Exhaust gas treatment catalyst and method for producing the same

Abstract

To provide an exhaust gas treatment catalyst having high nitrogen oxide removal efficiency even under existence of SOX.SOLUTION: Disclosed is an exhaust gas treatment catalyst in which the peak area ratio of MoO / MoO3 is 1.7 or more, and that of VOX / V2O5 is 2.3 or more when obtaining each peak area by performing the peak separation regarding the peaks of MoO, MoO3, VOX and V2O5 which include a complex oxide including vanadium / molybdenum fixing on the surface of titanium oxide and have a peak centroid at 800 to 1,000 cm-1 detected by analyzing spectra obtained by Raman spectrometry.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention is X The present invention relates to an exhaust gas treatment catalyst that has high nitrogen oxide removal efficiency even in the presence of nitrogen oxides, and a method for producing the same. [Background technology]

[0002] Conventionally, nitrogen oxides (NO X As an exhaust gas treatment catalyst that selectively reduces and removes NO with a reducing agent such as ammonia, a honeycomb-shaped catalyst molded product in which active components such as tungsten oxide and vanadium oxide are supported on a titanium oxide support is industrially used (Patent Documents 1 and 2). The valence of V and NO X Research is also being conducted into the relationship between the conversion rate and the amount of carbon dioxide produced (Non-Patent Documents 1 to 5). In recent years, they have also been used as catalysts to remove nitrogen oxides from exhaust gases from boilers, waste incinerators, etc., and from the viewpoint of suppressing the generation of dioxins, operation at temperatures of approximately 200°C or less is desired. As exhaust gas treatment catalysts that solve this problem, the exhaust gas treatment catalysts described in Patent Documents 1 to 3 have been proposed, and X There is a growing demand for exhaust gas treatment catalysts that are highly active even in the presence of sulfur dioxide. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-81995 [Patent Document 2] Japanese Patent Application Publication No. 11-165068 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-79716 [Non-patent literature]

[0004] [Non-Patent Document 1] Geert Silversmit et al., Determination of the V2p XPS binding energies for different vanadium oxidation states(V5+toV6+), J. Electron Spectroscopy and Related Phenomena, 2004, 135(2-3), 167-175. [Non-patent document 2] Geert Silversmit et al., An XPS study on the surface reduction of V2O5(001) induced by Ar+ion bombardment, Surface Science, 2006, 600(17), 3512-3517. [Non-patent document 3] Xuteng Zhao et al., A relationship between the V4+ / V5+ratio and the surface dispersion, surface acidity, and redox performance of V2O5-WO3 / TiO2 SCR catalysts, RSC Advances, 2018, 8, 31081-31093. [Non-patent document 4] Jiaoyan Zhou et al., Manipulating Behaviors from Heavy Tungsten Doping on interband Electronic Transition and Orbital Structure Variation of Vanadium Dioxide Films, ACS Appl. Mater. Interfaces, 2018, 10(36), 30548-30557, [Non-Patent Document 5] Jihene Arfaoui et al., A new V2O5 -MoO3 -TiO2 -SO4 2- nanostructured aerogel catalyst for diesel DeNO x technology, New Journal of Chemistry, Royal Society of Chemistry, 2020, 44 (37), pp.16119-16134 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention is X The present invention aims to provide an exhaust gas treatment catalyst that has high nitrogen oxide removal efficiency even in the presence of nitrogen oxides, and a method for producing the same. [Means for solving the problem]

[0006] The present inventors have conducted extensive research to solve the above problems and have completed the present invention. The present invention includes the following [1] to [3]. [1] A composite oxide containing vanadium and molybdenum is fixed to the surface of titanium oxide, The spectrum obtained by Raman spectroscopy was analyzed and detected in the 800-1000 cm -1 MoO, MoO3, and VO X The peak area ratio of MoO / MoO3 is 1.7 or more, and the peak area ratio of VO2O5 is 1.7 or more. X / V2O5 peak area ratio of 2.3 or more. [2] The exhaust gas treatment catalyst according to the above [1], wherein the composite oxide is made of a mixed-valence compound of vanadium and molybdenum containing trivalent, tetravalent, and pentavalent vanadium and hexavalent molybdenum. [3] 1) A step of preparing a mother liquor by mixing water, sulfuric acid, a vanadium raw material, a molybdenum raw material, and a complexing agent; 2) mixing titanium oxide powder with the mother liquor to prepare a mixture, and then mixing a precipitant into the mixture to obtain a molding mixture in which a coprecipitate of vanadium and molybdenum is adhered to the surface of the titanium oxide powder; 3) a step of molding the molding mixture to obtain a molded body; 4) firing the molded body to obtain an exhaust gas treatment catalyst in which a composite oxide of vanadium and molybdenum is adhered to the surface of the titanium oxide powder; A method for producing an exhaust gas treatment catalyst comprising: [Effects of the Invention]

[0007] The exhaust gas treatment catalyst of the present invention is X This exhaust gas treatment catalyst maintains high nitrogen oxide removal efficiency even in the presence of NO X Since the selective reduction activity of NO is high, it can be efficiently reduced not only in high temperature ranges but also in low temperature ranges below approximately 200°C. X can be removed. [Brief explanation of the drawings]

[0008] [Figure 1] 1 shows a Raman spectrum of the exhaust gas treatment catalyst obtained in Example 1. [Figure 2] 1 is a scanning electron microscope (SEM) image of the exhaust gas treatment catalyst obtained in Example 1. [Figure 3] 1 is a scanning electron microscope (SEM) image of the exhaust gas treatment catalyst obtained in Comparative Example 2. DETAILED DESCRIPTION OF THE INVENTION

[0009] The embodiments of the present invention will be described in further detail below.

[0010] <Exhaust gas treatment catalyst of the present invention> The exhaust gas treatment catalyst of the present invention has a composite oxide containing vanadium and molybdenum fixed to the surface of a titanium oxide, and is characterized by a Raman spectrum obtained by Raman spectroscopy. -1MoO, MoO3, and VO X The peak area ratio of MoO / MoO3 is 1.7 or more and the peak area ratio of VO2O5 is 1.7 or more. X / V2O5 peak area ratio is 2.3 or more.

[0011] The composite oxide of vanadium and molybdenum is preferably a mixed-valence compound containing trivalent, tetravalent, and pentavalent vanadium and hexavalent molybdenum. By analyzing the surface of this exhaust gas treatment catalyst of the present invention by X-ray photoelectron spectroscopy (XPS) described below, it can be confirmed that the catalyst is a composite oxide containing vanadium and molybdenum of these valences.

[0012] The composite oxide of vanadium and molybdenum referred to here is adhered to the surface of the titanium oxide. This is different from composite oxides in which vanadium, molybdenum, and titanium are mixed in the same crystal structure; the composite oxide of vanadium and molybdenum is adhered to the surface of the titanium oxide via oxygen. This allows the composite oxide phase and the titanium oxide phase to be clearly distinguished.

[0013] The composite oxide contains, based on the catalyst, vanadium in an amount of preferably 3.0 to 10.0 mass %, more preferably 3.0 to 8.0 mass %, calculated as V2O5, and molybdenum in an amount of preferably 3.0 to 20.0 mass %, more preferably 3.0 to 8.0 mass %, calculated as MoO3.

[0014] The exhaust gas treatment catalyst of the present invention is a catalyst in which vanadium and molybdenum are fixed on titanium in the form of oxides of suitable active species. The exhaust gas treatment catalyst of the present invention is also subjected to Raman spectroscopic analysis to obtain a Raman spectroscopic spectrum, and the spectrum is analyzed to detect a peak in the 800 to 1000 cm -1 MoO, MoO3, and VO X The peak area ratio of MoO / MoO3 is 1.7 or more and the peak area ratio of VO2O5 is 1.7 or more. XThe peak area ratio of V2O5 is 2.3 or more. X means trivalent and tetravalent vanadium oxides.

[0015] The titanium oxide is preferably titanium dioxide.

[0016] Conventionally, exhaust gas treatment catalysts with large specific surface areas have X In contrast, the exhaust gas treatment catalyst of the present invention has good NO selective reduction activity even though it has a small specific surface area. X It shows selective reduction activity. 2 / g, but 50m 2 / g or more 95m 2 / g or less, good NO x It exhibits selective reduction activity.

[0017] The exhaust gas treatment catalyst of the present invention may contain components other than the composite oxide of vanadium and molybdenum. For example, as components other than vanadium and molybdenum, metal components such as tungsten, chromium, manganese, iron, nickel, copper, silver, gold, palladium, yttrium, cerium, neodymium, indium, iridium, and antimony may be contained. These affect the catalytic performance as promoters, and the content (in terms of metal oxide) of these promoters is preferably 3 mass% or less.

[0018] The exhaust gas treatment catalyst of the present invention preferably contains sulfur. The sulfur content (SO4 equivalent) is preferably in the range of 0.1 mass% to 5 mass%, more preferably in the range of 0.5 mass% to 4 mass%, and particularly preferably in the range of 0.5 mass% to 3 mass%. The sulfur contained in the exhaust gas treatment catalyst of the present invention affects the band structure of vanadium and reduces NO X It has a positive effect on selective reduction activity.

[0019] In addition to these components, additives such as reinforcing materials and plasticizers may be added during molding. The catalyst may contain inorganic components such as glass fiber, silica, alumina, etc. as additives. These components have the function of increasing the moldability of the exhaust gas treatment catalyst and maintaining its strength. Furthermore, it is preferable to add an acrylate-based latex as an additive. By adding this additive and glass fiber, vanadium and molybdenum can be fixed to the titanium in a highly dispersed state in a suitable oxide state, which contributes to improving catalytic performance. When a reinforcing material or a plasticizer is used as an additive, the total content of the reinforcing material and the plasticizer is preferably 5 to 30 mass %, more preferably 5 to 15 mass %. When an acrylate latex (for example, one with a concentration of 45%) is used as an additive, the content of the acrylate latex is preferably 0.02 to 5.0% by mass, and more preferably 0.05 to 1.0% by mass.

[0020] The shape of the exhaust gas treatment catalyst of the present invention may be any conventionally known shape such as pellets or honeycomb, and is preferably honeycomb. Taking as an example a honeycomb having a square cross-sectional shape perpendicular to the longitudinal direction (penetration direction) of the through holes, the outer diameter of the honeycomb (the length of one side of the cross section) is preferably in the range of 30 mm or more and 300 mm or less, and more preferably in the range of 50 mm or more and 200 mm or less. The length of the honeycomb (the length in the longitudinal direction (penetrating direction) of the through holes) is preferably in the range of 100 mm or more and 3000 mm or less, and more preferably in the range of 300 mm or more and 1500 mm or less. The through holes of the honeycomb (hereinafter sometimes referred to as cell pitch) are preferably in the range of 1 mm or more and 15 mm or less, and more preferably in the range of 2 mm or more and 10 mm or less. The partition wall thickness of the honeycomb is preferably in the range of 0.1 mm or more and 2 mm or less, and more preferably in the range of 0.1 mm or more and 1.5 mm or less. The opening ratio of the honeycomb is preferably in the range of 60% to 85%, and more preferably in the range of 70% to 85%. When the honeycomb shape is within this range, the strength of the honeycomb structure is maintained while the NO per unit volume is x The selective reduction activity tends to be high.

[0021] The exhaust gas treatment catalyst of the present invention is X NO-containing exhaust gases, especially those from boilers or waste incinerators X and SO X NO is catalytically reduced by adding a reducing agent such as ammonia to exhaust gas containing heavy metals and dust. X The catalyst for treating exhaust gases can be used under the conditions of ordinary exhaust gas treatment, specifically, at a reaction temperature of 150°C to 400°C. In particular, the catalyst for treating exhaust gases of the present invention exhibits high activity in the temperature range of 170°C to 270°C, and exhibits good NO removal in the temperature range of 170°C to 200°C. X It exhibits selective reduction activity.

[0022] <Method for producing the exhaust gas treatment catalyst of the present invention> The method for producing the exhaust gas treatment catalyst of the present invention will be explained below. The exhaust gas treatment catalyst of the present invention can be prepared, for example, by using a production method comprising the following steps. 1) A step of preparing a mother liquor by mixing water, sulfuric acid, a vanadium raw material, a molybdenum raw material, and a complexing agent. 2) A step of mixing titanium oxide powder with the mother liquor to prepare a mixture, and then mixing a precipitant into the mixture to obtain a molding mixture in which a coprecipitate of vanadium and molybdenum is adhered to the surface of the titanium oxide powder. 3) A step of molding the molding mixture to obtain a molded body. 4) A step of calcining the molded body to obtain an exhaust gas treatment catalyst in which a composite oxide of vanadium and molybdenum is fixed to the surface of the titanium oxide powder.

[0023] Each step will be described in detail below. <Step of preparing mother liquor> In the step of preparing the mother liquor, a vanadium raw material, a molybdenum raw material, a complexing agent, and sulfuric acid are dissolved in water to prepare the mother liquor. Here, vanadium and molybdenum are raw materials for producing a composite oxide. The complexing agent coordinates with vanadium or molybdenum ions to form a complex. The mother liquor can be prepared by dissolving these raw materials in water.

[0024] As raw materials for vanadium and molybdenum, soluble salts are preferably used. For example, vanadium raw materials are preferably vanadate, vanadium sulfate, vanadium chloride, etc., and particularly preferably ammonium metavanadate. Vanadium oxide may also be dissolved in acid. As the molybdenum raw material, it is preferable to use molybdate, molybdenum sulfate, molybdenum chloride, etc., and it is particularly preferable to use ammonium molybdate.Molybdenum oxide may also be dissolved in acid. These may be used alone or in combination of two or more. The amounts of vanadium and molybdenum added as raw materials are adjusted appropriately according to the composition of the exhaust gas treatment catalyst that will ultimately be obtained.

[0025] The complexing agent is preferably a compound having an amine or a hydroxyl group, more preferably an alkanolamine, and particularly preferably ethanolamine. These complexing agents coordinate with vanadium ions or molybdenum ions in the mother liquor to form a complex and stabilize the ions. Therefore, the complexing agent is preferably added after the vanadium and molybdenum raw materials are dissolved in water.

[0026] In this case, the amount of the complexing agent added is preferably in the range of 0.1 to 6 moles, more preferably in the range of 0.5 to 3 moles, per mole of vanadium and molybdenum. By adding the amount of complexing agent necessary to form a complex, the vanadium and molybdenum ions are stabilized.

[0027] The amount of sulfuric acid added is preferably in the range of 0.001 mol to 0.1 mol, more preferably in the range of 0.01 mol to 0.05 mol, per mol of titanium.

[0028] In the step of preparing this mother liquor, other soluble components may be added, for example, raw materials containing the aforementioned components that will become the promoter components may be dissolved.

[0029] <Step of obtaining mixture for molding> In this step, the mother liquor prepared in the above-mentioned step of preparing the mother liquor is mixed with titanium oxide powder to prepare a mixture. The titanium oxide powder is preferably surface-modified in advance with an acid. The acid used here may be either an inorganic acid or an organic acid, such as citric acid, acetic acid, nitric acid, phosphoric acid, or sulfuric acid.

[0030] The mixture may contain additives such as a reinforcing material and a plasticizer that may be contained in the exhaust gas treatment catalyst of the present invention.

[0031] The mixing method can be a conventionally known method. For example, a kneader, a high-speed mixer, or a ball mill can be used. These methods are appropriately selected depending on the amounts of mother liquor and titanium oxide powder. If the mixture becomes clayey and places a strain on the equipment, it is preferable to use a kneader or a high-speed mixer.

[0032] The mixture is then mixed with a precipitant to prepare a molding mixture in which a coprecipitate of vanadium and molybdenum is adhered to the surface of the titanium oxide. Here, the mother liquor components contained in the mixture are neutralized to produce a coprecipitate of vanadium and molybdenum. This coprecipitate adheres to the surface of the titanium oxide powder to obtain a molding mixture.

[0033] Conventional precipitants can be used. For example, sodium carbonate, soda ash, and aqueous ammonia can be used. The amount of precipitant added is adjusted appropriately so that the pH of the mother liquor contained in the mixture is in the range of 6 to 9. If the mixture is clayey and pH measurement is difficult, the amount of precipitant required to neutralize the mother liquor can be determined experimentally in advance, and the amount added can be adjusted accordingly. If the mixture is not clayey, the moisture content can be adjusted, a binder can be added, and other steps can be performed to prepare a molding mixture suitable for molding.

[0034] <Step of obtaining a molded body> In the step of obtaining a molded body, the molding mixture is molded to prepare a molded body. The molded body can be molded into a conventionally known shape such as a pellet or a honeycomb. For use as an exhaust gas treatment catalyst, molding into a honeycomb is preferred. The molding method can be a conventionally known method, for example, molding into pellets or honeycomb using an extrusion molding machine. The molded body can be dried by a conventionally known method to prevent cracks, etc. The additives such as a reinforcing material and a plasticizer that may be contained in the exhaust gas treatment catalyst of the present invention may be incorporated into the molded body by molding the mixture for molding together with the additives.

[0035] <Process for obtaining exhaust gas treatment catalyst> In the process of obtaining the exhaust gas treatment catalyst, the molded body is calcined to prepare an exhaust gas treatment catalyst in which a composite oxide of vanadium and molybdenum is fixed to the surface of the titanium oxide. A conventionally known calcination method can be used. For example, a method of calcining in the atmosphere using a heating furnace such as an electric furnace or a gas furnace can be used. The calcination temperature is preferably 300°C or higher and 500°C or lower. The calcination time varies depending on the calcination temperature, but may be generally in the range of 1 hour to 48 hours. [Example]

[0036] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the contents of the examples.

[0037] [Measurement method] The measurement methods employed in this application are described below.

[0038] [1] Composition The exhaust gas treatment catalysts obtained in the examples and comparative examples were powdered to prepare evaluation samples, which were then dissolved in acid to prepare solutions, and the compositions of the various components were calculated using high-frequency inductively coupled plasma atomic emission spectroscopy (instrument name: ICPS-8100).

[0039] [2] Valence of vanadium and molybdenum The reactive surfaces (outer surfaces in the case of pellets, or outer surfaces of partition walls in the case of honeycomb) of the exhaust gas treatment catalysts obtained in the examples and comparative examples were broken into pieces so that they could be measured, and evaluation samples were prepared. These were set on a sample stage and subjected to X-ray photoelectron spectroscopy (XPS) under the following conditions. The spectrum obtained from this measurement was analyzed, and if peaks were detected in the following ranges, it was determined that the sample contained vanadium and molybdenum with these valences. <Measurement conditions> XPS measurements were performed using a ThermoFisher ESCALAB220IXL, with Al as the X-ray source, and the peak position was corrected based on the C-C bond of C1S at 284.8 eV. After placing the sample for evaluation in the instrument and confirming that a high vacuum had been reached, measurements were performed under the conditions of an acceleration voltage of 10 kV, an emission current of 10 mA, and 30 scans. <Calculation conditions> After scan integration, peak separation is performed, and V 3+ , V 4+ , V 5+ , Mo 6+ The presence or absence of peaks was confirmed.

[0040] [3] Number of cations of vanadium and molybdenum The surfaces of the exhaust gas treatment catalysts obtained in the examples and comparative examples were measured by SEM-EDS (energy dispersive X-ray spectroscopy) under the following conditions. <Measurement conditions> SEM measurements were performed using a JEOL JSM6010LA with W as the X-ray source. The exhaust gas treatment catalysts obtained in the examples and comparative examples were processed into fragments, and the surfaces that would become the denitrification reaction surfaces (the outer surface in the case of pellets, or the outer surface of the partition wall in the case of honeycomb) were measured. The acceleration voltage was adjusted to 20 kV-15 kV, and the SS was adjusted to 4 nm. The image was then magnified to 1.5 million times, the analysis position was probe-tracked, and EDS-line analysis was performed to trace the measurement position, followed by composition conversion using the ZAF method. The particle diameters of V and Mo were calculated from the peaks obtained. After adjusting the beam diameter to this particle diameter, the image was magnified to 1.5 million times, the analysis position was probe-tracked, and point analysis of Ti, V, and Mo was performed at four or more locations. This was repeated at different measurement locations, resulting in a total of more than 20 point analyses. <Calculation method> From the obtained data, 20 locations where Ti, V, and Mo were all detected were identified, and the average number of V cations at each location was calculated and used as the number of cations in that exhaust gas treatment catalyst. This number of cations was calculated based on the number of oxygen in a fully oxidized state (VO in the case of V), which is 24, and the number is 0 in a fully oxidized state.

[0041] [4] Raman spectroscopy The exhaust gas treatment catalysts obtained in the examples and comparative examples were broken into fragments so that the reactive surfaces (the outer surfaces in the case of pellets, or the outer surfaces of the partition walls in the case of honeycomb) could be measured, to prepare evaluation samples. These were set on a sample stage, and Raman spectroscopy was performed under the following conditions. The spectrum obtained from this measurement was analyzed, and if a peak with a peak center of gravity in the following range was detected, it was determined that the catalyst contained oxides of vanadium and molybdenum, respectively. MoO3: 800-820cm -1 MoO: 920~960cm -1 VO X :850~890cm -1 V2O5: 980-1000cm -1 <Measurement conditions> Using a Raman spectroscopic measuring device LabRAM ARAMIS manufactured by Horiba, Ltd., Raman spectroscopic analysis of the sample surface was carried out under the following measurement conditions. Excitation wavelength: 532 nm Diffraction grating lines: 600 lines / mm ND filter: D1 Objective lens magnification: 100x <Calculation conditions> After the measurement, the peaks were separated using the analysis software "Origin" to separate the MoO, MoO3, and VO X The intensity ratio was calculated using the peak area S of the peak corresponding to V2O5. MoO / MoO3=S MoO / S MoO3 VO X / V2O5=S VOX / S V2O5

[0042] [5] Strength A cube measuring 75 mm × 75 mm was cut out from the catalysts obtained in Examples 1 and 2 and Comparative Examples 1 and 2, and then compressed in a direction perpendicular to the honeycomb through-holes to measure the pressure at which the catalyst was completely destroyed. The results are shown in Table 1.

[0043] [6] Specific surface area The exhaust gas treatment catalysts obtained in the examples and comparative examples were pulverized to prepare evaluation samples. This evaluation sample (0.2 g) was placed in a measurement cell and degassed in a nitrogen gas stream at 300°C for 60 minutes. The sample was then maintained at liquid nitrogen temperature in a mixed gas stream of 30% by volume nitrogen and 70% by volume helium, allowing nitrogen to adsorb to the sample at equilibrium. Next, the temperature of the sample was gradually raised to room temperature while the mixed gas was being passed through. The amount of desorbed nitrogen was detected during this period, and the specific surface area of ​​the sample was measured using a previously prepared calibration curve.

[0044] [7] Denitrification performance (selective reduction catalyst (SCR) activity) The exhaust gas treatment catalysts obtained in the examples and comparative examples were cut into the following catalyst shapes to prepare evaluation samples. These were packed into a flow reactor, and the denitrification rate was evaluated. Specifically, the NOx reduction rate measured under the following conditions before and after contact with the catalyst was X The denitration rate was calculated from the concentration using the following formula: The denitration rate immediately after flowing gas having the following gas composition 1 for 3 hours was defined as the "initial denitration rate," and the denitration rate immediately after flowing gas having the following gas composition 2 for 100 hours was defined as the "denitration rate after deterioration test." In addition, the nitrogen oxides NO in the gas before and after contact with the catalyst X The concentration was measured using a chemiluminescence nitrogen oxide analyzer (ECL-88AO, manufactured by Anatech Yanaco Co., Ltd.). Denitrification rate (%) = [NO in gas before contact X (ppm)-NO in gas after contact X (ppm)] / NO in gas before contact X (ppm) x 100 <Test conditions> Catalyst shape: 4 x 4 holes, length 286 mm Reaction temperature: 175℃ Response time: 100 hours SV:18528.39h -1 Gas composition 1: NO x = 200 ppm, NH3 = 200 ppm, O2 = 5%, H2O = 10%, N2 = balance Gas composition 2: NO x = 200 ppm, NH3 = 200 ppm, O2 = 5%, H2O = 10%, SO2 = 80 ppm, N2 = balance

[0045] [Example 1] <Step of preparing mother liquor 1> 6000 g of water, 1359 g of monoethanolamine as a complexing agent, and 2544 g of ammonium metavanadate (manufactured by Shinko Chemical Co., Ltd.: V2O5 oxide concentration 78%) were prepared. After mixing these, the temperature was raised to 80-90°C and stirring was continued for 2 hours. This was then cooled to 40-60°C, and 2233 g of ammonium molybdate (manufactured by Taiyo Koko Co., Ltd.: MoO3 oxide concentration 81.5%) was added, followed by stirring for 5 minutes. 3654 g of sulfuric acid (concentration: 25% by mass) was then added to obtain mother liquor 1 containing vanadium and molybdenum.

[0046] <Step of obtaining molding mixture 1> 20,766 g of powdered titanium dioxide (Tronox: G5; TiO2 oxide concentration 82%), 2,272 g of anhydrous citric acid (Fuso Chemical Co., Ltd.), and 2,000 g of water were kneaded in a kneader for 10 minutes. Then, the aforementioned mother liquor 1 was added and kneaded for 30 minutes. 703 g of carboxymethyl cellulose (Nichirin Chemical Co., Ltd.; ammonium CMC) was added and kneaded for 10 minutes. 8,276 g of ammonia water (concentration: 15% by mass) was added as a precipitant to the resulting mixture, and the mixture was kneaded for 30 minutes while heating to remove moisture. 3,000 g of glass fiber (E-glass) was added as a reinforcing material and kneaded for 10 minutes. After that, 4,216 g of Nipol LX874 (Zeon Corporation), a 45% acrylate latex diluted 100 times with water, was added and kneaded for 20 minutes to obtain molding mixture 1.

[0047] <Step of Obtaining Molded Body 1> Using a screw-type vacuum extruder equipped with a honeycomb extrusion die, the molding mixture 1 obtained in the above step was molded into a honeycomb. After drying this honeycomb for a sufficient period of time, it was dried for 2 days while ventilating with hot air at 60°C, and molded body 1 was obtained.

[0048] <Step of obtaining exhaust gas treatment catalyst 1> Both ends of the axial direction (longitudinal direction) of the molded body 1 were trimmed, and the molded body 1 was fired in an electric furnace at 450°C for 5 hours in an atmospheric atmosphere to obtain an exhaust gas treatment catalyst 1 with a cell pitch of 2.8 mm and a wall thickness of 0.5 mm. The above-mentioned measurements were carried out on this exhaust gas treatment catalyst. The results are shown in Table 1.

[0049] FIG. 1 shows the Raman spectrum of the exhaust gas treatment catalyst obtained in Example 1.

[0050] In addition, Figure 2 shows a scanning electron microscope (SEM) image of the exhaust gas treatment catalyst obtained in Example 1. Figure 2 is an SEM image at 100x magnification. From this image, it appears that the adhesion between the glass fibers and the catalyst components is strong and there is little space created by the aggregation of the glass fibers.

[0051] [Example 2] <Step of preparing mother liquor 2> 6000 g of water, 1359 g of monoethanolamine as a complexing agent, and 2544 g of ammonium metavanadate (manufactured by Shinko Chemical Co., Ltd.: V2O5 oxide concentration 78%) were prepared. After mixing these, the temperature was raised to 80-90°C and stirring was continued for 2 hours. This was then cooled to 40-60°C, and 2870.8 g of ammonium molybdate (manufactured by Taiyo Koko Co., Ltd.: MoO3 oxide concentration 81.5%) was added, followed by stirring for 5 minutes. 3654 g of sulfuric acid (concentration: 25% by mass) was then added to obtain mother liquor 2 containing vanadium and molybdenum.

[0052] <Step of obtaining molding mixture 2> 20,766 g of powdered titanium dioxide (Tronox: G5; TiO2 oxide concentration 82%), 2,272 g of anhydrous citric acid (Fuso Chemical Co., Ltd.), and 2,000 g of water were kneaded in a kneader for 10 minutes. Then, the aforementioned mother liquor 2 was added and kneaded for 30 minutes. 703 g of carboxymethyl cellulose (Nichirin Chemical Co., Ltd.; ammonium CMC) was added and kneaded for 10 minutes. 8,276 g of ammonia water (concentration: 15% by mass) was added as a precipitant to the resulting mixture, and the mixture was kneaded for 30 minutes while heating to remove moisture. 3,000 g of glass fiber (E-glass) was added as a reinforcing material and kneaded for 10 minutes. After that, 4,216 g of Nipol LX874 (Zeon Corporation), a 45% acrylate latex diluted 100 times with water, was added and kneaded for 20 minutes to obtain molding mixture 2.

[0053] <Step of Obtaining Molded Body 2> Using a screw-type vacuum extruder equipped with a honeycomb extrusion die, the molding mixture 2 obtained in the above step was molded into a honeycomb. After drying this honeycomb for a sufficient period of time, it was dried for 2 days while ventilating with hot air at 60°C, and thus a molded body 2 was obtained.

[0054] <Step of obtaining exhaust gas treatment catalyst 2> Both ends of the axial direction (longitudinal direction) of the molded body 2 were trimmed, and the molded body 2 was fired in an electric furnace at 450°C for 5 hours in an air atmosphere to obtain an exhaust gas treatment catalyst 2 with a cell pitch of 2.8 mm and a wall thickness of 0.5 mm. The above-mentioned measurements were carried out on this exhaust gas treatment catalyst. The results are shown in Table 1.

[0055] [Comparative Example 1] <Step of preparing mother liquor 3> 3000 g of water, 330 g of monoethanolamine as a complexing agent, and 691.3 g of ammonium metavanadate (manufactured by Shinko Chemical Co., Ltd.: V2O5 oxide concentration 78%) were prepared. After mixing these, the temperature was raised to 80-90°C and stirring was continued for 2 hours. This was cooled to 40-60°C to prepare mother liquor 3.

[0056] <Step of obtaining molding mixture 3> 18,330 g of titanium dioxide (Ishihara Sangyo Kaisha: MC90: TiO2 oxide concentration 95% by mass), 1,411.99 g of ammonium metavanadate, 809.82 g of ammonium molybdate, and aqueous ammonia (concentration: 15% by mass) were kneaded in a kneader for 30 minutes. Then, the mother liquor 3 prepared in the previous step was added, and the mixture was kneaded for 30 minutes. Furthermore, 1,710 g of glass fiber was added as a reinforcing material, and the mixture was kneaded for 10 minutes. Furthermore, 300 g of an organic binder, which serves as a molding aid, was added, and the mixture was kneaded for 20 minutes, to obtain a molding mixture 3.

[0057] <Step of Obtaining Molded Body 3> The molding mixture 3 obtained in the above-mentioned step was molded into a honeycomb shape using a screw extruder, and dried to obtain a molded body 3.

[0058] <Step of obtaining exhaust gas treatment catalyst R1> This honeycomb molded body 3 was fired in an electric furnace at 470°C for 5 hours to obtain exhaust gas treatment catalyst R1. The above-mentioned measurements were carried out on this exhaust gas treatment catalyst. The results are shown in Table 1.

[0059] Comparative Example 2 <Step of preparing mother liquor 4> 6000 g of water, 1096.26 g of monoethanolamine as a complexing agent, and 2011.49 g of ammonium metavanadate (manufactured by Shinko Chemical Co., Ltd.: V2O5 oxide concentration 78%) were prepared. After mixing these, the temperature was raised to 80-90°C and stirring was continued for 2 hours. This was then cooled to 40-60°C, 765.54 g of ammonium molybdate was added, and stirring was continued for 5 minutes to obtain mother liquor 4 containing vanadium and molybdenum.

[0060] <Step of obtaining molding mixture 4> 17,590 g of titanium dioxide and the mother liquor 4 prepared in the previous step were kneaded in a kneader for 30 minutes. 1,480 g of ammonia water (concentration: 15% by mass) was added as a precipitant to the resulting kneaded mixture, and the mixture was kneaded for 45 minutes. 2,400 g of glass fiber was then added as a reinforcing material, and the mixture was kneaded for 10 minutes. 560 g of an organic binder, which served as a molding aid, was then added, and the mixture was kneaded for 20 minutes, yielding a molding mixture 4.

[0061] <Step of Obtaining Molded Body 4> Using a screw vacuum extruder equipped with a honeycomb extrusion die, the molding mixture 4 obtained in the above step was molded into a honeycomb, and dried for a sufficient time to obtain a molded body 4.

[0062] <Process for obtaining exhaust gas treatment catalyst R2> This honeycomb molded body 4 was dried for two days while ventilating with hot air at 60°C, and then both ends in the axial direction (longitudinal direction) were trimmed and fired in an electric furnace at 450°C for five hours in an atmospheric atmosphere to obtain exhaust gas treatment catalyst R2 with a cell pitch of 2.8 mm and a wall thickness of 0.5 mm. The above-mentioned measurements were carried out on this exhaust gas treatment catalyst. The results are shown in Table 1.

[0063] FIG. 3 shows a scanning electron microscope (SEM) image of the exhaust gas treatment catalyst obtained in Comparative Example 2. FIG. 3 is a 100x SEM image. From this image, it can be seen that the adhesion to the catalyst components is weak and that spaces are generated in the catalyst structure due to the aggregation of the glass fibers. Comparing FIG. 3 showing the comparative example with FIG. 2 showing the example, it appears that the adhesion between the glass fibers and the catalyst components is stronger in FIG. 2 of the example than in FIG. 3 of the comparative example, and that there are fewer spaces generated due to the aggregation of the glass fibers. As a result, the honeycomb structure in FIG. 2 has a high adhesion of the catalyst components including the glass fibers, and has a high strength (N / cm 2 ) is considered to be strong.

[0064] [Table 1]

Claims

1. A composite oxide containing vanadium and molybdenum is fixed to the surface of the titanium oxide, The spectrum obtained by Raman spectroscopy was analyzed and detected as a region between 800 and 1000 cm －１ MoO, MoO with peak centroid at ３ , V.O. ｘ (X is at least one of 1.5 and 2) and V ２ O ５ The peaks are separated and the area of ​​each peak is calculated. ３ The peak area ratio of VO is 1.7 or more, and ｘ / V ２ O ５ The exhaust gas treatment catalyst has a peak area ratio of 2.3 or more. Here, the peak centroids of MoO 3 , MoO, VO x and V 2 O 5 are in the following ranges, respectively. MoO3:800-820cm-1 MoO: 920-960cm -1 VOx: 850-890cm -1 V2O5:980~1000cm-1

2. 2. The exhaust gas treatment catalyst according to claim 1, wherein the composite oxide is made of a mixed-valence compound of vanadium and molybdenum containing trivalent, tetravalent, and pentavalent vanadium and hexavalent molybdenum.

3. 1) preparing a mother liquor by mixing water, sulfuric acid, a vanadium raw material, a molybdenum raw material, and a complexing agent; 2) mixing titanium oxide powder with the mother liquor to prepare a mixture, and then mixing a precipitant into the mixture to obtain a molding mixture in which a coprecipitate of vanadium and molybdenum is adhered to the surface of the titanium oxide powder; 3) a step of molding the molding mixture to obtain a molded body; 4) firing the molded body to obtain an exhaust gas treatment catalyst in which a composite oxide of vanadium and molybdenum is adhered to the surface of the titanium oxide powder; A method for producing an exhaust gas treatment catalyst comprising:

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