EWT molecular sieve and its preparation method and application

Abstract

The present invention discloses an EWT molecular sieve characterized by a framework aluminum to non-framework aluminum ratio of ≥3.0 as measured by nuclear magnetic resonance (NMR) carbon spectroscopy, and a ratio of Br(OH)2 ...

Description

Technical Field

[0001] The present invention relates to a molecular sieve and a preparation method and application thereof, and more particularly to a molecular sieve having an EWT structure and a preparation method thereof and application thereof in the alkylation reaction of benzene with ethylene. Background Art

[0002] As one of the most important catalytic materials at present, molecular sieves are divided into four types: small pore, medium pore, large pore and ultra-large pore. The pore size of small pore molecular sieves is between 3 angstroms and 5 angstroms, including CHA, LEV, SOD, LTA, etc.; the pore size of medium pore molecular sieves is between 5 angstroms and 7 angstroms, including MFI, EUO, TON, FER, etc.; the pore size of large pore molecular sieves is around 7 angstroms, including FAU, BEA, LTL, etc.; ultra-large pore molecular sieves have a pore size of >7 angstroms. Since ultra-large pore molecular sieves break through the pore limitations of molecular sieves, they have advantages in improving the reaction activity of large molecules, extending the service life of molecular sieves, and improving product selectivity. Therefore, they have relevant application prospects in oil refining and chemical industry.

[0003] The EWT molecular sieve, first successfully synthesized by ExxonMobil in 2012, is an ultra-large pore molecular sieve. With a three-dimensional pore structure of 21- and 10-membered rings, the EWT molecular sieve is the first large-pore silicon-alumina molecular sieve with excellent thermal stability.

[0004] CN103842294A discloses an EWT-structured molecular sieve EMM-23 synthesized using bis(N-propylpyrrolidinium)pentane dication or bis(N-propylpyrrolidinium)hexane dication as a template. The EMM-23 molecular sieve still has a high specific surface area and thermal stability after calcination at 540°C. CN106542539A uses a polyquaternary ammonium salt template to synthesize the EMM-23 molecular sieve, which reduces the synthesis cost while broadening the synthesis phase region of the EWT structure molecular sieve. CN112010325A discloses a method for synthesizing the EMM-23 molecular sieve, which reduces the three wastes generated by the synthesis of the EMM-23 molecular sieve by preparing a solid quaternary ammonium salt template, and reduces the minimum SiO2 / Al2O3 ratio of the synthesis phase region to 15. Although EWT structured molecular sieves may achieve good results in the gas-phase alkylation of benzene with ethylene to produce ethylbenzene, the currently synthesized EWT structured molecular sieves have poor activity stability and obvious deactivation of the Br(II) acid center after high-temperature calcination. Therefore, their application effect in this reaction and similar reactions dominated by Br(II) acid catalysis is poor. Summary of the Invention

[0005] The purpose of the present invention is to address the problem of poor activity stability in the prior art and, based on the existing EWT structured molecular sieve synthesis technology, to provide an EWT structured molecular sieve different from the prior art, and to provide a preparation method and application thereof.

[0006] In order to achieve the purpose of the present invention, the first aspect of the present invention provides an EWT structured molecular sieve, characterized in that the ratio of framework aluminum to non-framework aluminum characterized by nuclear magnetic carbon spectrum of the molecular sieve is ≥3.0 and the ratio of B acid to L acid at 350°C characterized by pyridine infrared is ≥0.22.

[0007] In order to achieve the purpose of the present invention, the second aspect of the present invention provides a preparation method of EWT structured molecular sieve, characterized in that the molecular sieve is obtained by hydrothermal crystallization of a synthetic system mixture of EWT structured molecular sieve to which an additive is added and the product is recovered, wherein the additive is a modified starch, and the modified starch is a non-ionic cross-linked starch whose cross-linking agent is epichlorohydrin, having starch units with a chain length of 10 or more glucose units, and the ratio of straight chains to branches in the modified starch is 1:9-8:2, and the modified starch has characteristic peaks at 60ppm, 73ppm, and 100ppm in the nuclear magnetic resonance carbon spectrum of the solid product when it is put into an aqueous solution with a pH ≥ 12 and measured under closed conditions at 120°C for 72 hours.

[0008] In order to achieve the purpose of the present invention, the third aspect of the present invention provides a gas-phase alkylation reaction of benzene and ethylene, characterized in that the EWT structured molecular sieve of the present invention or the EWT structured molecular sieve obtained by the preparation method of the present invention is used as the active component of the catalyst.

[0009] This invention incorporates a specific type of starch into the synthesis system of an EWT molecular sieve. The resulting EWT molecular sieve has a higher framework aluminum ratio and a higher B / L acid ratio at 350°C, thereby improving the activity and stability of the EWT molecular sieve. This also results in improved ethylene conversion and ethylated product selectivity in the vapor-phase alkylation reaction of benzene with ethylene. DETAILED DESCRIPTION

[0011] The EWT structure molecular sieve provided by the present invention is characterized in that the ratio of framework aluminum to non-framework aluminum characterized by nuclear magnetic carbon spectrum of the molecular sieve is ≥3.0 and the ratio of B acid to L acid at 350°C characterized by pyridine infrared is ≥0.22.

[0012] The framework aluminum and non-framework aluminum are characterized by NMR aluminum spectroscopy. In the spectrum, 40-70 represents framework aluminum, and -20-10 represents non-framework aluminum. Preferably, the molecular sieve has a framework aluminum to non-framework aluminum ratio of 3.0-4.5, more preferably 3.5-4.5, and a ratio of Br(II) acid to I(II) acid of 0.22-0.30, more preferably 0.24-0.29. The molecular sieve preferably has a molar ratio of silicon oxide to aluminum oxide of 75-150.

[0013] The EWT structured molecular sieve provided by the present invention has a higher ratio of framework aluminum to non-framework aluminum and a higher B / L acid ratio at 350° C. compared with conventional EWT molecular sieves.

[0014] The present invention also provides a preparation method of the above-mentioned EWT structured molecular sieve, characterized in that the molecular sieve is obtained by hydrothermal crystallization of a synthetic system mixture of the EWT structured molecular sieve to which an additive is added, wherein the additive is a modified starch, and the modified starch is a non-ionic cross-linked starch whose cross-linking agent is epichlorohydrin, having starch units with a chain length of 10 or more glucose units, and the ratio of straight chains to branches in the modified starch is 1:9-8:2. The modified starch has a solid product whose nuclear magnetic resonance carbon spectrum, when put into an aqueous solution with a pH ≥ 12 and measured under closed conditions at 120° C. for 72 hours, still has characteristic peaks at positions of 60 ppm, 73 ppm, and 100 ppm, that is, the effective ingredients in the starch can remain stable and are not easily decomposed.

[0015] Optionally, the synthesis system mixture is formed by uniformly mixing an alkali source, an organic template and water to form a solution, adding a silicon source and an aluminum source, and then adding the modified starch; or, the synthesis system mixture is formed by first uniformly mixing an alkali source, an organic template and water to form a solution, adding the modified starch, beating to form a suspension, and then adding an aluminum source and a silicon source.

[0016] Optionally, the mass ratio of the modified starch to the silicon source in the synthesis system mixture is 1:5-100, where the silicon source is calculated as SiO2. The organic template is 1,1,6,6-tetramethyl-1,6-diazacyclododecane-1,6-dihydroxide diimine having a double-chain diquaternary ammonium base structure. The alkali source is NaOH and / or KOH; the silicon source is silica gel or silica-alumina gel; and the aluminum source is selected from one or more of hydrated aluminum oxide, aluminum hydroxide, and silica-alumina gel.

[0017] In the preparation method, the molar ratio of the materials in the synthesis system mixture is preferably: SiO2 / Al2O3=80-200, alkali / SiO2=0.08-0.25, organic template / SiO2=0.08-0.2, H2O / SiO2=6-20.

[0018] The crystallization is carried out in two stages. The hydrothermal crystallization is carried out in a sealed container at 100-130°C for 10-30 hours and at 140-160°C for 100-180 hours. The preferred crystallization conditions are 120-130°C for 12-24 hours and 150-170°C for 120-150 hours.

[0019] The process of recovering the product by washing the product with water, filtering and drying it after hydrothermal crystallization to obtain the molecular sieve is well known to those skilled in the art and will not be described in detail here.

[0020] The present invention also provides an EWT structure molecular sieve obtained by the above preparation method.

[0021] The present invention further provides a gas-phase alkylation reaction of benzene and ethylene, which uses the EWT structure molecular sieve of the present invention or the EWT structure molecular sieve obtained by the preparation method of the present invention as the active component of the catalyst. The temperature of the gas-phase alkylation reaction of benzene and ethylene is generally higher than 330°C. The molecular sieve provided by the present invention has more skeleton aluminum, especially the Br acid / L acid ratio is higher at 350°C, indicating that more Br acid is retained, the molecular sieve has good thermal stability, and is more beneficial to the gas-phase alkylation reaction of benzene and ethylene. Therefore, the gas-phase alkylation reaction method of benzene and ethylene of the present invention has higher activity stability and ethylation selectivity. The gas-phase alkylation reaction of benzene and ethylene, the alkylation reaction conditions are: temperature 280-350°C, pressure 3.0-3.8Mpa, ethylene mass space velocity 0.3-0.7h -1 , benzene / olefin molar ratio 8.0-9.0. The preferred conditions are temperature 320-350°C, pressure 3.3-3.6 MPa, ethylene mass space velocity 0.5-0.6 h -1 , benzene / olefin molar ratio 8.2-8.5.

[0022] In the gas-phase alkylation reaction of benzene and ethylene, the EWT molecular sieve needs to be exchanged for an ammonium-type molecular sieve before use and then calcined to remove ammonium and become a hydrogen-type molecular sieve. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 1 and 2 are carbon NMR spectra of the etherified cross-linked starch used in Examples 1 and 2.

[0024] Figure 2 This is the XRD spectrum of sample E-1 in Example 1.

[0025] Figure 3 It is the NMR aluminum spectrum of sample E-1 of Example 1 and sample D1 of Comparative Example 1.

[0026] Figure 4 This is the XRD spectrum of sample D1 in comparative example 1.

[0027] Figure 5 This is a trend diagram of ethylene conversion in the gas-phase alkylation reaction of Example 7 and Comparative Example 7.

[0028] Figure 6 7 is a trend diagram of the selectivity of ethylation products in the gas-phase alkylation reaction of Example 7 and Comparative Example 7. DETAILED DESCRIPTION

[0029] The present invention will be further described below by way of examples, but the present invention is not limited thereto.

[0030] In the examples, X-ray diffraction (XRD) phase patterns were obtained by Philips Panalytical X'pert, and the test conditions were: Cu target, Kα radiation, Ni filter, ultra-high-energy detector, tube voltage 30 kV, and tube current 40 mA.

[0031] In the examples, the solid-state NMR results were obtained using a Bruker AVANCE III 600WB NMR spectrometer.

[0032] In the examples, pyridine infrared characterization (Py-IR) was performed using a 8700 Fourier transform infrared spectrometer produced by Thermo Fisher Scientific.

[0033] Example 1

[0034] Sodium metaaluminate solution (sodium oxide 287 g / L, aluminum oxide 159.7 g / L) and 1,1,6,6-tetramethyl-1,6-diazacyclododecane-1,6-dihydroxide diimine were added to deionized water and mixed evenly. 2 / g, 0.9 mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture, and finally cross-linked starch (moderate cross-linking, with a starch unit with a chain length of more than 10 glucose units, the cross-linking agent of which is epichlorohydrin, the nuclear magnetic resonance carbon spectrum of the modified starch has characteristic peaks at 60 ppm, 73 ppm, and 100 ppm, see Figure 1 (Example 1 curve) to obtain a reaction mixture having a molar ratio of SiO2:Al2O3:template:NaOH:H2O=100:1:0.15:0.18:10, and a mass ratio of starch to silica gel of 1:10. After the mixture was uniformly stirred, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor and heated to 120°C with stirring. Crystallization was carried out under autogenous pressure for 24 hours, followed by crystallization at 160°C for 120 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve sample designated E-1.

[0035] The XRD spectrum of E-1 is shown in Figure 2 , indicating that E-1 is EWT molecular sieve.

[0036] The NMR aluminum spectrum of the E-1 sample is shown in Figure 3 The ratio of skeleton aluminum to non-skeleton aluminum is shown in Table 1.

[0037] The Py-IR results of sample E-1 are shown in Table 2.

[0038] Example 2

[0039] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9 mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture, and finally cross-linked starch (mildly cross-linked, with a starch unit with a chain length of more than 10 glucose units, the cross-linking agent being epichlorohydrin, the nuclear magnetic resonance carbon spectrum of the modified starch has characteristic peaks at 60 ppm, 73 ppm, and 100 ppm, see Figure 1 (Example 2 curve) to obtain a reaction mixture having a molar ratio of SiO2:Al2O3:template:NaOH:H2O=100:1:0.15:0.10:7, and a mass ratio of starch to silica gel of 1:35. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor and heated to 120°C with stirring. Crystallization was carried out under autogenous pressure for 24 hours, followed by crystallization at 170°C for 100 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve sample designated E-2.

[0040] The XRD spectrum of E-2 has Figure 2 Characteristics indicate that E-2 is EWT molecular sieve.

[0041] The ratio of framework aluminum to non-framework aluminum of sample E-2 is shown in Table 1.

[0042] The Py-IR results of sample E-2 are shown in Table 2.

[0043] Example 3

[0044] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9 mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixed solution, and finally cross-linked starch (same as Example 1) was added to obtain a reaction mixture. The molar ratio of each component was SiO2: Al2O3: template: NaOH: H2O = 150: 1: 0.18: 0.12: 12, and the mass ratio of starch to silica gel was 1: 20. After stirring evenly, the obtained molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. Under stirring conditions, it was heated to 120 ° C. and crystallized under autogenous pressure for 24 hours, and then crystallized at 170 ° C. for 100 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110 ° C. for 12 hours to obtain a molecular sieve sample numbered E-3.

[0045] The XRD spectrum of E-3 has Figure 2 Characteristics indicate that E-3 is EWT molecular sieve.

[0046] The ratio of skeleton aluminum to non-framework aluminum of the E-3 sample is shown in Table 1.

[0047] The Py-IR results of sample E-3 are shown in Table 2.

[0048] Example 4

[0049] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9 mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixed solution, and finally cross-linked starch (same as Example 1) was added to obtain a reaction mixture. The molar ratio of each component was SiO2: Al2O3: template: NaOH: H2O = 150: 1: 0.09: 0.15: 11, and the mass ratio of starch to silica gel was 3: 100. After stirring evenly, the obtained molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor and heated to 120 ° C under stirring. Crystallization was carried out under autogenous pressure for 24 hours, and then crystallization was carried out at 170 ° C for 120 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110 ° C for 12 hours to obtain a molecular sieve sample numbered E-4.

[0050] The XRD spectrum of E-4 has Figure 2 Characteristics indicate that E-2 is EWT molecular sieve.

[0051] The ratio of skeleton aluminum to non-framework aluminum of the E-4 sample is shown in Table 1.

[0052] The Py-IR results of sample E-4 are shown in Table 2.

[0053] Example 5

[0054] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9 mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixed solution, and finally cross-linked starch (same as Example 1) was added to obtain a reaction mixture. The molar ratio of each component was SiO2: Al2O3: template: NaOH: H2O = 150: 1: 0.12: 0.15: 10, and the mass ratio of starch to silica gel was 3: 100. After stirring evenly, the obtained molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor and heated to 120 ° C under stirring. Crystallization was carried out under autogenous pressure for 24 hours, and then crystallization was carried out at 170 ° C for 100 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110 ° C for 12 hours to obtain a molecular sieve sample numbered E-5.

[0055] The XRD spectrum of E-5 has Figure 2 Characteristics indicate that E-5 is EWT molecular sieve.

[0056] The ratio of skeleton aluminum to non-framework aluminum of the E-5 sample is shown in Table 1.

[0057] The Py-IR results of sample E-5 are shown in Table 2.

[0058] Example 6

[0059] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9 mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixed solution, and finally cross-linked starch (same as in Example 1) was added to obtain a reaction mixture. The molar ratio of each component was SiO2:Al2O3:template:NaOH:H2O=150:1:0.18:0.12:9, and the mass ratio of starch to silica gel was 2:25. After stirring evenly, the obtained molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor and heated to 120°C under stirring. Crystallization was carried out under autogenous pressure for 24 hours, and then at 170°C for 100 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve sample numbered E-6.

[0060] The XRD spectrum of E-6 has Figure 2 Characteristics indicate that E-6 is EWT molecular sieve.

[0061] The ratio of skeleton aluminum to non-framework aluminum of E-6 sample is shown in Table 1.

[0062] The Py-IR results of E-6 sample are shown in Table 2.

[0063] Comparative Example 1

[0064] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixed solution to obtain a reaction mixture with a molar ratio of SiO2:Al2O3:template:NaOH:H2O=100:1:0.15:0.18:10. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. The mixture was heated to 120°C with stirring and crystallized under autogenous pressure for 24 hours, followed by crystallization at 160°C for 120 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain comparative molecular sieve sample D1.

[0065] The XRD spectrum of sample D1 is shown in Figure 4 , indicating that D1 is EWT molecular sieve.

[0066] The NMR carbon spectrum of D1 sample is shown in Figure 3 The ratio of skeleton aluminum to non-skeleton aluminum is shown in Table 1.

[0067] The Py-IR results of sample D1 are shown in Table 2.

[0068] Comparative Example 2

[0069] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture at a molar ratio of SiO2:Al2O3:template:NaOH:H2O=100:1:0.15:0.10:7. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. The reactor was heated to 120°C with stirring and crystallized under autogenous pressure for 24 hours, followed by crystallization at 170°C for 100 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a comparative molecular sieve sample, designated D2.

[0070] The XRD spectrum of sample D2 is the same as Figure 4 The characteristics indicate that it is an EWT structure molecular sieve.

[0071] The results of the ratio of framework aluminum to non-framework aluminum of sample D2 are shown in Table 1.

[0072] The Py-IR results of sample D2 are shown in Table 2.

[0073] Comparative Example 3

[0074] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture in a molar ratio of SiO2:Al2O3:template:NaOH:H2O = 150:1:0.18:0.12:12. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. While stirring, it was heated to 120°C and crystallized under autogenous pressure for 24 hours, followed by crystallization at 170°C for 100 hours. After the stainless steel reactor cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve comparison sample, designated D3.

[0075] The XRD spectrum of sample D3 is the same as Figure 4 The characteristics indicate that it is an EWT structure molecular sieve.

[0076] The results of the ratio of framework aluminum to non-framework aluminum of sample D3 are shown in Table 1.

[0077] The Py-IR results of sample D3 are shown in Table 2.

[0078] Comparative Example 4

[0079] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture in a molar ratio of SiO2:Al2O3:template:NaOH:H2O = 150:1:0.09:0.15:11. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. While stirring, it was heated to 120°C and crystallized under autogenous pressure for 24 hours, followed by crystallization at 170°C for 120 hours. After the stainless steel reactor cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve comparison sample, designated D4.

[0080] The XRD spectrum of sample D4 is the same as Figure 4 The characteristics indicate that it is an EWT structure molecular sieve.

[0081] The ratio of framework aluminum to non-framework aluminum of sample D4 is shown in Table 1.

[0082] The Py-IR results of sample D4 are shown in Table 2.

[0083] Comparative Example 5

[0084] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture at a molar ratio of SiO2:Al2O3:template:NaOH:H2O = 150:1:0.12:0.15:10. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. The reactor was heated to 120°C with stirring and crystallized under autogenous pressure for 24 hours, followed by crystallization at 170°C for 100 hours. After the stainless steel reactor was cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve comparison sample, designated D5.

[0085] The XRD spectrum of sample D5 is the same as Figure 4 The characteristics indicate that it is an EWT structure molecular sieve.

[0086] The ratio of skeleton aluminum to non-framework aluminum of D5 sample is shown in Table 1.

[0087] The Py-IR results of D5 sample are shown in Table 2.

[0088] Comparative Example 6

[0089] Sodium metaaluminate solution (sodium oxide 287g / L, aluminum oxide 159.7g / L) and template were added to deionized water and mixed evenly. Macroporous silica gel (150-250μm, 500m 2 / g, 0.9mL / g, Shandong Yiming Industry and Trade Co., Ltd.) was added to the mixture in a molar ratio of SiO2:Al2O3:template:NaOH:H2O = 150:1:0.18:0.12:9. After uniform stirring, the resulting molecular sieve precursor was transferred to a pressure-resistant stainless steel reactor. While stirring, it was heated to 120°C and crystallized under autogenous pressure for 24 hours, followed by crystallization at 170°C for 100 hours. After the stainless steel reactor cooled to room temperature, the solid product was separated, washed, and dried at 110°C for 12 hours to obtain a molecular sieve comparison sample, designated D6.

[0090] The XRD spectrum of sample D6 is the same as Figure 4 The characteristics indicate that it is an EWT structure molecular sieve.

[0091] The results of the ratio of framework aluminum to non-framework aluminum of sample D6 are shown in Table 1.

[0092] The Py-IR results of D6 sample are shown in Table 2.

[0093] Table 1 The ratio of framework aluminum to non-framework aluminum of molecular sieve characterized by NMR aluminum spectrum

[0094]

[0095] Table 2 Pyridine infrared characterization results of molecular sieves

[0096]

[0097] Example 7

[0098] This example illustrates the effect of the EWT structure molecular sieve provided by the present invention in the gas phase alkylation reaction of benzene and ethylene.

[0099] Sample E-1 from Example 1 was mixed with ammonium nitrate and water in a mass ratio of 1:1:10. The mixture was heated to 70°C and stirred for 1 hour. The mixture was then filtered and dried to obtain an ammonium-type EWT molecular sieve. The dried sample was ground uniformly and calcined at 550°C for 2 hours to obtain a hydrogen-type EWT molecular sieve. The hydrogen-type EWT molecular sieve was crushed and sieved to obtain 20-40 mesh particles to obtain catalyst BA-1.

[0100] The obtained catalyst was evaluated in the gas phase alkylation reaction of benzene with ethylene in a fixed bed microreactor. The operating conditions were: temperature 350°C, pressure 3.6 MPa, and ethylene mass space velocity 0.5 h -1 , benzene / olefin molar ratio 8.5.

[0101] The graph of ethylene conversion rate changing with time is shown in Figure 5 , the selectivity of ethylation products changes with time. Figure 6 .

[0102] Comparative Example 7

[0103] This comparative example illustrates the effect of the EWT structured molecular sieve comparative sample in the gas phase alkylation reaction of benzene and ethylene.

[0104] The sample D1 of comparative example 1 was mixed with ammonium nitrate and water in a mass ratio of 1:1:10, heated to 70°C and stirred for 1h, filtered and dried to obtain an ammonium-type EWT structural molecular sieve. The dried sample was ground evenly and calcined at 550°C for 2h to obtain a hydrogen-type EWT molecular sieve. The hydrogen-type EWT molecular sieve was pressed into tablets and crushed, and particles of 20-40 mesh were sieved to obtain catalyst BA-2. The obtained catalyst was evaluated for the gas-phase alkylation reaction of benzene and ethylene in a fixed-bed microreactor. The operating conditions were: temperature 350°C, pressure 3.6Mpa, and ethylene mass space velocity 0.5h -1 , benzene / olefin molar ratio 8.5.

[0105] The graph of ethylene conversion rate changing with time is shown in Figure 5, the selectivity of ethylation products changes with time. Figure 6 .

[0106] As can be seen from the data in Table 2, the EWT molecular sieve of the present invention exhibits slightly higher levels of medium-strong B acid than the comparative sample at a desorption temperature of 350°C, and the B / L acid ratio is also improved. Although the weak acid content at 200°C is low, the reaction temperature for the vapor-phase alkylation of benzene with ethylene is generally above 330°C, so a higher level of strong acid is more beneficial for the reaction.

[0107] Depend on Figure 5 、 Figure 6 The comparison of the BA-1 and BA-2 curves in FIG1 shows that the EWT structure molecular sieve of the present invention, which is used to catalyze the gas-phase alkylation reaction of benzene and ethylene, has higher activity stability and ethylation selectivity.

Claims

1. An EWT structure molecular sieve, characterized in that: The molecular sieve has a ratio of framework aluminum to non-framework aluminum characterized by nuclear magnetic aluminum spectrum of 3.0-4.5, and a ratio of B acid to L acid at 350° C. characterized by pyridine infrared spectrum of 0.22-0.

29.

2. The molecular sieve according to claim 1, wherein the molar ratio of silicon oxide to aluminum oxide is 75-150.

3. The method for preparing the EWT structured molecular sieve according to claim 1, characterized in that: The EWT structured molecular sieve is obtained by hydrothermal crystallization of a synthetic system mixture of an EWT structured molecular sieve to which an additive is added and the product is recovered, wherein the additive is a modified starch, the modified starch is a non-ionic cross-linked starch whose cross-linking agent is epichlorohydrin, and has starch units with a chain length of 10 or more glucose units, the ratio of linear chains to branches in the modified starch is 1:9-8:2, and the modified starch has a solid product whose nuclear magnetic resonance carbon spectrum, when put into an aqueous solution with a pH of ≥12 and measured under sealed conditions at 120°C for 72 hours, still has characteristic peaks at 60ppm, 73ppm, and 100ppm; the EWT structured molecular sieve to which an additive is added The synthesis system mixture of the T-structured molecular sieve is formed by uniformly mixing an alkali source, an organic template and water to form a solution, adding a silicon source and an aluminum source, and then adding the modified starch; or the synthesis system mixture of the EWT-structured molecular sieve with an additive is formed by first uniformly mixing an alkali source, an organic template and water to form a solution, adding the modified starch, beating to form a suspension, and then adding an aluminum source and a silicon source; the organic template is 1,1,6,6-tetramethyl-1,6-diazacyclododecane-1,6-dihydroxide diimine having a double-chain diquaternary ammonium base structure; in the synthesis system mixture of the EWT-structured molecular sieve with an additive, the molar ratio of the material composition is: SiO2 / Al2O3=80-200, alkali / SiO2=0.08-0.25, organic template / SiO2=0.08-0.2, H2O / SiO2=6-20, the mass ratio of the modified starch to the silicon source in the synthetic system mixture is 1:5-100, and the silicon source is calculated as SiO2; the hydrothermal crystallization is carried out in a closed container at 100-130°C for 10-30 hours, and then at 140-160°C for 100-180 hours.

4. The preparation method according to claim 3, wherein The alkali source is NaOH and / or KOH; the silicon source is silica gel or silica-alumina gel; and the aluminum source is selected from one or more of hydrated aluminum oxide, aluminum hydroxide and silica-alumina gel.

5. The EWT structure molecular sieve obtained by the preparation method of claim 3 or 4.

6. A method for the gas phase alkylation of benzene and ethylene, characterized in that: The EWT structure molecular sieve according to any one of claims 1-2 and 5 is used as the active component of the catalyst, and the alkylation reaction conditions are: temperature 280-350℃, pressure 3.0-3.8Mpa, ethylene mass space velocity 0.3-0.7h -1 , benzene / olefin molar ratio 8.0-9.

0.

7. The method for gas-phase alkylation of benzene with ethylene according to claim 6, wherein: The alkylation reaction conditions are: temperature 320-350°C, pressure 3.3-3.6 MPa, ethylene mass space velocity 0.5-0.6 h -1 , benzene / olefin molar ratio 8.2-8.5.

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