CN113929149A

CN113929149A - Preparation method of new polycrystalline microcrystal iron oxyhydroxide material

Info

Publication number: CN113929149A
Application number: CN202111345244.XA
Authority: CN
Inventors: 穆玮; 谢清源
Original assignee: Individual
Current assignee: Individual
Priority date: 2021-11-15
Filing date: 2021-11-15
Publication date: 2022-01-14

Abstract

The invention discloses a preparation method of polycrystalline microcrystal iron oxyhydroxide, which comprises the following steps: (1) mixing and stirring ferrous sulfate containing seven crystal waters and a solid alkaline substance; (2) controlling the pH value of the reaction mixture to be 8-9; (3) adding water in batches and stirring, and controlling the reaction temperature not to exceed 50 ℃; (4) introducing air to oxidize the slurry obtained in the step (2); (5) adjusting the pH value of the product obtained in the step (4) to about 8 by adding sodium hydroxide; (6) stirring and aging the obtained substance in the step (5); (7) washing and filtering the obtained product in the step (6); (8) drying the substance obtained in the step (7) to obtain polycrystalline microcrystal iron oxide hydroxide; the invention has simple preparation process and good operability, and the produced sewage is easy to treat and is suitable for industrial mass production.

Description

Preparation method of new polycrystalline microcrystal iron oxyhydroxide material

Technical Field

The invention relates to the field of chemical materials, in particular to a preparation method of a new polycrystalline microcrystal FeOOH material.

Background

In the fields of energy production and application, such as petroleum and natural gas exploitation, petroleum refining and chemical industry, coal chemical industry, biomass gas production and synthetic oil, many gas-liquid phase materials contain hydrogen sulfide in different concentrations. Hydrogen sulfide is a lethal gas, which, in addition to being extremely harmful to humans, causes corrosion of equipment, instruments, containers and pipes; cause poisoning of downstream catalysts; strong acid gas is formed after combustion and is discharged into the atmosphere, thereby seriously polluting the environment.

Common methods for removing hydrogen sulfide are mainly divided into wet desulfurization and dry desulfurization, and the two methods have the same advantages and disadvantages. The wet desulphurization is suitable for the working condition that the raw material handling capacity is large and the desulphurization amount is more than 1 ton/day. The wet desulphurization can be operated continuously, the cost is low, but the desulphurization process has large energy consumption, large equipment volume, large investment, long construction period, complex process and high requirement on the stability of material working conditions. The dry desulfurization is suitable for the working condition that the raw material treatment capacity is small and the desulfurization capacity is less than 1 ton/day. The dry desulfurization almost has no energy consumption, small equipment volume, less investment, short construction period, simple process and low requirement on the stability of material working conditions. Under the working condition of normal temperature, the dry desulfurization is carried out on active materials such as zinc oxide, copper oxide, active carbon loaded alkali, iron oxide and the like. The biggest problem of the traditional desulfurizer is that the desulfurization precision is not high, or the sulfur capacity (the capacity of removing hydrogen sulfide by the desulfurizer per unit mass) is low (about 5-15%).

Among the conventional desulfurization materials, the most widely used desulfurization material is iron oxide monohydrate, which belongs to the iron oxide group. Compared with other traditional desulfurizing materials, the desulfurizing agent prepared by the material has higher performance-price ratio. But also has the bottleneck problems of low sulfur capacity (about 10-15%), poor desulfurization precision and the like, and has low adaptability to the change of the working condition of the raw materials. The iron oxide type desulfurizing material also comprises other desulfurizing agents prepared by taking natural iron ore, iron ore slag, waste iron mud, sponge iron and the like as the desulfurizing material, and the desulfurizing effect is similar to that of a hydrated iron oxide desulfurizing agent. The desulfurization materials are more patented and the patent date is earlier. The material can not meet the requirement of modern energy purification on desulfurization precision when used for preparing the desulfurizer. In addition, the desulfurizer is frequently replaced, the comprehensive use cost is high, and the environmental protection problem of treating a large amount of waste agents is also prominent.

The iron oxyhydroxide is a high-quality material for preparing the high-performance desulfurizer, and has large sulfur capacity and high desulfurization precision. However, in the industrial production process, the problems of high production cost, high difficulty in sewage treatment and the like exist. Such as patents for preparing alpha-FeOOH, gamma-FeOOH, amorphous iron oxyhydroxide, and the like. The preparation process of the hydroxyl ferric oxide material with single crystal form has high control requirement, if the single crystal form with higher purity is required to be achieved, the preparation cost is high, and when the hydroxyl ferric oxide material is used for a desulfurization material, the cost advantage is low, and the cost performance is not high. Therefore, the single-crystal-form iron oxyhydroxide material is mostly used for preparing functional products and is used in specific fields. Amorphous iron oxyhydroxide materials are defined by published patents and literature as amorphous iron oxyhydroxides.

Iron oxyhydroxide materials with too small a crystal form, such as nano-sized crystals and amorphous iron oxyhydroxide materials, although providing relatively more sites of desulfurization activity, such as more lattice oxygen defects, more surface hydroxyls, etc., that are beneficial for desulfurization. However, relatively more ferric hydroxide colloids are easily generated in the material preparation process, and the colloids enter a filtrate system to become sewage, so that great difficulty is brought to sewage treatment, and the cost of sewage treatment is greatly increased.

When the hydroxyl ferric oxide with the overlarge crystal form is used for a desulfurization material, the active point positions are relatively few, and the desulfurization precision is influenced.

Disclosure of Invention

Technical problem to be solved

Based on the defects of the desulfurization material, the invention provides a preparation method of polycrystalline microcrystal FeOOH, which solves the problems of low desulfurization precision and low sulfur capacity of the traditional desulfurizer.

However, compared with the existing single crystal type material of the ferric hydroxide and amorphous ferric hydroxide material, the invention provides the preparation method of the polycrystalline microcrystalline ferric hydroxide, and solves the problems of cost control and environmental protection of sewage treatment in the production process of the high-performance ferric hydroxide.

alpha-FeOOH and gamma-FeOOH are high-performance desulfurization materials. Compared with gamma-FeOOH, the alpha-FeOOH phase has low desulfurization activity, but has high density and large desulfurization capacity; compared with alpha-FeOOH, the gamma-FeOOH has low density and low desulfurization capacity, but has high desulfurization activity, thereby having high desulfurization precision. Compared with the amorphous form, the microcrystal effectively avoids the problem of sewage treatment caused by the fact that ferric hydroxide colloid enters filtrate in the production process. Compared with large-size crystals, enough desulfurization active sites are still reserved. Therefore, the invention provides a preparation method of polycrystalline microcrystal iron oxyhydroxide, which effectively solves the balance relationship among sulfur capacity, desulfurization precision, production cost and environmental protection. The sulfur capacity of the desulfurizer prepared by the material can reach more than 40 percent in practical application.

(II) technical scheme

In order to achieve the purpose, the invention provides the following technical scheme: in order to solve the problems of the technology and the production cost, the invention provides a preparation method of polycrystalline microcrystal iron oxyhydroxide, which is characterized by comprising the following eight steps of:

mixing and stirring ferrous sulfate containing seven crystal waters and a solid alkaline substance;

controlling the pH value of the reaction mixture in the step (2) to be 8-9;

adding water in batches and stirring, and controlling the reaction temperature not to exceed 50 ℃;

step (4), introducing air into the slurry obtained in the step (2) for oxidation;

step (5), adding sodium hydroxide into the product obtained in the step (4), and adjusting the pH value to be about 8;

step (6) stirring and aging the product obtained in the step (5);

step (7), washing and filtering the obtained product in the step (6);

and (8) drying the product obtained in the step (7).

Preferably, in the step (1), the purity of the ferrous sulfate crystallized from heptahydrate is more than 95%, and the purity of other water-soluble ferrous salts is required to be more than 95%; the solid alkaline matter may be sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia water, etc.

Preferably, in the step (1), the mixing molar ratio of the ferrous salt to the sodium hydroxide, the sodium bicarbonate or the ammonia water is 1: 2-1: 3; the molar ratio of the ferrous salt to the sodium carbonate is 1: 1-1: 2.

Preferably, in the step (2), the pH value of the reactant system is controlled to be 8-9 by adjusting the ratio of the water-soluble ferrous salt to the solid alkali.

Preferably, in step (3), water is added in an amount of about 5 to 10% by weight of the reactants, and the mixture is added in portions and stirred.

Preferably, in step (3), the reaction mixture is stirred for about 10 to 15 minutes before the water is added to the reaction mixture, and is stirred for about 15 to 30 minutes after the water is added to the reaction mixture.

Preferably, in step (3), the reaction temperature is controlled not to exceed 50 ℃ by controlling the amount of water added.

Preferably, in the step (4), the slurry formed is stirred, and air is introduced for oxidation, wherein the large flow rate of air is about 5 to 10 minutes, and the small flow rate of air is about 10 to 30 minutes.

Preferably, in step (4), the low flow air rate is about one third of the high flow air rate.

Preferably, in step (4), air is introduced until the pH of the reaction product mixture is constant.

Preferably, in the step (5), after completion of the reaction, the pH of the product is 4 to 6. The pH of the product was adjusted to 8. + -. 0.5 by adding sodium hydroxide.

Preferably, in step (6), the aging time is about 2 hours.

Preferably, in step (7), the resulting mixture is washed with water to give a final product having a sodium sulfate or ammonium sulfate content of less than 3%.

Preferably, in the step (8), the product after water washing and filtration is dried at a drying temperature of 110 ± 5 ℃.

Preferably, the crystal forms of the prepared final products are mainly alpha-FeOOH and gamma-FeOOH, and the length of a microcrystal is about 3-5 mu m.

(III) advantageous effects

The invention provides a preparation method of polycrystalline microcrystal FeOOH, and compared with the traditional desulfurization material, the prepared desulfurizer has high sulfur capacity and high desulfurization precision.

The preparation method of the polycrystalline microcrystal FeOOH combines the advantages of two FeOOH crystals (alpha-FeOOH and gamma-FeOOH) in desulfurization, simplifies the production control process and effectively reduces the production cost.

In the existing preparation process of the hydroxyl ferric oxide, the ferric hydroxide colloid in the sewage is reduced by adjusting the proportion of the water-soluble ferrous salt and the solid alkali, so as to solve the problem of sewage treatment. However, this method is not reliable in practical industrial production. The invention provides a preparation method, which reduces the generation of ferric hydroxide colloid and greatly reduces the difficulty and cost of sewage treatment by controlling the reaction temperature, the pH value of a reaction system and the oxidation speed and degree while generating microcrystals with certain size. The desulfurization performance of the microcrystal is not reduced after the microcrystal is prepared into the desulfurizing agent.

Drawings

Figure 1 is a length SEM photograph of the microcrystals produced by the present invention.

FIG. 2 is an XRD spectrum of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to the drawings, example 1

In the specific implementation process, 156g of crystalline ferrous sulfate heptahydrate powder and 63g of sodium carbonate are stirred and mixed for 10 minutes. 11g of water were added in portions and stirred for a further 25 minutes. The reaction temperature was controlled to about 40 ℃. After the mixture is uniformly stirred, introducing large-flow air for 8 minutes, and then introducing small-flow air for 25 minutes until the pH value of the reaction system is unchanged, and finishing the oxidation. Then adding sodium hydroxide solution to adjust the pH value of the slurry product to 8 +/-0.5. Stirred and aged for 2 hours.

And (3) adding water into the obtained slurry for repeated washing, wherein the content of sodium sulfate in the final product is lower than 3%, and the washing is finished.

After washing and filtering, the filter cake is crushed and dried for 2 hours at 110 ℃. The polymorphic microcrystal iron oxyhydroxide of the invention can be prepared. The final product contained 95.6% iron oxyhydroxide, the balance water and sodium sulfate. The gamma-FeOOH content of the iron oxyhydroxide is about 73.8%, and the alpha-FeOOH content is about 26.2%.

Example 2

In a specific embodiment, 156g of crystalline ferrous sulfate heptahydrate powder is mixed with 56g of sodium hydroxide under stirring for 10 minutes. 11g of water were added in portions and stirred for a further 25 minutes. The reaction temperature was controlled to about 40 ℃. After the mixture is uniformly stirred, large-flow air is introduced for 5 minutes, and small-flow air is introduced for 20 minutes until the pH value of the reaction system is unchanged and the oxidation is finished. Then adding sodium hydroxide solution to adjust the pH value of the slurry product to 8 +/-0.5. Stirred and aged for 2 hours.

After washing and filtering, the filter cake is crushed and dried for 2 hours at 110 ℃. The polymorphic microcrystal iron oxyhydroxide of the invention can be prepared. The final product contained 96.3% iron oxyhydroxide, the balance being water and sodium sulfate. The gamma-FeOOH content of the iron oxyhydroxide is about 70.2%, and the alpha-FeOOH content is about 29.8%.

Example 3

In the specific implementation process, 200g of ammonia water (ammonia water concentration 25%) is gradually added into 156g of crystalline ferrous sulfate heptahydrate powder. Mix for 30 minutes with stirring. The reaction temperature was controlled to about 40 ℃. After the mixture is uniformly stirred, introducing large-flow air for 10 minutes, and then introducing small-flow air for 30 minutes until the pH value of the reaction system is unchanged, and oxidizing. Then adding sodium hydroxide solution or ammonia water to adjust the pH value of the slurry product to 8 +/-0.5. Stirred and aged for 2 hours.

And (3) adding water into the obtained slurry for repeated washing, wherein the content of ammonium sulfate in the final product is lower than 3%, and the washing is finished.

After washing and filtering, the filter cake is crushed and dried for 2 hours at 110 ℃. The polymorphic microcrystal iron oxyhydroxide of the invention can be prepared. The final product contained 97.7% iron oxyhydroxide, the balance water and ammonium sulfate. The iron oxyhydroxide had gamma-FeOOH of about 78.2% and alpha-FeOOH of about 21.8%.

30g of the polymorphic microcrystal FeOOH powder obtained in the 3 examples is respectively taken, 0.6g of CMC is added, 10g of water is added, the mixture is uniformly stirred, and the desulfurizer is prepared by extruding strips. Nitrogen is used as carrier gas, gas with 1 percent of hydrogen sulfide concentration is prepared as raw material gas, and the sulfur capacity is respectively measured as follows:

example numbering	Example 1	Example 2	Example 3
				Sulfur capacity%	44.3	46.5	42.8

In the specific implementation process, as shown in fig. 1, a length SEM photograph of the microcrystal prepared by the present invention shows that the microcrystal has a needle-like crystal form and a length of about 3 to 5 μm. FIG. 2 is an XRD spectrum of the present invention, in which diffraction peaks of two kinds of crystals can be seen.

The crystal forms of the prepared final products are mainly alpha-FeOOH and gamma-FeOOH, and the length of a microcrystal is about 3-5 mu m.

It is to be noted that the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims

1. The preparation method of the polycrystalline microcrystalline iron oxide hydroxide is characterized by comprising the following eight steps of:

mixing and stirring ferrous sulfate containing seven crystal waters and a solid alkaline substance; the ratio of the ferrous salt to the solid alkaline matter is 1: 1-1: 3;

controlling the PH value of a reaction mixture system to be 8-9 by adjusting the proportion of water-soluble ferrous salt and solid alkaline matter;

introducing air into the slurry formed by stirring in the step (2) for oxidation, wherein the large-flow air introduction time is about 5-10 minutes, and the small-flow air introduction time is about 10-30 minutes; the low flow air velocity is about one third of the high flow air velocity; the air is introduced until the pH value of the reaction product mixture is unchanged;

step (6) stirring and aging the product obtained in the step (5);

step (7), washing and filtering the obtained product in the step (6);

step (8) drying the substance obtained in step (7);

2. The method for preparing polymorphic microcrystalline iron oxyhydroxide according to claim 1, wherein in step (1), the purity of the iron sulfate of heptahydrate crystal is above 95%, and the purity of other water-soluble ferrous salts is above 95%; the solid alkaline matter can be sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonia water and the like;

the mixing molar ratio of the ferrous salt to sodium hydroxide, sodium bicarbonate or ammonia water is 1: 2-1: 3; the molar ratio of the ferrous salt to the sodium carbonate is 1: 1-1: 2.

3. The method according to claim 1, wherein in step (3), water is added in an amount of about 5 to 10% by weight of the reactants, and the mixture is stirred; stirring the reactants for about 10-15 minutes before adding water, and stirring for about 15-30 minutes after adding water; the reaction temperature is controlled not to exceed 50 ℃ by controlling the amount of added water.

4. The method according to claim 1, wherein in the step (5), after the reaction is completed, the pH of the product is 4-6; the pH of the product was adjusted to 8. + -. 0.5 by adding sodium hydroxide.

5. The method of claim 1, wherein in step (6), the aging time is about 2 hours.

6. The method of claim 1, wherein in step (7), the resulting mixture is washed with water to obtain a final product having a sodium or ammonium sulfate content of less than 3%.

7. The method of claim 1, wherein the filtered product is dried at a temperature of 110 ± 5 ℃ in step (8).