A polymer-modified ETS molecular sieve, its preparation method and application

Abstract

This invention discloses a polymer-modified ETS molecular sieve, its preparation method, and its applications, belonging to the field of adsorbent technology. The preparation method of the polymer-modified ETS molecular sieve includes the following steps: impregnating the ETS molecular sieve with a polyethylene glycol solution, performing solid-liquid separation, and drying the resulting solid to obtain the polymer-modified ETS molecular sieve. This invention uses a specific polymer to impregnate and modify the ETS molecular sieve, successfully preparing a polymer-modified ETS molecular sieve. The preparation method is simple, controllable, and low-cost. The prepared modified molecular sieve exhibits extremely low CH4 adsorption and a high N2 / CH4 separation ratio when separating N2 and CH4 mixed gases. The molecular sieve prepared by this invention can be used for purifying methane from coalbed methane, oilfield gas, or landfill gas.

Description

Technical Field

[0001] This invention belongs to the field of adsorption technology, and relates to a polymer-modified ETS molecular sieve, its preparation method, and its application. Background Technology

[0002] In recent years, to accelerate the development and application of tight oil and gas reservoirs, shale gas, and low-quality natural gas, natural gas denitrification processes have received increasing attention. Currently, industrial natural gas denitrification processes include solvent absorption, deep freezing, pressure swing adsorption (PSA), and membrane separation. Solvent absorption processes have been rarely used industrially in recent years due to disadvantages such as difficulty in solvent selection, large circulation volumes, and the need for refrigeration systems. Deep freezing processes are complex and costly, making them more suitable for large-scale denitrification units processing high-pressure natural gas with high nitrogen content. Pressure swing adsorption (PSA) utilizes the characteristic that the adsorption capacity (adsorption amount) of different components in natural gas varies significantly with pressure to achieve separation. As an ambient temperature gas separation and purification technology, PSA has advantages such as simple process, low energy consumption, strong adaptability, convenient operation, and low cost. It is mainly used for the removal and recovery of CO2 from natural gas, coalbed methane, ammonia synthesis shift gas, and kiln gas.

[0003] Developed by Engelhard Corporation in the United States, molecular gate pressure swing adsorption (PSA) has become a novel and advanced process for removing nitrogen from natural gas. Molecular gates utilize different types of molecular sieves as adsorbents. These sieves can be prepared according to different process requirements, achieving a precision within 0.1 Å, thus enabling precise gas separation based on pore size. Taking natural gas containing CO2 and N2 as an example, the diameters of CO2, N2, and CH4 molecules are 3.4 Å, 3.6 Å, and 3.8 Å, respectively. To separate these three gases, the adsorption system uses an adsorbent with a diameter of 3.7 Å. This adsorbent allows N2 and CO2 to pass through the pores and be adsorbed, while CH4 is excluded and flows directly through the fixed bed of adsorbent.

[0004] ETS (Engelhard Titano Silicate) is a type of mixed oxide containing silicon tetrahedra and titanium octahedrons. Its pore size can be reduced through ion exchange, hence it is also known as shrinkable titanium-silicon molecular sieves. Due to its shrinkable pore size, ETS molecular sieves can improve the static adsorption separation ratio and modify kinetic separation performance, providing a new option for the separation of CH4 and N2. However, how to improve the pore size of ETS molecular sieves to increase the separation ratio of CH4 and N2 has not yet been reported in the existing technology.

[0005] Chinese patent CN 110773122 A discloses a method for preparing ether-containing polymer-modified molecular sieves. The specific steps are as follows: The molecular sieve is impregnated with an ether-containing polymer solution, followed by solid-liquid separation and solid drying to obtain the ether-containing polymer-modified molecular sieve. This invention successfully prepares organically modified molecular sieves through impregnation modification. These molecular sieves can be used as selective adsorbents for N2 / CH4, O2 / CH4, and (N2+O2) / CH4 systems, with a focus on separating N2 / CH4 mixed systems. The molecular sieve used in this invention is preferably a carbon molecular sieve, which has a relatively poor separation effect when used to separate nitrogen and methane mixed systems.

[0006] Chinese patent CN 107324307 A discloses a method for preparing carbon molecular sieves that separate methane and nitrogen. The main steps include: (1) First, a mixture of methane and nitrogen containing a high concentration of methane is deposited at high temperature to coarsely adjust the pore size of the carbon molecular sieve precursor; (2) Second, a mixture of methane and nitrogen containing a low concentration of methane is deposited at low temperature to finely adjust the pore size of the carbon molecular sieve, thus preparing a carbon molecular sieve with high nitrogen adsorption and low methane adsorption. However, the preparation method of this invention requires the introduction of gas to adjust the pore size, and the two-step method for pore size adjustment is relatively complex.

[0007] Therefore, it is necessary to explore a simple, low-cost molecular sieve with a high nitrogen-to-methane separation ratio and its preparation method. Summary of the Invention

[0008] This invention provides a simple, low-cost method for preparing a polymer-modified ETS molecular sieve with a high nitrogen-to-methane separation ratio, and its preparation method. This invention forms an encapsulated composite adsorbent by coating the ETS with a polymer layer, aiming to create cross-channels between the ETS molecular sieve and the polymer layer. Through this modification, the adsorption capacity for methane is reduced, thereby effectively separating nitrogen and methane.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] First, a method for preparing polymer-modified ETS molecular sieves is provided, comprising the following steps:

[0011] (1) Preparation of polyethylene glycol solution: Add polyethylene glycol to the solvent and stir to dissolve to obtain polyethylene glycol solution;

[0012] (2) Grind the ETS molecular sieve, mix it with the polyethylene glycol solution obtained in step (1), then filter and separate it. Dry the solid obtained after separation to obtain the polymer-modified ETS molecular sieve.

[0013] Furthermore, the number average molecular weight of the polyethylene glycol mentioned in step (1) is 250-50000.

[0014] Preferably, the number average molecular weight of the polyethylene glycol in step (1) is 400-5000.

[0015] Further, the solvent in step (1) is water or an organic solvent, wherein the organic solvent is one or more of methanol, ethanol, isopropanol, benzene, toluene, methyl acetate, and ethyl acetate. To save costs, the solvent is preferably water.

[0016] Further, the concentration of the polyethylene glycol solution in step (1) is 0.5-15 vol%.

[0017] Preferably, the concentration of the polyethylene glycol solution in step (1) is 4-15 vol%.

[0018] Furthermore, the ratio of polyethylene glycol to ETS molecular sieve in step (2) is 9-11 mL: 1.5-2 g.

[0019] Furthermore, the ETS molecular sieve mentioned in step (2) is any one of ETS-4, ETS-10, and ETS-14.

[0020] Furthermore, the mixing method in step (2) is impregnation, which is either equal-volume impregnation or excessive impregnation.

[0021] Furthermore, the drying temperature in step (2) is set to 80-200℃.

[0022] Furthermore, the polymer-modified ETS molecular sieve obtained by the preparation method.

[0023] Furthermore, the polymer-modified ETS molecular sieve obtained by the preparation method, or the polymer-modified ETS molecular sieve, can be used as a selective adsorbent for nitrogen and methane mixtures, oxygen and methane mixtures, or nitrogen and oxygen mixtures.

[0024] Furthermore, the polymer-modified ETS molecular sieve obtained by the preparation method or the polymer-modified ETS molecular sieve can be used to purify methane from coalbed methane, oilfield gas or landfill gas.

[0025] In some specific embodiments, a method for preparing a polymer-modified ETS molecular sieve includes the following steps:

[0026] (1) Preparation of PEG400 aqueous solution: Mix 1 mL of PEG400 with 30 mL of deionized water, stir and dissolve the PEG400 until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 1 vol%. Similarly, obtain PEG400 aqueous solutions with a concentration of 0.5-15 vol%.

[0027] (2) Preparation of ETS-4 molecular sieve:

[0028] Solution 1: Dissolve 3.6g silica gel and 3g NaOH in 10mL of deionized water;

[0029] Solution 2: Add 0.37g NaOH to 24mL of deionized water, then add 1.8g of tetrabutyl titanate, and then quickly add 5mL of H2O2 (30 vol%) to dissolve the white precipitate until a light yellow solution is obtained.

[0030] Add solution 2 and 35 mL of deionized water to solution 1 and stir for 30 min. At this time, the turbidity disappears and the pH of the solution is about 12.1. Place it in a container lined with polytetrafluoroethylene and heat it to 200°C for 12-48 hours. Filter and wash the final product and dry it at 70°C for 24 hours to obtain ETS-4 molecular sieve.

[0031] (3) Grind the prepared ETS-4 molecular sieve to 10-20 mesh, take 1.5-2g of the ground molecular sieve and mix it with 9-11mL of the PEG400 aqueous solution obtained in step (1), then filter and separate it. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] (1) The present invention uses a specific polymer polyethylene glycol to impregnate and modify ETS molecular sieve, and successfully prepares polymer-modified ETS molecular sieve.

[0034] (2) The preparation method of the present invention is simple, controllable, and low in cost;

[0035] (3) The polymer-modified ETS molecular sieve prepared by the present invention is used to separate nitrogen and methane mixture system, with a large separation ratio and good separation effect. Detailed Implementation

[0036] It is worth noting that the raw materials used in this invention are all commercially available products, and their sources are not specifically limited.

[0037] Example 1

[0038] Preparation of polymer-modified ETS molecular sieves:

[0039] (1) Prepare PEG400 aqueous solution: Mix 0.5 mL of PEG400 with 30 mL of deionized water, stir and treat until PEG400 dissolves until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 0.5 vol%.

[0040] (2) Take 2g of ground ETS-4 molecular sieve (10-20 mesh) and mix it with 10mL of PEG400 aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0041] The adsorption capacity of the modified samples for nitrogen and methane was determined using the static adsorption method. The static adsorption method was performed according to the method disclosed in patent application 201911089480.2. The results are shown in Table 1.

[0042] Table 1

[0043]

[0044]

[0045] Example 2

[0046] Preparation of polymer-modified ETS molecular sieves:

[0047] (1) Prepare PEG400 aqueous solution: Mix 4 mL of PEG400 with 30 mL of deionized water, stir and treat until PEG400 dissolves until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 4 vol%.

[0048] (2) Take 2g of ground ETS-4 molecular sieve (10-20 mesh) and mix it with 10mL of PEG400 aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0049] The adsorption capacity of the modified sample for nitrogen and methane was determined using the static adsorption method described in Example 1, and the results are shown in Table 2.

[0050] Table 2

[0051]

[0052] Example 3

[0053] Preparation of polymer-modified ETS molecular sieves:

[0054] (1) Prepare PEG400 aqueous solution: Mix 10 mL of PEG400 with 30 mL of deionized water, stir and treat until PEG400 dissolves until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 10 vol%.

[0055] (2) Take 2g of ground ETS-4 molecular sieve (10-20 mesh) and mix it with 10mL of PEG400 aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0056] The adsorption capacity of the modified sample for nitrogen and methane was determined using the static adsorption method described in Example 1, and the results are shown in Table 3.

[0057] Table 3

[0058]

[0059] Example 4

[0060] Preparation of polymer-modified ETS molecular sieves:

[0061] (1) Prepare PEG400 aqueous solution: Mix 15 mL of PEG400 with 30 mL of deionized water, stir and treat until PEG400 dissolves until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 15 vol%.

[0062] (2) Take 2g of ground ETS-10 molecular sieve (10-20 mesh) and mix it with 10mL of PEG400 aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0063] The adsorption capacity of the modified sample for nitrogen and methane was determined using the static adsorption method described in Example 1, and the results are shown in Table 4.

[0064] Table 4

[0065]

[0066]

[0067] Comparative Example 1

[0068] Preparation of polymer-modified ETS molecular sieves:

[0069] (1) Prepare PEG400 aqueous solution: Mix 0.1 mL of PEG400 with 30 mL of deionized water, stir until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 0.1 vol%.

[0070] (2) Take 2g of ground ETS-4 molecular sieve (10-20 mesh) and mix it with 10mL of PEG400 aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0071] The adsorption capacity of the modified sample for nitrogen and methane was determined using the static adsorption method described in Example 1, and the results are shown in Table 5.

[0072] Table 5

[0073]

[0074]

[0075] Comparative Example 2

[0076] (1) Prepare PEG400 aqueous solution: Mix 20 mL of PEG400 with 30 mL of deionized water, stir and treat until PEG400 dissolves until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PEG400 aqueous solution with a concentration of 20 vol%.

[0077] (2) Take 2g of ground ETS-4 molecular sieve (10-20 mesh) and mix it with 10mL of PEG400 aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PEG400 modified ETS molecular sieve.

[0078] The adsorption capacity of the modified sample for nitrogen and methane was determined using the static adsorption method described in Example 1, and the results are shown in Table 6.

[0079] Table 6

[0080]

[0081] Comparative Example 3

[0082] Preparation of polymer-modified ETS molecular sieves:

[0083] (1) Prepare PVA aqueous solution: Mix 10 mL of polyvinyl alcohol (PVA) with 30 mL of deionized water, stir until the solution is clear and transparent, then transfer it to a 100 mL volumetric flask, rinse with deionized water 2-3 times and transfer to the volumetric flask, make up to volume, shake well and transfer to a reagent bottle to obtain a PVA aqueous solution with a concentration of 10 vol%.

[0084] (2) Take 2g of ground ETS-4 molecular sieve (10-20 mesh) and mix it with 10mL of PVA aqueous solution obtained in step (1). Then filter and separate the mixture. Dry the filter residue obtained after separation overnight at 150℃ to obtain PVA modified ETS molecular sieve.

[0085] The adsorption capacity of the modified sample for nitrogen and methane was determined using the static adsorption method described in Example 1, and the results are shown in Table 7.

[0086] Table 7

[0087]

[0088] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a high-molecular-modified ETS molecular sieve, characterized in that, consists of the following steps: (1) preparing a polyethylene glycol solution: adding polyethylene glycol into a solvent, stirring and dissolving to obtain a polyethylene glycol solution; (2) grinding ETS molecular sieve, mixing with the polyethylene glycol solution obtained in step (1), then filtering and separating, and drying the solid obtained after separation to obtain a high polymer modified ETS molecular sieve; The concentration of the polyethylene glycol solution in step (1) is 10 vol%. The ratio of the amount of the polyethylene glycol solution to ETS molecular sieve in step (2) is 10 mL: 2 g. The ETS molecular sieve is ETS-4.

2. The production method according to claim 1, characterized by, The number average molecular weight of the polyethylene glycol in step (1) is 250-50000.

3. The preparation method according to claim 2, characterized in that, The number average molecular weight of the polyethylene glycol in step (1) is 400-5000.

4. The method of claim 1, wherein, The solvent in step (1) is water or an organic solvent, and the organic solvent is one or more of methanol, ethanol, isopropyl alcohol, benzene, toluene, methyl acetate, and ethyl acetate.

5. The preparation method according to claim 1, characterized in that, The temperature for drying in step (2) is set to 80-200℃.

6. The high polymer modified ETS molecular sieve obtained by the preparation method in any one of claims 1-5.

7. The use of the high polymer modified ETS molecular sieve obtained by the preparation method in any one of claims 1-5 or the high polymer modified ETS molecular sieve in claim 6 as a selective adsorbent for a nitrogen and methane mixed system, an oxygen and methane mixed system, or a nitrogen and oxygen mixed system.

8. The use of the high polymer modified ETS molecular sieve obtained by the preparation method in any one of claims 1-5 or the high polymer modified ETS molecular sieve in claim 6 in purifying methane in coalbed methane, oilfield gas, or landfill gas.

Images