CN110668465B - MeAPSO-44 molecular sieve and preparation method thereof - Google Patents
MeAPSO-44 molecular sieve and preparation method thereof Download PDFInfo
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- 239000002808 molecular sieve Substances 0.000 title claims abstract description 80
- URGAHOPLAPQHLN-UHFFFAOYSA-N sodium aluminosilicate Chemical compound [Na+].[Al+3].[O-][Si]([O-])=O.[O-][Si]([O-])=O URGAHOPLAPQHLN-UHFFFAOYSA-N 0.000 title claims abstract description 80
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 241000209094 Oryza Species 0.000 claims abstract description 50
- 235000007164 Oryza sativa Nutrition 0.000 claims abstract description 50
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- 238000000034 method Methods 0.000 claims abstract description 37
- 238000002425 crystallisation Methods 0.000 claims abstract description 35
- 230000008025 crystallization Effects 0.000 claims abstract description 34
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 29
- 239000010703 silicon Substances 0.000 claims abstract description 29
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 29
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- 238000010532 solid phase synthesis reaction Methods 0.000 claims abstract description 25
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- 239000003795 chemical substances by application Substances 0.000 claims abstract description 9
- 239000000463 material Substances 0.000 claims abstract description 9
- 239000013078 crystal Substances 0.000 claims abstract description 7
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- 239000002149 hierarchical pore Substances 0.000 abstract description 4
- 229910000147 aluminium phosphate Inorganic materials 0.000 abstract description 3
- 239000013589 supplement Substances 0.000 abstract description 3
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 24
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- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 description 3
- 230000009471 action Effects 0.000 description 3
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- 229930091371 Fructose Natural products 0.000 description 2
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- TZCXTZWJZNENPQ-UHFFFAOYSA-L barium sulfate Chemical compound [Ba+2].[O-]S([O-])(=O)=O TZCXTZWJZNENPQ-UHFFFAOYSA-L 0.000 description 2
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- 229920002488 Hemicellulose Polymers 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
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- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 description 1
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- 229940073455 tetraethylammonium hydroxide Drugs 0.000 description 1
- LRGJRHZIDJQFCL-UHFFFAOYSA-M tetraethylazanium;hydroxide Chemical compound [OH-].CC[N+](CC)(CC)CC LRGJRHZIDJQFCL-UHFFFAOYSA-M 0.000 description 1
- 239000002341 toxic gas Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B39/00—Compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites; Their preparation; After-treatment, e.g. ion-exchange or dealumination
- C01B39/54—Phosphates, e.g. APO or SAPO compounds
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B37/00—Compounds having molecular sieve properties but not having base-exchange properties
- C01B37/06—Aluminophosphates containing other elements, e.g. metals, boron
- C01B37/08—Silicoaluminophosphates [SAPO compounds], e.g. CoSAPO
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geology (AREA)
- Materials Engineering (AREA)
- Silicates, Zeolites, And Molecular Sieves (AREA)
Abstract
The invention provides a preparation method of a MeAPSO-44 molecular sieve, which comprises the following steps: the method comprises the steps of pretreatment, solid phase or hydrothermal synthesis, crystallization and post-treatment, wherein the natural bauxite contains silicon element, iron element and titanium element. According to the technical scheme, natural bauxite which is cheap and easy to obtain is used as a raw material, the added rice husk can be used as a silicon source supplement and a hard template agent, and can promote metal heteroatoms to enter a molecular sieve framework, resources such as aluminum, silicon, iron, titanium and the like in the natural bauxite are effectively utilized, the bauxite is prepared into a microporous-mesoporous composite hierarchical pore by one step through a solid phase method, the specific surface area is 303-421m 2 MeAPSO-44 molecular sieves (Me = Fe, ti) per g. Oxides in natural bauxite and rice hulls are basically amorphous substances, which is beneficial to the synthesis of molecular sieves; and the bonding phenomenon can not occur in the process of adding phosphoric acid, which is beneficial to the uniformity of the solid-phase synthesis material. The MeAPSO-44 molecular sieve with complete crystal phase and large specific surface area can be synthesized by utilizing natural raw materials, and the rice hulls have the promotion effect on metal heteroatoms entering a molecular sieve framework.
Description
Technical Field
The invention relates to the field of mineral resource processing, in particular to a MeAPSO-44 molecular sieve and a preparation method thereof.
Background
In 1998, U.S. Pat. No. 9785098 discloses a process for the preparation of SAPO-44, or substantially pure SAPO-44, comprising silicoaluminophosphates, and the use of the prepared molecular sieves for oxidative conversion to olefins. SAPO-44 belongs to a silicoaluminophosphate molecular sieve, has similar physicochemical properties to SAPO-34, and has chabazite-type pores and three-dimensional cross channels formed by four-membered rings, double six-membered rings and eight-membered rings. The molecular sieve which embeds metal atoms into SAPO-44 and is named MeAPSO-44 has the pore opening and the self-acidity, and is changed due to the entrance of metal ions, thereby showing new structure and performance.
The specific synthesis method of the MeAPSO-44 molecular sieve is similar to the synthesis method of SAPO-44, and comprises a traditional hydrothermal synthesis method, a dry gel method, a microwave radiation crystallization method, a solid phase method and the like. The raw materials for synthesizing SAPO molecular sieves reported in the current literature mainly belong to three main types: chemical raw materials, natural aluminosilicate minerals with low price and wide sources and solid wastes. The adoption of the latter two natural aluminosilicate minerals and the solid waste can not only effectively reduce the synthesis cost, but also make the non-renewable mineral resources be utilized with high value, and make the solid waste be changed into valuables.
The Rui et al prepared SAPO-44 molecular sieve catalyst with transition metal load has great development potential in the automobile exhaust denitration technology. Metal-supported SAPO molecular sieves are extensively studied, sun et Al have synthesized four different types of heteroatomic aluminum phosphate molecular sieves (MeSAPO-5, -11, -34, -44, me =fe, ti) using traditional hydrothermal methods with bauxite to provide a single Al, si and Me that can be used as a catalyst to efficiently convert carbohydrates to HMF, and the MeSAPO is regenerated after maintaining good catalytic performance. In recent years, people pay attention to the research of synthesizing molecular sieves by using wastes, and the agricultural waste rice hulls are a renewable resource which is cheap and easy to collect in China. Most of the rice hulls are incinerated or directly discarded at the present stage, so that the comprehensive utilization rate is low, and the great waste of resources is caused. In the field of catalysis, rice hull silicon serving as a silicon source is used for synthesis of microporous and mesoporous molecular sieves, and a large number of documents report that the rice hulls are subjected to activation treatment such as calcination and the like, and a hydrothermal method is adopted to prepare the P-type molecular sieve. The method comprises the steps of taking rice hulls as raw materials, extracting silicon in the rice hulls through high-temperature alkali activation to serve as a silicon source for molecular sieve synthesis, and synthesizing the Y-type molecular sieve with a hierarchical pore structure by using carbon in carbonized rice hulls as a mesoporous template. The rice hulls are acidified and calcined to obtain amorphous silica which can be used for preparing MCM-4l.
In most reports of using natural minerals to prepare SAPO molecular sieves, complex pretreatment is required to be carried out on raw mineral materials to activate components such as aluminum, silicon, iron and the like in the minerals, and some inorganic mineralizers such as HF and the like with extremely strong corrosivity are required to be added. Before being used as a silicon source for synthesizing the molecular sieve, rice hull silicon also needs to be subjected to activation treatment in forms of ashing, acidification, high-temperature alkalization and the like. And the crystallization time of the hydrothermal method is longer, so that environmental pollution is easily caused in the crystallization or roasting process of the molecular sieve, or a larger amount of waste liquid is generated, or some toxic gases such as nitric oxide and the like are released.
Disclosure of Invention
Therefore, a new method for providing a MeAPSO-44 (Me = Fe, ti) molecular sieve with high raw material utilization rate, safety, environmental protection, economy and high efficiency is needed. In order to achieve the above object, the inventors provide a preparation method of a MeAPSO-44 molecular sieve, comprising the steps of:
pretreatment: removing impurities from natural bauxite, and performing ball milling to obtain pretreated powdered bauxite;
solid-phase synthesis: mixing bauxite with deionized water, stirring continuously, and adding phosphorus source (P) in turn during stirring 2 O 5 ) And supplementing silicon Source (SiO) 2 ) Mixing the template agent and the mixture uniformly, and stirring to obtain a paste mixture; the templating agent comprises Cyclohexylamine (CHA);
and (3) crystallization: crystallizing the paste mixture at 160-220 deg.C until MeAPSO-44 crystal is formed, centrifuging and washing the crystallized material until pH of the washing liquid is 6.3-6.5 to obtain precipitate;
and (3) post-treatment: drying and calcining the precipitate to obtain a MeAPSO-44 molecular sieve;
the natural bauxite contains aluminum element, silicon element, iron element and titanium element, and the supplementary silicon source comprises rice husk and silica sol.
Further, the alumina comprises the following active substances in percentage by mass:
Al 2 O 3 ：68-73％；SiO 2 ：8-13％；Fe 2 O 3 ：16-18％；TiO 2 ：1.6-1.8％。
further, in the pretreatment step, the ball milling speed is 500r/min, and the ball milling time is 2h.
Further, the solid phase synthesis step is to synthesize Al in the material 2 O 3 ：P 2 O 5 ：SiO 2 ：CHA：H 2 The molar ratio of O is 80-100:90-110:20-80:180-200:2000-4000.
Further, PEG20000 and Al are added in the solid phase synthesis step 2 O 3 The molar ratio of the PEG to 20000 is 90000-110000.
Further, in the solid phase synthesis step, the weight ratio of the pretreated bauxite to the rice hulls is 1400-1600:900-1100.
Further, in the crystallization step, the crystallization time is 2-96h.
Further, the post-treatment step is to dry the precipitate in a 110 ℃ oven for 4h and calcine the precipitate in a 550 ℃ muffle furnace under an air atmosphere for 4h.
The inventor also provides a MeAPSO-44 molecular sieve, wherein the MeAPSO-44 molecular sieve is prepared by adopting any one of the preparation methods.
Compared with the prior art, the technical scheme takes cheap and easily-obtained natural bauxite and rice hulls as raw materials, simultaneously effectively utilizes silicon in the rice hulls and resources such as aluminum, silicon, iron, titanium and the like in the natural bauxite, and prepares the composite hierarchical pore with micropores, mesopores and the like, the specific surface area is 285-398m 2 The MeAPSO-44 molecular sieve per gram (Me = Fe, ti) has the advantages of high utilization rate of raw materials, low cost, high product yield, simple process and no generation of waste liquid and waste residue. Oxides in natural bauxite and rice hulls are basically amorphous substances, which is beneficial to the synthesis of molecular sieves; and the bonding phenomenon can not occur in the process of adding the phosphoric acid, which is beneficial to the uniformity of the solid-phase synthesis material. The MeAPSO-44 molecular sieve with complete crystal phase and large specific surface area can be synthesized by utilizing natural raw materials, and the rice hulls have the promotion effect on metal heteroatoms entering a molecular sieve framework. The MeAPSO-44 (Me = Fe, ti) molecular sieve synthesized by the method has multi-stage pores, large specific surface area and proper pore diameter, so that the molecular sieve can be used for preparing 5-hydroxymethylfurfural and N through denitration reaction and fructose dehydration in tail gas treatment 2 /CH 4 Has good application prospect in separation, conversion of heavy oil into light oil, degradation of dye and the like。
Drawings
FIG. 1 is an XRD pattern for examples 1-8;
FIG. 2 is an XRD pattern for examples 9-17;
FIG. 3 is an SEM image of the MeAPSO-44 molecular sieve synthesized in example 1;
FIG. 4 is the isothermal adsorption and desorption curves and the pore size distribution diagram of nitrogen physisorption of the MeAPSO-44 molecular sieve synthesized in example 1;
FIG. 5 is the isothermal adsorption and desorption curves and the pore size distribution diagram of nitrogen physisorption of the MeAPSO-44 molecular sieve synthesized in example 4;
FIG. 6 is the isothermal adsorption-desorption curve and the pore size distribution diagram of the MeAPSO-44 molecular sieve nitrogen physical adsorption synthesized in example 5;
FIG. 7 is the isothermal adsorption-desorption curve and pore size distribution diagram of nitrogen physisorption of MeAPSO-44 molecular sieve synthesized in example 6;
FIG. 8 is a graph showing the isothermal adsorption and desorption curves and the pore size distribution of nitrogen physisorption of the MeAPSO-44 molecular sieve synthesized in example 7;
FIG. 9 is the isothermal adsorption-desorption curve and pore size distribution diagram of nitrogen physisorption of the MeAPSO-44 molecular sieve synthesized in example 8;
figure 10 is a graph of the ultraviolet diffuse reflectance spectrum of the MeAPSO-44 molecular sieve synthesized in example 1.
Detailed Description
In order to explain technical contents, structural features, objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in combination with the embodiments.
In this embodiment: analyzing the element composition of the sample of the bauxite and the rice hull by a solid X-ray fluorescence spectrometer; in this embodiment, the alumina mainly comprises the following components by mass percent: al (Al) 2 O 3 ：SiO 2 ：Fe 2 O 3 ：TiO 2 =69.51%:12.18%:17.1%:1.71 percent; the main chemical component of the rice hull is SiO 2 :10.1wt%, hemicellulose 29.6%, cellulose 31.1%, lignin 16.0%, and small amount of other trace elements.
Example 1 preparation of MeAPSO-44 molecular sieves (Me = Fe, ti)
Pretreatment: removing impurities from bauxite, and ball-milling in a ball mill with the rotation speed of 500r/min for 2h to obtain powdery bauxite;
solid-phase synthesis: weighing 1.5000g of pretreated powdered alumina in a polytetrafluoroethylene lining, and adding H 3 PO 4 (85 wt.%) is P 2 O 5 Source, silica Sol (SiO) 2 30wt%, alkaline), rice hulls; wherein the weight ratio of the bauxite to the rice husk is 1.5:1.0. according to the raw material mol ratio of Al 2 O 3 ：P 2 O 5 ：SiO 2 ：CHA：H 2 O =1.0, 0.9, 2.0, in that the following steps are performed in the order of deionized water, a phosphorus source, a supplemental silicon source, and a template agent, wherein the supplemental silicon source (silica sol is added first and then rice husk is added) is magnetically stirred for 30min for each addition of one of the raw materials. After the materials are added, magnetically stirring for 2 hours at normal temperature to obtain a uniform pasty mixture; and (3) crystallization: placing the paste mixture into a poly-tetra-ethyl-ene reaction kettle added with 1.1084g of deionized water, and then placing the mixture into a stainless steel outer kettle; crystallizing at 200 deg.C for 24 hr. After crystallization, centrifugally washing the product in the lining until the pH =6.4-6.7 to obtain a precipitate;
and (3) post-treatment: drying the precipitate in a drying oven at 110 ℃ for 4h to obtain molecular sieve raw powder; and (3) roasting the molecular sieve raw powder in a muffle furnace at 550 ℃ for 4h to remove the template agent to obtain the MeAPSO-44 molecular sieve (Me = Fe, ti).
Commonly used for synthesizing SAPO molecular sieves are morpholine, tetraethylammonium hydroxide, triethylamine, cyclohexylamine and the like, and Cyclohexylamine (CHA) with relatively low price is selected as a template agent in the embodiment. The rice hulls contain cellulose and have the function of expanding pores in the experiment, and in the isothermal adsorption and desorption curve and the pore size distribution diagram of nitrogen physical adsorption shown in figures 4-9, the specific surface area of the molecular sieve added with the rice hulls is obviously increased, the pore size is enlarged, and the function of a hard template agent is realized.
Example 2
The differences between example 2 and example 1 are: in the solid phase synthesis process of example 1, 1.5000g of pretreated powdered alumina is weighed; and crystallizing for 24 hours. Example 8 solid phase synthesis process, 5.0000g pretreated powdered alumina was weighed and crystallized for 16h.
Example 3
The difference between example 3 and example 1 is: example 1 during solid phase synthesis, the weight ratio of alumina to rice husk was 1.5:1.0, feeding; example 3 during the solid phase synthesis, the weight ratio of the alumina to the rice husk is 1.5:0.45 parts of the feed.
Example 4
The differences between example 4 and example 1 are: example 1 during solid phase synthesis, the weight ratio of alumina to rice husk was 1.5:1.0; example 4 during solid phase synthesis, the weight ratio of alumina to rice husk was 1.5:1.85, the rice hulls contain enough silicon to supplement the silicon source, and silica sol is not needed to be added.
Example 5:
the difference between example 5 and example 1 is: the silicon source supplement of example 5 is silica sol (30 wt%, alkaline), no rice hull is added, both PEG and rice hull have pore-expanding effect, PEG20000 is added, PEG20000 is the last material added, al 2 O 3 Molar ratio to PEG20000 90000.
Example 6
Example 6 differs from example 1 in that the ball-milled alumina was calcined at 550 ℃ for 4 hours, and solid phase synthesis was carried out using calcined alumina as the raw material.
Example 7
Example 7 differs from example 1 in that the supplemental silicon source of the comparative example was silica sol (30 wt%, basic) with no rice hull component.
Example 8
Example 8 differs from example 1 in that the solid phase synthesis method of comparative example is hydrothermal synthesis, and the molar ratio of the raw materials is Al 2 O 3 ：P 2 O 5 ：SiO 2 ：CHA：H 2 O = 1.0.
Example 9
The difference between example 9 and example 1 is that the crystallization conditions were changed from 24 hours at 200 ℃ to 2 hours at 200 ℃ in the crystallization.
Example 10
The difference between the example 10 and the example 1 is that the crystallization condition is changed from 24 hours at 200 ℃ to 4 hours at 200 ℃ in the crystallization.
Example 11
Example 11 differs from example 1 in that: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 8 hours at 200 ℃.
Example 12
Example 12 differs from example 1 in that: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 16 hours at 200 ℃.
Example 13
The difference between example 13 and example 1 is: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 48 hours at 200 ℃.
Example 14
Example 14 differs from example 1 in that: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 96 hours at 200 ℃.
Example 15
The difference between example 15 and example 1 is: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 24 hours at 220 ℃.
Example 16
Example 16 differs from example 1 in that: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 24 hours at 180 ℃.
Example 17
The difference between example 17 and example 1 is: in the crystallization, the crystallization condition is changed from 24 hours at 200 ℃ to 24 hours at 160 ℃.
Performance evaluation:
1. mass spectrometry was performed on MeAPSO-44 molecular sieves prepared in examples 1-8 (Me = Fe, ti):
as can be seen from XRD patterns of examples 1 to 8 in FIG. 1, meAPSO-44 molecular sieves (Me = Fe, ti) prepared by the method all have characteristic peaks of SAPO-44 (PDF: 47-0630) at 2 theta =9.5, 20.7, 30.8, 31.2, and meanwhile, no TiO appears in the XRD pattern 2 And Fe 2 O 3 The diffraction peak of (A) indicates that the metal enters the framework of the SAPO-44 molecular sieve. FIG. 1 shows that the solid-phase synthesis method has complete crystal phase and good crystallinity, and can be used for preparing the product with enlarged raw material consumptionAnd the crystallinity of a synthetic sample added with the rice hulls which are not subjected to ashing as part of silicon source is increased, which shows that the rice hulls have the function of promoting heteroatom iron and titanium to enter a molecular sieve framework.
Fig. 2, examples 11-17XRD patterns change the crystallization conditions of the sample synthesis, and it can be seen that the crystallization temperature is too low, e.g. 160 ℃, the crystallization time is too short, e.g. 2h, the crystalline phase is not complete, and the complete crystalline phase is obtained at 4h of crystallization, which has significantly reduced the synthesis time compared to the hydrothermal synthesis method. Varying the amount of rice hull added also has an effect on crystallinity, which is best in the example when the weight ratio of alumina to rice hull is 1.5.
2. SEM image:
FIG. 3 is an SEM image of the MeAPSO-44 molecular sieve synthesized in example 1, from which we can see that the morphology of the molecular sieve is cubic, consistent with the literature reports, thus demonstrating that the SAPO-44 molecular sieve is synthesized by the method; it can also be seen from the figure that the synthesized molecular sieve has a particle diameter of about 5 μm.
3、N 2 -adsorption/desorption characterization:
and (3) testing conditions:
the molecular sieve nitrogen physical adsorption performance characterization is carried out by adopting a MacaASAP 2460 type specific surface and porosity analyzer. Weighing about 100mg of sample, and carrying out vacuum pretreatment for 5h at 200 ℃; with N 2 For the adsorbate, the adsorption-desorption curve was determined at liquid nitrogen temperature (-196 ℃). According to the adsorption branch of the adsorption-desorption curve, the BET (Berrett-Emmett-Teller) is adopted to calculate the specific surface area of a related sample, and according to the adsorption-desorption branch of the adsorption-desorption curve, the Berret-Joyner-Halenda (BJH) method is adopted to calculate the pore volume and the pore diameter.
| Examples | Specific surface area/(m) 2 /g) | Pore volume/(cm) 3 /g) | Pore size/nm |
| Example 1 | 398.2 | 0.216 | 2.18 |
| Example 4 | 413 | 0.224 | 2.16 |
| Example 5 | 303.1 | 0.184 | 2.43 |
| Example 6 | 421.0 | 0.257 | 2.44 |
| Example 7 | 386.7 | 0.264 | 2.73 |
| Example 8 | 322.1 | 0.247 | 3.07 |
The difference between example 1 and example 4 is that rice husk is added as a partial supplementary silicon source in example 1, only rice husk is used as a supplementary silicon source in example 4, and the characterization result of XRD shows that the synthetic sample prepared from rice husk and silica sol together as the supplementary silicon source has better crystallinity, the weight ratio of alumina to rice husk is 1.5. Comparison of examples 1, 4 and 5 shows that rice hulls have a significant pore-enlarging effect on MeAPSO-44 molecular sieves compared to PEG. Example 6 is a molecular sieve synthesized from calcined alumina, and the specific surface area of the synthesized sample is increased after the calcination treatment of natural minerals, but the specific surface area is not particularly significant, but the technical process of the synthesis process is increased. Example 7 only silica sol was used as a supplementary silicon source, no rice husk was added, the XRD results were compared, the crystallinity of the product synthesized from molecular sieve by adding a suitable amount of rice husk was relatively high, and the results of nitrogen physical adsorption again demonstrate the pore-enlarging effect of rice husk. Example 8 the specific surface area of the molecular sieve synthesized by the traditional hydrothermal synthesis method is smaller than that of the molecular sieve synthesized by the solid phase method in example 1. In conclusion, the rice hulls can promote metal heteroatoms to enter the molecular sieve and also play a role in reaming.
Therefore, we can conclude that: oxides in natural bauxite and rice hulls are basically amorphous substances, which is beneficial to the synthesis of molecular sieves; and the bonding phenomenon can not occur in the process of adding the phosphoric acid, which is beneficial to the uniformity of the solid-phase synthesis material. The MeAPSO-44 molecular sieve with complete crystal phase and large specific surface area can be synthesized by utilizing natural raw materials, and the rice hulls have the promotion effect on metal heteroatoms entering a molecular sieve framework.
Fig. 4-9 are the isothermal adsorption/desorption curves and the pore size distribution diagrams of nitrogen physisorption of MeAPSO-44 (Me = Fe, ti) molecular sieves synthesized in examples 1, 4, 5, 6, 7, and 8, respectively, from which we can see that the adsorption/desorption curves of the molecular sieves synthesized by the present method all have hysteresis loops, some of which are less obvious, indicating that the number of mesopores is less; the isotherms all belong to type IV in the IUPAC classification, and the hysteresis loop is type H4. The adsorption capacity rapidly increases in the lower relative pressure region, at a pressure p/p 0 The adsorption capacity in the range of 0.01 to 0.6 presents a platform, which is the characteristic of the adsorption curve of microporous substances; when p/p is 0 >At 0.6, the adsorption capacity begins to increase and has a certain difference with the desorption curve, and the isothermal curve is p/p 0 >After 0.98, it showed an infinite growth trend, indicating that there was a certain amount of mesopores within the synthesized MeAPSO-44 molecular sieve crystals. The molecular sieve synthesized by the method is of a multi-stage pore structure through nitrogen adsorption and desorption characterization.
4. Diffuse reflection of ultraviolet light
And (3) testing conditions are as follows: the solid powder sample was measured by a Perkinelmer Lambda750 ultraviolet-visible near-infrared spectrophotometer and by a barium sulfate tabletting method.
FIG. 10 is a graph of the UV diffuse reflectance spectrum of example 1, which shows that there is a sharp absorption in the 200-280nm range, and no other absorption peak is found in the visible light region (after 400 nm), indicating that the heteroatoms Fe and Ti are located at the framework position of the molecular sieve. Further proves that the doped metal heteroatoms Fe and Ti enter the molecular sieve framework.
The MeAPSO-44 (Me = Fe, ti) molecular sieve synthesized by the method has hierarchical pores, large specific surface area and proper pore diameter, so that the molecular sieve can be used for preparing 5-hydroxymethylfurfural and N by denitration reaction and fructose dehydration in tail gas treatment 2 /CH 4 The separation, the conversion of heavy oil into light oil, the degradation of dye and the like have good application prospects.
It should be noted that, in this document, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or terminal that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or terminal. Without further limitation, an element defined by the phrases "comprising 8230; \8230;" or "comprising 8230; \8230;" does not exclude additional elements from existing in a process, method, article, or terminal device that comprises the element. Further, in this document, "greater than," "less than," "more than," and the like are understood to not include the present numbers; the terms "above", "below", "within" and the like are to be understood as including the present number.
It should be noted that, although the above embodiments have been described herein, the invention is not limited thereto. Therefore, based on the innovative concepts of the present invention, the technical solutions of the present invention can be directly or indirectly applied to other related technical fields by making changes and modifications to the embodiments described herein, or by using equivalent structures or equivalent processes performed in the content of the present specification and the attached drawings, which are included in the scope of the present invention.
Claims (6)
1. A preparation method of a MeAPSO-44 molecular sieve is characterized by comprising the following steps:
pretreatment: removing impurities from natural bauxite, and performing ball milling to obtain powdery bauxite;
solid-phase synthesis: sequentially adding deionized water, a phosphorus source, a supplementary silicon source and a template agent into the pretreated bauxite, and uniformly mixing and stirring to obtain a paste mixture, wherein the template agent comprises cyclohexylamine;
and (3) crystallization: crystallizing the paste mixture at 160-220 ℃ until MeAPSO-44 crystals are formed, and centrifugally washing the crystallized material until the pH of a washing liquid is =6.4-6.7 to obtain a precipitate;
and (3) post-treatment: drying and calcining the precipitate to obtain a MeAPSO-44 molecular sieve;
the natural bauxite contains aluminum element, silicon element, iron element and titanium element;
the supplementary silicon source comprises rice hulls and silica sol;
the alumina comprises the following active substances in percentage by mass:
Al 2 O 3 ：68-73%；SiO 2 ：8-13%；Fe 2 O 3 ：16-18%；TiO 2 ：1.6-1.8%;
the solid phase synthesis step, al in the synthetic material 2 O 3 ：P 2 O 5 ：SiO 2 ：CHA：H 2 The molar ratio of O is 8-10:9-11:2-8:18-20:200-400;
in the solid phase synthesis step, the weight ratio of the pretreated bauxite to the rice hull is 1400-1600:900-1100.
2. The preparation method according to claim 1, characterized in that in the pretreatment step, the ball milling is carried out for 2 hours in a ball mill rotating at 500 revolutions.
3. The method according to claim 1, wherein the solid phase synthesis step further comprises the addition of PEG20000, al 2 O 3 The molar ratio of the PEG to the PEG20000 is 90000-110000:4-6.
4. The method as claimed in claim 1, wherein the crystallization step is performed for a crystallization time of 2 to 96 hours at a crystallization temperature of 160 to 220 ℃.
5. The method according to claim 1, wherein the post-treatment step comprises drying the precipitate in an oven at 110 ℃ for 4 hours and calcining the precipitate in a muffle furnace at 550 ℃ for 4 hours under an air atmosphere.
6. A MeAPSO-44 molecular sieve, characterized in that the MeAPSO-44 molecular sieve is prepared by the preparation method according to any one of claims 1 to 5.
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