A heavy aromatics lightening catalyst and preparation method thereof

Abstract

The present invention relates to the field of catalyst technology and discloses a catalyst for lightweighting heavy aromatic hydrocarbons and a preparation method thereof. The present invention adds deionized water, a nickel source, and a molybdenum source to a container, stirs the solution, and pours it into a container containing a modified molecular sieve. After impregnation, the solution is dried, roasted, and cooled to obtain a catalyst for lightweighting heavy aromatic hydrocarbons. A large number of carboxyl groups, imino groups, and hydroxyl groups are introduced on the surface of the molecular sieve to form a coordination complex with nickel and molybdenum. After high-temperature calcination, the generated nickel-molybdenum oxide can be evenly distributed in the molecular sieve matrix, has more nickel-molybdenum catalytic active centers, and can effectively catalyze C 9+ The production of light aromatics BTX from heavy aromatics has a good practical application in the catalytic preparation of light aromatics BTX from heavy aromatics.

Description

Technical Field

[0001] The present invention relates to the technical field of catalysts, and in particular to a catalyst for lightweighting heavy aromatics and a preparation method thereof. Background Art

[0002] A large amount of heavy aromatic hydrocarbons with carbon atoms ≥ 9 are produced in processes such as petroleum reforming and ethylene cracking. These hydrocarbons contain monocyclic alkyl aromatic hydrocarbons and polycyclic aromatic hydrocarbons. The composition is very complex and difficult to separate and purify. Most heavy aromatic hydrocarbons can only be used as fuel, resulting in serious waste of resources. The lightweighting technology of heavy aromatic hydrocarbons can convert heavy aromatic hydrocarbons into light aromatic hydrocarbons such as benzene, toluene and xylene. It is an important technology to improve the utilization rate of heavy aromatic hydrocarbons. The development of catalysts for lightweighting of heavy aromatic hydrocarbons is a research focus.

[0003] Current catalysts for converting heavy aromatics to light aromatics primarily utilize molecular sieves as catalyst supports, loaded with metal oxide active catalytic centers. Improving the dispersion of the metal oxides within the support effectively enhances the catalyst's catalytic performance. Chinese patent application CN118028015A discloses a method for converting heavy aromatics to light aromatics. Using a ZrO2-modified USY molecular sieve as a support, the method improves the dispersibility and stability of the nickel-cobalt alloy, enhancing the catalyst's sintering resistance and catalytic activity. However, the catalyst's conversion rate to heavy aromatics was poor, and it also failed to demonstrate a high yield of light aromatics, indicating poor catalytic performance. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the present invention provides a catalyst for the lightweighting of heavy aromatics and a preparation method thereof, which solves the problem that nickel-molybdenum catalysts have poor effect in catalyzing the lightweighting of heavy aromatics.

[0005] In order to solve the above technical problems, the technical solution of the present invention is: a preparation method of a heavy aromatics lightweighting catalyst:

[0006] (1) Add 100 parts by weight of silica sol and an aqueous solution containing 0.4-0.7 parts by weight of sodium hydroxide into a container, stir for 1-1.5 hours, add 1-3.5 parts by weight of 3-aminopropyltrimethoxysilane, stir for 1-1.5 hours, add an aqueous solution containing 8-13 parts by weight of tetraethylammonium hydroxide, stir for 1-1.5 hours, place the sol in a reactor, crystallize at 140-150°C for 72-120 hours, cool, wash with water and ethanol, and dry to obtain an amino molecular sieve.

[0007] (2) Add solvent and amino molecular sieve to the reaction vessel, disperse by ultrasonication, then add sodium glycidyl glutamate, stir and react, then dropwise add 5-12% hydrochloric acid solution to adjust the pH to 4-5, filter, wash with water and ethanol in turn, and dry to obtain the modified molecular sieve. The preparation reaction formula is:

[0008] .

[0009] (3) Deionized water, nickel source, and molybdenum source are added to the container, stirred, and then the solution is poured into the container containing the modified molecular sieve, and immersed at 20-35°C for 4-7 hours; then dried at 100-120°C for 4-8 hours; finally, calcined in a muffle furnace at 500-550°C for 2-3 hours, cooled, and a heavy aromatics lightweighting catalyst is obtained.

[0010] Furthermore, the solvent in (2) is tetrahydrofuran, methanol or ethanol.

[0011] Furthermore, the mass ratio of (2) the amino molecular sieve and sodium epoxypropyl glutamate is 100:(120-300).

[0012] Furthermore, the reaction temperature in (2) is 50-75°C, and the reaction time is 18-24h.

[0013] Furthermore, the mass ratio of nickel source, molybdenum source and modified molecular sieve in (3) is (12-20):(25-45):100.

[0014] Furthermore, the nickel source is nickel nitrate or nickel sulfate.

[0015] Furthermore, the molybdenum source is ammonium molybdate tetrahydrate.

[0016] (III) Beneficial technical effects: The present invention utilizes sodium epoxypropylglycinate containing two carboxyl groups to react with amino molecular sieves, introducing a large number of carboxyl groups, imino groups, and hydroxyl groups on the surface of the molecular sieve, which react with nickel and molybdenum to form a coordination complex, so that the nickel-molybdenum precursor can be evenly dispersed in the molecular sieve matrix. After high-temperature calcination, the generated nickel-molybdenum oxide can be evenly distributed in the molecular sieve matrix, with more nickel-molybdenum catalytic active centers, which can effectively catalyze C 9+ The conversion of heavy aromatics to light aromatics BTX significantly increased the C 9+ The conversion rate of heavy aromatics, total BTX selectivity and BTX yield have good practical applications in the catalytic preparation of light aromatics BTX from heavy aromatics, and also have broad application prospects in oil hydrodesulfurization catalysis and other aspects. DETAILED DESCRIPTION

[0017] The mass fraction of silicon dioxide in the following silica sol is 30%.

[0018] Add 30 mL of deionized water and 2.94 g of glutamic acid to a reaction vessel, stir, and then dropwise add a 1 mol / L sodium hydroxide solution. Adjust the pH to 10, heat to 70°C, stir, and dropwise add 4.8 mL of epichlorohydrin. Control the addition time to 10 minutes. Heat to 80°C, react for 8 hours, concentrate under reduced pressure, dry, add ethanol, filter, concentrate the filtrate under reduced pressure, and dry to obtain sodium glycidyl glutamate. The structural formula is: .

[0019] Add 30 mL of deionized water and 3 g of glycine to a reaction vessel, stir, and then dropwise add a 1 mol / L sodium hydroxide solution. Adjust the pH to 11 and heat to 70°C. Stir and dropwise add 7.85 mL of epichlorohydrin over a 10-minute addition period. Heat to 80°C and react for 7 hours. Concentrate under reduced pressure, dry, and add ethanol. Filter, concentrate the filtrate under reduced pressure, and dry to obtain sodium glycidyl glycinate. The structural formula is: .

[0020] Example 1:

[0021] (1) Add 10 g of silica sol and 1 mL of an aqueous solution containing 0.05 g of sodium hydroxide into a container, stir for 1 h, add 0.16 g of 3-aminopropyltrimethoxysilane, stir for 1 h, add 5 mL of an aqueous solution containing 1.3 g of tetraethylammonium hydroxide, stir for 1.5 h, place the sol in a reactor, crystallize at 140 ° C for 120 h, cool, wash with water and ethanol, and dry to obtain an amino molecular sieve.

[0022] (2) Add 400 mL of tetrahydrofuran and 20 g of amino molecular sieves to the reaction vessel, ultrasonically disperse for 10 min, add 36 g of sodium glycidyl glutamate, heat to 60 ° C, stir and condense reflux for 18 h, add 12% mass fraction hydrochloric acid solution to adjust the pH to 4, filter, wash with water and ethanol in turn, and dry to obtain a modified molecular sieve.

[0023] (3) Add 12 mL of deionized water, 2.4 g of nickel nitrate, and 9 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 25 °C for 7 h; then dry it at 100 °C for 8 h; finally, calcine it at 500 °C in a muffle furnace for 3 h, and cool it to obtain a heavy aromatics lightweighting catalyst.

[0024] Example 2:

[0025] (1) Add 10 g of silica sol and 1 mL of an aqueous solution containing 0.04 g of sodium hydroxide into a container and stir for 1.5 h. Add 0.1 g of 3-aminopropyltrimethoxysilane and stir for 1.5 h. Add 5 mL of an aqueous solution containing 0.8 g of tetraethylammonium hydroxide and stir for 1 h. Place the sol in a reactor and crystallize at 145 ° C for 96 h. After cooling, wash with water and ethanol and dry to obtain an amino molecular sieve.

[0026] (2) Add 400 mL of methanol and 20 g of amino molecular sieves to the reaction vessel, ultrasonically disperse for 20 min, add 24 g of sodium glycidyl glutamate, heat to 50 ° C, stir and condense reflux for 24 h, add 5% hydrochloric acid solution by mass to adjust the pH to 5, filter, wash with water and ethanol in turn, and dry to obtain a modified molecular sieve.

[0027] (3) Add 14 mL of deionized water, 4 g of nickel sulfate, and 5 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 20 °C for 7 h; then dry it at 110 °C for 8 h; finally, calcine it at 500 °C in a muffle furnace for 3 h and cool it to obtain a catalyst for lightweighting heavy aromatics.

[0028] Example 3:

[0029] (1) Add 10 g of silica sol and 2 mL of an aqueous solution containing 0.07 g of sodium hydroxide into a container and stir for 1 h. Add 0.24 g of 3-aminopropyltrimethoxysilane and stir for 1.5 h. Add 5 mL of an aqueous solution containing 1 g of tetraethylammonium hydroxide and stir for 1 h. Place the sol in a reactor and crystallize at 140 ° C for 120 h. After cooling, wash with water and ethanol and dry to obtain an amino molecular sieve.

[0030] (2) Add 500 mL of ethanol and 20 g of amino molecular sieves to the reaction vessel, ultrasonically disperse for 10 min, add 60 g of sodium glycidyl glutamate, heat to 75 ° C, stir and condense reflux for 18 h, add 10% hydrochloric acid solution by mass fraction to adjust the pH to 4, filter, wash with water and ethanol in turn, and dry to obtain a modified molecular sieve.

[0031] (3) Add 14 mL of deionized water, 3.5 g of nickel sulfate, and 6.4 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 35 °C for 4 h; then dry it at 120 °C for 4 h; finally, calcine it at 550 °C in a muffle furnace for 2 h and cool it to obtain a heavy aromatics lightweighting catalyst.

[0032] Example 4:

[0033] (1) Add 10 g of silica sol and 2 mL of an aqueous solution containing 0.05 g of sodium hydroxide into a container, stir for 1.5 h, add 0.35 g of 3-aminopropyltrimethoxysilane, stir for 1 h, add 3 mL of an aqueous solution containing 1.2 g of tetraethylammonium hydroxide, stir for 1.5 h, place the sol in a reactor, crystallize at 150 ° C for 72 h, cool, wash with water and ethanol, and dry to obtain an amino molecular sieve.

[0034] (2) Add 500 mL of tetrahydrofuran and 20 g of amino molecular sieves to the reaction vessel, ultrasonically disperse for 20 min, add 48 g of sodium glycidyl glutamate, heat to 60 ° C, stir and condense reflux for 18 h, add 5% hydrochloric acid solution by mass to adjust the pH to 5, filter, wash with water and ethanol in turn, and dry to obtain a modified molecular sieve.

[0035] (3) Add 12 mL of deionized water, 3 g of nickel nitrate, and 7.7 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 25 °C for 7 h; then dry it at 100 °C for 6 h; finally, calcine it at 500 °C in a muffle furnace for 3 h and cool it to obtain a heavy aromatics lightweighting catalyst.

[0036] Comparative Example 1:

[0037] (1) 12 mL of deionized water, 2.4 g of nickel nitrate, and 9 g of ammonium molybdate tetrahydrate were added to a container, stirred, and then poured into a container containing 20 g of amino molecular sieve (prepared according to the method of Example 1), and immersed at 25°C for 7 h; then dried at 100°C for 8 h; finally, calcined in a muffle furnace at 500°C for 3 h, and cooled to obtain a heavy aromatics lightweighting catalyst.

[0038] Comparative Example 2:

[0039] (1) Add 10 g of silica sol and 1 mL of an aqueous solution containing 0.05 g of sodium hydroxide into a container and stir for 1 h. Add 5 mL of an aqueous solution containing 1.3 g of tetraethylammonium hydroxide and stir for 1.5 h. Place the sol in a reactor and crystallize at 140 °C for 120 h. After cooling, wash with water and ethanol and dry to obtain a molecular sieve.

[0040] (2) Add 400 mL of tetrahydrofuran and 20 g of molecular sieves to the reaction vessel, ultrasonically disperse for 10 min, add 36 g of sodium glycidyl glutamate, heat to 60 ° C, stir and reflux for 18 h, add 12% hydrochloric acid solution by mass to adjust the pH to 4, filter, wash with water and ethanol in turn, and dry to obtain a modified molecular sieve.

[0041] (3) Add 12 mL of deionized water, 2.4 g of nickel nitrate, and 9 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 25 °C for 7 h; then dry it at 100 °C for 8 h; finally, calcine it at 500 °C in a muffle furnace for 3 h, and cool it to obtain a heavy aromatics lightweighting catalyst.

[0042] Comparative Example 3:

[0043] (1) Add 400 mL of tetrahydrofuran and 20 g of amino molecular sieve (prepared according to the method of Example 1) to a reaction vessel, ultrasonically disperse for 10 min, add 36 g of sodium glycidyl glycinate, heat to 60 ° C, stir and react for 18 h, add 12% mass fraction hydrochloric acid solution dropwise to adjust the pH to 4, filter, wash with water and ethanol in sequence, and dry to obtain a modified molecular sieve.

[0044] (2) Add 12 mL of deionized water, 2.4 g of nickel nitrate, and 9 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 25 °C for 7 h; then dry it at 100 °C for 8 h; finally, calcine it at 500 °C in a muffle furnace for 3 h, and cool it to obtain a catalyst for lightweighting heavy aromatics.

[0045] Comparative Example 4:

[0046] (1) Add 400 mL of tetrahydrofuran and 20 g of amino molecular sieve (prepared according to the method of Example 1) to a reaction vessel, ultrasonically disperse for 10 min, add 36 g of propylene oxide, heat to 60 ° C, stir and react for 18 h, add 12% mass fraction hydrochloric acid solution dropwise to adjust the pH to 4, filter, wash with water and ethanol in sequence, and dry to obtain a modified molecular sieve.

[0047] (2) Add 12 mL of deionized water, 2.4 g of nickel nitrate, and 9 g of ammonium molybdate tetrahydrate into a container, stir, and pour the solution into a container containing 20 g of modified molecular sieves. Immerse the solution at 25 °C for 7 h; then dry it at 100 °C for 8 h; finally, calcine it at 500 °C in a muffle furnace for 3 h, and cool it to obtain a catalyst for lightweighting heavy aromatics.

[0048] The catalyst was ground into powder, 5 g was weighed and placed in a fixed bed reactor, activated in hydrogen at 500 °C for 2 h, and then heated to C 9+ Heavy aromatics were used as raw materials and injected at 370 °C with a space velocity of 2 h -1 , H2 and C 9+ The volume ratio of heavy aromatics was 1200:1, the reaction pressure was 5 MPa, and the reaction temperature was 380°C. The components of the raw materials and products were determined by gas chromatography. Calculation of C 9+ Heavy aromatics conversion, BTX (light aromatics benzene, toluene and xylene) total selectivity, BTX yield.

[0049] C 9+ Heavy aromatics conversion rate = (n0-n) / n0×100%, n0 is the C 9+ The molar amount of heavy aromatics, n is the C 9+ Molar amount of heavy aromatics.

[0050] Total BTX selectivity = (N-N0) / (n0-n) × 100%, where N is the molar amount of BTX in the product and N0 is the molar amount of light aromatic BTX in the feedstock.

[0051] BTX yield = C 9+ Heavy aromatics conversion × total BTX selectivity.

[0052] Table 1 Catalyst performance

[0053]

[0054] After testing, the C of comparative example 1 9+ The conversion rate of heavy aromatics and the yield of BTX are low, while the C 9+ The conversion rate of heavy aromatics reaches 65.14-77.63%, and the BTX yield reaches 48.38-75.98%, which has excellent performance in catalyzing heavy aromatics to light aromatics BTX. This is mainly because in each embodiment, sodium epoxypropyl glycinate is reacted with amino molecular sieve to introduce a large number of carboxyl groups, imino groups, and hydroxyl groups on the surface of the molecular sieve, which undergo coordination and complexation with nickel and molybdenum, so that the nickel-molybdenum precursor can be evenly dispersed in the molecular sieve matrix. After high-temperature calcination, the generated nickel-molybdenum oxide can be evenly distributed in the molecular sieve matrix, has more nickel-molybdenum catalytic active centers, and can effectively catalyze C 9+ Heavy aromatics generate light aromatics BTX.

[0055] The molecular sieve of Comparative Example 2 does not contain amino groups and cannot react with the epoxy matrix of sodium glycidyl glutamate. After washing, sodium glycidyl glutamate will be eluted and removed from the molecular sieve, resulting in the molecular sieve containing no carboxyl, imino, or hydroxyl groups, and having a low coordination and complexing effect with nickel and molybdenum, resulting in the nickel-molybdenum precursor and the generated nickel-molybdenum oxide being difficult to be evenly distributed in the molecular sieve matrix. There are fewer nickel-molybdenum catalytic active centers and the catalytic activity is poor, making it difficult to effectively catalyze heavy aromatics to produce light aromatics BTX, and the BTX yield is low.

[0056] Comparative Example 3 uses sodium epoxypropylglycinate containing one carboxyl group to react with amino molecular sieve. The carboxyl content of the obtained modified molecular sieve is less than that of Example 1, resulting in a lower coordination and complexation reaction between the molecular sieve and nickel and molybdenum than that of Example 1. The nickel-molybdenum precursor and the generated nickel-molybdenum oxide are difficult to be evenly distributed in the molecular sieve matrix. There are fewer nickel-molybdenum catalytic active centers and the catalytic activity is poor, resulting in C9+ The conversion rate of heavy aromatics and BTX yield are low.

[0057] Comparative Example 4 uses propylene oxide to react with amino molecular sieves. The modified molecular sieve obtained does not contain carboxyl groups, and the coordination and complexation with nickel and molybdenum is lower than that in Example 1, resulting in that the nickel-molybdenum precursor and the generated nickel-molybdenum oxide are difficult to be evenly distributed in the molecular sieve matrix, the nickel-molybdenum catalytic active centers are less, and the catalytic activity is poor, resulting in C 9+ The conversion rate of heavy aromatics and BTX yield are low.

Claims

1. A method for preparing a catalyst for lightweighting heavy aromatics, characterized in that: The preparation method comprises: (1) Adding a solvent and amino molecular sieves to a reaction vessel, dispersing them by ultrasonication, then adding sodium glycidyl glutamate, stirring for reaction, and then dropping a hydrochloric acid solution, filtering, washing, and drying to obtain a modified molecular sieve; (2) adding deionized water, nickel source, and molybdenum source into a container, stirring, and then pouring the solution into a container containing a modified molecular sieve, impregnating, drying, roasting, and cooling to obtain a heavy aromatics lightweighting catalyst; The mass ratio of amino molecular sieve and sodium glycidyl glutamate in (1) is 100:(120-300); The preparation method of the amino molecular sieve comprises the following steps: adding 100 parts by weight of silica sol and an aqueous solution containing 0.4-0.7 parts by weight of sodium hydroxide into a container, stirring for 1-1.5 hours, adding 1-3.5 parts by weight of 3-aminopropyltrimethoxysilane, stirring for 1-1.5 hours, adding an aqueous solution containing 8-13 parts by weight of tetraethylammonium hydroxide, stirring for 1-1.5 hours, placing the sol in a reaction kettle, crystallizing at 140-150° C. for 72-120 hours, cooling, washing, and drying to obtain the amino molecular sieve.

2. The method for preparing a catalyst for lightweighting heavy aromatics according to claim 1, wherein: The solvent in (1) is tetrahydrofuran, methanol or ethanol.

3. The preparation method of the heavy aromatics lightweighting catalyst according to claim 1, characterized in that: The reaction temperature in (1) is 50-75°C and the reaction time is 18-24h.

4. The method for preparing a catalyst for lightweighting heavy aromatics according to claim 1, wherein: In (1), hydrochloric acid solution is added dropwise to adjust the pH to 4-5; The mass fraction of the hydrochloric acid solution is 5-12%.

5. The method for preparing a catalyst for lightweighting heavy aromatics according to claim 1, wherein: The mass ratio of the nickel source, molybdenum source and modified molecular sieve in (2) is (12-20): (25-45):

100.

6. The method for preparing a catalyst for lightweighting heavy aromatics according to claim 5, characterized in that: The nickel source is nickel nitrate or nickel sulfate; the molybdenum source is ammonium molybdate tetrahydrate.

7. The method for preparing a catalyst for lightweighting heavy aromatics according to claim 1, wherein: The temperature for the immersion in (2) is 20-35°C and the time is 4-7h; the temperature for the drying is 100-120°C and the time is 4-8h; the temperature for the calcination is 500-550°C and the time is 2-3h.

8. A catalyst for lightening heavy aromatics obtained by the preparation method according to any one of claims 1 to 7.

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