Method for removing carbonyl iron in synthesis gas

Abstract

The invention discloses a method for removing carbonyl iron in synthesis gas, and belongs to the field of gas purification. The method comprises the following steps: enabling synthesis gas containing carbonyl iron to pass through a purifying agent bed layer, and reacting to obtain purified synthesis gas, the purifying agent bed layer is filled with an adsorbent I, a purifying agent and an adsorbent II in a combined manner; the purifying agent comprises a Y-type molecular sieve. After three-stage treatment of the adsorbent, the purifying agent and the adsorbent, the concentration of the carbonyl iron can be less than 0.01 ppm, and the decomposed carbonyl iron has no influence on subsequent working conditions and the catalyst. By adopting the purifying agent and the method disclosed by the invention, carbonyl iron in the synthesis gas can be effectively removed, and the service life of the catalyst can be prolonged.

Description

Technical Field

[0001] This application relates to a method for removing carbonyl iron from syngas, which belongs to the field of gas purification. Background Technology

[0002] Syngas, as a core raw material in industrial fields such as methanol synthesis and ammonia synthesis, directly determines the quality of downstream products and production efficiency. It is a crucial material supporting the stable operation of modern chemical industries and occupies an irreplaceable position in energy conversion and chemical production systems. However, syngas is prone to containing carbonyl iron impurities, mainly originating from the corrosion reaction between CO in the feedstock gas and equipment pipelines, as well as the combination reaction of CO with iron and nickel elements in the feedstock during gasification. This substance exists in gaseous form and is relatively stable under normal operating conditions. It can not only poison catalysts in downstream synthesis reactions, significantly shortening catalyst lifespan, but also potentially trigger side reactions that affect product purity, becoming a key issue restricting the efficient utilization of syngas. Currently, commonly used carbonyl iron removal methods in the industry, such as traditional physical adsorption and simple catalytic removal, generally have limitations such as limited adsorption capacity, insufficient purification precision (difficult to reduce the carbonyl iron concentration to below 0.01 ppm), easy generation of secondary pollution, or poor adaptability to operating conditions. They can no longer meet the current demand for high-purity syngas production. Developing a new carbonyl iron removal technology that is efficient, stable, and adaptable to industrial operating conditions has become an urgent industry problem to be solved. Summary of the Invention

[0003] Against this backdrop, this patent aims to provide a novel method for removing iron carbonyl from syngas, overcoming the shortcomings of existing technologies. Specifically, the core objective of this method is to achieve highly efficient removal of iron carbonyl from syngas. By passing syngas containing iron carbonyl through a purifying agent bed with a specific packing method, it is allowed to react fully under suitable reaction conditions, thereby obtaining purified syngas and ensuring that the concentration of iron carbonyl in the gas is less than 0.01 ppm (mol). Achieving this objective will effectively reduce the harmful effects of iron carbonyl on subsequent processes, providing a solid guarantee for the safe and efficient use of syngas. According to one aspect of this application, a method for removing carbonyl iron from syngas is provided.

[0004] A method for removing iron carbonyl from syngas, the method comprising: passing syngas containing iron carbonyl through a bed of purifying agents, reacting, and obtaining purified syngas; The purifying agent bed is filled with a combination of adsorbent I, purifying agent, and adsorbent II. The purifying agent includes a Y-type molecular sieve.

[0005] Optionally, the SiO2 / Al2O3 ratio of the Y-type molecular sieve is 5~30 in mol.

[0006] Preferably, the SiO2 / Al2O3 ratio of the Y-type molecular sieve is 5~20 in mol.

[0007] Optionally, the SiO2 / Al2O3 ratio of the Y-type molecular sieve, expressed in mol, is any value from 5, 6, 8, 10, 12, 14, 15, 16, 18, 20, 22, 24, 25, 26, 28, 30 or a range between any two.

[0008] Optionally, the NaO content of the Y-type molecular sieve is 0.4-7% by mass percentage.

[0009] Optionally, the NaO content of the Y-type molecular sieve is 0.5-6% by mass percentage.

[0010] Preferably, the NaO content of the Y-type molecular sieve is 1-4% by mass percentage.

[0011] Optionally, the NaO content of the Y-type molecular sieve, by mass percentage, is any value or a range between any two of 0.4%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, and 7%.

[0012] Optionally, the purifying agent is obtained by mixing Y-type molecular sieve, alumina and nitric acid, molding, and calcining.

[0013] In this application, Y-type molecular sieves are prepared into shaped samples for use as purifying agents. This can be achieved using conventional methods found in the prior art, such as mixing and molding Y-type molecular sieves, alumina, and 10% nitric acid in a mass ratio of 2.4:1:1.05, and then calcining the shaped sample in a muffle furnace at 550°C for 4 hours to obtain the purifying agent. The Y-type molecular sieves can be commercially available or synthesized using conventional methods.

[0014] In this application, existing technologies typically use Y-type molecular sieves as adsorbents and catalysts. 3A and 5A molecular sieves are commonly used as purifying agents for removing iron carbonyl from syngas. This application, however, uses Y-type molecular sieves as the purifying agent. Experiments have shown that after three stages of treatment—adsorbent, purifying agent (Y-type molecular sieve), and adsorbent again—the concentration of iron carbonyl is less than 0.01 ppm, and the decomposed iron carbonyl does not affect subsequent operating conditions or the catalyst. The purifying agent and method of this invention can effectively remove iron carbonyl from the syngas and extend the catalyst's lifespan.

[0015] Optionally, the adsorbent I and adsorbent II are independently at least one of activated carbon, diatomaceous earth, molecular sieve, and activated alumina.

[0016] Optionally, the mass ratio of adsorbent I, purifying agent, and adsorbent II is (0.05:1:0.05) to (0.4:1:0.4).

[0017] Preferably, the mass ratio of adsorbent I, purifying agent, and adsorbent II is (0.1:1:0.1) to (0.3:1:0.3).

[0018] In this application, the types of adsorbent I and adsorbent II can be the same or different, and the amounts used can be the same or different.

[0019] Optionally, the concentration of iron carbonyl in the synthesis gas containing iron carbonyl is 5 to 800 ppm in molar terms.

[0020] Optionally, the concentration of iron carbonyl in the synthesis gas containing iron carbonyl is 5 to 500 ppm in moles.

[0021] Optionally, the synthesis gas containing carbonyl iron includes dimethyl ether, CO, N2, and H2.

[0022] Optionally, the reaction conditions include: a reaction temperature of 20~260℃, a reaction pressure of 0~7MPa, and a reaction space velocity of 100~10000h. -1 .

[0023] Preferably, the reaction conditions include: a reaction temperature of 20~240℃; a reaction pressure of 0~5MPa; and a reaction space velocity of 1000~9000 h⁻¹. -1 .

[0024] Optionally, the reaction temperature is any value or a range between any two of 20℃, 40℃, 50℃, 60℃, 80℃, 100℃, 120℃, 140℃, 150℃, 160℃, 180℃, 200℃, 220℃, 240℃, 250℃, and 260℃.

[0025] Optionally, the reaction pressure is any value or a range between any two of 0 MPa, 0.5 MPa, 1 MPa, 1.5 MPa, 2 MPa, 2.5 MPa, 3 MPa, 3.5 MPa, 4 MPa, 4.5 MPa, 5 MPa, 5.5 MPa, 6 MPa, 6.5 MPa, and 7 MPa.

[0026] Optionally, the airspeed is 100 h. -1 200h -1 500h -1 800h-1 1000h -1 2000h -1 3000h -1 4000h -1 5000h -1 6000h -1 7000h -1 8000h -1 9000h -1 10000h -1 Any value in the range or any value between the two.

[0027] Optionally, the concentration of iron carbonyl in the purified syngas is less than 0.01 ppm on a molar basis. Furthermore, the decomposed iron carbonyl does not affect subsequent operating conditions or the catalyst.

[0028] This patent employs a unique purifying agent bed packing method. It uses a combination of Adsorbent I, Purifying Agent, and Adsorbent II, with the Purifying Agent containing a Y-type molecular sieve with specific parameters. This combination fully leverages the advantages of each component, forming a highly efficient removal system through three-stage treatment. Adsorbent I initially captures and adsorbs iron carbonyl molecules, laying the foundation for subsequent deep removal. The Y-type molecular sieve in the Purifying Agent plays a crucial role in the intermediate stage, reacting specifically with iron carbonyl through its unique structure and chemical properties, decomposing and fixing it, thereby achieving effective removal of iron carbonyl. Adsorbent II ensures that even after excessive use of the Purifying Agent, the decomposed iron carbonyl will not be carried over to subsequent processes. This synergistic effect significantly improves removal efficiency, ensuring that the concentration of iron carbonyl in the purified syngas meets stringent industrial requirements.

[0029] The beneficial effects that this application can produce include: The method for removing iron carbonyl from syngas provided in this application initially produces iron carbonyl in the syngas at a concentration of 5-800 ppm (mol). After three-stage treatment involving an adsorbent, a purifying agent, and another adsorbent, the iron carbonyl concentration can be reduced to less than 0.01 ppm. Furthermore, the decomposed iron carbonyl does not affect subsequent operating conditions or the catalyst. Using the purifying agent and method of this invention, iron carbonyl can be effectively removed from the syngas and the catalyst's lifespan can be extended. Detailed Implementation

[0030] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0031] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0032] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0033] In the examples, the concentration of 10% nitric acid is 10 mol / L.

[0034] The concentration of carbonyl metal compounds in the feed gas was determined by gas chromatography with an electron capture detector (GC-ECD). Quantitative detection of the carbonyl iron content in the synthesis gas was performed using gas chromatography, with specific operating conditions as disclosed in CN119881120A.

[0035] The preparation of the purifying agents in Examples 1-7 and the properties of the raw materials for molecular sieve synthesis are detailed in Table 1.

[0036] Table 1 Properties of Synthetic Raw Materials

[0037] Example 1 1. Preparation of purifying agent Step 1: Weigh a certain amount of sodium aluminate and sodium hydroxide, add a certain amount of deionized water, stir until completely dissolved, let stand for 10 minutes to remove air bubbles, and obtain solution A; then weigh a certain amount of sodium silicate, add a certain amount of deionized water, stir until the solution is transparent, and obtain solution B.

[0038] Step 2: Slowly add solution B dropwise to solution A (dropping rate 2-3 drops / second) while vigorously stirring with a magnetic stirrer (400 rpm) to avoid excessive local silicon concentration leading to amorphous precipitation. After the addition is complete, continue stirring for 60 minutes to form a homogeneous white gel. Control the pH of the system to approximately 13-14. If the pH is too low, add a small amount of NaOH solution to adjust it.

[0039] Step 3: Transfer the gel to a 100 mL PTFE-lined autoclave, filling it to 75%, and seal the autoclave. Stir the autoclave at 80 rpm to promote system homogeneity and reduce crystal agglomeration. Then, first raise the temperature to 80°C at a rate of 2°C / min and hold for 2 hours (pre-crystallization to induce crystal nucleation); then raise the temperature to 100–125°C at a rate of 1°C / min and hold for 14–36 hours.

[0040] Step 4: After crystallization, turn off the heating and place the autoclave in a cold water bath to rapidly cool to room temperature. Open the autoclave and filter the reaction mixture using a Buchner funnel. Wash the filter cake repeatedly with 80°C deionized water (approximately 50 mL each time, for a total of 5-6 washes) until the pH of the filtrate drops to 8-9. Transfer the filter cake to an oven and dry it at 110°C for 7 hours, then transfer it to a muffle furnace and calcine it at 550°C for 4 hours to obtain activated Y-type molecular sieve powder.

[0041] Step 5: Mix Y-type molecular sieve powder, alumina and 10% nitric acid at a mass ratio of 2.4:1:1.05, knead and shape the mixture, and place the shaped sample in a muffle furnace and calcine at 550℃ for 4 hours to obtain purifying agent J.

[0042] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed, with 1 g of purifying agent J used. The activated carbon H and purifying agent J were loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 800 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, H2 10 vol%). The reaction conditions were set as follows: temperature 20℃, pressure 5.0 MPa, and space velocity 2000 h⁻¹. -1 After the syngas passed through the purifying agent bed, the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. Simultaneously, the performance of the carbonylation catalyst in subsequent processes was tested. The test results and the loading ratios of activated carbon and purifying agent are shown in Table 2.

[0043] Example 2 1. Preparation of purifying agent The preparation process of the purifying agent is the same as in Example 1.

[0044] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed and loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 400 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, and H2 10 vol%). The reaction conditions were set as follows: temperature 120℃, pressure 4.5 MPa, and space velocity 7000 h⁻¹. -1 After the syngas passed through the purifying agent bed, the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. Simultaneously, the performance of the carbonylation catalyst in subsequent processes was tested. The test results and the loading ratios of activated carbon and purifying agent are shown in Table 2.

[0045] Example 3 1. Preparation of purifying agent The preparation process of the purifying agent is the same as in Example 1.

[0046] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed and loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 100 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, and H2 10 vol%). The reaction conditions were set as follows: temperature 180℃, pressure 2.0 MPa, and space velocity 9000 h⁻¹. -1 After the syngas passed through the purifying agent bed, the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. Simultaneously, the performance of the carbonylation catalyst in subsequent processes was tested. The test results and the loading ratios of activated carbon and purifying agent are shown in Table 2.

[0047] Example 4 1. Preparation of purifying agent The preparation process of the purifying agent is the same as in Example 1.

[0048] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed and loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 300 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, H2 10 vol%). The reaction conditions were set as follows: temperature 220℃, pressure 0 MPa (atmospheric pressure), and space velocity 5000 h⁻¹. -1 After the syngas passed through the purifying agent bed, the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. Simultaneously, the performance of the carbonylation catalyst in subsequent processes was tested. The test results and the loading ratios of activated carbon and purifying agent are shown in Table 2.

[0049] Example 5 1. Preparation of purifying agent The preparation process of the purifying agent is the same as in Example 1.

[0050] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed and loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 500 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, and H2 10 vol%). The reaction conditions were set as follows: temperature 240℃, pressure 4.0 MPa, and space velocity 8000 h⁻¹. -1 After the syngas passed through the purifying agent bed, the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. Simultaneously, the performance of the carbonylation catalyst in subsequent processes was tested. The test results and the loading ratios of activated carbon and purifying agent are shown in Table 2.

[0051] Example 6 1. Preparation of purifying agent The preparation process of the purifying agent is the same as in Example 1.

[0052] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed and loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 400 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, and H2 10 vol%). The reaction conditions were set as follows: temperature 190℃, pressure 4.5 MPa, and space velocity 7000 h⁻¹. -1 After the syngas passed through the purifying agent bed, the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. Simultaneously, the performance of the carbonylation catalyst in subsequent processes was tested. The test results and the loading ratios of activated carbon and purifying agent are shown in Table 2.

[0053] Example 7 1. Preparation of purifying agent The preparation process of the purifying agent is the same as in Example 1.

[0054] 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. A certain amount of activated carbon H and purifying agent J were weighed and loaded into a reaction tube (10 mm inner diameter) in the order H→J→H. Syngas with a carbonyl iron concentration of 450 ppm was prepared (the remaining components were dimethyl ether 10 vol%, CO 70 vol%, N2 10 vol%, H2 10 vol%). The reaction conditions were set as follows: temperature 180℃, pressure 4.5 MPa, and space velocity 8500 h⁻¹. -1 After the syngas passes through the purifier bed, the concentration of iron carbonyl in the outlet gas is detected by GC-ECD. At the same time, the performance of the carbonylation catalyst in the subsequent process is tested.

[0055] Example 8 The preparation of the purifying agents in Examples 1-7, and the detailed process of the analytical sieve synthesis are shown in Table 2.

[0056] The application of purifying agents and adsorbents in Examples 1-7, the loading quality of activated carbon and purifying agents, and the analysis and testing results after purification are detailed in Table 3.

[0057] Table 2. Molar ratio of synthetic raw materials, crystallization temperature, crystallization time, and SiO2 / Al2O3 and NaO content of the products.

[0058] Table 3. Packing mass of activated carbon H and purifying agent J, and analysis results after purification.

[0059] Comparative Example 1 1. Preparation of purifying agent The purifying agent is derived from existing industrial copper-based purifying agents. It is black in appearance, 3×5mm in size, and has a sheet-like structure. 2. The effect of the purifying agent A fixed-bed reactor was used. 1.4 g of 20-40 mesh copper-based purifying agent was weighed and filled into a reaction tube (10 mm inner diameter). The remaining experimental conditions were the same as in Example 7. Without H2 reduction, the synthesis gas passed through the purifying agent bed, and the concentration of iron carbonyl in the outlet gas was detected by GC-ECD. The result showed an iron carbonyl concentration of 263.25 ppm, far below the purification effect. The copper-based purifying agent was refilled and reduced under 80 vol% N2 and 20 vol% H2 conditions. The reduced purifying agent was evaluated according to the conditions of Example 7. The result showed an iron carbonyl concentration of 3.48 ppm in the outlet gas, again failing to achieve the effect of the present invention.

[0060] Industrial copper-based purifiers require reduction treatment under H2 conditions before use, which, compared to this invention, not only increases the process flow but also makes the removal of high-concentration carbonyl iron less effective.

[0061] Comparative Example 2 1. Preparation of purifying agent The purifying agent is derived from existing industrial 3A molecular sieves, which are gray in appearance and have a spherical structure of 3×3mm in size. 2. Application effects of purifying agents and adsorbents A fixed-bed reactor was used. 1.4g of 20-40 mesh 3A molecular sieve was weighed and filled into the reaction tube (inner diameter 10mm). The remaining experimental conditions were the same as in Example 7. After the synthesis gas passed through the purification agent bed, the carbonyl iron concentration in the outlet gas was detected by GC-ECD. The detection results showed that the carbonyl iron concentration was 196.33ppm, which was far from achieving the purification effect.

[0062] Industrially available 3A molecular sieves are mainly composed of elements such as potassium, sodium, aluminum, silicon, and oxygen. Although they can be used as desiccants and adsorbents, their pore size is relatively small, typically in the range of 0.3~0.5 nm, resulting in poor purification effects and a weak ability to remove carbonyl iron.

[0063] Comparative Example 3 The operation was the same as in Example 7, except that purifying agent J was not used, and only activated carbon H (1.4g) was used. The performance was evaluated according to the conditions of Example 7. The test results showed that the carbonyl iron concentration in the outlet gas was 310.94ppm, indicating that a good purification effect could not be achieved without using purifying agent J.

[0064] Comparative Example 4 The operation was the same as in Example 7, except that the purifier J was replaced with the reduced industrial copper-based purifier from Comparative Example 1. 0.15g of activated carbon H, 1g of the reduced industrial copper-based purifier, and 0.15g of activated carbon H were used. The performance was evaluated under the same conditions as in Example 7. The test results showed that the carbonyl iron concentration in the outlet gas was 35.78ppm, indicating that under the same conditions, the effect of using the reduced industrial copper-based purifier was far inferior to that of the purifier J of this application.

[0065] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for removing carbonyl iron from syngas, characterized in that, The method includes: passing syngas containing iron carbonyl through a bed of purifying agents, reacting, and obtaining purified syngas; The purifying agent bed is filled with a combination of adsorbent I, purifying agent, and adsorbent II. The purifying agent includes a Y-type molecular sieve.

2. The method according to claim 1, characterized in that, The SiO2 / Al2O3 ratio of the Y-type molecular sieve is 5~30 in mol. Preferably, the SiO2 / Al2O3 ratio of the Y-type molecular sieve is 5~20 in mol.

3. The method according to claim 1, characterized in that, The NaO content of the Y-type molecular sieve is 0.4-7% by mass. Preferably, the NaO content of the Y-type molecular sieve is 0.5-6% by mass percentage.

4. The method according to claim 1, characterized in that, The purifying agent is obtained by mixing Y-type molecular sieve, alumina and nitric acid, molding, and calcining.

5. The method according to claim 1, characterized in that, The adsorbent I and adsorbent II are independently at least one of activated carbon, diatomaceous earth, molecular sieve, and activated alumina.

6. The method according to claim 1, characterized in that, The mass ratio of adsorbent I, purifying agent, and adsorbent II is (0.05:1:0.05) to (0.4:1:0.4). Preferably, the mass ratio of adsorbent I, purifying agent, and adsorbent II is (0.1:1:0.1) to (0.3:1:0.3).

7. The method according to claim 1, characterized in that, The concentration of iron carbonyl in the synthesis gas containing iron carbonyl is 5-800 ppm in molar terms; Preferably, the concentration of iron carbonyl in the synthesis gas containing iron carbonyl is 5 to 500 ppm in molar terms.

8. The method according to claim 1, characterized in that, The reaction conditions include: a reaction temperature of 20–260°C, a reaction pressure of 0–7 MPa, and a reaction space velocity of 100–10000 h⁻¹. -1 ; Preferably, the reaction conditions include: a reaction temperature of 20~240℃; a reaction pressure of 0~5MPa; and a reaction space velocity of 1000~9000 h⁻¹. -1 .

9. The method according to claim 1, characterized in that, The concentration of carbonyl iron in the purified synthesis gas is less than 0.01 ppm on a molar basis.

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