Olefin polymerization catalyst slurry, preparation method and application thereof, and propylene polymerization method

Abstract

The invention relates to the field of olefin polymerization catalysts, and discloses an olefin polymerization catalyst slurry, a preparation method and application thereof, and a propylene polymerization method, the method comprises: (1) purifying a prepared catalyst suspension A for olefin polymerization to obtain a purified catalyst suspension B; (2) removing part of the washing solvent from the catalyst suspension B, and mixing the catalyst suspension B with inert grease C to obtain a mixed solution D; (3) in the presence of protective gas, performing vacuum steam stripping on the mixed solution D to obtain a mixed solution E; and (4) mixing the mixed solution E with inert grease C to obtain a catalyst slurry finished product G. When the catalyst slurry prepared by the method is used for a polymerization reaction, the catalyst slurry has good catalytic activity, hydrogen regulation sensitivity and orientation capability, less polymer fine powder is generated, and the safety quality risk is lower.

Description

Technical Field

[0001] The invention relates to the field of olefin polymerization catalysts, and in particular to an olefin polymerization catalyst slurry, a preparation method and application thereof, and a propylene polymerization method. Background Art

[0002] Polyolefin synthetic resins are widely used in various industries due to their excellent thermoplasticity, good mechanical properties, corrosion resistance, etc. More than 95% of polypropylene production still uses Ziegler-Natta (ZN) propylene polymerization catalysts, and the catalysts used in industrial production applications are still mainly the fourth-generation Ziegler-Natta propylene polymerization catalysts.

[0003] Catalysts have a significant impact on the performance and production operations of polypropylene products. The focus of their research and development mainly includes the development of new carriers and processes, internal and external electron donors and additive technologies, etc.

[0004] Commercial olefin polymerization catalysts are generally packaged in two forms: dry powder and slurry. Existing slurry catalysts are also first prepared as dry powder catalysts, and then inert oils (such as white oil, vaseline, etc.) are added to prepare them.

[0005] Existing commercial slurry catalysts mainly include a main catalyst, a co-catalyst (alkyl aluminum compound) and an external electron donor. The preparation process steps of the main catalyst are generally divided into the following steps: a. Preparation of catalyst dry powder: (1) Under the protection of inert gas, the carrier, low-boiling alkane, titanium compound and electron donor are subjected to loading reaction at a certain temperature, and after multiple high-temperature titanium compound treatments and low-boiling alkane washing, a suspension of the main catalyst in low-boiling alkane is obtained, and most of the low-boiling alkanes are removed by filtration; (2) Under the protection of inert gas, in a stirring and vibrating device, the low-boiling alkanes in the catalyst are removed by filtration and vacuum drying to obtain dry powder, and then the catalyst dry powder product is prepared through screening, multi-batch blending and other processes. b. Catalyst slurry configuration: According to the merchant's needs, the inert oil and the dry powder catalyst prepared in step a are mixed in a certain mass ratio, and the slurry catalyst is prepared by physical stirring and mixing at a certain temperature.

[0006] However, the preparation method of this type of catalyst slurry has the following shortcomings: (1) The process flow is long, the preparation cycle is long, and the risk of exposure to air during the catalyst turnover, blending, and transfer process is high. (2) During the vacuum extraction and screening process, the stirring friction of the catalyst in a dry state, the long-term vibration of the particles, and the dry extraction under a negative pressure environment will cause damage to the particle morphology of some catalysts. The broken catalyst is easy to form fine powder in the polymerization reaction, thereby affecting the long-term stable operation of the downstream polyolefin unit. (3) There are great safety risks in the turnover and hoisting process during the catalyst screening, blending, and slurry configuration process.

[0007] Therefore, there is an urgent need to provide a method for preparing an olefin polymerization catalyst slurry with a simple preparation process, which can reduce the risks caused by the hoisting and material turnover processes and reduce the content of fine powder and block materials in the catalyst slurry. Summary of the invention

[0008] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and to provide an olefin polymerization catalyst slurry and a preparation method thereof. The method can effectively shorten the process flow and improve production efficiency; reduce catalyst breakage caused by powder friction and long-term vibration in a dry state, increase polymer fine powder; and reduce the risks caused by hoisting and material turnover processes. In addition, compared with the existing process for preparing catalyst slurry, the catalyst slurry prepared by this method has good catalytic activity, hydrogen sensitivity and directional ability when used in polymerization reactions, and produces less polymer fine powder; and the wet drying method adopted by the present invention has lower safety and quality risks and significantly improves production efficiency.

[0009] In order to achieve the above object, the first aspect of the present invention provides a method for preparing an olefin polymerization catalyst slurry, the method comprising:

[0010] (1) purifying the prepared catalyst suspension A for olefin polymerization to obtain a purified catalyst suspension B;

[0011] (2) removing part of the washing solvent from the catalyst suspension B and mixing it with an inert oil C to obtain a mixed solution D;

[0012] (3) In the presence of a protective gas, the mixed liquid D is subjected to vacuum stripping to obtain a mixed liquid E;

[0013] (4) The mixed solution E is mixed with an inert oil C to obtain a finished catalyst slurry G.

[0014] The second aspect of the present invention provides an olefin polymerization catalyst slurry prepared by the method described in the first aspect.

[0015] The third aspect of the present invention provides use of the catalyst slurry described in the second aspect in olefin polymerization.

[0016] A fourth aspect of the present invention provides a method for propylene polymerization, wherein the method comprises: subjecting propylene to polymerization reaction in the presence of the catalyst slurry of the present invention.

[0017] Through the above technical solution, the present invention achieves the following beneficial technical effects:

[0018] (1) The catalyst slurry prepared by the method of the present invention is used in propylene polymerization reaction, and the catalyst has good activity, hydrogen adjustment sensitivity and directional ability.

[0019] (2) Compared with the prior art (a process of first preparing a dry powder catalyst and then configuring it into a slurry catalyst), when the catalyst slurry prepared by the method of the present invention is used for propylene polymerization, less polymer fine powder is produced, thereby ensuring the quality of the catalyst product.

[0020] (3) The wet drying method adopted in the present invention has lower safety and quality risks and significantly improves production efficiency.

[0021] (4) The preparation method of the present invention does not require steps such as catalyst screening and dry powder blending, thereby avoiding the need for dry powder materials to go through steps such as turnover barrels and hoisting, thereby reducing safety risks such as catalyst exposure and barrel falling. DETAILED DESCRIPTION

[0022] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0023] The first aspect of the present invention provides a method for preparing an olefin polymerization catalyst slurry, the method comprising:

[0024] (1) purifying the prepared catalyst suspension A for olefin polymerization to obtain a purified catalyst suspension B;

[0025] (2) removing part of the washing solvent from the catalyst suspension B and mixing it with an inert oil C to obtain a mixed solution D;

[0026] (3) In the presence of a protective gas, the mixed liquid D is subjected to vacuum stripping to obtain a mixed liquid E;

[0027] (4) The mixed solution E is mixed with an inert oil C to obtain a finished catalyst slurry G.

[0028] In the present invention, the hexane solvent is used to dissolve the hexane in the catalyst pores into the inert solvent, and the inert solvent fills and protects the catalyst pores while forming a protective oil film on the surface of the catalyst particles, thereby reducing the long-term stirring friction of the catalyst particles in the dry state and the damage and agglomeration of the catalyst in the vacuum environment, thereby better maintaining the activity, hydrogen sensitivity and directional ability of the catalyst. Reduce the content of polymer fine powder.

[0029] In the present invention, there is no particular limitation on the preparation method of the catalyst suspension A for olefin polymerization, and a conventional preparation method in the art can be used. The preparation method is: in the presence of a protective gas and at a certain temperature, a carrier, a low-boiling alkane, a titanium compound and an electron donor are subjected to a loading reaction, and the suspension of the main catalyst in the low-boiling alkane is obtained after multiple high-temperature titanium compound treatments and then washed with low-boiling alkane, and most of the low-boiling alkane is removed by filtration to obtain the catalyst suspension A.

[0030] In the present invention, the low boiling point alkane is a conventional inert alkane in the art, preferably a C5-C7 alkane, including branched or linear alkanes, such as at least one of n-pentane, isopentane, hexane and heptane, more preferably hexane.

[0031] In the present invention, the low-boiling alkane mainly acts as a solvent in the catalyst preparation process, which can reduce the concentration and reaction rate of the synthesis reaction, and the solvent itself does not participate in the reaction; in addition, this type of low-boiling alkane is easier to volatilize and remove in the subsequent catalyst drying, and is also easy to recycle and reuse.

[0032] In the present invention, in order to remove large particles and lumps in the catalyst suspension A, the catalyst suspension A needs to be purified. Some catalyst agglomerated particles and irregular materials can be initially filtered out through purification pretreatment.

[0033] According to some embodiments of the present invention, in step (1), the purification treatment is filtration.

[0034] Preferably, the filtering conditions include: the mesh aperture is 10-100 mesh, and the filtering pressure is 0.05 MPa-0.45 MPa, preferably 0.1-0.3 MPa.

[0035] More preferably, the filtering conditions include: the mesh size is 20-70 mesh, and the filtering pressure is 0.1 MPa-0.3 MPa.

[0036] In the present invention, the inert grease has good chemical stability and oxidation safety performance, and has a moderate operating viscosity, which is conducive to the stable dispersion of the catalyst slurry. Preferably, the inert grease C is white oil or vaseline.

[0037] According to some embodiments of the present invention, the inert oil is selected from at least one of 10# white oil, 15# white oil, 32# white oil, 68# white oil, 100# white oil or vaseline. Preferably, the inert oil is 68# white oil and / or 100# white oil.

[0038] In the present invention, the type of white oil is usually divided according to the size of the kinematic viscosity measured at 40°C. For example, 68# white oil means that the kinematic viscosity of white oil at 40°C is 68mm 2 / s.

[0039] According to some embodiments of the present invention, in step (2), the method for removing part of the washing solvent comprises: filtering the catalyst suspension B through a sieve with a pore size of 150-600 mesh to remove most of the supernatant, and then mixing the remaining suspension with the inert oil C.

[0040] In the present invention, the purpose of skimming off most of the supernatant is to directly filter out a large amount of free hexane in the supernatant layer after the catalyst suspension is settled through a movable filter rod, which can effectively reduce the hexane removal time in the subsequent direct configuration process and improve the preparation efficiency.

[0041] During the experiment, the inventors found that when the amount of hexane remaining in the mixed liquid D is too large, the hexane removal time in the subsequent configuration process will be prolonged. In order to shorten the configuration time and improve the preparation efficiency. When the amount of residual hexane solvent is too small, the catalyst wet material will stick together. Due to the large surface tension, after adding the inert grease C, stirring will not work, the resistance is large, and the catalyst particles will break, which will affect the product stability and continuous production of the device. Therefore, it is necessary to control the amount of residual hexane in the mixed liquid D within a certain range.

[0042] According to some embodiments of the present invention, in step (2), the mass ratio of the inert oil C to the solute in the mixed solution D is (0.5-7):1.

[0043] Preferably, the mass ratio of the inert oil C to the solute in the mixed solution D is (0.9-3):1.

[0044] In the present invention, in order to shorten the preparation time and improve the preparation efficiency, it is necessary to further remove the low-boiling-point alkanes remaining in the mixed liquid D.

[0045] According to some embodiments of the present invention, in step (3), the inert gas is nitrogen.

[0046] Preferably, the vacuum stripping conditions include: temperature 30-90°C, vacuum degree -100 kPa to -40 kPa, and time 1-40 h.

[0047] More preferably, the vacuum stripping conditions include: temperature of 50-80°C, vacuum degree of -95 kPa to -70 kPa, and time of 4-20 h.

[0048] In the present invention, when the vacuum stripping conditions meet the above range, the low-boiling-point alkanes remaining in the mixed liquid D can be removed more efficiently, and at the same time, it is beneficial to maintain the performance of each component in the catalyst slurry.

[0049] In the present invention, in order to quickly measure and control the concentration of the catalyst slurry, the inert oil C is mixed with the catalyst slurry twice. In addition, the experiment also found that the viscosity of the supernatant after the catalyst slurry is layered is lower than that of adding the same amount of white oil once, and the slurry concentration is better controlled, which is more conducive to packaging and transfer.

[0050] In the present invention, the catalyst slurry has a lower viscosity and the slurry discharge process is smoother. White oil is a mixture, in which low molecular weight oil accounts for a small proportion of white oil, but plays a key role in viscosity; during the vacuum stripping process to remove hexane, low molecular weight oil will be entrained with hexane, resulting in an increase in slurry viscosity and concentration, affecting the subsequent stability of the discharge, so the secondary addition of white oil can well solve this defect.

[0051] According to some embodiments of the present invention, in step (4), the mass ratio of the inert grease C to the solute in the mixed solution E is (0.2-2): 1. Preferably, the mass ratio of the inert grease C to the solute in the mixed solution E is (0.3-1): 1.

[0052] In the present invention, when the mass ratio of the inert oil C to the solute in the mixed liquid E satisfies the above range, the viscosity of the supernatant of the catalyst slurry can be effectively regulated, which is beneficial to smooth catalyst packaging and discharge, and ensures continuous and stable production; when the mass ratio of the inert oil C to the solute in the mixed liquid E does not meet the above range, the viscosity of the supernatant of the catalyst slurry will be too large, resulting in a slow filtration speed, affecting continuous production.

[0053] According to some embodiments of the present invention, in step (4), the mass ratio of the inert grease C to the solute in the finished catalyst slurry G is 1:(1-10). Preferably, the mass ratio of the inert grease C to the solute in the finished catalyst slurry G is 1:(1.5-6).

[0054] In the present invention, when the mass ratio of the inert grease C to the solute in the catalyst slurry meets the above conditions, the viscosity of the supernatant of the catalyst slurry can be effectively regulated, which is beneficial to smooth catalyst packaging and discharge, and ensures continuous and stable production.

[0055] According to some embodiments of the present invention, in step (4), the mixed liquid E and the inert oil C are mixed and then packaged and filtered.

[0056] Preferably, the packaging temperature is 40-70°C.

[0057] Preferably, the particle size of the sieve for filtering is 10-200 mesh, preferably 20-100 mesh, and more preferably 30-70 mesh.

[0058] The second aspect of the present invention provides an olefin polymerization catalyst slurry prepared by the method described in the first aspect.

[0059] The third aspect of the present invention provides use of the catalyst slurry described in the second aspect in olefin polymerization.

[0060] A fourth aspect of the present invention provides a method for propylene polymerization, wherein the method comprises: subjecting propylene to polymerization reaction in the presence of the catalyst slurry of the present invention.

[0061] Preferably, the polymerization reaction conditions include: temperature of 60-100° C., pressure of 2-3 MPa, and time of 1-3 h.

[0062] According to a particularly preferred embodiment of the present invention, the present invention provides a method for preparing an olefin polymerization catalyst slurry, which is as follows:

[0063] (1) The catalyst suspension A is pressurized to 0.15 MPa-0.3 MPa in a reactor, and is pressed into a slurry kettle through a 20-70 mesh filter, and filtered to obtain a purified catalyst suspension B;

[0064] (2) After filtering out most of the hexane filtrate from the catalyst suspension B in the slurry kettle through a mobile filter press (the sieve particle size of the filter is 150-600 mesh), the remaining catalyst suspension B is transferred to the slurry preparation kettle through the bottom pipeline of the kettle, and then the dehydrated and deoxygenated inert oil C is added to obtain a mixed liquid D;

[0065] Wherein, the mass ratio of the inert oil C to the solute in the mixed solution D is (0.9-3):1;

[0066] (3) Under nitrogen protection, the slurry kettle temperature is set to 50-80°C and the pressure is -95 kPa to -70 kPa, and the mixed solution D is evacuated for 4-20 hours to obtain a mixed solution E;

[0067] (4) After the mixed liquid E is kept at a constant temperature of 50-80°C for 2-3 hours in the slurry kettle, the dehydrated and deoxygenated inert oil C is added for the second time, the catalyst slurry concentration is adjusted, and the slurry is packaged at 40-70°C. The slurry is then filtered through a 30-70 mesh filter F and then divided into slurry packaging barrels to obtain the catalyst slurry product G1.

[0068] After filtering, the catalyst slurry is divided into slurry packaging barrels to obtain a finished catalyst slurry;

[0069] Wherein, the mass ratio of the inert oil C to the solute in the mixed solution E is (0.3-1):1;

[0070] Wherein, the mass ratio of the inert grease C to the solute in the finished catalyst slurry is 1:(1.5-6);

[0071] The D50 of the particles in the catalyst slurry is 20-80 μm; and the content of hexane in the catalyst slurry is 0.05-3 wt%.

[0072] The present invention will be described in detail below through examples.

[0073] The hexane content in the white oil was determined using an Agilent 7890 gas chromatograph.

[0074] The solid content of the catalyst in the slurry was determined in accordance with the "Q / SH 361 533 Gravimetric Method".

[0075] Preparation Example

[0076] The preparation method of catalyst suspension A is as follows: a certain amount of dialkoxymagnesium carrier (110 kg), toluene 600 L, di-n-butyl phthalate (42 kg), and titanium tetrachloride (1100 L) are mixed, reacted at 110° C. for 3 hours, and then heat-treated with a mixed liquid of 300 L of titanium tetrachloride and 1200 L of toluene at 100° C. for 3 times and washed with hexane at 60° C. for 4-5 times to obtain 790 kg of catalyst suspension A containing 120 kg of solid catalyst BCM-100H.

[0077] Example 1

[0078] A method for preparing an olefin polymerization catalyst slurry comprises the following steps:

[0079] (1) The catalyst suspension A is pressurized to 0.1 MPa in a reactor, and is pressed into a slurry kettle through a 30-mesh filter, and filtered to obtain a purified catalyst suspension B;

[0080] (2) After filtering the catalyst suspension B in the slurry kettle through a mobile filter press (the sieve particle size of the filter is 400 mesh) to obtain 500 kg of hexane filtrate, the remaining catalyst suspension B is transferred to the slurry preparation kettle through the bottom pipeline of the kettle, and 180 kg of 68# industrial white oil that has been dehydrated and deoxygenated is added to obtain a mixed solution D;

[0081] (3) Under nitrogen protection, the slurry kettle temperature was set to 60°C and the pressure was -80 kPa, and the mixed solution D was evacuated for 20 hours to obtain a mixed solution E;

[0082] (4) After the mixed liquid E was kept at a constant temperature of 60°C for 2 hours in the slurry kettle, 80 kg of 68# industrial white oil that had been dehydrated and deoxygenated was added for the second time, the concentration of the catalyst slurry was adjusted, and the slurry was packaged at 45°C. The slurry was then filtered through a 60-mesh filter F and then divided into slurry packaging barrels to obtain a catalyst slurry product G1. The solid content of the catalyst in the catalyst slurry in the catalyst slurry product G1 was 30.5 wt%, and the hexane content in the white oil was 0.08%.

[0083] Example 2

[0084] A method for preparing an olefin polymerization catalyst slurry comprises the following steps:

[0085] (1) The catalyst suspension A is pressurized to 0.12 MPa in a reactor, and is pressed into a slurry kettle through a 20-mesh filter, and filtered to obtain a purified catalyst suspension B;

[0086] (2) After the catalyst suspension B is filtered through a mobile filter press (the sieve particle size of the filter is 400 mesh) in the slurry kettle to obtain 550 kg of hexane filtrate, the remaining catalyst suspension B is transferred to the slurry preparation kettle through the bottom pipeline of the kettle, and 200 kg of 68# industrial white oil that has been dehydrated and deoxygenated is added for the first time to obtain a mixed liquid D;

[0087] (3) Under nitrogen protection, the slurry kettle temperature was set to 70°C and the pressure was -80 kPa, and the mixed solution D was evacuated for 20 hours to obtain a mixed solution E;

[0088] (4) After the mixed solution E was kept at a constant temperature of 70° C. for 2 hours in the slurry kettle, 60 kg of 68# industrial white oil that had been dehydrated and deoxygenated was added for the second time, the concentration of the catalyst slurry was adjusted, and the slurry was packaged at 45° C. The slurry was then filtered through a 60-mesh filter F and then divided into slurry packaging barrels to obtain a catalyst slurry product G2. The solid content of the catalyst in the catalyst slurry in the catalyst slurry product G2 was 29.7 wt%, and the hexane content in the white oil was 0.06%.

[0089] Example 3

[0090] A method for preparing an olefin polymerization catalyst slurry comprises the following steps:

[0091] (1) The catalyst suspension A is pressurized to 0.12 MPa in a reactor, and is pressed into a slurry kettle through a 20-mesh filter, and filtered to obtain a purified catalyst suspension B;

[0092] (2) After the catalyst suspension B is filtered through a mobile filter press (the sieve particle size of the filter is 400 mesh) in the slurry kettle to obtain 600 kg of hexane filtrate, the remaining catalyst suspension B is transferred to the slurry preparation kettle through the bottom pipeline of the kettle, and 220 kg of 68# industrial white oil that has been dehydrated and deoxygenated is added for the first time to obtain a mixed liquid D;

[0093] (3) Under nitrogen protection, the slurry kettle temperature was set to 80°C and the pressure was -90 kPa, and the mixed solution D was evacuated for 7 hours to obtain a mixed solution E;

[0094] (4) After the mixed solution E was kept at a constant temperature of 80°C for 2 hours in the slurry kettle, 40 kg of 68# industrial white oil that had been dehydrated and deoxygenated was added for the second time, the concentration of the catalyst slurry was adjusted, and the slurry was packaged at 45°C. The slurry was then filtered through a 60-mesh filter F and then divided into slurry packaging barrels to obtain a catalyst slurry product G3. The solid content of the catalyst in the catalyst slurry in the catalyst slurry product G3 was 30.5 wt%, and the hexane content in the white oil was 1.0%.

[0095] Example 4

[0096] The method of Example 1 was followed, except that 260 kg of 68# industrial white oil that had been dehydrated and deoxygenated was added at once in step (2) to obtain a catalyst slurry product G4. The solid content of the catalyst in the catalyst slurry product G4 was 34.4 wt%, and the hexane content in the white oil was 1.0%.

[0097] Example 5

[0098] The method of Example 1 is followed, except that in step (2), the catalyst suspension B is not filtered to remove part of the washing solvent, but is directly mixed with the inert oil C to obtain a catalyst slurry product G5. The solid content of the catalyst in the catalyst slurry in the catalyst slurry product G5 is 24.9wt%, and the hexane content in the white oil is 5.7%.

[0099] Example 6

[0100] The method of Example 1 was followed, except that in step (2), 55 kg of white oil was added (the mass ratio of inert oil C to the solute in the mixed solution D was 0.46:1), to obtain a catalyst slurry product G6. The solid content of the catalyst in the slurry in the catalyst slurry product G6 was 30.3 wt%, and the hexane content in the white oil was 1.2%.

[0101] Example 7

[0102] The method of Example 1 was followed, except that in step (4), 40 kg of white oil was added (the mass ratio of inert oil C to the solute in the mixed solution E was 0.33:1), to obtain a catalyst slurry product G7. The solid content of the catalyst in the slurry in the catalyst slurry product G7 was 29.8 wt%, and the hexane content in the white oil was 1.4%.

[0103] Comparative Example 1

[0104] A method for preparing an olefin polymerization catalyst slurry comprises the following steps:

[0105] (1) The catalyst suspension A is transferred to a draining kettle, and the excess hexane liquid is filtered out by a mobile filter press device, and vacuum dried for 30 hours at a constant temperature of 50° C., and then a 160-mesh screen is used to screen out the lumps and irregular shapes to obtain a semi-finished dry powder catalyst K1. Multiple batches of dry powder catalysts continuously produced by the device are poured into a blending kettle, and after physical mixing, a finished dry powder catalyst K1 is obtained;

[0106] (2) 120 kg of the finished dry powder catalyst K1 was taken, and the dry powder catalyst K1 and the dehydrated and deoxygenated 68# industrial white oil were added to the slurry preparation kettle at a mass ratio of 30:70. The 68# white oil was added first, and then the finished catalyst K1 was added. Then, the mixture was stirred and mixed at a constant temperature of 60° C. in the slurry kettle for 6 hours to obtain a catalyst K1 slurry. The catalyst slurry concentration in the finished catalyst K1 slurry was 31.0 wt%, and the hexane content in the white oil was 2.02%.

[0107] Test Case

[0108] The olefin polymerization catalyst slurries G1-G5 and K1 prepared in the above examples and comparative examples were subjected to polymerization reactions respectively, and the catalyst activity, polymer melt index, Ti content (main active component content), isotacticity, and fine powder content were measured. The specific results are shown in Table 1.

[0109] Method for determining the activity of the catalyst slurry: In a 5L autoclave, after being fully replaced by gaseous propylene, add 5mL of triethylaluminum hexane solution (the concentration of triethylaluminum is 0.5mmol / mL), 1mL of cyclohexylmethyldimethoxysilane (CHMMS) hexane solution (concentration 0.1mmol / mL) at room temperature, add 2L of liquid propylene, 0.9MPa of hydrogen and 6.0mg of catalyst dry powder (a small amount of catalyst slurry is taken, washed with hexane several times and then dried with nitrogen). Close the autoclave, stir the reaction for 10min, raise the temperature to 70℃, and polymerize for 1h at a kettle temperature of 70℃ and a kettle pressure of 3.0MPa. After the reaction is completed, stop stirring, remove the unpolymerized propylene monomer, collect the polymer, vacuum dry, weigh, and determine the catalyst activity, melt index and isotacticity of the polymer.

[0110] The Ti content in the catalyst slurry was determined according to "Q / SH 361 526" and the instrument model was 721 spectrophotometer.

[0111] The catalyst activity was measured according to "Q / SH 361 528", catalyst activity (kg / g Cat) = polymer weight (kg) / solid catalyst component weight (g Cat).

[0112] The polymer melt index (MI) refers to the melt index of a polymer obtained by using an olefin polymerization catalyst in a polymerization reaction, and is measured in accordance with GB / T3682-2000.

[0113] The isotacticity (II) of polymers is determined in accordance with GB / T 2412. The specific determination method is as follows: 2 g of dried polymer sample is placed in an extractor and extracted with boiling heptane for 6 hours. The residue is dried to constant weight, and the ratio of the polymer weight (g) to 2 (g) is the isotacticity.

[0114] Determination of polymer fine powder content: The polymer powder obtained by catalyst polymerization is sieved using a 150-mesh sieve, and the weight proportion of powder smaller than 150 mesh is characterized as the fine powder content.

[0115] Table 1

[0116]

[0117]

[0118] By comparing the data of Examples 1-7, Comparative Example 1 and Table 1, it can be seen that when the catalyst slurry prepared by the method of the present invention is used in propylene polymerization, the catalyst has good activity, hydrogen adjustment sensitivity and directional ability, the activity of the catalyst is above 61.9kg / g Cat, MI is above 25.2g / 10min, Ti content is above 2.27wt%, and the isotacticity is above 98.2%. At the same time, compared with the method of preparing dry powder catalyst first and then configuring slurry catalyst in the original process, the catalyst slurry prepared by the present method produces less polymer fine powder when participating in the polymerization reaction, and the subdivision content reaches 0.2wt%; and the safety and quality risks of the wet drying method of the present invention are smaller, and the production efficiency is significantly improved; while the olefin polymerization catalyst slurry prepared by the prior art in Comparative Example 1, the activity, hydrogen adjustment sensitivity and directional ability of the catalyst are all lower than those of the catalyst of the present invention.

[0119] In summary, according to the technical scheme of the present invention, the prepared olefin polymerization catalyst slurry has good properties. Compared with the prior art (preparing a dry powder catalyst first and then configuring it into a slurry catalyst process), the preparation method of the present invention has greatly improved production efficiency, reduced the amount of polymer fine powder, and can be free of catalyst screening, dry powder blending and other processes, effectively avoiding the need for dry powder materials to be circulated and hoisted in turnover barrels, reducing safety risks such as catalyst exposure and barrel falling. In addition, the catalyst slurry storage tank can be cleaned and reused, which further reduces the waste of resources compared to dry powder catalysts.

[0120] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing an olefin polymerization catalyst slurry, characterized in that: The method includes: (1) purifying the prepared catalyst suspension A for olefin polymerization to obtain a purified catalyst suspension B; (2) removing part of the washing solvent from the catalyst suspension B and mixing it with an inert oil C to obtain a mixed solution D; (3) In the presence of a protective gas, the mixed liquid D is subjected to vacuum stripping to obtain a mixed liquid E; (4) The mixed solution E is mixed with an inert oil C to obtain a finished catalyst slurry G.

2. The method according to claim 1, wherein: In step (1), the purification treatment is filtration; Preferably, the filtering conditions include: the mesh size is 10-100 mesh, and the filtering pressure is 0.1MPa-0.4MPa; More preferably, the filtering conditions include: the mesh aperture is 20-70 mesh, and the filtering pressure is 0.15 MPa-0.3 MPa.

3. The method according to claim 1 or 2, wherein: The inert oil is selected from at least one of 10# white oil, 15# white oil, 32# white oil, 68# white oil, 100# white oil or vaseline, preferably 68# white oil and / or 100# white oil.

4. The method according to any one of claims 1 to 3, wherein: In step (2), the method for removing part of the washing solvent comprises: filtering the catalyst suspension B through a sieve with a pore size of 150-600 mesh to remove most of the supernatant, and then mixing the remaining suspension with the inert oil C.

5. The method according to any one of claims 1 to 4, wherein: In step (2), the mass ratio of the inert oil C to the solute in the mixed solution D is (0.5-7):1, preferably (0.9-3):

1.

6. The method according to any one of claims 1 to 5, wherein: In step (3), the protective gas is nitrogen; Preferably, the conditions of the vacuum stripping include: temperature 30-90°C, vacuum degree -100 kPa to -40 kPa, time 1-40 h; More preferably, the conditions for the vacuum stripping include: a temperature of 50-80°C, a vacuum degree of -95 kPa to -70 kPa, and a time of 4-20 h.

7. The method according to claim 1, wherein: In step (4), the mass ratio of the inert oil C to the solute in the mixed solution E is (0.2-2):1, preferably (0.3-1):

1.

8. The method according to claim 1, wherein: In step (4), the mass ratio of the inert oil C to the solute in the catalyst slurry product G is 1:(1-10), preferably 1:(1.5-6).

9. The method according to claim 1, wherein: In step (4), the mixed liquid E and the inert oil C are mixed and then packaged and filtered; Preferably, the packaging temperature is 40-70°C; Preferably, the particle size of the filtering screen is 10-200 mesh, preferably 20-100 mesh, and more preferably 30-70 mesh.

10. The olefin polymerization catalyst slurry obtained by the method according to any one of claims 1 to 9; Preferably, the D50 of the particles in the catalyst slurry is 10-100 μm, preferably 20-80 μm; the content of hexane in the catalyst slurry is 0.01-4 wt%, preferably 0.05-3 wt%.

11. Use of the catalyst slurry according to claim 10 in olefin polymerization.

12. A method for propylene polymerization, characterized in that: The method comprises: subjecting propylene to polymerization reaction in the presence of the catalyst slurry as claimed in claim 10.

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