JPH0521026B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a thermally stable K-A type zeolite composition, and more specifically, it has excellent moisture adsorption properties, and when recycled by heat treatment after moisture adsorption, there is no regeneration deterioration. It concerns a K-A type zeolite composition with extremely low thermal stability. [Prior Art] It is well known that zeolite has been used as a selective adsorbent for moisture and gas by utilizing its adsorption ability. Especially as a desiccant for the purpose of removing moisture, A
Type zeolite is used industrially, but in this case it must be able to withstand thermal cycles of moisture adsorption and desorption. A typical zeolite that satisfies these requirements is, for example, A with a specific ion exchange ratio.
type zeolite (Special Publication No. 1987-3956, Special Publication No. 1973)
18160), or zeolite obtained by molding A-type zeolite in the presence of an alkaline earth metal compound (Japanese Patent Application Laid-open No. 196720/1983). [Problems to be solved by the invention] In general, A-type zeolite is M ₂ /nO・Al ₂ O ₃・2.0±0.5SiO ₂・yH ₂ O (where M is an ion-exchangeable cation and generally When M is Na, the effective pore diameter is It is about 4A, about 5A for Ca, and about 3A for K. It is used for adsorption separation of various substances by taking advantage of the difference in pore size and adsorption characteristics. Among these, In particular, K-A type zeolites (where M is K) have an effective pore diameter of about 3A.
Because it is small and hardly adsorbs anything other than water molecules,
It is widely used for dehydrating organic solvents and drying gases. However, the K-A type zeolite that has adsorbed this water is usually regenerated by heating to 200 to 400°C, so the adsorption capacity of the zeolite decreases during the repetition of this adsorption-heating (regeneration) cycle. It has been known for a long time. The cause of this regeneration deterioration of the adsorption capacity is that the crystal structure of the zeolite is affected by the hydrothermal action during regeneration. It is said that this is caused by the breakage of the Si-Al bonds in the material, but with conventional products it has been difficult to prevent this decrease in adsorption ability. The present invention improves the drawbacks of conventional K-A type zeolite, and provides a thermally stable K-A type zeolite composition that can withstand thermal cycles associated with moisture adsorption and desorption and has excellent adsorption ability. The purpose is to In view of the above objectives, the present inventors conducted intensive research to improve the thermal stability and water selective adsorption properties of K-A zeolite, and found that a large number of inorganic salts were added to K-A zeolite. The present invention was completed based on the finding that a composition obtained by adding calcium sulfate and firing the composition exhibits excellent performance with respect to the above-mentioned properties. [Means for Solving the Problems] That is, the present invention provides a thermally stable K-A type zeolite composition comprising a calcined composite molded product containing K-A type zeolite and calcium sulfate. be. The K-A type zeolite used in the present invention belongs to the 3A type zeolite, which is said to have an effective pore diameter of approximately 3 Å, and uses Na-A type zeolite as a raw material to convert part or all of the ion-exchangeable Na ⁺ into K ⁺ ions. Generally, at least 35% or more, preferably 40% or more of the ion exchange equivalent is substituted with K ⁺ . Moreover, the K-A type zeolite in the present invention is
It can be easily produced by using Na-A type zeolite as a starting material by a conventional method such as ion exchange treatment. The starting material Na-A zeolite is well known;
There are various manufacturing methods, but they can be used regardless of the manufacturing history, and here are some examples: 1. A-type zeolite made from sodium silicate and sodium aluminate 2. Made by heating and denaturing metakaolin in an alkali. A-type zeolite 3 Examples include A-type zeolite produced from silicic acid gel obtained by pickling acid clay and sodium aluminate. In this way, the Na-A type zeolite used as a starting material is not particularly limited in terms of particle size or shape, but in most cases the average particle size determined by the particle size distribution measurement method using the Coulter counter method is 0.5~ Preferably, the thickness is in the range of 7 μm. Next, in the production of K-A type zeolite, the method of ion exchange treatment of Na-A type zeolite as a starting material is well known. For example, contacting Na-A type zeolite with an aqueous metal salt solution to be ion-exchanged (Contact may be repeated over time as necessary)
Alternatively, ion exchange can be performed by simultaneously contacting with a mixed solution of metal salts. In this case, ion exchange may normally be carried out using a suspension of zeolite slurry, or alternatively a column method may be used. One specific example is a method in which a soluble potassium compound such as potassium chloride or potassium sulfate is added to a slurry of Na-A zeolite for ion exchange treatment. It goes without saying that the ion exchange treatment is carried out under conditions set so that the composition of the K-A type zeolite after the treatment is within the above range. Calcium sulfate in the present invention is not particularly limited, and a wide range of ordinary commercially available products can be used, and any of anhydrides, hemihydrates, dihydrates, etc. can be used. Further, the particle shape of the calcium sulfate is not particularly limited, and any shape can be used, but the particle size is such that the average particle diameter is 0.5 to
Fine particles of 10 μm, preferably 1 to 5 μm, and preferably smaller than the average particle diameter of K-A type zeolite are preferable. The content of calcium sulfate in the thermostable K-A zeolite composition according to the present invention is 1 to 15 parts by weight, preferably 2 to 15 parts by weight as CaSO ₄ based on 100 parts by weight of K-A zeolite (water content). The amount is preferably 10 parts by weight, and if it is less than 1 part by weight, the thermal stability of the K-A zeolite will not be improved. Moreover, if it exceeds 15 parts by weight, the adsorption capacity of the molded K-A zeolite composition decreases due to the dilution effect of calcium sulfate, which is not preferred in practice. The thermostable K-A type zeolite composition according to the present invention is obtained from a fired product of a composite molded product containing the above-mentioned K-A type zeolite and calcium sulfate within the above-mentioned specific composition range. It is what it is. Next, the method for producing the thermally stable K-A type zeolite composition of the present invention will be explained. Type A zeolite, calcium sulfate, binder if necessary,
Other additives, etc. are blended and molded into a desired shape using a molding machine to obtain a compounded molded product.Then, the dried molded product obtained by drying is heated to a temperature of 400°C or above and below the decomposition temperature of K-A type zeolite, preferably. can be obtained by heat treatment at a temperature range of 500 to 700°C for 0.5 to 4 hours, preferably 0.5 to 3 hours. Of course, such heat treatment can be carried out by heating and calcining the K-A type zeolite powder itself and calcium sulfate, but industrially, calcium sulfate is added to the filter cake of ion-exchanged K-A zeolite or its dry powder. It is advantageous to mold the material with a desired binder and other necessary auxiliary additives, dry it, and then heat and bake it. As the binder, one or two selected from clay minerals, silica sol, cements, alkali silicates, etc.
There are more than just seeds, and other auxiliary additives include organic substances that can adjust the pores of granules, such as starch and pulp powder. When used as an adsorbent, the thermally stable K-A type zeolite composition according to the present invention obtained by the above composition and heat treatment has excellent thermal stability that can withstand thermal cycles, and is extremely strong. It forms a sintered product with a high [Function] Since the thermostable K-A type zeolite composition according to the present invention is composed of a baked product of a compound molded product containing K-A type zeolite and calcium sulfate, the hardening effect of calcium sulfate causes the molded product to harden. Strength is developed and a fired product with preferable molding strength is formed. In addition, water such as crystallization water of K-A type zeolite and calcium sulfate or a small amount of added water added during molding may be present between the particles of K-A type zeolite and calcium sulfate, and an ion exchange reaction may occur during the calcination stage. It was made into K-A type zeolite.
Since Ca ⁺⁺ is substituted with Na ⁺ or K ⁺ and supported, it is thought to combine with the above-mentioned molding strength to exhibit excellent thermal stability that can withstand thermal cycles when used as an adsorbent. [Example] Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples. Example 1 No. 3 sodium silicate (Na ₂ O 9.22%, SiO ₂ 28.68%)
Add 77 parts by weight of water to 23 parts by weight, heat to 80°C, and separately add sodium arsinate solution (Na ₂ O 15.75%,
Prepare 100 parts by weight of Al ₂ O ₃ (5.59%) and heat to 80°C. Both solutions were rapidly mixed using a static mixer to obtain a silica-alumina gel. The composition of this silica-alumina gel is shown below. SiO ₂ /Al ₂ O ₃ = 2.00 Na ₂ O/SiO ₂ = 2.64 H ₂ O/Na ₂ O = 33 This silica-alumina gel was heated at 85° C. for 4 hours to form Na-A type zeolite. This zeolite was filtered and washed with water, and a portion of it was dried and subjected to X-ray diffraction to confirm that it was a type A zeolite. Add water again to the original filter cake to make a total of 200
The results were as follows: (0.597K ₂ O・0.403Na ₂ O)・Al ₂ O ₃・_1.98SiO2・
A K-A type zeolite having a composition of 3.80H ₂ O was obtained. To 100 parts by weight of K-A type zeolite prepared above (calculated as anhydride), 6.7 parts by weight of ground calcium sulfate (dihydrate) having an average particle size of 1.8 μm, 15 parts by weight of kaolin clay, and an appropriate amount of water were added. After kneading, prepare pellets with a diameter of 3.2 mm using an extrusion molding machine.
After drying, it was calcined at 650°C for about 2 hours to obtain a K-A type zeolite composition. The strength of this molded product was measured using a Kiya type hardness tester, and the average value of 10 pellets was 9.8 kg/piece. Example 2 Add 6.6 parts by weight of potassium chloride and perform ion exchange to obtain (0.38K ₂ O・0.619Na ₂ O)・Al ₂ O ₃・
A K-A zeolite composition was obtained in the same manner as in Example 1, except that 100 parts by weight (calculated as anhydride) of K-A zeolite having a composition of 1.96 SiO ₂ .3.73 H ₂ O was used. The strength of this molded product was measured in the same manner as in Example 1 and was found to be 12.5 kg/piece. Example 3 Example 1 except that 10 parts by weight of ground calcium sulfate (dihydrate) having an average particle size of 1.5 μm was used.
A K-A type zeolite composition was obtained by performing the same operation as above. The strength of this molded product was measured in the same manner as in Example 1 and was found to be 13.1 kg/piece. Comparative Example 1 A K-A type zeolite composition was obtained by performing the same operation as in Example 1 except that calcium sulfate (dihydrate) was not added. The strength of this molded product was measured in the same manner as in Example 1 and was found to be 5.9 kg/piece. (Moisture adsorption ability test) 100 g of the K-A type zeolite composition obtained in Examples 1 to 3 and Comparative Example 1 was placed in a cylindrical stainless wire mesh container (φ50 mm, height 130 mm), and the temperature was 25°C.
Absorb moisture for 24 hours in a constant temperature and humidity chamber with a relative humidity of 80%. The next day, regeneration was performed at 300°C for 2 hours in an electric furnace (φ300mm, height 300mm, Kanthal furnace). A part of this recycled product is used for measuring the water adsorption capacity, and the remaining part is again allowed to absorb moisture for 24 hours in the same temperature and humidity chamber as above. This thermal cycle operation was repeated 25 times. or,
The collected sample was subjected to moisture absorption treatment for 5 days in a constant humidity tank (relative humidity 80%) containing a saturated ammonium sulfate solution, and then baked at 800℃ for 2 hours. According to the calculation below,
The water adsorption capacity was determined. Moisture adsorption capacity (g/100g) = Loss on calcination (g) x 100/Sample weight after calcination (g) The results are shown in Table 1.

[Table] (CO ₂ adsorption capacity test) The K-A type zeolite compositions of each sample obtained in Examples 1 to 3 and Comparative Example 1, which were degassed at 400°C for 2 hours, were measured using a Soap Tomatic 1800 model specific surface area measuring device. (manufactured by Carlo Erba), the CO ₂ adsorption capacity was measured at 25° C. and under a measurement pressure of 250 mmHg.
The results are shown in Table 2.

〔Effect of the invention〕

The thermally stable K-A type zeolite composition according to the present invention has high molding strength and excellent thermal stability, and after adsorbing water, it can be recycled by heating without causing any substantial deterioration of adsorption capacity. Since it can be used for a long period of time and is also excellent as a selective water adsorbent, its industrial utility value is high.

Claims (1)

[Scope of Claims] 1. A thermostable K-A zeolite composition comprising a fired product of a blended molded product containing K-A zeolite and calcium sulfate. 2 K-A type zeolite has 35% of ion exchange equivalent
The thermostable K-A type zeolite composition according to claim 1, which is substituted with the above K ⁺ . 3 The blending amount of calcium sulfate is 1 as CaSO ₄ per 100 parts by weight of K-A type zeolite (hydrated material).
~15 parts by weight of claim 1 or 2.
The thermostable K-A type zeolite composition described in Section 1. 4. The thermostable K-A type zeolite composition according to claim 1 or 3, wherein the calcium sulfate has an average particle diameter in the range of 0.5 to 10 μm. 5. The fired product of the composite molded product is selected from clay minerals, silica gel, cements, or alkali silicate.
5. A thermostable K-A zeolite composition according to any one of claims 1 to 4, which contains one or more binders.