Y-type molecular sieve rich in secondary pores and preparation method thereof
阅读说明：本技术 一种富含二次孔的y型分子筛及其制备方法 (Y-type molecular sieve rich in secondary pores and preparation method thereof ) 是由 刘欣梅 张瑛梅 曾洪量 刘振 张占全 孙发民 阎子峰 于 2019-08-20 设计创作，主要内容包括：本发明提供了一种富含二次孔的Y型分子筛及其制备方法。该方法包括以下步骤：将原料Y型分子筛与无机酸溶液混合、搅拌,得到混合溶液；向上述混合溶液中滴加无机碱溶液,得到混合物；将上述混合物洗涤、过滤、干燥,得到富含二次孔的Y型分子筛。本发明还提供了一种富含二次孔的Y型分子筛,其是由上述方法制备得到的。本发明提供的方法操作简单、成本低廉且环保有效,所得的Y型分子筛不仅保留了其典型的微孔和良好的水热稳定性,还实现了二次孔的大幅度增加。所得的Y型分子筛的二次孔体积为0.2-0.4cm~3/g,二次孔比表面积为150-300m~2/g。(The invention provides a Y-type molecular sieve rich in secondary pores and a preparation method thereof. The method comprises the following steps: mixing and stirring a raw material Y-shaped molecular sieve and an inorganic acid solution to obtain a mixed solution; dropwise adding an inorganic alkali solution into the mixed solution to obtain a mixture; and washing, filtering and drying the mixture to obtain the Y-type molecular sieve rich in secondary pores. The invention also provides a Y-type molecular sieve rich in secondary pores, which is prepared by the method. The method provided by the invention is simple to operate, low in cost, environment-friendly and effective, and the obtained Y-shaped molecular sieve not only keeps the typical micropores and good hydrothermal stability, but also realizes the great increase of secondary pores. The secondary pore volume of the obtained Y-type molecular sieve is 0.2-0.4cm 3 (g) the specific surface area of the secondary pores is 150-300m 2 /g。)
1. A preparation method of a Y-type molecular sieve rich in secondary pores comprises the following steps:
(1) mixing a raw material Y-type molecular sieve with an inorganic acid solution with the concentration of 0.1-1mol/L according to the solid-liquid mass ratio of 1:5-1:10, and stirring for 2-8 hours at the temperature of 80-100 ℃ to obtain a mixed solution;
(2) adding an inorganic alkali solution with the concentration of 0.1-2mol/L into the mixed solution obtained in the step (1), wherein the solid-liquid mass ratio of the raw material Y-type molecular sieve to the inorganic alkali solution is 1:5-1:10, and continuously stirring at the temperature in the step (1) for 0.5-4 hours to obtain a mixture;
(3) and (3) washing, filtering and drying the mixture obtained in the step (2) by using deionized water to obtain the Y-shaped molecular sieve rich in secondary pores.
2. The method according to claim 1, wherein the inorganic acid in step (1) comprises one of nitric acid, hydrochloric acid, and hydrofluoric acid.
3. The preparation method according to claim 1, wherein the inorganic base in the step (2) comprises one of sodium hydroxide, potassium hydroxide and ammonia water.
4. The method of claim 1, wherein the feedstock Y-type molecular sieve comprises NaY molecular sieve, NH4One of Y molecular sieve, HY molecular sieve, USY molecular sieve and REY molecular sieve.
5. The preparation method of claim 1 or 4, wherein the molar silica-alumina ratio of the raw material Y-type molecular sieve is 3:1-10: 1.
6. The production method according to claim 1, wherein the drying temperature in the step (3) is 80 to 150 ℃ and the drying time is 2 to 12 hours.
7. The production method according to claim 1, wherein the production method comprises the steps of:
(1) mixing the USY molecular sieve with a nitric acid solution with the concentration of 0.1mol/L according to the solid-liquid mass ratio of 1:10, and stirring for 5 hours at 85 ℃ to obtain a mixed solution;
(2) adding a potassium hydroxide solution with the concentration of 0.3mol/L into the mixed solution obtained in the step (1), wherein the solid-liquid mass ratio of the USY molecular sieve to the potassium hydroxide solution is 1:10, and continuously stirring at 85 ℃ for 2 hours to obtain a mixture;
(3) and (3) washing, filtering and drying the mixture obtained in the step (2) by using deionized water to obtain the USY molecular sieve rich in secondary pores.
8. A Y-type molecular sieve enriched in secondary pores, which is prepared by the preparation method of any one of claims 1 to 7.
9. The Y-type molecular sieve of claim 8, wherein the Y-type molecular sieve has a secondary pore volume of 0.2-0.4cm3The specific surface area of the secondary pores of the Y-type molecular sieve is 150-300m2/g。
10. The Y-type molecular sieve according to claim 8 or 9,wherein the secondary pore volume of the Y-type molecular sieve is 0.36cm3The specific surface area of the secondary pores of the Y-type molecular sieve is 268m2/g。
Technical Field
The invention relates to synthesis of a new catalytic material, in particular to a Y-type molecular sieve rich in secondary pores and a preparation method thereof.
Background
The molecular sieve has shape selective performance, large specific surface area, strong acidity and high stability, and is widely applied to the fields of catalysis, adsorption, separation and the like. The basic structure of the molecular sieve framework is SiO4And AlO4Tetrahedra, crystals that form a three-dimensional network structure by combining oxygen atoms in common. By SiO4And AlO4Different framework frameworks are formed by different arrangement forms of tetrahedrons, and a pore channel structure with molecular level and uniform pore diameter is further formed. Different types of molecular sieves have different tetrahedral arrangement forms, the pore channel structures formed are different, and the types and the concentrations of the generated acid centers are greatly different.
The Y-type molecular sieve is a molecular sieve which has strong acidity, good hydrothermal stability, good catalytic activity and economy and applicability, and is commonly used in catalytic cracking and hydrocracking catalysts. The Y-type molecular sieve has an FAU-type framework structure, the aperture of the Y-type molecular sieve is concentrated at 0.74nm, but the size of heavy oil molecules is 1.5-15nm, so the conventional Y-type molecular sieve is not beneficial to effective diffusion of heavy oil macromolecules, surface reaction and quick escape of reaction intermediate products, secondary cracking is aggravated, and the selectivity of target products is influenced. In order to meet the requirement of heavy oil macromolecules on catalytic reaction, on the basis of traditional synthesis of Y-type molecular sieves, a moderate secondary pore (namely, a mesoporous pore is generated through aftertreatment) needs to be introduced, and the limitation caused by the pore size is reduced.
The construction method of the secondary pore of the Y-type molecular sieve mainly comprises a direct synthesis method and a post-modification method. The direct synthesis method refers to that molecular sieve synthesis precursors or molecular sieve microcrystals or secondary units obtained after special treatment are subjected to self-assembly under the induction action of a mesoporous template to construct regular secondary pores. After the molecular sieve is synthesized by the method, the template agent needs to be removed through later-stage roasting, and the obtained molecular sieve has low crystallinity and high synthesis cost. Although the method can construct secondary pores, the mesoporous template agent needed to be used is mostly an organic amine compound, and the problem of organic wastewater discharge pollution exists.
Another commonly used method is a post-modification method, which uses a commercially available molecular sieve as a raw material and is a generic name of a method for treating a molecular sieve that has already been crystallized. The post-modification method mainly adopts a hydrothermal aging method and a chemical treatment method to construct secondary pores. Researches show that the USY molecular sieve modified by a hydrothermal aging method has limited increase of secondary pores, the crystallinity, the specific surface area and the acid density are greatly reduced, and the generated non-framework aluminum is still retained in the pore channels of the molecular sieve to influence the reaction performance of the catalyst.
The chemical treatment method includes an acid treatment method and an alkali treatment method, wherein the types of acid and alkali and the treatment conditions used by the molecular sieves with different types and framework structures are greatly different. The acid treatment method for modifying the Y molecular sieve to construct the secondary pores is to remove aluminum elements in non-frameworks and frameworks from the molecular sieve through chemical reaction, and inorganic acid and organic acid can be adopted for treatment. For the Y-type molecular sieve, after the Y-type molecular sieve is treated and modified by a single inorganic acid, although the secondary pore content is increased, the acid density is sharply reduced, and the catalytic performance of the Y-type molecular sieve is influenced; when the concentration of the inorganic acid is too high, collapse of the molecular sieve framework is easily caused. Therefore, inorganic acid treatment under mild conditions is generally adopted to avoid collapse of the molecular sieve framework or reduction of acid density after treatment, but the construction effect of secondary pores is obviously influenced. If the Y-type molecular sieve is modified by using the organic acid solution, not only is the secondary pore construction effect weakened, but also organic wastewater is generated, and the environment is polluted.
The alkali treatment method is to desilicate the molecular sieve by using alkali as a treatment reagent by a chemical reaction to increase the content of secondary pores. The alkali treatment method has a good secondary pore construction effect on treating molecular sieves with high silica-alumina ratio, such as ZSM-5 molecular sieves. However, the silica-alumina ratio of the Y-type molecular sieve is relatively low compared to the high silica-alumina ratio molecular sieve, and thus the effect of the Y-type molecular sieve in treating with a low-concentration inorganic alkali solution is not significant when the Y-type molecular sieve is treated with a single alkali; however, in the treatment of high-concentration inorganic alkaline solution, the Y-type molecular sieve is excessively desilicated, so that the crystallinity and stability are obviously reduced. If the Y-type molecular sieve is modified by adopting the organic alkali solution, not only the secondary pore construction effect is weakened, but also the waste liquid of the Y-type molecular sieve causes pollution. Therefore, the adjustable range of the secondary pores constructed by singly treating the Y molecular sieve with alkali is limited at present. In addition, in the method, a surfactant or a template agent is added in the modification process, although the effect of constructing secondary pores can be achieved, the main action mechanism of the used surfactant or template agent is similar to that of a direct synthesis method, the cost and the energy consumption are increased, organic wastewater is generated, and the difficulty of sewage treatment is increased.
Disclosure of Invention
In order to solve the defects of the common single acid treatment and single alkali treatment modification methods, the invention aims to provide a Y-type molecular sieve rich in secondary pores and a preparation method thereof.
In order to achieve the above object, the present invention provides a method for preparing a Y-type molecular sieve rich in secondary pores, comprising the steps of:
(1) mixing a raw material Y-type molecular sieve with an inorganic acid solution with the concentration of 0.1-1mol/L according to the solid-liquid mass ratio of 1:5-1:10, and stirring for 2-8 hours at the temperature of 80-100 ℃ to obtain a mixed solution;
(2) adding an inorganic alkali solution with the concentration of 0.1-2mol/L into the mixed solution obtained in the step (1), wherein the solid-liquid mass ratio of the raw material Y-type molecular sieve to the inorganic alkali solution is 1:5-1:10, and continuously stirring at the temperature in the step (1) for 0.5-4 hours to obtain a mixture;
(3) and (3) washing, filtering and drying the mixture obtained in the step (2) by using deionized water to obtain the Y-shaped molecular sieve rich in secondary pores.
In the above preparation method, preferably, the inorganic acid in step (1) includes one of nitric acid, hydrochloric acid, and hydrofluoric acid.
In the above preparation method, preferably, the inorganic base in step (2) includes one of sodium hydroxide, potassium hydroxide, and aqueous ammonia.
In the above preparation method, preferably, the raw material Y-type molecular sieve comprises NaY molecular sieve, NH4One of Y molecular sieve, HY molecular sieve, USY molecular sieve and REY molecular sieve. More preferably, the molar silica to alumina ratio of the starting Y-type molecular sieve is from 3:1 to 10: 1.
In the above production method, preferably, the temperature of the drying in the step (3) is 80 to 150 ℃ and the time of the drying is 2 to 12 hours.
In some embodiments, the above preparation method may comprise the steps of:
(1) mixing the USY molecular sieve with a nitric acid solution with the concentration of 0.1mol/L according to the solid-liquid mass ratio of 1:10, and stirring for 5 hours at 85 ℃ to obtain a mixed solution;
(2) adding a potassium hydroxide solution with the concentration of 0.3mol/L into the mixed solution obtained in the step (1), wherein the solid-liquid mass ratio of the USY molecular sieve to the potassium hydroxide solution is 1:10, and continuously stirring at 85 ℃ for 2 hours to obtain a mixture;
(3) and (3) washing, filtering and drying the mixture obtained in the step (2) by using deionized water to obtain the USY molecular sieve rich in secondary pores.
The invention also provides a Y-type molecular sieve rich in secondary pores, which is prepared by the preparation method, and preferably, the secondary pore volume of the Y-type molecular sieve is 0.2-0.4cm3The specific surface area of the secondary pores of the Y-type molecular sieve is 150-300m2(ii)/g; more preferably, the secondary pore volume of the Y-type molecular sieve is 0.36cm3The specific surface area of the secondary pores of the Y-type molecular sieve is 268m2/g。
The invention has the beneficial effects that:
according to the invention, the Y-type molecular sieve is treated by the inorganic acid solution, a certain amount of primary pores are obtained, meanwhile, the opportunity of contact between the inorganic alkali and silicon sites is increased, and desiliconization treatment is carried out by the inorganic alkali solution to construct rich secondary pores. The method provided by the invention is simple to operate, low in cost, environment-friendly and effective, the prepared Y-type molecular sieve not only keeps the characteristics of typical micropores and good hydrothermal stability, but also realizes the great increase of secondary pores, and the secondary pore volume of the obtained Y-type molecular sieve is 0.2-0.4cm3(g) the specific surface area of the secondary pores is 150-300m2/g。
Detailed Description
The technical solutions of the present invention will be described in detail below in order to clearly understand the technical features, objects, and advantages of the present invention, but the present invention is not limited to the practical scope of the present invention.
Example 1
The embodiment provides a preparation method of a Y-type molecular sieve rich in secondary pores, which comprises the following specific steps:
a solution of 0.1mol/L nitric acid (analytically pure, Sjogren chemical Co., Ltd.) and a solution of 0.3mol/L sodium hydroxide (analytically pure, Sjogren chemical Co., Ltd.) were prepared.
Mixing USY molecular sieve (Shandong Qilu Huaxin Gaoki Co., Ltd., molar silica-alumina ratio SiO)2/Al2O39.2, mesoporous volume of 0.11cm3(g) the mesoporous specific surface area is 114m2And/g) adding the prepared nitric acid solution into a three-neck flask according to the solid-liquid mass ratio of 1:5, and stirring for 2 hours in a constant-temperature water bath at 85 ℃ to obtain a mixed solution.
And (3) dropwise adding the prepared sodium hydroxide solution into the mixed solution by using a dropping funnel according to the solid-liquid mass ratio of the USY molecular sieve to the sodium hydroxide solution of 1:5, keeping the temperature of the water bath, and continuously stirring for 1 hour to obtain a mixture.
After the reaction is finished, washing the mixture for a plurality of times by deionized water, filtering, drying in a drying oven at 110 ℃ for 12 hours to obtain the modified USY molecular sieve, wherein the secondary pore volume of the obtained molecular sieve is 0.22cm3/g、The specific surface area of the secondary pores is 178m2/g。
Example 2
The embodiment provides a preparation method of a Y-type molecular sieve rich in secondary pores, which comprises the following specific steps:
a0.1 mol/L nitric acid (analytically pure, Sjogren chemical Co., Ltd.) solution and a 0.4mol/L potassium hydroxide (analytically pure, Sjogren chemical Co., Ltd.) solution were prepared.
Mixing USY molecular sieve (Shandong Qilu Huaxin Gaoki Co., Ltd., molar silica-alumina ratio SiO)2/Al2O39.2, mesoporous volume of 0.11cm3(g) the mesoporous specific surface area is 114m2And/g) adding the prepared nitric acid solution into a three-neck flask according to the solid-liquid mass ratio of 1:5, and stirring for 2 hours in a constant-temperature water bath at 85 ℃ to obtain a mixed solution.
And (3) dropwise adding the prepared potassium hydroxide solution into the mixed solution by using a dropping funnel according to the solid-liquid mass ratio of the USY molecular sieve to the potassium hydroxide solution of 1:5, keeping the temperature of the water bath, and continuously stirring for 1 hour to obtain a mixture.
After the reaction is finished, washing the mixture for a plurality of times by deionized water, filtering, drying in an oven at 110 ℃ for 12 hours to obtain the modified USY molecular sieve, wherein the secondary pore volume of the obtained molecular sieve is 0.22cm3(iv)/g, secondary pore specific surface area 169m2/g。
Example 3
The embodiment provides a preparation method of a Y-type molecular sieve rich in secondary pores, which comprises the following specific steps:
a0.2 mol/L hydrochloric acid (analytically pure, Sichuan Xiong chemical Co., Ltd.) solution and a 0.3mol/L sodium hydroxide (analytically pure, Sichuan Xiong chemical Co., Ltd.) solution were prepared.
Mixing USY molecular sieve (Shandong Qilu Huaxin Gaoki Co., Ltd., molar silica-alumina ratio SiO)2/Al2O39.2, mesoporous volume of 0.11cm3(g) the mesoporous specific surface area is 114m2/g) adding the mixed solution and the prepared hydrochloric acid solution into a three-neck flask according to the solid-liquid mass ratio of 1:5, and carrying out constant-temperature water bath at 85 DEGAnd stirred for 2 hours to obtain a mixed solution.
And (3) according to the solid-liquid mass ratio of the USY molecular sieve to the sodium hydroxide solution of 1:5, dropwise adding the prepared sodium hydroxide solution into the mixed solution by using a dropping funnel, keeping the temperature of the water bath, and continuously stirring for 1 hour to obtain a mixture.
After the reaction is finished, washing the mixture for a plurality of times by deionized water, filtering, drying in a drying oven at 110 ℃ for 12 hours to obtain the modified USY molecular sieve, wherein the secondary pore volume of the obtained molecular sieve is 0.19cm3(ii)/g, secondary pore specific surface area 157m2/g。
Example 4
The embodiment provides a preparation method of a Y-type molecular sieve rich in secondary pores, which comprises the following specific steps:
hydrofluoric acid (national chemical reagent, Inc., analytical pure) solution with a concentration of 0.1mol/L and ammonia water (analytical pure, Sjogren chemical Co., Ltd., analytical pure) solution with a concentration of 0.4mol/L were prepared.
Mixing USY molecular sieve (Shandong Qilu Huaxin Gaoki Co., Ltd., molar silica-alumina ratio SiO)2/Al2O39.2, mesoporous volume of 0.11cm3(g) the mesoporous specific surface area is 114m2And/g) adding the mixed solution and the prepared hydrofluoric acid solution into a three-neck flask according to the solid-liquid mass ratio of 1:5, and stirring for 3 hours in a constant-temperature water bath at 85 ℃ to obtain a mixed solution.
And (3) according to the solid-liquid mass ratio of the USY molecular sieve to the ammonia water solution of 1:5, dropwise adding the prepared ammonia water solution into the mixed solution by using a dropping funnel, keeping the temperature of the water bath, and continuously stirring for 1 hour to obtain a mixture.
After the reaction is finished, washing the mixture for a plurality of times by deionized water, filtering, drying in a drying oven at 110 ℃ for 12 hours to obtain the modified USY molecular sieve, wherein the secondary pore volume of the obtained molecular sieve is 0.21cm3(per gram), secondary pore specific surface area 161m2/g。
Example 5
The embodiment provides a preparation method of a Y-type molecular sieve rich in secondary pores, which comprises the following specific steps:
a0.1 mol/L nitric acid (analytically pure, Sjogren chemical Co., Ltd.) solution and a 0.3mol/L potassium hydroxide (analytically pure, Sjogren chemical Co., Ltd.) solution were prepared.
Mixing USY molecular sieve (Shandong Qilu Huaxin Gaoki Co., Ltd., molar silica-alumina ratio SiO)2/Al2O39.2, mesoporous volume of 0.11cm3(g) the mesoporous specific surface area is 114m2And/g) adding the prepared nitric acid solution into a three-neck flask according to the solid-liquid mass ratio of 1:10, and stirring for 5 hours in a constant-temperature water bath at 85 ℃ to obtain a mixed solution.
And (3) according to the solid-liquid mass ratio of the USY molecular sieve to the potassium hydroxide solution of 1:10, dropwise adding the prepared potassium hydroxide solution into the mixed solution by using a dropping funnel, keeping the temperature of the water bath, and continuously stirring for 2 hours to obtain a mixture.
After the reaction is finished, washing the mixture for a plurality of times by using deionized water, filtering, and drying in an oven at 80 ℃ for 12 hours to obtain the modified USY molecular sieve, wherein the secondary pore volume of the obtained molecular sieve is 0.36cm3(iv) g, specific surface area of secondary pores 268m2/g。
Example 6
The embodiment provides a preparation method of a Y-type molecular sieve rich in secondary pores, which comprises the following specific steps:
a solution of 0.1mol/L nitric acid (analytically pure, Sjogren chemical Co., Ltd.) and a solution of 0.3mol/L sodium hydroxide (analytically pure, Sjogren chemical Co., Ltd.) were prepared.
Mixing USY molecular sieve (Shandong Qilu Huaxin Gaoki Co., Ltd., molar silica-alumina ratio SiO)2/Al2O39.2, mesoporous volume of 0.11cm3(g) the mesoporous specific surface area is 114m2And/g) adding the prepared nitric acid solution into a three-neck flask according to the solid-liquid mass ratio of 1:5, and stirring for 5 hours in a constant-temperature water bath at 95 ℃ to obtain a mixed solution.
And (3) according to the solid-liquid mass ratio of the USY molecular sieve to the sodium hydroxide solution of 1:5, dropwise adding the prepared sodium hydroxide solution into the mixed solution by using a dropping funnel, keeping the temperature of the water bath, and continuously stirring for 4 hours to obtain a mixture.
After the reaction is finished, washing the mixture for a plurality of times by deionized water, filtering, drying in an oven at 150 ℃ for 12 hours to obtain the modified USY molecular sieve, wherein the secondary pore volume of the obtained molecular sieve is 0.32cm3(ii)/g, secondary pore specific surface area of 216m2/g。
As can be seen from examples 1 to 6, the modified Y-type molecular sieve obtained by the preparation method provided by the present invention has a greatly increased secondary pore volume and secondary pore surface area compared to the molecular sieve before modification, wherein the modified USY molecular sieve obtained by the method of example 5 has the highest secondary pore volume and secondary pore specific surface area; the preparation method provided by the invention can be used for obtaining the Y-type molecular sieve rich in secondary pores, does not generate organic wastewater in the preparation process, and is simple to operate, low in cost, environment-friendly and effective.
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