Seed suspension and preparation method thereof, nanoscale FER molecular sieve and preparation method thereof, and preparation method and application of nanoscale hydrogen type FER molecular sieve

Abstract

The invention provides a seed crystal suspension and a preparation method thereof, a preparation method of a nanoscale FER molecular sieve, and a preparation method and application of a nanoscale hydrogen type FER molecular sieve, and belongs to the field of molecular sieves. The invention provides a preparation method of a seed crystal suspension, which comprises the following steps: mixing a first silicon source, a first inorganic metal alkali source, a first aluminum source, pyrrolidine and first water to obtain first gel; performing first hydrothermal crystallization on the first gel to generate a seed crystal of which the structure is an FER molecular sieve, so as to obtain a seed crystal suspension; the temperature of the first hydrothermal crystallization is 150-180 DEG C, and the time is 10-16 hours. According to the method, pyrrolidine is selected as an organic template agent, the temperature and time of hydrothermal crystallization are adjusted, the prepared seed crystal can effectively induce the formation of crystal nucleuses when the FER molecular sieve is prepared, more initial crystal nucleuses effectively inhibit the growth of the FER molecular sieve, and the size of the FER molecular sieve is reduced.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieves, and in particular to a seed suspension and a preparation method thereof, a preparation method of a nano-scale FER molecular sieve, a preparation method of a nano-scale hydrogen-type FER molecular sieve and applications thereof. Background Art

[0002] FER is a two-dimensional lamellar structure, belonging to a mesoporous molecular sieve, containing 10-MR channels along the c-axis direction. With the 8-MR channel along the b-axis The 6-MR channel is parallel to the c-axis, and the 8-MR channel and the 6-MR channel cross to form an alkali-magnesium zeolite cage [8 2 6 8 6 4 5 8 ]. Due to its unique pore structure, excellent hydrothermal / thermal stability and acidity adjustability, it is widely used in isomerization, cracking, aromatization of hydrocarbons and dimethyl ether carbonylation reactions. Its typical morphology is nanosheets, and the width of the nanosheets is generally in the micron level. Whether the reactant molecules enter 8-MR or 10-MR, they need to go through a long diffusion path, which often causes secondary reactions between the reacting molecules, thereby triggering the occurrence of carbon deposition side reactions, causing the catalyst to quickly deactivate due to carbon deposition. To a certain extent, reducing the particle size of the molecular sieve can effectively solve this problem.

[0003] Patent CN110877912A reports a method of rapidly synthesizing size-controllable FER molecular sieves using microwave-assisted seed addition. The resulting molecular sieve is a flower-like structure formed by cross-assembly of nanosheets, and the overall particle size is >8 μm, i.e., the resulting particle size is still relatively large. Summary of the invention

[0004] The invention provides a seed suspension and a preparation method thereof, a preparation method of a nanometer-level FER molecular sieve, a preparation method of a nanometer-level hydrogen-type FER molecular sieve and an application thereof. The seed suspension of the invention can reduce the size of the FER molecular sieve.

[0005] The present invention provides a method for preparing a seed crystal suspension, comprising the following steps:

[0006] Mixing a first silicon source, a first inorganic metal base source, a first aluminum source, pyrrolidine and first water to obtain a first gel;

[0007] Performing a first hydrothermal crystallization on the first gel to generate seed crystals with a structure of FER molecular sieve, thereby obtaining the seed crystal suspension;

[0008] The temperature of the first hydrothermal crystallization is 150-180° C., and the time is 10-16 hours.

[0009] Preferably, the first silicon source includes one or more of silica sol, silica gel powder and sodium silicate.

[0010] Preferably, the first aluminum source includes one or more of aluminum sulfate 18hydrate, sodium metaaluminate, aluminum isopropoxide, aluminum hydroxide and aluminum chloride.

[0011] Preferably, the first silicon source is calculated as SiO2, the first aluminum source is calculated as Al2O3, and the molar ratio of the first silicon source to the first aluminum source is 8 to 20:1.

[0012] The present invention also provides a seed crystal suspension prepared by the preparation method described in the above technical solution, wherein the particle size of the seed crystal is 50 to 90 nm, and the shape of the seed crystal is spherical.

[0013] The present invention also provides a method for preparing a nano-scale FER molecular sieve, comprising the following steps:

[0014] Mixing a second inorganic metal base source, a second aluminum source, a second silicon source, a second water and a seed crystal suspension to obtain a second gel;

[0015] performing a second hydrothermal crystallization on the second gel to obtain the nano-scale FER molecular sieve;

[0016] The seed crystal suspension is the seed crystal suspension described in the above technical solution.

[0017] The present invention also provides a nano-scale FER molecular sieve prepared by the preparation method described in the above technical solution, characterized in that the length of the nano-scale FER molecular sieve is 100 to 200 nm;

[0018] The nano-scale FER molecular sieve is in the shape of a sheet.

[0019] The present invention also provides a method for preparing a nanoscale hydrogen-type FER molecular sieve, comprising the following steps:

[0020] The pyrrolidine in the nano-scale FER molecular sieve described in the above technical solution is removed and then mixed with an ammonium salt solution for ion exchange to obtain the nano-scale hydrogen-type FER molecular sieve.

[0021] The present invention also provides a nano-scale hydrogen-type FER molecular sieve prepared by the preparation method described in the above technical solution, characterized in that the particle size of the nano-scale hydrogen-type FER molecular sieve is 100-200 nm.

[0022] The present invention also provides the use of the nano-scale hydrogen-type FER molecular sieve described in the above technical solution in the skeletal isomerization reaction of n-butene.

[0023] The present invention provides a method for preparing a seed crystal suspension, comprising the following steps:

[0024] Mixing a first silicon source, a first inorganic metal base source, a first aluminum source, pyrrolidine and first water to obtain a first gel;

[0025] Performing a first hydrothermal crystallization on the first gel to generate seed crystals with a structure of FER molecular sieve, thereby obtaining the seed crystal suspension;

[0026] The temperature of the first hydrothermal crystallization is 160° C., and the time is 10 to 16 hours.

[0027] The present invention selects pyrrolidine as an organic template, and adjusts the temperature and time of hydrothermal crystallization to prepare the seed crystals which can effectively induce the formation of crystal nuclei when preparing FER molecular sieves. More initial crystal nuclei can improve the yield of FER molecular sieves on the one hand, and can effectively inhibit the growth of FER molecular sieves on the other hand, thereby reducing the size of FER molecular sieves.

[0028] When the nano-scale hydrogen-type FER molecular sieve of the present invention is used as a catalyst, its smaller crystal size is conducive to improving the diffusion rate of reactants and products, and can effectively inhibit the occurrence of carbon deposition side reactions in the catalytic reaction, slowing down the deactivation of the catalyst, that is, it is conducive to improving the stability of the catalyst. In addition, the nano-scale FER molecular sieve prepared by using the seed suspension of the present invention can improve the contact effect between the reactants and the active sites, thereby helping to improve the conversion rate of n-butene. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is the XRD pattern of NF-PY1 in Application Example 1;

[0030] Figure 2 is the SEM image of NF-PY1 in Application Example 1;

[0031] Figure 3 is the SEM image of NF-PY2 in Application Example 2;

[0032] Figure 4 is the SEM image of NF-PY3 in Application Example 3;

[0033] Figure 5 This is the SEM image of F-EDA in comparative application example 1;

[0034] Figure 6 This is the SEM image of F-PY in comparative application example 2;

[0035] Figure 7 is the SEM image of NF-PY4 in Application Example 4;

[0036] Figure 8 These are the experimental results of the skeletal isomerization reaction of n-butene catalyzed by the hydrogen-form molecular sieve of Application Examples 1 to 4 and Comparative Application Examples 1 to 2. DETAILED DESCRIPTION

[0037] The present invention provides a method for preparing a seed crystal suspension, comprising the following steps:

[0038] Mixing a first silicon source, a first inorganic metal base source, a first aluminum source, pyrrolidine and first water to obtain a first gel;

[0039] Performing a first hydrothermal crystallization on the first gel to generate seed crystals with a structure of FER molecular sieve, thereby obtaining the seed crystal suspension;

[0040] The temperature of the first hydrothermal crystallization is 150-180° C., and the time is 10-16 hours.

[0041] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known in the art.

[0042] The present invention mixes a first silicon source, a first inorganic metal base source, a first aluminum source, pyrrolidine and first water to obtain a first gel.

[0043] In the present invention, the first silicon source is calculated as SiO2, and the molar ratio of the pyrrolidine to the first silicon source is preferably 0.2-0.5:1, more preferably 0.3-0.4:1; the first silicon source preferably includes one or more of silica sol, silica gel powder and sodium silicate; the solid content of the silica sol is preferably 40wt%.

[0044] In the present invention, the first aluminum source is calculated as Al2O3, the first silicon source is calculated as silicon oxide, and the molar ratio of the first silicon source to the first aluminum source is preferably 8 to 20:1, more preferably 8 to 15:1, and further preferably 10 to 12:1; the first aluminum source preferably includes one or more of aluminum sulfate 18hydrate, sodium aluminate, aluminum isopropoxide, aluminum hydroxide and aluminum chloride.

[0045] In the present invention, the first inorganic metal alkali source is calculated as M2O, where M is the metal element of the inorganic metal alkali source; the molar ratio of the first inorganic metal alkali source to silicon oxide is preferably 0.02-0.3:1, more preferably 0.03-0.25:1, and the first inorganic metal alkali source preferably includes sodium hydroxide.

[0046] In the present invention, when the first silicon source does not contain water, the molar ratio of the first silicon source to the first water is preferably 1:10 to 40, more preferably 1:15 to 25;

[0047] When the first silicon source contains water, the ratio of the amount of the first silicon source to the total amount of the first water and the water in the first silicon source is preferably 1:10-40, more preferably 1:15-25.

[0048] After obtaining the first gel, the present invention performs a first hydrothermal crystallization on the first gel to generate seed crystals with a structure of FER molecular sieve, thereby obtaining the seed crystal suspension.

[0049] In the present invention, the temperature of the first hydrothermal crystallization is 150-180°C, more preferably 160-170°C; the time is 10-16h, more preferably 12-15h; the first hydrothermal crystallization is preferably carried out in a high-pressure reactor placed in a rotary oven; the rotation speed of the rotary oven is preferably 0-20rpm, more preferably 5-15rpm.

[0050] After the first hydrothermal crystallization, the present invention preferably cools the obtained product to obtain the seed crystal suspension.

[0051] The present invention also provides a seed crystal suspension prepared by the preparation method described in the above technical solution, wherein the particle size of the seed crystal is 50 to 90 nm, and the shape of the seed crystal is spherical.

[0052] The present invention also provides a method for preparing a nano-scale FER molecular sieve, comprising the following steps:

[0053] Mixing a second inorganic metal base source, a second aluminum source, a second silicon source, a second water and a seed crystal suspension to obtain a second gel;

[0054] performing a second hydrothermal crystallization on the second gel to obtain the nano-scale FER molecular sieve;

[0055] The seed crystal suspension is the seed crystal suspension described in the above technical solution.

[0056] The present invention mixes a second inorganic metal alkali source, a second aluminum source, a second silicon source, a second water and a seed crystal suspension to obtain a second gel.

[0057] In the present invention, the mixed raw material preferably further comprises pyrrolidine; the second silicon source is calculated as SiO2, and the molar ratio of the pyrrolidine to the second silicon source is preferably 0.1 to 0.5:1, more preferably 0.3 to 0.4:1.

[0058] In the present invention, the second silicon source is calculated as SiO2, the second aluminum source is calculated as Al2O3, and the molar ratio of the second silicon source to the second aluminum source is preferably 8 to 40:1, more preferably 10 to 30:1, and further preferably 15 to 30:1; the second aluminum source preferably includes one or more of aluminum sulfate 18hydrate, sodium aluminate, aluminum isopropoxide, aluminum hydroxide and aluminum chloride; the second silicon source preferably includes one or more of silica sol, silica gel powder and sodium silicate.

[0059] In the present invention, the second inorganic metal alkali source is calculated as M2O, wherein M in M2O is a metal element of the inorganic metal alkali source; the molar ratio of the second inorganic metal alkali source to the second silicon source is preferably 0.2 to 0.6:1, more preferably 0.3 to 0.5:1; the second inorganic metal alkali source preferably includes sodium hydroxide.

[0060] In the present invention, when the second silicon source does not contain water, the molar ratio of the second silicon source to the second water is preferably 1:6 to 40, more preferably 1:10 to 30, and further preferably 1:10 to 20;

[0061] When the second silicon source contains water, the ratio of the amount of the first silicon source to the total amount of the second water and the water in the first silicon source is preferably 1:6-40, more preferably 1:10-30, and further preferably 1:10-20.

[0062] In the present invention, the seed crystal suspension is preferably 1 to 10% by mass of the second silicon source, and more preferably 2 to 5% by mass.

[0063] After obtaining the second gel, the present invention performs a second hydrothermal crystallization on the second gel to obtain the nano-scale FER molecular sieve.

[0064] In the present invention, the temperature of the second hydrothermal crystallization is preferably 150-180°C, more preferably 160-170°C, and the time is preferably 10-16h, more preferably 14-15h; the second hydrothermal crystallization is preferably carried out in a high-pressure reactor placed in a rotary oven; the rotation speed of the rotary oven is preferably 0-20rpm, more preferably 5-15rpm.

[0065] After the second hydrothermal crystallization, the present invention preferably filters the obtained product, and then washes and dries the filtered solid to obtain the nano-scale FER molecular sieve.

[0066] The present invention also provides a nano-scale FER molecular sieve prepared by the preparation method described in the above technical solution, wherein the particle size of the nano-scale FER molecular sieve is 100-200 nm; and the shape of the nano-scale FER molecular sieve is sheet-like.

[0067] The present invention also provides a method for preparing a nanoscale hydrogen-type FER molecular sieve, comprising the following steps:

[0068] The pyrrolidine in the nano-scale FER molecular sieve described in the above technical solution is removed and then mixed with an ammonium salt solution for ion exchange to obtain the nano-scale hydrogen-type FER molecular sieve.

[0069] In the present invention, the pyrrolidine removal preferably comprises: subjecting the nano-sized FER molecular sieve to a first heat treatment, a first temperature increase, a second heat treatment, a second temperature increase, and a third heat treatment in sequence.

[0070] In the present invention, the temperature of the first heat treatment is preferably 120°C, the holding time is preferably 2h, and the heating rate to the first heat treatment temperature is preferably 2°C / min; after the first heat treatment, the water molecules adsorbed on the surface are removed.

[0071] The temperature of the second heat treatment is preferably 470° C., the holding time is preferably 5 hours, and the heating time of the first heating is preferably 270 minutes; the second heat treatment can preliminarily decompose the template.

[0072] The temperature of the third heat treatment is preferably 570° C., the holding time is preferably 10 hours, and the heating rate of the second heating is preferably 1° C. / min. The organic template is removed by the third heat treatment.

[0073] The template agent remains in the pores of the molecular sieve and interacts with the framework of the molecular sieve. If calcined at this temperature only, the template agent will not be completely decomposed. If directly placed at a higher temperature, the template agent will violently oxidize and decompose, releasing a large amount of heat, which will cause certain damage to the microstructure of the catalyst. Therefore, a multi-stage calcination process is selected to minimize the damage to the crystal structure of the catalyst caused by calcination.

[0074] In the present invention, the ion exchange preferably includes a first ion exchange and a second ion exchange; after the first ion exchange is completed, the obtained product is filtered, and then the obtained solid is mixed with an ammonium salt solution to perform a second ion exchange.

[0075] The temperature of the first ion exchange and the second ion exchange is preferably independently 60 to 90° C., more preferably 70 to 80° C., and the time is preferably independently 4 hours;

[0076] During the first ion exchange and the second ion exchange, the solid-to-liquid ratio of the nano-FER molecular sieve after the organic template is removed to the ammonium salt solution is preferably independently 1:10 to 40, more preferably 1:15 to 30. In the present invention, the solid-to-liquid ratio refers to the ratio of the mass of the solid to the volume of the liquid, in g:mL. In the present invention, the NH4 + The concentration of is preferably 0.5-1 mol / L, more preferably 0.6-0.8 mol / L; the ammonium salt preferably independently includes one or more of ammonium sulfate, ammonium chloride and ammonium acetate.

[0077] After the ion exchange is completed, the present invention preferably filters the obtained product, and then washes, dries and heat-treats the obtained solid.

[0078] In the present invention, the heat treatment preferably includes a fourth heat treatment and a fifth heat treatment. The heat treatment decomposes the ammonium salt into ammonia molecules and leaves the molecular sieve in a gaseous form.

[0079] In the present invention, the temperature of the fourth heat treatment is preferably 120°C, the insulation time is preferably 1 to 2 hours, more preferably 1.5 to 1.8 hours, and the heating rate to the fourth heat treatment temperature is preferably 2 to 5°C / min, more preferably 3 to 4°C / min; after the fourth heat treatment, the water molecules adsorbed on the surface are removed.

[0080] The temperature of the fifth heat treatment is preferably 480-550°C, more preferably 500-520°C; the holding time is preferably 5-8h, more preferably 6-7h; the heating time from the fourth heat treatment temperature to the fifth heat treatment temperature is preferably 180-300min, more preferably 200-270min, further preferably 220-250min.

[0081] The present invention also provides a nano-scale hydrogen-type FER molecular sieve prepared by the preparation method described in the above technical solution, wherein the particle size of the nano-scale hydrogen-type FER molecular sieve is 100 nm.

[0082] The present invention also provides the use of the nano-scale hydrogen-type FER molecular sieve described in the above technical solution in the skeletal isomerization reaction of n-butene.

[0083] When the nano-scale hydrogen-type FER molecular sieve of the present invention is used as a catalyst, its smaller crystal size is conducive to improving the diffusion rate of reactants and products, and can effectively inhibit the occurrence of carbon deposition side reactions in the catalytic reaction, slowing down the deactivation of the catalyst, that is, it is conducive to improving the stability of the catalyst. In addition, the nano-scale FER molecular sieve prepared by using the seed suspension of the present invention can improve the contact effect between the reactants and the active sites, thereby helping to improve the conversion rate of n-butene.

[0084] The seed suspension and preparation method thereof, the preparation method of nano-FER molecular sieve, the preparation method of nano-hydrogen FER molecular sieve and application thereof provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0085] Example 1

[0086] Accurately weigh 2.3 g of sodium hydroxide, add 33.84 g of deionized water and stir to dissolve, add 2.56 g of aluminum isopropoxide while stirring, and slowly add 18.80 g of silica sol (solid content is 40 wt%) after stirring to dissolve, accurately weigh 1.80 g of pyrrolidine, stir for 30 min, transfer into a high-pressure reactor, place in a rotary oven at 160 ° C for dynamic crystallization for 15 h (the speed of the rotary oven is 5-15 rpm), take out and cool to obtain a seed suspension, recorded as F1.

[0087] Example 2

[0088] Accurately weigh 0.32g of sodium hydroxide, add 45g of deionized water and stir to dissolve, add 1.24g of sodium aluminate while stirring, and slowly add 15g of silica sol (solid content is 40wt%) and 2.51g of pyrrolidine solution after stirring for 30min. After stirring for 30min, transfer into a high-pressure reactor, place in a rotary oven at 160°C for dynamic crystallization for 15h (the speed of the rotary oven is 5-15rpm), take out and cool to obtain a seed suspension, recorded as F2.

[0089] Comparative Example 1

[0090] Accurately weigh 0.23g of sodium hydroxide, add 27g of deionized water and stir to dissolve, add 1.24g of sodium aluminate while stirring, and slowly add 15g of silica sol (solid content is 40wt%) after stirring to dissolve, accurately weigh 2.12g of ethylenediamine, stir for 30min, then transfer into a high-pressure reactor, place in a rotary oven at 160°C for dynamic crystallization for 15h (the speed of the rotary oven is 5-15rpm), take out and cool to obtain a seed suspension, recorded as EDA1.

[0091] Application Example 1

[0092] Accurately weigh 2.40 g of sodium hydroxide, add 34.58 g of deionized water and stir to dissolve, add 4.27 g of aluminum sulfate 18hydrate while stirring, slowly add 19.21 g of silica sol (solid content is 40 wt%) after stirring to dissolve, continue stirring for 30 min, dropwise add 0.15 g of seed suspension F1, continue stirring for 30 min, then transfer into a high-pressure reactor, place in a rotary oven at 170 ° C for dynamic crystallization for 14 h (the speed of the rotary oven is 5-15 rpm), after the crystallization is completed, the small-grain FER molecular sieve is obtained after centrifugal filtration, washing and drying, marked as NF-PY1.

[0093] The dried NF-PY1 was placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface. It was then heated to 470°C after 270 min and maintained for 5 h. It was then heated to 570°C at 1°C / min and maintained for 10 h to ensure complete removal of the organic template.

[0094] The above molecular sieve with organic template removed is subjected to NH4 +(The ammonium salt is ammonium nitrate, and the concentration of the ammonium salt solution is 1 mol / L) ion exchange, the solid-liquid ratio adopted is 1 g: 15 mL, reflux at 80°C for 4 h, and then filtered, the obtained solid is mixed with ammonium nitrate solution for ion exchange (solid-liquid ratio is 1 g: 15 mL, reflux at 80°C for 4 h), filtered, washed, and dried, the dried molecular sieve is placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface, and then heated to 550°C after 270 min and maintained for 5 h to obtain the corresponding hydrogen-type molecular sieve.

[0095] The XRD pattern of NF-PY1 is shown in Figure 1 shown.

[0096] Depend on Figure 1 It can be seen that the obtained sample is a high-crystallinity FER molecular sieve, and no other impurity phases exist in the sample.

[0097] The SEM image of NF-PY1 is shown in Figure 2 shown.

[0098] Depend on Figure 2 It can be seen that the sample obtained by using pyrrolidine as a template to synthesize liquid seeds and then adding them into the synthesis system is a nanocrystal of about 100 nm.

[0099] Application Example 2

[0100] Accurately weigh 2.09 g of sodium hydroxide, add 22.56 g of deionized water and stir to dissolve, add 3.48 g of aluminum sulfate 18hydrate while stirring, slowly add 18.80 g of silica sol (solid content is 40 wt%) after stirring to dissolve, continue stirring for 30 min, dropwise add 0.34 g of seed suspension F2, continue stirring for 30 min, then transfer into a high-pressure reactor, place in a rotary oven at 170 ° C for dynamic crystallization for 14 h (the speed of the rotary oven is 5-15 rpm), after the crystallization is completed, the small-grain FER molecular sieve is obtained after centrifugal filtration, washing and drying, marked as NF-PY2.

[0101] The dried NF-PY2 was placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface. It was then heated to 470°C after 270 min and maintained for 5 h. It was then heated to 570°C at 1°C / min and maintained for 10 h to ensure complete removal of the organic template.

[0102] The above molecular sieve with organic template removed is subjected to NH4 +(The ammonium salt is ammonium nitrate, and the concentration of the ammonium salt solution is 1 mol / L) ion exchange, the solid-liquid ratio adopted is 1 g: 15 mL, reflux at 80°C for 4 h, and then filtered, the obtained solid is mixed with ammonium nitrate solution for ion exchange (solid-liquid ratio is 1 g: 15 mL, reflux at 80°C for 4 h), filtered, washed, and dried, the dried molecular sieve is placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface, and then heated to 550°C after 270 min and maintained for 5 h to obtain the corresponding hydrogen-type molecular sieve.

[0103] The SEM image of NF-PY2 is shown in Figure 3 shown.

[0104] Depend on Figure 3 It can be seen that the obtained sample is a nanocrystal of about 100 nm, which indicates that both aluminum isopropoxide and sodium metaaluminate can be used as aluminum sources to prepare liquid seed crystals, so that the particle size of the final product is maintained at about 100 nm.

[0105] Application Example 3

[0106] Accurately weigh 2.61 g of sodium hydroxide, add 15.79 g of deionized water and stir to dissolve, add 5.22 g of aluminum sulfate 18hydrate while stirring, slowly add 18.80 g of silica sol (solid content is 40 wt%) after stirring to dissolve, continue stirring for 30 min, dropwise add 0.3 g of seed suspension F2, continue stirring for 30 min, then transfer into a high-pressure reactor, place in a rotary oven at 170 ° C for dynamic crystallization for 14 h (the speed of the rotary oven is 5-15 rpm), after the crystallization is completed, the small-grain FER molecular sieve is obtained after centrifugal filtration, washing and drying, marked as NF-PY3.

[0107] The dried NF-PY3 was placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface. It was then heated to 470°C after 270 min and maintained for 5 h. It was then heated to 570°C at 1°C / min and maintained for 10 h to ensure complete removal of the organic template.

[0108] The above molecular sieve with organic template removed is subjected to NH4 + (The ammonium salt is ammonium nitrate, and the concentration of the ammonium salt solution is 1 mol / L) ion exchange, the solid-liquid ratio adopted is 1 g: 15 mL, reflux at 80°C for 4 h, and then filtered, the obtained solid is mixed with ammonium nitrate solution for ion exchange (solid-liquid ratio is 1 g: 15 mL, reflux at 80°C for 4 h), filtered, washed, and dried, the dried molecular sieve is placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface, and then heated to 550°C after 270 min and maintained for 5 h to obtain the corresponding hydrogen-type molecular sieve.

[0109] The SEM image of NF-PY3 is shown in Figure 4 shown.

[0110] Depend on Figure 4 It can be seen that by reducing the silicon-aluminum ratio of the feed, the obtained product is also a nanocrystal of about 100nm.

[0111] Based on the three application examples, the molar ratio of silicon oxide to aluminum oxide is 16 to 24, and nanocrystals of about 100 nm can be obtained within this range.

[0112] Comparative application example 1

[0113] Preparation of FER molecular sieve: accurately weigh 2.09g of sodium hydroxide, add 22.56g of deionized water and stir to dissolve, add 3.48g of aluminum sulfate 18hydrate while stirring, slowly add 18.80g of silica sol (solid content is 40wt%) after stirring to dissolve, continue stirring for 30min, dropwise add 0.34g of seed suspension EDA1, continue stirring for 30min, then transfer into a high-pressure reactor, place in a rotary oven at 170°C for dynamic crystallization for 14h (the speed of the rotary oven is 5-15rpm), take out to cool, centrifuge and wash to obtain the target product, marked as F-EDA.

[0114] The dried F-EDA was placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 hours to remove water molecules adsorbed on the surface. It was then heated to 470°C after 270 minutes and maintained for 5 hours. It was then heated to 570°C at 1°C / min and maintained for 10 hours to ensure complete removal of the organic template.

[0115] The above molecular sieve with organic template removed is subjected to NH4 + (The ammonium salt is ammonium nitrate, and the concentration of the ammonium salt solution is 1 mol / L) ion exchange, the solid-liquid ratio adopted is 1:15, reflux at 80°C for 4 hours, repeated twice, washed and dried, the dried molecular sieve is placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 hours to remove the water molecules adsorbed on the surface, and then heated to 550°C after 270 minutes and maintained for 5 hours to obtain the corresponding hydrogen-type molecular sieve.

[0116] The SEM image of F-EDA is shown below: Figure 5 shown.

[0117] Depend on Figure 5 It can be seen that after changing the template used in the liquid seed synthesis to ethylenediamine, the final product obtained is a cross-assembly structure of micron-sized nanosheets, and the size of the nanosheets is larger.

[0118] Comparative Application Example 2

[0119] Accurately weigh 2.09 g of sodium hydroxide, add 22.56 g of deionized water and stir to dissolve, add 3.48 g of aluminum sulfate 18hydrate while stirring, slowly add 18.80 g of silica sol after stirring to dissolve, add 1.38 g of pyrrolidine solution, continue stirring for 30 min, transfer to a high-pressure reactor, place in a rotary oven at 170 ° C for dynamic crystallization for 14 h, take out to cool, centrifuge and wash, and the product obtained is marked as F-PY.

[0120] The dried F-PY was placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface. It was then heated to 470°C after 270 min and maintained for 5 h. It was then heated to 570°C at 1°C / min and maintained for 10 h to ensure complete removal of the organic template.

[0121] The above molecular sieve with organic template removed is subjected to NH4 + (The ammonium salt is ammonium nitrate, and the concentration of the ammonium salt solution is 1 mol / L) ion exchange, the solid-liquid ratio adopted is 1:15, reflux at 80°C for 4 hours, repeated twice, washed and dried, the dried molecular sieve is placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 hours to remove the water molecules adsorbed on the surface, and then heated to 550°C after 270 minutes and maintained for 5 hours to obtain the corresponding hydrogen-type molecular sieve.

[0122] The SEM image of F-PY is shown in Figure 6 shown.

[0123] Depend on Figure 6 It can be seen that when pyrrolidine is directly used as an organic template to synthesize FER molecular sieves, the resulting product is also a micron-sized flaky structure, and the overall particle size is larger than the sample size obtained by the method of first synthesizing liquid seeds using pyrrolidine, but smaller than the size of the final product obtained by synthesizing liquid seeds using ethylenediamine as a template.

[0124] Application Example 4

[0125] Accurately weigh 2.40 g of sodium hydroxide, add 34.58 g of deionized water and stir to dissolve, add 4.27 g of aluminum sulfate 18hydrate while stirring, slowly add 19.21 g of silica sol (solid content is 40 wt%) after stirring to dissolve, continue stirring for 30 min, dropwise add 0.15 g of seed suspension F1 and then add 1.38 g of pyrrolidine, continue stirring for 30 min, transfer to a high-pressure reactor, place in a rotary oven at 170 ° C for dynamic crystallization for 14 h (the speed of the rotary oven is 5-15 rpm), after the crystallization is completed, the small-grain FER molecular sieve is obtained after centrifugal filtration, washing and drying, marked as NF-PY4.

[0126] The dried NF-PY4 was placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface. It was then heated to 470°C after 270 min and maintained for 5 h. It was then heated to 570°C at 1°C / min and maintained for 10 h to ensure complete removal of the organic template.

[0127] The above molecular sieve with organic template removed is subjected to NH4 + (The ammonium salt is ammonium nitrate, and the concentration of the ammonium salt solution is 1 mol / L) ion exchange, the solid-liquid ratio adopted is 1 g: 15 mL, reflux at 80°C for 4 h, and then filtered, the obtained solid is mixed with ammonium nitrate solution for ion exchange (solid-liquid ratio is 1 g: 15 mL, reflux at 80°C for 4 h), filtered, washed, and dried, the dried molecular sieve is placed in a muffle furnace and heated to 120°C at 2°C / min and maintained for 2 h to remove water molecules adsorbed on the surface, and then heated to 550°C after 270 min and maintained for 5 h to obtain the corresponding hydrogen-type molecular sieve.

[0128] The SEM image of NF-PY4 is shown in Figure 7 shown.

[0129] Depend on Figure 7 It can be seen that, based on Application Example 1, pyrrolidine is additionally added, and the resulting product is also a nanoscale flake structure with a size of about 100 nm.

[0130] The results of the skeletal isomerization reaction of n-butene catalyzed by the hydrogen-form molecular sieves of Examples 1 to 4 and Comparative Examples 1 to 2 are as follows. Figure 8 As shown:

[0131] The isomerization test of n-butene was carried out in a high-pressure stainless steel micro fixed-bed reactor with an inner diameter of 8 mm. The amount of hydrogen-form molecular sieve (40-60 mesh) was 100 mg. It was treated with N2 (30 mL / min) at 773 K for 1 h and then cooled to 673 K. 10% n-butene / 2.5% Ar / He (volume ratio) was passed through a flow controller (50 mL / min, the space velocity of n-butene was 7.5 h -1 ) was introduced into the reactor, and the reaction pressure was normal pressure. The reaction product was analyzed online by an Agilent GC 7890A gas chromatograph equipped with TCD and FID detectors. An Al2O3 gas chromatography column (Agilent HPAL / M, 30m×0.53mm×15μm) was used for separation.

[0132] Depend on Figure 8It can be seen that the nano-scale small-grain hydrogen-type FER molecular sieve of the present invention can be used as a catalyst for the reaction of n-butene skeletal isomerization to isobutylene, and has high reaction activity, isobutylene selectivity and long catalytic stability: the nano-scale small-grain hydrogen-type FER molecular sieve of the present invention can achieve a n-butene conversion rate of up to 63.8-66.4% in the n-butene skeletal isomerization reaction, and the n-butene conversion rate remains above 60.6% after 150 hours of stable operation, and the isobutylene selectivity is maintained at 94.4%, with high butene skeletal isomerization catalytic performance. And the catalytic results of application examples 1-3 and application example 4 show that the additional addition of a template agent does not significantly help to further improve the performance.

[0133] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a seed suspension, characterized in that: The following steps are involved: Mixing a first silicon source, a first inorganic metal base source, a first aluminum source, pyrrolidine and first water to obtain a first gel; Performing a first hydrothermal crystallization on the first gel to generate seed crystals with a structure of FER molecular sieve, thereby obtaining the seed crystal suspension; The temperature of the first hydrothermal crystallization is 150-180° C., and the time is 10-16 hours.

2. The preparation method according to claim 1, characterized in that: The first silicon source includes one or more of silica sol, silica gel powder and sodium silicate.

3. The preparation method according to claim 1, characterized in that: The first aluminum source includes one or more of aluminum sulfate 18hydrate, sodium metaaluminate, aluminum isopropoxide, aluminum hydroxide and aluminum chloride.

4. The preparation method according to claim 1, characterized in that: The first silicon source is calculated as SiO2, the first aluminum source is calculated as Al2O3, and the molar ratio of the first silicon source to the first aluminum source is 8 to 20:

1.

5. The seed suspension prepared by the preparation method according to any one of claims 1 to 4, characterized in that: The seed crystal has a particle size of 50 to 90 nm and a spherical shape.

6. A method for preparing a nano-scale FER molecular sieve, characterized in that: The following steps are involved: Mixing a second inorganic metal base source, a second aluminum source, a second silicon source, a second water and a seed crystal suspension to obtain a second gel; performing a second hydrothermal crystallization on the second gel to obtain the nano-scale FER molecular sieve; The seed crystal suspension is the seed crystal suspension according to claim 5.

7. The nano-scale FER molecular sieve prepared by the preparation method of claim 6, characterized in that: The length of the nano-scale FER molecular sieve is 100 to 200 nm; The nano-scale FER molecular sieve is in the shape of a sheet.

8. A method for preparing a nano-scale hydrogen-type FER molecular sieve, characterized in that: The following steps are involved: The pyrrolidine in the nano-scale FER molecular sieve of claim 7 is removed and then mixed with an ammonium salt solution for ion exchange to obtain the nano-scale hydrogen-type FER molecular sieve.

9. The nanoscale hydrogen-type FER molecular sieve prepared by the preparation method of claim 8, characterized in that: The particle size of the nano-scale hydrogen-type FER molecular sieve is 100-200 nm.

10. Use of the nanoscale hydrogen-type FER molecular sieve according to claim 9 in the skeletal isomerization reaction of n-butene.

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