Preparation method of graded titanium silicalite molecular sieve containing framework manganese and application of graded titanium silicalite molecular sieve in preparation of adipic acid

Abstract

The invention discloses a preparation method of a graded titanium silicalite molecular sieve containing framework manganese and application of the graded titanium silicalite molecular sieve in preparation of adipic acid, and relates to the technical field of graded zeolite materials and catalysts. The preparation method comprises the following steps: dropwise adding IPA and deionized water into TEOS, dropwise adding tetrapropylammonium hydroxide, and stirring until complete hydrolysis to obtain hydrolysate; preparing a titanium trichloride aqueous solution and a manganese acetate tetrahydrate aqueous solution; dropwise adding into the hydrolysate, and stirring to obtain a colloid; heating and hydrolyzing the jelly, and aging at room temperature overnight to obtain an aging solution; adding a mesoporous template agent into the aging solution, further hydrolyzing, transferring into a hydrothermal kettle, crystallizing, filtering, washing, drying and calcining to obtain the graded titanium silicalite molecular sieve containing framework manganese. According to the method, one-step hydrothermal synthesis is adopted, molecular oxygen can be catalyzed and activated through the molecular sieve, adipic acid is prepared through one-step green oxidation, the technological process is simplified, energy consumption is reduced, three wastes are reduced, and the problem of equipment corrosion is solved.

Description

Technical Field

[0001] The invention relates to the technical field of graded zeolite materials and catalysts, and in particular to a method for preparing a graded titanium silicon molecular sieve containing framework manganese and an application thereof in preparing adipic acid. Background Art

[0002] Adipic acid is an important bulk chemical for the production of nylon-66 resin, food additives, plasticizers and drug synthesis. The global production capacity of adipic acid has reached 3.74 million tons / year, and it is showing a trend of increasing year by year, with an annual growth rate of more than 3.36%. At present, there are three main processes for the industrial preparation of adipic acid: cyclohexane oxidation, cyclohexene hydration, and phenol hydrogenation reduction. Among them, the two-step oxidation of cyclohexane to produce AA is the most widely used method. Specifically, cyclohexane is first oxidized to KA oil in the air, and then KA oil is oxidized with nitric acid to obtain adipic acid with a selectivity of more than 90% ( Figure 1 ).

[0003] However, the two-step oxidation of cyclohexane still has the following shortcomings: 1. The single-pass conversion rate of cyclohexane oxidized by air is low (3%-4%); 2. The process is divided into two steps, and the process flow is complicated; 3. The use of high-concentration nitric acid in the second step leads to high energy consumption and serious equipment corrosion problems; 4. The toxic nitrogen oxides produced during the reaction cause serious environmental pollution and greenhouse effect. Therefore, in order to achieve the goal of "green chemistry", it is of great industrial application significance to design excellent catalysts and develop a new preparation process to directly oxidize cyclohexane to AA using molecular oxygen, hydrogen peroxide and other green oxidants.

[0004] To solve this problem, many processes have proposed the use of green oxidants to produce adipic acid by one-step oxidation of cyclohexane. Yasutaka Ishii et al. developed a solvent-free cyclohexane oxidation process, using N-hydroxyphthalimide (NHPI), Mn(acac)2 and Co(OAc)2 as catalysts, molecular oxygen as an oxidant, and reacting at 100 °C for 20 h to directly oxidize cyclohexane to produce adipic acid, obtaining a cyclohexane conversion rate of 73% and adipic acid selectivity of 73%. Zhong Wenzhou et al. further improved this method, and prepared adipic acid by one-step oxidation of cyclohexane catalyzed by N-hydroxyphthalimide (NHPI) under no catalyst and metal-free conditions, obtaining a cyclohexane conversion rate of 27% and adipic acid selectivity of 79%. However, NHPI catalytic oxidation is a homogeneous reaction, which has problems such as difficult separation and long process flow. The study also found that metal porphyrins can catalyze the oxidation of cyclohexane to produce adipic acid through a green route. Patent CN105884598A uses heme, a catalyst with a single metallo-lene structure, to obtain a product selectivity of more than 90%. In addition, patents CN1247501C and CN1405131A both disclose the use of metalloporphyrin as a catalyst to catalyze the oxidation of cyclohexane to adipic acid, but metalloporphyrin catalysts are difficult to synthesize, expensive, and have a long reaction time, and further improvements are still needed.

[0005] There are also some catalysts such as: Patent CN110872224A discloses acid-modified sepiolite, Patent CN109095493A discloses two-dimensional ultra-thin CuO@SAPO-34 molecular sieve material, Patent CN115301228A discloses multi-metal quasi-crystalline alloy catalyst, Patent CN113559925A discloses heteropoly acid catalyst with multi-metal center, Patent CN115608370A discloses double metal hydroxide catalyst. However, these catalysts have problems such as complicated preparation process, poor solvent tolerance, low cyclohexane conversion rate, low adipic acid yield, etc. Summary of the invention

[0006] In order to solve the above technical problems, the purpose of the present invention is to provide a method for preparing a graded titanium silicon molecular sieve containing framework manganese and its application in the preparation of adipic acid. A one-step hydrothermal synthesis is adopted, and the obtained catalyst can catalytically activate molecular oxygen to achieve a one-step green oxidation preparation of adipic acid, which simplifies the process flow, reduces energy consumption, reduces three wastes, and avoids equipment corrosion problems.

[0007] The technical solution of the present invention to solve the above technical problem is as follows: a method for preparing a graded titanium silicon molecular sieve containing framework manganese is provided, comprising the following steps: (1) adding isopropyl alcohol (IPA, 99 wt%) and deionized water to tetraethyl orthosilicate (TEOS), and then adding tetrapropylammonium hydroxide, and stirring until the tetraethyl orthosilicate is completely hydrolyzed to obtain a hydrolyzate; (2) diluting 0.5 mL of titanium trichloride (20 wt%) in 2 mL of water to obtain a titanium trichloride aqueous solution; dissolving 0-0.624 g of manganese acetate tetrahydrate in 10 g of water to obtain a manganese acetate tetrahydrate aqueous solution; adding the titanium trichloride aqueous solution and the manganese acetate tetrahydrate aqueous solution dropwise to the hydrolyzate obtained in step (1), stirring, to obtain a colloid; (3) hydrolyzing the colloid obtained in step (2) at 55°C for 1 h, then heating to 85°C and continuing the hydrolysis for 8 h, and then aging at room temperature overnight to obtain an aged solution; (4) Add a mesoporous template to the aging solution obtained in step (3), hydrolyze at 80°C for 6 h, then transfer to a Teflon-lined hydrothermal autoclave and crystallize at 175°C for 3 days. After filtering, washing and drying, the temperature is raised to 550°C at a rate of 2°C / min and calcined for 6 h to obtain a graded titanium silicon molecular sieve containing framework manganese.

[0008] Furthermore, in step (1), the mass ratio of tetraethyl orthosilicate, isopropyl alcohol, deionized water and tetrapropylammonium hydroxide is 8-10 g: 3-5 g: 3-5 g: 15-17 g.

[0009] Furthermore, in step (1), the mass ratio of tetraethyl orthosilicate, isopropyl alcohol, deionized water and tetrapropylammonium hydroxide is 9.1 g: 4 g: 4 g: 16 g.

[0010] Furthermore, in step (3), in the aging solution, the molar ratio of SiO2, TiO2, MnO2, TPAOH, and H2O is 1:0.015:0-0.06:0.36:27.

[0011] Furthermore, in step (4), the mesoporous template agent is phenylaminopropyltrimethoxysilane.

[0012] Furthermore, in step (4), drying is performed at a temperature of 80°C.

[0013] The present invention also provides a graded titanium silicon molecular sieve containing framework manganese obtained by the preparation method of the graded titanium silicon molecular sieve containing framework manganese.

[0014] The hierarchical titanium silicon molecular sieve containing framework manganese is named HMTS-x (x=0, 1, 2, 3, 4), where x represents the molar ratio of Mn to Ti species.

[0015] The strategy of the present invention can allow multiple metal ions to enter the zeolite framework simultaneously and selectively, and the strategy is simple to operate. By selecting phenylaminopropyltrimethoxysilane as a mesoporant, it can promote the connection of agglomerated MFI small units by forming Si-O-Si covalent bonds with free metal ions and incorporating them into the framework. This method effectively promotes the formation of hierarchical structures and avoids the formation of titanium ore-type TiO2. This result is inferred from the solid ultraviolet and infrared characterization ( Figure 2 ).

[0016] The present invention also provides the use of the graded titanium silicon molecular sieve containing framework manganese in the preparation of adipic acid by oxidizing cyclohexane.

[0017] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: Cyclohexane, a solvent and a graded titanium silicon molecular sieve containing framework manganese as a catalyst are reacted at 120-150° C. and an oxygen pressure of 1-2.5 MPa for 2-12 h to obtain adipic acid.

[0018] Furthermore, the mass ratio of cyclohexane to solvent is 1:8-1:10; the mass ratio of graded titanium silicon molecular sieve containing framework manganese to cyclohexane is 1:40-1:60.

[0019] The present invention has the following beneficial effects: 1. The strategy of the present invention can simultaneously prepare manganese and titanium into the framework of the graded zeolite, and avoid the formation of anatase-type TiO2, thereby obtaining a multifunctional manganese-containing titanium-silicon molecular sieve zeolite with a graded structure; the addition of framework manganese enhances the surface acidity and oxygen vacancy concentration of the catalyst, which helps to activate oxygen. The framework titanium species is conducive to the activation of cyclohexane CH, and the two show good synergistic effects; under relatively mild conditions, HMTS can efficiently oxidize cyclohexane to prepare adipic acid in one pot, obtaining high cyclohexane conversion rate and adipic acid selectivity. The process is simple, the operation is convenient, the reaction energy consumption is low, the catalyst cost is low, and it has very good industrial application prospects.

[0020] 2. The titanium and manganese species of the catalyst coexist in the framework and will not induce the massive generation of rutile TiO2 and surface aggregated MnOx. The introduction of framework manganese not only increases the surface oxygen vacancies, but also produces stronger surface acidity through interaction with graded TS-1 zeolite. In the preparation process of the catalyst, we adopt the strategy of adding active species and re-coordination at the same time, using divalent manganese acetate as the manganese source. The coordination and calcination oxidation produce more framework manganese, which is highly dispersed in the framework. The catalyst prepared by the above method has a stable structure, low price, strong resistance to sintering and good recyclability. In the catalyst activity test, it shows excellent cyclohexane conversion rate. The present invention has the advantages of high selectivity for adipic acid and green process. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A comparison diagram of the method for preparing adipic acid by oxidizing cyclohexane according to the present invention and a commonly used industrial process; Figure 2 Solid ultraviolet and infrared characterization diagrams of the catalyst prepared in the present invention. DETAILED DESCRIPTION

[0022] The principles and features of the present invention are described below, and the examples are only used to explain the present invention and are not used to limit the scope of the present invention. If no specific conditions are specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially. Example

[0023] A graded titanium silicon molecular sieve containing framework manganese, the preparation method of which comprises the following steps: (1) Add 4 g of isopropyl alcohol (IPA, 99 wt%) and 4 g of deionized water to 9.1 g of tetraethyl orthosilicate (TEOS), and then add 16 g of tetrapropylammonium hydroxide, and stir until the tetraethyl orthosilicate is completely hydrolyzed to obtain a hydrolyzate; (2) diluting 0.5 mL of titanium trichloride (20 wt%) in 2 mL of water to obtain a titanium trichloride aqueous solution; dissolving 0-0.624 g of manganese acetate tetrahydrate in 10 g of water to obtain a manganese acetate tetrahydrate aqueous solution; adding the titanium trichloride aqueous solution and the manganese acetate tetrahydrate aqueous solution dropwise to the hydrolyzate obtained in step (1), stirring, to obtain a colloid; (3) The colloid obtained in step (2) is hydrolyzed at 55°C for 1 h, then heated to 85°C for further hydrolysis for 8 h, and then aged at room temperature overnight to obtain an aged solution; the molar ratio of SiO2, TiO2, MnO2, TPAOH, and H2O is 1:0.015:0-0.06:0.36:27; (4) Add a mesoporous template (phenylaminopropyltrimethoxysilane) to the aging solution obtained in step (3), hydrolyze at 80°C for 6 h, then transfer to a Teflon-lined hydrothermal autoclave and crystallize at 175°C for 3 days. After filtering and washing, dry at 80°C, heat to 550°C at a rate of 2°C / min and calcine for 6 h to obtain a graded titanium silicon molecular sieve containing framework manganese.

[0024] The obtained hierarchical titanium silicon molecular sieve containing framework manganese was named HMTS-x (x=0, 1, 2, 3, 4), where x represents the molar ratio of Mn to Ti species. Example

[0025] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HMTS-1) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0026] The conversion of cyclohexane was 58.3%, and the selectivity of adipic acid was 54.7%. Example

[0027] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HMTS-2) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0028] The conversion of cyclohexane was 74.4%, and the selectivity of adipic acid was 62.2%. Example

[0029] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HMTS-3) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0030] The conversion of cyclohexane was 81.6%, and the selectivity of adipic acid was 71.5%. Example

[0031] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of a graded titanium silicalite (HMTS-4) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0032] The conversion of cyclohexane was 79.1%, and the selectivity of adipic acid was 68.3%. Example

[0033] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HTS-1) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0034] The conversion of cyclohexane was 43.4%, and the selectivity of adipic acid was 41.1%. Example

[0035] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetone) and 0.05 g of hierarchical titanium silicon molecular sieve (HMTS-3) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0036] The conversion of cyclohexane was 61.6%, and the selectivity of adipic acid was 56.4%. Example

[0037] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 10 g of cyclohexane and 0.2 g of a hierarchical titanium silicon molecular sieve (HMTS-3) containing framework manganese as a catalyst were reacted at 140°C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0038] The conversion of cyclohexane was 28.5%, and the selectivity of adipic acid was 58.1%. Example

[0039] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HMTS-3) containing framework manganese as a catalyst were reacted at 140 °C and an oxygen pressure of 2.5 MPa for 6 h to obtain adipic acid.

[0040] The conversion of cyclohexane was 83.4%, and the selectivity of adipic acid was 69.8%. Example

[0041] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HMTS-3) containing framework manganese as a catalyst were reacted at 135 °C and an oxygen pressure of 2 MPa for 6 h to obtain adipic acid.

[0042] The conversion of cyclohexane was 68.8%, and the selectivity of adipic acid was 58.2%. Example

[0043] A method for preparing adipic acid by oxidizing cyclohexane comprises the following steps: 2.4 g of cyclohexane, 21 g of solvent (acetonitrile) and 0.05 g of graded titanium silicalite (HMTS-3) containing framework manganese as a catalyst were reacted at 135 °C and an oxygen pressure of 2 MPa for 12 h to obtain adipic acid.

[0044] The conversion of cyclohexane was 86.5%, and the selectivity of adipic acid was 69.8%.

[0045] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a graded titanium silicon molecular sieve containing framework manganese, characterized in that: The following steps are involved: (1) adding isopropyl alcohol and deionized water dropwise to tetraethyl orthosilicate, and then adding tetrapropylammonium hydroxide dropwise, and stirring until the tetraethyl orthosilicate is completely hydrolyzed to obtain a hydrolyzate; (2) diluting 0.5 mL of 20 wt% titanium trichloride in 2 mL of water to obtain a titanium trichloride aqueous solution; dissolving 0-0.624 g of manganese acetate tetrahydrate in 10 g of water to obtain a manganese acetate tetrahydrate aqueous solution; adding the titanium trichloride aqueous solution and the manganese acetate tetrahydrate aqueous solution dropwise to the hydrolyzate obtained in step (1), stirring, to obtain a colloid; (3) hydrolyzing the colloid obtained in step (2) at 55°C for 1 h, then heating to 85°C for further hydrolysis for 8 h, and then aging at room temperature overnight to obtain an aged solution; (4) Add a mesoporous template to the aging solution obtained in step (3), hydrolyze at 80°C for 6 h, then transfer to a Teflon-lined hydrothermal autoclave and crystallize at 175°C for 3 days. After filtering, washing and drying, the temperature is raised to 550°C at a rate of 2°C / min and calcined for 6 h to obtain a graded titanium silicon molecular sieve containing framework manganese.

2. The method for preparing a graded titanium silicon molecular sieve containing framework manganese according to claim 1, characterized in that: In step (1), the mass ratio of tetraethyl orthosilicate, isopropyl alcohol, deionized water and tetrapropylammonium hydroxide is 8-10 g: 3-5 g: 3-5 g: 15-17 g.

3. The method for preparing a graded titanium silicon molecular sieve containing framework manganese according to claim 1 or 2, characterized in that: In step (1), the mass ratio of tetraethyl orthosilicate, isopropyl alcohol, deionized water and tetrapropylammonium hydroxide is 9.1 g: 4 g: 4 g: 16 g.

4. The method for preparing a graded titanium silicon molecular sieve containing framework manganese according to claim 1, characterized in that: In step (3), in the aging solution, the molar ratio of SiO2, TiO2, MnO2, TPAOH, and H2O is 1:0.015:0-0.06:0.36:

27.

5. The method for preparing a graded titanium silicon molecular sieve containing framework manganese according to claim 1, characterized in that: In step (4), the mesoporous template is phenylaminopropyltrimethoxysilane.

6. The method for preparing a graded titanium silicon molecular sieve containing framework manganese according to claim 1, characterized in that: In step (4), drying is performed at 80°C.

7. The graded titanium silicon molecular sieve containing framework manganese obtained by the preparation method of the graded titanium silicon molecular sieve containing framework manganese according to any one of claims 1 to 5.

8. Use of the graded titanium silicon molecular sieve containing framework manganese as claimed in claim 7 in the preparation of adipic acid by oxidation of cyclohexane.

9. A method for preparing adipic acid by oxidizing cyclohexane, characterized in that: The following steps are involved: Cyclohexane, a solvent and the graded titanium silicon molecular sieve containing framework manganese as claimed in claim 7 as a catalyst are reacted at 120-150° C. and an oxygen pressure of 1-2.5 MPa for 2-12 h to obtain adipic acid.

10. The method for preparing adipic acid by oxidizing cyclohexane according to claim 9, characterized in that: The mass ratio of cyclohexane to solvent is 1:8-1:10; the mass ratio of graded titanium silicon molecular sieve containing framework manganese to cyclohexane is 1:40-1:60.

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