CN109517098B - Off-line prepolymerization catalyst and propylene homopolymerization and copolymerization method - Google Patents
Off-line prepolymerization catalyst and propylene homopolymerization and copolymerization method Download PDFInfo
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Abstract
The invention provides an off-line prepolymerized catalyst which is prepared by the following steps: firstly, performing offline prepolymerization reaction on a Ziegler-Natta catalyst component suitable for olefin polymerization, an organic aluminum cocatalyst and optionally an external electron donor and propylene at the temperature of-20-60 ℃ to obtain a prepolymerization catalyst with the prepolymerization multiple controlled at 0.1-15 g of polypropylene/g of catalyst; and then storing in an environment of-20 to 50 ℃ for not less than 2 seconds before being used for polymerization in the form of a dry powder or a slurry dispersed in an inert solvent. In the process of preparing olefin polymer in a gas phase polymerization device by adopting the off-line prepolymerization catalyst, the pipeline scaling and blockage caused by propylene polymerization in a feed pipe of the gas phase polymerization device can be effectively avoided, and the problems of polymer agglomeration, high fine powder content in polymer powder and the like caused by large fluctuation of polymerization reaction temperature and easy generation of hot spots in the gas phase polymerization can be further solved.
Description
Technical Field
The invention relates to a method for propylene polymerization or copolymerization, in particular to an off-line prepolymerization catalyst adopting low-multiple low-naked catalyst activity and a method for propylene homopolymerization or copolymerization in a gas-phase device.
Background
High-activity polyolefin catalysts are used in the polyolefin industry at present on a large scale, but the initial activity of the catalysts is high, which often causes the problems of high temperature fluctuation at the initial stage of polymerization reaction, easy generation of hot spots in the polymerization reaction, polymer agglomeration, catalyst breakage, high fine powder content in polymer powder and the like. To solve this problem, it is necessary to reduce the initial activity of the catalyst and to increase the strength of the catalyst particles.
Therefore, the method which is widely applied in the industry at present is to introduce an 'on-line' prepolymerization reactor, such as a Spheripol process, a Spherizone and the like, and basically adopts an 'on-line' prepolymerization process. The situation of industrial application shows that the polypropylene process adopting the prepolymerization process has stable polymerization reaction temperature control, no hot spot in polymerization reaction, basically no lump material and low fine powder content in polymer powder. However, since there is a large difference in the residence time of the catalyst particles in the continuous prepolymerization reactor, some particles have a long residence time in the reactor and others have a relatively short residence time, the resulting catalyst particles do not contain an equal amount of prepolymer. For example, the continuous prepolymerization reactor of patent CN200880019432.X gives catalyst particles with a uniform prepolymer content, but with an average value. Therefore, there are always some catalyst particles prepolymerized to a too high degree to cause serious activity decay in the latter stage, and some catalyst particles hardly prepolymerized to inevitably cause problems of unstable reactor control and high fine powder content. Meanwhile, the continuous prepolymerization process has a long route and relatively complex control, so that the practical application has more problems.
For gas phase process, such as Innovene process, Novolen process and Unipol process, no 'on-line' prepolymerization reactor is provided during design, and such processes have the problems of large polymerization temperature fluctuation, easy generation of hot spots in polymerization reaction, polymer agglomeration, high content of fine powder in polymer powder and the like. The introduction of the "on-line" prepolymerization process into the gas-phase polypropylene process can alleviate the above problems to some extent, but the inherent heterogeneity of the catalyst obtained by the continuous prepolymerization process cannot completely solve the problems; furthermore, the addition of a prepolymerization apparatus and process means the addition of new investment and relatively large equipment modifications, which are often impractical.
In conclusion, the problems of polymer agglomeration, high fine powder content in polymer powder and the like caused by large temperature fluctuation of polypropylene polymerization reaction and easy hot spot generation in polymerization reaction cannot be thoroughly solved by adopting the 'on-line' prepolymerization process, especially for a gas-phase polypropylene process which is not designed with an 'on-line' prepolymerization reactor.
In order to solve the problems, the off-line prepolymerization catalyst can be adopted, and the aims of increasing the particle strength and reducing the content of fine powder are fulfilled without changing the polymerization process flow and adding new equipment.
The pre-polymerization catalyst is obtained by polymerizing ethylene or propylene to wrap a polymer with a certain times through catalyst components, an organic aluminum cocatalyst and an optional external electron donor, and because a certain amount of the organic aluminum cocatalyst is remained in the final components and is still difficult to be completely removed even through full washing, the pre-polymerization catalyst meets an olefin monomer under the condition of proper temperature and pressure and can generate polymerization reaction even if the organic aluminum cocatalyst is not added any more. It is known that, in a feeding system of a propylene gas phase polymerization apparatus, a catalyst slurry prepared by using a propylene monomer as a dispersant, a transporting agent, or the like is generally fed to a feed port through a pipeline and sprayed into the polymerization apparatus, and since a prepolymerized catalyst contains an organoaluminum catalyst, a polymerization reaction occurs in the pipeline when propylene is encountered, and a polymer formed in the pipeline forms a wall which is likely to be fouled and may block the pipeline or the feed port in a serious case.
To avoid clogging of the feed lines and feed ports, the following methods are generally used: 1) pre-cooled low-temperature propylene monomers are used for cooling the pre-polymerized catalyst so as to achieve the purposes of reducing the activity and reducing the polymerization reaction in a pipeline; 2) increasing the transport speed of the prepolymerized catalyst mixture in the line, increasing the flushing effect, shortening the feed time to reduce polymerization in the line; 3) the inner wall of the pipeline is polished regularly to reduce the build-up of polymer structures.
Disclosure of Invention
In order to solve the problems, the invention provides an off-line prepolymerized catalyst with low prepolymerization times and low naked catalyst activity, and the prepolymerized catalyst can avoid the scaling and the blockage of a feed pipeline of a gas phase polymerization device in the propylene homopolymerization or copolymerization process, and solve the problems of large temperature fluctuation, easy generation of hot spots, high polymer fine powder content and the like in the gas phase polymerization device.
Another object of the present invention is to provide a process for polymerizing or copolymerizing propylene using the prepolymerized catalyst.
In order to achieve the object of the present invention, the present invention provides an "off-line" prepolymerized catalyst with low prepolymerization times and low "naked catalyst activity", which is prepared by the following steps:
1) carrying out offline prepolymerization reaction on a Ziegler-Natta catalyst component suitable for olefin polymerization, an organic aluminum cocatalyst and optionally an external electron donor and propylene at the temperature of-20-60 ℃ to obtain a catalyst with the prepolymerization multiple controlled at 0.1-15 g of polypropylene/g;
2) storing the catalyst obtained in the step 1) in an environment at-20-50 ℃ for not less than 2 seconds before being used for polymerization reaction in the form of dry powder or dispersed in slurry of an inert solvent, so that the evaluation of the activity of the naked catalyst without adding organic aluminum after storage is not higher than 200g of polymer/g of catalyst/h-1。
The Ziegler-Natta catalyst component in the step 1) of the invention is a titanium compound, a magnesium compound, halogen and an internal electron donor compound, and the Ziegler-Natta catalyst component in the prior art, such as CN201510043331.8 and the like, can be adopted.
The general formula of the titanium compound is TiXN(OR’)4-NWherein R' is C1～C20X is halogen, and N is 0 to 4. The titanium compound of the present invention includes titanium halide or alkoxy titanium halide, the titanium halide is titanium tetrachloride, titanium tetrabromide or titanium tetraiodide; the alkoxy titanium halide is selected from methoxy titanium trichloride, ethoxy titanium trichloride, propoxy titanium trichloride, n-butoxy titanium trichloride, dimethoxy titanium dichloride, diethoxy titanium dichloride, dipropoxy titanium dichloride, di-n-butoxy titanium dichloride, trimethoxy titanium chloride, triethoxy titanium chloride, tripropoxy titanium chloride and tri-n-butoxy titanium chloride. One or more of these titanium halides may be used in combination. Among them, titanium tetrachloride is preferably used.
The magnesium compound is selected from at least one of: xnMg(OR)2-n，MgCl2·mROH，R2-nMgXn，MgCl2/SiO2，MgCl2/Al2O3Or a mixture of a magnesium halide and a titanium alkoxide, wherein m is a number of 0.1 to 6, 0 ≦ n ≦ 2, X is a halogen, R is hydrogen or C1～C20A hydrocarbon group of (1). The magnesium compound of the present invention is preferably magnesium chloride, magnesium ethoxide, magnesium butoxide, magnesium chloride ethanol adduct, magnesium chloride butanol adduct, liquid magnesium compound (e.g., magnesium chloride dissolved in a mixed solution of a heteroatom-containing compound, etc.).
The internal electron donor compound is selected from Lewis bases containing one or more electronegative groups, electron donor compounds preferably selected from ethers, esters, ketones and amines, more preferably from diethers, aromatic dicarboxylic esters, succinates, aromatic and aliphatic glycol esters and amines.
The organic aluminum cocatalyst is shown as a general formula AlRnX(3-n)The organic aluminum compound of (1) is an organic aluminum compound, wherein R is hydrogen or a hydrocarbon group having 1-20 carbon atoms; x is halogen, n is an integer of 0-3. The organoaluminum compound is preferably an alkyl compound or an alkoxy compound of aluminum, preferably triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diethylaluminum monochloride, ethylaluminum dichloroide and methylalumoxane, more preferably triethylaluminum, triisobutylaluminum and methylalumoxane.
The external electron donor may or may not be used in step 1) of the present invention, and when the external electron donor is present, the external electron donor may be selected from those having the general formula R1 xR2 ySi(OR)zSiloxane compound of the formula (II) R, R1And R2Are identical or different C1～C18Optionally containing heteroatoms, x, y, z satisfy: x and y are not less than 0<4，0<z is less than or equal to 4, and x + y + z is 4. Preferably methylcyclopentyldimethoxysilane, methylphenyldimethoxysilane, methylcyclohexyldimethoxysilane, propyltrimethoxysilane, isobutyltrimethoxysilane, diisobutyldimethoxysilane, dicyclopentyldimethoxysilane or diisopropyldimethoxysilane.
The molar ratio of the dosage of the organic aluminum compound to the titanium element in the catalyst component is 0.1-100: 1, preferably 0.1 to 80: 1, more preferably 0.5 to 40: 1.
in the prepolymerization of the invention, hydrogen can be introduced simultaneously when propylene is introduced, and the molar ratio of propylene to hydrogen is 0-100, preferably 0-50, and more preferably 0-30.
The temperature of the off-line prepolymerization reaction is preferably-15-45 ℃, and more preferably-10-40 ℃.
The content of the olefin polymer generated by the prepolymerization reaction accounts for 1-99%, preferably 5-90%, and more preferably 10-80% of the weight of the catalyst component. The present invention can control the content of olefin polymer in the catalyst component by adjusting the amount of olefin entering the reactor per unit time, the reaction temperature, the molar ratio of the amount of the activator to the metal element in the olefin catalyst, etc.
The prepolymerization can take place in the presence of an inert medium comprising n-pentane, n-hexane, n-heptane, n-octane, cyclohexane, toluene, ethylbenzene, xylene.
In order to avoid non-uniform prepolymerization of the olefin polymerization catalyst particles, it is preferred that the prepolymerization reactor is operated in a batch process, i.e., each batch of the propylene polymerization catalyst is subjected to the same reaction history, to avoid catalyst particles having non-uniform distribution of catalyst residence time.
"prepolymerization multiple" means the weight ratio of polyolefin to catalyst component contained in the resulting prepolymerized catalyst. The pre-polymerization multiple is preferably 0.1-10 g of polypropylene/g of catalyst. The prepolymerization multiple can be realized by controlling prepolymerization conditions, and the adjustable prepolymerization conditions include but are not limited to: temperature, time, pressure, monomer flow rate of the prepolymerization.
Ziegler-Natta catalyst systems must use both a procatalyst component and an organoaluminum cocatalyst to polymerize olefin monomers, and are referred to as "naked catalysts" when they contain only the procatalyst component (which may or may not contain a polyolefin) and do not use the organoaluminum cocatalyst and other promoters. Usually if polymerizedThe "bare catalyst" cannot exhibit catalytic activity without using an organoaluminum cocatalyst, but exhibits polymerization activity on an olefin monomer even if the organoaluminum cocatalyst is not added any more at the time of polymerization under a certain temperature and pressure because a trace amount of organoaluminum remains in the prepolymerized catalyst. The term "naked catalyst activity" as used herein means an activity obtained when only a prepolymerized catalyst is contacted with a propylene monomer without adding an organoaluminum cocatalyst or other auxiliary agent during the contact. The evaluation conditions can adopt general bulk polymerization evaluation conditions commonly used in the industry, and the temperature and pressure ranges are general condition ranges commonly used in the industry. The general evaluation conditions were: the bulk polymerization temperature is 60-80 ℃, and the pressure is 2.5-4.0 MPa. The "naked catalyst activity" range of the present invention is preferably not more than 100g of polymer/g of catalyst h-1. Methods for controlling the activity of the bare catalyst below the above range include, but are not limited to: catalyst components using different carriers or internal electron donors, fully washing the prepolymerized catalyst, and inactivating the prepolymerized catalyst (such as using Lewis base inactivators such as alcohol and ester during prepolymerization, or mixing trace oxygen in the system, or non-low temperature storage, micro-oxygen environment storage, etc.).
The prepolymerized catalyst component may be stored in a separate line, and may be packaged, transported, stored and used in the form of a dry powder or a slurry. The inert dispersant in the step 2) of the invention is alkane solvent or aromatic hydrocarbon solvent or mineral oil or the mixture of any of the above substances. Aliphatic alkane solvents such as n-hexane, n-heptane, white oil, mineral oil, etc. are preferred.
The offline storage temperature of the prepolymerized catalyst is preferably-10 to 45 ℃, and more preferably 0 to 40 ℃.
The storage time is preferably not less than 2 minutes, more preferably not less than 30 minutes, and most preferably not less than 1 hour.
After off-line storage of the prepolymerized catalyst according to the invention under the above-mentioned conditions, the "bare catalyst activity" can be further reduced, especially in a low-purity inert gas environment, thereby facilitating smooth feeding of the gas phase apparatus.
The present invention also provides a process for preparing an olefin polymer in a gas phase polymerization plant using an off-line prepolymerized catalyst having a low prepolymerization multiple and a low "naked catalyst activity", comprising the steps of:
1) preparing slurry with the concentration of 1-60% by using an inert dispersant for the prepolymerization catalyst, and feeding propylene or other C2-C12 olefin monomers into a gas phase reactor, wherein the temperature of the olefin monomers is 0-60 ℃, and the speed of the prepolymerization catalyst slurry and monomer fluid in a feeding pipe is less than 6 m/s;
2) the prepolymerized catalyst is used for homopolymerizing propylene or copolymerizing propylene and optional other C2-C12 olefin monomers in a gas-phase reactor.
The concentration of the slurry of the prepolymerized catalyst in the step 1) of the present invention is preferably 1 to 55%, and more preferably 1 to 50%. The temperature of the monomer is preferably 10-50 ℃. The fluid flow rate is preferably not higher than 4 m/s.
The gas phase reactor is a gas phase fluidized bed, a vertical gas phase stirring kettle or a horizontal gas phase stirring kettle.
The prepolymerized catalyst of the invention is polymerized or copolymerized with propylene and/or optionally other C2-C12 olefin comonomers in a gas phase reactor. The olefins are preferably: linear olefins such as: ethylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-nonene, 1-decene; branched olefins such as: 3-methyl-1-butene and 4-methyl-1-pentene; dienes such as: butadiene, vinylcyclopentene, and vinylcyclohexene. These olefins may be used alone or in combination of two or more. The polymerization or copolymerization temperature is from 20 to 120 ℃, preferably from 40 to 100 ℃, most preferably from 50 to 90 ℃.
The propylene homopolymerization and copolymerization method is particularly suitable for being applied to a gas-phase polypropylene process without prepolymerization processes such as a gas-phase stirred bed, a gas-phase fluidized bed and the like, can avoid propylene polymerization in a gas-phase polymerization feed pipe by adopting an off-line prepolymerization catalyst with low prepolymerization times and low naked catalyst activity, does not need to use a low-temperature propylene monomer in the feed pipe, does not need to improve the material conveying speed, does not need to polish the inner wall of a pipeline, and can realize smooth feeding without blocking the pipeline; and further solves the problems of polymer agglomeration, high fine powder content in polymer powder and the like caused by large temperature fluctuation of polypropylene polymerization reaction and easy generation of hot spots in polymerization reaction.
Detailed Description
The present invention will be further described with reference to the following examples, which are provided for the purpose of illustration and are not intended to limit the scope of the present invention.
Characterization of
Determination of the Polymer content in the prepolymerized catalyst component
About 1g (m1) of the solid catalyst component was accurately weighed, soaked in 50 ml of a 1mol/L sulfuric acid solution, sonicated, shaken for 30 minutes, filtered, then washed 3 times with 50 ml of deionized water, and vacuum-dried to obtain a solid powder (m2), from which the content of the polymer was calculated: m2/m1 100%.
Determination of the content of fines
The fine powder is defined below 80 mesh for polypropylene (equivalent to a particle size of less than 180um) and below 200 mesh for polyethylene (equivalent to a particle size of less than 75um) as determined according to astm e 1187.
Determination of the Activity of bare catalysts
After a 5L stainless steel autoclave was sufficiently purged with nitrogen, 30mg of a (prepolymerization) catalyst was added, 10mL of hexane was added to flush the addition line, 2L (in a standard state) of hydrogen and 2.5L of purified propylene were added, and polymerization was carried out at this temperature for 1 hour. And after the reaction is finished, cooling the reaction kettle, stopping stirring, discharging a reaction product, drying to obtain a polymer, and calculating the activity.
Propylene gas phase polymerization Condition 1
The catalyst slurry was fed into a horizontal gas-phase polymerization reactor (basic size: inner diameter 400mm, length 1100mm, volume 138L) through a feed pipe. Controlling the concentration of each component in the reactor as follows: 1 vol% of hydrogen, 95 vol% of propylene and 4 vol% of nitrogen. Controlling the reaction temperature to be 66-68 ℃, the pressure of the reactor to be 2.5MPa, and the retention time to be 50 minutes. The external electron donor adopts methyl cyclohexyl dimethoxy silane, and the flow rate is 0.6 g/h; the catalyst feed was 1g/h (calculated as dry powder) and the triethylaluminium feed was 3.6 g/h.
Comparative example 1
1. Preparation of catalyst component:
the catalyst component was prepared by the method of example 4 in CN201510043331.8 and analyzed for titanium content of 2.9%.
2. Gas phase polymerization of propylene
The catalyst component was made into a slurry with a concentration of 30% (wt) with white oil, and propylene at 10 ℃ was fed into the feed line, and the flow rate of the slurry in the feed pipe was controlled to 4 m/s. The catalyst is fed into a horizontal gas-phase polymerization reactor through a feed pipe to carry out propylene polymerization. The polymerization conditions were as described above under "propylene gas phase polymerization conditions 1". The results are shown in Table 1.
Comparative example 2
1. Preparation of prepolymerized catalyst:
in a 5-neck flask with a stirrer, which was sufficiently replaced with nitrogen gas in 1L, 400mL of n-hexane was added to the flask, 20mL of a 0.5mol/L triisobutylaluminum hexane solution was added, 10g of the polypropylene catalyst prepared in comparative example 1 was added, the temperature was controlled at 30 ℃ and the temperature was maintained for 5 minutes; propylene was fed through a mass flow meter, the feeding rate of the fed propylene was controlled at 200g/h, and the reaction was carried out for 60 minutes. The propylene is stopped to enter, 156.1g of solid is obtained after normal hexane washing, filtration and vacuum drying, the analyzed titanium content is 0.2 (wt)%, the polymer content is 93.5 (wt)%, and the prepolymerization multiple of the propylene is 14.6. The prepolymerized catalyst was in the form of a dry powder under high purity nitrogen (99.999%, O)2≦ 0.001%) for the evaluation of the naked polymerization of the catalyst after storage at-10 ℃ for 1 hour under protection. The bare catalyst activity was 367g polymer/g catalyst.
2. Gas phase polymerization of propylene
The above prepolymerized catalyst was used for gas phase polymerization. The same feed conditions and polymerization conditions as in comparative example 1 were used except that the catalyst was fed into the feed line with propylene at 5 ℃ and the polymerization results are shown in Table 1.
Comparative example 3
1. Preparation of prepolymerized catalyst:
in a 5-neck flask with a stirrer, which was sufficiently replaced with nitrogen gas in 1L, 400mL of n-hexane was added to the flask, 20mL of a 0.5mol/L triisobutylaluminum hexane solution was added, 10g of the polypropylene catalyst prepared in comparative example 1 was added, the temperature was controlled at 20 ℃ and the temperature was maintained for 5 minutes; propylene was fed through a mass flow meter, the feeding rate of the fed propylene was controlled at 100g/h, and the reaction was carried out for 60 minutes. Stopping feeding propylene, washing with n-hexane, filtering, and vacuum-drying to obtain solid 63.3g, wherein the analyzed titanium content is 0.4 (wt)%, the polymer content is 84.1 (wt)%, and the prepolymerization multiple of propylene is 5.3. The prepolymerized catalyst was used directly for catalyst bare polymerization evaluation. The bare catalyst activity was 218g polymer/g catalyst.
2. Gas phase polymerization of propylene
The prepolymerized catalyst was used in the gas phase polymerization without being stored off-line. The same feeding conditions and polymerization conditions as in comparative example 1 were used. The polymerization results are shown in Table 1.
Example 1
1. Preparation of prepolymerized catalyst:
in a 500mL 5-neck flask with stirring which was sufficiently replaced with nitrogen, 300mL of n-hexane was added to the flask, 20mL of a 0.5mol/L triisobutylaluminum hexane solution was added, 10g of the polypropylene catalyst prepared in comparative example 1 was added, the temperature was controlled at 5 ℃ and the temperature was maintained for 5 minutes; propylene was fed through a mass flow meter, the feeding rate of the fed propylene was controlled at 20g/h, and the reaction was carried out for 60 minutes. The propylene is stopped to enter, 26.4g of solid is obtained after normal hexane washing, filtering and vacuum drying, the analyzed titanium content is 1.1 (wt)%, the polymer content is 62.0 (wt)%, and the prepolymerization multiple of the propylene is 1.6.
The prepolymerized catalyst was used as a dry powder in the presence of industrial nitrogen (99.999%, O)2≦ 0.001%) for the evaluation of the naked polymerization of the catalyst after 48 hours at 25 ℃. The bare catalyst activity was 23g polymer/g catalyst.
2. Gas phase polymerization of propylene
The catalyst component was made into a slurry with a concentration of 35% (wt) with white oil, and propylene at 10 ℃ was fed into the feed line, and the flow velocity of the slurry in the feed pipe was controlled to 3 m/s. The catalyst is fed into a horizontal gas-phase polymerization reactor through a feed pipe to carry out propylene polymerization. The polymerization conditions were as described above under "propylene gas phase polymerization conditions 1". The results are shown in Table 1.
Example 2
Prepolymerized catalyst preparation the same feeding conditions and polymerization conditions as in example 1 were used, except that the flow rate of the catalyst slurry in the feeding pipe was controlled to 2 m/s.
Example 3
Prepolymerized catalyst preparation the same feed conditions and polymerization conditions as in example 1 were used except that the catalyst was fed into the feed line with 25 ℃ propylene.
Example 4
1. Preparation of prepolymerized catalyst:
in a 500mL 5-neck flask with stirring which was sufficiently replaced with nitrogen, 300mL of n-hexane was added to the flask, 20mL of a 0.5mol/L triisobutylaluminum hexane solution was added, 10g of the polypropylene catalyst prepared in comparative example 1 was added, the temperature was controlled at 10 ℃ and the temperature was maintained for 5 minutes; propylene was fed through a mass flow meter, the feeding rate of the fed propylene was controlled to 40g/h, and the reaction was carried out for 60 minutes. The propylene is stopped to enter, 35.2g of solid is obtained after normal hexane washing, filtering and vacuum drying, the analyzed titanium content is 0.8 (wt)%, the polymer content is 71.4 (wt)%, and the prepolymerization multiple of the propylene is 2.5. The prepolymerized catalyst was used for evaluation of the bare polymerization of the catalyst after storage in the form of a dry powder at 20 ℃ for 720 hours under protection of high purity nitrogen. The bare catalyst activity was 37g polymer/g catalyst.
2. Gas phase polymerization of propylene
The catalyst component was made into a slurry with a concentration of 25% (wt) with white oil, and propylene at 15 ℃ was fed into the feed line, and the flow rate of the slurry in the feed pipe was controlled to 1.7 m/s. The catalyst is fed into a horizontal gas-phase polymerization reactor through a feed pipe to carry out propylene polymerization. The polymerization conditions were as described above under "propylene gas phase polymerization conditions 1". The results are shown in Table 1.
Example 5
Prepolymerized catalyst preparation As in example 4, the prepolymerized catalyst was used for catalyst bare polymerization evaluation after storage in the form of a dry powder at 30 ℃ for 1180 hours under high purity nitrogen. The bare catalyst activity was 19g polymer/g catalyst. The same polymerization conditions as in example 4 were employed except that the catalyst component was prepared into a slurry with a concentration of 30% (wt) using white oil, propylene at 20 ℃ was fed into the feed line, and the flow rate of the slurry in the feed pipe was controlled to 2 m/s.
Example 6
Prepolymerized catalyst preparation the same as in example 5. The same polymerization conditions as in example 5 were used, except that the catalyst was fed into the feed line with propylene at 10 ℃ and the flow rate of the slurry in the feed line was controlled to 1.8 m/s.
Example 7
1. Preparation of prepolymerized catalyst:
in a 500mL 5-neck flask with stirring which was sufficiently replaced with nitrogen, 300mL of n-hexane was added to the flask, 20mL of a 0.5mol/L triisobutylaluminum hexane solution was added, 10g of the polypropylene catalyst prepared in comparative example 1 was added, the temperature was controlled at 10 ℃ and the temperature was maintained for 5 minutes; propylene was fed through a mass flow meter, the feeding rate of the fed propylene was controlled at 15g/h, and the reaction was carried out for 60 minutes. The propylene is stopped to enter, 20.9g of solid is obtained after normal hexane washing, filtering and vacuum drying, the analyzed titanium content is 1.4 (wt)%, the polymer content is 52.2 (wt)%, and the prepolymerization multiple of the propylene is 1.1. The prepolymerized catalyst was used for evaluation of the bare polymerization of the catalyst after storage in the form of a dry powder at 25 ℃ for 0.5 hour under the protection of industrial nitrogen. The bare catalyst activity was 32g polymer/g catalyst.
2. Gas phase polymerization of propylene
The catalyst component was made into a slurry with a concentration of 30% (wt) with white oil, and propylene at 25 ℃ was fed into the feed line, and the flow rate of the slurry in the feed pipe was controlled to 2 m/s. The catalyst is fed into a horizontal gas-phase polymerization reactor through a feed pipe to carry out propylene polymerization. The polymerization conditions were as described above under "propylene gas phase polymerization conditions 1". The results are shown in Table 1.
Example 8
Prepolymerized catalyst preparation the same as in example 7. The same polymerization conditions as in example 7 were employed except that the catalyst was fed into the feed line with propylene at 30 ℃ and the flow rate of the slurry in the feed line was controlled to 2.5 m/s.
Example 9
Prepolymerized catalyst preparation the same as in example 7 except that the prepolymerized catalyst was used for catalyst bare polymerization evaluation in the form of a dry powder after storage at 25 ℃ for 320 hours under high purity nitrogen. The bare catalyst activity was 29g polymer/g catalyst. . The same polymerization conditions as in example 7 were employed except that the catalyst was fed into the feed line with propylene at 10 ℃ and the flow rate of the slurry in the feed line was controlled to 1.2 m/s.
TABLE 1
[ remarks ] a: units are g polymer/g catalyst;
b: the unit is kg polymer/g titanium.
As can be seen from the data in Table 1, comparative example 1, in which the catalyst was used directly in the gas phase polymerization without prepolymerization, produced a high amount of fines in the polymerization vessel, although no fouling was observed in the feed line. Comparative example 2 the prepolymerized catalyst had a high prepolymerization ratio and a high naked catalyst activity, and although the content of the obtained polypropylene fine powder was significantly reduced, fouling of the line could not be avoided even when the propylene monomer temperature was low (5 ℃ C.) and a higher conveying speed (5m/s) was used at the time of feeding. Comparative example 3 the prepolymerized catalyst had a low prepolymerization multiple but was not stored off-line, the bare catalyst had a high activity and fouling in the feed line.
The prepolymerization multiple of the prepolymerization catalyst adopted in the embodiments 1 to 3 is 1.6, the activity of the naked catalyst is low after the naked catalyst is stored for 48 hours in low pure nitrogen at 25 ℃, and when the temperature of a propylene monomer in a feeding pipeline is 10 to 25 ℃, and the conveying speed is low (2 to 3m/s), the fouling phenomenon is hardly caused. The prepolymerization times of the prepolymerization catalysts of the examples 4 to 6 are 2.5, and after the prepolymerization catalysts are stored at a high temperature (20 to 30 ℃) for a long time (720 to 1180h) in high-purity nitrogen, the feeding pipes can be kept free of scale at a low conveying speed. The pre-polymerized catalysts in examples 7-9 have lower activity of naked catalyst, and can keep the feeding pipe from scaling at a higher temperature of propylene monomer (10-30 ℃) and at a lower conveying speed (1.2-2.5 m/s). In addition, the temperature fluctuations of examples 1 to 9 were all smaller than those of comparative example 1, and the fine powder content in the final polymer was also significantly lower than that of comparative example 1. The results show that the use of a prepolymerized catalyst with a low prepolymerization multiple and low naked catalyst activity can avoid the structure and blockage in the feed pipe without lowering the propylene monomer temperature in the feed pipe or increasing the slurry transport speed, and can reduce the polymerization temperature fluctuation and the polymer fine powder content, and avoid agglomeration in the reactor.
Although the invention has been described in detail hereinabove with respect to a general description and specific embodiments thereof, it will be apparent to those skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined generally in dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
Claims (17)
1. An off-line prepolymerized catalyst, which is prepared by the following steps:
1) carrying out offline prepolymerization reaction on a Ziegler-Natta catalyst component suitable for olefin polymerization, an organic aluminum cocatalyst and optionally an external electron donor and propylene at the temperature of-15-45 ℃ to obtain a prepolymerization catalyst with the prepolymerization multiple controlled at 0.1-10 g of polypropylene/g of catalyst; the molar ratio of the dosage of the organic aluminum compound to the titanium element in the catalyst component is 0.1-80: 1;
2) storing the prepolymerized catalyst obtained in step 1) in an environment at-10 to 45 ℃ for not less than 2 minutes before being used in polymerization, in the form of dry powder or dispersed in a slurry of an inert solvent, so that the "naked catalyst activity" evaluated after storage without adding organoaluminum is not higher than 100g polymer/g catalyst.h-1。
2. The offline prepolymerized catalyst according to claim 1, wherein the Ziegler-Natta catalyst component in step 1) is a titanium compound, a magnesium compound, a halogen and an internal electron donor compound.
3. The offline prepolymerized catalyst according to claim 1, wherein the organoaluminum co-catalyst is of the general formula AlRnX(3-n)Wherein R is hydrogen or a hydrocarbon group having 1 to 20 carbon atoms; x is halogen and n is 0<n is an integer of 3 or less.
4. The offline prepolymerized catalyst according to claim 1, wherein the external electron donor is selected from the group consisting of those of the general formula R1 xR2 ySi(OR)zSiloxane compound of the formula (II) R, R1And R2Are identical or different C1～C18Optionally containing heteroatoms, x, y, z satisfy: x and y are not less than 0<4，0<z is less than or equal to 4, and x + y + z is 4.
5. The off-line prepolymerization catalyst according to claim 1, wherein the molar ratio of the amount of the organic aluminum compound to the titanium element in the catalyst component is 0.5-40: 1.
6. the offline prepolymerized catalyst according to claim 1, wherein the temperature of the offline prepolymerization in step 1) is-10 to 40 ℃.
7. The offline prepolymerized catalyst according to claim 1, wherein the storage temperature in step (2) is 0 to 40 ℃; the storage time is not less than 30 minutes.
8. The offline prepolymerized catalyst according to claim 7 wherein the storage time of step (2) is not less than 1 hour.
9. A process for homopolymerization or copolymerization of propylene, which comprises the step of polymerizing the prepolymerized catalyst according to any one of claims 1 to 8, comprising:
1) preparing the prepolymerization catalyst into slurry with the concentration of 1-60% by using an inert dispersant, and using propylene or other C2～C12The olefin monomer is fed into a gas phase reactor, the temperature of the olefin monomer is 0-60 ℃, and the speed of the prepolymerized catalyst slurry and the monomer fluid in a feed pipe is<6m/s；
2) The prepolymerized catalyst is used for homopolymerizing propylene or for homopolymerizing propylene and other C2～C12The olefin monomer is copolymerized.
10. The process for homo-or co-polymerization of propylene according to claim 9, wherein the concentration of the prepolymerized catalyst slurry in step 1) is 1 to 55%.
11. The process for homo-or co-polymerization of propylene according to claim 9, wherein the concentration of the prepolymerized catalyst slurry in step 1) is 1 to 50%.
12. The process for homo-or co-polymerization of propylene according to claim 9, wherein the temperature of the monomers in step 1) is 10 to 50 ℃.
13. Process for the homopolymerization or copolymerization of propylene according to claim 9, wherein said rate in step 1) is not higher than 4 m/s.
14. A process for the homopolymerization or copolymerization of propylene according to claim 9, wherein the gas-phase reactor is a gas-phase fluidized bed, a vertical gas-phase stirred tank, or a horizontal gas-phase stirred tank.
15. The process for homo-or co-polymerization of propylene according to claim 9, wherein the temperature of the homo-or co-polymerization in step 2) is 20 to 120 ℃.
16. The process for homo-or co-polymerization of propylene according to claim 15, wherein the temperature of the homo-or co-polymerization in step 2) is 40 to 100 ℃.
17. The process for homo-or co-polymerization of propylene according to claim 16, wherein the temperature of the homo-or co-polymerization in step 2) is 50 to 90 ℃.
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| JPS62115004A (en) * | 1985-11-13 | 1987-05-26 | Mitsubishi Petrochem Co Ltd | Storage of catalyst component for polymerization of olefin |
| CN101679559A (en) * | 2007-06-14 | 2010-03-24 | 博里利斯技术公司 | Process for the production of propylene copolymers using a prepolymerised catalyst |
| CN105646742A (en) * | 2016-03-25 | 2016-06-08 | 任丘市利和科技发展有限公司 | Olefin polymer-containing catalyst component and catalyst used for olefin polymerization |
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| JPS62115004A (en) * | 1985-11-13 | 1987-05-26 | Mitsubishi Petrochem Co Ltd | Storage of catalyst component for polymerization of olefin |
| CN101679559A (en) * | 2007-06-14 | 2010-03-24 | 博里利斯技术公司 | Process for the production of propylene copolymers using a prepolymerised catalyst |
| CN105646742A (en) * | 2016-03-25 | 2016-06-08 | 任丘市利和科技发展有限公司 | Olefin polymer-containing catalyst component and catalyst used for olefin polymerization |
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