Synthesis process of new structure silicon dioxide zeolite
阅读说明：本技术 一种新结构二氧化硅沸石的合成工艺 (Synthesis process of new structure silicon dioxide zeolite ) 是由 龙英才 沈威 于 2019-09-03 设计创作，主要内容包括：本发明提出一种新结构二氧化硅沸石的合成工艺,水热反应合成前驱体硅沸石-1,前驱体硅沸石-1在R-SiO<Sub>2</Sub>-H<Sub>2</Sub>O反应物体系中水热反应合成；前躯体硅沸石-1高温焙烧制新结构二氧化硅沸石,将所合成制备的前驱体硅沸石-1在一定的气氛和一定的温度区间,经过一定时间焙烧处理,通过晶格大幅收缩生成新结构二氧化硅沸石。本发明提出的硅沸石-3是将以高纯气相白炭黑或正硅酸乙酯水热反应合成的前驱体硅沸石-1在一定的气氛中500℃以上焙烧一定时间通过晶格严重收缩生成的,其具有特定的骨架结构以及孔道开口,其生成过程条件简单易实现,无任何废水废气排放。(The invention provides a synthesis process of silicon dioxide zeolite with a new structure, which is characterized in that precursor silicon zeolite-1 is synthesized by hydrothermal reaction, and the precursor silicon zeolite-1 is in R-SiO 2 ‑H 2 Performing hydrothermal reaction synthesis in an O reactant system; the precursor silicon zeolite-1 is baked at high temperature to fire new structure silicon dioxide zeolite, and the synthesized precursor silicon zeolite-1 is baked for a certain time in a certain atmosphere and a certain temperature interval, and the new structure silicon dioxide zeolite is generated by the large contraction of crystal lattice. The silicon zeolite-3 provided by the invention is prepared by roasting precursor silicon zeolite-1 synthesized by hydrothermal reaction of high-purity fumed silica or tetraethoxysilane at a temperature of more than 500 ℃ in a certain atmosphere for a certain time and severely shrinking crystal lattices, has a specific framework structure and pore canal openings, and has the advantages of simple and easily realized generation process conditions and no discharge of waste water and waste gas.)
1. A process for synthesizing new-structure silicon dioxide zeolite is characterized by that,
hydrothermal reaction to synthesize precursor silicon zeolite-1, wherein the precursor silicon zeolite-1 is in R-SiO2-H2Performing hydrothermal reaction synthesis in an O reactant system;
the precursor silicon zeolite-1 is baked at high temperature to fire new structure silicon dioxide zeolite, and the synthesized precursor silicon zeolite-1 is baked for a certain time in a certain atmosphere and a certain temperature interval, and the new structure silicon dioxide zeolite is generated by the large contraction of crystal lattice.
2. The process for synthesizing a new structure silicalite as claimed in claim 1, wherein R comprises C1-C4 quaternary ammonium base, C3-C6 alkyl amine, and the silicon source of the reactant system is at least one of high purity fumed silica and ethyl orthosilicate.
3. The process for synthesizing a new structure silicalite according to claim 2 wherein the reactant system has a molar composition in the range of R/SiO2＝0.1-0.5，H2O/SiO210-40, the hydrothermal reaction temperature is 110-.
4. The process for synthesizing a novel-structure silicalite as claimed in claim 1, wherein the atmosphere is a mixed gas of air and oxygen with a relative humidity of 10-40%, and the calcination is carried out at 500-800 ℃ for 1-4 hours to greatly shrink the crystal lattice of the precursor silicalite-1.
5. The process for synthesizing a novel-structure silica zeolite as claimed in claim 1, wherein the hydrothermal synthesis temperature of the reaction mixture is 120 ℃ and 200 ℃ and the reaction time is 5-100 h.
6. The process for synthesizing a novel-structure silica zeolite as claimed in claim 5, wherein the hydrothermal synthesis reaction comprises using 500mL of a stainless steel pressure-resistant reaction vessel with a capacity of 4F, pouring high-purity gas-phase white carbon black or ethyl orthosilicate as a silicon source, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide (TBA), or n-butylamine and triethylamine as a template agent R, sealing the stainless steel reaction vessel, placing the stainless steel reaction vessel in an oven, heating the stainless steel reaction vessel to 110 ℃ and 180 ℃ for 10-40 hours, cooling the reaction vessel after the reaction is finished, taking out the reaction product, filtering, washing, drying, and roasting the template to 450 ℃ and 500 ℃ for removing the template agent R to obtain the precursor silicon zeolite-1.
7. A process for synthesizing a novel structural silicalite as claimed in claim 5, wherein in the process of synthesizing the novel structural silicalite, the mixed gas released from the pressure-reducing valve of the steel cylinder is firstly introduced into a humidifying device, the humidifying device is composed of a constant-temperature water tank and a humidifying pipe arranged therein, after the carrier gas is introduced into the water in the humidifying pipe through a pipeline, the water vapor in the humidifying pipe is saturated, and the humidity of the gas flowing out of the humidifying pipe is controlled to be in the range of 10-50% relative humidity by adding ice into the constant-temperature water tank or increasing the temperature of the constant-temperature water tank to a certain degree to keep constant temperature.
8. A process for synthesizing a novel-structure silicalite as claimed in claim 7, wherein the gases humidified by said humidifying tubes are introduced into a quartz tube or a corundum tube placed in a tube furnace to form an atmosphere required for calcining the precursor-silicon zeolite-1, and the precursor-silicon zeolite-1 loaded in a quartz boat or a ceramic boat placed in the quartz tube or the corundum tube is heated to 500 ℃ or higher in the atmosphere to undergo substantial contraction of crystal lattice to obtain silicalite-3.
9. The process for synthesizing a new structure silicalite according to claim 7 wherein the new structure silicalite has a characteristic diffraction line d ═ 10.71 ± 0.1a (vs); 9.62 ± 0.1a (vs); 5.75 ± 0.05 a(s); 4.16 ± 0.02a (m); 3.70. + -. 0.01A (vs).
10. The process for synthesizing a new-structure silicalite as claimed in claim 7, wherein the new-structure silicalite has a mole ratio of silica to alumina of greater than 2000, a characteristic powder XRD diffraction spectrum, and two channel openings with a pore size of 4.4x5.6A and 5.1x 5.7A.
Technical Field
The invention relates to the technical field of silicon dioxide zeolite, in particular to a synthesis process of silicon dioxide zeolite with a new structure.
Background
Disclosure of Invention
In view of this, the invention provides a synthesis process of new structure silica zeolite.
The invention provides a synthesis process of new-structure silicon dioxide zeolite, which is characterized in that,
hydrothermal reaction to synthesize precursor silicon zeolite-1, wherein the precursor silicon zeolite-1 is in R-SiO2-H2Performing hydrothermal reaction synthesis in an O reactant system;
the precursor silicon zeolite-1 is baked at high temperature to fire new structure silicon dioxide zeolite, and the synthesized precursor silicon zeolite-1 is baked for a certain time in a certain atmosphere and a certain temperature interval, and the new structure silicon dioxide zeolite is generated by the large contraction of crystal lattice.
Further, the R comprises C1-C4 quaternary ammonium hydroxide and C3-C6 alkylamine, and the silicon source of the reactant system is at least one of high-purity gas-phase white carbon black and tetraethoxysilane.
Further, the molar composition range of the reactant system is R/SiO2＝0.1-0.5，H2O/SiO210-40, the hydrothermal reaction temperature is 110-.
Further, the atmosphere is a mixed gas of air and oxygen with the relative humidity of 10-40%, and the mixture is roasted for 1-4 hours at the temperature of 500-800 ℃ to ensure that the crystal lattice of the precursor silicalite-1 is greatly contracted.
Further, the temperature of hydrothermal synthesis of the reaction mixture is 120-200 ℃, and the reaction time is 5-100 h.
Further, in the hydrothermal synthesis reaction, a 500mL stainless steel pressure-resistant reaction kettle with a capacity of 4F is used, high-purity gas-phase white carbon black or ethyl orthosilicate is used as a silicon source, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide (TBA), or n-butylamine and triethylamine are used as a template agent R, the mixture is poured into the stainless steel reaction kettle, sealed and then placed in an oven to be heated to 110-.
Furthermore, in the synthesis process of the new structure silicon dioxide zeolite, the mixed gas released from a pressure reducing valve of a steel cylinder firstly enters a humidifying device, the humidifying device is composed of a constant temperature water tank and a humidifying pipe arranged in the constant temperature water tank, after carrier gas is led into water in the humidifying pipe through a pipeline, water vapor in the humidifying pipe is saturated, and the humidity of the gas flowing out of the humidifying pipe is controlled to be within the range of 10-50% of relative humidity by adding ice into the constant temperature water tank or increasing the temperature of the constant temperature water tank to a certain degree to keep constant temperature.
Further, the gas humidified by the humidifying pipe enters a quartz pipe or a corundum pipe of a pipe type electric furnace to become an atmosphere required to be kept for roasting the precursor silicon zeolite-1, the precursor silicon zeolite-1 loaded in a quartz boat or a ceramic boat arranged in the quartz pipe or the corundum pipe is heated to over 500 ℃ in the atmosphere, and the large contraction of crystal lattices is generated to prepare the silicon zeolite-3.
Further, the characteristic diffraction line of the silica zeolite with the new structure is d ═ 10.71 ± 0.1a (vs); 9.62 ± 0.1a (vs); 5.75 ± 0.05 a(s); 4.16 ± 0.02a (m); 3.70. + -. 0.01A (vs).
Furthermore, the new structure of the silicon dioxide zeolite has the mole ratio of silicon dioxide to aluminum oxide of the chemical composition of more than 2000, and has a characteristic powder XRD diffraction spectrum, and the pore diameters of two pore channel openings in the structure are respectively 4.4x5.6A and 5.1 x5.7A.
Compared with the prior art, the invention has the beneficial effects that the silicalite-3 provided by the invention is generated by roasting precursor silicalite-1 synthesized by hydrothermal reaction of high-purity fumed silica or tetraethoxysilane at a temperature of more than 500 ℃ in a certain atmosphere for a certain time through severe shrinkage of crystal lattices, has a specific framework shape and an opening of a pore channel, is simple and easy to realize in the generation process condition, and does not discharge any waste water or waste gas.
The proposed silicalite-3 has a BET surface area of more than 350m2The volume of the micropores is more than 0.20ml/g, the catalyst has good oleophylic and hydrophobic adsorption properties, and can be used for catalyst carriers, the adsorption and separation of micromolecule isomers and the removal of organic matters in waste water and waste gas. In the preparation process, a reaction mixture formed by mixing an amorphous silicon raw material and an organic guiding agent is subjected to hydrothermal reaction synthesis under a proper alkaline condition, and then is roasted for a certain time at a temperature of more than 500 ℃ in a certain atmosphere to prepare the hydrophobic Silicalite named as Silicalite-3 (Silicalite-3).
Drawings
FIG. 1 is a schematic structural view of a roasting apparatus with a humidifying pipe according to an embodiment of the present invention;
FIG. 2 is a powder diffraction XRD spectrum of self-made silicalite-1 and silicalite-3 generated therefrom according to an embodiment of the present invention;
FIG. 3 is a graph of the diffraction angle versus calcination temperature for silicalite-1 (051) according to example of the present invention;
FIG. 4 is a powder XRD spectrum of silicalite-1, silicalite-2 and silicalite-3 of examples of the present invention;
FIG. 5 is a schematic representation of the framework structure of silicalite-3 according to an embodiment of the invention;
FIG. 6 is a schematic diagram of the channel opening structure of silicalite-3 according to an embodiment of the present invention.
Detailed Description
The technical solutions of the present invention will be further described with reference to specific examples, but the scope of the claims is not limited thereto.
The hydrophobic Silicalite of the new structure of the embodiment of the invention is named as Silicalite-3 (Silicalite-3), has a characteristic powder XRD spectrum, and a characteristic diffraction line d is 10.71 +/-0.1A (vs); 9.62 ± 0.1a (vs); 5.75 ± 0.05 a(s); 4.16 ± 0.02a (m); 3.70. + -. 0.01A (vs).
Specifically, the new structure zeolite has a chemical composition with a silica to alumina molar ratio (SAR) greater than 2000.
Specifically, the new structure zeolite has two kinds of pore channels in its skeleton structure, and the open pore diameters are 4.4X5.6A and 5.1X5.7A, respectively.
In particular, the BET surface area of the new structure zeolite is more than 350m2(iv)/g, micropore volume greater than 0.20 ml/g.
Specifically, the new structure zeolite is produced by sintering the synthesized precursor silicon zeolite-1 (Silicalite-1 with MFI type structure) in a certain atmosphere and a certain temperature interval for a certain time, and greatly shrinking the crystal lattice. In particular, the precursor silicalite-1 is prepared by roasting at 800 ℃ for 1-4 hours in the atmosphere of air, oxygen, nitrogen, carbon dioxide or the mixed gas of air and oxygen with the relative humidity of 10-40% to greatly shrink the crystal lattice of the precursor silicalite-1. The zeolite with the new structure has good oleophylic and hydrophobic adsorption properties, and can be used for catalyst carriers, adsorption separation of small molecular isomers and removal of organic matters in waste water and waste gas.
Wherein the precursor silicon zeolite-1 is in the form of R (organic template) -SiO2-H2Synthesized by hydrothermal reaction in an O reactant system; r comprises C1-C4 quaternary ammonium base and C3-C6 alkylamine, the silicon source of the reactant system is high-purity gas-phase white carbon black and tetraethoxysilane, and the molar composition range of the reactant system is R/SiO2＝0.1-0.5，H2O/SiO210-40, the hydrothermal reaction temperature is 110-180 ℃, and the hydrothermal reaction time is 24-40 hours.
Specifically, the synthesis process of the new-structure silicalite of this example is: (deletion)
Step a, synthesizing precursor silicon zeolite-1 by hydrothermal reaction;
in this process, a 500mL pressure resistant stainless steel autoclave with a capacity of 4F was used for the hydrothermal reaction. High-purity gas-phase white carbon black or ethyl orthosilicate is used as a silicon source, TPAOH (tetrapropylammonium hydroxide), tetrabutylammonium hydroxide (TBA), or n-butylamine and triethylamine are used as template agents R, and the molar ratio of R/SiO is calculated2＝0.1-0.5，H2O/SiO2Pouring 10-40 prepared sol reactant into a stainless steel reaction kettle, sealing, and then placing in an oven to heat to 110-180 ℃, wherein the hydrothermal reaction time is 10-40 hours. After the reaction is finished, cooling the reaction kettle, taking out the reaction product, filtering, washing, drying, roasting to 450-DEG and 500-DEG, removing the template agent R, and obtaining the precursor silicon zeolite-1.
B, roasting the precursor silicalite-1 at a high temperature to obtain silicalite-3 with a new structure, namely, a synthesis process of the silicalite with the new structure;
referring to fig. 1, a quartz tube or a corundum tube is placed in a hearth of a tubular high-temperature electric furnace, and a quartz boat or a ceramic boat containing precursor silicon zeolite-1 powder is placed in the quartz tube or the corundum tube. The heating temperature of the tubular high-temperature electric furnace is controlled by an electronic temperature controller, and the temperature control precision is +/-1 ℃.
The roasting apparatus of the present embodiment includes: the pipe orifice at one side of the quartz pipe or corundum pipe which is provided with the precursor silicon zeolite-1 sample is provided with a pipeline of an external air source which is arranged in a
The new-structure silicalite-3 powder prepared in the embodiment of the invention is subjected to XRD identification, and the prepared silicalite-3 powder XRD diffraction spectrum is measured by using an XD-2 powder X-ray diffractometer produced by Beijing Pujingyu general instrument company Limited. The X-ray source is a copper target, 40KV, 30mA and graphite monochromator. The scanning range is 5 degrees to 35 degrees/2 theta, and the speed is 8 degrees (2 theta)/minute. And (3) scanning an XRD powder diffraction spectrum generated by a sample to be detected, and using data processing software carried by the XRD powder diffractometer to print the surface spacing (d) and relative diffraction intensity (I/I0) data of main diffraction peaks of the sample, and comparing the data with the data of characteristic diffraction peaks of the silicalite-3 to identify whether the sample to be detected belongs to the silicalite-3 structure. The characteristic diffraction line for silicalite-3 is d ═ 10.71 ± 0.1a (vs); 9.62 ± 0.1a (vs); 5.75 ± 0.05 a(s); 4.16 ± 0.02a (m); 3.70. + -. 0.01A (vs).
TABLE 2 list of names and structural pore sizes of commonly used silicalites
The combined figure 2 shows the powder diffraction XRD spectrum of the self-made silicalite-1 and the silicalite-3 generated by the self-made silicalite-1 in the embodiment of the invention; the graph clearly shows that the two diffraction peaks have obvious difference in the peak shape and the peak position, the 2 theta angle of the diffraction peak of the silicalite-3 is obviously shifted to a large angle compared with the silicalite-1, and the shift is increasingly prominent for the diffraction peak at a high angle. The 2 theta angle of the diffraction peak of the silicalite-1 was shifted from about 23.1 degrees to about 24.05 degrees of the silicalite-3 at a shift of nearly 1.0 degree as seen from the spectrum of silicalite-1. This indicates that the crystal structures of silicalite-1 and silicalite-3 differ substantially and should not be of the same structural type.
TABLE 3 diffraction angles of main diffraction peaks in powder XRD diffraction pattern of self-made silicalite-1 calcined at different temperatures
The data in Table 3 show that the positions of the three main characteristic diffraction peaks of the silicalite-1 all have a sudden change towards a large angle when the roasting temperature is above 500 ℃. This phenomenon is indicative of a sudden contraction of the crystal lattice. Thus, silicalite-3 differs in structure from silicalite-1.
FIG. 3 is a graph showing the relationship between the diffraction angle and the calcination temperature of silicalite-1 (051) according to the embodiment of the present invention; the diffraction angle diagram is the diffraction angle diagram of the (051) diffraction peak in a powder XRD diffraction diagram which is shot after self-made silicalite-1 (MFI type) with the silica-alumina molar ratio (SAR being 3000) is roasted for 2 hours and cooled under the nitrogen atmosphere with certain humidity. It can be seen that the diffraction angle of the diffraction peak suddenly increases at 500 ℃, indicating that the lattice shrinks significantly, and tends to be gentle above 700 ℃ and begins to stabilize at 780 ℃.
Specifically, the position of a diffraction peak in an XRD powder diffraction spectrum, namely the diffraction angle theta and the value of the surface distance (d) of the diffraction peak have the following formula relationship:
2d Sinθ＝nλ (1)
where λ is the wavelength of X-rays generated by the anode target material of the radiation source used in the XRD diffractometer, the XRD diffractometer used in the powder experiment of this example was a copper target with a characteristic wavelength of 1.5410A (i.e. 0.1541 nm). n is the number of diffraction orders; so n λ is constant for a particular diffraction peak. This formula shows that the diffraction angle θ of a diffraction peak is inversely related to the d value of the diffraction peak.
The lattice symmetry of silicalite-1 is that of an orthorhombic system, the three symmetry axes of the crystal lattice are perpendicular to each other, and the axial lengths (i.e., lattice constants) are a, b, and c, respectively. The value of d for each diffraction peak is related to the lattice constant by the following equation:
1/d2＝h2/a2+k2/b2+l2/c2(2)
wherein h, k and l are diffraction indices of the diffraction peaks, respectively.
According to the
TABLE 4 lattice constants of silicalite-1 and silicalite-3
Lattice constant/A
Literature data
Actual measurement data of silicalite-1
Actual measurement data of silicalite-3
a
20.02
19.78
19.20
b
19.90
19.42
17.28
c
13.38
13.26
13.39
V (lattice volume/A)3)
5332
5095
4442
Collection of Simulated XRD Powder Patterns for Zeolites,FifthRevised Edition,2007,p.279。
Table 3 shows the literature values and the measured values of the lattice parameters of silicalite-1 and the measured values of silicalite-3. Comparing the literature data and the measured data for silicalite-3 and silicalite-1 leads to the following conclusions: in the lattice constant of the silicalite-3, the a value is shortened by 3-4%, the b value is shortened by 11-13%, the c value is basically unchanged, and the lattice volume is reduced by 12-17%.
Referring to FIG. 4, there are shown powder XRD spectra of silicalite-1, silicalite-2, and silicalite-3 of examples of the present invention; in the illustration, the Powder XRD spectra of silicalite-1 and silicalite-2 are "theoretical" Powder diffraction spectra calculated by simulations with specialized software using the coordinates of the Si and oxygen atoms constituting the Zeolites in the crystal lattice obtained by single crystal structure determination, see references:collectionof multiplexed XRD Powder Patterns for Zeolites, Fifth RevisedEdition,2007, p.269, p.279. In the embodiment of the invention, it is obvious from the XRD spectrum of FIG. 4 that the XRD diffraction spectra of silicalite-3, silicalite-1 and silicalite-2 do not belong to the same framework structure type in terms of the number, position and intensity order distribution of peaks.
TABLE 5 characteristic diffraction Peak data for several silicalites
USP 4061724 (1977); i-diffraction intensity; vs-very strong, s-strong, m-moderate
Table 5 shows the literature values of the characteristic diffraction spectrum data of silicalite-1, the measured values of the zeolite synthesized experimentally in this example, and the measured values of the characteristic diffraction spectrum of silicalite-3 produced by the lattice contraction thereof. Obviously, the characteristic XRD diffraction data of the self-made silicalite-1 adopted in the embodiment are consistent with literature values and are obviously different from the silicalite-3 generated by strong lattice contraction, and further prove that the silicalite-3 is different from the silicalite-1 in crystalline phase.
Fig. 5 is a schematic diagram of the framework structure of silicalite-3 according to an embodiment of the present invention, and fig. 6 is a schematic diagram of the pore opening structure of silicalite-3 according to an embodiment of the present invention. The change in lattice constant from Table 4 for this example can be plotted by simple simulations, where the data show that the [100] direction channel opening size for silicalite-3 is 4.4X5.6A and the [010] direction channel opening is 5.1 X5.7A. The [100] direction channel opening size is 5.5X 5.1A and the [010] direction channel opening is 5.6X 5.3A compared to the literature value for silicalite-1. In contrast, silicalite-3 has smaller pore openings than silicalite-1, and apparently becomes "flat" in the [100] direction.
TABLE 6 adsorption statistics of silicalite-1 and silicalite-3
The data in Table 6 show that silicalite-3 has a lower surface area and pore volume and average pore diameter, as measured by low temperature nitrogen adsorption, than silicalite-1, compared to the data for silicalite-1, which is due to lattice shrinkage. The water adsorption of the two is lower than that of normal hexane, which shows that the two have good hydrophobicity. Particular mention should be made of n-hexane adsorption, silicalite-3 being 67mg/g and 56% of 119mg/g of silicalite-1. This is due to the reduction of the opening size of the [100] direction channel to 4.4X5.6A, which prevents n-hexane from adsorbing from the pore.
The new-structure silica and the synthesis process of this example are described below with reference to examples.
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