KR20220139712A - Nitrogen monoxide oxidation catalyst and its manufacturing method - Google Patents

Abstract

The present invention provides a nitrogen monoxide oxidation catalyst comprising a titania support supported with ruthenium and cobalt and a manufacturing method thereof. The catalyst can effectively oxidize nitrogen monoxide to be converted into easily adsorbable nitrogen dioxide.

Description

Nitrogen monoxide oxidation catalyst and its manufacturing method

The present invention relates to a nitrogen monoxide oxidation catalyst and a method for preparing the same.

Recently, the demand for high fuel efficiency vehicles is increasing due to the strengthening of regulations on carbon dioxide (CO ₂ ) emission throughout the industry. Demand for vehicles equipped with In the case of the diesel engine and the GDI engine, when the fuel is burned in the engine room, the fuel is burned using an excess of oxygen compared to the stoichiometric air-fuel ratio, so the combustion efficiency is high and the fuel efficiency is excellent, while nitrogen oxides (herein referred to as nitrogen oxides) As referring to both NO and NO2, the concentration of NOx) is high. Since these nitrogen oxides have a significant effect on air pollution and human health, emission regulations on nitrogen oxides are being strengthened worldwide.

In particular, a lot of effort is being made to remove NOx, which is the main cause of increased ozone concentration in the lower atmosphere, ozone layer destruction, and acid rain. It is known that the reduction method (Selective Catalytic Reduction, SCR) exhibits a high decomposition efficiency of NOx. The dual selective catalytic reduction method uses a reaction for reducing NOx to water and nitrogen on a catalyst using a hydrocarbon or a reducing agent such as ammonia or urea.

4NO + 4NH ₃ + O ₂ → 4N ₂ + 6H ₂ O

In the SCR, when the composition of NO and NO ₂ in the exhaust gas is 1:1, the denitration efficiency can be greatly improved, and this reaction is called Fast-SCR. Therefore, in order to improve the efficiency of the SCR catalyst, it is necessary to develop a catalyst capable of oxidizing nitrogen monoxide and converting it into nitrogen dioxide form. In addition, high concentrations of nitrogen oxides (NOx) are emitted in semiconductor processes or general manufacturing and industrial sites, and nitrogen oxides generated in the process are mainly emitted in the form of nitrogen monoxide (NO). Absorption/adsorption removal is performed at the facility using a scrubber or adsorbent. However, nitrogen monoxide has a disadvantage in that it has low solubility or difficult adsorption compared to nitrogen dioxide (NO ₂ ). Therefore, in order to more easily and economically remove nitrogen oxides, a method of oxidizing nitrogen monoxide to nitrogen dioxide and adsorbing/removing it has been proposed. Therefore, there is a need for the development of a catalyst capable of oxidizing nitrogen monoxide and converting it into nitrogen dioxide form.

Registered Patent No. 1057342

As seen in the background technology, the present invention decomposes adsorbed nitrate at a temperature of 250° C. or higher and converts it to nitrogen dioxide, and at a relatively low temperature, nitrogen monoxide and oxygen single-bonded to ruthenium particles react to convert to nitrogen dioxide. An object of the present invention is to provide a catalyst capable of oxidizing nitrogen monoxide without lowering activity in a wide range of temperatures by having a mechanism and a method for preparing the same.

The present invention provides a nitrogen monoxide oxidation catalyst comprising a titania support on which ruthenium and cobalt are supported, wherein the ruthenium and cobalt are mixed in a weight ratio of 1: 5 to 5: 1, to provide a nitrogen monoxide oxidation catalyst.

In one embodiment of the present invention, the ruthenium is characterized in that it is included in an amount of 0.1 to 10% by weight based on 100% by weight of the titania support.

In another embodiment of the present invention, the cobalt is included in an amount of 0.1 to 10% by weight based on 100% by weight of the titania support.

In another embodiment of the present invention, the nitrogen monoxide oxidation catalyst is characterized in that it exhibits a nitrogen monoxide oxidation efficiency of 20% or more at 200 °C or higher.

In another embodiment of the present invention, the titania support is characterized in that it has an anatase phase, a rutile phase, or a phase in which anatase phase and a rutile phase are mixed.

In addition, the present invention comprises the steps of preparing a mixed solution by mixing a ruthenium precursor solution and a cobalt precursor solution with titania (S1); and

After drying the mixed solution to remove moisture, and calcining (S2),

The ruthenium precursor solution and the cobalt precursor solution provide a method for producing a nitrogen monoxide oxidation catalyst, characterized in that mixed in a weight ratio of 1: 5 to 5: 1.

In an embodiment of the present invention, the ruthenium precursor is included in an amount of 0.1 to 10% by weight based on 100% by weight of titania.

In another embodiment of the present invention, the cobalt precursor is included in an amount of 0.1 to 10% by weight based on 100% by weight of titania.

In another embodiment of the present invention, the firing in step S2 is characterized in that the temperature is raised to a temperature of 300 to 800 °C for 2 to 12 hours at a temperature increase rate of 5 to 30 °C/min.

The nitrogen monoxide oxidation catalyst according to the present invention has the advantage that ruthenium and cobalt interact on the surface of titania, allowing oxidation of nitrogen monoxide even at low temperatures.

1 is a result confirming the NO oxidation efficiency of a catalyst prepared by supporting ruthenium and cobalt having different weight ratios on titania.
2 is a result of confirming the NO oxidation efficiency according to the temperature of the catalyst prepared by supporting ruthenium and cobalt having different weight ratios on titania.
3 is a result of analyzing the surface properties of the catalyst of Preparation Example 1 using FT-IR.
4 is a TPD analysis result performed to confirm the desorption temperature of nitrate in a catalyst prepared by supporting ruthenium and cobalt having different weight ratios on titania.
5 is an FT-IR analysis result of observing the reaction on the surface of the catalyst of Preparation Example 1.
6 is a result of confirming the simultaneous oxidation efficiency of NO and CO of the catalyst of Preparation Example 4 and the difference in decomposition temperature due to the deposition of soot.

The present invention can apply various transformations and can have various embodiments. Hereinafter, specific embodiments are illustrated in the drawings and described in detail in the detailed description. However, this is not intended to limit the present invention to specific embodiments, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, if it is determined that a detailed description of a related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The present invention is a nitrogen monoxide oxidation catalyst comprising a titania support on which ruthenium and cobalt are supported to achieve excellent nitrogen monoxide oxidation efficiency, wherein the ruthenium and cobalt are mixed in a weight ratio of 1: 5 to 5: 1, A catalyst for oxidation of nitrogen monoxide is provided.

The catalyst has a dual mechanism in which adsorbed nitrate is decomposed and converted to nitrogen dioxide at a temperature of 250° C. or higher, and nitrogen monoxide and oxygen single bonded to ruthenium particles react to react to convert to nitrogen dioxide at a relatively low temperature. It is possible to oxidize nitrogen monoxide without degradation.

The ruthenium and cobalt are characterized in that they interact with each other on the surface of titania. Accordingly, the mixing ratio of ruthenium and cobalt affects the activity of the catalyst, and may be mixed and used in a weight ratio of 1:5 to 5:1. In the catalyst, when the cobalt oxidation number is Co ³⁺ 40% or more, active interaction is shown, and nitrogen monoxide oxidation efficiency is excellent. The ruthenium and cobalt may be mixed in a weight ratio of preferably 1:1 to 2:1.

The ruthenium may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the titania support, and the cobalt may be included in an amount of 0.1 to 10% by weight based on 100% by weight of the titania support. Preferably, the cobalt exhibits excellent oxidation efficiency when included in an amount of 0.1 to 5% by weight, more preferably 1 to 3% by weight.

The nitrogen monoxide oxidation catalyst is characterized in that nitrogen monoxide is adsorbed as nitrate on the catalyst surface at 200° C. or higher, and then decomposed to form nitrogen dioxide. In addition, at 200° C. or less where the decomposition of the nitrate does not occur, since nitrogen monoxide and oxygen single-bonded to the ruthenium particles can react to be converted into nitrogen dioxide, the catalyst of the present invention has excellent oxidation efficiency in a wide range of temperatures.

The titania support may have an anatase phase, a rutile phase, or a phase in which anatase phase and a rutile phase are mixed, and preferably those having a phase in which anatase and rutile phases are mixed.

In addition, the present invention comprises the steps of preparing a mixed solution by mixing a ruthenium precursor solution and a cobalt precursor solution with titania (S1); and

After drying the mixed solution to remove moisture, and calcining (S2),

The ruthenium precursor solution and the cobalt precursor solution provide a method for producing a nitrogen monoxide oxidation catalyst, characterized in that mixed in a weight ratio of 1: 5 to 5: 1.

Conditions such as the mixing ratio of the ruthenium precursor and the cobalt precursor and the phase of the support are the same as described above.

The catalyst of the present invention is prepared through wet impregnation. A vacuum rotary evaporator, a dryer, etc. may be used for drying to remove moisture in step S2, but is not limited thereto, as long as it is a device or method for removing moisture contained in the catalyst in general.

As an embodiment of the present invention, the sintering in step S2 is preferably performed by raising the temperature to a temperature of 300 to 800 °C for 2 to 12 hours at a temperature increase rate of 5 to 30 °C/min.

Hereinafter, the present invention will be described in more detail based on preferred embodiments of the present invention. However, it goes without saying that the technical spirit of the present invention is not limited thereto and may be variously implemented by those skilled in the art.

<Production of catalyst>

The titania (TiO ₂ ) used in the catalyst preparation may be characterized as having an anatase or rutile phase, and more specifically, a titania in which anatase and rutile are mixed. First, using a ruthenium nitrosylnitrate (N ₄ O ₁₀ Ru, Alfa Aesar Co.) or ruthenium chloride (RuCl ₃ , Alfa Aesar Co.) precursor, the weight ratio of ruthenium to titania (TiO ₂ ) (wt.%) Calculate and dissolve in distilled water at room temperature. In the same manner, cobalt nitrate (Co(NO ₃ ) ₂ *6H ₂ O) precursor was used to calculate the weight ratio of cobalt to titania (TiO ₂ ) and dissolved separately in distilled water. At this time, the weight ratio of ruthenium and cobalt to titania was prepared to be 1 wt.%, respectively. The prepared ruthenium solution and cobalt solution are mixed with titania. Then, after drying using a vacuum rotary evaporator to remove moisture from the prepared mixed solution, it was dried sufficiently in a dryer at 103° C. for 24 hours or more. The resulting powder was heated to a temperature of 400 °C at a heating rate of 10 °C/min in a rectangular furnace and calcined in an air atmosphere for 4 hours to prepare ruthenium-cobalt-titania oxide.

In this example, the nitrogen monoxide oxidation performance according to the weight ratio of ruthenium and cobalt to titania was compared, and the weight ratio of the two materials is shown in Table 1 below.

weight ratio (%) ruthenium cobalt Comparative Preparation Example 1 One 0 Comparative Preparation Example 2 3 0 Comparative Preparation Example 3 5 0 Comparative Preparation Example 4 0 One Comparative Preparation Example 5 0 3 Preparation Example 1 One One Preparation 2 One 3 Preparation 3 One 5 Preparation 4 3 3 Preparation 5 5 3

<Result>

Experimental Example 1: NO oxidation efficiency according to temperature

1 shows the NO oxidation efficiency according to the temperature of the ruthenium/titania catalyst and the ruthenium-cobalt/titania catalyst in which cobalt is added as a co-catalyst by content (1-5 wt%). In Comparative Preparation Example 1 and Comparative Preparation Example 2, the NO oxidation efficiency was decreased at a temperature of 270° C. or less, and respectively 40% and 52% at 250° C. Therefore, Comparative Preparation Example 2 exhibited a difference in NO oxidation efficiency of about 12% at 250° C. despite a high ruthenium content compared to Comparative Preparation Example 1.

On the other hand, Preparation Example 1 and Preparation Example 2 showed 83% and 81% respectively at 250° C., and thus showed higher NO oxidation efficiency than Comparative Preparation Example 2, and Preparation Example 3 was 67% at 250° C., Preparation Example 1 Although the performance was decreased compared to that of Preparation Example 2 and Comparative Preparation Example 2, NO oxidation efficiency was higher than that of Comparative Preparation Example 2. Therefore, the catalyst in which cobalt is added as a cocatalyst to the ruthenium/titania catalyst has a tendency to increase the NO oxidation efficiency, and the content of cobalt added is preferably 0.1 to 5%, more preferably 1 to 3% is suitable. do.

Experimental Example 2: NO oxidation efficiency according to ruthenium content

2 shows the difference in NO oxidation efficiency according to the ruthenium content of the ruthenium/titania catalyst and the ruthenium-cobalt/titania catalyst in which cobalt is added as much as 3 wt.% as a cocatalyst. In Comparative Preparation Example 2 and Comparative Preparation Example 3, the NO oxidation efficiency started to decrease at a temperature of 270° C. or less, and exhibited almost the same efficiency as in FIG. 1 . On the other hand, Preparation Example 2, Preparation Example 4, and Preparation Example 5 in which cobalt was added exhibited NO oxidation efficiency of 90% or more even at 270°C or lower, and in Preparation Example 5, NO oxidation efficiency of 90% or more was exhibited up to 230°C. In addition, Comparative Preparation Example 2 and Comparative Preparation Example 3 showed an NO oxidation efficiency of 10% or less at 200°C, but in the case of Preparation Example 2, Preparation Example 4, and Preparation Example 5, 20%, 30%, and 48%, respectively The ruthenium content of the cobalt-added ruthenium-cobalt/titania catalyst is preferably 0.1 to 10%, and even more preferably 1 to 5% is suitable according to the NO oxidation efficiency of the catalyst.

Experimental Example 3: Confirmation of change in cobalt oxidation value of ruthenium-cobalt/titania catalyst

Comparative Preparation Example 4 Preparation Example 1 Preparation 2 Preparation 3 Preparation 4 Preparation 5 Co ²⁺ (%) 97.74 53.40 59.10 61.15 56 51.92 Co ³⁺ (%) 2.26 46.6 40.90 38.84 44 48.08

Table 2 shows the change in cobalt oxidation value of the ruthenium-cobalt/titania catalyst. The cobalt oxidation value of Comparative Preparation Example 4 was mainly present as Co ²⁺ and was 97.74%. However, Co ²⁺ of Preparation Examples 1 and 2 showed a tendency to decrease to 53.40% and 59.10%. In addition, Co ²⁺ of Preparation Examples 4 and 5, in which the content of ruthenium in Preparation Example 2 was increased to 3 wt.% and 5 wt.%, respectively, showed a tendency to gradually decrease to 56% and 51.92%. The change in the oxidation value of cobalt on the catalyst surface according to the addition of ruthenium means that ruthenium and cobalt are interacting in the ruthenium-cobalt/titania catalyst, and the catalyst with excellent NO oxidation efficiency has Co ³⁺ of 40% or more existence can be verified.

Experimental Example 4: NO oxidation reaction of ruthenium-cobalt/titania catalyst

According to previous studies (Catalysis Science & Technology, 7, 3440-3452, 2017), the NO oxidation reaction mechanism is a direct oxidation reaction in which NO is oxidized to NO ₂ on the catalyst surface, and NO is nitrate (NO ₃ ) on the catalyst surface. ) and decomposed at a certain temperature to convert to NO ₂ nitrate decomposition reaction was mentioned. 3 is a result of analyzing the surface properties of Preparation Example 1 in which NO is adsorbed using FT-IR to confirm the mechanism of the ruthenium-cobalt/titania catalyst. The experiment of FIG. 3 confirms the peak generated by adsorbing 1,000 ppm of NO and 10% of O ₂ to Preparation Example 1 at 50° C., stopping the injection of NO and O ₂ and injecting N ₂ alone to desorb each peak. The temperature was checked. When NO is adsorbed to the catalyst, it can be adsorbed in the form of NO ₃ , and as shown in FIG. 3 , the peak generated at each wavenumber (1625, 1583, 1520-1485, 1310, 1284 cm ^-1 ) is the adsorption form of NO ₃ means It was confirmed that the peak was maintained up to about 200 °C, and it was confirmed that the peak was decomposed at a temperature of 250 °C or higher.

Ru-NO ₃ → NO ₂ + Ru-O (Scheme 1)

As mentioned in FIG. 3 , NO-TPD analysis was performed to confirm the temperature at which NO ₃ adsorbed to the catalyst is desorbed to NO ₂ , and the results are shown in FIG. 4 . In the experimental method of FIG. 4 , after pretreatment by injecting 10% of O ₂ at a temperature of 400° C., NO was injected at 60° C. to adsorb on the catalyst surface, and then N ₂ was injected to desorb the physically adsorbed NO. Thereafter, the temperature at which NO ₃ adsorbed on the catalyst surface was desorbed was checked. According to the above results, it was confirmed that Preparation Example 1 was desorbed to NO ₂ at a lower temperature than Comparative Preparation Example 1 and Comparative Preparation Example 4. In addition, as Preparation Example 5 was desorbed at a lower temperature of about 14° C. compared to Preparation Example 1, the more the catalyst interacted with ruthenium and cobalt, the more NO ₂ was desorbed at a lower temperature.

Experimental Example 5: Confirmation of Reaction Mechanism of Ruthenium-Cobalt/Titania Catalyst

In FIG. 1, it was confirmed that the catalyst of Preparation Example 1 having an interaction between ruthenium and cobalt exhibits an NO oxidation efficiency of about 20% at a temperature of 200° C. in which NO ₃ is not decomposed. Therefore, FT-IR analysis was performed to confirm the reaction mechanism of the catalyst of Preparation Example 1 at 200°C. As an experimental method, 1,000 ppm of NO and 10% of O ₂ were adsorbed on the surface of the catalyst at 200° C. to confirm the adsorbed form on the surface of the catalyst.

As shown in FIG. 5 , peaks indicating the NO ₃ form generated at each wavenumber (1610, 1585, 1540-1490, 1300, 1244 cm ⁻¹ ) could be observed. In addition, a peak indicating NO (Ru-NO) single bound to the ruthenium particles was observed at 1880 cm ^-1 . The injection of NO was restricted to the corresponding catalyst, and 10% of O ₂ was injected to observe the reaction on the catalyst surface. As a result, the peak in the form of NO ₃ did not decrease but was maintained, but it was confirmed that the peak indicating NO (Ru-NO) single bonded to the ruthenium particles observed at 1880 cm -1 decreased. Through this experiment, it was confirmed that NO (Ru-NO) and oxygen, which were single bonded to the ruthenium particles, reacted to convert to NO2 at a temperature below 200 °C.

Ru-NO + Ru-O → NO2 (Scheme 2)

Therefore, the ruthenium-cobalt/titania catalyst (Preparation Example 1-5) to which cobalt was added through the contents described in FIGS. 1 and 2 showed excellent NO oxidation efficiency compared to the ruthenium/titania catalyst (Comparative Preparation Example 1-3). As shown in Table 1, it was confirmed that ruthenium and cobalt interact on the surface of titania through the change in cobalt oxidation according to the addition of ruthenium.

In addition, through the results of FIGS. 3 and 4 , it was confirmed that NO ₃ generated on the surface of the catalyst in which ruthenium and cobalt interact was decomposed at a lower temperature to form NO ₂ , and through the results of FIG. 5 , NO At a temperature of 200 °C where ₃ is not decomposed, it was observed that a single NO (Ru-NO) bound to ruthenium disappeared by the reaction.

Therefore, the catalyst prepared by the present invention is shown to have a dual-mechanism capable of generating NO ₂ by two mechanisms.

Experimental Example 6: Confirmation of simultaneous oxidation of NO and CO of ruthenium-cobalt/titania catalyst

As mentioned above, using Preparation Example 4 with excellent NO to NO2 conversion, the simultaneous oxidation efficiency was compared when NO and CO were simultaneously introduced, and decomposition according to the presence/absence of NO injection when soot was deposited on the catalyst surface. The temperature was checked. Simultaneous injection of NO and CO was conducted to confirm whether the oxidation efficiency was affected when both gases were simultaneously introduced into the catalyst. As an experimental method, 10 vol.% of oxygen and 950 ppm of NO were injected as a catalyst at a temperature of 270°C to check the conversion rate, and 6200 ppm of CO was additionally injected to check the effect on the oxidation efficiency of NO and CO. After that, the injection of CO is stopped and the efficiency is checked again when NO is injected alone. As a result of the experiment, the conversion rate to NO2 was 91% when NO alone was injected, and it was confirmed that the conversion rate to CO2 was mostly about 99% without affecting the NO oxidation efficiency when CO was injected at the same time. When the injection of CO was stopped and the oxidation efficiency of NO to NO2 was checked, the conversion rate was maintained as it is, and it was confirmed that the catalyst of Preparation Example 4 can simultaneously treat NO and CO with excellent efficiency.

Experimental Example 7: Confirmation of effect by soot deposition of ruthenium-cobalt/titania catalyst

When soot was deposited on the catalyst surface using Preparation Example 4 having an excellent NO to NO2 conversion as described above, the decomposition temperature according to the presence/absence of NO injection was confirmed.

When soot was deposited on the catalyst surface, the decomposition temperature was checked according to the presence/absence of NO injection. When NO was injected and 10 vol.% of O ₂ was injected, soot on the catalyst surface was oxidized by the catalyst at 326° C. and converted to CO ₂ . On the other hand, when NO was simultaneously injected and soot removal on the catalyst surface was confirmed, conversion to CO ₂ was confirmed at 301°C as low as 25°C. These results confirm that the injected NO is converted to NO ₂ on the catalyst surface, and the converted NO ₂ is used as an oxidizing agent so that soot can be decomposed at a relatively low temperature.

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, it is clear that this specific description is only a preferred embodiment, and the scope of the present invention is not limited thereby. something to do. Accordingly, the substantial scope of the present invention will be defined by the appended claims and their equivalents.

Claims (11)

As a nitrogen monoxide oxidation catalyst comprising a titania support on which ruthenium and cobalt are supported,
The ruthenium and cobalt 1: 5 to 5: 1 will be mixed in a weight ratio of, the nitrogen monoxide oxidation catalyst. According to claim 1,
The ruthenium is, characterized in that contained in 0.1 to 10% by weight based on 100% by weight of the titania support, nitrogen monoxide oxidation catalyst. According to claim 1,
The cobalt, nitrogen monoxide oxidation catalyst, characterized in that contained in 0.1 to 10% by weight based on 100% by weight of the titania support. According to claim 1,
The nitrogen monoxide oxidation catalyst is characterized in that it exhibits a nitrogen monoxide oxidation efficiency of 20% or more at 200 ° C. or higher, the nitrogen monoxide oxidation catalyst. According to claim 1,
The titania support is characterized in that it has an anatase phase, a rutile phase, or a phase in which anatase phase and a rutile phase are mixed. preparing a mixed solution by mixing the ruthenium precursor solution and the cobalt precursor solution with titania (S1); and
After drying the mixed solution to remove moisture, and calcining (S2),
The ruthenium precursor solution and the cobalt precursor solution are 1: 5 to 5: a method for producing a nitrogen monoxide oxidation catalyst, characterized in that mixed in a weight ratio of 1. 7. The method of claim 6,
The ruthenium precursor is a method for producing a nitrogen monoxide oxidation catalyst, characterized in that contained in 0.1 to 10% by weight based on 100% by weight of titania. 7. The method of claim 6,
The cobalt precursor is a method for producing a nitrogen monoxide oxidation catalyst, characterized in that contained in 0.1 to 10% by weight based on 100% by weight of titania. 7. The method of claim 6,
The nitrogen monoxide oxidation catalyst is a method for producing a nitrogen monoxide oxidation catalyst, characterized in that it exhibits a nitrogen monoxide oxidation efficiency of 20% or more at 200 ° C. or higher. 7. The method of claim 6,
The titania support is an anatase phase, a method for producing a nitrogen monoxide oxidation catalyst, characterized in that it has a rutile phase or a mixed phase of anatase phase and rutile phase. 7. The method of claim 6,
The firing in step S2,
A method for producing a nitrogen monoxide oxidation catalyst, characterized in that the temperature is increased for 2 to 12 hours at a temperature of 300 to 800 °C at a temperature increase rate of 5 to 30 °C/min.

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