JP2008272617A - Exhaust gas cleaning device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that unburned fuel is generated and may be accumulated in a lean NOx cleaning catalyst in any light oil injection heat deterioration and sulfur poisoning of the lean NOx cleaning catalyst are caused by combustion of the unburned fuel accumulated on the lean NOx cleaning catalyst although light oil is needed to be injected into an engine cylinder or into a lean exhaust gas in the case of enriching an exhaust gas flowing in the lean NOx cleaning catalyst in an internal combustion engine. <P>SOLUTION: The problem can be solved by locating an oxidizing agent for the unburned fuel at the upstream of a sulfur catching material. The oxidizing agent for the unburned fuel possesses the function of burning the unburned fuel contained in an exhaust gas. The sulfur catching material containing an alkali metal compound and/or an alkali earth metal compound as the main components catches the sulfur content contained in the exhaust gas and does not leave the once-caught sulfur content substantially by using a material which catches and does not discharge sulfur substantially as a part or the whole of the carrier. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust purification device and an exhaust purification catalyst for an internal combustion engine using a material that captures sulfur contained in exhaust gas from a diesel internal combustion engine.

  In order to purify nitrogen oxides generated from internal combustion engines, gasoline engines use a three-way catalyst that uses multiple precious metals as a technology to reduce nitrogen oxides to nitrogen, and that technology has almost reached completion. ing. In a diesel engine, the three-way catalyst cannot be used because the air-fuel ratio is larger than that of a normal gasoline engine. Thus, development and practical use of NOx purification catalysts that replace three-way catalysts are being promoted. In the present application, the NOx purification catalyst used in the air-fuel ratio lean is generically referred to as a lean NOx catalyst. Examples of the NOx purification method for the lean NOx purification catalyst include a selective catalytic reduction (SCR) catalyst method, a NOx trapping catalyst method, and a method combining both.

  In the selective catalytic reduction method, a reducing agent such as ammonia, urea, alcohols and hydrogen is supplied from the outside to reduce NOx to nitrogen, and a reducing agent such as hydrocarbon, carbon monoxide and hydrogen coexisting in the exhaust gas. And a method for selectively reacting NOx with NOx.

  In the NOx trapping catalyst method, when the air-fuel ratio is leaner than the stoichiometric air-fuel ratio, nitrogen oxide is trapped by the catalyst in the NOx trapping catalyst, and when the air-fuel ratio is less than the stoichiometric air-fuel ratio such as during acceleration, the trapped nitrogen oxidation The substance is reduced and purified to nitrogen using a reducing agent that coexists in the exhaust gas. In addition, as a form of capture, there are absorption and chemical adsorption.

  Furthermore, a method combining NOx trapping and ammonia selective reduction has been reported. For example, NOx trapped in lean is converted to ammonia when rich and trapped on an ammonia trap catalyst, and trapped ammonia and NOx in exhaust gas are reacted on the catalyst and reduced to nitrogen at the next lean.

  The lean NOx purification catalyst of an internal combustion engine used in a region where the air-fuel ratio is large has a problem that it is poisoned by sulfur contained in the fuel and causes a decrease in performance. This is because sulfur oxide derived from fuel or engine oil is taken into the lean NOx purification catalyst. The heavier fuel contains a larger amount of sulfur in the fuel. For this reason, in a diesel engine using light oil as a fuel, the activity of the above lean NOx purification catalyst is likely to decrease compared to an internal combustion engine using gasoline as a fuel.

  For the sulfur-poisoned lean NOx purification catalyst, a method is used in which the sulfur content is reduced by high-temperature treatment in a region where the air-fuel ratio is close to the stoichiometric air-fuel ratio, and the catalytic activity is recovered by releasing it in the form of hydrogen sulfide.

  For example, Japanese Patent Laid-Open No. 06-088518 (Patent Document 1) discloses that the air-fuel ratio is intermittently or continuously when the air-fuel ratio is larger than the stoichiometric air-fuel ratio and the exhaust gas is hot or when the lean NOx purification catalyst is hot. Then, a method is described in which the catalyst is regenerated by desorbing the sulfur component poisoning the lean NOx purification catalyst in the vicinity of the stoichiometric air-fuel ratio or smaller than the stoichiometric air-fuel ratio.

  Japanese Patent Laid-Open No. 6-66129 (Patent Document 2) is provided with a means for estimating the amount of sulfur content absorbed into the lean NOx purification catalyst, and when the sulfur content exceeding the set amount is absorbed, A method is described in which the exhausted sulfur is desorbed from the catalyst and regenerated by heating the exhaust gas with a heater and controlling the air-fuel ratio close to the stoichiometric air-fuel ratio.

  In Japanese Patent Laid-Open No. 6-336914 (Patent Document 3), a sulfur content absorbent is installed upstream of the exhaust with respect to the lean NOx purification catalyst, and means for adjusting the oxygen concentration flowing into each of them is provided. As a result, the oxygen concentration of the exhaust gas flowing into the lean NOx purification catalyst is reduced in advance to create a state in which the sulfur component is difficult to be absorbed by the catalyst, and then the oxygen concentration flowing into the sulfur component absorbent is decreased to absorb the sulfur component. It is possible to release the sulfur content absorbed by the material.

  WO 2005/090760 (Patent Document 4) describes that the sulfur content absorbed by the sulfur content absorbent is not released and the purification performance and fuel efficiency performance of nitrogen oxides are maintained. Further, in this case, control for removing the sulfur content is unnecessary, and it is possible to prevent complication of the exhaust treatment-related system.

  Japanese Patent Laid-Open No. 2005-133610 (Patent Document 5) has a property of releasing captured SOx when the temperature of the SOx trap catalyst is equal to or higher than the SOx release temperature when the air-fuel ratio of the exhaust gas flowing into the SOx trap becomes rich. In addition, the air-fuel ratio control means that keeps the air-fuel ratio of the exhaust gas flowing into the SOx trap catalyst lean during the engine operation without being rich, and the SOx trap catalyst among the SOx contained in the exhaust gas are captured. An estimation means for estimating the SOx trap rate indicating the ratio of SOx, and when the SOx trap rate falls below a predetermined rate, the exhaust gas air-fuel ratio increases the temperature of the SOx trap catalyst under lean, An exhaust emission control device for a compression ignition type internal combustion engine that recovers the SOx trap rate is disclosed.

  In Japanese Patent Application Laid-Open No. 2005-21862 (Patent Document 6), an exhaust purification catalyst comprising a catalyst supporting layer, a noble metal catalyst supported on the catalyst supporting layer and a SOx absorbent, the catalyst supporting layer being relatively This shows the distribution of the holding power of the sulfate in which there are a low sulfate holding portion and a high sulfate holding portion, and the noble metal catalyst is supported on the relatively low sulfate holding portion of the catalyst support layer. An exhaust purification catalyst is disclosed in which SOx oxidized by this noble metal is diffused and fixed in a portion having a relatively high retention of sulfate.

JP-A-6-088518 JP-A-6-66129 JP-A-6-336914 International Publication WO2005 / 090760 JP 2005-133610 A JP 2005-2111862 A

  In the methods of Patent Documents 1 to 6, when the exhaust gas flowing into the lean NOx purification catalyst is made rich, it is necessary to inject light oil into the engine cylinder or inject light oil into the lean exhaust gas. However, there is a concern that unburned fuel may be generated in any diesel oil injection and accumulated in the lean NOx purification catalyst. The unburned fuel contains a fuel-derived sulfur content. It is considered that combustion of the accumulated unburned gas oil causes thermal deterioration and sulfur poisoning of the lean NOx purification catalyst.

  An object of the present application is to provide an exhaust emission control device that solves the above-described problems and has high nitrogen oxide removal performance.

  The above-mentioned problem can be solved by arranging the unburned fuel oxidizing material upstream of the sulfur content capturing material. The unburned fuel oxidizing material has a function of burning unburned fuel contained in the exhaust gas.

  The present invention for solving the above-mentioned problems is an invention described in the claims, and is an exhaust gas purification device for purifying exhaust gas discharged from an internal combustion engine, which is not provided in an exhaust gas flow path of the internal combustion engine. It has a combustion fuel oxidizing material, a sulfur content capturing material, and a nitrogen oxide removal catalyst.

  With the above arrangement, unburned fuel contained in the exhaust gas can be prevented from reaching the lean NOx purification catalyst. Furthermore, both the sulfur content generated when the unburned fuel burns and the sulfur content contained in the engine combustion exhaust gas are captured by the sulfur content capturing material, and sulfur poisoning of the lean NOx purification catalyst can be prevented.

  In addition, by installing a sulfur content oxidizing material that oxidizes sulfur dioxide to sulfur trioxide upstream of the exhaust relative to the installation location of these sulfur content capturing materials, these sulfur content capturing materials can be used more effectively. Is possible. This is because the sulfur content is changed to sulfur trioxide by the sulfur content oxidizing material, and it becomes easy to react with the alkali metal-containing compound and alkaline earth metal-containing compound which are sulfur content-trapping components.

  According to the present invention, an exhaust purification device having high nitrogen oxide removal performance can be provided. Moreover, it is possible to maintain the purification performance of the NOx purification catalyst for a long period of time.

<Catalyst arrangement>
The arrangement method of each component of the purification apparatus having the sulfur content oxidizing material, the unburned fuel oxidizing material, the sulfur content capturing material, and the lean NOx purification catalyst is as follows.

  (1) From the upstream side of the exhaust gas flow path, the unburned fuel oxidizing material, the sulfur content oxidizing material, and the lean NOx purification catalyst are arranged in this order.

(2) A lean NOx purifying catalyst, a material having both an unburned fuel oxidation function and a sulfur content oxidation function, in which a sulfur component oxidizing material and an unburned fuel oxidizing material are arranged on the same carrier from the upstream side of the exhaust gas passage Arrange in the order of.
Further, in an exhaust purification apparatus that removes particulates contained in exhaust gas with an exhaust particulate filter, and purifies nitrogen oxides in the exhaust with a lean NOx purification catalyst on the gas downstream side of the exhaust particulate filter, sulfur poisoning is performed. The sulfur trapping material is installed integrally with the exhaust particulate filter so that the sulfur component is trapped upstream of the exhaust with respect to the received lean NOx purification catalyst, and the trapped sulfur component is not substantially desorbed. Also good. The exhaust gas from the diesel engine contains fine particles. There is a diesel particulate filter (DPF) as an exhaust particulate filter for removing the particulates. When using the DPF, there are the following arrangement methods.

  (3) From the upstream side of the exhaust gas passage, the unburned fuel oxidizing material, the DPF, the sulfur content oxidizing material, and the lean NOx purification catalyst are arranged in this order.

  (4) From the upstream side of the exhaust gas flow path, a material having both an unburned fuel oxidation function and a sulfur content oxidation function, a DPF, a lean NOx, in which a sulfur component oxidizing material and an unburned fuel oxidizing material are arranged on the same carrier Arrange in order of purification catalyst.

  If unburned fuel accumulates in the DPF, the DPF due to the high temperature exhaust gas when the unburned fuel burns may be damaged. With the arrangements (3) and (4), it is possible to prevent unburned fuel from accumulating in the DPF, and thus it is possible to prevent damage to the DPF.

<Integration of filter and sulfur trap>
When the sulfur content trapping material is integrated with the exhaust particulate filter, it is necessary to prevent the pressure loss in the filter from significantly increasing as compared with the case where the sulfur content trapping material is not provided.

  By integrating the sulfur trapping material with the filter, it is possible to suppress the installation space of the exhaust gas purification device to be equivalent to a conventional exhaust gas purification system that does not use the sulfur trapping material. For this purpose, it is necessary to install the sulfur content trapping material without blocking the through hole in the exhaust particulate filter wall. When the filling rate is high, the portion that was previously a gap is closed, and the pressure loss in the filter becomes large. Therefore, it is necessary to provide an appropriate gap in the filling portion.

  In order to provide the voids, the sulfur trapping material filled in the honeycomb voids is made granular or fibrous. Therefore, when integrating, the pores (voids) of the honeycomb constituting the exhaust particulate filter are filled with granular or fibrous sulfur trapping material, and an appropriate gap is provided in the filling part, thereby increasing the pressure loss. It is possible to incorporate the required amount of sulfur scavenger without doing so. As a result, it is possible to ensure an appropriate gap. Therefore, according to the above configuration, it is possible to provide a compact exhaust gas purification apparatus with little pressure loss and a large amount of sulfur trapped.

  By using the above exhaust purification device, exhaust gas purification from the internal combustion engine can be effectively performed.

<Unburned fuel oxidizer>
As a specific unburned fuel oxidizing material, a material containing a noble metal as an active component and an oxygen absorbing / releasing material can be used. The oxygen absorbing / releasing material absorbs oxygen in the exhaust gas when the oxygen concentration in the exhaust gas increases, and releases the absorbed oxygen when the oxygen concentration in the exhaust gas decreases. As the oxygen absorbing / releasing material, an oxide containing Ce, an oxide containing Ce and Zr, and the like are applicable. As a form of the unburned fuel oxidant, the noble metal and the oxygen absorbing / releasing material may be supported on a porous carrier such as alumina, silica, or zeolite. Moreover, the oxygen absorbing / releasing material may contain a noble metal.

<Sulfur content capture material>
As the sulfur trapping material, a material that traps sulfur and does not substantially release it, traps sulfur contained in the exhaust gas, and does not substantially desorb the trapped sulfur is used. Sulfur content trapping material uses a material that does not substantially capture and release sulfur content, especially on all or part of the carrier, and is supported by a sulfur content capture component mainly composed of alkali metals and / or alkaline earth metals. It is preferable that The sulfur trapping amount can be increased by further dispersing the sulfur trapping component on the sulfur trapping carrier. In addition, since a noble metal has a function which assists discharge | release of a sulfur content, it is preferable to use the sulfur content capture | acquisition material which does not contain a noble metal.

  The fact that the sulfur content is not substantially desorbed from the sulfur content capturing material means that the lean NOx purification catalyst installed at the subsequent stage of the sulfur content capturing material is sulfur poisoned in the exhaust temperature and exhaust composition atmosphere when the internal combustion engine is operated. This means that the amount is not so high that it does not deteriorate for a long time.

  By installing a capture material that does not substantially release the sulfur component upstream of the exhaust of the lean NOx purification catalyst, the sulfur content capture material is captured by the sulfur content capture material and is not substantially desorbed. The exhaust gas flowing into the lean NOx purification catalyst does not contain sulfur. This prevents the lean NOx purification catalyst from being poisoned, and makes it possible to maintain a stable nitrogen oxide purification function over a long period of time. In addition, by using a trapping material that does not substantially release the sulfur component, the sulfur component once trapped is not forcibly desorbed by external air-fuel ratio control, and such control becomes unnecessary. The control system can be simplified.

  The sulfur content captured by the sulfur content capturing material is finally stabilized by forming a sulfate. Since the decomposition temperature of sulfate is higher than the exhaust temperature of a normal internal combustion engine, once it is formed, it is extremely stable, and virtually no sulfur desorption occurs.

  As a specific example of the material that captures and does not substantially release the sulfur component used for the carrier, a composite oxide containing an alkali metal and / or an alkaline earth metal can be used. Further, a mixture of an alkali metal and / or alkaline earth metal carbonate and an oxide of one or more other elements can be used. Alternatively, it is possible to use a mixture of a composite oxide containing an alkali metal and / or alkaline earth metal, an alkali metal and / or alkaline earth metal carbonate, and an oxide of one or more other elements. is there. Furthermore, alkaline earth metal carbonates can be used.

  Specific examples of the alkali metal in the composite oxide used as all or part of the support material include lithium, sodium, potassium, rubidium, and cesium. Specific examples of the alkaline earth metal in the composite oxide or carbonate include magnesium, calcium, strontium, and barium.

  Further, the sulfur content trapping material may be one in which a sulfur content capture component containing alkali and / or alkaline earth is supported on a zeolite carrier. In the case of alkali metals, sodium and potassium are particularly preferable, and in the case of alkaline earth metals, barium and magnesium are preferable. The amount of these components supported is preferably 140 to 180 g / L in view of the relationship between the exhaust gas flow path and the capturing ability.

  As the zeolite carrier, for example, Y-type zeolite, mordenite, ferrierite, zeolite of structure code MFI, and beta-type zeolite can be used. These zeolites may be a single component or a mixture containing these as one of the main components.

  By installing such a sulfur content capturing material in the exhaust system of the internal combustion engine, it is possible to prevent poisoning of the lean NOx purification catalyst. In this case, these sulfur content capturing materials are exhausted from the lean NOx purification catalyst. It is necessary to arrange it upstream. Even if the trapped sulfur content is desorbed, the lean NOx purification catalyst on the downstream side is deteriorated. Therefore, it is necessary that the trapped sulfur content is not substantially desorbed.

<Sulfur content oxidation material>
Furthermore, the material for oxidizing the sulfur component is not limited as long as it has an ability to oxidize sulfur dioxide to sulfur trioxide under the internal combustion engine operating conditions. For example, the active component can be a noble metal, and the carrier can be configured as a group 3-6 element compound, an aluminum compound, a silicon compound, a mixture based on them, or a zeolite.

<Uses of exhaust gas purification equipment>
As an internal combustion engine using such an exhaust purification device, application to various types of engines using a fuel containing sulfur is conceivable, but it is particularly effective in a diesel engine.

  FIG. 1 shows an example of an exhaust purification device using a sulfur content capturing material according to the present invention. Exhaust gas discharged from the internal combustion engine 1 passes through the exhaust passage 2 and enters the unburned fuel oxidant 18 so that the unburned fuel is combusted. Next, the sulfur content oxidizing material 3 is entered. Here, the sulfur content in the exhaust is oxidized to sulfur trioxide. Sulfur trioxide is captured by the subsequent sulfur content capturing material 4. Since the exhaust gas from which the sulfur content has been removed still contains nitrogen oxides, it is further purified by the downstream lean NOx purification catalyst 5.

  The sulfur content once trapped in the sulfur content trapping material 4 does not substantially desorb from any exhaust composition and temperature, and flows out to the subsequent lean NOx purification catalyst. There is nothing. For this reason, the lean NOx purification catalyst is not poisoned by the sulfur content derived from the fuel and exhibits a stable purification performance over a long period of time.

  In this figure, the lean NOx purification catalyst is drawn away from the sulfur component oxidizing material and sulfur trapping material in the previous stage, but if the positional relationship is the same as in FIG. 1, the lean NOx purification catalyst is adjacent to the sulfur trapping material. Can be installed.

  For the sulfur content trapping material, it is possible to use a material with a structure in which a carrier is coated on the substrate of an inorganic material honeycomb such as cordierite by some method and the component for capturing the sulfur content is dispersed therein. It is. In addition, it is also possible to use a material having a structure in which a material for capturing sulfur is dispersed in a granular or fibrous substrate or carrier.

  FIG. 2 shows an example of an exhaust emission control device when an unburned fuel oxidizing material and a sulfur content oxidizing material are integrated. The exhaust gas after distribution of the unburned fuel oxidizing material and the sulfur oxidizing material 19 contacts the sulfur capturing material 4 and the lean NOx purification catalyst 5 in this order.

  FIG. 3 shows an example of an exhaust purification device when an unburned fuel oxidizing material, a sulfur content oxidizing material, and a sulfur content capturing material are integrated. The unburned fuel oxidizing material, the sulfur content oxidizing material, and the sulfur content capturing material integrated material 20 are discharged from the internal combustion engine, oxidize the unburned fuel and sulfur content, and further capture the sulfur content.

  FIG. 4 shows an example in which the DPF 21 is disposed downstream of the unburned fuel oxidizing material 18, and the sulfur oxidizing material 3 and further the sulfur capturing material 4 are disposed downstream of the DPF 21. By burning unburned fuel in the unburned fuel oxidant 18, accumulation of unburned fuel in the DPF 21 is prevented. Fine particles are accumulated in the DPF 21. A certain amount of accumulated particulates are burned off. Since the fine particles also contain sulfur, the fine particles-derived sulfur is generated even when the fine particles are burned and removed. Gaseous sulfur content discharged from the internal combustion engine, sulfur content derived from unburned fuel and fine particle-derived sulfur content are oxidized by the sulfur content oxidizing material 3 and removed by the sulfur content capturing material 4. As a result, sulfur poisoning of the lean NOx purification catalyst 5 is prevented, and stable nitrogen oxide purification is possible over a long period of time.

  FIG. 5 shows an example of an exhaust emission control device when the unburned fuel oxidizing material and the sulfur oxidizing material are integrated. The exhaust gas after the unburned fuel oxidizing material and the sulfur content oxidizing material 19 have been distributed contact the DPF 10, the sulfur content capturing material 4, and the lean NOx purification catalyst 5 in this order.

  FIG. 6 shows an example in which an exhaust particulate filter (DPF) 22 in which the sulfur component oxidizing material 3 and the sulfur content capturing material are integrated is arranged downstream of the unburned fuel oxidizing material 18. Since sulfur does not flow into the lean NOx purification catalyst 5, stable nitrogen oxide purification is possible over a long period of time.

  FIG. 7 shows a schematic diagram of an exhaust particulate filter integrated with a sulfur trap. This figure shows the concept of the present invention, and the actual dimensional ratio of each component is different from this figure. The exhaust particulate filter usually uses a honeycomb made of a ceramic such as cordierite or silicon carbide. The honeycomb wall 11 is porous and does not allow exhaust particulates to pass therethrough, but gas can permeate without undergoing a large pressure loss. In the honeycomb, adjacent honeycomb holes 15 and 16 are alternately plugged 12 at both ends, and the exhaust flow enters from one end and always passes through the honeycomb wall 11.

  The honeycomb hole 16 on the outlet side with respect to the exhaust flow is filled with a sulfur content capturing material 13. In FIG. 7, the particulate sulfur content capturing material is filled, and the sulfur content in the exhaust is captured by this. The sulfur content trapping material 13 is filled so as to leave an appropriate gap in the honeycomb hole, so that a large pressure loss does not occur when the exhaust gas passes through the layer of the sulfur content trapping material. The amount of voids needs to be 30% or more (filling rate is 70% or less). This is because if it is filled more than this, the pressure loss is high, and the sulfur content trapping material is not fully utilized. The sulfur-capturing material may be mixed with particles having different sizes and shapes, but the porosity is decreased particularly when large and small particles are mixed. When the porosity is 80% or less, the effect of the sulfur content capturing material can be obtained. In particular, if it is 70% or less, the activity can be obtained for most of the sulfur trapping materials in practical use.

  Further, a mesh 14 having an interval at which the exhaust gas flows out but the sulfur content capturing material does not pass is provided at the exhaust flow outlet of the outlet side honeycomb hole 16 so that the sulfur content capturing material does not spill out.

  The sulfur content once trapped in the sulfur content trapping material 13 is not substantially desorbed from any exhaust composition and temperature, and therefore, the lean component on the downstream side with respect to the exhaust flow. It does not flow out to the NOx purification catalyst. For this reason, the lean NOx purification catalyst is not poisoned by the sulfur content contained in the exhaust gas and exhibits a stable purification performance over a long period of time.

  FIG. 8 is a schematic view showing another example of the exhaust particle filter in which the sulfur trapping material according to the present invention is integrated. FIG. 8 also shows the function of the present invention in the same way as FIG. Exhaust gas enters from the inlet side honeycomb hole as in the case of FIG. 7, and particulates in the exhaust gas are captured when passing through the honeycomb wall 11. A fibrous sulfur content capturing material 17 is installed in the honeycomb hole on the outlet side with respect to the exhaust flow, and the sulfur content in the exhaust is captured by this. The fibrous sulfur-capturing material 17 has an appropriate gap, and no large pressure loss occurs even if the exhaust gas passes through this layer. When the shape of the sulfur content capturing material is granular, it may be spherical, cylindrical, or uniform in particle size or irregular. However, in any case, it is important to provide a void in the packed bed so that the pressure loss does not increase.

  The present invention will be specifically described below with reference to examples.

  Example 1 is an example of a sulfur content oxidizing material in which platinum is supported on a silica support, and a sulfur content capturing material in which sodium and barium are supported on a sodium titanium composite oxide support.

Sodium carbonate and anatase titania were weighed to a molar ratio of 2: 1, mixed using a ball mill, and treated in an electric furnace at 650 ° C. for 2 hours. As a result of analysis by powder X-ray diffraction, almost all of the processed powder was sodium titanate (Na ₂ TiO ₃ ).

  This powder was mixed with silica sol and water to prepare a slurry, which was then coated by using a cordierite honeycomb of 400 cells / in 2 to give an amount of 200 g / L. This was impregnated with a mixed solution of sodium nitrate and barium acetate to 11.5 g / L and 68.7 g / L in terms of sodium weight and barium weight, respectively, and then calcined at 650 ° C. for 1 hour in air. A sulfur-capturing material was used.

  On the other hand, a silica slurry was wash coated onto another cordierite honeycomb in an amount of 170 g / L. A dinitrodiammine platinum solution was used for this and impregnated so as to be 3 g / L in terms of platinum weight. This was calcined at 600 ° C. for 1 hour to obtain a sulfur-containing oxidized material.

Arranged in the quartz glass reaction tube in the order of the sulfur component oxidizing material honeycomb and the sulfur content capturing material honeycomb with respect to the gas flow direction, the temperature was raised to 300 ° C. in an electric furnace, and a gas containing sulfur content was circulated for 5 hours. The gas components are 10 vol% oxygen, 0.2 vol% carbon monoxide, 200 volppm nitrogen monoxide, 150 ppm sulfur dioxide, and the balance nitrogen when dry. Water was added to this so that it might be 3 vol% in terms of gas standard state volume with respect to the total amount of gas. The space velocity of gas distribution was 40,000 h- ¹ .

  A water trap was provided at the outlet, and a sulfur dioxide analyzer was placed at the subsequent stage to measure the sulfur dioxide concentration.

  The total sulfur content in the water trap was measured by the oxygen bomb combustion method, and the total sulfur dioxide content measured with the sulfur dioxide analyzer was added to this to obtain the sulfur content that could not be captured by the sulfur content scavenger. It was 0.5 wt% with respect to the amount.

After the gas flow test, the temperature was raised from normal temperature to 700 ° C. in an electric furnace while flowing a gas simulating a region where the air-fuel ratio was close to the theoretical air-fuel ratio, and the concentrations of sulfur dioxide and hydrogen sulfide were measured. The distribution gas composition was converted to the oxygen content of 0.5 vol%, carbon monoxide 0.5 vol%, nitrogen monoxide 800 volppm, and the balance nitrogen. Water was added to this so that it might be 3 vol% in terms of gas standard state volume with respect to the total amount of gas. The space velocity of gas distribution was 40,000 h- ¹ .

  The total sulfur amount in the water trap at the outlet, the analysis value of the sulfur dioxide analyzer, and the analysis value of hydrogen sulfide were 0.01 wt% with respect to the above-mentioned added sulfur content. .

  After these tests, the sulfur scavenger was crushed and the sulfur content in the powder was quantified using a sulfur analyzer. As a result, 99.4% of the amount initially added with sulfur dioxide was detected.

  From these results, it can be seen that almost all of the sulfur content is captured by the sulfur content trapping material and is not desorbed at 700 ° C. or lower.

  Example 2 is an example of a sulfur content trapping material in which a composite oxide of lithium, calcium, and zirconium is used as a carrier and potassium and barium are supported, and a sulfur content oxidizing material in which platinum is supported on a silica and alumina carrier.

Lithium nitrate, calcium nitrate tetrahydrate and zirconia powder were weighed to a molar ratio of 2: 1: 2 and mixed by a ball mill. This was treated in an electric furnace at 700 ° C. for 5 hours. As a result of analysis by powder X-ray diffraction, a mixture of lithium zirconate (Li ₂ ZrO ₃ ), lithium carbonate, calcium zirconate (CaZrO ₃ ), calcium carbonate and zirconia was obtained.

  In the same manner as in Example 1, this powder was wash coated on a cordierite honeycomb at an amount of 180 g / L, and further impregnated with potassium nitrate and barium acetate to prepare a sulfur scavenger.

  Cordierite honeycombs were wash coated with mordenite having a Si / Al ratio of 200 in an amount of 160 g / L. This was impregnated with a chloroplatinic acid solution so that platinum would be 2.6 g / L. This was calcined in a hydrogen stream at 600 ° C. for 1 hour to obtain a sulfur component oxidizing material.

  In the same manner as in Example 1, sulfur content capture processing in a region where the air-fuel ratio containing sulfur dioxide is large and sulfur content desorption processing in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur captured and retained by the sulfur content capturing material was 99.5% or more of the initial charge.

  As can be seen from this example, it is possible to use a mixture composed of a complex oxide of alkali metal, a carbonate of alkali metal and alkaline earth metal, and an oxide of another element as the support for the sulfur scavenger. .

  Example 3 is an example of a sulfur content-trapping material in which barium and niobium oxides and composite oxides are used as a carrier, and sodium and barium are supported, and a sulfur content oxidizing material in which porous silica is used as a carrier and platinum is supported. is there.

Barium acetate and niobium pentoxide were weighed to a molar ratio of 1: 1, mixed by a ball mill, and then treated at 750 ° C. for 1 hour in an electric furnace. As a result of analysis by powder X-ray diffraction, the treated powder was a mixture of barium niobate (BaNb ₂ O ₆ ), barium carbonate, and niobium pentoxide.

  This powder was wash coated onto the honeycomb in the same amount as in Example 1, but in an amount of 150 g / L, and further impregnated in the same manner as in Example 1 to obtain a sulfur content capturing material.

  As in Example 1, except that mesoporous silica (MCM-41) was used as the support, a sulfur-containing oxidized material was prepared.

  In the same manner as in Example 1, sulfur content capture processing in a region where the air-fuel ratio containing sulfur dioxide is large and sulfur content desorption processing in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur captured and retained by the sulfur content capturing material was 99.2% or more of the initial charge.

  Example 4 is an example of a sulfur content capturing material in which sodium and barium are supported on a magnesium support, and a sulfur content oxidizing material in which platinum is supported on a zirconia support.

  Basic magnesium carbonate was heat-treated at 600 ° C. for 2 hours in a carbon dioxide stream. As a result of analysis by powder X-ray diffraction, the composition of the powder after the treatment was magnesium carbonate.

  This powder was wash-coated on the honeycomb in the same amount as in Example 1, but in an amount of 150 g / L, and the sulfur-capturing component was impregnated in the same manner as in Example 1 to prepare a sulfur-capturing material.

  Using a cordierite honeycomb of 400 cells / in 2, zirconia powder was washcoated in an amount of 180 g / L. A dinitrodiammine platinum solution was used for this and impregnated so as to be 2.5 g / L of platinum. This was calcined in air at 600 ° C. for 1 hour to obtain a sulfur component oxidizing material.

  Similarly to Example 1, a sulfur content capturing process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorbing process in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. However, the trapping temperature was 350 ° C. and the trapping time was 1 hour. As a result, the sulfur trapped and retained by the sulfur trap was 99.8% or more of the initial charge.

  As can be seen in this example, an alkaline earth metal carbonate can be used as a support for the sulfur scavenger.

  Example 5 is an example of a sulfur content capturing material in which sodium and barium are supported on a strontium titanium composite oxide support, and a sulfur content oxidizing material in which platinum is supported on a silica support.

Strontium carbonate and 20% titania sol were weighed so that the molar ratio of strontium and titanium was 1: 1 and mixed by a ball mill. This was treated in an electric furnace at 650 ° C. for 1 hour. As a result of analysis by powder X-ray diffraction after the treatment, the composition of the powder was all strontium titanate (SrTiO ₃ ).

  This powder was wash-coated in the same manner as in Example 1, but in an amount of 175 g / L, and a sulfur-trapping component was impregnated as in Example 1 to obtain a sulfur-capturing material.

  As in Example 1, except that silica was wash-coated on the carrier in an amount of 160 g / L to obtain a sulfur-containing oxidizing material.

  In the same manner as in Example 1, sulfur content capture processing in a region where the air-fuel ratio containing sulfur dioxide is large and sulfur content desorption processing in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur captured and retained by the sulfur content capturing material was 99.4% or more of the initial charge.

  Example 6 is an example of a sulfur content capturing material in which rubidium, cesium, titanium oxide or composite oxide is used as a support, and sodium and barium are supported, and a sulfur content oxidizing material in which platinum is supported on a silica support.

Rubidium nitrate, cesium nitrate and rutile type titania were weighed so as to have a molar ratio of 1: 1: 1, mixed by a ball mill, and then treated at 700 ° C. for 1 hour in an electric furnace. As a result of analysis by powder X-ray diffraction, the composition of the powder was a mixture of rubidium titanate (Rb ₂ TiO ₃ ), cesium titanate (Cs ₂ TiO ₃ ), rubidium carbonate and titania.

  This powder was used to wash coat the honeycomb in an amount of 150 g / L in the same manner as in Example 1, and impregnated with a sulfur content capturing component as in Example 1 to obtain a sulfur content capturing material.

  As in Example 1, except that silica was wash-coated on the carrier in an amount of 200 g / L to obtain a sulfur-containing oxidizing material.

  In the same manner as in Example 1, sulfur content capture processing in a region where the air-fuel ratio containing sulfur dioxide is large and sulfur content desorption processing in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur trapped and retained by the sulfur content trapping material was 99.2% or more of the initial charge.

  In Example 7, calcium, silicon oxide, composite oxide, and potassium and zirconium composite oxide are used as supports, sulfur content-trapping material supporting sodium and barium, porous silica as support, and platinum. It is an example of the supported sulfur content oxidizing material.

Calcium carbonate and 20% silica sol were weighed so that the molar ratio of calcium to silicon was 1: 1, mixed with a ball mill, and then treated in an electric furnace at 750 ° C. for 1 h. As a result of performing powder X-ray diffraction on the obtained powder, the composition was a mixture of calcium silicate (CaSiO ₃ ), calcium carbonate and silica.

Potassium acetate and zirconia powder were weighed to a molar ratio of 2: 1, mixed with a ball mill, and then treated in an electric furnace at 700 ° C. for 1 hour. As a result of analyzing the composition of the obtained powder by powder X-ray diffraction, all were potassium zirconate (K ₂ ZrO ₃ ).

  These two types of heat-treated powders were mixed and slurried, and washed on a cordierite honeycomb of 400 cells / square inch at an amount of 180 g / L. This was impregnated with a sulfur trapping component in the same manner as in Example 1 to obtain a sulfur trap.

  In addition, a sulfur-containing oxidizing material was prepared in the same manner as in Example 3.

  In the same manner as in Example 1, sulfur content capture processing in a region where the air-fuel ratio containing sulfur dioxide is large and sulfur content desorption processing in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur trapped and retained by the sulfur trap was 99.5% or more of the initial charge.

  Example 8 is an example of a sulfur content capturing material in which titanium and barium oxides and composite oxides are used as a carrier and sodium and barium are supported, and a sulfur content oxidizing material in which platinum is supported on a silica and alumina carrier. .

Barium hydroxide octahydrate and anatase-type titania were weighed so as to have a molar ratio of 2: 1, mixed with a ball mill, and then treated in an electric furnace at 950 ° C. for 1 hour. As a result of analyzing the composition of the treated powder by powder X-ray diffraction, it was a mixture of barium titanate (BaTiO ₃ ), barium orthotitanate (Ba ₂ TiO ₄ ), and barium carbonate.

  This powder was slurried and washed on the honeycomb in the same manner as in Example 1 and then impregnated with a sulfur content capturing component to obtain a sulfur content capturing material.

  A sulfur-containing oxidized material was prepared in the same manner as in Example 1.

  Using these, as in Example 1, a sulfur content capture process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorption process in a region where the air-fuel ratio is close to the stoichiometric air-fuel ratio were performed. As a result, the sulfur captured and retained by the sulfur content capturing material was 99.3% or more of the initial charge.

  Example 9 is an example in which a plurality of sulfur content oxidizing materials and sulfur content capturing materials are used alternately.

  Using a sulfur content capturing material and a sulfur content oxidizing material having the same composition as in Example 1, a total of 6 layers of sulfur content oxidizing material and sulfur content capturing material were alternately arranged as shown in FIG.

  As a result of performing the same sulfur content capturing / desorption treatment as in Example 1, the sulfur captured and retained by the sulfur content capturing material was 99.6% or more of the initial charged amount.

  Example 10 is an example in which a nitrogen oxide purification catalyst is used together with a sulfur content oxidizing material and a sulfur content capturing material.

  Using the sulfur component oxidizing material and the sulfur content capturing material having the same composition as in Example 1 and arranging a nitrogen oxide purification catalyst downstream thereof, the time dependence of the nitrogen oxide purification performance of diesel engine exhaust was investigated. .

  Using a cordierite honeycomb of 400 cells / in 2, alumina was washcoated at an amount of 180 g / L. This includes Ce as 27 g / L, Rh as 0.1 g / L, Pt as 3 g / L, Pd as 1.5 g / L, Na as 12 g / L, K as 15 g / L, Mn as 14 g / L, Ti As a result, 5 g / L was supported by the impregnation method. As materials for the impregnation method, Ce, Rh, Na and Mn used nitric acid solutions. K was an acetic acid solution, Pt and Pd were dinitrodiamine solutions, and Ti was a titania sol. After impregnating each component, it was calcined in air at 600 ° C. for 1 hour to obtain a nitrogen oxide purification catalyst.

  The test was performed with 400 ppm thiophene added to the fuel for acceleration. The total sulfur content in the fuel after addition of thiophene is about 150 wtppm in terms of sulfur.

  The engine was operated for 1 minute at an air-fuel ratio of 14, and then a cycle of operating at an air-fuel ratio of 6 for 10 seconds was repeated. The operation was continued for a certain time, gas was sampled from before and after the nitrogen oxide purification catalyst, and the amount of nitrogen oxide was analyzed to determine the nitrogen oxide purification rate at the catalyst.

  FIG. 9 shows the change in the nitrogen oxide purification rate when the above operation pattern is carried out for a long time. For comparison, the change of the nitrogen oxide purification rate when the same test is carried out with the nitrogen oxide purification catalyst alone without inserting the sulfur component oxidizing material and the sulfur content capturing material is also shown. As can be seen from the figure, the purification rate of the nitrogen oxide purification catalyst alone decreases with the passage of operating time, whereas when the sulfur capture material and the sulfur content oxidation material are installed upstream of the nitrogen oxide purification catalyst, The purification rate hardly decreased.

  Example 11 is an example of a sulfur-capturing material in which Y-type zeolite, which is a composite oxide of alumina and silica, is used as a carrier and supporting sodium and barium, and a sulfur-containing oxidizing material in which platinum is supported on an alumina carrier.

  A cordierite honeycomb of 400 cells / square inch was 150 g / L washcoated with Y-type zeolite. This was impregnated with a mixed solution of sodium nitrate and barium acetate so as to be 11.5 g / L in terms of sodium weight and 68.7 g / L in terms of barium weight. Then, it baked at 650 degreeC in the air for 1 hour, and it was set as the sulfur content capture | acquisition material.

  The same 400 cell / square inch cordierite honeycomb was 150 g / L washcoated with γ-alumina. This was impregnated with a chloroplatinic acid solution to 3 g / L in terms of platinum weight. This was calcined in a hydrogen stream at 600 ° C. for 1 hour to obtain a sulfur component oxidizing material.

From the upstream side of the gas flow direction in the quartz glass reaction tube, the sulfur component oxidizing material honeycomb and the sulfur trapping material honeycomb are arranged in this order, the temperature is raised to 300 ° C. in an electric furnace, and the gas containing sulfur content is 5 Circulated for hours. The gas components are 10 vol% oxygen, 0.2 vol% carbon monoxide, 200 volppm nitric oxide, 150 ppm sulfur dioxide, and the balance nitrogen in terms of dryness. Water was added to this so that it would be 3 vol% in terms of gas standard state volume with respect to the total amount of gas. The space velocity of gas distribution was 40,000 h- ¹ .

  A water trap was provided at the outlet, and a sulfur dioxide analyzer was placed at the subsequent stage to measure the sulfur dioxide concentration. The total amount of sulfur in the water trap was measured by the oxygen bomb combustion method, and the total amount of sulfur dioxide measured by the sulfur dioxide analyzer was added thereto to determine the sulfur content that could not be captured by the sulfur content capturing material. As a result, it was 0.05 wt% with respect to the amount of sulfur added, and 99.95% was captured.

After the gas flow test, the temperature was raised from normal temperature to 700 ° C. in an electric furnace while flowing a gas simulating a region where the air-fuel ratio was close to the theoretical air-fuel ratio, and the concentrations of sulfur dioxide and hydrogen sulfide were measured. The distribution gas composition was converted to the oxygen content of 0.5 vol%, carbon monoxide 0.5 vol%, nitrogen monoxide 800 volppm, and the balance nitrogen. Water was added to this so that it might be 3 vol% in terms of gas standard state volume with respect to the total amount of gas. The space velocity of gas distribution was 40,000 h- ¹ . As a result of totaling the total amount of sulfur in the water trap at the outlet, the analytical value of the sulfur dioxide analyzer, and the analytical value of hydrogen sulfide, the amount of released sulfur was 0. It was 003 wt%, and 99.9% or more was retained after heating.

  After these tests, the sulfur scavenger was crushed and the sulfur content in the powder was quantified using a sulfur analyzer. As a result, about 99.9% of the amount initially added with sulfur dioxide was detected.

  From these results, it was found that almost all of the sulfur content was captured by the sulfur content capturing material and was not desorbed at 700 ° C. or lower.

  Example 12 is an example of a sulfur content trapping material in which mordenite, which is a composite oxide of alumina and silica, is used as a carrier and supporting sodium and barium, and a sulfur content oxidizing material in which platinum and rhodium are supported on a titania carrier.

  Similar to Example 11, a sulfur scavenger was prepared. However, 150 g / L of mordenite was used as a wash coat for the carrier of the sulfur content capturing material.

  Similarly to Example 11, a sulfur-containing oxidizing material was prepared. A 400 cell / square inch cordierite honeycomb was wash-coated with 175 g / L of titania. This was impregnated with a hexaammine platinum salt solution-rhodium nitrate solution so as to be 2.4 g / L of platinum and 0.2 g / L of rhodium. This was calcined in air at 600 ° C. for 1 hour to obtain a sulfur component oxidizing material.

  Similarly to Example 11, a sulfur content capturing process when sulfur dioxide was added in a region where the air-fuel ratio was large, and a sulfur content desorbing process were performed in a region where the air-fuel ratio was close to the stoichiometric air-fuel ratio. As a result, the sulfur trapped and retained by the sulfur trap was 99.9% or more of the initial charge.

Example 13 is an example of a sulfur content-trapping material in which sodium and barium are supported using ferrierite, which is a composite oxide of alumina and silica, and a sulfur content oxidizing material in which platinum and rhodium are supported on a silica support.

  Similar to Example 11, a sulfur scavenger was prepared. However, 150 g / L of ferrierite was washed and used as the carrier for the sulfur content capturing material.

  Similarly to Example 12, a sulfur-containing oxidized material was prepared. However, silica was used as the carrier.

  Similarly to Example 11, a sulfur content capturing process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorbing process in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur trapped and retained by the sulfur trap was 99.9% or more of the initial charge.

  Example 14 is an example of a sulfur-capturing material in which zeolite / alumina / silica composite oxide is supported and sodium / barium is supported, and a sulfur-containing oxidizing material in which platinum is supported on a Y-type zeolite support.

  Similar to Example 11, a sulfur content capturing material was prepared. However, 150 g / L of structure code MFI zeolite was used as a wash coat for the sulfur-capturing material carrier.

  In the same manner as in Example 11, a sulfur-containing oxidized material was prepared. However, 175 g / L Y-type zeolite was used as a wash coat for the carrier.

  Similarly to Example 11, a sulfur content capturing process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorbing process in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. However, the trapping temperature of the sulfur trapping treatment was 350 ° C., and the trapping time was 1 hour. As a result, the sulfur trapped and retained by the sulfur trap was 99.9% or more of the initial charge.

  Example 15 is an example of a sulfur trapping material in which a beta zeolite of a composite oxide of alumina and silica is used as a carrier and sodium and barium are supported, and a sulfur component oxidizing material in which ferrierite is used as a carrier and platinum and rhodium are supported. It is.

  Similar to Example 11, a sulfur scavenger was prepared. However, a 175 g / L beta zeolite was used as a wash coat for the carrier. As a sulfur trapping component, a mixed solution of potassium nitrate and barium acetate was used, and impregnated so as to be 19.6 g / L in terms of potassium weight and 68.7 g / L in terms of barium weight. Thereafter, it was baked in air at 650 ° C. for 1 hour.

  Similarly to Example 12, a sulfur-containing oxidizing material was prepared. However, 160 g / L ferrierite was used as a wash coat for the carrier.

  Similarly to Example 11, a sulfur content capturing process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorbing process in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur trapped and retained by the sulfur trap was 99.9% or more of the initial charge.

  Example 16 is an example of a sulfur content-trapping material in which mordenite, which is a composite oxide of alumina and silica, is supported, and sodium and barium are supported, and a sulfur content oxidizing material in which platinum is supported on a lanthanum and zirconium oxide support. It is.

  Similar to Example 11, a sulfur scavenger was prepared. However, 150 g / L of mordenite was used as a wash coat for the carrier.

  Similarly to Example 11, a sulfur-containing oxidizing material was prepared. A cordierite honeycomb of 400 cells / square inch was wash-coated with 180 g / L of lanthanum oxide 20 wt% -zirconia 80 wt% powder. This was impregnated with a dinitrodiammine platinum solution in an amount of 2.5 g / L in terms of platinum. This was baked in air at 600 ° C. for 1 hour.

  Similarly to Example 11, a sulfur content capturing process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorbing process in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur trapped and retained by the sulfur trap was 99.9% or more of the initial charge.

Example 17 is an example in which a nitrogen oxide purification catalyst is used together with the sulfur component oxidizing material and the sulfur content capturing material of Example 16.

  Using a cordierite honeycomb of 400 cells / in 2, alumina was washcoated at an amount of 180 g / L. This is 27 g / L for Ce, 0.1 g / L for Rh, 3 g / L for Pt, 1.5 g / L for Pd, 12 g / L for Na, 15 g / L for K, 14 g / L for Mn, Ti As a result, 5 g / L was supported by the impregnation method. As raw materials for the impregnation method, Ce, Rh, Na and Mn used nitric acid solutions. K was an acetic acid solution, Pt and Pd were dinitrodiamine solutions, and Ti was a titania sol. After impregnating each component, it was calcined in air at 600 ° C. for 1 hour to obtain a nitrogen oxide purification catalyst.

  A nitrogen oxide purification catalyst was placed downstream of the sulfur oxidizer and sulfur capture catalyst, and the time dependence of the nitrogen oxide purification performance of diesel engine exhaust was investigated. The sulfur content oxidizing material and the sulfur content capturing material are the same as in Example 15. The test was performed with 2000 ppm thiophene added to the fuel for acceleration. The total sulfur content in the fuel after addition of thiophene is about 600 wtppm in terms of sulfur. After the engine was operated at an air-fuel ratio of 10 minutes for 10 minutes, a cycle of operating at an air-fuel ratio of 1.5 minutes for 1 minute was repeated until a certain time was reached.

  FIG. 4 shows the change in the nitrogen oxide purification rate when the above operation pattern is implemented. The nitrogen oxide purification rate in the catalyst was determined by sampling the gas from before and after the nitrogen oxide purification catalyst and analyzing the amount of nitrogen oxide respectively. As a comparative example, the change of the nitrogen oxide purification rate is shown together when the same test is carried out with the nitrogen oxide purification catalyst alone without inserting the sulfur content oxidizing material and the sulfur content capturing material.

  As can be seen from FIG. 10, the purification rate of the nitrogen oxide purification catalyst alone decreases with the passage of operating time, whereas when the sulfur trapping material and the sulfur content oxidation material are installed upstream of the nitrogen oxide purification catalyst. The purification rate hardly decreased.

  Example 18 is an example in which the sulfur content capturing material is made granular and filled into the honeycomb holes.

  Barium carbonate and anatase type titania were weighed so as to have a molar ratio of barium to titanium of 2: 1, mixed using a ball mill, and treated in an electric furnace at 650 ° C. for 2 hours. This powder was mixed with polyvinyl alcohol and warm water to prepare a slurry, and granulated by spray drying. The granulated powder is degreased by heating at 650 ° C. for 2 hours, and the mixed solution of sodium nitrate and barium acetate is converted to sodium weight and barium weight to 11.5 g / L and 68.7 g / L, respectively. After the impregnation, the sulfur capturing material was fired in air at 650 ° C. for 1 hour. The sulfur trap was spherical and the average particle size was 150 μm.

  The sulfur content trapping material was filled in the hole on the outlet side of an exhaust particulate filter honeycomb (length: 20 mm) made of cordierite, and the outlet was closed with a 200 mesh net. The porosity of the outlet-side honeycomb holes determined from the relationship between the weight and the average particle diameter was 65%.

  A cordierite honeycomb was wash-coated with a silica slurry in an amount of 170 g / L. A dinitrodiammine platinum solution was used for this and impregnated so as to be 3 g / L in terms of platinum weight. This was calcined at 600 ° C. for 1 hour to obtain a sulfur-containing oxidized material.

Arranged in the quartz glass reaction tube in the order of the sulfur component oxidizing material honeycomb and the exhaust particulate filter with respect to the gas flow direction, the temperature was raised to 300 ° C. in an electric furnace and a gas containing sulfur was circulated for 5 hours. The gas components are 10 vol% oxygen, 0.2 vol% carbon monoxide, 200 volppm nitric oxide, 150 ppm sulfur dioxide, and the balance nitrogen in terms of dryness. Water was added to this so that it would be 3 vol% in terms of gas standard state volume with respect to the total amount of gas. The space velocity of gas distribution was 30000 h ⁻¹ . The differential pressure before and after the glass reaction tube was measured with a differential pressure gauge. As a result of measuring the pressure loss of only the sulfur-oxidized material, it was found that the pressure loss was almost negligible, and that most of the pressure loss was caused by the exhaust particulate filter.

After the gas flow test, the temperature was raised in an electric furnace from room temperature to 700 ° C. while flowing a gas simulating a region where the air-fuel ratio was close to the theoretical air-fuel ratio. The distribution gas composition was converted to the oxygen content of 0.5 vol%, carbon monoxide 0.5 vol%, nitrogen monoxide 800 volppm, and the balance nitrogen. Water was added to this so that it would be 3 vol% in terms of gas standard state volume with respect to the total amount of gas. The space velocity of gas distribution was 30000 h ⁻¹ .

  After these tests, the sulfur-capturing material was pulverized and the sulfur content in the powder was quantified using a sulfur analyzer. As a result, 99.4% of the amount initially added with sulfur dioxide was detected.

  The pressure loss before and after the glass reaction tube during the test was about 1.3 kPa.

  From these results, it can be seen that almost all of the sulfur content is captured by the sulfur content trapping material and is not desorbed at 700 ° C. or lower. Further, the pressure loss during the flow of these gases is 0.65 kPa / cm per filter length, which is a sufficiently practical pressure loss region.

  Example 19 is an example in which a sulfur content capturing material and a filter are integrated.

  A 30% acidic titania sol was mixed with strontium acetate dissolved in an acetic acid aqueous solution to prepare a dip solution. Silica fibers were immersed in this solution and pulled up at a speed of 10 mm / min. This was dried at 120 ° C. for 24 hours and then calcined at 600 ° C. for 1 hour. This was immersed in a potassium acetate solution, dried and fired at 650 ° C. to obtain a fibrous sulfur-capturing material. After the fibers were aligned, the exhaust particulate filter was prepared by inserting the sulfur particulate capturing material into the hole on the outlet side of the exhaust particulate filter.

  A cordierite honeycomb was wash-coated with a mordenite slurry in an amount of 200 g / L. A hexaammine platinum solution was used for this and impregnated so as to be 2.5 g / L in terms of platinum weight. This was calcined at 600 ° C. for 1 hour to obtain a sulfur-containing oxidized material.

  Similarly to Example 19, a sulfur content capturing process in a region where the air-fuel ratio containing sulfur dioxide is large and a sulfur content desorbing process in a region where the air-fuel ratio is close to the theoretical air-fuel ratio were performed. As a result, the sulfur trapped and retained by the sulfur trap was 99.1% or more of the initial charge. In this case, the pressure loss in the exhaust particulate filter was 0.55 kPa / cm.

  As can be seen from this example, even if a fibrous sulfur content trapping material is used, an exhaust particulate filter that has a sufficiently small pressure loss and can effectively capture the sulfur content can be configured.

  Example 20 is an example in which an exhaust particulate filter in which a sulfur content capturing material and a filter are integrated is arranged downstream of a sulfur content oxidizing material.

  A sulfur component oxidizing material having the same composition as in Example 19 and an exhaust particulate filter integrated with a sulfur content capturing material were used. However, both were 0.9L and 2.1L as the honeycomb for actual vehicles, respectively. A nitrogen oxide purification catalyst was arranged on the downstream side of these, and the time dependence of the nitrogen oxide purification performance of diesel engine exhaust was investigated.

  The test was performed with 400 ppm thiophene added to the fuel for acceleration. The total sulfur content in the fuel after addition of thiophene is about 150 wtppm in terms of sulfur.

  The engine was operated for 1 minute at an air-fuel ratio of 14, and then a cycle of operating at an air-fuel ratio of 6 for 10 seconds was repeated. The operation was continued for a certain time, gas was sampled from before and after the nitrogen oxide purification catalyst, and the amount of nitrogen oxide was analyzed to determine the nitrogen oxide purification rate at the catalyst.

  FIG. 11 shows the change in the nitrogen oxide purification rate when the above operation pattern is carried out for a long time. For comparison, the change in the nitrogen oxide purification rate when the same test was conducted with the configuration of the sulfur content oxidizing material, the exhaust purification catalyst, and the nitrogen oxide purification catalyst without inserting the sulfur content capture material into the exhaust particulate filter Are also shown. As can be seen from the figure, when the exhaust particulate filter filled with the sulfur content trapping material is not inserted, the purification rate decreases with the passage of operating time, whereas the sulfur content trapping material and the sulfur content oxidizing material are purified by nitrogen oxides. When installed upstream of the catalyst, the purification rate hardly decreased.

  In Example 20, an unburned fuel oxidation catalyst was further arranged upstream of the sulfur component oxidizing material, and a diesel engine exhaust test was conducted. In the unburned fuel oxidation catalyst, cordierite honeycomb was coated with 180 g / L of cerium oxide powder, and then supported with 3 g / L of Pt and 1.5 g / L of Pd. As a result of the test, when the unburned fuel oxidizing material was arranged, accumulation of unburned fuel in the exhaust particulate filter could be prevented as compared with the case where there was no unburned fuel oxidizing material.

  INDUSTRIAL APPLICABILITY The present invention can be used for an exhaust gas purification apparatus for an internal combustion engine. In particular, when a lean NOx purification catalyst is poisoned by a sulfur content, such as a diesel engine, the exhaust gas purification that has been regenerated by a special method in the past. It can be used in an apparatus.

1 is an example of an exhaust emission control device according to the present invention. It is another example of the exhaust gas purification apparatus by this invention. It is another example of the exhaust gas purification apparatus by this invention. It is another example of the exhaust gas purification apparatus by this invention. It is another example of the exhaust gas purification apparatus by this invention. It is another example of the exhaust gas purification apparatus by this invention. It is an example (schematic diagram) of an exhaust particulate filter integrated with a sulfur content capturing material. It is another example (schematic diagram) of the exhaust particulate filter which integrated the sulfur content capture material. It is the figure which showed an example of the time change of the NOx purification rate in the engine test by this invention. It is the figure which showed another example of the time change of the NOx purification rate in the engine test by this invention. It is the figure which showed another example of the time change of the NOx purification rate in the engine test by this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Exhaust passage 3 Sulfur content oxidation material 4 Sulfur content capture material 5 Lean NOx purification catalyst 11 Exhaust particulate filter honeycomb wall 12 Exhaust particulate filter plug 13 Sulfur content capture material (granular)
14 Mesh 15 Exhaust particulate filter inlet side honeycomb hole 16 Exhaust particulate filter outlet side honeycomb hole 17 Sulfur content trapping material (fibrous)
18 Unburned Fuel Oxidizer 19 Unburnt Fuel Oxidizer and Sulfur Content Oxide Integrated Material 20 Unburnt Fuel Oxidizer, Sulfur Oxide Material and Sulfur Content Capture Material Integrated Material 21 Exhaust Particulate Filter (DPF)
22 Exhaust particulate filter with integrated sulfur trap

Claims (12)

  In an exhaust gas purifying apparatus for a diesel internal combustion engine, a sulfur content capturing material for capturing a sulfur content is installed in the downstream of the unburned fuel oxidizing material that oxidizes unburned fuel contained in the exhaust gas from the internal combustion engine, and the sulfur content is captured. An exhaust gas purifying apparatus, characterized in that the material is made of an alkali metal compound and / or an alkaline earth metal compound as a main component and a material that captures sulfur and does not substantially release it for all or part of the carrier.   2. The exhaust gas purifying apparatus according to claim 1, further comprising a sulfur component oxidizing material that oxidizes sulfur dioxide to sulfur trioxide on the upstream side of the sulfur content capturing material.   3. The exhaust gas purifying apparatus according to claim 2, wherein the sulfur-containing oxidizing material is disposed downstream of the unburned fuel oxidizing material.   The exhaust gas purifying apparatus according to claim 2, wherein the sulfur-containing oxidizing material and the unburned fuel oxidizing material are arranged on the same carrier.   The sulfur content capturing material is installed upstream of the lean NOx purification catalyst so that the exhaust gas from the internal combustion engine contacts the sulfur content capturing material and then contacts the lean NOx purification catalyst. Exhaust gas purification device.   6. The exhaust gas according to claim 1, further comprising an exhaust particulate filter for removing particulates contained in the exhaust from the internal combustion engine, between the unburned fuel oxidizing material and the sulfur content capturing material. Purification equipment.   The exhaust emission control device according to claim 6, wherein the exhaust particulate filter is filled with a sulfur content trapping material.   8. The exhaust emission control device according to claim 7, wherein the sulfur trapping material is filled in an exhaust particulate filter at a filling rate of 30 to 80%.   The exhaust emission control device according to claim 8, wherein the sulfur content capturing material is in a fibrous or granular form.   In an exhaust gas purification apparatus for an internal combustion engine, a sulfur content capturing material for capturing sulfur content is installed in the downstream of the unburned fuel oxidizing material that oxidizes unburned fuel contained in the exhaust gas from the internal combustion engine, and the sulfur content capturing material Is a sulfur-capturing material characterized in that a material that contains an alkali metal compound and / or an alkaline earth metal compound as a main component and that captures and does not substantially release sulfur is used for all or part of the carrier.   11. The unburned fuel oxidizing material according to claim 10, wherein a noble metal is used as an active component and an oxygen absorption / release material is further contained.   11. The sulfur component oxidizing material for oxidizing sulfur dioxide into sulfur trioxide according to claim 10, further comprising a noble metal as an active component, the sulfur component oxidizing material having 3 to 3 noble metals. It is supported on a carrier containing a Group 6 element compound, an aluminum compound, a silicon compound, or zeolite.

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