KR102704526B1 - Method for retrofitting the device for purifying Exhaust gas - Google Patents

Abstract

The present invention relates to a method for improving an exhaust gas purification device, and more particularly, to a method for improving an exhaust gas purification device having an exhaust gas purification catalyst having an active metal supported on a monolithic support, the method comprising: (a) a step of dissolving a catalytically active metal precursor in a solvent to prepare a catalytically active metal precursor solution; and (b) a step of supporting the solution on a monolith mounted on an exhaust gas purification device by a dropping-blowing method.

Description

{Method for retrofitting the device for purifying exhaust gas}

The present invention relates to a method for improving an exhaust gas purification device and an improved exhaust gas purification device thereby. The present invention relates to a method for improving an exhaust gas purification device by supporting a catalyst on a monolith of an exhaust gas aftertreatment device by a dripping-blowing method and an improved exhaust gas purification device thereby.

The gases emitted from automobiles are divided into exhaust gas, blow-by gas, and evaporative gas. Of these, exhaust gas is a gas that functions by expanding after fuel is burned in the cylinder into a high-temperature and high-pressure gas, and is released into the atmosphere through the exhaust pipe. Most of this exhaust gas is water vapor and carbon dioxide ( _CO2 ), and there are also harmful substances such as carbon monoxide (CO), hydrocarbons (HC), and nitrogen oxides (NOx). Among the components in the exhaust gas, carbon monoxide, hydrocarbons, and nitrogen oxides, which are called ternary gases, cause very serious environmental pollution, so research is actively being conducted to reduce these substances.

The catalyst can be usefully applied in many fields including exhaust gas treatment of internal combustion engines such as automobiles and other gasoline-fueled engines, and a three-way catalytic converter as an exhaust gas purification device containing a suitable precious metal catalyst is installed in the exhaust gas duct of an internal combustion engine to promote decomposition of hydrocarbons, oxidation of carbon monoxide and reduction of nitrogen oxides to meet emission standards for the above-mentioned pollutants.

However, the above exhaust gas purification device is exposed to high temperatures generated from the combustion device for many years, and the catalyst becomes inactive due to sintering, aging by carbon and pollutants, poisoning, catalyst detachment, etc. due to repeated use of the catalyst. In such cases, the device is generally discarded after recovering only the expensive metal used as the catalyst material, which causes not only economic loss but also environmental pollution.

Therefore, efforts are currently being made to prevent environmental pollution and secure economic feasibility through resource recycling by regenerating and recycling the spent catalysts of these exhaust gas purification devices.

For example, Korean Patent Publication No. 10-2008-0088933 relates to a method for chemically regenerating a spent catalyst for purifying automobile exhaust gases, and discloses an improved method for regenerating a catalyst by immersing a spent catalyst for purifying automobile exhaust gases in an acidic solution to remove carbon or pollutants that are attached to the surface of the catalyst active site and cause deactivation of the catalyst.

However, in the case of the above prior literature, since the spent catalyst for exhaust gas purification must be immersed in an acidic solution for regeneration, the spent catalyst must be separated from the vehicle and disassembled into each part, and neutralization, washing, and drying are required after the acid treatment. Therefore, in the case of the above prior literature, there are limitations in simplifying the process and improving work efficiency.

Accordingly, Chinese Patent Publication No. 101890359A discloses that a nano precious metal catalyst filler can be sprayed and coated on a three-way catalyst device carrier. In the above-mentioned prior art, the converter is disassembled, and then a solution containing an active metal is spray-coated on the disassembled monolith, followed by a sintering step, so the process is complicated and there is a disadvantage in that it is not easy to uniformly disperse the metal.

On the other hand, Korean Patent Publication No. 10-2020-0134608 applied for by the present applicant includes a powder catalyst in which an iridium-ruthenium alloy is supported on an aluminum oxide support powder in a front-stage honeycomb catalyst section, and a three-way catalyst in a rear-stage catalyst section, thereby enhancing catalytic activity by enabling hydrocarbons and carbon monoxide to be oxidized together with nitrogen oxide reduction even in a slightly lean range where the air-fuel ratio is 1.00 to 1.05.

However, in the case of the above prior literature, the iridium-ruthenium metal is supported on an aluminum oxide support powder and included in the shear honeycomb catalyst section, so there is a disadvantage that the catalyst must be coated with slurry in order to be reprocessed.

Accordingly, the inventors of the present invention have conducted research and development to reprocess such a used exhaust gas aftertreatment device to increase the catalytic activity similar to or higher than that of a novel one, or to impart a novel functionality to the exhaust gas purification device. As a result, the inventors have found that the dropping-blowing method according to the present invention can uniformly disperse and support a catalytically active metal even in an exhaust gas purification device installed in a vehicle or the like, and that an exhaust gas purification device improved by the above method can restore activity that has fallen due to deactivation to its original state, or can impart a novel functionality to the exhaust gas purification device through a simple process, thereby completing the present invention.

Korean Patent Publication No. 10-2008-0088933 (2008.10.06.: Publication date) Korean Patent Publication No. 10-2020-0134608 (December 2, 2020: Publication date) Chinese Patent Publication No. 101890359A (2010.11.24.: Publication Date)

In order to solve the above-mentioned conventional problems, the present invention provides a method for improving an exhaust gas purification device by uniformly loading a catalytically active metal onto a monolith of the exhaust gas purification device by a dropping-blowing method, thereby improving the exhaust gas purification device.

In addition, the present invention provides an improved exhaust gas purification device by means of a method for improving the exhaust gas purification device.

In addition, the present invention provides an exhaust gas purification method for purifying exhaust gas using an improved exhaust gas purification device according to an improved method for improving the exhaust gas purification device.

In order to solve the above problems, the present invention provides a method for improving an exhaust gas purification device having an exhaust gas purification catalyst supported on a monolithic support, the method comprising: (a) a step of preparing a catalytically active metal precursor solution by dissolving a catalytically active metal precursor in a solvent; and (b) a step of supporting the solution on a monolith mounted on an exhaust gas purification device by a dropping-blowing method.

In one embodiment, the solvent may be at least one selected from the group consisting of distilled water, water, THF, ethyl ether, propyl ether, MEK, xylene, toluene, ethylbenzene, benzene, methanol, ethanol, butanol, propanol, ethylene glycol, propylene glycol, methylene chloride, chloroform, DMSO, DMF, DEF, ethylamine, ammonia, ethanol amine, diethanol amine, triethanol amine, triethylaminehexane, pentane, heptane, octane, nonane, and decane.

In one embodiment, the catalytically active metal in step (a) may be iridium and ruthenium, and the iridium metal precursor solution and the ruthenium metal precursor solution may each be prepared as separate solutions.

In one embodiment, step (b) may be performed while the monolith is mounted on an exhaust gas purification device.

As an example, the sintering of the catalytically active metal precursor supported on the monolithic support can be performed by exhaust gas emitted during operation of a vehicle after the exhaust gas purification device is mounted on the vehicle.

In addition, the present invention provides an exhaust gas purification device treated with the above-mentioned improved method as an exhaust gas purification device.

In addition, the present invention provides an exhaust gas purification method characterized in that exhaust gas is purified using an exhaust gas purification device.

The present invention enables the exhaust gas purification device to be improved through a simplified process by dispersing and supporting an active ingredient on a support while the exhaust gas purification device is mounted on an automobile by the dripping-blowing method.

Figure 1 shows the NOx conversion rate and _NH3 concentration according to the method for improving an exhaust gas purification device according to one embodiment of the present invention.

Hereinafter, the composition of the invention including preferred embodiments that can be easily carried out by a person having ordinary skill in the art to which the present invention belongs will be described in detail. In explaining the principles of preferred embodiments of the present invention in detail, if it is judged that a specific description of related known functions or configurations may unnecessarily obscure the gist of the present invention, such detailed descriptions will be omitted.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein is well known and commonly used in the art.

Throughout this specification, whenever a part is said to "include" a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

An exhaust gas purification device includes an exhaust gas purification catalyst in which an active metal is supported on a monolithic support, and converts gas components, which are harmful to the human body, such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx), among the combustion gas emitted from an engine, into harmless components, such as _H2O , _CO2 , and _N2. As the frequency of use increases, the active metal is detached from the support, thereby decreasing the content of the active metal, or the activity of the active metal itself decreases, thereby decreasing the exhaust gas purification efficiency. Therefore, there is a need for a method for improving an exhaust gas purification device, which can restore the activity decreased due to deactivation to its original state or can provide a new function to the exhaust gas purification device through a simple process.

According to one aspect of the present invention, a method for improving an exhaust gas purification device having an exhaust gas purification catalyst having an active metal supported on a monolithic support is provided, characterized in that the method comprises the steps of: (a) preparing a catalytically active metal precursor solution by dissolving a catalytically active metal precursor in a solvent; and (b) supporting the solution on a monolith mounted in an exhaust gas purification device by a dropping-blowing method.

In the present invention, step (a) is a step of preparing a catalytically active metal precursor solution by dissolving a catalytically active metal precursor in a solvent, and the concentration of the solution can be adjusted so that it can be uniformly dispersed and supported without flowing out when dripped and blown onto a monolith. The concentration of the solution can be adjusted in consideration of various conditions such as the type and size of the monolith, the type of catalyst, etc., but can be 0.005 to 3 M.

If it is less than 0.005 M, sufficient metal is not applied, so that it does not affect the catalytic performance, and if it exceeds 3 M, there are problems of uneven metal dispersion and decreased economic efficiency due to excessive use of metal. Therefore, the catalytically active metal precursor solution may be 0.005 to 3 M, and preferably 0.01 to 1 M.

In the above catalytically active metal precursor solution, the precursor may include a catalytically active metal generally known as an exhaust gas purification catalyst of an exhaust gas purification device, or an active metal capable of decomposing hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) components of exhaust gas, and may be selected from these so as to optimize exhaust gas purification efficiency.

For example, the catalytically active metal is not particularly limited by the type of metal, and may preferably be Pt, Pd, Rh, Ag, Ir, Ru, etc., which are widely used in exhaust gas purification catalysts, and more preferably, the catalytically active metal may be iridium and ruthenium, and the precursors of the metals may be dissolved in a solvent to prepare separate iridium metal precursor solutions, ruthenium metal precursor solutions, or may be a mixed solution in which the two metal precursors are mixed.

In the above catalytically active metal precursor solution, the solvent is not limited in type as long as it can dissolve the catalytically active metal precursor and disperse metal particles in a solution state, and can be selected by considering the type and content of the catalytically active metal.

For example, the solvent may be at least one selected from the group consisting of water such as distilled water; ethers such as THF, ethyl ether, propyl ether, and MEK; aromatic compounds such as xylene, toluene, ethylbenzene, and benzene; alcohols such as methanol, ethanol, butanol, propanol, ethylene glycol, and propylene glycol; chloride series such as methylene chloride and chloroform; sulfides or nitrides such as DMSO, DMF, DEF, ethylamine, ammonia, ethanol amine, diethanol amine, triethanol amine, and triethylamine; and aliphatic compounds such as hexane, heptane, octane, nonane, and decane.

In the present invention, step (b) is a step of loading the solution onto a monolith mounted on an exhaust gas purification device by a dropping-blowing method.

The above dripping-blowing is a method of dispersing and supporting a catalytically active metal on a monolith through a series of processes including dropping the catalytically active metal precursor solution in the form of droplets onto a monolith and then blowing it using gas. Compared to spray coating, it enables uniform metal loading and has the advantage of preventing clogging caused by dense accumulation of the precursor solution within the monolith cell.

For example, the dripping-blowing can be performed using two nozzles: a droplet-injecting nozzle that drops liquid onto a monolith, and a gas-injecting nozzle that moves immediately following the droplet-injecting nozzle and blows the dropped liquid with gas so that the droplets are evenly spread over the surface of the monolith. Alternatively, the droplets can be dropped over a wide area first, and then gas is sprayed all over the area so that the dropped droplets are spread over the surface of the monolith. At this time, the volume of the droplets is preferably set to an amount that does not cause the liquid to be discharged beyond the end of the monolith by blowing.

By using this dripping-blowing method, it is possible to add active metals to the monolith mounted on the existing exhaust gas purification device to give it new functions or to restore lost activity.

In addition, compared to the dipping method, it has the advantage of simplifying the process and preventing catalyst contamination. In the case of the dipping method, in order to support the catalytically active metal on the support, it is necessary to separate the monolithic support from the exhaust gas purification device, and when supporting the catalytically active metal, the monolithic support must be dipped in the catalytically active metal precursor solution. Therefore, the catalytically active metal solution may be contaminated during the process, and furthermore, the remaining solution is disposed of as waste, which reduces economic efficiency.

The above dripping-blowing can be performed by controlling the conditions such as distance and speed during dripping, pressure during blowing, etc. depending on the type of catalytically active metal precursor solution, type and condition of monolith, temperature, etc.

In addition, when the types of the catalytically active metal precursor solutions used in the dripping-blowing are two or more, the two or more solutions may be simultaneously dripped-blown onto the monolith or sequentially dripped-blown to support the catalytically active metal onto the monolith. For example, when the catalytically active metal is prepared as separate solutions of an iridium precursor solution and a ruthenium precursor solution, the solutions may be simultaneously dripped-blown onto the monolith or the ruthenium precursor solution may be first dripped-blown onto the monolith and then the iridium precursor solution may be dripped-blown to support the ruthenium and iridium onto the monolith.

The series of processes in step (b) above can be performed with the monolith removed from the exhaust gas purification device or with the monolith mounted on the exhaust gas purification device, thereby simplifying the catalyst improvement process and improving efficiency.

The step (b) may further include a step of loading the catalytically active metal precursor solution onto the monolith of the exhaust gas purification device by a dripping-blowing method, and then drying and calcining the solvent. The method of drying and calcining the solvent is not limited, but preferably, the calcination of the loaded catalytically active metal precursor can be performed by exhaust gas emitted during operation of the vehicle after the exhaust gas purification device is mounted on the vehicle, thereby omitting a separate calcination process and improving the efficiency of the catalyst improvement process.

The dripping-blowing method of the present invention can uniformly spray and support a catalytically active metal onto a monolithic support in a simplified process, thereby significantly improving the process efficiency for improving an exhaust gas purification device.

In addition, when the catalytically active metal is supplied and supported on the monolith, the three-way catalyst may or may not remain on the monolith. The three-way catalyst is a catalyst that can simultaneously oxidize and reduce hydrocarbons, carbon monoxide, and nitrogen oxides to convert them into carbon dioxide, nitrogen, and water, and even if it remains on the support, the degree of improvement in catalytic activity effect by combination with the supported catalytically active metal is minimal, so whether or not the three-way catalyst remains does not significantly affect the catalyst improvement of the exhaust gas purification device.

In addition, the monolithic support is not particularly limited in its type and can be used or is a material used in an exhaust gas purification device, but has a large surface area so as to enhance catalytic activity by dispersing and doping an active metal as widely as possible on the support while not having catalytic activity itself, and maximize the contact area with exhaust gas, and has thermal stability so as to maintain stability even when exposed to high temperatures because it is located close to an automobile engine. Such monolithic material may be a ceramic or metal monolith which is generally applied to an automobile exhaust gas aftertreatment device, and preferably, the monolith may be made of ceramic.

The above method for improving an exhaust gas purification device can provide an improved exhaust gas purification device.

In addition, an exhaust gas purification method for purifying exhaust gas using an exhaust gas purification device improved by the method for improving the above exhaust gas purification device can be provided.

Hereinafter, examples will be described in more detail to explain the present invention. However, the following examples are only preferred embodiments of the present invention, and the present invention is not limited to the following examples.

<Example>

Preparation of catalytically active metal precursor solution

xH₂O, Sigma-Alrich, 206245) 37.843g 및 루테늄 클로라이드 하이드레이트 (IrCl₃

xH₂O, Sigma-Alrich, 206229) 28.017g을 첨가한 뒤 상온에서 10분간 충분히 교반시켜 촉매활성금속 전구체 용액을 제조하였다. Iridium chloride hydrate (IrCl _{3 )} was added to 1,000 cc of prepared distilled water.

xH ₂ O, Sigma-Alrich, 206245) 37.843 g and ruthenium chloride hydrate (IrCl ₃

_xH2O , Sigma-Alrich, 206229) was added and stirred sufficiently at room temperature for 10 minutes to prepare a catalytically active metal precursor solution.

<Example 1>

With the three-way catalyst monolith assembled in the exhaust gas purification device, the precursor solution manufactured above was dripped and blown at a rate of 50 cc/min at room temperature until the solution was observed at the bottom of the monolith, thereby supporting the catalytically active metal on the monolith support. After the above process, calcination was replaced with 30 minutes of vehicle operation.

<Comparative Example 1>

In the above Example 1, an exhaust gas purification device that did not perform the dripping-blowing was used as Comparative Example 1.

<Comparative Example 2>

In the exhaust gas purification device having the same conditions as Example 1, IrRu was supported on a monolith support by a dipping method. Specifically, the exhaust gas purification device was disassembled, the three-way catalyst monolith support was taken out, and then dipped into a beaker containing the Ir/Ru active metal precursor solution manufactured above, and then taken out and air was blown to support the metal. After that, it was dried in an oven at 110° C. for 12 hours and then calcined at 500° C. for 5 hours under air conditions containing 10% moisture.

Performance measurement of exhaust gas purification devices

The conversion of NOx and the concentration of _NH3 of the exhaust gas purification device of Example 1 and Comparative Example were measured and shown in Fig. 1, and the measurement method is as follows.

<Measurement method>

In order to evaluate the catalytic performance of Example 1 and Comparative Examples 1 and 2 on a laboratory scale, each monolith support was separated from the exhaust gas purification device, and a 0.5 inch (D) * 1 inch (h) sized sample was collected and mounted in the reactor. Thereafter, while maintaining the reaction temperature at 400 ^o C and flowing the reaction gas, the catalytic NOx removal rate and _NH3 production concentration according to the air/fuel ratio λ were confirmed (reaction gas composition: 500 ppm NO, 1% CO, 0.3% _H2 , 500 ppm _{C3H6 ,} 10% _CO2 , 10% _H2O and _N2 bal. + _O2 variation), wherein λ was varied by controlling the _O2 concentration. Each reaction gas concentration was measured using an FT-IR spectrometer (Nicolet iS20, Thermo Fisher) equipped with a 2 M gas-cell. The catalytic NOx removal rate was calculated by the following formula.

NOx conversion rate = (NOx inlet concentration - NOx emission concentration) / NOx inlet concentration * 100% (1)

Through Fig. 1, the NOx conversion rate showed similar results in both Comparative Example 1 and the method of dipping (Comparative Example 2) or dripping-blowing (Example 1) the catalytically active metal into the device.

On the other hand, the NH ₃ concentration was significantly lowered in the case of dipping (Comparative Example 2) or dripping-blowing (Example 1) of the catalytically active metal compared to Comparative Example 1, confirming that the exhaust gas purification device was improved by the dipping or dripping-blowing method, and the degree of reduction in the NH ₃ concentration was similar in the case of the dipping (Comparative Example 2) and dripping-blowing (Example 1) methods.

The above-mentioned dripping-blowing method simplifies the process by supporting a catalytically active metal on a monolithic support without disassembling a separate purification device, compared to the dipping method that requires disassembly and recombination of an exhaust gas purification device, and thus it can be seen that the dripping-blowing method can improve an exhaust gas purification device more efficiently.

Claims (8)

A method for improving the catalytic activity of an exhaust gas purification device having an exhaust gas purification catalyst in which an active metal is supported on a monolithic support,
(a) a step of preparing a catalytically active metal precursor solution by dissolving a catalytically active metal precursor in a solvent;
(b) A method for improving the catalytic activity of an exhaust gas purification device, characterized by including a step of loading the solution into a monolith mounted on an exhaust gas purification device by a dropping-blowing method.
In the first paragraph,
A method for improving the catalytic activity of an exhaust gas purification device, characterized in that the solvent is at least one selected from the group consisting of distilled water, water, THF, ethyl ether, propyl ether, MEK, xylene, toluene, ethylbenzene, benzene, methanol, ethanol, butanol, propanol, ethylene glycol, propylene glycol, methylene chloride, chloroform, DMSO, DMF, DEF, ethylamine, ammonia, ethanol amine, diethanol amine, triethanol amine, triethylamine hexane, pentane, heptane, octane, nonane, and decane.
In the first paragraph,
A method for improving the catalytic activity of an exhaust gas purification device, characterized in that in the step (a) above, the catalytically active metal is iridium and ruthenium.
In the third paragraph,
A method for improving the catalytic activity of an exhaust gas purification device, characterized in that the iridium metal precursor solution and the ruthenium metal precursor solution are each prepared as separate solutions.
In the first paragraph,
A method for improving the catalytic activity of an exhaust gas purification device, characterized in that the step (b) above is performed while the monolith is mounted on the exhaust gas purification device.
In the first paragraph,
A method for improving the catalytic activity of an exhaust gas purification device, characterized in that the sintering of a catalytically active metal precursor supported on a monolithic support is performed by exhaust gas emitted while the vehicle is in operation after the exhaust gas purification device is installed in the vehicle.
As a device for purifying exhaust gas,
An exhaust gas purification device treated with the catalytic activity improvement method of any one of claims 1 to 6.
In a method for purifying exhaust gas,
An exhaust gas purification method characterized by purifying exhaust gas using the exhaust gas purification device of Article 7.