Preparation method of iron-molybdenum hydrogenation catalyst for coke-oven gas hydrogenation fine desulfurization
By introducing modified γ-Al2O3 support and anti-carbon deposition additives, combined with high-temperature segmented calcination and precise pre-sulfurization, a long-lasting iron-molybdenum catalyst was prepared, solving the problems of short catalyst life and decreased activity, and achieving a highly efficient hydrodesulfurization effect for coke oven gas.
Patent Information
- Application Number
- CN202511316321.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-16
- Publication Date
- 2025-12-12
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of catalyst preparation for coal chemical gas purification, in particular to a preparation method of an iron-molybdenum hydrogenation catalyst for hydrogenation and fine desulfurization of coke oven gas. BACKGROUND
[0002] As a byproduct of coking industry, coke oven gas is rich in hydrogen and methane, which are excellent raw materials for producing methanol. However, the coke oven gas also contains organic sulfides (such as thiophene and COS) and unsaturated hydrocarbons, which can seriously poison the catalysts in the subsequent processes. The organic sulfides can react with the Ni component of the hydrocarbon conversion catalyst and the Cu component of the methanol synthesis catalyst to form sulfides, resulting in permanent deactivation of the catalysts. The unsaturated hydrocarbons can also cause carbon deposition on the surface of the catalysts, blocking the active pores.
[0003] The existing iron-molybdenum catalyst has a core problem of extremely short service life (average 3-5 months). The traditional γ-Al2O3 carrier has high acidity, which easily adsorbs the tar components in the coke oven gas. The carbonization reaction of the tar in the micropores of the catalyst blocks the active sites and pores, resulting in a sharp decrease in the number of micropores and a rapid decrease in activity. In addition, the existing technology also has the following problems: ① uneven dispersion of active components, insufficient conversion rate of difficult-to-convert organic sulfur; ② rough pre-sulfurization, poor activity stability; ③ lack of carbonization resistance design, no optimization of components and preparation conditions for tar coke deposition. Therefore, it is necessary to optimize the preparation process from four dimensions of carrier acidity adjustment, anti-coking component introduction, high-temperature calcination acid control, and high-efficiency additive replacement to solve the problem of insufficient service life caused by tar carbonization, while ensuring the catalytic activity and anti-side reaction ability. SUMMARY
[0004] The purpose of the present application is to solve the above-mentioned problems of the existing iron-molybdenum hydrogenation catalyst, and to provide a preparation method of an iron-molybdenum hydrogenation catalyst.
[0005] To achieve the above-mentioned purpose, the technical solution adopted by the present application is as follows:
[0006] The preparation method of the iron-molybdenum hydrogenation catalyst for fine desulfurization of coke oven gas comprises six steps of carrier modification pretreatment, active component impregnation liquid preparation, equal volume impregnation, gradient drying, high-temperature staged calcination, and precise pre-sulfurization, and the specific steps are as follows:
[0007] Step 1: Carrier modification pretreatment
[0008] Select γ-Al2O3 as the carrier, and the specific surface area of the carrier is required to be 180-220m 2 / g, 8-12 nm in pore size, 0.65-0.75 kg / L in bulk density, and the basic oxide precursor is added in proportion, mixed with deionized water to form a suspension, stirred in a 50℃ constant temperature water bath for 1 h, so that the basic oxide is uniformly loaded on the surface of γ-Al2O3; then the γ-Al2O3 carrier is placed in a drying oven at 120-150℃ for 4-6 h to remove the adsorbed water on the surface of the carrier; the dried carrier is placed in a muffle furnace and calcined at 300-350℃ for 2-3 h, with a heating rate of 5℃ / min, to remove the residual organic impurities in the carrier and enhance the adsorption capacity of the carrier to the active components, thereby obtaining the alkali-modified γ-Al2O3 carrier;
[0009] Step two: preparation of active component impregnation solution: the raw materials are weighed according to the following mass proportions: based on the mass of the pretreated alkali-modified γ-Al2O3 carrier, the amount of iron nitrate is 3.0%-4.0% based on Fe2O3, the amount of ammonium heptamolybdate is 8.0%-9.5% based on MoO3, the amount of anti-carbon deposition additive is 0.5%-1.5% based on CeO2 / ZrO2, and the amount of washing aid is 1.0%-1.5% based on the mass of the carrier; the iron nitrate, ammonium heptamolybdate, anti-carbon deposition additive, and washing aid are sequentially added to deionized water, stirred in a 40-50℃ constant temperature water bath for 30-45 min, until completely dissolved, to obtain a clear and transparent active component impregnation solution; the total mass of the impregnation solution is calculated according to the equal volume impregnation ratio with the carrier, to ensure that the impregnation solution is completely adsorbed by the carrier pores;
[0010] Step three: equal volume impregnation: the pretreated alkali-modified γ-Al2O3 carrier is placed in a rotary impregnation tank, and the prepared active component impregnation solution is slowly added dropwise at room temperature and a rotation speed of 20-30 r / min, with a dropwise addition time of 30-45 min; after the dropwise addition is completed, the rotation is continued for 1-2 h to allow the active components to diffuse into the pores of the carrier and form a uniform adsorption layer;
[0011] Step four: gradient drying: the impregnated carrier is transferred to a vacuum drying oven, first dried at a vacuum degree of -0.08 to -0.07 MPa and a temperature of 60-70℃ for 2-3 h to preliminarily remove the free water on the surface; then the temperature is increased to 90-100℃, the vacuum degree is kept unchanged, and the drying is continued for 3-4 h to remove the residual water in the pores of the carrier;
[0012] Step 5: High-temperature segmented calcination: The dried support is placed in a programmed temperature muffle furnace and calcined according to the following procedure: First stage: The temperature is raised from room temperature to 250℃ at a rate of 3℃ / min and held for 1.5-2 hours to allow the nitrates and ammonium salts in the impregnation solution to decompose initially; Second stage: The temperature is raised from 250℃ to 600-700℃ at a rate of 3℃ / min and held for 2.5-3 hours to allow the Fe and Mo compounds to be completely converted into Fe2O3 and MoO3 active components, and the basic oxides to form a stable solid solution with γ-Al2O3, while reducing the strength of the β-acid sites; Third stage: The temperature is naturally cooled to room temperature to obtain the iron-molybdenum catalyst precursor.
[0013] Step Six: Precise Pre-sulfurization: First, the calcined catalyst precursor is loaded into the sulfidation reactor. Nitrogen gas with an H2S volume fraction of 1.0%-1.5% is used as the sulfiding gas. The specific parameters are as follows: First, the temperature rises from room temperature to 200℃ at a rate of 10℃ / h, while simultaneously introducing sulfiding gas and controlling the space velocity at 300-400 h⁻¹. This is then held at a constant temperature for 2 hours to complete the initial sulfidation of the catalyst surface. Next, the deep sulfidation stage begins, with the temperature rising from 200℃ to 350-380℃ at a rate of 8℃ / h. During this process, the sulfiding gas concentration and space velocity are maintained constant, and the temperature is held for 3-4 hours. Simultaneously, the H2S content in the sulfidation tail gas is monitored online. Sulfidation is considered complete when the H2S concentration in the tail gas stabilizes above 90% of the inlet concentration. Finally, cooling and passivation are performed. After sulfidation, the sulfiding gas supply is stopped, and pure nitrogen is used for purging for 1-2 hours, followed by purging at 15℃ / h. The temperature was reduced to room temperature at a certain rate, and the final product, iron-molybdenum hydrogenation catalyst, was obtained.
[0014] In a further preferred embodiment, the alkaline oxide precursor is any one of magnesium nitrate, calcium nitrate, or lanthanum nitrate.
[0015] Further optimization of the solution involves using cerium nitrate or zirconium nitrate as the anti-carbon deposit additive.
[0016] In a further preferred embodiment, the detergent additive is tartaric acid.
[0017] The present invention has the following beneficial effects:
[0018] This invention addresses the problem of existing iron-molybdenum hydrogenation catalysts having insufficient micropores and decreased activity due to internal carbonization of tar in the coal gas, resulting in an average service life of only 3-5 months. A long-lasting iron-molybdenum hydrogenation catalyst for coke oven gas hydrorefinement and desulfurization is prepared. This catalyst possesses the following excellent properties:
[0019] (1): Service life is significantly extended: by modifying the support with alkaline oxides to neutralize the strong acidity of γ-Al2O3, introducing anti-carbon deposit additives to inhibit carbon deposit formation and micropore collapse, and using high-temperature segmented calcination to reduce the strength of the β acid sites on the support, the three factors work together to reduce the carbonization rate of tar by 60%~70%, and extend the continuous operating life of the catalyst from the traditional 3~5 months to 12~18 months, which greatly solves the core problem of insufficient service life of existing catalysts;
[0020] (2): Excellent catalytic activity and stability: Tartaric acid with better chelating ability is selected as a competitive adsorption aid, which can promote the uniform dispersion of active components on the surface and in the pores of the support. The conversion rate of thiophene and other difficult-to-convert organic sulfur is ≥97.5%, and the activity retention rate of the catalyst after 1000 hours of continuous operation is ≥95%, which meets the long-term stable requirements of deep purification of coke oven gas.
[0021] (3): Strong resistance to side reactions: The reasonable regulation of the acidity of the carrier and the weakly basic sites formed after the competitive decomposition of the adsorption aid can effectively inhibit the occurrence of methanation side reactions and reduce energy consumption and cost in industrial production.
[0022] (4): Adaptable to industrial conditions: The anti-carbon deposit design gives the catalyst stronger tar tolerance and can be used in industrial conditions where the tar content in coke oven gas is ≤50mg / Nm³, the CO content is ≤10%, and the unsaturated olefin content is ≤5%, which broadens the application range of the catalyst and improves its industrial applicability. Detailed Implementation
[0023] The present invention will now be described clearly and completely in conjunction with its technical solutions. Obviously, the described embodiments are only a part of, and not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0024] Example 1
[0025] This embodiment provides an iron-molybdenum hydrogenation catalyst for coke oven gas hydrotreating and its preparation method, which includes the following steps:
[0026] Step 1. γ-Al2O3 was selected as the carrier, with a specific surface area of 200 m² / g, a pore size of 10 nm, and a bulk density of 0.7 kg / L. Magnesium nitrate (1.5% of the carrier mass based on MgO) was added and mixed with deionized water to form a suspension. The suspension was stirred in a constant temperature water bath at 50°C for 1 h. The mixed carrier was then dried in a drying oven at 130°C for 5 h, and then placed in a muffle furnace and heated to 320°C at a heating rate of 5°C / min for 2.5 h to complete the carrier pretreatment.
[0027] Step 2. Based on the mass of the pretreated carrier, weigh out 3.5% (as Fe2O3) of ferric nitrate ([Fe(NO3)3・9H2O]) and 9.0% (as MoO3) of ammonium heptamolybdate ([(NH4)6Mo7O)). 24 • 4H2O]), 1.0% (calculated as CeO2) of cerium nitrate, 1.5% of tartaric acid, added to deionized water to prepare an impregnation solution, and stirred in a constant temperature water bath at 45°C for 40 minutes until completely dissolved;
[0028] Step 3. Place the pretreated carrier into a rotary impregnation tank and slowly add the impregnation solution at room temperature and 25 r / min (complete the addition in 35 min). After the addition is complete, continue rotating for 1.5 h to achieve equal volume impregnation.
[0029] Step 4. Transfer the impregnated carrier to a vacuum drying oven and dry it at a vacuum of -0.075 MPa and 65°C for 2.5 hours. Then, raise the temperature to 95°C and continue drying at the same vacuum for 3.5 hours to complete the gradient drying.
[0030] Step 5. Place the dried support into a programmed temperature muffle furnace, raise the temperature to 250℃ at 3℃ / min (hold for 1.8h), then raise the temperature to 650℃ at 3℃ / min (hold for 2.8h), and allow it to cool naturally to obtain the catalyst precursor;
[0031] Step 6. The catalyst precursor is loaded into the sulfidation reactor, and nitrogen gas containing 1.2% H2S (space velocity 350 h⁻¹) is introduced. The temperature is increased to 200℃ at 10℃ / h (and held for 2 h), and then increased to 360℃ at 8℃ / h (and held for 3.5 h). The H2S concentration in the tail gas is monitored online. When the concentration stabilizes above 90% of the inlet concentration, sulfidation is stopped. Pure nitrogen gas is switched to purge for 1.5 h, and then the temperature is reduced to room temperature to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-1.
[0032] Example 2
[0033] This embodiment provides an iron-molybdenum hydrogenation catalyst for coke oven gas hydrotreating and its preparation method, which includes the following steps:
[0034] Step 1. γ-Al2O3 was selected as the carrier, with a specific surface area of 190 m² / g, a pore size of 9 nm, and a bulk density of 0.68 kg / L. Calcium nitrate (calculated as CaO, representing 2.0% of the carrier mass) was added and mixed with deionized water to form a suspension. The suspension was stirred in a constant temperature water bath at 50°C for 1 h. The mixed carrier was then dried in a drying oven at 125°C for 4.5 h, and subsequently placed in a muffle furnace and heated to 330°C at a heating rate of 5°C / min for 2 h to complete the carrier pretreatment.
[0035] Step 2. Based on the mass of the pretreated carrier, weigh 3.2% (as Fe2O3) of ferric nitrate, 8.5% (as MoO3) of ammonium heptamolybdate, 0.8% (as ZrO2) of zirconium nitrate, and 1.2% of tartaric acid, add them to deionized water to prepare an impregnation solution, and stir in a constant temperature water bath at 42℃ for 35 minutes until completely dissolved.
[0036] Step 3. Place the pretreated carrier into a rotary impregnation tank and slowly add the impregnation solution at room temperature and 22 r / min (complete the addition in 30 min). After the addition is complete, continue rotating for 1 hour to achieve equal volume impregnation.
[0037] Step 4. Transfer the impregnated carrier to a vacuum drying oven and dry it at a vacuum of -0.08 MPa and 62°C for 2 hours. Then, raise the temperature to 92°C and continue drying at the same vacuum for 3 hours to complete the gradient drying.
[0038] Step 5. Place the dried support into a programmed temperature muffle furnace, raise the temperature to 250℃ at 3℃ / min (hold for 1.5h), then raise the temperature to 620℃ at 4℃ / min (hold for 2.5h), and allow it to cool naturally to obtain the catalyst precursor;
[0039] Step 6. The catalyst precursor is loaded into the sulfidation reactor, and nitrogen gas containing 1.0% H2S (space velocity 320 h⁻¹) is introduced. The temperature is increased to 200℃ at 10℃ / h (and held for 2 h), and then increased to 350℃ at 8℃ / h (and held for 3 h). The H2S concentration in the tail gas is monitored online. When the concentration stabilizes above 90% of the inlet concentration, sulfidation is stopped. Pure nitrogen gas is switched to purge for 1 h, and then the temperature is reduced to room temperature to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-2.
[0040] Example 3
[0041] This embodiment provides an iron-molybdenum hydrogenation catalyst for coke oven gas hydrotreating and its preparation method, which includes the following steps:
[0042] Step 1. γ-Al2O3 was selected as the support, with a specific surface area of 210 m² / g, a pore size of 11 nm, and a bulk density of 0.72 kg / L. Lanthanum nitrate (1.0% of the support mass based on La2O3) was added and mixed with deionized water to form a suspension. The suspension was stirred in a constant temperature water bath at 50°C for 1 h. The mixed support was then dried in a drying oven at 135°C for 5.5 h, and then placed in a muffle furnace and heated to 310°C at a heating rate of 5°C / min for 3 h to complete the support pretreatment.
[0043] Step 2. Based on the weight of the pretreated carrier, weigh 3.8% (as Fe2O3) of ferric nitrate, 9.2% (as MoO3) of ammonium heptamolybdate, 1.2% (as CeO2) of cerium nitrate, and 1.8% of tartaric acid, add them to deionized water to prepare an impregnation solution, and stir in a constant temperature water bath at 48℃ for 45 minutes until completely dissolved;
[0044] Step 3. Place the pretreated carrier into a rotary impregnation tank and slowly add the impregnation solution dropwise at room temperature and 28 r / min (to be completed in 40 min). After the addition is completed, continue rotating for 2 hours to achieve equal volume impregnation.
[0045] Step 4. Transfer the impregnated carrier to a vacuum drying oven and dry it at a vacuum of -0.07 MPa and 68°C for 3 hours. Then, raise the temperature to 98°C and continue drying at the same vacuum for 4 hours to complete the gradient drying.
[0046] Step 5. Place the dried support into a programmed temperature muffle furnace, raise the temperature to 250℃ at 3℃ / min (hold for 2 hours), then raise the temperature to 680℃ at 3℃ / min (hold for 3 hours), and allow it to cool naturally to obtain the catalyst precursor;
[0047] Step 6. The catalyst precursor is loaded into the sulfidation reactor, and nitrogen gas containing 1.4% H2S (space velocity 380 h⁻¹) is introduced. The temperature is increased to 200℃ at 10℃ / h (and held for 2 h), and then increased to 370℃ at 8℃ / h (and held for 4 h). The H2S concentration in the tail gas is monitored online. When the concentration stabilizes above 90% of the inlet concentration, sulfidation is stopped. Pure nitrogen gas is switched to purge for 2 h, and then the temperature is reduced to room temperature to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-3.
[0048] Example 4
[0049] This embodiment provides an iron-molybdenum hydrogenation catalyst for coke oven gas hydrotreating and its preparation method, which includes the following steps:
[0050] Step 1. γ-Al2O3 was selected as the carrier, with a specific surface area of 180 m² / g, a pore size of 8 nm, and a bulk density of 0.65 kg / L. A mixture of magnesium nitrate and calcium nitrate (calculated as 2.5% of the carrier mass based on MgO+CaO, with a mass ratio of 1:1) was added and mixed with deionized water to form a suspension. The suspension was stirred in a constant temperature water bath at 50°C for 1 h. The mixed carrier was then dried in a drying oven at 120°C for 4 h, and then placed in a muffle furnace and heated to 340°C at a heating rate of 5°C / min for 2.2 h to complete the carrier pretreatment.
[0051] Step 2. Based on the weight of the pretreated carrier, weigh 3.0% (as Fe2O3) of ferric nitrate, 8.0% (as MoO3) of ammonium heptamolybdate, 0.5% (as ZrO2) of zirconium nitrate, and 1.0% of tartaric acid, add them to deionized water to prepare an impregnation solution, and stir in a 40℃ constant temperature water bath for 30 minutes until completely dissolved;
[0052] Step 3. Place the pretreated carrier into a rotary impregnation tank and slowly add the impregnation solution at room temperature and 20 r / min (complete the addition in 32 min). After the addition is complete, continue rotating for 1.2 h to achieve equal volume impregnation.
[0053] Step 4. Transfer the impregnated carrier to a vacuum drying oven and dry it at a vacuum of -0.078 MPa and 60°C for 2.2 hours. Then, raise the temperature to 90°C and continue drying at the same vacuum for 3.2 hours to complete the gradient drying.
[0054] Step 5. Place the dried support into a programmed temperature muffle furnace, raise the temperature to 250℃ at 3℃ / min (hold for 1.6h), then raise the temperature to 600℃ at 3℃ / min (hold for 2.6h), and allow it to cool naturally to obtain the catalyst precursor;
[0055] Step 6. The catalyst precursor is loaded into the sulfidation reactor, and nitrogen gas containing 0.9% H2S (space velocity 300 h⁻¹) is introduced. The temperature is increased to 200℃ at 10℃ / h (held at 2h), and then increased to 340℃ at 8℃ / h (held at 3.2h). The H2S concentration in the tail gas is monitored online. When the concentration stabilizes above 90% of the inlet concentration, sulfidation is stopped. Pure nitrogen gas is switched to purge for 1.2h, and then the temperature is reduced to room temperature to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-4.
[0056] Example 5
[0057] This embodiment provides an iron-molybdenum hydrogenation catalyst for coke oven gas hydrotreating and its preparation method, which includes the following steps:
[0058] Step 1. γ-Al2O3 was selected as the support, with a specific surface area of 220 m² / g, a pore size of 12 nm, and a bulk density of 0.75 kg / L. Lanthanum nitrate (3.0% of the support mass based on La2O3) was added and mixed with deionized water to form a suspension. The suspension was stirred in a constant temperature water bath at 50°C for 1 h. The mixed support was then dried in a drying oven at 140°C for 6 h, and then placed in a muffle furnace and heated to 300°C at a heating rate of 5°C / min for 2.8 h to complete the support pretreatment.
[0059] Step 2. Based on the mass of the pretreated carrier, weigh 4.0% (as Fe2O3) of ferric nitrate, 9.5% (as MoO3) of ammonium heptamolybdate, 1.5% (as CeO2+ZrO2, with a mass ratio of 1:1) of a mixture of cerium nitrate and zirconium nitrate, and 2.0% of tartaric acid. Add deionized water to prepare an impregnation solution and stir in a 50°C constant temperature water bath for 42 minutes until completely dissolved.
[0060] Step 3. Place the pretreated carrier into a rotary impregnation tank and slowly add the impregnation solution at room temperature and 30 r / min (to be completed in 45 min). After the addition is completed, continue rotating for 1.8 h to achieve equal volume impregnation.
[0061] Step 4. Transfer the impregnated carrier to a vacuum drying oven and dry it at a vacuum of -0.072 MPa and 70°C for 2.8 hours. Then, raise the temperature to 100°C and continue drying at the same vacuum for 3.8 hours to complete the gradient drying.
[0062] Step 5. Place the dried support into a programmed temperature muffle furnace, raise the temperature to 250℃ at 3℃ / min (hold for 1.9h), then raise the temperature to 700℃ at 3℃ / min (hold for 2.9h), and allow it to cool naturally to obtain the catalyst precursor;
[0063] Step 6. The catalyst precursor is loaded into the sulfidation reactor, and nitrogen gas containing 1.5% H2S (space velocity 400 h⁻¹) is introduced. The temperature is increased to 200℃ at 10℃ / h (held at 2h), and then increased to 380℃ at 8℃ / h (held at 3.8h). The H2S concentration in the tail gas is monitored online. When the concentration stabilizes above 90% of the inlet concentration, sulfidation is stopped. Pure nitrogen gas is switched to purge for 1.8h, and then the temperature is reduced to room temperature to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-5.
[0064] Comparative Example 1
[0065] This comparative example provides an iron-molybdenum hydrogenation catalyst, the preparation method of which does not employ support pretreatment, does not add anti-carbon deposition components, and does not involve high-temperature calcination. The specific steps are as follows:
[0066] 1. Using the same γ-Al2O3 support as in Example 1 (without added alkaline oxide), the support was directly placed in a 130°C drying oven for 5 hours, and then placed in a muffle furnace and heated to 320°C at a heating rate of 5°C / min for 2.5 hours.
[0067] 2. Based on the mass of the pretreated carrier, weigh 3.5% (as Fe2O3) of ferric nitrate, 9.0% (as MoO3) of ammonium heptamolybdate (without anti-carbon deposition components), and 1.5% of tartaric acid, add them to deionized water to prepare an impregnation solution, and stir in a constant temperature water bath at 45℃ for 40 minutes until completely dissolved.
[0068] 3. Perform equal-volume impregnation and gradient drying according to the method of Example 1;
[0069] 4. Place the dried support into a programmed temperature muffle furnace, raise the temperature to 250℃ at 3℃ / min (hold for 1.8h), then raise the temperature to 480℃ at 4℃ / min (low-temperature calcination, not reaching 600~700℃), hold for 2.8h, and allow it to cool naturally to obtain the catalyst precursor;
[0070] 5. Perform precise presulfurization as in Example 1 to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-D1.
[0071] Comparative Example 2
[0072] This comparative example provides an iron-molybdenum hydrogenation catalyst, the preparation method of which does not add anti-carbon deposition components, and the specific steps are as follows:
[0073] 1. The carrier was modified and pretreated in the same manner as in Example 1 (using MgO modification);
[0074] 2. Based on the mass of the pretreated carrier, weigh 3.5% (as Fe2O3) of ferric nitrate, 9.0% (as MoO3) of ammonium heptamolybdate (without CeO2 or other anti-carbon deposition components), and 1.5% of tartaric acid, add them to deionized water to prepare an impregnation solution, and stir in a constant temperature water bath at 45℃ for 40 minutes until completely dissolved;
[0075] 3. The catalyst precursor was obtained by performing equal-volume impregnation, gradient drying, and segmented calcination according to the method of Example 1;
[0076] 4. Perform precise presulfurization as in Example 1 to obtain the iron-molybdenum hydrogenation catalyst, denoted as Cat-D2.
[0077] Experimental Example 1
[0078] The Cat-1~Cat-5 prepared in Examples 1-5 and the Cat-D1~Cat-D2 prepared in Comparative Examples 1-2 were respectively applied to the two-stage hydrodesulfurization process of coke oven gas. Their catalytic activity, anti-carbon deposition performance and service life were tested to verify the effectiveness of the present invention in solving the problem of insufficient catalyst life.
[0079] Experimental conditions: The coke oven gas contained 8% CO, 4% unsaturated olefins, and 200 mg / Nm³ of organic sulfur (including thiophene). The primary hydrogenation temperature was 330℃, pressure 2.0 MPa, and space velocity 1500 h⁻¹; the secondary hydrogenation temperature was 350℃, pressure 2.0 MPa, and space velocity 1000 h⁻¹. The total organic sulfur conversion rate, catalyst activity retention rate after 1000 h of continuous operation, time to first carbon buildup exceeding the limit (lifetime, number of months of operation when activity drops to 80%), and catalyst carbon buildup (mass fraction) after 1000 h are shown in Table 1 below.
[0080] Table 1 Performance test results of iron-molybdenum hydrogenation catalyst
[0081] Catalyst Total conversion of organic sulfur (%) Activity retention rate after 1000h (%) Time of first carbon deposition exceeding standard (month) Carbon deposition amount after 1000h (%) Cat-1 98.2 96.5 16 1.1 Cat-2 97.6 95.2 14 1.3 Cat-3 98.5 97.1 18 0.9 Cat-4 97.0 94.0 12 1.5 Cat-5 98.8 97.8 17 0.8 Cat-D1 90.3 82.8 4 3.9 Cat-D2 95.1 89.5 8 2.5
[0082] The results analysis in Table 1 show that:
[0083] 1. The catalysts (Cat-1~Cat-5) in Examples 1-5 had an initial carbon deposition time exceeding the standard of 12-18 months, which is much longer than that of Comparative Example 1 (4 months) and Comparative Example 2 (8 months). This proves that the synergistic effect of modifying the support with alkaline oxides, introducing anti-carbon deposition components (CeO2 / ZrO2) and high-temperature roasting at 600~700℃ can effectively inhibit tar carbonization and solve the problem of short life of traditional catalysts.
[0084] 2. The total organic sulfur conversion rate of the catalyst in the example was ≥97.0%, and the activity retention rate after 1000h was ≥94.0%, which was significantly better than that of Comparative Example 1 (90.3% and 82.8%). This indicates that using tartaric acid as a competitive adsorption aid can ensure uniform dispersion of active components and maintain high catalytic activity.
[0085] 3. The amount of carbon deposited in the catalyst of the example after 1000h was only 0.8%~1.5%, which was much lower than that in the comparative example (2.5%~3.9%), verifying the effectiveness of the present invention in reducing tar adsorption and carbonization by adjusting the acidity of the support and introducing anti-carbon deposit components.
[0086] The long-lasting iron-molybdenum hydrocatalyst for coke oven gas hydrotreating and desulfurization described in this invention uses modified γ-Al2O3 as a support. This support is prepared by modifying γ-Al2O3 with the introduction of basic oxides (one or more of MgO, CaO, and La2O3), wherein the basic oxides account for 1.0% to 3.0% of the total mass of the support. The modified support retains the specific surface area, pore size, and bulk density of the γ-Al2O3 support, while also neutralizing the strong acidity of γ-Al2O3 through the basic oxides, reducing the adsorption of tar components in the coke oven gas on the support surface. The active components of the catalyst are Fe2O3 and MoO3, wherein the precursor of Fe2O3 is ferric nitrate, and the precursor of MoO3 is ammonium heptamolybdate. Based on the mass of the pretreated modified γ-Al2O3 support, Fe2O3... The dosage of 3 is 3.0%~4.0%, and the dosage of MoO3 is 8.0%~9.5%. At the same time, the catalyst is also added with anti-coking aid and competitive adsorption aid. The anti-coking aid is CeO2 or ZrO2, and its precursors are cerium nitrate or zirconium nitrate, respectively. The dosage of the anti-coking aid is 0.5%~1.5% of the carrier mass based on CeO2 or ZrO2. This aid can oxidize part of the carbon deposits by utilizing the oxygen storage capacity of CeO2 or enhance the structural stability of the carrier by ZrO2, inhibiting micropore collapse and thus reducing the carbonization rate of tar. The competitive adsorption aid is tartaric acid, with a dosage of 0.5%~1.5% of the carrier mass. Its chelating ability is better than that of traditional citric acid, which can more uniformly disperse the active components. After decomposition, it can form weakly basic sites on the catalyst surface, further inhibiting tar adsorption. The aforementioned γ-Al2O3, alkaline oxide precursor, ferric nitrate, ammonium heptamolybdate, anti-carbon deposition agent precursor, and competitive adsorption agent are all common industrial chemical materials with high stability and good dispersibility. They can ensure that each component is evenly distributed on the surface and in the pores of the carrier, which is suitable for the requirements of organic sulfur hydrogenation conversion and anti-tar carbonization in coke oven gas.
[0087] This invention is applicable to the feed gas pretreatment section of plants producing methanol and synthetic ammonia from coke oven gas, solving the industrial pain point of short catalyst life in traditional catalysts.
Claims
1. A method for preparing an iron-molybdenum hydrogenation catalyst for coke oven gas desulfurization, characterized in that, The process includes six steps: carrier modification pretreatment, preparation of active component impregnation solution, equal-volume impregnation, gradient drying, high-temperature segmented calcination, and precise pre-vulcanization, as detailed below: Step 1: Carrier modification pretreatment: γ-Al₂O₃ was selected as the support, with a required specific surface area of 180-220 m². 2 A γ-Al₂O₃ support with a pore size of 8-12 nm and a bulk density of 0.65-0.75 kg / L was prepared by adding an alkaline oxide precursor in a certain proportion and mixing it with deionized water. The suspension was stirred in a constant temperature water bath at 50℃ for 1 h to uniformly load the alkaline oxide onto the surface of γ-Al₂O₃. Subsequently, the γ-Al₂O₃ support was dried in a drying oven at 120-150℃ for 4-6 h to remove adsorbed water from the surface of the support. The dried support was then placed in a muffle furnace and calcined at 300-350℃ for 2-3 h with a heating rate controlled at 5℃ / min to remove residual organic impurities inside the support and enhance the adsorption capacity of the support for active components, thus obtaining an alkali-modified γ-Al₂O₃ support. Step 2: Preparation of the active component impregnation solution: Weigh the raw materials according to the following mass ratios: Based on the mass of the pretreated alkali-modified γ-Al2O3 carrier, the amount of ferric nitrate (calculated as Fe2O3) is 3.0%-4.0%, the amount of ammonium heptamolybdate (calculated as MoO3) is 8.0%-9.5%, the amount of anti-carbon deposition agent (calculated as CeO2 / ZrO2) is 0.5%-1.5%, and the amount of detergent builder is 1.0%-1.5% of the carrier mass; Add ferric nitrate, ammonium heptamolybdate, anti-carbon deposition agent, and detergent builder sequentially to deionized water, and stir in a constant temperature water bath at 40-50℃ for 30-45 minutes until completely dissolved to obtain a clear and transparent active component impregnation solution; The total mass of the impregnation solution is calculated according to the same volume impregnation ratio as the carrier to ensure that the impregnation solution is completely adsorbed by the carrier pores; Step 3: Equal volume impregnation: Place the pretreated alkali-modified γ-Al2O3 support into a rotary impregnation tank. Under the conditions of room temperature and a rotation speed of 20-30 r / min, slowly add the prepared active component impregnation solution dropwise, controlling the dropwise addition time to 30-45 min. After the dropwise addition is completed, continue to maintain the rotation state for 1-2 h to allow the active component to fully diffuse into the pores of the support and form a uniform adsorption layer. Step 4: Gradient drying: Transfer the impregnated carrier to a vacuum drying oven and dry it for 2-3 hours at a vacuum of -0.08 to -0.07 MPa and a temperature of 60-70℃ to initially remove free water from the surface; then raise the temperature to 90-100℃, keep the vacuum constant, and continue drying for 3-4 hours to remove residual moisture in the carrier pores. Step 5: High-temperature segmented calcination: The dried support is placed in a programmed temperature muffle furnace and calcined according to the following procedure: First stage: The temperature is raised from room temperature to 250℃ at a rate of 3℃ / min and held for 1.5-2 hours to allow the nitrates and ammonium salts in the impregnation solution to decompose initially; Second stage: The temperature is raised from 250℃ to 600-700℃ at a rate of 3℃ / min and held for 2.5-3 hours to allow the Fe and Mo compounds to be completely converted into Fe2O3 and MoO3 active components, and the basic oxides to form a stable solid solution with γ-Al2O3, while reducing the strength of the β-acid sites; Third stage: The temperature is naturally cooled to room temperature to obtain the iron-molybdenum catalyst precursor. Step Six: Precise Pre-sulfurization: First, the calcined catalyst precursor is loaded into the sulfidation reactor. Nitrogen gas with an H2S volume fraction of 1.0%-1.5% is used as the sulfiding gas. The specific parameters are as follows: First, the temperature rises from room temperature to 200℃ at a rate of 10℃ / h, while simultaneously introducing sulfiding gas and controlling the space velocity at 300-400 h⁻¹. This is then held at a constant temperature for 2 hours to complete the initial sulfidation of the catalyst surface. Next, the deep sulfidation stage begins, with the temperature rising from 200℃ to 350-380℃ at a rate of 8℃ / h. During this process, the sulfiding gas concentration and space velocity are maintained constant, and the temperature is held for 3-4 hours. Simultaneously, the H2S content in the sulfidation tail gas is monitored online. Sulfidation is considered complete when the H2S concentration in the tail gas stabilizes above 90% of the inlet concentration. Finally, cooling and passivation are performed. After sulfidation, the sulfiding gas supply is stopped, and pure nitrogen is used for purging for 1-2 hours, followed by purging at 15℃ / h. The temperature was reduced to room temperature at a certain rate, and the final product, iron-molybdenum hydrogenation catalyst, was obtained.
2. The method for preparing the iron-molybdenum hydrogenation catalyst for coke oven gas desulfurization according to claim 1, characterized in that, The alkaline oxide precursor is any one of magnesium nitrate, calcium nitrate, or lanthanum nitrate.
3. The method for preparing the iron-molybdenum hydrogenation catalyst for coke oven gas desulfurization according to claim 1, characterized in that, The anti-carbon deposit additive is cerium nitrate or zirconium nitrate.
4. The method for preparing the iron-molybdenum hydrogenation catalyst for coke oven gas desulfurization according to claim 1, characterized in that, The detergent additive mentioned is tartaric acid.