Preparation method of modified activated carbon fiber for H2S purification, modified activated carbon fiber and its application

Abstract

The present invention discloses a preparation method of modified activated carbon fibers for H₂S purification, comprising the following steps: (1) subjecting carbon fibers to ammonia activation treatment to obtain activated carbon fibers; (2) subjecting the activated carbon fibers to oxygen-low temperature plasma modification treatment to obtain modified activated carbon fibers for H₂S purification. The preparation method of the present invention first performs ammonia activation on carbon fibers, and then uses O₂-NTP to perform surface modification treatment on ACFs. The synergistic effect of the two can not only retain a certain content of nitrogen-containing functional groups but also increase an appropriate amount of acidic oxygen-containing functional groups, enabling the activated carbon fibers to have a large sulfur capacity and obtain a high selectivity for the product sulfate. The catalyst can efficiently remove H₂S and can better improve its regeneration performance. It can be regenerated by washing with normal temperature water, is convenient for recycling, and has a high recycling performance rate.

Description

Technical Field

[0001] The present invention belongs to the field of waste gas treatment, and particularly relates to a preparation method of a catalyst for H2S treatment, the obtained catalyst, and its application. Background Art

[0002] With the continuous development of cities, a large amount of domestic sewage will be generated, and a large amount of malodorous gas is emitted during the treatment of domestic sewage. As the main component of malodorous gas, H2S has an odor intensity reaching the strong odor level, which poses great harm to the living environment and human health.

[0003] Currently, the Claus process is the most widely used technology for removing H2S. However, due to thermodynamic limitations, it is difficult to reasonably and effectively remove H2S from the gas stream. With the continuous improvement of the efficiency standards required for environmental protection, new methods such as in-situ H2S precipitation, biofiltration, and membrane separation have emerged. However, due to their high costs, low efficiency, and difficult regeneration, these methods have not been well applied. Therefore, there is an urgent need to seek a solution for H2S gas treatment with environmental protection and low cost.

[0004] Currently, the method of selectively catalytically oxidizing H2S to elemental sulfur and sulfuric acid at room temperature is considered an ideal H2S purification strategy. The key catalyst is usually a carbon material with a developed pore structure, a large surface area, a high pore volume, and different surface functional groups, and this kind of catalyst has a high sulfur capacity. However, the elemental sulfur formed after the catalytic oxidation of H2S will deposit in the pore structure of the carbon material, resulting in catalyst deactivation. The H2S removal efficiency of the catalyst is limited. When the catalyst is regenerated by a high-temperature regeneration method, the process will be cumbersome and the cost will increase sharply, and the recyclability of the catalyst will also be greatly reduced. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the above-mentioned deficiencies and defects in the background art, and provide a preparation method of a modified activated carbon fiber for H2S purification with high removal efficiency and high recyclability, the modified activated carbon fiber, and its application. To solve the above technical problems, the technical solution proposed by the present invention is as follows:

[0006] A preparation method of a modified activated carbon fiber for H2S purification, comprising the following steps:

[0007] (1) Activate the carbon fiber with ammonia to obtain activated carbon fiber;

[0008] (2) Perform oxygen-low temperature plasma modification treatment on the activated carbon fiber to obtain a modified activated carbon fiber for H2S purification.

[0009] In the above preparation method, preferably, during the ammonia activation treatment, the gas flow rate is controlled to be 50 - 300 mL / min, the activation temperature is 800 - 1200 °C, the activation time is 1 - 3 h, and the ammonia purity is ≥99.999%.

[0010] In the above preparation method, preferably, during the ammonia activation treatment, the gas flow rate is controlled to be 50 - 200 mL / min, the activation temperature is 900 - 1100 °C, the activation time is 1 - 2 h, and the ammonia purity is ≥99.999%.

[0011] In the above preparation method, preferably, during the ammonia activation treatment, the gas flow rate is controlled to be 150 - 200 mL / min, the activation temperature is 925 - 1075 °C, the activation time is 1.25 - 1.75 h, and the ammonia purity is ≥99.999%.

[0012] In the above preparation method, preferably, during the oxygen - low - temperature plasma modification treatment, the radio - frequency power is controlled to be 50 - 300 W, the gas flow rate is 20 - 50 mL / min, the treatment time is 1 - 60 min, and the oxygen purity is ≥99.999%.

[0013] In the above preparation method, preferably, during the oxygen - low - temperature plasma modification treatment, the radio - frequency power is controlled to be 100 - 200 W, the gas flow rate is 25 - 40 mL / min, the treatment time is 5 - 30 min, and the oxygen purity is ≥99.999%.

[0014] In the above preparation method, preferably, during the oxygen - low - temperature plasma modification treatment, the radio - frequency power is controlled to be 125 - 175 W, the gas flow rate is 30 - 35 mL / min, the treatment time is 10 - 20 min, and the oxygen purity is ≥99.999%.

[0015] As a general technical concept, the present invention also provides an activated carbon fiber obtained by the preparation method of the above - mentioned activated carbon fiber for H2S purification.

[0016] As a general technical concept, the present invention also provides an application of the above - mentioned activated carbon fiber, using the activated carbon fiber as a catalyst for H2S purification.

[0017] In the above application, preferably, the catalyst is regenerated by washing with normal - temperature water.

[0018] The process of carbon materials as H2S conversion catalysts is generally as follows: First, the carbon materials adsorb water to form a water film, and then adsorb H2S and hydrolyze it into H + and HS - two kinds of ions, HS -It is oxidized to elemental sulfur (insufficient oxidation) or sulfate (sufficient oxidation). The factors affecting the oxidation products of H2S mainly include the following: 1. Considering the size difference between elemental sulfur and sulfate, the size of elemental sulfur is larger. When carbon fibers with larger micropores (>0.7 nm) are used as catalysts, the main product of H2S conversion is elemental sulfur. When carbon fibers with smaller micropores (<0.7 nm) are used as catalysts, due to the high surface energy of the small micropores at this time, it is more conducive to adsorbing a large amount of dissociatively adsorbed oxygen, and the high concentration of dissociatively adsorbed oxygen is conducive to dissociating HS generated by the dissociation of H2S - to be fully oxidized to sulfate, which helps the conversion of H2S to sulfate. 2. Considering that H2S is an acidic gas, when the carbon material surface contains a large amount of basic functional groups, it will be conducive to the hydrolysis of H2S, thereby increasing the sulfur capacity of the material. However, due to the large content of HS - at this time, the oxidation cannot proceed fully. Therefore, its catalytic oxidation product is mainly the intermediate oxidation product - elemental sulfur; when the carbon material surface contains a certain amount of acidic functional groups, it will inhibit the hydrolysis of H2S, thereby sacrificing part of the sulfur capacity. Due to the small content of HS - at this time, the oxidation can proceed fully. Therefore, its catalytic oxidation product is mainly the final oxidation product - sulfate. When the catalytic oxidation product is mainly elemental sulfur, the recycling and regeneration of the carbon material are relatively difficult, and generally high-temperature thermal regeneration is used, resulting in waste of resources and secondary pollution. However, if the catalytic oxidation product of the carbon material is mainly sulfate, it can be easily recycled by simple water washing.

[0019] That is, when carbon fibers with smaller micropores (<0.7 nm) are used as catalysts, it helps the conversion of H2S to sulfate, while when carbon fibers with larger micropores (>0.7 nm) are used as catalysts, the main product of H2S conversion is elemental sulfur. In addition, when the chemical property of the carbon fiber surface is 4.5 < pH < 7, it will promote the sulfate selectivity of the H2S catalytic oxidation product. The modified carbon material with sulfate-selective catalytic oxidation prepared by constructing suitable carbon fibers (good microporous structure and weakly acidic surface) in the present invention has a high H2S removal efficiency, and while having a high sulfate selectivity, it can be regenerated by simple water washing, avoiding the disadvantages of high-temperature regeneration.

[0020] Therefore, the regulation of the pore structure and surface chemical properties of carbon materials is the key to constructing high sulfur capacity materials during the catalytic oxidation process of H2S. In terms of the regulation of the pore structure of carbon materials: Activated carbon fibers (ACFs) have a more developed micropore volume, a more concentrated surface pore structure, faster adsorption and desorption rates, and a larger adsorption capacity. In terms of the surface modification of carbon materials: Non-thermal plasma (NTP) modification has the advantages of convenient operation, short time consumption, environmental protection and no pollution. It can change the physical and chemical properties of the adsorbent surface by etching, generate free radicals, introduce functional groups, and form a cross-linked structure layer. By adopting the above ACFs and then based on the NTP modification treatment, the synergistic effect of the two optimizes the pore structure and surface chemical properties of carbon materials, and the catalytic oxidation performance of H2S is good.

[0021] Specifically, the present invention proposes to synergistically prepare modified activated carbon fibers for efficient H2S purification by using ammonia activation and oxygen non-thermal plasma (O2-NTP) modification at room temperature. Ammonia activation can prepare nitrogen-doped ACFs with hierarchical pores and a large specific surface area. At the same time, due to the influence of the electronegativity of functional groups such as pyridine nitrogen introduced by activation, the lone pair electrons of C are easily captured by N, causing N to carry a negative charge and the C near N to carry a positive charge. The negatively charged N reacts with H + to promote the dissociation of H2S and improve the sulfur capacity. The positively charged C will adsorb O2 to form dissociative adsorbed oxygen, enabling the oxidation of HS - . At the same time, this difference in electronegativity is conducive to the reaction of high-energy particles generated by O2-NTP with the carbon fiber matrix, thereby improving the effect of grafting functional groups by plasma modification. The preparation of activated carbon fibers with a developed pore structure and rich nitrogen-containing functional groups formed by ammonia activation, as well as acidic oxygen-containing functional groups such as carboxyl groups introduced by O2-NTP treatment, is realized. At the same time, due to the bombardment of high-energy particles, more defect sites can be formed on the surface of ACFs, which helps to further improve the sulfur capacity of H2S conversion. It is worth emphasizing that the acidic oxygen-containing functional groups will cause the water film formed by the adsorption of the modified carbon fiber to be weakly acidic, which will inhibit the dissociation of H2S in the water film (i.e., sacrifice part of the sulfur capacity), and the amount of HS formed in the water film is less. The lower content of HS - -It will be fully oxidized into sulfate (i.e., the promoted oxidation product is sulfate), achieving the goal of improving the sulfate selectivity of the catalytic oxidation product, and solving the problem that it is difficult to remove the elemental sulfur in the catalytic oxidation product after the sample activated by ammonia alone is deactivated at the expense of a certain sulfur capacity. Therefore, the synergistic effect of ammonia activation and O2-NTP modification adopted in the present invention is obvious. On the one hand, ammonia activation is conducive to the reaction between the high-energy particles generated by O2-NTP and the carbon fiber matrix; on the other hand, O2-NTP modification will replace some of the groups brought by ammonia activation, which is conducive to improving the sulfate selectivity of the catalytic oxidation product; at the same time, O2-NTP modification can also assist in forming more defect sites, which is conducive to improving the effect of ammonia activation. On this basis, the modified ACFs prepared in the present invention have a high sulfur capacity and a high sulfate selectivity of the catalytic oxidation product at the same time, realizing the extension of the single-use time of the modified ACFs and improving the washing regeneration efficiency of the deactivated modified ACFs, thereby greatly reducing the cost consumption of H2S purification.

[0022] In the present invention, the carbon fiber is first activated by ammonia. By using the ablation effect of ammonia on the carbon fiber at high temperature, the carbon fiber can obtain a large number of microporous pore structures with surface openings and graft a large number of nitrogen-containing functional groups on its surface. The functional groups such as pyridine nitrogen introduced by ammonia activation will cause differences in the surface electronegativity of the carbon material, which is beneficial to improving the sulfur capacity of the material and also conducive to improving the modification effect of the high-energy particles generated by O2-NTP. Then, O2-NTP is used to perform surface modification on the ACFs, so that the number of oxygen-containing functional groups such as phenolic hydroxyl groups and carboxyl groups on the surface of the ACFs increases significantly, thereby achieving the purpose of retaining a certain amount of basic functional groups and introducing an appropriate amount of acidic functional groups. And the appropriate amount of acidic oxygen-containing functional groups helps to improve the sulfate selectivity of the catalytic oxidation product of H2S. Therefore, the modified ACFs prepared in the present invention have a high sulfur capacity and a high sulfate product selectivity for the catalytic oxidation performance of H2S gas, and can better improve their regeneration performance. The test results show that the modified ACFs provided by the present invention can efficiently remove H2S at the same time, with a sulfur capacity of up to 0.211 g H2S / g catalyst and a sulfate selectivity of 95.57%.

[0023] Through ammonia activation treatment, the present invention can form pores in the carbon fiber and graft a large number of nitrogen-containing functional groups on its surface, which become the catalytic oxidation sites of H2S and improve the sulfur capacity of the activated carbon fiber. After obtaining the activated carbon fiber, the present invention performs O2-NTP treatment on the activated carbon fiber to obtain modified activated carbon fiber for efficient removal of H2S. In order to achieve the purpose of having a high sulfur capacity and a high sulfate selectivity of the catalytic oxidation product at the same time, the process parameters of the above ammonia activation treatment and O2-NTP treatment need to be reasonably controlled. Specifically:

[0024] The process parameters of ammonia activation treatment mainly include three aspects, namely ammonia flow rate, activation temperature, and activation time. These three process parameters are determined after comprehensively considering various factors such as the pore structure characteristics of the target carbon material and the doping content of N, so as to obtain a carbon material with a yield suitable for industrial production and having a microporous structure (<0.7 nm) conducive to improving the sulfate selectivity of catalytic oxidation products, while ensuring a certain N introduction amount (retaining a high sulfur capacity). If each process parameter is not within the control range, for example: too high ammonia flow rate will cause a sharp drop in the specific surface area of the carbon material and too low a yield, which is not suitable for industrial production; too low ammonia flow rate, insufficient activation temperature, and insufficient activation time will all result in insufficient ammonia activation of the carbon material, underdeveloped pore structure, and too low N doping amount to obtain a suitable target carbon material; exceeding the range of activation temperature and activation time will all lead to excessive ammonia activation degree, serious damage to the pore structure of the carbon material, and adverse effects such as a decrease in nitrogen content instead of an increase.

[0025] Compared with traditional high-temperature plasma modification, O2-NTP treatment overcomes the damage to the material matrix by traditional high-temperature plasma modification at 2000 - 4000K. By adjusting the power, it acts on the surface of the material at room temperature to a depth of several nanometers without damaging the material matrix, while maintaining the pore structure of the activated carbon fiber during modification. The process parameters of O2-NTP treatment mainly include three aspects, namely oxygen flow rate, radio frequency power, and treatment time. These three process parameters are determined after comprehensively considering various factors such as the pore structure characteristics of the target carbon material and the content of acidic oxygen-containing functional groups such as carboxyl groups, so as not to damage the microporous structure (<0.7 nm) conducive to improving the sulfate selectivity of catalytic oxidation products obtained by ammonia activation, while balancing its N introduction amount (retaining a high sulfur capacity) and the content of acidic oxygen-containing functional groups such as carboxyl groups (obtaining a high sulfate selectivity) within a suitable range. If each process parameter is not within the control range, for example: too high oxygen flow rate will cause the plasma to be unable to glow discharge (glow discharge can only occur in rarefied gases), resulting in modification failure; too low oxygen flow rate will make the plasma gas too rarefied, leading to insufficient modification and too low content of functional groups such as carboxyl groups to improve the sulfate selectivity of the carbon material; too large radio frequency power and too long treatment time will both lead to excessive modification degree, serious damage to the pore structure of the carbon material, adverse effects such as a decrease in the content of functional groups such as carboxyl groups instead of an increase, and a sharp drop in the N content introduced by ammonia activation; too small radio frequency power and too short treatment time will both lead to too small modification degree and too low content of functional groups such as carboxyl groups, and the improvement of the sulfate selectivity of the carbon material will not play a positive role.

[0026] Compared with the prior art, the advantages of the present invention are as follows:

[0027] The preparation method of the present invention first activates carbon fibers with ammonia, and then performs surface modification on ACFs using O2-NTP. The synergistic effect of the two can not only retain a certain content of nitrogen-containing functional groups but also increase an appropriate amount of acidic oxygen-containing functional groups, enabling activated carbon fibers to have a large sulfur capacity and obtain a high selectivity for the product sulfate. The modified ACFs prepared by the present invention have a high sulfur capacity and a high sulfate product selectivity for the catalytic oxidation performance of H2S gas. The catalyst can efficiently remove H2S and can better improve its regeneration performance. It can be regenerated by washing with normal temperature water, is convenient for recycling, and has a high recycling performance rate.

[0028] The test results show that the modified ACFs provided by the present invention can efficiently remove H2S simultaneously. Its sulfur capacity can reach 0.211 g H2S / g catalyst, and the sulfate selectivity reaches 95.57%. Description of the Drawings

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0030] Figure 1 It is the pore structure diagram of the modified activated carbon fibers prepared in Examples 1-4.

[0031] Figure 2 It is the XPS peak fitting results of N1s of the modified activated carbon fibers prepared in Examples 1-4 and Comparative Examples 1-2.

[0032] Figure 3 It is the XPS peak fitting results of O1s of the modified activated carbon fibers prepared in Examples 1-4 and Comparative Examples 1-2.

[0033] Figure 4 It is the breakthrough curve of H2S of the modified activated carbon fibers prepared in Examples 1-4.

[0034] Figure 5 It is the XPS spectrum of the deactivated modified activated carbon fibers in Examples 1-4.

[0035] Figure 6 It is the pore structure diagram of the modified carbon fibers prepared in Comparative Examples 1-2 (Figures (a), (b)), the breakthrough curve of H2S (Figure (c)) and the XPS spectrum of the deactivated modified carbon fibers (Figure (d)). Detailed Embodiments

[0036] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0037] Unless otherwise defined, all the technical terms used hereinafter have the same meanings as those commonly understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0038] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchase or can be prepared by existing methods.

[0039] Example 1:

[0040] A preparation method of a modified activated carbon fiber for H2S purification, comprising the following steps:

[0041] (1) Activate the carbon fiber at 900 °C for 1 h with a flow rate of ammonia (purity ≥ 99.999%) of 50 ml / min to obtain an activated carbon fiber.

[0042] (2) Under the conditions of a radio frequency power of 100 W and a flow rate of oxygen (purity ≥ 99.999%) of 40 ml / min, perform O2-NTP modification on the activated carbon fiber for 25 min to obtain a modified activated carbon fiber for efficient removal of H2S.

[0043] The pore structure of the fresh modified activated carbon fiber is as Figure 1 shown. As can be seen from Figure 1 (a) therein, its specific surface area is 1513 m 2 / g. As can be seen from Figure 1 (b) therein, its pore structure is mainly micropores, and the proportion of small micropores less than 0.7 nm is 82.79%. The XPS peak fitting results of N1s and O1s are respectively as shown in Figure 2 (a) therein and Figure 3 (a) therein. The fiber surface contains abundant nitrogen-containing and oxygen-containing functional groups, the N-6 content is 0.81 at.%, and the COOH content is 2.64 at.%.

[0044] Perform a test on the H2S removal effect of the modified activated carbon fiber obtained in this example, and the method is as follows:

[0045] Place the prepared modified activated carbon fiber in a reactor, ensure that the H2S concentration at the inlet gas is 1000 ppm, the relative humidity is 80%, use nitrogen (99%) and oxygen (1%) as carrier gases, the gas flow rate is 50 mL / min, and the reaction temperature is room temperature. Test the concentration of H2S in the gas at the outlet and calculate the sulfur capacity of the activated modified carbon fiber.

[0046] The breakthrough curve of H2S is as shown in Figure 4 (a) in Figure 4 It can be seen from (a) in that the sulfur capacity of the modified activated carbon fiber is 0.270 g H2S / g catalyst.

[0047] The XPS spectrum of the deactivated modified activated carbon fiber is as shown in Figure 5 (a) in Figure 5 It can be seen from (a) in that the sulfate selectivity of the catalytic oxidation product is 81.09%, and it can be used after simple water washing.

[0048] Example 2:

[0049] A preparation method of a modified activated carbon fiber for H2S purification, comprising the following steps:

[0050] (1) Activate the carbon fiber at 1000 °C for 1.4 h with an ammonia gas (purity ≥ 99.999%) flow rate of 200 ml / min to obtain an activated carbon fiber.

[0051] (2) Modify the obtained activated carbon fiber for 20 min under the conditions of a radio frequency power of 130 W and an oxygen gas (purity ≥ 99.999%) flow rate of 35 ml / min to obtain a modified activated carbon fiber for efficient removal of H2S.

[0052] The pore structure of the fresh modified activated carbon fiber is as shown in Figure 1 As can be seen from Figure 1 (a) in, its specific surface area is 1502 m 2 / g. As can be seen from Figure 1 (b) in, its pore structure is mainly micropores, and the proportion of small micropores less than 0.7 nm is 83.28%. The XPS peak deconvolution results of N1s and O1s are respectively as shown in Figure 2 (a) and Figure 3 (a). The fiber surface contains abundant nitrogen-containing and oxygen-containing functional groups, the N-6 content is 0.28 at.%, and the COOH content is 3.60 at.%.

[0053] Test the H2S removal effect of the modified activated carbon fiber obtained in this example as follows:

[0054] Place the prepared modified activated carbon fiber in a reactor, ensure that the H2S concentration at the inlet is 1000 ppm, the relative humidity is 80%, use nitrogen gas (99%) and oxygen gas (1%) as carrier gases, the gas flow rate is 50 mL / min, and the reaction temperature is room temperature. Test the H2S concentration in the gas at the outlet and calculate the sulfur capacity of the activated carbon fiber.

[0055] The breakthrough curve of H2S is as shown inFigure 4 as shown in (b) of Figure 4 It can be seen from (b) of

[0056] The XPS spectrum of the deactivated modified activated carbon fiber is as shown in Figure 5 as shown in (b) of Figure 5 It can be seen from (b) of

[0057] Example 3:

[0058] A preparation method of a modified activated carbon fiber for H2S purification, comprising the following steps:

[0059] (1) Activate the carbon fiber at 1040 °C for 1.7 h with a flow rate of ammonia (purity ≥ 99.999%) of 190 ml / min to obtain an activated carbon fiber.

[0060] (2) Modify the obtained activated carbon fiber for 10 min under the conditions of a radio frequency power of 160 W and a flow rate of oxygen (purity ≥ 99.999%) of 30 ml / min to obtain a modified activated carbon fiber for efficient removal of H2S.

[0061] The pore structure of the fresh modified activated carbon fiber is as shown in Figure 1 It can be seen from Figure 1 (a) that its specific surface area is 1478 m 2 / g. It can be seen from Figure 1 (b) that its pore structure is mainly micropores, and the proportion of small micropores less than 0.7 nm is 77.63%. The XPS peak deconvolution results of N1s and O1s are respectively as shown in Figure 2 (a) and Figure 3 (a) of

[0062] Test the H2S removal effect of the modified activated carbon fiber obtained in this example as follows:

[0063] Place the prepared modified activated carbon fiber in a reactor, ensure that the H2S concentration at the inlet is 1000 ppm, the relative humidity is 80%, use nitrogen (99%) and oxygen (1%) as carrier gases, the gas flow rate is 50 mL / min, and the reaction temperature is room temperature. Test the concentration of H2S in the gas at the outlet and calculate the sulfur capacity of the activated carbon fiber.

[0064] The breakthrough curve of H2S is as shown in Figure 4 as shown in (c) of Figure 4As can be seen from Fig. (c), the sulfur capacity of the modified activated carbon fiber is 0.249 g H2S / g catalyst.

[0065] The XPS spectrum of the deactivated modified activated carbon fiber is as shown in Figure 5 Fig. (c). As can be seen from Figure 5 Fig. (c), the sulfate selectivity of the catalytic oxidation product is 92.72%, and it can be used after simple water washing.

[0066] Example 4:

[0067] A preparation method of a modified activated carbon fiber for H2S purification, comprising the following steps:

[0068] (1) Activate the carbon fiber at 1100 °C for 1.25 h with an ammonia (purity ≥ 99.999%) flow rate of 250 ml / min to obtain an activated carbon fiber.

[0069] (2) Modify the obtained activated carbon fiber for 15 min under the conditions of a radio frequency power of 175 W and an oxygen (purity ≥ 99.999%) flow rate of 20 ml / min to obtain a modified activated carbon fiber for efficient removal of H2S.

[0070] The pore structure of the fresh modified activated carbon fiber is as shown in Figure 1 Fig. As can be seen from Figure 1 Fig. (a), its specific surface area is 1409 m 2 / g. As can be seen from Figure 1 Fig. (b), its pore structure is mainly micropores, and the proportion of small micropores less than 0.7 nm is 72.12%. The XPS peak separation results of N1s and O1s are as shown in Figure 2 Fig. (a) and Figure 3 Fig. (a) respectively. The fiber surface contains abundant nitrogen - and oxygen - containing functional groups, with the N - 6 content being 0.59 at.%, and the COOH content being 2.69 at.%.

[0071] Test the H2S removal effect of the modified activated carbon fiber obtained in this example as follows:

[0072] Place the prepared modified activated carbon fiber in a reactor, ensure that the H2S concentration at the inlet is 1000 ppm, the relative humidity is 80%, use nitrogen (99%) and oxygen (1%) as carrier gases, with a gas flow rate of 50 mL / min, and the reaction temperature is at room temperature. Test the H2S concentration in the gas at the outlet and calculate the sulfur capacity of the activated carbon fiber.

[0073] The breakthrough curve of H2S is as shown in Figure 4 Fig. (d). As can be seen from Figure 4As can be seen from Fig. (d), the sulfur capacity of the modified activated carbon fiber is 0.254 g H2S / g catalyst.

[0074] The XPS spectrum of the deactivated modified activated carbon fiber is as shown in Figure 5 Fig. (d). As can be seen from Figure 5 Fig. (d), the sulfate selectivity of the catalytic oxidation product is 84.70%, and it can be used after simple water washing.

[0075] Taking into account the above-mentioned embodiments comprehensively, the modified activated carbon fiber obtained in Embodiment 2 has relatively better performance, which is mainly related to two factors: pore structure and surface chemical properties. In terms of pore structure, it can be seen from the specific surface area and pore size distribution diagram that the material still retains the pore structure characteristics after ammonia activation well after O2-NTP treatment. At the same time, due to the plasma treatment, the opening of some closed pore structures leads to an increase in the content of small micropores (<0.7 nm) suitable for sulfate formation; in terms of surface chemical properties, the surface of Embodiment 2 has a suitable pyridine nitrogen content (0.28 at.%) and carboxyl content (3.60 at.%), and the two are in a good balance state, which also enables the material to obtain a relatively considerable sulfur capacity (0.211 g H2S / g catalyst) and the highest catalytic oxidation product sulfate selectivity of 95.57%. After simple water washing, the catalyst can be regenerated and reused, and the recycling is convenient.

[0076] Comparative Example 1:

[0077] A preparation method of a modified activated carbon fiber for H2S purification includes the following steps:

[0078] Activating carbon fiber at 1000 °C for 1.4 h with a flow rate of ammonia gas (purity ≥ 99.999%) of 400 ml / min to obtain modified carbon fiber.

[0079] The pore structure of the fresh modified carbon fiber is as shown in Figure 6 Fig. As can be seen from Figure 6 Fig. (a), its specific surface area is 1533 m 2 / g. As can be seen from Figure 6 Fig. (b), its pore structure is mainly micropores, and the proportion of small micropores less than 0.7 nm is 69.45%. The XPS peak separation results of N1s and O1s are as shown in Figure 2 Fig. (b) and Figure 3 Fig. (b) respectively. The fiber surface contains rich nitrogen-containing and a small amount of oxygen-containing functional groups, the N-6 content is 0.91 at.%, and the COOH content is 1.27 at.%.

[0080] The difference between Comparative Example 1 and Examples 1-4 is that the modified carbon fiber obtained by directly activating with ammonia gas is used for H2S removal.

[0081] The breakthrough curve of H2S is as Figure 6 shown in (c) of Figure 6 As can be seen from (c) of

[0082] The XPS spectrum of the deactivated modified carbon fiber is as Figure 6 shown in (d) of Figure 6 As can be seen from (d) of

[0083] Comparative Example 2:

[0084] A preparation method of modified activated carbon fiber for H2S purification, comprising the following steps:

[0085] (1) The activated carbon fiber was modified for 30 min under the conditions of a radio frequency power of 150 W and an oxygen (purity ≥ 99.999%) flow rate of 30 ml / min to obtain modified carbon fiber.

[0086] The pore structure of the fresh modified carbon fiber is as Figure 6 shown, and from Figure 6 (a) of 2 it can be known that its specific surface area is 8 m Figure 6 / g, and from Figure 2 (b) of Figure 3 it can be known that there is basically no analyzable pore structure. The XPS peak fitting results of N1s and O1s are as shown in Figure 2 (b) and Figure 3 (b) respectively. The fiber surface contains a very small amount of nitrogen-containing and relatively rich oxygen-containing functional groups, with an N-6 content of 0.19 at.% and a COOH content of 1.95 at.%.

[0087] The difference between Comparative Example 2 and Examples 1-4 is that the carbon fiber modified by O2-NTP is directly used for H2S removal. The activity test of H2S shows that the modified carbon fiber has basically no sulfur capacity.

[0088] Comparative Example 3:

[0089] A preparation method of modified activated carbon fiber for H2S purification, comprising the following steps:

[0090] (1) The carbon fiber was activated at a flow rate of ammonia (purity ≥ 99.999%) of 500 ml / min and 1000 °C for 1.4 h to obtain activated carbon fiber.

[0091] (2) The obtained activated carbon fiber was modified for 20 min under the conditions of a radio frequency power of 130 W and an oxygen (purity ≥ 99.999%) flow rate of 35 ml / min to obtain modified activated carbon fiber for efficient H2S removal.

[0092] Through analysis, the specific surface area of the modified activated carbon fiber is 923 m 2 / g. There are basically no micropores in the material, mainly mesopores, and the proportion of small micropores less than 0.7 nm is only 11.33%. From the XPS peak fitting results, the N-6 content is 1.02 at.%, and the COOH content is 1.13 at.%.

[0093] The difference between Comparative Example 3 and Examples 1-4 is that the ammonia flow rate is too high. The activity test of H2S shows that the sulfur capacity of the modified carbon fiber is 0.523 g H2S / g catalyst, and the sulfate selectivity of the catalytic oxidation product is 47.13%.

[0094] Comparative Example 4:

[0095] A preparation method of a modified activated carbon fiber for H2S purification, comprising the following steps:

[0096] (1) Activate the carbon fiber at 1000 °C for 1.4 h with an ammonia (purity ≥ 99.999%) flow rate of 200 ml / min to obtain an activated carbon fiber.

[0097] (2) Modify the obtained activated carbon fiber for 20 min under the conditions of a radio frequency power of 300 W and an oxygen (purity ≥ 99.999%) flow rate of 35 ml / min to obtain a modified activated carbon fiber for efficient removal of H2S.

[0098] Through analysis, the specific surface area of the modified activated carbon fiber is 1103 m 2 / g. The proportion of small micropores less than 0.7 nm in the material is 65.03%. From the XPS peak fitting results, the N-6 content is 0.17 at.%, and the COOH content is 2.42 at.%.

[0099] The difference between Comparative Example 4 and Examples 1-4 is that the radio frequency power is too high. The activity test of H2S shows that the sulfur capacity of the modified carbon fiber is 0.113 g H2S / g catalyst, and the sulfate selectivity of the catalytic oxidation product is 77.03%.

[0100] As can be seen from the above examples and comparative examples, the activated carbon fibers prepared by the present invention simultaneously have a developed pore structure formed by ammonia activation, rich nitrogen-containing functional groups, and acidic oxygen-containing functional groups such as carboxyl groups introduced by O2-NTP treatment. More importantly, it is confirmed that the nitrogen-containing functional groups introduced in the ammonia activation stage will promote the modification of the material surface by high-energy particles in O2-NTP, increasing the number of introduced oxygen-containing functional groups. At the same time, the activated carbon fibers provided by the present invention for highly efficient H2S removal can achieve a high selectivity for sulfates of catalytic oxidation products while having a large sulfur capacity, and have high removal efficiency and recyclability.

Claims

1. A preparation method of a modified activated carbon fiber for H2S purification, characterized in that, It includes the following steps: (1) Activate carbon fiber with ammonia gas to obtain activated carbon fiber; (2) Perform oxygen-low temperature plasma modification treatment on the activated carbon fiber to obtain modified activated carbon fiber for H2S purification; During the ammonia gas activation treatment, control the gas flow rate to be 50 - 300 mL / min, the activation temperature to be 800 - 1200 °C, the activation time to be 1 - 3 h, and the ammonia purity ≥ 99.999%; During the oxygen-low temperature plasma modification treatment, control the radio frequency power to be 50 - 300 W, the gas flow rate to be 20 - 50 mL / min, the treatment time to be 1 - 60 min, and the oxygen purity ≥ 99.999%.

2. The preparation method according to claim 1, characterized in that, During the ammonia gas activation treatment, control the gas flow rate to be 50 - 200 mL / min, the activation temperature to be 900 - 1100 °C, the activation time to be 1 - 2 h, and the ammonia purity ≥ 99.999%.

3. The preparation method according to claim 2, characterized in that, During the ammonia gas activation treatment, control the gas flow rate to be 150 - 200 mL / min, the activation temperature to be 925 - 1075 °C, the activation time to be 1.25 - 1.75 h, and the ammonia purity ≥ 99.999%.

4. The preparation method according to claim 1, characterized in that, During the oxygen-low temperature plasma modification treatment, control the radio frequency power to be 100 - 200 W, the gas flow rate to be 25 - 40 mL / min, the treatment time to be 5 - 30 min, and the oxygen purity ≥ 99.999%.

5. The preparation method according to claim 4, characterized in that, During the oxygen-low temperature plasma modification treatment, control the radio frequency power to be 125 - 175 W, the gas flow rate to be 30 - 35 mL / min, the treatment time to be 10 - 20 min, and the oxygen purity ≥ 99.999%.

6. Modified activated carbon fiber obtained by the preparation method of the modified activated carbon fiber for H2S purification as described in any one of claims 1 - 5.

7. Use of the modified activated carbon fiber as described in claim 6, characterized in that, Use the modified activated carbon fiber as a catalyst for H2S purification.

8. The application according to claim 7, characterized in that, When regenerating the catalyst, use normal temperature water washing for regeneration.

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