Phosphorized ZSM-5 molecular sieve and synthesis method and application thereof

Abstract

The invention discloses a phosphatized ZSM-5 molecular sieve as well as a synthesis method and application thereof. Only one phosphorus morphological characteristic peak exists at a chemical shift position of-45 + / -10 in a < 31 > P NMR spectrogram of the phosphatized ZSM-5 molecular sieve. The phosphatized ZSM-5 molecular sieve has the advantage of high hydrothermal stability, and is suitable for aromatic hydrocarbon alkylation reaction; the product selectivity of the catalyst is improved and the service life of the catalyst is prolonged in the reaction.

Description

Technical Field

[0001] The invention belongs to the field of ZSM-5 molecular sieves, and specifically relates to a phosphated ZSM-5 molecular sieve and a synthesis method and application thereof. Background Art

[0002] Molecular sieves are synthesized by hydrothermal treatment of silica-alumina gel at a certain time and temperature. Parameters such as stirring speed, crystal seeds, crystallization temperature, gel composition, pH value, silica-alumina ratio and template concentration can control the synthesis and physicochemical properties of molecular sieves. Zeolite molecular sieves are a type of microporous crystalline material with regular pore structure and surface acid properties. They have a pore structure of specific size and shape, a large specific surface area and strong adjustable acid properties. They are widely used in the process of petroleum refining and processing, such as catalytic cracking, alkane isomerization, catalytic reforming and toluene disproportionation.

[0003] With the shortage and heavy quality of crude oil, molecular sieve catalysts are often needed to treat heavy fractions, low-quality oil raw materials containing impurities such as water and sulfur, which leads to the rapid deactivation of molecular sieve catalysts. In order to improve the hydrothermal stability and anti-coking ability of the catalyst, molecular sieves can be modified by phosphorus, which can significantly adjust the acid properties of molecular sieves and improve their hydrothermal stability.

[0004] Wei Qiang et al. (Acta Petrolei Sinica·Petroleum Processing, February 2012, Vol28(1), p15-20) found that when phosphorus was impregnated on Y molecular sieve, the phosphorus existed mainly in the form of amorphous phosphide. 31 In the P MAS-NMR spectrum, there is only a peak at the chemical shift of 0, while in the direct synthesis of the phosphated Y molecular sieve, two peaks appear at the chemical shifts of δ 0 and -33, and the peak areas of the two peaks are basically the same, indicating that the phosphated Y molecular sieve contains both phosphorus that has entered the molecular sieve framework and amorphous phosphorus on the surface of the molecular sieve.

[0005] Regarding methanol conversion technology in the petrochemical industry, since the raw materials contain oxygen atoms, at a reaction temperature of 400-600°C, water inevitably generated in the product exists in the form of high-temperature water vapor, which has an adverse effect on the life and regeneration of the catalyst. In order to improve the hydrothermal stability of the catalyst, phosphorus-modified ZSM-5 molecular sieves have been widely used in methanol reactions such as MTP, MTG, and alkylation due to their good hydrothermal stability. In the research progress on P modification of ZSM-5 molecular sieves by Feng Bing et al. (Industrial Catalysis 2019, Vol27(3), p6-13), it is discussed that under conventional conditions, phosphoric acid impregnation, trimethyl phosphite vapor deposition, AlPO 4The phosphorus modification of ZSM-5 is carried out by preparing core-shell molecular sieves with ZSM-5. After modification, the phosphorus species are mainly distributed on the surface of ZSM-5 molecular sieve in a non-skeleton form, which has a low degree of improvement on the hydrothermal stability of the molecular sieve and is easy to block the pores of the molecular sieve, resulting in a serious loss of micropore volume, reducing the accessibility of the active center of the molecular sieve and reducing the conversion rate. On the other hand, due to the high silicon-aluminum ratio of ZSM-5, phosphorus is difficult to enter the molecular sieve body phase. Therefore, direct hydrothermal synthesis of phosphorized ZSM-5 molecular sieves that can enter the molecular sieve body phase will significantly improve the hydrothermal stability and reduce the production cost of molecular sieves.

[0006] In summary, in recent years, methanol conversion technologies such as MTP, MTG, and methanol methylation have made certain progress. However, the high-temperature water vapor in the reaction process has a serious effect on the removal of framework aluminum in the molecular sieve, and the molecular sieve has insufficient hydrothermal stability, resulting in a short catalyst life and poor regeneration, which restricts the industrialization process of methanol technology. Summary of the invention

[0007] In view of the problems of insufficient hydrothermal stability, low conversion rate, and many side reactions of the ZSM-5 molecular sieve used as a catalyst in the existing methanol conversion technology, the present invention provides a phosphated ZSM-5 molecular sieve and its synthesis method and application. The phosphated ZSM-5 molecular sieve has the advantages of high hydrothermal stability and is suitable for aromatic alkylation reactions; the product selectivity of the catalyst is improved and the catalyst life is prolonged in the reaction.

[0008] The first aspect of the present invention provides a phosphated ZSM-5 molecular sieve. 31 There is only one characteristic peak of phosphorus form at the chemical shift of -45±10 in the P NMR spectrum.

[0009] According to the present invention, as a non-limiting example, the phosphated ZSM-5 molecular sieve 31 In the P NMR spectrum, there is only one characteristic peak of phosphorus form at the chemical shift of -54, -52, -50, -48, -42, -40, -38 or -36.

[0010] According to the present invention, in the phosphated ZSM-5 molecular sieve, the SiO 2 / Al 2 O 3 The molar ratio is 20 to 500. The specific surface area of ​​the phosphated ZSM-5 molecular sieve is 230 to 580 m 2 / g.

[0011] According to the present invention, in the phosphated ZSM-5 molecular sieve, based on the mass of the phosphated ZSM-5 molecular sieve, 2 O 5The phosphorus content is 0.2% to 20%, preferably 0.2% to 5.0%.

[0012] According to the present invention, the phosphated ZSM-5 molecular sieve is directly synthesized by a hydrothermal method. The phosphated ZSM-5 molecular sieve is not synthesized and then phosphated.

[0013] The second aspect of the present invention provides a method for synthesizing the above-mentioned phosphated ZSM-5 molecular sieve. The synthesis method comprises:

[0014] (1) pretreating a first phosphorus source;

[0015] (2) After mixing water, silicon source, aluminum source, inorganic base M, template R, and an optional second phosphorus source, the pretreated product of step (1) is added, aged, hydrothermally crystallized, and calcined to obtain a phosphated ZSM-5 molecular sieve.

[0016] According to the present invention, the pretreatment of the first phosphorus source in step (1) is to mix the first phosphorus source, water, silicon source and template and then perform hydrothermal pretreatment at low temperature. The hydrothermal pretreatment conditions are: temperature 60-120° C., time 3-40 hours.

[0017] According to the present invention, further, in the pre-treated material system of step (1), the first phosphorus source is P 2 O 5 The silicon source is SiO 2 , template agent R, in moles, P 2 O 5 / SiO 2 =0.05~0.50, R / SiO 2 =0.05~2,H 2 O / SiO 2 =10~50.

[0018] According to the present invention, further, the pre-treated material system in step (1) also contains ethanol. In terms of moles, ethanol / SiO 2 =0.1~10.

[0019] According to the present invention, further, the material system in step (1) is pretreated to obtain a uniform colloidal solution. Preferably, the first phosphorus source, water, silicon source and template are mixed under stirring for 10 to 30 hours.

[0020] According to the present invention, in step (1), the first phosphorus source includes at least one of phosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, and ethyl phosphate. The silicon source includes at least one of tetraethyl orthosilicate, silica sol, and white carbon black. The template agent is an organic amine, and preferably, the template agent includes at least one of tetrapropylammonium hydroxide (TPAOH) and tetrapropylammonium bromide (TPABr).

[0021] According to the present invention, in step (2), the silicon source includes at least one of tetraethyl orthosilicate, silica sol, and white carbon black. The aluminum source includes at least one of aluminum isopropoxide, aluminum sulfate, sodium aluminate, and diaspore. The second phosphorus source includes at least one of phosphoric acid, ammonium phosphate, ammonium hydrogen phosphate, and ethyl phosphate. The inorganic base M includes at least one of sodium hydroxide, sodium carbonate, and potassium hydroxide. The template R is an organic amine, and preferably, the template R includes at least one of tetrapropylammonium hydroxide and tetrapropylammonium bromide. The first phosphorus source and the second phosphorus source may be of the same or different types.

[0022] According to the present invention, in step (2), in the mixture of water, silicon source, aluminum source, inorganic base M, optional second phosphorus source, and template R, the silicon source is SiO 2 Aluminum source is Al 2 O 3 The second phosphorus source is P 2 O 5 Template R, in moles, R / Al 2 O 3 =1~18,SiO 2 / Al 2 O 3 =10~200,H 2 O / Al 2 O 3 =20~1500; the pH value of the mixed material is 9~13, P 2 O 5 / Al 2 O 3 = 0 to 12. When the feed in step (2) contains a second phosphorus source, preferably, the aluminum source is Al 2 O 3 The second phosphorus source is P 2 O 5 The molar ratio, P 2 O 5 / Al 2 O 3 =0.1~12.

[0023] According to the present invention, in step (2), the pre-treated product of step (1) accounts for 3% to 15% of the weight of the mixture obtained by mixing in step (2) in terms of aluminum oxide and silicon oxide in terms of silicon oxide.

[0024] According to the present invention, in step (2), the conditions for hydrothermal crystallization are: hydrothermal crystallization at 100-195°C for 24-120h, preferably 24-60h. The crystallization equipment is a crystallization tank. The conditions for roasting the crystallized product are: roasting at 350-650°C for 2-20h. Washing and drying can be performed before roasting. The drying conditions are: drying temperature 90-150°C, time 4-40h. Preferably, the hydrothermal crystallization temperature of step (2) is higher than the first phosphorus source pretreatment temperature of step (1), preferably at least 10°C higher, more preferably at least 20°C higher. The solid filtered after crystallization is quenched.

[0025] According to the present invention, in step (2), hydrothermal pre-crystallization can be performed before hydrothermal crystallization. The hydrothermal pre-crystallization can be performed multiple times, for example, 1 to 3 times. The pre-crystallization temperature is 60 to 100° C. and the time is 24 to 50 hours.

[0026] According to the present invention, in step (2), the aging is carried out under stirring at a temperature of 10 to 50° C. for 2 to 12 hours.

[0027] According to the present invention, in step (2), the phosphated ZSM-5 molecular sieve can be subjected to ammonium exchange and molding treatment. The molding can be carried out in a conventional molding manner, such as tablet molding, extrusion molding, etc.

[0028] The third aspect of the present invention provides the use of the phosphated ZSM-5 molecular sieve or the phosphated ZSM-5 molecular sieve prepared by the above method in the alkylation reaction of aromatic hydrocarbons.

[0029] According to the present invention, in the application, preferably, benzene and a methylating agent are contacted and reacted under the action of a phosphated ZSM-5 molecular sieve catalyst to obtain a mixture rich in aromatic hydrocarbons such as toluene, xylene, trimethylbenzene, etc. The methylating agent is preferably methanol.

[0030] According to the present invention, in the application, the reaction conditions include: the molar ratio of benzene to the methylating agent is 1:10 to 10:1, the weight space velocity of benzene is 1 to 10 hr -1 , the reaction temperature is 370-600°C, and the reaction pressure is 0.01-3.5MPa.

[0031] Compared with the prior art, the present invention has the following main beneficial effects:

[0032] 1. In the molecular sieve of the present invention, the phosphated ZSM-5 molecular sieve 31There is only one characteristic peak of phosphorus form at the chemical shift of -45±10 in the P NMR spectrum. The molecular sieve has strong hydrothermal stability and still maintains good XRD crystallinity after being treated with water vapor at 700°C for 20 hours. The phosphated ZSM-5 molecular sieve is suitable for aromatic alkylation reaction; in the reaction, the product selectivity of the catalyst is improved and the catalyst life is prolonged.

[0033] 2. The phosphated ZSM-5 molecular sieve of the present invention is directly prepared by hydrothermal synthesis, rather than the conventional technique of synthesizing the molecular sieve and then performing the phosphating treatment. In the synthesis method of the present invention, the phosphorus species enters the molecular sieve body and interacts with the framework aluminum. Compared with the impregnation-modified phosphorus mainly distributed on the outer surface, it can better inhibit the removal of Al elements from the molecular sieve under the action of water vapor generated in the reaction, improve the Al stability of the molecular sieve framework, and thus prolong the catalyst life.

[0034] In the synthesis method of the phosphated ZSM-5 molecular sieve of the present invention, the phosphated ZSM-5 molecular sieve is obtained by controlling the phosphorus species and the hydrothermal synthesis means in the hydrothermal synthesis process, in particular, controlling the temperature of the low-temperature pretreatment (step (1)) and the temperature of the high-temperature hydrothermal crystallization (step (2)). In the hydrothermal synthesis process, phosphorus partially replaces aluminum and enters the framework, thereby improving the stability of the framework aluminum in the molecular sieve, achieving the effect of improving the hydrothermal stability of the molecular sieve and extending the life of the catalyst.

[0035] 3. Compared with the existing phosphorus-containing ZSM-5 molecular sieve, the catalyst prepared by the phosphorized ZSM-5 molecular sieve of the present invention is used in the aromatic hydrocarbon alkylation reaction, and under the same reaction conditions, the catalyst life can be increased by 1.2 to 1.5 times. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The P-NMR spectra of the molecular sieves of Example 1 and Comparative Example 1 are shown.

[0037] Figure 2 The XRD spectra of the molecular sieve samples of Example 1 and Comparative Example 1 are shown in FIG. 1 , wherein (1) is the XRD spectra of the molecular sieve of Comparative Example 1, and (2) is the XRD spectra of the molecular sieve of Example 1.

[0038] Figure 3 The XRD spectra of the molecular sieve samples of Example 1 and Comparative Example 1 after being treated with water vapor at 700° C. for 20 hours. DETAILED DESCRIPTION

[0039] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited by the examples.

[0040] In the present invention, the silicon-aluminum ratio is measured by using a S4 Pioneer X-ray fluorescence spectrometer through the Si / Al molar ratio of the obtained zeolite sample.

[0041] In the present invention, 31 P NMR spectrum characterization was carried out on a VARIANINOVA300 superconducting nuclear magnetic resonance instrument to measure the 31 Magic angle spin resonance spectrum of P 31 P MAS-NMR) using a solid double resonance probe, 7.5 mm ZrO 2 Rotor (i.e. sample tube), 31 The resonance frequency of P is 121.413 MHz, the magic angle speed is 3 kHz, the sampling time is 0.02 s, the pulse width is 1.2 μs, the cycle delay time is 5 s, and the number of scans is 8500.

[0042] In the present invention, the molecular sieve XRD spectrum characterization adopts Bruker D8 Advance diffractometer for phase analysis, and the X-ray source is Cu Kα. The X-ray diffraction (XRD) pattern is collected under the voltage of 40kV and the current of 50mA radiation. The scanning range is 2θ=5-50°, and the scanning speed is 4° / min.

[0043] In the present invention, the activity and life test experiments are as follows: the molecular sieve to be tested is tableted, crushed and sieved to obtain 20-40 mesh particles, and tested under the reaction conditions of the application example, and the deactivation is considered when the benzene conversion rate is less than 10wt%, and the reaction time is the life time. The reaction activity data and life time are specifically shown in Table 1.

[0044] [Example 1]

[0045] (1) Water, tetraethyl orthosilicate, tetrapropylammonium hydroxide, and phosphoric acid were mixed at a molar ratio of TPAOH / SiO 2 =0.3, P 2 O 5 / SiO 2 =0.08, H 2 O / SiO 2 = 25, stirred for 12 h, and subjected to hydrothermal pretreatment at 100 °C for 24 h to obtain a uniform, non-stratified milky white colloid C1.

[0046] (2) Water, tetraethyl orthosilicate, ammonium phosphate, sodium aluminate, sodium hydroxide and tetrapropylammonium bromide are mixed at a molar composition of TPABr / Al 2 O 3 =15,SiO 2 / Al 2 O 3 =150, P 2 O 5 / Al2 O 3 =12,H 2 O / Al 2 O 3 =850, pH 11, and a mixed solution was obtained.

[0047] After stirring evenly, add colloid C1 to the mixed solution according to the ratio of the pretreatment product of step (1) to the weight of the mixture of step (2) in terms of alumina and silica, in terms of silica. Place in a 2-liter reactor with stirring, and stir and age for 3 hours at room temperature of 20°C. Gradually heat to 60°C, maintain for 24 hours, then heat to 150°C within 1 hour, and hydrothermally crystallize for 48 hours. After completion, cool rapidly, filter the solid product, wash with deionized water, dry at 120°C for 12 hours, and calcine at 600°C for 5 hours to obtain the phosphated ZSM-5 molecular sieve M1.

[0048] The molecular sieve 31 There is only one characteristic peak of phosphorus form at the chemical shift of -37 in the P NMR spectrum. 31 The PMAS-NMR spectrum shows that phosphorus in the M1 molecular sieve has entered the framework.

[0049] Phosphated ZSM-5 molecular sieve M1 was added to 10wt% ammonium nitrate solution, and ion exchange was performed at 90°C for 4 hours under stirring. The exchange was repeated 3 times, and the mixture was filtered, washed, dried, and calcined at 550°C for 5 hours to obtain phosphated ZSM-5 molecular sieve Z-1.

[0050] [Example 2]

[0051] (1) Water, tetraethyl orthosilicate, tetrapropylammonium hydroxide, and trimethyl phosphate were mixed according to the molar composition of each component and the ratio of TPAOH / SiO 2 =0.4, P 2 O 5 / SiO 2 =0.32, H 2 O / SiO 2 = 35, stirred for 12 h, and subjected to hydrothermal pretreatment at 120 °C for 40 h to obtain a uniform, non-stratified milky white colloid C2.

[0052] (2) Water, silica sol, aluminum sulfate, sodium hydroxide and tetrapropylammonium bromide are mixed at a molar composition of TPABr / Al 2 O 3 =12,SiO 2 / Al 2 O 3 =250, H 2 O / Al 2 O 3 =1200, pH 12, and a mixed solution was obtained.

[0053] After stirring evenly, add colloid C2 according to the ratio of the pre-treatment product of step (1) to the weight of the mixture of step (2) in terms of alumina and silica in terms of silica. Place in a 2-liter reactor with stirring, stir and age for 12 hours at room temperature of 20°C, gradually heat to 60°C, keep for 24 hours, then heat to 170°C within 1 hour, and hydrothermally crystallize for 36 hours. After completion, cool rapidly, filter the solid product, wash with deionized water, dry at 120°C for 12 hours, and calcine at 600°C for 5 hours to obtain phosphated ZSM-5 molecular sieve M2.

[0054] The molecular sieve is 31 In the P NMR spectrum, there is only one characteristic peak of phosphorus form at a chemical shift of -50. 31 PNMR spectrum characterization shows that phosphorus in the M2 molecular sieve has entered the framework.

[0055] The phosphated ZSM-5 molecular sieve M2 was added to a 10 wt% ammonium nitrate solution, and ion exchange was performed at 90°C for 4 hours under stirring. The exchange was repeated 3 times, and the mixture was filtered, washed, dried, and calcined at 550°C for 5 hours to obtain the phosphated ZSM-5 molecular sieve Z-2.

[0056] [Example 3]

[0057] (1) Water, tetraethyl orthosilicate, trimethyl phosphate, and tetrapropylammonium hydroxide were mixed according to the molar composition of each component and the ratio of TPAOH / SiO 2 =0.15, P 2 O 5 / SiO 2 =0.15, H 2 O / SiO 2 = 25, stirred for 12 h, and subjected to hydrothermal pretreatment at 100 °C for 24 h to obtain a uniform, non-stratified milky white colloid C3.

[0058] (2) Water, tetraethyl orthosilicate, trimethyl phosphate, aluminum sulfate, sodium hydroxide and tetrapropylammonium hydroxide are mixed at a molar composition of TPAOH / Al 2 O 3 =15,SiO 2 / Al 2 O 3 =25,P 2 O 5 / Al 2 O 3 =7,H 2 O / Al 2 O 3 =800, pH 13, and a mixed solution was obtained.

[0059] After stirring evenly, add colloid C3 according to the ratio of the pre-treatment product of step (1) to the weight of the mixture of step (2) in terms of alumina and silica in terms of silica. Place in a 2-liter reactor with stirring, stir and age for 12 hours at room temperature of 20°C, gradually heat to 60°C, keep for 24 hours, then heat to 160°C within 1 hour, and hydrothermally crystallize for 24 hours. After completion, cool rapidly, filter the solid product, wash with deionized water, dry at 120°C for 12 hours, and calcine at 600°C for 5 hours to obtain phosphated ZSM-5 molecular sieve M3.

[0060] The molecular sieve is 31 In the P NMR spectrum, there is only one characteristic peak of phosphorus form at a chemical shift of -35. 31 PNMR spectrum characterization shows that phosphorus in the M3 molecular sieve has entered the framework.

[0061] Phosphated ZSM-5 molecular sieve M3 was added to 10wt% ammonium nitrate solution, and ion exchange was performed at 90°C for 4 hours under stirring. The exchange was repeated 3 times, and the mixture was filtered, washed, dried, and calcined at 550°C for 5 hours to obtain phosphated ZSM-5 molecular sieve Z-3.

[0062] [Example 4]

[0063] (1) Water, tetraethyl orthosilicate, tetrapropylammonium hydroxide, diammonium phosphate, and ethanol were mixed according to the molar composition (calculated as oxides) of each component and the ratio of TPAOH / SiO 2 =0.3, P 2 O 5 / SiO 2 =0.18, H 2 O / SiO 2 =45, EtOH / SiO 2 = 5, stirred for 12 h, and subjected to hydrothermal pretreatment at 80 °C for 24 h to obtain a uniform, non-stratified milky white colloid C4.

[0064] (2) Water, tetraethyl orthosilicate, diammonium hydrogen phosphate, sodium aluminate, sodium hydroxide and tetrapropylammonium bromide are mixed at a molar composition of TPABr / Al 2 O 3 =15,SiO 2 / Al 2 O 3 =100, P 2 O 5 / Al 2 O 3 =12, / H 2 O / Al 2 O 3 =1500, pH 9, and a mixed solution was obtained.

[0065] Then, after stirring evenly, add colloid C4 according to the ratio of the pre-treatment product of step (1) to the weight of the mixture of step (2) in terms of alumina and silica in terms of silica. Place in a 2-liter reactor with stirring, stir and age for 12 hours at room temperature of 20°C, gradually heat to 60°C, keep for 24 hours, then heat to 100°C within 1 hour, and hydrothermally crystallize for 36 hours. After completion, cool rapidly, filter the solid product, wash with deionized water, dry at 120°C for 12 hours, and calcine at 600°C for 5 hours to obtain phosphated ZSM-5 molecular sieve M4.

[0066] The molecular sieve is 31 In the P NMR spectrum, there is only one characteristic peak of phosphorus form at a chemical shift of -42. 31 PNMR spectrum characterization shows that phosphorus in M4 molecular sieve has entered the framework.

[0067] Phosphated ZSM-5 molecular sieve M4 was added to 10wt% ammonium nitrate solution, and ion exchange was performed at 90°C for 4 hours under stirring. The exchange was repeated 3 times, and the mixture was filtered, washed, dried, and calcined at 550°C for 5 hours to obtain phosphated ZSM-5 molecular sieve Z-4.

[0068] [Example 5]

[0069] (1) Water, tetraethyl orthosilicate, tetrapropylammonium hydroxide, trimethyl phosphate, and ethanol were mixed according to the molar composition of each component and the ratio of TPAOH / SiO 2 =0.3, P 2 O 5 / SiO 2 =0.28, H 2 O / SiO 2 =50, EtOH / SiO 2 = 10, stirred for 12 h, and subjected to hydrothermal pretreatment at 120 °C for 24 h to obtain a uniform, non-stratified milky white colloid C5.

[0070] (2) Water, tetraethyl orthosilicate, diammonium hydrogen phosphate, sodium aluminate, sodium hydroxide and tetrapropylammonium bromide are mixed at a molar composition of TPABr / Al 2 O 3 =12,SiO 2 / Al 2 O 3 =680,P 2 O 5 / Al 2 O 3 =10,H 2 O / Al 2 O 3 =1500, pH 10. A mixed solution was obtained.

[0071] After stirring evenly, the pre-treated product of step (1) is calculated as silicon oxide, accounting for 10% of the weight of the mixture in step (2) in terms of aluminum oxide and silicon oxide, and then colloid C5 is added, and the mixture is placed in a 2-liter reactor with stirring, stirred and aged at room temperature of 20°C for 12 hours, gradually heated to 60°C, maintained for crystallization for 24 hours, heated to 180°C within 1 hour, and hydrothermally crystallized for 48 hours. After completion, the mixture is rapidly cooled, the solid product is filtered, washed with deionized water, dried at 120°C for 12 hours, and calcined at 600°C for 5 hours to obtain the phosphated ZSM-5 molecular sieve M5.

[0072] The molecular sieve is 31 In the P NMR spectrum, there is only one characteristic peak of phosphorus form at a chemical shift of -45. 31 PNMR spectrum characterization shows that phosphorus in the M5 molecular sieve has entered the framework.

[0073] Phosphated ZSM-5 molecular sieve M5 was added to 10wt% ammonium nitrate solution, and ion exchange was performed at 90°C for 4 hours under stirring. The exchange was repeated 3 times, and the mixture was filtered, washed, dried, and calcined at 550°C for 5 hours to obtain phosphated ZSM-5 molecular sieve Z-5.

[0074] [Comparative Example 1]

[0075] Water, tetraethyl orthosilicate, sodium aluminate, sodium hydroxide and tetrapropylammonium bromide were mixed at a molar composition of TPABr / Al 2 O 3 =15,SiO 2 / Al 2 O 3 =150,H 2 O / Al 2 O 3 =850, pH 11, to obtain a mixed solution. After stirring evenly, gradually heat to 165°C and maintain for 96 hours. After completion, quench, filter the solid product, wash with deionized water, dry at 120°C for 12 hours, calcine at 600°C for 5 hours, and characterize by XRD. The obtained powder is ZSM-5 molecular sieve M-0.

[0076] Add ZSM-5 molecular sieve M-0 to 10wt% ammonium nitrate solution and stir at 90℃ for 4 hours for ion exchange. Repeat the exchange 3 times, filter, wash and dry. After ion exchange, take 10g ammonium type M-0, add it to 7wt% phosphoric acid solution, soak in equal volumes, place at room temperature 20℃ for 12h, dry at 110℃, and calcine at 550℃ for 5 hours to obtain phosphorus-loaded modified ZSM-5 molecular sieve Z-0. 31 There is no single peak at -45±10 chemical shift in the PMAS-NMR spectrum.

[0077] [Comparative Example 2]

[0078] (1) Water, tetraethyl orthosilicate, and tetrapropylammonium hydroxide were mixed at a molar composition of TPAOH / SiO 2 =0.3, H 2 O / SiO 2 = 25, stirred for 12 h, and crystallized at 100 °C for 24 h to obtain a uniform, non-stratified milky white colloid C0-2.

[0079] (2) Water, tetraethyl orthosilicate, ammonium phosphate, sodium aluminate, sodium hydroxide and tetrapropylammonium hydroxide are mixed at a molar composition of TPAOH / Al 2 O 3 =15,SiO 2 / Al 2 O 3 =150, P 2 O 5 / Al 2 O 3 =12, / H 2 O / Al 2 O 3 =850, pH 11, and a mixed solution was obtained.

[0080] Under stirring, add colloid C0-2 in a ratio of 15% by weight of the pre-treated product of step (1) in terms of silicon oxide to the mixture in step (2) in terms of aluminum oxide and silicon oxide, place in a 2-liter reactor with stirring, and stir and age for 3 hours at room temperature of 20°C. Gradually heat to 60°C, maintain for 24 hours, then heat to 150°C within 1 hour, and hydrothermally crystallize for 48 hours. After completion, cool rapidly, filter the solid product, wash with deionized water, dry at 120°C for 12 hours, and calcine at 600°C for 5 hours to obtain phosphated ZSM-5 molecular sieve M0-2.

[0081] The molecular sieve 31 There is no single peak at -45±10 chemical shift in the P MAS-NMR spectrum.

[0082] ZSM-5 molecular sieve M0-2 was added to 10 wt% ammonium nitrate solution, and ion exchange was performed at 90°C for 4 hours under stirring. The exchange was repeated 3 times, and the mixture was filtered, washed, dried, and calcined at 550°C for 5 hours to obtain phosphorus-containing ZSM-5 molecular sieve Z0-2.

[0083]

Application examples

[0084] The above catalysts were used in the reaction under the following conditions: benzene to methanol molar ratio = 1, benzene weight space velocity 5hr -1 , the reaction temperature is 450°C and the reaction pressure is 1.5MPa.

[0085] The properties of each phosphated ZSM-5 molecular sieve are shown in Table 1. The reaction test results of each phosphated ZSM-5 molecular sieve are shown in Table 2.

[0086] Table 1 Molecular sieve properties

[0087]

[0088] * Note: The phosphated ZSM-5 molecular sieve 31 Is there only one characteristic peak of phosphorus form at the chemical shift of -45±10 in the P NMR spectrum?

[0089] Table 2 Molecular sieve application test results

[0090]

[0091] In addition, the hydrothermal stability test was conducted on the molecular sieve Z-1 obtained in Example 1 and the molecular sieve Z-0 obtained in Comparative Example 1. The test conditions were: steam treatment at 700°C for 20 hours. Figure 2 , Figure 3 . Figure 2 XRD patterns of the samples before water vapor treatment. Figure 3 The XRD spectrum of the sample after water vapor treatment. From the crystallinity peak height in the XRD spectrum before and after the hydrothermal test, it can be seen that the phosphated ZSM-5 molecular sieve of the present invention has good hydrothermal stability.

Claims

1. A phosphated ZSM-5 molecular sieve, characterized in that: The phosphated ZSM-5 molecular sieve 31 There is only one characteristic peak of phosphorus form at the chemical shift of -45±10 in the P NMR spectrum.

2. The molecular sieve according to claim 1, characterized in that: The SiO2 / Al2O3 molar ratio of the molecular sieve is 20 to 500; and / or the specific surface area of ​​the phosphated ZSM-5 molecular sieve is 230 to 580 m 2 / g.

3. The molecular sieve according to claim 1, characterized in that: In the phosphated ZSM-5 molecular sieve, based on the mass of the phosphated ZSM-5 molecular sieve and calculated as P2O5, the phosphorus content is 0.2% to 20%, preferably 0.2% to 5.0%.

4. A method for synthesizing the molecular sieve according to any one of claims 1 to 3, comprising: (1) pretreating a first phosphorus source; (2) After mixing water, silicon source, aluminum source, inorganic base M, template R, and an optional second phosphorus source, the pretreated product of step (1) is added, aged, hydrothermally crystallized, and calcined to obtain a phosphated ZSM-5 molecular sieve.

5. The synthesis method according to claim 4, characterized in that: The pretreatment of the first phosphorus source in step (1) is to mix the first phosphorus source, water, silicon source and template and then perform hydrothermal pretreatment at low temperature; more preferably, the treatment conditions are: temperature 60-120° C., time 3-40 hours.

6. The synthesis method according to claim 4, characterized in that: In the pretreatment material system of step (1), the first phosphorus source is calculated as P2O5, the silicon source is calculated as SiO2, and the template R is calculated in moles, P2O5 / SiO2=0.05~0.50, R / SiO2=0.05~2, H2O / SiO2=10~50.

7. The synthesis method according to claim 4, characterized in that: In step (2), in the mixture of water, silicon source, aluminum source, inorganic base M, optional second phosphorus source, and template R, the silicon source is calculated as SiO2, the aluminum source is calculated as Al2O3, the second phosphorus source is calculated as P2O5, and the template R, in moles, R / Al2O3=1~18, SiO2 / Al2O3=10~200, H2O / Al2O3=20~1500, P2O5 / Al2O3=0~12; the pH value of the mixture is 9~13.

8. The synthesis method according to claim 4, characterized in that: In step (2), the pre-treated product of step (1) accounts for 3% to 15% of the weight of the mixture obtained by mixing in step (2) in terms of aluminum oxide and silicon oxide, in terms of silicon oxide.

9. The synthesis method according to claim 4 or 5, characterized in that: In step (2), the conditions for hydrothermal crystallization are: hydrothermal treatment at 100-195° C. for 24-120 h, preferably 24-60 h.

10. The synthesis method according to claim 5 or 9, characterized in that: The hydrothermal crystallization temperature of step (2) is higher than the first phosphorus source pretreatment temperature of step (1), preferably at least 10° C. higher, more preferably at least 20° C. higher.

11. The synthesis method according to claim 4, characterized in that: The calcination conditions of step (2) are: calcination at 350-650° C. for 2-20 hours.

12. Use of the molecular sieve according to any one of claims 1 to 3 or the molecular sieve prepared by the synthesis method according to any one of claims 4 to 11 in an aromatic hydrocarbon alkylation reaction.

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