CN111057170B - Chromium-neodymium-cobalt-loaded trimetal catalyst and preparation method and application thereof - Google Patents

Abstract

The invention relates to a modified chromium polyethylene catalyst and a preparation method and application thereof, the catalyst comprises a porous inorganic carrier and three loaded active components, the three active components comprise chromium oxide, neodymium oxide and cobalt oxide, and the preparation method comprises the following steps: the solution containing chromium, neodymium and cobalt is jointly impregnated into an inorganic carrier, and then the inorganic carrier is dried and roasted to obtain the trimetal catalyst for ethylene polymerization, the catalyst can produce an ethylene polymer with wide molecular weight distribution and multimodal distribution, and has the advantages of high catalytic activity, short polymerization time, simple preparation, high hydrogen regulation sensitivity, wide molecular weight distribution and the like.

Description

A kind of supported chromium neodymium cobalt trimetal catalyst and its preparation method and application

technical field

The invention belongs to the technical field of catalysts, and relates to a supported trimetallic catalyst and a preparation method and application thereof.

Background technique

Polyethylene is one of the largest general-purpose plastics in the world. Due to its excellent mechanical properties, electrical insulation and chemical resistance, it is widely used in various fields such as industry, agriculture, automobiles, communications, and daily life. The performance mainly depends on the production process, catalyst technology and post-processing technology of polyethylene, among which the catalyst technology is the core technology of the polyolefin industry. The modification of the catalyst can effectively improve the production capacity of polyethylene, optimize the production process, save costs, avoid The waste of raw materials and the reduction of environmental pollution have therefore received extensive attention and research in industry and academia.

In 1958, JP Hogan and RLBank reported the silica-supported chromium oxide catalyst in patent US2825721, which was later known as the first-generation Phillips catalyst, and created an important scientific and technological field of chromium-based catalysts for olefin polymerization. Phillips catalysts are highly sensitive to changes in carrier composition, so by changing the composition of the carrier or the class of the carrier, the second generation of Phillips catalysts is produced, which is a catalyst and polyethylene product with new properties prepared by surface modification of the carrier , chromium is the only active component in the modified Phillips catalyst. The third-generation Phillips catalyst uses triethylboron as a co-catalyst to increase the low molecular weight part of the polymer. The addition of triethylboron only affects the number of chromium active centers and broadens the molecular weight distribution of the product. The fourth generation of Phillips catalysts was invented in 1990, using aluminum phosphate, alumina or silica-alumina as a support to obtain bimodal polymers. Compared with the first-generation Phillips catalyst, the aluminum catalyst supported on AlPO ₄ has a higher sensitivity to hydrogen regulation, and products with different molecular weights can be obtained by adjusting the hydrogen concentration in the reactor.

At present, the polyethylene produced by chromium-based catalysts in industry contains long-chain branching and a small amount of ultra-high molecular weight polyethylene components. The relative molecular weight distribution of the polymer is wide, and the resin has excellent processing performance. Although there are many different polyolefin catalysts, the chromium-based catalysts still have the disadvantages of low catalytic activity and long polymerization time. There is no report on multi-active-site polyethylene catalysts loaded with three metal oxides of chromium, neodymium, and cobalt. .

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a supported chromium, neodymium, and cobalt trimetallic catalyst, which can be used for ethylene homopolymerization or copolymerization, can produce olefin polymers with wide molecular weight distribution and multimodal distribution, has high catalytic activity, short polymerization time, and can be prepared It has the advantages of simplicity, high hydrogen regulation sensitivity, and wide molecular weight distribution.

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A supported chromium, neodymium, and cobalt trimetallic catalyst is characterized in that: it comprises a porous inorganic carrier and three active components supported, wherein the three active components include chromium oxide, neodymium oxide and cobalt oxide, and the total loading amount of chromium is the total amount of the catalyst. 0.5%-5.5wt% of the total weight of Cr, based on the weight of Cr; the total loading of neodymium is 0.5%-5.5wt% of the total weight of the catalyst, based on the weight of Nd; The total loading of cobalt is 0.5%-5.5% of the total weight of the catalyst wt% by weight of Co.

The porous inorganic carrier is at least one of silicon oxide, aluminosilicate, titanium oxide, magnesium oxide, and calcium oxide; the specific surface area of the porous inorganic carrier is 100-600 m ² /g, and the pore volume is 1.0- 6.0 cm ³ /g, and the average pore size is 2-20 nm.

The raw material of the chromium oxide is selected from at least one of chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate, and basic chromium acetate, and the raw material of the neodymium oxide is selected from neodymium nitrate, acetic acid At least one of neodymium, neodymium acetylacetonate, and neodymium citrate, and the raw material of the cobalt oxide is selected from at least one of cobalt acetate, cobalt chloride, and cobalt sulfate.

Another object of the present invention is to provide a preparation method of a supported chromium, neodymium, and cobalt trimetallic catalyst for polyethylene, which has the characteristics of simple preparation process and easy industrial implementation.

The preparation method of the supported chromium neodymium cobalt trimetallic catalyst of the present invention comprises the following steps:

(1) Chromium compound, neodymium compound and cobalt compound are prepared into active ingredient solution with deionized water, then a porous inorganic carrier is added to it, stirred evenly, and then left to stand for 3-8h immersion;

(2) drying at 60-150°C for 10-20h to obtain a catalyst support;

(3) calcining and activating the catalyst support at a high temperature in an air or oxygen atmosphere, the calcining temperature is 300-600° C., the time is 2-8 h, and the catalyst is cooled to obtain a catalyst supported with three metals of chromium, neodymium, and cobalt.

The chromium compound is selected from at least one of chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate, and basic chromium acetate, and the neodymium compound is selected from neodymium nitrate, neodymium acetate, acetylacetone At least one of neodymium and neodymium citrate, and the cobalt compound is selected from at least one of cobalt acetate, cobalt chloride, and cobalt sulfate.

The present invention also provides the application of the supported chromium, neodymium, and cobalt trimetallic catalyst in the production of ethylene polymers, which is characterized in that: it is used for the production of ethylene homopolymers or copolymers. The olefin is contacted with the supported chromium neodymium cobalt trimetal catalyst and at least one cocatalyst under polymerization conditions, and a molecular weight regulator is also added during the polymerization reaction; the cocatalyst is alkyl aluminum.

The beneficial effects of the present invention are as follows:

(1) The supported chromium, neodymium, and cobalt trimetal catalyst of the present invention has high catalytic activity, short polymerization time, high hydrogen regulation sensitivity, superior copolymerization performance, and can produce multimodal polyethylene products with wide molecular weight distribution, and its polymerization activity should be significantly better. due to the polymerization activity of the supported bimetallic catalyst, and the polymerization time was significantly shortened.

(2) The preparation method of the present invention can obtain an ethylene catalyst with multiple centers, the preparation process is simple, and the industrial implementation is easy.

Detailed ways

Preparation of catalyst:

Example 1: Impregnate 20 g of porous silica in a certain concentration of chromium nitrate, neodymium nitrate, and cobalt nitrate aqueous solutions, wherein the chromium loading (by mass) is 3.5% Cr, and the neodymium loading (by mass) is 1.8% Nd with a cobalt loading (by mass) of 1.5% Co. After continuous stirring for 6 hours and immersion, it was taken out and heated and dried at 120°C for 16 hours. The supported porous silica carrier is calcined at a high temperature in a high-temperature furnace, the calcination temperature is 550° C., the time is 3.5 h, and the catalyst is cooled to obtain a supported chromium, neodymium, and cobalt trimetallic catalyst. Among them, the porous silica support has a pore volume of 5.2 cm ³ /g, a surface area of 423 m ² /g, and an average pore diameter of 5.6 nm.

Comparative Example 1: Impregnate 20 g of porous silica in a certain concentration of chromium nitrate and cobalt nitrate aqueous solution, wherein the chromium loading (by mass) is 2.5% Cr, and the cobalt loading (by mass) is 3.3% Co . After continuous stirring for 6 hours and immersion, it was taken out and heated and dried at 120°C for 16 hours. The loaded porous silica carrier is calcined at a high temperature in a high-temperature furnace, the calcination temperature is 550° C., the calcination time is 3.5 h, and the catalyst is cooled to obtain a catalyst loaded with two metals, chromium and cobalt. Among them, the porous silica support has a pore volume of 5.2 cm ³ /g, a surface area of 423 m ² /g, and an average pore diameter of 5.6 nm.

Comparative Example 2: 20 g of porous silica was dipped in a certain concentration of chromium nitrate and neodymium nitrate aqueous solution, wherein the chromium loading (by mass) was 2.5% Cr, and the neodymium loading (by mass) was 3.3% Nd . After continuous stirring for 6 hours and immersion, it was taken out and heated and dried at 120°C for 16 hours. The supported porous silica carrier is calcined at a high temperature in a high-temperature furnace, the calcination temperature is 550° C., the calcination time is 3.5 h, and the catalyst is cooled to obtain a catalyst loaded with chromium and neodymium. Among them, the porous silica support has a pore volume of 5.2 cm ³ /g, a surface area of 423 m ² /g, and an average pore diameter of 5.6 nm.

Aggregation test:

Weigh 200 mg of the supported trimetallic catalyst of Example 1, the supported chromium-cobalt bimetallic catalyst of Comparative Example 1, and the supported chromium-neodymium bimetallic catalyst of Comparative Example 2 to carry out polymerization experiments. Replace the stainless steel polymerization kettle with high-purity nitrogen for no less than three times, then add n-hexane to the polymerization kettle, add a certain concentration of triethylaluminum and the above-mentioned solid catalyst, and finally fill the reaction kettle with ethylene to 0.6MPa, and continue to feed Ethylene was kept at this pressure. After the reaction was carried out at 80° C. for 1 hour, a mixed solution of hydrochloric acid/ethanol was added to terminate the reaction, and the polymer was vacuum-dried and weighed and analyzed.

The ethylene homopolymerization activity of table 1 embodiment 1 and comparative example 1, comparative example 2

Catalysts used in polymerization tests Activity (g_PE·gcat^-1·h^-1) Catalyst of Example 1 481.35 Catalyst of Comparative Example 1 355.43 Catalyst of Comparative Example 2 310.25

It can be seen from Table 1 that the polymerization activity of the supported chromium, neodymium, and cobalt trimetallic catalysts in the polymerization test is significantly higher than that of the supported chromium, neodymium, and cobalt bimetallic catalysts, indicating that the polymerization of the supported chromium, neodymium, and cobalt trimetallic catalysts The time is significantly shortened and the production efficiency is improved.

In addition, in the present invention, three different metal sources, ie, chromium source, neodymium source and cobalt source, are jointly supported on the same catalyst carrier, and factors such as the amount of co-catalyst, polymerization temperature, molecular weight regulator, etc. can be changed conveniently. The molecular weight and molecular weight distribution of ethylene homo- or copolymers are adjusted so that polymers with desired properties can be easily obtained. The preparation method of the invention can obtain the polyethylene catalyst with multiple active centers, the preparation process is simple, and the industrial implementation is easy.

The above are only exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention. Inside.

Claims (5)

1. a kind of supported chromium neodymium cobalt trimetallic catalyst for producing ethylene homopolymer or copolymer, it is characterized in that: comprise three kinds of active components of porous inorganic carrier and load, three kinds of active components comprise chromium oxide, neodymium oxide and cobalt oxide, the total loading of chromium is 3.5 wt% of the total weight of the catalyst, based on the weight of Cr; the total loading of neodymium is 1.8 wt% of the total weight of the catalyst, based on the weight of Nd; the total loading of cobalt is the catalyst 1.5wt% of the total weight, based on the weight of Co; under polymerization conditions, the olefin is contacted with the supported chromium, neodymium, and cobalt trimetallic catalyst and alkyl aluminum cocatalyst, and a molecular weight regulator is also added during the polymerization reaction. 2. the supported chromium neodymium cobalt trimetallic catalyst for producing ethylene homopolymer or copolymer according to claim 1, is characterized in that: described porous inorganic carrier is silicon oxide, aluminosilicate, titanium oxide, At least one of magnesium oxide and calcium oxide; the porous inorganic carrier has a specific surface area of 100-600 m ² /g, a pore volume of 1.0-6.0 cm ³ /g, and an average pore diameter of 2-20 nm. 3. the supported chromium neodymium-cobalt trimetallic catalyst for producing ethylene homopolymer or copolymer according to claim 1, is characterized in that: the raw material of described chromium oxide is selected from chromium nitrate, chromium acetate, chromium chloride , at least one of chromium sulfate, ammonium dichromate, and basic chromium acetate, the raw material of the neodymium oxide is selected from at least one of neodymium nitrate, neodymium acetate, neodymium acetylacetonate, and neodymium citrate, and the cobalt The raw material of the oxide is selected from at least one of cobalt acetate, cobalt chloride, and cobalt sulfate. 4. the arbitrary described preparation method of the supported chromium neodymium cobalt trimetallic catalyst for producing ethylene homopolymer or copolymer of claim 1-3, is characterized in that, comprises the steps: (1) Use deionized water to prepare chromium compound, neodymium compound and cobalt compound into active ingredient solution, then add porous inorganic carrier to it, stir evenly, and let it stand for 3-8h immersion; (2) drying at 60-150°C for 10-20h to obtain the catalyst support; (3) The catalyst supported material is calcined and activated at a high temperature in an air or oxygen atmosphere, the calcination temperature is 300-600° C., the time is 2-8 h, and the catalyst is cooled to obtain a catalyst supported with three metals of chromium, neodymium, and cobalt. 5. preparation method according to claim 4 is characterized in that: described chromium compound is selected from at least one in chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate, basic chromium acetate , the neodymium compound is selected from at least one of neodymium nitrate, neodymium acetate, neodymium acetylacetonate, and neodymium citrate, and the cobalt compound is selected from at least one of cobalt acetate, cobalt chloride, and cobalt sulfate.