CN1033503C - The preparation method of small grain NaY molecular sieve - Google Patents

Abstract

The invention discloses a method for preparing NaY molecular sieve with small grains by adopting improved directing agent technology. The preparation process is as follows: firstly, sodium silicate solution is added to a conventional directing agent with a light transmittance of <30% to obtain a molar composition of (12-180)Na ₂ O: _{Al 2} O ₃ :(17-210 ) SiO ₂ : (160-3100) H ₂ O light transmittance> 75% of the improved directing agent solution, and then the improved directing agent is used in NaY hydrothermal synthesis of different formulations, prepared according to the conventional NaY molecular sieve preparation method Crystalline NaY molecular sieve products.

Description

The preparation method of small grain NaY molecular sieve

The invention belongs to molecular sieve synthesis technology, in particular to a preparation method of small crystal NaY molecular sieves.

With the in-depth understanding of the role of NaY molecular sieves in the catalytic cracking process, people found that small-grained NaY molecular sieves have better catalytic performance. EP0,204,236 (1986) reported that the cracking catalyst made from small-grain NaY molecular sieves had higher activity and better selectivity for heavy oil catalytic cracking compared with large-grain NaY molecular sieves.

Corma believes that NaY molecular sieves with high SiO ₂ /Al ₂ O ₃ ratio and small crystal grains can increase gasoline octane number and have better water and thermal stability (ACS Symp Ser., 375, Chap, 2, 1988, P.17).

There are many reports about the synthetic method of small-grain NaY molecular sieves, which mainly include:

1. Increase the alkalinity during NaY synthesis and add more directing agents (US3,755,538). For example, the total ratio of NaY synthesis is 6.5Na ₂ O: Al ₂ O ₃ : 16SiO ₂ : 280H ₂ O, the molar composition is 16Na _{2 O} : Al ₂ O ₃ : 15SiO ₂ : 320H ₂ O, and the amount of directing agent added is 20%. (Based on the total moles of Al ₂ O ₃ in the system). The crystal grain diameter of the NaY molecular sieve synthesized by this method is 0.06 microns, and the unit cell constant is 24.66 nanometers.

2. By controlling the aging time, temperature and other factors of the directing agent, improve the seed crystal and prepare small-grain NaY molecular sieve (CKR8601-488B).

3. Add dispersion medium. For example, adding methanol, ethanol, dimethyl sulfoxide, and dextrose and dextrose as dispersion media can produce X.Y type I small-grain molecular sieves with a grain diameter of 0.01-0.1 microns (US3,516,786; EP0.041,338) .

4. By improving the process conditions, such as low-temperature gelation, high-speed long-term stirring, and microwave heating, etc., small-grain Y-type, X-type, and ZSM-5 molecular sieves (GB1,223,592; US4,587,115 ; US4,778,666).

The common feature of the small crystal NaY molecular sieves synthesized by the above methods is that the product has a low SiO ₂ /Al ₂ O ₃ ratio, which is only suitable for the synthesis of X-type molecular sieves and Y-type molecular sieves with a SiO ₂ /Al ₂ O ₃ ratio ≤ 5 Molecular sieve.

There are many reports on the preparation of NaY molecular sieves with a high SiO ₂ /Al ₂ O ₃ ratio. For example, the use of crystallization-oriented technology to replace expensive silica sol with cheap sodium silicate to synthesize high-silicon Y-type molecular sieves has attracted more and more attention. people's attention. The industrialized high SiO ₂ /Al ₂ O ₃ ratio-NaY molecular sieve is mainly made of sodium silicate, sodium metaaluminate, sodium hydroxide and aluminum sulfate as raw materials (US4,166,099; CN85102733A; "Petroleum Refining "Phase 11-12, P22-25, 1978), but it is also limited to NaY molecular sieves with a grain diameter) of 0.30 microns.

EP0.204,455 reports a technology for preparing a directing agent capable of improving the strength of molecular sieve catalysts, that is, adding an effective amount of sodium silicate solution to a conventional directing agent to generate a clear and transparent improved directing agent solution. This improved directing agent has a long service life, and the clay microsphere catalyst prepared by in-situ crystallization using the directing agent has the characteristics of high strength, but the patent does not mention the grain size of the synthesized NaY molecular sieve.

The purpose of the present invention is to provide a method for preparing small crystal NaY molecular sieves by adopting improved directing agent technology. The method can not only synthesize small grain NaY molecular sieve with SiO ₂ /Al ₂ O ₃ ratio ≤ 5, but also synthesize small grain NaY molecular sieve with Si ₂ /Al ₂ O ₃ ratio > 5.

The preparation steps of said small grain NaY molecular sieve of the present invention are as follows:

1. Preparation of conventional directing agent: the modulus is 0.5-3.5, preferably 1.0-3.3, the concentration is 20-65% by weight, preferably 25-60% by weight of sodium silicate solution, and the caustic ratio is 10-12 High alkali sodium metaaluminate solution and deionized water are mixed and stirred at 0-45°C, preferably 5-40°C for 0.5-2 hours, and then aged at 15-60°C, preferably at 20-40°C 6-30 hours, the light transmittance is less than 30%, and the molar composition is (13-36)Na ₂ O:Al ₂ O ₃ :(12-21)SiO ₂ :(250-800)H ₂ O, the best It is a conventional directing agent for (15-19)Na ₂ O:Al ₂ O ₃ :(14-19)SiO ₂ :(300-380)H ₂ O;

2. Preparation of improved directing agent: Add the sodium silicate solution with the same specifications as in step 1 to the conventional directing agent prepared in step 1 in an amount of 5-80% by volume, preferably 10-70% by volume. After standing for 0.5-2 hours, the light transmittance>75%, the molar composition is (12-180)Na ₂ O:Al ₂ O ₃ :(17-210)SiO ₂ :(160-3100)H ₂ O, the most Preferably it is (16-150) Na ₂ O: _{Al 2} O ₃ : (20-180) SiO ₂ : (250-2500) H ₂ O improved directing agent solution;

3. The sodium silicate solution with the same specifications as in step 1, the improved directing agent solution prepared in step 2, the aluminum sulfate solution with _{an Al2O3} content of 0.085-0.095 g/ml and the low alkali with a caustic ratio of 1.0-3.0 Sodium metaaluminate solution carries out the NaY hydrothermal synthesis of different formulations according to the preparation method of conventional NaY molecular sieves, wherein the addition of the improved directing agent is 0.5-25%, preferably 1.0-20% (based on the total Al in the system ₂ O ₃ moles), stirred for 0.5-2 hours, heated to 95-100° C., crystallized for 5-35 hours, filtered, and dried to obtain NaY molecular sieve products with small grains.

Compared with the NaY molecular sieve synthesized by using the conventional directing agent, the NaY molecular sieve synthesized by the improved directing agent technology in the present invention has the characteristics of small crystal grains and short crystallization time.

If the modulus of the sodium silicate solution added to the conventional directing agent in the present invention is reduced, the life of the improved directing agent will be prolonged, the crystallization time will be shortened, and the crystal grains of the NaY molecular sieve product will be reduced.

Compared with conventional directing agents, the improved directing agent of the present invention has the characteristics of high activity, long service life, high temperature resistance of about 95°C, and the like.

When the improved directing agent and conventional directing agent are used in the hydrothermal synthesis of NaY, the grain size of the obtained NaY molecular sieve is between that of the NaY molecular sieve synthesized separately using the two directing agents.

The SiO ₂ /Al ₂ O ₃ ratio of the small-grain NaY molecular sieve synthesized by the invention can be ≤5.0 or >5.0. The latter is also a feature of the present invention.

Fig. 1 is the scanning electron micrograph (×9400) of example 4 of the present invention, and its grain diameter is 0.22 micron, and SiO ₂ /Al ₂ O ₃ ratio is 5.4;

Fig. 2 is a scanning electron micrograph (×9400) of Comparative Example 2, the grain diameter of which is 0.63 μm, and the ratio of SiO ₂ /Al ₂ O ₃ is 5.4.

The following examples further illustrate the invention.

Example 1

Preparation of sodium metaaluminate solution: Dissolve sodium hydroxide (Zhejiang Wenzhou Pharmaceutical Purchasing and Supply Station, chemically pure) into deionized water, then evenly add aluminum hydroxide powder (Shandong Aluminum Factory, industrially pure), and react at 120 ° C for 5 Hours, after the solution is clear and transparent, cool it down to below 60°C, and prepare sodium metaaluminate solutions with different caustic ratios (Na ₂ O/Al ₂ O ₃ molar ratio) according to the needs of the test.

Mix 158 milliliters of sodium silicate solution (modulus 3.28, specific gravity 1.261, concentration 27.3% by weight, Tianjin Soda Soda Factory) with 109 milliliters of high alkali sodium metaaluminate solution (caustic ratio=11.76, specific gravity 1.343) and 12 milliliters of deionized Water was mixed and stirred at 35°C for 1 hour, and then aged at 35°C for 6 hours to prepare a conventional directing agent with a molar composition of 16Na ₂ O:Al ₂ O ₃ :15SiO ₂ :320H ₂ O and a light transmittance of <30%.

158 milliliters of sodium silicate solution with the same specifications as above was added to the conventional directing agent in an amount of 36.2% by volume, and after standing at 30°C for 1.5 hours, the obtained light transmittance was 90%, and the molar composition was 20.6Na ₂ O:Al ₂ O ₃ : 30SiO ₂ : 495H ₂ O is a clear and transparent improved directing agent solution, which is used after standing at room temperature for 24 hours.

According to the NaY hydrothermal synthesis formula with a molar ratio of 3.84Na ₂ O: Al ₂ O ₃ : 12SiO ₂ : 220H ₂ O, 316 milliliters of sodium silicate solution with the same specifications as above, and 437 milliliters of the above-mentioned improved directing agent solution (the addition of _{the improved} directing agent is 20% based on the total _Al2O3 moles in the system), 204 milliliters of _Al2O3 content is 0.0856 g/ml (specific gravity=1.262) aluminum sulfate solution (Xingta, Jinshan County, Shanghai) Chemical plant, chemically pure) and 12 ml of low-alkali sodium metaaluminate solution (caustic ratio 2.45, specific gravity = 1.239) were mixed and stirred for 1 hour, then heated to 97 ° C, crystallized for 26 hours, filtered, and dried to obtain SiO ₂ /Al The ratio of ₂ O ₃ is 5.8, and it is a NaY molecular sieve product with small grain size. The analysis results are shown in Table 1.

in FIG. 1:

1. Determination of unit cell constant of NaY molecular sieve by X-ray diffraction method.

The relationship between the product SiO ₂ /Al ₂ O ₃ ratio and the crystal packet constant a ₀ is:

2. The determination of the external specific surface data adopts the t-pLot method, the t value ranges from 0.6 to 0.8 nanometers, and the relationship between the grain diameter D (micron) and the external specific surface Sex is:

Among them, ρ is the ideal particle size of NaY molecular sieve, which is 1.92 g/cm ³ , and Sex is the external specific surface (m ² /g)

3. Crystallization time: from the start of crystallization at 97°C to 2 hours after the end of crystallization.

Instance 2

Except that the addition of the improved directing agent was 5.0% (based on the total Al ₂ O ₃ moles in the system), other experimental procedures were the same as in Example 1, and the crystallization was performed for 34 hours. The analysis results of the obtained product are shown in Table 1.

Example 3

Except that the conventional directing agent aging time was changed from 6 hours to 20 hours, the addition amount of the directing agent was improved, and other experimental procedures were the same as in Example 2. The product analysis results are shown in Table 1.

Comparative example 1

Except that the conventional directing agent was used instead of the _improved directing agent, other preparation steps were the same as in Example 2, and the addition of the conventional directing agent was 5.0% (based on the total _Al2O3 moles in the system). The analysis results of the obtained product are shown in Table 1.

As can be seen from the analysis results of examples 1-3 and comparative example 1: the NaY molecular sieve prepared by the present invention is compared with the NaY molecular sieve prepared by adopting conventional directing agents, and has small grains and short crystallization time characteristics, and the SiO of the resulting product _{The 2} /Al ₂ O ₃ ratio can be as high as 5.8. Like Example 2 and Comparative Example 1 SiO ₂ /Al ₂ O ₃ ratio is the same (5.8), and the amount of directing agent added is 5.0% (in terms of Al ₂ O ₃ moles in the system), but the crystal grains of the former are only 0.16 microns, and the latter The latter is 0.78 microns; the crystallization time of the former is 34 hours, and the latter is 55 hours (the latter crystallizes for 34 hours, and the crystallization is trace amount).

Table 1

Example 4

The ratio of the directing agent, the raw materials and _the preparation method are the same as in Example 1, the addition of the improved directing agent is 5% (based on the total _Al2O3 moles in the system), and the proportioning of the synthetic NaY molecular sieve is _3.0Na2O: Al ₂ O ₃ : 9.4SiO ₂ : 180H ₂ O, crystallized for 24 hours, and other experimental procedures were the same as Example 1. The analysis results of the product are shown in Table 2, and the scanning electron microscope photos are shown in Fig. 1.

Comparative example 2

Except that the conventional directing agent is used to replace the improved directing agent, other preparation steps are the same as in Example ₄ , the addition of the conventional directing agent is 5.0% (based on the total _Al2O3 moles in the system), the analytical results of the product are shown in Table 2, scan The electron microscope photo is shown in Figure 2.

It can be seen from Table 2 and Fig. 1 and Fig. 2 that the NaY molecular sieve prepared by the present invention has the characteristics of small crystal grains and short crystallization time compared with the NaY molecular sieve synthesized by conventional directing agents. Like example 4 and comparative example 2, SiO ₂ /Al ₂ O ₃ ratios are all 5.4, and example 4 is the NaY molecular sieve that makes by the present invention, and its grain diameter is 0.22 micron, and crystallization time is 24 hours, and comparative example 2 is NaY molecular sieve prepared by conventional directing agent, its crystal grain diameter is 0.63 microns, and the crystallization time reaches 32 hours (the latter crystallizes for 24 hours, and the crystallization is trace amount).

Table 2

Example 5

The preparation methods of the conventional directing agent and the improved directing _agent are the same as in Example 2, except that the addition of the improved directing agent is 1.0% (based on the total _Al2O3 moles in the system), and the proportion of the synthetic NaY molecular sieve is _3.6Na2O : _Al2 O ₃ : 9.8 _{SiO 2} : 202H ₂ O, crystallized for 14 hours, the analysis result of the obtained product was: SiO ₂ /Al ₂ O ₃ ratio 4.9; crystal grain diameter 0.15 micron.

Instances 6-9

The proportioning of directing agent, raw material and preparation method are the same as example 1, the addition of improved directing agent is 20% (in the system total Al ₂ O ₃ moles), the improved directing agent placement time is 1 hour according to the example number, 4 hours, 15 hours, 52 hours.

The ratio of synthetic NaY molecular sieve was 3.6Na ₂ O : Al ₂ O ₃ : 9.8 SiO ₂ : 200H ₂ O, and crystallized for 16 hours. The other steps were the same as Example 1. The analysis results of the product are shown in Table 3.

Comparative example 3

Except that the conventional directing agent is used to replace the improved directing agent, the proportioning, raw materials and preparation method of the directing agent are the same as in _Example 1, and the addition of the conventional directing agent is 20% (based on the total _Al2O3 moles in the system), and the synthetic NaY The proportioning of molecular sieve, raw material and preparation method are the same as Example 6, and the analysis result of product is shown in Table 3.

From the analysis results of Examples 6-9 and Comparative Example 3, it can be seen that the improved directing agent prepared according to Example 1 was placed for about 50 hours, and the crystal grains of the NaY molecular sieve obtained were still smaller than those of the NaY molecular sieve prepared by the conventional directing agent.

table 3

Instance 10

The ratio of the conventional directing agent, the raw materials and the preparation method are the same as in Example 1, and the specifications of the sodium silicate solution added to the conventional directing agent are the same as in Example 1, except that the amount added is 12.5% by volume. After the addition, it is left for 20 hours to obtain a clear and transparent The directing agent solution was improved, and its light transmittance was 85%. The proportion, raw materials and preparation method of the synthetic NaY molecular sieve were the same as in Example 2. The analysis results of the product obtained after crystallization for 34 hours are shown in Table 4.

Comparative example 4

Except that the conventional directing agent is used to replace the improved directing agent, other preparation steps are the same as in Example ₂ , the addition of the conventional directing agent is 5.0% (based on the total _Al2O3 moles in the system), crystallization for 32 hours, and the analysis of the resulting product The results are shown in Table 4.

As can be seen from Table 4: when the crystallization time was 34 hours, the SiO ₂ /Al ₂ O ₃ ratio and the grain size of the products of Example 2 and Example 10 were basically the same, while in the same time period of Comparative Example 4, the product The crystals are in trace amount, and can only be crystallized after 55 hours of crystallization, and the crystal grain diameter is 0.78 μm, as shown in Comparative Example 1.

Table 4

注※：对比例4在34小时内，产品的结晶为痕量。

Note ※: In Comparative Example 4, within 34 hours, the crystallization of the product was trace.

Example 11

Mix 50 milliliters of sodium silicate solution with the same raw material specifications as Example 1, 27 milliliters of high-alkaline sodium metaaluminate solution, and 3 milliliters of deionized water, stir at room temperature for 1 hour, and then stand and age in a water bath at 45°C for 12 hours to prepare A conventional directing agent with a light transmittance of 28% and a molar composition of 17.6Na ₂ O:Al ₂ O ₃ :19SiO ₂ :369H ₂ O was obtained.

The modulus is 2.0 and the concentration is 40.1% by weight, and 80 milliliters of sodium silicate solution (accounting for 50% of the total volume after adding) of 1.473 specific gravity is added in the above-mentioned conventional directing agent, and after 1 hour, a light transmittance of 86% is obtained. The clear and transparent improved directing agent solution was used after standing for 10 days. At this time, the light transmittance was 91%, and the molar composition was 40.4Na ₂ O:Al ₂ O ₃ :64.7SiO ₂ :710H ₂ O.

The raw material proportioning preparation method of the synthetic NaY molecular sieve is the same as Example 6, the addition of the improved directing agent is 5.0% (based on the total _Al2O3 moles in the system), the crystallization time is 12 hours, and the analysis results of _the obtained product are shown in the table 5.

Example 12

The modulus of the sodium silicate solution is 1.0, the concentration is 40.6% by weight, and the specific gravity is 1.549. The addition is 120 milliliters (accounting for 60% of the total volume after adding), and it is left for 15 days to obtain a light transmittance of 92%. The molar composition A clear and transparent improved directing agent solution of 72.3Na ₂ O:Al ₂ O ₃ :73.7SiO _{2 :} 903H ₂ O. In addition, other preparation steps are the same as Example 11, crystallization for 10 hours, and the analysis results of the obtained product are shown in Table 5.

From the analysis result of the NaY molecular sieve product of example 9,11,12 gained, can find out: the modulus of the sodium silicate solution that joins in the conventional directing agent reduces, and the service life of improving directing agent prolongs, and crystallization time shortens, and the product's The grains become smaller.

table 5

注：※硅酸钠溶液的模数＝SiO2/Na2O摩尔比

Note: ※The modulus of sodium silicate solution = SiO2/Na2O molar ratio

Instance 13

The improved directing agent prepared in Example 2 was heated to 95° C. for 30 minutes, and then lowered to normal temperature for use. Other technical formulas and preparation methods were the same as Example 4. The analysis results of the obtained product are shown in Table 6. From the product analysis results of Example 13, it can be seen that the improved directing agent can still maintain the activity of the directing agent after being treated at 95° C. for 30 minutes, and the performance of the product is equivalent to that of Example 4.

Example 14

The NaY synthesis formula and preparation method are the same as in Example 4, the conventional directing agent and the improved directing agent prepared according to Example 4 are added respectively, and the addition of the mixed directing agent is 5.0% (based on the _total Al in the system O ₃ moles), Wherein two kinds of directing agents respectively account for 2.0% and 3.0%, the analytical results of the products are shown in Table 6, as can be seen from the analytical results of the example 14 product: the NaY molecular sieve its crystallite size prepared by mixing the conventional directing agent with the improved directing agent It is between the grain sizes of NaY molecular sieves synthesized with two directing agents.

Table 6

Note: The mixed directing agent refers to the directing agent mixed with conventional directing agent and improved directing agent.

Instance 15

The preparation method of conventional directing agent and improved directing agent is the same as example 1, the synthetic formula of NaY molecular sieve is 4.4Na ₂ O: Al ₂ O ₃ : 10SiO ₂ : 182H ₂ O, the addition of improved directing agent is 5.% (based on system Table 7 shows the analysis results of the _obtained product after _{crystallization} for 6 hours.

Instance 16

The preparation method of conventional directing agent and improved directing agent is the same as Example 1, the synthetic formula of NaY molecular sieve is 3.0NaO ₂ : Al ₂ O ₃ : 6.5SiO ₂ : 170H ₂ O, the addition of improved directing agent is 5.0% (in the system Total Al ₂ O ₃ moles), crystallized for 10 hours, the analysis results of the obtained product are shown in Table 7.

It can be seen from Table 7 that the present invention can synthesize NaY molecular sieves with SiO ₂ /Al ₂ O ₃ ratio≤5 and small crystal grains.

Table 7

Claims (8)

1. a kind of preparation method of small-grain NaY molecular sieve adopts by sodium silicate solution, sodium metaaluminate solution, aluminum sulfate solution and directing agent solution to synthesize according to conventional NaY hydrothermal synthesis method, it is characterized in that said directing Agent solution is that sodium silicate solution is added in conventional directing agent to obtain light transmittance＞75% improved directing agent solution, the preparation steps of this small grain NaY molecular sieve are: (1) A sodium silicate solution with a modulus of 0.5-3.5 and a concentration of 20-65% by weight, a high alkali sodium metaaluminate solution with a caustic ratio of 10-12 and deionized water are mixed and stirred at 0-45°C for 0.5 -2 hours, then aged at 15-60°C for 6-30 hours, the light transmittance was less than 30%, and the molar composition was (13-36)Na ₂ O:Al ₂ O ₃ :(12-21)SiO ₂ : (250-800) H ₂ O conventional directing agent; (2) Add a sodium silicate solution with a modulus of 0.5-3.5 and a concentration of 20-65% by weight into the conventional directing agent prepared in (1) in an amount of 5-80% by volume, and place it at room temperature for 0.5-2 hours to obtain an improved directing agent solution with a light transmittance>75% and a molar composition of (12-180) _{Na2O : Al2O3} :(17-210) _SiO2 :(160-3100) _H2O ; (3) the sodium silicate solution _that modulus is 0.5-3.5, concentration is 20-65% by weight, improving directing agent solution, Al ₂ O Content is the aluminum sulfate solution of 0.085-0.095 g/ml and caustic ratio is 1.0 The low-alkali sodium metaaluminate solution of -3.0 carries out NaY hydrothermal synthesis according to the preparation method of conventional NaY molecular sieves, wherein the addition of the improved directing agent is _0.5-25 % (based on the total _Al2O3 moles in the system), stirring After 0.5-2 hours, heat up to 95-100°C, crystallize for 5-35 hours, filter, and dry to obtain NaY molecular sieve products with small grains. 2. The preparation method according to claim 1, characterized in that the modulus of the sodium silicate solution in (1) is 1.0-3.3. 3. The preparation method according to claim 1, characterized in that the concentration of the sodium silicate solution in (1) is 25-60% by weight. 4. The preparation method according to claim 1, characterized in that the molar composition of the conventional directing agent prepared in (1) is (15-19) Na ₂ O: Al ₂ O ₃ : (14-19) SiO ₂ : (300-380)H ₂ O. 5. The preparation method according to claim 1, characterized in that the mixing temperature in (1) is 5-40°C. 6. The preparation method according to claim 1, characterized in that the aging temperature in (1) is 20-40°C. 7. according to the said preparation method of claim 1, it is characterized in that the add-on of said sodium silicate solution in (2) is 10-70 volume %. 8. The preparation method according to claim 1, characterized in that the molar composition of the improved directing agent solution in (2) is (16-150) Na ₂ O: Al ₂ O ₃ : (20-180) SiO ₂ : (250-2500) _H2O . 9. The preparation method according to claim 1, characterized in that the improved directing agent solution in (2) can be stored at room temperature for 15 days. 10. The preparation method according to claim 1, characterized in that the added amount of the improved directing agent solution in (3) is 1.0-20% (based on the total moles of Al ₂ O ₃ in the system).