Method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method

Abstract

The present disclosure provides a method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method, a natural aluminosilicate clay mineral treated and activated by an alkali is used as a crystal seed for synthesis of the aluminosilicate molecular sieve, and the target molecular sieve product is synthesized by hydrothermal crystallization, wherein the synthesis process does not require addition of conventional crystal seeds of a molecular sieve or use of any organic template agent, thus the synthesized product does not require a calcination process to remove the template agent. The method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method can meet the requirements of both crystallinity and nucleation time, and greatly reduce costs of synthesizing the aluminosilicate molecular sieve, and reduce the environmental pollution caused by removal of the template agent by calcinating.

Claims

1. A method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method, comprising: performing activating treatment of a natural aluminosilicate clay mineral raw material with an alkali source, so as to prepare an activated crystal seed; mixing an alkali source aqueous solution with an aluminum source until a clear and transparent mixture is obtained, adding a silica sol dropwise into the mixture and stirring constantly, so as to prepare a reactant gel with an element composition controlled to be consistent with a composition of a target molecular sieve product; adding the activated crystal seed to the reactant gel and mixing to form a reactant precursor; putting the reactant precursor into a reactor for crystallization, wherein a crystallization temperature is 150-190° C., and a crystallization time is 36-72 h; and filtering a crystallization product, and washing to be neutral, then drying, so as to obtain the aluminosilicate molecular sieve; wherein the aluminosilicate molecular sieve is a ZSM-35 molecular sieve, a molar ratio of each component in the reactant gel is controlled as Na.sub.2O:K.sub.2O:SiO.sub.2:Al.sub.2O.sub.3:H.sub.2O=1.5:2.0-3.0:20-30:1:400-1200.

2. The method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method according to claim 1, wherein an additive amount of the activated crystal seed is 5.0-8.0% with respect to a total mass of a silicon source calculated in terms of silica in the reactant gel.

3. The method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method according to claim 1, wherein the natural aluminosilicate clay mineral raw material used for preparing the activated crystal seed is at least one selected from kaolin, rectorite, bentonite, illite, montmorillonite, mullite and diatomite.

4. The method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method according to claim 1, wherein the activating treatment comprises thermal activation, alkali fusion activation, sub-molten salt activation or quasi-solid-phase activation.

5. The method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method according to claim 1, wherein the crystallization comprises dynamic crystallization or static crystallization.

6. The method of synthesizing an aluminosilicate molecular sieve by a crystal seed-assisted method according to claim 1, wherein the alkali source used for preparing the activated crystal seed and the reactant gel is sodium hydroxide, potassium hydroxide or mixture thereof; the aluminum source comprises one or more selected from sodium aluminate, aluminum sulfate, aluminum nitrate, aluminum chloride and aluminum hydroxide.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a X-ray diffraction (XRD) pattern of a ZSM-35 molecular sieve prepared by Example 1 of the present disclosure;

(2) FIG. 2 is a field emission scanning electron microscope (SEM) image, at a magnification of 2000 times, of a ZSM-35 molecular sieve prepared by Example 1 of the present disclosure;

(3) FIG. 3 is a N.sub.2 adsorption-desorption isotherm of a ZSM-35 molecular sieve prepared by Example 1 of the present disclosure;

(4) FIG. 4 is a BJH pore size distribution diagram (the ordinate is the pore volume expressed in logarithmic coordinate) of a ZSM-35 molecular sieve prepared by Example 1 of the present disclosure;

(5) FIG. 5 is an .sup.27Al MAS NMR spectrum of a ZSM-35 molecular sieve prepared by Example 1 of the present disclosure;

(6) FIG. 6 is an XRD pattern of a ZSM-35 molecular sieve prepared by Example 2 of the present disclosure;

(7) FIG. 7 is an XRD pattern of a ZSM-35 molecular sieve prepared by Example 3 of the present disclosure;

(8) FIG. 8 is an XRD pattern of a ZSM-35 molecular sieve prepared by Example 4 of the present disclosure;

(9) FIG. 9 is an XRD pattern of a ZSM-35 molecular sieve prepared by Example 5 of the present disclosure;

(10) FIG. 10 is an XRD pattern of a mordenite molecular sieve prepared by Example 6 of the present disclosure;

(11) FIG. 11 is an XRD pattern of a mordenite molecular sieve prepared by Example 7 of the present disclosure;

(12) FIG. 12 is an XRD pattern of a mordenite molecular sieve prepared by Example 8 of the present disclosure;

(13) FIG. 13 is an XRD pattern of a ZSM-35 molecular sieve prepared by Comparative Example 1 of the present disclosure;

(14) FIG. 14 is a SEM image, at a magnification of 2000 times, of a ZSM-35 molecular sieve prepared by Comparative Example 1 of the present disclosure;

(15) FIG. 15 is a N.sub.2 adsorption-desorption isotherm of a ZSM-35 molecular sieve prepared by Comparative Example 1 of the present disclosure;

(16) FIG. 16 is a BJH pore size distribution diagram (the ordinate is the pore volume expressed in logarithmic coordinate) of a ZSM-35 molecular sieve prepared by Comparative Example 1 of the present disclosure;

(17) FIG. 17 is an .sup.27Al MAS NMR spectrum of a ZSM-35 molecular sieve prepared by Comparative Example 1 of the present disclosure;

(18) FIG. 18 is an XRD pattern of a ZSM-35 molecular sieve prepared by Comparative Example 2 of the present disclosure;

(19) FIG. 19 is an .sup.27Al MAS NMR spectrum of a ZSM-35 molecular sieve prepared by Comparative Example 2 of the present disclosure;

(20) FIG. 20 is an XRD pattern of a ZSM-35 molecular sieve prepared by Comparative Example 3 of the present disclosure;

(21) FIG. 21 is an XRD pattern of a mixed crystal product of a ZSM-35 molecular sieve and a mordenite molecular sieve prepared by Comparative Example 4 of the present disclosure;

(22) FIG. 22 is an XRD pattern of a mordenite molecular sieve prepared by Comparative Example 5 of the present disclosure;

(23) FIG. 23 is an XRD pattern of a mordenite molecular sieve prepared by Comparative Example 6 of the present disclosure.

DESCRIPTION OF EMBODIMENTS

(24) In order to make the objectives, technical solutions and advantages of the present disclosure more explicit, technical solutions in embodiments of the present disclosure is illustrated clearly and completely in combination with the accompanying drawings and embodiments hereinafter. Obviously, embodiments described are only a part of embodiments of the present disclosure, and are not all of embodiments thereof. Based on the embodiments of the present disclosure, all the other embodiments obtained by those skilled in the art without any creative works are within the protection scope of the present disclosure.

(25) In the following examples and comparative examples:

(26) The XRD pattern is measured by German Bruck AXS D8 Advance X-ray diffractometer;

(27) The SEM image is obtained by German Zeiss ULTRA 55 field emission scanning electron microscope;

(28) The N.sub.2 adsorption-desorption isotherm and pore structure parameters of a sample are measured using Quanta Chrome Autosorb iQ high-performance automatic gas adsorption instrument; where the specific surface area of the sample is calculated using BET equation based on the adsorption equilibrium isotherm of the relative pressure between 0.05-0.25; the total pore volume is calculated by converting the adsorption volume to liquid nitrogen volume at a relative pressure of 0.99; the specific surface area and volume of micropores of a sample are calculated through the t-plot model; the mesoporous and micropore pore size distribution of a sample is calculated by the Barrett-Joyner-Halenda (BJH) method.

(29) The present disclosure uses the relative crystallinity to evaluate the crystallization effect of the molecular sieve, that is:

(30) The relative crystallinity of the ZSM-35 molecular sieve mentioned refers to the ratio of the sum of peak areas at 2θ=9.3°, 22.3°, 22.5°, 23.3°, 23.5°, 24.4°, 25.2° and 25.6° in the XRD pattern of the synthesized product and the ZSM-35 molecular sieve sample (Comparative Example 1) synthesized by the traditional crystal seed-assisted method, in percentages. The crystallinity of the ZSM-35 molecular sieve sample (Comparative Example 1) synthesized by the traditional crystal seed-assisted method is defined as 100%.

(31) The relative crystallinity of the mordenite molecular sieve mentioned refers to the ratio of the sum of peak areas at 2θ=6.51°, 9.77°, 13.45°, 22.2°, 25.63°, 26.25° and 27.67° in the XRD pattern of the synthesized product and the mordenite molecular sieve sample (Comparative Example 5) synthesized by the traditional crystal seed-assisted method, in percentages. The crystallinity of the mordenite molecular sieve sample (Comparative Example 5) synthesized by the traditional crystal seed-assisted method is defined as 100%.

Example 1

(32) The quasi-solid-phase activation is used to activate kaolin to prepare a crystal seed, and steps of preparing the crystal seed are as follows: mixing kaolin and sodium hydroxide according to the mass ratio of 1:1.2, adding a certain amount of deionized water (the additive amount of water accounts for 10% of the solid feeding mass) and kneading in a banded extruder for about 10 minutes, then extruding to obtain a wet strip with a diameter of approximately 1.5 mm, and then placing the wet strip in an oven at 150° C. to dry for about 3 hours, and cooling the dried product to room temperature; crushing and sieving to below 300 mesh to prepare the kaolin activated by QSP.

(33) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) quasi-solid-phase activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes for aging, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(34) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 102%, as shown in FIG. 1.

(35) As determined by SEM, the morphology of the synthetic product is irregularly clustered and the clustered aggregation is agglomerated by small spherical aggregates, and these small spherical aggregates are cross-aggregated from lamellae about 1 μm in size, as shown in FIG. 2.

(36) As determined by a gas adsorption instrument, the N.sub.2 adsorption-desorption isotherm is of type I, and there is a long and narrow H4-type hysteresis loop, indicating that it contains narrow cracking pores produced by cross-stacking of lamellar monocrystals, as shown in FIG. 3. It can also be seen in FIG. 3 that the adsorption isotherm shows a clear upward warping at a relative pressure close to 1.0, which also indicates that it contains a certain amount of macropores. Therefore, the synthesized product is a ZSM-35 molecular sieve with micro-meso-macroporous pore structure.

(37) The BET specific surface area of the molecular sieve is 342 m.sup.2/g, the area of the micropore is 293 m.sup.2/g, the area of the mesoporous is 49 m.sup.2/g, the pore volume of the micropore is 0.12 cm.sup.3/g, the pore volume of the mesoporous is 0.07 cm.sup.3/g. It can be seen from the pore size distribution diagram that the synthesized product has a certain amount of mesopores in the range of 20-50 nm and a certain amount of macropores distributed in the range above 50 nm, as shown in FIG. 4.

(38) As determined by .sup.27Al MAS NMR, the synthesized product has a nuclear magnetic peak at δ=54 ppm, which belongs to the tetra-coordinated framework aluminum of the molecular sieve, and a faint nuclear magnetic peak at δ=0 ppm, which belongs to non-framework aluminum, indicating that the atomic utilization rate of the system and the skeleton integrity of the product are both high, as shown in FIG. 5. It has been determined that the nucleation induction period is less than 9 h, and the rapid growth period is 9-20 h.

Example 2

(39) The preparation method of the quasi-solid-phase activated kaolin crystal seed is the same as that of Example 1.

(40) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. Adding 8.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) quasi-solid-phase activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 190° C. for 36 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(41) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 100.5%, as shown in FIG. 6.

Example 3

(42) The sub-molten salt activation method is used to activate kaolin to prepare a crystal seed, and steps of preparing the crystal seed are as follows: mixing kaolin, sodium hydroxide and deionized water according to the mass ratio of 1:1.5:6, then placing the mixture in an oven at 250° C. to dry for 3 hours, and cooling the dried product to room temperature; crushing and sieving to below 300 mesh to prepare the kaolin activated by sub-molten salt activation.

(43) 1.89 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.64 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 32.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant precursor. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:400H.sub.2O. Adding 6.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) sub-molten salt activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant gel obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 150° C. for 60 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(44) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 97%, as shown in FIG. 7.

Example 4

(45) The preparation method of the quasi-solid-phase activated rectorite crystal seed is the same as that of Example 1.

(46) 1.1 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 0.62 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 18.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:3.0K.sub.2O:30SiO.sub.2:1Al.sub.2O.sub.3:1200H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) quasi-solid-phase activated rectorite to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(47) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 99%, as shown in FIG. 8.

Example 5

(48) The alkali fusion activation method is used to activate kaolin to prepare a crystal seed, and steps of preparing the crystal seed are as follows: mixing kaolin and sodium hydroxide according to the mass ratio of 1:1.35, then placing the mixture in a muffle furnace at 600° C. to dry for 4 hours, and cooling the calcined product to room temperature; crushing and sieving to below 300 mesh to prepare the kaolin activated by alkali fusion activation.

(49) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) alkali fusion activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(50) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 92%, as shown in FIG. 9.

Example 6

(51) The preparation method of the quasi-solid-phase activated kaolin crystal seed is the same as that of Example 1.

(52) 0.78 g of sodium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.33 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 19.5 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant precursor. The molar ratio of each component (in terms of its oxide) in the reactant gel is 2.5Na.sub.2O:15SiO.sub.2:Al.sub.2O.sub.3:500H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) quasi-solid-phase activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for static crystallization. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(53) As determined by XRD, the phase of the synthetic product belongs to the mordenite molecular sieve, and the relative crystallinity is 98%, as shown in FIG. 10. It has been determined that the nucleation induction period is less than 16 h.

Example 7

(54) The preparation method of the quasi-solid-phase activated kaolin crystal seed is the same as that of Example 1.

(55) 1.12 g of sodium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 0.72 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 21 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 5.0Na.sub.2O:30SiO.sub.2:1Al.sub.2O.sub.3:1000H.sub.2O. Adding 10.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) quasi-solid-phase activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for static crystallization. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(56) As determined by XRD, the phase of the synthetic product belongs to the mordenite molecular sieve, and the relative crystallinity is 100.6%, as shown in FIG. 11.

Example 8

(57) The preparation method of the quasi-solid-phase activated kaolin crystal seed is the same as that of Example 1.

(58) 2.55 g of quasi-solid-phase activated kaolin crystal seed is weighed and used as the aluminum source, 63 g of deionized water is added, stirring for 15 min to obtain a suspension, and then 17.95 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the above suspension, then is placed in a 60° C. water bath and continuously stirred for 4 h, so as to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 3.45Na.sub.2O: 20SiO.sub.2:1Al.sub.2O.sub.3:700H.sub.2O. The obtained reactant gel is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for static crystallization. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(59) As determined by XRD, the phase of the synthetic product belongs to the mordenite molecular sieve, and the relative crystallinity is 120%, as shown in FIG. 12.

Comparative Example 1

(60) The steps for synthesizing crystal seed of the ZSM-35 molecular sieve are as follows: 0.74 g of sodium hydroxide and 0.82 g of sodium aluminate (NaAlO.sub.2, 80 wt %) are weighed, and dissolved with deionized water, and stirring until a clear and transparent solution is obtained; and then adding 24.0 g of a silica sol (SiO.sub.2, 30 wt %) dropwise into the solution; after the dropwise addition, stirring for 2 h, and then adding 3.42 g of pyrrolidine dropwise thereinto, aging at room temperature for 2 h. The molar ratio of each component in the reactant gel is 3.3Na.sub.2O:30SiO.sub.2:1Al.sub.2O.sub.3:12Pyrrolidine:900H.sub.2O. The obtained reactant precursor is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 72 h for dynamic crystallization. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h, and finally calcinated at 550° C. to remove the template agent, so as to obtain the crystal seed of the ZSM-35 molecular sieve.

(61) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) ZSM-35 molecular sieve to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is filtered and washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(62) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 100%, as shown in FIG. 13.

(63) As determined by SEM, the morphology of the product is typically lamellar, a few of lamellae are stacked in agglomeration, as shown in FIG. 14.

(64) As determined by a gas adsorption instrument, the N.sub.2 adsorption-desorption isothermal curve is of type I, and there is a long and narrow H4 hysteresis loop, indicating that it contains narrow cracking pores produced by cross-stacking of lamellar monocrystals, as shown in FIG. 15.

(65) The measured BET specific surface area of the molecular sieve is 325 m.sup.2/g, the area of the micropore is 309 m.sup.2/g, the area of the mesoporous is 16 m.sup.2/g, the pore volume of the micropore is 0.13 cm.sup.3/g, the pore volume of the mesoporous is 0.03 cm.sup.3/g. It can be seen from the pore size distribution diagram that the product has a certain amount of mesopores in the range of 20-50 nm, as shown in FIG. 16.

(66) As determined by .sup.27Al MAS NMR, the synthesized product has a nuclear magnetic peak at δ=54 ppm, which belongs to tetra-coordinated framework aluminum of the molecular sieve, and a faint nuclear magnetic peak at δ=0 ppm, which belongs to non-framework aluminum, indicating that the atomic utilization rate of the system and the skeleton integrity of the product are both high, as shown in FIG. 17. It has been determined that the nucleation induction period is less than 9 h, and the rapid growth period is 9-20 h.

Comparative Example 2

(67) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. The obtained reactant precursor is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization. After crystallization, the obtained synthesized product is washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(68) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 85%, as shown in FIG. 18.

(69) As determined by .sup.27Al MAS NMR, the synthesized product respectively has nuclear magnetic peaks at δ=54 ppm, 39 ppm and 0 ppm, which belong to tetra-coordinated framework aluminum structure, penta-coordinated framework aluminum and six-coordinated non-framework aluminum, respectively, indicating that there is no system of crystal seed, and the atomic utilization rate of the product and the skeleton integrity are both low, as shown in FIG. 19. It has been determined that the nucleation induction period is 16 h, and the rapid growth period is 16-56 h.

Comparative Example 3

(70) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) unactivated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization. After crystallization, the obtained synthesized product is washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(71) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve, and the relative crystallinity is 84%, as shown in FIG. 20. It indicates as follows: when the unactivated kaolin is used as the crystal seed, unreacted kaolin residual exists in the reaction product, reducing the crystallinity of the molecular sieve.

Comparative Example 4

(72) The preparation method of the quasi-solid-phase activated kaolin crystal seed is the same as that of Example 1.

(73) 1.42 g of potassium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.23 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 24.0 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 1.5Na.sub.2O:2.0K.sub.2O:20SiO.sub.2:1Al.sub.2O.sub.3:600H.sub.2O. Adding 15.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) quasi-solid-phase activated kaolin to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for dynamic crystallization, where the speed of rotation is controlled to be 30-60 rpm during the crystallization process. After crystallization, the obtained synthesized product is washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(74) As determined by XRD, the phase of the synthetic product belongs to the ZSM-35 molecular sieve and the mordenite molecular sieve, indicating that the additive amount of the crystal seed is too large to synthesize the pure phase ZSM-35 molecular sieve, as shown in FIG. 21.

Comparative Example 5

(75) 0.78 g of sodium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.33 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 19.5 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 2.5Na.sub.2O:15SiO.sub.2:1Al.sub.2O.sub.3:500H.sub.2O. Adding 5.0 wt % (the mass percentage is calculated based on the total mass of SiO.sub.2 in the reactant gel) mordenite molecular sieve (purchased from Nankai Catalyst Plant, molar ratio of SiO.sub.2/Al.sub.2O.sub.3=50) to the reactant gel as the crystal seed, and continuously stirring for about 30 minutes, then a reactant precursor obtained is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for static crystallization. After crystallization, the obtained synthesized product is washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(76) As determined by XRD, the phase of the synthetic product belongs to the mordenite molecular sieve, and the relative crystallinity is 100%, as shown in FIG. 22. It has been determined that the nucleation induction period is less than 16 h.

Comparative Example 6

(77) 0.78 g of sodium hydroxide is weighed, and dissolved with deionized water, stirring until a clear and transparent solution is obtained; 1.33 g of sodium aluminate (NaAlO.sub.2, 80 wt %) is added, stirring until the solution is clear and transparent; afterwards, 19.5 g of a silica sol (SiO.sub.2, 30 wt %) is added dropwise into the solution, stirring intensively for about 30 minutes to obtain a reactant gel. The molar ratio of each component (in terms of its oxide) in the reactant gel is 2.5Na.sub.2O:15SiO.sub.2:1Al.sub.2O.sub.3:500H.sub.2O. The obtained reactant gel is transferred into a 100 mL reactor lined with PTFE, and is placed in an oven at 175° C. for 48 h for static crystallization. After crystallization, the obtained synthesized product is washed with deionized water until the pH of the filtrate becomes neutral, and then dried at 120° C. for 6 h to obtain a synthetic product.

(78) As determined by XRD, the phase of the synthetic product belongs to the mordenite molecular sieve, and the relative crystallinity is 85%, as shown in FIG. 23. It has been determined that the nucleation induction period is less than 24 h. It indicates that the synthesized mordenite molecular sieve has a relatively low crystallinity and a relatively long nucleation induction period, without using a template agent and a crystal seed.

(79) Finally, it should be noted that the above embodiments are merely used to illustrate the technical solutions of the present disclosure and shall not be construed as limitation; although the present disclosure has been described in detail with reference to the above embodiments, those skilled in the art will understand that they may still modify the technical solutions described in the above embodiments, or equivalently substitute some or all of the technical features therein; and the modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of various embodiments of the present disclosure.