Low-cost preparation method of ZSM-35 molecular sieve

Abstract

The invention discloses a low-cost preparation method of a ZSM-35 molecular sieve. Belongs to the field of molecular sieve synthesis. Comprising the following steps: mixing an aluminum source, a silicon source, a template agent, potassium hydroxide, sodium hydroxide and water at room temperature to obtain a mixed solution, putting the mixed solution into a closed container, crystallizing, centrifuging, washing, drying and roasting to obtain the ZSM-35 molecular sieve, according to the method, a silicon source and an aluminum source are subjected to a crystallization reaction in an alkaline environment, and the ZSM-35 molecular sieve with good crystal crystallinity is prepared at low cost by reducing parameters such as process temperature in different stages through a specific feeding sequence. The preparation process of the traditional ZSM-35 molecular sieve is simplified, the production efficiency is improved, the energy is saved, and the cost is reduced.

Description

Technical Field

[0001] The present application relates to a low-cost preparation method of ZSM-35 molecular sieve, belonging to the field of molecular sieve synthesis. Background Art

[0002] ZSM-35 molecular sieve (also known as ferrier zeolite) is a FER type microporous material with unique two-dimensional cross-pores. Channel and 8-membered ring The intersection of channels 1-3 forms a unique two-dimensional pore system, which provides a good foundation for the molecular sieve in shape-selective catalytic reactions. Due to its unique pore structure, excellent acid properties and good stability, it is widely used in new energy, petrochemicals, adsorption separation, green environmental protection and other fields. The silicon-aluminum ratio of ZSM-35 molecular sieve is adjustable. By adjusting the silicon-aluminum ratio, the acidity and hydrothermal stability of the molecular sieve can be changed to meet different industrial needs.

[0003] In the process of synthesizing ZSM-35 molecular sieve, the optimization of synthesis process conditions is crucial to obtain high-performance molecular sieve catalysts. The synthesis method, feeding sequence, control of silicon-aluminum ratio, crystallization time and temperature are all key factors affecting the quality of molecular sieves. Among them, hydrothermal synthesis is currently the main method for synthesizing ZSM-35 molecular sieves. Under high temperature and high pressure conditions, a crystallization reaction is carried out using silicon source and aluminum source in an alkaline environment to form a molecular sieve with a specific structure, and the crystallization time and temperature are directly related to the crystallinity and phase purity of the molecular sieve.

[0004] In the past few decades, researchers have conducted extensive research on the synthesis process of ZSM-35 molecular sieves. Studies have shown that the choice of synthesis method has a significant effect on the morphology and crystal phase of the molecular sieve. Hydrothermal synthesis and non-aqueous synthesis are two common synthesis methods. Hydrothermal synthesis can usually obtain molecular sieves with higher crystallinity, while non-aqueous synthesis can obtain larger crystals in some cases. The selection of templates is also an important factor in the synthesis of molecular sieves. Different templates will lead to differences in the pore structure and external morphology of the molecular sieve. The adjustment of the silicon-aluminum ratio can be achieved by changing the feed ratio of the silicon source and the aluminum source. Different silicon-aluminum ratios will affect the acidity and hydrothermal stability of the molecular sieve. The control of crystallization time and temperature is crucial to the crystallinity and phase purity of the molecular sieve. Appropriate crystallization conditions can promote the growth of molecular sieve crystals and improve their catalytic performance.

[0005] Patent CN113998708A discloses a method for synthesizing high-crystallinity ZSM-35 molecular sieve without amine, wherein a solution containing an aluminum source and a seed crystal is aged at 40-99°C to obtain a mixture A. Patent CN109502606A discloses a method for preparing a ZSM-35 molecular sieve, wherein the aging conditions in the preferred scheme are: aging at 30-70°C for 6-24h. Patent CN112537780 A discloses a method for producing isobutylene from a ferrierite molecular sieve and a skeletal isomerization of n-butene, wherein a silicon source, an aluminum source, a molecular sieve template, water and an alkali source are added to a reactor to perform a first crystallization reaction; after the first crystallization reaction is completed, the temperature is lowered, and then an aluminum source is added and a mesoporous template is added to perform a second crystallization reaction; after the second crystallization reaction is completed, the ferrierite molecular sieve raw powder is obtained through cooling, filtering, drying, ion exchange and calcination. In the above-mentioned ZSM-35 molecular sieve preparation method, the initial reaction temperature needs to be higher than room temperature, or multiple steps of crystallization reaction are required, which has high process requirements, complicated experimental operation, high production cost, and is not conducive to industrial operation. Summary of the invention

[0006] The present invention adopts a hydrothermal synthesis strategy, by adjusting the feeding order of silicon source, aluminum source, template, alkali solution and water, and adjusting the process parameters at the same time, the crystallinity, SAR (molecular sieve silicon-aluminum ratio), product yield and specific surface area of ​​ZSM-35 molecular sieve catalyst are improved. In addition, we have also introduced two alkali metal ions, and the synergistic effect of the two and the template is utilized to expand the interval range in which ZSM-35 molecular sieve can be synthesized, and the catalyst activity can be effectively improved. By selecting suitable raw materials and changing the traditional process flow and parameters, not only can the utilization rate of raw materials be improved and the production cost of molecular sieves be reduced, but also it is conducive to reducing the pollution to the environment, and has great social effects and economic value.

[0007] The object of the present invention is to provide a low-cost preparation method of ZSM-35 molecular sieve.

[0008] Another object of the present invention is to provide a low-cost preparation method of ZSM-35 molecular sieve and apply the synthesized ZSM-35 molecular sieve in the field of new energy.

[0009] According to one aspect of the present application, a low-cost preparation method of ZSM-35 molecular sieve is provided, comprising the following steps:

[0010] At room temperature, an aluminum source, a silicon source, a template, potassium hydroxide, sodium hydroxide and water are mixed to obtain a mixed solution, and the mixed solution is placed in a sealed container, crystallized, centrifuged, washed, dried and calcined to obtain the ZSM-35 molecular sieve;

[0011] Optionally, the following steps are included:

[0012] (1) mixing sodium hydroxide, potassium hydroxide and water to obtain alkali solution;

[0013] (2) treating the silicon source and / or aluminum source with an alkali solution, i.e., dissolving the silicon source and / or aluminum source in the alkali solution and stirring until a transparent solution is obtained;

[0014] (3) slowly dropping the silicon source into the aluminum source or slowly dropping the aluminum source into the silicon source;

[0015] (4) The template can be added to the silicon source and / or aluminum source before the silicon source and the aluminum source are mixed, or added after the silicon source and the aluminum source are mixed.

[0016] The molar ratio of the aluminum source, silicon source, template, potassium hydroxide, sodium hydroxide and water is Al 2 O 3 :SiO 2 :R:K 2 O:Na 2 O:H 2 O=1:30~120:5~40:1~3:1~5:500~1000.

[0017] The aluminum source is selected from at least one of aluminum isopropoxide, aluminum sol, aluminum sulfate, sodium aluminate, aluminum hydroxide, and pseudo-boehmite;

[0018] The silicon source is selected from at least one of tetraethyl orthosilicate, white carbon black, silica sol (25%wt-40%wt), and fumed silica;

[0019] The template agent is selected from at least one of ethylenediamine, cyclohexylamine, n-butylamine, pyrrolidine, hexamethyleneimine, and 1,4-cyclohexanediamine.

[0020] The alkalinity of the mixed solution is OH - / SiO 2 It is 0.25~0.5.

[0021] Optionally, the alkalinity of the mixed solution is OH - / SiO 2 It can be any value among 0.25, 0.3, 0.35, 0.4, 0.45, 0.5, or any range between any two of them.

[0022] Optionally, the molar ratio of silicon source to aluminum source is SiO 2 / Al 2 O 3 30~120:1;

[0023] Optionally, the molar ratio of template to silicon source R / SiO 2 0.16~1.6:1

[0024] The closed container is a reaction kettle.

[0025] The crystallization is dynamic crystallization or static crystallization;

[0026] Optionally, the crystallization is first static crystallization and then dynamic crystallization.

[0027] The crystallization temperature is 140-220°C;

[0028] Optionally, the crystallization temperature is any value of 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, or a range between any two of them.

[0029] The crystallization time is 48 to 96 hours;

[0030] Optionally, the crystallization time is any value among 48h, 60h, 72h, 84h, 96h, or a range between any two of them.

[0031] The stirring speed of the crystallization is 20-50 rpm.

[0032] Optionally, the stirring speed of the crystallization is any value among 20 rpm, 30 rpm, 40 rpm, 50 rpm, or any range between the two.

[0033] The washing is performed with deionized water.

[0034] The drying temperature is 100-120°C;

[0035] Optionally, the drying temperature is any value among 100° C., 110° C., 120° C., or any range between the two.

[0036] The calcination temperature is 450-550°C;

[0037] Optionally, the calcination temperature is any value among 450° C., 500° C., 550° C., or any range between the two.

[0038] The calcination time is 3 to 6 hours.

[0039] Optionally, the calcination time is any value among 3h, 4h, 5h, 6h, or a range between any two of them.

[0040] According to another aspect of the present application, a ZSM-35 molecular sieve prepared by the above-mentioned preparation method is provided.

[0041] According to another aspect of the present application, an application of the above-mentioned ZSM-35 molecular sieve is provided, which can be widely used in the fields of petrochemical industry, adsorption separation, green environmental protection, etc. The ZSM-35 molecular sieve exhibits excellent catalytic performance in the processes of isomerization, polymerization, aromatization and cracking, such as the skeletal isomerization reaction of straight-chain olefins, the selective catalytic reduction reaction of NOx, the carbonylation reaction of dimethyl ether, the alkylation reaction of aromatics, and the reaction of naphtha upgrading. Among them, the skeletal isomerization reaction of n-butene, especially the combination of the isomerization process and the process of synthesizing MTBE, can not only increase the production of MTBE with high economic value, but also greatly improve the utilization rate of n-butene in cheap carbon four. This method is currently the most promising method for increasing the production of isobutylene using ZSM-35 molecular sieve catalyst.

[0042] The present invention is carried out at room temperature from preparing alkali solution to feeding materials in a fixed ratio and a specific order. Since the raw materials selected by the present invention are all common chemicals with low prices, the early process temperature is adjusted to room temperature, and there is no need to consume energy to increase the process temperature, which not only reduces the production cost but also increases the safety factor, and is conducive to industrial operation. The synthesized ZSM-35 molecular sieve crystal form is a thin sheet stacking shape, has the advantages of small particle size and high crystallinity, and can be used in reactions such as isomerization, aromatization, polymerization and cracking, and has broad application prospects.

[0043] The beneficial effects of this application include:

[0044] (1) Compared with other existing ZSM-35 synthesis methods, the raw materials used are cheap, no seed crystals are required, and the initial process temperature is directly carried out at room temperature, without consuming more energy, which is in line with the concept of green chemistry;

[0045] (2) The preparation method saves the amount of template, reduces the recycling pressure, reduces environmental pollution, reduces the cost of raw materials, and conforms to the concept of green environmental protection;

[0046] (3) The preparation conditions of molecular sieves are simple and the energy consumption is low, which is conducive to industrial production;

[0047] (4) The synthesized molecular sieve has complete crystal form and small grains, which is beneficial to enhancing the mass transfer capacity of the molecular sieve and improving the activity and life of the catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the XRD spectrum of the ZSM-35 molecular sieve raw powder obtained in Example 1.

[0049] Figure 2 This is a SEM image of the ZSM-35 molecular sieve raw powder obtained in Example 1, with a scale of 10 microns.

[0050] Figure 3This is the SEM image of the ZSM-35 molecular sieve raw powder obtained in Example 2, with a scale of 10 microns.

[0051] Figure 4 This is the XRD spectrum of the ZSM-35 molecular sieve raw powder obtained in Comparative Example 1.

[0052] Figure 5 This is the SEM spectrum of the ZSM-35 molecular sieve raw powder obtained in Comparative Example 2, with a scale of 10 microns. DETAILED DESCRIPTION

[0053] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0054] Unless otherwise specified, the raw materials in the examples of this application were purchased through commercial channels.

[0055] Example 1

[0056] Take 1.10g of sodium hydroxide and 0.85g of potassium hydroxide and dissolve them in 22.10g of deionized water, and stir evenly at room temperature. Add 1.00g of sodium aluminate and stir until a transparent solution is obtained at room temperature. Add 7.40g of cyclohexylamine and continue to add 36.48g of silica sol (25% wt), and stir vigorously for 2h at room temperature. Transfer the mixed solution to the para-polyphenylene (PPL) liner, then load it into the reactor, seal it, move it into the oven, and crystallize it by autogenous pressure. First, statically crystallize it at room temperature for 3h, heat it to 170℃, and dynamically crystallize it for 72h. The crystallized product is centrifuged, washed, dried at 100℃, and calcined at 550℃ to obtain ZSM-35 molecular sieve raw powder.

[0057] Example 2

[0058] Take 1.36g of sodium hydroxide and 0.84g of potassium hydroxide and dissolve them in 25.02g of deionized water, and stir them evenly at room temperature. Add 2.20g of aluminum sol and stir until a transparent solution is obtained at room temperature. Add 7.50g of cyclohexylamine and continue to add 36.48g of silica sol (25% wt), and stir vigorously for 2h at room temperature. Transfer the mixed solution to the para-polyphenylene (PPL) liner, then load it into the reactor, seal it, move it into the oven, and crystallize it by autogenous pressure. First, statically crystallize it at room temperature for 3h, heat it to 170℃, and dynamically crystallize it for 72h. The crystallized product is centrifuged, washed, dried at 100℃, and calcined at 550℃ to obtain ZSM-35 molecular sieve raw powder.

[0059] Comparative Example 1

[0060] Take 1.10g of sodium hydroxide and 0.85g of potassium hydroxide and dissolve them in 22.10g of deionized water, and stir evenly at 40°C. Add 1.00g of sodium aluminate and stir at 40°C until a transparent solution. Add 7.40g of cyclohexylamine and continue to add 36.48g of silica sol (25%wt), and stir vigorously at 40°C for 2h. Transfer the mixed solution to the para-polyphenylene (PPL) liner, then load it into the reactor, seal it, move it into the oven, and crystallize it by autogenous pressure. First, statically crystallize it at 40°C for 3h, heat it to 170°C, and dynamically crystallize it for 72h. The crystallized product is centrifuged, washed, dried at 100°C, and calcined at 550°C to obtain ZSM-35 molecular sieve raw powder.

[0061] Comparative Example 2

[0062] Take 1.36g of sodium hydroxide and 0.84g of potassium hydroxide and dissolve them in 52.02g of deionized water, and stir them evenly at 40°C. Add 36.50g of silica sol (25% wt) and stir at 70°C until a transparent solution. Add 7.50g of cyclohexylamine and continue to add 2.14g of aluminum sol, and stir vigorously at 40°C for 2h. Transfer the mixed solution to the para-polyphenylene (PPL) liner, then load it into the reactor, seal it, move it into the oven, and crystallize it by autogenous pressure. First, statically crystallize it at 40°C for 3h, heat it to 170°C, and dynamically crystallize it for 72h. The crystallized product is centrifuged, washed, dried at 100°C, and calcined at 550°C to obtain ZSM-35 molecular sieve raw powder.

[0063] Figure 1 This is the XRD spectrum of the ZSM-35 molecular sieve raw powder obtained in Example 1.

[0064] Figure 2 This is a SEM image of the ZSM-35 molecular sieve raw powder obtained in Example 1, with a scale of 10 microns.

[0065] Figure 3 This is the SEM image of the ZSM-35 molecular sieve raw powder obtained in Example 2, with a scale of 10 microns.

[0066] Figure 4 This is the XRD spectrum of the ZSM-35 molecular sieve raw powder obtained in Comparative Example 1.

[0067] Figure 5 This is the SEM spectrum of the ZSM-35 molecular sieve raw powder obtained in Comparative Example 2, with a scale of 10 microns.

[0068] from Figure 1 and Figure 4It can be seen that the ZSM-35 molecular sieve raw powder obtained in Example 1 has a very high purity, and there are no impurity peaks in the XRD diagram, while there are some impurity peaks in the XRD diagram of Comparative Example 1, indicating that the ZSM-35 molecular sieve raw powder obtained is impure.

[0069] from Figure 2 , Figure 3 and Figure 5 It can be seen that the ZSM-35 molecular sieve powder obtained in Examples 1 and 2 has a good morphology. Thin sheet-like crystals and no impurity crystals can be clearly seen under the electron microscope. However, the morphology of the ZSM-35 molecular sieve powder obtained in Comparative Example 2 is not good. Irregular impurity crystals can be clearly observed under the electron microscope.

[0070] Example 3

[0071] The molecular sieve powder obtained in Example 1 was pressed into tablets, then ground and sieved with a sieve, and 0.5 g of the 40-60 mesh sieved sample was taken and loaded into a fixed bed reactor. A normal pressure micro fixed bed reactor was used to carry out the isomerization reaction of n-butene, using n-butene as the raw material, nitrogen as the carrier gas, hydrogen as the fuel gas, and an FID detector. The reaction temperature was 400°C for 2 hours under nitrogen, and the space velocity was 5-8 hours. -1 . Set the furnace heating program according to the reaction conditions, start sample activation, adjust the heating belt temperature to 150℃, observe the furnace temperature change and tail gas output every half an hour to ensure that it is the required temperature. Turn on the gas chromatograph, wait for it to be fully turned on, turn on the workstation, and select the required method. Adjust the injection temperature according to the reaction conditions, run the gas chromatography program, click Run Control, and run the sequence. After the reaction starts, isobutylene can be clearly observed in the gas chromatograph.

[0072] The technical solution of the present application can still achieve similar technical effects as those of Examples 1, 2, and 3 after being scaled up to the kilogram level.

[0073] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A low-cost preparation method of ZSM-35 molecular sieve, characterized in that: The following steps are involved: At room temperature, an aluminum source, a silicon source, a template, potassium hydroxide, sodium hydroxide and water are mixed to obtain a mixed solution, and the mixed solution is placed in a sealed container, crystallized, centrifuged, washed, dried and calcined to obtain the ZSM-35 molecular sieve; The molar ratio of the aluminum source, silicon source, template, potassium hydroxide, sodium hydroxide and water is Al2O3:SiO2:CHA:K2O:Na2O:H2O=1:30-120:5-40:1-3:1-5:500-1000.

2. The preparation method according to claim 1, characterized in that: The aluminum source is selected from at least one of aluminum isopropoxide, aluminum sol, aluminum sulfate, sodium aluminate, aluminum hydroxide, and pseudo-boehmite; The silicon source is selected from at least one of tetraethyl orthosilicate, white carbon black, silica sol, and fumed silica; The template agent is selected from at least one of ethylenediamine, cyclohexylamine, n-butylamine, pyrrolidine, hexamethyleneimine, and 1,4-cyclohexanediamine.

3. The preparation method according to claim 1, characterized in that: The alkalinity of the mixed solution is OH - / SiO2 is 0.25~0.

5.

4. The preparation method according to claim 1, characterized in that: The crystallization is dynamic crystallization or static crystallization; The crystallization temperature is 140-220°C; The crystallization time is 48 to 96 hours; The stirring speed of the crystallization is 20-50 rpm.

5. The preparation method according to claim 1, characterized in that: The drying temperature is 100-120°C; The calcination temperature is 450-550°C; The calcination time is 3 to 6 hours.

6. A ZSM-35 molecular sieve prepared by the preparation method according to any one of claims 1 to 5.

7. An application of the ZSM-35 molecular sieve according to claim 6, characterized in that: Used for skeletal isomerization of linear olefins.

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