Complex iron desulfurizer as well as preparation method and application thereof

Abstract

The invention belongs to the field of pollutant treatment, and particularly relates to a complex iron desulfurizer and a preparation method and application thereof. According to the specific technical scheme, the complexing agent is characterized by comprising Fe < 3 + >, Ce < 4 + >, 4, 4 '-carbonyl bis (pyridine-2, 6-dicarboxylic acid) and isooctyl alcohol. The invention provides a novel desulfurizing agent which is especially suitable for treating working conditions with high hydrogen sulfide content, the preparation method is simple, and the desulfurizing effect is ideal.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of pollutant treatment, and particularly relates to a complex iron desulfurizer and a preparation method and application thereof. BACKGROUND

[0002] Bio-NG is renewable natural gas produced by biogas purification, and the main component is methane (CH4, content > 90%), which can directly replace fossil natural gas and be used for power generation, heating, transportation fuel or injection into natural gas pipeline network.

[0003] The concentration of hydrogen sulfide in bio-NG is one of the important factors limiting its application. If the concentration of hydrogen sulfide in bio-NG is high, there may be safety hazards, and it will also reduce the service life of equipment, cause environmental pollution, and possibly reduce the utilization efficiency of bio-NG. Specifically, H2S is a highly toxic gas that can cause damage to the respiratory system and nervous system after being inhaled by the human body, and even cause suffocation or death. When the concentration of H2S in biogas exceeds the safety threshold, it will directly threaten the health of operating personnel. Moreover, after H2S is mixed with air, an explosive mixture may be formed within a certain concentration range, increasing the safety hazards in the process of biogas utilization. In addition, H2S dissolves in water to form sulfuric acid (H2SO3), which has strong corrosive properties and can accelerate the corrosion of metal equipment (such as pipelines, storage tanks, and engines), shorten the service life of equipment, and increase maintenance costs. Moreover, in the process of biogas power generation or purification, H2S can poison the catalyst (such as methanation catalyst), leading to a decrease in reaction efficiency or even failure, affecting system stability.

[0004] Therefore, desulfurization (H2S) pretreatment is often carried out before biogas utilization and bio-NG preparation. However, the commonly used complex iron desulfurizers all have obvious defects. Among them, the biodegradation rate of EDTA-based desulfurizers is extremely low, generally ≤ 30%; the carcinogenic rate of NTA series desulfurizers is relatively high, and the stability is poor; and MDEA-based desulfurizers are prone to volatilization and have low compatibility with biogas desulfurization.

[0005] Moreover, since a strong redox reaction occurs between H2S and Ln-Fe (Ln is any one or more of EDTA, NTA, CDTA, DOTA, MGDA, and ZKE-L2 complexes), therefore, when evaluating the effect of complex iron desulfurizers, the complexing ability of the complex and the regeneration ability of the desulfurizer need to be considered. In the biogas desulfurization process, O2 in the air is introduced into the regeneration tank by a regeneration blower to carry out the oxidation reaction of Fe 2+ . However, the oxygen demand of most biogas desulfurization processes is too large, resulting in insufficient regeneration of iron ions, and Fe 3+The loss is serious and the desulfurization effect is not ideal. The existing EDTA, NTA, CDTA, DOTA, MGDA complex iron series desulfurizer is only suitable for low hydrogen sulfide (2000-5000 ppmv) working condition, and the desulfurization effect of the desulfurizer on the gas with high hydrogen sulfide content such as biogas is not ideal.

[0006] Therefore, the desulfurizer capable of treating high hydrogen sulfide content and having low oxygen demand has great application prospect. SUMMARY

[0007] The application aims to provide a complex iron desulfurizer and a preparation method and application thereof.

[0008] To achieve the above application purposes, the technical scheme adopted by the application is as follows: a complexing agent, which comprises Fe 3+ , Ce 4+ , 4,4'-carbonyl bis (pyridine-2,6-dicarboxylic acid) and isooctanol. In terms of molar ratio, Fe 3+ : Ce 4+ : 4,4'-carbonyl bis (pyridine-2,6-dicarboxylic acid) : isooctanol = (20-30) : (1-1.5) : (30-40) : (10-25). The Fe 3+ is from a solid mixture of Fe(OH)3 and Fe2O3. The Ce 4+ is from a solid mixture of CeO2 and Ce(NO3)3.

[0009] Correspondingly, the preparation method of the complexing agent comprises the following steps:

[0010] (1) at 20-30℃, Fe 3 is added into an aqueous solution of 4,4'-carbonyl bis (pyridine-2,6-dicarboxylic acid), and then 14,4'-carbonyl bis (pyridine-2,6-dicarboxylic acid) is added dropwise to adjust the pH value to 5-6;

[0011] (2) after the solution is left to stand for 10-15 minutes, an aqueous solution of isooctanol is added under continuous stirring;

[0012] (3) Ce 4+ is added under stirring to adjust the pH of the system to 6-6.5, and then the solution is left to stand for 10-15 minutes to obtain the required complexing agent.

[0013] Correspondingly, the application of the complexing agent or the complexing agent prepared by the preparation method in desulfurization.

[0014] Correspondingly, the desulfurizer prepared by using the complexing agent or the complexing agent prepared by the preparation method.

[0015] Correspondingly, a desulfurizer, the formulation of the desulfurizer includes the complexing agent or the complexing agent prepared by the preparation method.

[0016] The present invention has the following beneficial effects: The present invention provides a new desulfurizer, which is particularly suitable for treating working conditions with a relatively high hydrogen sulfide content (the content is about 8000 - 15000 ppmv).

[0017] The present invention introduces a double-metal multi-component complex desulfurizer to assist in the regeneration of Fe 3+ , maintaining its activity. Although there are currently some reports on adding transition metals such as Cu, Mn, Co, etc. to the complex iron solvent for synergistic effects, the effects are generally poor and it is impossible to achieve good synergistic desulfurization. And the redox potential of Ce 4+ / Ce 3+ is about -1.7 eV, and that of Fe 3+ / Fe 2+ is about -1.05 eV. This energy level difference enables the reaction (Ce 4+ + Fe 2+ → Ce 3+ + Fe 3+ ) to proceed smoothly, thus playing a very high role in maintaining the activity of iron ions during the regeneration process, significantly reducing the aeration volume and saving costs.

[0018] However, the limitation of this reaction is that the desulfurizer system is in an acidic system. Adding Ce 4+ in desulfurization complexing agent systems such as EDTA, NTA, CDTA, DOTA, MGDA, etc. has poor effects. Because in the dissolved state of H2S, the system is in an acidic state, which will inhibit the reaction of H2S, especially for biogas with a relatively high H2S concentration. And the ZKE-L2 provided by the present invention can almost completely purify H2S under weakly acidic conditions (the hydrogen sulfide removal rate reaches more than 99.99%), and does not affect the dissolution of H2S.

[0019] In the present invention, isooctanol can improve the physical solubility of H2S and the dissolution ability of other organic molecules. In the formulation system of the present invention, only long-chain alcohols are suitable for introduction, and other alcohols cannot adapt to this system. But if the carbon chain is too long, it may instead degrade the physical solubility of H2S. Therefore, isooctanol is selected as the formulation raw material.

[0020] 4,4'-Carbonylbis(pyridine-2,6-dicarboxylic acid) in the formulation has a symmetric molecular structure, and the N-containing heterocycle has an electron-donating effect. While promoting molecular stability, it can improve the activity of carboxyl oxygen atoms.

[0021] In the preparation, NaOH is better for adjusting pH. This is because, due to the solubility of Ce, it will not only combine with complex, but also be free in the solution. If only acid is used to adjust pH or pH is not adjusted, a large amount of hydrogen ions will be ionized, and a small amount of NaOH can better adjust the pH value to the best dissolution state of Fe and Ce. DETAILED DESCRIPTION

[0022] The present application provides a new complex iron desulfurizer ZKE-L2, the formula of the desulfurizer comprising: Fe 3+ , Ce 4+ , 4,4'-carbonyl bis (pyridine-2, 6-dicarboxylic acid) (C 15 H 10 N2O9) and isooctanol.

[0023] The chemical structural formula of 4,4'-carbonyl bis (pyridine-2, 6-dicarboxylic acid) is as follows:

[0024]

[0025] Preferably, in terms of molar ratio, Fe 3+ : Ce 4+ : 4,4'-carbonyl bis (pyridine-2, 6-dicarboxylic acid) : isooctanol = (20-30) : (1-1.5) : (30-40) : (10-25).

[0026] Preferably, the Fe 3+ from the Fe(OH)3 / Fe2O3 solid mixture, in terms of molar ratio, Fe(OH)3: Fe2O3 = 1: (2-2.5). If other iron-containing compounds are used, impurities will be introduced. And the present application needs to be stably reacted with acid, and Cl - , SO4 2+ and the like have corrosive effect on stainless steel, other iron-containing salt compounds are easy to react to produce by-products, affecting the purity of sulfur in the product, so that sulfur paste becomes hazardous waste, and the by-products may also cause blockage of pipelines and equipment. If the amount of Fe(OH)3 is too large, it is easy to cause the hydrolysis reaction of Fe 3+ , Ce 4+ .

[0027] Preferably, the Ce 4+ from the CeO2 / Ce(NO3)3 solid mixture, in terms of molar ratio, CeO2: Ce(NO3)3 = (2-3) : 1. Because nitrate will not cause corrosion of stainless steel in the solution, and will not cause the production of by-products, the sulfate and chloride are abandoned, and Ce(NO3)3 is selected. CeO2 and Ce(NO3)3 need to be used at the same time, because the two compounds have different potentials and valence states, and only by using them at the same time can the oxidation reaction and the reduction reaction occur at the same time.

[0028] The application also provides a preparation method of the complex desulfurizer, comprising the following steps: adding a Fe(OH)3 / Fe2O3 mixture solid into a 15-20 wt% 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) aqueous solution at 20-30 ℃, stirring until the solid is completely dissolved, standing until the solution returns to room temperature, then adding 15-20 wt% 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) aqueous solution drop by drop (1 drop for 2 s) through a pipette, adjusting the pH value to 5-6, and dissolving the remaining small amount of precipitate; after the solution is standing for 10-15 minutes, adding 40-50 wt% isooctanol aqueous solution under continuous stirring, and then adding CeO2 / Ce(NO3)3 powder under stirring; after the powder is added, the stirring is continued for more than 5 minutes to allow the Ce 4+ better adhere to the complexing agent carrier. Then, 15-20 wt% 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) aqueous solution and an alkaline reagent (preferably 30 wt% NaOH) are used to adjust the pH value of the system to 6-6.5 (if the pH value is not adjusted, the pH value of the system is 4-5, and the desulfurization effect of the obtained complexing agent desulfurizer cannot reach the most ideal effect). Then, the solution is standing for 10-15 minutes to obtain a complex desulfurizer ZKE-L1-Fe stock solution. The water used in the whole configuration is deionized water. The reaction system is a red liquid in a clear state, and no solid impurities are generated, which is regarded as the completion of the reaction, and a stable ZKE-L1-Fe stock solution is obtained.

[0029] The application also provides a desulfurization method using the desulfurizer. The complex desulfurizer is directly added to the environment / substrate to be desulfurized. If the environment to be desulfurized is a gas environment, for example, the desulfurization of biogas is needed, the complex desulfurizer can be placed in the gas environment or sprayed into the gas environment. If the substrate to be desulfurized is a liquid, the complex desulfurizer is added to the liquid. If the substrate to be desulfurized is a solid, the complex desulfurizer is mixed with the solid or applied to the surface of the substrate.

[0030] The technical solutions in the embodiments of the application will be clearly and completely described below. Obviously, the described embodiments are only some of the embodiments of the application, not all the embodiments. If not specifically indicated, the technical means used in the embodiments are conventional means familiar to those skilled in the art, and the obtained data are all average values obtained after at least 3 repetitions, and the data obtained in each repetition are all valid data.

[0031] Example 1: Preparation of desulfurizer and comparison of basic performance

[0032] 1. Preparation of experimental group:

[0033] The reaction was carried out in a reaction kettle. At 25°C, 20wt% aqueous solution of 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) was added with Fe(OH)3 / Fe2O3 mixture solid (molar ratio 1:2), and stirred until the solid was completely dissolved. After the solution was restored to room temperature, 20wt% aqueous solution of 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) was added dropwise (1 drop 2s) by pipette. After the pH = 6 solution was adjusted and stood for 15 minutes, 50wt% aqueous solution of isooctanol was added under continuous stirring, and then CeO2 / Ce(NO3)3 powder was added under stirring. After the powder was added, the stirring was continued for 5 minutes. Then 20wt% aqueous solution of 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) and 30wt% NaOH were used to adjust the pH to 6. The solution was then allowed to stand for 10-15 minutes to obtain the complex desulfurizer ZKE-L1-Fe stock solution. The stock solution was a clear, red liquid without solid impurities. Different ZKE-L1-Fe (experimental group) was prepared by adjusting the amount of raw materials (molar ratio) according to the manner of Table 1.

[0034] Table 1: Comparison of raw material molar ratio in each group of ZKE-L1-Fe

[0035] Group Fe 3+ ]] Ce 4+ ]]> 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) isooctanol Experiment group 1 20 1 30 10 Experiment group 2 25 1.3 40 20 Experiment group 3 40 1.3 40 20 Experiment group 4 25 2 40 20 Experiment group 5 25 1.3 20 20 Experiment group 6 25 1.3 40 10

[0036] 2, Control group: Control group 1: EDTA-Fe (sodium iron ethylenediaminetetraacetate); Control group 2: NTA-Fe (iron nitlotriacetate); Control group 3: CDTA-Fe (iron cyclohexanediaminetetraacetate); Control group 4: DOTA-Fe (iron tetraazacyclododecanetetraacetate); Control group 5: MGDA-Fe (iron methylglycinediacetate). Control groups 1-5 are mature prior art, which can be purchased or prepared by known methods, and the preparation method is not described here.

[0037] Control group 6: based on experimental group 2, all other conditions are exactly the same as experimental group 2, except that after adding CeO2 / Ce(NO3)3 powder, the pH is not adjusted, and the complex desulfurizer is obtained directly after standing.

[0038] Control group 7: based on experimental group 2, all other conditions are exactly the same as experimental group 2, except that isooctanol is replaced with propanol, and the amount is the same.

[0039] Example 2: Comparison of desulfurization performance of each desulfurizer

[0040] 1. Desulfurization effect display:

[0041] Taking the on-site experimental data of Mianyang Zhongke as an example, the removal rate η of hydrogen sulfide in biogas by each desulfurizer prepared in Example 1 was verified. The experiment was carried out for 3 days, and 1 kind of complex iron desulfurizer with different concentrations (mass concentrations were: 10wt%, 25wt%, 40wt%) was tested each day.

[0042] η=(C0 - C t ) / C0; C0 is the hydrogen sulfide concentration PPMv before the reaction, and C t is the hydrogen sulfide concentration PPMv after the reaction. <s

[0043] 1t of aqueous solutions of each desulfurizer in Example 1 with 3 different concentrations (10wt%, 25wt%, 40wt%) were prepared, and the raw biogas was purified using a desulfurization tower and a regeneration tower. The treatment method was as follows: The desulfurizer was pumped into the regeneration tank in the chemical addition tank, reflux tank and reflux pump. The initial solvent dosage was 2t (the effective component contents were: 10wt%, 25wt%, 40wt%, respectively diluted to the required concentration with soft water). The desulfurization liquid was transported between the desulfurization tower and the regeneration tank by a rich and lean liquid pump to maintain the liquid level balance. The initial composition of the raw biogas was: biogas volume 1250 Nm 3 / h, hydrogen sulfide content 9000 - 11000 ppmv, methane 60%, CO2 35%, circulation volume 30 - 35 m 3 / h, reaction temperature ⒛ - 40 °C, reaction pressure 5 - 40 kpag. During desulfurization, oxygen was continuously sent into the regeneration tank through an air blower to react with Fe 3+ to generate Fe 2+ , and then it was pumped into the desulfurization tower through a reflux pump for reaction. The air distribution volume for each group was controlled to be 390 m 3 / h. Using a hydrogen sulfide detector AT, after each day's treatment, the component contents of the biogas before and after purification were analyzed, and the results were averaged. The results are shown in Table 2.

[0044] Table 2 Comparison table of desulfurization effects (24h) of different desulfurizers

[0045]

[0046]

[0047] 2. Comparison of aeration volume:

[0048] In the desulfurization test in Step 1, oxygen was continuously sent into the regeneration tank through an air blower to react with Fe 3+ to generate Fe 2+Afterwards, the reaction is carried out by feeding into the desulfurization tower through the reflux pump. If the hydrogen sulfide concentration is 10±2 ppm after 24 hours of reaction, it is judged that the oxygen feeding amount is appropriate, if the hydrogen sulfide concentration is too high, the air supply amount needs to be increased, otherwise the air supply amount is reduced, so as to select the best air supply amount of each group. Record the overall aeration amount (ventilation amount) of each group in the experiment (24 hours), and the results are shown in Table 3.

[0049] Table 3 Comparison table of aeration amount corresponding to different desulfurizers

[0050]

[0051]

[0052] The above-described embodiments are only to describe the preferred modes of the present application, and not to limit the scope of the present application. Without departing from the design spirit of the present application, various modifications, variations, modifications, replacements of the technical solutions of the present application made by those skilled in the art shall fall within the protection scope determined by the claims of the present application.

Claims

1. A complexing agent characterized in that: The complexing agent comprises Fe 3+ , Ce 4+ , 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid) and isooctanol.

2. The complexing agent according to claim 1, characterized in that: Among the complexing agents, Fe 3+ : Ce 4+ : 4,4'-carbonylbis(pyridine-2,6-dicarboxylic acid): isooctanol = (20-30):(1-1.5):(30-40):(10-25).

3. The complexing agent according to claim 1 or 2, characterized in that: The Fe 3+ Solid mixture from Fe(OH)3and Fe2O3.

4. The complexing agent according to claim 1 or 2, characterized in that: The Ce 4+ Solid mixture from CeO2and Ce(NO3)3.

5. Process for the preparation of the complexing agent according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: (1) In 4,4'-carbonyl bis (pyridine-2, 6-dicarboxylic acid) aqueous solution, add Fe 3 , and then adjust the pH value to 5-6 with 14,4'-carbonyl bis (pyridine-2, 6-dicarboxylic acid) dropwise (2) After the solution is left to stand for 10-15 minutes, add an aqueous isooctanol solution under continuous stirring; (3) Ce was added under stirring 4+ The solution was then left to stand for 10-15 minutes to obtain the desired complexing agent.

6. The method of claim 5, wherein: Step (1) is carried out at 20-30°C.

7. The method of claim 5, wherein: Step (3) addition of Ce 4+ After that, the pH of the system is adjusted to 6-6.5 and the solution is left to stand for 10-15 minutes.

8. Use of the complexing agent according to any one of claims 1-4 or prepared by the method according to any one of claims 5-7 in desulfurization.

9. A desulfurizer prepared using the complexing agent according to any one of claims 1-4 or prepared by the method according to any one of claims 5-7.

10. A desulfurizer characterized by: The desulfurizer comprises the complexing agent according to any one of claims 1-4 or prepared by the method according to any one of claims 5-7 in its formulation.

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