Exhaust gas treatment method and HVAC system

Abstract

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

Description

[Technical Field]

[0001] The present invention relates to a method for treating exhaust gas, particularly exhaust gas containing carbon monoxide (CO) and / or one or more volatile organic compounds (VOCs), using a PGM-free catalyst article. The present invention also relates to an HVAC system including a PGM-free catalyst article. [Background technology]

[0002] It is well known that catalysts containing platinum group metals (PGMs) can be used for the catalytic oxidation of harmful emissions such as CO and VOCs. PGM catalysts are ubiquitous in catalysts for treating automotive exhaust emissions and emissions from industrial processes. PGM catalysts possess high catalytic activity and good thermal stability. However, PGMs are expensive, and there is a desire to reduce the cost of catalyst materials without losing catalytic activity. This is particularly true for industrial processes such as the catalytic oxidation of tail gas in terephthalic acid synthesis, and for other systems used to treat large volumes of exhaust gas, such as HVAC systems, which require significant investment in expensive PGMs.

[0003] As an alternative to PGM catalysts, PGM-free catalysts containing base metals are known. Although base metals are considerably cheaper, there is still a need for such catalysts that exhibit high catalytic activity to provide improved CO and VOC oxidation activity.

[0004] International Publication No. 03 / 101612 relates to catalyst compositions for treating emissions from industrial and commercial processes, as well as processes for generating electricity from hydrocarbon fuels such as coal, oil, and gas. In particular, the present invention relates to catalyst compositions for oxidizing carbon monoxide (CO) and volatile organic compounds (VOCs), and in one embodiment provides a catalyst composition for use as a hydrogenation catalyst, comprising at least two different high-surface-area oxide support materials, wherein at least one of the high-surface-area support materials supports at least one base metal accelerator.

[0005] International Publication No. 2010 / 123731 relates to copper and manganese-containing base metal catalysts for the oxidation of carbon monoxide and volatile organic compounds. The catalyst composition comprises at least one base metal accelerator and at least one base metal catalyst supported on an oxide support material containing one or more of alumina, silica, zirconia, ceria, and titania (e.g., lanthanum-stabilized alumina and / or zirconium-stabilized ceria).

[0006] International Publication No. 2014 / 138397 relates to base metal catalysts and methods of using the same, in particular to catalysts comprising a first base metal catalyst in contact with an oxygen-donating support substantially free of alumina, and at least one second base metal catalyst. In some embodiments, the catalyst comprises 10-20 wt% CuO, and the catalyst comprises 5-10 wt% MnO. [Overview of the project]

[0007] The inventors developed the present invention with the aim of overcoming problems related to the prior art, providing an improved method for treating exhaust gas containing CO and / or one or more VOCs, or at least a commercially useful alternative.

[0008] Accordingly, a first aspect of the present invention provides a method for treating exhaust gas containing one or more volatile organic compounds (VOCs), comprising contacting the exhaust gas with a PGM-free catalyst article containing a mixed oxide of Mn, Cu, Mg, Al, and La.

[0009] The present disclosure will now be further described. Different aspects / embodiments of the present disclosure will be defined in more detail in the following sections. Each of the aspects / embodiments defined in this way may be combined with any other aspects / embodiments or aspects / embodiments unless otherwise expressly indicated. In particular, any feature indicated as preferred or advantageous may be combined with any other or more features indicated as preferred or advantageous.

[0010] The present invention relates to a method for treating exhaust gas. The exhaust gas contains carbon monoxide and / or one or more volatile organic compounds. In one embodiment, the exhaust gas contains CO and one or more VOCs.

[0011] VOCs are defined by the WHO as any organic compound having a boiling point in the range of (50°C to 100°C) to (240°C to 260°C) and a saturated vapor pressure greater than 102 kPa at 25°C, as cited in ISO 16000-6. Examples of VOCs include alcohols, aldehydes, amines, esters, ethers, hydrocarbons (up to approximately C10), ketones, nitrogen-containing compounds, phenols, indoles and other aromatic compounds, terpenes, and sulfur-containing compounds.

[0012] This method involves contacting exhaust gas with a PGM-free catalyst article containing a mixed oxide of manganese (Mn), copper (Cu), magnesium (Mg), aluminum (Al), and lanthanum (La). Platinum group metals (PGMs) are a known class of precious metals, referring to the group consisting of ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), iridium (Ir), and platinum (Pt). Therefore, the mixed metal oxide does not contain any PGM (e.g., as a metal, or as an oxide or salt). As is understood, all metals in the mixed metal oxide (i.e., Mn, Cu, Mg, Al, and La) exist as oxides, as opposed to being in a metallic state.

[0013] The inventors have found that a mixed metal oxide containing Mn, Cu, Mg, Al, and La provides a particularly effective PGM-free catalyst for the catalytic oxidation of CO and VOCs. Such oxides have been found to provide improved activity even at relatively low temperatures. The inventors have found that this catalyst is particularly effective for the catalytic oxidation of methanol, ethanol, acetaldehyde, formaldehyde, propene (propylene), and ethene (ethylene). Therefore, it is preferable that the VOC contains one or more compounds selected from methanol, ethanol, acetaldehyde, formaldehyde, propene, and ethylene.

[0014] Preferably, the exhaust gas is from a heating, ventilation, and air conditioning (HVAC) system, or is tail gas from a chemical synthesis process, preferably terephthalic acid synthesis. That is, the exhaust gas may be tail gas from a process for producing purified terephthalic acid (PTA). PTA plants release CO, as well as various VOCs such as methyl bromide, benzene, acetate, xylene, acetic acid, and methanol. Such CO and various VOCs together cause smog. Methyl bromide is also a stratospheric ozone depletor.

[0015] In commercial processes for producing PTA, terephthalic acid can be produced by the oxidation of p-xylene with oxygen using acetic acid as the solvent. This can be done in the presence of a catalyst such as cobalt-manganese with the use of a bromide accelerator. The product can be purified by hydrogenation while in an aqueous solution and then cooled. The tail gas in the purified terephthalic acid (PTA) process may contain oxygen, nitrogen, nitrogen oxides, methyl bromide, benzene, methane, carbon monoxide, methyl acetate, and water. Specifically, a typical PTA process exhaust gas may contain 30 parts per million (ppm) methyl bromide, 10 ppm benzene, 100 ppm methane, 1000 ppm carbon monoxide, 500 ppm methyl acetate, 1.5 mol% water, 4 mol% oxygen, and the remainder nitrogen. In addition, mixed metal oxides can also oxidize and convert other volatile organic compounds such as methyl ethyl ketone, methanol, butane, or butene.

[0016] The PTA process tail gas may also contain about 2 mol% water vapor / moisture. Similarly, an HVAC system may be required to handle the water / moisture-containing gas. The mixed oxide must be stable and be able to function effectively in a moisture-containing environment. Certain catalysts and supports, such as zeolites, are known to degrade under hydrothermal conditions, especially over a certain period of time. However, the mixed metal oxides described herein can withstand and function effectively in gases containing water vapor, e.g., 1.5 mol% to 5 mol% moisture, at temperatures above 400°C, or between 200°C and 400°C, 200°C and 325°C, 200°C and 300°C, 200°C and 250°C, or below 325°C, below 300°C, or below 250°C.

[0017] When a gas such as tail gas from a PTA process containing water vapor, CO, and VOC contacts a mixed metal oxide, CO and VOC are oxidized. For example, if the process effluent gas contains water vapor, CO, and methyl bromide, this process effluent may be preheated and pass through a catalyst bed in the presence of excess oxygen, and the contaminating components in the stream are oxidized to carbon dioxide (CO2) and hydrogen bromide (HBr). Hydrogen bromide from downstream of the catalyst can be easily removed from the effluent by passing the gas through a caustic scrubber, and thus contaminants can be removed from the effluent before discharging the effluent to the atmosphere.

[0018] The oxides (which may be referred to herein as mixed metal oxides or mixed oxides) are preferably not supported on a mixed oxide support such as a La, Al, Zr, or Ce mixed oxide. Instead, some of these oxides, specifically the oxides of Al and La, are incorporated into the lattice structure of the mixed metal oxides described herein. Thus, the mixed metal oxide can be represented by a single formula, for example, Mn

[0021] , , ,

[0020] , , , , ,

[0019] Cu b Mg c Al d La e O f (where a, b, c, d, e, and f are the molar amounts of the elements).

[0019] The inventors have found that the mixed metal oxide is particularly effective when the Mn and La contents are higher. Preferably, the mixed oxide contains at least 30% by weight of Mn based on only the metal. More preferably, the mixed oxide contains at least 35% by weight, even more preferably at least 40% by weight of Mn. Preferably, the amount of Mn is at most 60% by weight, more preferably at most 55% by weight, even more preferably at most 50% by weight.

[0020] Preferably, the mixed oxide contains at least 35% by weight of La and / or at most 45% by weight of La, preferably at least 39% by weight of La and / or at most 43% by weight of La.

[0021] All weight percentages (i.e., weight %) described herein with respect to the metals of the mixed metal oxide are provided based on only the metals. That is, the weight % of a given metal is provided as the weight percentage of the total amount of metal in the mixed metal oxide, thus excluding the weight provided by oxygen (O).

[0022] Similarly, the inventors have found that it is preferable for copper to be present in an amount of at least 5 weight %. Preferably, the amount of copper is at most 10 weight %.

[0023] For example, the inventors have found that, in particular, a mixed metal oxide containing 40 - 50 weight % of Mn and at least 5 weight % of copper is a preferred combination of Mn and Cu.

[0024] Furthermore, the inventors have found that preferably the mixed oxide contains at least 3 weight % of Mg and / or at most 6 weight % of Mg. Preferably, the mixed oxide contains at least 1 weight % of Al and / or at most 3 weight % of Al.

[0025] Thus, in a particularly preferred embodiment, the mixed oxide contains, based on only the metals, the following. 40 - 50 weight % of Mn, 6 - 8 weight % of Cu, 3 - 6 weight % of Mg, 1 - 3 weight % of Al, 35 - 45 weight % of La.

[0026] Even more preferably, the mixed oxide contains, based on only the metals, the following. 42 - 48 weight % of Mn, About 7 weight % of Cu, About 4.5 weight % of Mg,[[ID=Z37]] About 2 weight % of Al, 39 - 43 weight % of La.

[0027] Preferably, the term "about" refers to within ±10%, more preferably within ±5%, while at the same time disclosing the value itself within experimental error. Thus, the mixed oxide preferably contains at least 6.3 wt% of Cu and / or at most 7.7 wt% of Cu, for example, 6.3 wt% - 7 wt%, 7 wt% - 7.7 wt% or 6.3 wt% - 7.7 wt%. Similarly, the mixed oxide preferably contains at least 4.05 wt% of Mg and / or at most 4.95 wt% of Mg, for example, 4.05 wt% - 4.5 wt%, 4.5 wt% - 4.95 wt% or 4.05 wt% - 4.95 wt%. Preferably, the mixed oxide preferably contains at least 1.8 wt% of Al and / or at most 2.2 wt% of Al, for example 1.8 wt% - 2 wt%, 2 wt% - 2.2 wt% or 1.8 wt% - 2.2 wt%. The same applies to the preferred range of ±5%.

[0028] In a preferred embodiment, the mixed oxide consists essentially of Mn, Cu, Mg, Al and La, and oxygen (O). That is, the mixed metal oxide can be represented by a single formula, for example Mn a Cu b Mg c Al d La e O f (where a, b, c, d, e and f are the molar amounts of the elements). Similarly, the total weight percentage of the metals Mn, Cu, Mg, Al and La is essentially equal to 100 wt%.

[0029] The molar ratio of Mn to La is preferably at least 2.5:1 and / or at most 3:1. For example, the molar ratio of Mn to La is preferably 2.5:1 - 3:1. In other words, the ratio a:e is 2.5:1 - 3:1. The Mn to Al ratio is preferably at least 10:1 and / or at most 12:1, for example the ratio a:d is preferably 10:1 - 12:1. The Mn to Mg ratio is preferably at least 4:1 and / or at most 5:1, for example the ratio a:c is preferably 4:1 - 5:1. The Mn to Cu ratio is preferably at least 7:1 and / or at most 7.5:1, for example the ratio a:b is preferably 7:1 - 7.5:1.

[0030] In a further aspect of the present invention, an HVAC system is provided that includes a PGM-free catalyst article comprising a mixed oxide of Mn, Cu, Mg, Al, and La.

[0031] Preferably, mixed oxides of Mn, Cu, Mg, Al, and La are those described herein in relation to methods for treating exhaust gases. For example, the mixed oxides preferably include, based solely on the metals: 40-50% by weight of Mn, 6-8% by weight of Cu, 3-6% by weight of Mg, 1-3% by weight of Al, 35-45% by weight of La.

[0032] The inventors have found that a mixed metal oxide containing Mn, Cu, Mg, Al, and La exhibits greater VOC oxidation activity along with selectivity for CO2. As a result, this oxide is particularly effective in removing harmful VOC pollutants from the air in HVAC systems for providing purified indoor air. In particular, the mixed metal oxide is especially effective as an oxidation catalyst at relatively low temperatures and is therefore particularly suitable for such low-temperature applications.

[0033] In the following, catalyst A is a comparative catalyst, and catalyst MO is an example of the present invention. [Brief explanation of the drawing]

[0034] The present invention will now be further described with reference to the following non-limiting figures. [Figure 1A] The results of Example 1 are provided, and the conversion rates of formaldehyde and methanol, respectively, against temperature under gas engine test conditions are plotted for catalyst MO and catalyst A, a known comparative base metal catalyst. [Figure 1B]The results of Example 1 are provided, and the conversion rates of formaldehyde and methanol, respectively, against temperature under gas engine test conditions are plotted for catalyst MO and catalyst A, a known comparative base metal catalyst. [Figure 2A] The results of Example 2 are provided, and the conversion rates of CO and NO, respectively, against temperature under gas engine test conditions are plotted for both catalyst MO and catalyst A. [Figure 2B] The results of Example 2 are provided, and the conversion rates of CO and NO, respectively, against temperature under gas engine test conditions are plotted for both catalyst MO and catalyst A. [Figure 3A] The results of Example 3 are provided, and the conversion rates of methanol and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 3B] The results of Example 3 are provided, and the conversion rates of methanol and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 3C] For both catalyst MO and catalyst A, the observed concentrations of formaldehyde and CO2, respectively, are plotted against temperature. [Figure 3D] For both catalyst MO and catalyst A, the observed concentrations of formaldehyde and CO2, respectively, are plotted against temperature. [Figure 4A] The results of Example 4 are provided, and the conversion rates of ethanol and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 4B] The results of Example 4 are provided, and the conversion rates of ethanol and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 4C] For both catalyst MO and catalyst A, the observed concentrations of acetaldehyde and formaldehyde, respectively, are plotted against temperature. [Figure 4D] For both catalyst MO and catalyst A, the observed concentrations of acetaldehyde and formaldehyde, respectively, are plotted against temperature. [Figure 5A] The results of Example 5 are provided, and the conversion rates of propene and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 5B] The results of Example 5 are provided, and the conversion rates of propene and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 6A] The results of Example 6 are provided, and the conversion rates of ethylene and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 6B] The results of Example 6 are provided, and the conversion rates of ethylene and CO, respectively, against temperature under VOC test conditions for catalyst MO along with catalyst A are plotted. [Figure 7A] The results of Example 7 are provided, and the conversion rates of ethylene, propene, and CO, respectively, against temperature under VOC test conditions for catalyst MO together with catalyst A are plotted. [Figure 7B] The results of Example 7 are provided, and the conversion rates of ethylene, propene, and CO, respectively, against temperature under VOC test conditions for catalyst MO together with catalyst A are plotted. [Figure 7C] The results of Example 7 are provided, and the conversion rates of ethylene, propene, and CO, respectively, against temperature under VOC test conditions for catalyst MO together with catalyst A are plotted. [Examples]

[0035] Manufacturing of mixed metal oxides Coprecipitation involves the use of metal nitrates (Mn, Cu, Mg, Al, La) in solution. An alkaline solution is used as a precipitant (NaOH / Na2CO3). The metal nitrate solution is obtained by dissolving the metal nitrate precursor with demineralized water in one container. To prepare the alkaline solution, NaOH and Na2CO3 are mixed together and demineralized water is added. Both solutions are stirred, and then both solutions are transferred from the container to the reactor using a liquid pump.

[0036] [Table 1]

[0037] [Table 2]

[0038] Coprecipitation was performed by adding both solutions from Tables 1 and 2 with stirring at a controlled addition rate that allowed the pH to be kept constant at approximately 10–11. The pH could be monitored using a standard pH electrode.

[0039] The addition may be carried out over approximately one hour, and the reaction mixture may be stirred for another hour after the addition is complete.

[0040] After coprecipitation is complete, washing and filtration are necessary. A large amount of demineralized water is passed through a precipitating agent until the conductivity of the water reaches that of fresh demineralized water (e.g., about 100 μS).

[0041] Finally, the solid material is dried overnight in air at 105-110°C, then pulverized, and subsequently calcined, for example, at 500°C in air for 2 hours. The resulting mixed metal oxide may be referred to herein as catalyst MO.

[0042] Testing of mixed metal oxides The mixed metal oxides were tested against catalyst A, a known commercially available PGM-free base metal catalyst used for comparison.

[0043] Catalyst A was prepared according to International Publication No. 2010 / 123731 and comprises a support containing lanthanum-stabilized alumina and cerium-stabilized zirconia. Manganese was added as acetate to the washcoat slurry and applied to a ceramic substrate in two passes at a concentration of 3.3 g / in. 3 (0.2g / cm 3 ) provides the target wash coat load. Then, copper nitrate is added at 375 g / ft. 3 (13,243g / m 3The target is impregnated. As determined by ICP, catalyst A contains 3 wt% Mn and 2 wt% Cu based solely on metals.

[0044] Catalyst core A was crushed, pelletized, pulverized, and sieved. Sieve fractions with a sieve size of 355-250 μm were used for testing. A total of 0.2 g of sieved material was tested.

[0045] The mixed oxide was in powder form and therefore did not need to be crushed. The sample was also pelletized, ground, and sieved before testing.

[0046] Example 1 (Activity of formaldehyde and methanol): Gas engine test conditions: 100 ppm CH4, 20 ppm CH2O, 200 ppm NO x , 540ppm CO, 10%O2, 10%CO2, 10%H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0047] The results are shown in Figures 1A and 1B. The mixed metal oxide (i.e., catalyst MO) achieved a 50% formaldehyde conversion rate at 175°C, while catalyst A achieved a 50% formaldehyde conversion rate at 220°C. Similarly, the mixed metal oxide achieved a 50% methanol conversion at a lower temperature of 211°C compared to 270°C required by catalyst A.

[0048] Example 2 (Activity of CO and NO): Gas engine test conditions: 100 ppm CH4, 20 ppm CH2O, 200 ppm NO x , 540ppm CO, 10%O2, 10%CO2, 10%H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0049] The results are shown in Figures 2A and 2B. The mixed metal oxide (i.e., catalyst MO) achieved a 50% CO conversion rate at 243°C, while catalyst A achieved a 50% CO conversion rate at 272°C. Similarly, the NO conversion initiation temperature for the mixed metal oxide was approximately 225°C, while the NO conversion initiation temperature for catalyst A was approximately 300°C.

[0050] Example 3 (Oxidation of methanol and CO): VOC test conditions: 500 ppm methanol 、 1000ppm CO, 15%O2, 5% H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0051] The results are shown in Figures 3A and 3B. The mixed metal oxide (i.e., catalyst MO) achieved a methanol conversion rate of 50% at 191°C, while catalyst A achieved a methanol conversion rate of 50% at 260°C. Similarly, the mixed metal oxide achieved a CO conversion rate of 50% at a lower temperature of 222°C compared to 275°C required by catalyst A.

[0052] Furthermore, as can be seen in Figures 3C and 3D, the mixed metal oxides exhibit greater selectivity for CO2 generation, resulting in a reduction in the amount of formaldehyde produced.

[0053] Example 4 (Oxidation of ethanol and CO): VOC test conditions: 500 ppm ethanol 、 1000ppm CO, 15%O2, 5% H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0054] The results are shown in Figures 4A and 4B. The mixed metal oxide (i.e., catalyst MO) achieved a 50% ethanol conversion rate at 198°C, while catalyst A achieved a 50% ethanol conversion rate at 261°C. Similarly, the mixed metal oxide achieved a 50% CO conversion rate at a lower temperature of 236°C compared to the 288°C required by catalyst A.

[0055] Furthermore, as can be seen in Figures 4C and 4D, the mixed metal oxide produces less formaldehyde than catalyst A.

[0056] Example 5 (Oxidation of propene and CO): VOC test conditions: 500 ppm propene 、 1000ppm CO, 15%O2, 5% H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0057] The results are shown in Figures 5A and 5B. The mixed metal oxide (i.e., catalyst MO) achieves a 50% propene conversion rate at 284°C, while catalyst A achieves a 50% propene conversion rate at a significantly higher temperature of 390°C. Similarly, the mixed metal oxide achieves a 50% CO conversion rate at a lower temperature of 207°C compared to the 262°C required by catalyst A.

[0058] Example 6 (Oxidation of ethylene and CO): VOC test conditions: 500 ppm ethylene 、 1000ppm CO, 15%O2, 5% H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0059] The results are shown in Figures 6A and 6B. The mixed metal oxide (i.e., catalyst MO) achieves a 50% ethylene conversion rate at 346°C, while catalyst A achieves a 50% ethylene conversion rate at a significantly higher temperature of 475°C. Similarly, the mixed metal oxide achieves a 50% CO conversion rate at a lower temperature of 196°C compared to the 259°C required by catalyst A.

[0060] Example 7 (Oxidation of propylene, ethylene, and CO): VOC test conditions: 500 ppm propene, 500 ppm ethylene 、1000ppm CO, 15%O2, 5%H2O, balance N2; 0.2g catalyst (355~250μm), flow rate = 3.3L / min, T ramp = 110~500℃.

[0061] The results are shown in Figures 7A to 7C. The mixed metal oxide (i.e., catalyst MO) achieves a 50% ethylene conversion rate at 335°C and a 50% propene conversion rate at 247°C, while catalyst A achieves 50% ethylene and propene conversion rates at significantly higher temperatures of 435°C and 355°C, respectively. Similarly, the mixed metal oxide achieves a 50% CO conversion rate at a lower temperature of 195°C compared to the 226°C required by catalyst A.

[0062] As used herein, the singular forms “a,” “an,” and “the” include multiple referents unless the context clearly indicates otherwise. The use of the term “comprising” is intended to be interpreted as including such features but not excluding other features, and is intended to include a selection of features that are necessarily limited to those described. In other words, the term also includes the limitations of “essentially consisting of” (intended to mean that certain further components may exist on the condition that they do not substantially affect the essential properties of the described feature) and “consisting of” (intended to mean that if the components are expressed as percentages by their proportions, these together amount to 100%, while explaining any unavoidable impurities, but not including any other features).

[0063] The detailed description above is provided for illustrative and illustrative purposes only and is not intended to limit the scope of the appended claims. Many modifications of the currently preferred embodiments shown herein will be obvious to those skilled in the art and remain within the scope of the appended claims and their equivalents.

Claims

1. A method for treating exhaust gas containing carbon monoxide (CO) and / or one or more volatile organic compounds (VOCs), comprising contacting the exhaust gas with a PGM-free catalyst article containing a mixed oxide of Mn, Cu, Mg, Al, and La, The aforementioned mixed oxide is based solely on metal, 40-50% by weight of Mn, At least 5% by weight of Cu, 3-6% by weight of Mg, 1-3% by weight of Al, A method comprising 35-45% by weight of La.

2. The aforementioned mixed oxide is based solely on metal, 6-8% by weight of Cu The method according to claim 1, including the method described in claim 1.

3. The aforementioned mixed oxide is based solely on metal, 42-48% by weight of Mn, 7% by weight of Cu, 4.5% by weight of Mg, 2% by weight of Al, The method according to claim 1, comprising 39 to 43% by weight of La.

4. The method according to claim 2, wherein the mixed oxide essentially consists of Mn, Cu, Mg, Al, and La, and oxygen.

5. The method according to claim 1, wherein the molar ratio of Mn to La is 2.5:1 to 3:

1.

6. The method according to claim 1, wherein the VOC comprises one or more compounds selected from methanol, ethanol, acetaldehyde, formaldehyde, propene, and ethylene.

7. The method according to claim 1, wherein the exhaust gas is from an HVAC system or is tail gas from a chemical synthesis process, preferably terephthalic acid synthesis.

8. An HVAC system comprising a PGM-free catalyst article containing a mixed oxide of Mn, Cu, Mg, Al, and La, wherein the mixed oxide is based solely on metals, 40-50% by weight of Mn, 6-8% by weight of Cu, 3-6% by weight of Mg, 1-3% by weight of Al, HVAC system containing 35-45% by weight of La.

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