CN108557841B - Preparation method for synthesizing CHA molecular sieve by using tetraethylenepentamine as template agent - Google Patents

Preparation method for synthesizing CHA molecular sieve by using tetraethylenepentamine as template agent Download PDF

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CN108557841B
CN108557841B CN201810727247.1A CN201810727247A CN108557841B CN 108557841 B CN108557841 B CN 108557841B CN 201810727247 A CN201810727247 A CN 201810727247A CN 108557841 B CN108557841 B CN 108557841B
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molecular sieve
tetraethylenepentamine
cha molecular
template agent
deionized water
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CN108557841A (en
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刘庆岭
吕双春
吴晗
宋春风
纪娜
马德刚
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Tianjin University
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    • C—CHEMISTRY; METALLURGY
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    • 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
    • C01B39/02—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof; Direct preparation thereof; Preparation thereof starting from a reaction mixture containing a crystalline zeolite of another type, or from preformed reactants; After-treatment thereof
    • C01B39/46—Other types characterised by their X-ray diffraction pattern and their defined composition
    • C01B39/48—Other types characterised by their X-ray diffraction pattern and their defined composition using at least one organic template directing agent
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    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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Abstract

The invention discloses a preparation method for synthesizing a CHA molecular sieve by taking tetraethylenepentamine as a template agent. And transferring the obtained mixture into a high-pressure reaction kettle, crystallizing for a period of time at a certain temperature, cooling at room temperature after crystallization is finished, washing and drying the solid-phase product by deionized water, and roasting at 550 ℃ in air to obtain the CHA molecular sieve. The single template agent used by the CHA molecular sieve synthesized by the invention has low price, the production cost is reduced, and the synthesized molecular sieve has good crystallinity and high solid phase yield, and has important significance for industrial popularization and application of the CHA molecular sieve.

Description

Preparation method for synthesizing CHA molecular sieve by using tetraethylenepentamine as template agent
Technical Field
The invention belongs to the technical field of catalysts (molecular sieve preparation methods), and relates to a synthesis method of a CHA molecular sieve.
Background
Light olefins are important basic chemical raw materials in the modern chemical industry, and the demand of the light olefins is increasing along with the development of the modern industry. The traditional preparation method of ethylene and propylene is petroleum cracking, but in consideration of the problems of limited petroleum resources and the like, a method for preparing olefin from methanol is proposed to replace the traditional process. The key point of Methanol To Olefin (MTO) lies in the selection of a catalyst, and catalysts which can be used for preparing the MTO include chabazite, erionite, ZK-5 molecular sieve and the like, but carbon deposition is easily formed due to the limitation of a pore structure to cause the deactivation of the catalyst. A CHA-type structure molecular sieve, belonging to 8-membered ring structure of phosphorus-aluminum molecular sieve, belonging to trigonal system[1-2]. The molecular sieve has the characteristics of high selectivity, high hydrothermal stability, proper acidity and the like, and has better catalytic performance when being used in an MTO process, so that the molecular sieve is used as a main catalyst of the MTO process.
In recent years, CHA molecular sieves have been constructed with tetraethyl hydroxideAmmonium chloride, n-propylamine, morpholine and the like are used as template agents for synthesis, and the system has high synthesis cost and is harmful to the environment, so that the large-scale application of the CHA molecular sieve is limited. In order to reduce the production cost and reduce the pollution, researchers have developed a series of studies to explore cheap templates for synthesis. Researches show that the CHA molecular sieve can be synthesized by adding diethylamine, an organic amine promoter and the like[3-5]. However, these organic amines have problems such as high cost, low solid-phase yield, and poor crystallinity. Therefore, the development of a template agent with low price, high solid phase yield and good crystallinity is of great significance for further research and large-scale industrial application of the synthesized CHA molecular sieve.
[ reference documents ]
[1]Xu X T,Zhai J P,Chen Y P,et al.Synthesis of large optically clear SAPO-47 single crystals using n-propylamine as template[J].Journal of Crystal Growth,2015,426:123-128.
[2]Najafi N,Askari S,Halladj R.Hydrothermal synthesis of nanosized SAPO-34 molecular sieves by different combinations of multi templates[J].Powder Technology,2014,254(2):324-330.
[3]Qiao Y,Wu P,Xiang X,et al.SAPO-34 synthesized with n-butylamine as a template and its catalytic application in the methanol amination reaction[J].Chinese Journal of Catalysis,2017,38(3):574-582.
[4] A process for synthesizing SAPO-47 silicoaluminophosphate molecular sieve, Wangzhongyu, Jiashiyuan, Wangbaoyi, CN104445268A [ P ] 2015.
[5] A process for synthesizing the molecular sieve of silicon aluminium phosphate from Niulian shouhui (Niuhuai crane) includes CN 100395184C P.2008.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a preparation method for synthesizing a CHA molecular sieve by using tetraethylenepentamine as a template agent, and the template agent is low in cost and reduces the pollution to the environment; the CHA molecular sieve further synthesized has high solid phase yield and good crystallinity, greatly reduces the production cost, and has very important significance for further research and large-scale industrial application of the synthesized CHA molecular sieve.
In order to solve the technical problems, the invention provides a preparation method for synthesizing a CHA molecular sieve by using tetraethylenepentamine as a template, which comprises the following steps:
step one, uniformly mixing phosphoric acid and deionized water, adding an aluminum source into the mixture, and fully stirring the mixture for 0.5 to 2 hours at room temperature to obtain a mixed solution A; in the mixed solution A, the molar ratio of the phosphoric acid to the deionized water is 0.015-0.05; the aluminum source is one or more of sodium metaaluminate, pseudo-boehmite and alumina; al in the sodium metaaluminate2O350% of the pseudoboehmite Al2O3Is 75%, and the aluminum oxide contains Al2O3The content of (A) is 99%; the aluminum source is Al2O3Measured on Al2O3The molar ratio of the deionized water to the deionized water is 0.01-0.1;
step two, adding a silicon source into the mixed solution A obtained in the step one, and stirring for 10-60min at room temperature to obtain a mixed solution B, wherein the silicon source is one or two of white carbon black and silica sol; SiO in the silica sol2The content of (A) is 40%; silicon source of SiO2Meter, SiO2With Al2O3The molar ratio of (A) to (B) is 0.1-2;
step three, taking tetraethylenepentamine as a template agent, dropwise adding the tetraethylenepentamine into the mixed solution B obtained in the step two, and mixing the template agent and Al2O3The molar ratio of the organic solvent to the organic solvent is 1-5, and stirring for a certain time at room temperature until a uniform gel mixture is formed;
transferring the uniform gel mixture obtained in the step three to a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene lining, and crystallizing for 72-144 hours at the temperature of 160-280 ℃; naturally cooling to room temperature, filtering and recovering the solid phase product, washing with deionized water for multiple times, drying, and roasting at 550 ℃ in air to obtain the CHA molecular sieve.
In the third step, the template is mono-template tetraethylenepentamine.
In the fourth step, the drying temperature is 80-150 ℃.
Compared with the prior art, the invention has the beneficial effects that:
the low-cost tetraethylenepentamine is used as a template agent, so that the production cost is greatly reduced; in addition, the synthesis process of using tetraethylenepentamine as a template agent has good effects on reducing production cost and improving crystallinity. The CHA molecular sieve synthesized by the method has high solid phase yield and good crystallinity, and has very important significance for further research and large-scale industrial application of the synthesized CHA molecular sieve.
Drawings
FIG. 1 is the XRD pattern of the CHA molecular sieve prepared in example 1;
FIG. 2 is an XRD characterization of the CHA molecular sieve prepared in example 3.
FIG. 3 is an SEM representation of the CHA molecular sieve prepared in example 4
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings and specific examples, which are given by way of illustration only and are not intended to limit the invention.
Example 1: the preparation method for synthesizing the CHA molecular sieve by using tetraethylenepentamine as a template agent comprises the following steps:
the method comprises the following steps: 2.09g of phosphoric acid is weighed and added into 7ml of deionized water to be uniformly mixed, and then 1.36g of pseudoboehmite, Al of which is added into the solution2O3Was stirred at room temperature for 1 hour to obtain a mixed solution A.
Step two: 1.97g of silica sol is weighed and added into the mixed solution A, and SiO in the silica sol2Was stirred at room temperature for 30min at a content of 40% to obtain a mixed solution B.
Step three: weighing 3.38g of tetraethylenepentamine, dropwise adding the tetraethylenepentamine into the mixed solution B, continuously stirring for 1h to obtain milky uniform mixed gel, and adding Al in the mixed gel2O3：P2O5：SiO2: tetraethylenepentamine: h2The molar ratio of O is 1: 0.9: 0.9: 1.6: 52.
step four: transferring the uniform gel mixture obtained in the step three into a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene lining, and crystallizing for 4 days at the temperature of 200 ℃ under a static condition; and naturally cooling to room temperature, recovering the solid-phase product by filtering, washing with deionized water for multiple times, drying at 100 ℃ overnight, and finally roasting in a muffle furnace at 550 ℃ for 6 hours to finally obtain the CHA molecular sieve.
The CHA molecular sieve was synthesized as evidenced by the XRD pattern of the CHA molecular sieve shown in fig. 1. The CHA molecular sieve has good crystallinity as can be seen from the peak of the spectrum.
Example 2: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: the crystallization conditions in step four changed from 200 ℃ for 4 days to 160 ℃ for 4 days, resulting in the CHA-type molecular sieve, but with poor crystallinity and a partially amorphous gel state.
Example 3: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: the crystallization condition in the fourth step is changed from crystallization at 200 ℃ for 4 days to crystallization at 160 ℃ for 6 days, and finally the CHA molecular sieve with better crystallinity is obtained with higher yield. The XRD characterization pattern is shown in fig. 2.
Example 4: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: and in the fourth step, the crystallization condition is changed from crystallization at 200 ℃ for 4 days to crystallization at 200 ℃ for 4.5 days, and finally the CHA molecular sieve with better crystallinity is obtained and has regular appearance. As shown in the SEM characterization chart of fig. 3.
Example 5: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: in the first step, the molar ratio of phosphoric acid to deionized water is changed from 0.017 to 0.03, and finally the CHA-type molecular sieve is synthesized, and the obtained CHA molecular sieve has incomplete crystallization.
Example 6: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: template agent and Al2O3The molar ratio of (1.6) to (2), and the final CHA molecular sieve has higher crystallinityGood results are obtained.
Example 7: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: the mole ratio of silica to alumina in the gel was changed from 0.9 to 2, and the final CHA molecular sieve had poor crystallinity.
Example 8: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: al (Al)2O3The mol ratio of the molecular sieve to the deionized water is changed from 0.019 to 0.01, and the CHA molecular sieve is finally obtained with higher yield.
Example 9: the preparation method of CHA molecular sieve by using tetraethylenepentamine as template agent is the same as the preparation method of the example 1, except that: al (Al)2O3The mol ratio of the CHA molecular sieve to the deionized water is changed from 0.019 to 0.06, and the finally obtained CHA molecular sieve has an incomplete shape structure.
As can be seen from the above examples 1 to 9, the crystallization temperature and crystallization time both affect the synthesized crystal morphology and crystallinity; the synthesis of the CHA molecular sieve is facilitated by increasing the crystallization temperature and prolonging the crystallization time. The influence of the gel silica-alumina ratio on synthesis is larger, and the crystallinity of the gel silica-alumina ratio is poor when the gel silica-alumina ratio is increased too much. The amount of the template agent and the phosphoric acid has certain influence on the crystallinity, and the synthesis of the molecular sieve is facilitated by properly increasing the amount of the template agent.
While the present invention has been described with reference to the accompanying drawings, the present invention is not limited to the above-described embodiments, which are illustrative only and not restrictive, and various modifications which do not depart from the spirit of the present invention and which are intended to be covered by the claims of the present invention may be made by those skilled in the art.

Claims (2)

1. The preparation method for synthesizing the CHA molecular sieve by using tetraethylenepentamine as a template agent is characterized by comprising the following specific steps of:
step one, uniformly mixing phosphoric acid and deionized water, then adding an aluminum source into the mixture, and fully stirring the mixture for 0.5 to 2 hours at room temperature to obtain a mixtureMixing the solution A; in the mixed solution A, the molar ratio of the phosphoric acid to the deionized water is 0.015-0.017; the aluminum source is one or more of sodium metaaluminate, pseudo-boehmite and alumina; al in the sodium metaaluminate2O350% of the pseudoboehmite Al2O3Is 75%, and the aluminum oxide contains Al2O3The content of (A) is 99%; the aluminum source is Al2O3Measured on Al2O3The molar ratio of the deionized water to the deionized water is 0.01-0.019;
step two, adding a silicon source into the mixed solution A obtained in the step one, and stirring for 10-60min at room temperature to obtain a mixed solution B, wherein the silicon source is one or two of white carbon black and silica sol; SiO in the silica sol2The content of (A) is 40%; silicon source of SiO2Meter, SiO2With Al2O3The molar ratio of (A) to (B) is 0.1 to 0.9;
step three, taking tetraethylenepentamine as a template agent, dropwise adding the tetraethylenepentamine into the mixed solution B obtained in the step two, and mixing the template agent and Al2O3The molar ratio of the organic solvent to the organic solvent is 1-5, and stirring for a certain time at room temperature until a uniform gel mixture is formed;
step four, transferring the uniform gel mixture obtained in the step three into a stainless steel high-pressure reaction kettle with a polytetrafluoroethylene lining, and crystallizing for 144 hours at the temperature of 160 ℃; naturally cooling to room temperature, filtering and recovering the solid phase product, washing with deionized water for multiple times, drying, and roasting at 550 ℃ in air to obtain the CHA molecular sieve.
2. The method of claim 1, wherein in step three, the template is mixed with Al2O3Is 2.
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CN109382137B (en) * 2018-11-14 2020-04-10 福州大学 Preparation method and application of mesoporous Fe-Cu-SSZ-13 molecular sieve
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CN107934981A (en) * 2017-11-03 2018-04-20 上海绿强新材料有限公司 A kind of method of 34 molecular sieves of Fast back-projection algorithm SAPO

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CN107934981A (en) * 2017-11-03 2018-04-20 上海绿强新材料有限公司 A kind of method of 34 molecular sieves of Fast back-projection algorithm SAPO

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