CN111233000B - Synthetic method of MTT type molecular sieve with low silicon-aluminum ratio - Google Patents
Synthetic method of MTT type molecular sieve with low silicon-aluminum ratio Download PDFInfo
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Abstract
The invention relates to a method for synthesizing an MTT type molecular sieve. The synthesis method comprises the following specific implementation steps: fully mixing a silicon source, an aluminum source, a template agent and water, and then heating and crystallizing for a certain time to prepare a precursor mixture; and adding a certain amount of aluminum source and water into the precursor mixture, and continuously heating and crystallizing for a certain time to obtain the MTT type molecular sieve with the low silicon-aluminum ratio. The low silicon-aluminum ratio MTT type molecular sieve prepared by the invention has the Si/Al of as low as 5, has the characteristics of strong acidity and large acid amount, and has potential application in the fields of petroleum refining, petrochemical industry, coal chemical industry and the like. The synthesis method provided by the invention has the advantages of low cost, safe and simple operation and environmental friendliness.
Description
Technical Field
The invention relates to a synthesis method of a molecular sieve, in particular to a synthesis method of a low silicon-aluminum ratio MTT type molecular sieve.
Background
The zeolite molecular sieve is an inorganic crystal material, has the characteristics of unique pore channel structure, larger specific surface area, adjustable acidity and the like, and has wide application in the fields of petroleum refining, petrochemical industry, coal chemical industry and the like.
The MTT type molecular sieve has one-dimensional pore canal with teardrop ten-membered ring window, and belongs to high-silicon molecular sieve. The molecular sieve with the structure is firstly synthesized by C.J. plank and the like in the 70 th 20 th century. The most representative molecular sieves having the MTT structure are ZSM-23, and also molecular sieves named as KZ-1, ISI-4, EU-13, SSZ-32, and the like. Except for the ten-membered ring channel windows, the ZSM-23 molecular sieve has the channel diameter of 0.56nm multiplied by 0.45nm and no crossed channels in the framework. The unique pore channel structure can meet the requirements of certain reactions on shape-selective catalysis, so that the catalyst shows excellent catalytic performance and potential application value in a plurality of catalytic reactions.
When the molecular sieve acts in the acid catalysis reaction process, the catalytic performance of the molecular sieve is closely related to acidity. The more molecular sieve acid, the higher the catalyst activity and the lower the temperature required to achieve the target conversion. However, in the current literature reports, the Si/Al of MTT type molecular sieve is generally higher than 50, thereby limiting the increase of acid amount. By using special template agent, some silicon-aluminium molecular sieves with low silicon-aluminium ratio can be synthesized. For example, the template used in the laboratory synthesis by Corma et Al for the silico-aluminum molecular sieve yielded molecular sieve MTW type of Si/Al =12 (new j. Chem.,2016, 40, 4140); jintao Li et Al obtained MTW-type molecular sieves with Si/Al =8-23 (Catalysis Communications,50 (2014), 97-100) using the template synthesized in the experiment. These methods for synthesizing low silica-alumina ratio silica-alumina molecular sieves all require the use of a template agent synthesized in a laboratory, have high synthesis cost and limit the large-scale application thereof. The development of a method for synthesizing the MTT type molecular sieve with a large amount of acid at low cost can possibly expand the further application of the molecular sieve in the acid catalytic reaction.
Disclosure of Invention
The invention aims to provide a novel method for synthesizing an MTT type molecular sieve with a low silicon-aluminum ratio.
The above purpose is realized by the following technical scheme:
1) Preparation of the precursor mixture: mixing a silicon source, an aluminum source, sodium hydroxide, organic amine and water according to a certain proportion, and stirring the mixture evenly to form a precursor mixture A, wherein Al in the precursor mixture A 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1;
2) Heating and crystallizing the prepared precursor mixture A at the temperature of 80-250 ℃ for 5-72 h, and cooling to room temperature to obtain a mixture B;
3) Adding a certain amount of aluminum source and water into the mixture B, and stirring the mixture to be uniform to obtain a mixture C, wherein Al in the mixture C 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1;
4) Heating and crystallizing the mixture C at the temperature of 100-250 ℃ for 5-120 h;
5) And after crystallization is finished, cooling the mixture to room temperature, filtering, washing and drying, and roasting at 300-600 ℃ for 5-36 h to obtain the solid MTT type molecular sieve with low silica-alumina ratio.
In the method, in the step 1), the silicon source is one or more than two of silica sol, water glass, white carbon black and tetraethoxysilane;
in the method, in the step 1), the aluminum source is one or more than two of aluminum isopropoxide, sodium metaaluminate, pseudo-boehmite, aluminum sulfate and aluminum nitrate;
in the method, in the step 1), the organic amine is one or more than two of dimethylamine, N-dimethylformamide, pyrrolidine, N-propylamine, isopropylamine, N-butylamine and the like.
The method comprises the step 1) of preparing Al in the mixture A 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1.
In the method, the preferable crystallization temperature of the mixture A in the step 2) is 100-200 ℃; the preferred crystallization time is 10h to 48h.
The method comprises the step 3) and Al in the mixture C 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1.
In the method, the preferable crystallization temperature of the mixture C in the step 4) is 100-200 ℃; the preferred crystallization time is 12h to 100h.
In the method, the preferred roasting temperature in the step 5) is 450-550 ℃; the preferred calcination time is 12h to 24h.
The silicon source, the aluminum source and the template agent are crystallized at a certain temperature for a certain time to generate the MTT type molecular sieve with low crystallinity, and at the moment, the system contains the MTT type molecular sieve with low crystallinity, silicon-aluminum amorphous substances, the template agent and water. After an aluminum source is added into the system, the MTT type molecular sieve with low crystallinity plays a role of seed crystal, in the crystallization process at a certain temperature, the added aluminum source can enter the molecular sieve more easily under the action of the seed crystal, so that more aluminum enters a molecular sieve framework, and the MTT type molecular sieve with low silicon-aluminum ratio is prepared after crystallization.
Compared with the MTT type molecular sieve synthesized by the prior art, the synthesis method of the MTT type molecular sieve has the following characteristics:
(1) Provides a new method for synthesizing the MTT type molecular sieve with low silicon-aluminum ratio.
(2) The prepared MTT type molecular sieve has a large acid content.
(3) The synthesis method has low cost, only needs commercial template agent for synthesis, is simple and convenient to operate, and has stronger economy.
Detailed Description
The invention will be further described with reference to specific examples, but it should be understood that the invention is not limited thereto.
Comparative example 1
Weighing 11.9g of sodium hydroxide, 56.8g of dimethylamine (40% aqueous solution) and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into a 175 ℃ oven, crystallizing for 4 days, cooling to room temperature, washing with deionized water for 3 times, drying in the 120 ℃ oven, and roasting at 550 ℃ for 12 hours to prepare the MTT type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Comparative example 2
Weighing 11.9g of sodium hydroxide, 56.8g of dimethylamine (40% aqueous solution) and 11.1g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into a 175 ℃ oven, crystallizing for 4 days, cooling to room temperature, washing with deionized water for 3 times, drying in the 120 ℃ oven, and roasting at 550 ℃ for 12 hours to obtain an amorphous product, wherein the MTT type molecular sieve is not obtained. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Example 1
Weighing 11.9g of sodium hydroxide, 56.8g of dimethylamine (40% aqueous solution) and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into a 170 ℃ oven, keeping the temperature for 1 day, cooling to room temperature, taking out, adding 7.4g of aluminum sulfate and 18g of water, uniformly stirring, transferring the mixed solution into the stainless steel reaction kettle with the polytetrafluoroethylene lining, heating to 175 ℃, keeping the temperature for 2 days, cooling to room temperature, washing with deionized water for 3 times, drying in the 120 ℃ oven, and roasting at 550 ℃ for 12 hours to obtain the MTT-type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Example 2
Weighing 11.9g of sodium hydroxide, 35.6g of pyrrolidine and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into a 170 ℃ oven, keeping the temperature for 1 day, cooling to room temperature, taking out, adding 9.6g of aluminum sulfate and 18g of water, uniformly stirring, transferring the mixed solution into the stainless steel reaction kettle with the polytetrafluoroethylene lining, heating to 175 ℃ for 2 days, cooling to room temperature, washing with deionized water for 3 times, drying in the 120 ℃ oven, roasting at 550 ℃ for 12 hours, and obtaining the MTT type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Example 3
Weighing 11.9g of sodium hydroxide, 36.5g of N, N-dimethylformamide and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into a 175 ℃ oven, keeping for 10h, cooling to room temperature, taking out, adding 11.1g of aluminum sulfate and 18g of water, uniformly stirring, transferring the mixed solution into the stainless steel reaction kettle with the polytetrafluoroethylene lining, heating to 175 ℃, keeping for 2 days, cooling to room temperature, washing with deionized water for 3 times, drying in the 120 ℃ oven, and roasting at 550 ℃ for 12h to obtain the MTT-type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Example 4
Weighing 11.9g of sodium hydroxide, 36.5g of N, N-dimethylformamide and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into a 175-DEG C oven, keeping the temperature for 18h, cooling to room temperature, taking out, adding 13g of aluminum sulfate and 18g of water, uniformly stirring, transferring the mixed solution into the stainless steel reaction kettle with the polytetrafluoroethylene lining, heating to 175 ℃, keeping the temperature for 2 days, cooling to room temperature, washing with deionized water for 3 times, drying in the 120-DEG C oven, and roasting at 550 ℃ for 12h to obtain the MTT-type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Example 5
Weighing 11.9g of sodium hydroxide, 36.5g of isobutylamine and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting into a 175 ℃ oven, keeping for 30h, cooling to room temperature, taking out, adding 29.6g of aluminum sulfate and 36g of water, uniformly stirring, transferring the mixed solution into the stainless steel reaction kettle with the polytetrafluoroethylene lining, heating to 175 ℃ and keeping for 30h, cooling to room temperature, washing with deionized water for 3 times, drying in the 120 ℃ oven, and roasting at 550 ℃ for 12h to obtain the MTT type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
Example 6
Weighing 11.9g of sodium hydroxide, 36.5g of n-butylamine and 3.7g of aluminum sulfate, adding 256g of water, fully stirring, adding 100g of 30% silica sol, uniformly stirring, transferring the mixed solution into a stainless steel reaction kettle with a polytetrafluoroethylene lining, putting the stainless steel reaction kettle into an oven with the temperature of 170 ℃, keeping the temperature for 30h, cooling to room temperature, taking out, adding 62.9g of aluminum sulfate and 36g of water, uniformly stirring, transferring the mixed solution into the stainless steel reaction kettle with the polytetrafluoroethylene lining, heating to 175 ℃, keeping the temperature for 2 days, cooling to room temperature, washing with deionized water for 3 times, drying in the oven with the temperature of 120 ℃, roasting at the temperature of 550 ℃ for 12h, and preparing the MTT type molecular sieve. The Si/Al and acid content characterization results of the obtained MTT type molecular sieve are summarized in Table 1.
TABLE 1 characterization results of crystal form, si/Al and acid amount of the obtained molecular sieve in comparative example and example
The low silicon-aluminum ratio MTT type molecular sieve prepared by the invention has the Si/Al of as low as 5, has the characteristics of strong acidity and large acid amount, and has potential application in the fields of petroleum refining, petrochemical industry, coal chemical industry and the like. The synthesis method provided by the invention has the advantages of low cost, safe and simple operation and environmental friendliness.
Claims (6)
1. A synthetic method of MTT type molecular sieve with low silicon-aluminum ratio is characterized in that: synthesizing an MTT type molecular sieve with a low silicon-aluminum ratio by using organic amine as a template agent and using a silicon source, an aluminum source and sodium hydroxide; the method comprises the following steps:
1) Preparation of the precursor mixture: mixing a silicon source, an aluminum source, sodium hydroxide, organic amine and water according to a certain proportion, and stirring the mixture uniformly to form a precursor mixture A, wherein Al in the precursor mixture A 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1;
2) Heating and crystallizing the prepared precursor mixture A at the temperature of 80-250 ℃ for 5-72 h, and cooling to room temperature to obtain a mixture B;
3) Adding a certain amount of aluminum source and water into the mixture B, and stirring the mixture B uniformly to obtain a mixture C, wherein Al in the mixture C 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1;
4) Heating and crystallizing the mixture C at the temperature of 100-250 ℃ for 5-120 h;
5) After crystallization is finished, cooling the mixture to room temperature, filtering, washing and drying, and roasting at 300-600 ℃ for 5-36 h to obtain a solid MTT type molecular sieve with low silica-alumina ratio;
in the step 1), the silicon source is one or more than two of silica sol, water glass, white carbon black and tetraethoxysilane;
the aluminum source is one or more than two of aluminum isopropoxide, sodium metaaluminate, pseudo-boehmite, aluminum sulfate and aluminum nitrate;
the organic amine is one or more of dimethylamine, N-dimethylformamide, pyrrolidine, N-propylamine, isopropylamine, N-butylamine and the like;
the silicon-aluminum ratio of the low silicon-aluminum ratio MTT type molecular sieve is 5-30.
2. A method of synthesis according to claim 1, characterized in that: step 1) Al in the mixture A 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1.
3. A method of synthesis according to claim 1, characterized in that: step 2), the crystallization temperature of the mixture A is 100-200 ℃; the crystallization time is 10-48 h.
4. A method of synthesis according to claim 1, characterized in that: step 3) Al in the mixture C 2 O 3 :SiO 2 :Na 2 O organic amine H 2 The molar ratio of O is 1.
5. A method of synthesis according to claim 1, characterized in that: step 4), the crystallization temperature of the mixture C is 100-200 ℃; the crystallization time is 12-100 h.
6. A method of synthesis according to claim 1, characterized in that: the roasting temperature in the step 5) is 450-550 ℃; the roasting time is 6-24 h.
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| FR2805255B1 (en) * | 2000-02-21 | 2002-04-12 | Inst Francais Du Petrole | ZEOLITHE MTT COMPRISING CRYSTALS AND CRYSTAL AGGREGATES OF SPECIFIC GRANULOMETRIES AND ITS USE AS A CATALYST FOR ISOMERIZATION OF LINEAR PARAFFINS |
| CN101613114B (en) * | 2009-08-10 | 2012-05-23 | 上海卓悦化工科技有限公司 | ZSM-23 molecular sieve preparation method |
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| CN103880037B (en) * | 2012-12-20 | 2015-07-22 | 中国石油化工股份有限公司 | ZSM-5 molecular sieve and preparation method thereof |
| CN104418341B (en) * | 2013-08-22 | 2016-05-18 | 中国石油化工股份有限公司 | A kind of ZSM-48/Silicalite-1 composite molecular screen and preparation method thereof |
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