Preparation method of metallocene catalyst transmission electron microscope sample

Abstract

The invention discloses a metallocene catalyst transmission electron microscope sample preparation method, which comprises: S1, taking polyolefin catalyst powder in a glove box under inert gas protection, adding into a centrifuge tube, dropwise adding cyclohexane as a dispersion liquid, sealing the centrifuge tube, transferring the centrifuge tube out of the glove box in a vacuum transfer manner after the sealing is completed, performing ultrasonic dispersion; s2, after ultrasonic dispersion is finished, transferring the sample into the glove box in a vacuum transfer manner, dropwise adding the liquid in the centrifugal tube onto the copper mesh, and drying the copper mesh dropwise added with the sample by using a baking lamp at the drying temperature of 100-200 DEG C; and S3, after the copper net is cooled, the copper net is transferred into an electron microscope device in a vacuum transfer mode. The method can overcome the problem that the metallocene catalyst is sensitive to water and air, and the transmission electron microscope sample of the metallocene catalyst is obtained.

Description

Technical Field

[0001] The present invention belongs to the technical field of sample detection, and particularly relates to a method for preparing a transmission electron microscope sample of a metallocene catalyst. Background Art

[0002] In industrial production, catalysts play a very important role. Polyolefin catalyst products are the core of the downstream polyolefin polymerization technology and have high technical barriers. Common polyolefin catalysts mainly include Ziegler-Natta catalysts, metallocene catalysts, non-metallocene catalysts, bifunctional catalysts and other polyolefin composite catalysts.

[0003] The structure of the catalyst is directly related to its performance. Accurately determining the basic structure of the catalyst is of great significance for the high-quality research and development of polyolefin catalysts. The transmission electron microscope is a microscope with high resolution and high magnification, and is an important means for materials science research. It can provide information on the organizational structure, crystal structure and chemical composition of extremely fine materials. The resolution of the transmission electron microscope is 0.1-0.2 nm, and the magnification is tens of thousands to hundreds of thousands of times. The transmission electron microscope technology has become an important means for studying polyolefin catalysts. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a transmission electron microscope sample of a metallocene catalyst, which can overcome the problem that the metallocene catalyst is sensitive to water and air, and obtain a transmission electron microscope sample of the metallocene catalyst.

[0005] To achieve the above purpose, the present invention provides a method for preparing a transmission electron microscope sample of a metallocene catalyst, including the following steps:

[0006] S1, Take polyolefin catalyst powder into a centrifuge tube in a glove box protected by inert gas, add cyclohexane as a dispersion liquid, seal the centrifuge tube, and after sealing, transfer the centrifuge tube out of the glove box by vacuum transfer for ultrasonic dispersion;

[0007] S2, After the ultrasonic dispersion is completed, transfer it back into the glove box by vacuum transfer again, and drop the liquid in the centrifuge tube onto a copper mesh, and dry the copper mesh with the dropped sample with a baking lamp, and the drying temperature is 100-200 °C;

[0008] S3, After the copper mesh is cooled, transfer it to the electron microscope device by vacuum transfer.

[0009] In the method for preparing a transmission electron microscope sample of the metallocene catalyst of the present invention, the inert gas is one or more of nitrogen, helium, argon, carbon dioxide and ethane.

[0010] In the method for preparing a transmission electron microscope sample of the metallocene catalyst of the present invention, the inert gas is nitrogen.

[0011] The method for preparing a transmission electron microscopy sample of the metallocene catalyst described in the present invention, the frequency of ultrasonic dispersion is 20 - 120 Hz, and the dispersion time is 5 - 10 min.

[0012] The method for preparing a transmission electron microscopy sample of the metallocene catalyst described in the present invention, the copper grid is one or several of a carbon support film, an ultra-thin carbon support film, a pure carbon microgrid, and a lace microgrid, preferably an ultra-thin carbon support film.

[0013] The method for preparing a transmission electron microscopy sample of the metallocene catalyst described in the present invention, the drying time in step S2 is 10 - 20 min.

[0014] The metallocene catalyst described in the present invention, the metallocene catalyst refers to a catalytic system composed of a Group IVB transition metal element complex as the main catalyst and an alkylaluminoxane or an organic boride as the cocatalyst.

[0015] Advantages of the present invention:

[0016] The present invention provides a method for preparing and transferring a transmission electron microscopy sample of a water- and oxygen-sensitive metallocene catalyst, which can quickly obtain high-resolution transmission electron microscopy images of polyolefin catalysts. The method is simple and reliable, solves the problem of microscopic scale characterization of metallocene catalysts, and can be used in the fields of catalyst structure and performance research, catalyst formulation optimization, and deactivation reason analysis. Description of the Drawings

[0017] Figure 1 The transmission electron microscopy image of the catalyst obtained by the method described in Example 1;

[0018] Figure 2 The transmission electron microscopy image of the catalyst obtained by the method described in Example 2;

[0019] Figure 3 The transmission electron microscopy image of the catalyst obtained by the method described in Example 3;

[0020] Figure 4 The transmission electron microscopy image of the catalyst obtained by the method described in Comparative Example 1;

[0021] Figure 5 The transmission electron microscopy image of the catalyst obtained by the method described in Comparative Example 2;

[0022] Figure 6 The transmission electron microscopy image of the catalyst obtained by the method described in Comparative Example 3. Detailed Embodiments

[0023] The present invention will be specifically described below by way of examples. It is necessary to point out here that the following examples are only used to further illustrate the present invention and should not be construed as limiting the protection scope of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above content of the present invention.

[0024] Example 1

[0025] Select the metallocene catalyst (Grace AC103D) as the analysis sample. Under the protection of nitrogen in the glove box, take 0.5 - 1 mg of the metallocene catalyst sample and place it at the bottom of the centrifuge tube, and drop 1 - 2 ml of cyclohexane; seal the centrifuge tube opening twice with paraffin sealing film, take out the centrifuge tube from the glove box by vacuum transfer, and ultrasonically disperse the sample for 10 min at a frequency of 80 Hz, then transfer the centrifuge tube back to the glove box protected by nitrogen by vacuum transfer. Open the centrifuge tube, take a drop of the supernatant and drop it on the ultra-thin carbon film, and dry it with a baking lamp at 100 °C for 15 min. Wait for the ultra-thin carbon film to cool, put it into the water- and oxygen-isolated electron microscope sample rod, put on the protective sleeve and take it out of the glove box, load it into the electron microscope, pre-pump the vacuum for 45 min, and then push the sample into the electron microscope vacuum system. The shooting effect is shown in Figure 1 , and clear lattice fringes of the metallocene active phase can be seen.

[0026] Example 2

[0027] Select the metallocene catalyst (Grace AC103D) as the analysis sample. Under the protection of argon in the glove box, take 0.5 - 1 mg of the metallocene catalyst sample and place it at the bottom of the centrifuge tube, and drop 1 - 2 ml of cyclohexane; seal the centrifuge tube opening twice with paraffin sealing film, take out the centrifuge tube from the glove box by vacuum transfer, and ultrasonically disperse the sample for 10 min at a frequency of 40 Hz, then transfer the centrifuge tube back to the glove box protected by nitrogen by vacuum transfer. Open the centrifuge tube, take a drop of the supernatant and drop it on the ultra-thin carbon film, and dry it with a baking lamp at 150 °C for 10 min. Wait for the ultra-thin carbon film to cool, put it into the water- and oxygen-isolated electron microscope sample rod, put on the protective sleeve and take it out of the glove box, load it into the electron microscope, pre-pump the vacuum for 45 min, and then push the sample into the electron microscope vacuum system. The shooting effect is shown in Figure 2 , and clear lattice fringes of the metallocene active phase can be seen.

[0028] Example 3

[0029] Select the metallocene catalyst (Grace AC103D) as the analysis sample. Under the protection of nitrogen in the glove box, place 0.5 - 1 mg of the metallocene catalyst sample at the bottom of a centrifuge tube, and add 1 - 2 ml of cyclohexane dropwise; seal the centrifuge tube opening twice with paraffin sealing film. After taking the centrifuge tube out of the glove box by vacuum transfer, disperse the sample by ultrasonic treatment at a frequency of 120 Hz for 5 min. Transfer the centrifuge tube back into the nitrogen - protected glove box by vacuum transfer. Open the centrifuge tube, take a drop of the supernatant and drop it on the ultra - thin carbon film, and dry it with a baking lamp at 200 °C for 20 min. After the ultra - thin carbon film cools down, place it in a water - and oxygen - isolated electron microscope sample rod, put on the protective sleeve and take it out of the glove box, and load it into the electron microscope. After pre - evacuating for 45 min, push the sample into the electron microscope vacuum system. The shooting effect is shown in Figure 3 , and the lattice fringes of the clear metallocene active phase can be seen.

[0030] Comparative Example 1

[0031] Select the metallocene catalyst (Grace AC103D) as the analysis sample. Under the protection of nitrogen in the glove box, place 0.5 - 1 mg of the metallocene catalyst sample at the bottom of a centrifuge tube, and add 1 - 2 ml of absolute ethanol dropwise; seal the centrifuge tube opening twice with paraffin sealing film. After taking the centrifuge tube out of the glove box by vacuum transfer, disperse the sample by ultrasonic treatment at a frequency of 80 Hz for 10 min. Transfer the centrifuge tube back into the nitrogen - protected glove box by vacuum transfer. Open the centrifuge tube, take a drop of the supernatant and drop it on the ultra - thin carbon film, and dry it with a baking lamp at 100 °C for 15 min. After the ultra - thin carbon film cools down, place it in a water - and oxygen - isolated electron microscope sample rod, put on the protective sleeve and take it out of the glove box, and load it into the electron microscope. After pre - evacuating for 45 min, push the sample into the electron microscope vacuum system. The structure of the metallocene active phase in the sample is damaged and there is no lattice structure.

[0032] Comparative Example 2

[0033] Select the metallocene catalyst (Grace AC103D) as the analysis sample. Under the protection of nitrogen in the glove box, place 0.5 - 1 mg of the metallocene catalyst sample at the bottom of a centrifuge tube, and add 1 - 2 ml of cyclohexane dropwise; seal the centrifuge tube opening twice with paraffin sealing film. After taking the centrifuge tube out of the glove box by vacuum transfer, disperse the sample by ultrasonic treatment at a frequency of 80 Hz for 10 min. Transfer the centrifuge tube back into the nitrogen - protected glove box by vacuum transfer. Open the centrifuge tube, take a drop of the supernatant and drop it on the ultra - thin carbon film, and dry it with a baking lamp at 70 °C for 15 min. The sample shows a solvent ring and cannot be characterized Figure 5 , and a solvent ring appears around the sample.

[0034] Comparative Example 3

[0035] Select the metallocene catalyst (Grace AC103D) as the analysis sample. Under the protection of nitrogen in the glove box, place 0.5 - 1 mg of the metallocene catalyst sample at the bottom of the centrifuge tube, and add 1 - 2 ml of cyclohexane dropwise; seal the centrifuge tube opening twice with paraffin sealing film. After taking the centrifuge tube out of the glove box by vacuum transfer, ultrasonically disperse the sample at a frequency of 80 Hz for 10 min. Transfer the centrifuge tube back to the nitrogen-protected glove box by vacuum transfer again. Open the centrifuge tube and take a drop of the supernatant and drop it on the ultra-thin carbon film, and dry it with a baking lamp at 240 °C for 15 min. The shooting effect is shown in Figure 6 , Figure 6 The structure of the active phase of the metallocene in the sample is damaged, and only a small amount of lattice structure appears.

[0036] Of course, the present invention can also have many other embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding changes and deformations should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a metallocene catalyst transmission electron microscopy sample, characterized in that: The following steps are involved: S1, in a glove box protected by inert gas, taking polyolefin catalyst powder into a centrifuge tube, adding cyclohexane as a dispersion liquid, sealing the centrifuge tube, and after sealing, transferring the centrifuge tube out of the glove box by vacuum transfer, and performing ultrasonic dispersion; S2, after the ultrasonic dispersion is completed, the sample is moved into the glove box again by vacuum transfer, and the liquid in the centrifuge tube is dripped onto the copper mesh, and the copper mesh with the sample dripped is dried with a drying lamp at a drying temperature of 100-200°C; S3, after the copper mesh is cooled, it is transferred to the electron microscope device by vacuum transfer.

2. The method for preparing metallocene catalyst transmission electron microscopy samples according to claim 1, characterized in that: The inert gas is one or more of nitrogen, helium, argon, carbon dioxide and ethane.

3. The method for preparing metallocene catalyst transmission electron microscopy samples according to claim 1, characterized in that: The inert gas is nitrogen.

4. The method for preparing metallocene catalyst transmission electron microscope samples according to claim 1, characterized in that: The frequency of the ultrasonic dispersion is 20-120 Hz, and the dispersion time is 5-10 min.

5. The method for preparing metallocene catalyst transmission electron microscopy samples according to claim 1, characterized in that: The copper mesh is one or more of a carbon support film, an ultra-thin carbon support film, a pure carbon micro-grid and a lace micro-grid, preferably an ultra-thin carbon support film.

6. The method for preparing metallocene catalyst transmission electron microscopy samples according to claim 1, characterized in that: The drying time in step S2 is 10-20 minutes.

7. The method for preparing metallocene catalyst transmission electron microscope samples according to claim 1, characterized in that: The metallocene catalyst refers to a catalyst system composed of a complex of a transition metal element of group IVB as a main catalyst and an alkylaluminoxane or an organic boron compound as a co-catalyst.

Images