CN115155518A - A kind of high-strength molecular sieve and preparation method thereof - Google Patents

Abstract

The invention provides a high-strength molecular sieve and a preparation method thereof. The preparation method includes placing the shaped molecular sieve in a slow-flowing glass fiber aqueous solution, and utilizing the circulating fluidity of the liquid to drive the molecular sieve to suspend and rotate, so that the micron-scale glass fibers are evenly wrapped in the glass fiber. The surface of the shaped molecular sieve is washed, dried and roasted to obtain a shaped molecular sieve wrapped with glass fibers; the shaped molecular sieve wrapped with glass fibers is subjected to secondary crystallization, and the solid product is washed, dried and roasted to obtain a high-strength molecular sieve. The high-strength molecular sieve provided by the present invention not only has higher mechanical strength and lower wear rate than the shaped molecular sieve prepared by the conventional method, but also has smoother pores and does not cause problems such as the reduction of the activity of the molecular sieve due to molding.

Description

A kind of high-strength molecular sieve and preparation method thereof

technical field

The invention belongs to the technical field of petrochemical industry, and in particular relates to a high-strength molecular sieve and a preparation method thereof, which are applied to gas/liquid adsorption separation and the like.

Background technique

Due to its special pore structure and chemical properties, molecular sieves are widely used as catalysts and adsorbents in acid-catalyzed reactions and gas/liquid separation, dehydration, desulfurization and other petrochemical processes. In the process of industrial application, molecular sieves need to be regenerated frequently. For example, due to the strong acidity of molecular sieves, when catalyzing various alkane reactions, it is particularly easy to coke and generate carbon, which will deactivate the catalyst. This requires the catalyst to be periodically regenerated by burning carbon. Pressure swing adsorption is to use the difference in the adsorption characteristics of different gases on the adsorbent, as well as the characteristics of the adsorption capacity changing with the pressure change, to realize the separation or purification of the gas through the pressure change, so the molecular sieve as the adsorbent needs to face the pressure alternately rise and fall . In addition, molecular sieves for gas dehydration or desulfurization also need regular dehydration or desulfurization regeneration after adsorption saturation. All these regeneration or pressure swing processes will cause damage to the structure of the molecular sieve, resulting in the loss of molecular sieve pulverization, and the catalytic or adsorption performance also decreases with the increase of the number of regenerations. Therefore, the development of high-strength molecular sieves is beneficial to prolong the service life of molecular sieve adsorbents/catalysts, and has important practical significance.

In order to improve the mechanical strength of the molecular sieve, it is usually necessary to add a binder, a structural enhancer or an organic solvent to the molecular sieve during the molding process of the molecular sieve to improve the strength of the shaped molecular sieve. There have been many literature reports on the preparation of high-strength molecular sieves. For example, the patent CN2011103715680 introduces the addition of structural reinforcing agents and binders to molecular sieves. The obtained molecular sieves have significantly higher lateral pressure than ordinary molecular sieves, and at the same time, the wear rate is significantly reduced. . Patent CN2006800294206 reports a preparation method for improving the abrasion resistance of methanol-to-olefin catalysts. The method is to add a binder containing sodium silicate and acid alum to SAPO molecular sieve to increase the strength. Patent CN1044980C is to immerse molecular sieve or molecular sieve catalyst in an organic solution containing silicon compounds, aluminum compounds, zirconium compounds, etc. for a period of time, and then recover the organic solvent. The obtained molecular sieve is dried and roasted to obtain a finished product, and its mechanical strength is increased improve. Patent US3354096 uses phosphate aqueous solution to treat molecular sieve, and the mechanical strength of the finished molecular sieve is improved to a certain extent.

However, while improving the strength of the molecular sieve in the prior art method, it is difficult to ensure that the activity of the molecular sieve is not affected, and the addition of components such as structural enhancers and binders will block the micropores of the molecular sieve to a certain extent and reduce the activity of the molecular sieve. Therefore, under the premise of not affecting the activity of the molecular sieve as a catalyst or an adsorbent, the stability and strength of the molecular sieve can be further improved to better meet the requirements of industrial applications.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a high-strength molecular sieve with good mechanical strength and a preparation method thereof without affecting the activity of the molecular sieve. Glass fiber is an inorganic non-metallic material with excellent performance, which has the advantages of strong heat resistance, good corrosion resistance and high mechanical strength. The invention utilizes the slow flow of the liquid to evenly wrap the micron-scale glass fibers in the solution on the surface of the shaped molecular sieve, and then makes the glass fibers form a strong interaction with the shaped molecular sieve material through secondary crystallization to enhance the strength of the molecular sieve material; at the same time, the original The formed molecular sieve dissolves in the silicon source or aluminum source added as a binder during the forming process and participates in the secondary crystallization process, resulting in smoother pores.

The technical scheme of the present invention is as follows:

A preparation method of high-strength molecular sieve, comprising the steps:

The first step: preparation of glass fiber wrapped molecular sieve

Put the molded molecular sieve into the slow-flowing glass fiber aqueous solution, and use the circulating fluidity of the liquid to drive the molded molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molded molecular sieve, and the glass fiber wrap is obtained by washing, drying and roasting. forming molecular sieve; the flow rate of the glass fiber aqueous solution is 0.01-0.2m/s; the second step: secondary crystallization of molecular sieve

The shaped molecular sieve wrapped by the glass fiber is subjected to secondary crystallization, so that the shaped molecular sieve and the glass fiber form a strong interaction, and the solid product is washed, dried and roasted to obtain a high-strength molecular sieve.

The shaped molecular sieves are shaped molecular sieves that can be prepared by engineers familiar with the art, and the shapes include spherical, bar-shaped, special-shaped, microspheres and other shapes; the raw materials of the shaped molecular sieves include aluminosilicate molecular sieves and binders ; Further, the aluminosilicate molecular sieves are A-type molecular sieves, X-type molecular sieves, Y-type molecular sieves, Beta molecular sieves or ZSM series molecular sieves.

The binder includes silicon element and aluminum element.

The monofilament diameter of the glass fiber is below 15 microns, and further, the monofilament diameter of the glass fiber is below 6 microns.

The mass percentage of the glass fiber aqueous solution is 0.1%-10%; the time of the shaped molecular sieve in the glass fiber aqueous solution is 1-50 hours.

Step 1 also includes recycling the glass fiber aqueous solution for reuse.

In step 1, the drying temperature is 100-120°C, and the drying time is 12-24 hours; the roasting temperature is 500-600°C, and the roasting time is 5-12 hours.

Engineers familiar with the field can use the synthesis methods reported in the existing published literature and patents, select the synthesis formula and conditions of the corresponding molecular sieve, and perform secondary hydrothermal crystallization of the glass fiber-coated molecular sieve.

In step 2, the washing process includes washing the solid product with deionized water to pH=8-9; the drying temperature is 100-120 ° C, and the drying time is 12-24 hours; the roasting temperature is 500-600 ° C, and the roasting time is 5-12 hours.

The present invention also provides a high-strength molecular sieve obtained by the above method.

Compared with the prior art, the beneficial effects of the present invention are as follows:

Using the fluidity of the liquid, the highly dispersed micron glass fibers, which have high mechanical strength, are coated on the surface of the molded molecular sieve, and then undergo secondary hydrothermal crystallization, so that the glass fiber and the molded molecular sieve form a strong interaction. Moreover, in the hydrothermal crystallization process, the silicon source or aluminum source added as a binder in the forming process of the original molecular sieve can be dissolved to participate in the secondary crystallization process. Therefore, the high-strength molecular sieve provided by the present invention not only has higher mechanical strength and lower wear rate than the shaped molecular sieve prepared by the conventional method, but also has smoother pores and will not cause problems such as the decrease of the activity of the molecular sieve due to molding.

Detailed ways

Example 1

Weigh 10g of industrial grade spherical 13X molecular sieve (5-6mm) and put it into a 2% (mass percent) glass fiber aqueous solution with a flow rate of 0.1m/s slow-flowing, the glass fiber monofilament diameter is 8 microns, soaked for 8 hours, using liquid The circulating fluidity drives the molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molecular sieve. The molecular sieves were taken out, dried at 110°C for 10 hours, and calcined at 540°C for 5 hours. Put 50g of 0.8M NaOH aqueous solution and 10g of spherical 13X molecular sieves coated with glass fibers into a high-pressure hydrothermal crystallization kettle, and crystallized at 90° C. for 24 hours. The obtained solid product was washed with deionized water to pH=8-9. After drying at 110°C for 10 hours, and calcining at 540°C for 6 hours, high-strength spherical 13X molecular sieves (denoted as A) are obtained.

Example 2

Weigh 10g of industrial grade spherical 13X molecular sieve (0.5-0.6mm) and put it into a 0.12% glass fiber aqueous solution with a slow flow rate of 0.02m/s. The diameter of the glass fiber monofilament is 4 microns, soaked for 2.5 hours, and the circulating flow of the liquid is used. Sex drives the molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molecular sieve. The molecular sieves were taken out, dried at 110°C for 10 hours, and calcined at 540°C for 5 hours. 50g of 0.3M NaOH aqueous solution and 10g of spherical 13X molecular sieves coated with glass fibers were put into a high-pressure hydrothermal crystallization kettle, and crystallized at 90° C. for 6 hours. The obtained solid product was washed with deionized water to pH=8-9. After drying at 110°C for 10 hours, and calcining at 540°C for 6 hours, high-strength spherical 13X molecular sieves (denoted as B) are obtained.

Example 3

Weigh 10g of industrial-grade strip ZSM-5 molecular sieve (Φ3×8mm) into a 5% glass fiber aqueous solution with a flow rate of 0.15m/s slowly flowing, the glass fiber monofilament diameter is 12 microns, soak for 5 hours, and use the liquid The circulating fluidity drives the molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molecular sieve. The molecular sieves were taken out, dried at 110°C for 10 hours, and calcined at 540°C for 5 hours. Put 50g of 0.6% tetrapropylammonium hydroxide alkali solution, 0.06g of alumina and 10g of bar ZSM-5 molecular sieves coated with glass fibers into a high-pressure hydrothermal crystallization kettle, and crystallized at 170 ° C for 24 hours, the obtained solid The product was washed with deionized water to pH=8-9, dried at 110°C for 10 hours, and calcined at 540°C for 6 hours to obtain high-strength strip ZSM-5 molecular sieve (denoted as C).

Example 4

Weigh 10g of industrial grade bar-shaped Beta molecular sieve (Φ3×10mm) and put it into a 4% glass fiber aqueous solution with a flow rate of 0.15m/s. Sex drives the molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molecular sieve. The molecular sieves were taken out, dried at 110°C for 10 hours, and calcined at 540°C for 5 hours. Put 50g of 0.6% tetraethylammonium hydroxide alkali solution, 0.06g of alumina and 10g of bar-shaped Beta molecular sieves coated with glass fibers into a high-pressure hydrothermal crystallization kettle, and crystallized at 150 ° C for 24 hours. Washed with deionized water to pH=8-9, dried at 110° C. for 10 hours, and calcined at 540° C. for 6 hours to obtain high-strength strip-shaped Beta molecular sieve (denoted as D).

Example 5

Weigh 10g of industrial grade spherical 3A molecular sieve (3-5mm) and put it into a 2% glass fiber aqueous solution with a flow rate of 0.08m/s. Drive the molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molecular sieve. The molecular sieves were taken out, dried at 110°C for 10 hours, and calcined at 540°C for 5 hours. Put 50g of 0.5M NaOH aqueous solution, 0.01g of sodium metaaluminate and 10g of spherical 3A molecular sieve coated with glass fiber into a high-pressure hydrothermal crystallization kettle, and crystallized at 100 ° C for 4 hours, and the obtained solid product was washed with deionized water to pH=8-9, drying at 110° C. for 10 hours, and calcining at 540° C. for 6 hours to obtain high-strength spherical 3A molecular sieve (denoted as E).

Example 6

Weigh 10g of industrial-grade strip-shaped NaY molecular sieve (Φ3×10mm) into a 2% glass fiber aqueous solution with a flow rate of 0.1m/s, the diameter of the glass fiber monofilament is 10 microns, soak for 10 hours, and use the circulating flow of the liquid Sex drives the molecular sieve to suspend and rotate, so that the micron glass fibers are evenly wrapped on the surface of the molecular sieve. The molecular sieves were taken out, dried at 110°C for 10 hours, and calcined at 540°C for 5 hours. Put 50g 0.8M NaOH aqueous solution and 10g strip NaY molecular sieve coated with glass fiber into the high pressure hydrothermal crystallization kettle, and crystallize at 90 DEG C for 8 hours, the obtained solid product is washed with deionized water to pH=8-9, After drying at 110°C for 10 hours, and calcining at 540°C for 6 hours, high-strength strip NaY molecular sieves (denoted as F) are obtained.

Test Example 1

The lateral compressive strength and wear rate of the above samples were measured respectively. As shown in Table 1, the lateral compressive strength and wear rate of the original industrial sample and each sample (A-F) prepared by the present invention are listed. It can be seen that the present invention is prepared. The molecular sieves have higher mechanical strength and lower wear rate than industrial shaped molecular sieves prepared by conventional methods.

Table 1 Lateral compressive strength and wear rate of samples

Test case 2

Material texture measurements were performed on technical grade spherical 13X (5-6mm and 0.5-0.6mm) and Examples 1-2 (A and B) by nitrogen physisorption, and the results are shown in Table 2. As shown in the data in the table, the specific surface area, pore volume and other data of the formed molecular sieve prepared by this method and the original formed molecular sieve have a certain degree of increase, so that the pores are more unobstructed than the original molding material.

Table 2 Material texture of industrial grade spherical 13X (5-6mm and 0.5-0.6mm) and molecular sieve products of Examples 1-2 (A and B)

Claims (7)

1. A preparation method of a high-strength molecular sieve is characterized by comprising the following steps: the method comprises the following steps:

the first step is as follows: preparation of glass fiber wrapped molecular sieve

Placing the formed molecular sieve into a slow flowing glass fiber aqueous solution, driving the formed molecular sieve to suspend and rotate by utilizing the circulating fluidity of liquid, uniformly wrapping micron-sized glass fibers on the surface of the formed molecular sieve, and washing, drying and roasting to obtain the formed molecular sieve wrapped by the glass fibers; the flow rate of the glass fiber aqueous solution is 0.01-0.2m/s;

the second step is that: secondary crystallization of molecular sieve

And (3) carrying out secondary crystallization on the formed molecular sieve wrapped by the glass fiber, and washing, drying and roasting the solid product to obtain the high-strength molecular sieve.

2. The method of claim 1, wherein the step of preparing a high strength molecular sieve comprises: the raw materials of the formed molecular sieve comprise an aluminosilicate molecular sieve and a binder.

3. The method of claim 2, wherein the step of preparing a high strength molecular sieve comprises: the aluminosilicate molecular sieve is an A-type molecular sieve, an X-type molecular sieve, a Y-type molecular sieve, a Beta molecular sieve or a ZSM series molecular sieve.

4. The method of claim 1, wherein the step of preparing a high strength molecular sieve comprises: the monofilament diameter of the glass fiber is less than 15 microns.

5. The method of claim 1, wherein the step of preparing a high strength molecular sieve comprises: the mass percent of the glass fiber aqueous solution is 0.1-10%; the time of the formed molecular sieve in the glass fiber aqueous solution is 1-50 hours.

6. The method of claim 1, wherein the step of preparing a high strength molecular sieve comprises: the first step also comprises the recycling of the glass fiber aqueous solution.

7. A high strength molecular sieve obtainable by the process of claim 1.