JPH09155184A - Production of surface modified titania carrier - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the adsorbing capacity of an NOx adsorbent using a surface modified titania carrier. SOLUTION: A non-combustible fiber preform is impregnated with a mixed soln. of titania colloid and an aq. soln. or emulsion of an org. polymeric substance to be dried. Titania containing the org. polymeric substance formed to the non-combustible fiber preform is impregnated with an aq. Mn salt soln. to be dried. The non-combustible fiber preform holding titania, the org. polymeric substance and the Mn salt is baked.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a surface-modified titania carrier, and more specifically, it contains a large amount of moisture such as a ventilation gas for road tunnels and a low concentration nitrogen oxide (NOx) of several ppm. NO used in a denitration device (NOx treatment device) that efficiently adsorbs and removes NOx from gas
x relates to a method for producing a surface-modified titania carrier applied to an adsorbent.

[0002]

2. Description of the Related Art Conventionally, as this type of NOx adsorbent, those obtained by supporting oxides of Ru, Ce, etc. on anatase type titania carrier, and firing, zeolite, silica. It is known that a support made of alumina or the like also carries an oxide such as Ru or Ce and is baked.

However, the adsorbent using the anatase-type titania carrier has a problem in heat resistance. For example, NOx adsorption performance is drastically lowered by heating at 400 ° C. in air. Further, even if heating at 300 ° C., the NOx adsorption performance gradually deteriorates, and considering that heating at around 250 ° C. is required for regeneration of the adsorbent, it becomes a practical problem.

On the other hand, A such as zeolite and silica-alumina
An adsorbent using a carrier of 1-Si-based composite oxide has sufficient heat resistance, and NOx adsorption performance is not deteriorated even by heating at about 400 ° C. However, this is inferior in acid resistance, and adsorption performance is deteriorated by repeating adsorption / desorption of NOx.

Therefore, the present applicant has previously proposed to use the Mn-Ti-based surface-modified titania carrier in order to solve the above problems.
A NOx adsorbent supporting an oxide of Ru and / or Ce was proposed (see Japanese Patent Application No. 7-7180). In this prior application, the Mn-Ti-based surface-modified titania carrier is manufactured by impregnating a non-combustible fiber preform with a titania colloid, drying this, and then adding a Mn compound and firing. It was

However, as a result of various experiments and studies conducted by the present inventors, it was found that the Mn-Ti composite oxide of the titania carrier greatly contributes to the NOx adsorption performance, and it is described in the previous application. In the titania carrier produced by the method, there is a limit to the formation of Mn-Ti composite oxide, and the Mn-Ti composite cannot be sufficiently advanced, and the NOx adsorbent using this cannot satisfy NOx. It was found that the adsorption performance could not be obtained. That is, crystallization of titania occurs above 200 ° C.
Since it progresses relatively quickly at a temperature of ℃ or higher, complexation with Mn occurs at a temperature of 250 ℃ or higher, and proceeds rapidly at a temperature of 400 ℃ or higher.
It has been found that it is necessary to heat rapidly from 0 ° C to around 300 ° C. In the method of the above-mentioned prior application, when the Mn compound is added and fired, a temperature distribution is generated in the thickness direction of the noncombustible fiber preform body, and near the high temperature surface, crystallization of titania and Mn Although the composite formation proceeds almost at the same time, it was revealed that since the central part of the paper is gradually heated, crystallization of titania precedes and the composite formation of Mn-Ti is inhibited.

An object of the present invention is to solve the above problems and to provide a method for producing a surface-modified titania carrier suitable for obtaining a NOx adsorbent having a better adsorption performance.

[0008]

In a first method for producing a surface-modified titania carrier according to the present invention, an incombustible fiber preform is impregnated with a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer. Then, this was dried, and the titania containing the organic polymer formed in the incombustible fiber preform was impregnated with the aqueous solution of Mn salt, and this was dried to retain the titania, the organic polymer and Mn salt. A non-combustible fiber preform body is fired.

According to the first method described above, it is possible to produce a surface-modified titania carrier in which Mn-Ti compounding is sufficiently advanced. As a result of examination of the reason by the present inventors, it was found to be as follows. That is, the present inventors confirmed that the latter occurs at a lower temperature between the temperature at which TiO ₂ is stabilized and the temperature at which the organic polymer is burned (the former 200 ° C. or higher and the latter 200 ° C. or lower). ), When the organic polymer is uniformly blended with the titania (in consideration of the catalytic action of the coexisting Mn oxide), it is nonflammable at a temperature of 200 ° C. or higher at which the crystallization of titania starts during firing. The organic polymer material burns at a good speed in all parts in the thickness direction of the fiber preform body, does not cause the above-mentioned temperature distribution, and the crystallization and the compounding proceed simultaneously throughout. Therefore, the crystallization of TiO ₂ and the compounding of Mn-Ti can be simultaneously progressed by firing the organic polymer, whereby the compounding can be sufficiently performed.
It is possible to improve the adsorption performance of the NOx adsorbent carrying the.

In the method of the present invention, examples of the organic polymer include acrylic resin, epoxy resin, vinyl acetate resin and phenol resin.

A second method for producing a surface-modified titania carrier according to the present invention is a corrugated plate-shaped non-combustible fiber preform body and a flat plate-shaped non-combustible fiber preform body, in which a titania colloid and an organic polymer material are used. It is impregnated with an aqueous solution or a mixed solution with an emulsion, and then a plurality of corrugated plate-shaped noncombustible fiber preforms and plate-shaped noncombustible fiber preforms are alternately laminated, or a corrugated plate-shaped noncombustible fiber preform. A plurality of bodies are laminated to form a honeycomb structure, which is dried to bond the noncombustible fiber preforms to each other to form a laminated body, which contains the organic polymer formed in the noncombustible fiber preform of the laminated body. Titanium impregnated with an aqueous solution of Mn salt and dried to obtain a honeycomb structure composed of noncombustible fiber preforms holding titania, an organic polymer and Mn salt. Which is then burned Jo laminate.

According to the second method described above, the obtained titania carrier has a so-called honeycomb structure, which reduces pressure loss when a gas containing NOx is circulated and dust contained in the gas. It is possible to pass the kind.

In the above-mentioned method, the non-combustible fiber preform may be impregnated with the titania colloid and dried before impregnation with the mixed solution of the titania colloid and the aqueous solution or emulsion of the organic polymer. .
In this case, the TiO in the surface-modified titania carrier produced
The content of ₂ can be appropriately adjusted and increased.

In the above method, the concentration of the organic polymer in the mixed solution of the titania colloid and the aqueous solution or emulsion of the organic polymer is preferably 5 to 50 wt%. The reason is that if it is less than 5 wt%, crystallization of titania and compounding of Mn—Ti are simultaneously performed during firing in the subsequent step,
Further, it is not possible to proceed sufficiently, and if it exceeds 50 wt%, the amount of TiO ₂ retained becomes small, and the NOx adsorption performance of the NOx adsorbent to which the titania carrier is applied may deteriorate. Moreover, in the case of the second method, if the above-mentioned concentration is less than 5 wt%, the adhesive force between the non-combustible fiber preforms may be weakened. The above concentration is 1
It is desirable to be 0 to 30 wt%.

In the above method, examples of the Mn salt include Mn (NO ₃ ) ₂ , MnCl ₂ and Mn (C
H ₃ COO) _{2 and the} like, and the concentration of the Mn salt aqueous solution is
Generally, it is about 0.5 to 5 mol / l.

In the above method, the non-combustible fiber preform body is impregnated with a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer, followed by drying.
It may be performed at a temperature of 0 ° C. or lower. A more preferable drying temperature is 50 to 150 ° C. In this case, the titania can be kept in an unstable state only by thermally decomposing the organic polymer while preventing the stabilization of titania before supporting Mn and removing the volatile component. Therefore, Mn is added in a later step by adding Mn and firing.
The composite of Ti can be sufficiently advanced, and as a result, the NOx adsorption performance of the NOx adsorbent using this carrier can be improved. That is, the stabilization of titania occurs at a temperature higher than 200 ° C. and progresses relatively quickly at a temperature of 250 ° C. or higher.
When heated at a temperature higher than 00 ° C., titania is stabilized, and as a result, Mn—Ti complexation is hindered and NOx adsorption performance is reduced. This is because heating at a temperature higher than 200 ° C. burns the organic polymer, and the heat raises the temperature of the titania surface, which facilitates the stabilization of titania.

In the second method, a honeycomb structured laminate composed of non-combustible fiber preforms holding titania, organic polymer and Mn salt is fired by passing a heating gas through the honeycomb structure. In doing so, the temperature up to the firing temperature is raised stepwise rather than continuously,
Hold in the range of 180-190 ℃ for 1.5 hours or more and 2
It is preferable to maintain the temperature in the range of 10 to 240 ° C. for 1 hour or more. Generally, the firing temperature is about 400 to 500 ° C. However, if the temperature is continuously raised or raised at a constant rate up to this firing temperature, heat is accumulated in the honeycomb channels due to the rapid combustion of the organic polymer, so that the temperature of the carrier is increased. A part that rises too much may occur, and the carrier may be burnt out, and it becomes difficult to form a Ti—Mn composite favorable for performance. The temperature at which the rapid combustion of organic polymer materials occurs is 290 to 300 ° C.
Therefore, by maintaining a temperature lower than this for a certain period of time and gradually burning the organic polymer, mild combustion becomes possible. Therefore, the temperature is raised to the firing temperature stepwise, and the temperature is maintained in the range of 180 to 190 ° C. for 1.5 hours or more, preferably 1.5 to 2.5 hours.
It is preferable to maintain the temperature in the range of 0 to 240 ° C. for 1 hour or more, preferably 1 to 2 hours.

Further, the heating gas is set to 0.8 at room temperature.
Flowing at a flow rate of Nm / s or more is preferable from the viewpoint that milder combustion can be performed by ventilation. The more preferable flow rate of the heating gas is 1 to 3 Nm / s.

Further, in the second method, when the oxygen concentration in the heating gas to be circulated is less than 21 vol%, the temperature at which the rapid combustion of the organic polymer material occurs becomes higher and the heat is generated. It is preferable because the amount is small. 21 vol% is the oxygen concentration in normal air, and the more preferable oxygen concentration in the heating gas is 5 to 20 vol%.
It is.

A NOx adsorbent is produced by supporting Ru ions, Ce ions, and in some cases copper ions on the surface-modified titania carrier produced by the method of the present invention.

The loading of these metals can be carried out by immersing the titania carrier in an aqueous solution of these metal salts. For example, 0.1 to 1 mol / l of RuCl ₃
It is preferable to use an aqueous solution, an aqueous solution of about 1 to 10 mol / l Ce (NO ₃ ) _{3 or an} aqueous solution of about 0.1 to 1 mol / l of Cu (NO ₃ ) ₂ .

[0022]

EXAMPLES Specific examples of the present invention will be described below.

Example 1 Ceramic paper manufactured by Nippon Inorganic Co., Ltd. (thickness: 0.5 m)
m, size; 20 mm × 80 mm, composition; Al ₂ O ₃ : S
TiO ₂ = 1: 1) is impregnated with anatase type titania colloid (TiO ₂ solid content: 30 wt%).
After drying at ℃, it was immersed in a mixed liquid of anatase-type titania colloid and an aqueous solution of an acrylic polymer. Concentration of acrylic polymer in the mixture is 12.5wt
I set it as%. Then, the ceramic paper was dried at 110 ° C. to obtain a titania holding plate having a TiO ₂ content of 255 g / m ² .

Then, the titania holding plate-like body was treated with Mn.
The plate was immersed in an aqueous solution of (NO ₃ ) ₂ (concentration of 1 mol / l), excess liquid was hung off, dried at 110 ° C., and then fired at 450 ° C. using a tubular ventilation oven. A Mn-Ti surface-modified titania carrier was obtained.

Then, on the titania carrier, RuCl ₃ aqueous solution (0.14 mol / l concentration), Ce (NO ₃ ) ₃ aqueous solution (3 mol / l concentration), Cu (NO ₃ ) ₂ aqueous solution (0.5 mol / l concentration). In order of dipping, sagging, drying and firing to support each metal and NOx.
An adsorbent was obtained. Immersion of RuCl ₃ aqueous solution, firing temperature after drying is 250 ° C, immersion of Ce (NO ₃ ) ₃ aqueous solution, firing temperature after drying is 330 ° C, immersion of Cu (NO ₃ ) ₂ aqueous solution, firing temperature after drying It was 330 ° C.

As a result of analyzing this adsorbent, Mn; 4.9 wt%, Ru; 2.1 wt%, Ce; 3 with respect to TiO ₂ .
It was confirmed to contain 1.2 wt% and Cu; 2.7 wt%. This is designated as Sample A.

Example 2 The same ceramic paper as in Example 1 was impregnated with the same anatase-type titania colloid as in Example 1 and dried at 110 ° C., and then the same anatase-type titania colloid and acrylic polymer as in Example 1 were used. The mixed solution with the aqueous solution of was applied on one side with a brush. Then, the ceramic paper was dried at 110 ° C. to obtain a titania holding plate having a TiO ₂ content of 192 g / m ² .

Thereafter, in the same manner as in Example 1, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as Sample B.

Example 3 The same ceramic paper as in Example 1 was impregnated with the same anatase-type titania colloid as in Example 1, dried at 110 ° C., and then impregnated with this titania colloid again.
After drying at 0 ° C. (dipping twice) to increase the TiO ₂ content, it was immersed in the same mixed solution of the anatase-type titania colloid and the acrylic polymer aqueous solution as in Example 1.
Then, this ceramic paper was dried at 110 ° C. to obtain a titania holding plate having a TiO ₂ content of 341 g / m ² .

Thereafter, a Mn-Ti surface-modified titania carrier and a NOx adsorbent were obtained in the same manner as in Example 1.
This is designated as Sample C.

Example 4 The same ceramic paper as in Example 1 was immersed in a mixed solution of the same anatase-type titania colloid as in Example 1 and an aqueous solution of an acrylic polymer. Then, the ceramic paper is dried at 110 ° C. to obtain a TiO ₂ content of 133.
A g / m ² titania holding plate was obtained.

Thereafter, in the same manner as in Example 1, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as Sample D.

Comparative Example 1 The same ceramic paper as in Example 1 was immersed in the same anatase-type titania colloid as in Example 1 to impregnate it with the titania colloid. After impregnating the titania colloid, the ceramic paper was dried at 110 ° C to obtain a TiO ₂ content of 1
78 g / m ² of titania holding plate was obtained.

Thereafter, in the same manner as in Example 1, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as Sample E.

As a result of analysis of this adsorbent, Mn; 4.6 wt%, Ru; 2.0 wt%, Ce; 3 with respect to TiO ₂
It was confirmed to contain 1.0 wt% and Cu; 2.5 wt%.

Comparative Example 2 The same ceramic paper as in Example 1 was immersed in the same anatase-type titania colloid as in Example 1 to impregnate it with the titania colloid. After impregnation with the titania colloid, the ceramic paper was dried at 110 ° C. to scrub off excess TiO ₂ to obtain a titania holding plate having a TiO ₂ content of 165 g / m ² .

Thereafter, in the same manner as in Example 1, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as Sample F.

Comparative Example 3 The same ceramic paper as in Example 1 was immersed in the same anatase-type titania colloid as in Example 1 to impregnate it with the titania colloid. After titania colloidal impregnation, drying the ceramic paper at 110 ° C., increasing the TiO ₂ content by drying at 110 ° C. is again impregnated titania colloidal (twice pickled), TiO ₂ content 26
A 5 g / m ² titania holding plate was obtained.

Thereafter, in the same manner as in Example 1, a Mn-Ti surface-modified titania carrier was obtained, and further a NOx adsorbent was obtained.
This is designated as Sample G.

Performance test 1 Samples A to G were separately packed into a tubular reactor at a rate of 8 and air containing a high concentration of NOx (NOx concentration; 200 pp)
m, relative humidity; 70%, flow rate; 2 liter / min), and the inlet NOx concentration and outlet NOx concentration at that time were measured. Then, it was adsorbed until the outlet concentration became 90% of the inlet concentration (the adsorption amount at this time is the saturated adsorption amount).
The saturated adsorption amount was obtained by integrating the difference between the NOx concentration at the inlet and the outlet and the air flow rate. The unit is the amount of NOx adsorbed per 1 m ² of the adsorbent [cc / m ² ]. TiO
The relationship between the _two amounts and the saturated adsorption amount is shown in FIG.

As is clear from FIG. 1, the saturated adsorption amount increases as the TiO ₂ content increases, and the NOx adsorption performance improves.

Although all of Samples A to D and Samples E to G have this relationship, when compared at the same TiO ₂ content, the mixture of the anatase type titania colloid and the aqueous solution of the organic polymer is impregnated. It can be seen that the NOx adsorbent prepared in this way has a higher saturated adsorption amount and thus a higher adsorption performance.

Example 5 Ceramic paper (thickness: 0.5 m, manufactured by Nippon Inorganic Co., Ltd.)
m, composition; Al ₂ O ₃ : SiO ₂ = 1: 1, and anatase-type titania colloid (TiO ₂ solid content: 30)
%) And was corrugated while being dried to obtain a titania holding corrugated plate. Further, the same ceramic paper was impregnated with the same anatase-type titania colloid and dried to obtain a titania-supporting flat plate-shaped body.

Then, the corrugated plate and the plate were impregnated with the same mixed solution of the anatase-type titania colloid and the acrylic polymer aqueous solution as in Example 1, respectively. Then, a plurality of corrugated plates and flat plates were alternately laminated and then dried at 150 ° C. to obtain a titania holding laminate (dimensions: 0.2 m × 0.2 m × 0.5 m, containing TiO _2). amount;
160 g / m ² ).

Thereafter, in the same manner as in Example 1, a Mn-Ti surface-modified titania carrier was obtained, and further a NOx adsorbent was obtained.

As a result of analyzing this adsorbent, Mn: 5.0 wt%, Ru: 2.10 wt%, Ce: 3 with respect to TiO ₂ .
It was confirmed to contain 1.5 wt% and Cu; 2.3 wt%. This is designated as Sample H.

Example 6 In the same manner as in Example 5, a plurality of the mixed-solution-impregnated titania-holding corrugated plates and the titania-holding flat plates were alternately laminated and then 2
Pre-baking of acrylic polymer at 60 ° C (removal of organic matter)
To obtain a titania holding laminate (dimension: 0.2 m ×
0.2 m × 0.5 m, TiO ₂ content; 160 g /
m ² ).

Thereafter, in the same manner as in Example 5, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.

As a result of analysis of this adsorbent, Mn; 5.1 wt%, Ru; 2.1 wt%, Ce; 3 with respect to TiO ₂ .
It was confirmed to contain 2.0 wt% and Cu; 2.0 wt%. This is designated as Sample I.

Performance test 2 Samples H and I were separately charged into a tubular reactor,
Air containing a high concentration of NOx is made to flow under the same conditions as in the case of performance test 1, the inlet NOx concentration and the outlet NOx concentration at that time are measured, and the breakthrough rate (outlet NOx concentration / inlet NOx concentration)
And the amount of adsorption to each sample were determined. The result is shown in FIG.

Performance Test 3 Plate-shaped test pieces were cut out from Samples H and I, and eight plate-shaped test pieces each consisting of each sample were individually charged into a tubular reactor, and the same procedure as in Performance Test 1 was performed. The saturated adsorption amount was determined. As a result, the sample H had 1200 cc / m ² , and the sample I had 770 cc / m ² .

From the results of the performance tests 2 and 3, the adsorption performance of the adsorbent using the carrier produced by heating before immersion in the aqueous solution of Mn salt at a temperature of 200 ° C. or lower is higher than that at 200 ° C. It can be seen that the adsorption performance of the adsorbent using the carrier produced by carrying out at a high temperature is superior to that of the adsorbent.

Example 7 The same ceramic paper as in Example 5 was impregnated with the same anatase-type titania colloid as in Example 5, and dried to obtain a titania-retaining flat plate (size: 20 mm × 80 m).
m).

Then, a titania-supporting flat plate was prepared in Example 5.
After impregnating a mixed solution of the same anatase-type titania colloid and an aqueous solution of an acrylic polymer, the titania-supporting flat plate was dried at 110 ° C.

Thereafter, in the same manner as in Example 5, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as Sample J.

Example 8 Except that pre-baking (removal of organic matter) of an acrylic polymer at 260 ° C. was carried out instead of drying at 110 ° C. after impregnation with a mixed solution containing an organic polymer. A surface-modified titania carrier was obtained in the same manner as in Example 7, and NO
x adsorbent was obtained. This is designated as Sample K.

Comparative Example 4 The same ceramic paper as in Example 5 was impregnated with the same anatase-type titania colloid as in Example 5, and then 110 ° C.
A titania-supported flat plate was manufactured by drying at.

Thereafter, in the same manner as in Example 5, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as sample L.

Comparative Example 5 The same ceramic paper as in Example 5 was impregnated with the same anatase-type titania colloid as in Example 5, and dried to obtain a titania-retaining flat plate (size: 20 mm × 80 m).
m). Then, the titania holding plate-shaped body was fired at 300 ° C.

Thereafter, in the same manner as in Example 5, a Mn-Ti surface-modified titania carrier was obtained, and a NOx adsorbent was obtained.
This is designated as sample M.

Comparative Example 6 A surface-modified titania carrier was obtained in the same manner as in Comparative Example 5 except that the firing temperature was 500 ° C., and further a NOx adsorbent was obtained. This is designated as Sample N.

Performance Test 4 In the same manner as Performance Test 1, the saturated adsorption amounts of Samples J to N were determined. Table 1 shows the results.

[0063]

[Table 1] As is clear from Table 1, the NOx adsorbent prepared by impregnating the mixed solution of the anatase-type titania colloid and the aqueous solution of the organic polymer has a higher saturated adsorption amount and a higher adsorption performance. Further, the adsorption performance of the adsorbent using the carrier produced by heating before the immersion of the Mn salt aqueous solution at a temperature of 200 ° C. or lower is the carrier produced by performing the heating at a temperature higher than 200 ° C. It can be seen that it is superior to the adsorption performance of the adsorbent using.

Example 9 Ceramic paper manufactured by Nippon Inorganic Co., Ltd. (thickness: 0.5 m
m, composition; Al ₂ O ₃ : SiO ₂ = 1: 1, and anatase-type titania colloid (TiO ₂ solid content: 30)
%) And was corrugated while being dried to obtain a titania holding corrugated plate. Further, the same ceramic paper was impregnated with the same anatase-type titania colloid and dried to obtain a titania-supporting flat plate-shaped body. Then
The corrugated plate and the plate were impregnated with the same mixed solution of the anatase-type titania colloid as in Example 1 and an aqueous solution of an acrylic polymer. Then, a plurality of corrugated plates and a plurality of flat plates are alternately laminated, and then dried at 150 ° C. using a hot air circulation type electric furnace, and a TiO ₂ retention amount of 168 g /
m ² titania-supporting honeycomb-shaped carrier was obtained (dimension: 20
mm × 20 mm × 50 mm).

Two of these honeycomb carriers were mixed with Mn (NO ₃ )
_{2 After} immersing in an aqueous solution (1 mol / l concentration) and cutting off excess liquid, make sure that the honeycomb channels are oriented vertically inside the electric heater type ventilation firing furnace (2) shown in FIG. The two layers were stacked, dried and fired by passing hot air from below the honeycomb carrier (1).

That is, FIG. 3 is a schematic view showing the structure of a firing apparatus, which is a blower (4) for sending out air.
And an electric heater that heats the sent air to a predetermined temperature
(3), a ventilation firing furnace (2) that allows hot air from the heater (3) to flow upward from below, and a device (not shown) that processes the exhaust gas emitted from the firing furnace (2) . By controlling the electric heater (3) with a programmable temperature controller, the air is heated to a predetermined temperature and the drying and firing temperatures are controlled.

The flow rate of the heating gas in this example was 1.0 Nm / s as the room temperature gas, and the temperature of the circulating heating gas was controlled as shown in FIG. That is, FIG. 4 is a graph showing the temperature control of the circulating heating gas, in which the horizontal axis represents the gas passage time (Hr) and the vertical axis represents the gas temperature (° C.). The characteristic of this temperature control is that in order to completely burn the remainder of the adhesive used when making the ceramic paper, it was kept at about 180 to 190 ° C for a predetermined time, and the binder mixed with the titania sol was burned as much as possible. In order to maintain the temperature, the temperature is kept at 210 to 240 ° C. for a predetermined time. After raising the temperature, finally 45
Baking at 0 ° C. for 3 hours.

The Mn-Ti surface-modified titania carrier thus obtained was subsequently treated with an aqueous RuCl ₃ solution (0.14
(mol / l concentration), soaked, dried in an air stream, and calcined at 250 ° C. for 1 hour. Continue to Ce (NO
₃ ) Dip in ₃ aqueous solution (concentration of 3 mol / l), drip,
After being dried in air, it is calcined at 330 ° C for 3 hours, further immersed in a Cu (NO ₃ ) ₂ aqueous solution (0.5 mol / l concentration), hung down, dried in air, and then calcined at 330 ° C for 3 hours. Then, a NOx adsorbent was obtained.

As a result of analysis of this adsorbent, Mn; 5.1 wt%, Ru; 2.0 wt%, Ce; 3 with respect to TiO ₂ .
It was confirmed to contain 1.8 wt% and Cu; 2.2 wt%. This is designated as sample P.

Example 10 In the same manner as in Example 9, the amount of TiO ₂ retained was 168 g / m ^2.
A titania-supporting honeycomb-shaped carrier was obtained (dimension: 20 mm
X 20 mm x 50 mm).

Two pieces of this honeycomb carrier were mixed with Mn (NO ₃ )
_{2 After} immersing in an aqueous solution (concentration of 1 mol / l) and cutting off excess liquid, the honeycomb channels are oriented vertically inside the LPG gas-fired furnace ventilation furnace (2) shown in FIG. As described above, the honeycomb carrier (1) was dried and fired by passing hot air from below the honeycomb carrier (1).

That is, FIG. 5 is a schematic diagram showing the structure of the firing apparatus, and is the same as that of FIG. 3 except that the electric heater (3) in FIG. 3 is replaced by an LPG-fired burner (5). .

The LPG gas-fired furnace type ventilation furnace is L
The hot exhaust gas of air (atmosphere) mixed with the combustion exhaust gas of the PG-fired burner (5) is circulated. By controlling the amount of combustion LPG by the program temperature controller, the heating gas of the predetermined temperature is generated. You can get it. The oxygen concentration in the heated gas in this example is 17.2.
〜19.6 vol% (average oxygen concentration is 18.0 vol%), and the flow rate of the heating gas is 1.0 Nm as normal temperature gas.
The flow rate was / s.

The temperature control of the heating gas in this embodiment is
It carried out as shown in FIG. In this temperature control, the holding time at each temperature is shorter than that in the case of the ninth embodiment.
The total time required to reach the firing temperature of ° C is also shortened. After raising the temperature, it was finally baked at 450 ° C. for 3 hours.

The Mn-Ti surface-modified titania carrier thus obtained was subsequently treated with an aqueous RuCl ₃ solution (0.14
(mol / l concentration), soaked, dried in an air stream, and calcined at 250 ° C. for 1 hour. Continue to Ce (NO
₃ ) Dip in ₃ aqueous solution (concentration of 3 mol / l), drip,
After being dried in air, it is calcined at 330 ° C for 3 hours, further immersed in a Cu (NO ₃ ) ₂ aqueous solution (0.5 mol / l concentration), hung down, dried in air, and then calcined at 330 ° C for 3 hours. Then, a NOx adsorbent was obtained.

As a result of analysis of this adsorbent, Mn: 5.0 wt%, Ru: 2.1 wt%, Ce: 3 with respect to TiO ₂ .
It was confirmed to contain 1.7 wt% and Cu; 2.3 wt%. This is designated as sample Q.

Performance test 4 Samples P and Q were separately charged into a tubular reactor,
Air containing a high concentration of NOx is made to flow under the same conditions as in the case of performance test 1, the inlet NOx concentration and the outlet NOx concentration at that time are measured, and the breakthrough rate (outlet NOx concentration / inlet NOx concentration)
And the amount of adsorption to each sample were determined. FIG. 7 shows the result.

From the results of the performance test 4, both samples P and Q are excellent in NOx adsorption performance, but in the firing of the honeycomb carrier after impregnated with manganese nitrate, it was obtained by firing in a heating gas with a reduced oxygen concentration. Sample Q is better than sample P
Is superior to NOx adsorption performance.

As described above, it is considered that the Ti-Mn composite, which is preferable in terms of performance, was formed by the mild combustion of the organic polymer by the stepwise temperature increase to the firing temperature. Further, it is clear that when the honeycomb carrier after impregnated with manganese nitrate is fired in a heating gas having a reduced oxygen concentration, an adsorbent having a better adsorption performance can be obtained. In addition, the time required for heating can be shortened, and the adsorbent production cost can be reduced.

[0080]

As described above, the NOx adsorbent using the surface-modified titania carrier produced by the method of the present invention has improved adsorption performance.

[Brief description of the drawings]

FIG. 1 is a graph showing the results of performance test 1 and showing the relationship between the amount of TiO ₂ and the saturated adsorption amount.

FIG. 2 is a graph showing the results of performance test 2 and showing the relationship between the breakthrough rate and the adsorption amount.

FIG. 3 is a schematic diagram showing a configuration of an electric heater type baking apparatus.

FIG. 4 is a graph showing a temperature control of a heating gas (gas passage time (Hr) VS. gas temperature (° C.)).

FIG. 5 is a schematic diagram showing a configuration of an LPG gas-fired furnace-type firing apparatus.

FIG. 6 is a graph showing the temperature control of heating gas (gas passage time (Hr) VS. gas temperature (° C.)).

FIG. 7 is a graph showing the results of performance test 4 and showing the relationship between the breakthrough rate and the adsorption amount.

[Explanation of symbols]

 (1) ... Honeycomb carrier (2) ... Ventilation firing furnace (3) ... Electric heater (4) ... Blower (5) ... LPG fired burner

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shuji Kobayashi 5-3 28, Nishikujo, Konohana-ku, Osaka City Hitachi Shipbuilding Co., Ltd. Issue Hitachi Shipbuilding Co., Ltd.

Claims (9)

[Claims] 1. A non-combustible fiber preform body is impregnated with a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer, which is dried to form an organic polymer formed on the non-combustible fiber preform body. The titania containing the substance is impregnated with an aqueous solution of Mn salt, dried, and titania,
A method for producing a surface-modified titania carrier, which comprises firing a non-combustible fiber preform having an organic polymer and Mn salt. 2. A corrugated plate-shaped noncombustible fiber preform body and optionally a plate-shaped noncombustible fiber preform body are impregnated with a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer, and then the corrugated plate A plurality of plate-shaped noncombustible fiber preforms and plate-shaped noncombustible fiber preforms are alternately laminated one by one, or a plurality of corrugated plate-shaped noncombustible fiber preforms are laminated to form a honeycomb structure, which is dried. The non-combustible fiber preforms are adhered to each other to form a laminate, and the titania containing the organic polymer formed in the noncombustible fiber preforms of the laminate is impregnated with an aqueous solution of Mn salt and dried. A method for producing a surface-modified titania carrier, which comprises firing a honeycomb structured laminate composed of a non-combustible fiber preform holding a titania, an organic polymer and an Mn salt. 3. When firing a honeycomb structured laminate comprising a non-combustible fiber preform body holding a titania, an organic polymer and an Mn salt by firing a heating gas in the honeycomb structure, firing up to a firing temperature The temperature is raised stepwise, not continuously, and is maintained in the range of 180 to 190 ° C for 1.5 hours or more and in the range of 210 to 240 ° C for 1 hour or more. The method for producing a surface-modified titania carrier according to claim 2, wherein the surface-modified titania carrier is circulated at a flow rate of 0.8 Nm / s or more. 4. The method for producing the surface-modified titania carrier according to claim 3, wherein the oxygen concentration in the heated gas to be circulated is less than 21 vol%. 5. A non-combustible fiber preform body is impregnated with a titania colloid and dried before impregnation with a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer. 4. The method for producing the surface-modified titania carrier according to any one of 4. 6. The organic polymer concentration in a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer is 5 to 50 wt%, according to any one of claims 1 to 5. Method for producing surface-modified titania carrier. 7. The organic polymer concentration in a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer is 10 to 30 wt%, according to any one of claims 1 to 5. Method for producing surface-modified titania carrier. 8. The method according to claim 1, wherein the non-combustible fiber preform is impregnated with a mixed solution of a titania colloid and an aqueous solution or emulsion of an organic polymer, and then dried at a temperature of 200 ° C. or lower. The method for producing the surface-modified titania carrier according to any one of the above. 9. A method for producing a NOx adsorbent, which comprises supporting Ru ions and Ce ions on the surface-modified titania carrier produced by the method according to any one of claims 1 to 8.