MXene-loaded polyethylene catalyst and preparation method thereof

Abstract

The invention discloses a catalyst for catalyzing ethylene polymerization, a preparation method of the catalyst and a method for preparing polyethylene by using the catalyst. According to the ethylene polymerization catalyst for catalyzing ethylene polymerization, an active component of the ethylene polymerization catalyst is loaded on the surface of MXene, the catalytic component is halide of Ti (OR1) pX (4-p), and in the formula, R1 is any one of C1-C20 alkyl, aryl or aralkyl; x is halogen; p is 0 < = plt; 4 is an integer. The catalyst active component is loaded on the surface of MXene, and the MXene / polyethylene composite material is obtained through in-situ ethylene polymerization, so that the dispersibility of MXene in polyethylene is good, the content of MXene in polyethylene can reach 0.1-3%, the mechanical property of polyethylene is remarkably improved, and the conductivity and antistatic property of polyethylene are also remarkably improved.

Description

Technical Field

[0001] The present invention relates to a catalyst for catalyzing ethylene polymerization, a method for preparing the catalyst, and a method for preparing polyethylene using the catalyst. More specifically, it relates to a MXene-loaded polyethylene catalyst for preparing MXene / polyethylene by in-situ polymerization. Background Art

[0002] Polyethylene is the fastest-growing lightweight polyolefin material. With the rapid advancement of science and technology, the demands on the performance of polyethylene materials are becoming increasingly stringent. For example, polymers are expected to exhibit both excellent toughness and high hardness; they must be both heat-resistant and easy to process and mold; and they must offer both excellent performance and affordability. A single polyethylene material often fails to meet these diverse demands. In recent years, research on polyethylene modification has garnered increasing attention and has become a key avenue for developing new, high-performance polyethylene materials. Among these, the preparation of nanomaterial / polymer composites through direct compounding or in-situ polymerization has become a key area of ​​polymer modification. Previously, researchers used rigid particles to modify polymers, hoping to achieve polyethylene composites with enhanced stiffness and toughness. However, achieving these performance requirements requires the use of large amounts of these traditional rigid particle fillers, which inevitably compromises the mechanical and processing properties of the polymers. The emergence of MXenes offers new avenues for polymer modification.

[0003] MXene is a new type of two-dimensional material belonging to transition metal carbon / nitride (TMC / TMN), whose precursor is MAX phase. The general formula of MAX is M n+1 AX n , where n = 1 ~ 3), M represents early transition metals, such as Sc, Ti, Zr, V, Nb, Cr, Ta and Mo; A usually represents chemical elements of the third and fourth main groups, such as Al or Si; X represents C or N elements. In the MAX phase, X atoms are filled into the octahedral structure formed by the close stacking of M atoms, while A atoms are located between the layers of MX. Due to the weak bonding between the A atomic layer and the MX atomic layer, MX can be obtained by selectively etching the A atomic layer. Since the MX product has a "graphene-like" structure and properties, it is named MXene. MXene materials have excellent metallic conductivity, good hydrophilicity, very high volumetric capacity and excellent mechanical strength. In addition, the rich -F, -O and / or -OH groups on the surface of MXene make it easy to achieve surface functionalization. Ti3C2T synthesized by etching element A in Ti3AlC2 with hydrofluoric acid (HF) x It is the first MXene to be successfully etched, and the etched Ti3C2T xThe surface contains abundant functional groups (T x are -F, -O and -OH).

[0004] Currently, MXene / polyethylene composites are primarily prepared by blending modified MXene with polyethylene. For example, CN202010637070.3 reports that the dispersion of modified MXene on the surface of modified ultra-high molecular weight ethylene improves its conductivity, significantly enhancing its antistatic properties and electromagnetic shielding capabilities. However, the modified MXene has limited adhesion to the surface of modified ultra-high molecular weight ethylene, and the MXene easily falls off, affecting its service life. CN202310822189.1 reports on flame-retardant, UV-resistant modified lignin hybrid MXene / polyethylene composites and their preparation methods. The preparation method of this material includes: reacting lignin, urea, and phosphoric acid to produce a lignin-based flame retardant (LNP); further hydrothermal hybridization with MXene prepared by etching Ti2AlC3 (MAX) to produce an MX@LNP flame retardant; compounding the MX@LNP flame retardant with ammonium polyphosphate (APP) to produce a flame retardant (MA); and melt-compounding the MA with polyethylene to produce a flame-retardant, UV-resistant, phosphorus-nitrogen-modified lignin hybrid MXene / polyethylene composite material. Compared with existing technologies, the flame-retardant, UV-resistant modified lignin hybrid MXene / polyethylene composite material obtained by this invention exhibits excellent flame retardancy, UV resistance, and mechanical properties, with excellent overall performance, making it suitable for a wide range of applications. However, the MXene in this composite material prepared by this method has limited dispersibility, which limits its performance improvement. Summary of the Invention

[0005] The present invention provides a catalyst for catalyzing ethylene polymerization and a method for preparing the catalyst, which can overcome the shortcomings of the prior art.

[0006] The present invention provides an ethylene polymerization catalyst for catalyzing ethylene polymerization, wherein the active component of the ethylene polymerization catalyst is loaded on the surface of MXene, wherein the catalytic component is Ti(OR1) p X （4－p） Halides, where R1 is C1~C 20 any one of an alkyl group, an aryl group or an aralkyl group; X is a halogen; and p is an integer of 0≦p<4.

[0007] The method for preparing the ethylene polymerization catalyst for catalyzing ethylene polymerization of the present invention is: 1) Add MAX phase solid powder and high concentration NaOH solution into the autoclave, blow out the air with N2 and seal it, then fully react at high temperature. After the reaction is completed, remove the upper high concentration NaOH, stir and wash it with deionized water, separate the suspension, collect the precipitate and dry it to obtain MXene. The general formula of MAX is M n+1 AX n, wherein n = 1 to 3, M is any transition metal, preferably any one of Sc, Ti, Zr, V, Nb, Cr, Ta or Mo; A is any element of the third or fourth main group except carbon, and X is C or N; 2) The obtained MXene is dispersed in an inert solvent to form a suspension. The suspension is refluxed at -50 to 10 °C with the catalytic component titanium for 1 to 5 hours to obtain a MXene-supported polyethylene catalyst. The catalytic component titanium is of the general formula Ti(OR1) p X （4－p） Provided by titanium halide, where R1 is C1~C 20 alkyl, aryl or aralkyl; X is a halogen; p is an integer of 0≦p<4, and the molar ratio of MXene to titanium is 1:5 to 1:100.

[0008] Preferably, in the method for preparing an ethylene polymerization catalyst for catalyzing ethylene polymerization of the present invention, M in step 1) is any one of Ti, Ta, Nb or Mo. More preferably, in the method for preparing an ethylene polymerization catalyst for catalyzing ethylene polymerization of the present invention, MAX in step 1) is any one of Ti3AlC2, Mo2AC, Nb3AlC4, Ta3AlC4 or Ti3AlCN, the titanium halide is titanium tetrachloride, the molar ratio of MXene to titanium is 1:10 to 1:50, A is Al, and X is C; and the inert solvent used in step 2) is toluene.

[0009] The catalyst of the present invention can be used to catalyze the polymerization of ethylene using various methods in the prior art, without particular limitation. The present invention particularly provides an embodiment of ethylene slurry polymerization. The specific method is: 1) After the reaction vessel is fully purged with nitrogen and ethylene, 0.3 kg of hexane is first added, followed by 1 g of catalyst and 10 mL of co-catalyst triethylaluminum; 2) Ethylene is continuously introduced into the reaction vessel, the ethylene pressure is controlled at 0.2-1.5 MPa, the polymerization temperature is 0-80°C, and the reaction pressure is controlled at 0.8 MPa. After the polymerization reaction is completed, the unreacted ethylene is vented and the solvent is removed to obtain a MXene / polyethylene composite material.

[0010] Preferably, the ethylene slurry polymerization method of the present invention is to continuously introduce ethylene into the reaction vessel, control the ethylene pressure at 0.5-1.0 MPa, polymerize at 20-70°C, and preferably use hexane as the alkane solvent.

[0011] Compared to existing technologies, this invention loads the active catalyst components onto the surface of MXene and uses in-situ ethylene polymerization to produce a MXene / polyethylene composite. This allows for excellent dispersion of the MXene in the polyethylene, with the MXene content in the polyethylene reaching 0.1% to 3%. This significantly improves not only the mechanical properties of the polyethylene but also its electrical conductivity and antistatic properties. In contrast, existing technology (2020106370703) physically mixes MXene and polyethylene to produce a composite. However, the MXene has poor dispersion in the polyethylene, resulting in insignificant improvements in the mechanical and electrical properties of the polyethylene. DETAILED DESCRIPTION

[0012] Examples of the present invention and comparative examples are provided below. Example

[0013] (1) Ti3C2T x (MXene) material preparation (1) Weigh 82.5 g of NaOH and dissolve it thoroughly in 75 mL of deionized water. Weigh 2 g of Ti3AlC2 solid powder and 50 mL of NaOH solution into a 100 mL autoclave, blow out the air with N2, and seal. Heat in an electric blast drying oven for 12 h at a reaction temperature of 270 °C. Remove the Al in Ti3AlC2 with NaOH to obtain Ti3C2T x (T x are -F, -O and -OH).

[0014] (2) After the hydrothermal treatment is completed, pour out the high-concentration NaOH etching solution on the top, wash out the black suspension at the bottom, and let it stand for 10 minutes. Add a large amount of deionized water and stir thoroughly and place it in an ultrasonic cleaner to wash away the Ti3C2T x After the ultrasonic treatment, the suspension was poured into a centrifuge tube and centrifuged. The bottom precipitate was washed with deionized water and centrifuged again. The above operation was repeated several times until the pH of the suspension was about 7. The precipitate at the bottom of the centrifuge tube was washed with 95% ethanol and collected in a beaker. It was dried in a blast drying oven at 50 °C to obtain Ti3C2T x (T x is -OH or -O).

[0015] (2) Catalyst loading (1) Take 1.5 g of MXene and put it into a flask, add 100 mL of hexane, and sonicate in an ultrasonic bath for 3 hours to obtain a MXene dispersion; (2) Replace the flask with nitrogen three times, cool the dispersion to -30 °C, and slowly add 20 mL of TiCl4, controlling the reaction temperature to be no higher than 0 °C; (3) After adding TiCl4, slowly raise the temperature to 120℃ and react for 2 hours; (4) After the reaction is completed, cool to room temperature and extract the upper liquid after the solid is completely precipitated; wash the lower solid three times with hexane and drain to obtain the catalyst.

[0016] (3) Ethylene slurry polymerization (1) In a 1-liter reaction flask that has been vacuum-dried and fully replaced with nitrogen and ethylene, first add 0.3 kg of hexane, then add 1 g of the above-mentioned supported catalyst, where the molar ratio of titanium in the supported catalyst to aluminum in the co-catalyst is 1:10, and then add 10 mL of triethylaluminum.

[0017] (2) Ethylene was continuously introduced, and the reaction pressure was controlled at 0.8 MPa. The reactor temperature was raised to 75°C, and the polymerization reaction was carried out for 1 hour. The unreacted ethylene was vented to obtain a MXene / polyethylene composite material. The performance results of the tested polymers are shown in Table 1. Example

[0018] (1) Mo2CT x (MXene) material preparation (1) Weigh 82.5 g of NaOH and dissolve it thoroughly in 75 mL of deionized water. Weigh 2.5 g of Mo2AlC solid powder and 50 mL of NaOH solution into a 100 mL autoclave. Purge the air with N2 and seal the autoclave. Heat in an electric forced air drying oven for 12 h at 270 °C.

[0019] (2) After the hydrothermal treatment is completed, pour out the high-concentration NaOH etching solution on the top, wash out the black suspension at the bottom, and let it stand for 10 minutes. Add a large amount of deionized water, stir thoroughly, and place it in an ultrasonic cleaner to wash away Mo2CT x After the ultrasonic treatment, the suspension was poured into a centrifuge tube and centrifuged. The bottom precipitate was washed with deionized water and centrifuged again. The above steps were repeated several times until the pH of the suspension was about 7. The precipitate at the bottom of the centrifuge tube was washed with 95% ethanol and collected in a beaker. Mo2CT was obtained by drying in a 50°C forced air drying oven. x (T x is -OH or -O).

[0020] (2) Catalyst loading The catalyst loading method is the same as that in Example 1.

[0021] (3) Ethylene slurry polymerization The ethylene polymerization method was the same as in Example 1. The performance results of the tested polymers are shown in Table 1. Example

[0022] (1) Ta4C3T x (MXene) material preparation (1) Weigh 82.5 g of NaOH and dissolve it thoroughly in 75 mL of deionized water. Weigh 2.5 g of Ta4AlC3 solid powder and 50 mL of NaOH solution into a 100 mL autoclave. Purge the air with N2 and seal the autoclave. Heat in an electric forced air drying oven for 12 h at 270 °C.

[0023] (2) After the hydrothermal treatment is completed, pour out the high-concentration NaOH etching solution on the top, wash out the black suspension at the bottom, and let it stand for 10 minutes. Add a large amount of deionized water, stir thoroughly, and place it in an ultrasonic cleaner to wash away Ta4C3T x After the ultrasonic treatment, the suspension was poured into a centrifuge tube and centrifuged. The bottom precipitate was washed with deionized water and centrifuged again. The above steps were repeated several times until the pH of the suspension was about 7. The precipitate at the bottom of the centrifuge tube was washed with 95% ethanol and collected in a beaker. The Ta4C3T x (T x is -OH or -O).

[0024] (2) Catalyst loading The catalyst loading method is the same as that in Example 1.

[0025] (3) Ethylene slurry polymerization The ethylene polymerization method was the same as in Example 1. The performance results of the tested polymers are shown in Table 1. Example

[0026] (1) Nb4C3T x (MXene) material preparation (1) Weigh 82.5 g of NaOH and dissolve it thoroughly in 75 mL of deionized water. Weigh 2.5 g of Nb4AlC3 solid powder and 50 mL of NaOH solution into a 100 mL autoclave. Purge the air with N2 and seal the autoclave. Heat in an electric forced air drying oven for 12 h at 270 °C.

[0027] (2) After the hydrothermal treatment is completed, pour out the high-concentration NaOH etching solution on the top, wash out the black suspension at the bottom, and let it stand for 10 minutes. Add a large amount of deionized water, stir thoroughly, and place it in an ultrasonic cleaner to wash away Nb4C3T x After the ultrasonic treatment, the suspension was poured into a centrifuge tube and centrifuged. The bottom precipitate was washed with deionized water and centrifuged again. The above steps were repeated several times until the pH of the suspension was about 7. The precipitate at the bottom of the centrifuge tube was washed with 95% ethanol and collected in a beaker. The Nb4C3T3O4 was dried in a 50°C forced air drying oven.x (T x is -OH or -O).

[0028] (2) Catalyst loading The catalyst loading method is the same as that in Example 1.

[0029] (3) Ethylene slurry polymerization The ethylene polymerization method was the same as in Example 1. The performance results of the tested polymers are shown in Table 1. Example

[0030] (1) Ti3CNT x (MXene) material preparation (1) Weigh 82.5 g of NaOH and dissolve it thoroughly in 75 mL of deionized water. Weigh 2.5 g of Ti3AlCN solid powder and 50 mL of NaOH solution into a 100 mL autoclave. Purge the air with N2 and seal the autoclave. Heat in an electric forced air drying oven for 12 h at 270 °C.

[0031] (2) After the hydrothermal treatment is completed, pour out the high-concentration NaOH etching solution on the top, wash out the black suspension at the bottom, and let it stand for 10 minutes. Add a large amount of deionized water, stir thoroughly, and place it in an ultrasonic cleaner to wash away the Ti3CNT x After the ultrasonic treatment, the suspension was poured into a centrifuge tube for centrifugation. The bottom precipitate was washed with deionized water and centrifuged again. The above operation was repeated several times until the pH of the suspension was about 7. The precipitate at the bottom of the centrifuge tube was washed with 95% ethanol and collected in a beaker. Ti3CNT was dried in a blast drying oven at 50°C to obtain x (T x is -OH or -O).

[0032] (2) Catalyst loading The catalyst loading method is the same as that in Example 1.

[0033] (3) Ethylene slurry polymerization The ethylene polymerization method was the same as in Example 1. The performance results of the tested polymers are shown in Table 1.

[0034] Comparative Example 1 The catalyst carrier used was MgCl2•2.8C2H5OH, and the catalyst loading method was the same as that in Example 1.

[0035] The ethylene polymerization method was the same as in Example 1. The performance results of the tested polymers are shown in Table 1.

Claims

1. An ethylene polymerization catalyst for catalyzing ethylene polymerization, wherein the active component of the ethylene polymerization catalyst is supported on the surface of MXene, characterized in that The catalytic component is Ti(OR1) p X （4－p） Halides, where R1 is C1~C 20 any one of an alkyl group, an aryl group or an aralkyl group; X is a halogen; and p is an integer of 0≦p<4.

2. The method for preparing an ethylene polymerization catalyst for catalyzing ethylene polymerization according to claim 1, wherein: 1) Add MAX phase solid powder and high concentration NaOH solution into the autoclave, blow out the air with N2 and seal it, then fully react at high temperature. After the reaction is completed, remove the upper high concentration NaOH, stir and wash it with deionized water, separate the suspension, collect the precipitate and dry it to obtain MXene. The general formula of MAX is M n+1 AX n , where n = 1 to 3, M is a transition metal; A is any element of the third or fourth main group except carbon, and X represents C or N; 2) The obtained MXene is dispersed in an inert solvent to form a suspension. The suspension is refluxed at -50 to 10 °C with the catalytic component titanium for 1 to 5 hours to obtain a MXene-supported polyethylene catalyst. The catalytic component titanium is of the general formula Ti(OR1) p X （4－p） Provided by titanium halide, where R1 is C1~C 20 alkyl, aryl or aralkyl; X is a halogen; p is an integer of 0≦p<4, and the molar ratio of MXene to titanium is 1:5 to 1:

100.

3. The method for preparing an ethylene polymerization catalyst for catalyzing ethylene polymerization according to claim 2, wherein In step 1), M is any one of Sc, Ti, Zr, V, Nb, Cr, Ta or Mo.

4. The method for preparing an ethylene polymerization catalyst for catalyzing ethylene polymerization according to claim 3, wherein In step 1), M is any one of Ti, Ta, Nb or Mo.

5. The method for preparing an ethylene polymerization catalyst for catalyzing ethylene polymerization according to claim 2, 3 or 4, characterized in that In step 1), MAX is any one of Ti3AlC2, Mo2AC, Nb3AlC4, Ta3AlC4 or Ti3AlCN, the titanium halide is titanium tetrachloride, the molar ratio of MXene to titanium is 1:10 to 1:50, A is Al, and X is C; the inert solvent used in step 2) is toluene.

6. Use the ethylene polymerization catalyst for catalyzing ethylene polymerization according to claim 1 to carry out ethylene polymerization.

7. A method for carrying out ethylene polymerization slurry polymerization using the ethylene polymerization catalyst for catalyzing ethylene polymerization according to claim 6, characterized in that: 1) After the reaction vessel is fully purged with nitrogen and ethylene, 0.3 kg of hexane is first added, followed by 1 g of catalyst and 10 mL of co-catalyst triethylaluminum; 2) Ethylene is continuously introduced into the reaction vessel, the ethylene pressure is controlled at 0.2-1.5 MPa, the polymerization temperature is 0-80 °C, and the reaction pressure is controlled at 0.8 MPa. After the polymerization reaction is completed, the unreacted ethylene is vented and the solvent is removed to obtain a MXene / polyethylene composite material.

8. The method of ethylene polymerization slurry polymerization according to claim 7, wherein: Ethylene is continuously introduced into the reaction vessel, and the ethylene pressure is controlled at 0.5-1.0 MPa. The polymerization temperature is 20-70° C., and hexane is preferably used as the alkane solvent.

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