JPS5910345A - Carrier of catalyst - Google Patents

Abstract

PURPOSE:To produce easily and surely a titled carrier, by laminating paper obtd. by using ceramic fibers as a basic constituting material with an adhesive agent incorporated with a silicon compd. such as colloidal silica or the like. CONSTITUTION:Paper is made by compounding 80-96wt% ceramic fibers, 2- 10wt% org. fibers of PE, acrylic, polyester fibers or the like, and 2-10wt% an org. binder (for example, an acrylic resin, vinyl acetate resin, melamine resin, etc.) Sheets of such paper are superposed alternately by using an adhesive agent consisting of refined bentonite, or the same added with titanium oxide, silica powder, alumina sol, etc., or alumina powder and kaolin added with colloidal silica or ceramic fibers, zirconia powder and colloidal silica, whereby a ceramic fiber sheet is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a carrier suitable for a catalyst for gas phase chemical reactions.

Conventionally, extrusion-molded copierite or mullite, and molded asbestos paper have been used as carriers for gas-phase chemical reaction catalysts. Various other carriers have also been proposed, for example, in JP-A-47-136.
Publication No. 12 describes a carrier made by paper-making a ceramic material together with organic fibers and sintering the obtained paper sheets. However, these conventional carriers had to have a fairly dense structure in order to have the mechanical strength and durability required for practical use. Therefore, even though it is known that increasing the number of fine communicating pores is effective in increasing the catalyst supporting capacity, there are no examples of success in reaching the limits of this and imparting the necessary physical properties. , the conventional carrier has a porosity of at most 30
~50% (note that porosity has the same meaning as porosity indicating the degree of porosity of paper, and is a value determined from the following formula).

The present inventors have discovered a catalyst that is better as a carrier for catalysts used under harsh conditions, such as catalysts for various gas-phase chemical reactions, especially catalysts for treating nitrogen oxides, sulfur oxides, and organic substances in combustion exhaust gas. As a result of various researches in view of the demand for products with high performance, we have developed a new high-performance carrier, a sheet-like aggregate of ceramic fibers interconnected by silicic acid gel, with a porosity of 75%. We have invented a carrier characterized by the above characteristics.

The carrier according to the present invention has ceramic fibers as its basic constituent material, and the electron micrograph shown in FIG. 1 (magnification: 3
00 times), it has a large porosity, so the surface area and pore volume per unit weight are significantly larger than conventional carriers made of ceramic structures. In addition to this unique structure, the carrier of the present invention exhibits many excellent properties as detailed below.

To explain in more detail the structure of the antibody of the present invention,
In this carrier, the ceramic fibers preferably account for 80 to 96% by weight of the total weight of the carrier. Ceramic fibers include highly heat-resistant inorganic fibers such as silica fibers, alumina fibers, aluminum 7-silicate fibers, and Sylphnia fibers (for example, Fineflex and Chias KK products).
, Refura Seal (manufactured by HITCO), etc. are used.

The silicic acid gel is mainly present at the contact points between the ceramic i*i and plays the role of a binder that binds the imt at that point. This binder has high heat resistance and rigidity, and thus, in combination with the rigid properties of the ceramic fibers, makes the carrier good in shape retention, even though its amount is relatively small.

The porosity is 75% or more, or about 75 to 80%.
%.

Items with a porosity of less than 75%, even if they are made of ceramic fibers and silicic acid gel, have poor catalyst support capacity, catalyst performance when used with a supported catalyst, and their stability and durability. , it is inferior in performance, which is considered most important as a carrier. On the other hand, a high porosity of more than 80% is not preferable because it will be difficult to manufacture and will lead to insufficient mechanical strength, and the basic performance as a carrier will not be further improved. Although the thickness of the sheet is not particularly limited, it is practically desirable to set it to about 0.15 to 0.5 mm. There are no restrictions on the shape of the sheet; in addition to flat sheets of any size, flat sheets with holes, corrugated sheets (the wave shapes are not limited to sine waves, but square waves, sawtooth waves, etc.). (Optional.)
, or one in which these are laminated with ventilation gaps provided. 2 to 5 are perspective views showing processed laminates having a structure particularly suitable as carriers. In these examples, the tunnel-shaped portion between the flat plate-shaped portion and the corrugated plate-shaped portion serves as a flow path for the gas to be treated.

It is extremely difficult to manufacture carriers such as ``2-strand'' from rigid ceramic fibers, especially those having at least a portion of a corrugated sheet-like molding, using conventional manufacturing methods for this type of sheet-like material. We must solve various problems that arise in many processes, such as papermaking of ceramic fibers, molding of paper products, and processing to bond fibers together while ensuring a high porosity of 75% or more. However, according to the production method invented by the present inventors, the above carrier can be produced easily and reliably.

The method for manufacturing a catalyst carrier by the present inventors uses ceramic &
fiber 80-96% by weight, taw1. Paper is made from a mixture of 2 to 10% by weight of fiber and 2 to 10% by weight of organic binder, and the resulting paper or its molded product is impregnated with froidal silicate or ethyl silicate, and then the silicon compound is converted into silicic acid gel. The method is characterized in that the paper or molded article after the above-mentioned treatment is burned to burn out the organic fibers and organic binder in the paper.

Hereinafter, this carrier manufacturing method will be explained in detail with respect to the plugs.

First, paper is made from a mixture of ceramic fibers m, organic fibers, and an organic binder.

The best suitable W1 fibers are hydrophilic, highly dispersible in water, and non-thermoplastic fibers, such as cellulose fibers such as rayon A fibers and wood pulp, but vinylon fibers M[,
It is possible to use various synthetic fibers such as polyethylene fiber, acrylic fiber, and polyester fiber. It is desirable that the fineness is 3 deniers or less and the fiber length is about 3 to 10 deniers from the viewpoint of fiber dispersibility in water and paper strength.

In this manufacturing method, organic fibers have three roles; the first is 4- In the papermaking process, through a synergistic effect with the organic binder, they promote the dispersion of rigid and non-self-adhesive ceramic fibers, improving papermaking properties. It is about increasing. The other two roles will be discussed later.

In addition, organic binders are used to improve the dispersibility of fibers and further bond fibers to increase paper strength before firing, and fibrous polyvinyl alcohol resin is the best choice because it has a good yield during papermaking. However, acrylic resins, vinyl acetate resins, ethylene/vinyl acetate resins, urea resins, melamine resins, CMC, starch, etc. can also be used in the form of aqueous solutions, emulsions, powders, fibers, and the like.

The blending ratio of the papermaking raw materials as described above is ceramic wL fiber 8
0 to 96% by weight, organic 41ffi 2 to 10% by weight (preferably 3 to 6% by weight), and organic binder 2 to 10% by weight (preferably 3 to 6% by weight). The greater the amount of organic matter, the easier the paper making and the shaping process before firing described below, but the final product is likely to lack strength, so it is desirable that the total amount be within 15% by weight.

In addition to the above-mentioned papermaking raw materials, auxiliaries commonly used in this type of sheet making may also be used, but inorganic ones, especially those containing ingredients that may remain in the final product and become catalyst poisons, should not be used. It is desirable to avoid.

The raw material for papermaking is made into a slurry with a concentration of about 1 to 0.3% by a conventional method (1), and then processed into a slurry with a thickness of 0°15-0. S Omm, density 0, 2-0
, 4 B7cm3 (all values are for dry matter).

The obtained paper is then shaped into a shape suitable as a catalyst carrier.
Of course, this processing is unnecessary. ). Processing the paper into the desired shape can be carried out on the final product if it does not involve bending, such as gluing or perforation, but bending processes such as wavy shaping must be carried out at this stage.

The forming process uses, for example, a full-gate processing machine for manufacturing corrugated board to give a waveform with an arbitrary wave height and wave interval.

The second role of Ariiso fiber M in this manufacturing method is to improve the workability in the molding process described in -1- and to improve the shape retention of the resulting molded product during subsequent processing. Paper made only of rigid ceramic fibers cannot reliably perform the detailed molding described above.

In addition to the above-mentioned bending process, the forming process at this stage may include bonding process and other processes to form a three-dimensional structure. For example, the products that have undergone full gate processing in step 1 are alternately stacked and glued together with unprocessed flat sheets of paper to create a structure similar to the product shown in Figure 2. Organic adhesives are unsuitable; an inorganic adhesive must be selected that can withstand the firing process described later and can also withstand use conditions ranging from several hundred degrees to 1000°C. . However, alkali metal ions, etc.
It is desirable to avoid using products that contain components that may poison the catalyst. Specific examples of preferred adhesives include the following.

■ Refined bentonite or products to which titanium oxide, silica powder, alumina sol, etc. are added.

■ Made of silica powder and alumina powder.

■ Alumina powder and kaolin with colloidal silica or ceramic fibers.

■ Consisting of luconia powder and colloidal silica.

(Water is used as a diluent in both cases.) Commercially available products include FF adhesive (Chias KK product), Sumiceram (Suminami Kagaku Kogyo KK product), and the like.

Paper that has been formed or that is to be finished into a flat sheet without forming is then uniformly impregnated with colloidal silica or ethyl silicate, and then the impregnated silicon compound is converted into a silicic acid gel and cured. Subject to processing to make

When impregnated with colloidal silica, 150 to 170
The above curing is completed by drying at °C.

When impregnated with ethyl silicate, the ethyl silicate is hydrolyzed within the paper matrix to form a silicic acid gel. For this purpose, a method is adopted, such as impregnating with an ethyl silicate stock solution or solution and then exposing it to high temperature steam, or adding hydrochloric acid or the like as a catalyst to the ethyl silicate solution to be impregnated, and leaving it for several hours after impregnation.

The method using ethyl silicate is more preferable than the method using colloidal silica because it is easier to obtain a uniform treatment effect.

With either method, the amount of impregnation must be limited so as not to reduce the porosity of the final product below 75%. On the other hand, the amount of impregnation must be sufficient to cause silicic acid gel to be present at substantially all contact points between ceramic fibers in the state after the paper is fired,
If it is less than this, the product will have poor shape retention. The range of the amount of impregnation that satisfies these conditions varies depending on the characteristics and composition of the raw materials, as well as the paper-making conditions, so it can only be confirmed by experiment, but in most cases, the amount of impregnation that gives favorable results is as follows: It is about 60 to 120 g per 100 g of paper, assuming 5 in2.

After producing the silicic acid gel, the organic fibers and the organic binder are burned by firing the paper or its molded product in an oxidizing atmosphere at a temperature below about 1000°C, resulting in a ceramic bonded with the silicic acid gel. A sheet of fiber remains. This sheet inherits the shape given to the paper in the above-mentioned forming process. Moreover, after the organic fibers and organic binder burn and disappear, fine pores or unevenness are left in the silicic acid gel portion of the sheet, so the catalyst supporting power of this sheet (support surface - catalyst amount binding force) is
This is much larger than that of a sheet of similar composition and the same density produced directly from ceramic fibers and a silicate gel-forming binder (the final formation of the fine pores and irregularities is the This is the third role.)

The ceramic fiber sheet obtained as described above can be used as it is, or if it is appropriately processed such as cutting, perforating, or bonding again in order to have the size, shape, and structure required as a carrier, it can be used as it is, or it can be used as a carrier according to the present invention. Becomes a catalyst carrier.

Based on the above-described structure, the carrier according to the present invention can support a large amount of catalyst that is effectively used not only on the sheet surface but also in the sheet, and the coating treatment for supporting the catalyst is usually required. Moreover, the catalyst supported in this way is difficult to fall off even under severe usage conditions, and has excellent catalyst supporting ability. Therefore, when supporting the same amount of catalyst, the support of the present invention is easier to process and easier to obtain than the conventional support made of a ceramic structure obtained by sintering an extrusion or paper product. Catalyst performance is much better. The particular advantage of the support of the present invention is that it not only has an excellent catalyst supporting ability, but also that the catalyst obtained using this support can be used even if there are slight variations in the quality of the support, especially in the porosity. It shows extremely stable performance without being affected by this (see test side below). This indicates that as the porosity of the carrier increases, the catalytic performance significantly improves with the porosity of about 7.
This is due to the interesting fact that at 5% or more, catalyst performance is almost constant regardless of the porosity, and this is an extremely advantageous property that leads to increased reliability of catalyst performance. Due to these features, when the carrier of the present invention is used with a catalyst supported, the amount of catalyst required per unit gas processing unit can be reduced (in other words, the space occupied by the catalyst in the reactor can be reduced). ), the reactor can be made smaller accordingly. Due to its unique structure, the catalyst of the present invention is also light and has good self-shape retention despite its high porosity. Moreover, it has the advantage of being resistant to thermal shock, and has greater heat resistance, durability, and catalyst support capacity than asbestos paper carriers.
It is far superior in that it does not cause deterioration of the catalyst due to catalyst poisoning.

Next, an example will be shown. The "buckling strength" in Table 1 is based on JIS
Measured according to Z0401, and "heat resistance" is measured by measuring the buckling strength of samples heated at various temperatures for 3 hours, and indicating the heating temperature when the value becomes 50% of the initial strength. This is what I did.

Examples 1 to 4 Chias KK product made of alumina-silica ceramic A-fiber/fine flex, thickness 2.6-3. Ou, length 5-3
0a+m), rayon fiber <1, 5 clX 5mm
> and a fibrous polyvinyl alcohol resin as an organic binder are dispersed in 340 times the amount of water, and then paper is made by a conventional method using a circular mesh paper machine, and the obtained paper is full-gate processed at 180°C using a corrugated board processing machine. (Wave height 2.2 mm
). Then ethyl silicate (silica solid content 40%)
11- 8.0 parts, 13 parts of ethyl alcohol, 6 parts of water and 5%
A mixed solution of 1 part of hydrochloric acid was used as 5102, 100g/paper io
Spray at a rate of 0.3 oz., leave in humid air for 3 hours, and then dry. Thereafter, the paper is fired in an oxidizing atmosphere at 800°C to burn off the organic matter.

Catalyst carriers made of ceramic fiber sheets obtained as described above with various raw material blending ratios and base paper before firing (
Table 1 shows the characteristic values of the full day (1 body).

Example 5, 6 Polypropylene fiber (1,5 d
A carrier made of ceramic fiber paper was produced using the same raw materials and processing conditions as in Examples 1 to 4, except that a paper (X5 mm) was used. The results are shown in Table 1.

Example 7.8 Ceramic N was produced using the same raw materials and processing conditions as in Examples 1 to 4, except that 3 d x 7 mm rayon fiber or a mixture of this and beaten wood pulp was used as the organic fiber.
A carrier made of tL fiber paper was produced. The results are shown in Table 1.

Comparative Examples 1 and 2 A carrier made of ceramic fiber paper was produced in the same manner as in Examples 1 to 4, except that the blending ratio of rayon wkAM and polyvinyl alfur resin was outside the range of the present invention. The results are shown in Table 1. In the case of Comparative Example 2, in which the amounts of organic fibers and organic binder were insufficient, the paper produced was rough and rigid and could hardly be corrugated, so the buckling strength could not be measured (for this reason, (Further processing was canceled). On the other hand, in the case of Comparative Example 1 in which rayon fibers and polyvinyl alcohol resin were used in excess, the paper strength was high at the base paper stage and cordate processing was easy, but after firing, the strength was 0.1 Kg/am2. As is clear from the extremely low buckling strength, the shape retention was poor and it could not be used as a molded carrier.

Comparative Example 3 Eight types of ceramic fiber papers were made using the same raw material formulation and papermaking method as in Examples 1 to 8, except that rayon fibers and wood pulp were not used. Next, the obtained papers were subjected to full-gate processing in the same manner as in Examples 1 to 4, but all papers were hardly processed because of their lack of flexibility.

Comparative Example 4 Example 1~ except that polyvinyl alcohol resin is not used
Eight types of ceramic fiber papers were made using the same raw material composition and paper-making method as in Section 8, but all of the papers obtained had extremely low strength and could not withstand subsequent processing such as cordate processing. Ta.

Comparative Examples 5 and 6 A full-gate processed paper was produced in the same manner as in Example 5, and then this paper was well impregnated with Froegl Siri force to give about 160%
After drying at °C, it was fired at 800 °C. The properties of the obtained product are shown in Table 1.

Test Examples A denitrification catalyst was produced by the following method using the carriers obtained in Examples 2, 4.8 and Comparative Example 5.6 and a commercially available mullite carrier.

3 parts by weight of vanadium pentoxide, titanium oxide (average particle size 1
μ size.

Specific surface area 75I + 127g) 30 parts by weight, silica sol (
Slurry consisting of 18 parts by weight of silica (solid content 20%) and 58 parts by weight of water (viscosity 12 centipoise at room temperature)
was prepared, and using this slurry, Examples 2, 4.
, 8 was coated twice, and the others were coated three times (the number of coatings was different to equalize the amount of catalyst deposited).

Thereafter, it is dried at 120°C and fired at 4()0°C for 3 hours.

The following performance tests were conducted on the catalyst obtained by the above method.

A catalyst was loaded into a reactor in an oven adjusted to a predetermined temperature, and the composition was No. 200 ppm, NH320.
0ppm, 820 10%, 023%, 5O2100
SV 17,2 of the test gas, which is p,
00/Hr (NTP) and the gas passing through was analyzed to determine the nitrogen oxide removal rate and the ratio of the reaction rate for each test example to 0/ for the reaction rate in the case of the catalyst using the support according to Example 4. to ask for.

The test results were as shown in Table 2.

[Brief explanation of the drawing]

Part 1: Electron micrograph of an example of a carrier according to the present invention. FIGS. 2 to 5 are perspective views showing specific examples of carriers according to the present invention. Agent Patent Attorney Itaben - Taki 18 - Year 1 figure

Claims (1)

[Claims] A carrier for a gas phase/reaction catalyst, which is made of a sheet-like aggregate of ceramic fibers mutually bonded by silicic acid gel, and has a porosity of 75% or more.