CN104787777A - High-dispersion small-crystal-grain ZSM-5 molecular sieve and preparation method thereof - Google Patents

Abstract

The invention provides a highly dispersed small-grain ZSM-5 molecular sieve and a preparation method thereof. The silicon-aluminum ratio of the molecular sieve is 20-150, and the grain size of the molecular sieve is 50-500nm. The method comprises the following steps: dissolving cellulose in a mixed solution of sodium hydroxide/urea/water, stirring and degrading, centrifuging to obtain degradation solution A, and standing still; dissolving sodium hydroxide, aluminum salt, and template agent in water to obtain aluminum Salt solution B; add silicon source and degradation solution A to aluminum salt solution B and mix well, so that the molar ratio of each component in the mixture is 20-150:1 in terms of SiO ₂ : Al ₂ O ₃ : H ₂ O : template: 130-3000: 1-20, then add sodium hydroxide to adjust the pH value to alkaline; crystallize the mixture after adjusting the pH value, and then undergo post-treatment to obtain the ZSM-5 molecular sieve. The obtained ZSM-5 molecular sieve has uniform grain size and good dispersibility.

Description

A kind of highly dispersed small grain ZSM-5 molecular sieve and preparation method thereof

technical field

The invention belongs to the field of molecular sieve synthesis, and in particular relates to a highly dispersed small-grain ZSM-5 molecular sieve and a preparation method thereof.

Background technique

ZSM-5 molecular sieve (USP 3702886) is an aluminosilicate zeolite molecular sieve developed by Mobil Corporation of the United States. It is bent in a Z shape, the corner of the channel is about 150°, and the hole diameter is The channel of the ten-membered ring parallel to the c-axis is linear, and the diameter of the elliptical channel is This special pore structure and size make it have good shape-selective properties, and at the same time have the advantages of adjustable silicon-aluminum ratio, lipophilicity, thermal stability and high catalytic activity, so it has become one of the most important molecular sieve catalytic materials at present. , Widely used in catalytic fields such as petroleum processing, coal chemical industry and fine chemical industry.

Compared with the traditional large-grain ZSM-5 molecular sieve, the small-grain has a shorter intra-crystalline diffusion channel length and a larger external specific surface area, and more exposed pores allow reactants and products to enter and exit more efficiently Pores are conducive to increasing the contact probability between reactants and active sites in the micropores, improving the activity of the reaction; at the same time, shortening the diffusion path of the product, reducing the residence time of the product in the molecular sieve, and inhibiting the occurrence of secondary reactions , so as to effectively increase the target product and improve the selectivity of the molecular sieve; in addition, the high external area enables the small crystal grains to have higher carbon storage capacity, which improves the life of the molecular sieve.

Qin Guanlin et al. (Petroleum Refining, 1978, 11:85) and Wang Zhongnan et al. (Petrochemical Industry, 1983, 12:744) adopted a hydrothermal synthesis method at low temperature (100-120°C) using tetrapropylammonium, Ethylamine and propylamine were used as templates to synthesize small-grain ZSM-5 molecular sieves, and the crystallization time was about 300 hours. Because the synthesis temperature is low, the crystal growth rate is slow, and the synthesis period is long, which is not conducive to production.

Verduijn J P (EP 0753482) etc. and Van Grieken R etc. (Micropor. Mesopor. Mater. 2000, 39 (1-2): 135) adopt clear liquid synthesis method, use orthoethyl silicate (TEOS) as silicon source, Small-grain ZSM-5 molecular sieves were synthesized in a sodium-free or low-sodium system. The existence of sodium ions would reduce the nucleation efficiency and make the crystal grains significantly larger. However, too low sodium content is not conducive to the entry of aluminum into the zeolite framework. Synthetic zeolites tend to have higher silica-to-alumina ratios. There are problems with the industrialization process using tetraethyl orthosilicate silicon source. In addition, the synthesis system has high alkalinity and low product yield. Guo Hongchen et al. (CN 1699173A) used water glass as a silicon source, synthesized a silicon-aluminum ratio of about 90, and a small grain ZSM-5 molecular sieve with a grain size of about 60nm under a system with a higher sodium content, but the crystal form of the molecular sieve product The appearance is irregular, especially the phenomenon of reunion is more serious.

Since ZSM-5 molecular sieve is a solid acid catalyst, the acid site is its active center, and the acid site is produced by the skeleton aluminum. It is generally believed that the acidity of the molecular sieve is directly proportional to its silicon-aluminum ratio. High silicon aluminum has less acid content than ZSM-5, so there are fewer active centers on the unit catalyst, and the catalytic efficiency is low; moreover, as the reaction progresses, the carbon deposit covering a little acid site will obviously reduce the activity of the catalyst and shorten the life of the catalyst.

Therefore, appropriately reducing the silicon-aluminum ratio of molecular sieves can help improve reaction efficiency and catalytic life. However, as the ratio of silicon to aluminum decreases, the common agglomeration phenomenon of small grains will become more obvious. Agglomeration will reduce the effective surface area and active sites of small-grained molecular sieves, reduce the reactivity and anti-coking ability, and also affect the dispersion of molecular sieves in the matrix during the catalyst forming process, seriously affecting the catalytic performance of the catalyst.

At present, the method of synthesizing nano-ZSM-5 with hard template is mostly used, that is, the crystallization process of molecular sieve is carried out in a limited space, so as to prevent the agglomeration of small crystal grains. Schmidt I etc. (Inorg.Chem.2000,39(11):2279) and Kim S S etc. (Chem.Mater.2003,15(8):1664) by silicon source, aluminum source, templating agent, alkali and water mixing, then impregnated into porous carbon black for crystallization, and then calcined to remove the template to obtain ZSM-5 molecular sieve with small crystal grains. Although this method can prepare molecular sieves with a narrow grain range and is not easy to agglomerate, it requires that the pore size of the template material must be uniform, and it is also necessary to ensure that the crystallization process occurs in the pores of the template agent rather than on the surface. In addition, this special medium The porous material itself requires a complex preparation process and is expensive, resulting in high cost of synthesized nano-molecular sieves. The hard template is generally removed by roasting and cannot be reused. Therefore, industrial applications will be greatly limited.

Contents of the invention

The present invention aims at the above-mentioned problems such as easy agglomeration of nanometer and submicron molecular sieves, and mainly solves the problem of low-silicon-aluminum-ratio small-grain ZSM-5 zeolite molecular sieves in the prior art, especially nanometer and submicron size, which have irregular crystal forms and are easy to agglomerate. The problem is to provide a highly dispersed small grain ZSM-5 molecular sieve and its preparation method. The method adds a small amount of degraded cellulose to the synthesis system to prepare small-grain ZSM-5 molecular sieves, especially for molecular sieves with low silicon-aluminum ratio, which have the advantages of regular crystal shape, good dispersion and not easy to agglomerate.

In order to solve the problems of the technologies described above, the technical scheme adopted in the present invention is as follows:

A ZSM-5 molecular sieve with high dispersion and small crystal grains, the silicon-aluminum ratio of the molecular sieve is 20-150, and the grain size of the molecular sieve is 50-500nm.

According to the ZSM-5 molecular sieve of the present invention, preferably, the grain size of the molecular sieve is 100-300nm.

The molecular sieve provided by the invention has low silicon-aluminum ratio, regular crystal shape, good dispersibility and is not easy to agglomerate.

According to the ZSM-5 molecular sieve of the present invention, the preferred ZSM-5 molecular sieve of the present invention is prepared by a preparation method comprising the following steps:

(1) dissolving cellulose in a mixed solution of sodium hydroxide/urea/water, stirring and degrading, and centrifuging to obtain degradation solution A;

(2) dissolving sodium hydroxide, aluminum salt, and template in water to obtain aluminum salt solution B;

(3) Add silicon source and degradation solution A to aluminum salt solution B and mix well, so that the molar ratio of each component in the mixture is 20-150:1:130 in terms of SiO ₂ : Al ₂ O ₃ : H ₂ O : template -3000: 1-20, then add sodium hydroxide to adjust the pH to alkaline;

(4) crystallize the mixture after adjusting the pH value in step (3), and then obtain the ZSM-5 molecular sieve through post-treatment.

According to the ZSM-5 molecular sieve of the present invention, in some preferred embodiments of the present invention, in step (1), the mixed solution of sodium hydroxide/urea/water is pre-cooled to -20-0°C, and then cellulose is added in the Stir and degrade at high temperature, and obtain degradation solution A after centrifugation.

This can reduce the crystallinity of the polymer, facilitate the deep swelling of the cellulose, and accelerate the dissolution equilibrium of the cellulose.

According to the ZSM-5 molecular sieve of the present invention, in some embodiments of the present invention, the prepared degradation solution A is placed at -20-0°C before use.

According to the ZSM-5 molecular sieve of the present invention, it is also preferred that in the mixed solution of sodium hydroxide/urea/water in the step (1), the total weight of the mixed solution is 100%, and the sodium hydroxide content is 3-10% %, the urea content is 8-16%.

According to the ZSM-5 molecular sieve of the present invention, the cellulose described in step (1) can be commercially available conventionally used cellulose, which can be extracted from conventional plant cellulose; in some preferred embodiments of the present invention One or more of cotton linter pulp, bamboo pulp and wood pulp;

In some of the more preferred embodiments, the wood pulp is hardwood pulp or softwood pulp.

According to the ZSM-5 molecular sieve of the present invention, the aluminum salt described in step (2) can be an aluminum salt conventionally used in the art, and the present invention is preferably one or more of aluminum sulfate, sodium metaaluminate and aluminum isopropoxide. Several kinds.

According to the ZSM-5 molecular sieve of the present invention, the template agent described in step (2) can be a template agent conventionally used in the art, and the present invention is preferably one of n-butylamine, ethylenediamine and tetrapropylammonium bromide. species or several.

According to the ZSM-5 molecular sieve of the present invention, it is also preferred that the water in step (2) is deionized water.

According to the ZSM-5 molecular sieve of the present invention, the amount of sodium hydroxide added in step (2) can be determined according to the aluminum salt, and the amount of sodium hydroxide added can ensure that the aluminum salt is completely dissolved.

According to the ZSM-5 molecular sieve of the present invention, the added amount of degradation solution A in step (3) is preferably 5-10% of the total weight of the mixture after sodium hydroxide is added.

According to the ZSM-5 molecular sieve of the present invention, in order to better mix uniformly, it is preferable to add the silicon source and the degradation solution A to the aluminum salt solution B dropwise in step (3).

According to the ZSM-5 molecular sieve of the present invention, it is also preferred to add sodium hydroxide in step (3) to adjust the pH value to 10-14.

According to the ZSM-5 molecular sieve of the present invention, the silicon source described in step (3) can be a conventional silicon source in the art, and the present invention is preferably one or more of silica sol, coarse-pore silica gel and white carbon black .

It can be understood that, in step (3) of the present invention, the silicon source and the degradation solution A are added to the aluminum salt solution B, wherein the order of adding the silicon source and the degradation solution A is not particularly required, and the silicon source and the degradation solution A can be added simultaneously or in any order. Add the source and degradation solution A to the aluminum salt solution B.

According to the ZSM-5 molecular sieve of the present invention, the crystallization described in the preferred step (4) is two-stage crystallization;

Among them, it is further preferred that the crystallization temperature of the first stage is 80-110°C, and the crystallization time is 10-40h; the crystallization temperature of the second stage is 150-180°C, and the crystallization time is 20-50h.

According to the ZSM-5 molecular sieve of the present invention, wherein the crystallization described in step (4) can also be one-stage crystallization;

Among them, the preferred stage of crystallization is specifically: the crystallization temperature is 150-180°C, and the crystallization time is 30-60h.

According to the ZSM-5 molecular sieve of the present invention, the post-treatment in step (4) can adopt conventional post-treatment operations in the art, for example, can include at least one of filtering, washing and drying.

The preparation method of ZSM-5 molecular sieve described in any one of the present invention, described method comprises the steps:

(1) dissolving the cellulose in a mixed solution of sodium hydroxide/urea/water, stirring and degrading, centrifuging to obtain the degradation solution A, and standing;

(2) dissolving sodium hydroxide, aluminum salt, and template in water to obtain aluminum salt solution B;

(3) Add silicon source and degradation solution A to aluminum salt solution B and mix well, so that the molar ratio of each component in the mixture is 20-150:1:130 in terms of SiO ₂ : Al ₂ O ₃ : H ₂ O : template -3000: 1-20, then add sodium hydroxide to adjust the pH to alkaline;

(4) crystallize the mixture after adjusting the pH value in step (3), and then obtain the ZSM-5 molecular sieve through post-treatment.

Wherein the present invention can be more specifically:

(1) Use the pre-cooled sodium hydroxide/urea/water mixed solution to degrade the cellulose with low-temperature stirring, centrifuge to obtain the degradation solution A, and store it at low temperature;

(2) Dissolving sodium hydroxide, aluminum salt, template agent Q with deionized water, aluminum salt solution B;

(3) Slowly add the silicon source and the degradation solution A to the aluminum salt solution B simultaneously, so that the molar ratio of the total composition of the mixture is SiO ₂ : Al ₂ O ₃ : H ₂ O: Q=20-150:1 : 130-3000: 1-20, then add NaOH to adjust the pH value to 10-14;

(4) The reaction mixture is crystallized in two stages: the crystallization temperature of the first stage is 80-110°C, and the crystallization time is 10-40 hours; the crystallization temperature of the second stage is 150-180°C, and the crystallization time is 20- 50 hours.

In summary, the present invention provides a highly dispersed small-grain ZSM-5 molecular sieve and a preparation method thereof. Technical scheme of the present invention has following advantage:

The invention provides a method for synthesizing small-grain ZSM-5 molecular sieves with a silicon-aluminum ratio of 20-150. In the method, the polymer produced by cellulose degradation is adsorbed on the surface of nanoparticles to change the charge distribution on the surface of the particles and increase the The steric hindrance between the large particles can play a dispersing effect. At the same time, by controlling the composition of the solution, the defects of irregular crystal form and easy agglomeration of ZSM-5 molecular sieves with low silicon-aluminum ratio and small crystal grains in the past have been well solved. The obtained ZSM-5 molecular sieve has uniform grain size, the size is between 50-500nm, and the dispersion is good.

Description of drawings

Fig. 1 is the XRD pattern of examples 1 product.

Figure 2 is a SEM image of the product of Comparative Example 1.

Fig. 3 is the SEM figure of embodiment 1 product.

Fig. 4 is the laser particle size distribution figure of embodiment 1 product.

Fig. 5 is the SEM picture of the product of embodiment 4.

Fig. 6 is the laser particle size distribution diagram of the product of embodiment 4.

Fig. 7 is the SEM picture of the product of embodiment 5.

Figure 8 is a laser particle size distribution diagram of the product of Example 5.

Fig. 9 is the SEM picture of the product of embodiment 7.

Figures 2, 3, 5, 7, and 9 all use FEI QUANTA-200 scanning electron microscope to visually observe the surface morphology and grain size of molecular sieves.

Figures 4, 6, and 8 use the Malvern Mastersizer 2000 laser particle size analyzer to conduct particle size analysis using the light scattering phenomenon of particles, and perform statistical measurements on the particle size distribution of the entire sample.

Detailed ways

The implementation process and beneficial effects of the present invention are described in detail below through specific examples, aiming to help readers better understand the essence and characteristics of the present invention, and not as a limitation to the scope of implementation of this case.

Example 1

Take 6g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 10g of urea, stir and dissolve, put it in -20°C environment for 2 hours and refrigerate it for 2 hours; take 4g of cotton linter pulp, add the above NaOH/ Degrade in urea/water solution, centrifuge to obtain degradation solution, and store at -10°C. Take 18g of sodium hydroxide, 4g of sodium metaaluminate, and 40g of tetrapropylammonium bromide, and dissolve them in 150g of deionized water; take 250g of silica sol and 30g of degradation solution, and slowly add them dropwise to the aluminum salt solution, and then add NaOH Adjust the pH value to 14; put the reaction mixture into a reaction kettle, crystallize at 100°C for 36 hours, then raise the temperature to 170°C, and crystallize for 24 hours. After filtering, washing and drying, the average grain size of the obtained product is About 100nm, SiO ₂ /Al ₂ O ₃ is 30. The XRD pattern is shown in Figure 1, the SEM image is shown in Figure 3, and the particle size distribution is shown in Figure 4.

Example 2

Take 7g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 12g of urea, stir and dissolve, put it in -20℃ for 2 hours; take 4g of cotton linter pulp, add the above NaOH/ Degrade in urea/water solution, centrifuge to obtain degradation solution, and store at -10°C. Take 20g of sodium hydroxide, 6.8g of aluminum isopropoxide, and 40g of tetrapropylammonium bromide, and dissolve them with 250g of deionized water; take 100g of white carbon black and 30g of degradation solution, and slowly add them dropwise to the aluminum salt solution, and then Add NaOH to adjust the pH value to 14; put the reaction mixture into the reaction kettle, crystallize at 100°C for 36 hours, then raise the temperature to 170°C, and crystallize for 24 hours. After filtering, washing and drying, the average crystal grain The size is around 70nm, SiO ₂ /Al ₂ O ₃ is 40.

Example 3

Take 6g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 10g of urea, stir and dissolve, put it in -20°C environment for 2 hours and refrigerate it for 2 hours; take 4g of cotton linter pulp, add the above NaOH/ Degrade in urea/water solution, centrifuge to obtain degradation solution, and store at -10°C. Take 20g of sodium hydroxide, 2g of sodium metaaluminate, and 40g of tetrapropylammonium bromide, and dissolve them in 250g of deionized water; take 100g of coarse-pore silica gel and 30g of degradation solution, and slowly add them dropwise to the aluminum salt solution, and then add Adjust the pH value to 14 with NaOH; put the reaction mixture into a reaction kettle, crystallize at 100°C for 36 hours, then raise the temperature to 170°C, and crystallize for 24 hours. After filtering, washing and drying, the average grain size of the obtained product is At around 100 nm, SiO ₂ /Al ₂ O ₃ is 50.

Example 4

Take 6g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 10g of urea, stir to dissolve, put it in -15℃ for 2 hours and refrigerate it for 2 hours; take 4g of bamboo pulp, put it into the NaOH/urea/ Degrade in aqueous solution, centrifuge to obtain the degradation solution, and store it at -5°C. Take 18g of sodium hydroxide, 2g of sodium metaaluminate, and 20g of n-butylamine, and dissolve them in 250g of deionized water; take 100g of coarse-pore silica gel and 30g of degradation solution, and slowly add them dropwise to the aluminum salt solution, and then add NaOH to adjust the pH The value is 14; put the reaction mixture into a reaction kettle, crystallize at 100°C for 36 hours, then raise the temperature to 170°C, and crystallize for 24 hours. After filtering, washing and drying, the average grain size of the obtained product is about 150nm , SiO ₂ /Al ₂ O ₃ is 50. Its SEM image is shown in Figure 5, and the particle size distribution is shown in Figure 6.

Example 5

Take 6g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 10g of urea, stir and dissolve, put it in -20℃ for 2 hours; take 4g of bamboo pulp, put it into the above-mentioned NaOH/urea/ Degrade in aqueous solution, centrifuge to obtain the degradation solution, and store it at -10°C. Take 18g of sodium hydroxide, 6g of aluminum sulfate, and 18g of ethylenediamine, and dissolve them in 400g of deionized water; take 100g of coarse-pore silica gel and 30g of degradation solution and slowly add them dropwise to the aluminum salt solution, and then add NaOH to adjust the pH value to 13 ;Put the reaction mixture in the reaction kettle, and crystallize at 170°C for 48 hours. After filtering, washing and drying, the obtained product has an average grain size of about 300nm and a SiO ₂ /Al ₂ O ₃ ratio of 100. Its SEM image is shown in Figure 7, and the particle size distribution is shown in Figure 8.

Example 6

Take 6g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 10g of urea, stir and dissolve, put it in -20℃ for 2 hours; take 4g of hardwood pulp, add the above-mentioned NaOH/urea Degraded in / aqueous solution, centrifuged to obtain the degradation solution, stored at -10°C. Take 18g of sodium hydroxide, 4g of aluminum sulfate, and 18g of ethylenediamine, and dissolve them in 400g of deionized water; take 100g of coarse-pore silica gel and 30g of degradation solution and slowly add them dropwise to the aluminum salt solution, and then add NaOH to adjust the pH value to 13 ;Put the reaction mixture in a reaction kettle, and crystallize at 170°C for 48 hours. After filtering, washing and drying, the obtained product has an average grain size of about 300nm and a SiO ₂ /Al ₂ O ₃ ratio of 140.

Example 7

Take 5g of NaOH, add 80g of deionized water to it, make it fully dissolved, then add 10g of urea, stir and dissolve, put it in -10℃ for 2 hours; take 4g of coniferous wood pulp, add the above-mentioned NaOH/urea Degraded in / aqueous solution, centrifuged to obtain the degradation solution, stored at -10°C. Take 16g of sodium hydroxide, 4g of sodium metaaluminate, and 40g of tetrapropylammonium bromide, and dissolve them in 500g of deionized water; take 100g of coarse-pore silica gel and 40g of degradation solution, and slowly add them dropwise to the aluminum salt solution, and then add Adjust the pH value to 12.5 with NaOH; put the reaction mixture into a reaction kettle, crystallize at 100°C for 20 hours, then raise the temperature to 170°C, and crystallize for 24 hours. After filtering, washing and drying, the average grain size of the obtained product is At around 500nm, SiO ₂ /Al ₂ O ₃ is 100. Its SEM image is shown in Figure 9.

Comparative example 1

This comparative example is a small grain ZSM-5 molecular sieve prepared according to the method provided by CN 200810019849.8. The specific preparation method is as follows: Take 0.28mol (60g) of ethyl orthosilicate, add 5.6mol (100.8g) of deionized water to it, make it fully dissolved, then add 2g of concentrated sulfuric acid, adjust the pH of the solution to 1.0, and then add 0.0068mol (4.5g) of aluminum sulfate, 0.027mol (7.2g) of tetrapropylammonium bromide, 0.5g of ZSM-5 zeolite seed crystal, fully hydrolyzed by stirring at 20°C for 6h, adding 0.0125mol (0.5g) of NaOH solid, and adjusting The pH of the crystallization solution is 10, stirred evenly, packaged in a high-pressure hydrothermal kettle, and statically crystallized at 180°C for 15 hours. The obtained product is washed, filtered, dried, and roasted to obtain ZSM-5 zeolite raw powder. The XRD analysis structure of the raw zeolite powder is ZSM-5, and its silicon-aluminum ratio is 27. The SEM image is shown in Figure 2, and the grain size is 100-200nm.

Claims (10)

1. a high dispersive ZSM-5 molecular sieve with small crystal grains, is characterized in that, described molecular sieve silica alumina ratio is 20-150, and zeolite crystal particle diameter is 50-500nm, and wherein preferred described zeolite crystal particle diameter is 100-300nm.

2. ZSM-5 molecular sieve according to claim 1, is characterized in that, described ZSM-5 molecular sieve is prepared by the preparation method comprised the steps:

(1) cellulose dissolution is stirred degraded in the mixing solutions of sodium hydroxide/urea/water, centrifugally obtain degradation solution A; Preferred described Mierocrystalline cellulose adds the 3-6% that weight is mixing solutions weight; Preferred described Mierocrystalline cellulose is one or more in cotton linter pulp, bamboo pulp and wood pulp; More preferably described wood pulp is hardwood pulp or softwood pulp;

(2) by sodium hydroxide, aluminium salt, template water dissolution, aluminum salt solution B is obtained; Preferred described aluminium salt is one or more in Tai-Ace S 150, sodium metaaluminate and aluminum isopropylate; Preferred described template is one or more in n-Butyl Amine 99, quadrol and 4-propyl bromide;

(3) silicon source and degradation solution A are added in aluminum salt solution B mix, to make in mixture each component molar ratio with SiO ₂: Al ₂o ₃: H ₂o: template counts 20-150:1:130-3000:1-20, then add sodium hydroxide adjust ph to alkalescence; Preferred described silicon source is one or more in silicon sol, silochrom and white carbon black;

(4) mixture after step (3) adjust ph is carried out crystallization, then obtain described ZSM-5 molecular sieve through aftertreatment.

3. ZSM-5 molecular sieve according to claim 2, is characterized in that, step (1) is that the mixing solutions of sodium hydroxide/urea/water is chilled to-20-0 DEG C in advance, adds Mierocrystalline cellulose and stirs degraded at such a temperature, obtain degradation solution A after centrifugal.

4. ZSM-5 molecular sieve according to claim 2, it is characterized in that, in the mixing solutions of the sodium hydroxide/urea/water in step (1), in this mixing solutions gross weight for 100%, sodium hydrate content is 3-10%, and urea content is 8-16%.

5. ZSM-5 molecular sieve according to claim 2, is characterized in that, the add-on of degradation solution A is the 5-10% that described mixture adds the gross weight after sodium hydroxide in step (3).

6. ZSM-5 molecular sieve according to claim 2, is characterized in that, is to be added drop-wise in aluminum salt solution B in silicon source and degradation solution A in step (3).

7. ZSM-5 molecular sieve according to claim 2, is characterized in that, adds sodium hydroxide adjust ph to 10-14 in step (3).

8. ZSM-5 molecular sieve according to claim 2, is characterized in that, crystallization described in step (4) is one section of crystallization or two sections of crystallization; Preferably one section of crystallization is: crystallization temperature 150-180 DEG C, and crystallization time is 30-60h; Preferably two sections of crystallization are: first paragraph crystallization temperature is 80-110 DEG C, crystallization time 10-40h; Second segment crystallization temperature is 150-180 DEG C, crystallization time 20-50h.

9. ZSM-5 molecular sieve according to claim 2, is characterized in that, aftertreatment described in step (4) comprises at least one in filtration, washing and drying.

10. the preparation method of the ZSM-5 molecular sieve described in claim 2 ~ 9 any one, is characterized in that, described method comprises the steps:

(1) cellulose dissolution is stirred degraded in the mixing solutions of sodium hydroxide/urea/water, centrifugally obtain degradation solution A, leave standstill;

(2) by sodium hydroxide, aluminium salt, template water dissolution, aluminum salt solution B is obtained;

(3) silicon source and degradation solution A are added in aluminum salt solution B mix, to make in mixture each component molar ratio with SiO ₂: Al ₂o ₃: H ₂o: template counts 20-150:1:130-3000:1-20, then add sodium hydroxide adjust ph to alkalescence;

(4) mixture after step (3) adjust ph is carried out crystallization, then obtain described ZSM-5 molecular sieve through aftertreatment.