Afi molecular sieves, methods of making and using the same

Abstract

The present application relates to the field of molecular sieve, in particular to a kind of AFI molecular sieve and its preparation method and application.The molecular sieve has the schematic chemical composition shown in formula "mP2O5.nAl2O3.pM x O y " Wherein, M is metal, 0.80≤n / m≤1, 0.02≤(xp) / (2m)≤0.20;The ratio of mesoporous pore volume and micropore volume of the molecular sieve is not less than 5.The AFI molecular sieve of the present application has hierarchical pore structure, and the ratio of mesoporous pore volume and micropore volume is not less than 5, and the heteroatom doping makes it have more excellent acid catalytic activity, has higher cycle stability;The channel structure provides good mass transfer performance, conducive to the rapid progress of reaction, while having strong anti-carbon capacity;AFI crystal structure ensures that molecular sieve crystal structure and stable and active component are not easy to lose, to ensure that it can be recycled multiple times.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of molecular sieve, in particular to an AFI molecular sieve and a preparation method and application thereof. BACKGROUND

[0002] AlPO-5 molecular sieve has the topology structure of AFI, in which [AlO4] tetrahedron and [PO4] tetrahedron are strictly connected in alternation to form a three-dimensional electrically neutral structure, and the Al / P ratio is 1. Unlike the silicon-aluminum molecular sieve, the framework of the AlPO-5 crystal is electrically neutral, so it does not have a proton acid site and ion exchange performance, and is difficult to be used in acid catalytic chemical reactions. However, the atoms in the AlPO-5 framework can be replaced by heteroatoms, and the non-equivalent substitution can introduce a proton acid site in the framework, so that the framework properties change and have acid sites and ion exchange performance. The AlPO-5 molecular sieve is applied to the field of acid catalysis or adsorption separation.

[0003] In recent years, research on the catalytic conversion of biomass has been rising. Unlike the catalytic conversion system of petroleum, the conversion of biomass raw material molecules often does not require strong acid catalysis, because the biomass raw material molecules usually contain more oxygen, and strong acid sites are easy to cause side reactions of the biomass raw material, such as condensation and oligomerization. On the other hand, when the reactant molecules are large, or the system is prone to carbon deposition, higher requirements are put forward for the mass transfer performance and carbon deposition resistance of the molecular sieve catalyst. At this time, the catalyst often requires a developed mesoporous structure.

[0004] Para-xylene, i.e. PX, is one of the important bulk chemicals, and the annual consumption of PX in China has reached more than 35 million tons. It is mainly used for oxidation to prepare terephthalic acid monomer, and then polymerized with ethylene glycol monomer to prepare PET polyester (polyethylene terephthalate polyester), which is widely used in the plastic and fiber industries. At present, most of the PX still comes from petroleum raw materials, but there are already plastic bottles or textile fibers made of bio-based PX. The bio-based PX can be prepared from biomass-derived 2,5-dimethylfuran (DMF) and ethylene. The acidity of the solid acid is the key to the degree of reaction and the level of PX selectivity. Because 2,5-hexanedione (HDO) and DMF can be selectively converted to each other under acidic conditions, 2,5-hexanedione can also be used to prepare PX with ethylene. Suitable acidity can catalyze the dehydration of the main reaction, i.e. D-A addition, to selectively obtain the product PX, while minimizing the catalysis of side reactions, such as the condensation and alkylation side reactions of HDO which require strong acid catalysis. Because the raw material molecules DMF or HDO in this reaction system are relatively active, they are easy to oligomerize and carbonize themselves, so the catalyst also requires a large external specific surface area to resist carbon deposition and deactivation.

[0005] For the reaction of DMF and ethylene to prepare PX, the crystal type molecular sieve catalyst widely used in the field of petrochemical industry, such as ZSM-5, Beta, Y and the like, is easy to catalyze polymerization side reaction due to its excessively strong acidity, resulting in low PX selectivity, and easy to cause serious carbon deposition to cause rapid deactivation of the catalyst. Patent US20140296600A1 reports that H-type molecular sieve is used as a catalyst for preparing PX from DMF and ethylene, and when H-Y molecular sieve is used as a catalyst, the PX selectivity reaches 75%, and when H-Beta molecular sieve is used as a catalyst, the PX selectivity reaches 90%. CN109569677B reports that amorphous phosphate solid acid has high PX selectivity, but it has no crystal structure and amorphous shape, resulting in easy loss of active sites and poor stability. SUMMARY

[0006] The purpose of the present application is to overcome the problems of unsuitable acidity of the catalyst, easy loss of active sites and poor stability in the prior art, and to provide an AFI molecular sieve, a preparation method and application thereof. The molecular sieve has high acid catalytic reaction activity, strong carbon deposition resistance and high cycle stability.

[0007] In order to achieve the above-mentioned purpose, the first aspect of the present application provides an AFI molecular sieve, which has a schematic chemical composition represented by the formula "mP2O5·nAl2O3·pM x O y ", wherein M is a metal, 0.80≤n / m≤1, 0.02≤(xp) / (2m)≤0.20; the ratio of mesopore volume to micropore volume of the molecular sieve is not less than 5.

[0008] The second aspect of the present application provides a preparation method of the molecular sieve of the first aspect, which comprises: mixing a phosphorus source, an aluminum source, an M source, a soft template agent, a fatty amine and water, hydrothermal crystallization, washing and calcination; wherein the soft template agent is selected from at least one of quaternary ammonium salt, crown ether compound, sugar compound and organic acid.

[0009] The third aspect of the present application provides an application of the molecular sieve of the first aspect in organic conversion reaction.

[0010] The fourth aspect of the present application provides a preparation method of para-xylene, which comprises: contacting a reaction raw material with ethylene under optional solvent and catalyst conditions; wherein the catalyst is the molecular sieve of the first aspect; and the reaction raw material comprises 2,5-dimethylfuran and / or 2,5-hexanedione.

[0011] Through the above technical solution, the present application has the following beneficial effects:

[0012] The AFI molecular sieve of this invention has a hierarchical pore structure with a mesopore volume to micropore volume ratio of not less than 5. Heteroatom doping gives it superior acid catalytic activity and higher cycle stability. This pore structure provides good mass transfer performance, which is conducive to rapid reaction and has strong resistance to carbon deposition. The AFI crystal structure ensures the stability of the molecular sieve crystal structure and prevents the loss of active components, ensuring that it can be recycled multiple times. At the same time, the molecular sieve contains abundant acidic sites and few strong acid sites, making it suitable for biomass catalytic conversion reactions that do not require strong acid catalysis.

[0013] For example, by using the molecular sieve of the present invention as a catalyst, 2,5-dimethylfuran and / or 2,5-hexanedione can react with ethylene to convert to p-xylene (PX) with high efficiency and high selectivity, especially in the reaction of DMF and ethylene to prepare PX, where it exhibits high catalytic performance and high selectivity for PX. Attached Figure Description

[0014] Figure 1 The XRD pattern of the molecular sieve obtained in Example 1;

[0015] Figure 2 The image shows the SEM image of the molecular sieve obtained in Example 1.

[0016] Figure 3 The NH3-TPD diagram of the molecular sieve obtained in Example 1;

[0017] Figure 4 The image shows the py-FTIR spectrum of the molecular sieve obtained in Example 1;

[0018] Figure 5 The image shows the SEM image of the molecular sieve obtained in Comparative Example 1.

[0019] Figure 6 The image shows the SEM image of the molecular sieve obtained in Comparative Example 2. Detailed Implementation

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] This invention provides an AFI molecular sieve having the formula "mP₂O₅·nAl₂O₃·pM x O yThe schematic chemical composition shown is as follows: M is a metal, 0.80≤n / m≤1, 0.02≤(xp) / (2m)≤0.20; the ratio of mesopore volume to micropore volume of the molecular sieve is not less than 5. x and y are adjusted according to the type and valence state of the metal element to satisfy the condition of compound M. x O y The total valence of all elements in it is zero.

[0022] The AFI molecular sieve of this invention has a hierarchical pore structure with a mesopore volume to micropore volume ratio of not less than 5. Heteroatom doping gives it superior acid catalytic activity and higher cycle stability. This pore structure provides good mass transfer performance, which is conducive to rapid reaction and has strong resistance to carbon deposition. The AFI crystal structure ensures the stability of the molecular sieve crystal structure and prevents the loss of active components, ensuring that it can be recycled multiple times. At the same time, the molecular sieve contains abundant acidic sites and few strong acid sites, making it suitable for biomass catalytic conversion reactions that do not require strong acid catalysis.

[0023] According to a preferred embodiment of the present invention, 0.82 ≤ n / m ≤ 0.98, 0.02 ≤ (xp) / (2m) ≤ 0.18. By adopting the aforementioned preferred scheme, the acid catalytic activity, carbon deposition resistance, and stability of the molecular sieve can be further improved.

[0024] According to a preferred embodiment of the present invention, the ratio of mesopore volume to micropore volume of the molecular sieve is 5.0-20.0, preferably 9-18. By adopting the aforementioned preferred embodiment, the acid catalytic activity, carbon deposition resistance, and stability of the molecular sieve can be further improved.

[0025] According to a preferred embodiment of the present invention, the mesopore volume of the molecular sieve of the material is 0.20-1.00 cm³. 3 / g, and / or the micropore volume of the molecular sieve of the material is 0.03-0.12 cm³. 3 / g.

[0026] According to a preferred embodiment of the present invention, the ratio of the external specific surface area to the internal specific surface area of ​​the molecular sieve is not less than 1, preferably 1.0-2.0. By adopting the aforementioned preferred embodiment, the acid catalytic activity, carbon deposition resistance, and stability of the molecular sieve can be further improved.

[0027] According to a preferred embodiment of the present invention, the molecular sieve of the material has an external specific surface area of ​​50-150 m². 2 / g, preferably 75-150m 2 / g; and / or the internal specific surface area of ​​the molecular sieve of the material is 50-150m². 2 / g, preferably 75-150m 2 / g.

[0028] According to a preferred embodiment of the present invention, the total acidity of the molecular sieve of the material is 200-900 μmol / g, preferably 300-700 μmol / g.

[0029] According to a preferred embodiment of the present invention, the strong acid content of the molecular sieve in the material is no more than 15%, preferably no more than 12%. By adopting the aforementioned preferred embodiment, the acid catalytic activity, carbon deposition resistance, and stability of the molecular sieve can be further improved.

[0030] According to a preferred embodiment of the present invention, the molecular sieve of the material has Lewis / The ratio is 1.0-8.0. By adopting the aforementioned preferred scheme, the acid catalytic activity, carbon deposition resistance, and stability of the molecular sieve can be further improved.

[0031] According to a preferred embodiment of the present invention, M is at least one of Group IVA, Group IVB, Group VIIB, and Group VIII metals, preferably at least one of Sn, Zr, Co, Ti, Fe, and Mn. By adopting the aforementioned preferred embodiment, the acid catalytic activity, carbon deposition resistance, and stability of the molecular sieve can be further improved.

[0032] According to a preferred embodiment of the present invention, M is Sn and / or Co. In some embodiments, a bimetallic source is used to modulate the acidity, which can further improve the conversion or selectivity of a particular reaction.

[0033] This invention provides a method for preparing the aforementioned molecular sieve, the method comprising: mixing a phosphorus source, an aluminum source, an M source, a soft template agent, a fatty amine, and water; hydrothermal crystallization; washing; and calcination; wherein the soft template agent is selected from at least one of quaternary ammonium salts, crown ether compounds, sugar compounds, and organic acids.

[0034] According to a preferred embodiment of the present invention, the soft template agent is selected from at least one of C1-C16 alkyl-substituted ammonium halides, C12-C20 crown ethers, monosaccharides, and C4-C10 organic acids, preferably at least one of hexadecyltrimethylammonium bromide, 15-crown-5-ether, 18-crown-6-ether, glucose, and citric acid. By adopting the aforementioned preferred embodiment, the mesopores on the outer surface of the molecular sieve can be further increased, providing the molecular sieve catalytic material with a large specific surface area for the reaction, while also exhibiting strong resistance to carbon deposition.

[0035] According to a preferred embodiment of the present invention, the soft template agent is glucose.

[0036] According to a preferred embodiment of the present invention, the fatty amine is selected from at least one of N-cyclohexyldimethylamine, N,N-dicyclohexylmethylamine, triethylamine, and tripropylamine.

[0037] According to a preferred embodiment of the present invention, the hydrothermal crystallization conditions include: crystallization at 140-190℃ for 0.5-3.0 days, preferably at 160-180℃ for 0.75-1.50 days.

[0038] According to a preferred embodiment of the present invention, the mixing conditions include: the molar ratio of P source (calculated as P), Al source (calculated as Al), M source (calculated as M element), soft template agent, fatty amine and H2O is 1:(0.80-1.00):(0.02-0.20):(0.05-2.00):(0.20-1.50):(10-50), preferably the molar ratio of each substance is 1:(0.90-1.00):(0.02-0.12):(0.30-1.50):(0.25-1.00):(14-30).

[0039] According to a preferred embodiment of the present invention, the P source is selected from at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and ammonium phosphate, preferably phosphoric acid and / or ammonium dihydrogen phosphate.

[0040] According to a preferred embodiment of the present invention, the Al source is selected from at least one of aluminum sulfate, aluminum hydroxide, boehmite, and aluminum isopropoxide, preferably boehmite and / or aluminum hydroxide.

[0041] According to a preferred embodiment of the present invention, the M source is selected from a soluble salt of the corresponding metal.

[0042] According to a preferred embodiment of the present invention, the hydrothermal crystallization process is dynamic crystallization, and the rotation speed is 10-200 rpm, preferably 10-50 rpm.

[0043] According to a preferred embodiment of the present invention, both washing and calcination can be carried out according to conventional methods in the art, such as centrifugation and washing with deionized water to obtain a solid product, followed by drying and calcination. The drying can be carried out at 80-120°C, and the calcination can be carried out at 350-700°C for 2-8 hours.

[0044] This invention provides an application of the molecular sieve described above in organic conversion reactions, preferably in the catalytic DA reaction followed by a dehydration reaction.

[0045] This invention provides a method for preparing p-xylene, the method comprising: contacting reactants with ethylene under optional solvent and catalyst conditions; wherein the catalyst is the molecular sieve described above; and the reactants include 2,5-dimethylfuran and / or 2,5-hexanedione.

[0046] In this invention, the amount of catalyst used is not particularly limited as long as the purpose of this invention can be achieved. According to a preferred embodiment of this invention, the conditions for the contact reaction include: the mass ratio of the reactants to the catalyst is 3-18:1, preferably 5-15:1.

[0047] In this invention, ethylene is a gaseous raw material. During the reaction, ethylene is first introduced into the reaction system. As long as the purpose of this invention can be achieved, there is no special limitation on the pressure of introducing ethylene. According to a preferred embodiment of this invention, the conditions for the contact reaction include: the ethylene is pressurized to 1-6 MPa, preferably 3-4 MPa.

[0048] In order to make the reaction efficient, according to a preferred embodiment of the present invention, the conditions for the contact reaction include: a reaction temperature of 225-325°C, preferably 260-300°C.

[0049] According to a preferred embodiment of the present invention, the conditions for the contact reaction include: a reaction time of 4-48 hours, preferably 8-24 hours.

[0050] According to a preferred embodiment of the present invention, when xylene is prepared in the presence of a solvent, the concentration of the raw material in the solvent is not less than 10 wt%. The use of a solvent can reduce the polymerization of the raw material and improve product selectivity and raw material conversion rate, but a lower reaction solution concentration increases separation energy consumption; preferably, the raw material concentration is 15-30 wt%.

[0051] According to a preferred embodiment of the present invention, the solvent comprises an aprotic organic solvent.

[0052] According to a preferred embodiment of the present invention, the aprotic organic solvent is selected from one or more of tetrahydrofuran, n-hexane, cyclohexane, n-heptane, n-octane, dichloromethane, diethyl ether, and ethyl acetate.

[0053] In this invention, the XRD pattern of the material was obtained using a Bruker D8 Advance X-ray diffractometer in Germany, employing a CuKα ray source.

[0054] Scanning electron microscope (SEM) images were obtained using an S-4800II field emission scanning electron microscope.

[0055] In this invention, the NH3 temperature-programmed desorption (NH3-TPD) experiment was conducted on a TPD / TPR Altamira AMI-3300 instrument. The total acid content was calculated by fitting and peaking the obtained spectrum. Acids with desorption temperatures of 100-240℃ were defined as weak acids, acids with desorption temperatures of 240-320℃ were defined as medium-strong acids, and acids with desorption temperatures of 320-500℃ were defined as strong acids. The proportion of strong acids was then calculated.

[0056] In this invention, the acid type of the catalyst is determined using pyridine adsorption-FTIR (py-FTIR). The py-FTIR spectrum is obtained on a Nicolet Model 710 spectrometer. The specific operation steps are as follows: a) Sample preparation and pretreatment: Approximately 15 mg of sample is compressed into a thin disc with a diameter of 13 mm and placed in the infrared sample cell; then the sample is pretreated at 400℃ under vacuum conditions for 2 h. The background spectrum of the sample is obtained by scanning at 150℃, 250℃, and 350℃. b) After the sample cell cools to room temperature, pyridine is adsorbed for 10 min. Vacuum desorption is performed at 150℃ for 10 min, and the infrared absorption spectrum is scanned and recorded. The infrared absorption spectra are then scanned and recorded sequentially at 250℃ and 350℃. The difference spectrum before and after pyridine adsorption is the obtained Py-FTIR spectrum. 1450 cm⁻¹ -1 The absorption peak for L-acid is at 1540 cm⁻¹. -1 The peak at this location represents the absorption peak of Brønsted acid (B acid). The peak area at 150℃ is used to calculate the ratio of Lewis acid to Brønsted acid. The formula for calculating the acid content of the sample based on the spectrum is as follows:

[0057]

[0058] Where r and w are the diameter (cm) and mass (g) of the catalyst disc, respectively, and A is the integral absorbance value at the specified wavenumber peak based on the scanned pyridine adsorption-infrared absorption spectrum. IMEC is the integral molar extinction coefficient. L Version 2.22, IMEC B It is 1.67. C L With C B The ratio is Lewis / Acid ratio.

[0059] In this invention, the elemental composition of the molecular sieve was measured by an Agilent 725-ES inductively coupled plasma atomic emission spectrometer (ICP), and the elemental content was expressed in moles.

[0060] The present invention will be described in detail below through embodiments.

[0061] Unless otherwise specified in the following examples, all raw materials are commercially available products;

[0062] In this invention, the components of the reaction solution were qualitatively analyzed using an Agilent 7890A gas chromatography-mass spectrometry (GC-MS, Agilent Technologies, USA), and quantitatively analyzed using an Agilent 7890B gas chromatograph (GC, Agilent Technologies, USA), equipped with a flame ionization detector (FID) and a Wax polar capillary column. The conversion rate of the reactants and the selectivity of the products were calculated based on the molar amounts of the substances determined by gas chromatography.

[0063] In this invention, the formula for calculating the raw material conversion rate is:

[0064] Conversion rate of raw materials % = (Initial molar amount of raw materials - Remaining molar amount of raw materials) / (Initial molar amount of raw materials) × 100%.

[0065] In this invention, the formula for calculating product selectivity is:

[0066] Product selectivity % = (molar amount of product generated) / (molar amount of initial raw material - molar amount of remaining raw material) × 100%.

[0067] Example 1

[0068] 3.506 g of SnCl4·5H2O was added to 31.540 g of water, followed by 11.540 g of 85 wt% phosphoric acid and 6.555 g of pseudoboehmite (70% dry weight of Al2O3). After stirring until homogeneous, 7.206 g of glucose and 19.492 g of N,N-dicyclohexylmethylamine were added. The molar ratio of the mixture (P source as P, Al source as Al, Sn source as Sn, soft template agent, aliphatic amine, and H2O) was 1:0.90:0.10:0.50:1.00:20. The mixture was crystallized at 175 °C for 15 h. The resulting solid product was centrifuged, washed, dried at 80 °C for 12 h, and then calcined at 550 °C for 6 h to obtain the molecular sieve catalyst.

[0069] The obtained XRD pattern is as follows Figure 1 As shown, its crystal structure is an AFI topology. The SEM image is shown below. Figure 2 As shown, it is composed of stacked nanosheets and contains abundant interlayer mesopores. BET measured the internal specific surface area to be 98 m². 2 / g, micropore volume is 0.05cm³ 3 / g, with an external specific surface area of ​​136m² 2 / g, mesoporous pore volume is 0.63cm³ 3 / g, the ratio of external specific surface area to internal specific surface area is 1.39, and the ratio of mesopore volume to micropore volume is 12.6. ICP measurements showed an Al / P ratio of 0.91 and a Sn / P ratio of 0.11. The NH3-TPD diagram is shown below. Figure 3As shown, the total acid content is 658 μmol / g, and the strong acid content is 11%. The Py-FTIR spectrum is shown below. Figure 4 As shown, the calculated ratio of L acid to Brønsted acid is 3.7.

[0070] Example 2

[0071] Unlike Example 1, the amounts of each component were adjusted so that the molar ratio of P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.85:0.15:1.00:0.80:20, while all other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 64 m². 2 / g, micropore volume is 0.03cm³ 3 / g, with an external specific surface area of ​​147m² 2 / g, mesoporous pore volume is 0.81cm³ 3 The surface area ratio (A / g) was 2.30, and the ratio of mesopore volume to micropore volume was 27. ICP analysis showed an Al / P ratio of 0.87 and a Sn / P ratio of 0.15. NH3-TPD analysis revealed a total acid content of 674 μmol / g, with a strong acid content of 10%. Py-FTIR analysis showed a Li-to-B ratio of 2.6.

[0072] Example 3

[0073] Unlike Example 1, the amounts of each component were adjusted so that the molar ratio of P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.95:0.05:0.30:1.50:20, while all other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 80 m². 2 / g, micropore volume is 0.04cm³ 3 / g, with an external specific surface area of ​​82m² 2 / g, mesoporous pore volume is 0.49cm³ 3 The surface area ratio (A / g) was 1.03, and the ratio of mesopore volume to micropore volume was 12.25. ICP analysis showed an Al / P ratio of 0.96 and a Sn / P ratio of 0.06. NH3-TPD analysis revealed a total acid content of 524 μmol / g, with a strong acid content of 14%. Py-FTIR analysis showed a Li-to-B ratio of 4.2.

[0074] Example 4

[0075] Unlike Example 1, the soft template agent glucose was replaced with 15-crown-5-ether, and the molar ratio of the P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.90:0.10:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 113 m². 2 / g, micropore volume is 0.06cm³ 3 / g, with an external specific surface area of ​​145m² 2 / g, mesoporous pore volume is 0.84cm³ 3 The surface area ratio (A / g) was 1.28, and the ratio of mesopore volume to micropore volume was 14. ICP analysis showed an Al / P ratio of 0.92 and a Sn / P ratio of 0.12. NH3-TPD analysis determined the total acid content to be 588 μmol / g, with a strong acid content of 9%. Py-FTIR analysis showed a Li-to-B ratio of 2.8.

[0076] Example 5

[0077] Unlike Example 1, the soft template agent glucose was replaced with 18-crown-6-ether, and the molar ratio of the P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.90:0.10:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 141 m². 2 / g, micropore volume is 0.08cm³ 3 / g, with an external specific surface area of ​​148m² 2 / g, mesoporous pore volume is 0.91cm³ 3 The surface area ratio (A / g) was 1.05, and the ratio of mesopore volume to micropore volume was 11.38. ICP analysis showed an Al / P ratio of 0.92 and a Sn / P ratio of 0.11. NH3-TPD analysis revealed a total acid content of 641 μmol / g, with a strong acid content of 8%. Py-FTIR analysis showed a Li-to-B ratio of 2.1.

[0078] Example 6

[0079] Unlike Example 1, the soft template agent was replaced with 18-crown-6-ether, the fatty amine was replaced with triethylamine, and the molar ratio of P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.90:0.10:1.50:1.50:20, while all other steps remained the same. The final product XRD pattern is similar to... Figure 1Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 127 m². 2 / g, micropore volume is 0.07cm³ 3 / g, with an external specific surface area of ​​139m² 2 / g, mesoporous pore volume is 0.81cm³ 3 The surface area ratio (A / g) was 1.09, and the ratio of mesopore volume to micropore volume was 11.57. ICP analysis showed an Al / P ratio of 0.91 and a Sn / P ratio of 0.11. NH3-TPD analysis determined the total acid content to be 578 μmol / g, with a strong acid content of 10%. Py-FTIR analysis showed a Li-to-B ratio of 1.9.

[0080] Example 7

[0081] Unlike Example 1, the amounts of Al and Sn sources added were varied, and the molar ratio of P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.82:0.18:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 73 m². 2 / g, micropore volume is 0.03cm³ 3 / g, with an external specific surface area of ​​128m² 2 / g, mesoporous pore volume is 0.54cm³ 3 The surface area ratio (A / g) was 1.75, and the ratio of mesopore volume to micropore volume was 18. ICP analysis showed an Al / P ratio of 0.84 and a Sn / P ratio of 0.17. NH3-TPD analysis determined the total acid content to be 767 μmol / g, with a strong acid content of 9%. Py-FTIR analysis showed a Li-to-B ratio of 1.5.

[0082] Example 8

[0083] Unlike Example 1, the amounts of Al and Sn sources added were varied, and the molar ratio of P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.97:0.03:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 145 m². 2 / g, micropore volume is 0.09cm³ 3 / g, with an external specific surface area of ​​147m² 2 / g, mesoporous pore volume is 0.82cm³3 The surface area ratio (A / g) was 1.01, and the ratio of mesopore volume to micropore volume was 9.11. ICP analysis showed an Al / P ratio of 0.98 and a Sn / P ratio of 0.03. NH3-TPD analysis revealed a total acid content of 248 μmol / g, with a strong acid content of 14%. Py-FTIR analysis showed a Li-to-B ratio of 3.5.

[0084] Example 9

[0085] Unlike Example 1, the modulated metal source was zirconium isopropoxide, and the molar ratio of P source, Al source, Zr source, soft template agent, aliphatic amine, and H2O in the mixture was 1:0.90:0.10:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 124 m². 2 / g, micropore volume is 0.07cm³ 3 / g, with an external specific surface area of ​​137m² 2 / g, mesoporous pore volume is 0.75cm³ 3 The surface area ratio (A / g) was 1.10, and the ratio of mesopore volume to micropore volume was 10.71. ICP analysis showed an Al / P ratio of 0.91 and a Zr / P ratio of 0.12. NH3-TPD analysis revealed a total acid content of 387 μmol / g, with a strong acid content of 15%. Py-FTIR analysis showed a Li-to-B ratio of 5.1.

[0086] Example 10

[0087] Unlike Example 1, the metal source was changed to cobalt nitrate, and the molar ratio of P source, Al source, Co source, soft template agent, fatty amine, and H2O in the mixture was 1:0.90:0.10:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 115 m². 2 / g, micropore volume is 0.06cm³ 3 / g, with an external specific surface area of ​​140m² 2 / g, mesoporous pore volume is 0.76cm³ 3 The surface area ratio (A / g) was 1.22, and the ratio of mesopore volume to micropore volume was 12.67. ICP analysis showed an Al / P ratio of 0.92 and a Co / P ratio of 0.12. NH3-TPD analysis revealed a total acid content of 312 μmol / g, with a strong acid content of 10%. Py-FTIR analysis showed a Li-to-B ratio of 6.2.

[0088] Example 11

[0089] Unlike Example 1, two metal sources, Sn and Co, were used, with a Sn to P source ratio of 0.07 and a Co to P source ratio of 0.03. The molar ratio of the mixture of P source, Al source, total metal source, soft template agent, aliphatic amine, and H₂O was 1:0.90:0.10:0.50:1.00:20, while all other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it is an AFI topology. SEM diagram and... Figure 2 Similarly, BET measured the internal specific surface area to be 10⁸ m². 2 / g, micropore volume is 0.05cm³ 3 / g, with an external specific surface area of ​​142m² 2 / g, mesoporous pore volume is 0.79cm³ 3 The surface area ratio (A / g) was 1.31, and the ratio of mesoporous pore volume to microporous pore volume was 15.8. ICP analysis showed an Al / P ratio of 0.92, a Sn / P ratio of 0.08, and a Co / P ratio of 0.03. NH3-TPD analysis revealed a total acid content of 465 μmol / g, with a strong acid content of 10%. Py-FTIR analysis showed a Li-acid to Beta-acid ratio of 5.8.

[0090] Example 12

[0091] The molecular sieve catalysts from Examples 1-11 were used to prepare PX from 2,5-dimethylfuran (DMF) and ethylene under the following conditions: the reaction solvent was n-heptane, the mass concentration of DMF in the solvent was 30%, the mass ratio of DMF to catalyst was 5:1, the reaction temperature was 270℃, and the reaction time was 24 h. 1.2 g of the molecular sieve catalyst from Examples 1-10, 6.0 g of DMF, and 14.0 g of n-heptane were added to a 100 mL magnetically stirred high-pressure reactor, and ethylene was introduced at 3.0 MPa. The reaction was carried out at 270℃ for 24 h. The DMF conversion and PX selectivity of the reaction solution were calculated by gas phase analysis, as shown in Table 1.

[0092] Table 1

[0093] Catalyst No. DMF conversion (%) PX selectivity (%) Example 1 98.5 96.1 Example 2 97.5 94.0 Example 3 92.8 95.2 Example 4 95.3 96.3 Example 5 97.8 97.0 Example 6 96.3 95.1 Example 7 99.1 95.2 Example 8 91.4 94.5 Example 9 91.5 93.8 Example 10 90.7 96.7 Example 11 96.7 97.2

[0094] Example 13

[0095] Using the molecular sieve catalyst from Example 5, 1.2 g of catalyst, 6.0 g of 2,5-hexanedione (HDO), and 14.0 g of n-heptane were added to a 100 mL magnetically stirred high-pressure reactor, which was then charged with ethylene at 3.0 MPa. The reaction was carried out at 270 °C for 24 h to obtain the reaction solution. Gas phase analysis of the reaction solution showed that the HDO conversion rate was 99.2% and the PX selectivity was 96.3%.

[0096] Experiments have shown that HDO is also an effective raw material in the preparation of PX.

[0097] Example 14

[0098] Using the molecular sieve catalyst from Example 5, 3.0 g of catalyst and 20.0 g of DMF were added to a 100 mL magnetically stirred high-pressure reactor, and ethylene was introduced at 3.0 MPa. The reaction was carried out at 270 °C for 24 h to obtain a reaction solution. Gas phase analysis of the reaction solution showed that the DMF conversion rate was 88.5% and the PX selectivity was 94.8%.

[0099] Example 15

[0100] Using the molecular sieve catalyst from Example 5, 3.0 g of catalyst, 20.0 g of 2,5-hexanedione (HDO), and 14.0 g of tetrahydrofuran were added to a 100 mL magnetically stirred high-pressure reactor, which was then charged with ethylene at 3.0 MPa. The reaction was carried out at 300 °C for 24 h to obtain the reaction solution. Gas phase analysis of the reaction solution showed that the HDO conversion rate was 94.6% and the PX selectivity was 93.9%.

[0101] Example 16

[0102] Using the molecular sieve catalyst from Example 5, 1.2 g of catalyst, 6.0 g of DMF, and 14.0 g of n-heptane were added to a 100 mL magnetically stirred high-pressure reactor, and ethylene was introduced at 3.0 MPa. The reaction was carried out at 300 °C for 48 h to obtain a reaction solution. Gas phase analysis of the reaction solution showed that the DMF conversion rate was 99.6% and the PX selectivity was 97.0%.

[0103] Example 17

[0104] Cyclic performance tests were conducted using the molecular sieve catalyst from Example 5. 1.2 g of catalyst, 6.0 g of DMF, and 14.0 g of n-heptane were added to a 100 mL magnetically stirred high-pressure reactor, which was then charged with ethylene at 3.0 MPa. The reaction was carried out at 270 °C for 24 h. The DMF conversion and PX selectivity of the reaction solution were calculated by gas phase analysis. The molecular sieve catalyst was recovered, regenerated by calcination in air at 550 °C for 6 h, and then fed into the next cycle. The results are shown in Table 1. The DMF conversion and PX selectivity remained essentially unchanged, indicating that the catalyst structure is stable and has good cyclic performance.

[0105] Table 1

[0106] Cycle No. DMF conversion (%) PX selectivity (%) 1 97.8 97.0 2 97.7 97.0 3 97.1 96.9 4 97.4 97.0 5 97.6 96.9

[0107] Comparative Example 1

[0108] Unlike Example 1, no soft template agent was added, and the molar ratio of P source, Al source, Sn source, soft template agent, fatty amine, and H2O in the mixture was 1:0.90:0.10:0:1.00:20, while all other steps remained the same. The final product XRD pattern is similar to... Figure 1 Similarly, it follows an AFI topology. SEM, such as... Figure 5 As shown, the entire crystal grain surface is regular, with fewer surface mesopores than in the example. The internal specific surface area measured by BET is 169 m². 2 / g, micropore volume is 0.10cm³ 3 / g, with an external specific surface area of ​​15m² 2 / g, mesoporous pore volume is 0.14cm³ 3 / g. ICP analysis showed an Al / P ratio of 0.90 and a Sn / P ratio of 0.11. NH3-TPD analysis showed a total acid content of 593 μmol / g, with a strong acid content of 13%. Py-FTIR analysis showed a Li-to-B ratio of 4.5.

[0109] Using this molecular sieve catalyst, 1.2 g of catalyst, 6.0 g of DMF, and 14.0 g of n-heptane were added to a 100 mL magnetically stirred high-pressure reactor, which was then charged with ethylene at 3.0 MPa. The reaction was carried out at 270 °C for 24 h. Gas phase analysis of the reaction solution yielded a DMF conversion of 69.7% and a PX selectivity of 64.2%. The relatively small external specific surface area and mesoporous pore volume led to a decrease in catalytic activity.

[0110] Comparative Example 2

[0111] Unlike Example 1, SnCl4·5H2O was not added, and the molar ratio of P source, Al source, metal source, soft template agent, fatty amine, and H2O in the mixture was 1:1.00:0:0.50:1.00:20, while other steps remained the same. The final product XRD pattern is similar to...Figure 1 Similarly, it follows an AFI topology. SEM, such as... Figure 6 As shown, BET measured the internal specific surface area to be 125 m². 2 / g, micropore volume is 0.07cm³ 3 / g, with an external specific surface area of ​​138m² 2 / g, mesoporous pore volume is 0.75cm³ 3 / g. The Al / P ratio determined by ICP was 1.00. The total acid content determined by NH3-TPD was 24 μmol / g, and the strong acid content was 0%. The ratio of Litho- and Beta-acids determined by Py-FTIR was 8.7.

[0112] Using this molecular sieve catalyst, 1.2 g of catalyst, 6.0 g of DMF, and 14.0 g of n-heptane were added to a 100 mL magnetically stirred high-pressure reactor, which was then charged with ethylene at 3.0 MPa. The reaction was carried out at 270 °C for 24 h. Gas phase analysis of the reaction solution yielded a DMF conversion of 15.2% and a PX selectivity of 32.4%. The lack of heteroatoms resulted in a lack of acidic sites, leading to low catalytic activity of the molecular sieve.

[0113] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. An AFI molecular sieve, characterized in that, This molecular sieve has the formula "mP2O5•nAl2O3•pM". x O y The schematic chemical composition shown is given, where M is a metal, 0.80≤n / m≤1, 0.02≤(xp) / (2m)≤0.20; The ratio of the mesopore volume to the micropore volume of the molecular sieve is not less than 5.

2. The molecular sieve according to claim 1, wherein, 0.82≤n / m≤0.98, 0.02≤(xp) / (2m)≤0.18; and / or The ratio of mesopore volume to micropore volume of the molecular sieve is 5.0-20.

0.

3. The molecular sieve according to claim 2, wherein, The molecular sieve has a mesopore volume of 0.20-1.00 cm³. 3 / g, and / or the micropore volume of the molecular sieve is 0.03-0.12cm³. 3 / g.

4. The molecular sieve according to any one of claims 1-3, wherein, The ratio of the external specific surface area to the internal specific surface area of ​​the molecular sieve is not less than 1.

5. The molecular sieve according to claim 4, wherein, The ratio of the external specific surface area to the internal specific surface area of ​​the molecular sieve is 1.0-2.

0.

6. The molecular sieve according to claim 5, wherein, The molecular sieve has an external specific surface area of ​​50-150 m². 2 / g; and / or the internal specific surface area of ​​the molecular sieve is 50-150 m². 2 / g.

7. The molecular sieve according to any one of claims 1-3, wherein, The total acidity of the molecular sieve is 200-900 µmol / g; and / or The strong acid content of the molecular sieve is no more than 15%; and / or The Lewis / Brønsted ratio of the molecular sieve is 1.0-8.

0.

8. The molecular sieve according to claim 7, wherein, The total acidity of the molecular sieve is 300-700 µmol / g; and / or The strong acid content of the molecular sieve is no more than 12%.

9. The molecular sieve according to any one of claims 1-3, wherein, M is at least one of Group IVA, Group IVB, Group VIIB, and Group VIII metals.

10. The molecular sieve according to claim 9, wherein, M is at least one of Sn, Zr, Co, Ti, Fe and Mn.

11. The molecular sieve according to claim 10, wherein, M is Sn and / or Co.

12. The method for preparing the molecular sieve according to any one of claims 1-11, characterized in that, The method includes: mixing a phosphorus source, an aluminum source, an M source, a soft template agent, a fatty amine, and water, followed by hydrothermal crystallization, washing, and calcination; The soft template agent is selected from at least one of quaternary ammonium salts, crown ether compounds, sugar compounds, and organic acids.

13. The preparation method according to claim 12, wherein, The soft template agent is selected from at least one of C1-C16 alkyl-substituted ammonium halides, C12-C20 crown ether compounds, monosaccharides, and C4-C10 organic acids; and / or The fatty amine is selected from at least one of N-cyclohexyldimethylamine, N,N-dicyclohexylmethylamine, triethylamine, and tripropylamine.

14. The preparation method according to claim 13, wherein, The soft template agent is at least one selected from hexadecyltrimethylammonium bromide, 15-crown-5-ether, 18-crown-6-ether, glucose, and citric acid.

15. The preparation method according to claim 14, wherein, The soft template agent is glucose.

16. The preparation method according to any one of claims 12-15, wherein, The conditions for hydrothermal crystallization include: crystallization at 140-190℃ for 0.5-3.0 days; and / or The conditions for mixing include: The molar ratio of P source (calculated as P), Al source (calculated as Al), M source (calculated as M element), soft template agent, fatty amine and H2O is 1:(0.80-1.00):(0.02-0.20):(0.05-2.00):(0.20-1.50):(10-50).

17. The preparation method according to claim 16, wherein, The hydrothermal crystallization conditions include: crystallization at 160-180℃ for 0.75-1.50 days; and / or The conditions for mixing include: The molar ratio of P source (calculated as P), Al source (calculated as Al), M source (calculated as M element), soft template agent, fatty amine and H2O is 1:(0.90-1.00):(0.02-0.12):(0.30-1.50):(0.25-1.00):(14-30).

18. The use of the molecular sieve according to any one of claims 1-11 in organic conversion reactions.

19. The application according to claim 18, wherein, The molecular sieve is used in the catalytic DA reaction followed by a dehydration reaction.

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