Composite extractant and method for separating metal elements in polyolefin fluids

Abstract

The application discloses a composite extractant and a method for separating metal elements in polyolefin fluid by using the composite extractant, wherein the composite extractant is composed of water and a hydroxyl pyran compound, and the percentage of each component is as follows: 40-90wt% water and 10-60wt% hydroxyl pyran compound. The composite extractant and the method for separating metal elements in polyolefin fluid by using the composite extractant can improve the removal rate of metal elements, greatly reduce the usage amount of solid adsorbents, and the generated extractant can be reused without polluting the environment after filtration and recovery.

Description

Technical Field

[0001] This invention relates to a composite extractant and a method for separating metal elements from polyolefin fluids, belonging to the field of polyolefin catalyst separation technology. Background Technology

[0002] Numerous metal compounds have been widely used as catalysts in the synthesis of functional polyolefin fluids. To avoid residual metal elements affecting the performance of polyolefin products, metal elements in polyolefin fluids must be removed to below 10 ppm when obtaining high-purity polyolefin fluids.

[0003] US Patent 5088941 discloses a method for removing alkylaluminum catalysts from polyolefin solutions. Molecular oxygen is introduced into the polyolefin solution containing the alkylaluminum catalyst, causing the solution to fully oxidize and form a gel. Activated carbon is then added to the system for adsorption, promoting the aggregation of nickel compounds and thus removing the metal content from the solution. However, this method has a long oxidation reaction time, requires a large amount of activated carbon, and is not suitable for industrial scale-up.

[0004] Patent CN111996061A discloses a system and method for separation processes in the preparation of mPAO. The crude product obtained after the polymerization reaction is discharged into a diatomaceous earth adsorption tank and subjected to stirring and adsorption treatment at a specific temperature and time. After the polymerization product is filtered to separate the metallocene catalyst and co-catalyst, the reaction product is sent to an olefin separator. Unreacted α-olefins are distilled off from the top of the olefin separator, and the remaining product enters an oligomer separator to sequentially obtain unreacted monomers and dimers. A purified product is obtained at the bottom of the oligomer separator and is finally transported to the hydrogenation unit.

[0005] ExxonMobil Chemicals disclosed a technique for removing metallocene catalysts using solid adsorbents in patent US2008 / 0020928A1. After the polymerization reaction is complete, a trace amount of water or alcohol (or other terminator) of 10–200 ppm is added to the polyolefin mixture. Then, 1–3% of a solid adsorbent, such as solid diatomaceous earth, cellulose powder, or calcium oxide, is added to the reactor. After stirring at 1200–1600 rpm for 1–3 hours, the mixture is filtered to obtain a purified product with a removal rate of ≥90% for aluminum and a metal content of less than 3 ppm.

[0006] Patent US2008 / 0020928A1 discloses a method where, after the polymerization reaction is complete, 10–200 ppm of trace amounts of water or alcohol as a terminator are first added to the polyolefin mixture. Then, 1–3% of a solid adsorbent, such as solid diatomaceous earth, cellulose powder, or calcium oxide, is added to the reactor. After stirring at 1200–1600 rpm for 1–3 hours, the purified product is obtained by filtration. However, when this technology is scaled up, a large amount of heavy metal solid slag is generated during the catalyst separation process, which is non-recyclable and pollutes the environment.

[0007] US Patent 581696 discloses a method for removing Group VIII metal hydrogenation catalyst residues from polymer solutions using water and alkylaluminum. This method involves adding a certain amount of water and alkylaluminum to the reaction system, stirring for a period of time, and then removing the hydrogenation catalyst by filtration, centrifugation, or sedimentation. However, this technique requires the addition of large quantities of expensive alkylaluminum, with a molar ratio of alkylaluminum to Group VIII metal ranging from 20 to 160, resulting in a large reagent consumption. Furthermore, the removal of metal catalyst residues from the polymerization solution requires a long reaction time and has low efficiency, making it unsuitable for industrial production.

[0008] At present, the metal elements in polyolefin fluids in my country are treated with solid adsorbents. However, the amount of solid adsorbents used is relatively large, accounting for about 1 to 3% of the crude product of polyolefin fluids. After use, the adsorbents contain a large number of heavy metal elements, which are difficult to recycle and reuse. As waste, they are discharged, seriously polluting the environment.

[0009] Therefore, developing novel polyolefin fluid metal element separation technologies and reducing adsorbent emissions has become a key challenge in the current development of polyolefin fluid technologies. Summary of the Invention

[0010] To address the problems of high adsorbent usage, non-recyclability, and environmental pollution associated with current methods for separating metal elements from polyolefin fluids, this invention provides a composite extractant and a method for separating metal elements from polyolefin fluids using this extractant. The method utilizes the strong coordination ability of hydroxypyran compounds with metal elements in a catalyst to form metal alkoxide compounds. These metal alkoxide compounds further undergo a condensation reaction with water to form a flocculent MOM (metal-organic phase) insoluble in oil and water. After filtration and adsorption removal, a purified product is obtained. This method for separating metal elements from polyolefin fluids can improve the removal rate of metal elements and significantly reduce the amount of solid adsorbent used while achieving the same adsorption effect as existing technologies.

[0011] To achieve the above objectives, the present invention provides a composite extractant composed of water and a hydroxypyran compound, wherein the percentage of each component is: 40-90 wt% water and 10-60 wt% hydroxypyran compound.

[0012] The composite extractant of the present invention comprises a hydroxypyran compound selected from at least one of 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one, 2-hydroxy-tetrahydropyran, tetrahydropyran-4-ol, 4-hydroxy-6-methyl-2-pyranone, 3-(tetrahydro-2H-pyran-2-yloxy)propane-1-ol, and (tetrahydro-2H-pyran-4-yl)methanol.

[0013] In the composite extractant of the present invention, the percentage of the hydroxypyran compound is 30-50 wt%.

[0014] The present invention also provides a method for separating metal elements from polyolefin fluids, the method comprising the following steps:

[0015] (1) By adding a composite extractant to a polyolefin fluid containing at least one metal element, stirring, letting stand, filtering through a filter screen, and separating the upper organic phase, a primary purified product is obtained.

[0016] (2) Add solid adsorbent to the primary purified product obtained in step (1), stir to adsorb, filter with a filter screen to obtain purified product.

[0017] The method for separating metal elements in polyolefin fluid of the present invention further includes, before performing step (2), atmospheric distillation of the primary purified product obtained in step (1), wherein the temperature of atmospheric distillation is 150-280°C and the time is 0.5-5h.

[0018] In the method for separating metal elements in polyolefin fluid of the present invention, in step (1), the amount of the composite extractant is 0.1 to 5 wt% of the polyolefin fluid, preferably 0.1 to 3 wt%.

[0019] In the method for separating metal elements from polyolefin fluids according to the present invention, in step (2), the amount of the solid adsorbent is 0.01 to 0.5 wt% of the primary purified product, preferably 0.1 to 0.5%.

[0020] The method for separating metal elements in polyolefin fluid of the present invention has the following operating conditions for step (1): temperature 30-150℃, preferably 30-100℃; time 0.5-10h, preferably 0.5-5h.

[0021] The method for separating metal elements in polyolefin fluids according to the present invention, wherein the solid adsorbent is diatomaceous earth, clay, cellulose powder, calcium hydroxide, or magnesium oxide, and the particle size of the solid adsorbent is 30–100 μm, preferably 50–70 μm.

[0022] In the method for separating metal elements in polyolefin fluid of the present invention, in step (2), the temperature of the stirring adsorption is 30-100℃, preferably 30-80℃; and the time of the stirring adsorption is 0.5-10h, preferably 0.5-3h.

[0023] In the method for separating metal elements in polyolefin fluid of the present invention, in step (1) or step (2), the number of filter screens is 300 to 2000 mesh, preferably 500 to 1000 mesh.

[0024] The present invention relates to a method for separating metal elements from polyolefin fluids, wherein the polyolefin fluids include at least one of the following: crude α-olefin base oil, crude polybutene, and crude polyisobutylene; wherein the polyolefin fluids contain 20–1000 ppm aluminum and 1–100 ppm zirconium.

[0025] The present invention can also be described in detail below:

[0026] (1) At a certain temperature, 1-10 wt% of a composite extractant is added to a polyolefin fluid containing at least one metal element, the mixture is stirred for a period of time, and then allowed to stand for a period of time. The mixed solution is then filtered through a filter screen of a certain mesh size to separate the upper organic phase and obtain the primary purified product. The lower aqueous phase is recovered for later use.

[0027] (2) The obtained primary purified product is subjected to atmospheric distillation at a certain temperature.

[0028] (3) Add 0.1-0.5% solid adsorbent to the distilled product at a certain temperature, stir and adsorb for a period of time, filter through a filter screen of a certain mesh size, and the organic phase is the purified product.

[0029] The composite extractant of the present invention and the method for separating metal elements in polyolefin fluids using the extractant first utilize the hydroxyl group in the hydroxypyran compound to undergo a coordination reaction with alkyl aluminum or zirconium metal in the reaction system to form a metal alkoxide compound MOR. 2 With alkane gas R 1 H, metal alkoxide compound MOR 2 It reacts with water to form MOH compounds and alcohol R 2 OH, producing MOH and MOR 2 A condensation reaction occurs to form a large molecular weight MOM condensate, or the MOM itself undergoes a condensation reaction due to dehydration to form a gel-like MOM condensation product. The reaction principle is as follows:

[0030] (1) MR 1 +R 2 OH→MOR 2 +R 1 H↑

[0031] (2)MOR 2 +H₂O→MOH+R 2 OH

[0032] (3)MOR 2 +MOH→MO-M+R 2 OH

[0033] (4) M-OH + HO-M → MO-M + H2O

[0034] Because crude polyolefin products have low density, they tend to form an oil phase on the top layer. Water, with its high density, forms a terminating phase in the lower layer. Gel-type MOM condensation products have a higher density than the oil phase but lower than the water phase, forming a flocculent phase between the oil phase and the terminating phase.

[0035] In existing technologies, 1-3% solid adsorbent is used to separate metal elements from polyolefins. The large amount of waste generated during the separation process cannot be recycled and, upon discharge, pollutes the environment. The composite extractant of this invention and the method for separating metal elements from polyolefin fluids using this extractant have a short process flow and are easy to implement. They use a low amount of solid adsorbent, the extractant can be recycled, the metal element removal rate is ≥95%, and the total metal content in the purified product is ≤3ppm. The amount of solid adsorbent used is significantly reduced to below 0.5%. This composite extractant and the method for separating metal elements from polyolefin fluids using this extractant can improve the metal element removal rate and significantly reduce the amount of solid adsorbent used. Furthermore, the generated extractant can be filtered, recycled, and reused without polluting the environment. Detailed Implementation

[0036] The present invention will be further described below with reference to embodiments and comparative examples, but the present invention is not limited to the following specific embodiments.

[0037] Table 1 Raw Material Specifications and Manufacturers

[0038]

[0039] Evaluation and analysis method: ICP elemental analysis

[0040] Example 1:

[0041] The composite extractant comprises the following components by weight percentage: 50 wt% 2-hydroxy-tetrahydropyran and 50 wt% deionized water.

[0042] The separation of metal elements in polyolefin fluids using this composite extractant is achieved through the following steps:

[0043] (1) Add 2wt% of a composite extractant to 200g of crude metallocene polyalphaolefin (mPAO) containing 70.00ppm aluminum and 5.00ppm zirconium at 50℃. Stir at 800r / min for 1h, let stand for 1h, filter through a 300-mesh filter, separate the liquid, and obtain the upper organic phase as the primary purified product;

[0044] (2) Add 0.35wt% of diatomaceous earth (particle size 30um) of crude mPAO to the obtained primary purified product at 50℃, stir and adsorb for 1h at a speed of 1700r / min, and then filter with a 500 mesh filter to obtain the purified product.

[0045] (3) A small amount of the purified product was subjected to ICP elemental analysis. The aluminum content in the purified product was determined to be 2.35 ppm and the zirconium content to be 0.36 ppm. After calculation, the removal rates of aluminum and zirconium were 96.64% and 92.80%, respectively, and the total removal rate of metal elements was 96.38%. The amount of adsorbent used was 0.35 wt% of the amount of polyolefin fluid used.

[0046] Example 2:

[0047] The composite extractant comprises the following components by weight percentage: 35 wt% tetrahydropyran-4-ol and 65 wt% deionized water.

[0048] (1) Add 1.5wt% of a composite extractant to 400g of crude polyisobutylene containing 150.00ppm aluminum and 15.00ppm zirconium at 70℃. Stir for 2 hours at 1800r / min, let stand for 2 hours, filter through a 600-mesh filter, and separate the upper organic phase to obtain the primary purified product.

[0049] (2) At 70°C, 0.25 wt% of diatomaceous earth with a particle size of 30 μm was added to the obtained primary purified product. After stirring at 800 r / min for 2 h, the purified product was obtained by filtering with a 600 mesh filter.

[0050] (3) A small amount of the purified product was taken for ICP elemental analysis. The aluminum content in the purified product was determined to be 2.72 ppm and the zirconium content was 0.84 ppm. After calculation, the removal rates of aluminum and zirconium were 98.18% and 94.40%, respectively, and the total removal rate of metal elements was 97.84%. The amount of adsorbent used was 0.25 wt% of the amount of polyolefin fluid used.

[0051] Example 3:

[0052] The composite extractant comprises the following components by weight percentage: 25 wt% of 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one and 75 wt% of deionized water.

[0053] (1) Add 3wt% of a composite extractant to 300g of crude polyisobutylene containing 200.00ppm aluminum and 30.00ppm zirconium at 80℃. Stir for 2 hours at 1500r / min, let stand for 2 hours, filter through a 300-mesh filter, and separate the upper organic phase to obtain the primary purified product.

[0054] (2) Add 0.40wt% of diatomaceous earth with a particle size of 30um to the obtained primary purified product at 100℃, stir at 1200r / min for 2h, and then filter with a 500 mesh filter to obtain the purified product.

[0055] (3) A small amount of the purified product was taken for ICP elemental analysis. The aluminum content in the purified product was determined to be 2.51 ppm and the zirconium content was 0.36 ppm. After calculation, the removal rates of aluminum and zirconium were 98.75% and 98.80%, respectively, and the total removal rate of metal elements was 98.75%. The amount of adsorbent used was 0.40 wt% of the amount of polyolefin fluid used.

[0056] Example 4:

[0057] The composite extractant comprises the following components by weight percentage: 50 wt% 4-hydroxy-6-methyl-2-pyranone and 50 wt% deionized water.

[0058] (1) Add 2wt% of a composite extractant to 250g of crude polyisobutylene containing 80.00ppm aluminum and 10.00ppm zirconium at 60℃. Stir for 3h at 1600r / min, let stand for 2h, filter with a 300-mesh filter, and separate the upper organic phase to obtain the primary purified product.

[0059] (2) Add 0.24wt% of diatomaceous earth with a particle size of 30um to the obtained primary purified product at 80℃, stir at 1600r / min for 2h, and then filter with a 500 mesh filter to obtain the purified product.

[0060] (3) A small amount of the purified product was taken for ICP elemental analysis. The aluminum content in the purified product was determined to be 1.45 ppm and the zirconium content to be 1.05 ppm. After calculation, the removal rates of aluminum and zirconium were 98.39% and 89.50%, respectively, and the total removal rate of metal elements was 97.50%. The amount of adsorbent used was 0.24 wt% of the amount of polyolefin fluid used.

[0061] Comparative Example 1:

[0062] (1) 2 wt% ethanol was added to 200 g of crude product containing 70.00 ppm aluminum and 5.00 ppm zirconium metallocene mPAO synthetic base oil at 50℃. The stirring was controlled at 800 r / min and stirred for 1 h. After standing for 1 h, the mixture was filtered through a 300 mesh filter and the upper organic phase was separated to obtain the primary purified product.

[0063] (2) Add 0.35wt% of crude mPAO and diatomaceous earth with a particle size of 30um to the obtained primary purified product at 50℃, stir at 1700r / min for 1h, and then filter with a 300 mesh filter to obtain the purified product.

[0064] (3) A small amount of the purified product was taken for ICP elemental analysis. The aluminum content in the purified product was determined to be 45.64 ppm and the zirconium content was 3.82 ppm. After calculation, the removal rates of aluminum and zirconium were 29.37% and 23.60%, respectively, and the total removal rate of metal elements was 34.05%.

[0065] Comparative Example 2:

[0066] (1) Add 4wt% water to 200g mPAO synthetic base oil containing 70.00ppm aluminum and 5.00ppm zirconium at 50℃. Stir for 1h while controlling the rotation speed at 800r / min, let it stand for 1h to settle, filter with a 300-mesh filter, and separate the upper organic phase to obtain the primary purified product.

[0067] (2) At 50℃, add 0.35wt% of crude mPAO and diatomaceous earth with a particle size of 30um to the obtained primary purified product. After stirring and adsorbing for 1 hour at a speed of 1700r / min, filter with a 500-mesh filter to obtain the purified product.

[0068] (3) A small amount of the purified product was subjected to ICP elemental analysis. The aluminum content in the purified product was determined to be 33.28 ppm and the zirconium content to be 2.37 ppm. After calculation, the removal rates of aluminum and zirconium were 52.45% and 52.60%, respectively, and the total removal rate of metal elements was 52.46%.

[0069] Comparative Example 3:

[0070] (1) 2 wt% deionized water and 0.35 wt% diatomaceous earth with a particle size of 30 μm were added to 200 g of crude metallocene polyalphaolefin (mPAO) containing 70.00 ppm aluminum and 5.00 ppm zirconium at 50 °C. The mixture was stirred at 1700 r / min for 1 h, then filtered through a 500 mesh filter. The purified product was obtained by separating the upper organic phase.

[0071] (2) A small amount of the purified product was subjected to ICP elemental analysis. The aluminum content in the purified product was determined to be 3.17 ppm and the zirconium content to be 1.24 ppm. After calculation, the removal rates of aluminum and zirconium were 95.71% and 75.20%, respectively, and the total removal rate of metal elements was 94.12%.

[0072] Comparative Example 4:

[0073] (1) Add 2wt% ethanol to 250g of crude polyisobutylene containing 80.00ppm aluminum and 10.00ppm zirconium at 60℃. Stir for 3h at 1600r / min, let stand for 2h, filter with a 300-mesh filter, and separate the upper organic phase to obtain the primary purified product.

[0074] (2) Add 1.5wt% of diatomaceous earth with a particle size of 30um to the obtained primary purified product at 80℃, control the rotation speed at 1600r / min, stir for 2h, filter with a 500 mesh filter, and separate the upper organic phase to obtain the purified product.

[0075] A small amount of the purified product was subjected to ICP elemental analysis. The aluminum content in the purified product was determined to be 2.27 ppm and the zirconium content to be 1.64 ppm. The removal rates of aluminum and zirconium were calculated to be 97.16% and 83.60%, respectively, and the total removal rate of metal elements was 95.65%. The amount of adsorbent used was 1.5 wt% of the amount of polyolefin fluid used.

[0076] The results of Example 1 and Comparative Example 1 show that the composite extractant of the present invention can significantly improve the removal rate of metal elements in polyolefin fluids. The results of Example 1 and Comparative Example 2 show that, under the same conditions, even with an increased amount of extractant in Comparative Example 2, the removal rate of metal elements in polyolefin fluids by the composite extractant of the present invention could not be achieved, further confirming that the composite extractant of the present invention can significantly improve the removal rate of metal elements in polyolefin fluids. The results of Example 1 and Comparative Example 3 show that the method for separating metal elements in polyolefin fluids using the present invention can improve the removal rate of metal elements. The results of Example 4 and Comparative Example 4 show that, when the removal rates of metal elements in polyolefin fluids are comparable, the composite extractant of the present invention significantly reduces the amount of diatomaceous earth used as the solid adsorbent.

[0077] Of course, the present invention may have other embodiments and variations. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and variations according to the present invention, but these corresponding changes and variations should all fall within the protection scope of the claims of the present invention.

Claims

1. A composite extractant, characterized in that, It is composed of water and hydroxypyran compounds, with the following percentages: 40-90 wt% water and 10-60 wt% hydroxypyran compounds. The hydroxypyran compound is selected from at least one of 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one, 2-hydroxy-tetrahydropyran, tetrahydropyran-4-ol, 4-hydroxy-6-methyl-2-pyranone, 3-(tetrahydro-2H-pyran-2-yloxy)propane-1-ol, and (tetrahydro-2H-pyran-4-yl)methanol.

2. The composite extractant according to claim 1, characterized in that, The percentage of the hydroxypyran compound is 30-50 wt%.

3. A method for separating metal elements from polyolefin fluids, characterized in that, Includes the following steps: (1) By adding the composite extractant of any one of claims 1-2 to a polyolefin fluid containing at least one metal element, stirring, standing, filtering through a filter screen and separating the upper organic phase, a primary purified product is obtained. (2) Add solid adsorbent to the primary purified product obtained in step (1), stir to adsorb, filter with a filter screen to obtain purified product.

4. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, Before performing step (2), the primary purified product obtained in step (1) is subjected to atmospheric distillation at a temperature of 150~280℃ for 0.5~5h.

5. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, In step (1), the amount of the composite extractant is 0.1 to 5 wt% of the polyolefin fluid.

6. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, In step (2), the amount of the solid adsorbent is 0.01 to 0.5 wt% of the primary purified product.

7. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, The operating conditions for step (1) are: temperature 30~150℃, time 0.5~10h.

8. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, The solid adsorbent is diatomaceous earth, kaolin, cellulose powder, calcium hydroxide, or magnesium oxide, and the particle size of the solid adsorbent is 30~100 μm.

9. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, In step (2), the temperature of the stirring adsorption is 30~100℃ and the time is 0.5~10h.

10. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, In step (1) or step (2), the number of filter screens is 300 to 2000 mesh.

11. The method for separating metal elements from polyolefin fluids according to claim 3, characterized in that, The polyolefin fluid includes at least one of crude α-olefin base oil, crude polybutene, and crude polyisobutylene, wherein the polyolefin fluid contains 20-1000 ppm aluminum and 1-100 ppm zirconium.

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