A sulfur-containing malodor and VOCs competitive inhibition type adsorbent, a preparation method and application thereof

Abstract

This invention belongs to the field of waste gas treatment, catalysis, and adsorption separation technology, and relates to a sulfur-containing odor-competitive inhibitor against VOCs, its preparation method, and its application. The preparation method includes: dispersing phenolic resin in ethanol to form a homogeneous resin-ethanol solution; adding hexamethylenetetramine and a nitrogen source and mixing; then mixing with a polyvinyl alcohol solution and stirring the reaction mixture; filtering the reaction solution to obtain a solid; washing and drying the solid; and then performing a high-temperature secondary crosslinking; carbonizing the crosslinked solid under an inert gas atmosphere to obtain a carbonized material; activating the carbonized material, washing, and drying it to obtain the sulfur-containing odor-competitive inhibitor against VOCs. The adsorbent prepared by this invention has a specific surface area of ​​760-1000 m². 2 / g, the carbon structure is doped with pyridine N, pyrrole N, graphite N, etc., which can inhibit the competitive adsorption of VOCs and sulfur-containing odorous substances on the adsorption material.

Description

Technical Field

[0001] This invention belongs to the field of waste gas treatment, catalysis and adsorption separation technology, and relates to the synergistic treatment of VOCs and sulfur-containing odors and the preparation of activated carbon. Specifically, it relates to a sulfur-containing odor competitive inhibitory adsorbent and its preparation method and application. Background Technology

[0002] Industrial sources often contain sulfur-containing odors with complex compositions, frequently accompanied by other non-sulfur VOCs (such as alkanes and aromatics), sometimes containing dozens or even hundreds of different compounds. Typical examples of such process gases include rubber waste gas, wastewater treatment plant waste gas, and papermaking / pulping waste gas. Complex compounds exhibit various interactions during comprehensive treatment, such as competitive effects, synergistic effects, reaction effects, and masking effects. Therefore, industrial waste gas treatment processes must simultaneously consider multiple complex components, significantly increasing the difficulty of controlling sulfur-containing industrial odors.

[0003] Adsorption, with its advantages of low cost and mild reaction conditions, has become a promising technology for treating sulfur-containing odors, with the adsorbent being the core of this method. Studies have found that activated carbon has an adsorption capacity 3-8 times greater for sulfur-containing odors (CS2) than molecular sieves and macroporous resins. Furthermore, activated carbon is a non-polar adsorbent, capable of forming π-π bonds, which is beneficial for the adsorption of non-polar molecules. These factors make activated carbon the primary choice for adsorbing sulfur-containing odors.

[0004] The adsorption advantage of activated carbon for sulfur-containing substances faces serious challenges in complex VOCs coexisting scenarios. Previous research by the applicant found that toluene easily competes with CS2 adsorbed on activated carbon, with the CS2 breakthrough time being only 1 / 5 that of toluene (toluene to CS2 concentration ratio 4:1). Researchers using activated carbon to adsorb odor substances from sewage systems have found removal rates of at least 85% for benzene, toluene, and xylene, while the removal efficiency for sulfur-containing compounds such as CS2, CH3SCH3, and CH3SSCH3 is 0% or even negative. Therefore, the core of adsorption material development lies in promoting the adsorption of sulfur-containing compounds and inhibiting the competition between sulfur-containing compounds and VOC molecules.

[0005] Chinese patent application CN116265082A discloses a method for preparing furfuryl alcohol resin-based porous carbon spheres, but it does not mention how to control the micropore distribution characteristics of activated carbon, nor does it further elaborate on its main functional advantages as an adsorbent. Chinese patent application CN118307733A discloses a method for preparing modified phenolic resin microspheres, using propanol to modify phenolic resin, ultimately obtaining activated carbon spheres with higher sphericity and strength; this shows that this modification method is feasible for controlling resin-based activated carbon, but the modification in this patent only focuses on the surface properties of the activated carbon material, without improving its specific adsorption function. It is evident that in the preparation and modification of resin-based spherical activated carbon, there are still few cases of developing new materials with specific functions, limiting the application of materials in practical engineering scenarios. Existing technology has not yet developed an activated carbon material suitable for treating industrial waste gases with complex compositions that inhibits competitive adsorption.

[0006] Nitrogen doping and micropore regulation are two major strategies for improving the selectivity of activated carbon. Microporous structure is the foundation of adsorption, while nitrogen doping enhances sulfur adsorption through specific effects. On the one hand, nitrogen atoms can strengthen sulfur adsorption by altering the electronic structure of the carbon skeleton; on the other hand, nitrogen doping may weaken the microporous effect that dominates physisorption. Preparing an activated carbon that balances micropores and nitrogen doping, and synergistically utilizing chemical modification and pore structure regulation, has become a key breakthrough in solving the competitive adsorption problem.

[0007] Chinese patent application CN110444411A discloses a phenolic resin-based porous carbon composite material. The curing agent used is any one of hexamethylenetetramine, hexamethylenetetramine, or melamine. The formaldehyde released from the curing agent upon heating reacts with unreacted ortho- and para-active sites, simultaneously losing water to form methylene bonds, transforming the resin from thermoplastic to thermosetting. Further polycondensation yields an insoluble, three-dimensional cured product. The curing agents used in this patent, such as hexamethylenetetramine, hexamethylenetetramine, and melamine, introduce nitrogen atoms into the activated carbon material, which to some extent constitutes nitrogen doping. However, the introduced nitrogen structure is generally relatively simple, mainly acting as a crosslinking agent. The nitrogen atom is responsible for connecting methyl groups to form a solid substance, while the remaining nitrogen elements escape into the air as ammonia gas. It is impossible to control the type of doped nitrogen (e.g., pyridine N, pyrrole N, or graphite N). The curing agent content also only focuses on the crosslinking effect, without mentioning the crucial role of nitrogen doping in the activated carbon material.

[0008] In summary, it is necessary to provide a novel, inexpensive, and easily prepared adsorbent material for suppressing the competitive adsorption of VOCs and sulfur-containing odorous substances in industrial waste gas. Summary of the Invention

[0009] To address the problem of VOCs and sulfur-containing odorous substances coexisting in existing industrial waste gas, but with significant competition for adsorption on activated carbon, the primary objective of this invention is to provide a method for preparing a sulfur-containing odor-inhibiting adsorbent that competes with VOCs.

[0010] Another object of the present invention is to provide a sulfur-containing odor-competitive inhibitory adsorbent for VOCs prepared by the above method.

[0011] Another object of the present invention is to provide the application of the above-mentioned sulfur-containing odor-competitive VOCs-inhibiting adsorbent.

[0012] The objective of this invention is achieved through the following technical solution:

[0013] A method for preparing a sulfur-containing odor-competitive VOCs-inhibiting adsorbent includes the following steps:

[0014] S1. Phenolic resin is dispersed in ethanol to form a homogeneous resin-ethanol solution; then hexamethylenetetramine (HMTA) and a nitrogen source are added to obtain a mixture;

[0015] S2. Mix the mixture obtained in S1 with the polyvinyl alcohol solution, and then react for 90-120 min under stirring conditions while keeping the system at boiling point (98-100℃).

[0016] S3. After the reaction in S2 is completed, the reaction solution is filtered to obtain the solid, which is then washed and dried, and subjected to high-temperature secondary cross-linking; the solid after secondary cross-linking is then carbonized under the protection of an inert gas to obtain carbonized material.

[0017] S4. The carbonized material obtained in S3 is activated, washed and dried to obtain ultra-microporous nitrogen-doped activated carbon, which is the sulfur-containing odor-competitive VOCs inhibitory adsorbent.

[0018] Preferably, in step S1, the ethanol is anhydrous ethanol; the mass ratio of phenolic resin to anhydrous ethanol is 3:2. An excessively dilute resin-ethanol solution will hinder the formation of activated carbon spheres; the adsorbent prepared at this ratio will have a spherical morphology.

[0019] Preferably, in step S1, phenolic resin is added to ethanol and stirred and dissolved at 25-40°C for 30-120 min to form a homogeneous resin-ethanol solution, preferably at room temperature.

[0020] Preferably, in step S1, the amount of hexamethylenetetramine added is 8%-15% of the mass of phenolic resin, and the amount of nitrogen source added is 2%-5% of the mass of phenolic resin.

[0021] Preferably, in step S1, the nitrogen source is urea or melamine. Most preferably, the nitrogen source is melamine.

[0022] Preferably, in step S2, the temperature for the high-temperature secondary crosslinking is 180-250℃, and the time is 120-180 minutes. Secondary crosslinking prevents the microspheres from collapsing and sticking together during carbonization. The most preferred secondary crosslinking conditions are 180℃ and 120 minutes.

[0023] Preferably, in step S2, the concentration of the polyvinyl alcohol solution is 0.5 wt%-1.0 wt%; the amount of polyvinyl alcohol added is 5%-15% of the mass of the phenolic resin.

[0024] Preferably, in step S2, the mixture obtained in S1 is added dropwise to the polyvinyl alcohol solution at a rate of 2-3 mL / min; the stirring speed is 1000-1200 rpm.

[0025] Preferably, in step S3, the washing and drying refers to washing with hot water and drying with hot air at 110±5℃ for 120-180 minutes.

[0026] Preferably, in step S3, the carbonization is carried out under nitrogen atmosphere at a temperature of 500-700℃ for 50-70 minutes. More preferably, high-purity nitrogen (99.9% purity) is continuously introduced during the carbonization process at a flow rate of 400±10 mL / min.

[0027] Preferably, in step S4, the activation process is carried out at a temperature of 800-1000℃ for a time of 80-120 minutes.

[0028] Preferably, in step S4, the activator used in the activation process is at least one of KOH, water vapor, or CO2.

[0029] More preferably, the activator is KOH, and the activation process is carried out under nitrogen conditions with a nitrogen flow rate of 400 mL / min, and the temperature is increased to the target temperature of 800-1000℃ at a rate of 5℃ / min.

[0030] More preferably, the activator is water vapor, and the activation process is carried out at 900-950°C for 80-120 minutes.

[0031] Most preferably, the activator is water vapor, and the activation process is carried out at 900°C for 120 minutes.

[0032] The sulfur-containing odor-inhibiting adsorbent prepared by this invention has the effect of inhibiting the competitive adsorption of VOCs and sulfur-containing odor-inhibiting substances, and can be used for the treatment of industrial waste gas.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] 1. The in-situ modification method provided by this invention solves the problem of difficult synergistic regulation of activated carbon micropore control and nitrogen doping. In addition to conventional curing agents, an extra nitrogen source is directly added to the activated carbon precursor. The curing agent mainly plays the role of crosslinking. Urea and other nitrogen source molecules are too small to form multiple hydrogen bonds with adjacent polymer chains at the same time, so they cannot play the role of crosslinking. Instead, they appear as nitrogen sources in other positions of the resin molecular structure.

[0035] 2. This invention achieves synergistic regulation of micropores and nitrogen doping in a one-step process by rationally controlling carbonization and activation conditions. The prepared sulfur-containing odor-competitive VOCs-inhibiting adsorbent is a nitrogen-doped ultramicroporous activated carbon. The material's dominant pore size is controlled below 0.71 nm, and its specific surface area is 760-1000 m². 2 / g, the carbon structure is doped with pyridine N, pyrrole N, graphite N, etc., which can inhibit the competitive adsorption of VOCs and sulfur-containing odorous substances on the adsorption material. Attached Figure Description

[0036] Figure 1 This is a flowchart illustrating the preparation process of the sulfur-containing odor-competitive VOCs-inhibiting adsorbent described in this invention.

[0037] Figure 2 Images of the adsorbent materials prepared in Example 1 (left) and Example 2 (right).

[0038] Figure 3 The figures show the micropore distribution test diagrams of the adsorbent materials prepared in Examples 2 and 3, and commercially available coal-based activated carbon. The commercially available coal-based activated carbon in the figures represents the commercially available coal-based activated carbon described in the test experiments.

[0039] Figure 4 The image shows the XPS spectrum of the adsorbent material prepared in Example 3.

[0040] Figure 5 The figure shows the breakthrough curves of the adsorbent materials prepared in Examples 1-3 and commercially available coal-based activated carbon adsorbing a mixture of toluene and CS2. The commercially available coal-based activated carbon in the figure represents the commercially available coal-based activated carbon used in the test experiments. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto. All raw materials involved in the present invention can be purchased directly from the market. For process parameters not specifically specified, conventional techniques can be referred to.

[0042] The commercially available coal-based activated carbon described in the following examples is raw coal crushed carbon from Datong Coal Mine in Shanxi Province, with an iodine value of 800 mg / g.

[0043] Example 1

[0044] A method for preparing a sulfur-containing odor-competitive VOCs-inhibiting adsorbent includes the following steps:

[0045] S1. Disperse 30.00g of phenolic resin in 20.00g of anhydrous ethanol to form a homogeneous resin-ethanol solution; then add 3.0g of hexamethylenetetramine (HMTA) and 1.5g of urea powder to obtain a mixture;

[0046] S2. Dissolve 2.50g of PVA in 500mL of deionized water at 80℃ to obtain a polyvinyl alcohol solution; mix the mixture obtained in S1 with the polyvinyl alcohol solution, and then react for 90min under stirring (1000rpm) while keeping the system boiling (98-100℃);

[0047] S3. After the reaction in S2 is completed, the reaction solution is filtered to obtain the solid. The solid is washed with water and dried at 110℃ for 120 min. Then, it is subjected to high-temperature secondary crosslinking at 180℃ for 120 min. The solid after secondary crosslinking is then carbonized at 500℃ for 60 min under a nitrogen atmosphere at a rate of 5℃ / min to obtain the carbonized material. The nitrogen atmosphere flow rate is 400 mL / min.

[0048] S4. Take 5.0g of the carbonized material obtained in step S3 and mix it with 5.0mol / L KOH solution, with an alkali-to-carbon mass ratio of 2:1, and impregnate for 24h; after impregnation, dry at 110℃ to constant weight;

[0049] Then, the carbonized material was activated in a stepwise manner under nitrogen conditions. First, the temperature was increased to 350℃ at a rate of 2℃ / min and held for 30min. Then, the temperature was increased to 850℃ at a rate of 5℃ / min for 120min. The nitrogen atmosphere flow rate was 400mL / min.

[0050] Finally, the material is washed (by boiling it in deionized water) until the pH of the filtrate is neutral, and then dried at 110°C to constant weight to obtain the sulfur-containing odor-competitive VOCs inhibitory adsorbent.

[0051] Example 2

[0052] A method for preparing a sulfur-containing odor-competitive VOCs-inhibiting adsorbent includes the following steps:

[0053] S1. Disperse 30.00g of phenolic resin in 20.00g of anhydrous ethanol to form a homogeneous resin-ethanol solution; then add 3.0g of hexamethylenetetramine (HMTA) and 1.5g of urea powder to obtain a mixture;

[0054] S2. Dissolve 2.50g of PVA in 500mL of deionized water at 80℃ to obtain a polyvinyl alcohol solution; mix the mixture obtained in S1 with the polyvinyl alcohol solution, and then react for 90min under stirring (1000rpm) while keeping the system boiling (98-100℃);

[0055] S3. After the reaction in S2 is completed, the reaction solution is filtered to obtain the solid. The solid is washed with water and dried at 110℃ for 120 min. Then, it is subjected to high-temperature secondary crosslinking at 180℃ for 120 min. The solid after secondary crosslinking is then carbonized at 500℃ for 60 min under a nitrogen atmosphere at a rate of 5℃ / min to obtain the carbonized material. The nitrogen atmosphere flow rate is 400 mL / min.

[0056] S4. Take 2.50g of the carbonized material obtained in step S3 and load it into a tube furnace. Under nitrogen conditions with a flow rate of 400mL / min, the temperature is raised to 950℃ at a rate of 5℃ / min. Then, turn off the nitrogen and introduce steam for activation for 120min. After activation, switch to nitrogen protection.

[0057] Finally, the material is washed (by boiling it in deionized water) until the pH of the filtrate is neutral, and then dried at 110°C to constant weight to obtain the sulfur-containing odor-competitive VOCs inhibitory adsorbent.

[0058] Example 3

[0059] A method for preparing a sulfur-containing odor-competitive VOCs-inhibiting adsorbent includes the following steps:

[0060] S1. Disperse 30.00g of phenolic resin in 20.00g of anhydrous ethanol to form a homogeneous resin-ethanol solution; then add 2.4g of hexamethylenetetramine (HMTA) and 0.75g of melamine powder to obtain a mixture;

[0061] S2. Dissolve 2.50g of PVA in 500mL of deionized water at 80℃ to obtain a polyvinyl alcohol solution; mix the mixture obtained in S1 with the polyvinyl alcohol solution, and then react for 90min under stirring (1000rpm) while keeping the system boiling (98-100℃);

[0062] S3. After the reaction in S2 is completed, the reaction solution is filtered to obtain the solid. The solid is washed with water and dried at 110℃ for 120 min. Then, it is subjected to high-temperature secondary crosslinking at 180℃ for 120 min. The solid after secondary crosslinking is then carbonized at 500℃ for 60 min under a nitrogen atmosphere at a rate of 5℃ / min to obtain the carbonized material. The nitrogen atmosphere flow rate is 400 mL / min.

[0063] S4. Take 2.50g of the carbonized material obtained in step S3 and load it into a tube furnace. Under nitrogen conditions with a flow rate of 400mL / min, the temperature is raised to 900℃ at a rate of 5℃ / min. Then, turn off the nitrogen and introduce steam for activation for 120min. After activation, switch to nitrogen protection.

[0064] Finally, the material is washed (by boiling it in deionized water) until the pH of the filtrate is neutral, and then dried at 110°C to constant weight to obtain the sulfur-containing odor-competitive VOCs inhibitory adsorbent.

[0065] Table 1 shows the specific surface area and micropore volume of the adsorbent materials prepared in Examples 1-3 and commercially available coal-based activated carbon. The specific experimental method was as follows: the adsorbent was degassed at 250℃ for 180 min using a Bestech 3H-2000PSII instrument, followed by 1.0 × 10⁻⁶ micropores at -196℃. -7 Nitrogen adsorption and desorption were performed within the range of -1.0P / P0. Based on the N2 adsorption-desorption isotherm, the specific surface area and micropore volume and distribution of the adsorbent were determined by the Brunauer-Emmet-Teller (BET) method and the Horvath-Kawazoe (HK) method, respectively.

[0066] Table 1. Specific surface area and micropore volume of the adsorbent materials prepared in Examples 1-3 and commercially available coal-based activated carbon.

[0067] <![CDATA[Specific surface area (m 2 / g)]]> 813 760 985 802 Micropore volume (ml / g) 0.42 0.29 0.51 0.32

[0068] As shown in Table 1, the adsorbent prepared in Example 1 has a specific surface area close to that of commercially available coal-based activated carbon, but its micropore volume is significantly larger. The adsorbent prepared in Example 2 has a micropore volume close to that of commercially available coal-based activated carbon, but its specific surface area is smaller due to limitations in the preparation conditions. The adsorbent prepared in Example 3 has both a larger specific surface area and a larger micropore volume than commercially available coal-based activated carbon. This indicates that the preparation method described in this invention is more conducive to the formation of micropores.

[0069] Figure 2 Images of two adsorbent materials prepared in Examples 1 and 2 are shown. The average diameter of the adsorbent is about 2 mm.

[0070] Figure 3 The micropore distribution of the adsorbent material prepared in the above embodiments is shown, and the specific experimental methods are the same as those in Table 1. Figure 3 As can be seen, compared with commercially available coal-based activated carbon, the adsorbent material prepared by the method of this invention has a smaller pore size, less than 0.71 nm, and a greater number of micropores.

[0071] The nitrogen doping type of the adsorbent material prepared in Example 3 was quantitatively analyzed using an ESCALAB 250 XI X-ray photoelectron spectroscopy (XPS) instrument. The results are as follows: Figure 4 As shown, peak fitting of the N1s peak revealed that nitrogen atoms were doped onto the activated carbon surface in the form of pyridine N (398.2 eV), pyrrole N (399.4 eV), and graphitic N (400.9 eV), indicating that Example 3 successfully prepared various types of nitrogen-doped activated carbon.

[0072] The adsorbent materials prepared in Examples 1-3 above were subjected to competitive adsorption tests against commercially available coal-based activated carbon. These tests were conducted in a continuous flow fixed bed under atmospheric pressure. The specific experimental procedure was as follows: CS2 and toluene (0.05% CS2 with residual N2; 0.10% toluene with residual N2) from a gas cylinder were diluted with dry air to the desired concentration. Air containing pollutants was introduced into the bed containing 0.3 g of adsorbent at a rate of 400 mL / min. The adsorption bed was maintained at a constant temperature of 40°C using a thermostat. The tail gas was analyzed every 1.5 min using a gas chromatograph (GC9790, Fuli, China), and the concentrations of toluene and CS2 were determined using a flame ionization detector (FID) and a flame photometric detector (FPD), respectively. To control the adsorption time, all adsorption experiments were conducted under conditions where the inlet concentration of CS2 was 30 ppm and the inlet concentration of toluene was 132 ppm. The breakthrough curves for obtaining the adsorption of a mixture of toluene and carbon disulfide (CS2) are shown below. Figure 5 As shown.

[0073] Figure 5 The data show that, compared with commercially available coal-based activated carbon, the adsorbent materials prepared in Examples 1-3 exhibit significantly reduced peak areas (the portion where the CS2 outlet concentration / inlet concentration > 1) of CS2, indicating a marked reduction in competitive adsorption. This demonstrates that the adsorbents obtained by the preparation method described in this invention have a significant inhibitory effect on competitive adsorption, which is presumably the result of the combined effect of micropores and nitrogen doping. The adsorption capacity of toluene is: Example 2 < Example 1 < Example 3, due to the following relationship between the micropore volume and specific surface area of ​​the three: Example 2 < Example 1 < Example 3.

[0074] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. The application of a sulfur-containing odor-competitive VOCs inhibitory adsorbent in industrial waste gas treatment, characterized in that, The sulfur-containing odor-competitive VOCs-inhibiting adsorbent is prepared through the following steps: S1. Phenolic resin is dispersed in ethanol to form a homogeneous resin-ethanol solution; then hexamethylenetetramine and a nitrogen source are added to obtain a mixture; the nitrogen source is melamine; the amount of hexamethylenetetramine added is 8%-15% of the mass of phenolic resin, and the amount of nitrogen source added is 2%-5% of the mass of phenolic resin; S2. Mix the mixture obtained in S1 with a polyvinyl alcohol solution, and then react under stirring conditions, keeping the system at a boiling state for 90-120 min; the concentration of the polyvinyl alcohol solution is 0.5 wt% - 1.0 wt%; the amount of polyvinyl alcohol added is 5%-15% of the mass of the phenolic resin; S3. After the reaction in S2 is completed, filter the reaction solution to obtain the solid, wash and dry it, and then perform a secondary crosslinking at high temperature; The solid after secondary cross-linking is then carbonized under the protection of an inert gas to obtain carbonized material; the carbonization is carried out under nitrogen conditions, the carbonization temperature is 500-700 ℃, and the time is 50-70 min. S4. Activate the carbonized material obtained in S3. The activator used in the activation process is at least one of KOH, water vapor or CO2. After washing and drying, the sulfur-containing odor-competitive VOCs inhibitory adsorbent can be obtained.

2. Use according to claim 1, characterized in that, In step S1, the ethanol is anhydrous ethanol; the mass ratio of phenolic resin to anhydrous ethanol is 3:

2.

3. Use according to claim 1, characterized in that, In step S3, the temperature for the high-temperature secondary crosslinking is 180-250 ℃, and the time is 120-180 min.

4. Use according to claim 1, characterized in that, In step S4, the activation process is carried out at a temperature of 800-1000 ℃ for a time of 80-120 min.

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