CN-122011243-A - Chromium-based polyethylene catalyst for loop slurry polymerization process and preparation method thereof

CN122011243ACN 122011243 ACN122011243 ACN 122011243ACN-122011243-A

Abstract

The application belongs to the technical field of polyethylene catalysts, and particularly provides a chromium-based polyethylene catalyst for a loop slurry polymerization process and a preparation method thereof. The chromium polyethylene catalyst for the loop slurry polymerization process comprises a modified carrier and a chromium active component, wherein the modified carrier is prepared by compounding modified silica gel with modified POSS (polyhedral oligomeric silsesquioxane), the modified silica gel is prepared by phenyl silane modified silica gel, the modified POSS is prepared by reacting phenyl triethoxysilane, lithium hydroxide monohydrate and 4-nitrophthalonitrile, and the chromium active component is chromium acetate. The chromium-based polyethylene catalyst prepared by the application has good polymerization activity, and the prepared polyethylene product is relatively more uniform and has good processability.

Inventors

ZHANG ZHICHUAN
MA LIJUN
Bi Fangmin
WANG SHAOSHUAI
ZHANG BINHUA

Assignees

淄博新塑化工有限公司

Dates

Publication Date: 20260512
Application Date: 20260414

Claims (10)

1. A chromium-based polyethylene catalyst for loop slurry polymerization process is characterized by comprising a modified carrier and a chromium active component; the modified carrier is prepared by compounding modified silica gel and modified POSS; the modified silica gel is prepared from phenylsilane modified silica gel; The modified POSS is prepared by reacting phenyl triethoxysilane, lithium hydroxide monohydrate and 4-nitrophthalonitrile; The chromium active component is chromium acetate.
2. The chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 1, wherein the preparation method of the modified carrier comprises the steps of dispersing modified POSS and modified silica gel in toluene respectively, mixing, stirring at room temperature, washing and drying.
3. The chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 1, wherein the preparation method of the modified silica gel comprises the following steps of carrying out reflux reaction on trimethoxyphenylsilane and silica gel.
4. The chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 1, wherein the preparation method of the modified POSS comprises the following steps of A1, preparing phenyl trisilanol POSS by catalytic reaction of lithium hydroxide monohydrate, and preparing the modified POSS by nucleophilic substitution reaction of A2, phenyl trisilanol POSS and 4-nitrophthalonitrile.
5. Chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 4, characterized in that the molar ratio of phenyltrisilanolposs to 4-nitrophthalonitrile in A2 is 1:0.5-1.
6. A method for preparing a chromium-based polyethylene catalyst for loop slurry polymerization according to any one of claims 1 to 5, comprising the steps of S1 adding a modified carrier into a chromium acetate solution, immersing, stirring and drying to obtain a chromium-based polyethylene catalyst precursor, S2 roasting the polyethylene catalyst precursor according to a roasting procedure, naturally cooling to obtain an activated polyethylene catalyst, and S3 reducing the activated polyethylene catalyst with aluminum alkyl, and drying to obtain the chromium-based polyethylene catalyst.
7. The method for preparing a chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 6, wherein in S1, the chromium acetate loading is 0.5 to 1.5wt%.
8. The method for preparing a chromium-based polyethylene catalyst for loop slurry polymerization according to claim 6, wherein in S2, the calcination procedure is to raise the temperature from room temperature to 150 ℃ under nitrogen atmosphere, bake for 1-1.5 hours, raise the temperature to 250 ℃ and bake for 1.5-2 hours, raise the temperature to 400 ℃ and bake for 2-2.5 hours, and then switch to raise the temperature to 600 ℃ and bake for 4 hours.
9. The method for preparing a chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 6, wherein in S3, the alkylaluminum is one of triethylaluminum, triisobutylaluminum and ethoxydiethylaluminum.
10. The method for preparing a chromium-based polyethylene catalyst for loop slurry polymerization process according to claim 6, wherein the molar ratio of Al to Cr in S3 is 5 to 10:1.

Description

Chromium-based polyethylene catalyst for loop slurry polymerization process and preparation method thereof Technical Field The application belongs to the technical field of polyethylene catalysts, and particularly relates to a chromium-based polyethylene catalyst for a loop slurry polymerization process and a preparation method thereof. Background Polyethylene is widely applied to various fields of life and production, and Phillips chromium catalyst is used as one of three polyethylene catalysts, so that the catalyst has high catalytic activity, simple production process, wide molecular weight distribution regulation and control capability, unique long-chain branched chain and ultrahigh molecular weight component generation characteristics, and can endow products with excellent mechanical properties and processability, and ethylene polymerization can be realized without adding any cocatalyst. However, the catalyst has the problems of long initiation induction period, poor hydrogen regulation sensitivity, weak copolymerization capability and the like, and the application of the catalyst in preparing high-performance polyolefin materials is limited. In order to solve the problems, a chromium-based polyethylene catalyst and a preparation method thereof are disclosed in the patent application publication No. CN112409514A, wherein the active components are uniformly distributed by adopting an ultrasonic treatment mode when the active components are loaded, and particles are not broken, so that the catalyst with a relatively uniform particle shape and relatively high polymerization activity is prepared. However, the above documents are mainly directed to uniformity of physical morphology of the carrier and dispersibility of the active ingredient, and do not relate to chemical regulation of electronic environment and spatial structure of the chromium active center. Disclosure of Invention In order to further improve the polymerization activity of the chromium-based polyethylene catalyst, the application provides a chromium-based polyethylene catalyst for loop slurry polymerization process and a preparation method thereof. The application firstly provides a chromium-based polyethylene catalyst for a loop slurry polymerization process, which comprises a modified carrier and a chromium active component; the modified carrier is prepared by compounding modified silica gel and modified POSS; the modified silica gel is prepared from phenylsilane modified silica gel; The modified POSS is prepared by reacting phenyl triethoxysilane, lithium hydroxide monohydrate and 4-nitrophthalonitrile; The chromium active component is chromium acetate. Further, the preparation method of the modified carrier comprises the following steps of dispersing the modified POSS and the modified silica gel in toluene respectively, mixing, stirring at room temperature, washing and drying. Further, the preparation method of the modified silica gel comprises the following steps of carrying out reflux reaction on trimethoxyphenyl silane and silica gel. The preparation method of the modified POSS comprises the following steps of A1, preparing phenyl trisilicon alcohol POSS by catalytic reaction of phenyl triethoxysilane through lithium hydroxide monohydrate, and preparing the modified POSS by nucleophilic substitution reaction of the phenyl trisilicon alcohol POSS and 4-nitrophthalonitrile. Further, in A2, the molar ratio of the phenyltrisilanol POSS to the 4-nitrophthalonitrile is 1:0.5-1. The application further provides a preparation method of the chromium-based polyethylene catalyst for the loop slurry polymerization process, which comprises the following steps of S1, adding a modified carrier into a chromium acetate solution, dipping, stirring and drying to obtain a chromium-based polyethylene catalyst precursor, S2, roasting the polyethylene catalyst precursor according to a roasting procedure, naturally cooling to obtain an activated polyethylene catalyst, and S3, reducing the activated polyethylene catalyst by using aluminum alkyl, and drying to obtain the chromium-based polyethylene catalyst. Further, in the S1, the chromium acetate loading is 0.5-1.5wt%. Further, in the step S2, the roasting procedure is that the temperature is raised to 150 ℃ from room temperature under the nitrogen atmosphere, the roasting is carried out for 1-1.5h, the temperature is raised to 250 ℃ and the roasting is carried out for 1.5-2h, the temperature is raised to 400 ℃ and the roasting is carried out for 2-2.5h, and then the temperature is raised to 600 ℃ by switching to high-purity air, and the roasting is carried out for 4h. Further, in the step S3, the alkyl aluminum is one of triethyl aluminum, triisobutyl aluminum and diethyl aluminum ethoxide. Further, in S3, the molar ratio of Al to Cr is 5-10:1. Compared with the prior art, the application has the following beneficial effects: In the chromium-based polyethylene catalyst, a modified carrier is connected with