CN116615473A

CN116615473A - Method

Info

Publication number: CN116615473A
Application number: CN202180076911.0A
Authority: CN
Inventors: T·V·霍雷曼斯
Original assignee: Ineos USA LLC
Current assignee: Ineos USA LLC
Priority date: 2020-11-17
Filing date: 2021-11-10
Publication date: 2023-08-18
Also published as: US11512150B2; US20220153880A1

Abstract

The present invention relates to a process for supplying a polymerization catalyst component to a polymerization reactor, comprising: a. providing a first stream comprising the catalyst component, b. Providing a diluent stream in a second line, c. Contacting the first stream and the diluent stream to form a mixed stream and flowing the mixed stream to a polymerization reactor, and further characterized by at least one of the following: i) The volume of the mixing chamber is less than 150ml, ii) the volume of the mixing chamber is such that the residence time of the flow rate is less than 5 seconds based on the total volume of the mixing stream, iii) the mixing chamber is free of mechanical agitation, the mixing chamber having a cover that is removable to allow cleaning of the mixing chamber in situ.

Description

Method

Technical Field

The present invention relates to a process for supplying a polymerization catalyst component to a polymerization reactor, and in particular wherein the catalyst component is mixed with a diluent stream and passed into the polymerization reactor.

Background

Catalytic polymerization of olefin monomers to produce polymers is well known and many processes are operated industrially, including in the gas phase, solution and slurry phases. The catalyst or catalyst system generally comprises several catalyst components, such as a transition metal containing catalyst (often referred to simply as a "procatalyst"), an alkyl metal cocatalyst or modifier. In a continuous commercial process, all of the catalyst components and monomers are provided to the reactor.

Because of the relatively high productivity of modern polymerization catalysts, it is neither necessary nor economical to attempt to recover the catalyst components from the product, and thus it is necessary to provide a continuous process to replace the catalyst components withdrawn with the product continuously or discontinuously with fresh catalyst components. Another consequence of the relatively high productivity of modern polymerization catalysts is the need to provide relatively small amounts of catalyst components.

Depending on the process, the catalyst may be provided in supported or unsupported form and may be injected directly or mixed with the other components of the reaction. In many cases, it is advantageous to mix the catalyst with a dilution liquid to form a slurry, which is then passed into the reactor, especially because it is generally easier to control the addition of catalyst to the reactor by metering the diluted catalyst slurry using a pump.

EP 1660231 relates to a process for preparing a catalyst slurry and supplying it to a polymerization reactor in which polyethylene is prepared. The catalyst is initially present in the form of a "concentrated" slurry and diluted in an agitated mixing vessel to form a diluted catalyst slurry. The diluted slurry was then pumped into the reactor using a diaphragm pump.

The mixing vessel in EP 1660231 is relatively large in volume, sufficient to prepare a large batch of diluted catalyst slurry, including a volume sufficient to fill the daily amount storage tank when preparing a new batch.

Although the system of EP 1660231 is capable of preparing large batches of catalyst and passing it into the reactor, it is necessary to carefully manage its inventory, both to ensure that a new batch of diluted catalyst is prepared before the old batch is fully used and to ensure that not too much diluted catalyst is prepared before the catalyst is replaced, which may result in batches of unused catalyst having to be dumped to prepare a different catalyst. The process in EP 1660231 is also a "heavy duty" apparatus requiring multiple agitation vessels and interconnecting piping, as well as pumps for transferring the diluted slurry from the mixing vessel to the reactor and additional pumps or metering valves for first transferring the concentrated slurry to the mixing vessel.

Disclosure of Invention

The present invention provides an improved process for preparing a dilute slurry containing a catalyst component, which can be carried out continuously in a relatively small chamber, and which uses the flow of the diluent stream to provide adequate mixing and transfer of the mixture to a downstream reactor.

Accordingly, in a first aspect, the present invention provides a process for supplying a polymerisation catalyst component to a polymerisation reactor comprising:

a. a first stream comprising a catalyst component is provided in a first line connected to and downstream of the pump outlet or flow control valve,

b. a diluent stream is provided in a second line,

c. contacting the first stream and the diluent stream to form a mixed stream and flowing the mixed stream to a polymerization reactor,

characterized in that the mixing of the first stream and the diluent stream is performed by providing the first stream from the first line and the diluent stream from the second line, respectively, to a mixing chamber having an enlarged cross section compared to the first and second lines, and in that at least one of the following applies:

i) The volume of the mixing chamber is less than 150cm ³ ，

ii) the volume of the mixing chamber is such that the residence time of the flow rate is less than 5 seconds based on the total volume of the mixed stream,

iii) The mixing chamber is not mechanically agitated and,

iv) the mixing chamber has a lid that is removable to allow cleaning of the mixing chamber in situ.

Drawings

The figures are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures is represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. In the drawings:

FIG. 1 shows in diagrammatic form a top view of a cylindrical mixing chamber; and

fig. 2 shows in diagrammatic form a side view of the same mixing chamber.

Detailed Description

The present invention provides a method for supplying a polymerization catalyst component to a polymerization reactor. Typical catalyst components, although depending on the particular catalyst, are well known in the art. However, for the avoidance of doubt, it is noted that the term "catalyst component" generally includes the following:

a) A polymerization catalyst which is active and which can be used in the absence of any other catalyst component (i.e. the catalyst is a catalyst component),

b) All components in the polymerization catalyst, which comprise a main catalyst component (hereinafter "main catalyst") and a cocatalyst component (hereinafter "cocatalyst"), wherein the latter is required to provide the main catalyst component with a suitable catalytic activity, and

c) Any catalyst modifier component (hereinafter "modifier") that can be used with the catalyst in (a) or (b).

The term "catalyst" may sometimes be used in the prior art to refer to the catalysts according to (a) above, but also to the "procatalyst" according to (b) above. However, although different terms may be used, examples of two "types" of polymerization catalysts, and thus, examples of catalyst components that constitute the present invention, are well known in the art. Further, and again for the avoidance of any doubt, any of the above "types" of catalysts (a) and (b) may be used with other catalyst components. For example, either type may be used with the modifier according to (c), while those of type (a) may be used with the cocatalyst component, if not necessary. (some examples of the different components are discussed further below.)

More generally, the specific characteristics of the catalyst component in the first stream of the present invention are not as critical as the manner in which it is mixed with the diluent stream in the mixing chamber. In particular, the invention is characterized in that at least one of the features (i) to (iv) applies. Preferably, at least two of features (i) to (iv) apply, such as at least 3 of them, and most preferably all of them apply.

Options (i) and (ii) are directly or indirectly related to the size of the mixing chamber.

It is particularly preferred that the mixing chamber is relatively small, which may be defined in absolute terms as in option (i) or by the residence time of the mixed stream (or both) as in option (ii).

With respect to absolute volume, the mixing chamber preferably has a volume of less than 120cm ³ Such as less than 100cm ³ Is defined by the total volume of (2). The volume is preferably at least 5cm ³ . In a particularly preferred embodiment, the volume is from 25 to 75cm ³ Such as 30-60cm ³ 。

With respect to the residence time, this is defined herein as the total volumetric flow rate based on the mixed flow, which means that the residence time is equal to the volume of the mixing chamber divided by the volumetric flow rate of the mixed flow. This is preferably less than 4 seconds, such as less than 2 seconds, and even more preferably less than 1 second. The residence time is typically at least 0.05 seconds, and most preferably in the range of 0.1 seconds to 0.5 seconds.

The mixing chamber has an enlarged cross-section compared to the first and second lines. In a preferred embodiment, the mixing chamber has a cylindrical cross section, preferably with an inner diameter of 2-10 times the inner diameter of the first line. The cylindrical cross section may have a length to diameter ratio of 0.5-10.

In case the mixing chamber has a cylindrical cross section, the mixing chamber may comprise a first inlet for the first stream from the first line, a first inlet located at the side of the cylinder and a second inlet for the diluent stream from the second line, located at an angle of 15 ° -90 °, and preferably 45 ° -90 °, to the first inlet. The mixing chamber is also provided with an outlet through which the mixed stream exits the mixing chamber to pass into the polymerisation reactor, and preferably the outlet is located opposite the cylindrical first inlet (i.e. at an angle of at least 90 ° to the first inlet in either direction) and preferably at an angle of at least 90 ° to the first inlet in the opposite direction to the second inlet (such that the outlet is at least 105 °, preferably at least 135 ° to the second inlet). Preferably, the outlet is at a degree of 135 ° -225 ° from the first inlet.

This configuration provides the most efficient mixing of the first stream and diluent stream, as well as allows the momentum in the incoming diluent stream to be most efficiently utilized to provide mixing and transfer the mixed stream to a downstream reactor.

Either stream, but particularly the diluent stream, may optionally enter the mixing chamber tangentially to enhance mixing.

The mixed stream passes from the mixing chamber into the polymerization reactor, preferably without any additional pumping or metering devices in the flow path between the two. Most preferably, the mixing chamber is connected to the reactor by a conduit without any intermediate pump, vessel or other mixing means.

The mixing chamber may provide internal components that aid in mixing. However, it is preferred that no mechanical agitation is provided in the mixing chamber, which means that there is no agitator or other agitator that needs to be driven by a motor. Most preferably, no internals are provided to aid mixing.

In feature (iv) of the invention, the mixing chamber is provided with a lid that is removable to allow cleaning of the mixing chamber in situ. In particular, some polymerization catalyst components may react with impurities in the diluent stream to produce deposits. For example, a Ziegler-Natta procatalyst may react with residual moisture to precipitate a viscous titanium-containing deposit, and an alkyl aluminum cocatalyst, such as triethylaluminum, may react with moisture to form an aluminum hydroxide deposit. Although most diluents have strict specifications that define a maximum water content, even minute amounts (less than 1 ppm) of water can result in slow deposit build-up over time.

In the present invention, the mixing of the first stream and the diluent stream is performed by providing the first stream from the first line and the diluent stream from the second line, respectively, to a mixing chamber having an enlarged cross section compared to the first. The separate provision of these two streams ensures that mixing occurs in the mixing chamber rather than in the upstream narrower line, while the enlarged cross-section of the mixing chamber allows the deposit to build up to some extent without the chamber becoming plugged. This increases the time required before the mixing system has to be cleaned.

However, the mixing chamber may still require periodic cleaning. A removable cover is provided to allow in situ cleaning of the mixing chamber and then to enable such cleaning to be performed without physically disconnecting the mixing chamber from the upstream (first and second) and downstream (lines to the reactor) lines. ( "in situ" as used in this context means that the mixing chamber can be cleaned without moving and disconnecting the mixing chamber from the upstream and downstream lines. Typically, the mixing chamber is isolated from the first line, the second line, and downstream systems to the polymerization reactor so that no flow can occur, and then the cap can be removed. )

While this is preferred, alternatively the mixing chamber may be designed to be isolated from the system and physically removed for off-line cleaning, or simply replaced with a new mixing chamber, which may be connected to the first line, the second line and the downstream system.

The first stream is provided in a first line connected to and downstream of the pump outlet or flow control valve. The first stream is typically in liquid form, such as a slurry of the catalyst components in a carrier liquid. A pump or flow control valve controls the flow of the first stream to the mixing chamber. Preferably, the first line is connected to and downstream of the pump outlet. The use of a pump rather than a control valve generally provides for more accurate and reliable flow of the first stream. The preferred pump for pumping the first stream, particularly when the first stream comprises a catalyst or a procatalyst slurry, is a progressive cavity pump. Diaphragm pumps may also be used.

The first stream and the diluent stream are typically continuously supplied to the mixing chamber. This then provides a continuous supply of the mixed stream comprising the catalyst components to the polymerization reactor. Although continuous supply is preferred, it is not excluded that the supply of the first stream to the mixing chamber may be interrupted, either occasionally or temporarily, to interrupt the supply of the catalyst components to the reactor. In this case, the total time of any one or more interruptions should be shorter than the total time during which the first stream is supplied. For example, the first stream should be supplied to the mixing chamber at least 80% of the time during which the polymerization is carried out in the polymerization reactor. This may be considered as the first stream and diluent stream being supplied to the mixing chamber "substantially continuously".

In a preferred embodiment of the invention, the mixing chamber forms a low point of the first stream in the first line, in particular when the first stream comprises a catalyst component comprising particles, such as a supported procatalyst. As used herein, this means that if the pump for the first line fails or the flow to the first line is otherwise stopped, any particles in the first line will collect in the mixing chamber under the influence of gravity. This empties the solids of the first line between the pump outlet or control valve and the mixing chamber, preventing solids from settling into the first line and possibly clogging the line. It is apparent that this is particularly relevant where the first stream is a slurry of catalyst or procatalyst particles, which are preferred embodiments described further below.

The enlarged volume of the mixing chamber generally reduces the risk of settled particles blocking the chamber. However, even if it does clog, the removable cap provided enables cleaning of that portion of the mixing system without disconnection.

In a preferred embodiment, two (or more) sets of parallel first lines, second lines and mixing chambers connected to the polymerization reactor may be provided so that one mixing chamber may be cleaned while continuing to feed the catalyst components to the reactor via the second mixing chamber. This enables the polymerization to be operated even when one mixing chamber is cleaned, which enables continuous operation.

The process of the present invention may be applied to any suitable polymerization process wherein the polymerization catalyst component is diluted in a diluent stream prior to being passed to the reactor.

In one embodiment, the polymerization reactor may be a slurry phase polymerization reactor. Such reactors are well known and include, for example, slurry stirred tank reactors and slurry loop reactors.

In another embodiment, the polymerization reactor may be a gas phase polymerization reactor, such as a gas phase fluidized bed polymerization reactor, such as a vertical directional fluidized bed reactor, or a gas phase polymerization reactor that in use contains a subfluidized particulate bed of polymer, such as a vertical stirred bed polymerization reactor or a horizontal stirred bed polymerization reactor.

Preferably, the polymerization reactor is a reactor for the polymerization of ethylene and/or propylene, and in particular for the polymerization of propylene. Particularly preferred polymerization reactors to which the process can be applied are propylene polymerization reactors, especially vertical or horizontal stirred bed propylene polymerization reactors.

The first stream comprises a catalyst component. As already mentioned, the polymerization catalyst may comprise several catalyst components, such as a procatalyst, cocatalyst or modifier containing a transition metal.

Examples of suitable catalysts known in the art are Ziegler-Natta, metallocene and chromium catalysts. Ziegler-Natta catalysts generally contain a transition metal compound such as a titanium halide and a group 2 metal compound such as magnesium chloride. Ziegler-Natta catalysts may also include inert support materials such as metal oxides or alumina-based metal oxides, for example alumina or silica. The metallocene catalyst is typically a silica/MAO supported transition metallocene complex. The chromium catalyst is typically a silica-supported chromium compound activated at an elevated temperature to produce a silica-supported chromium oxide compound.

The procatalyst for the above catalysts may use a cocatalyst to become catalytically active. Cocatalysts may also be used to improve catalyst performance. The cocatalyst is generally selected from group 3 metal alkyls, preferably boron or aluminum alkyls. Examples of suitable aluminum alkyls include trialkylaluminum, dialkylaluminum hydride, alkylaluminum dihydride, dialkylaluminum halide, alkylaluminum dihalide, dialkylaluminum alkoxide, such as Triethylaluminum (TEAL) or diethylaluminum Dichloride (DEAC). Examples of suitable boranes include trialkylboron, such as Trimethylboron (TEB).

Also as previously described, the catalyst may also include a modifier. A "modifier" as defined herein is a compound added in addition to any cocatalyst, and which modifies the catalyst performance and/or polymer properties. Preferably, the modifier contains at least one functional group capable of donating electrons to a metal atom of the catalyst or procatalyst. A "functional group" as defined herein is a group containing at least one heteroatom such as oxygen, sulfur, nitrogen, phosphorus, etc., capable of donating an electron to a metal atom. Most preferably, the functional group is an ether group, an ester group, an amine group, an amide group, or a phosphine group. Examples of modifiers are selectivity control agents that modify the stereoselectivity of the catalyst in olefin polymerization and activity control agents that modify the activity of the catalyst.

Examples of selectivity control agents are alkoxysilane or diether compositions. The alkoxysilane has the general formula: siR (SiR) _m (OR’) _4-m Wherein R is independently each occurrence a hydrocarbyl or amino group optionally substituted with one or more substituents containing one or more group 14, 15, 16 or 17 heteroatoms. R contains up to 20 atoms excluding hydrogen and halogen, R' is C1-20 alkyl, and m is 0, 1, 2 or 3. In one embodiment, R is C6-12 aryl or aralkyl, C1-20 alkyl, C3-12 cyclopropyl, C3-12 branched alkyl, or C3-12 cyclic amino, R' is C1-4 alkyl, and m is 1 or 2. Examples of suitable alkoxysilanes include dicyclopentyl dimethoxy silane, di-tert-butyldimethoxy silane, methylcyclohexyl dimethoxy silane, ethylcyclohexyl dimethoxy silane, diphenyldimethoxy silane, diisopropyldimethoxy silane, di-n-propyldimethoxy silane, diisobutyldimethoxy silane, isobutylisopropyldimethoxy silane, di-n-butyldimethoxy silaneMethoxysilane, cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, diethylaminotriethoxysilane, cyclopentylpyrrolidinyldimethoxysilane, bis (pyrrolidinyl) dimethoxysilane, bis (perhydroisoquinolino) dimethoxysilane and dimethyldimethoxysilane. In one embodiment, the alkoxysilane may be dicyclopentyl dimethoxy silane, methylcyclohexyl dimethoxy silane, n-propyl trimethoxy silane, or any combination thereof. In another embodiment, the alkoxysilane composition includes two or more of the above alkoxysilanes.

The diethers have the general formula: RR' C (CH) ₂ -CH ₂ OR”) ₂ Wherein R, R 'and R' are each independently C1-20 alkyl optionally substituted with one or more substituents containing one or more heteroatoms. Examples of suitable diethers are 2, 2-diisobutyl-1, 3-dimethoxypropane, 2-isobutyl-2-isopropyl-1, 3-dimethoxypropane or 2, 2-dicyclopentyl-1, 3-dimethoxypropane.

Examples of activity control agents are carboxylic acid esters, poly (alkylene glycols), poly (alkylene glycol) esters and polymeric or oligomeric compounds containing more than one ether group.

The carboxylic acid esters may be aromatic mono-or poly-carboxylic acid esters or aliphatic acid esters when used.

Examples of suitable aromatic carboxylic acids include C1-10 alkyl or cycloalkyl esters of aromatic monocarboxylic acids. Suitable substituted derivatives thereof include compounds substituted on both the aromatic ring or ester group with one or more substituents containing one or more group 14, 15, 16 or 17 heteroatoms, especially oxygen. Examples of such substituents include (poly) alkyl ethers, cycloalkyl ethers, aryl ethers, aralkyl ethers, alkyl sulfides, aryl sulfides, dialkylamines, diarylamines, and trialkylsilyl groups. The aromatic carboxylic acid ester may be a C1-20 hydrocarbyl ester of benzoic acid in which the hydrocarbyl group is unsubstituted or substituted with one or more substituents containing a group 14, 15, 16 or 17 heteroatom and its C1-20 (poly) hydrocarbyl ether derivative, or its C1-4 alkyl benzoate and C1-4 cycloalkyl derivative, or methyl benzoate, ethyl benzoate, n-propyl benzoate, methyl p-methoxybenzoate, methyl p-ethoxybenzoate, ethyl p-methoxybenzoate and ethyl p-ethoxybenzoate. In one embodiment, the aromatic monocarboxylic acid is ethyl p-ethoxybenzoate.

The activity controlling agent may be an aliphatic acid ester. The aliphatic acid esters may be fatty acid esters, may be C4-C30 aliphatic acid esters, may be mono or poly (two or more) esters, may be linear or branched, may be saturated or unsaturated, and any combination thereof. The C4-C30 aliphatic acid esters may also be substituted by one or more substituents containing heteroatoms of groups 14, 15 or 16 or 17. Examples of suitable C4-C30 aliphatic acid esters include C1-20 alkyl esters of aliphatic C4-30 monocarboxylic acids, C1-20 alkyl esters of aliphatic C8-20 monocarboxylic acids. C1-4 allyl mono-and diesters of aliphatic C4-20 mono-and dicarboxylic acids, C1-4 alkyl esters of aliphatic C8-20 mono-and dicarboxylic acids, and C4-20 alkyl mono-or polycarboxylic ester derivatives of C2-100 (poly) diols or C2-100 (poly) glycol ethers. In another embodiment, the C4-C30 aliphatic ester may be isopropyl myristate, di-n-butyl sebacate, (poly) (alkylene glycol) mono-or diacetate, (poly) (alkylene glycol) mono-or dimyristate, (poly) (alkylene glycol) mono-or dilaurate, (poly) (alkylene glycol) mono-or dioleate, (poly) (alkylene glycol) mono-or distearate, glyceryl triacetate of C2-40 aliphatic carboxylic acids, and mixtures thereof.

In the case where the first stream comprises a liquid catalyst component, then the catalyst component may be used as the first stream "neat" or as a solution in a diluent. When used, the diluent may be the same or different in composition from the diluent stream used in step (b). The diluent in such a solution is preferably a component already used in the polymerization process, such as a monomer or an inert diluent. Examples are isobutane for slurry loop ethylene polymerization processes and propylene for bulk propylene polymerization processes, as described further below with respect to diluent flow.

Even if already provided as a solution in a diluent, the first stream in step (a) may in this embodiment be considered "concentrated" and after mixing with the diluent stream it may be considered "diluted". ( In this case, "concentrated" generally means that the concentration of the catalyst component in the first stream is at least 5wt%, and preferably at least 10wt%. The concentration may be up to and including 100% (if the catalyst components are used in "pure"). )

In a most preferred embodiment, the first stream comprises a procatalyst, and most preferably comprises a procatalyst slurry.

The procatalyst in this embodiment may be any procatalyst commonly used in such polymerization reactions, including Ziegler-Natta, chromium and metallocene procatalysts. The procatalyst is preferably a Ziegler-Natta procatalyst.

The procatalyst slurry as provided in step (a) of this embodiment generally comprises procatalyst particles suspended in a carrier liquid. The carrier liquid may be the same or different in composition from the diluent stream used in step (b).

It should also be noted, and as will be apparent from some examples below, that a "carrier liquid" may comprise a mixture of diluent compounds, and the term "carrier liquid" is used to include such a mixture as well as individual compounds. (and for the avoidance of doubt, when the first stream comprises the catalyst component in the form of a solution in the diluent, this also applies to the diluent in the first stream.)

The procatalyst slurry as provided in step (a) in this embodiment may be considered "concentrated". In the present invention, this means that the concentration of the procatalyst in the carrier liquid may be at least 5wt%, and preferably at least 10wt%, typically 10-40wt%. The carrier liquid is preferably an inert diluent. Examples of typical inert diluents include mineral oils, but any inert diluent, especially alkanes or mixtures of alkanes, may be used as carrier liquid.

( For the avoidance of doubt, the term "inert diluent" as used herein may refer to a single inert compound or a mixture of inert compounds in a manner similar to that in which the term "carrier liquid" is used to include the mixture as well as the single compounds. According to the invention, compounds are considered inert if they do not react with the procatalyst in the polymerization reactor. )

In general, the polymerization procatalyst may be supplied in solid (dry) form. If this is the case, the procatalyst slurry used in step (a) of this embodiment may then be prepared from the solid procatalyst by adding the loading solution to form a slurry suitable for further dilution according to the invention.

Or the procatalyst may be supplied, for example, in the form of a slurry in mineral oil, in which case such procatalyst slurry may be used "as supplied" in step (a), or may be "pre-diluted" to form the first stream before it is further diluted according to the invention. (in the latter case, the carrier liquid is then the supplied main catalyst slurry and the liquid mixture for pre-dilution.)

More generally, the catalyst component (such as the procatalyst) and whether initially solid or liquid/slurry is mixed with the liquid carrier or any upstream of the diluent to form the first stream can be carried out, for example, by dilution in an upstream mixing tank. The carrier liquid and diluent suitable for any such step will generally depend on the polymerization process and may be the same as the diluent stream provided in step (b) of the present invention, examples of which are described below, or may be different.

However, it is preferred that any diluent/carrier liquid in the first stream as provided in step (a) is an inert diluent, whereas the diluent stream used in step (b) may be an inert diluent but may also comprise or consist of monomers as discussed further below.

The diluent stream provided in the second line will be selected according to the polymerization process and according to the catalyst components in the first stream. Which may be the same as any diluent/carrier liquid present in the first stream prior to mixing. However, where the first stream comprises catalyst or procatalyst slurry in a carrier liquid, the diluent stream is typically different from the carrier liquid.

In some embodiments, the diluent stream may be an inert diluent. The diluent stream may be one or more C2-C6 alkanes. For example, for slurry polymerization of ethylene in a loop reactor, the diluent stream will preferably be the inert diluent used in the reaction, most typically isobutane. For the gas phase polymerization of ethylene in a fluidized bed polymerization reactor, the diluent stream may be an inert hydrocarbon, such as one or more pentanes, which also serves as a condensing agent in the reactor. In the propylene polymerization process, an inert diluent such as propane may be used, or the monomer itself may be used as the diluent.

In a preferred embodiment, the diluent stream comprises monomers to be polymerized in the polymerization reactor. In a particularly preferred embodiment of the invention, the diluent stream in the second line comprises propylene, and more preferably propylene. Typically, but especially where the first stream comprises the procatalyst, the diluent stream is preferably propylene, such as fresh (polymerization grade) propylene, which has not been previously contacted with an alkyl aluminum compound. ("fresh" means propylene that is first introduced into the polymerization reactor (via the described process) and which can be contrasted with recycled propylene recovered from downstream processing.)

The relative mass flow rates of the first stream and diluent stream will be selected based on the desired concentration of catalyst components in the mixed stream, which itself will depend on the concentration of catalyst components in the first stream prior to mixing. However, the mass flow rate of the diluent stream preferably significantly exceeds the first stream in the first line, such as at least 5 times the mass flow rate of the first stream in the first line.

With respect to the first stream comprising catalyst or procatalyst slurry, the mass flow rate of the diluent stream is preferably at least 10 times the mass flow rate of the first stream (catalyst/procatalyst slurry) in the first line. For example, when propylene is used as the diluent, the preferred ratio is 20-1000 times the mass flow rate of the diluent stream in the second line as the mass flow rate of the slurry in the first line. In particular, where the diluent stream comprises reactants in a subsequent polymerization reactor, there is no particular concern about feeding a large amount of diluent stream and thus a relatively large flow of diluent stream may be used. In fact, a large amount of diluent is preferred because it reduces the residence time of the catalyst or procatalyst in the transfer line to the reactor and improves process control.

Especially in this embodiment, and more typically, it is preferred that the residence time between the mixing chamber and the reactor is less than 20 seconds.

It is possible, but not necessary, to provide external heating or cooling to the mixing process/mixing stream (e.g., by heating or cooling the first stream, diluent stream and/or mixing chamber, or transfer line to the reactor). In one embodiment, mixing may be performed at a sub-ambient temperature, for example by using one or more coolings applied to the first or second lines or mixing chamber, or preferably by providing a previously cooled diluent stream. This may reduce the reaction of the procatalyst with monomer such as propylene (when used) or the catalyst components with any moisture present in the diluent stream. However, the residence time in the present invention is preferably minimized and/or, when the first stream comprises the main catalyst, the diluent stream in the second line does not comprise propylene previously contacted with an alkyl aluminum compound to avoid the need for cooling.

The mixing is preferably carried out at or near ambient temperature, such as in the range of 5-35 ℃.

In another embodiment, the invention provides an apparatus for use in the above process.

Accordingly, the present invention also provides an apparatus for supplying a polymerization catalyst component to a polymerization reactor, the apparatus comprising:

a. a first line for a first stream comprising the catalyst component, the first line being connected to and downstream of the pump outlet or flow control valve,

b. a second line for the flow of diluent,

c. a mixing chamber configured to contact the first stream in the first line and the diluent stream in the second line to form a mixed stream, and

d. a transfer line for passing the mixed stream through the polymerization reactor,

characterized in that the first and second lines are connected to a mixing chamber, respectively, and that the mixing chamber has an enlarged cross section compared to the first and second lines, and in that at least one of the following applies:

i) The volume of the mixing chamber is less than 150ml,

iii) The mixing chamber is not mechanically agitated and,

Examples

The invention will now be described with reference to the accompanying drawings and the following examples in which a procatalyst slurry is mixed with propylene, wherein:

fig. 2 shows in diagrammatic form a side view of the same mixing chamber.

As shown in fig. 1 and 2, the mixing chamber comprises a first inlet (1) for a first line (2), a second inlet (3) for a second line (4) and an outlet (5) with a line (6) to a polymerization reactor (not shown). The second inlet is at an angle of 45 deg. to the first inlet and the outlet is located opposite the cylindrical first inlet from the angle of 135 deg.. The mixing chamber has a diameter D and a length L, resulting in a total volume V. No internals or mechanical agitation are provided.

As illustrated in fig. 2, removable covers (7, 8) are provided on either side of the chamber to enable cleaning.

Example 1

This example describes the supply of concentrated Ziegler-Natta catalyst to a propylene polymerization process using fresh polymerization grade propylene as the diluent stream.

The mixing chamber, as shown in FIGS. 1 and 2, had a diameter of 44mm and a length of 30mm, giving a total volume of 45.6cm ³ . The inner diameters of lines 2, 4 and 6 are each 13.9mm, corresponding to the 15mm Schedule 80 pipe.

A concentrated Ziegler-Natta procatalyst slurry having a concentration of 30wt% in mineral oil was passed through line (2) and inlet (1) at a mass flow rate of 1 g/s. Polymerization grade propylene was passed through the second line (4) and inlet (3) at a mass flow rate of 114 g/s. The total flow rate was 115g/s.

The density of the mixed flow was 0.47g/cm ³ About 240cm is obtained ³ Volumetric flow rate/s and residence time of 0.19 seconds.

The process is operated in the second line at the same propylene flow rate for more than one year, but the mass flow rate of the procatalyst varies as required between 0.14 and 1.7g/s depending on the polymerization grade produced.

The method operates successfully without clogging the mixing chamber.

Example 2 (comparative))

This example describes the supply of concentrated Ziegler-Natta procatalyst to a propylene polymerization process using fresh polymerization grade propylene as the diluent stream, but without a mixing chamber.

A concentrated Ziegler-Natta procatalyst slurry, 30wt% in mineral oil, was passed through a stainless steel tube having an ID of 9.5mm at a mass flow rate of about 1 g/s. The polymerization grade propylene was fed from the top through a 90 degree tee at a mass flow rate of 114g/s and a total flow rate of 115g/s.

Traces of moisture in the polymerization grade propylene react with the procatalyst to form viscous residues which collect and slowly accumulate at the mixing point. This residue limited the outlet sufficiently that the diluent at the desired flow rate could not be added at the allowable pressure drop of the feed system during 6-9 months. This requires replacement of the tee and a small portion of the downstream piping to restore the main catalyst feed system to normal use.

Claims

1. A method for supplying a polymerization catalyst component to a polymerization reactor, comprising:

a. providing a first stream comprising the catalyst component in a first line connected to and downstream of the pump outlet or flow control valve,

b. a diluent stream is provided in a second line,

i) The volume of the mixing chamber is less than 150ml,

iii) The mixing chamber is not mechanically agitated,

2. The process according to claim 1, wherein the first stream comprises a catalyst component that is liquid.

3. The process of claim 1, wherein the first stream comprises a slurry of polymerization procatalyst.

4. A process according to claim 3 wherein the polymerization procatalyst is a Ziegler-Natta procatalyst.

5. The method according to any of the preceding claims, wherein the volume of the mixing chamber is such that the residence time of the flow rate is less than 5 seconds and the volume of the mixing chamber is less than 150ml based on the total volume of the mixed flow.

6. The method according to any of the preceding claims, wherein the mixing chamber is free of mechanical agitation.

7. A method according to any one of the preceding claims, wherein the mixing chamber has a lid that is removable to allow cleaning of the mixing chamber in situ.

8. A method according to any one of the preceding claims, wherein at least two of features (i) to (iv) apply.

9. A method according to any one of the preceding claims, wherein the first line is connected to the pump outlet, preferably a progressive cavity or a diaphragm pump, and downstream of the pump outlet, preferably a progressive cavity or a diaphragm pump.

10. The process according to any one of the preceding claims, wherein the mixing chamber forms a low point of the first stream in the first line.

11. A method according to any one of the preceding claims, wherein the mixing chamber has a cylindrical cross section with an inner diameter of 2-10 times the inner diameter of the first line.

12. The method according to any of the preceding claims, wherein the mixing chamber has a cylindrical cross section with a length to diameter ratio of 0.5-10.

13. The method according to any of the preceding claims, wherein the volume of the mixing chamber is 5-100cm ³ 。

14. The process of any of the preceding claims wherein the mixing chamber has a cylindrical cross section and comprises a first inlet for the first stream from the first line and located at the side of the cylinder, a second inlet for the diluent stream from the second line located at the side of the cylinder at an angle of 15 ° to 90 ° to the first inlet and an outlet through which the mixed stream exits the mixing chamber to pass into the polymerization reactor, wherein the outlet is located opposite the first inlet of the cylinder thereby at an angle of 135 ° to 225 ° degrees.

15. The process according to any one of the preceding claims, wherein the mass flow rate of the diluent stream in the second line is 20-1000 times the mass flow rate of the first stream in the first line.

16. A method according to any one of the preceding claims, wherein the diluent flow enters the mixing chamber tangentially.

17. The process according to any one of the preceding claims, wherein two or more sets of parallel first lines, second lines and mixing chambers connected to the polymerization reactor are provided such that one mixing chamber can be cleaned while continuing to feed catalyst components to the reactor via the second mixing chamber.

18. The process according to any of the preceding claims, wherein the diluent stream is an inert diluent, in particular one or more C2-C6 alkanes, and is preferably selected from propane, butane, in particular isobutane, pentane and hexane.

19. The process according to any of the preceding claims, wherein the dilution liquid comprises the monomer to be polymerized in the polymerization reactor, and preferably wherein the dilution liquid comprises propylene, and most preferably consists essentially of propylene.

20. The process according to any of the preceding claims, wherein the polymerization reactor is a propylene polymerization reactor, such as a horizontal stirred bed propylene polymerization reactor.

21. An apparatus for supplying a polymerization catalyst component to a polymerization reactor, the apparatus comprising:

b. a second line for the flow of diluent,

characterized in that the first and second lines are connected to a mixing chamber, respectively, and that said mixing chamber has an enlarged cross section compared to the first and second lines, and in that at least one of the following applies:

i) The volume of the mixing chamber is less than 150ml,

iii) The mixing chamber is not mechanically agitated,