A modified enhanced molecular sieve and its application in hydrocarbon dehydration

Abstract

The invention relates to the field of molecular sieves, and discloses a modified enhanced molecular sieve and application thereof in hydrocarbon dehydration. The modified enhanced molecular sieve is prepared by mixing 4A molecular sieve raw powder, modified sheep liver soil and deionized water into a spherical shape, calcining the mixture in a muffle furnace, crystallizing the mixture with a sodium hydroxide solution, and then replacing the mixture with a potassium chloride solution. The mass ratio of the 4A molecular sieve raw powder, the modified sheep liver soil and the deionized water is 5.5-6:1:1.2-1.6. The modified sheep liver soil is prepared by calcining the sheep liver soil in a muffle furnace and pre-treating the mixture with acid leaching, then modifying the mixture with γ-aminopropyltriethoxysilane amination, and further in-situ growing silicon dioxide nanoparticles on the surface of the amination sheep liver soil through electrostatic assembly. The modified enhanced molecular sieve is prepared by sphering-calcining-alkaline environment crystallization-potassium chloride replacement, so that the static adsorption amount of the modified enhanced molecular sieve is increased to about 24%, and the modified enhanced molecular sieve has good application in hydrocarbon dehydration.

Description

Technical Field

[0001] The invention belongs to the technical field of molecular sieves, and in particular relates to a modified enhanced molecular sieve and application thereof in hydrocarbon dehydration. Background Art

[0002] Molecular sieve is a synthetic aluminosilicate or natural zeolite with the function of screening molecules. It has several channels with uniform pore sizes and neatly arranged holes in its structure. The most basic structure of the molecular sieve skeleton is SiO4 and AlO4 tetrahedrons, which are combined by shared oxygen atoms to form a three-dimensional network structure. Each unit cell of type A molecular sieve contains 8 α cages (diameter about 1.14nm) and 8 β cages (diameter about 0.66nm). + The diameter of the filled pores is reduced to 0.4 nm, which is 4A molecular sieve; + Replace Na + After that, the pore diameter is reduced to 0.3nm, which is 3A molecular sieve.

[0003] Molecular sieves have a preferential adsorption capacity for polar molecules and unsaturated molecules. Water molecules are polar molecules, so molecular sieves have good adsorption properties for water molecules. At present, the more mature 3A molecular sieves or 4A molecular sieves are generally used in petrochemical systems to adsorb moisture to achieve static dehydration of hydrocarbon raw materials. The current national consumption of hydrocarbon raw materials is as high as tens of thousands of tons. In the existing technology, 3A molecular sieves are made by mixing 80% 3A molecular sieve raw powder and 20% clay. The static adsorption capacity of 3A molecular sieves does not exceed 21%, which is relatively low. Summary of the invention

[0004] In order to solve the deficiencies mentioned in the above background technology, the purpose of the present invention is to provide a modified enhanced molecular sieve and its application in hydrocarbon dehydration, using 4A molecular sieve powder and modified sheep liver soil with a mass ratio of 5.5~6:1 as raw materials, and preparing the modified enhanced molecular sieve through balling-calcination-alkaline environment crystallization-potassium chloride replacement, so that the static adsorption capacity of the modified enhanced molecular sieve is increased to about 24%, and it has good application in hydrocarbon dehydration.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A modified enhanced molecular sieve, wherein the modified enhanced molecular sieve is obtained by mixing 4A molecular sieve raw powder, modified sheep liver soil and deionized water into a spherical shape, calcining in a muffle furnace, crystallizing with a sodium hydroxide solution, and then replacing with a potassium chloride solution, wherein the mass ratio of the 4A molecular sieve raw powder, the modified sheep liver soil and the deionized water is 5.5-6:1:1.2-1.6, and the modified sheep liver soil is obtained by calcining the sheep liver soil in a muffle furnace and pre-treating it by acid leaching, then modifying it by amination with γ-aminopropyltriethoxysilane, and further growing silicon dioxide nanoparticles in situ on the surface of the amination sheep liver soil by electrostatic assembly.

[0007] Preferably, the method for preparing the modified enhanced molecular sieve comprises the following steps:

[0008] S1. Take 4A molecular sieve raw powder and modified sheep liver soil, add deionized water and mix evenly, form by a ball forming machine, place in an oven at 105-120°C for drying, and then place in a muffle furnace at 600-650°C for calcination for 2-3h to prepare a calcined molded body;

[0009] S2, taking the calcined molded body and adding it to a sodium hydroxide solution, heating it to 45-55° C. for aging for 1-3 hours, and then heating it to 85-95° C. for crystallization for 2-3 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body;

[0010] S3. Take the crystallized body and add it to a potassium chloride solution, place it at 90-100°C to react for 2-4 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 300-350°C for 2-3 hours to prepare a modified enhanced molecular sieve.

[0011] Preferably, the concentration of the sodium hydroxide solution in step S2 is 3-7 mol / L.

[0012] Preferably, the concentration of the potassium chloride solution in step S3 is 1-2 mol / L.

[0013] Preferably, the preparation method of the modified sheep liver soil comprises the following steps:

[0014] A. Take the sheep liver soil and put it into a crucible, place it in a muffle furnace and calcine it at 250-400° C. for 3-5 hours, then add it to a hydrochloric acid solution with a concentration of 3-7 mol / L, place it at 85-100° C. for reflux reaction for 3-4 hours, and after the reaction is completed, centrifuge, wash, and dry to prepare pretreated sheep liver soil;

[0015] B. Pretreated sheep liver soil was placed in a reactor, toluene solvent was added, the temperature was raised to 55-65° C., and stirring was performed for 15-30 min. Then γ-aminopropyltriethoxysilane was added to react for 3-4 h. After the reaction was completed, the soil was filtered, washed, and dried to obtain amino-treated sheep liver soil.

[0016] C. Take the aminated sheep liver soil and ultrasonically disperse it in a citric acid solution to obtain a dispersion. Take sodium water glass and add deionized water. Add ethanol under stirring. Place it at 70-85°C and add the dispersion to stir and mix. Then adjust the pH value of the reaction system to 5.5-6.0, add ethanol and stop the reaction when the temperature of the reaction system is maintained at 70-85°C. After the reaction is completed, age it for 2-3 hours, centrifuge and discard the supernatant in the reaction system. Wash and dry the precipitate to prepare modified sheep liver soil.

[0017] Preferably, in step B, the mass ratio of the pretreated sheep liver soil to γ-aminopropyltriethoxysilane is 1:0.5-0.9.

[0018] Preferably, the concentration of the citric acid solution in step C is 1.5-2.5 mol / L.

[0019] Preferably, in step C, the addition ratio of the amination of sheep liver soil, sodium water glass and deionized water is 1g: 60-80g: 200-250mL.

[0020] The modified and enhanced molecular sieve described above is used in the dehydration of hydrocarbons.

[0021] Beneficial effects of the present invention:

[0022] The present invention uses 4A molecular sieve raw powder and modified sheep liver soil with a mass ratio of 5.5 to 6:1 as raw materials, and prepares the modified enhanced molecular sieve through balling-firing-alkaline environment crystallization-potassium chloride replacement. The present invention places the sheep liver soil in a muffle furnace for calcination and acid leaching for pretreatment, thereby improving the purity of the sheep liver soil, providing a maximum silicon source, and exposing a larger surface area. Then, the silicon hydroxyl groups in the γ-aminopropyltriethoxysilane structure are condensed with the hydroxyl groups on the surface of the pretreated sheep liver soil to prepare the amination sheep liver soil. Then, the hydroxyl-rich silicon dioxide nanoparticles are in situ grown on the surface of the amination sheep liver soil by an electrostatic assembly method. Due to the confinement effect of the sheep liver soil after the amination of γ-aminopropyltriethoxysilane on silicate ions, the growth of the silicon dioxide particles is inhibited, so that the silicon dioxide particles The particle size is controlled at a smaller specification, and the agglomeration of silica particles is suppressed to a great extent, so that the modified sheep liver soil has better dispersibility. In addition, the hydroxyl-rich silica loaded on the surface of the amination sheep liver soil is beneficial to improve the hydrophilicity of the amination sheep liver soil surface. At the same time, silica nanoparticles can be used as the reinforcing phase of the amination sheep liver soil, making full use of its silicon source, and synergistically acting with the amination sheep liver soil to improve the adsorption performance. The crystallization process can provide a suitable sodium source and alkalinity for the calcined molded body. The modified sheep liver soil is converted into a 4A molecular sieve by sodium supplementation under alkaline conditions, and potassium ions replace the sodium ions in the 4A molecular sieve, and then the potassium ions squeeze the 4A molecular sieve to make it a high-adsorption 3A molecular sieve, so that the static adsorption capacity of the modified and enhanced molecular sieve is increased to about 24%, which has a good application in hydrocarbon dehydration. DETAILED DESCRIPTION

[0023] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] Example 1 A method for preparing modified sheep liver soil comprises the following steps:

[0025] A. Take 10g of sheep liver soil and put it into a crucible, place it in a muffle furnace and calcine it at 350°C for 5h, then add it to 400mL of 5mol / L hydrochloric acid solution, place it at 95°C for reflux reaction for 4h, and after the reaction is completed, centrifuge, wash and dry to prepare pretreated sheep liver soil;

[0026] B. Take 5g of pretreated sheep liver soil in a reactor, add 100mL of toluene solvent, heat to 60°C and stir for 30min, then add 3.8g of γ-aminopropyltriethoxysilane and react for 4h. After the reaction is completed, filter, wash and dry to prepare amination sheep liver soil;

[0027] C. Take 5g of amination-modified sheep liver soil and ultrasonically disperse it in 200mL of 2mol / L citric acid solution to obtain a dispersion. Take 270g of sodium water glass and add it to 1000mL of deionized water. Add 12mL of ethanol under stirring. Add the dispersion at 80°C and stir to mix. Then use dilute sulfuric acid solution to adjust the pH value of the reaction system to 6.0. Add 500mL of ethanol and stop the reaction when the temperature of the reaction system is maintained at 80°C. After the reaction is completed, age it for 2h, centrifuge and discard the supernatant in the reaction system. Wash and dry the precipitate to prepare modified sheep liver soil.

[0028] Example 2 A method for preparing a modified enhanced molecular sieve comprises the following steps:

[0029] S1. Take 4A molecular sieve powder and modified sheep liver soil prepared in Example 1, add deionized water and mix evenly, the mass ratio of 4A molecular sieve powder, modified sheep liver soil and deionized water is 5:1:1.2, form by a ball forming machine, place in an oven at 105°C for drying, and then place in a muffle furnace at 600°C for calcination for 2h to prepare a calcined molded body;

[0030] S2, taking the calcined molded body and adding it to a 3 mol / L sodium hydroxide solution, heating it to 45°C for aging for 2 hours, and then heating it to 85°C for crystallization for 3 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body;

[0031] S3. Take the crystallized body and add it to 1 mol / L potassium chloride solution, place it at 90°C for reaction for 4 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 300°C for 3 hours to prepare a modified enhanced molecular sieve.

[0032] Example 3 A method for preparing a modified enhanced molecular sieve comprises the following steps:

[0033] S1. Take 4A molecular sieve powder and modified sheep liver soil prepared in Example 1, add deionized water and mix evenly, the mass ratio of 4A molecular sieve powder, modified sheep liver soil and deionized water is 5.6:1:1.4, form by a ball forming machine, place in an oven at 110°C for drying, and then place in a muffle furnace at 620°C for calcination for 3h to prepare a calcined molded body;

[0034] S2, taking the calcined molded body and adding it to a 5 mol / L sodium hydroxide solution, heating it to 50°C for aging for 3 hours, and then heating it to 90°C for crystallization for 2 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body;

[0035] S3. Take the crystallized body and add it to a 2 mol / L potassium chloride solution, place it at 95°C to react for 3 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 320°C for 3 hours to prepare a modified enhanced molecular sieve.

[0036] Example 4 A method for preparing a modified enhanced molecular sieve comprises the following steps:

[0037] S1. Take 4A molecular sieve powder and modified sheep liver soil prepared in Example 1, add deionized water and mix evenly, the mass ratio of 4A molecular sieve powder, modified sheep liver soil and deionized water is 6:1:1.5, form by a ball forming machine, place in an oven at 110°C for drying, and then place in a muffle furnace at 650°C for calcination for 2h to prepare a calcined molded body;

[0038] S2, taking the calcined molded body and adding it to a 7 mol / L sodium hydroxide solution, heating it to 55°C for aging for 1 hour, and then heating it to 95°C for crystallization for 3 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body;

[0039] S3. Take the crystallized body and add it to a 2 mol / L potassium chloride solution, place it at 100°C for reaction for 2 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 350°C for 2 hours to prepare a modified enhanced molecular sieve.

[0040] Comparative Example 1 A method for preparing a modified enhanced molecular sieve comprises the following steps:

[0041] S1. Take 4A molecular sieve powder and sheep liver soil, add deionized water and mix evenly, the mass ratio of 4A molecular sieve powder, sheep liver soil and deionized water is 5.6:1:1.4, form by a ball forming machine, place in an oven at 110°C for drying, and then place in a muffle furnace at 620°C for calcination for 3h to prepare a calcined molded body;

[0042] S2, taking the calcined molded body and adding it to a 5 mol / L sodium hydroxide solution, heating it to 50°C for aging for 3 hours, and then heating it to 90°C for crystallization for 2 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body;

[0043] S3. Take the crystallized body and add it to a 2 mol / L potassium chloride solution, place it at 95°C to react for 3 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 320°C for 3 hours to prepare a modified enhanced molecular sieve.

[0044] Comparative Example 2 A method for preparing a modified enhanced molecular sieve comprises the following steps:

[0045] S1. Take 4A molecular sieve powder and attapulgite, add deionized water and mix evenly, the mass ratio of 4A molecular sieve powder, attapulgite and deionized water is 5.6:1:1.4, form by a ball forming machine, place in an oven at 110°C for drying, and then place in a muffle furnace at 620°C for calcination for 3h to prepare a calcined molded body;

[0046] S2, taking the calcined molded body and adding it to a 5 mol / L sodium hydroxide solution, heating it to 50°C for aging for 3 hours, and then heating it to 90°C for crystallization for 2 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body;

[0047] S3. Take the crystallized body and add it to a 2 mol / L potassium chloride solution, place it at 95°C to react for 3 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 320°C for 3 hours to prepare a modified enhanced molecular sieve.

[0048] Comparative Example 3 A method for preparing a modified enhanced molecular sieve comprises the following steps:

[0049] S1. Mix 3A molecular sieve powder and attapulgite evenly, the mass ratio of 3A molecular sieve powder and attapulgite is 4:1, put the blend into a granulator, adjust the speed to 30r / min, and the water mist spray flow rate to 0.75L / min, and granulate to obtain spherical particles;

[0050] S2, calcining the spherical particles at low temperature, with the air inlet temperature of 145°C, the temperature of zone III of 110°C, the temperature of zone II of 105°C, the temperature of zone I of 100°C, and the dehumidification temperature of 75°C until the dehydration rate reaches 25%;

[0051] S3. After low-temperature calcination, the spherical particles are activated by high-temperature calcination, with the rotation speed adjusted to 30 r / min and the temperature to 750°C until the water content is less than 1.5%, thereby obtaining a modified enhanced molecular sieve.

[0052] Performance testing:

[0053] a. Saturated water absorption test: (1) The temperature of the bellows is set to 100°C, the crucible and the weighing bottle are baked in the bellows for not less than 2 hours, and the mass of the weighing bottle is m1; (2) The modified and enhanced molecular sieves prepared in Examples 2-4 and Comparative Examples 1-3 are quickly added to the crucible respectively; (3) The crucible is placed in a high-temperature resistance furnace, heated to 550°C, and kept warm for not less than 2 hours, and then placed in a dryer to cool the molecular sieve to room temperature; (4) The cooled modified and enhanced molecular sieve is spread flat in the weighing bottle, and the molecular sieve must not be piled up. The mass m2 is measured, and it is kept at 35°C for 24 hours in a saturated salt water space, and the mass m3 is weighed; (5) The static saturated water absorption is calculated according to the formula: μ = (m3-m2) / (m2-m1) × 100%, and the data results are shown in Table 1.

[0054] b. Dehydration depth test: The modified enhanced molecular sieves prepared in Examples 2-4 and Comparative Examples 1-3 were tested for dehydration depth of benzene, toluene and n-hexane using a fixed bed device. The test conditions were: 15-35°C temperature, and the AKF-3N Coulometric Karl Fischer moisture analyzer from Shanghai Hegong Scientific Instrument Co., Ltd. was used to detect the moisture content in the raw materials. The moisture content in the raw materials was about 50 ppm, and the test selected a space velocity of 1 h -1 , the temperature is (25±5)℃, and the data results are shown in Table 1.

[0055] Table 1 Test results of sample performance

[0056] ;

[0057] It can be seen from the data in Table 1 that the saturated water absorption rate of the modified and reinforced molecular sieve prepared in Examples 2-4 of the present invention can reach about 24%, wherein the sheep liver soil was not modified in Comparative Example 1, and the modified sheep liver soil was replaced with attapulgite in equal amounts in Comparative Example 2. In Comparative Example 3, 3A molecular sieve powder and attapulgite with a mass ratio of 4:1 were used as raw materials. The measured static saturated water absorption rate of Comparative Examples 1-3 was lower than that of Examples 2-4, indicating that the static adsorption capacity of the modified and reinforced molecular sieve prepared by 4A molecular sieve powder and modified sheep liver soil was high, and the minimum water content in benzene measured in Examples 2-4 was 2.8~3.1ppm, the minimum water content in toluene was 3.0~3.2ppm, and the minimum water content in n-hexane was 2.5~2.8ppm. The modified and reinforced molecular sieve prepared in Example 2-4 has a higher dehydration depth for benzene, toluene and n-hexane than that of Comparative Examples 1-3.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0059] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. A modified enhanced molecular sieve, characterized in that: The modified enhanced molecular sieve is prepared by mixing 4A molecular sieve raw powder, modified sheep liver soil and deionized water into a spherical shape, calcining in a muffle furnace, crystallizing with a sodium hydroxide solution, and then replacing with a potassium chloride solution. The mass ratio of the 4A molecular sieve raw powder, the modified sheep liver soil and the deionized water is 5.5-6:1:1.2-1.

6. The modified sheep liver soil is prepared by calcining the sheep liver soil in a muffle furnace and pre-treating it by acid leaching, then modifying it by amino modification with γ-aminopropyltriethoxysilane, and further growing silicon dioxide nanoparticles in situ on the surface of the amino sheep liver soil by electrostatic assembly.

2. The modified and enhanced molecular sieve according to claim 1, characterized in that: The preparation method of the modified enhanced molecular sieve comprises the following steps: S1. Take 4A molecular sieve raw powder and modified sheep liver soil, add deionized water and mix evenly, form by a ball forming machine, place in an oven at 105-120°C for drying, and then place in a muffle furnace at 600-650°C for calcination for 2-3h to prepare a calcined molded body; S2, taking the calcined molded body and adding it to a sodium hydroxide solution, heating it to 45-55° C. for aging for 1-3 hours, and then heating it to 85-95° C. for crystallization for 2-3 hours, and then washing it with deionized water until it is neutral, to prepare a crystallized molded body; S3. Take the crystallized body and add it to a potassium chloride solution, place it at 90-100°C to react for 2-4 hours, cool it to room temperature, wash it with deionized water, place it in an oven to dry, and then transfer it to a muffle furnace and calcine it at 300-350°C for 2-3 hours to prepare a modified enhanced molecular sieve.

3. The modified and enhanced molecular sieve according to claim 2, characterized in that: The concentration of the sodium hydroxide solution in step S2 is 3-7 mol / L.

4. The modified and enhanced molecular sieve according to claim 2, characterized in that: The concentration of the potassium chloride solution in step S3 is 1-2 mol / L.

5. The modified and enhanced molecular sieve according to claim 1, characterized in that: The preparation method of the modified sheep liver soil comprises the following steps: A. Take the sheep liver soil and put it into a crucible, place it in a muffle furnace and calcine it at 250-400° C. for 3-5 hours, then add it to a hydrochloric acid solution with a concentration of 3-7 mol / L, place it at 85-100° C. for reflux reaction for 3-4 hours, and after the reaction is completed, centrifuge, wash, and dry to prepare pretreated sheep liver soil; B. Pretreated sheep liver soil was placed in a reactor, toluene solvent was added, the temperature was raised to 55-65° C., and stirring was performed for 15-30 min. Then γ-aminopropyltriethoxysilane was added to react for 3-4 h. After the reaction was completed, the soil was filtered, washed, and dried to obtain amino-treated sheep liver soil. C. Take the aminated sheep liver soil and ultrasonically disperse it in a citric acid solution to obtain a dispersion. Take sodium water glass and add deionized water. Add ethanol under stirring. Place it at 70-85°C and add the dispersion to stir and mix. Then adjust the pH value of the reaction system to 5.5-6.0, add ethanol and stop the reaction when the temperature of the reaction system is maintained at 70-85°C. After the reaction is completed, age it for 2-3 hours, centrifuge and discard the supernatant in the reaction system. Wash and dry the precipitate to prepare modified sheep liver soil.

6. The modified and enhanced molecular sieve according to claim 5, characterized in that: The mass ratio of the pretreated sheep liver soil and γ-aminopropyltriethoxysilane in step B is 1:0.5-0.

9.

7. The modified and enhanced molecular sieve according to claim 5, characterized in that: The concentration of the citric acid solution in step C is 1.5-2.5 mol / L.

8. The modified and enhanced molecular sieve according to claim 5, characterized in that: In the step C, the addition ratio of the amination of sheep liver soil, sodium water glass and deionized water is 1g: 50-70g: 200-250mL.

9. Use of the modified and enhanced molecular sieve according to any one of claims 1 to 8 in hydrocarbon dehydration.