AFI molecular sieve and preparation method and application thereof

Abstract

The invention relates to the field of molecular sieves, in particular to an AFI molecular sieve and a preparation method and application thereof. The molecular sieve has a schematic chemical composition shown in a formula of mP2O5.nAl2O3.pMxOy, M is a metal, n / m is more than or equal to 0.80 and less than or equal to 1, and (xp) / (2m) is more than or equal to 0.02 and less than or equal to 0.20; the ratio of the mesopore volume to the micropore volume of the molecular sieve is not less than 5. The AFI molecular sieve has a hierarchical pore structure, the ratio of the pore volume of mesopores to the pore volume of micropores is not less than 5, and heteroatoms are doped, so that the AFI molecular sieve has better acid catalytic activity and higher cycle stability; the porous structure provides good mass transfer performance, is beneficial to rapid proceeding of the reaction, and has strong anti-carbon deposition capability; the AFI crystal structure ensures that the molecular sieve crystal structure is stable, the active components are not easy to lose, and the molecular sieve can be recycled for multiple times.

Description

Technical Field

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

[0002] AlPO-5 molecular sieve has an AFI topological structure, in which [AlO4] tetrahedrons and [PO4] tetrahedrons are strictly connected alternately to form a three-dimensional electrically neutral structure, in which the Al / P ratio is 1. Unlike silica-alumina molecular sieves, the framework of AlPO-5 crystals is electrically neutral, so it does not have proton acid sites and ion exchange properties, and is difficult to use in acid-catalyzed chemical reactions. However, the atoms in the AlPO-5 framework can be replaced by heteroatoms, and non-equivalent substitutions can introduce proton acid sites into the framework, thereby changing the properties of the framework and having acid sites and ion exchange properties. This allows AlPO-5 molecular sieves to be applied to acid catalysis or adsorption separation fields.

[0003] In recent years, research on biomass catalytic conversion has emerged. Unlike the catalytic conversion system of petroleum, the conversion of biomass raw material molecules often does not require strong acid catalysis, because biomass raw material molecules usually contain more oxygen, and strong acid sites are prone to cause side reactions of biomass raw materials, 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 placed on the mass transfer performance and anti-carbon deposition performance of the molecular sieve catalyst, and the catalyst is often required to have a developed mesoporous structure.

[0004] Paraxylene, or PX, is one of the important bulk chemicals. China's annual consumption of PX has reached more than 35 million tons. It is mainly used to oxidize terephthalic acid monomers, and then polymerize with ethylene glycol monomers to prepare PET polyester (polyethylene terephthalate polyester), which is widely used in the plastics and fiber industries. At present, most of PX still comes from the refining of petroleum raw materials, but plastic bottles or textile fibers made of bio-based PX have appeared. Its 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 selectivity of PX. Since 2,5-hexanedione (HDO) and DMF can be highly selectively converted to each other under acidic conditions, 2,5-hexanedione can also be used to prepare PX with ethylene. The appropriate acidity can catalyze the main reaction, i.e., DA addition followed by dehydration, to selectively obtain the product PX, while minimizing the catalytic side reactions, such as the condensation side reaction and alkylation side reaction of HDO that require strong acid catalysis. Since the raw material molecules DMF or HDO in this reaction system are relatively active and prone to self-oligomerization and carbon deposition, this reaction also requires the catalyst to have a large external specific surface area to resist carbon deposition and deactivation.

[0005] For the reaction of preparing PX from DMF and ethylene, the crystal-type molecular sieve catalysts widely used in the petrochemical field, such as ZSM-5, Beta, Y and other molecular sieves, are too acidic. When preparing PX, they are easy to catalyze polymerization side reactions, resulting in low PX selectivity, and are easy to cause serious carbon deposition, resulting in rapid deactivation of the catalyst. Patent US20140296600A1 reported that H-type molecular sieves were used to catalyze the preparation of PX from DMF and ethylene. When HY molecular sieves were used for catalysis, the PX selectivity reached 75%, and when H-Beta molecular sieves were used for catalysis, the PX selectivity reached 90%. CN109569677B reported amorphous phosphate solid acids, which have high PX selectivity, but have no crystalline structure and are amorphous, resulting in easy loss of active sites and poor stability. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of inappropriate acidity, easy loss of active sites, poor stability and the like of the catalyst in the prior art, and to provide an AFI molecular sieve and its preparation method and application. 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 object, the present invention provides an AFI molecular sieve in the first aspect, wherein the molecular sieve has a formula of "mP2O5·nAl2O3·pM x O y ” is a schematic chemical composition shown in FIG. 1 , wherein M is a metal, 0.80≤n / m≤1, 0.02≤(xp) / (2m)≤0.20; and the ratio of the mesopore volume to the micropore volume of the molecular sieve is not less than 5.

[0008] The second aspect of the present invention provides a method for preparing the molecular sieve described in the first aspect, the method comprising: mixing a phosphorus source, an aluminum source, an M source, a soft template, a fatty amine and water, hydrothermally crystallizing, washing and calcining; wherein the soft template is selected from at least one of a quaternary ammonium salt, a crown ether compound, a sugar compound and an organic acid.

[0009] The third aspect of the present invention provides a use of the molecular sieve described in the first aspect in an organic conversion reaction.

[0010] The fourth aspect of the present invention provides a method for preparing paraxylene, which comprises: contacting the reaction raw materials with ethylene under optional solvent and catalyst conditions; wherein the catalyst is the molecular sieve described in the first aspect; and the reaction raw materials include 2,5-dimethylfuran and / or 2,5-hexanedione.

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

[0012] The AFI molecular sieve of the present invention has a multi-level pore structure, and the ratio of the mesopore volume to the micropore volume is not less than 5. Heteroatom doping makes it have better acid catalytic activity and higher cycle stability; the pore structure provides good mass transfer performance, which is conducive to the rapid reaction and has strong anti-carbon deposition ability; the AFI crystal structure ensures that the molecular sieve crystal structure is stable and the active components are not easy to lose, ensuring that it can be recycled for many times; at the same time, the molecular sieve contains abundant acid sites and fewer strong acid sites, and is 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 be efficiently and selectively converted into para-xylene (PX), especially in the reaction of DMF and ethylene to prepare PX, it has high catalytic performance and high selectivity for PX. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0015] Figure 2 is a SEM image of the molecular sieve obtained in Example 1;

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

[0017] Figure 4 is the py-FTIR graph of the molecular sieve obtained in Example 1;

[0018] Figure 5 is a SEM image of the molecular sieve obtained in Comparative Example 1;

[0019] Figure 6 This is the SEM image of the molecular sieve obtained in Comparative Example 2. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0021] The present invention provides an AFI molecular sieve having a formula of "mP2O5·nAl2O3·pM x O y" shows a schematic chemical composition, wherein 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. Wherein, x and y are adjusted according to the valence state of the metal element so as to satisfy the compound M x O y The total valence of the elements is zero.

[0022] The AFI molecular sieve of the present invention has a multi-level pore structure, and the ratio of the mesopore volume to the micropore volume is not less than 5. Heteroatom doping makes it have better acid catalytic activity and higher cycle stability; the pore structure provides good mass transfer performance, which is conducive to the rapid reaction and has strong anti-carbon deposition ability; the AFI crystal structure ensures that the molecular sieve crystal structure is stable and the active components are not easy to lose, ensuring that it can be recycled for many times; at the same time, the molecular sieve contains abundant acid sites and fewer strong acid sites, and is 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 above preferred embodiment, 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 the mesopore volume to the micropore volume of the molecular sieve is 5.0-20.0, preferably 9-18. By adopting the above preferred solution, 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 mesoporous pore volume of the molecular sieve of the material is 0.20-1.00 cm 3 / g, and / or the micropore volume of the molecular sieve of the material is 0.03-0.12cm 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 above preferred scheme, 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 ​​50-150m 2 / g, preferably 75-150m 2 / g; and / or the internal specific surface area of ​​the molecular sieve of the material is 50-150m 2 / g, preferably 75-150m 2 / g.

[0028] According to a preferred embodiment of the present invention, the total acid content 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 of the material is not more than 15%, preferably not more than 12%. By adopting the above preferred solution, 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 Lewis / The ratio is 1.0-8.0. By adopting the above preferred solution, 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 metals, Group IVB metals, Group VIIB metals, and Group VIII metals, preferably at least one of Sn, Zr, Co, Ti, Fe, and Mn. By adopting the above 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, the acidity is regulated by using a bimetallic source, which can further improve the conversion rate or selectivity of a specific reaction.

[0033] The invention provides a method for preparing the molecular sieve, which comprises: mixing a phosphorus source, an aluminum source, an M source, a soft template agent, a fatty amine and water, hydrothermally crystallizing, washing and roasting; 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 is selected from at least one of C1-C16 alkyl-substituted ammonium halides, C12-C20 crown ether compounds, 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 scheme, the mesopores on the outer surface of the molecular sieve can be further increased, so that the molecular sieve catalytic material provides a large specific surface area for the reaction, and at the same time has a strong ability to resist 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° C. for 0.5-3.0 days, preferably crystallization at 160-180° C. 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 as P, Al source as Al, M source as M element, soft template, fatty amine and H2O is 1:(0.80-1.00):(0.02-0.20):(0.05-2.00):(0.20-1.50):(10-50), and the preferred 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, pseudo-boehmite, and aluminum isopropoxide, preferably pseudo-boehmite and / or aluminum hydroxide.

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

[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, washing and calcining can be carried out according to conventional methods in the art, such as washing with deionized water by centrifugation to obtain a solid product, and then calcining after drying, wherein the drying can be carried out at 80-120°C, and the calcination can be carried out at 350-700°C for 2-8h.

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

[0045] The present invention provides a method for preparing p-xylene, which comprises: contacting reaction raw materials with ethylene under optional solvent and catalyst conditions; wherein the catalyst is the molecular sieve; and the reaction raw materials include 2,5-dimethylfuran and / or 2,5-hexanedione.

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

[0047] In the present invention, ethylene is a gaseous raw material. When the reaction is carried out, ethylene is first charged into the reaction system. As long as the purpose of the present invention can be achieved, the pressure of the charged ethylene is not particularly limited. According to a preferred embodiment of the present invention, the conditions of the contact reaction include: the ethylene is pressurized to 1-6MPa, preferably 3-4MPa.

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

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

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

[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, ether and ethyl acetate.

[0053] In the present invention, the XRD spectrum of the material was obtained on a D8 Advance X-ray diffractometer of Bruker, Germany, using a CuKα ray source.

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

[0055] In the present invention, the NH3 temperature programmed desorption (NH3-TPD) experiment is carried out on a TPD / TPR Altamira AMI-3300 instrument, and the total acid amount is calculated by fitting and peak separation of the obtained spectrum, and the acid corresponding to the desorption temperature of 100-240°C is defined as a weak acid, the acid corresponding to the desorption temperature of 240-320°C is defined as a medium-strong acid, and the acid corresponding to the desorption temperature of 320-500°C is defined as a strong acid, thereby calculating the proportion of strong acid.

[0056] In the present invention, the pyridine adsorption infrared (py-FTIR) method is used to determine the type of catalyst acid, and the py-FTIR spectrum is obtained on a Nicolet Model 710 spectrometer. The specific operating steps are as follows: a. Sample preparation and pretreatment, about 15 mg of sample is pressed into a thin disc with a diameter of 13 mm and loaded into an infrared sample tank; then the sample is pretreated at 400°C in a vacuum cell for 2 hours. The sample is scanned at 150°C, 250°C, and 350°C to obtain a background spectrum. b. Wait for the sample tank to cool to room temperature, and pyridine is adsorbed for 10 minutes. Vacuum desorption is carried out at 150°C for 10 minutes, and the infrared absorption spectrum is scanned and recorded. The infrared absorption spectrum is scanned and recorded at 250°C and 350°C in sequence. The difference spectrum before and after pyridine adsorption is the obtained Py-FTIR spectrum. 1450cm -1 The absorption peak of L acid is 1540cm -1 The absorption peak of B acid is at 150℃. The peak area is calculated to get the ratio of L acid to B 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, A is the integral value of the absorbance at the specified wave number peak based on the scanning pyridine adsorption-infrared absorption spectrum. IMEC is the integrated molar extinction coefficient, IMEC L 2.22, IMEC B is 1.67. L With C B The ratio is Lewis / Acid ratio.

[0059] In the present invention, the element content composition of the molecular sieve is measured by Agilent 725-ES inductively coupled plasma atomic emission spectrometer (ICP), and the element content is measured in moles.

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

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

[0062] In the present invention, the reaction liquid components are analyzed qualitatively by Agilent 7890A gas chromatograph (GC-MS, Agilent, USA), the chromatographic column used is a Wax polar capillary column, and the quantitative analysis is performed by Agilent 7890B gas chromatograph (GC, Agilent, USA), which is equipped with a hydrogen ion flame detector (FID) and a Wax polar capillary column. The conversion rate of the raw material and the product selectivity are calculated based on the molar amount of the substance measured by the gas chromatography.

[0063] In the present invention, the raw material conversion rate calculation formula is:

[0064] The conversion rate of the raw material % = (initial molar amount of the raw material - the remaining molar amount of the raw material) / (initial molar amount of the raw material) × 100%.

[0065] In the present invention, the product selectivity calculation formula is:

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

[0067] Example 1

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

[0069] The obtained XRD pattern is as follows Figure 1 As shown in Figure 2, it can be seen that its crystal structure is an AFI topological structure. Figure 2 As shown in the figure, it is composed of nanosheets and contains abundant interlayer mesopores. The internal specific surface area measured by BET is 98m 2 / g, micropore volume is 0.05cm 3 / g, external specific surface area is 136m 2 / g, and the mesopore volume is 0.63cm 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 measured Al / P ratio of 0.91, Sn / P ratio of 0.11. NH3-TPD diagram as shown Figure 3As shown in Figure 2, the total acid content is 658 μmol / g and the strong acid content is 11%. Figure 4 As shown, the ratio of L acid to B acid is calculated to be 3.7.

[0070] Example 2

[0071] The difference from Example 1 is that the amount of each component added is adjusted so that the molar ratio of the P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.85:0.15:1.00:0.80:20, and the other steps remain the same. The XRD pattern of the final product is the same as Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​64 m 2 / g, micropore volume is 0.03cm 3 / g, external specific surface area is 147m 2 / g, and the mesopore volume is 0.81cm 3 / g, the ratio of external specific surface area to internal specific surface area is 2.30, and the ratio of mesopore volume to micropore volume is 27. ICP measured the Al / P ratio to be 0.87, and the Sn / P ratio to be 0.15. NH3-TPD measured the total acid content to be 674μmol / g, and the strong acid content to be 10%. Py-FTIR measured the ratio of L acid to B acid to be 2.6.

[0072] Example 3

[0073] The difference from Example 1 is that the amount of each component added is adjusted so that the molar ratio of the P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.95:0.05:0.30:1.50:20, and the other steps remain the same. The XRD pattern of the final product is the same as Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​80 m 2 / g, micropore volume is 0.04cm 3 / g, external specific surface area is 82m 2 / g, and the mesopore volume is 0.49cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.03, and the ratio of mesopore volume to micropore volume is 12.25. ICP measured the Al / P ratio to be 0.96 and the Sn / P ratio to be 0.06. NH3-TPD measured the total acid content to be 524μmol / g and the strong acid content to be 14%. Py-FTIR measured the ratio of L acid to B acid to be 4.2.

[0074] Example 4

[0075] The difference from Example 1 is that the soft template glucose is replaced by 15-crown-5-ether, the molar ratio of the P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.90:0.10:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​113 m 2 / g, micropore volume is 0.06cm 3 / g, external specific surface area is 145m 2 / g, and the mesopore volume is 0.84cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.28, and the ratio of mesopore volume to micropore volume is 14. ICP measured the Al / P ratio to be 0.92, and the Sn / P ratio to be 0.12. NH3-TPD measured the total acid content to be 588μmol / g, and the strong acid content to be 9%. Py-FTIR measured the ratio of L acid to B acid to be 2.8.

[0076] Example 5

[0077] The difference from Example 1 is that the soft template glucose is replaced by 18-crown-6-ether, the molar ratio of the P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.90:0.10:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​141 m 2 / g, micropore volume is 0.08cm 3 / g, external specific surface area is 148m 2 / g, and the mesopore volume is 0.91cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.05, and the ratio of mesopore volume to micropore volume is 11.38. ICP measured the Al / P ratio to be 0.92, and the Sn / P ratio to be 0.11. NH3-TPD measured the total acid content to be 641μmol / g, and the strong acid content to be 8%. Py-FTIR measured the ratio of L acid to B acid to be 2.1.

[0078] Example 6

[0079] The difference from Example 1 is that the soft template is replaced by 18-crown-6-ether, the fatty amine is replaced by triethylamine, and the molar ratio of the P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.90:0.10:1.50:1.50:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​127 m 2 / g, micropore volume is 0.07cm 3 / g, external specific surface area is 139m 2 / g, and the mesopore volume is 0.81cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.09, and the ratio of mesopore volume to micropore volume is 11.57. ICP measured the Al / P ratio to be 0.91 and the Sn / P ratio to be 0.11. NH3-TPD measured the total acid content to be 578μmol / g and the strong acid content to be 10%. Py-FTIR measured the ratio of L acid to B acid to be 1.9.

[0080] Example 7

[0081] The difference from Example 1 is that the amount of Al source and Sn source added is adjusted, and the molar ratio of P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.82:0.18:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​73 m 2 / g, micropore volume is 0.03cm 3 / g, external specific surface area is 128m 2 / g, and the mesopore volume is 0.54cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.75, and the ratio of mesopore volume to micropore volume is 18. ICP measured the Al / P ratio to be 0.84, and the Sn / P ratio to be 0.17. NH3-TPD measured the total acid content to be 767μmol / g, and the strong acid content to be 9%. Py-FTIR measured the ratio of L acid to B acid to be 1.5.

[0082] Example 8

[0083] The difference from Example 1 is that the amount of Al source and Sn source added is adjusted, and the molar ratio of P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.97:0.03:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​145 m 2 / g, micropore volume is 0.09cm 3 / g, external specific surface area is 147m 2 / g, and the mesopore volume is 0.82cm3 / g, the ratio of external specific surface area to internal specific surface area is 1.01, and the ratio of mesopore volume to micropore volume is 9.11. ICP measured the Al / P ratio to be 0.98, and the Sn / P ratio to be 0.03. NH3-TPD measured the total acid content to be 248μmol / g, and the strong acid content to be 14%. Py-FTIR measured the ratio of L acid to B acid to be 3.5.

[0084] Example 9

[0085] The difference from Example 1 is that the metal source is zirconium isopropoxide, and the molar ratio of the mixture of P source, Al source, Zr source, soft template, fatty amine, and H2O is 1:0.90:0.10:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​124 m 2 / g, micropore volume is 0.07cm 3 / g, external specific surface area is 137m 2 / g, and the mesopore volume is 0.75cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.10, and the ratio of mesopore volume to micropore volume is 10.71. ICP measured the Al / P ratio to be 0.91 and the Zr / P ratio to be 0.12. NH3-TPD measured the total acid content to be 387μmol / g and the strong acid content to be 15%. Py-FTIR measured the ratio of L acid to B acid to be 5.1.

[0086] Example 10

[0087] The difference from Example 1 is that the metal source is cobalt nitrate, and the molar ratio of the mixture of P source, Al source, Co source, soft template, fatty amine, and H2O is 1:0.90:0.10:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 2 Similarly, the BET measured internal specific surface area of ​​115 m 2 / g, micropore volume is 0.06cm 3 / g, external specific surface area is 140m 2 / g, and the mesopore volume is 0.76cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.22, and the ratio of mesopore volume to micropore volume is 12.67. ICP measured the Al / P ratio to be 0.92 and the Co / P ratio to be 0.12. NH3-TPD measured the total acid content to be 312μmol / g and the strong acid content to be 10%. Py-FTIR measured the ratio of L acid to B acid to be 6.2.

[0088] Embodiment 11

[0089] The difference from Example 1 is that two metal sources Sn and Co are used, and the ratio of Sn source to P source is 0.07, the ratio of Co source to P source is 0.03, and the molar ratio of P source, Al source, total metal source, soft template, fatty amine, and H2O in the mixture is 1:0.90:0.10:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is the same as Figure 1 Similar to AFI topology. Figure 2 Similarly, the internal specific surface area measured by BET is 108m 2 / g, micropore volume is 0.05cm 3 / g, external specific surface area is 142m 2 / g, and the mesopore volume is 0.79cm 3 / g, the ratio of external specific surface area to internal specific surface area is 1.31, and the ratio of mesopore volume to micropore volume is 15.8. ICP measured the Al / P ratio to be 0.92, Sn / P ratio to be 0.08, and Co / P ratio to be 0.03. NH3-TPD measured the total acid content to be 465μmol / g, and the strong acid content to be 10%. Py-FTIR measured the ratio of L acid to B acid to be 5.8.

[0090] Example 12

[0091] The molecular sieve catalyst in the above-mentioned Example 1-11 was used to prepare PX from 2,5-dimethylfuran (DMF) and ethylene, and the reaction conditions were as follows: 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°C; and the reaction time was 24h. 1.2g of the molecular sieve catalyst in the above-mentioned Example 1-10, 6.0g of DMF and 14.0g of n-heptane were added to a 100mL magnetically stirred autoclave, and 3.0MPa of ethylene was charged. The reaction was carried out at 270°C for 24h, and the DMF conversion rate and PX selectivity of the reaction liquid were calculated by gas phase analysis, as shown in Table 1.

[0092] Table 1

[0093] Catalyst No. DMF conversion rate (%) 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 Embodiment 11 96.7 97.2

[0094] Example 13

[0095] Using the molecular sieve catalyst in Example 5, 1.2 g of the catalyst, 6.0 g of 2,5-hexanedione (HDO) and 14.0 g of n-heptane were added to a 100 mL magnetically stirred autoclave, and 3.0 MPa of ethylene was charged. The reaction was carried out at 270° C. for 24 h to obtain a reaction liquid, and the reaction liquid was analyzed by gas phase to obtain an HDO conversion rate of 99.2% and a PX selectivity of 96.3%.

[0096] Through experiments, it is found that HDO is also an effective raw material in the preparation of PX.

[0097] Embodiment 14

[0098] Using the molecular sieve catalyst in Example 5, 3.0 g of the catalyst and 20.0 g of DMF were added to a 100 mL magnetically stirred autoclave, and 3.0 MPa of ethylene was charged. The reaction was carried out at 270° C. for 24 h to obtain a reaction liquid, and the DMF conversion rate and PX selectivity were calculated by gas phase analysis to be 88.5% and 94.8%.

[0099] Embodiment 15

[0100] Using the molecular sieve catalyst in Example 5, 3.0 g of the catalyst, 20.0 g of 2,5-hexanedione (HDO) and 14.0 g of tetrahydrofuran were added to a 100 mL magnetically stirred autoclave, and 3.0 MPa of ethylene was charged. The reaction was carried out at 300° C. for 24 h to obtain a reaction liquid, and the reaction liquid was analyzed by gas phase to obtain an HDO conversion rate of 94.6% and a PX selectivity of 93.9%.

[0101] Example 16

[0102] Using the molecular sieve catalyst in Example 5, 1.2 g of the catalyst, 6.0 g of DMF and 14.0 g of n-heptane were added to a 100 mL magnetically stirred autoclave, and 3.0 MPa of ethylene was charged. The reaction was carried out at 300° C. for 48 h to obtain a reaction liquid, and the DMF conversion rate and PX selectivity were calculated by gas phase analysis of the reaction liquid to be 99.6% and 97.0%.

[0103] Embodiment 17

[0104] The molecular sieve catalyst in Example 5 was used for the cycle performance test. 1.2g of catalyst, 6.0g of DMF and 14.0g of n-heptane were added to a 100mL magnetically stirred autoclave and filled with 3.0MPa of ethylene. The reaction was carried out at 270°C for 24h, and the DMF conversion rate and PX selectivity of the reaction liquid were calculated by gas phase analysis. The molecular sieve catalyst was recovered, calcined in an air environment at 550°C for 6h, regenerated and put into the next cycle. The results are shown in Table 1. The DMF conversion rate and PX selectivity were basically unchanged, indicating that the catalyst structure was stable and had good cycle performance.

[0105] Table 1

[0106] Cycle times DMF conversion rate (%) 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] The difference from Example 1 is that no soft template is added, and the molar ratio of the P source, Al source, Sn source, soft template, fatty amine, and H2O in the mixture is 1:0.90:0.10:0:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 5 As shown, it can be seen that the surface of the entire crystal particle is regular and the surface mesopores are less than those in the embodiment. The internal specific surface area measured by BET is 169m 2 / g, micropore volume is 0.10cm 3 / g, external specific surface area is 15m 2 / g, and the mesopore volume is 0.14cm 3 / g. ICP measured the Al / P ratio to be 0.90 and the Sn / P ratio to be 0.11. NH3-TPD measured the total acid content to be 593 μmol / g and the strong acid content to be 13%. Py-FTIR measured the ratio of L acid to B acid to be 4.5.

[0109] Using this molecular sieve catalyst, 1.2g catalyst, 6.0g DMF and 14.0g n-heptane were added to a 100mL magnetically stirred autoclave, and 3.0MPa ethylene was charged. The reaction was carried out at 270℃ for 24h, and the DMF conversion rate and PX selectivity were calculated by gas phase analysis. The smaller external specific surface and mesopore volume led to a decrease in catalytic activity.

[0110] Comparative Example 2

[0111] The difference from Example 1 is that SnCl4·5H2O is not added, and the molar ratio of the P source, Al source, metal source, soft template, fatty amine, and H2O in the mixture is 1:1.00:0:0.50:1.00:20, and the other steps remain the same. The XRD pattern of the final product is Figure 1 Similar to AFI topology. Figure 6 As shown, the BET measured internal specific surface area is 125m 2 / g, micropore volume is 0.07cm 3 / g, external specific surface area is 138m 2 / g, and the mesopore volume is 0.75cm 3 / g. ICP measured the Al / P ratio to be 1.00. NH3-TPD measured the total acid content to be 24μmol / g, and the strong acid content to be 0%. Py-FTIR measured the ratio of L acid to B acid to be 8.7.

[0112] Using this molecular sieve catalyst, 1.2g of catalyst, 6.0g of DMF and 14.0g of n-heptane were added to a 100mL magnetically stirred autoclave, and 3.0MPa of ethylene was charged. The reaction was carried out at 270°C for 24h, and the DMF conversion rate and PX selectivity were calculated by gas phase analysis. The lack of heteroatoms leads to the lack of acidic sites, and the molecular sieve has low catalytic activity.

[0113] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. An AFI molecular sieve, characterized in that: The molecular sieve has the formula "mP2O5·nAl2O3·pM x O y ” Schematic chemical composition shown, wherein 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 the mesopore volume to the micropore volume of the molecular sieve is 5.0-20.

0. Preferably, the mesopore volume of the molecular sieve of the material is 0.20-1.00 cm 3 / g, and / or the micropore volume of the molecular sieve of the material is 0.03-0.12cm 3 / g.

3. The molecular sieve according to claim 1 or 2, wherein: 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; more preferably, The molecular sieve of the material has an external specific surface area of ​​50-150m 2 / g; and / or the internal specific surface area of ​​the molecular sieve of the material is 50-150m 2 / g.

4. The molecular sieve according to any one of claims 1 to 3, wherein: The total acid content of the molecular sieve of the material is 200-900 μmol / g, preferably 300-700 μmol / g; and / or The molecular sieve of the material has a strong acid content of no more than 15%, preferably no more than 12%; and / or The molecular sieve of the material The ratio is 1.0-8.

0.

5. The molecular sieve according to any one of claims 1 to 4, wherein: M is at least one of Group IVA metals, Group IVB metals, Group VIIB metals, and Group VIII metals, preferably at least one of Sn, Zr, Co, Ti, Fe, and Mn, and more preferably Sn and / or Co.

6. The method for preparing the molecular sieve according to any one of claims 1 to 5, characterized in that: The method comprises: mixing a phosphorus source, an aluminum source, an M source, a soft template, a fatty amine and water, hydrothermally crystallizing, washing and roasting; Wherein, the soft template agent is selected from at least one of quaternary ammonium salts, crown ether compounds, sugar compounds and organic acids.

7. The preparation method according to claim 6, wherein: The soft template is selected from at least one of C1-C16 alkyl-substituted ammonium halides, C12-C20 crown ether compounds, 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, preferably glucose; and / or The fatty amine is selected from at least one of N-cyclohexyldimethylamine, N,N-dicyclohexylmethylamine, triethylamine and tripropylamine.

8. The preparation method according to claim 6 or 7, wherein: The hydrothermal crystallization conditions include: crystallization at 140-190° C. for 0.5-3.0 days, preferably crystallization at 160-180° C. for 0.75-1.50 days; and / or The mixing conditions include: The molar ratio of P source as P, Al source as Al, M source as M element, soft template, 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 1:(0.90-1.00):(0.02-0.12):(0.30-1.50):(0.25-1.00):(14-30).

9. Use of the molecular sieve according to any one of claims 1 to 5 in an organic conversion reaction, preferably in catalyzing a DA reaction followed by a dehydration reaction.

10. A method for preparing p-xylene, characterized in that: The preparation method comprises: optionally contacting the reaction raw materials with ethylene under solvent and catalyst conditions; wherein, The catalyst is the molecular sieve according to any one of claims 1 to 5; The reaction raw materials include 2,5-dimethylfuran and / or 2,5-hexanedione; Preferably, The conditions of the contact reaction include: The mass ratio of the reaction raw materials to the catalyst is 3-18:1, preferably 5-15:1; and / or Ethylene pressure is 1-6MPa, preferably 3-4MPa; and / or The reaction temperature is 225-325°C, preferably 260-300°C; and / or The reaction time is 4-48h, preferably 8-24h.

Images