carrier fluid at low temperatures, even if the concentration of the one or more aldehyde is low. The method may therefore comprise contacting the carrier fluid with the catalyst at a temperature of at least 10°C, optionally at least 15°C, optionally at least 20°C, optionally at least 25°C, optionally at least 30°C, optionally at least 35°C and optionally at least 40°C.

[0023] As mentioned above, manganese IV oxide and cryptomelane are effective at removing aldehydes from a carrier fluid at low temperatures. The method may therefore comprise contacting the carrier fluid with the catalyst at a temperature of no more than 120°C, optionally no more than 110°C, optionally no more than 100°C, optionally no more than 90°C, optionally no more than 80°C, optionally no more than 70°C, optionally no more than 60°C and optionally no more than 50°C.

[0024] The method may comprise contacting the carrier fluid with the catalyst at a temperature of from 10°C to 120°C and optionally from 20°C to 100°C.

[0025] Those skilled in the art will realise that one or both of the carrier fluid and the catalyst may be heated and / or cooled. For example, the carrier fluid may be heated or cooled to the desired temperature, and contacted with the catalyst. Alternatively, the catalyst may be heated or cooled to the desired temperature.

[0026] Manganese IV oxide and cryptomelane are effective removers of aldehydes at low temperatures. In this connection, the method may comprise contacting the carrier fluid with the catalyst at a temperature of from 20°C to 60°C, optionally from 20°C to 50°C, optionally from 20°C to 40°C and optionally from 20°C to 30°C.

[0027] While manganese IV oxide and cryptomelane work unexpectedly well at low temperatures, like many such catalysts, they operate more effectively at higher temperatures. The method may therefore comprise contacting the carrier fluid with the catalyst at a temperature of from 40°C to 120°C, optionally from 40°C to 100°C and optionally 60°C to 100°C. 04 04 25

[0028] The catalyst may consist essentially of a support and cryptomelane, and optionally one or more binders. The support (and one or more binders, if present) may be substantially as described above.

[0029] The catalyst may consist essentially of a support and manganese IV oxide, and optionally one or more binders. The support (and one or more binders, if present) may be substantially as described above.

[0030] The method may comprise contacting a flow of the carrier fluid with the catalyst. The flow rate of the carrier fluid may optionally be at least lOL / min. per g of catalyst. The flow rate of the carrier fluid may be configured to provide a reduction in the aldehyde content of the carrier fluid of at least 30%, optionally of at least 40%, optionally of at least 50%, optionally of at least 60% and optionally of at least 70%.

[0031] The carrier fluid may comprise at least Ippb one or more aldehydes, optionally at least 5ppb one or more aldehydes, optionally at least lOppb one or more aldehydes, optionally at least 50ppb one or more aldehydes and optionally at least lOOppb one or more aldehydes. For the avoidance of doubt, the ppb levels mentioned herein are for the total of all aldehydes in the carrier fluid, unless the context of a statement dictates otherwise. For example, if the carrier fluid comprises lOOppb propanal and lOOppb butanal, the carrier fluid comprises 200ppb one or more aldehydes.

[0032] The carrier fluid may comprise no more than 10,000ppb one or more aldehydes, optionally no more than 8,000ppb one or more aldehydes, optionally no more than 5,000ppb one or more aldehydes, optionally no more than 3,000ppb one or more aldehydes, optionally no more than 2,000ppb one or more aldehydes and optionally no more than l,000ppb one or more aldehydes.

[0033] The carrier fluid may comprise from Ippb to 10,000ppb one or more aldehydes, optionally from lOppb to 5,000ppb one or more aldehydes, optionally from 50ppb to 3,000ppb one or more aldehydes and optionally from lOOppb to 2,500ppb aldehydes, optionally from 200ppb to 2000ppb, and optionally from lOOppb to 200ppb. The method as described herein has been found to be particularly effective for removing relatively low levels of one or more aldehyde at low temperatures. In this connection, the method comprises contacting a carrier fluid comprising lOOppb to 2500ppb one or more aldehyde 04 04 25 (optionally lOOppb to 200ppb) with the catalyst at a temperature of up to 100°C, optionally up to 80°C and optionally up to 60°C, optionally at a temperature of from 20°Cto 60°C and optionally at a temperature of from 35°C to 60°C.

[0034] The carrier fluid may optionally be at ambient (atmospheric) pressure of when contacted with the catalyst. The carrier fluid may optionally be at less than ambient pressure when contacted with the catalyst, particularly if the carrier fluid comprises, or optionally consists essentially of, air (optionally ambient air). The carrier fluid may be at a pressure of from 80% to 99% of ambient pressure when contacted with the catalyst. Ambient pressure is the pressure of the surrounding medium, optionally the pressure of the surrounding air. The method may comprise passing the carrier fluid through a filter, optionally prior to contacting the carrier fluid with the catalyst (i.e. the filter is upstream of the catalyst). A compressor or fan may be used to draw the carrier fluid through a filter, into contact with the catalyst. The use of such a compressor or fan may facilitate the carrier fluid being at a pressure less than ambient pressure when it contacts the catalyst.

[0035] The method as described herein may be considered to be a method of purifying the carrier fluid. The aldehyde content of the purified carrier fluid (i.e. the carrier fluid having passed through or over the catalyst) may be no more than 50% of the initial aldehyde content of the unpurified carrier fluid (the carrier fluid before having been passed through or over the catalyst), optionally no more than 40% of the aldehyde content of the unpurified carrier fluid, optionally no more than 30% of the aldehyde content of the unpurified carrier fluid, optionally no more than 20% of the aldehyde content of the unpurified carrier fluid and optionally more than 10% of the aldehyde content of the unpurified carrier fluid.

[0036] The catalyst may have high surface area. The catalyst may be porous.

[0037] Without wishing to be bound by theory, it is anticipated that contacting the one or more aldehydes with the catalyst causes the formation of water and carbon dioxide.

[0038] The method as described herein may be performed by a domestic air treatment device. 04 04 25

[0039] According to a second aspect there is also provided use of manganese IV oxide and / or cryptomelane to remove one or more aldehydes from a carrier fluid. As mentioned above in relation to the method of the first aspect, the method of the second aspect may comprise use of manganese IV oxide and / or cryptomelane to destroy one or more aldehydes carried in a carrier fluid.

[0040] The use of the second aspect may comprise those features described above in relation to the method of the first aspect. For example, the one or more aldehydes may have one or more of the features described above in relation to the method of the first aspect. The carrier fluid may have one or more of the features described above in relation to the method of the first aspect.

[0041] In accordance with a third aspect, there is provided a catalyst for use in the use of the first aspect and / or the method of the second aspect.

[0042] The catalyst may have one or more of the features described above in relation to the method of the first aspect.

[0043] In accordance with a fourth aspect, there is provided a domestic air treatment device comprising a catalyst in accordance with the third aspect.

[0044] The catalyst may comprise one or more of the features described above in relation to the method of the first aspect. The domestic air treatment device of the fourth aspect may be used to remove one or more aldehydes from a carrier fluid. The domestic air treatment device of the fourth aspect may therefore be operated in a method in accordance with the first aspect.

[0045] It will of course be appreciated that features described in relation to one aspect may be incorporated into other aspects. For example, the method may incorporate any of the features described with reference to the apparatus and vice versa.

[0046] Embodiments will now be described by way of example only. DETAILED DESCRIPTION

[0047] The ability of cryptomelane to remove aldehydes from a stream of air was investigated. A gas comprising acetaldehyde, propanal, butanal, crotonaldehyde, isopropyl alcohol, acetone and methyl acetate in air was passed through 50g of catalyst (BASF SE) comprising cryptomelane mounted on a metal support. The estimated cryptomelane content is 5-20wt% of the weight of the catalyst. Samples of gas having passed through the cryptomelane were analysed as a function of time using a gas chromatography mass spectrometer, and the results are shown in Table 1. The temperature was 90° C, and the concentration of each of acetaldehyde, propanal, butanal, crotonaldehyde, isopropyl alcohol, acetone and methyl acetate was 0.5ppm. The flow rate was 7.51itres / second, with 39.1 / s GHSV (gas hourly space velocity). 04 04 25 Time (mins) Height of GCMS peak (% passing through catalyst, ±3%) Example 1 Propanal Example 2 Butanal Example 3 Crotanaldehyde Comparative Example 1 Isopropyl alcohol Comparative Example 2 Acetone Comparative Example 3 Methyl acetate 0 18 60 55 12 90 90 15 6 12 12 20 100 90 30 2 3 2 8 60 90 45 1 0 2 3 50 90 Table 1 challenge agents passing through cryptomelane catalyst

[0048] The data of Table 1 show that, surprisingly, cryptomelane is particularly effective at removing aldehydes from a carrier gas (in this case, aldehydes comprising three and four carbon atoms) at relatively low temperatures, but was far less effective at removing a variety of other challenges, such as alcohols (e.g. isopropyl alcohol), ketones (e.g. acetone) and esters (methyl acetate).

[0049] Example 4

[0050] The ability of manganese IV oxide to remove aldehydes from a stream of air at about 100°C was also investigated. A flow of air (251 / min) comprising 0.5ppm acetaldehyde was passed over 0.5g of 60-mesh manganese IV oxide (SUPPLIER) at about 100°C initial temperature, and the concentration of acetaldehyde in the air was 04 04 25 measured. It is estimated that the temperature of the catalyst during measurement. In the absence of the catalyst, the concentration of acetaldehyde was determined to be 0.53ppm. Immediately after insertion of the catalyst, the concentration of acetaldehyde in the air that had been passed through the catalyst was 0.20ppm, rising slightly over a period of about 1 hour to a steady level of about 0.30ppm. After removal of the catalyst, the concentration of the acetaldehyde in the airflow was determined to be about 0.48ppm.

[0051] This demonstrates that manganese IV oxide is particularly effective at removing aldehydes (in particular, acetaldehyde) from a stream of air at relatively low temperatures.

[0052] Comparative Examples

[0053] The method of Example 4 was repeated using different prospective catalysts, in this case manganese II oxide (Comparative Example 4), manganese II, III oxide (Comparative Example 5), Li2Mn2O4 (Comparative Example 6) and Fe2O3 (Comparative Example 7). None of the catalysts of Comparative Examples 4-7 worked effectively under the conditions of Example 4. Catalysts comprising Pd or Pt (Comparative Example 8) were also investigated for their ability to remove acetaldehyde, but temperatures much higher than 100°C were needed for effective removal of acetaldehyde and did not yield high single pass efficiencies, gram-for-gram.

[0054] Examples 5-8

[0055] The ability of cryptomelane to remove various concentrations of acetaldehyde from an air flow was investigated as a function of temperature. 15g of catalyst comprising cryptomelane supported on aluminium (BASF SE was subjected to a challenge of acetaldehyde at 0.2ppm (Example 5), 0.3ppm (Example 6), 0.4ppm (Example 7) and 0.5ppm (Example 8) (flow rate was 25 litres / minute, 33.9 / s space velocity. The single pass efficiency (SPE) was measured as a function of temperature at each stated concentration of acetaldehyde, and it was found that cryptomelane is a surprisingly effective catalyst for removing aldehydes (in this case, acetaldehyde), even at very low temperatures (e.g. 30°C). Moreover, at slightly elevated temperatures (e.g. 70°C), cryptomelane is a very efficient catalyst for removing aldehydes from an airflow. 04 04 25 Furthermore, for these conditions at least, it was found that the efficiency of the catalyst was independent of the concentration of the challenge.

[0056] Examples 9 and 10

[0057] The ability of cryptomelane to remove acetaldehyde, propanal and crotanaldehyde from an air flow was investigated as a function of temperature. 33.6g of a catalyst comprising cryptomelane supported on aluminium was subjected to a challenge of acetaldehyde at 0.5ppm (Example 11), propanal at 0.5 ppm (Example 9) and crotanaldehyde at 0.5ppm (Example 10) (flow rate of 7.51itres / second, 39.1 / s GHSV). The single pass efficiency for acetaldehyde was 14% at 50°C and 28% at 70°C. The single pass efficiency for propanal was 14% at 50°C and 28% at 70°C. The single pass efficiency for crotanaldehyde was 25% at 50°C and 29% at 70°C. Examples 9 and 10 demonstrate that cryptomelane is surprisingly effective at removing longer chain aldehydes, such as propanal and crotanaldehyde, from an air flow, even at relatively low temperatures.

[0058] It will be appreciated by those of ordinary skill in the art that the present disclosure lends itself to many different variations not specifically illustrated herein. By way of example only, certain possible variations will now be described.

[0059] The examples above demonstrate the use of one particular type of manganese IV oxide. Those skilled in the art will realise that other manganese IV oxides may be used.

[0060] The examples above demonstrate the use of unsupported manganese IV oxide. Those skilled in the art will realise that it is possible for the manganese IV oxide to be on a support.

[0061] The examples above demonstrate the use of cryptomelane on a support, such as on a foam or metal support. Those skilled in the art will realise that other supports are possible, and that cryptomelane may be used unsupported.

[0062] The examples above demonstrate how manganese IV oxide and cryptomelane may be used to remove aldehydes having up to four carbon atoms. Those skilled in the art will realise that manganese IV oxide and cryptomelane may be used to remove aldehydes with more than four carbon atoms. 04 04 25

[0063] The examples above show how manganese IV oxide and cryptomelane may be used by themselves to remove aldehydes from a carrier fluid. Those skilled in the art will realise that it would be possible to use manganese IV oxide and cryptomelane with other catalyst components. For example, manganese IV oxide and cryptomelane may be used together, for example, with both manganese IV oxide and cryptomelane on the same support. Alternatively or additionally, manganese IV oxide may be used sequentially with cryptomelane, for example, by first contacting carrier fluid with, say, manganese IV oxide, and then contacting the carrier fluid with cryptomelane.

[0064] Where in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present invention, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the invention that are described as preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims. Moreover, it is to be understood that such optional integers or features, whilst of possible benefit in some embodiments of the invention, may not be desirable, and may therefore be absent, in other embodiments. 04 04 25

Claims

1. A method of removing one or more aldehydes from a carrier fluid comprising ambient air, the method comprising:contacting the carrier fluid comprising one or more aldehydes with a catalyst comprising manganese IV oxide at a temperature of at least 20 °C and no more than 100°C; andcontacting the carrier fluid with the catalyst at a pressure less than ambient pressure.

2. The method of claim 1 wherein at least one aldehyde comprises at least two carbon atoms.

3. The method of claim 1 wherein at least one aldehyde comprises at least three carbon atoms.

4. The method of any preceding claim wherein at least one aldehyde comprises up to six carbon atoms.

5. The method of any preceding claim wherein the catalyst comprises a support on or in which the manganese IV oxide is supported.

6. The method of claim 5 wherein the support comprises a foam and / or a metal support.

7. The method according to claim 5 or claim 6 wherein the catalyst comprises at least 10wt% support, and optionally up to 90wt% support.

8. The method according to any preceding claim wherein the catalyst comprises a binder, the binder optionally comprising alumina or a polymer.

9. The method according to claim 8 wherein the catalyst comprises up to 60wt% binder.04 2510. The method of any preceding claim wherein the carrier fluid consists essentially of ambient air.

11. The method of claim 1 comprising contacting the carrier fluid with the catalyst at a temperature of from 20°C to 60°C.

12. The method of claim 1 comprising contacting the carrier fluid with the catalyst at a temperature of from 60°C to 100°C.

13. The method of any preceding claim comprising contacting a flow of the carrier fluid with the catalyst, the flow rate of the carrier fluid being configured to provide a reduction in the aldehyde content of the carrier fluid of at least 30%.

14. The method of any preceding claim wherein the carrier fluid comprises at least Ippb one or more aldehydes, and optionally at least 5ppb one or more aldehydes.

15. The method of any preceding claim wherein the catalyst further comprises cryptomelane.