A modified molecular sieve, its preparation method and application

Abstract

The present invention relates to the field of manufacturing crystalline aluminosilicate materials, and discloses a modified molecular sieve, a preparation method thereof and an application thereof. The method includes: (1) in the presence of water, carrying out a first mixing of aluminum isopropoxide and an alkali source to obtain a mixture I; the molar ratio of the aluminum isopropoxide to the alkali source is 1:1 - 10; (2) bringing the mixture I into contact reaction with a raw material molecular sieve to obtain the modified molecular sieve; the temperature of the contact reaction is 50 - 100 °C, and the time is 10 - 50 h. The modified molecular sieve prepared by the technical solution provided by the present invention has a significantly decreased silicon-aluminum ratio, does not generate impurity phases, has a high crystallinity, and maintains good textural properties, and can be widely applied to the fields of gas adsorption separation and acid catalysis.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing crystalline aluminosilicate materials, and particularly to a modified molecular sieve, a preparation method thereof, and an application thereof. Background Art

[0002] Zeolites refer to crystalline microporous aluminosilicates. The framework of zeolites is constructed by corner-sharing TO4 (T = Si or Al) tetrahedra, forming periodic and highly stable one-dimensional to three-dimensional channels, with a unique porous structure and pore diameters usually less than 2 nm. In the framework of zeolites, each AlO4 tetrahedron gives the framework a negative charge, which is balanced by extra-framework cations (such as H + , Na + , K + , Ca 2+ , Ni 2+ , Co 2+ , Cu 2+ etc.) in the pore space or at the window positions. Molecular sieves with a lower silicon-aluminum ratio require more framework cations to balance the charge and have a greater ion exchange degree. The cations in the pore channels of molecular sieves are important factors affecting their catalytic or adsorption properties. Therefore, modulating the silicon-aluminum ratio of molecular sieves is of great significance in industry.

[0003] Many domestic and foreign literatures have reported methods for modulating the silicon-aluminum ratio of molecular sieves, which are divided into direct synthesis methods and post-synthesis methods. The direct synthesis method mainly reduces the silicon-aluminum ratio in the synthesis gel. However, changing the gel ratio easily generates impurity crystals. Taking molecular sieves with the FAU structure as an example, when synthesizing low-silicon-aluminum ratio X-type molecular sieves (LSX molecular sieves), gels with a lower silicon-aluminum ratio often generate impurity crystals of type A or type S. The post-synthesis method mainly proceeds by desilication and aluminum supplementation, but desilication often causes the collapse of the framework. For example, US5366720A discloses a method for reducing the silicon-aluminum ratio of X-type molecular sieves using sodium aluminate and sodium hydroxide solutions, but this method easily clogs the pore channels, resulting in a decrease in the specific surface area of the molecular sieve, and this method is limited to molecular sieves with the FAU structure.

[0004] Therefore, finding a synthesis method that can reduce the silicon-aluminum ratio of silicon-aluminum molecular sieves, while not generating impurity crystals and maintaining good crystallinity and textural properties, is of great significance for actual industrial production. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method of a modified molecular sieve that can reduce the silicon-aluminum ratio of the molecular sieve, while not generating impurity crystals and maintaining good crystallinity and textural properties.

[0006] To achieve the above purpose, the first aspect of the present invention provides a method for preparing a modified molecular sieve, the method comprising:

[0007] (1) In the presence of water, aluminum isopropoxide and an alkali source are mixed for the first time to obtain mixture I; the molar ratio of the aluminum isopropoxide to the alkali source is 1:1 - 10;

[0008] (2) The mixture I is contacted with the raw material molecular sieve for a reaction to obtain the modified molecular sieve; the temperature of the contact reaction is 50 - 100 °C, and the time is 10 - 50 h;

[0009] Control the reaction conditions of the method so that the silica-alumina ratio of the modified molecular sieve is 0.4 - 0.8 times that of the raw material molecular sieve;

[0010] The raw material molecular sieve is selected from at least one of Y-type, ZSM-11 type, and ZSM-5 type.

[0011] The second aspect of the present invention provides a modified molecular sieve prepared by the method described in the first aspect above.

[0012] The third aspect of the present invention provides the application of the modified molecular sieve described in the second aspect above in the fields of gas adsorption separation and / or acid catalysis.

[0013] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0014] (1) The technical solution provided by the present invention does not require the addition of a silicon source, has a simple preparation process, low cost, and good reproducibility.

[0015] (2) The technical solution provided by the present invention can be simultaneously applied to the modification of raw material molecular sieves of Y-type, ZSM-11 type, and ZSM-5 type, and has stronger universality.

[0016] (3) The modified molecular sieve prepared by the technical solution provided by the present invention does not generate heterophase, has high crystallinity, and maintains good texture properties, and can be widely applied in the fields of gas adsorption separation and acid catalysis. Description of the Drawings

[0017] Figure 1 is the XRD pattern of the modified molecular sieve prepared in Examples 1 to 4;

[0018] Figure 2 is the XRD pattern of the modified molecular sieve prepared in Example 5;

[0019] Figure 3 is the XRD pattern of the modified molecular sieve prepared in Example 6;

[0020] Figure 4 is the XRD pattern of the modified molecular sieve prepared in Comparative Example 1 and Comparative Example 2;

[0021] Figure 5 is the SEM image of the modified molecular sieve prepared in Example 3;

[0022] Figure 6 is the SEM image of the modified molecular sieve prepared in Example 5;

[0023] Figure 7 is the SEM image of the modified molecular sieve prepared in Example 6;

[0024] Figure 8 is the SEM image of the modified molecular sieve prepared in Comparative Example 1. Detailed Description of the Invention

[0025] The endpoints and any values disclosed herein in ranges are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of each range, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0026] In the present invention, the silica-alumina ratio of the molecular sieve refers to the molar ratio of silicon dioxide to aluminum oxide in the molecular sieve.

[0027] As described above, the first aspect of the present invention provides a method for preparing a modified molecular sieve, the method comprising:

[0028] (1) In the presence of water, aluminum isopropoxide and an alkali source are mixed for the first time to obtain a mixture I; the molar ratio of the aluminum isopropoxide to the alkali source is 1:1 - 10;

[0029] (2) The mixture I is contacted with a raw material molecular sieve for a reaction to obtain the modified molecular sieve; the temperature of the contact reaction is 50 - 100 °C, and the time is 10 - 50 h;

[0030] Control the reaction conditions of the method such that the silica-alumina ratio of the modified molecular sieve is 0.4 - 0.8 times that of the raw material molecular sieve;

[0031] The raw material molecular sieve is selected from at least one of Y-type, ZSM-11 type, and ZSM-5 type.

[0032] Preferably, control the reaction conditions of the method such that the silica-alumina ratio of the modified molecular sieve is 0.5 - 0.7 times that of the raw material molecular sieve, and more preferably 0.6 - 0.7 times.

[0033] Preferably, the relative crystallinity of the modified molecular sieve with respect to the raw material molecular sieve is 70-100%, preferably 80-100%. The technical solution provided by the present invention can reduce the silica-alumina ratio of the raw material molecular sieve without damaging the structure of the raw material molecular sieve.

[0034] More preferably, the raw material molecular sieve is of the Y type, and the relative crystallinity of the modified molecular sieve with respect to the raw material molecular sieve is 90-100%.

[0035] More preferably, the raw material molecular sieve is of the ZSM-11 type and / or the ZSM-5 type, and the relative crystallinity of the modified molecular sieve with respect to the raw material molecular sieve is 70-85%.

[0036] Preferably, in step (1), the molar ratio of the amounts of aluminum isopropoxide, the alkali source, and water is 1:1.5-9:60-120. The inventors of the present invention found in their research that using aluminum isopropoxide as the aluminum source for aluminum supplementation of the raw material molecular sieve can reduce the silica-alumina ratio of the raw material molecular sieve to a greater extent and will not block the pores of the prepared modified molecular sieve, ensuring that the modified molecular sieve has excellent textural properties.

[0037] Preferably, in step (1), the alkali source is selected from at least one of sodium hydroxide, sodium acetate, and sodium carbonate.

[0038] More preferably, the alkali source is a combination of sodium hydroxide and sodium acetate, and the molar ratio of the amounts of sodium hydroxide and sodium acetate is 3-5:1.

[0039] More preferably, the alkali source is a combination of sodium hydroxide and sodium carbonate, and the molar ratio of the amounts of sodium hydroxide and sodium carbonate is 3-5:1.

[0040] According to a preferred specific embodiment, the raw material molecular sieve is of the Y type, the molar ratio of the amounts of aluminum isopropoxide and the alkali source is 1:4-7, the temperature of the contact reaction is 70-90 °C, and the time is 20-40 h. The inventors of the present invention found in their research that under these preferred conditions, the modified molecular sieve obtained by the present invention has a lower silica-alumina ratio and more excellent textural properties.

[0041] According to another preferred specific embodiment, the raw material molecular sieve is of the ZSM-11 type and / or the ZSM-5 type, the molar ratio of the amounts of aluminum isopropoxide and the alkali source is 1:1.5-3, the temperature of the contact reaction is 70-90 °C, and the time is 20-40 h. The inventors of the present invention found in their research that under these preferred conditions, the modified molecular sieve obtained by the present invention has a lower silica-alumina ratio and more excellent textural properties.

[0042] The present invention has no special restrictions on the conditions of the first mixing, as long as the components in the system can be mixed evenly. An exemplary preferred specific implementation manner is provided hereinafter in the present invention, and those skilled in the art should not understand it as a limitation to the present invention.

[0043] Preferably, the method in step (2) further includes: after contacting the mixture I with the raw material molecular sieve, stirring and treating at 15 - 30 °C for 0.2 - 0.8 h, and then introducing the obtained product into a reaction kettle, and performing the operation of the contact reaction under a static state to obtain the modified molecular sieve.

[0044] The reaction time of the contact reaction described in the present invention refers to the reaction time under a static state, and does not include the time of the stirring treatment.

[0045] Preferably, in step (2), the mass ratio of the raw material molecular sieve to the mixture I is 1:5 - 8, and more preferably 1:6 - 7.

[0046] Preferably, the method in step (2) further includes: sequentially performing acid treatment and drying treatment on the product obtained after the contact reaction to obtain the modified molecular sieve.

[0047] Preferably, the pH value of the acid treatment is 3 - 5.5.

[0048] Preferably, the acid substance used for the acid treatment is selected from at least one of hydrochloric acid, sulfuric acid, hydrochloride, and sulfate.

[0049] As described above, the second aspect of the present invention provides a modified molecular sieve prepared by the method described in the first aspect above.

[0050] As described above, the third aspect of the present invention provides the application of the modified molecular sieve described in the second aspect above in the fields of gas adsorption separation and / or acid catalysis.

[0051] The present invention will be described in detail below through examples. In the following examples, unless otherwise specified, the raw materials used are commercially available products. In the following examples, the room temperature all represents 25 ± 2 °C, and the pH value being neutral means the pH value is 7.0 ± 0.5.

[0052] Aluminum isopropoxide: C9H 21 AlO3, with a purity of 98 wt%;

[0053] Sodium hydroxide: NaOH, with a purity of 96 wt%;

[0054] Sodium acetate trihydrate: CH3COONa·3H2O, with a purity of 99.88 wt%;

[0055] Sodium carbonate: Na2CO3, with a purity of 99.8 wt%;

[0056] X-type raw molecular sieve: purchased from Zhuoran Environmental Protection Technology Co., Ltd.;

[0057] Y-type raw molecular sieve: purchased from Tianjin Yuanli Chemical Co., Ltd.;

[0058] ZSM-11 type raw molecular sieve: purchased from Shandong Hefa Environmental Protection Technology Co., Ltd.;

[0059] ZSM-5 type raw molecular sieve: purchased from Nanfen Experimental Reagent Distribution Company.

[0060] Example 1

[0061] (1) Under stirring conditions, aluminum isopropoxide and an alkali source were successively dissolved in water to obtain mixture I;

[0062] The amount of aluminum isopropoxide used was 0.016 mol, the alkali source was sodium hydroxide, and the molar ratio of the amounts of aluminum isopropoxide, alkali source, and water used was 1:6.06:90.83;

[0063] (2) The raw molecular sieve was added to mixture I, and stirring was continued at room temperature and 400 rpm for 0.5 h. Then, the obtained intermediate product was loaded into a 200 mL stainless steel autoclave and left standing at 80 °C for a contact reaction for 30 h to obtain mixture II;

[0064] The raw molecular sieve was of the Y type and the amount used was 5 g;

[0065] (3) Mixture II was subjected to solid-liquid separation. The solid product was washed with distilled water until the pH value was neutral, and then dried at 100 °C for 12 h. The dried product was added to a 200 mL hydrochloric acid solution with a pH value of 3 - 5.5, and stirred at room temperature and 400 rpm for 0.5 h; after pickling, filtration and washing were carried out in sequence, and then dried at 120 °C for 12 h to obtain the modified molecular sieve.

[0066] Examples 2 - 6 were carried out using a process similar to that of Example 1. The difference was that the condition parameters used were different, as specifically listed in Table 1;

[0067] The modified molecular sieve was prepared.

[0068] Example 7

[0069] A process similar to that of Example 1 was used. The difference was that the amount of the alkali source was kept unchanged, the type of the alkali source was adjusted, and a combination of sodium hydroxide and sodium carbonate with a molar ratio of 4:1 was used as the alkali source, and the rest remained unchanged;

[0070] The modified molecular sieve was prepared.

[0071] Example 8

[0072] The process similar to that in Example 1 was adopted, except that the temperature of the contact reaction was adjusted from 80 °C to 50 °C, and the rest remained unchanged;

[0073] A modified molecular sieve was prepared.

[0074] Example 9

[0075] The process similar to that in Example 1 was adopted, except that the amounts of aluminum isopropoxide and water were kept unchanged, and the amount of the base source sodium hydroxide was adjusted so that the molar ratio of aluminum isopropoxide, base source, and water was 1:9:90.83; the rest remained unchanged;

[0076] A modified molecular sieve was prepared.

[0077] For Comparative Examples 1-2, the process similar to that in Example 1 was adopted, except that the condition parameters used were different, as specifically listed in Table 1;

[0078] A modified molecular sieve was prepared.

[0079] Comparative Example 3

[0080] The process similar to that in Example 1 was adopted, except that aluminum isopropoxide was replaced with an equimolar amount of sodium metaaluminate, and the rest remained unchanged;

[0081] A modified molecular sieve was prepared.

[0082] Comparative Example 4

[0083] The process similar to that in Example 1 was adopted, except that aluminum isopropoxide was replaced with an equimolar amount of aluminum sulfate, and the rest remained unchanged;

[0084] A modified molecular sieve was prepared.

[0085] Table 1

[0086]

[0087] Test Example 1

[0088] The silica-alumina ratios of the X- and Y-type raw molecular sieves and the modified molecular sieves prepared by this type were calculated by the Breck-Flangigen empirical formula (see: Liu Xiyao, Analysis and Testing Characterization of Industrial Catalysts [M]. Beijing, China Petrochemical Press, 1993: 172-174):

[0089] SiO2 / Al2O3 = (25.858 - a0) / (a0 - 24.191), where a0 For determining the unit cell parameters of a sample by X-ray diffraction method.

[0090] The silica-aluminum ratio of the raw material molecular sieves of ZSM-11 type and ZSM-5 type and the modified molecular sieves prepared by using this type is determined by X-ray fluorescence (XRF) spectrometry.

[0091] Method for determining and calculating the relative crystallinity of the modified molecular sieve: After calculating the peak areas of the characteristic peaks in the XRD pattern of the molecular sieve, calculate the ratio of the sum of the characteristic peak areas of the raw material molecular sieve sample and the modified molecular sieve sample according to formula (I), so as to calculate the relative crystallinity of the modified molecular sieve sample.

[0092] X i = X R (∑A i / ∑A R ) Formula (I)

[0093] X R : Crystallinity of the raw material molecular sieve (100%); ∑A i : Sum of the peak areas of the characteristic crystal plane diffraction peaks of the modified molecular sieve sample; ∑A R : Sum of the corresponding characteristic peak areas of the raw material molecular sieve sample.

[0094] Table 2

[0095]

[0096] Test Example 2

[0097] Test method for the total specific surface area (S BET ), micropore specific surface area (S MIC ), mesopore specific surface area (S MES ), total pore volume (V POR ), and micropore pore volume (V MIC ) of the raw material molecular sieve or the modified molecular sieve:

[0098] Perform a low-temperature nitrogen physical adsorption and desorption experiment on the prepared zeolite catalyst by using a Micromeritics TriSTAR 3020 type physical adsorption instrument in the United States to obtain the physical texture property data of the molecular sieve. First, estimate the required sample mass (the estimation method is that the product of the estimated specific surface area and the sample mass is between 40 and 120), slightly grind the sample to make it powdery, dry it at 120 °C for 4 h, and then load it into a quartz tube. Then, perform dehydration and impurity removal treatment in a vacuum (about 1.33 Pa) environment at 350 °C for more than 8 hours and set aside. The specific surface area of the sample is calculated by the BET method, the pore volume is calculated by the t-plot method, and the pore size distribution is calculated by the BJH method of the desorption curve.

[0099] Table 3

[0100] <![CDATA[S BET (m 2 g -1 )]]> <![CDATA[S MIC (m 2 g -1 )]]> <![CDATA[S MES (m 2 g -1 )]]> <![CDATA[V POR (cm 3 g -1 )]]> <![CDATA[V MIC (cm 3 g -1 )]]> Y-type raw molecular sieve 704 671 33 0.36 0.33 ZSM-11 type raw molecular sieve 384 268 116 0.39 0.13 ZSM-5 type raw molecular sieve 249 212 37 0.13 0.10 Example 1 (Y-type) 551 536 15 0.30 0.24 Example 2 (Y-type) 639 596 43 0.35 0.29 Example 3 (Y-type) 612 574 38 0.33 0.28 Example 4 (Y-type) 709 666 43 0.37 0.33 Example 5 (ZSM-11 type) 335 227 108 0.54 0.11 Example 6 (ZSM-5 type) 251 149 102 0.27 0.07 Example 7 (Y-type) 601 558 43 0.31 0.27 Example 8 (Y-type) 591 548 43 0.30 0.27 Example 9 (Y-type) 581 527 54 0.32 0.26

[0101] Figure 1 are the XRD patterns of the modified molecular sieves prepared in Examples 1 to 4 and the Y-type raw material molecular sieves. Figure 2 are the XRD patterns of the modified molecular sieves prepared in Example 5 and the ZSM-11 type raw material molecular sieves. Figure 3 are the XRD patterns of the modified molecular sieves prepared in Example 6 and the ZSM-5 type raw material molecular sieves. Figure 4 are the XRD patterns of the modified molecular sieves prepared in Comparative Example 1 and Comparative Example 2 and the X-type raw material molecular sieves. It can be seen from Figures 1 to 4 that after aluminating the molecular sieve with the solution configured in the present invention, the silica-alumina ratio of the molecular sieve can be reduced, and the crystal structure of the molecular sieve still remains relatively complete, the molecular sieve does not show obvious collapse, and no impurity crystal peaks appear.

[0102] Figure 5 is the SEM pattern of the modified molecular sieve prepared in Example 3 of the present invention. It can be seen from Figure 5 that the particle sizes of the molecular sieves are uniform, maintained at 200 - 500 nm, the surface is smooth, still maintaining the morphology of X-type molecular sieves, and no impurity crystals appear.

[0103] Figure 6 is the SEM pattern of the modified molecular sieve prepared in Example 5 of the present invention. It can be seen from Figure 6 that the particle sizes of the molecular sieves are uniform, still maintaining the morphological characteristics of ZSM-11, and no impurity crystals appear.

[0104] Figure 7 is the SEM pattern of the modified molecular sieve prepared in Example 6 of the present invention. It can be seen from Figure 7 that the molecular sieve is in the typical flaky ZSM-5 morphology, and no impurity crystals appear.

[0105] Figure 8 is the SEM pattern of the modified molecular sieve prepared in Comparative Example 1 of the present invention. It can be seen from Figure 8 that the molecular sieve presents a typical octahedral structure, with uniform size, and no impurity crystals appear.

[0106] From the above results, it can be seen that for the modified molecular sieve prepared by adopting the technical solution provided by the present invention, its silica-alumina ratio is significantly reduced, and at the same time, no impurity crystals are generated. It not only has excellent crystallinity, but also the textural properties are well maintained, having good economic value and broad market application prospects.

[0107] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited thereto. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solutions of the present invention, including the combination of each technical feature in any other suitable manner. These simple modifications and combinations should also be regarded as the content disclosed by the present invention and fall within the protection scope of the present invention.

Claims

1. A method for preparing a modified molecular sieve, characterized in that, The method includes: (1) First, mixing aluminum isopropoxide with an alkali source in the presence of water to obtain mixture I; (2) Contacting the mixture I with the raw material molecular sieve to obtain the modified molecular sieve; the temperature of the contact reaction is 70 - 90 °C; the time of the contact reaction is 20 - 40 h; The alkali source is selected from at least one of sodium hydroxide, sodium acetate, and sodium carbonate; Controlling the reaction conditions of the method such that the silica-alumina ratio of the modified molecular sieve is 0.4 - 0.7 times that of the raw material molecular sieve; the relative crystallinity of the modified molecular sieve with respect to the raw material molecular sieve is 70 - 100%; The raw material molecular sieve is of Y type, and the molar ratio of the amounts of aluminum isopropoxide to the alkali source is 1:4 - 7; Alternatively, the raw material molecular sieve is of ZSM-11 type and / or ZSM-5 type, and the molar ratio of the amounts of aluminum isopropoxide to the alkali source is 1:1.5 - 3.

2. The method according to claim 1, wherein The relative crystallinity of the modified molecular sieve with respect to the raw material molecular sieve is 80 - 100%.

3. The method according to claim 1, wherein, In step (1), the molar ratio of the amounts of aluminum isopropoxide, the alkali source, and water is 1:1.5 - 9:60 - 120.

4. The method according to claim 1, wherein The alkali source is a combination of sodium hydroxide and sodium acetate, and the molar ratio of the amounts of sodium hydroxide and sodium acetate is 3 - 5:

1.

5. The method according to claim 1, wherein The alkali source is a combination of sodium hydroxide and sodium carbonate, and the molar ratio of the amounts of sodium hydroxide and sodium carbonate is 3 - 5:

1.

6. The method according to claim 1, wherein, In step (2), the mass ratio of the amounts of the raw material molecular sieve to the mixture I is 1:5 - 8.

7. The method according to claim 1, wherein The method in step (2) further includes: sequentially performing acid treatment and drying treatment on the product obtained after the contact reaction to obtain the modified molecular sieve.

8. The method according to claim 7, wherein, The pH value of the acid treatment is 3 - 5.

5.

9. A modified molecular sieve prepared by the method according to any one of claims 1 - 8.

10. Use of the modified molecular sieve according to claim 9 in the fields of gas adsorption separation and / or acid catalysis.

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