METHOD FOR THE TREATMENT OF AN EXHAUST GAS AND AN HVAC SYSTEM

Abstract

The present invention relates to a method for the treatment of an exhaust gas comprising carbon monoxide (CO) and/or one or more volatile organic compounds (VOCs) using a PGM-free catalyst article comprising a mixed oxide of Mn, Cu, Mg, Al and La. The present invention also relates to an HVAC system comprising a PGM-free catalyst article.

Claims

1. A method for the treatment of an exhaust gas comprising carbon monoxide (CO) and/or one or more volatile organic compounds (VOCs), the method comprising, contacting the exhaust gas with a PGM-free catalyst article comprising a mixed oxide of Mn, Cu, Mg, Al and La.

2. The method according to claim 1, wherein the mixed oxide comprises 40 to 50 wt % Mn and at least 5 wt % copper, on a metal-only basis.

3. The method according to claim 1, wherein the mixed oxide comprises, on a metal-only basis: 40 to 50 wt % Mn; 6 to 8 wt % Cu; 3 to 6 wt % Mg; 1 to 3 wt % Al; 35 to 45 wt % La.

4. The method according to claim 1, wherein the mixed oxide comprises, on a metal-only basis: 42 to 48 wt % Mn; about 7 wt % Cu; about 4.5 wt % Mg; about 2 wt % Al; 39 to 43 wt % La.

5. The method according to claim 3, wherein the mixed oxide consists essentially of Mn, Cu, Mg, Al and La, and oxygen.

6. The method according to claim 1, wherein a molar ratio of Mn to La is from 2.5:1 to 3:1.

7. The method according to claim 1, wherein the VOCs comprise one or more compounds selected from methanol, ethanol, acetaldehyde, formaldehyde, propene and ethylene.

8. The method according to claim 1, wherein the exhaust gas is from an HVAC system or is a tail-gas from a chemical synthesis process.

9. An HVAC system comprising a PGM-free catalyst article comprising a mixed oxide of Mn, Cu, Mg, Al and La.

10. An HVAC system of claim 9, wherein the mixed oxide comprises, on a metal-only basis: 40 to 50 wt % Mn; 6 to 8 wt % Cu; 3 to 6 wt % Mg; 1 to 3 wt % Al; 35 to 45 wt % La.

11. The method according to claim 1, wherein the exhaust gas is from a terephthalic acid synthesis process.

Description

FIGURES

[0049] The present invention will now be described further with reference to the following non-limiting Figures in which:

[0050] FIGS. 1A and 1B provide the results of Example 1 and plot the conversion of formaldehyde and methanol, respectively, against temperature under gas engine test conditions for Catalyst MO together with a known comparison base metal catalyst, Catalyst A.

[0051] FIGS. 2A and 2B provide the results of Example 2 and plot the conversion of CO and NO, respectively, against temperature under gas engine test conditions for both Catalyst MO together with Catalyst A.

[0052] FIGS. 3A and 3B provide the results of Example 3 and plot the conversion of methanol and CO, respectively, against temperature under VOC testing conditions for Catalyst MO together with Catalyst A. FIGS. 3C and 3D plot the observed concentrations of formaldehyde and CO2, respectively, against temperature for both Catalyst MO and Catalyst A.

[0053] FIGS. 4A and 4B provide the results of Example 4 and plot the conversion of ethanol and CO, respectively, against temperature under VOC testing conditions for Catalyst MO together with Catalyst A. FIGS. 4C and 4D plot the observed concentrations of acetaldehyde and formaldehyde, respectively, against temperature for both Catalyst MO and Catalyst A.

[0054] FIGS. 5A and 5B provide the results of Example 5 and plot the conversion of propene and CO, respectively, against temperature under VOC testing conditions for Catalyst MO together with Catalyst A.

[0055] FIGS. 6A and 6B provide the results of Example 6 and plot the conversion of ethylene and CO, respectively, against temperature under VOC testing conditions for Catalyst MO together with Catalyst A.

[0056] FIGS. 7A, 7B and 7C provide the results of Example 7 and plot the conversion of ethylene, propene and CO, respectively, against temperature under VOC testing conditions for Catalyst MO together with Catalyst A.

EXAMPLES

Preparation of Mixed Metal Oxide

[0057] Co-precipitation involves the use of metal nitrates in solution (Mn, Cu, Mg, Al, La). An alkali solution is used as the precipitation agent (NaOH/Na.sub.2CO.sub.3). The metal nitrate solution is obtained by dissolving the metal nitrate precursors together in one container with demineralised water. For the preparation of the alkali solution, NaOH and Na.sub.2CO.sub.3 are mixed together and demineralised water is added. Both solutions are stirred and then transferred from their containers to the reactor by using liquid pumps.

TABLE-US-00001 TABLE 1 Preparation of alkali solution Alkali Target mass (Kg) NaOH 3.36 (2.8M) Na.sub.2CO.sub.3 4.77 (1.5M) Water for alkali solution Target volume = 30 L

TABLE-US-00002 TABLE 2 Preparation of metal nitrate solution Metal Nitrate Target mass (Kg) Manganese (II) Nitrate solution 9.85 kg solution (4.92 kg Mn nitrate + 4.92 kg H.sub.2O) (27.45 mol) Copper (II) Nitrate 0.87 (3.74 mol) hemi(pentahydrate) Lanthanum (III) Nitrate 4.33 (9.9998 mol) Hexahydrate Magnesium Nitrate Hexahydrate 1.6 (6.24 mol) Aluminium Nitrate Nonahydrate 0.94 (2.5 mol) Water for nitrates solution Target volume = 20 L 4.92 L from Mn solution, need to add about 15 L demineralised H.sub.2O

[0058] The co-precipitation was carried out by adding both solutions from Tables 1 and 2 at a controlled addition rate, with stirring, that allows to keep a pH constant at about 10-11. pH may be monitored using a standard pH electrode.

[0059] The addition may be carried out over a period of about 1 hour and the reaction mixture stirred for another hour after complete addition.

[0060] Once the co-precipitation has finished it is necessary to wash and filter. Large amounts of demineralised water is flushed through the precipitant until the conductivity of the water is that of the fresh demineralised water (e.g. about 100 μS).

[0061] Finally, the solid material is dried overnight at 105-110° C. in air overnight before grinding followed by calcination at, for example, 500° C. in air for 2 hours. The resulting mixed metal oxide may be referred to herein as Catalyst MO.

Testing of Mixed Metal Oxide

[0062] The mixed metal oxide was tested against a comparative known commercial PGM-free base metal catalyst, Catalyst A.

[0063] Catalyst A is prepared in accordance with WO 2010/123731 and comprises a support comprising a lanthanum stabilised alumina and cerium stabilised zirconia. Manganese is added as an acetate to the washcoat slurry which is applied to a ceramic substrate in two passes to provide a target washcoat loading of 3.3 g/in3 (0.2 g/cm3). Copper nitrate is then impregnated targeting 375 g/ft3 (13,243 g/m3). As determined by ICP, Catalyst A comprises 3 wt % Mn and 2 wt % Cu on a metal-only basis.

[0064] The Catalyst A core was crushed, pelletised, ground and sieved. Sieve fractions of 355-250 um were used for testing. A total of 0.2 g of sieved material was tested.

[0065] The mixed oxide is powder, therefore, it did not need crushing. The sample was also pelletised, ground and sieved before testing.

Example 1 (Formaldehyde and Methanol Activity)

[0066] Gas Engine Test Conditions: 100 ppm CH4, 20 ppm CH2O, 200 ppm NOx, 540 ppm CO, 10% O2, 10% CO2, 10% H2O, Balance N2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0067] The results are shown in FIGS. 1A and 1B. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% formaldehyde conversion at 175° C. whereas Catalyst A achieves 50% formaldehyde conversion at 220° C. Similarly, the mixed metal oxide achieves 50% methanol conversion at the lower temperature of 211° C. when compared to 270° C. as required by Catalyst A.

Example 2 (CO and NO Activity)

[0068] Gas Engine Test Conditions: 100 ppm CH4, 20 ppm CH2O, 200 ppm NOx, 540 ppm CO, 10% O2, 10% CO2, 10% H2O, Balance N2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0069] The results are shown in FIGS. 2A and 2B. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% CO conversion at 243° C. whereas Catalyst A achieves 50% CO conversion at 272° C. Similarly, the start temperature for NO conversion for the mixed metal oxide is about 225° C. whereas that of Catalyst A is about 300° C.

Example 3 (Methanol and CO Oxidation)

[0070] VOC Test Conditions: 500 ppm methanol, 1000 ppm CO, 15% O.sub.2, 5% H.sub.2O, Balance N.sub.2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0071] The results are shown in FIGS. 3A and 3B. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% methanol conversion at 191° C. whereas Catalyst A achieves 50% methanol conversion at 260° C. Similarly, the mixed metal oxide achieves 50% CO conversion at the lower temperature of 222° C. when compared to 275° C. as required by Catalyst A.

[0072] Additionally, as seen in FIGS. 3C and 3D, the mixed metal oxide shows greater selectivity to producing CO.sub.2 resulting in a reduction in the amount of formaldehyde produced.

Example 4 (Ethanol and CO Oxidation)

[0073] VOC Test Conditions: 500 ppm ethanol, 1000 ppm CO, 15% O.sub.2, 5% H.sub.2O, Balance N.sub.2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0074] The results are shown in FIGS. 4A and 4B. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% ethanol conversion at 198° C. whereas Catalyst A achieves 50% ethanol conversion at 261° C. Similarly, the mixed metal oxide achieves 50% CO conversion at the lower temperature of 236° C. when compared to 288° C. as required by Catalyst A.

[0075] Additionally, as seen in FIGS. 4C and 4D, the mixed metal oxide produces less formaldehyde than Catalyst A.

Example 5 (Propene and CO Oxidation)

[0076] VOC Test Conditions: 500 ppm propene, 1000 ppm CO, 15% O2, 5% H2O, Balance N2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0077] The results are shown in FIGS. 5A and 5B. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% propene conversion at 284° C. whereas Catalyst A achieves 50% propene conversion at a significantly higher temperature of 390° C. Similarly, the mixed metal oxide achieves 50% CO conversion at the lower temperature of 207° C. when compared to 262° C. as required by Catalyst A.

Example 6 (Ethylene and CO Oxidation)

[0078] VOC Test Conditions: 500 ppm ethylene, 1000 ppm CO, 15% O.sub.2, 5% H.sub.2O, Balance N.sub.2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0079] The results are shown in FIGS. 6A and 6B. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% ethylene conversion at 346° C. whereas Catalyst A achieves 50% ethylene conversion at a significantly higher temperature of 475° C. Similarly, the mixed metal oxide achieves 50% CO conversion at the lower temperature of 196° C. when compared to 259° C. as required by Catalyst A.

Example 7 (Propylene, Ethylene and CO Oxidation)

[0080] VOC Test Conditions: 500 ppm propene, 500 ppm ethylene, 1000 ppm CO, 15% O2, 5% H2O, Balance N2; 0.2 g catalyst (355-250 μm), Flow=3.3 L/min, T ramp=110-500° C.

[0081] The results are shown in FIGS. 7A-7C. The mixed metal oxide (i.e. Catalyst MO) achieves a 50% ethylene conversion at 335° C. and a 50% propene conversion at 247° C. whereas Catalyst A achieves 50% ethylene and propene conversion at significantly higher temperatures of 435° C. and 355° C., respectively. Similarly, the mixed metal oxide achieves 50% CO conversion at the lower temperature of 195° C. when compared to 226° C. as required by Catalyst A.

[0082] As used herein, the singular form of “a”, “an” and “the” include plural references unless the context clearly dictates otherwise. The use of the term “comprising” is intended to be interpreted as including such features but not excluding other features and is also intended to include the option of the features necessarily being limited to those described. In other words, the term also includes the limitations of “consisting essentially of” (intended to mean that specific further components can be present provided they do not materially affect the essential characteristic of the described feature) and “consisting of” (intended to mean that no other feature may be included such that if the components were expressed as percentages by their proportions, these would add up to 100%, whilst accounting for any unavoidable impurities), unless the context clearly dictates otherwise.

[0083] The foregoing detailed description has been provided by way of explanation and illustration, and is not intended to limit the scope of the appended claims. Many variations of the presently preferred embodiments illustrated herein will be apparent to one of ordinary skill in the art, and remain within the scope of the appended claims and their equivalents.