Modified 5a molecular sieve and preparation method thereof

Abstract

The application discloses a modified 5A molecular sieve, and a preparation method thereof. The modified 5A molecular sieve is characterized in that the modified 5A molecular sieve is composed of 5A molecular sieve and a silicon-containing compound, wherein the mass ratio of the 5A molecular sieve to the silicon-containing compound is 1:0.005-0.25, and the average crystal grain size of the modified 5A molecular sieve is not more than 1 mu m. The preparation method of the modified 5A molecular sieve comprises the preparation of 5A molecular sieve and silanization treatment.

Description

Technical Field

[0001] This invention relates to the field of molecular sieves, specifically to a modified 5A molecular sieve and its preparation method. Background Technology

[0002] Type A molecular sieves were first successfully synthesized by Union Carbide Corporation (UCC) in 1954 and put into industrial production in 1957. The empirical formula for the chemical composition of type A molecular sieves is (M... 2+ M + O·Al2O3·SiO2·yH2O, with its tunable regular three-dimensional channels, is widely used in selective adsorption, ion exchange, catalysis and other fields.

[0003] Synthetic methods for type A molecular sieves include solvothermal synthesis, dry gel conversion, and microwave irradiation.

[0004] Solvothermal synthesis is the most mature and widely used method for molecular sieve synthesis. This method utilizes alkali metals or organic amines as structure-directing agents, with crystallization temperatures typically above 100℃. The synthesized molecular sieve crystals are relatively large, generally ranging from 3 to 5 μm in size. Because small-sized Type A molecular sieves with crystal sizes between 1 and 1000 nm possess larger specific surface areas, shorter diffusion distances, and more accessible active sites, they can significantly improve the selective adsorption performance of molecular sieves in adsorption and separation.

[0005] CN 103435062B discloses a simple and rapid method for synthesizing nano-type A molecular sieves. This method uses acid as a catalyst for the hydrolysis of tetraethyl orthosilicate, accelerating the hydrolysis rate. Simultaneously, tetramethylammonium hydroxide is introduced during the preparation process to shorten the synthesis cycle of the molecular sieve. The nano-type A molecular sieves obtained by this method have a particle size of less than 100 nm and are uniformly distributed. CN 104276584A discloses a method for preparing submicron NaA molecular sieves by hydrothermal crystallization using sodium silicate, sodium aluminate, and deionized water as raw materials and polyethylene glycol 1000 (PEG1000) as a dispersant. CN 106542541A discloses a method that adds a sugar compound as an inhibitor to hinder crystal nucleus growth, shortening the crystallization time and preparing A-type molecular sieves with crystal sizes between 0.5-1 μm. CN 110498423A discloses a method that uses a cellulose derivative as a gelling agent added to a gel system to prepare nano-type A molecular sieves.

[0006] The above-described method for preparing small-sized type A molecular sieves is currently the most commonly used method for preparing nanoscale type A molecular sieves in the laboratory. Although the addition of organic templates, dispersants, and inhibitors can greatly promote the nucleation process of molecular sieves, organic templates are usually expensive, removing organic templates is energy-intensive, and the addition of dispersants and inhibitors reduces the yield of molecular sieves, thus all of which are not conducive to industrial production.

[0007] Existing technologies such as CN103318913B, CN103848436B, and CN104828837B disclose a template-free two-step hydrothermal synthesis method for ultrafine type A molecular sieves. During the synthesis process, they effectively reduce the crystal size of the molecular sieve by employing low-temperature nucleation and heated crystallization, resulting in a more uniform crystal density distribution and a shorter crystallization cycle.

[0008] Reducing the size of molecular sieve crystals enhances the adsorption of low-carbon olefin molecules at the active adsorption sites of the molecular sieve, but it also enhances the competitive adsorption of other impurity molecules at these sites, leading to a decrease in the adsorption capacity and selectivity of the target molecules. Summary of the Invention

[0009] The purpose of this invention is to address the problems existing in the prior art by providing a modified 5A molecular sieve that differs from the prior art and to provide a method for preparing the modified 5A molecular sieve.

[0010] To achieve the objectives of this invention, a first aspect of this invention provides a modified 5A molecular sieve, characterized in that the modified 5A molecular sieve is composed of a 5A molecular sieve and a silicon-containing compound, wherein the mass ratio of the 5A molecular sieve to the silicon-containing compound is 1:0.005-0.25, and the average grain size of the modified 5A molecular sieve is not greater than 1 μm.

[0011] To achieve the objectives of this invention, a second aspect of this invention provides a method for preparing the above-mentioned modified 5A molecular sieve, comprising the preparation of the 5A molecular sieve and silanization treatment.

[0012] Surprisingly, the modified 5A molecular sieve provided by this invention has small crystal size and high crystallinity, making it a high-quality adsorbent for ethylene / ethane adsorption and separation applications. The preparation method of the modified 5A molecular sieve of this invention is simple, highly operable, and yields a high molecular sieve, showing strong promise for industrial applications. Attached Figure Description

[0013] Figure 1 This is a scanning electron microscope image of the modified 5A molecular sieve prepared in Example 1.

[0014] Figure 2 The image shows the XRD pattern of the modified 5A molecular sieve prepared in Example 1.

[0015] Figure 3 The adsorption curves of the modified 5A molecular sieve prepared in Example 7 for ethylene and ethane in a 1:1 ratio at 25°C and 0-100 kPa are shown. Detailed Implementation

[0016] The present invention provides a modified 5A molecular sieve, which is composed of 5A molecular sieve and silicon-containing compound, wherein the mass ratio of 5A molecular sieve to silicon-containing compound is 1:0.005-0.25, preferably 1:0.02-0.10, the average grain size is not greater than 1 μm, preferably not greater than 0.9 μm, more preferably 0.70-0.85 μm, and the relative crystallinity is not less than 80%, preferably not less than 90%.

[0017] The mass ratio of 5A molecular sieve to silicon-containing compound in the modified 5A molecular sieve is obtained by the change in the mass of 5A molecular sieve before and after silanization treatment. In a preferred embodiment, the mass ratio of 5A molecular sieve to silicon-containing compound in the modified 5A molecular sieve is 1:0.010067.

[0018] The average grain size of the modified 5A molecular sieve was obtained by observation and statistical analysis using a scanning electron microscope (SEM). For example, the average grain size of the modified 5A molecular sieve could be determined using a Hitachi S4800 SEM from Japan, with an accelerating voltage of 20 kV, a working distance of 8 mm, and a magnification of 5 k to 50 k. The size of each grain was measured according to the scale bar on the SEM image, with at least 100 grains measured and then statistically analyzed. Excessively large molecular sieve grain sizes are detrimental to the interaction between ethylene and the active adsorption sites of the 5A molecular sieve, while excessively small grain sizes promote competitive adsorption of other adsorbates within the 5A molecular sieve, affecting the adsorption capacity and selectivity of ethylene. The modified 5A molecular sieve of this invention reduces competitive adsorption of other adsorbates within the 5A molecular sieve without significantly reducing the ethylene adsorption capacity, thereby improving the selectivity of ethylene. In a preferred embodiment, the average grain size of the modified 5A molecular sieve is 796 nm.

[0019] In this invention, the relative crystallinity of the modified 5A molecular sieve is obtained by scanning with an Empyrean X-ray diffractometer from Malvern Panalytical, using a 40kV tube voltage, 40mA tube current, a one-dimensional scintillation detector, a Ni filter, a step size of 0.0131°, and a scanning range of 2θ = 5°–50°. The relative crystallinity of the modified 5A molecular sieve is determined according to the ASTM D5357-19 standard method. In a preferred embodiment, the relative crystallinity of the modified 5A molecular sieve is 91.5%.

[0020] In this invention, the modified 5A molecular sieve is evaluated based on its ethylene / ethane adsorption and separation performance. The ethylene adsorption capacity is determined by obtaining the ethylene adsorption isotherm on the molecular sieve using an intelligent gravimetric adsorption analyzer. Ethylene selectivity is determined by fitting the ethylene adsorption isotherm to an ideal solution adsorption theory model in a 1:1 ethylene / ethane volume ratio mixture. More specifically, the ethylene adsorption capacity of the modified 5A molecular sieve is measured using an intelligent gravimetric adsorption analyzer (IGA) from Hiden Isochema, at a test temperature of 25°C and a test pressure of 0-100 kPa.

[0021] The present invention also provides a method for preparing modified 5A molecular sieve, comprising: a 5A molecular sieve preparation step and a silanization treatment step.

[0022] The preparation steps of the 5A molecular sieve include:

[0023] (1) Sodium hydroxide, aluminum source, silicon source and deionized water are mixed evenly at 15-30℃ according to the molar ratio of Na2O:Al2O3:SiO2:H2O of 2.5-4.0:0.8-1.0:1.9-3.8:100-150 to obtain the initial reaction gel.

[0024] (2) The initial reaction gel described in step (1) is aged at a temperature of 25-40℃ for 4-120h to obtain a mixed solution;

[0025] (3) The mixed solution described in step (2) is crystallized under hydrothermal reaction conditions at a temperature of 50-90℃ for 2-12 hours, and after filtration, washing and drying, 4A molecular sieve is obtained.

[0026] (4) The 4A molecular sieve described in step (3) is mixed with soluble calcium salt and deionized water at a mass ratio of 1:0.5-3:5-20 and stirred at 60-90℃ for 0.5-5h. After filtration, washing and drying, 5A molecular sieve is obtained.

[0027] In step (1), the preferred molar ratio of the raw materials sodium hydroxide, aluminum source, silicon source and deionized water, Na2O:Al2O3:SiO2:H2O is 2.5-3.5:0.9-1.0:1.9-2.5:110-130; the aluminum source is selected from at least one of aluminum salts, aluminates, activated alumina, alkoxyaluminum, pseudoboehmite, and pseudoboehmite, and the aluminum source is preferably at least one of aluminates and pseudoboehmite; the silicon source is selected from at least one of silica, silica sol, silica gel, water glass, activated silica, and orthosilicate, and the silicon source is preferably at least one of tetraethyl orthosilicate, water glass and silica sol.

[0028] In step (2), the initial reaction gel is aged to obtain a mixed solution. The aging temperature is 25-40℃, preferably 30-40℃, and the aging time is 4-120h, preferably 12-72h.

[0029] Step (3) The mixed solution is crystallized in a hydrothermal reactor at a temperature of 50-90℃, preferably 70-90℃, and for a time of 2-12h, preferably 4-12h. After filtration, washing and drying, 4A molecular sieve is obtained.

[0030] Step (4) Mix 4A molecular sieve with soluble calcium salt and deionized water at a mass ratio of 1:0.5-3:5-20, stir at 60-90℃ for 0.5-5h, and obtain 5A molecular sieve after filtration, washing and drying; the soluble calcium salt is selected from at least one of calcium nitrate, calcium chloride, calcium dihydrogen phosphate, calcium bicarbonate and calcium bisulfate, preferably, the soluble calcium salt is selected from at least one of calcium nitrate and calcium chloride.

[0031] In the preparation method of this invention, the silanization step involves mixing 5A molecular sieve, a silanizing agent, and n-hexane at a mass ratio of 1:0.025-1.25:5-20. The silanizing agent is a compound with the following formula:

[0032]

[0033] R1, R2, R3, and R4 are each independently a halogen, alkyl, alkoxy, aromatic, or amino group, and at least one of them is an alkyl, alkoxy, aromatic, or amino group; the alkyl, alkoxy, and amino groups each have an independent C1-C2 carbon atom number. 18 .

[0034] The silanizing agent is preferably selected from at least one or more of dimethyldichlorosilane, methyltrichlorosilane, trimethylchlorosilane, 1,7-dichlorooctylmethyltetrasiloxane, [3-trimethoxysilylpropyl]dimethyloctadecylammonium bromide, N-phenyl-3-aminopropyltrimethoxysilane, phenyltriethoxysilane, hexamethyldisilazane, hexamethyldisilazane, methyltriethoxysilane, tert-butyldimethylchlorosilane, hexadecyltrimethoxysilane, and octyltriethoxysilane. More preferably, the silanizing agent is selected from at least one or more of dimethyldichlorosilane, N-phenyl-3-aminopropyltrimethoxysilane, methyltriethoxysilane, and hexadecyltrimethoxysilane. The resulting mixture is heated to a temperature of 100-160°C, preferably 120-140°C, for a time of 6-24 h, preferably 10-20 h. After filtration through filter paper and washing with anhydrous ethanol more than three times, the modified 5A molecular sieve was obtained by drying in an oven.

[0035] In this invention, the definitions within the broadest scope and the preferred definitions can be combined with each other to form new technical solutions, which are also considered to be disclosed in this specification.

[0036] The present invention is illustrated below by way of examples, but should not be construed as limiting the scope of the invention.

[0037] Example

[0038] I. Instruments

[0039] Hydrothermal reaction equipment (KLJX-811 homogeneous reactor manufactured by Yantai Keli Chemical Equipment Co., Ltd.)

[0040] Magnetic stirring equipment (DF-101S heat-collecting magnetic heating stirrer manufactured by Jiangsu Jinyi Instrument Technology Co., Ltd.)

[0041] Vacuum filtration equipment with Buchner funnel and filtration flask (SHZ-D(III) type circulating water vacuum pump manufactured by Gongyi Yuhua Instrument Co., Ltd.).

[0042] II. Raw Materials

[0043] All reagents used in the synthesis of 5A molecular sieves were of analytical grade and purchased from Beijing Innocare Technology Co., Ltd.

[0044] All silanizing reagents were chemically pure and purchased from Alfa Aesar, USA.

[0045] Ethylene (purity >99.99%) and ethane (99.95%) were purchased from Beijing Helium North Branch Gas Industry Co., Ltd.

[0046] III.5A Molecular Sieves Detection Methods

[0047] The mass ratio of 5A molecular sieve to silicon-containing compound in modified 5A molecular sieve was determined using a ME 204 / 02 analytical balance from Mettler Toledo, Switzerland, with a resolution of 0.1 mg. The mass ratio of 5A molecular sieve to silicon-containing compound was obtained based on the mass difference of 5A molecular sieve before and after silanization treatment.

[0048] The average grain size of the modified 5A molecular sieve was determined using a Hitachi S4800 scanning electron microscope (SEM) with an accelerating voltage of 20 kV, a working distance of 8 mm, and a magnification of 5 kV-50 kV. The size of each grain was measured according to the scale on the image, with at least 100 grains measured, and then statistically analyzed.

[0049] The relative crystallinity of the modified 5A molecular sieve was determined using an Empyrean X-ray diffractometer (Malvern Panalytical) with a tube voltage of 40 kV, a tube current of 40 mA, a one-dimensional scintillation detector, a Ni filter, a step size of 0.0131°, and a scanning range of 2θ = 5°–50°. The relative crystallinity of the modified 5A molecular sieve was determined according to the ASTM D5357-19 standard method.

[0050] Example 1

[0051] 2.47 g NaOH, 1.68 g boehmite, and 8 g water glass (SiO2 251.5 g / L, Na2O 176.65 g / L) were added to 33 mL of deionized water and stirred to obtain a gel. The gel was transferred to a high-pressure hydrothermal reactor and aged at 30 °C for 72 h. After aging, the temperature was raised to 90 °C and crystallized for 4 h. The obtained hydrothermal reaction product was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 4A molecular sieve. 3 g and 4.5 g of the obtained 4A molecular sieve were weighed out. CaCl2 and 15g of deionized water were mixed and subjected to ion exchange in a water bath at 70℃ for 3h. The mixture was then filtered and washed with deionized water until neutral. After drying at 100℃, 5A molecular sieve was obtained. 2g of the above 5A molecular sieve and 0.2g of dimethyldichlorosilane were dissolved in 20g of n-hexane and treated at 100℃ for 6h. The mixture was then filtered to obtain a solid powder and dried at 100℃ to obtain modified 5A molecular sieve.

[0052] Scanning electron microscope image of modified 5A molecular sieve is shown below. Figure 1 As can be seen from the figure, the prepared modified 5A molecular sieve presents a regular cube shape with uniform particle size.

[0053] The XRD pattern of the modified 5A molecular sieve is shown in the figure. Figure 2 ,from Figure 2 The diffraction peaks are sharp and the crystallinity is good.

[0054] Comparative Example 1

[0055] Add 2.47g NaOH, 1.68g boehmite, and 8g water glass (SiO2 251.5g / L, Na2O 176.65g / L) to 33mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30℃ for 72h, after aging, raise the temperature to 90℃ and crystallize for 4h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 4.5g CaCl2, mix with 15g of deionized water, perform ion exchange at 70℃ for 3h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0056] Example 2

[0057] Add 3.5g NaOH, 1.35g sodium aluminate, and 1.88g solid silica gel to 38.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30℃ for 72h, after aging, raise the temperature to 80℃ and crystallize for 6h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 1.5g of calcium dihydrogen phosphate, mix with 15g of deionized water, perform ion exchange at 80℃ for 2h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve; dissolve 2g of the above 5A molecular sieve and 0.05g of dimethyldichlorosilane in 20g of n-hexane, treat at 100℃ for 8h, filter to obtain solid powder, and dry at 100℃ to obtain modified 5A molecular sieve.

[0058] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0059] Comparative Example 2

[0060] Add 3.5g NaOH, 1.35g sodium aluminate, and 1.88g solid silica gel to 38.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30℃ for 72h, after aging, raise the temperature to 80℃ and crystallize for 6h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 1.5g of calcium dihydrogen phosphate, mix with 15g of deionized water, perform ion exchange at 80℃ for 2h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0061] Example 3

[0062] Add 2.47g to 33mL of deionized water. NaOH, 3.36 g aluminum isopropoxide, and 8 g water glass (SiO2 251.5 g / L, Na2O 176.65 g / L) were stirred to prepare a gel, which was then transferred to a high-pressure hydrothermal reactor and aged at 25 °C for 4 h. After aging, the temperature was raised to 80 °C and crystallized for 12 h. The resulting hydrothermal reaction product was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 4A molecular sieve. 3 g of the obtained 4A molecular sieve was weighed and mixed with 9 g CaCl2 and 60 g deionized water. Ion exchange was carried out in a 60 °C water bath for 5 h. The mixture was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 5A molecular sieve. 2 g of the above 5A molecular sieve and 0.2 g hexadecyltrimethoxysilane were dissolved in 20 g n-hexane and treated at 120 °C for 12 h. The solid powder was obtained by filtration and dried at 100 °C to obtain modified 5A molecular sieve.

[0063] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0064] Comparative Example 3

[0065] Add 2.47g NaOH, 3.36g aluminum isopropoxide, and 8g water glass (SiO2 = 251.5g / L, Na2O = 176.65g / L) to 33mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 25℃ for 4h, after aging, raise the temperature to 80℃ and crystallize for 12h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 9g of CaCl2, mix with 60g of deionized water, perform ion exchange at 60℃ water bath for 5h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0066] Example 4

[0067] Add 5.27g NaOH, 3.36g aluminum isopropoxide, and 13.02g tetraethyl orthosilicate to 44.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 40℃ for 24h, after aging, raise the temperature to 90℃ and crystallize for 12h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 3g CaCl2, mix with 30g of deionized water, perform ion exchange at 90℃ for 0.5h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve; dissolve 2g of the above 5A molecular sieve and 2.5g of hexadecyltrimethoxysilane in 20g of n-hexane, treat at 160℃ for 24h, filter to obtain solid powder, and dry at 100℃ to obtain modified 5A molecular sieve.

[0068] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0069] Comparative Example 4

[0070] Add 5.27g NaOH, 3.36g aluminum isopropoxide, and 13.02g tetraethyl orthosilicate to 44.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 40℃ for 24h, after aging, raise the temperature to 90℃ and crystallize for 12h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 3g of CaCl2, mix with 30g of deionized water, perform ion exchange at 90℃ water bath for 0.5h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0071] Example 5

[0072] Add 3.29 g NaOH, 1.34 g boehmite, and 1.88 g solid silica gel to 41.5 mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30 °C for 96 h, after aging, raise the temperature to 70 °C and crystallize for 2 h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100 °C to obtain 4A molecular sieve; weigh 3 g of the obtained 4A molecular sieve and 3 g CaCl2, mix with 45 g of deionized water, perform ion exchange at 80 °C for 1.5 h, filter, wash with deionized water until neutral, and dry at 100 °C to obtain 5A molecular sieve; dissolve 2 g of the above 5A molecular sieve and 1.5 g dimethyldichlorosilane in 20 g n-hexane, treat at 120 °C for 8 h, filter to obtain solid powder, and dry at 100 °C to obtain modified 5A molecular sieve.

[0073] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0074] Comparative Example 5

[0075] Add 3.29 g NaOH, 1.34 g boehmite, and 1.88 g solid silica gel to 41.5 mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30 °C for 96 h, after aging, raise the temperature to 70 °C and crystallize for 2 h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100 °C to obtain 4A molecular sieve; weigh 3 g of the obtained 4A molecular sieve and 3 g of CaCl2, mix with 45 g of deionized water, perform ion exchange at 80 °C for 1.5 h, filter, wash with deionized water until neutral, and dry at 100 °C to obtain 5A molecular sieve.

[0076] Example 6

[0077] Add 3.95g NaOH, 1.52g boehmite, and 7.54g tetraethyl orthosilicate to 38.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 40℃ for 24h, after aging, raise the temperature to 60℃ and crystallize for 10h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g and 6g CaCl2 of the obtained 4A molecular sieve, mix with 36g of deionized water, perform ion exchange at 70℃ for 4h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve; dissolve 2g of the above 5A molecular sieve and 2g of dimethyldichlorosilane in 20g of n-hexane, treat at 120℃ for 18h, filter to obtain a solid powder, and dry at 100℃ to obtain modified 5A molecular sieve.

[0078] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0079] Comparative Example 6

[0080] Add 3.95g NaOH, 1.52g boehmite, and 7.54g tetraethyl orthosilicate to 38.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 40℃ for 24h, after aging, raise the temperature to 60℃ and crystallize for 10h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 6g of CaCl2, mix with 36g of deionized water, perform ion exchange at 70℃ for 4h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0081] Example 7

[0082] 1.07 g NaOH, 1.08 g sodium aluminate, and 8 g water glass (SiO2 251.5 g / L, Na2O 176.65 g / L) were added to 35.9 mL of deionized water and stirred to obtain a gel. The gel was transferred to a high-pressure hydrothermal reactor and aged at 30 °C for 96 h. After aging, the temperature was raised to 70 °C and crystallized for 8 h. The obtained hydrothermal reaction product was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 4A molecular sieve. 3 g and 7.5 g of the obtained 4A molecular sieve were weighed out. CaCl2 and 54g of deionized water were mixed and subjected to ion exchange in a 90℃ water bath for 1h. The mixture was then filtered and washed with deionized water until neutral. After drying at 100℃, 5A molecular sieve was obtained. 2g of the above 5A molecular sieve and 2g of hexadecyltrimethoxysilane were dissolved in 20g of n-hexane and treated at 140℃ for 8h. The mixture was then filtered to obtain a solid powder and dried at 100℃ to obtain modified 5A molecular sieve.

[0083] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0084] Comparative Example 7

[0085] 1.07 g NaOH, 1.08 g sodium aluminate, and 8 g water glass (SiO2 251.5 g / L, Na2O 176.65 g / L) were added to 35.9 mL of deionized water and stirred to obtain a gel. The gel was transferred to a high-pressure hydrothermal reactor and aged at 30 °C for 96 h. After aging, the temperature was raised to 70 °C and crystallized for 8 h. The obtained hydrothermal reaction product was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 4A molecular sieve. 3 g of the obtained 4A molecular sieve was weighed and mixed with 7.5 g CaCl2 and 54 g deionized water. Ion exchange was carried out in a 90 °C water bath for 1 h. The mixture was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 5A molecular sieve.

[0086] Example 8

[0087] Add 4.74 g NaOH, 1.08 g sodium aluminate, and 1.88 g solid silica gel to 44.5 mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30 °C for 120 h, after aging, raise the temperature to 50 °C and crystallize for 12 h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100 °C to obtain 4A molecular sieve; weigh 3 g and 9 g of the obtained 4A molecular sieve and mix with 45 g of deionized water, perform ion exchange at 80 °C for 2.5 h, filter, wash with deionized water until neutral, and dry at 100 °C to obtain 5A molecular sieve; dissolve 2 g of the above 5A molecular sieve and 1 g of hexadecyltrimethoxysilane in 20 g of n-hexane, treat at 120 °C for 8 h, filter to obtain solid powder, and dry at 100 °C to obtain modified 5A molecular sieve.

[0088] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0089] Comparative Example 8

[0090] Add 4.74g NaOH, 1.08g sodium aluminate, and 1.88g solid silica gel to 44.5mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30℃ for 120h, after aging, raise the temperature to 50℃ and crystallize for 12h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g and 9g of calcium dihydrogen phosphate from the obtained 4A molecular sieve, mix with 45g of deionized water, perform ion exchange at 80℃ for 2.5h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0091] Example 9

[0092] Add 1.81g NaOH, 1.35g sodium aluminate, and 8g water glass (SiO2 251.5g / L, Na2O 176.65g / L) to 33mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 30℃ for 36h, after aging, raise the temperature to 70℃ and crystallize for 10h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g and 6g of the obtained 4A molecular sieve and mix with 24g of deionized water, perform ion exchange at 90℃ for 2h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve; 2g and 0.1g of the above 5A molecular sieve... N-Phenyl-3-aminopropyltrimethoxysilane was dissolved in 20g of n-hexane, treated at 160℃ for 8h, filtered to obtain a solid powder, and dried at 100℃ to obtain modified 5A molecular sieve.

[0093] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0094] Comparative Example 9

[0095] 1.81 g NaOH, 1.35 g sodium aluminate, and 8 g water glass (SiO2 251.5 g / L, Na2O 176.65 g / L) were added to 33 mL of deionized water and stirred to obtain a gel. The gel was transferred to a high-pressure hydrothermal reactor and aged at 30 °C for 36 h. After aging, the temperature was raised to 70 °C and crystallized for 10 h. The obtained hydrothermal reaction product was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 4A molecular sieve. 3 g of the obtained 4A molecular sieve and 6 g of calcium dihydrogen phosphate were weighed and mixed with 24 g of deionized water. Ion exchange was carried out in a 90 °C water bath for 2 h. The mixture was filtered, washed with deionized water until neutral, and dried at 100 °C to obtain 5A molecular sieve.

[0096] Example 10

[0097] Add 4.61g NaOH, 1.35g sodium aluminate, and 11.98g tetraethyl orthosilicate to 29.6mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 40℃ for 12h, after aging, raise the temperature to 60℃ and crystallize for 12h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 4.5g CaCl2, mix with 30g deionized water, perform ion exchange at 60℃ for 4.5h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve; dissolve 2g of the above 5A molecular sieve and 1g dimethyldichlorosilane in 20g n-hexane, treat at 110℃ for 8h, filter to obtain solid powder, and dry at 100℃ to obtain modified 5A molecular sieve.

[0098] The scanning electron microscope (SEM) image and XRD pattern of the modified 5A molecular sieve have the following characteristics: Figure 1 , Figure 2 Its characteristics.

[0099] Comparative Example 10

[0100] Add 4.61g NaOH, 1.35g sodium aluminate, and 11.98g tetraethyl orthosilicate to 29.6mL of deionized water, stir to obtain a gel, transfer to a high-pressure hydrothermal reactor, age at 40℃ for 12h, after aging, raise the temperature to 60℃ and crystallize for 12h; filter the obtained hydrothermal reaction product, wash with deionized water until neutral, and dry at 100℃ to obtain 4A molecular sieve; weigh 3g of the obtained 4A molecular sieve and 4.5g CaCl2, mix with 30g of deionized water, perform ion exchange at 60℃ for 4.5h, filter, wash with deionized water until neutral, and dry at 100℃ to obtain 5A molecular sieve.

[0101] Test case

[0102] The molecular sieves prepared in the examples and comparative examples were used to measure the adsorption curves of ethylene and ethane on the molecular sieves and the amount of ethylene adsorbed, respectively, in a mixed system of ethylene / ethane volume ratio of 1:1 at 25 °C and 0-100 kPa. The adsorption selectivity of ethylene was then calculated using the IAST-DSLF model.

[0103] The adsorption curves of pure ethylene and ethane gases from the modified 5A molecular sieve in Example 7 are shown below. Figure 3 .

[0104] Table 1 shows the evaluation data of the mass ratio of 5A molecular sieve to silicon-containing compound, crystal size, relative crystallinity, and corresponding ethylene adsorption capacity and selectivity in the modified 5A molecular sieve of the above embodiments.

[0105] The evaluation data for the crystal size, relative crystallinity, and corresponding ethylene adsorption capacity and selectivity of the 5A molecular sieves in the above comparative examples are shown in Table 1.

[0106] Table 1

[0107]

Claims

1. A modified 5A molecular sieve characterized by, The modified 5A molecular sieve is composed of 5A molecular sieve and a silicon-containing compound, wherein the mass ratio of 5A molecular sieve to silicon-containing compound is 1:0.005-0.25, and the average grain size of the modified 5A molecular sieve is no greater than 1 μm. The modified 5A molecular sieve is obtained by the following method: preparation of 5A molecular sieve and silanization treatment, wherein the silanization treatment includes mixing 5A molecular sieve, silanizing reagent, and n-hexane at a mass ratio of 1:0.025-1.25:5-20, heating, filtering, washing, and drying, wherein the heating is carried out at a temperature of 100-160℃ for 6-24 hours. The silanizing agent is dimethyldichlorosilane, N-phenyl-3-aminopropyltrimethoxysilane, or hexadecyltrimethoxysilane.

2. The modified 5A molecular sieve of claim 1, wherein, The modified 5A molecular sieve has a mass ratio of 5A molecular sieve to silicon-containing compound of 1:0.02-0.10, and the average grain size of the modified 5A molecular sieve is no greater than 0.9 μm.

3. The modified 5A molecular sieve of claim 2, wherein, The average grain size is 0.70-0.85 μm.

4. The modified 5A molecular sieve of claim 1, wherein, The relative crystallinity of the modified 5A molecular sieve is not less than 80%.

5. The modified 5A molecular sieve of claim 4, wherein, The relative crystallinity of the modified 5A molecular sieve is not less than 90%.

6. The modified 5A molecular sieve of claim 1, wherein, The preparation steps of the 5A molecular sieve include: (1) Sodium hydroxide, aluminum source, silicon source and deionized water are mixed evenly at 10-30℃ according to the molar ratio of Na2O:Al2O3:SiO2:H2O of 2.5-4.0:0.8-1.0:1.9-3.8:100-150 to obtain the initial reaction gel; (2) The initial reaction gel described in step (1) is aged at a temperature of 25-40℃ for 4-120 h to obtain a mixed solution; (3) The mixed solution described in step (2) is crystallized under hydrothermal reaction conditions at a temperature of 50-90℃ for 2-12 h, and after filtration, washing and drying, 4A molecular sieve is obtained; (4) The 4A molecular sieve described in step (3) is mixed with soluble calcium salt and deionized water at a mass ratio of 1:0.5-3:5-20 and stirred at 60-90 °C for 0.5-5 h. After filtration, washing and drying, 5A molecular sieve is obtained.

7. The modified 5A molecular sieve according to claim 6, wherein, The aluminum source is selected from at least one of aluminum salts, aluminates, activated alumina, alkoxyaluminum, pseudoboehmite, and pseudoboehmite.

8. The modified 5A molecular sieve according to claim 6, wherein, The aluminum source is at least one of aluminate and pseudoboehmite.

9. The modified 5A molecular sieve according to claim 6, wherein, The silicon source is selected from at least one of silica, silica sol, silica gel, water glass, activated silica, and orthosilicate.

10. The modified 5A molecular sieve according to claim 6, wherein, The soluble calcium salt is selected from at least one of calcium nitrate, calcium chloride, calcium dihydrogen phosphate, calcium bicarbonate, and calcium bisulfate.

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