A method for preparing a carbon monoxide methanation catalyst

Abstract

The invention discloses a method for preparing a carbon monoxide methanation catalyst, which belongs to the technical field of methanation catalyst preparation. The method comprises the following steps: putting a waste catalytic cracking catalyst into a sulfuric acid solution for acid leaching, and filtering to obtain an acid leaching solution; adjusting the pH value of the acid leaching solution, extracting vanadium, and obtaining a raffinate; adding an ethanol solution containing terephthalic acid to the raffinate, stirring and mixing, performing a hydrothermal reaction, solid-liquid separation, washing, and drying to obtain a solid M-Al-MOF; and calcining and reducing in a hydrogen atmosphere to obtain a carbon monoxide methanation catalyst MAl2O3. The invention uses a raffinate generated in a wet vanadium extraction process as a precursor, wherein the raffinate contains metals such as aluminum, vanadium, nickel, manganese, and iron, and terephthalic acid is added as a ligand to obtain M-Al-MOF; and a carbon monoxide methanation catalyst with high dispersibility, high activity, and long service life is obtained by reduction calcination.

Description

Technical Field

[0001] The invention relates to a method for preparing a carbon monoxide methanation catalyst, and belongs to the technical field of methanation catalyst preparation. Background Art

[0002] During the catalytic cracking (FCC) process of crude oil, organic metal compounds in the raw oil decompose, and heavy metals such as vanadium are deposited on the catalyst, resulting in a decrease in catalyst activity or even deactivation. FCC catalyst is currently the most widely used catalyst in the oil refining industry. The waste catalyst generated after use is about 150,000 tons per year, which has become one of the main solid wastes in the oil refining industry. The main component of FCC catalyst is silicon-aluminum composite oxide. The surface of the deactivated catalyst contains some elements such as vanadium. If not properly handled, it will cause environmental pollution and waste of resources. Vanadium batteries are considered to be a large-scale energy storage technology with great potential, but the cost of vanadium electrolytes limits their large-scale development. If vanadium is recovered from waste FCC catalysts to prepare vanadium sulfate electrolytes, it can not only reduce costs but also utilize resources.

[0003] The Chinese invention patent document with publication number CN112342389A discloses a method for recovering valuable metals from waste chemical catalysts, and recycling the metals contained therein in stages. However, a large amount of metal ions contained in the leaching solution have not been recycled.

[0004] The Chinese invention patent document with publication number CN103071507A discloses a complete methanation catalyst, its preparation method and application. The aluminum oxide-supported catalyst is prepared by co-precipitation. However, nickel aluminum spinel is easily generated during the calcination process and is difficult to be reduced during the reaction, resulting in fewer exposed active sites and reduced catalytic activity.

[0005] The Chinese patent document with publication number CN117504860A discloses a catalyst for carbon monoxide methanation reaction and a preparation method thereof, which uses Ru as an active component. Ru is a precious metal and is expensive, and does not utilize large-scale production of the catalyst. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a carbon monoxide methanation catalyst. The carbon monoxide methanation catalyst prepared by the method has high catalytic activity and strong stability.

[0007] To solve the above problems, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for preparing a carbon monoxide methanation catalyst, comprising the following steps:

[0009] (1) placing the spent catalytic cracking catalyst in a sulfuric acid solution for acid leaching, and filtering to obtain an acid leaching solution;

[0010] (2) adjusting the pH value of the acid leaching solution to extract vanadium, obtaining a raffinate and a vanadyl sulfate stripping solution, concentrating the vanadyl sulfate stripping solution to obtain a vanadyl sulfate electrolyte; using nickel in the raffinate as an active component, and using metallic vanadium, iron, and manganese as metal additives;

[0011] (3) Adding an ethanol solution containing terephthalic acid to the raffinate, stirring and mixing, carrying out a hydrothermal reaction, solid-liquid separation, washing, and drying to obtain a solid M-Al-MOF; and calcining and reducing in a hydrogen atmosphere to obtain a carbon monoxide methanation catalyst M / Al2O3.

[0012] Preferably, in step (1), the mass fraction of the sulfuric acid solution is 5 to 20 wt %; the mass ratio of the spent catalytic cracking catalyst to the sulfuric acid solution is 1:2 to 4; the acid leaching temperature is 60 to 120° C., and the acid leaching time is 1 to 6 h.

[0013] Preferably, in step (2), the pH value of the acid leaching solution is controlled at 1.5 to 2.4.

[0014] Preferably, in step (3), the volume ratio of the raffinate to the ethanol solution is 1:0.5-2; the volume fraction of terephthalic acid in the ethanol solution is 30-50%; the hydrothermal reaction temperature is 140-180°C; the hydrothermal reaction time is 8-18h; the roasting reduction temperature is 400-600°C; and the roasting time is 2-4h.

[0015] Compared with the prior art, the present invention has the following beneficial effects:

[0016] (1) The prior art uses commercial Al2O3 as a carrier to load active components through an impregnation method to prepare a catalyst. The specific surface area of ​​commercial Al2O3 is small, and the attachment sites provided for active metals are few. The active metal has poor dispersion, and the interaction between the metal and the carrier is weak. In addition, during the high-temperature reaction, the metal agglomerates due to the weak interaction, resulting in catalyst sintering and further deactivation. The technical solution of the present invention uses terephthalic acid as a ligand to form an M-Al-MOF by complexing with the metal elements in the raffinate. The obtained Al2O3 has rich porosity and a large specific surface area, which helps to enhance the anchoring force between the active component and the carrier, accelerate the mass transfer during the reaction, and facilitate the reaction. At the same time, the ligand cooperates with all metals, the metals are evenly dispersed, and the nickel active sites are fully exposed, thereby improving the catalytic activity.

[0017] (2) The prior art uses a single metal nickel to prepare a catalyst, but due to the dispersibility of the active metal and the interaction between the active metal and the carrier, the catalyst activity and stability are poor. The present invention uses nickel in the raffinate as an active component through a complexation method, and utilizes metal vanadium, iron, and manganese as metal additives. Because the change in the multivalent state of the additive metal helps to increase the oxygen vacancies of the catalyst, improve the adsorption and dissociation ability of carbon monoxide, and thus improve the reaction activity of the catalyst; at the same time, the synergistic relationship of the additive plays a spacing role in the catalyst, which is conducive to the separation of the active metal nickel, improves its dispersibility, and thus improves the catalytic activity; and the additive enters the Al2O3 lattice in a substitution manner to form oxygen vacancies, increase the mobility of oxygen species, and facilitate the reaction of oxygen species with carbon deposits to eliminate carbon deposits and maintain the stability of the catalyst.

[0018] (3) The prior art produces a large amount of raffinate during the wet vanadium extraction process. The raffinate contains a large amount of metal ions. If not properly handled, it will cause resource waste and environmental pollution. The technical solution of the present invention uses the metal elements in the raffinate as the raw materials of the catalyst to synthesize the carbon monoxide methanation catalyst, without adding additional metal raw materials, and obtains the vanadyl sulfate electrolyte product, realizing the resource utilization of the waste catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0020] Figure 1 TEM image of catalyst M3 / Al2O3 of Example 3;

[0021] Figure 2 This is the TEM image of the nickel lattice lines of the catalyst M3 / Al2O3 of Example 3. DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solution and the effects of the present invention clearer, the technical solution of the present invention will be described in detail below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention. Example 1

[0023] (1) Mix the spent FCC catalyst with 5 wt% sulfuric acid in a mass ratio of 1:2, place in an 80°C oil bath and stir for 4 h; and filter to obtain an acid leaching solution;

[0024] (2) adding sodium hydroxide to the acid leaching solution, adjusting the pH value of the acid leaching solution to 1.5, and then performing five-stage extraction, and obtaining a raffinate and an organic phase after separation; using 5wt% sulfuric acid for six-stage stripping to obtain a vanadyl sulfate stripping solution, and then removing impurities, removing oil, and concentrating to obtain a vanadyl sulfate electrolyte; the main components of the raffinate are detected and analyzed as follows: vanadium 138 mg / L, iron 148 mg / L, nickel 325 mg / L, manganese 98 mg / L, aluminum 10985 mg / L;

[0025] (3) Add an ethanol solution containing terephthalic acid to the raffinate, wherein the volume fraction of terephthalic acid in the ethanol solution is 40%, and the volume ratio of the raffinate to the ethanol solution is 1:0.5; after stirring and mixing, transfer the mixture to a hydrothermal reactor and react at 180°C for 8 h to obtain a suspension, separate the solid and liquid, wash, and dry to obtain a solid M-Al-MOF; transfer the mixture to a tubular furnace and calcine at 450°C for 3 h to obtain a carbon monoxide methanation catalyst M1 / Al2O3, which is named catalyst #1. Example 2

[0026] (1) Mix the spent FCC catalyst with 10 wt% sulfuric acid, with the mass ratio of the spent FCC catalyst to the sulfuric acid solution being 1:4, and place in a 100°C oil bath and stir for 2 h; then filter to obtain an acid leaching solution;

[0027] (2) adding sodium hydroxide to the acid leaching solution, adjusting the pH value of the acid leaching solution to 2.2, and then performing five-stage extraction, and obtaining a raffinate and an organic phase after separation; using 5wt% sulfuric acid for six-stage stripping to obtain a vanadyl sulfate stripping solution, and then removing impurities, removing oil, and concentrating to obtain a vanadyl sulfate electrolyte; the main components of the raffinate after detection and analysis include: vanadium 147 mg / L, iron 166 mg / L, nickel 337 mg / L, manganese 105 mg / L, aluminum 11285 mg / L;

[0028] (3) Add an ethanol solution containing terephthalic acid to the raffinate, wherein the volume fraction of terephthalic acid in the ethanol solution is 50%, and the volume ratio of the raffinate to the ethanol solution is 1:1; after stirring and mixing, transfer the mixture to a hydrothermal reactor and react at 165°C for 12 h to obtain a suspension, separate the solid and liquid, wash, and dry to obtain a solid M-Al-MOF; transfer the mixture to a tubular furnace and calcine at 400°C for 4 h to obtain a carbon monoxide methanation catalyst M2 / Al2O3, which is named catalyst #2. Example 3

[0029] (1) Mix the spent FCC catalyst with 15 wt% sulfuric acid in a mass ratio of 1:3, place in a 120°C oil bath and stir for 1 hour; filter to obtain an acid leaching solution;

[0030] (2) adding sodium hydroxide to the acid leaching solution, adjusting the pH value of the acid leaching solution to 1.8, and then performing five-stage extraction, and obtaining a raffinate and an organic phase after separation; using 5wt% sulfuric acid for six-stage stripping to obtain a vanadyl sulfate stripping solution, and then removing impurities, removing oil, and concentrating to obtain a vanadyl sulfate electrolyte; the main components of the raffinate are detected and analyzed as follows: vanadium 130 mg / L, iron 132 mg / L, nickel 315 mg / L, manganese 93 mg / L, aluminum 10653 mg / L;

[0031] (3) Add an ethanol solution containing terephthalic acid to the raffinate, wherein the volume fraction of terephthalic acid in the ethanol solution is 30%, and the volume ratio of the raffinate to the ethanol solution is 1:1.5; after stirring and mixing, transfer the mixture to a hydrothermal reactor and react at 150°C for 16 hours to obtain a suspension, separate the solid and the liquid, wash, and dry to obtain a solid M-Al-MOF; transfer the mixture to a tubular furnace and calcine at 500°C for 2 hours to obtain a carbon monoxide methanation catalyst M3 / Al2O3, which is named catalyst #3. Example 4

[0032] (1) Mix the waste FCC catalyst with 20 wt% sulfuric acid, with the mass ratio of the waste FCC catalyst to the sulfuric acid solution being 1:2, and place in a 60°C oil bath and stir for 6 hours; then filter to obtain an acid leaching solution;

[0033] (2) adding sodium hydroxide to the acid leaching solution, adjusting the pH value of the acid leaching solution to 2.4, and then performing five-stage extraction, and obtaining a raffinate and an organic phase after separation; using 5wt% sulfuric acid for six-stage stripping to obtain a vanadyl sulfate stripping solution, and then removing impurities, removing oil, and concentrating to obtain a vanadyl sulfate electrolyte; the main components of the raffinate are detected and analyzed as follows: vanadium 123 mg / L, iron 115 mg / L, nickel 306 mg / L, manganese 86 mg / L, aluminum 10237 mg / L;

[0034] (3) Add an ethanol solution containing terephthalic acid to the raffinate, wherein the volume fraction of terephthalic acid in the ethanol solution is 30%, and the volume ratio of the raffinate to the ethanol solution is 1:2; after stirring and mixing, transfer the mixture to a hydrothermal reactor and react at 140°C for 18 hours to obtain a suspension, separate the solid and the liquid, wash, and dry to obtain a solid M-Al-MOF; transfer the mixture to a tubular furnace and calcine at 600°C for 2 hours to obtain a carbon monoxide methanation catalyst M4 / Al2O3, which is named catalyst 4#.

[0035] The inventors have found that the pH range of the acid leaching solution affects the extraction process of vanadium ions, and a pH value outside the range of 1.5-2.4 is not conducive to the extraction of vanadium. Comparative Example 1

[0036] 0.078 g of nickel nitrate was weighed and dissolved in 50 mL of deionized water to obtain a nickel nitrate solution, to which 2.0 g of solid Al2O3 was added. After drying, the solution was transferred to a tube furnace and calcined at 500°C for 2 h to obtain a carbon monoxide methanation catalyst Ni / Al2O3 (the element mass ratio was the same as in Example 3), named catalyst #5. Comparative Example 2

[0037] 6.7 g of aluminum sulfate and 0.078 g of nickel nitrate solid were weighed and dissolved in an aqueous solution, and an ethanol solution containing 30% terephthalic acid was added to the solution, with the volume ratio of the aluminum sulfate solution to the ethanol solution being 1:1.5; after stirring and mixing, the mixture was transferred to a hydrothermal kettle and reacted at 150° C. for 16 h, washed with deionized water, and dried to obtain a solid Ni-Al-MOF, which was calcined at 500° C. for 2 h to obtain a carbon monoxide methanation catalyst Ni / Al2O3 (the element mass ratio was the same as in Example 3), named catalyst #6.

[0038] Morphology observation

[0039] The JEM-2010 transmission electron microscope (TEM) was used to observe the microscopic morphology of the catalyst. The sample was fully ground and ultrasonically dispersed in anhydrous ethanol. After standing, the upper layer of solution was dropped on a copper mesh to prepare the sample, and then tested after drying.

[0040] Figure 2 is the transmission electron microscope image of Example 3, Figure 2 It can be seen that the Al2O3 carrier obtained after calcining M-Al-MOF is evenly distributed and has no obvious agglomeration phenomenon. Figure 2 The figure shows the nickel particles on the catalyst surface in Example 3. The catalyst surface is mainly distributed with 0.20 nm lattice fringes, corresponding to the (111) crystal plane of Ni. The nickel particles are small in size and evenly distributed, indicating that they have a high degree of dispersion. At the same time, no lattice fringes of other metals were found, indicating that the auxiliary metal has a high degree of dispersion in the catalyst, which is mainly due to the formation of the M-Al-MOF structure, which helps to disperse various metals.

[0041] Activity test

[0042] Weigh an appropriate amount of catalyst sample, press, granulate, and sieve, then load it into a fixed-bed reactor for carbon monoxide methanation, introduce hydrogen, heat it to 500°C at a heating rate of 2°C / min, keep it constant for 2h, then reduce the temperature to 200°C, introduce CO to make the volume ratio of CO / H2 1:3, keep it constant for 0.5h, analyze the sample using gas chromatography, and after sampling, heat it to 240°C, keep it constant for 0.5h, and analyze the sample. Repeat this process until the reaction reaches 600°C.

[0043] Stability test

[0044] At a reaction temperature of 400°C, a pressure of 1.0 MPa, and a mass space velocity (WHSV) of 20,000 mL g -1 ·h -1 Under the above conditions, the carbon monoxide methanation stability test was carried out for 100 hours.

[0045] The samples of Examples 1 to 4 and Comparative Examples 1 to 2 were subjected to activity tests (400° C.) and stability tests, and the results are listed in Table 1.

[0046]

[0047] The results show that the CO conversion rate and CH4 selectivity in Examples 1-4 are both greater than 90%, and the activity is relatively excellent, because the catalyst is prepared by forming a MOF structure, which has rich porosity and a large specific surface area, which helps to improve the dispersion of active metal nickel and accelerate the reaction; at the same time, the presence of auxiliary metal iron, manganese, and vanadium elements helps to increase the oxygen vacancies of the catalyst and helps the adsorption and activation of the reactant carbon monoxide; in addition, after 100h of reaction, it still maintains a relatively excellent catalytic activity, because the formation of a complex with the complex enhances the interaction between the active component and the carrier, and is not easy to cause sintering and agglomeration problems; at the same time, the auxiliary agent enters the Al2O3 lattice in a substitution manner, forms oxygen vacancies, increases the mobility of oxygen species, is conducive to the reaction of oxygen species with carbon deposition, and alleviates the problem of catalyst carbon deposition, so the catalyst has excellent stability. At the same time, the CO conversion rate and selectivity show a trend of first increasing and then decreasing, which is because the content of active metal nickel elements in the raffinate increases first and then decreases, and the number of exposed active sites also changes accordingly. Comparative Example 1 uses commercial Al2O3 as a carrier, then loads active metal nickel by an impregnation method, and obtains a catalyst Ni / Al2O3 by calcination reduction. Its CO conversion rate and CH4 selectivity are 75.1% and 68.6%, respectively, which are much lower than the activity of the example. This is because the carrier has a small specific surface area, which is not conducive to the dispersion of the active metal; at the same time, the impregnation method easily leads to a weak interaction between the metal and the carrier, poor dispersion of the active metal, few exposed active sites, and poor activity and stability; Comparative Example 2 lacks additives, and the single active component nickel is not conducive to the adsorption and activation of the reactant carbon monoxide, and has poor activity; compared with the example, the interaction between the active component and the carrier is weak and there are oxygen vacancies. In the stability test, it is easy to cause the problem of nickel carbon deposition and peeling, resulting in catalyst deactivation and poor stability.

Claims

1. A method for preparing a carbon monoxide methanation catalyst, It is characterized in that The steps include: (1) placing the spent catalytic cracking catalyst in a sulfuric acid solution for acid leaching, and filtering to obtain an acid leaching solution; (2) adjusting the pH value of the acid leaching solution to extract vanadium, obtaining a raffinate and a vanadyl sulfate stripping solution, and concentrating the vanadyl sulfate stripping solution to obtain a vanadyl sulfate electrolyte; The nickel in the raffinate is used as an active component, and the metal vanadium, iron and manganese are used as metal additives; (3) Adding an ethanol solution containing terephthalic acid to the raffinate, stirring and mixing, performing a hydrothermal reaction, solid-liquid separation, washing, and drying to obtain a solid M-Al-MOF; calcining and reducing in a hydrogen atmosphere to obtain a carbon monoxide methanation catalyst M / Al 2 O 3 .

2. The preparation method according to claim 1, It is characterized in that In the step (1), the mass fraction of the sulfuric acid solution is 5 to 20 wt %; the mass ratio of the waste catalytic cracking catalyst to the sulfuric acid solution is 1:2 to 4; the acid leaching temperature is 60 to 120° C., and the acid leaching time is 1 to 6 hours.

3. The preparation method according to claim 1, It is characterized in that In the step (2), the pH value of the acid leaching solution is controlled at 1.5 to 2.

4.

4. The preparation method according to claim 1, It is characterized in that In the step (3), the volume ratio of the raffinate to the ethanol solution is 1:0.5-2; the volume fraction of terephthalic acid in the ethanol solution is 30-50%; the hydrothermal reaction temperature is 140-180°C; the hydrothermal reaction time is 8-18h; the roasting reduction temperature is 400-600°C; and the roasting time is 2-4h.

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