Preparation method of methyl carbonate quaternary ammonium salt template agent, molecular sieve and application of molecular sieve

Abstract

The invention belongs to the technical field of molecular sieve catalysts, and discloses a preparation method of a methyl carbonate quaternary ammonium salt template agent, a molecular sieve and application of the molecular sieve. Dimethyl carbonate is adopted as a methylation reagent and is subjected to a contact reaction with tetramethyl diamine, and a methyl carbonate quaternary ammonium salt template agent for preparing the molecular sieve is obtained; a molecular sieve is prepared from a methyl carbonate quaternary ammonium salt template agent; the molecular sieve can be applied to catalytic thermal cracking, aromatization, isomerization and alkylation reactions; the template agent provided by the invention is convenient to prepare, low in price and non-toxic, a mineralizer containing metal cations is not used, and the synthesized molecular sieve is special in morphology, has high crystallinity and yield, and especially shows excellent catalytic activity in C8 aromatic isomerization reaction.

Description

Technical Field

[0001] The present invention belongs to the technical field of molecular sieve catalysts, and specifically relates to a preparation method of a quaternary ammonium salt template agent for methyl carbonate, a molecular sieve, and their applications. Background Art

[0002] Due to the unique properties of zeolite molecular sieves, including uniform pore size distribution, high specific surface area, good ion exchange ability, tunable acidity, and excellent framework and hydrothermal stability, they are widely used as adsorbents, ion exchangers, and heterogeneous catalysts (such as catalytic cracking, isomerization, aromatization, etc.) in the petrochemical field.

[0003] CN106542539B discloses a method for synthesizing macroporous EMM-23 molecular sieve using polyquaternary ammonium salt as a template agent. In the method, the silica-alumina ratio only needs to be greater than 15, which greatly broadens the phase region of the synthesized molecular sieve and reduces the synthesis difficulty of the product. CN106698456B discloses a method for synthesizing alumin-containing ITQ-13 zeolite molecular sieve by a one-step method using a novel linear polyquaternary ammonium base organic template agent, which reduces the usage cost of the organic template agent and introduces aluminum into the framework of ITQ-13 zeolite molecular sieve under the condition of no germanium. CN104556104B discloses a method for synthesizing titanium-silicon molecular sieve using organic quaternary ammonium salt and organic base as template agents, which reduces the use of expensive organic quaternary ammonium salts.

[0004] CN108946756 discloses a method for hydrothermally synthesizing hierarchical pore EU-1 molecular sieve using a bisquaternary ammonium salt with a bis-hexacyclic heterocyclic group-substituted alkane structure as a template agent and a long-chain silane compound as a crystallization aid. CN202111179813.8 discloses a synthesis method of a 3,5-dimethylpiperidinium salt template agent, and a novel molecular sieve with relatively high crystallinity and good catalytic performance is synthesized using this as a template agent. CN202311518187.X discloses a method for preparing an organic template piperidinium derivative for molecular sieve, and SSZ-39 molecular sieve is prepared using the template agent, which improves the yield of the product and also reduces the usage amount of the organic template. The template agents used in the above methods for synthesizing molecular sieves are relatively expensive and toxic. On the other hand, the preparation process of the template agent is complex and energy-consuming, which is greatly limited in industrial large-scale production.

[0005] CN202210336502.6 discloses a method for preparing SSZ-39 molecular sieve using cheap templates, using organic ion salts or organic ion bases as template A, and C4-C16 fatty amines as template B, which greatly reduces the preparation cost of SSZ-39 molecular sieves. CN202410300299.6 discloses a method for synthesizing Silicalite-1 molecular sieves using n-butylamine as a template. This method uses cheap n-butylamine as a template, and the amount of template is small, the synthesis time is short, and the product yield is high. Although the above method solves the problem of expensive and large amounts of templates to a certain extent, in addition to the addition of silicon source, aluminum source, template and water during the synthesis process, it is usually necessary to introduce OH - As a mineralizer, it will inevitably bring metal cations. Therefore, the synthesized product usually needs to be ion exchanged with inorganic ammonium salts to obtain a hydrogen-type molecular sieve with catalytic activity. In the ion exchange process, a large amount of wastewater is generated, which is time-consuming and energy-consuming, posing a huge challenge to environmental protection.

[0006] In summary, how to develop a molecular sieve template that is easy to prepare, cheap and non-toxic, and avoid the use of mineralizers containing metal cations is a technical problem that needs to be solved urgently. Summary of the invention

[0007] The invention overcomes the shortcomings of the prior art and provides a preparation method of a methyl carbonate quaternary ammonium salt template, a molecular sieve and application thereof.

[0008] The present invention is achieved through the following technical solutions: A method for preparing a methyl carbonate quaternary ammonium salt template agent, using dimethyl carbonate as a methylating agent, and carrying out a contact reaction with tetramethyl diamine having a structure of formula I to obtain a methyl carbonate quaternary ammonium salt template agent for preparing a molecular sieve; Formula I: In the formula I, R = 2 to 12; The general structural formula of the methyl carbonate quaternary ammonium salt template is shown in Formula II: Formula II: ; In the formula II, R = 2 to 12.

[0009] Preferably, the molar ratio of dimethyl carbonate to tetramethyldiamine is 1:0.125-0.5.

[0010] Preferably, the contact reaction temperature is 90-150° C. and the time is 8-36 h.

[0011] Molecular sieve prepared by using the methyl carbonate quaternary ammonium salt template agent described above.

[0012] Preferably, the methyl carbonate quaternary ammonium salt template agent is mixed and stirred with a silicon source, an aluminum source, deionized water, and seed crystals to form a gel, and the gel is subjected to hydrothermal crystallization reaction in a reaction kettle to obtain the molecular sieve.

[0013] Preferably, the silicon source is selected from one of fumed silica, silica sol, coarse pore silica gel, tetraethyl orthosilicate, water glass, and vapor phase silicon dioxide, the aluminum source is selected from one of sodium aluminate, aluminum nitrate, pseudo-boehmite, and aluminum isopropoxide, and the seed crystal is an EU-1 seed crystal.

[0014] Preferably, the molar ratio of the silicon source, aluminum source, deionized water, and methyl carbonate quaternary ammonium salt template agent is 1∶0.033~0.008∶12.5~20∶0.05~0.2; the addition amount of the EU-1 seed crystal is 0.5%~5% of the total mass of the gel.

[0015] Preferably, the molecular sieve is a TYU type molecular sieve; the size of the TYU type molecular sieve crystal is 1.5 μm~5 μm, and the total specific surface area is 351.2 m 2 / g.

[0016] Preferably, the temperature of the hydrothermal crystallization reaction is 170~190 ℃, and the time is 24~96 h.

[0017] Application of the molecular sieve prepared by using the methyl carbonate quaternary ammonium salt template agent in catalytic thermal cracking, aromatization, isomerization, and alkylation reactions.

[0018] Preferably, the isomerization is C8 aromatic hydrocarbon isomerization; More preferably, the C8 aromatic hydrocarbon isomerization reaction is carried out under hydrogenation conditions, the reaction pressure is 0.5~2.0 MPa, the reaction temperature is 250~450 ℃, and the weight hourly space velocity is 5~30 h -1 .

[0019] The beneficial effects of the present invention compared with the prior art are as follows: (1) The present invention provides a preparation method of a molecular sieve using a methyl carbonate quaternary ammonium salt as a template agent. The template agent uses inexpensive and non-toxic dimethyl carbonate as a raw material, the preparation process is simple, the energy consumption is low, the production cost is low, and it has good industrial application prospects.

[0020] (2)When synthesizing molecular sieves using the quaternary ammonium salt of methyl carbonate as a template agent, the synthesis steps are simple, the raw material utilization rate is high, and it can also provide the alkalinity required for synthesizing molecular sieves, avoiding the use of metal cation mineralizing agents and eliminating the need for ion exchange before being used in catalytic reactions; the synthesized molecular sieves have special morphologies, high crystallinity and high yields, which are of great significance in industrial production.

[0021] (3)The molecular sieves prepared by the present invention can be applied to catalytic pyrolysis, aromatization, isomerization and alkylation reactions, and particularly exhibit excellent catalytic activity in the isomerization reaction of C8 aromatics, showing excellent catalytic activity and having high industrial production value. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 X-ray diffraction (XRD) pattern of the TYU-1 molecular sieve synthesized in Example 3; Figure 2 Scanning electron microscopy (SEM) image of the TYU-1 molecular sieve synthesized in Example 3; Figure 3 XRD pattern of the TYU-1 molecular sieve synthesized in Example 7; Figure 4 SEM image of the TYU-1 molecular sieve synthesized in Example 7; Figure 5 XRD pattern of the TYU-2 molecular sieve synthesized in Example 9; Figure 6 SEM image of the TYU-2 molecular sieve synthesized in Example 9; Figure 7 XRD pattern of the TYU-3 molecular sieve synthesized in Example 11; Figure 8 SEM image of the TYU-3 molecular sieve synthesized in Example 11.

[0023] Figure 9 SEM image of the EU-1 molecular sieve synthesized in Comparative Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments and drawings. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The technical solutions of the present invention will be described in detail below in conjunction with the embodiments and drawings, but the protection scope is not limited thereto.

[0025] Example 1 A preparation method of a quaternary ammonium salt of methyl carbonate template agent, specifically the following steps: Take 10.46 g of dimethyl carbonate in a 250 mL three-necked flask, add 10 g of N,N,N',N'-tetramethyl-1,6-hexanediamine during stirring, and carry out condensation reflux for 24 h under stirring conditions in an oil bath at 100 °C. After the reaction is completed, the product is washed and filtered with dimethyl carbonate, dried at 50 °C for standby, and stored in a dry and light-proof manner.

[0026] Example 2 A preparation method of TYU-1 molecular sieve is specifically as follows: Using the product prepared in Example 1 as a template agent, successively add 4.55 g of deionized water, 1.08 g of template agent, 0.1543 g of pseudo-boehmite (76%, calculated by mass fraction of Al2O3), and 10 g of silica sol (30 wt%, calculated by mass fraction of SiO2) into a 100 mL beaker, stir at room temperature for 2 h, then add 0.12 g of EU-1 seed crystal, continue to stir for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner, and carry out hydrothermal reaction at 170 °C for 48 h. After the reaction is completed, quickly cool, wash with deionized water until neutral, and dry at 100 °C to obtain a TYU-1 molecular sieve sample with EUO topological structure.

[0027] Example 3 A preparation method of TYU-1 molecular sieve is specifically as follows: Using the product prepared in Example 1 as a template agent, successively add 4.55 g of deionized water, 2.16 g of template agent, 0.1543 g of pseudo-boehmite (76%, calculated by mass fraction of Al2O3), and 10 g of silica sol (30 wt%, calculated by mass fraction of SiO2) into a 100 mL beaker, stir at room temperature for 2 h, then add 0.12 g of EU-1 seed crystal, continue to stir for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner, and carry out hydrothermal reaction at 180 °C for 48 h. After the reaction is completed, quickly cool, wash with deionized water until neutral, and dry at 100 °C to obtain a TYU-1 molecular sieve sample with EUO topological structure.

[0028] Example 4 A preparation method of methyl carbonate quaternary ammonium salt template agent is specifically as follows: Take 20.92 g of dimethyl carbonate in a 250 mL three-necked flask, add 10 g of N,N,N',N'-tetramethyl-1,6-hexanediamine during stirring, and carry out condensation reflux for 24 h under stirring conditions in an oil bath at 100 °C. After the reaction is completed, the product is washed and filtered with dimethyl carbonate, dried at 50 °C for standby, and stored in a dry and light-proof manner.

[0029] Example 5 A preparation method of TYU-1 molecular sieve, specifically including the following steps: Using the product prepared in Example 4 as a template agent, sequentially add 4.55 g of deionized water, 2.16 g of template agent, 0.0671 g of pseudo-boehmite (76%, calculated based on the mass fraction of Al2O3), and 10 g of silica sol (30 wt%, calculated based on the mass fraction of SiO2) into a 100 mL beaker. Stir at room temperature for 2 h, then add 0.12 g of EU-1 seed crystals, continue to stir for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner. Carry out hydrothermal reaction at 190 °C for 48 h. After the reaction is completed, rapidly cool, wash with deionized water until neutral, and dry at 100 °C to obtain a TYU-1 molecular sieve sample with EUO topological structure.

[0030] Example 6 A preparation method of TYU-1 molecular sieve, specifically including the following steps: Using the product prepared in Example 4 as a template agent, sequentially add 4.55 g of deionized water, 2.16 g of template agent, 0.1543 g of pseudo-boehmite (76%, calculated based on the mass fraction of Al2O3), and 3 g of white carbon black (99%, calculated based on the mass fraction of SiO2) into a 100 mL beaker. Stir at room temperature for 2 h, then add 0.12 g of EU-1 seed crystals, continue to stir for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner. Carry out hydrothermal reaction at 190 °C for 48 h. After the reaction is completed, rapidly cool, wash with deionized water until neutral, and dry at 100 °C to obtain a TYU-1 molecular sieve sample with EUO topological structure.

[0031] Example 7 A preparation method of TYU-1 molecular sieve, specifically including the following steps: Using the product prepared in Example 4 as a template agent, sequentially add 4.55 g of deionized water, 2.16 g of template agent, 0.1543 g of pseudo-boehmite (76%, calculated based on the mass fraction of Al2O3), and 10 g of silica sol (30 wt%, calculated based on the mass fraction of SiO2) into a 100 mL beaker. Stir at room temperature for 2 h, add 0.4625 g of NH4F, continue to stir for 0.5 h, then add 0.12 g of EU-1 seed crystals, stir for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner. Carry out hydrothermal reaction at 180 °C for 72 h. After the reaction is completed, rapidly cool, wash with deionized water until neutral, and dry at 100 °C to obtain a TYU-1 molecular sieve sample with EUO topological structure.

[0032] Example 8 A preparation method of methyl carbonate quaternary ammonium salt template agent, specifically including the following steps: Take 24.81 g of dimethyl carbonate in a 250 mL three-necked flask. Add 8 g of N,N,N',N'-tetramethylethylenediamine during stirring, and carry out condensation reflux for 24 h under stirring conditions in an oil bath at 100 °C to obtain the template agent for TYU-2 molecular sieve.

[0033] Example 9 A preparation method of TYU-2 molecular sieve, specifically the following steps: Use the product prepared in Example 8 as the template agent. In a 100 mL beaker, sequentially add 4.55 g of deionized water, 2.22 g of the template agent, 0.1118 g of pseudoboehmite (76%, calculated based on the mass fraction of Al2O3), and 10 g of silica sol (30 wt%, calculated based on the mass fraction of SiO2). Stir at room temperature for 2 h, then add 0.12 g of EU-1 seed crystal, continue stirring for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner, and carry out hydrothermal reaction at 180 °C for 72 h. After the reaction is completed, rapidly cool, wash with deionized water until neutral, and dry at 100 °C to obtain the TYU-2 molecular sieve sample.

[0034] Example 10 A preparation method of a quaternary ammonium salt template agent for methyl carbonate, specifically the following steps: Take 22.11 g of dimethyl carbonate in a 250 mL three-necked flask. Add 8 g of N,N,N',N'-tetramethyl-1,3-propanediamine during stirring, and carry out condensation reflux for 24 h under stirring conditions in an oil bath at 100 °C to obtain the template agent for TYU-3 molecular sieve.

[0035] Example 11 A preparation method of TYU-3 molecular sieve, specifically the following steps: Use the product prepared in Example 10 as the template agent. In a 100 mL beaker, sequentially add 4.55 g of deionized water, 2.32 g of the template agent, 0.1118 g of pseudoboehmite (76%, calculated based on the mass fraction of Al2O3), and 10 g of silica sol (30 wt%, calculated based on the mass fraction of SiO2). Stir at room temperature for 2 h, then add 0.12 g of EU-1 seed crystal, continue stirring for 1 h, and then pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner liner, and carry out hydrothermal reaction at 180 °C for 72 h. After the reaction is completed, rapidly cool, wash with deionized water until neutral, and dry at 100 °C to obtain the TYU-3 molecular sieve sample.

[0036] Comparative Example 1 In a 100 mL beaker, 18 g of deionized water, 0.42 g of sodium hydroxide, 0.21 g of sodium metaaluminate (41%, calculated as the mass fraction of Al2O3), 2.5 g of hexamethonium bromide, and 10 g of silica sol (30 wt%, calculated as the mass fraction of SiO2) were added in sequence. Stir for 2 h at room temperature. Pour the prepared gel into a reaction kettle equipped with a polytetrafluoroethylene inner lining and carry out hydrothermal reaction at 180 °C for 72 h. After the reaction, quench rapidly, wash with deionized water until neutral, and dry at 100 °C to obtain EU-1 molecular sieve. The measured total specific surface area is 346.4 m 2 / g.

[0037] Application Example 1 In order to investigate the catalytic performance of the molecular sieve prepared by the present invention, the TYU-1 molecular sieve synthesized in Example 3 was selected to prepare a C8 aromatic hydrocarbon isomerization catalyst, and its catalytic performance was investigated. The specific steps are as follows: (1) Preparation of isomerization catalyst: Mix the prepared TYU-1 molecular sieve and pseudo-boehmite in a mass ratio of 1:1, and add a nitric acid solution with a mass fraction of 2.0% - 5.0%. Extrude into strips, dry the product at 120 °C, and then calcine in an air atmosphere at 550 °C for 6 h. Impregnate with 0.03% platinum by equal-volume impregnation, dry and calcine after impregnation for 12 h.

[0038] (2) Evaluation of catalytic performance: Use a fixed-bed reactor to evaluate the C8 aromatic hydrocarbon isomerization performance of the catalyst. The specific operation steps are as follows: Uniformly mix 1 g of catalyst (20 - 40 mesh) with 2 g of quartz sand, fill it in the middle section of the reaction tube, and fill quartz sand in the upper and lower sections; Reduce the temperature to 370 °C for catalytic reaction after reducing for 6 - 10 h at a temperature of 420 °C and a H2 flow rate of 20 ml / min; The raw material (including 93% m-xylene and 7% ethylbenzene by mass fraction) enters the fixed-bed reactor through a micro pump. The reaction pressure is 0.8 MPa, and the mass space velocity is 8 h -1 .

[0039] (3) Use a GC-950 chromatograph equipped with a hydrogen flame ionization detector (FID) and a Zhongke Antai PEG-20M (50 m × 0.32 mm × 0.5 μm) chromatographic column to analyze the products, and finally calculate the catalytic performance results through chromatographic data.

[0040] The catalytic results show that after reacting for 48 h under the conditions described in Application Example 1, the isomerization catalyst prepared from the TYU-1 molecular sieve still has high catalytic activity: the conversion rate of ethylbenzene is 16.95%, the isomerization activity is 24.04%, and the loss rate of xylene is 1.90%.

[0041] The above content is a further detailed description of the present invention in combination with specific preferred embodiments. It cannot be determined that the specific embodiments of the present invention are limited thereto. For those of ordinary skill in the technical field to which the present invention pertains, without departing from the present invention, several simple deductions or substitutions can still be made, which should all be regarded as falling within the scope of patent protection determined by the claims submitted for the present invention.

Claims

1. A preparation method of a quaternary ammonium salt template agent of methyl carbonate, characterized in that, Dimethyl carbonate is used as a methylation reagent and contacted with tetramethyldiamine having the structure of formula I to obtain a methyl carbonate quaternary ammonium salt template agent for preparing molecular sieves; Formula Ⅰ: In the formula I, R = 2 - 12; The structural general formula of the methyl carbonate quaternary ammonium salt template agent is as shown in formula II: Formula II: ； In the formula II, R = 2 - 12.

2. The preparation method of a quaternary ammonium salt template agent of methyl carbonate according to claim 1, characterized in that, The molar ratio of dimethyl carbonate to the tetramethyldiamine is 1:0.125 - 0.

5.

3. The preparation method of a quaternary ammonium salt template agent of methyl carbonate according to claim 1, characterized in that, The temperature of the contact reaction is 90 - 150 °C and the time is 8 - 36 h.

4. A molecular sieve prepared by using the methyl carbonate quaternary ammonium salt template agent according to any one of claims 1 - 3.

5. The molecular sieve prepared by using a methyl carbonate quaternary ammonium salt template agent according to claim 4, wherein The methyl carbonate quaternary ammonium salt template agent is mixed and stirred with a silicon source, an aluminum source, deionized water, and seed crystals to form a gel, and the gel is subjected to hydrothermal crystallization reaction in a reaction kettle to obtain the molecular sieve.

6. The molecular sieve prepared by using a methyl carbonate quaternary ammonium salt template according to claim 5, characterized in that The silicon source is selected from one of fumed silica, silica sol, coarse pore silica gel, tetraethyl orthosilicate, water glass, and vapor phase silicon dioxide, the aluminum source is selected from one of sodium aluminate, aluminum nitrate, pseudo-boehmite, and aluminum isopropoxide, and the seed crystal is an EU-1 seed crystal.

7. The molecular sieve prepared by using a quaternary ammonium salt of methyl carbonate as a templating agent according to claim 6, characterized in that, The molar ratio of the silicon source, the aluminum source, deionized water, and the methyl carbonate quaternary ammonium salt template agent is 1∶0.033 - 0.008∶12.5 - 20∶0.05 - 0.2; the addition amount of the EU-1 seed crystal is 0.5% - 5% of the total mass of the gel.

8. The molecular sieve prepared by using a methyl carbonate quaternary ammonium salt template agent according to claim 7, wherein The molecular sieve is a TYU type molecular sieve; the crystal size of the TYU type molecular sieve is 1.5 μm to 5 μm, and the total specific surface area is 351.2 m 2 / g.

9. The molecular sieve prepared by using a methyl carbonate quaternary ammonium salt template agent according to claim 5, wherein The temperature of the hydrothermal crystallization reaction is 170 - 190 °C and the time is 24 - 96 h.

10. Use of the molecular sieve prepared by using the methyl carbonate quaternary ammonium salt template agent according to claim 8 in catalytic thermal cracking, aromatization, isomerization, and alkylation reactions.

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