Preparation method of polyethylene wax

Abstract

The invention discloses a preparation method of polyethylene wax, a three-level pore channel supported catalyst TiCl4 / MgCl2. MSiO2 with a micropore-mesopore-macropore hierarchical structure is created for the first time, a high-density active site supporting space is combined with a hexagonal mesopore through network formed by self-assembly of a template agent, so that the substance diffusion rate is increased by 3-5 times, the diffusion gradient in particles is eliminated, and the stability of the particles is improved. The ethylene and hydrogen can be quickly diffused to the active center, the escape of wax molecules is accelerated, the pore channel blockage can be effectively prevented, and the molecular weight distribution PDI of the polyethylene wax is less than 1.2 and can reach 1.05. MgCl2 crystal lattices are embedded into a SiO2 skeleton to form a cage-shaped structure, so that the dispersity of the active center of Ti is gt; the catalytic effect is improved by 40-50%, and the single service life is prolonged by more than 300%. Borate [Ph3C] [B (C6F5) 4] is innovatively adopted to replace traditional aluminum alkyl to serve as a cocatalyst, the yield of ethylene oligomerization by-products (C4-C8) is smaller than 0.8 wt%, and the selectivity of main products is larger than 99%; functional silane tert-butyl-cyclohexyldimethoxysilane is adopted as an electron donor, so that the hydrogen chain transfer efficiency is improved by 20-30%.

Description

Technical Field

[0001] The invention relates to the technical field of polymer material synthesis, and in particular to a method for preparing polyethylene wax. Background Art

[0002] Polyethylene wax is a versatile synthetic wax. Its high melting point, low viscosity, excellent chemical stability, lubricity, and good compatibility with a wide range of materials make it an indispensable multifunctional additive in modern industry. In plastics processing, it acts as a lubricant and release agent, improving the processing fluidity of materials like PVC and PE. In the coatings and inks industries, it enhances the matte finish and wear resistance of coatings. In the rubber industry, it acts as a softener to optimize mixing efficiency. Due to its unique properties, polyethylene wax has become a key material for improving processing efficiency and product performance across numerous industries. With technological advancements, it is showing broad application prospects in emerging fields such as new energy and precision injection molding.

[0003] Among existing methods for preparing polyethylene wax, metallocene-catalyzed polymerization can achieve an extremely narrow molecular weight distribution and ultra-high purity, making it suitable for high-end applications. However, this method carries extremely high technical barriers and costs. Thermal cracking of polyethylene offers low cost and simplicity, but suffers from a wide molecular weight distribution, high levels of impurities, and poor product color and odor. Byproduct recovery methods offer low cost but unstable performance, reliance on the primary method, and limited supply. In contrast, the Ziegler process, through the polymerization of ethylene monomers, allows for precise molecular weight control, resulting in a product of high purity, white color, and stable performance, meeting the stringent requirements for material safety and consistency in high-end applications such as cosmetics and food packaging.

[0004] The low-pressure catalytic polymerization method of polyethylene wax (based on Ziegler-Natta catalyst) has many technical difficulties. In terms of catalysts, Ziegler-Natta catalysts are extremely sensitive to impurities such as oxygen and water, are easily deactivated, and need to be strictly controlled in an inert atmosphere; at the same time, the active centers of the catalyst are unevenly distributed, resulting in a wide molecular weight distribution of the product, affecting the uniformity of the polyethylene wax, and the residual titanium-based catalyst may affect the color of the product, requiring subsequent deashing treatment to increase costs. In terms of co-catalysts, alkyl aluminum co-catalysts are easy to react with impurities, have high consumption and pose safety hazards, and the ratio of co-catalysts to main catalysts requires precision, and slight deviations will significantly reduce the catalytic activity. In terms of electron donors, internal electron donors (such as siloxanes) may decompose during the polymerization process, resulting in a decrease in catalyst stability; external electron donors need to be continuously added to maintain stereoselectivity, which increases the complexity of the method; therefore, the development of a safe, efficient and economical method for preparing polyethylene wax is of great practical significance. Summary of the Invention

[0005] The present invention improves upon the deficiencies of the prior art and provides a method for preparing polyethylene wax, specifically a method for preparing polyethylene wax using a tertiary pore catalyst TiCl4 / MgCl2·mSiO2 in combination with a co-catalyst triphenylcarbonium tetrakis(pentafluorophenyl)borate and an electron donor tert-butyl-cyclohexyldimethoxysilane.

[0006] To achieve the above-mentioned purpose, the present invention is implemented through the following technical solutions:

[0007] The present invention discloses a method for preparing polyethylene wax, comprising the following steps:

[0008] 1) Preparation of a three-stage pore-supported catalyst TiCl4 / MgCl2·mSiO2;

[0009] 2) The dried autoclave was replaced with nitrogen 3-4 times, and dehydrated and deoxygenated n-hexane solvent was injected under continuous nitrogen protection, stirring was started, and heating was performed to 80-100°C;

[0010] 3) Under nitrogen protection and strict anhydrous and oxygen-free operation, the co-catalyst triphenylcarbonium tetrakis(pentafluorophenyl)borate [Ph3C][B(C6F5)4], the external electron donor tert-butyl-cyclohexyldimethoxysilane, and the main catalyst TiCl4 / MgCl2·mSiO2 were added to the kettle in sequence and stirred to form a uniform catalytic system;

[0011] 4) Turn on the gas source and introduce ethylene and high-purity hydrogen into the system simultaneously, control the gas partial pressure ratio by a mass flow meter, and react at a predetermined temperature and pressure for 1-2 hours;

[0012] 5) After the reaction is completed, the gas source is turned off and a 10-20% isopropyl alcohol n-hexane solution is injected to quench the reaction. After depressurization, the product is filtered and washed with n-hexane to obtain a crude product, which is then distilled under reduced pressure to recover the solvent;

[0013] 6) The crude product is dissolved in xylene at 120-130°C, the catalyst is recovered by hot filtration, the filtrate is distilled under reduced pressure to recover xylene, the residue is removed from oligomers under reduced pressure at 170-180°C, and finally the product polyethylene wax is obtained by melt spray cooling.

[0014] As a further improvement, the preparation method of the TiCl4 / MgCl2·mSiO2 composite catalyst in step 1) of the present invention comprises:

[0015] 1) MgCl2·6H2O was dissolved in ethanol and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer template was added. TEOS tetraethoxysilane was then added dropwise, and polystyrene microspheres were simultaneously introduced. The three-level pore carrier MgCl2·mSiO2 was obtained by stepwise calcination.

[0016] 2) The dried support was placed in a fixed-bed chemical vapor deposition reactor, evacuated and heated, and TiCl4 vapor was introduced at 80-85°C using nitrogen as the carrier gas. After the vapor was in contact with the support surface for 1-2 hours, free TiCl4 was purged with high-purity nitrogen gas to obtain a three-stage pore-supported TiCl4 / MgCl2·mSiO2 catalyst.

[0017] As a further improvement, the amount of triphenylcarbonium tetrakis(pentafluorophenyl)borate used in step 3) of the present invention is 0.8-1.2 times the molar number of the main catalyst Ti.

[0018] As a further improvement, the amount of tert-butyl-cyclohexyldimethoxysilane used in step 3) of the present invention is 20-40 times the molar amount of Ti.

[0019] As a further improvement, the amount of the main catalyst TiCl4 / MgCl2·mSiO2 used in step 3) of the present invention is 0.1-0.2 g / L based on the volume of n-hexane.

[0020] As a further improvement, the hydrogen / ethylene partial pressure ratio in step 4) of the present invention is 0.15-0.3.

[0021] As a further improvement, the polyethylene wax product prepared by the method described in the present invention has a molecular weight of 800-1200 g / mol, a molecular weight distribution PDI <1.2, which can reach 1.05, a hydrogen consumption H2 / C2H4 = 0.15-0.3, which is >0.3 in traditional processes, and a melt viscosity at 149°C <15 cP.

[0022] The beneficial effects of the present invention are as follows:

[0023] This invention pioneers a three-level pore-supported catalyst, TiCl4 / MgCl2·mSiO2, with a hierarchical microporous-mesoporous-macroporous structure. The high-density active site loading space (Mg dispersion >90%), combined with the hexagonal mesoporous network formed by template self-assembly, increases the diffusion rate by 3-5 times, eliminating intraparticle diffusion gradients, allowing ethylene and hydrogen to diffuse rapidly to the active centers, and accelerating the escape of wax molecules. This effectively prevents pore blockage and achieves a polyethylene wax molecular weight distribution (PDI) of less than 1.2, potentially reaching 1.05. The "cage-like structure" formed by the MgCl2 lattice embedded in the SiO2 framework enhances its surface adsorption capacity, allowing it to carry more active centers per unit carrier. Through directional coordination (Ti-O-Si bonding) between the surface hydroxyl groups (-OH) and the TiCl4, the dispersion of the Ti active centers reaches >95%, improving the catalytic effect by 40-50%, and increasing the single-cycle service life by >300%.

[0024] The present invention innovatively uses borate [Ph3C][B(C6F5)4] to replace traditional alkyl aluminum as a co-catalyst, eliminating the impact of aluminum residue on wax products from the root. + Capture Ti-Cl bond electrons to form [Ti] + active species, while [B(C6F5)4]- cannot coordinate due to the steric hindrance of perfluorophenyl, keeping the active center exposed, thereby improving the catalytic efficiency; the restricted space effect inhibits the β-H elimination reaction, making the yield of ethylene oligomerization by-products (C4-C8) less than 0.8wt% and the selectivity of the main product greater than 99%; because B(C6F5)4 - The strong chain transfer properties of anions can reduce the amount of hydrogen used, thereby effectively reducing the energy consumption of the gas phase circulation system.

[0025] The present invention innovatively uses functional silane tert-butyl-cyclohexyldimethoxysilane as an electron donor. The large steric hindrance groups of tert-butyl or cyclohexyl enhance the spatial shielding of the active center, thereby increasing the hydrogen chain transfer efficiency by 20-30%. This allows for more precise control of low molecular weight, enabling precise regulation of Mn = 800±40. Furthermore, the "three-dimensional shield" constructed by the large steric hindrance groups increases the tolerance threshold of the active center to H2O by several times, maintaining over 85% of the initial activity in a raw material containing 5 ppm of impurities, thereby extending the service life of the catalyst. DETAILED DESCRIPTION

[0026] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but the scope of the present invention is not limited to the embodiments.

[0027] Example 1

[0028] 1) MgCl2·6H2O is dissolved in ethanol and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer template is added. Then, TEOS tetraethoxysilane is dropwise added, and polystyrene microspheres are simultaneously introduced. The catalyst is subjected to stepwise calcination to obtain a three-level pore support MgCl2·mSiO2. The dried support is then placed in a fixed-bed chemical vapor deposition reactor, evacuated and heated, and TiCl4 vapor is introduced at 80°C using nitrogen as the carrier gas. After the vapor is allowed to react with the support surface for 1 hour, high-purity nitrogen gas is purged to remove free TiCl4, thereby obtaining a three-level pore-supported TiCl4 / MgCl2·mSiO2 catalyst.

[0029] 2) Nitrogen was replaced three times in a 5 L reactor. 3.5 L of dehydrated and deoxygenated n-hexane was added under a nitrogen atmosphere. Stirring and heating were started, and the temperature was raised to 80°C.

[0030] 3) Add 0.16g [Ph3C][B(C6F5)4] (Ti molar ratio 0.8) and 1.12g tert-butyl-cyclohexyldimethoxysilane (Ti molar ratio 20) and stir for 10 minutes, then add 0.35g main catalyst TiCl4 / MgCl2·mSiO2;

[0031] 4) Synchronously introduce H2 and C2H4 gases, control the partial pressure ratio to 0.15, maintain the total pressure at 1.0 MPa, and react at 80°C for 60 minutes;

[0032] 5) After the reaction is completed, the ethylene and hydrogen inlet valves are closed, and a 10% isopropyl alcohol-hexane solution is injected for quenching. The reaction is terminated by depressurization, and the crude product is filtered and washed with hexane to obtain a crude product; the solvents, isopropyl alcohol and n-hexane, are recovered by vacuum distillation.

[0033] 6) The crude product is dissolved in xylene at 120-130° C., the catalyst is recovered by filtration, the solvent is recovered by vacuum distillation, oligomers are removed under reduced pressure at 170-180° C., and finally the product polyethylene wax is obtained by melt spray cooling.

[0034] Result analysis: The molecular weight of the polyethylene wax is 1200 g / mol, the molecular weight distribution PDI is less than 1.2, the hydrogen consumption H2 / C2H4 is 0.2, and the melt viscosity at 149°C is less than 15 cP.

[0035] Example 2

[0036] 1) MgCl2·6H2O is dissolved in ethanol and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer template is added. Then, TEOS tetraethoxysilane is dropwise added, and polystyrene microspheres are simultaneously introduced. The catalyst is subjected to stepwise calcination to obtain a three-level pore support MgCl2·mSiO2. The dried support is then placed in a fixed-bed chemical vapor deposition reactor, evacuated and heated, and TiCl4 vapor is introduced at 82°C using nitrogen as the carrier gas. After the vapor is allowed to react with the support surface for 1.5 hours, high-purity nitrogen gas is purged to remove free TiCl4, thereby obtaining a three-level pore-supported TiCl4 / MgCl2·mSiO2 catalyst.

[0037] 2) Nitrogen was replaced three times in a 5 L reactor. 3.5 L of dehydrated and deoxygenated n-hexane was added under a nitrogen atmosphere. Stirring and heating were started, and the temperature was raised to 90°C.

[0038] 3) Add 0.3g [Ph3C][B(C6F5)4] (Ti molar ratio 1.0) and 2.1g tert-butyl-cyclohexyldimethoxysilane (Ti molar ratio 30) and stir for 10 minutes, then add 0.525g main catalyst TiCl4 / MgCl2·mSiO2;

[0039] 4) Synchronously introduce H2 and C2H4 gases, control the partial pressure ratio to 0.2, maintain the total pressure at 1.5 MPa, and react at 90°C for 90 minutes;

[0040] 5) After the reaction is completed, the ethylene and hydrogen inlet valves are closed, and a 15% isopropyl alcohol-n-hexane solution is injected for quenching. The pressure is released to terminate the reaction, and the crude product is filtered and washed with hexane to obtain a crude product; the solvents, isopropyl alcohol and n-hexane, are recovered by vacuum distillation.

[0041] 6) The crude product is dissolved in xylene at 120-130° C., the catalyst is recovered by filtration, the solvent is recovered by vacuum distillation, oligomers are removed under reduced pressure at 170-180° C., and finally the product polyethylene wax is obtained by melt spray cooling.

[0042] Result analysis: The molecular weight of the polyethylene wax is 800 g / mol, the molecular weight distribution PDI is less than 1.05, the hydrogen consumption H2 / C2H4 is 0.15, and the melt viscosity at 149°C is less than 12 cP.

[0043] Example 3

[0044] 1) MgCl2·6H2O is dissolved in ethanol and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer template is added. Then, TEOS tetraethoxysilane is dropwise added, and polystyrene microspheres are simultaneously introduced. The catalyst is subjected to stepwise calcination to obtain a three-level pore support MgCl2·mSiO2. The dried support is then placed in a fixed-bed chemical vapor deposition reactor, evacuated and heated, and TiCl4 vapor is introduced at 85°C using nitrogen as the carrier gas. After the vapor is in contact with the support surface for 2 hours, free TiCl4 is purged with high-purity nitrogen gas to remove free TiCl4, thereby obtaining a three-level pore-supported TiCl4 / MgCl2·mSiO2 catalyst.

[0045] 2) Nitrogen was replaced three times in a 5 L reactor. 3.5 L of dehydrated and deoxygenated n-hexane was added under a nitrogen atmosphere. Stirring and heating were started, and the temperature was raised to 100°C.

[0046] 3) Add 0.48g [Ph3C][B(C6F5)4] (Ti molar ratio 1.2) and 3.36g tert-butyl-cyclohexyldimethoxysilane (Ti molar ratio 40) and stir for 10 minutes, then add 0.7g main catalyst TiCl4 / MgCl2·mSiO2;

[0047] 4) Synchronously introduce H2 and C2H4 gases, control the partial pressure ratio to 0.3, maintain the total pressure at 2 MPa, and react at 100°C for 120 minutes;

[0048] 5) After the reaction is completed, the ethylene and hydrogen inlet valves are closed, and a 20% isopropyl alcohol-n-hexane solution is injected for quenching. The pressure is released to terminate the reaction, and the crude product is filtered and washed with hexane to obtain a crude product; the solvents, isopropyl alcohol and n-hexane, are recovered by vacuum distillation.

[0049] 6) The crude product is dissolved in xylene at 120-130° C., the catalyst is recovered by filtration, the solvent is recovered by vacuum distillation, oligomers are removed under reduced pressure at 170-180° C., and finally the product polyethylene wax is obtained by melt spray cooling.

[0050] Result analysis: polyethylene wax molecular weight 1000g / mol, molecular weight distribution PDI <1.1, hydrogen consumption H2 / C2H4 = 0.3, traditional > 0.3, 149 ° C melt viscosity <14cP.

[0051] Comparative Example 1

[0052] No main catalyst TiCl4 / MgCl2·mSiO2 was added, and other conditions were the same as in Example 2. The experimental results showed that the reaction system had no polymerization activity, the ethylene conversion rate was less than 0.1%, and no wax product was detected.

[0053] Comparative Example 2

[0054] The main catalyst TiCl4 / MgCl2·mSiO2 was replaced by MgCl2·mSiO2 catalyst, and other conditions were the same as in Example 2. The experimental results showed that the ethylene conversion rate was only 1.2%, and the product was liquid alkane (C 20 Below), no solid wax is formed.

[0055] Comparative Example 3

[0056] The main catalyst TiCl4 / MgCl2·mSiO2 was replaced with TiCl4·mSiO2 catalyst, and other conditions were the same as in Example 2. The experimental results showed that the catalyst activity decreased by 62%, the product molecular weight distribution was significantly broadened to PDI=2.8, and the wax product was light yellow.

[0057] Comparative Example 4

[0058] The main catalyst TiCl4 / MgCl2·mSiO2 was replaced with TiCl4 catalyst, and other conditions were the same as in Example 2. The experimental results showed that the reaction broke out violently, with the local temperature >150°C within 10 minutes, the product was high molecular weight polyethylene accompanied by coking, and the inner wall of the reactor was severely sticky.

[0059] It can be seen that in Example 2, compared with Control Examples 1, 2, 3, and 4, the main catalyst is a necessary active center for initiating ethylene polymerization, among which the Ti active center is the core of ethylene chain growth. The lack of the anchoring effect of the MgCl2 lattice on Ti will cause the active center to be unevenly dispersed and easy to lose. The tertiary pore carrier is crucial to controlling the reaction heat and molecular weight.

[0060] Comparative Example 5

[0061] No co-catalyst triphenylcarbonium tetrakis(pentafluorophenyl)borate was added, and other conditions were the same as in Example 2. The experimental results showed that the molecular weight of the product was >5000 g / mol.

[0062] Comparative Example 6

[0063] The co-catalyst triphenylcarbonium tetrakis(pentafluorophenyl)borate was replaced with triethylaluminum, and other conditions were the same as in Example 2. The experimental results showed that the ash content of the wax product reached 1200 ppm, the residual alkyl aluminum was hydrolyzed to cause the product to have a noticeable odor, and the melt viscosity at 149° C. increased to 35 cP.

[0064] It can be seen that, compared with Example 2 and Control Examples 5 and 6, borate is indispensable for activating Ti active centers, and the traditional aluminum co-catalyst introduces metal residues, which deteriorates product quality.

[0065] Comparative Example 7

[0066] No electron donor tert-butyl-cyclohexyldimethoxysilane was added, and other conditions were the same as in Example 2. The experimental results showed that the hydrogen chain transfer efficiency was greatly reduced, the molecular weight control was inaccurate, PDI>1.35, and the catalyst deactivation rate after 60 minutes was>40%.

[0067] Comparative Example 8

[0068] The electron donor tert-butyl-cyclohexyldimethoxysilane was replaced by dicyclopentyldimethoxysilane, and other conditions were the same as in Example 2. The experimental results showed that the molecular weight distribution of the product was broadened to PDI=1.8, and the softening point of the wax product fluctuated by ±15°C.

[0069] It can be seen that, compared with Example 2 and Comparative Examples 7 and 8, the "steric shield" effect of the specific steric silane is the key to controlling the molecular weight distribution.

[0070] Comparative Example 9

[0071] The partial pressure ratio of hydrogen was less than 0.15, and other conditions were the same as those in Example 2. The experimental results showed that the molecular weight of the product increased to 2200 g / mol, and the melt viscosity was greater than 50 cP.

[0072] Comparative Example 10

[0073] The partial pressure ratio of hydrogen is greater than 0.3, and other conditions are the same as those in Example 2. The experimental results show that excessive hydrogenation of ethylene produces C4-C 10 Liquid hydrocarbons (accounting for >30%), wax yield decreased by 52%.

[0074] It can be seen that, compared with Example 2 and Control Examples 9 and 10, insufficient hydrogen will lead to the inhibition of chain transfer, resulting in an excessively large molecular weight, while too high a hydrogen partial pressure will lead to excessive chain transfer, resulting in an excessively small molecular weight and the generation of low-molecular liquid hydrocarbons.

[0075] Finally, it should be noted that the above examples are merely specific implementation examples of the present invention. Obviously, the present invention is not limited to the above examples and is subject to numerous variations. All variations that can be directly derived or conceived by a person of ordinary skill in the art from the disclosure of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A method for preparing polyethylene wax, characterized in that, The following steps are involved: 1) Preparation of a three-stage pore-supported catalyst TiCl4 / MgCl2·mSiO2; 2) The dried autoclave was replaced with nitrogen 3-4 times, and dehydrated and deoxygenated n-hexane solvent was injected under continuous nitrogen protection, stirring was started, and heating was performed to 80-100°C; 3) Under nitrogen protection and strict anhydrous and oxygen-free operation, the co-catalyst triphenylcarbonium tetrakis(pentafluorophenyl)borate [Ph3C][B(C6F5)4], the external electron donor tert-butyl-cyclohexyldimethoxysilane, and the main catalyst TiCl4 / MgCl2·mSiO2 were added to the kettle in sequence and stirred to form a uniform catalytic system; 4) Turn on the gas source and introduce ethylene and high-purity hydrogen into the system simultaneously, control the gas partial pressure ratio by a mass flow meter, and react at a predetermined temperature and pressure for 1-2 hours; 5) After the reaction is completed, the gas source is turned off and a 10-20% isopropyl alcohol n-hexane solution is injected to quench the reaction. After depressurization, the product is filtered and washed with n-hexane to obtain a crude product, which is then distilled under reduced pressure to recover the solvent; 6) The crude product is dissolved in xylene at 120-130°C, the catalyst is recovered by hot filtration, the filtrate is distilled under reduced pressure to recover xylene, the residue is removed from oligomers under reduced pressure at 170-180°C, and finally the product polyethylene wax is obtained by melt spray cooling.

2. The method for preparing polyethylene wax according to claim 1, wherein The preparation method of the TiCl4 / MgCl2·mSiO2 composite catalyst in step 1) comprises: 1) MgCl2·6H2O was dissolved in ethanol and a polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer template was added. TEOS tetraethoxysilane was then added dropwise, and polystyrene microspheres were simultaneously introduced. The three-level pore carrier MgCl2·mSiO2 was obtained by stepwise calcination. 2) The dried support was placed in a fixed-bed chemical vapor deposition reactor, evacuated and heated, and TiCl4 vapor was introduced at 80-85°C using nitrogen as the carrier gas. After the vapor was in contact with the support surface for 1-2 hours, free TiCl4 was purged with high-purity nitrogen gas to obtain a three-stage pore-supported TiCl4 / MgCl2·mSiO2 catalyst.

3. The method for preparing polyethylene wax according to claim 1, wherein In the step 3), the amount of triphenylcarbonium tetrakis(pentafluorophenyl)borate used is 0.8-1.2 times the molar number of the main catalyst Ti.

4. The method for preparing polyethylene wax according to claim 1, 2 or 3, wherein: In the step 3), the amount of tert-butyl-cyclohexyldimethoxysilane used is 20-40 times the molar number of Ti.

5. The method for preparing polyethylene wax according to claim 4, wherein The amount of the main catalyst TiCl4 / MgCl2·mSiO2 used in step 3) is 0.1-0.2 g / L based on the volume of n-hexane.

6. The method for preparing polyethylene wax according to claim 5, wherein In the step 4), the partial pressure ratio of hydrogen to ethylene is 0.15-0.

3.

7. The method for preparing the polyethylene wax according to claim 1 or 2 or 3 or 5 or 6, wherein: The polyethylene wax product prepared by the method has a molecular weight of 800-1200 g / mol, a molecular weight distribution PDI of less than 1.2 and can reach 1.05, a hydrogen consumption H2 / C2H4 of 0.15-0.3, which is greater than 0.3 in traditional processes, and a melt viscosity at 149°C of less than 15 cP.