Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a zinc-doped AlPO-36 molecular sieve single crystal and a preparation method thereof, and aims to solve the problems that the size of the AlPO-36 molecular sieve crystal prepared by the existing synthesis method is small and a serious twin phenomenon exists.
The technical scheme of the invention is as follows:
a preparation method of a zinc-doped AlPO-36 molecular sieve single crystal is disclosed, wherein tripropylamine is used as a template agent, aluminum isopropoxide is used as an aluminum source, zinc acetate dihydrate is used as a zinc source, phosphoric acid is used as a phosphorus source, and deionized water is used as a solvent; uniformly mixing the tripropylamine, the aluminum isopropoxide, the zinc acetate dihydrate, the phosphoric acid and the deionized water, and carrying out hydrothermal crystallization reaction to obtain the zinc-doped AlPO-36 molecular sieve monocrystal; al is respectively used as the aluminum isopropoxide, the zinc acetate dihydrate, the phosphoric acid, the tripropylamine and the deionized water2O3、ZnO、P2O5、TPA、H2Measuring O; in terms of mole ratio, Al2O3:ZnO:P2O5:TPA:H2O=1.0:(0~0.6):1.0:(1.0~1.55):(128~296)。
Optionally, the preparation method of the zinc-doped AlPO-36 molecular sieve single crystal specifically comprises the following steps:
mixing aluminum isopropoxide, zinc acetate dihydrate and deionized water, and stirring for the first time to obtain gel A;
adding phosphoric acid into deionized water for dilution to obtain a solution B;
adding the solution B into the gel A, and stirring for the second time to obtain a colloid C;
adding tripropylamine into deionized water for dilution to obtain a solution D;
adding the solution D into the colloid C, and stirring for the third time to obtain a colloid E;
and carrying out hydrothermal crystallization reaction on the colloid E to prepare the zinc-doped AlPO-36 molecular sieve monocrystal.
Optionally, the time for the first stirring is 6h-24 h.
Optionally, in the step of adding the solution B to the gel A, the adding is carried out in a dropwise manner.
Optionally, the time for the second stirring is 1h-8 h.
Optionally, in the step of adding the solution D to the colloid C, the adding is performed by dropwise addition.
Optionally, the third stirring time is 1h-8 h.
Optionally, the temperature of the hydrothermal crystallization reaction is 150 ℃ and the time is 50 h.
The zinc-doped AlPO-36 molecular sieve single crystal is prepared by the preparation method.
Optionally, the size of the zinc-doped AlPO-36 molecular sieve single crystal is 150 μm × 30 μm.
Has the advantages that: the invention provides a zinc-doped AlPO-36 molecular sieve single crystal and a preparation method thereof, wherein tripropylamine is used as a template agent, aluminum isopropoxide is used as an aluminum source, zinc acetate dihydrate is used as a zinc source, phosphoric acid is used as a phosphorus source, and deionized water is used as a solvent, the twin crystal phenomenon of the AlPO-36 molecular sieve crystal is eliminated by optimizing the proportion of reaction materials, and the AlPO-36 molecular sieve single crystal with the largest size so far is prepared under the fluorine-free condition for the first time.
Detailed Description
The invention provides a zinc-doped AlPO-36 molecular sieve single crystal and a preparation method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
The inventor finds that in the existing preparation method of AlPO-36 molecular sieve crystals, the synthesized product is basically nano-scale crystals, and twinning is serious. In particular twinning, is present in all reported AlPO-36 molecular sieves. It is noted that any change in conditions during the synthesis of the molecular sieve will have a significant effect on the product, including product morphology, size, phase, etc.
Aiming at the problem that the synthesized product is basically nano-level crystal and the twin crystal is serious in the existing preparation method of the AlPO-36 molecular sieve crystal, the embodiment of the invention prepares the zinc-doped large-size AlPO-36 molecular sieve single crystal by optimizing the proportion of reaction materials.
Based on the above, the embodiment of the invention provides a preparation method of a zinc-doped AlPO-36 molecular sieve single crystal, wherein tripropylamine is used as a template agent, aluminum isopropoxide is used as an aluminum source, zinc acetate dihydrate is used as a zinc source, phosphoric acid is used as a phosphorus source, and deionized water is used as a solvent; uniformly mixing the tripropylamine, the aluminum isopropoxide, the zinc acetate dihydrate, the phosphoric acid and the deionized water, and carrying out hydrothermal crystallization reaction to obtain the zinc-doped AlPO-36 molecular sieve monocrystal;
al is respectively used as the aluminum isopropoxide, the zinc acetate dihydrate, the phosphoric acid, the tripropylamine and the deionized water2O3、ZnO、P2O5、TPA、H2Measuring O; in terms of mole ratio, Al2O3:ZnO:P2O5:TPA:H2O=1.0:(0~0.6):1.0:(1.0~1.55):(128~296)。
In the embodiment, tripropylamine is used as a template agent, aluminum isopropoxide is used as an aluminum source, zinc acetate dihydrate is used as a zinc source, phosphoric acid is used as a phosphorus source, and deionized water is used as a solvent, so that a stable formula is obtained by optimizing the proportion of reaction materials. By adopting the formula, the twin crystal phenomenon of the AlPO-36 molecular sieve crystal is eliminated, and the AlPO-36 molecular sieve single crystal with the largest size so far is prepared under the fluorine-free condition for the first time.
In this example, when the addition amount of zinc acetate dihydrate was 0, AlPO-36 molecular sieve single crystal was prepared. The AlPO-36 molecular sieve single crystal has a unique one-dimensional twelve-membered ring channel structure (along the c axis), and the channel size is
Has good thermal stability and is an ideal main body material.
In this example, when the addition amount of zinc acetate dihydrate is not 0, a zinc-doped AlPO-36 molecular sieve single crystal was prepared. The AlPO-36 crystal is neutral in electricity and has weak channel adsorption capacity, and the doping of zinc element into the skeleton of the aluminum phosphate molecular sieve can bring some new physical and chemical property changes, so that divalent Zn is adopted in the embodiment2+Doped into AlPO-36 crystal skeleton to replace Al3+So as to obtain a negatively charged framework, thereby enhancing the adsorption force of the pore channels.
In one embodiment, the preparation method of the zinc-doped AlPO-36 molecular sieve single crystal specifically comprises the following steps:
s1, mixing aluminum isopropoxide, zinc acetate dihydrate and deionized water, and stirring for the first time to obtain gel A;
s2, adding phosphoric acid into deionized water for dilution to obtain a solution B;
s3, adding the solution B into the gel A, and stirring for the second time to obtain a colloid C;
s4, adding tripropylamine into deionized water for dilution to obtain a solution D;
s5, adding the solution D into the colloid C, and stirring for the third time to obtain a colloid E;
s6, carrying out hydrothermal crystallization reaction on the colloid E to prepare the zinc-doped AlPO-36 molecular sieve single crystal.
In step S1, in one embodiment, the first stirring time is 6h to 24 h.
In step S3, in one embodiment, the solution B is added to the gel a dropwise to better disperse the solution B in the gel a.
In one embodiment, the second stirring is for a time period of 1h to 8 h.
In step S5, in one embodiment, the solution D is added to the colloid C dropwise.
In one embodiment, the third stirring time is from 1h to 8 h.
In step S6, in one embodiment, the temperature of the hydrothermal crystallization reaction is 150 ℃ and the time is 50 hours. In the embodiment, the zinc-doped AlPO-36 molecular sieve single crystal is prepared by further optimizing crystallization reaction conditions.
In one embodiment, step S6 specifically includes:
carrying out hydrothermal crystallization reaction on the colloid E, wherein the reaction temperature is 150 ℃, and the reaction time is 50 h;
after the reaction is finished, washing, filtering and drying the hydrothermal crystallization product in sequence under the ultrasonic condition to obtain pure zinc-doped AlPO-36 molecular sieve single crystal.
The embodiment of the invention carefully discusses the specific influence of the change of the proportion of the reaction materials on the zinc-doped AlPO-36 molecular sieve crystal, realizes the preparation of the zinc-doped AlPO-36 molecular sieve large single crystal by summarizing the rule, optimizing the proportion of the reaction materials and further optimizing the crystallization reaction conditions, and synthesizes the hundred-micron grade twin-free zinc-doped AlPO-36 molecular sieve single crystal for the first time. In the process of adjusting the initial gel ratio, the following were found:
1. AlPO-5 (code: AFI) heterocrystal phase is easily generated in a system without Zn doping, AlPO-36 pure phase is obtained along with the gradual increase of the proportion of zinc, but no crystal is generated due to the overhigh proportion;
2. the crystal quality shows a trend of increasing first and then decreasing along with the increase of the content of the tripropylamine template, and when excessive tripropylamine exists, the twin phenomenon is aggravated;
3. the crystal size tends to increase and then decrease along with the increase of the water content, and AlPO-36 crystals cannot be obtained when excessive water exists in the system;
4. when the crystallization temperature is too low, AlPO-36 crystals cannot be obtained, but too high crystallization temperature brings AlPO-5 (code: AFI) heterocrystal phase. At the critical temperature at which AlPO-36 crystals can be nucleated, the twinning phenomenon of the product can be effectively inhibited or even eliminated;
5. the crystal size increases with the crystallization time, but when the crystallization time reaches a certain critical point, the crystal size will not continue to grow.
The embodiment of the invention also provides the zinc-doped AlPO-36 molecular sieve single crystal prepared by the preparation method.
In one embodiment, the zinc-doped AlPO-36 molecular sieve single crystal has a size of 150 μm by 30 μm.
The zinc-doped AlPO-36 molecular sieve single crystal with the largest size and no twin crystal so far is prepared by the embodiment of the invention, and the crystal surface is smooth.
The following examples illustrate the sources of the reaction materials of the examples of the invention:
aluminum isopropoxide (greater than or equal to 98%, Shanghai Aladdin Biotechnology Co., Ltd.), zinc acetate dihydrate (99%, Shanghai Aladdin Biotechnology Co., Ltd.), phosphoric acid (greater than or equal to 85%, Shanghai Lingman Chemicals Co., Ltd.), tripropylamine (99%, Shanghai Aladdin Biotechnology Co., Ltd.), and deionized water (prepared from a Hetai Master-S15UV low-organic-matter type ultrapure water machine).
The invention is further illustrated by the following specific examples.
Example 1
And performing powder XRD characterization on the prepared zinc-doped AlPO-36 molecular sieve single crystal by optimizing gel components and crystallization conditions. As shown in fig. 1, (a) is a standard card, and (b) is the zinc-doped AlPO-36 molecular sieve single crystal prepared in this example, from this figure, it can be seen that the diffraction peak of the AlPO-36 molecular sieve single crystal prepared in this example has a high goodness of fit with the standard card, and no other impurity exists, which indicates that the zinc-doped AlPO-36 molecular sieve single crystal prepared in this example has a high crystallinity and no other impurities.
Example 2
The zinc-doped AlPO-36 molecular sieve single crystal prepared after optimization is characterized by a scanning electron microscope and an optical microscope, which are respectively shown in FIG. 2 and FIG. 3. As can be seen from the figures 2 and 3, the zinc-doped AlPO-36 molecular sieve monocrystal prepared by the embodiment is a hundred-micron-grade large monocrystal, has high crystal quality and eliminates twin crystal phenomenon.
FIG. 4 is a comparison of scanning electron microscopy of the single crystal of zinc-doped AlPO-36 prepared in this example (FIG. f) with other published AlPO-36 crystals (FIGS. a-e). From this figure, it is clearly observed that the size and quality of the zinc-doped AlPO-36 molecular sieve single crystal prepared in this example are greatly improved compared to other published AlPO-36 crystals.
In conclusion, the invention provides a zinc-doped AlPO-36 molecular sieve single crystal and a preparation method thereof, a stable formula is obtained by optimizing the proportion of reaction materials, and the crystallization reaction conditions are further optimized on the basis of obtaining the stable formula, so that the twin crystal phenomenon of the AlPO-36 molecular sieve crystal is eliminated, and the AlPO-36 molecular sieve single crystal with the largest size so far is prepared under the fluorine-free condition for the first time.
It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.