KR960003793B1 - Catalyst filter for particle removal from diesel vehicle and the manufacturing process thereof - Google Patents

Abstract

Catalyst for removing particles from diesel vehicle exhaust gas has a support of Al phosphate or P-doped Al2O3, which is on the surface of a heat-resistant filter and is impregnated with Pt, Pd and/or Rh. The catalyst is stable at high temp., is effective for long periods and is not deactivated by SO3. Al phosphate/P-doped Al2O3 also reduce the regeneration temperature.

Description

Catalyst body for removing particulate matter from diesel vehicles and its manufacturing method

The present invention relates to a catalyst body for removing particulate matter in exhaust gas discharged from a diesel vehicle, a method for preparing the same, and a method for removing particulate matter using the same.

Particulate matters emitted by exhaust gas of diesel vehicles are unburned carbon particles with average diameter of 0.3μm, which is the main cause of air pollution in Korea, where the proportion of diesel vehicles is 42% of the total vehicles. In addition, when the concentration of particulate matter exceeds the environmental standard value (smoke regulation value of 40% for Haevichi cars in 1993), it causes not only visual discomfort, but also causes harmful diseases such as cancer. Therefore, strict emission regulations of such particulate matter are required.

For heavy duty diesel vehicles, regulations have been tightened to 0.67g / HP.Hour in 1996 and 0.1g / HP.Hour in the United States since 1994. Is being actively performed.

The development direction of the removal of particulate matter includes the suppression of the production of unburned materials through the high efficiency of the engine, the improvement of the combustion performance using the fuel additive, and the post-treatment technology of the particulate matter. By increasing the combustion effect in the interior, it is possible to fundamentally reduce harmful substances such as particulate matter and soot, but it is excessively expensive and is not easily suppressed by the current technology level, and is finally discharged through exhaust gas. There is a situation.

The post-treatment technology consists of a filtration technology for filtering particulate matter in the exhaust gas and a regeneration technology for regenerating the filter material by burning the filtered particulate matter, and the filtration technology effectively captures particulate matter in the exhaust gas. The focus is on the selection of this excellent filter and its application to real vehicles.

However, the increase in back pressure of the engine exhaust passage due to the filtration of particulate matter damages the filter medium and causes the performance of the engine to deteriorate. The particulate matter causes thermal shock when the filtered filter medium is burned under high temperature conditions. Seriously, there has been a need for the development of regeneration technology to effectively burn particulate matter at low temperatures. The most widely known regeneration technology to date is a method of supplying secondary energy by using a burner, a heater, etc., or increasing the exhaust gas temperature by throttling, and adding an catalyst to a fuel or depositing a catalyst on a filter medium to activate an oxidation reaction. There is a method to reduce the regeneration.

Particularly, the catalytic method has been studied as a method for removing particulate matter in these regeneration technologies. Ceramic foam, wire mesh, metal foam, will flow ceramic honeycomb and open are deposited on the catalyst material capable of burning particulate matter. A trap containing a refractory three-dimensional structure, such as a flow ceramic honeycomb or a metal honeycomb, is used to filter the particulate matter in the exhaust gas of the diesel engine and under the exhaust conditions (gas composition and temperature) of the exhaust gas under normal diesel engine operating conditions. It is composed of burning particulate matter.

Generally required performance as a catalyst for purifying exhaust gas of a diesel engine is as follows. First, as well as carbon fine particles should be able to remove the harmful components such as unburned hydrocarbons at a high efficiency by combustion even at low temperature and, second, the SO ₂ derived from a sulfur component, which is much contained in the case is used as the fuel SO ₃ It should be possible to prevent the abrupt decrease of catalytic activity by SO ₃ as well as the low emission of SO ₃ , which is fatal to the human body due to the low conversion activity. Third, durability must be high to withstand continuous operation even at high temperatures. The techniques vary depending on the physical and chemical properties such as the type, amount of catalyst used and the surface area of the catalyst component.

To date, various proposals have been made to improve the efficiency of removing particulate matter by combustion. In order to uniformly support the platinum group metal, which is known as a combustion catalyst for particulate matter, and to provide a wide reaction surface, these conventional methods deposit the support substrate such as activated alumina or titania in advance on the filter medium, and then filter the filter medium with a solution containing platinum group salt. Supporting methods have been used, which did not necessarily give a satisfactory catalytic effect.

That is, the conventional alumina is thermally stable even at a high temperature of about 800 ° C., and has sufficient durability for continuous operation at a high temperature, but in the case, it reacts with sulfur trioxide, which is emitted by the combustion of sulfur component, which is contained in a large amount, to aluminum sulfate. As a result of conversion, the surface area decreases, the pore structure changes, and the activity of the alumina-based catalyst rapidly decreases.

In addition, the conventional titania is chemically stable to such sulfur trioxide, and there is no activity deterioration due to sulfur trioxide, but it is thermally unstable at 500 ° C or higher to exhaust the exhaust gas at about 300 to 600 ° C, which is the actual operating condition of a diesel vehicle. It is degraded at gas temperatures and is particularly active due to the destruction of pore structure due to the reduction of surface area and phase change (ie crystalline tutile in anatase form) in the case of repeated exposure to soot combustion, i.e. rapid high temperature rise during trap regeneration. And durability deteriorates.

Thus, no catalyst has yet been found to fully satisfy the three performances required as a diesel engine exhaust gas purification catalyst.

Accordingly, it is an object of the present invention to provide a catalyst body which is thermally stable at high temperature, can maintain a high catalytic effect for a long time, and has no deterioration in catalytic activity due to sulfur oxides generated after combustion of diesel.

Another object of the present invention is to provide a method for producing a catalyst body for removing particulate matter of a diesel engine using the prepared deposition support.

Another object of the present invention to provide a diesel vehicle particulate matter removal method using the prepared catalyst body.

As a result of numerous experiments and studies, the present inventors have found that a catalyst body in which at least one platinum group metal selected from platinum, palladium, and rhodium is dispersed and supported on alumina containing aluminum phosphate or phosphorus is used as a deposition support for alumina or titania. It was completed based on the discovery that the thermal stability at high temperature and the chemical stability to sulfur trioxide can be significantly improved than the conventional catalysts prepared.

In order to achieve the above object, the catalyst body for removing particulate matter of the diesel vehicle of the present invention has a deposition support made of aluminum phosphate or phosphorus-containing alumina deposited on the surface of the filter medium, and at least selected from platinum, rhodium, and palladium. It consists of one precious metal deposited.

Method for producing a diesel vehicle particulate matter catalyst body of the present invention to achieve the above another object is a) preparing alumina containing aluminum phosphate or phosphorus as the deposition support, b) the deposition support of step a) Depositing on the filter medium, c) supporting the platinum group metal solution in the filter medium prepared in step b), and d) heating the resultant product of step c) to a high temperature.

In the present invention, alumina containing aluminum phosphate and phosphorus is used as a material to be deposited on the filter medium for supporting the catalyst.

Aluminum phosphate is prepared by reacting aluminum nitrate and ammonium phosphate in an aqueous solution. Specifically, an alumina nitrate aqueous solution and an ammonium phosphate aqueous solution are prepared so that the weight ratio of phosphorus to aluminum is preferably 0.5 to 1.5. Next, the pH is adjusted to 7-9 preferably by adding concentrated ammonia water. At this time, the produced hydrogel is dried, and then prepared by heat treatment at 500 ° C or higher. The heat treatment temperature is also possible at 800 ~ 900 ℃ as needed, there is no particular limitation.

In addition, phosphorus-containing alumina is prepared by mixing alumina and an aqueous solution of phosphoric acid, specifically, alumina having a specific surface area of at least 1 m 2 / g, preferably at least 10 m 2 / g based on alumina and alumina, preferably 0.001 / 1. To 0.3 / 1% by weight of the aqueous solution containing phosphoric acid is mixed. It is dried and heat-treated at 500 ° C. or higher to prepare phosphorus in the form of aluminum phosphate. The heat treatment temperature is also possible at 800 ~ 900 ℃ as needed, there is no particular limitation.

When the weight ratio of phosphoric acid to alumina is less than 0.001 / 1, the concentration of phosphorus to alumina is too low to sufficiently prevent the sulfur oxide reaction, and when the weight ratio of phosphoric acid to alumina is 0.3 / 1 or more, the factor decreases the catalytic activity of the alumina. Stirring acts as a catalyst poison.

The filter media used in the present invention are all three-dimensional structures already known to be useful for filtration of diesel particulates such as ceramic foam, ceramic fiber filter, open flow ceramic honeycomb, wall flow honeycomb monolith, open flow metal honeycomb, metal foam or metal mesh. This can be used and there is no particular limitation.

The deposition support used in the present invention preferably deposits 5 to 200 g per liter based on the filter medium. If it is less than 5g, the catalytic effect is lowered due to insufficient surface area, and if it is 200g or more, the exhaust gas pressure is excessively increased to lower the engine operating efficiency.

The platinum group metal used in the present invention is at least one platinum group metal solution selected from platinum group metal compounds such as platinum, rhodium, palladium, and the content of platinum, rhodium, palladium is preferably 0-6 g, 0-6 g, and 1 L of filter medium, respectively. 0 to 3 g. In addition, the ratio of the amount (precious metal / deposition support weight ratio) in which at least one precious metal selected from platinum and palladium is deposited on the deposition support is preferably in the range of 0.001 / 1 to 0.2 / 1.

The filter medium on which the platinum group metal solution is supported is heated to a temperature of, for example, 500 to 600 ° C. to finally obtain a catalyst body in the form of a metal or metal oxide.

In addition, the removal method for achieving another object of the present invention comprises the removal of diesel vehicle particulate matter using the catalyst body or the catalyst body produced by the various methods.

When the catalyst body containing the catalyst support prepared by the above method is mounted in the filter trap and the filter medium is regenerated, thermal stability at high temperature and chemical stability against sulfur oxides generated during diesel combustion are excellent, so that the particulate matter of the diesel vehicle is excellent. The ability to remove material can be maintained for a long time.

Hereinafter, the configuration and effects of the present invention will be described in detail through examples. However, this example does not limit the scope of the present invention.

Example 1

[Production Method of Sample]

1. Manufacture of aluminum phosphate

4.9 kg of aluminum nitrate and 3.3 kg of ammonium phosphate are dissolved in 5.7 L of water, respectively, and the two aqueous solutions are mixed with each other, followed by addition of concentrated ammonia water to a pH of 8 to form a hydrogel, which is filtered. The aluminum phosphate was dried at 120 ° C. for 16 hours, and then calcined at 500 ° C. for 2 hours in air.

2. Preparation of Phosphorous Alumina (P doped Alumina)

7.1l was prepared by mixing water with 1.92Kg of 85% phosphoric acid. The aqueous solution was evenly mixed with 10Kg of alumina at room temperature for 10 minutes, dried at 160 ° C for 16 hours, and calcined at 500 ° C in air for 3 hours.

[Catalyst Sample Preparation]

Alumina (comparative), titania (comparative), aluminum phosphate and phosphorus-containing alumina in each 200 g of chloroplatinic acid, palladium chloride aqueous solution as shown in Table 1 below, the weight ratio of the precious metal to the deposition support is 0.01 / 1 It was supported to be.

TABLE 1

Example 2

[Evaluation of Acid Catalyst]

1. CO conversion rate

2 g of each of the catalysts 1 to 8 prepared in Example 1 was charged to a microreactor and the reactor temperature was increased to 200 ° C. Air containing 200 ppm of CO is adjusted to pass through the reactor at a space velocity of 24,000 / h, and then the exhaust gas exiting the reactor is collected to measure the conversion of CO.

2. C ₃ H ₈ conversion rate

The conversion rate is measured for C ₃ H ₈ at 300 ° C. in the same manner as the CO conversion rate measurement method.

3. CO conversion rate

The conversion rate is measured for SO ₂ at 400 ° C. in the same manner as the CO conversion rate measurement method.

4. Soot combustion temperature

2 g of each of the catalysts 1 to 8 prepared in Example 1 was mixed, and 0.5 g of soot powder was mixed evenly and filled in a microreactor. The temperature is raised by 10 ° C per minute to reach 200 ° C and then increased by 1 ° C per minute to measure the temperature at which the temperature rises rapidly (soot combustion temperature). To the conversion and the soot combustion temperature of the measured _{CO, C 3 H 8, SO} 2 are shown in Table 2 below.

Example 3

[Durability Evaluation at High Temperature]

2 g of each of the catalysts 1 to 8 prepared in Example 1 was taken and calcined in air at 600 ° C. for 7 days. These catalysts were combined under the same conditions as in Example 2 to measure the conversion and soot combustion temperature of CO, C ₃ H ₈ and SO ₂ and the results are shown in Table 2 below.

Example 4

Evaluation of Chemical Stability for Sulfur Oxides

2 g of each of the catalysts 1 to 8 prepared in Example 1 was taken and calcined in dry air containing 2000 ppm SO ₃ at 400 ° C. for 7 days. The catalysts in Example 2 to experiment under the same conditions as for the conversion and the soot combustion temperature of the _{CO, C 3 H 8, SO} 2 are shown in Table 2 below.

TABLE 2

Note) T means soot combustion temperature (℃) and HC means C ₂ H ₈ .

As shown in Table 2, the deposition support prepared from alumina containing aluminum phosphate or phosphorus has excellent thermal stability at high temperature and chemical stability by sulfur oxides, and thus has excellent durability as a catalyst for removing particulate matter of a real diesel vehicle. It can be seen that.

Example 5

[Chemical Preparation]

After depositing 100 g per 1 liter of the deposition support described in Table 3 below in six US Corning Corporation EX-54 ceramic mono-filter, the catalyst so that the methyl content described in Table 3 below is 1wt% based on the deposition support The metal was supported. It was dried at 120 ° C. for 12 hours and then calcined at 500 ° C. for 2 hours to prepare 6 catalyst bodies up to 1-6.

In order to evaluate the durability of the catalyst body, the catalyst bodies 2 and 4 were left in air at 600 ° C. for 7 days, and the catalyst bodies 3, 5 and 6 were left at 400 ° C. for 7 days in air containing 200 ppm of SO ₃ .

TABLE 3

Example 6

[Evaluation of Regeneration Performance of Catalyst]

After mounting the catalyst body prepared in Example 5 to the Peterson AV-B supercharged single cylinder diesel engine of the United Kingdom, respectively, operating speed 2250rpm, cooling water temperature 100 ℃, oil temperature 90 ℃, oil pressure 2.5bar air inlet Close the engine bypass valve and open the filter trap valve at normal operating pressure of 2230 mbar. When the throttle was opened slightly and regeneration did not occur, the regeneration of the filter medium was tested while increasing the exhaust gas temperature by opening the throttle further.

When regeneration occurs, the collected particulate matter is burned by the catalyst ignition, and the back pressure of the engine exhaust pipe decreases and the temperature after the filter trap increases.

In addition, the amount of sulfur trioxide in the exhaust gas was collected in a mixed solution of isopropyl alcohol and water with a volume ratio of 60:40 by collecting a certain amount of exhaust gas with a vacuum pump for 2 minutes, and compared with the standard solution by ion liquid chromatography. . In the above test method, the regeneration temperature and sulfur trioxide emissions of the six catalysts prepared in Example 5 were measured and shown in Table 4 below.

TABLE 4

As shown in [Table 4], the deposition support prepared from alumina containing aluminum phosphate or phosphorus shows an excellent catalytic effect of regenerating the filter medium by burning particulate matter even at a lower temperature than the conventional catalyst body. Its excellent thermal stability and chemical stability against sulfur oxides make it a good catalyst for removing particulate matter from diesel vehicles.

Claims (17)

A catalyst for removing diesel particulate matter, wherein a deposition support made of aluminum phosphate or phosphorus-containing alumina is deposited on a surface of a filter medium, and at least one precious metal selected from platinum, rhodium, and palladium is deposited thereon. The diesel engine according to claim 1, wherein the filter material is a refractory three-dimensional structure such as ceramic foam, ceramic fiber filter, metal foam, ceramic honeycomb, wall flow honeycomb monolith, open flow metal honeycomb, metal foam or metal mesh. Catalyst for removing particulate matter. The catalyst body for removing particulate matter according to claim 1, wherein the deposition support aluminum phosphate is 0.5 / 1 to 1.5 / 1 in a weight ratio (P / Al) of phosphorus to aluminum. The catalyst body for removing diesel particulate matter according to claim 1, wherein the alumina containing phosphorus as the deposition support is a weight ratio of phosphoric acid to alumina in a range of 0.001 / 1 to 0.3 / 1. The catalyst body for removing particulate matter of claim 1, wherein the deposition support is 5 to 200 g per liter of the filter medium. The catalyst body for removing diesel particulate matter according to claim 1, wherein the selected at least one precious metal is 0-6 g of platinum, 0-6 g of palladium, and 0-3 g of rhodium per liter of the filter medium. The catalyst body for removing diesel particulate matter according to claim 1, wherein the weight ratio of the noble metal and the deposition support is 0.001 / 1 to 0.2 / 1. a) preparing alumina containing aluminum phosphate or phosphorus as the deposition support; b) depositing the deposition support of step a) on the filter medium; c) supporting the platinum group metal solution on the filter medium prepared in step b). And d) heating the product at a high temperature as a result of step c) to produce a catalyst body for removing particulate matter from a diesel engine. 9. The method of claim 8, wherein the aluminum phosphate is prepared by reacting aluminum nitrate with ammonium phosphate in an aqueous solution. 10. The diesel particulate particulate material of claim 9, wherein the weight ratio (P / Al) of aluminum to aluminum is 0.5 / 1 to 1.5 / 1 when aluminum nitrate and ammonium phosphate are reacted in aqueous solution. Method of producing a catalyst body for removal. 10. The method for preparing a catalyst body for removing particulate matter of a diesel engine according to claim 9, wherein the pH of the aluminum phosphate is 7-9. The method of claim 8, wherein the specific surface area of the alumina used in the production of the alumina containing phosphorus is 1 m 2 / g or more. [Claim 9] The catalyst body for removing particulate matter of a diesel engine according to claim 8, wherein an aqueous solution containing phosphoric acid in a weight ratio of 0.001 / 1 to 0.3 / 1 based on alumina is used in the preparation of alumina containing phosphorus. Manufacturing method. 9. The method of claim 8, wherein the deposition support in step b) is 5 to 200 g per liter of the filter medium. 9. The diesel engine particulate matter according to claim 8, wherein at least one precious metal selected in step c) is 0-6 g of platinum, 0-6 g of palladium, and 0-3 g of rhodium per liter of the filter medium. Method of producing a catalyst body for removal. The method of claim 8, wherein the weight ratio of the noble metal and the deposition support is 0.001 / 1 to 0.2 / 1. A method of removing particulate matter from a diesel vehicle using a catalyst body prepared by the method of claim 1 or 8.