KR20040073712A - Process for preparing zsm-5 type zeolite - Google Patents

Abstract

PURPOSE: A process for preparing environmentally friendly ZSM-5 type zeolite having high unit productivity is provided. CONSTITUTION: The process for preparing ZSM-5 type zeolite comprises a step of proceeding hydrogelation reaction by adding a sodium aluminate aqueous solution to a composition silica source in which the inside of pores of the support is activated by adding water and sodium hydroxide aqueous solution to a porous silica support in such a way that composition for the whole reactant is controlled as in the following formula 1:£Na2O|4 to 11£Al2O3|1.0£SiO2|25 to 100£H2O|900 to 4500; and a step of hydrothermal synthesizing the whole reactant as agitating the whole reactant, wherein the porous silica support is an amorphous silica selected from white carbon, silica gel and fumed silica.

Description

Process for preparing ZSM-5 zeolite {Process for preparing ZSM-5 type zeolite}

The present invention relates to a method for producing a ZSM-5 zeolite, and more particularly, in a hydrothermal synthesis of a zeolite, sodium aluminate in a silica source that activates the inside of pores of a porous silica carrier by treating the porous silica carrier with an aqueous sodium hydroxide solution. Absorbing an aqueous solution to combine the activated silica source and the alumina source in the pores to hydrogelize to synthesize fine and uniform ZSM-5 crystal grains, the ZSM-5 crystal grains trapped in the pores of the porous silica carrier By suppressing the growth of single crystals and producing ZSM-5 aggregates of polycrystalline phases, the production yield of ZSM-5 zeolites can be greatly improved, and the filtration efficiency can be dramatically improved after production, thereby reducing manufacturing costs and eco-friendly effects. Of improved ZSM-5 zeolite It relates to a manufacturing method.

In general, zeolites have a unique three-dimensional crystal structure of aluminosilicates, and have a larger cavity than other aluminosilicate crystals, and have excellent ion exchange properties, and thus are widely used as catalysts, adsorbents, molecular sieves, and ion exchangers. Used. Natural zeolites are limited to special parts due to structural constraints, but the use of synthetic zeolites is gradually expanding. In order to diversify the use of zeolites, it is necessary to be able to arbitrarily control the crystal size, distribution and shape of the zeolite, as well as an economical synthesis method.

ZSM-5 zeolites all form three-dimensional pores consisting of a 10-tetra hedron ring and are about the size of zeolites A, X and zeolite Y. It is a kind of pentasil zeolite, a shape-selective catalyst that exhibits unique adsorption and diffusion characteristics.It has a high SiO ₂ / Al ₂ O ₃ ratio, which is generally thermally stable, hydrophobic, and has a high Lewis acid point. The Br ?? nsted scatter is small. In particular, it is known that a gasoline fraction having a high octane number directly from methanol can be obtained directly by an MTG process and excellent in selectivity with respect to gasoline fraction.

ZSM-5 zeolite having the above characteristics was first developed by US Mobil, Inc. (US Pat. No. 3,702,886), and then used as a catalyst for petrochemicals. ZSM-5 manufacturing method is mainly manufactured by hydrothermal synthesis, and there is a slight difference in method and composition. Generally, the composition of the reactive material in the synthesis of ZSM-5 zeolite is aNa ₂ O · bAl ₂ O ₃ · cSiO ₂ DH ₂ O.e (TPA) ₂ O (a / c: 0.02 to 0.43 c / b: 30 to ??), reaction temperature 150 to 195 °, synthesis time 24 to 120 hours. . Interest in the industrial manufacturing aspects of ZSM-5 focuses on homogeneous synthesis of ZSM-5 with better properties in a more environmentally friendly and cheaper way.

Conventionally, ZSM-5, a crystalline zeolite, was synthesized using an organic compound, template, which is involved in crystal structure formation. It is known that there are many restrictions such as harmfulness and economics due to the use of relatively expensive organic templates.

In order to solve the above problems, a method of synthesizing ZMS-5 excluding the use of organic materials is mentioned in German Patents (Original German) Nos. 207185 and 207186. It is reported that ZSM-5 crystallization reactions under the exclusion of organic matter are very sensitive to the reaction conditions of choice, and thus require careful attention. Factors affecting the ZSM-5 crystallization reaction mechanism include the type of silica source, the content of Si / Al, the concentration of the alkaline solution, the mixing order of the reactants, the reaction temperature, the reaction time, the degree of aging and the presence of agitation. have. Among these factors, the type of silica source is known as the most important factor. Water glass (water galss) and silica sol (silica sol) were used as the silica source type. In the case of water glass, a solid silicate was added to water to dissolve it. There is a difficulty in controlling the reactant composition, and the synthesis method of controlling the alkali concentration by converting the alkali component in the water glass into the form of salt using sulfuric acid or aluminum sulfate is difficult in reaction conditions, resulting in uneven ZSM-5 crystallization, removal of salt, etc. Problems such as high post-treatment cost are caused [East German Patent No. 207185]. Silica sol is highly reactive and easy to handle, but has higher raw material cost than other silica sources, silica component is dispersed in large amount of water in colloidal state, and diluted to prevent alumina component and rapid hydrogel formation. Inevitably, the two components are in contact. In the above case, not only the solid content of the crystallized particles in the ZSM-5 synthesis process is low, but also the ZSM-5 crystal grains are undispersed in the unit particle state, which causes a large load in the filtrate separation and washing process. As a result, a large amount of unreacted components in the filtrate and the washing liquid are discharged, resulting in low unit productivity, which is a problem as an industrial production method [East German Patent No. 207186].

On the other hand, it was difficult to prepare small crystals suitable for catalyst use when organic template was not used in the ZSM-5 synthesis process. However, in Korean Patent Publication No. 96-002621, a sulfuric acid solution was added to an aqueous solution of sodium silicate to precipitate silica components as a precipitate. After the preparation, the resultant was filtered / washed, treated with no sulfate group, and seeded to about 0.05 μm to synthesize ZSM-5 having a fine particle size. In this case, the silica precipitate was filtered / washed. In addition to the consumption of a large amount of water in the process, the crystal growth must be suppressed so that the ZSM-5 crystal grain size is 0.1 μm or less in the synthesis process, so that a large amount of unreacted components remain in the liquid phase, resulting in low crystallization yield. The filtrate is separated because fine ZSM-5 crystal grains of In order to wash the water, it is impossible to introduce a general filtration process such as centrifugation, pressure filtration, vacuum filtration and the like. It is also believed that the concept of sidra is problematic in producing ambiguous and reproducible results.

Accordingly, in the present invention, as a result of research efforts to solve the problems described above, ZSM-5 crystal particles are synthesized by absorbing an aqueous sodium aluminate solution into a porous silica carrier activated by treating with aqueous sodium hydroxide solution to activate the pores. 5 When crystal grains produce ZSM-5 aggregates in the crystalline phase trapped in the pores of the porous silica carrier, single crystal formation is suppressed and polycrystalline ZSM-5 aggregates are produced. Thus, the production yield and production process of ZSM-5 zeolite The present invention has been found to be able to improve the efficiency, significantly reduced the amount of unreacted material in the filtrate compared to the conventional manufacturing method can significantly reduce the load in the filtration and washing process.

Accordingly, an object of the present invention is to provide a method for producing a ZSM-5 zeolite having high unit productivity and environment-friendly.

1 is a process diagram schematically showing a manufacturing process of a ZSM-5 zeolite according to the present invention.

2 is an electron scanning microscope (SEM) photograph of the ZSM-5 zeolite prepared by the embodiment of the present invention.

3 is an electron scanning micrograph of the ZSM-5 zeolite prepared by Comparative Example 1. FIG.

4 is an electron scanning micrograph of the ZSM-5 zeolite prepared by Comparative Example 2. FIG.

The present invention is a hydrogelation reaction by adding water and sodium hydroxide aqueous solution to the porous silica carrier to the composition comprising a silica source activated to the inside of the pores, by adding an aqueous sodium aluminate solution to adjust the composition of the entire reactant as shown in the following formula (1) It proceeds, and characterized in that the method for producing a ZSM-5 zeolite hydrothermally synthesized while stirring the entire reactant.

[Na ₂ O] _4-11 [Al ₂ O ₃ ] _1.0 [SiO ₂ ] _25-100 [H ₂ O] _900-4500

The present invention will be described in detail as follows.

In the present invention, in the hydrothermal synthesis of zeolite, the porous silica carrier is treated with an aqueous sodium hydroxide solution to absorb an aqueous sodium aluminate solution into a silica source that activates the inside of the pores of the porous silica carrier, thereby binding the activated silica source and the alumina source pores. It is an improved method for producing a ZSM-5 based zeolite to form a fine and uniform ZSM-5 crystal particles by allowing them to hydrogelize. At this time, since the ZSM-5 crystal grains are trapped in the pores of the porous silica carrier to form crystal grains, growth of single crystals is suppressed, whereas ZSM-5 aggregates of polycrystalline phase can be efficiently generated, and thus ZSM-5 Not only can the production yield of the zeolite be significantly improved than the existing method, but also the filtration efficiency is significantly improved after manufacturing, resulting in a reduction in manufacturing cost, and at the same time, an environmentally friendly effect due to the absence of organic materials.

In the present invention, the activated silica source and the alumina source are porous silica carriers by absorbing the sodium aluminate solution after activating by contacting the aqueous sodium hydroxide solution inside the white carbon pores in which the large pores are well developed. Hydrogelization by binding in the pores of the hydrothermal synthesis process, the crystallization proceeds in the state in which the silica source and the alumina source are trapped inside the pores of the porous silica carrier, thereby inhibiting single crystal growth and having a polycrystalline aggregated shape. It is characterized by a method for producing a ZSM-5 zeolite.

That is, the present invention is to add a sodium aluminate aqueous solution to the silica source activated by the addition of water and aqueous sodium hydroxide solution to the porous silica carrier to activate the inside of the pores, and to control the composition of the entire reactant as shown in Formula 1, It is a manufacturing method of ZSM-5 type zeolite which hydrothermally synthesizes with stirring.

The porous silica carrier may use amorphous silica selected from among white carbon, silica gel, and fumed silica in which amorphous silica components are aggregated. In the present invention, the silica source is inexpensive and macropores in the pores. ) Is developed so that the desired effect can be obtained when using the white carbon which is excellent in water absorption. As for the white carbon, it is generally more preferable to use an SiO ₂ content of 93% by weight or more.

The molar ratio of the silica source composition to which water and aqueous sodium hydroxide solution are added to the white carbon as described above is adjusted to be Na ₂ O / SiO ₂ = 0.02 to 0.22, H ₂ O / Na ₂ O = 60 to 1150, and 10 to 60? The silica component on the inner surface of the pores of the white carbon is activated while stirring for 0.1 to 1.0 hours. If the molar ratio of the composition containing the silica source is out of the above range, it is not preferable in terms of insufficient activation of the silica source.

In the present invention, it is very important to treat the white carbon as a porous silica carrier with an aqueous sodium hydroxide solution to activate the silica component in the pores and is also a characteristic part of the present invention. At this time, when the aqueous sodium hydroxide solution and the porous silica carrier are contacted at an excessively high temperature for a long time, the aggregated silica source is undispersed due to reaction with alkali, making it difficult to form the ZSM-5 aggregate intended in the present invention. On the other hand, contact with aqueous sodium hydroxide solution at low temperature for a short time makes it difficult to penetrate the alumina source into the white carbon pores in which the alkali and silica sources form aggregates, and thus the hydrogelation reaction between the silica source and the alumina source does not proceed smoothly. There is a problem that a large amount of unreacted silica component remains in the product. Therefore, the reaction temperature of the sodium hydroxide aqueous solution and the porous silica carrier is 10 to 60 ° C. It is good to make it react, maintaining the range, reaction time for 0.1 to 1.0 hour, and stirring speed at 50-300 rpm.

Aqueous sodium aluminate solution is prepared by dissolving sodium aluminate in water or by adding sodium hydroxide and water in aluminum hydroxide at 100 to 180 ° C. The molar ratio of the composition is Na ₂ O / Al ₂ O ₃ = 0.60. ~ 5.50, is adjusted such that the _{H 2 O / Na 2 O =} 160 ~ 1150. If the molar ratio of the aqueous solution of sodium aluminate solution is out of the above range, hydrolysis occurs or becomes inadequate to be absorbed by the silica source.

The composition comprising the silica source prepared as described above and the aqueous sodium aluminate solution are preferably prepared freshly before use, and the porous composition is activated by adding a predetermined amount while stirring the composition comprising the silica source and the aqueous sodium aluminate solution. Hydrogelation is performed by allowing the alumina source to be slowly absorbed into the pores of the silica carrier. At this time, the molar ratio of the composition subjected to the hydrogelation reaction is adjusted to SiO ₂ / Al ₂ O = 25 to 100, Na ₂ O / SiO ₂ = 0.04 to 0.45, H ₂ O / Na ₂ O = 80 to 1125, the molar ratio If is out of the above range ZSM-5 crystallization proceeds unevenly.

The composition subjected to the hydrogelation reaction prepared as described above was heated with stirring the reactants to 140 to 195 ° C. at a rate of temperature increase of 2 to 10 ° C./min, and hydrothermally synthesized for 6 to 72 hours in the above temperature range. The 5 crystal grain size is in the range of 0.1 to 0.5 μm, and the ZSM-5 crystal particles are aggregated to prepare a ZSM-5 aggregate having a size of 10 to 50 μm. The ZSM-5 aggregate prepared as described above may be filtered, washed with water and dried to obtain the final ZSM-5 zeolite intended in the present invention, and the yield is 95% or more.

ZSM-5 zeolite prepared according to the present invention according to the present invention is applied as a constituent of the catalyst because it is easily dispersed into fine unit particles when wet mixing with other additives commonly used when applied to the catalyst production, etc. There is no problem.

The present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Example

Water (11.73 kg) and 2N aqueous sodium hydroxide solution (3.27 kg) were added to white carbon (SiO ₂ content: 95% by weight) (3.75 kg), and the silica source was activated by stirring at 25 ° C for 30 minutes to activate the inside of the pores. The composition was prepared.

Further, aluminum hydroxide (130 g) was added to 8N aqueous sodium hydroxide solution (650 g), heated to 105 ° C. to dissolve, cooled to room temperature, and water (14.62 kg) was added to prepare an aqueous sodium aluminate solution.

After stirring the silica source composition, an aqueous sodium aluminate solution was added to absorb the pores into the pores. The hydrogelation reaction was carried out in a pressurized reactor, and the reaction mixture was heated up to 190 ° C at a heating rate of 3 ° / min while stirring the composition having undergone the hydrogelation at 120 rpm for 16 hours while maintaining the temperature. Hydrothermally synthesized and then cooled to 60 ° C.

The cooled reactant was placed in a 45 cm diameter Luce filter equipped with a polyethylene filter cloth and filtered under reduced pressure at 625 mmHg to measure the time for the solid to be separated from the reaction mother liquor. 40 ° distilled water (65 kg) was added to the cake separated from the reaction mother liquor and filtered under reduced pressure under the same conditions twice. The remaining filtrate was washed with water, removed and dried at 120 ° C. for 8 hours to obtain 3.92 kg of water. The final product was obtained.

Comparative Example 1

The white carbon was treated in the same manner as in the above example except that the white carbon was contacted with an aqueous sodium hydroxide solution at 90 ° C. for 3 hours to obtain 3.54 kg of the final product.

Comparative Example 2

Silica sol (SiO ₂ content: 31% by weight) (11.51 kg) was added to H ₂ O (3.79 kg) and 2N aqueous sodium hydroxide solution (3.27 kg) to prepare a silica source composition in the same manner as in the above example Treatment gave 3.42 kg of final product.

The filtration time measured in Examples and Comparative Examples 1-2 and the amount of ZSM-5 theoretically produced in the initial reaction and the yields based on solids recovered in the final product are shown in Table 1 below. The final product obtained by the above method was confirmed by XRD analysis to determine the crystal type and crystallinity, and the results of comparing the ZSM-5 type zeolite data defined in the Joint Committee on Powder Diffraction Standard (JCPDS) of the United States is shown in Table 1 below.

The process for producing the ZSM-5 zeolite of the present invention is shown briefly in FIG. 1, and the results of observing the unit crystal grains and the aggregated state through an electron microscope (SEM) are shown in FIGS. 2 to 4. Represented in each.

yield(%) Filtration time (second) Zeolite Type * Crystallinity * Example 97.2 45 ZSM-5 Good Comparative Example 1 87.6 260 ZSM-5 Good Comparative Example 2 84.7 342 ZSM-5 Good * Based on US JCPDS 37-361

According to the results of Table 1, it can be seen that the products prepared according to the examples according to the present invention show ZSM-5 types of the same crystallinity when compared with the products prepared according to Comparative Examples 1 and 2, and yields. This is more than 95%, it was confirmed that the effect of reducing the filtration time by more than five times.

In addition, Figure 2 is an electron micrograph of the product prepared according to the embodiment Figure 2 shows that the finely aggregated ZSM-5 agglomerated form of fine unit particles of 0.2 ~ 0.4 ㎛, Figure 3 As shown in FIG. 4, the crystal form in which the relatively large unit particles of 2 to 7 μm in size were dispersed was confirmed by electron microscopic observation.

As described above, the present invention treats the porous silica carrier with an aqueous sodium hydroxide solution to activate the inside of the pores, and absorbs the sodium aluminate solution to hydrothermally synthesize the ZSM-5 crystal particles to trap single crystal growth in the pores of the porous silica carrier. On the other hand, by producing a polycrystalline ZSM-5 aggregate, the production yield of ZSM-5 zeolite can be significantly improved to 95% or more, and the filtration efficiency after manufacturing is dramatically improved to 5 times or more, thereby reducing manufacturing cost. It can bring an effect.

In addition, it does not use an organic template that is toxic as in the conventional method shows a more eco-friendly effect at the same time.

Claims (6)

To the composition comprising a silica source activated by the addition of water and aqueous sodium hydroxide solution to the porous silica carrier to activate the pores inside, the aqueous solution of sodium aluminate was added to adjust the composition of the entire reactant as shown in Formula 1 to proceed with the hydrogelation reaction. And hydrothermal synthesis while stirring all the reactants. [Formula 1] [Na ₂ O] _4-11 [Al ₂ O ₃ ] _1.0 [SiO ₂ ] _25-100 [H ₂ O] _900-4500 The method of claim 1, wherein the porous silica carrier is amorphous silica selected from white carbon, silica gel, and fumed silica. The method of claim 1, wherein the silica composition is Na ₂ O / SiO ₂ = 0.02 to 0.22, the molar ratio of H ₂ O / Na ₂ O = 60 to 1150, 0.1 to 10 to 60 ℃ while stirring at 50 to 300 rpm A method for producing a ZSM-5 zeolite, which is prepared by treating it for 1.0 hour. The method of claim 1, wherein the sodium aluminate aqueous solution is Na ₂ O / Al ₂ O ₃ = 0.60 to 5.50, H ₂ O / Na ₂ O = 160 to 1150 to prepare a ZSM-5-based zeolite, characterized in that Way. The method for producing a ZSM-5 zeolite according to claim 1, wherein the hydrothermal synthesis is carried out at 140 to 195 ° C for 6 to 72 hours under its own pressure. According to claim 1, wherein the ZSM-5 crystal particles synthesized in the porous silica carrier is in the size range of 0.1 to 0.5 ㎛, ZSM-5 aggregates of the crystal phase in which the ZSM-5 crystal particles are trapped has a size of 10 to 50 ㎛ It is a range, the manufacturing yield is 95% or more, and the manufacturing method of ZSM-5 zeolite characterized by the easy filtration / washing.