阅读说明：本技术 一种具有多孔结构的花状铁掺杂二氧化铈的制备及其脱硫应用 (Preparation of flower-like iron-doped cerium dioxide with porous structure and desulfurization application of flower-like iron-doped cerium dioxide ) 是由 江莉龙 郑小海 沈丽娟 曹彦宁 郑笑笑 于 2019-11-22 设计创作，主要内容包括：本发明公开了一种具有多孔结构的花状铁掺杂二氧化铈的制备方法,属于催化剂制备技术领域。该方法以铈盐、铁盐和氨水溶液为原料,添加聚乙烯吡咯烷酮、柠檬酸和不同的扩孔剂,合成具有多孔结构的花状铁掺杂二氧化铈。该催化剂具有多孔结构,相比模板法工艺更加简单,可重复性强。铁离子的掺杂会引起二氧化铈晶格扭曲,使材料晶格内出现更多的晶格缺陷和氧空位,进一步增加储氧能力和氧化还原能力。并且铁与铈离子的电子转移会抑制副产物SO<Sub>2</Sub>被氧化成SO<Sub>3</Sub>,从而减少硫酸铈的生成。另外,多孔结构暴露丰富的活性位点,有效地促进了反应的进行,使催化剂在选择性催化氧化H<Sub>2</Sub>S反应中表现出更高的催化活性、硫单质选择性和稳定性。(The invention discloses a preparation method of flower-like iron-doped cerium dioxide with a porous structure, and belongs to the technical field of catalyst preparation. The method takes cerium salt, ferric salt and ammonia water solution as raw materials, and adds polyvinylpyrrolidone, citric acid and different pore-expanding agents to synthesize the flower-shaped iron-doped cerium dioxide with a porous structure. The catalyst has a porous structure, and compared with a template method, the catalyst has the advantages of simpler process and strong repeatability. The doping of iron ions can cause the crystal lattice of cerium dioxide to be distorted, so that more crystal lattice defects and oxygen vacancies appear in the crystal lattice of the material, and further increase the storage capacityOxygen capacity and redox capacity. And the electron transfer of iron and cerium ions can inhibit the by-product SO 2 Is oxidized into SO 3 Thereby reducing the formation of cerium sulfate. In addition, the porous structure exposes abundant active sites, effectively promotes the reaction, and enables the catalyst to selectively catalyze and oxidize H 2 The S reaction has higher catalytic activity, sulfur simple substance selectivity and stability.)

1. A preparation method of flower-like iron-doped cerium dioxide with a porous structure is characterized by comprising the following steps: the method comprises the following steps:

(1) weighing 12 mmol of cerium salt and 0.48-1.44 mmol of iron salt, and respectively dissolving in a certain amount of distilled water;

(2) adding a certain amount of pore-expanding agent, citric acid and surfactant polyvinylpyrrolidone (PVP) into the salt solution, dissolving, then dropwise adding 10 wt% ammonia water solution, and stirring for a period of time at room temperature;

(3) transferring the solution obtained in the step (2) to a 100 mL high-pressure reaction kettle for hydrothermal treatment, naturally cooling at room temperature, filtering the precipitate, washing, and drying in an oven;

(4) roasting at 500 ℃ to obtain the final product, namely flower-like iron-doped cerium dioxide with a porous structure.

2. The method for preparing flower-like iron-doped ceria having a porous structure according to claim 1, wherein: in the step (1), the cerium salt is cerium chloride or cerium nitrate, and the iron salt is ferric chloride or ferric nitrate.

3. The method for preparing flower-like iron-doped ceria having a porous structure according to claim 1, wherein: the amount of the distilled water used in the step (1) is 10-30 mL.

4. The method for preparing flower-like iron-doped ceria having a porous structure according to claim 1, wherein: in the step (2), the pore-expanding agent is urea or ammonium bicarbonate; the dosage of the compound is 0.2-0.5 g; the dosage of the polyvinyl pyrrolidone is 20 mmol, the dosage of the citric acid is 0.2-0.5 g, and the stirring time at room temperature is 10-30 minutes.

5. The method for preparing flower-like iron-doped ceria having a porous structure according to claim 1, wherein: and (3) carrying out hydrothermal treatment in a 100 mL high-pressure reaction kettle at 120-150 ℃ for 24 h.

6. The method for preparing flower-like iron-doped ceria having a porous structure according to claim 1, wherein: and (3) washing by using distilled water and absolute ethyl alcohol, and drying at the temperature of 80-110 ℃ for 12 hours.

7. The method for preparing flower-like iron-doped ceria having a porous structure according to claim 1, wherein: the roasting in the step (3) is carried out for 2-4 h at 500 ℃, and the roasting temperature rise rate is 2-5 ℃/min.

8. Use of flower-like iron-doped ceria with a porous structure prepared by the preparation method according to any one of claims 1 to 7, characterized in that: for selective catalytic oxidation of H₂S。

9. Use of flower-like iron-doped ceria with porous structure according to claim 8, characterized by: for selectingSelective catalytic oxidation of H₂S, the reaction temperature is 100-250 ℃.

10. Use of flower-like iron-doped ceria with porous structure according to claim 8, characterized by: the raw material gas comprises the following components in sequence: 2500 ppm O₂And 5000 ppm H₂S，N₂Is balance gas; the flow rate of the raw material gas is 40 mL.min^-1The reaction space velocity is 12000 mL^-1•h^-1。

Technical Field

The invention relates to the field of preparation technology and application of an environmental catalyst, in particular to a preparation method of flower-like iron-doped cerium dioxide with a porous structure and application of the flower-like iron-doped cerium dioxide in H oxidation₂And (5) application in the aspect of S.

Background

Associated H in production processes of natural gas exploitation, petroleum processing and the like₂S and other sulfur-containing gases not only corrode production equipment and poison catalysts, but also severely pollute the environment. Current treatment H₂The most common technique for S is the Claus process, which recovers elemental sulfur (2H) from a sulfur-containing gas₂S + SO₂⇆ 3S + 2H₂O). However, due to thermodynamic limitations of the Claus equilibrium reaction, about 4% of H is still present in the vented tail gas₂And S. In order to completely remove residual H₂S, people developed H₂S is selectively oxidized into elemental sulfur. The reaction formula is shown as follows:

selective catalytic oxidation removal of H₂S, having a reaction not limited by thermodynamic equilibrium, can convert H₂S is completely converted and elemental sulfur is recycled, the unique advantage of sulfur resource utilization is realized, and the reaction process is simple and the process is advanced, so that the method is one of the desulfurization technologies with the most application prospect. The key to this technology is the development of efficient selective oxidation catalysts.

TiO₂、Cr₂O₃、V₂O₅The metal oxides are widely used in H as common catalysts or catalyst carriers₂S in the selective oxidation reaction. However, they still have deficiencies that limit the further development of these catalytic materials. For example, TiO₂The catalyst is easy to deactivate in the presence of water, and Cr₂O₃And V₂O₅The toxicity of the product is high.

CeO₂As a good oxygen storage material, due to rich oxygen vacancy, controllable surface acidity and alkalinity and Ce³⁺And Ce⁴⁺The redox ability in between is widely used. The material is in H₂The selective oxidation of S has been studied initially, but the reported results in the literature show that CeO₂Selective oxidation of materials by H₂S is less stable, probably because of the use of CeO₂At H₂Stable sulfate is easily generated in the oxidation reaction of S, and the generated sulfate covers active centers to reduce the number of active sites, so that the long-term reaction cannot be satisfied. The doping of iron ions can cause the distortion of cerium dioxide crystal lattices, so that more crystal lattice defects and oxygen vacancies appear in the material crystal lattices, the oxygen storage capacity and the oxidation reduction capacity are further increased, and the catalytic activity is further improved. And the electron transfer of iron ions and cerium ions can inhibit the by-product SO₂Is oxidized into SO₃Thereby reducing the generation of cerium sulfate and improving the activity stability of the material. Therefore, the preparation of the flower-like iron-doped cerium dioxide material with the porous structure is expected to improve the number of oxygen vacancies of the material and the sufficient exposure of active sites by regulation, so that the H can be efficiently and selectively oxidized with high selectivity₂S is elemental sulfur and has good stability.

Disclosure of Invention

The invention aims to provide a preparation method and application of flower-like iron-doped cerium dioxide with a porous structure aiming at the defects of the prior art, and solves the problem of H in the prior art₂Poor S selective oxidation catalyst activity, poor selectivity, poor stability and the like. Flower-shaped iron-doped cerium dioxide with porous structure makes full use of lattice distortion and iron separation of cerium oxide caused by doping of ironThe valence state of the ions and the cerium ions are balanced, the oxygen vacancy of the cerium material is improved, the oxygen storage capacity and the oxidation reduction capacity are further increased, and H is selectively catalyzed and oxidized₂The S aspect has higher catalytic activity and stability.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a preparation method of flower-like iron-doped cerium dioxide with a porous structure comprises the following steps:

(1) weighing 12 mmol of cerium salt and 0.48-1.44 mmol of iron salt, and respectively dissolving in a certain amount of distilled water;

(2) adding a certain amount of pore-expanding agent, citric acid and surfactant polyvinylpyrrolidone (PVP) into the salt solution, dropwise adding 10 wt% ammonia water solution after dissolving, and stirring for a period of time at room temperature;

(3) then transferring the solution obtained in the step (2) to a 100 mL high-pressure reaction kettle, performing hydrothermal treatment at 120-150 ℃ for 24 hours, naturally cooling at room temperature, filtering the precipitate, washing and drying;

(4) roasting at 500 ℃ to obtain the final product, namely flower-like iron-doped cerium dioxide with a porous structure.

Preferably, in the step (1), the cerium salt is cerium chloride or cerium nitrate, the iron salt is ferric nitrate or ferric chloride, the amounts of distilled water in the solutions of iron and cerium are respectively 10mL and 30 mL, and the molar ratio of iron to cerium is 0-0.12.

Preferably, the pore-expanding agent in the step (2) is urea or ammonium bicarbonate; the dosage of the citric acid, the pore-expanding agent and the PVP is 0.5g, 0.1-0.3 g and 10-30 mmol respectively; the amount of the aqueous ammonia solution was 10 mL.

Preferably, the stirring time of the step (2) is 10-30 minutes.

Preferably, the washing in the step (3) is exchange washing with distilled water and anhydrous ethanol. And the drying is carried out for 12 hours at the temperature of 80-110 ℃.

Preferably, the temperature rise rate of the roasting treatment in the step (4) is 2-5 ℃/min, and the roasting time is 2-4 h.

Preferably, the particle size of the screened flower-like iron-doped cerium dioxide with a porous structure in the final product is 20-40 meshes.

The application of the preparation method for preparing flower-shaped iron-doped cerium dioxide with a porous structure comprises the following steps: for selective catalytic oxidation of H₂S。

Preferably, the selective catalytic oxidation of H₂In the feed gas for S reaction, H₂S concentration of O ₂2 times the concentration.

Preferably, the reaction temperature range for the selective catalytic oxidation is 100-250 ℃.

Preferably, the flower-like iron-doped ceria with a porous structure has a loading of 0.2 g; h₂The concentration of S is 5000 ppm, O₂Has a concentration of 2500 ppm, N₂Is balance gas; the space velocity of the raw material gas is 12000 mL.g^-1•h^-1(ii) a The flow rate of the raw material gas is 35 mL.min^-1。

The invention has the following advantages and beneficial effects:

1. the flower-like iron-doped cerium dioxide with the porous structure prepared by the method has strong pore diameter adjustability, rich pore structures are more beneficial to the dispersion of active components, and the raw materials are low in price, simple in preparation process, easy to realize industrial production and wide in application prospect;

2. the flower-like iron-doped cerium dioxide with the porous structure synthesized by the method has the flower-like morphology characteristic, and the specific surface area is 60-90 m²In the selective catalytic oxidation of H₂The S aspect has good activity and selectivity;

3. compared with undoped cerium dioxide, the flower-like iron-doped cerium dioxide with the porous structure prepared by the invention has more excellent sulfation resistance and stability.

Drawings

FIG. 1 is an X-ray powder diffraction pattern of cerium oxides prepared in examples 1 to 3 of the present invention and comparative example 1;

FIG. 2 is a graph showing N of ceric oxides prepared in examples 1 to 3 of the present invention and comparative example 1₂Physical adsorption and desorption curves and aperture distribution maps;

FIG. 3 is a scanning electron micrograph (A) and a transmission electron micrograph (B) of cerium oxide prepared according to example 2 of the present invention;

FIG. 4 shows the cerium oxide in H prepared in examples 1 to 3 of the present invention and comparative example 1₂H in S selective catalytic oxidation₂S conversion rate curve diagram;

FIG. 5 shows the cerium oxide in H prepared in examples 1 to 3 of the present invention and comparative example 1₂S selective catalytic oxidation reaction sulfur selectivity curve diagram;

FIG. 6 shows the cerium oxide in H prepared in examples 1 to 3 of the present invention and comparative example 1₂S is a yield curve diagram of sulfur simple substance in selective catalytic oxidation reaction;

FIG. 7 shows ceric oxide prepared in example 2 of the present invention, comparative example 1 and comparative example commercial Fe₂O₃At 220 ℃ H₂Stability profile during S selective catalytic oxidation reaction.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in detail below with reference to the embodiments and the accompanying drawings, which are used for further description of the present invention and are not intended to limit the present invention.