CN111057170A - Chromium-neodymium-cobalt-loaded trimetal catalyst and preparation method and application thereof - Google Patents
Chromium-neodymium-cobalt-loaded trimetal catalyst and preparation method and application thereof Download PDFInfo
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- CN111057170A CN111057170A CN201911247310.2A CN201911247310A CN111057170A CN 111057170 A CN111057170 A CN 111057170A CN 201911247310 A CN201911247310 A CN 201911247310A CN 111057170 A CN111057170 A CN 111057170A
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F10/02—Ethene
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F110/02—Ethene
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P20/00—Technologies relating to chemical industry
- Y02P20/50—Improvements relating to the production of bulk chemicals
- Y02P20/584—Recycling of catalysts
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
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
Polyethylene is one of the most productive general plastics in the world, and is widely applied to various fields such as industry, agriculture, automobiles, communication, daily life and the like due to excellent mechanical property, electrical insulation property and chemical corrosion resistance, the excellent properties mainly depend on the production process, catalyst technology, post-processing technology and the like of polyethylene, wherein the catalyst technology is the core technology of polyolefin industry, and the modification of the catalyst can effectively improve the production capacity of polyethylene, optimize the production process, save the cost, avoid the waste of raw materials and reduce the environmental pollution, so the polyethylene is widely concerned and researched by the industrial and academic fields.
In 1958, J.P Hogan and R.L. Bank both reported silica gel supported chromium oxide catalysts in patent US2825721, the first Phillips catalyst known to be the later generation, which opened up an important scientific field for the use of chromium based catalysts for olefin polymerization. The Phillips catalysts are highly sensitive to variations in support composition and therefore a second generation of Phillips catalysts, which are catalysts and polyethylene products with new properties prepared by surface modification of the support, can be produced by changing the composition of the support or the type of support, chromium being the only active component in the modified Phillips catalyst. The third generation Phillips catalyst adopts triethylboron as a cocatalyst, so that the low molecular weight part in the polymer is increased, and the addition of the triethylboron only affects the number of chromium active centers, so that the molecular weight distribution of the product is widened. The fourth generation of Phillips catalysts was invented in 1990 by using aluminum phosphate, alumina or silica gel-alumina as a support to obtain bimodal polymers. Compared with the first generation Phillips catalyst, the catalyst is loaded on AlPO4The aluminum catalyst has high hydrogen regulation sensitivity, and products with different molecular weights can be obtained by regulating the hydrogen concentration in the reactor.
At present, polyethylene produced by industrially adopting chromium catalysts contains long-chain branching and a small amount of polyethylene components with ultrahigh relative molecular mass, the relative molecular mass distribution of the polymer is wide, and the processing performance of the resin is excellent. Although various polyolefin catalysts exist, the chromium-based catalyst still has the defects of low catalytic activity and long polymerization time, and reports on a multi-active-center polyethylene catalyst loaded with three metal oxides of chromium, neodymium and cobalt are not found at present.
Disclosure of Invention
The invention aims to provide a chromium-neodymium-cobalt-loaded trimetallic catalyst which can be used for ethylene homopolymerization or copolymerization, can produce olefin polymers 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.
In order to achieve the purpose, the invention adopts the following technical scheme:
a chromium-neodymium-cobalt loaded trimetal catalyst is characterized in that: the catalyst comprises a porous inorganic carrier and three loaded active components, wherein the three active components comprise chromium oxide, neodymium oxide and cobalt oxide, and the total loading amount of chromium is 0.5-5.5 wt% of the total weight of the catalyst, based on the weight of Cr; the total load of neodymium accounts for 0.5-5.5 wt% of the total weight of the catalyst, based on the weight of Nd; the total loading of cobalt is 0.5-5.5 wt% of the total weight of the catalyst, based on the 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 m2Per g, pore volume of 1.0-6.0 cm3(ii)/g, the average pore diameter is 2-20 nm.
The chromium oxide raw material is selected from at least one of chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate and basic chromium acetate, the neodymium oxide raw material is selected from at least one of neodymium nitrate, neodymium acetate, neodymium acetylacetonate and neodymium citrate, and the cobalt oxide raw material is selected from at least one of cobalt acetate, cobalt chloride and cobalt sulfate.
The invention also aims to provide a preparation method of the supported chromium-neodymium-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 trimetal catalyst comprises the following steps:
(1) preparing a chromium compound, a neodymium compound and a cobalt compound into an active ingredient solution by using deionized water, then adding a porous inorganic carrier into the active ingredient solution, uniformly stirring, standing and soaking for 3-8 hours;
(2) drying at 60-150 ℃ for 10-20h to obtain a catalyst loading substance;
(3) and (3) carrying out high-temperature roasting activation on the catalyst load in air or oxygen atmosphere, wherein the roasting temperature is 300-600 ℃, and the time is 2-8h, and cooling to obtain the chromium-neodymium-cobalt-trimetal-loaded catalyst.
The chromium compound is selected from at least one of chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate and 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.
The invention also provides the application of the chromium-neodymium-cobalt loaded trimetallic catalyst in the production of ethylene polymers, which is characterized in that: for the production of ethylene homo-or copolymers. Under the condition of polymerization, making the olefin contact with the supported chromium-neodymium-cobalt trimetallic catalyst and at least one cocatalyst, and adding a molecular weight regulator during the polymerization reaction; the cocatalyst is aluminum alkyl.
The invention has the following beneficial effects:
(1) the supported chromium-neodymium-cobalt trimetal catalyst has the advantages of high catalytic activity, short polymerization time, high hydrogen regulation sensitivity and excellent copolymerization performance, can produce multimodal polyethylene products with wide molecular weight distribution, and has polymerization activity obviously superior to that of the supported bimetallic catalyst and obviously shortened polymerization time.
(2) The preparation method can obtain the ethylene catalyst with multiple centers, has simple preparation process and is easy for industrial implementation.
Detailed Description
Preparation of the catalyst:
example 1: 20g of porous silica was impregnated with an aqueous solution of chromium nitrate, neodymium nitrate, and cobalt nitrate at a concentration where the chromium loading (by mass) was 3.5% Cr, the neodymium loading (by mass) was 1.8% Nd, and the cobalt loading (by mass) was 1.5% Co. Continuously stirring for 6 hr, soaking, taking out, and heating at 120 deg.CDrying for 16 h. And (3) roasting the loaded porous silica carrier at high temperature in a high-temperature furnace, wherein the roasting temperature is 550 ℃, and the roasting time is 3.5 hours, and cooling to obtain the chromium-neodymium-cobalt loaded trimetal catalyst. Wherein the pore volume of the porous silica carrier is 5.2cm3(ii)/g, surface area 423m2In terms of/g, the mean pore diameter is 5.6 nm.
Comparative example 1: 20g of porous silica was impregnated with an aqueous solution of chromium nitrate and cobalt nitrate at a concentration where the chromium loading (by mass) was 2.5% Cr and the cobalt loading (by mass) was 3.3% Co. After the immersion was continued for 6 hours with stirring, the resultant was taken out and dried by heating at 120 ℃ for 16 hours. And (3) roasting the loaded porous silicon dioxide carrier at the high temperature of 550 ℃ for 3.5 hours in a high-temperature furnace, and cooling to obtain the chromium-cobalt loaded catalyst. Wherein the pore volume of the porous silica carrier is 5.2cm3(ii)/g, surface area 423m2In terms of/g, the mean pore diameter is 5.6 nm.
Comparative example 2: 20g of porous silica was impregnated with an aqueous solution of chromium nitrate and neodymium nitrate at a concentration where the chromium loading (by mass) was 2.5% Cr and the neodymium loading (by mass) was 3.3% Nd. After the immersion was continued for 6 hours with stirring, the resultant was taken out and dried by heating at 120 ℃ for 16 hours. And (3) roasting the loaded porous silicon dioxide carrier at the high temperature of 550 ℃ for 3.5 hours in a high-temperature furnace, and cooling to obtain the chromium-neodymium two-metal loaded catalyst. Wherein the pore volume of the porous silica carrier is 5.2cm3(ii)/g, surface area 423m2In terms of/g, the mean pore diameter is 5.6 nm.
Polymerization test:
polymerization experiments were carried out by weighing 200mg 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, respectively. Replacing a stainless steel polymerization kettle with high-purity nitrogen for at least three times, adding normal hexane into the polymerization kettle, adding triethyl aluminum and the solid catalyst with certain concentration, filling ethylene into the reaction kettle to 0.6MPa, continuously introducing ethylene and keeping the pressure, reacting at 80 ℃ for 1 hour, adding a hydrochloric acid/ethanol mixed solution to terminate the reaction, drying the polymer in vacuum, weighing and analyzing.
TABLE 1 ethylene homopolymerization Activity of example 1 and comparative examples 1 and 2
| Catalysts for polymerization experiments | 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-cobalt trimetallic catalyst in the polymerization test is significantly higher than the catalytic activities of the supported chromium-neodymium two-metal catalyst and the supported chromium-cobalt two-metal catalyst, which indicates that the polymerization time of the supported chromium-neodymium-cobalt trimetallic catalyst is significantly shortened and the production efficiency is improved.
In addition, the invention can conveniently adjust the molecular weight and molecular weight distribution of the ethylene homopolymer or copolymer by loading three different metal sources, namely a chromium source, a neodymium source and a cobalt source on the same catalyst carrier, and changing the factors such as the using amount of a cocatalyst, the polymerization temperature, a molecular weight regulator and the like, thereby easily obtaining the polymer with the required performance. The preparation method can obtain the polyethylene catalyst with multiple active centers, has simple preparation process and is easy for industrial implementation.
The present invention is not limited to the above exemplary embodiments, and any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. A chromium-neodymium-cobalt loaded trimetal catalyst is characterized in that: the catalyst comprises a porous inorganic carrier and three loaded active components, wherein the three active components comprise chromium oxide, neodymium oxide and cobalt oxide, and the total loading amount of chromium is 0.5-5.5 wt% of the total weight of the catalyst, based on the weight of Cr; the total load of neodymium accounts for 0.5-5.5 wt% of the total weight of the catalyst, based on the weight of Nd; the total loading of cobalt is 0.5-5.5 wt% of the total weight of the catalyst, based on the weight of Co.
2. The supported chromium-neodymium-cobalt trimetallic catalyst of claim 1, wherein: 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 m2Per g, pore volume of 1.0-6.0 cm3(ii)/g, the average pore diameter is 2-20 nm.
3. The supported chromium-neodymium-cobalt trimetallic catalyst of claim 1, wherein: the chromium oxide raw material is selected from at least one of chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate and basic chromium acetate, the neodymium oxide raw material is selected from at least one of neodymium nitrate, neodymium acetate, neodymium acetylacetonate and neodymium citrate, and the cobalt oxide raw material is selected from at least one of cobalt acetate, cobalt chloride and cobalt sulfate.
4. A method for preparing a supported chromium-neodymium-cobalt trimetallic catalyst as recited in any one of claims 1-3, comprising the steps of:
(1) preparing a chromium compound, a neodymium compound and a cobalt compound into an active ingredient solution by using deionized water, then adding a porous inorganic carrier into the active ingredient solution, uniformly stirring, standing and soaking for 3-8 hours;
(2) drying at 60-150 ℃ for 10-20h to obtain a catalyst loading substance;
(3) and (3) carrying out high-temperature roasting activation on the catalyst load in air or oxygen atmosphere, wherein the roasting temperature is 300-600 ℃, and the time is 2-8h, and cooling to obtain the chromium-neodymium-cobalt-trimetal-loaded catalyst.
5. The method of claim 4, wherein: the chromium compound is selected from at least one of chromium nitrate, chromium acetate, chromium chloride, chromium sulfate, ammonium dichromate and 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.
6. Use of a supported chromium neodymium cobalt trimetallic catalyst according to any one of claims 1 to 3 or a supported chromium neodymium cobalt trimetallic catalyst prepared by the preparation process according to any one of claims 4 to 5 in the production of ethylene polymers, characterized in that: the catalyst is used to produce ethylene homopolymers or copolymers.
7. Use according to claim 6, characterized in that: contacting an olefin under polymerization conditions with the supported chromium neodymium cobalt trimetallic catalyst, at least one cocatalyst.
8. Use according to claim 6, characterized in that: a molecular weight regulator is also added during the polymerization reaction.
9. Use according to claim 6, characterized in that: the cocatalyst is aluminum alkyl.
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