CN100586565C - Preparation method of ZSM-5/mordenite composite molecular sieve - Google Patents

Abstract

The invention relates to a preparation method of a ZSM-5/mordenite composite molecular sieve, which mainly solves the relatively complicated problems of adding crystal seeds or segmental crystallization in the synthesis process of the existing composite molecular sieve. The present invention preferably solves this problem by adopting the technical scheme of preparing a composite molecular sieve with an adjustable ratio of ZSM-5 and mordenite by controlling a certain silicon-aluminum ratio and pH value during the synthesis process of the molecular sieve. The molecular sieve prepared by the method can be used in the industrial production of ethylene propylene by catalytic cracking of naphtha.

Description

Preparation method of ZSM-5/mordenite composite molecular sieve

technical field

The invention relates to a preparation method of ZSM-5/mordenite composite molecular sieve.

Background technique

ZSM-5 molecular sieve and mordenite are widely used in petrochemical and other fields due to their good shape-selective catalytic performance and good thermal stability. However, because the two molecular sieves have uniform and single pore sizes, they cannot handle complex components separately, and their catalytic properties for the same reactants are different. Composite molecular sieves containing two components can handle complex components with different molecular diameters, and can also exert their synergistic catalytic effect.

Documents CN1565967A and CN1565970A report using ZSM-5 molecular sieve or mordenite as a seed crystal, respectively adding mordenite or ZSM-5 molecular sieve to the synthesis solution, and synthesizing a mixed crystal material of ZSM-5 and mordenite. Its catalytic effect is better than the effect of mechanical mixing of two molecular sieves, but different crystal seeds need to be added as inducers during the synthesis process, and fluoride also needs to be added.

Document CN1393403 reports that a meso-microporous composite molecular sieve composition was synthesized by segmented crystallization method for heavy oil processing. The synthesis method is to first prepare the reaction mixture gel for synthesizing microporous molecular sieves, and then carry out the first-stage crystallization at 30-300°C. After crystallization for 3-300 hours, adjust the pH value of the reaction mixture to 9.5-12 , and add the template agent used for synthesizing mesoporous molecular sieves, and then carry out the second stage of hydrothermal crystallization under self-pressure at 30-170°C, the crystallization time is 15-480 hours, and obtain the mesoporous composite molecular sieve composition, However, the synthesis process of molecular sieves requires segmental crystallization, and the pH value must be adjusted in the middle, and the synthesis method is also relatively complicated.

Document CN03133557.8 reported that under static conditions, a molecular sieve with a composite structure having two structures of TON and MFI was synthesized. The molecular sieve added a small amount of seed crystals and salts during the preparation of the gel, and controlled the crystallization parameters to obtain two kinds of crystals. Molecular sieves with different proportions, the molar ratio of silicon to aluminum on the lattice of the molecular sieve is greater than 50, and the composite molecular sieve of the present invention can be used in the reaction process of mixtures such as petroleum fractions. However, the synthetic process of the invention also needs to add seed crystals and salts.

Document CN1583562 has reported a kind of double microporous zeolite molecular sieve and preparation method, it is characterized in that adopt orderly synthesis method, firstly synthesize Y-type zeolite according to certain material ratio; Ammonium chloride solution was mixed, and finally a certain amount of silica sol was added and stirred thoroughly to make it uniform, crystallized at 130°C-140°C for 4-7 days, and a composite zeolite molecular sieve with Y/β double microporous structure was obtained. This method also Similar to segmental crystallization.

Contents of the invention

The technical problem to be solved by the present invention is the complex technical problem of needing to add crystal seeds or segmental crystallization in the synthesis process of the composite molecular sieve in the prior art, and to provide a new preparation method of ZSM-5/mordenite composite molecular sieve . The method has the advantages of simple molecular sieve synthesis process and adjustable ratio of ZSM-5 molecular sieve and mordenite.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is as follows: a preparation method of ZSM-5/mordenite composite molecular sieve, using metasilicate or silicon oxide as the silicon source, using metaaluminate or aluminum salt As an aluminum source, at least one selected from ethylenediamine, ethylamine, triethylamine, n-butylamine or tetrapropylammonium bromide is used as a template M, and the above-mentioned raw materials are prepared into a solution according to the required proportion, and adjusted The pH value of the solution is between 10 and 13, and the ZSM-5/mordenite composite molecular sieve is obtained by hydrothermal crystallization at a crystallization temperature of 120 to 200°C for 15 to 100 hours, wherein the molar ratio of the solution is:

Si:Al:M:H ₂ O=1:0.01-0.2:0.1-0.6:30-300.

In the above technical solution, the molar ratio of the solution is preferably in the range of: Si:Al:M:H ₂ O = 1:0.05-0.17:0.2-0.4:35-50, and the pH value of the solution is preferably in the range of 10.5-12.5. The preferred range of crystallization temperature is 160-180°C, the preferred range of crystallization time is 20-40 hours, and the template agent M is preferably at least one selected from ethylenediamine or ethylamine. The ZSM-5 molecular sieve content in the composite molecular sieve preferably ranges from 1 to 99%, and more preferably ranges from 20 to 99%. The SiO ₂ /Al ₂ O ₃ molar ratio of the composite molecular sieve preferably ranges from 12 to 100, more preferably ranges from 14 to 40.

The synthesis method of the composite molecular sieve is to take the required silicon source and aluminum source according to the required ratio of the materials, dissolve them in distilled water to make a solution, then mix the two solutions, stir vigorously, and then add the required amount of template agent, Adjust the pH value to 10-13 with dilute acid while stirring. Put the sol in an autoclave, control the temperature of 120-200°C to crystallize for 15-100 hours, take it out, wash it, dry it, and roast it to obtain a composite molecular sieve of ZSM-5 and mordenite.

In the present invention, due to adopting the template agent suitable for ZSM-5 molecular sieve and mordenite synthesis at the same time, adjusting the pH range suitable for the growth of the two, controlling the silicon-alumina ratio and the crystallization temperature suitable for the growth of the two, under hydrothermal conditions, The ZSM-5 molecular sieve crystal seed and the mordenite zeolite seed crystal can be induced in the mixed sol at the same time, and then the ZSM-5/mordenite composite molecular sieve is generated in an environment suitable for the growth of the two. Since the surface chemical potential, acidity and specific surface of the composite molecular sieve are quite different from those of the mechanical mixing of the two molecular sieves, it has good catalytic performance. It is used in the reaction of catalytic cracking of naphtha to produce ethylene and propylene. The total yield of ethylene and propylene is The rate can reach 48.85%, and a good technical effect has been achieved.

Description of drawings

Figure 1 is the XRD patterns of composite molecular sieves synthesized at different pH values.

Figure 2 is the XRD patterns of composite molecular sieves with different ratios of silicon to aluminum.

Fig. 3 is the XRD spectrum of the composite molecular sieve synthesized in Examples 12-15.

Fig. 4 is the XRD spectrum of the composite molecular sieve synthesized in Examples 16-18.

Fig. 5 is the XRD spectrum of the composite molecular sieve synthesized in Examples 19-21.

The present invention will be further elaborated below by embodiment.

Detailed ways

【Example 1】

Take 284 grams of sodium metasilicate, dissolve it into solution A with 300 grams of distilled water, take 33.3 grams of aluminum sulfate, and make solution B with 100 grams of distilled water, slowly pour B solution into A solution, stir vigorously, and then add 24.4 grams of B Diamine, after stirring for a period of time, adjust the pH value at 11.5 with dilute sulfuric acid, control the molar ratio of the sol: Si: Al: ethylenediamine: H ₂ O = 1: 0.1: 0.4: 40, put the mixed solution into In an autoclave, keep warm at 180°C for 40 hours, then take out the composite molecular sieve of ZSM-5 and mordenite, which is prepared by washing, drying, and roasting, which is recorded as FH-1, and the average silicon-alumina mole of ZSM-5/mordenite composite molecular sieve The ratio is 20. The XRD spectrum of the molecular sieve is shown in Figure 1, and the ratio of ZSM-5 molecular sieve and mordenite in the composite molecular sieve determined by XRD quantitative analysis method is shown in Table 6.

[Embodiments 2-6]

According to the method of Example 1, the pH of the control solution was different, and the composite molecular sieves were synthesized respectively, as shown in Table 1, which were respectively recorded as FH-2, FH-3, and FH-4. The XRD spectrum of the molecular sieve is shown in Figure 1, and the ratio of ZSM-5 and mordenite is shown in Table 6.

Table 1

Example Solution pH Sample serial number Example 2 10.6 FH-2 Example 3 11 FH-3 Example 4 11.2 FH-4 Example 1 11.5 FH-1 Example 5 11.8 FH-5 Example 6 12.5 FH-6

[Embodiments 7-11]

According to the method of Example 1, the composite molecular sieves synthesized by controlling the different silicon-aluminum ratios of the solution are shown in Table 2, the XRD pattern of the molecular sieve is shown in Figure 2, and the ratio of ZSM-5 and mordenite is shown in Table 6.

Table 2

Example Si-aluminum ratio (molar ratio) Sample serial number Example 7 Si:Al=14 FH-7 Example 8 Si:Al=16 FH-8 Example 9 Si:Al=25 FH-9 Example 10 Si:Al=30 FH-10 Example 11 Si:Al=40 FH-11

[Example 12-15]

According to the method of Example 1, the composite molecular sieve synthesized respectively by controlling the different water consumption of the synthetic mixed solution is shown in Table 3, the XRD pattern of the molecular sieve is shown in Figure 3, and the ratio of ZSM-5 and mordenite is shown in Table 6.

table 3

Example Water-silicon ratio (molar ratio%) Sample serial number Example 12 35 FH-12 Example 13 50 FH-13 Example 14 60 FH-14 Example 15 100 FH-15

[Example 16-18]

According to the method of Example 1, the composite molecular sieves synthesized respectively by controlling different crystallization temperatures are shown in Table 4, the XRD spectrum of the molecular sieve is shown in Figure 4, and the ratio of ZSM-5 and mordenite is shown in Table 6.

Table 4

Example Crystallization temperature (℃) Sample serial number Example 16 150 FH-16 Example 17 160 FH-17 Example 18 170 FH-18

[Example 19-21]

According to the method of Example 1, the composite molecular sieves synthesized by controlling different crystallization times are shown in Table 5, and the XRD patterns of the molecular sieves are shown in Figure 5, and the ratios of ZSM-5 and mordenite are shown in Table 6.

table 5

Example Crystallization time (hours) Sample serial number Example 19 20 FH-19 Example 20 30 FH-20 Example 20 50 FH-21

Table 6

Sample serial number ZSM-5 molecular sieve content (weight%) Mordenite content (weight%) FH-1 85.5 14.5 FH-2 96.4 3.6 FH-3 93.5 6.5 FH-4 90.5 9.5 FH-5 56.0 44.0 FH-6 34.7 65.3 FH-7 8.5 91.5 FH-8 21.4 78.6 FH-9 81.2 18.8 FH-10 92.6 7.4 FH-11 97.5 2.5 FH-12 96.4 3.6 FH-13 95.5 4.5 FH-14 94.6 5.4 FH-15 85.5 14.5 FH-16 97.5 2.5 FH-17 95.4 4.6 FH-18 94.5 5.5 FH-19 88.4 11.6 FH-20 90.5 9.5 FH-21 95.5 4.5

[Example 22]

Using the FH-1 molecular sieve prepared in Example 1, take 20-40 mesh particles and put them into a fixed-bed reactor, and use _C4 - _C10 naphtha as a raw material [the composition of the raw material weight percentage is as follows: alkane 65.2% (wherein Normal paraffin is 32.5%), cycloalkane is 28.4%, olefin is 0.17%, aromatic hydrocarbon is 6.2%], is 650 ℃ at reaction temperature, and liquid space velocity is 0.5 hour ^-1 , and water/naphtha weight ratio is Evaluation under the condition of 3:1, the results are as follows: the ethylene yield is 21.76% (weight), the propylene yield is 27.09% (weight), and the total yield is 48.85% (weight).

Claims (10)

1, a kind of preparation method of ZSM-5/ mordenite composite molecular sieve, oxide with metasilicate or silicon is the silicon source, with meta-aluminate or aluminium salt is the aluminium source, to be selected from least a in ethylenediamine, ethamine, triethylamine, n-butylamine or the 4-propyl bromide is template agent M, above-mentioned raw materials is made solution by required proportioning, regulator solution pH value is between 10～13, hydrothermal crystallizing got the ZSM-5/ mordenite composite molecular sieve in 15～100 hours under 120～200 ℃ of crystallization temperatures, and wherein the mole proportioning of solution is:

Si∶Al∶M∶H ₂O＝1∶0.01～0.2∶0.1～0.6∶30～300。

2,, it is characterized in that the mole proportioning of solution is according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1:

Si∶Al∶M∶H ₂O＝1∶0.05～0.17∶0.2～0.4∶35～100。

3, according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1, the pH value that it is characterized in that solution is 10.5～12.5.

4,, it is characterized in that crystallization temperature is 160～180 ℃ according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1.

5,, it is characterized in that crystallization time is 20～40 hours according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1.

6,, it is characterized in that template agent M is selected from least a in ethylenediamine or the ethamine according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1.

7,, it is characterized in that in the composite molecular screen that the ZSM-5 molecular sieve content is 1～99% by weight percentage according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1.

8,, it is characterized in that in the composite molecular screen that the ZSM-5 molecular sieve content is 20～99% by weight percentage according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 7.

9,, it is characterized in that the SiO of composite molecular screen according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1 ₂/ Al ₂O ₃Mol ratio is 12～100.

10,, it is characterized in that the SiO of composite molecular screen according to the preparation method of the described ZSM-5/ mordenite composite molecular sieve of claim 1 ₂/ Al ₂O ₃Mol ratio is 14～40.

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