阅读说明：本技术 一种MeAPSO-44分子筛及其制备方法 (MeAPSO-44 molecular sieve and preparation method thereof ) 是由 王世铭 张琼丹 王琼生 文伟样 于 2019-09-30 设计创作，主要内容包括：本发明提供了一种MeAPSO-44分子筛的制备方法,包括以下步骤：预处理、固相或水热合成、晶化、后处理,所述天然铝土中含有硅元素、铁元素和钛元素成分。上述技术方案以廉价易得的天然铝土为原料,加入稻壳可作为补充硅源、硬模板剂,又能促进金属杂原子进入分子筛骨架,有效利用天然铝土中的铝、硅、铁、钛等资源,将铝土由固相法一步制备具有微孔-介孔复合多级孔,比表面积为303-421m<Sup>2</Sup>/g的MeAPSO-44分子筛(Me＝Fe,Ti)。天然铝土里的氧化物及稻壳,基本为无定型物,有利于分子筛的合成；且在加入磷酸的过程中不会出现粘结现象,有利于固相合成的物料均匀。利用天然原料即可合成出晶相完整,比表面积较大的MeAPSO-44分子筛,稻壳对于金属杂原子进入到分子筛骨架有促进作用。(The invention provides a preparation method of a MeAPSO-44 molecular sieve, which comprises the following steps: pretreatment, solid phase or hydrothermal synthesis, crystallization and post-treatment, wherein the natural bauxite contains silicon element, iron element and titanium element. The technical scheme takes cheap and easily-obtained natural alumina 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 alumina are effectively utilized, and the alumina is prepared into microporous-mesoporous composite hierarchical pores with specific surface area of 303-421m and with microporous-mesoporous composite hierarchical pores by a solid phase method in one step 2 (ii) 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 and the rice husk with complete crystal phase and large specific surface area can be synthesized by using natural raw materialsPromoting the metal heteroatom to enter the molecular sieve framework.)

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 value 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.

2. The preparation method of claim 1, wherein the alumina comprises the following active substances in percentage by mass:

Al₂O₃：68-73％；SiO₂：8-13％；Fe₂O₃：16-18％；TiO₂：1.6-1.8％。

3. the preparation method according to claim 1, wherein in the pretreatment step, the ball milling is performed for 2 hours in a ball mill rotating at 500 revolutions.

4. The method according to claim 1, wherein in the step of solid-phase synthesis, Al is contained in the synthesis material₂O₃：P₂O₅：SiO₂：CHA：H₂The molar ratio of O is 8-10: 9-11: 2-8: 18-20: 200-400.

5. The method as claimed in claim 1, wherein the solid phase synthesis step comprises the following steps of mixing the pretreated bauxite and the rice hull in a weight ratio of 1400-1600: 900-1100.

6. The method according to claim 1, wherein the solid phase synthesis step further comprises the addition of PEG20000, Al₂O₃The molar ratio of PEG to 20000 is 90000-110000: 4-6.

7. The method as claimed in claim 1, wherein the crystallization step has a crystallization time of 2-96h and a crystallization temperature of 160-220 ℃.

8. The preparation 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 ℃ in a hollow atmosphere for 4 hours.

9. A MeAPSO-44 molecular sieve, characterized in that said MeAPSO-44 molecular sieve has been prepared by the preparation method according to any one of claims 1 to 8.

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 the 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 fall into three main categories: 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 have been 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 catalysts 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 rice hulls are incinerated or directly discarded at the present stage, so that the comprehensive utilization rate is low, and the resource is greatly wasted. 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 the 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-4 l.

The reports of using natural minerals to prepare SAPO molecular sieves require complex pretreatment of raw mineral materials to activate components such as aluminum, silicon, iron and the like in the minerals, and some of the raw mineral materials also need to be added with inorganic mineralizers such as HF and the like with extremely strong corrosivity. 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 long, so that environmental pollution is easily caused in the crystallization or roasting process of the molecular sieve, or a large amount of waste liquid is generated, or 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 sequence during stirring₂O₅) 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 ℃ until MeAPSO-44 crystals are formed, and centrifugally washing the crystallized material until the pH value of a washing liquid is 6.3-6.5 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, and the supplementary silicon source comprises rice husk and silica sol.

Further, the active substances contained in the alumina and the mass percentage content thereof are as follows:

Al₂O₃：68-73％；SiO₂：8-13％；Fe₂O₃：16-18％；TiO₂：1.6-1.8％。

further, in the pretreatment step, the ball milling speed is 500r/min, and the ball milling time is 2 h.

Further, the solid phase synthesis step is to synthesize Al in the material₂O₃：P₂O₅：SiO₂：CHA：H₂The 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 step₂O₃The molar ratio of PEG to 20000 is 90000-110000: 4-6.

Further, in the solid phase synthesis step, the weight ratio of the pretreated bauxite to the rice hull is 1400-1600: 900-1100.

Further, in the crystallization step, the crystallization time is 2-96 h.

Further, the post-treatment step is to dry the precipitate in an oven at 110 ℃ for 4h and calcine the precipitate in a muffle furnace at 550 ℃ for 4h in a hollow atmosphere.

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.

Different from the prior art, the technical scheme takes cheap and easily-obtained natural bauxite and rice husk as raw materials, effectively utilizes silicon in the rice husk and resources such as aluminum, silicon, iron, titanium and the like in the natural bauxite, and prepares the composite hierarchical pore with micropore-mesopore and the like and the specific surface area of 285-398m and 398m by one step through a solid phase method²The MeAPSO-44 molecular sieve (Me ═ Fe, Ti) has high utilization rate of raw material, low cost, high yield of product and technological processSimple and no 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 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 and 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 treatment₂/CH₄The separation, the conversion of heavy oil into light oil, the degradation of dye and the like have good application prospects.

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-desorption curve and the pore size distribution diagram of the MeAPSO-44 molecular sieve nitrogen physical adsorption synthesized in example 1;

FIG. 5 is the isothermal adsorption-desorption curve and the pore size distribution diagram of the MeAPSO-44 molecular sieve nitrogen physical adsorption 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

To explain technical contents, structural features, and objects and effects of the technical solutions in detail, the following detailed description is given with reference to the accompanying drawings in conjunction 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)₂O₃：SiO₂：Fe₂O₃：TiO₂69.51%: 12.18%: 17.1%: 1.71 percent; the main chemical component of the rice hull is SiO₂: 10.1 wt%, hemicellulose 29.6%, cellulose 31.1%, lignin 16.0%, and small amount of other trace elements.