Method for synthesizing defect type zeolite molecular sieve rich in hydroxyl pits
阅读说明：本技术 一种富含羟基窝的缺陷型沸石分子筛合成方法 (Method for synthesizing defect type zeolite molecular sieve rich in hydroxyl pits ) 是由 刘家旭 贺宁 于 2021-08-31 设计创作，主要内容包括：本发明提供一种富含羟基窝的缺陷型沸石分子筛的合成方法,以无机硅源和有机硅源作为混合硅源,与铝源、OSDA模板剂混合,得到溶胶,进行晶化；所得固体经过滤、干燥、焙烧得到富含羟基窝的缺陷型沸石分子筛；所述有机硅源为烷基硅氧烷。本发明在分子筛构建骨架的过程中引入烷基硅氧烷,形成了部分Si-C键连,随后在分子筛焙烧过程中C被烧除掉从而形成分子筛单一T位的骨架点位缺陷形成羟基窝,这种点位缺陷几乎对材料的结晶度无影响,而且极大程度保持了分子筛骨架的完整度；在合成过程中通过控制烷基硅氧烷的种类、含量可相对精确控制分子筛缺陷的程度从而得到富含羟基窝的缺陷型沸石分子筛。(The invention provides a method for synthesizing a defective zeolite molecular sieve rich in hydroxyl pits, which comprises the steps of mixing an inorganic silicon source and an organic silicon source serving as mixed silicon sources with an aluminum source and an OSDA template agent to obtain sol, and crystallizing; filtering, drying and roasting the obtained solid to obtain the defective zeolite molecular sieve rich in hydroxyl pits; the organic silicon source is alkyl siloxane. The method introduces alkyl siloxane in the process of constructing the framework by the molecular sieve to form partial Si-C bond connection, and then C is burnt off in the roasting process of the molecular sieve to form a framework point position defect of a single T position of the molecular sieve to form a hydroxyl pit, wherein the point position defect almost has no influence on the crystallinity of the material, and the integrity of the framework of the molecular sieve is maintained to a great extent; the defect degree of the molecular sieve can be relatively accurately controlled by controlling the type and the content of the alkyl siloxane in the synthesis process, so that the defect type zeolite molecular sieve rich in the hydroxyl pits can be obtained.)
1. A method for synthesizing a defect type zeolite molecular sieve rich in hydroxyl pits is characterized in that: the method comprises the following steps:
s1, mixing inorganic silicon source Inorg-Si and organic silicon source Org-Si as mixed silicon sources with an aluminum source and an OSDA template agent to obtain sol, and crystallizing;
filtering, drying and roasting the solid obtained from S2 to obtain the defect type zeolite molecular sieve rich in hydroxyl nests;
the organic silicon source is alkyl siloxane, and the organic silicon source isSiO in sol2-Inorg-Si with SiO2-The mole ratio of Org-Si is 1: 0.001-0.2.
2. The method for synthesizing the defective zeolite molecular sieve rich in hydroxyl pits of claim 1, wherein the method comprises the following steps: the zeolite molecular sieve is a ZSM-5 zeolite molecular sieve, and the S1 specifically comprises the following steps:
(1) preparation of initial raw material silicon solution: under vigorous stirring, uniformly mixing an inorganic silicon source, an organic silicon source, sodium hydroxide and water to prepare an initial raw material silicon solution and fully stirring;
(2) preparation of initial raw material aluminum solution: under the condition of violent stirring, uniformly mixing an aluminum source, sulfuric acid and water to prepare an initial raw material aluminum solution and fully stirring;
(3) slowly dropping an initial raw material aluminum solution completely dissolved into an initial raw material silicon solution, adding OSDA, stirring at room temperature for 4-10 hours to obtain sol, wherein the sol comprises the following molar components:
18Na2O:96.8～99.9SiO2-Inorg-Si:0.1～3.2SiO2-Org-Si:0.5～4Al2O3:12SO4 2-:4000H2O:16.5～40.7OSDA；
(4) putting the obtained sol into a high-pressure autoclave lined with polytetrafluoroethylene to carry out hydrothermal crystallization reaction, wherein the hydrothermal crystallization temperature is 130-190 ℃, and the hydrothermal crystallization time is 5 minutes-48 hours.
3. The method for synthesizing the defective zeolite molecular sieve rich in hydroxyl pits of claim 1, wherein the method comprises the following steps: the zeolite molecular sieve is a Beta zeolite molecular sieve, and the S1 specifically comprises the following steps:
(1) preparation of initial raw material silicon solution: under vigorous stirring, uniformly mixing an inorganic silicon source, an organic silicon source, sodium hydroxide and water to prepare an initial raw material silicon solution and fully stirring;
(2) slowly adding an aluminum source and OSDA into the initial raw material silicon solution under vigorous stirring, continuing to vigorously stir for 5-120 minutes, and then carrying out high-speed shearing emulsification for 10 minutes by using a shearing emulsifierObtaining the sol, wherein the molar composition in the sol is as follows: 8.9 to 16.4Na2O:26.2～59.6SiO2-Inorg-Si:0.4～3.8SiO2-Org-Si:1Al2O3:480～960H2O:10～40OSDA；
(3) Putting the obtained sol into a high-pressure autoclave lined with polytetrafluoroethylene to carry out hydrothermal crystallization reaction, wherein the hydrothermal crystallization temperature is 120-160 ℃, and the hydrothermal crystallization time is 5 minutes-28 hours.
4. The method for synthesizing the defective molecular sieve rich in hydroxyl pits of claims 1 to 3, wherein the method comprises the following steps: the inorganic silicon source is selected from one or more of silica sol, white carbon black, water glass and solid silica gel.
5. The method for synthesizing the defective molecular sieve rich in hydroxyl pits of claims 1 to 3, wherein the method comprises the following steps: the alkyl siloxane is methyl siloxane.
6. The method for synthesizing the defective zeolite molecular sieve rich in hydroxyl pits of claim 5, wherein the method comprises the following steps: the methyl siloxane is one or more of dimethyl siloxane, dimethyl dimethoxy silane, dimethyl diethoxy silane and methyl triethoxy silane.
7. The method for synthesizing the defective molecular sieve rich in hydroxyl pits of claims 1 to 3, wherein the method comprises the following steps: the aluminum source is one or more of aluminum oxide, aluminum nitrate, sodium metaaluminate and aluminum isopropoxide.
8. The method for synthesizing the defective zeolite molecular sieve rich in hydroxyl pits of claim 2, wherein the method comprises the following steps: the OSDA is one or more of methylamine, ethylamine, propylamine, n-butylamine, tetrapropylammonium hydroxide and tetrapropylammonium bromide.
9. The method for synthesizing the defective zeolite molecular sieve rich in hydroxyl pits of claim 3, wherein the method comprises the following steps: the OSDA is at least one of tetraethyl bromide and tetraethyl ammonium hydroxide.
10. The method for synthesizing the defective molecular sieve rich in hydroxyl pits of claims 1 to 3, wherein the method comprises the following steps: in the step S2, the roasting temperature is 500-600 ℃, and the roasting time is 10 hours.
Technical Field
The invention belongs to the field of synthesis of aluminosilicate zeolite, and particularly relates to a synthesis method of a defect type zeolite molecular sieve rich in hydroxyl pits.
Background
Zeolite molecular sieves are the most widely distributed inorganic microporous materials in nature. After a swedish scientist Cronstedt discovers natural zeolite for the first time in 1756 years, the natural zeolite is widely concerned by researchers due to the characteristics of unique molecular sieving capability, good adsorption performance and the like, and is gradually applied to the actual production life of people. Although natural zeolite has the characteristics of various varieties, wide distribution, large reserves, low cost and the like, the natural zeolite has more impurities and low purity, and the large-scale industrial application is limited, so the artificial synthesis of the zeolite becomes a new direction for people to study. At the end of the 40 s of the 20 th century, the first batch of low-silicon zeolite molecular sieves were successfully prepared by Barrer, an outstanding chemist in the field of molecular sieve synthesis, by using a low-temperature hydrothermal synthesis technology, with a silica-alumina ratio of 1.0-1.5. In 1964, the Y-type molecular sieve with the silicon-aluminum ratio of 1.5-3.0 is successfully synthesized and developed by Breck in the industry, and shows excellent performance in industrial catalysis, thereby promoting the development of artificially synthesized zeolite. Since then, with the development of science and technology and various innovative attempts of researchers, the synthesis methods of zeolite molecular sieves are increasing, and researchers have been exploring the synthesis of zeolite molecular sieves from the conventional hydrothermal synthesis methods which simulate the environment of natural zeolite formation from the beginning to the subsequent solvothermal synthesis methods, dry gel methods, seed crystal assisted synthesis and solvent-free methods.
However, in either synthesis method, it is the ultimate goal to produce nearly perfect or minimally defective molecular sieves. With the continuous and intensive scientific research, scientists find that the defect sites of the molecular sieve framework have certain special properties, such as: the hydroxyl nest has relatively strong acidity due to mutual disturbance of hydrogen bonds with each other, is an important adsorption site in VOC adsorption, and can contain certain metal ions to enable metal heteroatoms to enter a molecular sieve framework; the titanium hydroxyl TiOH at the defect site of the titanium-silicon molecular sieve is a catalytic active center of olefin epoxidation reaction, and the like. The currently more common method is a method by post-treatment, namely: the zeolite molecular sieve containing defect sites is prepared by a post-modification method of removing partial framework aluminum or silicon of a molecular sieve matrix by soaking in acid/alkali liquor, but how to accurately control the position and the size of the defect sites without damaging the topological structure of the molecular sieve framework is a great challenge in synthesizing the molecular sieve rich in the defect sites.
Disclosure of Invention
In order to fully utilize the special properties of the defect sites of the molecular sieve, the invention provides a method for synthesizing a defect type zeolite molecular sieve rich in hydroxyl pits. The defect degree of the molecular sieve can be relatively accurately controlled by controlling the type and the content of the alkyl siloxane in the synthesis process, so that the defect type zeolite molecular sieve rich in the hydroxyl pits can be obtained.
The technical scheme of the invention is as follows:
a method for synthesizing a defective zeolite molecular sieve rich in hydroxyl pits comprises the following steps:
s1, mixing an inorganic silicon source (Inorg-Si) and an organic silicon source (Org-Si) as a mixed silicon source with an aluminum source and an OSDA template agent to obtain sol, and crystallizing;
s2 is filtered, dried and roasted to obtain the defect zeolite molecular sieve rich in hydroxyl nests;
the organic silicon source is alkyl siloxane, and SiO in the sol2Inorg-Si (SiO in inorganic silicon source)2) With SiO2-Org-Si (SiO in organic silicon source)2) The molar ratio of (A) to (B) is 1: 0.001-0.2.
The zeolite molecular sieve is a ZSM-5 zeolite molecular sieve, a Beta zeolite molecular sieve, an MCM22 zeolite molecular sieve or an SSZ13 zeolite molecular sieve.
The zeolite molecular sieve is a ZSM-5 zeolite molecular sieve, and the S1 specifically comprises the following steps:
(1) preparation of initial raw material silicon solution: under vigorous stirring, uniformly mixing an inorganic silicon source, an organic silicon source, sodium hydroxide and water to prepare an initial raw material silicon solution and fully stirring;
(2) preparation of initial raw material aluminum solution: under the condition of violent stirring, uniformly mixing an aluminum source, sulfuric acid and water to prepare an initial raw material aluminum solution and fully stirring;
(3) slowly dropping an initial raw material aluminum solution completely dissolved into an initial raw material silicon solution, adding OSDA, stirring at room temperature for 4-10 hours to obtain sol, wherein the sol comprises the following molar components:
18Na2O:96.8～99.9SiO2Inorg-Si (SiO in inorganic silicon source)2):0.1～3.2SiO2-Org-Si (SiO in organic silicon source)2):0.5～4Al2O3:12SO4 2-:4000H2O:16.5～40.7OSDA；
(4) Putting the obtained sol into a high-pressure autoclave lined with polytetrafluoroethylene to carry out hydrothermal crystallization reaction, wherein the hydrothermal crystallization temperature is 130-190 ℃, and the hydrothermal crystallization time is 5 minutes-48 hours.
The zeolite molecular sieve is a Beta zeolite molecular sieve, and the S1 specifically comprises the following steps:
(1) preparation of initial raw material silicon solution: under vigorous stirring, uniformly mixing an inorganic silicon source, an organic silicon source, sodium hydroxide and water to prepare an initial raw material silicon solution and fully stirring;
(2) slowly adding an aluminum source and OSDA into an initial raw material silicon solution under vigorous stirring, continuously and vigorously stirring for 5-120 minutes, and then carrying out high-speed shearing emulsification treatment for 10 minutes by using a shearing emulsifier to obtain sol, wherein the sol comprises the following molar compositions:
8.9～16.4Na2O:26.2～59.6SiO2Inorg-Si (SiO in inorganic silicon source)2):0.4～3.8SiO2-Org-Si (SiO in organic silicon source)2):1Al2O3:480～960H2O:10～40OSDA；
(3) Putting the obtained sol into a high-pressure autoclave lined with polytetrafluoroethylene to carry out hydrothermal crystallization reaction, wherein the hydrothermal crystallization temperature is 120-160 ℃, and the hydrothermal crystallization time is 5 minutes-28 hours.
The inorganic silicon source is selected from one or more of silica sol, white carbon black, water glass and solid silica gel.
The alkyl siloxane is methyl siloxane, and further the methyl siloxane is one or more of dimethyl siloxane, dimethyl dimethoxy silane, dimethyl diethoxy silane and methyl triethoxy silane.
The aluminum source is one or more of aluminum oxide, aluminum nitrate, sodium metaaluminate and aluminum isopropoxide.
In the synthesis of the ZSM-5 zeolite molecular sieve, OSDA is one or more of methylamine, ethylamine, propylamine, n-butylamine, tetrapropylammonium hydroxide and tetrapropylammonium bromide.
In the synthesis of the Beta zeolite molecular sieve, OSDA is at least one of tetraethyl bromide and tetraethyl ammonium hydroxide. A
In the step S2, the drying temperature is 110 ℃, and the drying time is 8 hours; the roasting temperature is 500-600 ℃, and the roasting time is 10 hours.
Compared with the prior art, the invention has the following beneficial effects:
the traditional post-treatment method, namely the method for removing part of framework silicon or aluminum by acid-base treatment, is difficult to control the removal degree, and the framework atoms removed by the post-treatment method are generally flaked to form larger defect vacancies, so that the crystallinity and the framework integrity of the material are damaged to a certain degree. The method utilizes organic silicon sources such as inorganic silicon source and siloxane as mixed silicon source to be mixed and crystallized with a conventional aluminum source and template agent, forms partial Si-C bond connection due to the introduction of organic siloxane as partial silicon source in the process of constructing the framework of the molecular sieve, and then burns off C in the roasting process of the molecular sieve to form the framework point position defect of single T position of the molecular sieve to form the hydroxyl nest. The point position defect almost has no influence on the crystallinity of the material, and the integrity of the molecular sieve framework is maintained to a great extent. More importantly, the hydroxyl nest formed by the single T-site defect has the most hydrogen bond interference and the most unique chemical property. Therefore, the defect degree of the molecular sieve can be relatively accurately controlled by controlling the type and the content of siloxane in the synthesis process by the method, so that the defect type zeolite molecular sieve rich in the hydroxyl pits can be obtained.
Drawings
Fig. 1 is an XRD spectrum of comparative example D1# and example samples # 1 and # 2.
FIG. 2 is a hydroxyl group infrared spectrum of comparative example D1# and example samples 1-3 #.
FIG. 3 is a hydroxyl radical IR spectrum of comparative example D2# and example Nos. 6# and 9 #.
Detailed Description
Comparative example 1
0.75g NaOH, 50g sodium Silicate (SiO) was weighed260% by mass of Na210 percent of O) is added into 22.5g of deionized water and stirred evenly by a magnetic stirrer; then 4.28g of aluminium sulphate was completely dissolved in 5g of water, 2.25g of concentrated sulphuric acid (98%) was slowly added; slowly dropping the completely dissolved aluminum sulfate solution into the solution containing sodium silicate, adding 25.9g of tetrapropyl ammonium hydroxide TPAOH, and stirring at room temperature for 6 hours to obtain sol, wherein the molar composition in the sol is as follows: 18Na2O:100SiO2:2.5Al2O3:12SO4 2-:4000H2O is 25.4 TPAOH; putting the obtained sol into a high-pressure kettle lined with polytetrafluoroethylene, and controlling the hydrothermal crystallization temperature to be 170 ℃ and the hydrothermal crystallization time to be 26 hours; filtering, drying at 110 deg.C for 8 hr, and calcining at 540 deg.C for 10 hr to obtain crystallized ZSM-5, and recording as D1 #.
Comparative example 2
Uniformly mixing 60g of white carbon black, 21.6g of sodium hydroxide and 32g of water, slowly adding 4.9g of sodium metaaluminate under vigorous stirring, then adding 73.5g of tetraethylammonium hydroxide, continuously and vigorously stirring for 1 hour, and then carrying out high-speed shearing emulsification treatment for 10 minutes by using a shearing emulsifying machine to obtain sol, wherein the molar composition in the sol is as follows: 8.9Na2O:30SiO2:1Al2O3:960H2O15 TEAOH; putting the obtained sol into a high-pressure kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 150 ℃, and the hydrothermal crystallization time is 48 hours; filtering, drying at 110 deg.C for 8 hr, and calcining at 540 deg.C for 10 hr to obtain crystallized Beta molecular sieve, and recording as D2 #.
Example 1
0.75g NaOH, 49.8g sodium Silicate (SiO) was weighed260% by mass of Na210 percent of O) is added into 22.5g of deionized water, 0.36g of methyltriethoxysilane is added and stirred evenly by a magnetic stirrer; then 4.28g of aluminium sulphate was completely dissolved in 5g of water, 2.25g of concentrated sulphuric acid (98%) was slowly added; slowly dropping completely dissolved aluminum sulfate solution into solution containing sodium silicate, adding 25.9g of tetrapropyl ammonium hydroxide TPAOH, stirring at room temperature for 6 hours to obtain sol, and dissolving the solThe medium molar composition is as follows: 18Na2O:99.6SiO2-Inorg-Si:0.4SiO2-Org-Si:2.5Al2O3:12SO4 2-:4000H2O is 25.4 TPAOH; putting the obtained sol into a high-pressure kettle lined with polytetrafluoroethylene, and controlling the hydrothermal crystallization temperature to be 170 ℃ and the hydrothermal crystallization time to be 25 hours; filtering the obtained solid, drying at 110 ℃ for 8 hours, and roasting at 540 ℃ for 10 hours to obtain the defective ZM-5 zeolite molecular sieve rich in hydroxyl nests. The product obtained is recorded as sample # 1.
Example 2
0.75g NaOH, 49.25g sodium Silicate (SiO) was weighed260% by mass of Na210 percent of O) is added into 22.5g of deionized water, 1.34g of methyltriethoxysilane is added and stirred evenly by a magnetic stirrer; then 4.28g of aluminium sulphate was completely dissolved in 5g of water, 2.25g of concentrated sulphuric acid (98%) was slowly added; slowly dropping the completely dissolved aluminum sulfate solution into the solution containing sodium silicate, adding 30.7g of tetrapropyl ammonium hydroxide TPAOH, and stirring at room temperature for 6 hours to obtain sol, wherein the molar composition in the sol is as follows: 18Na2O:98.5SiO2-Inorg-Si:1.5SiO2-Org-Si:2.5Al2O3:12SO4 2-:4000H2O is 30.2 TPAOH; putting the obtained sol into a high-pressure kettle lined with polytetrafluoroethylene, and controlling the hydrothermal crystallization temperature to be 170 ℃ and the hydrothermal crystallization time to be 25 hours; filtering the obtained solid, drying at 110 ℃ for 8 hours, and roasting at 540 ℃ for 10 hours to obtain the defective ZM-5 zeolite molecular sieve rich in hydroxyl nests. The product obtained is recorded as sample # 2.
Example 3
0.75g NaOH, 48.6g sodium Silicate (SiO) was weighed260% by mass of Na210 percent of O) is added into 22.5g of deionized water, 2.50g of methyltriethoxysilane is added and stirred evenly by a magnetic stirrer; then 4.28g of aluminium sulphate was completely dissolved in 5g of water, 2.25g of concentrated sulphuric acid (98%) was slowly added; slowly dropping the completely dissolved aluminum sulfate solution into the solution containing sodium silicate, adding 30.7g of tetrapropyl ammonium hydroxide TPAOH, and stirring at room temperature for 6 hours to obtain sol, wherein the molar composition in the sol is as follows: 18Na2O:97.2SiO2-Inorg-Si:2.8SiO2-Org-Si:2.5Al2O3:12SO4 2-:4000H2O is 30.2 TPAOH; putting the obtained sol into a high-pressure kettle lined with polytetrafluoroethylene, and controlling the hydrothermal crystallization temperature to be 170 ℃ and the hydrothermal crystallization time to be 25 hours; filtering the obtained solid, drying at 110 ℃ for 8 hours, and roasting at 540 ℃ for 10 hours to obtain the defective ZM-5 zeolite molecular sieve rich in hydroxyl nests. The resulting product was designated sample # 3.
Examples 4 to 5
The procedure was as in example 3, except that the organic silicon source and the quality were changed, as shown in Table 1, and the other operations were the same.
TABLE 1 deficient ZM-5 zeolite molecular sieves rich in hydroxyl pits obtained with different organic silicon sources and qualities
Example numbering
Sample numbering
Kind of organosilicon Source
Mass of organic silicon source
Example 4
4#
Dimethyldiethoxysilane
2.22g
Example 5
5#
Dimethylsiloxane
1.49g
Example 6
Uniformly mixing 60g of white carbon black, 3.6g of methyltriethoxysilane, 21.6g of sodium hydroxide and 32g of water, slowly adding 4.9g of sodium metaaluminate under vigorous stirring, then adding 73.5g of tetraethylammonium hydroxide, continuing to vigorously stir for 1 hour, and then carrying out high-speed shearing emulsification treatment for 10 minutes by using a shearing emulsifier; obtaining sol, wherein the molar composition in the sol is as follows: 8.9Na2O:30SiO2(Inorg-Si):0.6SiO2(Org-Si):1Al2O3:960H2O15 TEAOH; putting the obtained sol into a high-pressure kettle with a polytetrafluoroethylene lining, wherein the crystallization temperature is 150 ℃, and the hydrothermal crystallization time is 48 hours; filtering, drying at 110 deg.C for 8 hr, and calcining at 540 deg.C for 10 hr to obtain the defective Beta zeolite molecular sieve rich in hydroxyl nest. The product obtained is recorded as sample # 6.
Examples 7 to 9
The procedure was the same as in example 6, except that the organic silicon source and the quality were changed, and the other procedures were the same.
TABLE 2 deficient Beta zeolite molecular sieves rich in hydroxyl pits obtained from different organic silicon sources and qualities
Example numbering
Sample numbering
Kind of organosilicon Source
Mass of organic silicon source
Example 7
7#
Methyltriethoxysilane
4.8g
Example 8
8#
Dimethyldiethoxysilane
3.2g
Example 9
9#
Dimethyldimethoxysilane
2.4g
Example 10
XRD characterization was performed on the samples obtained in the above examples, taking comparative example D1# and example samples 1#, 2# as examples, and the XRD spectrum is shown in FIG. 1; comparative example D1# and example samples 1-5# the relative crystallinity data is shown in Table 3. The result shows that all samples accord with the structural characteristics of ZSM-5 through XRD analysis, namely, the obtained solid samples are ZSM-5 molecular sieves, and the defect type molecular sieves prepared by introducing the organic silicon source have complete frameworks, so that the relative crystallinity of the samples is not obviously reduced.
TABLE 3 relative crystallinity of different samples
Sample numbering
Relative degree of crystallinity
D1#
100％
1#
97.3％
2#
99.1％
3#
98.8％
4#
99.4％
5#
98.9％
Example 11
The hydroxyl groups of the samples prepared in the above examples were characterized by infrared, and the hydroxyl groups of comparative example D1# and example samples 1-3# were shown in FIG. 2. The results show that comparative example No. D1 is 3500cm-1The absence of vibration indicates that the sample has no hydroxyl pit, while the sample introduced with the organic silicon source can be at 3500cm-1Clear peak inclusions are seen, which indicates that the samples have abundant hydroxyl pit defect sites, and the degree of material defects is obviously increased along with the increase of the amount of the organic silicon source.
Example 12
Infrared hydroxyl radical characterization was performed on Beta series samples and the hydroxyl radical IR spectra of comparative example D2# and example samples 6# and 9# are shown in FIG. 3. In addition, XRD testing showed that the 6# and 9# defective molecular sieves had intact frameworks. It has the same effect as the ZSM-5 series.
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