Activated carbon-based desulfurization catalyst, preparation method thereof and flue gas purification device

Abstract

The invention discloses an activated carbon-based desulfurization catalyst, a preparation method thereof and a flue gas purification device, and aims to solve the technical problem that the activated carbon-based desulfurization catalyst has strong hydrophilicity, so that the adsorption of SO2 is facilitated, and meanwhile, the deactivation of the activated carbon-based desulfurization catalyst is accelerated. The activated carbon-based desulfurization catalyst is obtained by carrying out modification treatment on an activated carbon base material, and the modification treatment comprises the following steps: first modification treatment: introducing a nitrogen-containing functional group on the activated carbon base material, so that nitrogen on the surface of the activated carbon-based desulfurization catalyst mainly exists in forms of pyridine nitrogen and pyrrole nitrogen; and second modification treatment: carrying out hydrophobicity adjustment on the activated carbon base material subjected to the first modification treatment, so that the water contact angle of the activated carbon-based desulfurization catalyst in a water contact experiment is more than 90 degrees and less than or equal to 145 degrees.

Description

Technical Field

[0001] The present invention relates to an activated carbon-based desulfurization catalyst, a preparation method thereof, and a flue gas purification device. Background Art

[0002] The basic principle of catalytic flue gas desulfurization is as follows: sulfur dioxide, water, and oxygen in the flue gas to be desulfurized are adsorbed on the activated carbon-based desulfurization catalyst, and react under the catalysis of the active component to generate sulfuric acid; when the sulfuric acid attached to the activated carbon-based desulfurization catalyst reaches a certain level, a regeneration liquid (usually dilute sulfuric acid and / or water) can be used to wash the activated carbon-based desulfurization catalyst, thereby removing the attached sulfuric acid on the activated carbon-based desulfurization catalyst and releasing the active sites of the desulfurization catalyst.

[0003] The inventors have found that: existing activated carbon-based desulfurization catalysts often have strong hydrophilicity, which helps to adsorb the hydrophilic substance SO2 and promote the catalytic oxidation of SO2. However, the strong hydrophilicity of the activated carbon-based desulfurization catalyst will also cause it to more easily adsorb water molecules, so that the active sites on the activated carbon-based desulfurization catalyst are occupied at a faster rate, thereby accelerating the inactivation of the activated carbon-based desulfurization catalyst. Coincidentally, in response to such a contradiction, the current practice within the applicant is to emphasize the adsorption of SO2 on the activated carbon-based desulfurization catalyst while shortening the regeneration cycle of the activated carbon-based desulfurization catalyst.

[0004] On the other hand, existing activated carbon-based desulfurization catalysts mostly use columnar granular activated carbon. Activated carbon fiber is a high-efficiency adsorption functional material, which is mainly prepared by carbonizing and activating various fibers. It has a relatively small adsorption leakage, a large adsorption capacity, a developed specific surface area and excellent micropore size, which are its advantages. If it is applied to the activated carbon-based desulfurization catalyst, the performance of the activated carbon-based desulfurization catalyst in catalytically oxidizing SO2 can be improved. However, existing activated carbon fibers have very strong hydrophilicity, and water will be instantaneously absorbed by the activated carbon fibers in the water contact experiment. Therefore, when activated carbon fibers are used as the activated carbon-based desulfurization catalyst, they will be quickly inactivated. Summary of the Invention

[0005] The object of the present invention is to provide an improved activated carbon-based desulfurization catalyst, a preparation method thereof, and a flue gas purification device, so as to solve the technical problem of the contradiction that the strong hydrophilicity of the activated carbon-based desulfurization catalyst helps to adsorb SO2 but also accelerates the inactivation of the activated carbon-based desulfurization catalyst.

[0006] In a first aspect, an activated carbon-based desulfurization catalyst is provided, which is obtained by performing a modification treatment on an activated carbon substrate. The modification treatment includes: a first modification treatment: introducing nitrogen-containing functional groups onto the activated carbon substrate so that the nitrogen on the surface of the activated carbon-based desulfurization catalyst mainly exists in the forms of pyridine nitrogen and pyrrole nitrogen; a second modification treatment: performing a hydrophobicity adjustment on the activated carbon substrate that has undergone the first modification treatment so that the water contact angle of the activated carbon-based desulfurization catalyst in a water contact experiment is > 90° and ≤ 145°. Optionally, the activated carbon substrate is made of activated carbon fibers.

[0007] Optionally, the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is 95° - 115°, more preferably 95° - 110°, and still more preferably 100° - 105°.

[0008] Optionally, the modification treatment further includes a pretreatment performed before the first modification treatment. The pretreatment includes calcining the activated carbon substrate in a nitrogen atmosphere at a temperature of 450°C - 600°C for 1 h - 3 h.

[0009] Specifically, the first modification treatment specifically includes: a nitrogen doping impregnation operation: dissolving thiourea in an ethanol solution to prepare a mixed solution with a thiourea content of 0.1 mol / L - 1.0 mol / L, then uniformly spraying the mixed solution onto the activated carbon substrate according to a dosage with a mass ratio of the mixed solution to the activated carbon substrate of 8 - 11, and then drying; a calcining operation: placing the dried activated carbon substrate in a nitrogen atmosphere and calcining it at a temperature of 800°C - 1000°C for 1 h - 3 h.

[0010] Specifically, the second modification treatment specifically includes: dissolving trimethyloxysilane in absolute ethanol to prepare a trimethylsiloxane solution with a mass fraction of 5% - 20%, then uniformly spraying the trimethylsiloxane solution onto the activated carbon substrate that has undergone the first modification treatment according to a dosage with a mass ratio of the trimethylsiloxane solution to the activated carbon substrate of 8 - 11, and then drying.

[0011] Second aspect, a preparation method of an activated carbon-based desulfurization catalyst is provided, which performs modification treatment on an activated carbon substrate. The modification treatment includes: Pretreatment: roasting the activated carbon substrate in a nitrogen atmosphere at a temperature of 450°C - 600°C for 1h - 3h; First modification treatment, the first modification treatment specifically includes: Nitrogen-doped impregnation operation: Dissolve thiourea in an ethanol solution to prepare a mixed solution with a thiourea content of 0.1mol / L - 1.0mol / L, and then evenly spray the mixed solution on the activated carbon substrate according to the mass ratio of the mixed solution to the pretreated activated carbon substrate of 8 - 11, and then dry; Roasting operation: Place the dried activated carbon substrate in a nitrogen atmosphere and roast it at a temperature of 800°C - 1000°C for 1h - 3h; Second modification treatment, the second modification treatment specifically includes: Dissolve trimethyloxysilane in absolute ethanol to prepare a trimethylsiloxane solution with a mass fraction of 5% - 20%, and then evenly spray the trimethylsiloxane solution on the activated carbon substrate according to the mass ratio of the trimethylsiloxane solution to the activated carbon substrate after the first modification treatment of 8 - 11, and then dry. Optionally, the activated carbon substrate uses activated carbon fibers.

[0012] Optionally, through the second modification treatment, ensure that the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is 95° - 115°, more preferably 95° - 110°, and still more preferably 100° - 105°.

[0013] Third aspect, a flue gas purification device is provided, including a catalytic flue gas desulfurization device, and the catalytic flue gas desulfurization device uses the activated carbon-based desulfurization catalyst of the first aspect above.

[0014] The above activated carbon-based desulfurization catalyst, its preparation method and flue gas purification device of the present invention are based on the following concept: First, introduce nitrogen-containing functional groups on the activated carbon substrate through the first modification treatment, so that the nitrogen on the surface of the activated carbon-based desulfurization catalyst mainly exists in the form of pyridine nitrogen and pyrrole nitrogen. The two types of nitrogen-containing functional groups of pyridine nitrogen and pyrrole nitrogen have certain weak basicity, so as to improve the adsorption affinity and catalytic activity of the activated carbon-based desulfurization catalyst for SO2 gas; Second, then perform hydrophobicity adjustment on the activated carbon substrate after the first modification treatment through the second modification treatment, so that the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is > 90° and ≤ 145°, thereby improving the hydrophobicity of the activated carbon-based desulfurization catalyst. In this way, the activated carbon-based desulfurization catalyst can automatically desorb the sulfuric acid formed by catalytic oxidation of SO2 on the activated carbon-based desulfurization catalyst to a certain extent. Thereby, solve the technical problem of the contradiction that the strong hydrophilicity of the activated carbon-based desulfurization catalyst helps the adsorption of SO2 but also accelerates the inactivation of the activated carbon-based desulfurization catalyst.

[0015] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. The additional aspects and advantages provided by the present invention will be partially given in the following description, partially become apparent from the following description, or be understood through practice. Description of the Drawings

[0016] The drawings forming a part of the present invention are used to assist in understanding the present invention. The content provided in the drawings and the related descriptions in the present invention can be used to explain the present invention, but do not constitute an improper limitation to the present invention.

[0017] Figure 1 It is a schematic structural diagram of a flue gas purification device according to an embodiment of the present invention.

[0018] Figure 2 It is a side scanning electron micrograph (5,000 times) of the activated carbon fiber used in the preparation method of an activated carbon-based desulfurization catalyst according to an embodiment of the present invention.

[0019] Figure 3 It is a cross-sectional scanning electron micrograph (10,000 times) of the activated carbon fiber used in the preparation method of an activated carbon-based desulfurization catalyst according to an embodiment of the present invention.

[0020] Figure 4 It is a side scanning electron micrograph (5,000 times) of the activated carbon-based desulfurization catalyst prepared by the preparation method of an activated carbon-based desulfurization catalyst according to an embodiment of the present invention.

[0021] Figure 5 It is a cross-sectional scanning electron micrograph (10,000 times) of the activated carbon-based desulfurization catalyst prepared by the preparation method of an activated carbon-based desulfurization catalyst according to an embodiment of the present invention.

[0022] Figure 6 It is a desulfurization efficiency graph of the original sample used in the experiment (i.e., the activated carbon fiber of model STF-1900 produced by Jiangsu Sutong Carbon Fiber Co., Ltd.) and the activated carbon-based desulfurization catalyst samples of Experimental Example 1 - Experimental Example 6. In the figure, the abscissa is time and the ordinate is desulfurization efficiency.

[0023] Figure 7 It is an X-ray photoelectron spectroscopy graph of the original sample used in the experiment (i.e., the activated carbon fiber of model STF-1900 produced by Jiangsu Sutong Carbon Fiber Co., Ltd.), the activated carbon-based desulfurization catalyst sample of Experimental Example 3 (Example 3), and the activated carbon-based desulfurization catalyst sample of Experimental Example 5 (Comparative Example 1). In the figure, the abscissa is the electron binding energy and the ordinate is the measured intensity of the photoelectron.

[0024] Figure 8 It is a photo of the water contact angle test of the activated carbon-based desulfurization catalyst sample of Experimental Example 1 (Example 1) of the present invention.

[0025] Figure 9This is a test photo of the water contact angle of the activated carbon-based desulfurization catalyst sample in Experimental Example 3 (Example 3) of the present invention. Detailed implementation manners

[0026] The present invention will be clearly and completely described below with reference to the accompanying drawings. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly noted that:

[0027] In each part including the following descriptions, the technical solutions and technical features provided, without conflict, these technical solutions and technical features can be combined with each other. In addition, where possible, these technical solutions, technical features and related combinations can be given specific technical themes and be protected by relevant patents.

[0028] The embodiments of the present invention involved in the following descriptions are usually only some embodiments rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art without creative work based on these embodiments should fall within the scope of patent protection.

[0029] The terms "comprising", "including" and any variations thereof in this specification, the corresponding claims and relevant parts are intended to cover non-exclusive inclusion. Other relevant terms and units can be reasonably interpreted based on the relevant content provided by the present invention.

[0030] The basic principle of catalytic flue gas desulfurization is that sulfur dioxide, water and oxygen in the flue gas to be desulfurized are adsorbed on the activated carbon-based desulfurization catalyst and react to form sulfuric acid under the catalytic action of the active component; when the sulfuric acid attached to the activated carbon-based desulfurization catalyst reaches a certain degree, a regenerating liquid (usually dilute sulfuric acid and / or water) can be used to wash the activated carbon-based desulfurization catalyst to remove the attached sulfuric acid on the activated carbon-based desulfurization catalyst and release the active sites of the desulfurization catalyst.

[0031] The inventors found that: existing activated carbon-based desulfurization catalysts often have strong hydrophilicity, which helps to adsorb hydrophilic substances such as SO2 and promote the catalytic oxidation of SO2. However, the strong hydrophilicity of the activated carbon-based desulfurization catalyst will also cause it to more easily adsorb water molecules, so that the active sites on the activated carbon-based desulfurization catalyst are occupied at a faster rate, thereby accelerating the inactivation of the activated carbon-based desulfurization catalyst.

[0032] The purpose of the present invention is to provide an improved activated carbon-based desulfurization catalyst, its preparation method and a flue gas purification device to solve the technical problem of the contradiction that the strong hydrophilicity of the activated carbon-based desulfurization catalyst helps to adsorb SO2 but also accelerates the inactivation of the activated carbon-based desulfurization catalyst.

[0033] First, the flue gas purification device for the specific application of the activated carbon-based desulfurization catalyst of the present invention will be described below. Of course, the activated carbon-based desulfurization catalyst of the present invention is not limited to this flue gas purification device.

[0034] Figure 1 It is a schematic structural diagram of a flue gas purification device according to an embodiment of the present invention. As Figure 1 shown, the flue gas purification device of this embodiment at least includes: a catalytic flue gas desulfurization module 3, a low-temperature SCR denitrification module 4, and a heat exchange module 2. This flue gas purification device provides an integrated desulfurization and denitrification solution, and its applicable scenarios are very rich, covering many industrial furnace flue gas desulfurization and denitrification occasions.

[0035] Among them, the catalytic flue gas desulfurization module 3 includes a desulfurization reactor, which has an inlet for flue gas to be desulfurized, an outlet for desulfurized flue gas, and a filling space for the activated carbon-based desulfurization catalyst located in the desulfurization reactor; when desulfurizing, the flue gas enters the desulfurization reactor from the inlet for flue gas to be desulfurized, then is desulfurized by the activated carbon-based desulfurization catalyst and then discharged from the outlet for desulfurized flue gas. Sulfur dioxide in the flue gas reacts on the activated carbon-based desulfurization catalyst to form sulfuric acid when passing through the activated carbon-based desulfurization catalyst. This desulfurization reactor cancels the previous regeneration liquid spraying device, which will be specifically described later.

[0036] Among them, the low-temperature SCR denitrification module 4 includes an SCR denitrification reactor and a mixer (for mixing a reducing agent such as ammonia with flue gas) provided before the SCR denitrification reactor. The SCR denitrification reactor has an inlet for flue gas to be denitrified, an outlet for denitrified flue gas, and a filling space for the denitrification catalyst located in the SCR denitrification reactor. The filling space for the denitrification catalyst is used to fill the denitrification catalyst, and the working temperature of the denitrification catalyst is 120°C - 200°C (therefore, this denitrification catalyst is called a low-temperature denitrification catalyst); when denitrifying, the flue gas mixed with the denitrification reducing agent enters the SCR denitrification reactor from the inlet for flue gas to be denitrified, then is denitrified by the denitrification catalyst and then discharged from the outlet for denitrified flue gas.

[0037] Among them, the heat exchange module 2 includes a first heat exchanger 21. The first heat exchanger 21 has a first inlet for flue gas to be cooled, a first outlet for cooled flue gas, a first inlet for flue gas to be heated, a first outlet for heated flue gas, and a first heat exchange channel and a second heat exchange channel of the first heat exchanger for indirect heat exchange located in the first heat exchanger 21. The two ends of the first heat exchange channel of the first heat exchanger are respectively communicated with the first inlet for flue gas to be cooled and the first outlet for cooled flue gas, and the two ends of the second heat exchange channel of the first heat exchanger are respectively communicated with the first inlet for flue gas to be heated and the first outlet for heated flue gas.

[0038] In addition, in the flue gas purification device of this embodiment, the first flue gas inlet to be cooled is used to connect to the source of industrial furnace flue gas, the first flue gas outlet after cooling is used to connect to the flue gas inlet to be desulfurized, the flue gas outlet after desulfurization is used to connect to the first flue gas inlet to be heated, the first flue gas outlet after heating is used to connect to the flue gas inlet to be denitrified, and the flue gas outlet after denitrification is used to output the denitrified flue gas from the flue gas purification device.

[0039] Generally speaking, the temperature of the flue gas to be desulfurized at the flue gas inlet to be desulfurized can be 50°C - 100°C; the temperature of the flue gas after heating at the first flue gas outlet after heating can be 120°C - 220°C.

[0040] The working principle of the flue gas purification device of this embodiment is as follows: The relatively high-temperature flue gas (for example, with a temperature of 130°C - 170°C) from the source of industrial furnace flue gas enters the first heat exchanger 21 through the first flue gas inlet to be cooled. The first heat exchanger 21 discharges the cooled flue gas (for example, with a temperature of 60°C - 80°C) from the first flue gas outlet after cooling. The cooled flue gas enters the catalytic flue gas desulfurization module 3 as the flue gas to be desulfurized. The desulfurized flue gas output by the catalytic flue gas desulfurization module 3 returns to the first heat exchanger 21 from the first flue gas inlet to be heated. The first heat exchanger 21 discharges the heated flue gas (for example, with a temperature of 120°C - 160°C) from the first flue gas outlet after heating. The heated flue gas enters the low-temperature SCR denitrification module 4 as the flue gas to be denitrified. The low-temperature SCR denitrification module 4 outputs the denitrified flue gas. In the first heat exchanger 21, the relatively high-temperature flue gas from the source of industrial furnace flue gas exchanges heat indirectly with the relatively low-temperature desulfurized flue gas output by the catalytic flue gas desulfurization module 3. Therefore, on the one hand, the flue gas purification device of this embodiment reduces the temperature of the flue gas to be desulfurized through the first heat exchanger 21; on the other hand, the temperature of the flue gas to be denitrified can be raised to the temperature range required by the low-temperature SCR denitrification module 3 through the first heat exchanger 21. Since the first heat exchanger 21 exchanges heat indirectly between the relatively high-temperature flue gas from the source of industrial furnace flue gas and the relatively low-temperature desulfurized flue gas output by the catalytic flue gas desulfurization module 3, no extra energy consumption is generated for heating the flue gas to be denitrified.

[0041] As Figure 1As shown in the figure, in the flue gas purification device of this embodiment, when the temperature of the flue gas from the industrial furnace flue gas source is too high, for example, exceeding 170 °C (such as coke oven flue gas), a second heat exchanger 22 can also be provided in the heat exchange module 2. The second heat exchanger 22 has a second flue gas inlet to be cooled and a second flue gas outlet that has been cooled. The first flue gas outlet that has been cooled is used to connect to the second flue gas inlet to be cooled, and the second flue gas outlet that has been cooled is used to connect to the flue gas inlet to be desulfurized. The second heat exchanger 22 can adopt a waste heat boiler. The function of the second heat exchanger 22 is that when the temperature of the flue gas from the industrial furnace flue gas source is too high, by further recovering the heat of the flue gas, both the effective utilization of waste heat is achieved, and at the same time, the temperature of the flue gas to be desulfurized and the temperature of the flue gas to be denitrified can be controlled within an ideal range. In order to control the first heat exchanger 21 or the flue gas outlet direction, a control valve 23 is provided between the first heat exchanger 21 and the second heat exchanger 22.

[0042] As Figure 1 As shown in the figure, in the flue gas purification device of this embodiment, a dust removal module 1 is usually further included. The dust removal module 1 includes a dry flue gas dust collector, and the dry flue gas dust collector is used to connect to the first flue gas inlet to be cooled, and after dust removal of the flue gas from the industrial furnace flue gas source, it is transported to the first flue gas inlet to be cooled. The dry flue gas dust collector can adopt an electrostatic precipitator, an electrostatic bag precipitator, a bag filter, a ceramic filter, a metal filter, etc. Generally speaking, the dust removal module 1 needs to control the dust content in the output flue gas to be below 50 mg / Nm 3 The following, which can not only ensure the heat exchange efficiency of the heat exchange module 2 (if the dust content in the flue gas is too large, it will cause dust to adhere to the pipes in the heat exchange module 2 and affect the heat exchange efficiency), but also avoid blockage of the activated carbon-based desulfurization catalyst in the catalytic flue gas desulfurization module 3 by dust, thereby increasing the operating resistance of the industrial furnace flue gas purification system and affecting the desulfurization efficiency and the quality of sulfuric acid by-products.

[0043] In the above flue gas purification device, the activated carbon-based desulfurization catalyst loaded in the desulfurization reactor is specifically prepared by the following preparation method of the activated carbon-based desulfurization catalyst. The preparation method of this activated carbon-based desulfurization catalyst is to carry out modification treatment on the activated carbon substrate, and the modification treatment includes:

[0044] 1) Pretreatment: Bake the activated carbon substrate in a nitrogen atmosphere at a temperature of 450 °C - 600 °C for 1 h - 3 h.

[0045] 2) First modification treatment, the specific content of the first modification treatment includes: nitrogen-doped impregnation operation: Dissolve thiourea in an ethanol solution to prepare a mixed solution with a thiourea content of 0.1 mol / L - 1.0 mol / L, and then spray the mixed solution evenly on the pretreated activated carbon substrate according to the mass ratio of the mixed solution to the pretreated activated carbon substrate of 8 - 11, and then dry it; calcination operation: Place the dried activated carbon substrate in a nitrogen atmosphere and calcine it at a temperature of 800°C - 1000°C for 1 h - 3 h.

[0046] 3) Second modification treatment, the specific content of the second modification treatment includes: Dissolve trimethyloxysilane in absolute ethanol to prepare a trimethylsiloxane solution with a mass fraction of 5% - 20%, and then spray the trimethylsiloxane solution evenly on the activated carbon substrate after the first modification treatment according to the mass ratio of the trimethylsiloxane solution to the activated carbon substrate after the first modification treatment of 8 - 11, and then dry it to obtain an activated carbon-based desulfurization catalyst.

[0047] In this embodiment, the activated carbon substrate uses activated carbon fibers. Activated carbon fibers are a kind of high-efficiency adsorption functional material, which are mainly prepared by carbonizing and activating various fibers. Their adsorption leakage is relatively small, the adsorption capacity is large, and their developed specific surface area and excellent micropore diameter are their advantages. Applying them to the activated carbon-based desulfurization catalyst can improve the performance of the activated carbon-based desulfurization catalyst in catalytically oxidizing SO2. At the same time, after the above modification treatment, the hydrophobicity of the activated carbon fibers is greatly improved, which can prevent the rapid deactivation of the activated carbon-based desulfurization catalyst.

[0048] The main purpose of the above pretreatment is to remove some oxygen-containing functional groups and physically adsorbed water on the surface of the activated carbon substrate to provide a better environment for the next impregnation.

[0049] The main purpose of the above first modification treatment is to introduce nitrogen-containing functional groups on the activated carbon substrate, so that the nitrogen on the surface of the activated carbon-based desulfurization catalyst mainly exists in the form of pyridine nitrogen and pyrrole nitrogen. The two types of nitrogen-containing functional groups, pyridine nitrogen and pyrrole nitrogen, can improve the adsorption affinity and catalytic activity of the activated carbon-based desulfurization catalyst for SO2 gas due to their certain weak basicity. In addition, since the nitrogen-doped impregnation operation is to dissolve thiourea in an ethanol solution to prepare a mixed solution, the above first modification treatment can also introduce thiophene functional groups on the activated carbon substrate, and the thiophene functional group is also weakly basic, which can enhance the adsorption capacity of the activated carbon-based desulfurization catalyst for SO2 and improve the selective adsorption effect of the activated carbon-based desulfurization catalyst for SO2.

[0050] The main purpose of the above-mentioned second modification treatment is to introduce silicon-oxygen bonds on the surface of the activated carbon-based desulfurization catalyst. As non-polar substances, silicon-oxygen bonds have relatively low surface tension, making it impossible for water molecules to be evenly distributed on their surfaces, thereby achieving the purpose of hydrophobicity. The above-mentioned first modification treatment introduced nitrogen-containing functional groups, and the activated carbon fiber itself has a large specific surface area. Therefore, the siloxanes and silicon-oxygen bonds on the surface of the activated carbon-based desulfurization catalyst adhere firmly and cannot be easily detached, enabling the hydrophobic property to be stably maintained.

[0051] The activated carbon-based desulfurization catalyst of the present invention and its preparation method will be further described through experiments below.

[0052] Experimental method

[0053] Raw materials used: Activated carbon fiber prepared by subjecting viscose fiber to conventional processes such as web laying, needling, carbonization, and activation is used as the activated carbon substrate. Specifically, activated carbon fiber of model STF-1900 produced by Jiangsu Sutong Carbon Fiber Co., Ltd. is used, with a specific surface area of 1739.3 m 2 / g, a total pore volume of 0.76 mL / g, and a most probable pore diameter of 1.79 nm. As shown in Figures 2 - 3 the surface of this raw material is relatively smooth, without obvious impurities, and has relatively smooth spots and abundant worm-shaped stripes.

[0054] Samples of the activated carbon-based desulfurization catalyst are prepared through different experimental examples, and then these samples are tested. Some experimental examples (specifically Experimental Examples 1-4, which can also be respectively referred to as Examples 1-4) respectively use the above raw materials and prepare samples of the activated carbon-based desulfurization catalyst according to the above preparation method of the activated carbon-based desulfurization catalyst. Experimental Examples 5 and 6 are Comparative Example 1 and Comparative Example 2 respectively.

[0055] The tests mainly include hydrophobicity tests and performance tests for removing SO2 (desulfurization efficiency tests). The hydrophobicity test uses a contact angle device to test the contact angle of the activated carbon-based desulfurization catalyst sample with deionized water.

[0056] Performance test for removing SO2: Using N2 cylinder gas, O2 cylinder gas, and SO2 cylinder gas, first mix N2 and O2 and introduce them into a steam generation device to carry out a certain amount of water vapor, then mix with SO2, and finally pass the mixed gas (SO2 is 3000 ppm (volume concentration), O2 is 5% (volume ratio)) through the bed layer of the activated carbon-based desulfurization catalyst sample, and then use a SO2 analyzer to measure the SO2 concentration in the original mixed gas and the SO2 concentration after passing through the bed layer of the activated carbon-based desulfurization catalyst sample.

[0057] Experimental Example 1 (Example 1)

[0058] The preparation method of the activated carbon-based desulfurization catalyst includes the following steps:

[0059] I. Place the activated carbon fiber in a tubular furnace for pretreatment. The pretreatment conditions are: introduce nitrogen and calcine at 500 °C for 2 h with a heating rate of 5 °C.

[0060] II. Nitrogen-doped impregnation. Dissolve thiourea in a 90% (volume fraction) ethanol solution by heating in a water bath at 60 °C to prepare a 0.5 mol / L mixed solution. Spray the mixed solution evenly on the pretreated activated carbon fiber. The mass ratio of the mixed solution to the activated carbon fiber is 10, and leave it to dry in the shade at room temperature for 24 h.

[0061] III. Calcination. Place the air-dried activated carbon fiber in a ventilated condition at 80 °C to dry, then place it in a tubular furnace, introduce nitrogen and calcine at 800 °C for 2 h with a heating rate of 5 °C.

[0062] IV. Hydrophobic impregnation. Dissolve trimethyloxysilane in absolute ethanol to prepare a 20% (mass fraction) trimethylsiloxane solution. Spray the solution evenly on the pretreated activated carbon fiber. The mass ratio of the solution to the activated carbon fiber is 8, then leave it to dry in the shade at room temperature for 24 h, and dry it at 150 °C under certain conditions.

[0063] Experimental Example 2 (Example 2)

[0064] The preparation method of the activated carbon-based desulfurization catalyst includes the following steps:

[0065] I. Place the selected activated carbon fiber in a tubular furnace for pretreatment. The pretreatment conditions are: introduce nitrogen and calcine at 500 °C for 2 h with a heating rate of 5 °C.

[0066] II. Nitrogen-doped impregnation. Dissolve thiourea in a 90% (volume fraction) ethanol solution by heating in a water bath at 60 °C to prepare a 0.5 mol / L mixed solution. Spray the mixed solution evenly on the pretreated activated carbon fiber. The mass ratio of the mixed solution to the activated carbon fiber is 10, and leave it to dry in the shade at room temperature for 24 h.

[0067] III. Calcination. Place the air-dried activated carbon fiber in a ventilated condition at 80 °C to dry, then place it in a tubular furnace, introduce nitrogen and calcine at 800 °C for 2 h with a heating rate of 5 °C.

[0068] IV. Hydrophobic impregnation. Dissolve trimethyloxysilane in absolute ethanol to prepare a 15% (mass fraction) trimethylsiloxane solution. Spray the solution evenly on the pretreated activated carbon fiber. The mass ratio of the solution to the activated carbon fiber is 9, then leave it to dry in the shade at room temperature for 24 h, and dry it at 150 °C under certain conditions.

[0069] Experimental Example 3 (Example 3)

[0070] The preparation method of the activated carbon-based desulfurization catalyst comprises the following steps:

[0071] I. Place the selected activated carbon fibers in a tubular furnace for pretreatment. The pretreatment conditions are as follows: Introduce nitrogen and calcine at 500 °C for 2 h with a heating rate of 5 °C.

[0072] II. Nitrogen-doped impregnation. Dissolve thiourea in a 90% (volume fraction) ethanol solution by heating in a water bath at 60 °C to prepare a 0.5 mol / L mixed solution. Spray the mixed solution evenly on the pretreated activated carbon fibers. The mass ratio of the mixed solution to the activated carbon fibers is 10, and let it stand in the shade at room temperature to dry for 24 h.

[0073] III. Calcination. Place the air-dried activated carbon fibers in a ventilated condition at 80 °C to dry, and then place them in a tubular furnace. Introduce nitrogen and calcine at 800 °C for 2 h with a heating rate of 5 °C.

[0074] IV. Hydrophobic impregnation. Dissolve trimethyloxysilane in absolute ethanol to prepare an 8% (mass fraction) trimethylsiloxane solution. Spray the solution evenly on the pretreated activated carbon fibers. The mass ratio of the solution to the activated carbon fibers is 10, and then let it stand in the shade at room temperature to dry for 24 h, and dry at 150 °C under certain conditions.

[0075] Experimental Example 4 (Example 4)

[0076] The preparation method of the activated carbon-based desulfurization catalyst comprises the following steps:

[0077] I. Place the selected activated carbon fibers in a tubular furnace for pretreatment. The pretreatment conditions are as follows: Introduce nitrogen and calcine at 500 °C for 2 h with a heating rate of 5 °C.

[0078] II. Nitrogen-doped impregnation. Dissolve thiourea in a 90% (volume fraction) ethanol solution by heating in a water bath at 60 °C to prepare a 0.5 mol / L mixed solution. Spray the mixed solution evenly on the pretreated activated carbon fibers. The mass ratio of the mixed solution to the activated carbon fibers is 10, and let it stand in the shade at room temperature to dry for 24 h.

[0079] III. Calcination. Place the air-dried activated carbon fibers in a ventilated condition at 80 °C to dry, and then place them in a tubular furnace. Introduce nitrogen and calcine at 1000 °C for 1 h with a heating rate of 10 °C.

[0080] IV. Hydrophobic impregnation. Trimethyloxysilane was dissolved in absolute ethanol to prepare a trimethylsiloxane solution with a mass fraction of 5%. This solution was evenly sprayed on the pretreated activated carbon fibers, and the mass ratio of the solution to the activated carbon fibers was 11. Then, it was left to dry in the shade at room temperature for 24 h and dried at 150 °C under certain conditions.

[0081] Experimental Example 5 (Comparative Example 1)

[0082] The activated carbon fibers were placed in a tubular furnace for pretreatment. The pretreatment conditions were: nitrogen was introduced and calcined at 500 °C for 2 h at a heating rate of 5 °C.

[0083] Experimental Example 6 (Comparative Example 2)

[0084] The preparation method of the activated carbon-based desulfurization catalyst includes the following steps:

[0085] I. The selected activated carbon fibers were placed in a tubular furnace for pretreatment. The pretreatment conditions were: nitrogen was introduced and calcined at 500 °C for 2 h at a heating rate of 5 °C.

[0086] II. Nitrogen doping impregnation. Thiourea was dissolved in a 90% ethanol solution by heating in a water bath at 60 °C to prepare a mixed solution with a concentration of 0.5 mol / L. This solution was evenly sprayed on the pretreated activated carbon fibers, and the mass ratio of the solution to the activated carbon fibers was 10. It was left to dry in the shade at room temperature for 24 h.

[0087] III. Calcination. The air-dried activated carbon fibers were dried under ventilation conditions at 80 °C, and then placed in a tubular furnace. Nitrogen was introduced and calcined at 800 °C for 2 h at a heating rate of 5 °C.

[0088] Desulfurization efficiency

[0089] Figure 6 It is the desulfurization efficiency diagram of the original sample used in the experiment (i.e., the activated carbon fibers of model STF-1900 produced by Jiangsu Sutong Carbon Fiber Co., Ltd.) and the activated carbon-based desulfurization catalyst samples of Experimental Examples 1 - 6. In the figure, the abscissa is time and the ordinate is desulfurization efficiency.

[0090] As Figure 6 shown, the untreated original sample and the material after pretreatment of the original sample (i.e., the activated carbon-based desulfurization catalyst sample of Comparative Example 1) did not show good desulfurization performance under a high concentration of SO2 of 3000 ppm. The desulfurization performance of the material impregnated and calcined with thiourea under certain conditions (i.e., the activated carbon-based desulfurization catalyst sample of Comparative Example 2) was greatly improved, but the desulfurization efficiency decreased significantly with time, indicating that the active sites such as micropores, basic nitrogen-containing functional groups, and acidic functional groups inside the material were occupied by the products of catalytic oxidation of SO2, resulting in a rapid decline in desulfurization efficiency.

[0091] The desulfurization performance of the material impregnated and calcined with thiourea under certain conditions and hydrophobically modified with trimethyloxysilane under certain conditions (i.e., the activated carbon-based desulfurization catalyst samples of Examples 1-4) has been significantly improved, and a certain level of desulfurization efficiency can be maintained for a certain period of time. The reason for the analysis is that after SO2 is catalytically oxidized to form H2SO4, due to the presence of water, the product of the catalytic oxidation of SO2 occupies the pores and active sites of the material in the form of sulfuric acid solution. As the catalytic oxidation reaction proceeds, the sulfuric acid solutions converge together under the action of hydrogen bonds. At this time, the desulfurization efficiency will temporarily decrease. However, due to the certain hydrophobic property of the material and the gravity and gas resistance of the convergence of the sulfuric acid solution itself, the sulfuric acid solution will periodically fall off from the active sites and the surface of the material, thereby releasing new pores and active sites. At this time, the desulfurization efficiency will correspondingly increase, which is also the reason for the continuous fluctuation of the desulfurization efficiency curve. The siloxane bond of the hydrophobic agent will combine with some functional groups on the material surface, making the siloxane bond that plays the main hydrophobic role not easily fall off from the material surface, so that the desulfurization efficiency can be maintained at a certain level for a long time, so as to achieve the purpose of efficiently removing high-concentration SO2, efficiently reducing the SO2 concentration, realizing the automatic desorption of the catalytic oxidation of SO2, and maintaining the catalytic oxidation-regeneration cycle of the material.

[0092] Specific surface area test

[0093] See Table 1 below.

[0094] Table 1: Specific surface area test results of activated carbon-based desulfurization catalyst samples of Experimental Examples 1-6

[0095] Specimen Specific surface area ㎡ / g Total pore volume ml / g Most probable pore diameter nm Original sample 1739.3 0.76 1.79 Example 1 1513.6 0.92 1.79 Example 2 1584.3 0.89 1.79 Example 3 1634.8 0.86 1.78 Example 4 1705.1 1.75 1.79 Comparative example 1 1725.8 1.76 1.78 Comparative example 2 1891.8 0.97 1.78

[0096] XPS (X-ray photoelectron spectroscopy) test

[0097] Figure 7 X-ray photoelectron spectroscopy diagrams of the original sample used in the experiment (i.e., activated carbon fiber of model STF-1900 produced by Jiangsu Sutong Carbon Fiber Co., Ltd.), the activated carbon-based desulfurization catalyst sample of Experimental Example 3 (Example 3), and the activated carbon-based desulfurization catalyst sample of Experimental Example 5 (Comparative Example 1). In the figure, the abscissa is the electron binding energy, and the ordinate is the measured intensity of the photoelectrons.

[0098] As Figure 7As shown, after peak separation and fitting, it can be seen that the nitrogen-containing species in the original sample are mainly graphitic nitrogen, with less amino nitrogen and pyridine nitrogen. For Comparative Example 1, i.e., the original sample after pretreatment roasting, the content of each nitrogen-containing species slightly increases, but it is still mainly graphitic nitrogen. For Example 3, i.e., the optimal sample after pretreatment roasting, thiourea impregnation roasting, and hydrophobic modification, the graphitic nitrogen and amino nitrogen species decrease and transform towards pyrrole nitrogen and pyridine nitrogen, and the amounts of pyrrole nitrogen and pyridine nitrogen species increase. Among these different nitrogen-containing species, i.e., basic nitrogen-containing functional groups, pyridine nitrogen has the highest activity, and the high contents of pyridine nitrogen and pyrrole nitrogen are also important reasons for the high performance of the material.

[0099] Water contact angle test

[0100] Figure 8 This is a photograph of the water contact angle test of the activated carbon-based desulfurization catalyst sample in Experimental Example 1 (Example 1) of the present invention. Figure 9 This is a photograph of the water contact angle test of the activated carbon-based desulfurization catalyst sample in Experimental Example 3 (Example 3) of the present invention.

[0101] Figure 8 In [reference], the activated carbon-based desulfurization catalyst sample in Example 1 has strong hydrophobicity (the water contact angle in the water contact experiment is 139.9°). At this time, the purpose of reducing high-concentration SO2 to low-concentration SO2 and automatic desorption can be achieved. However, due to its strong hydrophobic property, the overall desulfurization efficiency is lower than that of the activated carbon-based desulfurization catalyst sample in Example 3 (refer to Figure 6 ). Figure 9 In [reference], the activated carbon-based desulfurization catalyst sample in Example 3 shows general hydrophobicity (the water contact angle in the water contact experiment is 100.8°). At this time, while the activated carbon fiber reduces high-concentration SO2 to low-concentration SO2 and realizes automatic desorption, it has a high desulfurization efficiency (refer to Figure 6 ).

[0102] Therefore, it can be considered that: by adjusting the hydrophobicity to make the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment > 90° and ≤ 145°, the activated carbon-based desulfurization catalyst can have the function of automatic desorption. Among them, considering the automatic desorption performance and desulfurization efficiency of the activated carbon-based desulfurization catalyst comprehensively, the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is preferably 95° - 115°, more preferably 95° - 110°, and still more preferably 100° - 105°.

[0103] Finally, it should be pointed out that when the activated carbon-based desulfurization catalyst of the present invention is applied to a desulfurization reactor, the desulfurization reactor cancels the previous regenerant spraying device. Since the activated carbon-based desulfurization catalyst of the present invention has the function of automatic desorption, it provides a prerequisite for canceling the regenerant spraying device. No longer washing and regenerating the activated carbon-based desulfurization catalyst with regenerant can also prevent the activated carbon fiber from absorbing water and collapsing.

[0104] The above describes the relevant content of the present invention. Those of ordinary skill in the art will be able to implement the present invention based on these descriptions. Based on the above content of this specification, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of the present invention.

Claims

1. Activated carbon-based desulfurization catalyst, characterized in that: It is obtained by carrying out modification treatment on an activated carbon substrate, and the modification treatment includes: The first modification treatment: introducing nitrogen-containing functional groups on the activated carbon substrate, so that the nitrogen on the surface of the activated carbon-based desulfurization catalyst mainly exists in the forms of pyridine nitrogen and pyrrole nitrogen; The second modification treatment: carrying out hydrophobicity adjustment on the activated carbon substrate after the first modification treatment, so that the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is >90° and ≤145°.

2. The activated carbon-based desulfurization catalyst according to claim 1, wherein: The activated carbon substrate uses activated carbon fibers.

3. The activated carbon-based desulfurization catalyst according to claim 1, characterized in that: The water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is 95°-115°, more preferably 95°-110°, and still more preferably 100°-105°.

4. The activated carbon-based desulfurization catalyst according to claim 1, characterized in that: The modification treatment further includes a pretreatment carried out before the first modification treatment, and the pretreatment includes calcining the activated carbon substrate at a temperature of 450°C-600°C for 1h-3h in a nitrogen atmosphere.

5. The activated carbon-based desulfurization catalyst according to claim 1, characterized in that: The first modification treatment specifically includes: Nitrogen-doped impregnation operation: Dissolve thiourea in an ethanol solution to prepare a mixed solution with a thiourea content of 0.1mol / L-1.0mol / L, and then evenly spray the mixed solution on the activated carbon substrate according to the mass ratio of the mixed solution to the activated carbon substrate of 8-11, and then dry it; Calcination operation: Place the dried activated carbon substrate in a nitrogen atmosphere and calcine it at a temperature of 800°C-1000°C for 1h-3h.

6. The activated carbon-based desulfurization catalyst according to claim 1, characterized in that: The second modification treatment specifically includes: Dissolve trimethyloxysilane in absolute ethanol to prepare a trimethylsiloxane solution with a mass fraction of 5%-20%, and then evenly spray the trimethylsiloxane solution on the activated carbon substrate according to the mass ratio of the trimethylsiloxane solution to the activated carbon substrate after the first modification treatment of 8-11, and then dry it.

7. A preparation method of an activated carbon-based desulfurization catalyst, characterized in that: Carry out modification treatment on the activated carbon substrate, and the modification treatment includes: Pretreatment: Calcine the activated carbon substrate at a temperature of 450°C-600°C for 1h-3h in a nitrogen atmosphere; The first modification treatment, the first modification treatment specifically includes: Nitrogen-doped impregnation operation: Dissolve thiourea in an ethanol solution to prepare a mixed solution with a thiourea content of 0.1mol / L-1.0mol / L, and then evenly spray the mixed solution on the pretreated activated carbon substrate according to the mass ratio of the mixed solution to the activated carbon substrate of 8-11, and then dry it; Calcination operation: Place the dried activated carbon substrate in a nitrogen atmosphere and calcine it at a temperature of 800°C-1000°C for 1h-3h; The second modification treatment, the second modification treatment specifically includes: Dissolve trimethyloxysilane in absolute ethanol to prepare a trimethylsiloxane solution with a mass fraction of 5%-20%, and then evenly spray the trimethylsiloxane solution on the activated carbon substrate after the first modification treatment according to the mass ratio of the trimethylsiloxane solution to the activated carbon substrate of 8-11, and then dry it to obtain the activated carbon-based desulfurization catalyst.

8. The preparation method of the activated carbon-based desulfurization catalyst according to claim 7, characterized in that: The activated carbon substrate uses activated carbon fibers.

9. The preparation method of the activated carbon-based desulfurization catalyst according to claim 7, characterized in that: Ensure that the water contact angle of the activated carbon-based desulfurization catalyst in the water contact experiment is 95°-115°, more preferably 95°-110°, and even more preferably 100°-105° through the second modification treatment.

10. Flue gas purification device, including a catalytic flue gas desulfurization device, characterized in that: The catalytic flue gas desulfurization device uses the activated carbon-based desulfurization catalyst described in any one of claims 1-6.

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