Process for the preparation of a catalyst for the polymerization of propylene resistant to sedimentation

Abstract

The application discloses a preparation method of a propylene polymerization catalyst resistant to sedimentation, and comprises the following steps: modifying poly-1,3-butadiene by a modifier A to obtain product A, and then modifying a polymerization catalyst by the product A; the catalyst surface of the application exists aliphatic long chains, according to the principle of similarity compatibility, the phase solubility with light oil and light hydrocarbon substances is improved, the sedimentation speed in the light oil and light hydrocarbon substances is low, so that the catalyst is resistant to sedimentation in the long-time storage and transportation process, the roller operation is needed when the catalyst is used in a device, the plugging risk of the catalyst tank and pipeline is reduced, and the long-time continuous operation of a polypropylene device is facilitated.

Description

Technical Field

[0001] This invention belongs to the field of catalysts, specifically relating to a method for preparing a catalyst for propylene polymerization that is resistant to sedimentation. Background Technology

[0002] Since Natta invented the catalyst system for propylene polymerization in 1954, after more than 60 years of development, the production process of polypropylene using fourth and fifth generation catalysts is now the mainstream in industrial production.

[0003] Currently, the catalysts used in various types of polypropylene process units are highly active. To ensure a stable and sustainable catalyst feed rate during the process design phase, light oil and light hydrocarbons are added for dilution during catalyst preparation. For example, the Innoven and Unipol processes use a mixture of catalyst and white oil. However, a drawback of this method is that the catalyst is prone to precipitation in the light oil and light hydrocarbons. Precipitated catalyst in the catalyst tank or pipelines can sometimes clog the feed line, thus affecting the stability of the unit's operation. Furthermore, since catalyst manufacturers provide a catalyst / light oil / light hydrocarbon mixed slurry, it requires prolonged drum operation before use, increasing labor and equipment costs.

[0004] An effective solution is to add hydrocarbon esters during the preparation stage. In the Spheripol process, the temperature is raised to 70°C during the preparation stage, and white oil, dry catalyst powder, and mineral esters are added sequentially. After cooling, the mixture becomes a paste. However, this type of catalyst has high viscosity, poor stirring effect in the catalyst preparation tank, requires a plunger pump with a certain volume for transportation, has a long catalyst preparation process, and needs to maintain the temperature below 10°C throughout the feeding stage, resulting in high energy consumption.

[0005] Therefore, it is of great significance to develop a method for preparing a catalyst for propylene polymerization that is resistant to sedimentation and to solve the problem of sedimentation resistance of catalyst slurry during storage and transportation. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a sedimentation-resistant catalyst for propylene polymerization. The catalyst of this invention has aliphatic long chains on its surface, which, according to the principle of similar compatibility, improves its compatibility with light oils and light hydrocarbons. It has a low sedimentation rate in light oils and light hydrocarbons, thus resisting sedimentation during long-term storage and transportation. This solves the problem of needing to operate the catalyst in a drum, reduces the risk of blockage in the catalyst tank and pipelines, and is beneficial for the long-term continuous operation of the polypropylene plant.

[0007] The present invention provides a method for preparing a catalyst resistant to sedimentation in propylene polymerization, comprising the following steps:

[0008] (1) Add solvent, modifier A and initiator to high pressure reactor, introduce 1,3-butadiene, heat and stir to initiate polymerization to obtain product A;

[0009] (2) Dissolve magnesium chloride in an organic alcohol, add the resulting solution to petroleum jelly and stir until homogeneous, heat to a molten state, add titanium tetrachloride and stir until homogeneous, and then add to a haloalkane to obtain spherical product B.

[0010] (3) Heat the haloalkane suspension of the spherical product B obtained in step (2) and add it to the product A obtained in step (1), stir and react to obtain product C.

[0011] (4) The final product C obtained in step (3) above is washed and dried with an alkane solvent, and then mineral oil is added. After stirring, a catalyst for propylene polymerization with a sedimentation slurry is obtained.

[0012] The modifier A is a trithioester, preferably a trithiocarbonate, and more preferably S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate.

[0013] In step (1) of the present invention, the mass ratio of modifier A to initiator is 4-50, preferably 20-25.

[0014] The solvent used in this invention is a C6-C12 short-chain alkane, preferably one or more of n-heptane or n-decane, and the amount used reaches 1 / 2-3 / 4 of the volume of the reaction vessel.

[0015] The initiator described in this invention is a peroxide initiator, preferably one or both of tert-butyl hydroperoxide and tert-amyl hydroperoxide.

[0016] Preferably, the mass ratio of the added 1,3-butadiene to modifier A is 15-50.

[0017] Preferably, the polymerization reaction temperature in step (1) is 60-80℃ and the reaction pressure is 0.5-1MPa.

[0018] This invention utilizes a reversible addition-fragmentation chain transfer polymerization method to prepare 1,3-butadiene polymers capped with modifier A using a peroxide initiator. Due to the presence of modifier A, the free radical polymerization chain growth rate initiated by the polymerization reaction is low. By controlling the ratio of modifier A to butadiene monomer, the degree of polymerization can be effectively controlled between 100 and 300.

[0019] In step (2) of the present invention, the mass ratio of each reaction component m(magnesium chloride):m(organic alcohol):m(titanium tetrachloride) = (5-20):(50-200):1, preferably, the mass ratio of each component m(magnesium chloride):m(organic alcohol):m(titanium tetrachloride) = (5-10):(120-200):1.

[0020] Vaseline primarily functions as a solvent, and its dosage can be adjusted by those skilled in the art.

[0021] The organic alcohols described in this invention are selected from C1-C10 organic alcohols, preferably one or more of ethanol, propanol, butanol, hexanol, 2-methylpentanol, n-heptanol, 2-ethylhexanol, n-octanol and isooctanol.

[0022] The haloalkane described in this invention is selected from one or more of dichloromethane, dichloroethane, and dichlorocyclopentane.

[0023] In step (2) of the present invention, the molten mixture can be pumped into the haloalkane through a melt pump and a stainless steel pipe. The melt pump is selected from either a screw pump or a diaphragm pump.

[0024] The stainless steel pipe used in this invention has an inner diameter of 0.1-1 mm, preferably 0.1-0.5 mm.

[0025] In step (2), the mass ratio of the amount of haloalkanes to the amount of petrolatum is m(haloalkanes):m(petrolatum) = 1-2.

[0026] In step (2), a catalyst powder with catalytic function is synthesized by the principle of compensating for defects in the magnesium chloride lattice with titanium tetrachloride. However, this powder has the same problem as general catalyst powder, namely, it is easy to settle by gravity in light hydrocarbons, light oils and hydrocarbon esters, resulting in stratification. The fundamental reason is that the density of the catalyst is different from that of light hydrocarbons, light oils and hydrocarbon esters.

[0027] In step (3) of the present invention, the rate of adding product A is 1-5 g / min, preferably 1-2 g / min.

[0028] Preferably, the amount of product A added is 2-5% of the mass of the spherical product B.

[0029] Preferably, in step (3), the reaction temperature is 50-150℃.

[0030] Through high temperature and stirring, product A prepared in step (1) is a long-chain aliphatic compound with end groups of modifier A, which has good compatibility with haloalkanes. At the same time, the ester bond in modifier A can easily coordinate with Lewis acids (magnesium chloride, titanium chloride, etc.) in the catalyst, thus stably linking them on the catalyst surface. Excess haloalkanes are removed by washing. The catalyst particles with surface aliphatic long-chain groups are dispersed in mineral oil in step (3) to prepare a catalyst for propylene polymerization in a sedimentation-resistant slurry liquid.

[0031] Preferably, the mineral oil added in step (4) is an alkane or a branched cycloalkanes, preferably with a density of 0.85-0.90 kg / m³. 3The volume ratio of mineral oil added to the mass ratio of the washed and dried product C is 4-6 L / kg.

[0032] Preferably, the alkane solvent in step (4) is selected from propane, butane, hexane, cyclohexane, and cyclopentane, with hexane or cyclohexane being the most preferred.

[0033] The catalyst slurry prepared by this invention exhibits excellent sedimentation resistance for more than 12 months in a stable environment, without sedimentation or stratification. Furthermore, when used in propylene polymerization, it ensures a catalyst activity greater than 25000 gPP / gcat, with xylene-soluble content below 3%. It is suitable for various types of propylene polymerization processes. Detailed Implementation

[0034] To better understand the technical solution of the present invention, the following embodiments and comparative examples will further illustrate the present invention, but they do not limit the present invention.

[0035] The main raw material information of the embodiments and comparative examples of this invention is as follows:

[0036] Table 1 Reagent Information

[0037]

[0038] Example 1

[0039] (1) Add 3 liters of n-heptane, 15 g of S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate and 1 g of tert-amyl hydrogen peroxide to a 5L high-pressure reactor, purge with nitrogen for 30 minutes to verify that there is no leakage in the reactor, evacuate to 100 kPa and purge with nitrogen at 0.5 MPa, repeat three times, introduce 700 g of 1,3-butadiene with a metering pump, heat to 80 degrees Celsius, turn on the reactor and stir to 500 rpm, react for 30 minutes to initiate polymerization to obtain product A, and control the degree of polymerization to 300.

[0040] (2) Add 500 g of magnesium chloride to 1250 g of ethanol and soak for 30 minutes. Add 200 g of petroleum jelly and stir evenly. Heat to 120 degrees Celsius to reach the molten state. Add 25 g of titanium tetrachloride and stir evenly. Pump the melt into a stainless steel tube using a screw pump. Control the screw pump speed to 25 revolutions per minute. Control the other side to continuously drip the spherical melt into 200 g of dichloroethane to obtain a suspension of spherical product B.

[0041] (3) Heat the suspension obtained in step (2) to 50°C and gradually add the product A obtained in step (1) at a rate of 2 g / min. Stop adding when the product B reaches 2% of the mass and stir for 8 hours to obtain product C.

[0042] (4) The final product C obtained in step (3) above is washed with n-hexane. After washing 6 times, the product C is dried and mineral oil is added at a ratio of 1 liter for every 180 grams. After stirring, a slurry catalyst for propylene polymerization is obtained.

[0043] Example 2

[0044] Except that the amount of 1,3-butadiene used in step (1) of Example 1 is changed to 500g, and the degree of polymerization is controlled at 220.

[0045] In step (2), the mass ratio of each reaction component m(magnesium chloride):m(organic alcohol):m(titanium tetrachloride) = 10:120:1, and the rest is the same as in Example 1.

[0046] Example 3

[0047] Except for the amount of 1,3-butadiene changed to 400g in step (1) of Example 1, the degree of polymerization is controlled at 180, and in step (2), the organic alcohol is isooctyl alcohol, and the mass ratio of each reaction component m(magnesium chloride):m(organic alcohol):m(titanium tetrachloride) = 8:180:1, the rest is the same as in Example 1.

[0048] Example 4

[0049] The main difference between this embodiment and Example 1 is that n-decane is used as the solvent in step (1), the amount of product A added in step (3) is 4% of the mass of the spherical product B, and the reaction temperature is 60℃.

[0050] Comparative Example 1

[0051] Except that S-1-dodecyl-S′-(α,α′-dimethyl-α"-acetic acid) trithiocarbonate was not used in step (1) of Example 2, and the degree of polymerization was not controlled to obtain a long-chain butene polymer, the rest is the same as in Example 1.

[0052] Comparative Example 2

[0053] (1) Add 500 g of magnesium chloride to 1250 g of ethanol and soak for 30 minutes. Add 200 g of petroleum jelly and stir evenly. Heat to 120 degrees Celsius to reach the melting state. Add 25 g of titanium tetrachloride and stir evenly. Pump the melt into a stainless steel tube using a screw pump. Control the screw pump speed to 25 revolutions per minute. Control the other side to continuously drip the spherical melt into 200 g of dichloroethane to obtain a suspension of spherical product B.

[0054] (2) After drying the product B obtained in the above steps, mineral oil is added at a ratio of 1 liter for every 180 grams, and after stirring, a slurry catalyst for propylene polymerization is obtained.

[0055] Comparative Example 3

[0056] (1) Add commercially available domestic fourth-generation catalyst (CS series, Yingkou Xiangyang catalyst) to mineral oil at a ratio of 180 grams per liter, and stir to obtain slurry catalyst for propylene polymerization.

[0057] Comparative Example 4

[0058] (1) Add commercially available imported fourth-generation catalyst (ZN series, Basell catalyst) to mineral oil at a ratio of 180 grams per liter, and stir to obtain a slurry catalyst for propylene polymerization.

[0059] There is no national standard reference for the method of comparing the sedimentation resistance of eight catalysts from Examples 1-4 and Comparative Examples 1-4. The self-made method involves sealing the catalysts in 20*200mm test tubes, filling them with nitrogen to isolate them from air, and placing them vertically in a room temperature environment (25℃). The degree of separation and sedimentation of the catalysts in the test tubes is observed over a long period of time. As shown in Table 2, compared with Comparative Examples 1-4, Examples 1-4 of this patent solution show different degrees of improvement in sedimentation resistance. The sedimentation resistance effect varies depending on the degree of polymerization of product A in patent step (1).

[0060] Table 2

[0061] Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 1 day No settlement No settlement No settlement No settlement settlement settlement settlement settlement 3 days No settlement No settlement No settlement No settlement 7 days No settlement No settlement No settlement No settlement January No settlement No settlement No settlement No settlement March settlement No settlement settlement No settlement June No settlement No settlement

[0062] Because the traditional catalyst system is modified, unlike traditional catalyst synthesis methods, the polymerization performance of the catalyst needs to be evaluated. 25 mg of the slurry catalyst obtained in Examples 1-4, 5 ml of triethylaluminum mol / L hexane solution, and 65 mg of the external electron donor cyclohexylmethyldimethoxysilane were added to a 5 L polymerization reactor in the absence of air. 800 g of propylene was introduced, and the temperature was raised to 70 °C. After polymerization for 1 hour, the product was discharged, and the reaction activity of the obtained polypropylene product was characterized by weighing. Table 3 shows that the catalysts prepared in Examples 1-4 of this patent scheme possess the ability to catalyze propylene polymerization, which is comparable to commercially available catalysts.

[0063] Table 3

[0064]

[0065] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for producing a catalyst for propylene polymerization resistant to sedimentation, characterized by, The method comprises the following steps: (1) adding solvent, modifier A and initiator into a high-pressure reactor, introducing 1,3-butadiene, heating and stirring to initiate polymerization to obtain product A; (2) dissolving magnesium chloride in organic alcohol to obtain a solution, adding the solution into vaseline and stirring to be uniform, heating to a molten state, adding titanium tetrachloride and stirring to be uniform, then adding into halogenated alkane to obtain spherical product B; (3) heating the halogenated alkane suspension of the spherical product B prepared in step (2) and adding the product A prepared in step (1), stirring to react to obtain product C; (4) washing and drying the product C prepared in step (3) with alkane solvent, then adding mineral oil, stirring to obtain a slurry liquid propylene polymerization catalyst resistant to sedimentation; The modifier A is S-1-dodecyl-S'-(α,α'-dimethyl-α"-acetic acid) trithiocarbonate; In step (1), the mass ratio of the modifier A to the initiator is 4-50, and the mass ratio of the added 1,3-butadiene to the modifier A is 15-50.

2. The production method according to claim 1, characterized by, In step (1), the mass ratio of the modifier A to the initiator is 20-25.

3. The preparation method according to claim 1, characterized in that, The solvent is C6-C12 short-chain alkane.

4. The preparation method according to claim 3, characterized in that, The solvent is one or both of n-heptane and n-decane.

5. The preparation method according to claim 1, characterized in that, The amount of the solvent is 1 / 2-3 / 4 of the volume of the reactor.

6. The method of claim 1, wherein, The initiator is peroxide initiator.

7. The preparation method according to claim 6, characterized in that, The initiator is one or both of tert-butyl hydroperoxide and tert-amyl hydroperoxide.

8. The method of claim 1, wherein, The polymerization degree of the product A is 100-300.

9. The preparation method according to claim 1, characterized in that, The polymerization reaction temperature of step (1) is 60-80℃, and the reaction pressure is 0.5-1 MPa.

10. The method of claim 1, wherein, In step (2), the mass ratio of the reaction components is m(magnesium chloride):m(organic alcohol):m(titanium tetrachloride)=(5-20):(50-200):

1.

11. The method of claim 10, wherein, The mass ratio of the reaction components is m(magnesium chloride):m(organic alcohol):m(titanium tetrachloride)=(5-10):(120-200):

1.

12. The method of claim 1, wherein, The organic alcohol is selected from C1-C10 organic alcohols.

13. The method of claim 12, wherein, The organic alcohol is one or more of ethanol, propanol, butanol, hexanol, 2-methylpentanol, n-heptanol, 2-ethylhexanol, n-octanol and isooctanol.

14. The method of claim 1, wherein, The halogenated alkane is one or more of dichloromethane, dichloroethane and dichlorocyclopentane.

15. The method of claim 1, wherein, In step (2), the molten mixture is pumped into the halogenated alkane through a melt pump and a stainless steel pipe, and the melt pump is selected from one of a screw pump and a diaphragm pump.

16. The method of claim 1, wherein, In step (2), the mass ratio of the amount of the halogenated alkane to the amount of the vaseline is m(halogenated alkane):m(vaseline)=1-2.

17. The method of claim 1, wherein, In step (3), the rate of adding the product A is 1-5 g / min.

18. The method of claim 17, wherein, In step (3), the rate of adding the product A is 1-2 g / min.

19. The method of claim 1, wherein, The amount of the product A added is 2-5% of the mass of the spherical product B.

20. The method of claim 1, wherein, In step (3), the reaction temperature is 50-150℃.

21. The method of claim 1, wherein, The type of the mineral oil added in step (4) is alkane or branched cycloalkane.

22. The method of claim 21, wherein, The mineral oil added in step (4) is a mineral oil having a density in the range of 0.85-0.90 kg / m 3 .

23. The method of claim 1, wherein, The volume of the mineral oil added is 4-6 L / kg of the mass of the product C after washing and drying.

24. The method of claim 1, wherein, The alkane solvent in step (4) is selected from one of propane, butane, hexane, cyclohexane, cyclopentane.

25. The method of claim 24, wherein, The alkane solvent in step (4) is selected from hexane or cyclohexane.

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