Nano high-silicon SAPO-17 molecular sieve as well as synthesis method and application thereof

Abstract

The invention discloses a nano high-silicon SAPO-17 molecular sieve as well as a synthesis method and application thereof, and belongs to the technical field of molecular sieves. The nano SAPO-17 molecular sieve is synthesized by introducing a proper amount of phosphorus source, aluminum source and template agent aqueous solution into a ball-milled SAPO molecular sieve serving as a precursor. And roasting the nano SAPO-17 molecular sieve to obtain the SAPO-17 molecular sieve catalyst. The synthesized silicoaluminophosphate molecular sieve SAPO-17 can be used as a catalyst for an acid catalytic reaction, such as a methanol to olefin (MTO) catalyst; the invention also discloses an application of the SAPO-17 molecular sieve loaded with Cu ions as a denitration catalyst (NH3-SCR).

Description

Technical Field

[0001] The present invention relates to the technical field of molecular sieves, and in particular to a nano high-silicon SAPO-17 molecular sieve and a synthesis method and application thereof. Background Art

[0002] Silicoaluminophosphate molecular sieve (SAPO-n) has important application value in gas adsorption, separation and industrial catalysis due to its diverse and regular molecular-scale pore structure, medium-strong acidity and good hydrothermal stability. SAPO-17 is a kind of 8-membered ring pore with three-dimensional small pores. and SAPO molecular sieves with ERI cage structure.

[0003] The synthesis of SAPO-17 molecular sieves usually adopts the hydrothermal method, and the selected templates include cyclohexylamine (J.Membr.Sci.2016,520,507) and the non-commercial template 1,1,6,6-tetramethyl-1,6-diazacyclododecane-1,6-diammonium hydroxide (TDDH) (Inorg.Chem.2022,61,8066) and the like.

[0004] The SAPO-17 molecular sieve synthesized by cyclohexylamine has a thin rod-like morphology, a crystal size of about 10 μm, and a silicon content of no more than 17% when T zeolite is introduced as a seed. When more silicon sources are introduced, a competitive phase of SAPO-56 often exists in the product, and the crystal morphology of SAPO-17 molecular sieve is difficult to control in one step.

[0005] The SAPO-17 molecular sieve synthesized using TDDH has a spherical shape of nanoparticles, a crystal size of less than 1 μm, and a silicon content of up to 8%. In addition, TDDH is a non-commercial product synthesized in the laboratory, which leads to a high synthesis cost of SAPO-17 molecular sieve, limiting its further application. Summary of the invention

[0006] In view of this, the present invention provides a nano high-silicon SAPO-17 molecular sieve and its synthesis method and application, the main purpose of which is to solve the technical problems of low silicon content, large crystal size and difficult to control crystal morphology in SAPO-17 molecular sieve.

[0007] On the one hand, the present invention provides a nano-high silicon SAPO-17 molecular sieve, the anhydrous chemical composition of which is: mTMHDA·(Si x Al y P z ) 2 ;

[0008] Wherein, the TMHDA is N,N,N',N'-tetramethyl-1,6-hexanediamine;

[0009] m is per mole (Si x Al y P z ) 2 The number of moles of TMHDA in the mixture is m = 0.05 to 0.3;

[0010] x represents the molar fraction of Si, x = 0.15 to 0.35,

[0011] y represents the molar fraction of Al, y = 0.35 to 0.55,

[0012] z represents the molar fraction of P, z=0.25-0.45, and x+y+z=1.

[0013] Optionally, x is selected from any value among 0.15, 0.20, 0.25, 0.30, 0.35, or any range therebetween.

[0014] Optionally, y is selected from any value among 0.35, 0.40, 0.45, 0.50, 0.55, or any range therebetween.

[0015] Optionally, z is selected from any value among 0.20, 0.25, 0.30, 0.35, 0.40, 0.45, or any range therebetween.

[0016] Optionally, the TMHDA in the SAPO-17 molecular sieve is distributed in the molecular sieve cage; the SAPO-17 molecular sieve has a hexagonal prism morphology, and the length of the hexagonal prism is 200 to 500 nm.

[0017] Optionally, the column length is selected from any value among 200, 250, 300, 350, 400, 450, 500, or any range between two values, and the unit is nm.

[0018] Optionally, the X-ray diffraction spectrum of the SAPO-17 molecular sieve includes X-ray diffraction peaks at least at the positions shown in the following table:

[0019]

[0020]

[0021] The nano-high-silicon SAPO-17 molecular sieve containing N,N,N,N-tetramethyl-1,6-hexanediamine of the present invention has a hexagonal prism morphology with a hexagonal prism length of 200 to 500 nm. The molecular sieve, as an acid catalyst, exhibits excellent catalytic performance in the reaction of converting methanol or dimethyl ether to light olefins; as a catalyst carrier, it exhibits excellent performance in the ammonia selective reduction denitration reaction after being loaded with Cu ions.

[0022] In a second aspect, the present invention provides a method for preparing the above-mentioned nano-high silicon SAPO-17 molecular sieve, comprising the following steps:

[0023] S1: obtaining a high-silicon SAPO molecular sieve, wherein the high-silicon SAPO molecular sieve is subjected to ball milling to obtain a precursor Q;

[0024] S2: mixing an aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, an aluminum source, a phosphorus source and the precursor Q in step S1 to obtain an initial gel mixture;

[0025] S3: The initial gel mixture is subjected to a hydrothermal reaction under sealed conditions, and the product after complete crystallization is separated, washed, and dried to obtain a nano-high-silicon SAPO-17 molecular sieve.

[0026] Optionally, in step S1, the high-silicon SAPO molecules are selected from SAPO-34, SAPO-56 or DNL-6.

[0027] Optionally, in step S2, the mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is 2% to 50%.

[0028] Optionally, the mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is selected from any value of 2, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50% or any range between two values; preferably 5% to 30%.

[0029] Optionally, in step S2, the molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5;

[0030] The phosphorus source is P 2 O 5 The aluminum source is Al 2 O 3 count;

[0031] The mass ratio of the precursor Q to the total amount of the aluminum source and the phosphorus source is 0.5 to 20;

[0032] The mass of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution and the precursor Q is 1-50.

[0033] Optionally, the molar ratio of the phosphorus source to the aluminum source is selected from any value of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or any range therebetween.

[0034] Optionally, the mass ratio of the precursor Q to the total amount of the aluminum source and the phosphorus source is selected from any value among 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20% or any range value between two thereof; preferably 1 to 10%.

[0035] Optionally, the masses of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution and the precursor Q are any value selected from 1, 5, 10, 15, 20, 25, 30, 35, 40, 50 or any range between two values; preferably 5 to 20.

[0036] Optionally, in step S3, the temperature of the hydrothermal reaction is 130-220° C., and the crystallization is carried out under autogenous pressure for 5-72 hours.

[0037] Optionally, the temperature of the hydrothermal reaction is selected from any value of 130, 140, 150, 160, 170, 180, 190, 200, 210, 220°C or any range between two thereof; preferably 140-220°C, further preferably 160-200°C.

[0038] Optionally, the crystallization time is selected from any value of 5, 7, 10, 13, 15, 18, 20, 22, 25, 28, 30, 35, 40, 45, 50, 55, 60, 65, 70, 72 hours or any range between two thereof; preferably 7 to 36 hours.

[0039] Optionally, in step S2, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide and pseudo-boehmite.

[0040] Optionally, in step S2, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, diethyl trichloromethylphosphonate and phosphorus-containing oxides.

[0041] Optionally, in step S1, the ball milling process includes: dispersing the high-silicon SAPO molecular sieve from which the organic template is removed by calcination in water, rotating the sieve in a ball mill to obtain a slurry, and drying the slurry to obtain the solid precursor Q.

[0042] Optionally, in step S3, the crystallization process is performed in a static or dynamic state.

[0043] In a third aspect, the present invention provides a nanoscale catalyst. The product obtained by calcining the nano-high-silicon SAPO-17 molecular sieve or the nano-high-silicon SAPO-17 molecular sieve prepared by the above preparation method in air at 400-800°C is the nanoscale catalyst.

[0044] In a fourth aspect, the present invention provides a catalyst for the conversion of oxygen-containing compounds to olefins. The product obtained by calcining the above-mentioned nano-high-silicon SAPO-17 molecular sieve or the nano-high-silicon SAPO-17 molecular sieve prepared by the above-mentioned preparation method in air at 400-800°C is the nanoscale catalyst.

[0045] In a fifth aspect, the present invention provides a catalyst for ammonia selective reduction denitrification reaction, wherein the nano high-silicon SAPO-17 molecular sieve or the nano high-silicon SAPO-17 molecular sieve prepared by the above-mentioned preparation method is first subjected to copper ion exchange loading and then calcined in air at 400-800°C to obtain a product, which is the nanoscale catalyst.

[0046] In a sixth aspect, the present invention provides the use of the above-mentioned nano high-silicon SAPO-17 molecular sieve or the nano high-silicon SAPO-17 molecular sieve prepared by the above-mentioned preparation method or the above-mentioned nano catalyst in the conversion of oxygen-containing compounds to olefins or in the ammonia selective reduction denitrification reaction.

[0047] In a seventh aspect, the present invention provides a method for preparing olefins from methanol, the method comprising: after the catalyst is calcined, it is loaded into a reactor and activated by nitrogen at 500-600°C, and methanol reacts at 400-500°C to generate olefins; the catalyst is the above-mentioned nanoscale catalyst.

[0048] In an eighth aspect, the present invention provides a NH 3 -SCR catalytic reaction method, including: molecular sieve is subjected to copper ion exchange, and then calcined at 550-650℃ for 2-6h to obtain a catalyst; the catalyst is loaded into a reactor and activated by reacting raw gas at 550-650℃ for 30min, cooled to 110-150℃, and tested point by point. Wait for 20min at each temperature point until the reaction is stable, and record the data; the test temperature range is 150-650℃;

[0049] The reaction raw gas composition includes: NO: 500ppm, NH 3 :500ppm,O 2 : 5%, H 2 O: 5%, N 2 As the balance gas, the gas flow rate is 1000mL / min, and the corresponding space velocity is 180000h -1 ;

[0050] The molecular sieve is the nano-high-silicon SAPO-17 molecular sieve mentioned above or the nano-high-silicon SAPO-17 molecular sieve prepared by the above preparation method.

[0051] Compared with the prior art, the present invention has the following technical effects:

[0052] (1) The method of the present invention uses a cheap organic template to synthesize nano-scale SAPO-17 molecular sieves with a high silicon content. The crystals have a hexagonal morphology and a particle size of about 200 nm to 500 nm.

[0053] (2) The SAPO-17 molecular sieve prepared by the present invention exhibits excellent catalytic performance in the reaction of converting methanol or dimethyl ether into light olefins.

[0054] (3) The SAPO-17 molecular sieve prepared by the present invention is used for DeNO x It exhibits excellent catalytic performance in catalytic selective reduction denitrification. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is the X-ray diffraction spectrum of the SAPO-17 sample prepared in Example 1 of the present invention;

[0056] Figure 2 The SAPO-17 sample prepared in Example 2 of the present invention was heated in NH 3 -Selective catalytic reduction of NO x (NH 3 -SCR) performance test result curve chart;

[0057] Figure 3 The SAPO-17 sample prepared in Example 1 of the present invention 13 C solid state NMR spectrum. DETAILED DESCRIPTION

[0058] The present invention will be further described below in conjunction with examples, but the present invention is not limited to these examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods without specifying specific conditions in the following examples are usually based on conventional conditions or according to the conditions recommended by the manufacturer. Without special instructions, the raw materials used in this application are all purchased through commercial channels and are directly used without special treatment.

[0059] The analysis method in the examples of this application is as follows:

[0060] X-ray powder diffraction phase analysis (XRD) was performed using an X'Pert PRO X-ray diffractometer from PANalytical of the Netherlands, with a Cu target, a Kα radiation source (λ=0.15418 nm), a voltage of 40 kV, and a current of 40 mA.

[0061] The instrument used for scanning electron microscopy (SEM) testing is Hitachi SU8020 field emission scanning electron microscope with an accelerating voltage of 2 kV.

[0062] The bulk element composition in the examples was determined using a Magix 2424 X-ray fluorescence analyzer (XRF) from Philips.

[0063] The samples were tested using a Bruker Avance III 600 (14.1 Tesla) spectrometer. 13 C and 29 Si solid state NMR.

[0064] Example 1-7 (Synthesis of SAPO-17 Molecular Sieve)

[0065] (1) The preparation method of the precursor Q used in Examples 1-7 is as follows: 5 g of high-silicon SAPO molecular sieves that have been calcined to remove the organic template are evenly dispersed in 20 g of water, placed in a ball mill, balanced with agate balls, and then milled at high speed at 500 Hz for 5 hours. The sauce is then collected and placed in an oven to dry the collected solids for later use as the precursor Q.

[0066] (2) preparing a certain concentration of N,N,N,N-tetramethyl-1,6-hexanediamine (R) aqueous solution, adding a certain amount of precursor Q, phosphorus source and aluminum source thereto in sequence, stirring evenly at room temperature, and transferring the gel to a stainless steel reactor; placing the reactor in an oven, heating it to 140-220°C for a certain period of time, and then cooling it to complete crystallization; centrifuging the solid product, washing it, and drying it in air at 120°C to obtain a molecular sieve raw powder sample; the specific synthesis method and results are shown in Table 1;

[0067] Table 1. Synthesis conditions and results of molecular sieve SAPO-17

[0068]

[0069] The seven samples prepared in Examples 1 to 7 were analyzed for phase, morphology and composition:

[0070] The samples of Examples 1-7 were characterized by XRD powder diffraction, and the results showed that they all had characteristic diffraction peaks of SAPO-17, proving that they were ERI crystal phases. Taking Example 1 as an example, the XRD diffraction spectrum of the obtained sample is as follows: Figure 1 The peak position and shape of the XRD spectrum of sample 2-7 are the same as those of Example 1, except that the peak intensity fluctuates by about 10%.

[0071] Table 2 X-ray diffraction peak data of SAPO-17-1 of Example 1

[0072] No. 2θ 1 7.69 2 9.73 3 11.81 4 13.32 5 15.70 6 16.66 7 19.05 8 19.53 9 20.71 10 21.48 11 23.81 12 24.68

[0073] XRF was used to analyze the inorganic composition of samples 1 to 7. The results are shown in Table 1. The product composition is as follows: Al 0.47Si 0.16 P 0.37 O 2 、Al 0.46 Si 0.20 P 0.34 O 2 、Al 0.49 Si 0.25 P 0.26 O 2 、Al 0.46 Si 0.18 P 0.36 O 2 、Al 0.49 Si 0.15 P 0.36 O 2 、Al 0.49 Si 0.18 P 0.33 O 2 、Al 0.50 Si 0.15 P 0.35 O 2 . The silicon content is more than 15%.

[0074] The synthesized samples 1-7 were analyzed by SEM, and the morphology of the samples was all hexagonal prisms with a length of 200-500nm.

[0075] The samples of Examples 1-7 were 13 C MAS NMR solid state nuclear magnetic analysis, such as Figure 3 As shown, it is confirmed that the characteristic peak of N,N,N',N'-tetramethyl-1,6-hexanediamine is indeed present in the sample.

[0076] Application Example 1 (MTO catalytic reaction)

[0077] The SAPO-17-5 molecular sieve prepared in Example 5 was first tableted and crushed to 20-40 mesh, and then calcined at 600°C for 4 hours by passing air; 0.3 g of the sample was loaded into a fixed bed reactor (self-made) as a catalyst for MTO reaction evaluation, and the reactor was a quartz tube; nitrogen was passed through at 550°C for 1 hour for activation, and then the temperature was lowered to 450°C for reaction; methanol was carried by nitrogen, and the methanol space velocity was 1h -1 The reaction products were analyzed by online gas chromatography (Agilent A7890) with a PoraPlot-Q-HT column. The results are shown in Table 3.

[0078] Table 3. MTO catalytic performance of synthesized samples a

[0079]

[0080] aReaction conditions: 450°C, methanol space velocity 1h -1 ; Lifetime is defined as the length of time when methanol conversion is greater than 99%, and selectivity gives the result when ethylene plus propylene selectivity is highest.

[0081] Application Example 2 (NH 3 -SCR catalytic reaction)

[0082] First, add 5g of SAPO-17-2 molecular sieve prepared in Example 2 to 100g of 0.02mol / L copper acetate solution, perform ion exchange at 80°C for 5h, then centrifuge the sample and wash it with deionized water until it is neutral. After drying in an oven at 120°C, calcine it at 600°C for 5h. Further, press the calcined sample into tablets and sieve them, weigh 0.3g of 60 to 80 mesh sample and mix it with 1.9g of quartz sand (60 to 80 mesh), and load it into a fixed bed reactor. Activate with nitrogen at 600°C for 40min, then cool to 150°C to start the reaction, and test point by point; wait for 20min at each temperature point, and record the data after the reaction stabilizes. The test temperature range is 150-650°C;

[0083] The reaction raw gas is: NO: 500ppm, NH 3 :500ppm,O 2 : 5%, H 2 O: 5%, N 2 As the balance gas, the gas flow rate is 1000mL / min, and the corresponding space velocity is 18,0000h -1 .

[0084] The reaction tail gas was analyzed by online FTIR using a Bruker Tensor 27 instrument. The Cu content in the sample was 3 wt%. The reaction results are shown in Figure 2 It can be seen that the sample has a wide active temperature window and good hydrothermal stability.

[0085] The above are only a few embodiments of the present application and do not constitute any form of limitation to the present application. Although the present application is disclosed as above with preferred embodiments, it is not intended to limit the present application. Any technician familiar with the profession, without departing from the scope of the technical solution of the present application, using the technical content disclosed above to make slight changes or modifications are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A nano-high silicon SAPO-17 molecular sieve, characterized in that: The anhydrous chemical composition of the SAPO-17 molecular sieve is: mTMHDA·(Si x Al y P z )O2; Wherein, the TMHDA is N,N,N',N'-tetramethyl-1,6-hexanediamine; m is per mole (Si x Al y P z ) The number of moles of TMHDA in O2, m = 0.05 to 0.3; x represents the molar fraction of Si, x = 0.15 to 0.35, y represents the molar fraction of Al, y = 0.35 to 0.55, z represents the molar fraction of P, z=0.25-0.45, and x+y+z=1.

2. A nano-high silicon SAPO-17 molecular sieve according to claim 1, characterized in that: The TMHDA in the SAPO-17 molecular sieve is distributed in the molecular sieve cage; the SAPO-17 molecular sieve has a hexagonal prism morphology, and the length of the hexagonal prism is 200-500 nm.

3. The nano-high silicon SAPO-17 molecular sieve according to claim 1, characterized in that: The X-ray diffraction spectrum of the SAPO-17 molecular sieve includes X-ray diffraction peaks at least at the positions shown in the following table: 。 4. The method for preparing a nano-high silicon SAPO-17 molecular sieve according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: S1: obtaining a high-silicon SAPO molecular sieve, wherein the high-silicon SAPO molecular sieve is subjected to ball milling to obtain a precursor Q; S2: mixing an aqueous solution of N,N,N',N'-tetramethyl-1,6-hexanediamine, an aluminum source, a phosphorus source and the precursor Q in step S1 to obtain an initial gel mixture; S3: The initial gel mixture is subjected to a hydrothermal reaction under sealed conditions, and the product after complete crystallization is separated, washed, and dried to obtain a nano-high-silicon SAPO-17 molecular sieve.

5. The method for preparing a nano-high silicon SAPO-17 molecular sieve according to claim 4, characterized in that: In step S1, the high-silicon SAPO molecules are selected from SAPO-34, SAPO-56 or DNL-6; Preferably, in step S2, the mass percentage of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution is 2% to 50%; The molar ratio of the phosphorus source to the aluminum source is 0.5 to 1.5; The phosphorus source is calculated as P2O5, and the aluminum source is calculated as Al2O3; The mass ratio of the precursor Q to the total amount of the aluminum source and the phosphorus source is 0.5 to 20; The mass of the N,N,N',N'-tetramethyl-1,6-hexanediamine aqueous solution and the precursor Q is 1-50.

6. The method for preparing a nano-high silicon SAPO-17 molecular sieve according to claim 4, characterized in that: In step S3, the temperature of the hydrothermal reaction is 130-220° C., and the crystallization is carried out under autogenous pressure for 5-72 hours; Preferably, in step S2, the aluminum source is selected from at least one of aluminum nitrate, activated alumina, aluminum hydroxide, aluminum isopropoxide and pseudo-boehmite; Preferably, in step S2, the phosphorus source is selected from at least one of orthophosphoric acid, ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, diethyl trichloromethylphosphonate and phosphorus-containing oxides; Preferably, in step S1, the ball milling process comprises: dispersing the high-silicon SAPO molecular sieve from which the organic template is removed by calcination in water, rotating the sieve in a ball mill to obtain a slurry, and drying the slurry to obtain the solid precursor Q; In step S3, the crystallization process is performed in a static or dynamic state.

7. A nanoscale catalyst, characterized in that: The product obtained by calcining the nano-high-silicon SAPO-17 molecular sieve described in any one of claims 1 to 3 or the nano-high-silicon SAPO-17 molecular sieve prepared by the preparation method described in any one of claims 4 to 6 in air at 400 to 800° C. is the nanoscale catalyst.

8. Use of the nano-high-silicon SAPO-17 molecular sieve described in any one of claims 1 to 3, or the nano-high-silicon SAPO-17 molecular sieve prepared by the preparation method described in any one of claims 4 to 6, or the nanoscale catalyst described in claim 7 in the conversion of oxygen-containing compounds to olefins or in ammonia selective reduction denitrification reactions.

9. A method for preparing olefins from methanol, characterized in that: The method comprises: the catalyst is loaded into a reactor after being calcined and activated by nitrogen at 500-600°C, and methanol reacts at a reaction temperature of 400-500°C to generate olefins; the catalyst is the nano-scale catalyst according to claim 7.

10. A method for NH3-SCR catalytic reaction, characterized in that: The method comprises: the molecular sieve is subjected to copper ion exchange, and then calcined at 550-650° C. for 2-6 hours to obtain a catalyst; the catalyst is loaded into a reactor and activated by reaction raw gas at 550-650° C. for 30 minutes, cooled to 110-150° C., and tested point by point; each temperature point is waited for 20 minutes until the reaction is stable, and data is recorded, and the test temperature range is 150-650° C.; The reaction raw gas composition includes: NO: 500ppm, NH3: 500ppm, O2: 5%, H2O: 5%, N2 as the balance gas, the gas flow rate is 1000mL / min, and the corresponding space velocity is 180000h -1 ; The molecular sieve is the nano-high-silicon SAPO-17 molecular sieve described in any one of claims 1 to 3 or the nano-high-silicon SAPO-17 molecular sieve prepared by the preparation method described in any one of claims 4 to 6.

Images