Preparation method of catalyst for preparing ethylene sulfate by oxidizing vinylene sulfate

Abstract

The invention discloses a preparation method of a catalyst for preparing ethylene sulfate by oxidizing vinylene sulfate, and belongs to the technical field of catalysts. Mixing water, an alkaline organic template agent, a silicon source, a titanium source, an additive and a seed crystal according to a certain feeding ratio to prepare initial gel, and performing crystallization after formation at normal temperature; then adding a proper amount of alkaline organic template agent to the mixture, and carrying out secondary crystallization; the hierarchical pore TS-1 molecular sieve is synthesized by adopting a strategy of dynamic control and gradient alkali concentration; the prepared molecular sieve has a rich mesoporous structure, and is beneficial to rapid diffusion of reactants and products from a catalyst, so that the catalytic activity is remarkably improved; the problem of insufficient catalyst activity caused by diffusion resistance in the prior art is effectively solved, and the performance of the catalyst is remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of catalysts and relates to a method for preparing a catalyst for preparing vinyl sulfate by oxidizing vinylidene sulfate. Background Art

[0002] As an important chemical raw material, vinyl sulfate (ES) has attracted much attention due to its application in lithium-ion battery electrolytes. Vinyl sulfate can effectively inhibit the decline in the initial capacity of the battery, increase the initial discharge capacity, and reduce the battery expansion at high temperatures, thereby reducing capacity decay and internal resistance and improving the stability of the graphite negative electrode. Vinyl sulfate can also be used to synthesize antihypertensive drugs and new dual surfactants. With the rapid development of new energy vehicles around the world, the market demand for vinyl sulfate is increasing, which has prompted the research and development of its green and efficient synthesis methods.

[0003] At present, the synthesis methods for preparing vinyl sulfate mainly include direct acylation method, substitution method, addition method, oxidation method, etc. The oxidation method is mainly used in industry, and the key to this method lies in the selection of catalyst. However, there are many challenges in the preparation of vinyl sulfate in the traditional oxidation process, such as the high cost of using precious metal catalysts, the generation of a large amount of salt-containing wastewater, and the difficulty in recycling the catalyst. Therefore, the development of a new catalyst to achieve efficient and environmentally friendly synthesis of vinyl sulfate, reduce waste emissions, and reduce production costs has become a hot topic in this field.

[0004] TS-1 molecular sieve, full name titanium silicon molecular sieve, is a highly efficient catalyst with MFI topology. It is famous for its unique pore structure and specific surface area. The tetracoordinated Ti atoms in its framework replace silicon atoms to form a tetracoordinated TiO4 structure in the framework. These tetracoordinated Ti atoms are the active centers for catalytic selective oxidation reactions. Together with silicon atoms, they form a framework Si-O-Ti bond with special properties. This structure gives TS-1 molecular sieve excellent catalytic oxidation activity and shape-selective catalytic performance. Because there are no strongly acidic Al ions in the framework, TS-1 exhibits strong hydrophobicity, which makes it have unique catalytic performance in the oxidation reactions of various organic compounds with the participation of H2O2. Using TS-1 molecular sieve as a catalyst, the oxidation of vinylene sulfate to vinyl sulfate can be efficiently catalyzed even at a mild temperature (35°C) under the condition of H2O2 as an oxidant. Importantly, this process does not produce other harmful chemical components, so it is considered to be an environmentally friendly green process. This green synthesis method not only improves the production efficiency of vinyl sulfate, but also reduces the impact on the environment, demonstrating the important application potential of TS-1 molecular sieve in chemical synthesis.

[0005] However, in the process of vinylene sulfate oxidation to vinyl sulfate, the design of TS-1 molecular sieve catalyst is a key factor in achieving efficient conversion. Compared with the traditional high-temperature process, the reduction in molecular diffusion rate under mild temperature liquid phase conditions becomes a limiting factor, which limits the effective contact between liquid reactants and catalyst active sites. To overcome this challenge, the TS-1 molecular sieve catalyst design strategy can focus on improving the accessibility of catalyst active sites. The commonly used method is to prepare multi-level pore TS-1 molecular sieve.

[0006] The strategies for synthesizing hierarchical molecular sieves mainly include soft template method, hard template method, post-treatment method, seed method and kinetic control method. Among these methods, the kinetic control method is particularly favored because it does not require the addition of expensive or toxic mesoporous template agents. In his degree thesis at Jilin University, Zhang Qiang elaborated on the concept of molecular sieve growth kinetics in detail, pointing out that by finely controlling multiple parameters in the synthesis system, such as the type of raw materials, the nature and dosage of the template agent, the amount of water and alkalinity in the system, the temperature and time of crystallization, and whether to introduce seed crystals, the diffusion rate and agglomeration mode of atoms, clusters and nanoparticles can be effectively controlled. This precise control method can ultimately achieve precise control of the crystal nucleation and growth process. In this way, molecular sieves with hierarchical pores can be precisely designed and synthesized to optimize their catalytic performance and application potential.

[0007] In the field of molecular sieve synthesis, the activation energy requirement in the nucleation stage is significantly higher than that in the crystal growth stage. This phenomenon indicates that the synthesis process of molecular sieves is mainly controlled by the nucleation of zeolites. Studies have shown that excessive alkalinity is not conducive to the nucleation process, but a high alkalinity environment is conducive to the formation of small crystals or mesoporous molecular sieves. Moreover, in the prior art, the traditional method of synthesizing multi-level pore TS-1 molecular sieves often requires the introduction of mesoporous templates (whether soft templates or hard templates), or relies on complex post-processing steps. These processes are not only cumbersome, but may also affect the quality and performance of multi-level pore molecular sieves. Summary of the invention

[0008] The present invention overcomes the shortcomings of the prior art and proposes a method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinyl sulfate; specifically, a method for synthesizing a multi-level pore TS-1 molecular sieve, wherein the prepared TS-1 molecular sieve has a rich mesoporous structure, which is conducive to rapid diffusion of reactants and products from the catalyst at a reaction temperature of 35°C-40°C, thereby significantly improving the catalytic activity. The present invention is achieved by the following technical solutions: A method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate comprises the following steps: S1. Mix water, alkaline organic template, silicon source, titanium source, additive and seed crystal according to the feeding ratio to prepare an initial gel, then cure at room temperature for 0.5-2 hours, and then crystallize at a temperature range of 140°C to 170°C for 2-48 hours; the feeding molar ratio of the initial gel is H2O: alkaline organic template: SiO2: TiO2: additive = 10-30: 0.1-0.3: 1: 1 / 40-1 / 100: 0.1; S2: After the above steps are completed, the reactor is opened, and an alkaline organic template is added thereto for a second time, and secondary crystallization is performed at a temperature range of 140°C to 170°C for 12 to 48 hours; after the reaction is completed, separation, washing and drying are performed; the mass ratio of the alkaline organic template added for the second time is 0.5 to 1 times the mass ratio of the alkaline organic template added for the first time.

[0009] Preferably, the alkaline organic template is tetrapropylammonium hydroxide or tetraethylammonium hydroxide.

[0010] Preferably, the silicon source is one of tetraethyl orthosilicate, silica sol, fumed silica, and silica gel.

[0011] Preferably, the titanium source is tetraethyl titanate or n-butyl titanate.

[0012] Preferably, the additive is one of triethanolamine, N-methylpyrrolidone, amide additives, and isopropanol.

[0013] Preferably, the amount of seed crystal added is 5%-30% of the mass of the silicon source.

[0014] More preferably, the amount of seed crystal added is 5%-15% of the mass of the silicon source.

[0015] Preferably, the seed crystal is Silicalite-1 molecular sieve.

[0016] Preferably, in step S1, the crystallization temperature is 150° C. to 170° C., and the crystallization time is 12 to 24 hours.

[0017] Preferably, in step S2, the crystallization temperature is 150° C. to 170° C., and the time is 12 to 24 hours.

[0018] The beneficial effects of the present invention compared with the prior art are as follows: The present invention successfully overcomes the limitations of traditional methods by introducing Silicalite-1 molecular sieve seeds into the initial gel and adopting kinetic control and gradient alkali concentration strategy to synthesize multi-level pore TS-1 molecular sieve. In addition, due to the growth under high alkalinity conditions, this method can also promote the rearrangement of titanium (Ti) atoms in the framework, thereby forming more active sites, further improving the catalytic activity and selectivity of the molecular sieve. This innovative method not only simplifies the synthesis process of multi-level pore TS-1 molecular sieve, but also improves its performance, and has important industrial application value.

[0019] The present invention adopts a strategy of adding alkaline organic templates in stages to optimize nucleation and growth conditions. Specifically, the nucleation process is promoted under low alkalinity conditions, and then crystal growth is carried out under high alkalinity conditions to facilitate the formation of small grains or mesoporous molecular sieves. In addition, the process can also effectively dissolve the introduced seed crystals, thereby successfully preparing a TS-1 molecular sieve with a multi-level pore structure. This synthesis strategy not only optimizes the nucleation and growth conditions, but also provides an effective way to prepare high-performance multi-level pore TS-1 molecular sieves. Through this strategy, the microstructure of the molecular sieve can be accurately controlled, thereby improving its catalytic performance and application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The XRD diagrams of the TS-1 molecular sieves of Comparative Example 1 and Examples 1 to 3 are shown.

[0021] Figure 2 The SEM images of the TS-1 molecular sieves of Comparative Example 1 and Examples 1 to 3 are shown.

[0022] Figure 3 The external surface area data of the TS-1 molecular sieves of Comparative Example 1 and Examples 1 to 3 are shown.

[0023] Figure 4 The mesopore volume data of the TS-1 molecular sieves of Comparative Example 1 and Examples 1 to 3 are shown. DETAILED DESCRIPTION

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention is further described in detail in conjunction with the embodiments and the accompanying drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. The technical solutions of the present invention are described in detail below in conjunction with the embodiments and the accompanying drawings, but the scope of protection is not limited thereto. The preparation method of the catalyst for preparing vinyl sulfate by oxidation of vinyl sulfate of the present invention is further described by specific embodiments, specifically a synthetic method of a multi-stage pore TS-1 molecular sieve.

[0025] Example 1 This embodiment provides a method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to the present invention, specifically a method for synthesizing a multi-level pore TS-1 molecular sieve, comprising: Step (1): First, 6.25 g of deionized water, 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%), 6.0 g of silica sol (mass fraction 25%) and 7.5% of Silicalite-1 molecular sieve were added to a beaker in sequence and mixed evenly to obtain solution A. Next, 0.2 g of tetrabutyl titanate (purity 98.5%) and 0.18 g of isopropanol (purity 99.0%) were mixed in another container and stirred thoroughly until uniform to obtain solution B. Then, solution A and solution B were mixed at room temperature and stirred continuously for 30 minutes, and then the mixed solution was charged into a stainless steel reactor. Crystallization treatment was performed at a reaction temperature of 170 °C for 24 hours.

[0026] Step (2): Open the stainless steel reactor and add 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%). After the addition, stir the mixture in the reactor at room temperature for 2 hours to ensure that the tetrapropylammonium hydroxide is fully mixed with other components in the system. After the stirring is completed, the reactor is reset to 170 ° C and crystallized at this temperature for 24 hours. After the crystallization process is completed, the reactor is quickly cooled, and through centrifugation and washing and drying steps, the sample of Example 1 is finally obtained, which is recorded as S-1. This process is intended to optimize the crystallization conditions to obtain a multi-level pore TS-1 molecular sieve.

[0027] Example 2 This embodiment provides a method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to the present invention, specifically a method for synthesizing a multi-level pore TS-1 molecular sieve, comprising: Step (1): First, 6.25 g of deionized water, 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%), 6.0 g of silica sol (mass fraction 25%) and 10.5% of Silicalite-1 molecular sieve were added to a beaker in sequence and mixed evenly to obtain solution A. Next, 0.4 g of tetrabutyl titanate (purity 98.5%) and 0.18 g of isopropanol (purity 99.0%) were mixed in another container and stirred thoroughly until uniform to obtain solution B. Then, solution A and solution B were mixed at room temperature and stirred continuously for 30 minutes, and then the mixed solution was charged into a stainless steel reactor. Crystallization treatment was performed at a reaction temperature of 165 °C for 12 hours.

[0028] Step (2): Open the stainless steel reactor and add 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%). After the addition, stir the mixture in the reactor at room temperature for 2 hours to ensure that the tetrapropylammonium hydroxide is fully mixed with other components in the system. After the stirring is completed, the reactor is reset to 160 ° C and crystallized at this temperature for 13 hours. After the crystallization process is completed, the reactor is quickly cooled, and through centrifugation and washing and drying steps, the sample of Example 2 is finally obtained, which is recorded as S-2. This process is intended to optimize the crystallization conditions to obtain a multi-level pore TS-1 molecular sieve.

[0029] Example 3 This embodiment provides a method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to the present invention, specifically a method for synthesizing a multi-level pore TS-1 molecular sieve, comprising: Step (1): First, 6.25 g of deionized water, 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%), 6.0 g of silica sol (mass fraction 25%) and 15% of Silicalite-1 molecular sieve were added to a beaker in sequence and mixed evenly to obtain solution A. Next, 0.2 g of tetrabutyl titanate (purity 98.5%) and 0.18 g of isopropanol (purity 99.0%) were mixed in another container and stirred thoroughly until uniform to obtain solution B. Then, solution A and solution B were mixed at room temperature and stirred continuously for 30 minutes, and then the mixed solution was charged into a stainless steel reactor. Crystallization treatment was performed at a reaction temperature of 170 °C for 24 hours.

[0030] Step (2): Open the stainless steel reactor and add 3.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%). After the addition, stir the mixture in the reactor at room temperature for 2 hours to ensure that the tetrapropylammonium hydroxide is fully mixed with other components in the system. After the stirring is completed, the reactor is reset to 155 ° C and crystallized at this temperature for 18 hours. After the crystallization process is completed, the reactor is quickly cooled, and through centrifugation and washing and drying steps, the sample of Example 3 is finally obtained, which is recorded as S-3. This process is intended to optimize the crystallization conditions to obtain a multi-level pore TS-1 molecular sieve.

[0031] Example 4 This embodiment provides a method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to the present invention, specifically a method for synthesizing a multi-level pore TS-1 molecular sieve, comprising: Step (1): First, 10.25 g of deionized water, 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%), 6.0 g of silica sol (mass fraction 25%) and 7.5% of Silicalite-1 molecular sieve were added to a beaker in sequence and mixed evenly to obtain solution A. Next, 0.3 g of tetrabutyl titanate (purity 98.5%) and 0.18 g of isopropanol (purity 99.0%) were mixed in another container and stirred thoroughly until uniform to obtain solution B. Then, solution A and solution B were mixed at room temperature and stirred continuously for 30 minutes, and then the mixed solution was charged into a stainless steel reactor. Crystallization treatment was performed at a reaction temperature of 170 °C for 20 hours.

[0032] Step (2): Open the stainless steel reactor and add 6.09 g of tetrapropylammonium hydroxide (TPAOH, mass fraction 25%). After the addition, stir the mixture in the reactor at room temperature for 2 hours to ensure that the tetrapropylammonium hydroxide is fully mixed with other components in the system. After the stirring is completed, the reactor is reset to 170 ° C and crystallized at this temperature for 16 hours. After the crystallization process is completed, the reactor is quickly cooled, and through centrifugation and washing and drying steps, the sample of Example 4 is finally obtained, which is recorded as S-4. This process is intended to optimize the crystallization conditions to obtain a multi-level pore TS-1 molecular sieve.

[0033] Example 5 This embodiment provides a method for preparing a catalyst for producing vinyl sulfate by oxidation of vinylene sulfate of the present invention, specifically a method for synthesizing a multi-level pore TS-1 molecular sieve. The difference from Example 1 is that the silicon source in step 1 is replaced with tetraethyl orthosilicate of the same molar ratio; finally, the sample of Example 5 is obtained, which is recorded as S-5.

[0034] Example 6 This embodiment provides a method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate of the present invention, specifically a method for synthesizing a multi-level pore TS-1 molecular sieve, and the difference from embodiment 1 is that the reaction temperature of step 2 is 155° C. Finally, the sample of embodiment 6 is obtained, which is recorded as S-6.

[0035] Comparative Example 1 In order to illustrate the difference between the present invention and the prior art, a traditional method is used as comparative example 1.

[0036] First, 6.25 grams of deionized water, 6.09 grams of tetrapropylammonium hydroxide (TPAOH, mass fraction of 25%), 6.0 grams of silica sol (mass fraction of 25%) and 7.5% of Silicalite-1 molecular sieve were added to a beaker in turn, and solution A was obtained after mixing evenly. Next, 0.2 grams of tetrabutyl titanate (purity of 98.5%) and 0.18 grams of isopropanol (purity of 99.0%) were mixed in another container and stirred until uniform to obtain solution B. Then, solution A and solution B were mixed at room temperature and stirred for 30 minutes, and then the mixed solution was charged into a stainless steel reactor. Crystallization treatment was carried out at a reaction temperature of 170 ° C for 48 hours. After the crystallization process was completed, the reactor was quickly cooled, and the sample of comparative example 1 was obtained by centrifugation and washing and drying steps, which was recorded as S-0.

[0037] Figure 1 The XRD diagrams of Comparative Example 1 and Examples 1 to 3 are shown. It can be seen from the diagram that the method of the present invention can synthesize pure phase TS-1 molecular sieve.

[0038] Figure 2 The SEM images of Comparative Example 1 and Examples 1 to 3 show that the morphology of the sample synthesized by the method of the present invention is smaller than that of the sample in Comparative Example 1.

[0039] Figure 3 This is the total specific surface area data of Comparative Example 1 and Examples 1 to 3. It can be seen from the figure that compared with the sample synthesized in Comparative Example 1, the external specific surface area of ​​the sample synthesized by the method of the present invention is increased.

[0040] Figure 4 2 is the mesopore volume of Comparative Example 1 and Examples 1 to 3. It can be seen from the figure that compared with the sample synthesized in Comparative Example 1, the mesopore volume of the sample synthesized by the method of the present invention increases.

[0041] Experimental Example 1 In the following examples and comparative examples, the performance of the prepared samples was tested in the catalyst reaction of vinyl sulfate oxidation to vinyl sulfate. The specific operation is as follows: First, take 1 gram of the catalyst prepared by the present invention, which has been granulated and screened and has a particle size of 40-60 mesh, and put it into a glass reaction container containing 0.49 grams of vinyl sulfate, 0.34 grams of hydrogen peroxide and 10 ml of dichloromethane. Then, the mixture was stirred and reacted for 60 minutes at 35 degrees Celsius. After the reaction was completed, the catalyst was separated from the reaction product by suction filtration. Finally, the content of vinyl sulfate in the product was determined by gas chromatograph, and the activity (i.e., conversion rate) of the catalyst was calculated based on this.

[0042] The above content is a further detailed description of the present invention in combination with a specific preferred embodiment. It cannot be determined that the specific embodiments of the present invention are limited to this. For ordinary technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the present invention, which should be regarded as belonging to the present invention and the scope of patent protection determined by the submitted claims.

Claims

1. A method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate, characterized in that: The following steps are involved: S1. Mix water, alkaline organic template, silicon source, titanium source, additive and seed crystal according to the feeding ratio to prepare an initial gel, then cure at room temperature for 0.5-2 hours, and then crystallize at a temperature range of 140°C to 170°C for 2-48 hours; the feeding molar ratio of the initial gel is H2O: alkaline organic template: SiO2: TiO2: additive = 10-30: 0.1-0.3: 1: 1 / 40-1 / 100: 0.1; S2: After the above steps are completed, the reactor is opened, and an alkaline organic template is added thereto for a second time, and secondary crystallization is performed at a temperature range of 140°C to 170°C for 12 to 48 hours; after the reaction is completed, separation, washing and drying are performed; the mass ratio of the alkaline organic template added for the second time is 0.5 to 1 times the mass ratio of the alkaline organic template added for the first time.

2. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: The alkaline organic template is tetrapropylammonium hydroxide or tetraethylammonium hydroxide.

3. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: The silicon source is one of ethyl orthosilicate, silica sol, fumed silica and silica gel.

4. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: The titanium source is tetraethyl titanate or n-butyl titanate.

5. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: The additive is one of triethanolamine, N-methylpyrrolidone, amide additives and isopropyl alcohol.

6. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: The amount of seed crystal added is 5%-30% of the mass of the silicon source.

7. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 6, characterized in that: The amount of seed crystal added is 5%-15% of the mass of the silicon source.

8. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, 6 or 7, characterized in that: The seed crystal was Silicalite-1 molecular sieve.

9. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: In step S1, the crystallization temperature is 150°C to 170°C, and the time is 12 to 24 hours.

10. The method for preparing a catalyst for preparing vinyl sulfate by oxidation of vinylene sulfate according to claim 1, characterized in that: In step S2, the crystallization temperature is 150°C to 170°C, and the time is 12 to 24 hours.

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