JPS6219363B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a novel method for producing zeolite molded bodies. More specifically, the present invention relates to a method for producing a zeolite molded body having excellent mechanical strength and high wear resistance. Various natural or synthetic zeolites mainly composed of aluminosilicate are used in many industrial fields, taking advantage of their adsorption performance and having applications depending on the characteristics of the various zeolites. By the way, in general, these zeolites themselves do not have very high cohesiveness between particles, and when used industrially, they are rarely used as they are in the form of small agglomerates, etc., and in many cases, Zeolite is granulated and molded into pellets, tablets, spherules, and other suitable granular forms, which are then fired to form molded bodies that have increased mechanical strength and are used. The commonly performed zeolite granulation and molding processes can be roughly divided into mixing, molding, drying,
It consists of four steps: firing (sintering). That is, in the mixing step, zeolite powder obtained by pulverization using a pulverizer such as a ball mill or a rod mill is mixed with a suitable binder, such as an inorganic binder based on a clay material such as kaolin, bentonite, or acid clay, or as necessary. Depending on the requirements, additives such as dispersants, lubricants, and extrusion aids are added, and wet kneading is performed in the presence of water to create a homogeneous mixture. In the next molding process, this mixture is transformed into an intermediate having an appropriate shape. Form into a target agglomerate. Furthermore, in the drying process, this intermediate aggregate is dried to remove most of the moisture, and then in the calcination process, an appropriate temperature range is selected depending on the properties of the various zeolites, and calcination is performed in that temperature range. Finally, we obtained a zeolite molded body. By the way, in the past, in the production of zeolite molded bodies, inorganic clay materials have often been used as binders as described above, but the use of such binders makes it possible to form zeolite aggregates or molded bodies. Although the bonding force between particles increases, the original adsorption performance and ion conversion performance decrease depending on the amount of clay-based substances that remain and are distributed as constituents in the final zeolite molded product. There are drawbacks. Also, depending on the type of zeolite material used, when only clay-based materials are used as a binder, the mechanical strength of the zeolite molded body gradually weakens as the amount of water adsorption increases, and then rapidly decreases as it approaches water saturation. A so-called deterioration phenomenon is observed in which the strength of the molded product decreases and eventually becomes fine powder. By improving these drawbacks in the production of conventional zeolite molded bodies, we have created a zeolite molded body that maintains the inherent adsorption performance of zeolite for as long as possible, and has excellent mechanical strength and high abrasion resistance that can withstand various industrial applications. Developing a manufacturing method to obtain it was considered an important issue. As a result of various studies on improving zeolite molded bodies in order to eliminate the drawbacks of such conventional methods, the present inventor has found that, according to the present invention, urea is mixed with zeolite in the presence of water, the mixture is molded, and dried. We have found that a zeolite molded body with excellent mechanical strength and high wear resistance can be obtained by firing at a temperature of 360 to 730°C. The present invention is based on this knowledge. Therefore, the present invention first involves mixing urea with powdered or granular natural or synthetic zeolite in the presence of moisture, molding the mixture, and drying the resulting molded product. The present invention provides a method for producing a zeolite molded body (hereinafter referred to as the first method), which is characterized in that the method is then fired at a temperature of 360°C to 730°C. The present inventor also found that in the above production method, when a known clay-based binder is used in combination with urea, in addition to the effect obtained by mixing urea, the amount of clay-based binder used can be reduced. It has been found that the effect can be significantly reduced. Therefore, the second aspect of the present invention is to mix a clay-based binder and urea in powdered or granular natural or synthetic zeolite in the presence of water, mold the mixture, and mold the resulting molded product. The present invention provides a method for producing a molded zeolite body (hereinafter referred to as the second method), which is characterized in that the body is dried and then calcined at a temperature of 360° to 730°C. The present invention will be explained in detail below. The method for producing a zeolite molded body of the present invention basically involves mixing urea with powdered or granular natural or synthetic zeolite in the presence of moisture, molding the mixture, and producing a molded body. The zeolite used as a raw material in the method of the present invention is a natural product or a synthetic material. Any product is acceptable. As is well known, zeolite is composed of a crystalline substance having a three-dimensional structure of porous aluminosilicate, and its crystal form differs depending on the type of zeolite. Natural zeolites include clinoptilolite, mordenite, chaabasite, erionite, filipsite, and calalite, and synthetic zeolites include A-type zeolites (e.g., MS-3A, 4A,
5A), X-type zeolite (e.g. MS-13X), Y-
Typical examples include type zeolite and synthetic mordenite. These zeolites are usually used in powder or granule form. In the method of the present invention, urea is added to a powdered or granular natural or synthetic zeolite material, wet mixing is performed while maintaining an appropriate moisture content, and the resulting mixture is formed into an appropriate shape such as pellets or tablets. Mold. Next, the molded body is dried to remove most of the adhering water, and finally the molded body is fired in a temperature range of 360° to 730°C. In the above-mentioned mixing, the shape of the natural or synthetic zeolite used is preferably in the form of fine particles or fine powder, preferably fine particles of at least 20 meshes or more. In the case of natural zeolite, such a shape of zeolite can be easily obtained by pulverizing a dry lump with an appropriate pulverizer, and in the case of synthetic zeolite, a powder much finer than the 20 mesh mentioned above can be obtained during synthesis. The synthetic powder can be used as a raw material for molding without being pulverized. In wet kneading in the method of the present invention, urea is added to the zeolite material and kneaded for an appropriate time using a kneader in the presence of moisture.
The amount of urea added is preferably 0.5 to 15% (by weight). Although the amount of water added and the mixing time naturally vary depending on the zeolite material used, it is usually possible to obtain a homogeneous mixture in 1 to 5 hours. When adding the above-mentioned urea, if a solution of urea is prepared in advance and added to the zeolite material and kneaded, there is an advantage that the urea additive can be uniformly dispersed in the zeolite phase. Additionally, in the kneading process, the amount of water added varies depending on the type of zeolite material; for example, when using natural zeolite powder, it is around 25 to 35%, and when using synthetic A-type or X-type zeolite, the amount of water added varies. When doing so, drink water
It is recommended as a preferable condition that the content be maintained at about 29 to 40% and kneading is carried out for 1.5 to 3 hours. In the method of the present invention, since zeolite and urea are mixed and molded in the presence of moisture, the molded product contains a considerable amount of water, so first, it is dried at a normal temperature of around 100°C. The moisture adhering to the molded body is removed, and the final firing is then carried out at 360°C.
The process is carried out at a temperature of ~730°C to obtain the final product.
If a wet molded body is rapidly heated to the firing temperature without drying the molded body as described above before the firing process, not only will the molded body crack of various sizes, but it will also crack in the presence of a large amount of moisture. The heating causes deterioration and destruction of the zeolite crystal structure. The incorporation of urea into the zeolite in the process according to the invention offers significant specific advantages as described below. That is, in the method of the present invention,
The urea added in the kneading process is dispersed on the surface of the zeolite particles or between the particles, and in the next drying process and calcination process, the urea is hydrolyzed and thermally decomposed to form CO(NH ₂ ) ₂ +H ₂ O→CO ₂ +2NH. A decomposition reaction like ₃ occurs. Since the substances CO ₂ and NH ₃ produced as a result of this decomposition reaction are both gases, the porosity of the zeolite molded body further increases due to the foaming phenomenon, and the specific surface area and pore volume also become extremely favorable. increase Since the urea used becomes a gas from the zeolite molded body phase during the heating process and is completely released, no residual substance remains in the structure of the zeolite molded body itself. As a result, the adsorption performance of the final product zeolite is not affected. This is because the use of conventional inorganic binders has the effect of strengthening the bonding force between zeolite particles, but it remains in the final product, resulting in a decrease in adsorption performance. This is a characteristic advantage that deserves special mention. The second method mentioned above is basically carried out in the same manner as the first method, but the amount of urea used is 0.3 to 12% based on the zeolite material, and the amount of clay-based binder used is different from the zeolite material. A preferable amount is 17% or less. In the second method, the effect of adding urea is as described above, but by using urea, the amount of clay-based binder used can be significantly reduced. Examples of the present invention are listed below, but the present invention is not limited by these Examples. Example 1 This example is an example in which bentonite was used as the clay material based on the second molding method of the present invention, and zeolite was molded in the presence of bentonite and urea. Synthetic zeolite powder (particle size: finer than 200 mesh; chemical composition: 1.02Na ₂ O・Al ₂ O ₃・
Add bentonite powder binder finer than 150 mesh to about 4 kg of 1.99SiO ₂ xH ₂ O; A-type zeolite; micropore-4Å) dried at 105° to 110°C.
% and mixing was carried out using a V-mixer for about 3 hours. Next, a 4% urea solution was added to the above mixture, and wet mixing was performed for about 2 hours using a kneader. In this case, the moisture content was maintained at approximately 33%. After the mixing process is completed, a molding machine is used to make 1/8" pellets (diameter: 3
mm; length: 5 to 7 mm), and then the molded pellets were dried at 105° to 110°C. Subsequently, the dried pellets were fired at 510°C for 3 hours to obtain a final product, a fired pellet. Hardness test of fired pellets...The fired 1/8" pellets obtained in this example were sampled and inspected to measure their mechanical strength. As a result, an average hardness value of 6.35 kg load/pellet was obtained. On the other hand, commercially available MS-
Mechanical strength was measured using exactly the same method as above using 4A1/8" pellets, and the average hardness value of the pellets was
A load of 5.23Kg/pellet was obtained. Furthermore, the above commercial product was re-fired under exactly the same conditions as in this example (510°C;
The hardness of the pellet was measured using a sampling method, and an average value of 5.74 kg load/pellet was obtained. It is clear that the fired 1/8" pellet molded body obtained by the second molding method of the present invention has clearly superior strength compared to the commercially available product than the above comparison. Adsorption performance test: A performance evaluation test as an adsorbent was conducted using the calcined 1/8'' pellets obtained in this example. That is, after the above-mentioned adsorbent was activated by heating, the water adsorption ability was measured and the results shown in Table 1 were obtained. The table shows constant water vapor pressure (mmHg)
water below

[Table] The amount of adsorption is shown in units of mg/g-adsorbent. The values shown are for homogeneous commercially available adsorbents such as MS-4A, 1/
This shows that the molded product obtained by the method of the present invention exhibits at least the same performance as the water adsorption capacity of 8" pellets. It is clearer that the second method of the present invention is carried out than in this example. As a result, a final molded product with favorable pellet strength and adsorption performance can be obtained.In addition, since bentonite and urea are used together in this molding, the amount of bentonite used is extremely large compared to conventional known methods. It is clearer than this example that there is an effect of reducing urea.Example 2 This example is an example in which natural zeolite was molded in the presence of urea based on the first molding method of the present invention. Approximately 5 kg of dried natural mordenite powder was used as the natural zeolite.The zeolite used for molding had the following particle size and chemical composition.Dried natural mordenite powder used for molding Particle size distribution: 100-250 meshes (76.9%); 250
Metsuyupath (23.1%) Chemical composition: SiO ₂ (71.88%); Al ₂ O ₃ (12.01
%); _NO2O (1.59%); _K2O
(1.56%); CaO (2.35%); MgO
(0.14%); Molar ratio of other components (heavy metal oxides, water of crystallization, etc.):
SiO ₂ /Al ₂ O ₃ 〓10 The above natural mordenite powder (dry product) approx. 5Kg
Add 3% urea solution to the mixture and mix using a kneader for 2 hours30
Wet mixing was carried out for several minutes. In this case the moisture content is 36
%. After the mixing process, use a molding machine to
The pellets were formed into 8" pellets (diameter: 3 mm; length: 5-7 mm) and then dried at 105° to 110°C. The dried pellets were then calcined at 540° to 560°C.
C. for 3 hours and 30 minutes to obtain a final pellet fired product. Hardness test of fired pellets...The hardness test of the fired 1/8" pellets obtained in this example was conducted according to Example 1, and the average hardness value was 13.96.
Kg load/pellet was obtained. The above hardness values indicate that adsorbent pellets with extremely excellent mechanical strength can be obtained by the first molding method of the present invention, and this strength is more than sufficient for industrial use. Adsorption performance test of calcined pellets: A performance evaluation test as an adsorbent was conducted using the calcined 1/8" pellets obtained in this example. That is, the adsorbent obtained by the above molding method was heated and activated. After the reaction, the saturated adsorption amount of ammonia gas was measured at ₂₅ °C, and _the results shown in Table 2 were obtained. Expressed in units of mg/g-adsorbent.

[Table] In order to compare the performance of the 1/8" pellet obtained in this example and the natural mordenite material used in this molding, the following test was conducted. Namely, the same natural mordenite material used in Example 2 was used. A powder was taken as a sample, and after heating and activation at 550°C, the adsorption isotherm for ammonia gas (25°C) was determined. On the other hand, from the measured values in Table 2, the adsorption isotherm for ammonia gas when using 1/8" pellets was determined. The line (25℃) was determined.
It was found that the two adsorption isotherms matched perfectly within experimental error. From this, the effects of the present invention using urea are clear. Example 3 This example is an example in which clinoptilolite was used as the natural zeolite and molding was carried out in accordance with Example 2. Since the molding method is basically the same as in Example 2, only the main points will be described below. Clinoptilolite material for molding Powder (dry product; powder finer than 200 mesh); At the end of kneading): 34% Wet mixing time: 2 hours Drying temperature for 1/8″ pellets: 105° to 110°C Calcining of 1/8″ pellets: 540°C (4 hours) 1/8″ pellets (baked) ) hardness average value: 7.28Kg
Load/Pellet 1/8″ pellets obtained in Example 3 (calcined;
The activated product (diameter: 3 mm; length: 5-7 mm) showed the following adsorption amount (at 25°C) for nitrogen gas. However, the unit of adsorption amount is N ₂ − adsorption amount at 25℃ 1.51 (30.9 mmHg); 6.03 (220.1 mmHg); 13.9
(760.0mmHg) is N ₂ ml/g - adsorbent (pellet)
(NTP), and the value in parentheses is the nitrogen pressure at the time of measurement (mmHg)
It shows. On the other hand, the same clinoptilolite powder used in the main molding was activated by heating at 540℃, and the adsorption isotherm of nitrogen gas (25℃) for it was
I asked for As a result, 3 using the above pellets
It was found that the measured values at the points followed the adsorption isotherm of clinoptilolite powder within error.

Claims (1)

[Claims] 1. Urea is mixed with powdered or granular natural or synthetic zeolite in the presence of moisture, the mixture is molded, the resulting molded product is dried, and then heated at 360°C or A method for producing a zeolite molded body characterized by firing at a temperature of 730°C. 2. Powdered or granular natural or synthetic zeolite is mixed with a clay binder and urea in the presence of moisture, the mixture is molded, the resulting molded body is dried, and then 360° A method for producing a zeolite molded body characterized by firing at a temperature of ~730°C.