Composite adsorbent as well as preparation method and application thereof

Abstract

The invention discloses a composite adsorbent and a preparation method and application thereof, and belongs to the technical field of adsorbents, the composite adsorbent comprises the following raw materials by mass: 40-80 parts of aminated loofah sponge, 20-60 parts of chitosan, 4-20 parts of diatomite, 20-36 parts of halloysite, and 5-20 parts of a cross-linking agent. The preparation method comprises the following steps: acidifying diatomite and halloysite, adding the acidified diatomite and halloysite into a chitosan acetic acid solution, mixing, adding aminated loofah sponge, stirring and mixing, dropwise adding a cross-linking agent, stirring and cross-linking, and stirring to be colloidal. And drying and crushing to obtain the composite adsorbent. According to the composite adsorbent provided by the invention, due to the combination of different porous structures of the loofah sponge, the diatomite and the halloysite, the adsorbent is endowed with a secondary porous structure of a macroscopic pore structure and a microcosmic pore structure, the adsorption capacity is enhanced, and by virtue of the interaction of the aminated loofah sponge, the chitosan and the halloysite with fatty acid, the adsorption capacity is improved. The composite adsorbent is promoted to adsorb free fatty acid and the acid value of crude oil is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of adsorbents, and specifically relates to a composite adsorbent and a preparation method and application thereof. Background Art

[0002] Transformers are the main power equipment in the power grid, and the key to maintaining the long-term safe and stable operation of traditional power transformers lies in the insulating oil in them. Traditional insulating oil is mainly mineral insulating oil, which has a flash point of about 160°C. Once the temperature inside the transformer is too high, it is easy to cause an explosion. The flash point of vegetable insulating oil is as high as 300°C, and it has the advantages of being renewable and naturally degradable. Therefore, it is considered to be a good substitute for mineral insulating oil. Vegetable insulating oil is prepared from natural oil crops through processes such as pressing and refining.

[0003] Important indicators of vegetable insulating oil quality include acid value and dielectric loss factor. Acid value refers to the sum of organic acid and inorganic acid in insulating oil. Too high acid value not only easily corrodes equipment, but also affects the insulation strength and dielectric properties of the oil, reducing insulation performance. Dielectric loss factor is an important indicator to measure the insulation performance of insulating oil. In addition to being related to the water content in the oil, the dielectric loss factor is also related to the content of metal ions, colloids, microorganisms, organic acids and other polar impurities in the oil.

[0004] In view of the characteristics of crude oil with many impurities, high acid value and easy oxidation, in order to meet the requirements of insulating oil, refining treatment is required. The refining treatment includes dewaxing, decolorization, deodorization, alkali refining, water washing, compounding, drying and other processes, and the process is complicated and cumbersome. The alkali refining process is to remove free fatty acids by adding alkaline solution for neutralization treatment, but this method produces a large amount of soap stock, has a large refining consumption, and a low refining yield. Adsorbent adsorption and deacidification can remove free fatty acids (FFA) through adsorption and reaction. The method is simple and has low energy consumption, but the commonly used deacidification adsorbents generally have the problem of high consumption; the decolorization process uses adsorbents to remove impurities such as pigments and reduce chroma and dielectric loss factor, but the acid residue in the traditional decolorization process using activated clay adsorbent is high. Therefore, the traditional alkali refining and decolorization process is used, and the process flow is complicated and the adsorbent consumption is large. Summary of the invention

[0005] The object of the present invention is to provide a composite adsorbent and a preparation method and application thereof, wherein the composite adsorbent can reduce the acid value, chromaticity and dielectric loss factor of crude oil, thereby simplifying the refining process for preparing vegetable insulating oil.

[0006] The purpose of the present invention can be achieved through the following technical solutions: The present invention provides a composite adsorbent, which comprises the following raw materials in parts by mass: 40-80 parts of amino-modified loofah, 20-60 parts of chitosan, 4-20 parts of diatomaceous earth, 20-36 parts of halloysite, and 5-20 parts of a cross-linking agent.

[0007] Luffa is the vascular bundle in the loofah fruit, which has a unique porous physical structure and excellent mechanical strength. The loofah is made up of ligaments interwoven to form a macroscopic porous tissue. There is also a microscopic through-hole structure composed of honeycomb tube bundles inside the loofah. This secondary porous structure gives the loofah the characteristics of light weight and small size microstructure. As a natural material, loofah has the characteristics of low density, high strength and high toughness. Its porous structure gives it significant advantages in environmental protection and sustainability.

[0008] Chitosan is a natural polymer compound that contains a large number of hydroxyl (OH) and amino (NH3) groups in its molecular structure. The hydroxyl and amino groups of chitosan also have antioxidant properties.

[0009] Diatomaceous earth has a porous structure, which is mainly composed of mesopores and macropores, among which mesopores are the largest, followed by macropores, and micropores are relatively rare. The porous structure of diatomaceous earth gives it good adsorption properties. The surface of diatomaceous earth is covered with a large number of silanol groups (Si-OH), which exist not only on the surface of diatomaceous earth, but also on the inner surface of micropores.

[0010] Halloysite is a 1:1 layered silicate mineral belonging to the kaolinite family. Due to the size mismatch between silicon-oxygen tetrahedrons and aluminum-oxygen octahedrons, and the presence of interlayer water molecules, adjacent structural unit layers cannot maintain balance through hydrogen bonds. Therefore, the structural unit layers of halloysite curl up to form a nanotubular structure. This nanotubular structure gives halloysite a large specific surface area and rich pore structure, giving it adsorption capacity.

[0011] Further, the preparation process of described amination loofah is as follows: Add anhydrous ethanol to a 10-30wt% sodium hydroxide solution, the volume ratio of the sodium hydroxide solution to anhydrous ethanol is 0.5-2:1, stir evenly to obtain a mixed solution, add a 1-2cm 3 Small pieces of loofah, the solid-liquid mass ratio of loofah to the mixed liquid is 0.1-1:10, soak for 8-12 hours, filter after soaking, wash with deionized water to neutrality, and dry to obtain alkalized loofah, add aminosilane coupling agent to 60-80wt% ethanol aqueous solution to prepare a solution, the concentration of aminosilane coupling agent in the solution is 10-20wt%, add alkalized loofah to the solution at a mass ratio of 1-5:20, heat to 50-70℃, stir and react for 4-6 hours, filter after the reaction, wash to neutrality, and dry to obtain amino loofah.

[0012] Further, the amino-silane coupling agent includes one of 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane.

[0013] Further, the particle size of the diatomite is 100 - 300 μm.

[0014] Further, the diameter of the halloysite is 0.1 - 0.5 μm.

[0015] Further, the crosslinking agent is one of glutaraldehyde and citric acid.

[0016] Further, the particle size of the composite adsorbent is 0.1 - 1 mm.

[0017] The present invention also provides a preparation method of the composite adsorbent as described above, comprising the following steps: Step 1: Place the diatomite in one beaker and the halloysite in another beaker. Add 0.1 - 0.5 mol / L hydrochloric acid solution to each beaker, control the solid-liquid mass ratio in both beakers to be 1:5 - 10, stir at room temperature and soak for 10 - 16 h, filter and wash with deionized water until neutral, and dry to obtain acidified diatomite and acidified halloysite; Step 2: Dissolve chitosan in a 2 - 4 wt% acetic acid solution to obtain a chitosan solution, add the acidified diatomite and acidified halloysite to the chitosan solution, and stir evenly to form a mixture.

[0018] Step 3: Add amino-functionalized loofah sponge to the mixture, stir and mix evenly, dropwise add the crosslinking agent while stirring, continue to stir after the addition is complete to form a colloidal state, dry and crush to obtain the composite adsorbent.

[0019] Further, the mass fraction of chitosan in the chitosan solution is 1 - 4%.

[0020] The present invention also provides an application of the composite adsorbent as described above, and the composite adsorbent can be used in the adsorption process of vegetable insulating oil.

[0021] Advantages of the present invention: (1) In the present invention, an amino-functionalized loofah sponge, chitosan, diatomite and halloysite are formed into a composite adsorbent under the action of a crosslinking agent. The combination of different porous structures of the loofah sponge, diatomite and halloysite endows the composite adsorbent with a secondary porous structure of macro-pore structure and micro-pore structure, increases the specific surface area of the composite adsorbent, improves its adsorption capacity, reduces the dielectric loss factor of crude oil and reduces impurities.

[0022] (2) Introduce amino groups into loofah sponge. On the one hand, it realizes the cross-linking effect, and on the other hand, it can form an electrostatic bridging effect with the carboxyl groups of free fatty acids to adsorb free fatty acids. The electrostatic bridging effect of the amino groups of amino-functionalized loofah sponge and chitosan, and the aluminum hydroxyl groups on the surface of halloysite can form hydrogen bond interactions with the carbonyl groups of fatty acids in oils and fats, which can promote the composite adsorbent to adsorb free fatty acids and reduce the acid value of crude oil.

[0023] (3) The loofah sponge in the composite adsorbent has high toughness. Its ligament-interlaced fiber network structure enhances the cohesive force of the composite adsorbent during the mixing and cross-linking process with chitosan, diatomite, and halloysite. The prepared composite adsorbent is not easy to loosen during the adsorption process and is convenient for recycling. Specific embodiments

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0025] Example 1 Preparation of amino-functionalized loofah sponge: Add anhydrous ethanol to a 30 wt% sodium hydroxide solution. The volume ratio of the sodium hydroxide solution to anhydrous ethanol is 0.5:1. Stir evenly to obtain a mixed solution, and add loofah sponge cut into small pieces of 1-2 cm 3 and soak for 12 h. The solid-liquid mass ratio of the loofah sponge to the mixed solution is 1:10. After soaking, filter, wash with deionized water until neutral, and dry to obtain alkalized loofah sponge. Dissolve 3-aminopropyltrimethoxysilane in a 60 wt% ethanol aqueous solution to prepare a solution with a concentration of 10 wt% of the amino-silane coupling agent. Add the alkalized loofah sponge to the solution at a mass ratio of 1:20, heat to 50 °C and stir for 6 h. After the reaction, filter, wash until neutral, and dry to obtain amino-functionalized loofah sponge.

[0026] This example provides a composite adsorbent, which includes the following raw materials by mass fraction: 40 parts of amino-functionalized loofah sponge, 60 parts of chitosan, 20 parts of diatomite (particle size 100-300 μm), 20 parts of halloysite (diameter 0.1-0.5 μm), and 10 parts of glutaraldehyde. The specific preparation steps are as follows: Step 1: Place diatomite in one beaker and halloysite in another beaker. Add 0.5 mol / L hydrochloric acid solution to each beaker, control the solid-liquid mass ratio in both beakers to be 1:5, stir at room temperature and soak for 10 h, filter, wash with deionized water until neutral, and dry to obtain acidified diatomite and acidified halloysite.

[0027] Step 2: Dissolve chitosan in 4 wt% acetic acid solution to obtain a chitosan solution with a chitosan mass fraction of 3%. Add acidified diatomite and acidified halloysite to the chitosan solution and stir evenly to form a mixture.

[0028] Step 3: Add amino-functionalized loofah sponge to the mixture, stir and mix evenly. While stirring, dropwise add glutaraldehyde. After the addition is complete, continue to stir to form a colloidal state. Dry and crush to obtain a composite adsorbent with a particle size of 0.1 - 1 mm.

[0029] Refine crude soybean oil through degumming and dewaxing to obtain crude oil. Refer to the "DLT 1360-2014 Quality Standard for Soybean Plant Transformer Oil" to detect the dielectric loss factor, acid value, and appearance of the crude oil. The results are shown in Table 1.

[0030] Add the adsorbent prepared in this example to the crude oil according to a mass fraction of 3 wt%. The adsorption temperature is 50 °C, and the adsorption time is 2 h. After cooling, filter. Refer to the "DLT 1360-2014 Quality Standard for Soybean Plant Transformer Oil" to detect the dielectric loss factor, acid value, and appearance of the filtered soybean oil. The results are shown in Table 1.

[0031] Example 2 The difference from Example 1 is only that the mass fraction of diatomite is adjusted to 10 parts, and the mass fraction of high-quality high-white halloysite is adjusted to 30 parts. Other steps and conditions are the same as in Example 1.

[0032] Add the adsorbent prepared in this example to the crude oil according to a mass fraction of 1 wt%. The adsorption temperature is 50 °C, and the adsorption time is 2 h. After cooling, filter. Refer to the "DLT 1360-2014 Quality Standard for Soybean Plant Transformer Oil" to detect the dielectric loss factor, acid value, and appearance of the filtered soybean oil. The results are shown in Table 1.

[0033] Example 3 The difference from Example 1 is only that the mass fraction of diatomite is adjusted to 4 parts, and the mass fraction of high-quality high-white halloysite is adjusted to 36 parts. Other steps and conditions are the same as in Example 1.

[0034] Add the adsorbent prepared in this example to the crude oil at a mass fraction of 1 wt%, with an adsorption temperature of 50 °C and an adsorption time of 2 h. After cooling, filter. The filtered soybean oil is tested for the dielectric loss factor, acid value, and appearance with reference to the "DLT 1360-2014 Quality Standard for Soybean Plant Transformer Oil". The results are shown in Table 1.

[0035] Example 4 The difference from Example 2 is only that the mass fraction of amino-functionalized loofah sponge is adjusted to 60 parts, and the mass fraction of chitosan is adjusted to 40 parts. Other steps and conditions are the same as in Example 2.

[0036] Add the adsorbent prepared in this example to the crude oil at a mass fraction of 1 wt%, with an adsorption temperature of 50 °C and an adsorption time of 2 h. After cooling, filter. The filtered soybean oil is tested for the dielectric loss factor, acid value, and appearance with reference to the "DLT 1360-2014 Quality Standard for Soybean Plant Transformer Oil". The results are shown in Table 1.

[0037] Example 5 The difference from Example 2 is only that the mass fraction of amino-functionalized loofah sponge is adjusted to 80 parts, and the mass fraction of chitosan is adjusted to 20 parts. Other steps and conditions are the same as in Example 2.

[0038] Add the adsorbent prepared in this example to the crude oil at a mass fraction of 1 wt%, with an adsorption temperature of 50 °C and an adsorption time of 2 h. After cooling, filter. The filtered soybean oil is tested for the dielectric loss factor, acid value, and appearance with reference to the "DLT 1360-2014 Quality Standard for Soybean Plant Transformer Oil". The results are shown in Table 1.

[0039] Comparative Example 1 Compared with Example 1, in the adsorbent raw materials of this comparative example, amino-functionalized loofah sponge is not added, and the step of preparing amino-functionalized loofah sponge is omitted.

[0040] This comparative example provides a composite adsorbent, which includes the following raw materials by mass fraction: 60 parts of chitosan, 20 parts of diatomite (particle size 100 - 300 μm), 20 parts of halloysite (diameter 0.1 - 0.5 μm), and 10 parts of glutaraldehyde. The specific preparation steps are as follows: Step 1: Place the diatomite in one beaker and the halloysite in another beaker. Add 0.5 mol / L hydrochloric acid solution to each beaker, control the solid-liquid mass ratio in both beakers to be 1:5, stir and soak at room temperature for 10 h, filter, wash with deionized water until neutral, and dry to obtain acidified diatomite and acidified halloysite.

[0041] Step 2: Dissolve chitosan in a 4 wt% acetic acid solution to obtain a chitosan solution with a chitosan mass fraction of 3% in the chitosan solution. Add acidified diatomite and acidified halloysite to the chitosan solution, stir evenly, dropwise add glutaraldehyde while stirring, continue stirring after the addition is complete to form a colloid, dry and then crush to obtain a composite adsorbent with a particle size of 0.1 - 1 mm.

[0042] The specific detection steps are the same as those in Example 1.

[0043] Comparative Example 2 Compared with Example 1, halloysite is not added to the adsorbent raw materials in this comparative example. This comparative example provides a composite adsorbent, which includes the following raw materials by mass parts: 40 parts of amino-functionalized loofah sponge, 60 parts of chitosan, 20 parts of diatomite (particle size of 100 - 300 μm), and 10 parts of glutaraldehyde. The preparation steps are as follows: Step 1: Place diatomite in a beaker, add a 0.5 mol / L hydrochloric acid solution, control the solid-liquid mass ratio in the beaker to be 1:5, stir and soak at room temperature for 10 h, filter and wash with deionized water until neutral, and dry to obtain acidified diatomite.

[0044] Step 2: Dissolve chitosan in a 4 wt% acetic acid solution to obtain a chitosan solution with a chitosan mass fraction of 3% in the chitosan solution. Add acidified diatomite to the chitosan solution and stir evenly to form a mixture.

[0045] Step 3: Add amino-functionalized loofah sponge to the mixture, stir and mix evenly, dropwise add glutaraldehyde while stirring, continue stirring after the addition is complete to form a colloid, dry and then crush to obtain a composite adsorbent with a particle size of 0.1 - 1 mm.

[0046] The specific detection steps are the same as those in Example 1.

[0047] Comparative Example 3 Compared with Example 1, diatomite is not added to the adsorbent raw materials in this comparative example. This comparative example provides a composite adsorbent, which includes the following raw materials by mass parts: 40 parts of amino-functionalized loofah sponge, 60 parts of chitosan, 20 parts of halloysite (diameter of 0.1 - 0.5 μm), and 10 parts of glutaraldehyde. The specific preparation steps are as follows: Step 1: Place halloysite in a beaker, add a 0.5 mol / L hydrochloric acid solution, control the solid-liquid mass ratio in the beaker to be 1:5, stir and soak at room temperature for 10 h, filter and wash with deionized water until neutral, and dry to obtain acidified halloysite.

[0048] Step 2: Dissolve chitosan in a 4 wt% acetic acid solution to obtain a chitosan solution with a chitosan mass fraction of 3% in the chitosan solution. Add acidified halloysite to the chitosan solution and stir evenly to form a mixture.

[0049] Step 3: Add amino-functionalized loofah sponge to the mixture and stir evenly. While stirring, dropwise add glutaraldehyde. After the addition is completed, continue stirring to form a colloidal state. Dry and then crush to obtain a composite adsorbent with a particle size of 0.1 - 1 mm.

[0050] The specific detection steps are the same as those in Example 1.

[0051] 。

[0052] As can be seen from Table 1, in Examples 1 - 3, the porous structure of the composite adsorbent was controlled by adjusting the mass fraction ratio of diatomite and halloysite. Among them, under the ratio of Example 2, the prepared composite adsorbent has a relatively high adsorption capacity, and the acid value and dielectric loss factor of the crude oil are significantly reduced compared with those in Example 1. In Examples 4 and 5, based on Example 2, the proportion of amino-functionalized loofah sponge was increased and the proportion of chitosan was decreased. In Example 5, due to the relatively small proportion of chitosan, the adsorption capacity of the composite adsorbent for fatty acids is inferior to that in Example 2, and the performance of the composite adsorbent in Example 4 is the best among the examples. In Comparative Examples 1 - 3, since the amino-functionalized loofah sponge, halloysite or diatomite was not added, the porous structure of the adsorbent changed, its adsorption capacity for impurities such as pigments was inferior to that in Example 1, the dielectric loss factor was relatively high, and there was a slightly turbid phenomenon in the visual appearance.

[0053] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover a non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device.

[0054] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A composite adsorbent, characterized in that, By mass fraction, it includes the following raw materials: 40 - 80 parts of aminated loofah sponge, 20 - 60 parts of chitosan, 4 - 20 parts of diatomite, 20 - 36 parts of halloysite, 5 - 20 parts of crosslinking agent; The preparation steps of the aminated loofah sponge are as follows: Add absolute ethanol to a sodium hydroxide solution of 10 - 30 wt%, with the volume ratio of the sodium hydroxide solution to absolute ethanol being 0.5 - 2:

1. Stir evenly to obtain a mixed solution, and add loofah sponge cut into small pieces of 1 - 2 cm 3 . The solid-liquid mass ratio of the loofah sponge to the mixed solution is 0.1 - 1:

10. Soak for 8 - 12 h, filter after soaking, wash with deionized water until neutral, and dry to obtain alkalized loofah sponge. Add an amino-silane coupling agent to an ethanol aqueous solution of 60 - 80 wt% to prepare a solution, with the concentration of the amino-silane coupling agent in the solution being 10 - 20 wt%. Add the alkalized loofah sponge to the solution at a mass ratio of 1 - 5:20, heat to 50 - 70 °C, stir and react for 4 - 6 h. Filter after the reaction, wash until neutral, and dry to obtain amino-functionalized loofah sponge.

2. The composite adsorbent according to claim 1, wherein The amino silane coupling agent includes one of 3 - aminopropyltrimethoxysilane and 3 - aminopropyltriethoxysilane.

3. A composite adsorbent according to claim 1, characterized in that, The particle size of the diatomite is 100 - 300μm.

4. A composite adsorbent according to claim 1, characterized in that, The halloysite is high - quality high - white halloysite with a diameter of 0.1 - 0.5μm.

5. The composite adsorbent according to claim 1, characterized in that, The crosslinking agent is one of glutaraldehyde and citric acid.

6. The composite adsorbent according to claim 1, characterized in that, The particle size of the composite adsorbent is 0.1 - 1mm.

7. A method for preparing a composite adsorbent according to any one of claims 1-6, characterized in that, It includes the following steps: Step 1: Place the diatomite in one beaker and the halloysite in another beaker. Add 0.1 - 0.5mol / L hydrochloric acid solution to each beaker, control the solid - liquid mass ratio in both beakers to be 1:5 - 10, stir and soak at room temperature for 10 - 16h, filter and wash with deionized water until neutral, and dry to obtain acidified diatomite and acidified halloysite; Step 2: Dissolve chitosan in a 2 - 4wt% acetic acid solution to obtain a chitosan solution. Add the acidified diatomite and acidified halloysite to the chitosan solution and stir evenly to form a mixture; Step 3: Add the aminated loofah sponge to the mixture, stir and mix evenly. While stirring, dropwise add the crosslinking agent. After the addition is completed, continue to stir to form a colloidal state, dry and then crush to obtain the composite adsorbent.

8. The preparation method of a composite adsorbent according to claim 7, characterized in that, The mass fraction of chitosan in the chitosan solution is 1 - 4%.

9. Use of a composite adsorbent according to any one of claims 1-6, characterized in that, The composite adsorbent can be used in the adsorption process of plant insulating oil.