P-modified metal-doped MWW molecular sieve as well as preparation method and application thereof

Abstract

The invention relates to the field of molecular sieves, in particular to a P-modified metal-doped MWW molecular sieve as well as a preparation method and application thereof. AP delta-7 / AP in the molecular sieve is greater than or equal to 50%, AP delta-7 represents the peak area of a P species signal peak of a terminal group with P chemical shift at-7ppm + / -15ppm in a 31P MAS NMR spectrogram, and AP represents the total peak area of a signal peak in the 31P MAS NMR spectrogram. The molecular sieve provided by the invention has high activity, selectivity and stability, and excellent carbon deposition resistance.

Description

Technical Field

[0001] The invention relates to the field of molecular sieves, and in particular to a P-modified metal-doped MWW molecular sieve and a preparation method and application thereof. Background Art

[0002] Since the beginning of the 21st century, countries have been actively seeking new technologies that use biomass, a renewable resource, as raw materials. In the chemical industry, the technology of replacing traditional petroleum-based chemicals with bio-based chemicals has flourished. Paraxylene, or PX, is one of the most important bulk chemicals. It is mainly used for oxidation to produce terephthalic acid, and further polymerized with ethylene glycol to prepare polyethylene terephthalate polyester. It is widely used in the polyester fiber and polyester plastic industries. China's PX demand in 2021 is about 35 million tons. At present, most of PX comes from petroleum raw materials, but bio-based PX is beginning to appear in renewable plastic bottles and polyester fibers. One of the promising routes is the preparation of PX from biomass-derived 2,5-dimethylfuran (DMF) and ethylene.

[0003] DMF and ethylene first undergo a Diels–Alder cycloaddition reaction to generate a cycloaddition intermediate oxa-norbornene, which then undergoes a dehydration reaction under acid catalysis to generate PX and water. Since 2,5-hexanedione and DMF can be converted into each other under acidic conditions, 2,5-hexanedione can also be used as a raw material to prepare PX with ethylene under the catalysis of solid acid. In the reaction system for generating PX, side reactions include (1) side reactions triggered by DMF hydrolysis, i.e., DMF is hydrolyzed to 2,5-hexanedione and further dehydrated to 3-methyl-2-cyclopentene-1-one; (2) alkylation side reactions, i.e., cycloaddition intermediates undergo alkylation reactions with electron-rich molecules such as ethylene to generate over-alkylated products of PX; (3) oligomerization side reactions, i.e., oligomerization reactions of DMF or 2,5-hexanedione itself; and (4) isomerization of cycloaddition intermediates. DMF molecules are relatively active, and strong acids can easily cause self-polymerization of DMF molecules and trigger DMF hydrolysis and condensation side reactions. And suitable acidity satisfies the main reaction, i.e., DA addition and subsequent dehydration, and the product can be obtained with high selectivity. Therefore, the catalytic material should avoid strong acid sites in design, or use modification means to eliminate the strong acid sites on the catalyst. In addition, the oligomeric side reaction causes serious carbon deposition problems, and the catalytic material will be rapidly deactivated due to the carbon deposition problem on the surface, so it is required that the catalyst has a large external specific surface area to resist carbon deposition. Traditional silicon-aluminum molecular sieves usually have small external specific surface areas and strong acidity, but SCM-1 is a two-dimensional layered material with a huge external specific surface area, and the disadvantage is that it has strong acidity. Although CN113831238A and CN113831308A successfully prepared the modified SCM-1 material Sn-Al-SCM-1 or Zr-Al-SCM-1, strong acid sites still exist, and the problem of eliminating strong acid sites is not solved, and the catalyst will be difficult to catalyze DMF and ethylene to prepare PX with high selectivity.

[0004] CN103814005A reported the use of homogeneous metal salts as Lewis acid catalysts, which inevitably had the disadvantages of being difficult to recover and recycle, and could not meet the requirements of industrial production. CN102482177B reported on acid-washed activated carbon, and WO2014 / 043468A1 reported on supported metal salt catalysts, which used metal salts or acids as active sites of the catalysts, or loaded them on carriers, and had the disadvantages of easy loss of active components, and their cyclic performance would inevitably decrease gradually, and could not meet the requirements of industrial production. CN109569677B reported the use of amorphous phosphate solid acids for the reaction of DMF and ethylene to prepare PX, which had a high PX selectivity of 96%, but the application prospects of such non-crystalline catalysts still needed further investigation.

[0005] In summary, the main problems of the prior art are inappropriate acidity of the catalyst, and the acid strength of the molecular sieve catalyst is often too high, resulting in low product selectivity or easy loss of catalyst active sites and poor stability, which brings challenges to practical industrial applications. Summary of the invention

[0006] The purpose of the present invention is to overcome the problems of low product selectivity, easy loss of catalyst active sites and poor stability caused by excessively high acid strength of molecular sieve catalysts in the prior art, and to provide a P-modified metal-doped MWW molecular sieve and a preparation method and application thereof. The molecular sieve has high product selectivity, strong resistance to carbon deposition and high cyclic stability.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a P-modified metal-doped MWW molecular sieve, wherein A Pδ-7 / A P ≥50%.

[0008] The second aspect of the present invention provides a method for preparing the molecular sieve described in the first aspect of the present invention, the method comprising: using H-type MWW molecular sieve as a matrix, optionally removing part or all of the Al and then optionally grafting a non-aluminum metal M, and then performing P modification.

[0009] The third aspect of the present invention provides the use of the molecular sieve described in the first aspect of the present invention as a catalyst in the preparation of p-xylene using 2,5-dimethylfuran as a raw material and / or 2,5-hexanedione as a raw material.

[0010] Through the above technical solution, the present invention has the following advantages:

[0011] The molecular sieve of the present invention has high activity, selectivity, and stability, and excellent resistance to carbon deposition. 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). The two-dimensional layered structure of the molecular sieve gives good mass transfer performance, which is conducive to the smooth progress of the reaction, and has strong resistance to carbon deposition; compared with the molecular sieve not modified by P, the acid strength is greatly reduced after modification, so that its suitable acid strength effectively reduces the occurrence of strong acid-catalyzed alkylation, isomerization and various polymerization side reactions, and the content of key impurities (such as polyalkylbenzenes, isomerization products of cycloaddition intermediates, and oligomers of 2,5-dimethylfuran) is extremely low, which not only achieves high PX selectivity, but also greatly reduces the pressure of subsequent separation and purification of PX. P modification not only forms a new acid site with suitable acid strength, provides a small amount of B acid, but also its combination with the metal plays a role in stabilizing the active sites of the catalyst, and the catalyst is recycled without significant changes in activity. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is the XRD pattern of the P-Al-SCM-1 molecular sieve obtained in Example 1;

[0013] Figure 2 This is a SEM image of the P-Al-SCM-1 molecular sieve obtained in Example 1;

[0014] Figure 3 The P-Al-SCM-1 molecular sieve obtained in Example 1 31 P MAS NMR spectra;

[0015] Figure 4 is the NH 3 -TPD graph;

[0016] Figure 5 This is the Py-FTIR graph of the P-Al-SCM-1 molecular sieve obtained in Example 1. DETAILED DESCRIPTION

[0017] 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.

[0018] In the present invention, A Pδ-7 represent 31 The peak area of ​​the P species signal peak of the terminal group with a P chemical shift of -7ppm±15ppm in the P MAS NMR spectrum, A P Represents 31 P is the peak area of ​​the total signal peak in the MAS NMR spectrum.

[0019] The present invention provides a P-modified metal-doped MWW molecular sieve, wherein A Pδ-7 / A P ≥50%.

[0020] The PM-MWW molecular sieve of the present invention has high activity, selectivity, and stability, and excellent anti-carbon deposition ability.

[0021] According to a preferred embodiment of the present invention, the molecular sieve A Pδ-7 / A P ≥70%. For example, A in molecular sieve Pδ-7 / A PIt can be 70%, 80%, 90%, 100%. By adopting the above preferred solution, the activity, selectivity, stability and anti-carbon deposition ability can be further improved.

[0022] In the present invention, the molecular sieve is 31 There is also a signal peak with a P chemical shift of -26ppm±15ppm in the P MAS NMR spectrum, which is the signal peak of P species of pyrophosphate and polyphosphate.

[0023] According to a preferred embodiment of the present invention, the metal in the molecular sieve is selected from at least one of Group IVB, Group VB, Group VIB, Group IIIA, and Group IVA metals, preferably selected from at least one of Al, Sn, Ti, W, Zr, Nb, Ta, and Ga, more preferably at least one of Al, Sn, W, and Nb, and more preferably Sn. By adopting the above preferred scheme, the activity, selectivity, stability, and carbon deposition resistance of the molecular sieve can be further improved.

[0024] According to a preferred embodiment of the present invention, the MWW molecular sieve is at least one of MCM molecular sieves, ITQ molecular sieves and SCM molecular sieves, preferably SCM molecular sieves.

[0025] According to a preferred embodiment of the present invention, the SCM-type molecular sieve is selected from SCM-1 molecular sieve and / or SCM-2 molecular sieve, preferably SCM-1.

[0026] According to a preferred embodiment of the present invention, the crystals of the molecular sieve are two-dimensional layered structures. By adopting the above preferred solution, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0027] The two-dimensional layered structure refers to the thin nanosheet structure of the MWW type molecular sieve, which provides a large external specific surface area and is conducive to mass transfer.

[0028] According to a preferred embodiment of the present invention, the internal specific surface area of ​​the molecular sieve is 80-300m 2 / g, preferably 100-200m 2 By adopting the above preferred scheme, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0029] According to a preferred embodiment of the present invention, the external specific surface area of ​​the molecular sieve is 50-200m 2 / g, preferably 100-200m 2 By adopting the above preferred scheme, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0030] According to a preferred embodiment of the present invention, the Lewis / The ratio is not less than 1. By adopting the above preferred scheme, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0031] According to a preferred embodiment of the present invention, the total acid content of the molecular sieve is 400-900 μmol / g, preferably 500-700 μmol / g, wherein the strong acid content is ≤15%, preferably ≤10%. By adopting the above preferred scheme, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0032] According to a preferred embodiment of the present invention, the Si / metal molar ratio in the molecular sieve is 13-100, preferably 15-50. By adopting the above preferred scheme, the activity, selectivity, stability and carbon deposition resistance of the molecular sieve can be further improved.

[0033] According to a preferred embodiment of the present invention, the Si / P molar ratio in the molecular sieve is 15-100, preferably 20-50. By adopting the above preferred solution, the activity, selectivity, stability and carbon deposition resistance of the molecular sieve can be further improved.

[0034] The present invention provides a method for preparing the molecular sieve of the present invention, the method comprising: using H-type MWW molecular sieve as a matrix, optionally removing part or all of Al and optionally grafting non-aluminum metals, and then performing P modification. The molecular sieve of the present invention can be prepared by the method of the present invention.

[0035] According to a preferred embodiment of the present invention, the H-MWW molecular sieve is prepared by conventional methods in the art, and the structure directing agent in the MWW molecular sieve (for example, the SCM-1 molecular sieve synthesized by the preparation method described in CN104511271B) is calcined to remove the structure directing agent, and calcined in air or oxygen at 400-700° C. for 1-6 h; ion exchange is performed in an ammonium salt solution and then calcined. The conditions for ion exchange and calcination can be conventionally selected in the art, for example, in 1 mol / L NH 4 The mixture was exchanged in a Cl solution at 80°C for 1 h, and repeated 3 times; and calcined again in air or oxygen at 400-700°C for 1-6 h to obtain H-MWW.

[0036] In the present invention, there is no special requirement for the method of removing part or all of Al. According to a preferred embodiment of the present invention, the method of removing part or all of Al is: firstly subjecting the H-type MWW molecular sieve to a steam hydrothermal treatment, and then eluting with an acid solution. By adopting the above preferred scheme, the activity, selectivity, stability and anti-carbon deposition ability of the prepared molecular sieve can be further improved.

[0037] In the present invention, the acid solution has a wide optional range. According to a preferred embodiment of the present invention, the acid solution is selected from at least one of hydrochloric acid solution, oxalic acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution, preferably nitric acid solution.

[0038] In the present invention, the conditions for the water vapor hydrothermal treatment may be conventionally selected in the art. According to a preferred embodiment of the present invention, the conditions for the water vapor hydrothermal treatment include: being carried out in an inert gas atmosphere, wherein the inert atmosphere refers to a gas that does not participate in the reaction, and in the present invention, for example, may be nitrogen, air, argon, etc. The function of the gas is to carry water vapor through the material.

[0039] According to a preferred embodiment of the present invention, the conditions of the water vapor hydrothermal treatment include: the water vapor partial pressure is 10-100%, that is, this process can be achieved in pure water vapor, that is, 100% water vapor partial pressure, preferably the water vapor partial pressure is 30-70%.

[0040] According to a preferred embodiment of the present invention, the conditions of the water vapor hydrothermal treatment include: a temperature of 600-900°C, preferably 700-800°C.

[0041] According to a preferred embodiment of the present invention, the conditions of the water vapor hydrothermal treatment include: a time of 1-48 hours, preferably 6-12 hours.

[0042] By adopting the aforementioned preferred steam hydrothermal treatment conditions, the activity, selectivity, stability and carbon deposition resistance of the prepared molecular sieve can be further improved.

[0043] In the present invention, the elution conditions may be conventionally selected in the art. According to a preferred embodiment of the present invention, the elution conditions include: the concentration of the acid solution is 1 mol / L-14 mol / L.

[0044] According to a preferred embodiment of the present invention, the elution conditions include: a temperature of 20-120°C, preferably 80-110°C.

[0045] According to a preferred embodiment of the present invention, the elution conditions include: a time of 6-48 hours, preferably 12-24 hours.

[0046] According to a preferred embodiment of the present invention, the elution conditions include: eluting to a Si / Al molar ratio of 25-180, preferably 100-180.

[0047] By adopting the aforementioned preferred elution conditions, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0048] In the present invention, the method of grafting non-aluminum metal M can be a conventional choice in the art. According to a preferred embodiment of the present invention, the method of grafting non-aluminum metal M is a solvent reflux method, comprising: placing the molecular sieve from which part or all of Al has been removed in an organic solution containing a non-aluminum metal M source for reflux, followed by a first solid-liquid separation, a first washing, a first drying, and a first calcination. By adopting the aforementioned preferred scheme, the activity, selectivity, stability, and anti-carbon deposition ability of the prepared molecular sieve can be further improved.

[0049] According to a preferred embodiment of the present invention, the non-aluminum metal M source is selected from a compound of at least one metal selected from Sn, Ti, W, Zr, Nb, Ta, and Ga, preferably a compound of Sn and / or W and / or Nb metal, and more preferably at least one of tin tetrachloride, dimethyltin dichloride, niobium pentachloride, and tungsten hexachloride.

[0050] According to a preferred embodiment of the present invention, the organic solvent is selected from at least one of alkanes, aromatic hydrocarbons, and halogenated hydrocarbons, for example, dichloromethane and n-hexane.

[0051] According to a preferred embodiment of the present invention, the Si / M molar ratio in the grafted molecular sieve is 13-100, preferably 15-50.

[0052] According to a preferred embodiment of the present invention, the conditions for the first calcination include: a temperature of 400-700°C, preferably 500-600°C.

[0053] According to a preferred embodiment of the present invention, the conditions for the first calcination include: a time of 3-12 hours, preferably 4-8 hours.

[0054] By adopting the aforementioned method of preferably grafting non-aluminum metal M, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0055] In the present invention, there is no particular requirement for the conditions of the first solid-liquid separation, the first washing, and the first drying, as long as the purpose of the present invention can be achieved.

[0056] In the present invention, the P modification method can be a conventional choice in the art. According to a preferred embodiment of the present invention, the P modification method is: placing the molecular sieve grafted with non-aluminum metal M in an organic solution containing a phosphorus source for reflux, and then performing a second solid-liquid separation, a second washing, and a second calcination. By adopting the above preferred scheme, the activity, selectivity, stability, and carbon deposition resistance of the prepared molecular sieve can be further improved.

[0057] According to a preferred embodiment of the present invention, the phosphorus source is selected from at least one of dimethyl phosphoric acid, phosphorus oxychloride and phosphorus pentachloride.

[0058] In the present invention, as long as the purpose of the present invention can be achieved, there is no special requirement for the amount of the phosphorus source added. According to a preferred embodiment of the present invention, the amount of the P source added is 1 / 20-1 of the molar amount of silicon in the molecular sieve.

[0059] According to a preferred embodiment of the present invention, the organic solvent is selected from at least one of alkanes, aromatic hydrocarbons and halogenated hydrocarbons.

[0060] According to a preferred embodiment of the present invention, the Si / P molar ratio in the P-modified molecular sieve is 15-100, preferably 20-50.

[0061] According to a preferred embodiment of the present invention, the conditions for the second calcination include: a temperature of 400-700°C, preferably 500-600°C.

[0062] According to a preferred embodiment of the present invention, the conditions for the second calcination include: a time of 3-12 hours, preferably 4-8 hours.

[0063] By adopting the aforementioned method of preferably grafting non-aluminum metal M, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0064] In the present invention, there is no particular requirement for the reflux time, and the reflux time may be, for example, 0.5-12 hours.

[0065] In the present invention, there is no particular requirement for the conditions of the second solid-liquid separation and the second washing, as long as the purpose of the present invention can be achieved.

[0066] In the present invention, the microstructure (two-dimensional layered structure, thickness), pore structure and acidity of the H-type MWW molecular sieve can affect the product prepared by the present invention. According to a preferred embodiment of the present invention, the H-type MWW molecular sieve is selected from at least one of the H-type MCM molecular sieve, ITQ molecular sieve, and SCM molecular sieve; preferably, the H-type SCM molecular sieve; further preferably, the H-type SCM-1 molecular sieve and / or the H-type SCM-2 molecular sieve, more preferably the H-type SCM-1. By adopting the aforementioned preferred scheme, the activity, selectivity, stability and anti-carbon deposition ability of the molecular sieve can be further improved.

[0067] The present invention provides an application of the molecular sieve of the present invention as a catalyst in the preparation of p-xylene using 2,5-dimethylfuran and / or 2,5-hexanedione as a raw material.

[0068] Reaction:

[0069]

[0070] In the present invention, the reaction liquid components are analyzed qualitatively by Agilent 7890A gas chromatograph (GC-MS) of Agilent, USA, and the chromatographic column is a Wax polar capillary column, and the quantitative analysis is performed by Agilent 7890B gas chromatograph (GC) of Agilent, USA, equipped with a hydrogen ion flame detector (FID) and a Wax polar capillary column. The conversion rate and selectivity of the substance are calculated based on the molar amount of the substance measured by the gas chromatography.

[0071] In the present invention, the raw material conversion rate calculation formula is:

[0072] The conversion rate of the raw material (%) = (the molar amount of the raw material initially added - the molar amount of the remaining raw material) / (the molar amount of the raw material initially added) × 100%.

[0073] In the present invention, the product selectivity calculation formula is:

[0074] Product selectivity % = (molar amount of product generated by the reaction) / (molar amount of raw material initially added-molar amount of remaining raw material)×100%.

[0075] In the present invention, the XRD spectrum was obtained on a D8 Advance X-ray diffractometer from Bruker, Germany, using a CuKα ray source.

[0076] In the present invention, the element content composition of the molecular sieve is measured by an Agilent 725-ES inductively coupled plasma atomic emission spectrometer (ICP), the molecular sieve sample is digested with hydrofluoric acid, and the element content is measured in moles.

[0077] Scanning electron microscopy (SEM) images were obtained on a S-4800II field emission scanning electron microscope.

[0078] solid 31 Magic angle spinning NMR ( 31 P MAS NMR) spectra were obtained on a Varian 400 MHz NMR instrument. 3 PO 4 Use as 31 P Chemical shift reference.

[0079] In the present invention, NH 3 Programmed temperature desorption (NH 3 The TPD / TPR experiment was carried out on an Altamira AMI-3300 instrument, and the total acid content was calculated by fitting and peak separation of the obtained spectrum.

[0080] 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 100°C, 200°C, and 400°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 100°C for 10 minutes, and the infrared absorption spectrum is scanned and recorded. The infrared absorption spectrum is scanned and recorded at 200°C and 400°C in turn. 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 1450cm -1 and 1540cm -1 The ratio of the total absorption peak area at 40°C to the total absorption peak area of ​​pyridine at 100°C is the strong acid ratio.

[0081] The present invention will be described in detail below through examples.

[0082] Example 1

[0083] The SCM-1 molecular sieve raw powder was synthesized according to the preparation method described in patent CN 104511271B, and the structure directing agent was removed by calcination. Then, ion exchange and calcination were performed to obtain H-SCM-1. The silicon-to-aluminum ratio (atomic ratio) of the molecular sieve was 15.2 as measured by ICP.

[0084] The steps for preparing P-modified P-Al-SCM-1 molecular sieve from H-SCM-1 are as follows:

[0085] (1) The H-SCM-1 molecular sieve was subjected to high-temperature steam hydrothermal treatment at 700° C. in a nitrogen atmosphere and 60% steam partial pressure for 10 h;

[0086] (2) Preparation of P-Al-SCM-1: The hydrothermally treated molecular sieve was directly refluxed in a dichloromethane solution and treated with dimethylphosphoric acid for 1 hour. The amount of P source added was 1 / 10 of the molar amount of silicon in the molecular sieve. The solid product was obtained by centrifugation and washing with dichloromethane. The solid product was calcined at 550°C for 4 hours to obtain P-Al-SCM-1. The Si / Al ratio measured by ICP was 15.2 and the Si / P ratio was 21.2. The XRD spectrum is shown in the figure below. Figure 1 As shown in Figure 2, the MWW topology is still well maintained, SEM ( Figure 2 ) shows that it is a two-dimensional layered structure, and the internal specific surface area measured by BET is 93m 2 / g, external specific surface area is 136m 2 / g. Figure 3 As shown, the catalyst 31 A of P MAS NMR spectrum Pδ-7 / A P NH 3 -TPD spectrum such as Figure 4 As shown in the figure, the total acid content is calculated to be 684 μmol / g, and there is less NH 3 The adsorption amount indicates that there are fewer strong acid sites. Pyridine infrared spectrum ( Figure 5 ) shows that the overall L / B ratio is 1.9 at 100°C, and the pyridine molecules that are still not desorbed at 400°C are adsorbed on strong acid sites, and it is calculated that the proportion of strong acid is 9%.

[0087] Example 2

[0088] The difference from Example 1 is that the H-SCM-1 molecular sieve is treated at 600°C in a nitrogen atmosphere at 50% water vapor partial pressure for 48 hours, and the other steps remain the same to obtain the P-Al-SCM-1 molecular sieve. The Si / Al ratio measured by ICP is 15.2, and the Si / P ratio is 20.5. The internal specific surface area measured by BET is 105m 2 / g, external specific surface area is 127m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 674 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 2.4, and the calculated strong acid content was 12%.

[0089] Example 3

[0090] The difference from Example 1 is that the mixture is refluxed in n-hexane and treated with phosphorus oxychloride for 8 hours, and the amount of P source added is 1 / 10 of the molar amount of molecular sieve silicon. The solid product is obtained by centrifugation and washing with n-hexane, and calcined at 550°C for 4 hours. The other steps remain the same to obtain P-Al-SCM-1 molecular sieve. The Si / Al ratio measured by ICP is 15.2, and the Si / P ratio is 18.7. The internal specific surface area measured by BET is 84m 2 / g, external specific surface area is 108m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 754 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 1.8, and the calculated strong acid content was 7%.

[0091] Example 4

[0092] The SCM-1 molecular sieve raw powder was synthesized according to the preparation method described in patent CN 104511271B, and the structure directing agent was removed by calcination. Then, ion exchange and calcination were performed to obtain H-SCM-1. The silicon-to-aluminum ratio (atomic ratio) of the molecular sieve was 15.2 as measured by ICP.

[0093] P-Sn-SCM-1 modified by P is prepared from H-SCM-1. Al can be removed to different degrees to obtain P-Sn-SCM-1 molecular sieve.

[0094] The steps are:

[0095] (1) H-SCM-1 molecular sieve was subjected to high temperature steam hydrothermal treatment at 900°C nitrogen atmosphere and 10% water vapor partial pressure for 10 h;

[0096] (2) Al was partially eluted by acid solution using concentrated nitric acid 14 M at 120 °C for 48 h. The final Si / Al ratio was measured to be 142.

[0097] (3) Solvent reflux method to obtain Sn-SCM-1, the above-mentioned SCM-1 molecular sieve after de-Al is placed in anhydrous SnCl 4 CH 2 Cl 2 The solution was refluxed, and then CH 2 Cl 2 After washing and drying, Sn-SCM-1 was obtained by calcining at 550°C for 4 h.

[0098] (4) Treat Sn-SCM-1 molecular sieve with dimethylphosphoric acid for 1 hour in a dichloromethane solution, and add a P source in an amount of 1 / 10 of the molar amount of silicon in the molecular sieve. Centrifuge and wash with dichloromethane to obtain a solid product, which is calcined at 550°C for 4 hours to obtain P-Al-SCM-1. ICP measured the Si / Sn ratio to be 35.3 and the Si / P ratio to be 21.6. BET measured the internal specific surface area to be 101m 2 / g, external specific surface area is 116m 2 / g. The catalyst A Pδ-7 / A P 85%. NH 3 -TPD calculated the total acid content to be 641 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 2.8, and the calculated strong acid content was 6%.

[0099] Example 5

[0100] The difference from Example 4 is that the Al is partially eluted with an acid solution, and 1M nitric acid is used for elution at 80°C for 12h. The final Si / Al ratio is 25.5. The other steps remain the same to obtain P-Sn-SCM-1. The ICP measured Si / Sn ratio is 47.1, and the Si / P ratio is 28.9. The BET measured internal specific surface area is 124m 2 / g, external specific surface area is 178m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 852 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 2.2, and the calculated strong acid content was 11%.

[0101] Example 6

[0102] Different from Example 4, when preparing Sn-SCM-1, dimethyltin dichloride was used for reflux, and the other steps remained the same to obtain P-Sn-SCM-1. The Si / Sn ratio measured by ICP was 42.6, and the Si / P ratio was 35.6. The internal specific surface area measured by BET was 135m 2 / g, external specific surface area is 168m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 679 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 3.1, and the calculated strong acid content was 9%.

[0103] Example 7

[0104] Different from Example 4, when preparing Ti-SCM-1, TiCl 4 Reflow, other steps remain the same to obtain P-Ti-SCM-1. ICP measured Si / Ti ratio of 27.8, Si / P ratio of 23.6. BET measured internal specific surface area of ​​145m 2 / g, external specific surface area is 179m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 705 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 1.9, and the calculated strong acid content was 8%.

[0105] Example 8

[0106] Different from Example 4, when preparing Nb-SCM-1, NbCl 5Reflow, other steps remain the same to obtain P-Nb-SCM-1. ICP measured Si / Nb ratio of 29.0, Si / P ratio of 25.8. BET measured internal specific surface area of ​​94m 2 / g, external specific surface area is 141m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 478 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 2.1, and the calculated strong acid content was 11%.

[0107] Example 9

[0108] Different from Example 4, when preparing W-SCM-1, WCl 6 Reflow, other steps remain the same to obtain PW-SCM-1. ICP measured Si / W ratio of 22.5, Si / P ratio of 20.6. BET measured internal specific surface area of ​​85m 2 / g, external specific surface area is 128m 2 / g. The catalyst A Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 490 μmol / g. The infrared spectrum of pyridine showed an L / B ratio of 3.3, and the calculated strong acid content was 9%.

[0109] Example 10

[0110] The molecular sieve catalyst in the above-mentioned Example 1-9 was used for the reaction of preparing PX from 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 15%; the mass ratio of DMF to catalyst was 6:1; the reaction temperature was 250°C; and the reaction time was 12h. 0.5g of the catalyst in the above-mentioned Example 1-9, 3.0g of DMF and 17g of n-heptane were added to a magnetically stirred autoclave, and 2.0MPa of ethylene was charged. The reaction was carried out at 250°C for 12h, and the DMF conversion rate and PX selectivity of the reaction liquid were calculated by gas phase analysis, as shown in Table 1.

[0111] Table 1

[0112] Catalyst No. DMF conversion rate (%) PX selectivity (%) Example 1 98.1 97.4 Example 2 98.3 96.9 Example 3 97.0 97.7 Example 4 97.1 98.0 Example 5 96.9 95.4 Example 6 98.1 97.7 Example 7 93.5 94.9 Example 8 97.6 92.8 Example 9 96.7 94.1

[0113] Embodiment 11

[0114] Using the P-Al-SCM-1 molecular sieve in Example 1 as a catalyst, 0.5 g of the catalyst, 3.0 g of 2,5-hexanedione (HDO) and 17 g of n-heptane were added to a magnetically stirred high-pressure reactor, and 2.0 MPa of ethylene was charged, and the reaction was carried out at 250° C. for 12 h to obtain a reaction liquid. The reaction liquid was calculated by gas phase analysis to obtain an HDO conversion rate of 97.5% and a PX selectivity of 96.5%.

[0115] Through experiments, it is found that HDO is also an effective raw material in the preparation of PX.

[0116] Example 12

[0117] Using the P-Al-SCM-1 molecular sieve in Example 1 as a catalyst, 2.0 g of the catalyst and 15.0 g of DMF were added to a magnetically stirred high-pressure reactor, and 6.0 MPa of ethylene was charged. The reaction was carried out at 250° C. for 12 h to obtain a reaction liquid. The reaction liquid was analyzed by gas phase analysis to obtain a DMF conversion rate of 48.2% and a PX selectivity of 92.3%.

[0118] Through experiments, it was found that in the preparation of PX, the raw materials can achieve higher PX selectivity in the presence of organic solvents. However, in the absence of organic solvents, high reaction liquid concentration and product concentration can be achieved, and the output per unit reactor volume is higher.

[0119] Embodiment 13

[0120] Using the P-Al-SCM-1 molecular sieve in Example 1 as a catalyst, 1.0 g of the catalyst, 3.0 g of HDO and 17 g of n-hexane were added into a magnetically stirred high-pressure reactor, and 3.0 MPa of ethylene was charged. The reaction was carried out at 250° C. for 24 h to obtain a reaction liquid. The reaction liquid was analyzed by gas phase and the HDO conversion rate was calculated to be 98.2%, and the PX selectivity was 96.7%.

[0121] Embodiment 14

[0122] Using the P-Al-SCM-1 molecular sieve in Example 1 as a catalyst, 0.5 g of the catalyst, 3.0 g of DMF and 17.0 g of tetrahydrofuran were added into a magnetically stirred high-pressure reactor, and 4.0 MPa of ethylene was charged. The reaction was carried out at 300° C. for 3 h to obtain a reaction liquid. The reaction liquid was analyzed by gas phase analysis to obtain a DMF conversion rate of 95.2% and a PX selectivity of 97.0%.

[0123] The experiments of Examples 13 and 14 show that commonly used organic solvents are suitable for this reaction. As shown in Example 22, the reaction temperature was increased to 300°C, which can shorten the reaction time. However, the disadvantage is that the reactor has a higher requirement for high temperature resistance.

[0124] Embodiment 15

[0125] Using the P-Al-SCM-1 molecular sieve in Example 1 as a catalyst, 0.5 g of the catalyst, 3.0 g of HDO and 17 g of tetrahydrofuran were added into a magnetically stirred high-pressure reactor, and 1.0 MPa of ethylene was charged. The reaction was carried out at 270° C. for 24 h to obtain a reaction liquid. The reaction liquid was analyzed by gas phase to obtain an HDO conversion rate of 98.1% and a PX selectivity of 96.1%.

[0126] Example 16

[0127] Using the P-Al-SCM-1 molecular sieve in Example 1 as a catalyst, 0.5 g of the catalyst, 3.0 g of DMF and 17 g of tetrahydrofuran were added into a magnetically stirred high-pressure reactor, and 3.0 MPa of ethylene was charged. The reaction was carried out at 235° C. for 24 h to obtain a reaction liquid. The reaction liquid was analyzed by gas phase analysis to obtain a DMF conversion rate of 94.3% and a PX selectivity of 96.7%.

[0128] Embodiment 17

[0129] The P-Al-SCM-1 molecular sieve catalyst in the above-mentioned Example 1 was tested for the cyclic reaction activity of the reaction of preparing PX from DMF and ethylene. The reaction conditions were as follows: the reaction solvent was n-heptane, the mass concentration of DMF in the solvent was 15%; the mass ratio of DMF to catalyst was 6:1; the reaction temperature was 250°C; and the reaction time was 12h. 0.5g of the above-mentioned catalyst, 3.0g of DMF and 17g of n-heptane were added to a magnetically stirred high-pressure reactor, and 2.0MPa of ethylene was filled. The reaction was carried out at 250°C for 12h, and the DMF conversion rate and PX selectivity of the reaction liquid were calculated by gas phase analysis. After the reaction was completed, the used catalyst was centrifuged, and the carbon deposits were removed and put into the next cycle. Its performance is shown in Table 2. It can be seen that the DMF conversion rate and PX selectivity are basically unchanged, and the catalyst has excellent cyclic stability.

[0130] Table 2

[0131] Cycle times DMF conversion rate (%) PX selectivity (%) 1 98.1 97.4 2 98.0 97.6 3 98.3 97.0 4 97.5 97.3 5 98.0 97.3

[0132] Embodiment 18

[0133] Different from Example 1, the P modification in step (2) adopts the equal volume impregnation method, the amount of P source added is 1 / 10 of the molar amount of molecular sieve silicon, the dimethylphosphoric acid dichloromethane solution is impregnated, dried, and calcined at 550°C for 4h to obtain P-Al-SCM-1. The ICP measured Si / Al ratio is 15.2, and the Si / P ratio is 10.0. The BET measured internal specific surface area is 81m 2 / g, external specific surface area is 102m 2 / g. The catalyst31 A of P MAS NMR spectrum Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 863 μmol / g. The infrared spectrum of pyridine showed that the L / B ratio was 1.1, and the calculated strong acid ratio was 8%. 0.5 g of the catalyst, 3.0 g of DMF and 17 g of n-heptane were added to a magnetically stirred autoclave, and 2.0 MPa of ethylene was charged. The reaction was carried out at 250 ° C for 12 hours, and the reaction liquid was analyzed by gas phase to calculate the DMF conversion rate to be 90.2% and the PX selectivity to be 76%.

[0134] Comparative Example 1

[0135] The difference from Example 1 is that P-Al-Beta is obtained by using Beta molecular sieve from Tianjin Nanhua Catalyst Co., Ltd. The steps for preparing P-modified P-Al-Beta molecular sieve from H-Beta are exactly the same as those in Example 1.

[0136] The Si / Al ratio measured by ICP was 18.8, and the Si / P ratio was 24.3. The internal specific surface area measured by BET was 271 m 2 / g, external specific surface area is 19m 2 / g. The catalyst 31 A of P MAS NMR spectrum Pδ-7 / A P NH 3 -TPD calculated the total acid content to be 598μmol / g. The infrared spectrum of pyridine showed that the L / B ratio was 1.4, and the calculated strong acid ratio was 19%. 0.5g of the catalyst, 3.0g of DMF and 17g of n-heptane were added to a magnetically stirred high-pressure reactor, and 2.0MPa of ethylene was charged. The reaction was carried out at 250℃ for 12h, and the reaction liquid was analyzed by gas phase to calculate the DMF conversion rate to be 77.1% and the PX selectivity to be 68.2%.

[0137] It can be seen from the results of the examples that the molecular sieve prepared by the method of the present invention has abundant external specific surface area and suitable acidity, and especially has excellent properties of catalyzing the reaction of 2,5-dimethylfuran and / or 2,5-hexanedione as raw materials with ethylene to produce p-xylene. Compared with the catalyst of the comparative example, it has significantly better effect.

[0138] 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. A P-modified metal-doped MWW molecular sieve, characterized in that: The molecular sieve A Pδ-7 / A P ≥50%, A Pδ-7 represent 31 The peak area of ​​the P species signal peak of the terminal group with a P chemical shift of -7ppm±15ppm in the P MAS NMR spectrum, A P Represents 31 P is the peak area of ​​the total signal peak in the MAS NMR spectrum.

2. The molecular sieve according to claim 1, wherein The molecular sieve A Pδ-7 / A P ≥ 70%; and / or The metal in the molecular sieve is selected from at least one of Group IVB, Group VB, Group VIB, Group IIIA, and Group IVA metals, preferably the metal in the molecular sieve is selected from at least one of Al, Sn, Ti, W, Zr, Nb, Ta, and Ga, more preferably at least one of Al, Sn, W, and Nb; and / or The MWW molecular sieve is at least one selected from MCM molecular sieves, ITQ molecular sieves, and SCM molecular sieves, preferably SCM molecular sieves, and further preferably, the SCM molecular sieve is selected from SCM-1 molecular sieves and / or SCM-2 molecular sieves, more preferably SCM-1.

3. The molecular sieve according to claim 1 or 2, wherein: The crystals of the molecular sieve are two-dimensional layered structures; and / or The internal specific surface area of ​​the molecular sieve is 80-300m 2 / g, preferably 100-200m 2 / g; and / or The external specific surface area of ​​the molecular sieve is 50-200m 2 / g, preferably 100-200m 2 / g; and / or The Lewis / is not less than 1; and / or The total acid content of the molecular sieve is 400-900 μmol / g, preferably 500-700 μmol / g, wherein the strong acid content is ≤15%, preferably ≤10%.

4. The molecular sieve according to any one of claims 1 to 3, wherein: The Si / metal molar ratio in the molecular sieve is 13-100, preferably 15-50; and / or The Si / P molar ratio in the molecular sieve is 15-100, preferably 20-50.

5. The method for preparing the molecular sieve according to any one of claims 1 to 4, characterized in that: The method comprises: using H-type MWW molecular sieve as a matrix, optionally removing part or all of Al and then optionally grafting non-aluminum metal, and then performing P modification.

6. The preparation method according to claim 5, wherein: The method for removing part or all of Al is: first subjecting the H-type MWW molecular sieve to a steam hydrothermal treatment, and then subjecting it to an acid solution elution; preferably, The acid solution is selected from at least one of hydrochloric acid solution, oxalic acid solution, nitric acid solution, sulfuric acid solution and phosphoric acid solution, preferably nitric acid solution; and / or The conditions of the steam hydrothermal treatment include: The water vapor partial pressure is 10-100%, preferably 30-70%; and / or The temperature is 600-900°C, preferably 700-800°C; and / or The time is 1-48h, preferably 6-12h; and / or The elution conditions include: The concentration of the acid solution is 1 mol / L-14 mol / L; and / or The temperature is 20-120°C, preferably 80-110°C; and / or The time is 6-48h, preferably 12-24h; and / or The elution is performed to a Si / Al molar ratio of 25-180, preferably 100-180.

7. The preparation method according to claim 5 or 6, wherein: The method for grafting non-aluminum metal M is a solvent reflux method, comprising: placing the molecular sieve from which some or all of Al has been removed in an organic solution containing a non-aluminum metal M source for reflux, and then performing a first solid-liquid separation, a first washing, a first drying, and a first calcination; preferably, The non-aluminum metal M source is a compound of at least one metal selected from Sn, Ti, W, Zr, Nb, Ta, and Ga; and / or The organic solvent is selected from at least one of alkanes, aromatic hydrocarbons, and halogenated hydrocarbons; and / or The Si / M molar ratio in the grafted molecular sieve is 13-100, preferably 15-50; and / or The first calcination conditions include: The temperature is 400-700°C, preferably 500-600°C; and / or The time is 3-12h, preferably 4-8h.

8. The preparation method according to any one of claims 5 to 7, wherein: The P modification method is: placing the molecular sieve grafted with non-aluminum metal M in an organic solution containing a phosphorus source for reflux, and then performing a second solid-liquid separation, a second washing, and a second calcination; preferably, The phosphorus source is selected from at least one of dimethyl phosphoric acid, phosphorus oxychloride and phosphorus pentachloride; and / or The organic solvent is selected from at least one of alkanes, aromatic hydrocarbons, and halogenated hydrocarbons; and / or The Si / P molar ratio in the P-modified molecular sieve is 15-100, preferably 20-50; and / or The second calcination conditions include: The temperature is 400-700°C, preferably 500-600°C; and / or The time is 3-12h, preferably 4-8h.

9. The preparation method according to any one of claims 5 to 8, wherein: The H-type MWW molecular sieve is at least one of H-type MCM molecular sieves, ITQ molecular sieves, and SCM molecular sieves; preferably, H-type SCM molecular sieves; further preferably, H-type SCM-1 molecular sieves and / or H-type SCM-2 molecular sieves, and more preferably, H-type SCM-1.

10. Use of the molecular sieve according to any one of claims 1 to 4 as a catalyst in the preparation of p-xylene using 2,5-dimethylfuran and / or 2,5-hexanedione as raw materials.

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