Preparation and application of molecular sieve with different silicon-aluminum ratio mor

Abstract

The application provides preparation and application of MOR molecular sieves with different silicon aluminum ratios, and mainly solves the problem of ethylene adsorption separation and purification in industry. The application adjusts the content of aluminum source in the initial system in the synthesis process of the MOR molecular sieves, and performs adsorption and breakthrough characterization on the synthesized series of MOR-x molecular sieves with different silicon aluminum ratios, so that the MOR-x molecular sieves have the application of one-step purification of C2H4 in low carbon hydrocarbons, especially in C2H4 / C2H6 mixture; the MOR molecular sieves prepared by the application have the advantages of simple synthesis process, no template agent and other toxic organic solvents, and environmental protection; the MOR-x molecular sieves with the silicon aluminum ratio of 8.6-12.1 have the performance of high selectivity in capturing C2H4 in C2H4 / C2H6 mixed gas, the regeneration time is greatly shortened compared with the breakthrough Ag loaded adsorbent, and can be well applied to the adsorption purification industrial production.

Description

Technical Field

[0001] This invention belongs to the field of molecular sieves, specifically relating to the preparation and application of MOR with different silicon-to-aluminum ratios. Background Technology

[0002] Ethylene (C2H4) is the most important olefin product in the petrochemical industry. Currently, C2H4 production mainly relies on the cracking of hydrocarbons, but a certain amount of ethane is produced during ethylene production. Industrially, multi-step cooling and cryogenic distillation techniques are used to separate these products, which significantly increases energy consumption.

[0003] In existing technologies, there are few applications of using molecular sieves to control the silicon-to-aluminum ratio and its adsorption and separation of C2H4 in low-carbon hydrocarbons. Most methods focus on improving the performance of molecular sieves through modification. Patent CN115646436A discloses an in-situ silver-modified pure silicon molecular sieve and its application in capturing low-concentration ethylene under humid conditions. This molecular sieve can increase the adsorption capacity of ethylene. By controlling the structure through silver ions, a method is ultimately achieved to enhance the ability to capture low-concentration ethylene, even under high relative humidity and certain carbon dioxide influences. Although it possesses good static adsorption isotherms and selectivity, its adsorption and separation performance for ethylene and ethane is difficult to significantly improve, and removal and separation are relatively difficult. In practical adsorption and separation applications, most ethylene is difficult to remove, requiring further modification and increasing the preparation process cost.

[0004] Based on this, the present invention is proposed to achieve precise control of adsorption performance by regulating the Al content of the molecular sieve framework, so that ethylene has a greater adsorption capacity than ethane, ethylene is superior to ethane in adsorption-desorption kinetics, and ethylene is superior to ethane in adsorption thermodynamics. Summary of the Invention

[0005] This invention provides a method for preparing and applying MOR molecular sieves with different silica-to-alumina ratios. The MOR molecular sieves are MOR-x molecular sieves with different silica-to-alumina ratios synthesized via a hydrothermal method. C2H4 is enriched and purified in a C2H4 / C2H6 mixed gas, solving the problem of adsorption and separation of ethane and ethylene in industrial ethylene production purification. The technical solution of this invention includes the following steps:

[0006] Step 1: Sodium aluminate, sodium hydroxide, silicon source and water are mixed to obtain a gel;

[0007] Step 2: The prepared gel is placed in a reaction vessel for hydrothermal crystallization;

[0008] Step 3: Remove the blocky product from the reactor, filter it, air dry it naturally, and then put it into an oven to dry it.

[0009] Step 4: After drying, the resulting solid block is the prepared MOR-x molecular sieve.

[0010] Furthermore, the amount of sodium aluminate used in step 1 is used as a variable to control the silicon-aluminum ratio;

[0011] Furthermore, the silicon source mentioned in step 1 is one or more of silica sol, silica fume, and sodium silicate;

[0012] Furthermore, in step 1, the effective components of the gel are SiO2, Al2O3, Na2O and H2O;

[0013] Furthermore, the molar ratio of SiO2 to Al2O3 is 4 to 30:1;

[0014] Further, in step 1, the molar ratio of sodium hydroxide to sodium aluminate is 4-6:1; the molar ratio of H2O to sodium aluminate is 200-250:1.

[0015] Furthermore, in step 2, the hydrothermal crystallization temperature is controlled at 160-190℃.

[0016] Furthermore, in step 2, the hydrothermal crystallization time is controlled between 1.5 and 14 days;

[0017] Furthermore, in step 3, the natural air drying time is 12-24 hours, the oven drying temperature is 60-120°C, and the oven drying time is 8-12 hours.

[0018] A MOR-x molecular sieve is suitable for the adsorption and purification of ethylene gas in industrial tail gas containing ethylene, such as the C2H4 / C2H6 system. The MOR molecular sieve is a MOR-x molecular sieve with a silica-alumina ratio of 8.6-12.1. The silica-alumina ratio is the molar ratio of silica and aluminum in the MOR-x molecular sieve.

[0019] Technical effect

[0020] This invention provides a simple preparation method for MOR-x molecular sieves, enabling them to purify C2H4 from low-carbon hydrocarbons, particularly in C2H4 / C2H6 mixtures, in a single step. The MOR molecular sieves prepared by this invention have environmental advantages due to their simple synthesis process, avoiding the use of template agents and other toxic organic solvents. Characterization of MOR-x molecular sieves with different silica-to-alumina ratios, including adsorption and breakthrough, reveals that MOR-x molecular sieves with silica-to-alumina ratios of 8.6-12.1 exhibit high selectivity for capturing C2H4 from C2H4 / C2H6 mixed gases. The regeneration time is significantly shorter compared to breakthrough Ag-supported adsorbents, making them well-suited for adsorption purification in industrial production.

[0021] Figure and Table Description

[0022] Figure 1 XRD pattern of low silica-to-alumina ratio MOR molecular sieve;

[0023] Figure 2 XRD pattern of high silica-to-alumina ratio MOR molecular sieve;

[0024] Figure 3 Adsorption-desorption kinetics of ethane and ethylene using high silica-to-alumina ratio MOR molecular sieves;

[0025] Figure 4 Adsorption-desorption kinetics of ethane and ethylene using MOR molecular sieves with low silica-to-alumina ratio;

[0026] Figure 5 Breakthrough curves and purge-desorption plots of ethane and ethylene from low silica-to-alumina ratio MOR molecular sieves;

[0027] Figure 6 Breakthrough curves and purge-desorption plots of ethane and ethylene from high silica-to-alumina ratio MOR molecular sieves;

[0028] Figure 7 Schematic diagram of the MOR-10.1 molecular sieve ethane-ethylene cycle breakthrough experiment;

[0029] Figure 8 Ethylene purge rate and dynamic adsorption capacity of MOR molecular sieves with different silica-to-alumina ratios in ethane-ethylene breakthrough experiments. Detailed Implementation

[0030] The following detailed embodiments illustrate the implementation of the technical solution of the present invention and its beneficial effects, but should not be construed as any limitation on the scope of implementation of the present invention.

[0031] Table 1 shows the relevant silicon-aluminum ratios for each embodiment, comparative example, and product.

[0032] Table 1. Silicon-to-aluminum ratio and XRD characteristics of the synthesized products

[0033]

[0034] Example 1

[0035] MOR-4.8 with a silicon-to-aluminum ratio of 4.8 was prepared by adding 0.9475 g of sodium hydroxide and 1.1165 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0036] Example 2

[0037] MOR-5.0 with a silicon-to-aluminum ratio of 5.0 was prepared by adding 0.9475 g of sodium hydroxide and 1.015 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0038] Example 3

[0039] MOR-5.2 with a silicon-to-aluminum ratio of 5.2 was prepared by adding 0.9475 g of sodium hydroxide and 0.9135 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0040] Example 4

[0041] MOR-6.2 with a silicon-to-aluminum ratio of 6.2 was prepared by adding 0.9475 g of sodium hydroxide and 0.812 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0042] Example 5

[0043] MOR-6.7 with a silicon-to-aluminum ratio of 6.7 was prepared by adding 0.9475 g of sodium hydroxide and 0.7105 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0044] Example 6

[0045] MOR-7.5 with a silicon-to-aluminum ratio of 7.5 was prepared by adding 0.9475 g of sodium hydroxide and 0.609 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0046] Example 7

[0047] MOR-8.6 with a silicon-to-aluminum ratio of 8.6 was prepared by adding 0.9475 g of sodium hydroxide and 0.55825 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0048] Example 8

[0049] MOR-10.1 with a silicon-to-aluminum ratio of 10.1 was prepared by adding 0.9475 g of sodium hydroxide and 0.5075 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0050] Example 9

[0051] MOR-12.1 with a silicon-to-aluminum ratio of 12.1 was prepared by adding 0.9475 g of sodium hydroxide and 0.45675 g of sodium aluminate to 23.53 g of deionized water and stirring until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The silicon-to-aluminum ratio of the product was determined by ICP characterization.

[0052] Comparative Example 1

[0053] Preparation of MOR-aluminum-rich A: 0.9475 g of sodium hydroxide and 1.126875 g of sodium aluminate were added to 23.53 g of deionized water and stirred evenly. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out, and the product was obtained by filtration and drying. The product was identified by XRD.

[0054] Comparative Example 2

[0055] Preparation of MOR-rich aluminum B: 0.9475 g of sodium hydroxide and 1.5225 g of sodium aluminate were added to 23.53 g of deionized water and stirred evenly. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 h. Hydrothermal crystallization was then carried out. The product was obtained by filtration and drying and was identified by XRD.

[0056] Comparative Example 3

[0057] Preparation of MOR-rich aluminum C: 0.9475 g of sodium hydroxide and 2.03 g of sodium aluminate were added to 23.53 g of deionized water and stirred until homogeneous. Then, 14.186 g of 30 wt% silica sol was slowly added and stirred for 4 hours. Hydrothermal crystallization was then carried out, followed by filtration and drying to obtain the product. The product was identified by XRD.

[0058] Comparative Example 4

[0059] Preparation of MOR-High Silicon A: 0.9475g of sodium hydroxide and 0.406g of sodium aluminate were added to 23.53g of deionized water and stirred evenly. Then, 14.186g of 30wt% silica sol was slowly added and stirred for 4h. Hydrothermal crystallization was then carried out, and the product was obtained by filtration and drying. The product was identified by XRD.

[0060] Comparative Example 5

[0061] Preparation of MOR-High Silicon B: 0.9475g of sodium hydroxide and 0.33525g of sodium aluminate were added to 23.53g of deionized water and stirred evenly. Then, 14.186g of 30wt% silica sol was slowly added and stirred for 4 hours. Hydrothermal crystallization was then carried out, and the product was obtained by filtration and drying. The product was identified by XRD.

[0062] Comparative Example 6

[0063] Preparation of MOR-High Silicon B: 0.9475g of sodium hydroxide and 0.3045g of sodium aluminate were added to 23.53g of deionized water and stirred evenly. Then, 14.186g of 30wt% silica sol was slowly added and stirred for 4h. Hydrothermal crystallization was then carried out, and the product was obtained by filtration and drying. The product was identified by XRD.

[0064] Comparative Example 7

[0065] Preparation of MOR-high silicon B: 0.9475g of sodium hydroxide and 0.25375g of sodium aluminate were added to 23.53g of deionized water and stirred evenly. Then, 14.186g of 30wt% silica sol was slowly added and stirred for 4h. Hydrothermal crystallization was then carried out. The product was obtained by filtration and drying. The product was identified by XRD.

[0066] As shown in Table 1, when the silica-alumina ratio of the feed is greater than 14, the resulting product is amorphous. When it is below 5, there are also amorphous products with different contents. It can be seen that a stable MOR molecular sieve can be obtained when the silica-alumina ratio of the feed is in the range of 5-13.

[0067] As can be seen from Examples 1-9 and Control Groups 1-7, Figures 1-2This indicates that stable MOR can only be obtained when the silicon-to-aluminum ratio is within a certain range. All examples and control examples were characterized by XRD. The adsorption kinetics of C2H4 and C2H6 were tested at 298 K in selected examples, and breakthrough experiments were performed to demonstrate the adsorption separation of C2H4 and C2H6. Figures 3-6 as well as Figure 8 The experimental results show that MOR-x molecular sieves with a silica-to-alumina ratio of 8.6-12.1 possess high selectivity for capturing C2H4 in C2H4 / C2H6 mixed gases. In particular, MOR-10.1 exhibits excellent C2H4 / C2H6 separation capability, high dynamic adsorption capacity, rapid regeneration, and high room-temperature ethylene purge removal rate. Figure 7 It can be seen that the MOR-10.1 molecular sieve ethane-ethylene cycle breakthrough experiment diagram shows that regeneration can be achieved in a short time without additional heating treatment.

[0068] In summary, MOR-x with different silicon-to-aluminum ratios exhibits varying effects on the separation of ethylene and acetylene. Only within a certain range of silicon-to-aluminum ratios can MOR-x achieve good C2H4 / C2H6 separation capacity and high dynamic adsorption capacity. MOR-x molecular sieves with silicon-to-aluminum ratios of 8.6-12.1 possess the ability to selectively capture C2H4 in C2H4 / C2H6 mixed gases, and the regeneration time is significantly shortened compared to Ag-supported adsorbents, making them well-suited for adsorption purification in industrial production.

Claims

1. A type of MOR-x molecular sieve with different silica-to-alumina ratios, characterized in that, The MOR-x molecular sieve is suitable for the purification of ethylene in a C2H4 / C2H6 mixture; the MOR-x molecular sieve is a MOR-x molecular sieve with a silica-alumina ratio of 8.6-12.1; the silica-alumina ratio is the molar ratio of silica and aluminum in the MOR-x molecular sieve. The specific steps of the preparation method of the MOR-x molecular sieve are as follows: Step 1: Sodium aluminate, sodium hydroxide, silicon source and water are mixed to obtain a gel; Step 2: The prepared gel is placed in a reaction vessel for hydrothermal crystallization; Step 3: Remove the blocky product from the reactor, filter it, air dry it naturally, and then put it into an oven to dry it. Step 4: After drying, the resulting solid block is the prepared MOR-x molecular sieve. The amount of sodium aluminate used in step 1 is used as a variable to control the silicon-aluminum ratio; The silicon source mentioned in step 1 is one or more of silica sol, silica fume, and sodium silicate. In step 1, the effective components of the gel are SiO2, Al2O3, Na2O and H2O, and the molar ratio of SiO2 to Al2O3 is 4 to 30:

1. In step 1, the molar ratio of sodium hydroxide to sodium aluminate is 4-6:1, and the molar ratio of H2O to sodium aluminate is 200-250:

1.

2. A MOR-x molecular sieve with different silica-to-alumina ratios as described in claim 1, characterized in that, In step 2, the hydrothermal crystallization temperature is controlled at 160-190℃.

3. A MOR-x molecular sieve with different silica-to-alumina ratios as described in claim 1, characterized in that, In step 2, the hydrothermal crystallization time is controlled between 1.5 and 14 days.

4. A MOR-x molecular sieve with different silica-to-alumina ratios as described in claim 1, characterized in that, In step 3, the natural air drying time is 12-24 hours, the oven drying temperature is 60-120°C, and the oven drying time is 8-12 hours.

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