A heat-resistant complex iron desulfurizer and its preparation method and application

Abstract

The invention discloses a heat-resistant complex iron desulfurizer and a preparation method and application thereof, and relates to the technical field of desulfurizers. The heat-resistant complex iron desulfurizer is obtained by chelating n-alkanoic acid-modified carboxymethyl chitosan, fulvic acid, polymaleic acid and soluble iron salt; wherein the n-alkanoic acid-modified carboxymethyl chitosan, fulvic acid and polymaleic acid all have good temperature stability, react quickly with hydrogen sulfide under high temperature conditions, thereby realizing efficient desulfurization, and can still perform rapid desulfurization and regeneration reactions at 60°C, and can meet the needs of most high-temperature desulfurization in production. For example, when the desulfurization reaction is performed at a temperature above 60°C, the use days of the desulfurizer can be reduced or the use amount can be increased for adjustment.

Description

Technical Field

[0001] The invention relates to the technical field of desulfurizing agents, in particular to a temperature-resistant complex iron desulfurizing agent and a preparation method and application thereof. Background Art

[0002] Hydrogen sulfide is a colorless, flammable gas with a rotten egg smell. It is one of the key industrial emission pollutants. In the fields of coal, petroleum, and chemical industry, many factory exhaust gases contain hydrogen sulfide gas. In addition, hydrogen sulfide is hydrosulfuric acid when dissolved in water, which is acidic and extremely corrosive to industrial equipment and pipelines. If hydrogen sulfide gas exists in the equipment pipeline for a long time, it will seriously shorten the pipeline life and increase the operating costs of the enterprise.

[0003] At present, wet desulfurization is mainly used in industry to remove hydrogen sulfide. Wet desulfurization is to pass hydrogen sulfide gas into a solution containing certain chemical components. The chemical components in the solution react or combine with hydrogen sulfide to remove hydrogen sulfide. Wet desulfurization has both physical adsorption and chemical adsorption, and has the advantages of low cost and high efficiency in removing hydrogen sulfide. At present, the environment suitable for the desulfurizer to work is generally below 40°C. In industry, cooling water is needed to cool the desulfurization liquid or the gas to be desulfurized. However, in summer, the temperature usually exceeds 40°C, and some can even reach 50°C. Using cooling water for cooling is not only time-consuming and labor-intensive, but also increases the cost.

[0004] Patent CN 115337775 B discloses a complex iron desulfurizer, which is compounded with soluble iron salt or soluble ferrous salt, fulvic acid and its salt, sodium alginate, iminodisuccinic acid and its salt, etc., wherein the addition of sodium alginate can play a good role in dispersion and stability, and the carboxyl group in sodium alginate can chelate with iron ions, which is helpful to improve the desulfurization effect. However, sodium alginate swells severely after absorbing water, resulting in excessive viscosity of the system, so that the desulfurizer cannot keep the system uniform during use, which seriously affects the use effect. CN 115318098 B discloses a complex iron desulfurizer, which is compounded with soluble iron salt or soluble ferrous salt, fulvic acid and its salt, polymaleic acid, iminodisuccinic acid and its salt, etc. The desulfurizer can be used at high temperatures above 55°C. Polymaleic acid is a good substitute for sodium alginate and will not cause the system to become viscous. However, polymaleic acid molecules are more hydrophilic, while fulvic acid is an amphiphilic molecule. In addition to the hydrophilic carboxyl group, its structure also contains hydrophobic structures such as benzene rings and long-chain alkyl groups. It is not very compatible with polymaleic acid, resulting in poor system uniformity.

[0005] Therefore, the industry is in urgent need of developing a complex iron desulfurizer that is resistant to high temperatures, has good stability, and is easy to handle after use. Summary of the invention

[0006] In order to solve the above problems, the purpose of the present invention is to provide a temperature-resistant complex iron desulfurizer and a preparation method and application thereof.

[0007] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0008] A temperature-resistant complex iron desulfurizer is obtained by chelating n-alkanoic acid-modified carboxymethyl chitosan, fulvic acid, polymaleic acid and soluble iron salt.

[0009] The present invention also includes a method for preparing a temperature-resistant complex iron desulfurizer, comprising the following steps:

[0010] ① In parts by weight, 2 to 4 parts of a long-chain n-alkanoic acid are added to 200 to 280 parts of a first sodium chloride aqueous solution, and 6 to 12 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4 to 9 parts of N-hydroxysuccinimide are added under stirring, and stirred at 15 to 35° C. for 20 to 60 minutes to obtain a mixed solution for standby use;

[0011] Under stirring, the obtained mixed solution is added to 400-600 parts of carboxymethyl chitosan solution in 3-6 times, and after adding, it is stirred at 20-50° C. for 18-24 hours, and the obtained reaction solution is dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0012] The mass concentration of the first sodium chloride aqueous solution is 0.5-2 mol / L;

[0013] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 0.5-2 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 15-20:350-400;

[0014] ② Add 30-45 parts of fulvic acid and 20-34 parts of polymaleic acid to 1000 parts of water, stir and dissolve, add 14-17 parts of soluble iron salt and 0.5-1 part of soluble copper salt, stir and dissolve, add 5-20 parts of n-alkanoic acid modified carboxymethyl chitosan obtained in step ①, stir and dissolve, adjust the pH value to 8.5-10 with alkali, and obtain a temperature-resistant complex iron desulfurizer.

[0015] Preferably, the long-chain n-alkanoic acid is n-dodecanoic acid or n-tetradecanoic acid.

[0016] Preferably, the degree of substitution of the carboxymethyl chitosan is ≥90%, and the isoelectric point is 3-4.

[0017] Preferably, the mass concentration of the first sodium chloride is 1 mol / L.

[0018] Preferably, the soluble iron salt is ferric chloride or ferric nitrate.

[0019] Preferably, the base is potassium hydroxide, sodium hydroxide, sodium carbonate or potassium carbonate.

[0020] Preferably, the soluble copper salt is copper chloride or copper nitrate.

[0021] The present invention also includes the application of the above-mentioned temperature-resistant complex iron desulfurizing agent for removing hydrogen sulfide gas.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] The temperature-resistant complex iron desulfurizer of the present invention is obtained by chelating carboxyl groups and iron ions in n-alkanoic acid-modified carboxymethyl chitosan, fulvic acid and polymaleic acid, wherein the n-alkanoic acid-modified carboxymethyl chitosan, fulvic acid and polymaleic acid all have good temperature stability, react quickly with hydrogen sulfide under high temperature conditions, thereby realizing efficient desulfurization, and can still perform rapid desulfurization and regeneration reactions at 60°C, thereby meeting the needs of most high-temperature desulfurization in production. For example, when the desulfurization reaction is performed at a temperature above 60°C, the use days of the desulfurizer can be reduced or the use amount can be increased for adjustment.

[0024] The present invention replaces sodium alginate with n-alkanoic acid-modified carboxymethyl chitosan. The raw material carboxymethyl chitosan has excellent water solubility, and its water solubility is not greatly affected after being modified with n-alkanoic acid, which can avoid the problem of excessive expansion and viscosity after sodium alginate is added and dissolved in water in the prior art. Moreover, n-alkanoic acid-modified carboxymethyl chitosan is an amphiphilic substance, which has better compatibility with polymaleic acid and fulvic acid, and can effectively solve the problem of system inhomogeneity when polymaleic acid and fulvic acid exist at the same time. In addition, the amphiphilic n-alkanoic acid-modified carboxymethyl chitosan can form a stable microgel system in the solution system, but will not cause the system to be overly viscous, so that the system has higher catalytic activity and stability, and better temperature resistance. DETAILED DESCRIPTION

[0025] The purpose of the present invention is to provide a temperature-resistant complex iron desulfurizer and a preparation method and application thereof. The present invention is further described below in conjunction with specific embodiments.

[0026] If the soluble iron salt is a hydrate of iron salt, the amount added is calculated based on the amount of water of crystallization removed.

[0027] Example 1 A method for preparing a temperature-resistant complex iron desulfurizer comprises the following steps:

[0028] ① Add 0.2 kg of n-dodecanoic acid to 20 kg of 0.5 mol / L sodium chloride aqueous solution, add 0.6 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.4 kg of N-hydroxysuccinimide under stirring, stir at 15° C. for 60 minutes to obtain a mixed solution for standby use;

[0029] Under stirring, the obtained mixed solution was added to 40 kg of carboxymethyl chitosan solution in three times, and stirred at 20° C. for 24 hours after the addition. The obtained reaction solution was dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0030] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 0.5 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 15:350;

[0031] ② Add 3kg of fulvic acid and 2kg of polymaleic acid into 100kg of water, stir to dissolve, add 1.4kg of ferric chloride and 0.05kg of cupric chloride, stir to dissolve, add 0.5kg of n-alkanoic acid-modified carboxymethyl chitosan obtained in step ①, stir to dissolve, adjust the pH value to 8.5 with potassium hydroxide, and obtain a temperature-resistant complex iron desulfurizer.

[0032] Example 2 A method for preparing a temperature-resistant complex iron desulfurizer comprises the following steps:

[0033] ① Add 0.4 kg of n-tetradecanoic acid to 28 kg of 2 mol / L sodium chloride aqueous solution, add 1.2 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.9 kg of N-hydroxysuccinimide under stirring, stir at 35° C. for 20 minutes to obtain a mixed solution for standby use;

[0034] Under stirring, the obtained mixed solution was added to 60 kg of carboxymethyl chitosan solution in 6 times, and stirred at 50° C. for 18 hours after the addition. The obtained reaction solution was dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0035] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 2 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 20:400;

[0036] ② Add 4.5kg fulvic acid and 3.4kg polymaleic acid into 100kg water, stir to dissolve, add 1.7kg ferric nitrate and 0.1kg copper nitrate, stir to dissolve, add 2kg n-alkanoic acid modified carboxymethyl chitosan obtained in step ①, stir to dissolve, adjust the pH value to 10 with sodium hydroxide, and obtain a temperature-resistant complex iron desulfurizer.

[0037] Example 3 A method for preparing a temperature-resistant complex iron desulfurizer comprises the following steps:

[0038] ① Add 0.25 kg of n-dodecanoic acid to 21 kg of 0.8 mol / L sodium chloride aqueous solution, add 0.7 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.5 kg of N-hydroxysuccinimide under stirring, stir at 20° C. for 30 minutes to obtain a mixed solution for standby use;

[0039] Under stirring, the obtained mixed solution was added to 45 kg of carboxymethyl chitosan solution in 4 times, and stirred at 25° C. for 20 hours after the addition. The obtained reaction solution was dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0040] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 1 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 18:380; the degree of substitution of the carboxymethyl chitosan is ≥90%, and the isoelectric point is 3-4;

[0041] ② Add 4kg of fulvic acid and 2.5kg of polymaleic acid to 100kg of water, stir to dissolve, add 1.5kg of ferric chloride and 0.08kg of copper nitrate, stir to dissolve, add 1kg of n-alkanoic acid-modified carboxymethyl chitosan obtained in step ①, stir to dissolve, adjust the pH value to 9.5 with sodium carbonate, and obtain a temperature-resistant complex iron desulfurizer.

[0042] Example 4 A method for preparing a temperature-resistant complex iron desulfurizer comprises the following steps:

[0043] ① Add 0.35 kg of n-tetradecanoic acid to 26 kg of 1 mol / L sodium chloride aqueous solution, add 0.8 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.8 kg of N-hydroxysuccinimide under stirring, stir at 25° C. for 40 minutes to obtain a mixed solution for standby use;

[0044] Under stirring, the obtained mixed solution was added to 50 kg of carboxymethyl chitosan solution in 5 times, and stirred at 40° C. for 20 hours after the addition. The obtained reaction solution was dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0045] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 1 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 16:385; the degree of substitution of the carboxymethyl chitosan is ≥90%, and the isoelectric point is 3-4;

[0046] ② Add 3.8kg of fulvic acid and 2.8kg of polymaleic acid to 100kg of water, stir to dissolve, add 1.6kg of ferric nitrate and 0.06kg of cupric chloride, stir to dissolve, add 1.8kg of n-alkanoic acid-modified carboxymethyl chitosan obtained in step ①, stir to dissolve, adjust the pH value to 9.0 with potassium carbonate, and obtain a temperature-resistant complex iron desulfurizer.

[0047] Example 5 A method for preparing a temperature-resistant complex iron desulfurizer comprises the following steps:

[0048] ① Add 0.25 kg of n-dodecanoic acid to 24 kg of 1.8 mol / L sodium chloride aqueous solution, add 0.9 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.6 kg of N-hydroxysuccinimide under stirring, stir at 25° C. for 50 minutes to obtain a mixed solution for standby use;

[0049] Under stirring, the obtained mixed solution was added to 50 kg of carboxymethyl chitosan solution in 5 times, and stirred at 30° C. for 20 hours after the addition. The obtained reaction solution was dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0050] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 1.5 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 16:360; the degree of substitution of the carboxymethyl chitosan is ≥90%, and the isoelectric point is 3-4;

[0051] ② Add 3.5kg of fulvic acid and 2.4kg of polymaleic acid to 100kg of water, stir to dissolve, add 1.5kg of ferric chloride and 0.09kg of copper nitrate, stir to dissolve, add 1.2kg of n-alkanoic acid-modified carboxymethyl chitosan obtained in step ①, stir to dissolve, adjust the pH value to 9.5 with potassium hydroxide, and obtain a temperature-resistant complex iron desulfurizer.

[0052] Example 6 A method for preparing a temperature-resistant complex iron desulfurizer comprises the following steps:

[0053] ① Add 0.35 kg of n-tetradecanoic acid to 25 kg of 1 mol / L sodium chloride aqueous solution, add 0.85 kg of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 0.65 kg of N-hydroxysuccinimide under stirring, stir at 30° C. for 45 minutes to obtain a mixed solution for standby use;

[0054] Under stirring, the obtained mixed solution was added to 50 kg of carboxymethyl chitosan solution in 6 times, and stirred at 40° C. for 20 hours after the addition. The obtained reaction solution was dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan;

[0055] The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 1 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 18:360; the degree of substitution of the carboxymethyl chitosan is ≥90%, and the isoelectric point is 3-4;

[0056] ② Add 3.5kg of fulvic acid and 2.8kg of polymaleic acid into 100kg of water, stir to dissolve, add 1.6kg of ferric chloride and 0.08kg of cupric chloride, stir to dissolve, add 1.5kg of n-alkanoic acid-modified carboxymethyl chitosan obtained in step ①, stir to dissolve, adjust the pH value to 9 with potassium carbonate, and obtain a temperature-resistant complex iron desulfurizer.

[0057] Comparative Example 1

[0058] 3.5 kg of fulvic acid and 2.8 kg of polymaleic acid were added to 100 kg of water, stirred to dissolve, 1.6 kg of ferric chloride and 0.08 kg of cupric chloride were added, stirred to dissolve, and the pH value was adjusted to 9 with potassium carbonate to obtain a complex iron desulfurizer.

[0059] Comparative Example 2

[0060] On the basis of Example 6, the content of the cupric chloride component was changed to 8 g, and the contents of other components and the operating steps remained unchanged.

[0061] Desulfurizer minimum sulfur capacity test

[0062] Take 1000 ml of the heat-resistant complex iron desulfurizer obtained in Examples 1 to 6 above and place it in a long-necked glass container. Take 20 ml of the desulfurizer and dilute it to 200 ml with water. 3 The hydrogen sulfide gas is injected into the glass container at a rate of 30 ml / min through the gas distribution head placed at the bottom of the glass container. The upper end of the glass container is provided with an opening, and the outlet hydrogen sulfide is detected by a hydrogen sulfide detector once a minute until the outlet hydrogen sulfide can be detected. The ventilation time is recorded and the minimum sulfur capacity is calculated. The results are shown in Table 1. The minimum sulfur capacity calculation formula is:

[0063] C min =c×v×T / (1000V);

[0064] Among them C min is the minimum sulfur capacity, g / L; c is the hydrogen sulfide concentration, g / m 3 ; v is the hydrogen sulfide flow rate, L / min; T is the ventilation time when hydrogen sulfide is detected, min; V is the desulfurizer volume, L.

[0065] Desulfurizer regeneration speed test: Take the remaining liquid after measuring the minimum sulfur content of the desulfurizer and continue to introduce hydrogen sulfide. When the desulfurized liquid is completely milky white and the difference between the outlet hydrogen sulfide gas volume and the inlet hydrogen sulfide gas volume is within 10%, stop introducing hydrogen sulfide. Take a small blower and place the gas distribution head of the outlet pipe of the small blower in the above glass container until the amount of foam in the glass container decreases, the desulfurized liquid turns wine red, and more sulfur appears in the container. At this time, the desulfurizer has been completely regenerated. The ventilation time is recorded as the regeneration time. The results are shown in Table 1.

[0066] Table 1 Test results of minimum sulfur capacity and regeneration time of heat-resistant complex iron desulfurizer

[0067]

[0068] It can be seen from the results in Table 1 that the minimum sulfur capacity of the desulfurizer of the present invention is relatively high, which can reach more than 5.5 g / L, and the regeneration time is short. The regeneration time is related to the amount of copper ions added relative to iron ions. The larger the relative amount of copper ions, the shorter the regeneration time. In addition, it can be observed during the regeneration process that the sulfur particles are larger and most of the sulfur particles are attached to the bubbles.

[0069] In Comparative Example 1, since no n-alkanoic acid-modified carboxymethyl chitosan is added, fulvic acid, polymaleic acid and ferric chloride are chelated, the minimum sulfur capacity is low, and since the addition ratio of copper ions and iron ions is consistent with that of Example 6, the regeneration time is not greatly affected. In Comparative Example 2, since the addition ratio of copper chloride is reduced, the effect on the minimum sulfur capacity is small, but the regeneration time is greatly increased, and copper ions will act as a catalyst when iron ions are regenerated, accelerating the regeneration process of the desulfurizer.

[0070] When conducting the minimum sulfur capacity test, the traditional method of adding sodium carbonate solution in the experiment to maintain the pH of the desulfurizer at the initial pH during the test was not adopted. The inventors found that the pH value of the solution has little effect on the minimum sulfur capacity of the heat-resistant complex iron desulfurizer obtained by this technology, which further saves customers the operating steps in the process of using the heat-resistant complex iron desulfurizer.

[0071] High temperature desulfurization of desulfurizer

[0072] The experimental device includes an absorption tower, a regeneration tower, a foam storage tank, a plate and frame filter press, a lean liquid circulation pump, a rich liquid circulation pump, a regeneration fan, etc. Among them, the absorption tower is the place for removing hydrogen sulfide. The rich liquid obtained after desulfurization enters the regeneration tower through the rich liquid pump. The regeneration tower is the place where sulfur foam is generated and the desulfurizer is regenerated. During the regeneration process, the generated sulfur foam enters the plate and frame press for filtration. At the same time, air is blown in through the regeneration fan to regenerate the desulfurized liquid. The regenerated desulfurized liquid enters the absorption tower through the lean liquid circulation pump. During the regeneration process, the generated sulfur foam enters the defoaming tank. When there is a certain amount of sulfur foam in the defoaming tank, the plate and frame filter press is used to filter it to obtain sulfur. The structure of the entire desulfurization device is a conventional structure in the field.

[0073] Take the heat-resistant complex iron desulfurizer obtained in Examples 1 to 6 and dilute it 50 times. Use the industrial waste gas from the side line of a fertilizer plant in Shandong as the gas source. The hydrogen sulfide content is 20-30 g / m 3 The industrial waste gas is used as the gas source. During the desulfurization process, the gas volume is 5m 3 / h, the desulfurization liquid volume is 0.5m 3 . At the same time, the temperature of the desulfurized liquid was adjusted to 50°C, 60°C, and 70°C by external heating for testing. During the experiment, 64g of the above-mentioned temperature-resistant complex iron desulfurizer was added for every 1kg of sulfur output. During the experiment, the hydrogen sulfide content at the exhaust port (i.e., the hydrogen sulfide content in the purified gas) was measured. During the entire test process, no waste liquid was discharged to the outside. The final results are shown in Tables 2 to 4.

[0074] Table 2 Desulfurization test results at 50℃

[0075]

[0076] Table 3 Desulfurization test results at 60℃

[0077]

[0078] Table 4 Desulfurization test results at 70℃

[0079]

[0080] It can be seen from the results of Tables 2 to 4 that the heat-resistant complex iron desulfurizer of the present invention can still remove hydrogen sulfide well at higher temperatures, can tolerate higher desulfurization temperatures, and has a good regeneration effect. As the temperature increases, the desulfurization efficiency of the heat-resistant complex iron desulfurizer of the present invention also decreases, and rapid desulfurization and regeneration reactions can still be performed at 60°C, which can meet the needs of most high-temperature desulfurization in production. For example, when the desulfurization reaction is performed at a temperature above 60°C, the use days of the desulfurizer can be reduced or the amount used can be increased for adjustment. When the heat-resistant complex iron desulfurizer of the present invention is used, there is no problem of excessive viscosity, which prolongs the use time of the desulfurizer, and makes the system have higher catalytic activity and stability, and better temperature resistance.

Claims

1. A temperature-resistant complex iron desulfurizer, characterized in that: It is obtained by chelating carboxymethyl chitosan modified by n-alkanoic acid, fulvic acid, polymaleic acid and soluble iron salt; The temperature-resistant complex iron desulfurizer is prepared according to the following steps: ① In parts by weight, 2 to 4 parts of a long-chain n-alkanoic acid are added to 200 to 280 parts of a first sodium chloride aqueous solution, and 6 to 12 parts of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride and 4 to 9 parts of N-hydroxysuccinimide are added under stirring, and stirred at 15 to 35° C. for 20 to 60 minutes to obtain a mixed solution for standby use; The long-chain n-alkanoic acid is n-dodecanoic acid or n-tetradecanoic acid; Under stirring, the obtained mixed solution is added to 400-600 parts of carboxymethyl chitosan solution in 3-6 times, and after adding, it is stirred at 20-50° C. for 18-24 hours, and the obtained reaction solution is dialyzed with a dialysis bag with a molecular weight of 3500D, and freeze-dried to obtain n-alkanoic acid-modified carboxymethyl chitosan; The mass concentration of the first sodium chloride aqueous solution is 0.5-2 mol / L; The carboxymethyl chitosan solution is obtained by dissolving carboxymethyl chitosan in a second sodium chloride aqueous solution with a mass concentration of 0.5-2 mol / L; wherein the mass ratio of the carboxymethyl chitosan to the second sodium chloride aqueous solution is 15-20:350-400; ② Add 30-45 parts of fulvic acid and 20-34 parts of polymaleic acid to 1000 parts of water, stir and dissolve, add 14-17 parts of soluble iron salt and 0.5-1 part of soluble copper salt, stir and dissolve, add 5-20 parts of n-alkanoic acid modified carboxymethyl chitosan obtained in step ①, stir and dissolve, adjust the pH value to 8.5-10 with alkali, and obtain a temperature-resistant complex iron desulfurizer.

2. A temperature-resistant complex iron desulfurizer according to claim 1, characterized in that: The degree of substitution of the carboxymethyl chitosan is ≥90%, and the isoelectric point is 3-4.

3. A temperature-resistant complex iron desulfurizer according to claim 1, characterized in that: The mass concentration of the first sodium chloride is 1 mol / L.

4. A temperature-resistant complex iron desulfurizer according to claim 1, characterized in that: Soluble iron salts are ferric chloride or ferric nitrate.

5. A temperature-resistant complex iron desulfurizer according to claim 1, characterized in that: The alkali is potassium hydroxide, sodium hydroxide, sodium carbonate or potassium carbonate.

6. A temperature-resistant complex iron desulfurizer according to claim 1, characterized in that: The soluble copper salt is copper chloride or copper nitrate.

7. The use of a temperature-resistant complex iron desulfurizer according to claim 1, characterized in that: Used to remove hydrogen sulfide gas.

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