Method for supplying a polymerization catalyst component to a polymerization reactor and apparatus therefor

Abstract

The 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 stream of diluent in a second line, c. contacting the first stream and the stream of diluent to form a mixed stream and passing the mixed stream to a polymerization reactor, and further characterized in that at least one of the following applies: i) the volume of the mixing chamber is less than 150 ml, ii) the volume of the mixing chamber is such that the residence time based on the total volume flow rate of the mixed stream is less than 5 seconds, iii) the mixing chamber is free of mechanical agitation, the mixing chamber having a lid that is removable to allow in situ cleaning of the mixing chamber.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for supplying a polymerisation catalyst component to a polymerisation reactor, and in particular where the catalyst component is mixed with a diluent stream and passed into a polymerisation reactor. BACKGROUND

[0002] Catalytic polymerisation of olefin monomers to produce polymers is well known and many processes are operated industrially, including in the gas phase, solution and slurry phases. Catalysts or catalyst systems generally comprise several catalyst components, such as a transition metal containing catalyst (often referred to simply as the "main catalyst"), an alkyl metal cocatalyst or modifier. In continuous commercial processes, all catalyst components and monomer are provided to the reactor.

[0003] As the productivity of modern polymerisation catalysts is relatively high, it is neither necessary nor economic to attempt to recover catalyst components from the product, and so a continuous process must be provided to replace the catalyst components taken out with the product, either continuously or discontinuously, with fresh catalyst components. Another consequence of the relatively high productivity of modern polymerisation catalysts is the need to provide relatively small amounts of catalyst components.

[0004] Depending on the process, the catalyst can be provided in supported or unsupported form, and can be injected directly or mixed with other components of the reaction. In many cases, it is advantageous to mix the catalyst with a diluent liquid to form a slurry, which is then passed into the reactor, especially as it is generally easier to control the addition of catalyst to the reactor by using a pump to meter the diluted catalyst slurry.

[0005] EP 1660231 relates to a method for preparing a catalyst slurry and supplying it to a polymerisation reactor in which polyethylene is prepared. The catalyst is initially present in the form of a "concentrated" slurry and is diluted in an agitated mixing vessel to form a diluted catalyst slurry. This diluted slurry is then pumped into the reactor using a diaphragm pump.

[0006] The mixing vessel in EP 1660231 is relatively large in volume, sufficient to prepare large batches of diluted catalyst slurry, including a volume sufficient to fill a day tank when a new batch is prepared.

[0007] Although the system of EP 1660231 is capable of making large batches of catalyst and passing them into a reactor, it is necessary to carefully manage its inventory, both to ensure that a new batch of diluted catalyst is made before the old batch is all used, and to ensure that too much diluted catalyst is not made before the catalyst is changed, which can result in unused catalyst having to be dumped to make a batch of a different catalyst. The process in EP 1660231 is also "heavy" equipment, requiring multiple agitated vessels and interconnecting piping, as well as a pump for transferring the diluted slurry from the mixing vessel to the reactor and either a further pump or a metering valve for first transferring the concentrated slurry to the mixing vessel. SUMMARY

[0008] The present invention provides an improved method for making a diluted slurry containing a catalyst component, the method can be carried out continuously in a relatively small chamber, and the method uses the flow of the diluent stream to provide sufficient mixing and transfer of the mixed stream to a downstream reactor.

[0009] Thus, in a first aspect, the present invention provides a method for supplying a polymerisation catalyst component to a polymerisation reactor, comprising:

[0010] a. providing a first stream comprising a catalyst component in a first line, which first line is connected to and downstream of a pump outlet or flow control valve,

[0011] b. providing a diluent stream in a second line,

[0012] c. contacting the first stream and the diluent stream to form a mixed stream and passing the mixed stream to a polymerisation reactor,

[0013] characterised in that the mixing of the first stream and the diluent stream is carried out by providing the first stream from the first line and the diluent stream from the second line to a mixing chamber having an enlarged cross section compared to the first and second lines respectively, and further characterised in that at least one of the following applies:

[0014] i) the volume of the mixing chamber is less than 150 cm 3 ,

[0015] ii) the volume of the mixing chamber is such that the residence time based on the total volumetric flow rate of the mixed stream is less than 5 seconds,

[0016] iii) the mixing chamber is free of mechanical agitation,

[0017] iv) the mixing chamber has a lid which is removable to allow in situ cleaning of the mixing chamber. BRIEF DESCRIPTION OF DRAWINGS

[0018] The drawings are not intended to be to scale. In the drawings, like or similar components throughout the figures are denoted by the same numbers. For clarity, not every component can be marked in every drawing. In the drawings:

[0019] Figure 1 a top view of a cylindrical mixing chamber is shown in diagrammatic form; and

[0020] Figure 2 a side view of the same mixing chamber is shown in diagrammatic form. DETAILED DESCRIPTION

[0021] The present invention provides a process for supplying a polymeric 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:

[0022] 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 the catalyst component),

[0023] b) all components in a polymerization catalyst, including a procatalyst component (hereinafter "procatalyst") and a cocatalyst component (hereinafter "cocatalyst"), where the latter is required to provide suitable catalytic activity to the procatalyst component, and

[0024] c) any catalyst modifier component (hereinafter "modifier") which can be used with the catalyst in (a) or (b).

[0025] The prior art sometimes uses the term "catalyst" to refer to the catalyst according to (a) above, but also to the "procatalyst" according to (b) above. However, examples of the two "types" of polymerization catalyst, and thus of catalyst components in the present invention, are well known in the art, although different terminology can be used. Further, and again for the avoidance of doubt, either of the "types" of catalyst (a) and (b) above can be used with other catalyst components. For example, either type can be used with a modifier according to (c), and those of type (a) can be used with a cocatalyst component, if not necessary. (Some examples of the different components will be discussed further below.)

[0026] More generally, the specific features of the catalyst component in the first stream of the present invention are not as critical as the way in which it is mixed with the diluent stream in the mixing chamber. In particular, the present invention is characterized by at least one of features (i) to (iv) being applicable. Preferably, at least two of features (i) to (iv) are applicable, such as at least 3 of them, and most preferably all of them.

[0027] Options (i) and (ii) relate directly or indirectly to the size of the mixing chamber.

[0028] It is particularly preferred that the mixing chamber is relatively small, which can be defined in absolute terms as in option (i), or by the residence time of the mixed stream as in option (ii), or both.

[0029] In terms of absolute volume, the mixing chamber preferably has a total volume of less than 120 cm 3 , such as less than 100 cm 3 . The volume is preferably at least 5 cm 3 . In particularly preferred embodiments, the volume is 25-75 cm 3 , such as 30-60 cm 3 .

[0030] In terms of residence time, this is defined herein on the basis of the total volumetric flow rate of the mixed stream, which means that the residence time is equal to the volume of the mixing chamber divided by the volumetric flow rate of the mixed stream. 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 0.1-0.5 seconds.

[0031] The mixing chamber has an enlarged cross-section compared to the first and second lines. In preferred embodiments, the mixing chamber has a cylindrical cross-section, preferably with an internal diameter which is 2-10 times the internal diameter of the first line. The cylindrical cross-section can have a length to diameter ratio of 0.5-10.

[0032] Where the mixing chamber has a cylindrical cross-section, the mixing chamber can comprise a first inlet for the first stream from the first line, located on the side of the cylinder, and a second inlet for the diluent stream from the second line, located on the side of the cylinder at an angle of 15°-90°, and preferably 45°-90°, to the first inlet. The mixing chamber is also provided with an outlet by which the mixed stream exits the mixing chamber to pass into the polymerisation reactor, and preferably the outlet is located on the opposite side of the cylinder to the 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 (so that the outlet is at an angle of at least 105°, preferably at least 135°, to the second inlet). Preferably, the outlet is at an angle of 135°-225° to the first inlet.

[0033] This configuration provides the most efficient mixing of the first stream and the diluent stream, and allows the momentum in the incoming diluent stream to be used most efficiently to provide mixing and to transfer the mixed stream to the downstream reactor.

[0034] Any of the streams, but particularly the diluent stream, can optionally enter the mixing chamber tangentially to enhance mixing.

[0035] The mixed stream passes from the mixing chamber to 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 piping without any intermediate pumps, vessels or other mixing devices.

[0036] The mixing chamber can be provided with internal members that aid in mixing. However, it is preferred that no mechanical agitation is provided in the mixing chamber, meaning that there are no stirrers or other agitators that need to be driven by a motor. Most preferably, no internal members that aid in mixing are provided.

[0037] In feature (iv) of the invention, the mixing chamber is provided with a lid that is removable to allow in-situ cleaning of the mixing chamber. In particular, some polymerization catalyst components can react with impurities in the diluent stream to produce deposits. For example, Ziegler-Natta procatalysts can react with residual moisture to precipitate a sticky titanium-containing deposit, while alkyl aluminum cocatalysts, such as triethyl aluminum, can react with moisture to form aluminum hydroxide precipitates. While most diluents have strict specifications that limit the maximum water content, even trace amounts (less than 1 ppm) of water can cause deposits to slowly build up over time.

[0038] In the present invention, the mixing of the first stream and the diluent stream is carried out by providing the first stream from the first line and the diluent stream from the second line separately to a mixing chamber that has an enlarged cross section compared to the first. The separate provision of the two streams ensures that mixing occurs in the mixing chamber and not in the narrower lines upstream, while the enlarged cross section of the mixing chamber allows deposits to build up to some extent without the chamber becoming clogged. This increases the time required before the mixing system must be cleaned.

[0039] However, the mixing chamber can still require periodic cleaning. The provision of a removable lid to allow in-situ cleaning of the mixing chamber then enables such cleaning to be carried out without physically disconnecting the mixing chamber from the upstream (first and second) and downstream (line to reactor) lines. (The use of "in-situ" 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 the downstream system to the polymerization reactor so that no flow can occur, and then the lid is removed.)

[0040] While this is preferred, as an alternative the mixing chamber can be designed to be isolated from the system and physically removed for cleaning off-line, or simply replaced with a new mixing chamber, the mixing chamber can be connected to the first line, the second line and the downstream system.

[0041] A first stream is provided in a first line, which is connected to and downstream of a pump outlet or flow control valve. The first stream is typically in liquid form, such as a slurry of catalyst components in a carrier liquid. The 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 more precise and reliable flow of the first stream. A preferred pump for pumping the first stream, particularly when the first stream comprises a catalyst or master catalyst slurry, is a progressive cavity pump. A diaphragm pump can also be used.

[0042] The first stream and diluent stream are generally supplied to the mixing chamber continuously. This then provides a continuous supply of mixed stream comprising catalyst components to the polymerisation reactor. Although continuous supply is preferred, it is not excluded that the supply of the first stream to the mixing chamber can be occasionally or temporarily interrupted to interrupt the supply of catalyst components to the reactor. In such a case, the total time of any one or more interruptions should be less than the total time during which the first stream is supplied. For example, the first stream should be supplied to the mixing chamber for at least 80% of the time during which polymerisation is carried out in the polymerisation reactor. This can be considered as the first stream and diluent stream being supplied to the mixing chamber "substantially continuously".

[0043] In a preferred embodiment of the application, particularly when the first stream comprises a catalyst component comprising particles, such as a supported master catalyst, the mixing chamber forms a low point in the first line of the first stream. As used herein, this means that if the pump for the first line fails or 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 first line between the pump outlet or control valve and the mixing chamber of solids, preventing the solids from settling in the first line and potentially clogging the line. It will be clear that this is particularly relevant in the case that the first stream is a slurry of catalyst or master catalyst particles, which is a preferred embodiment described further below.

[0044] The enlarged volume of the mixing chamber generally reduces the risk of settled particles clogging the chamber. However, even if it does get clogged, the provided removable lid enables cleaning of this part of the mixing system without having to open it.

[0045] In a preferred embodiment, two sets (or more sets) of parallel first lines, second lines and mixing chambers connected to the polymerisation reactor can be provided, such that one mixing chamber can be cleaned while continuing to feed catalyst components to the reactor via the second mixing chamber. This enables the polymerisation to be operated even while one mixing chamber is being cleaned, enabling continuous operation.

[0046] The process of the present application can be applied in any suitable polymerisation process in which the polymerisation catalyst components are diluted in a stream of diluent prior to being passed to the reactor.

[0047] In one embodiment, the polymerisation reactor can be a slurry phase polymerisation reactor. Such reactors are well known and include, for example, slurry stirred tank reactors and slurry loop reactors.

[0048] In another embodiment, the polymerisation reactor can be a gas phase polymerisation reactor, such as a gas phase fluidised bed polymerisation reactor, such as a vertical, directed flow fluidised bed reactor, or a gas phase polymerisation reactor containing in use a sub-fluidised particulate bed of polymer, such as a vertical stirred bed polymerisation reactor or a horizontal stirred bed polymerisation reactor.

[0049] Preferably, the polymerisation reactor is a reactor for the polymerisation of ethylene and / or propylene, and in particular for the polymerisation of propylene. A particularly preferred polymerisation reactor in which the process can be applied is a propylene polymerisation reactor, in particular a vertical or horizontal stirred bed propylene polymerisation reactor.

[0050] The first stream comprises a catalyst component. As already mentioned, the polymerisation catalyst can comprise several catalyst components, such as a main catalyst containing a transition metal, a co-catalyst or a modifier.

[0051] 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 titanium halide, and a Group 2 metal compound, such as magnesium chloride. Ziegler-Natta catalysts can also include an inert support material, such as a metal oxide or an alumina-based metal oxide, for example alumina or silica. Metallocene catalysts are generally silica / MAO supported transition metal metallocene complexes. Chromium catalysts are generally silica supported chromium compounds which are activated at elevated temperatures to produce silica supported chromium oxide compounds.

[0052] The main catalyst for the above catalysts can be rendered catalytically active using a co-catalyst. Co-catalysts can also be used to improve catalyst performance. Co-catalysts are generally selected from Group 3 metal alkyls, preferably boron or aluminium alkyls. Examples of suitable aluminium alkyls include trialkylaluminium, dialkylaluminium hydrides, alkylaluminium dihydrides, dialkylaluminium halides, alkylaluminium dihalides, dialkylaluminium alkoxides, for example triethylaluminium (TEAL) or diethylaluminium dichloride (DEAC). Examples of suitable boron alkyls include trialkylboron, for example trimethylboron (TEB).

[0053] As also previously described, the catalyst can also include a modifier. A "modifier" as defined herein is a compound added in addition to any cocatalyst and which modifies catalyst performance and / or polymer properties. Preferably, the modifier contains at least one functional group capable of donating an electron 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 the polymerization of olefins and activity control agents that modify the activity of the catalyst.

[0054] An example of a selectivity control agent is an alkoxysilane or diether composition. The alkoxysilane has the general formula: SiR m (OR') 4-m where R is independently in each occurrence a hydrocarbyl or an 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 not including hydrogen and halogen, R' is a C1-20 alkyl group, and m is 0, 1, 2, or 3. In one embodiment, R is a C6-12 aryl or aralkyl group, a C1-20 alkyl group, a C3-12 cycloalkenyl group, a C3-12 branched alkyl group, or a C3-12 cyclic amino group, R' is a C1-4 alkyl group, and m is 1 or 2. Examples of suitable alkoxysilanes include dicyclopentyl dimethoxysilane, di-t-butyl dimethoxysilane, methylcyclohexyl dimethoxysilane, ethylcyclohexyl dimethoxysilane, diphenyl dimethoxysilane, diisopropyl dimethoxysilane, di-n-propyl dimethoxysilane, diisobutyl dimethoxysilane, isobutyl isopropyl dimethoxysilane, di-n-butyl dimethoxysilane, cyclopentyl trimethoxysilane, isopropyl trimethoxysilane, n-propyl trimethoxysilane, n-propyl triethoxysilane, ethyl triethoxysilane, tetramethoxysilane, tetraethoxysilane, diethylamino triethoxysilane, cyclopentyl pyrrolidinyl dimethoxysilane, bis(pyrrolidinyl) dimethoxysilane, bis(perhydroisoquinolinyl) dimethoxysilane, and dimethyl dimethoxysilane. In one embodiment, the alkoxysilane can be dicyclopentyl dimethoxysilane, methylcyclohexyl dimethoxysilane, n-propyl trimethoxysilane, or any combination thereof. In another embodiment, the alkoxysilane composition includes two or more of the above alkoxysilanes.

[0055] Diethers have the general formula: RR'C(CH2-CH2OR")2, wherein R, R' and R" are each independently C1-20alkyl 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.

[0056] Examples of activity control agents are carboxylic acid esters, poly(alkylene glycol)s, poly(alkylene glycol) esters and polymeric or oligomeric compounds containing more than one ether group.

[0057] Carboxylic acid esters, when used, can be aromatic mono- or polycarboxylic acid esters or aliphatic acid esters.

[0058] Examples of suitable aromatic carboxylic acids include C1-10alkyl 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 ether, cycloalkyl ether, aryl ether, aralkyl ether, alkyl sulphide, aryl sulphide, dialkyl amine, diaryl amine, diaryalkyl amine and trialkyl silyl groups. The aromatic carboxylic acid ester can be a C1-20hydrocarbyl ester of benzoic acid, wherein the hydrocarbyl group is unsubstituted or substituted with one or more substituents containing a Group 14, 15, 16 or 17 heteroatom and C1-20(poly)hydrocarbyl ether derivatives thereof, or C1-4alkyl benzoate and C1-4cycloalkylated derivatives thereof, 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.

[0059] The activity control agent can be an aliphatic acid ester. The aliphatic acid ester can be a fatty acid ester, can be a C4-C30 aliphatic acid ester, can be a mono or poly (two or more) ester, can be straight chain or branched, can be saturated or unsaturated, and any combination thereof. The C4-C30 aliphatic acid ester can also be substituted with one or more substituents containing a Group 14, 15, or 16 or 17 heteroatom. 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 di-esters of aliphatic C4-20 monocarboxylic and dicarboxylic acids, C1-4 alkyl esters of aliphatic C8-20 monocarboxylic and dicarboxylic acids, and C4-20 alkyl mono- or polycarboxylic acid ester derivatives of C2-100 (poly)glycols or C2-100 (poly)glycol ethers. In another embodiment, the C4-C30 aliphatic ester can be isopropyl myristate, di-n-butyl sebacate, (poly)(alkylene glycol) mono- or di-acetate, (poly)(alkylene glycol) mono- / or di-myristate, (poly)(alkylene glycol) mono- or di-laurate, (poly)(alkylene glycol) mono- or di-oleate, (poly)(alkylene glycol) mono- or di-stearate, glyceryl triacetate, glyceryl triesters of C2-40 aliphatic carboxylic acids, and mixtures thereof.

[0060] In the event that the first stream comprises a liquid catalyst component, then the catalyst component can be used as the first stream "neat" or as a solution in a diluent. When used, this diluent can be the same or different from the diluent stream used in step (b). The diluent in such a solution is preferably a component that has already been used in the polymerization process, such as a monomer or an inert diluent. Examples are isobutane for a slurry loop ethylene polymerization process and propylene for a bulk propylene polymerization process, as further described below with respect to the diluent stream.

[0061] Even if provided as a solution in a diluent, the first stream in step (a) in this embodiment can be considered to be "concentrated", while after mixing with the diluent stream it can be considered to be "diluted". (In this context, "concentrated" generally means that the concentration of catalyst component in the first stream is at least 5 wt%, and preferably at least 10 wt%. The concentration can be up to and including 100% (if the catalyst component is used "neat").)

[0062] In a most preferred embodiment, the first stream comprises a procatalyst, and most preferably a procatalyst slurry.

[0063] The procatalyst in this embodiment can be any procatalyst generally used for such polymerization reactions, including Ziegler-Natta, chromium, and metallocene procatalysts. The procatalyst is preferably a Ziegler-Natta procatalyst.

[0064] The master catalyst slurry as provided in step (a) of this embodiment will generally comprise master catalyst particles suspended in a carrier liquid. This carrier liquid can be the same as or different from the diluent stream used in step (b).

[0065] It should also be noted, and will be clear from some of the examples below, that the "carrier liquid" can comprise a mixture of diluent compounds, and that the term "carrier liquid" is used to include such mixtures as well as individual compounds. (And, for the avoidance of doubt, when the first stream comprises a catalyst component in solution in a diluent, this also applies to the diluent in the first stream.)

[0066] The master catalyst slurry as provided in step (a) of this embodiment can be considered to be "concentrated". In the present application, this means that its master catalyst concentration in the carrier liquid can 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 oil, but any inert diluent, especially an alkane or mixture of alkanes, can be used as the carrier liquid.

[0067] (For the avoidance of doubt, the term "inert diluent" as used herein can refer to an individual inert compound or a mixture of inert compounds, in a similar manner to the way in which the term "carrier liquid" is used to include mixtures as well as individual compounds. According to the present application, compounds are considered to be inert if they do not react with the master catalyst in the polymerisation reactor.)

[0068] In general, the polymerisation master catalyst can be supplied in solid (dry) form. If this is the case, then the master catalyst slurry used in step (a) of this embodiment can then be prepared from the solid master catalyst by the addition of a carrier liquid to form a slurry suitable for further dilution according to the present application.

[0069] Alternatively, the master catalyst can be supplied in a slurry, for example in mineral oil, in which case this master catalyst slurry can be used "as supplied" in step (a), or can be "pre-diluted" to form the first stream before it is further diluted according to the present application. (In the latter case, the carrier liquid is then the mixture of the supplied master catalyst slurry and the liquid used for pre-dilution.)

[0070] More generally, the catalyst components (such as the master catalyst) and whether initially solid or liquid / slurry, any upstream mixing of the catalyst components with a liquid carrier or with a 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 polymerisation process, and can be the same as the diluent stream provided in step (b) of the present application, as described for example below, or can be different.

[0071] However, preferably the case is that any diluent / carrier liquid in the first stream as provided in step (a) is an inert diluent, and the diluent stream used in step (b) can be an inert diluent but can also comprise or consist of monomer as discussed further below.

[0072] The diluent stream provided in the second line will be selected depending on the polymerisation process and depending on the catalyst components in the first stream. It can be the same as any diluent / carrier liquid present in the first stream prior to mixing. However, in the case that the first stream comprises a catalyst or master catalyst slurry in a carrier liquid, the diluent stream will typically be different from the carrier liquid.

[0073] In some embodiments, the diluent stream can be an inert diluent. The diluent stream can be one or more C2-C6alkanes. For example, for slurry polymerisation of ethylene in a loop reactor, the diluent stream will preferably be the inert diluent used in the reaction, which most typically is isobutane. For gas phase polymerisation of ethylene in a fluidised bed polymerisation reactor, the diluent stream can be an inert hydrocarbon which is also used as condensing agent in the reactor, such as one or more pentanes. In propylene polymerisation processes, an inert diluent such as propane can be used, or the monomer itself as diluent.

[0074] In preferred embodiments, the diluent stream comprises the monomer to be polymerised in the polymerisation reactor. In particularly preferred embodiments of the application, the diluent stream in the second line comprises propylene, and more preferably is propylene. Typically, but especially in the case that the first stream comprises a master catalyst, the diluent stream is preferably propylene which has not been in contact with an aluminium alkyl compound, such as fresh (polymer grade) propylene. ("Fresh" means propylene which is passed into the polymerisation reactor for the first time (via the process described), and it can be contrasted with recycled propylene which is recovered from downstream processing.)

[0075] The relative mass flow rates of the first stream and the diluent stream will be selected based on the concentration of catalyst components required in the mixed stream, which will itself depend on the concentration of catalyst components in the first stream prior to mixing. However, the mass flow rate of the diluent stream is preferably significantly in excess of 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.

[0076] With respect to the first stream comprising the 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, a preferred ratio is that the mass flow rate of the diluent stream in the second line is 20-1000 times the mass flow rate of the slurry in the first line. In particular, where the diluent stream comprises a reactant in a subsequent polymerisation reactor, then there is no particular concern about feeding a large amount of diluent stream and therefore a larger relative flow of the diluent stream can be used. Indeed, a large amount of diluent is preferred as it reduces the residence time of the catalyst or procatalyst in the transfer line to the reactor and improves process control.

[0077] In particular in this embodiment, and more generally, it is preferred that the residence time between the mixing chamber and the reactor is less than 20 seconds.

[0078] It is possible, but not essential, to provide external heating or cooling to the mixing process / mixed stream (e.g. by heating or cooling the first stream, the diluent stream and / or the mixing chamber, or the transfer line to the reactor). In one embodiment, the mixing can be carried out below ambient temperature, for example by using one or more cooling applied to the first or second line or the mixing chamber, or preferably by providing a previously cooled diluent stream. This can reduce the reaction of the procatalyst with monomers such as propylene (when used) or the catalyst components with any moisture present in the diluent stream. However, the residence time in the present application is preferably minimised and / or, when the first stream comprises a procatalyst, the diluent stream in the second line does not comprise propylene which has been previously contacted with an aluminium alkyl compound to avoid the need for cooling.

[0079] The mixing is preferably carried out at or near ambient temperature, such as in the range 5-35°C.

[0080] In another embodiment, the present application provides an apparatus for use in the above process.

[0081] Accordingly, the present application also provides an apparatus for supplying a polymerisation catalyst component to a polymerisation reactor, the apparatus comprising:

[0082] a. a first line for a first stream comprising a catalyst component, the first line being connected to and downstream of a pump outlet or flow control valve,

[0083] b. a second line for a diluent stream,

[0084] 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

[0085] d. a transfer line for passing the mixed stream into the polymerization reactor,

[0086] characterized in that the first and second lines are connected to a mixing chamber, and that the mixing chamber has an enlarged cross section compared to the first and second lines, and further characterized in that at least one of the following applies:

[0087] i) the volume of the mixing chamber is less than 150 ml,

[0088] ii) the volume of the mixing chamber is such that the residence time based on the total volumetric flow rate of the mixed stream is less than 5 seconds,

[0089] iii) the mixing chamber is free of mechanical agitation,

[0090] iv) the mixing chamber has a lid that is removable to allow in-situ cleaning of the mixing chamber.

[0091] Embodiment

[0092] The present invention will now be illustrated with reference to the accompanying drawings and the following embodiment, in which a master catalyst slurry is mixed with propylene, wherein:

[0093] Figure 1 a top view of a cylindrical mixing chamber is shown in diagrammatic form; and

[0094] Figure 2 a side view of the same mixing chamber is shown in diagrammatic form.

[0095] As shown in Figure 1 and 2 the mixing chamber comprises a first inlet (1) for the first line (2), a second inlet (3) for the second line (4) and an outlet (5) with a line (6) leading to the polymerization reactor (not shown). The second inlet is at an angle of 45° to the first inlet, and the outlet is on the opposite side of the cylinder to the first inlet at an angle of 135°. The diameter of the mixing chamber is D and the length is L, giving a total volume of V. No internal components or mechanical agitation are provided.

[0096] As shown diagrammatically in Figure 2 removable lids (7, 8) are provided on either side of the chamber to enable cleaning.

[0097] Example 1

[0098] This example describes the supply of a concentrated Ziegler-Natta catalyst to a propylene polymerization process, using fresh polymer grade propylene as the diluent stream.

[0099] The mixing chamber is as shown in Figure 1 and 2The diameter is 44 mm and the length is 30 mm, resulting in a total volume of 45.6 cm 3 The internal diameter of lines 2, 4 and 6 is 13.9 mm each, corresponding to 15 mm Schedule 80 pipe.

[0100] A concentrated Ziegler-Natta procatalyst slurry in mineral oil at 30 wt% concentration was passed through line (2) and inlet (1) at a mass flow rate of 1 g / s. Polymer 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 115 g / s.

[0101] The density of the mixed stream was 0.47 g / cm 3 resulting in a volumetric flow rate of about 240 cm 3 / s and a residence time of 0.19 seconds.

[0102] The process was operated in the second line with the same propylene flow rate for over a year, but the mass flow rate of the procatalyst was varied between 0.14-1.7 g / s as required by the grade of polymer produced.

[0103] The process was successfully operated without plugging the mixing chamber.

[0104] Example 2 (comparative )

[0105] This example describes the supply of concentrated Ziegler-Natta procatalyst to a propylene polymerization process using fresh polymer grade propylene as the diluent stream, but without a mixing chamber.

[0106] A concentrated Ziegler-Natta procatalyst slurry in mineral oil at 30 wt% concentration was passed through a stainless steel pipe with an ID of 9.5 mm at a mass flow rate of about 1 g / s. Polymer grade propylene was added from the top through a 90 degree tee at a mass flow rate of 114 g / s, for a total flow rate of 115 g / s.

[0107] Trace amounts of moisture in the polymer grade propylene reacted with the procatalyst to form viscous residues that collected at the mixing point and slowly built up. Within 6-9 months, this residue sufficiently restricted the outlet so that the required flow rate of diluent could not be added at the pressure drop allowable in the feed system. This required replacement of the tee and a small portion of the downstream pipe to restore the procatalyst feed system to normal use.

Claims

1. A method for supplying a polymeric catalyst component to a polymerization reactor comprising: a. providing a first stream comprising the catalyst component in a first line, which first line is connected to and downstream of a pump outlet or flow control valve, b. providing a diluent stream in a second line, c. contacting the first stream and the diluent stream to form a mixed stream and passing the mixed stream to the 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 to a mixing chamber having an enlarged cross section compared to the first and second lines, respectively, and in that at least one of the following applies: i) the volume of the mixing chamber is less than 150 ml, ii) the volume of the mixing chamber is such that the residence time based on the total volumetric flow rate of the mixed stream is less than 5 seconds, iii) the mixing chamber is free of mechanical agitation, iv) the mixing chamber has a lid that is removable to allow in situ cleaning of the mixing chamber, and 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°-90° to the first inlet and an outlet through which the mixed stream exits the mixing chamber to pass to the polymerization reactor, wherein the outlet is located on the opposite side of the cylinder to the first inlet thereby at an angle of 135°-225° degrees, and 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.

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

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

4. The method according to claim 3, wherein the polymerization procatalyst is a Ziegler-Natta procatalyst.

5. The method according to claim 1, wherein the volume of the mixing chamber is such that the residence time based on the total volumetric flow rate of the mixed stream is less than 5 seconds and the volume of the mixing chamber is less than 150 ml.

6. The method according to claim 1, wherein the mixing chamber is free of mechanical agitation.

7. The method according to claim 1, wherein the mixing chamber has a lid that is removable to allow in situ cleaning of the mixing chamber. at least two of (i) to (iv) apply.

8. The method of claim 1, wherein the feature 9. The method according to any one of claims 1-8, wherein the first line is connected to and downstream of a pump outlet.

10. The method according to any one of claims 1-8, wherein the mixing chamber forms a low point in the first line for the first stream.

11. The method according to any one of claims 1-8, wherein the mixing chamber has a cylindrical cross section with an inner diameter that is 2-10 times the inner diameter of the first line.

12. The method according to any one of claims 1-8, wherein the mixing chamber has a cylindrical cross section with a length to diameter ratio of 0.5-10. ​ 13. The method of any one of claims 1-8, wherein the volume of the mixing chamber is 5-100 cm3. 3 .

14. The process according to any one of claims 1-8, wherein the diluent stream enters the mixing chamber tangentially.

15. The process according to any one of claims 1-8, wherein two or more sets of parallel first and 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 a second mixing chamber.

16. The process according to any one of claims 1-8, wherein the diluent stream is an inert diluent selected from the group consisting of propane, butane, pentane and hexane.

17. The process according to any one of claims 1-8, wherein the diluent stream comprises monomers to be polymerized in the polymerization reactor.

18. The process according to claim 17, wherein the diluent stream consists essentially of propylene.

19. The process according to any one of claims 1-8, wherein the polymerization reactor is a propylene polymerization reactor.

20. The process according to claim 19, wherein the polymerization reactor is a horizontal stirred bed propylene polymerization reactor.

21. 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 a pump outlet or flow control valve, b. a second line for a diluent stream, c. a mixing chamber configured for contacting the first stream in the first line and the diluent stream in the second line to form a mixed stream, and d. a delivery line for passing the mixed stream into the polymerization reactor, characterized in that the first and second lines are connected to the mixing chamber, respectively, and that the mixing chamber has an enlarged cross section compared to the first and second lines, and wherein at least one of the following applies: i) the volume of the mixing chamber is less than 150 ml, ii) the mixing chamber is free of mechanical agitation, iii) the mixing chamber has a lid that is removable to allow cleaning of the mixing chamber in situ, and 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°-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 at the opposite side of the cylinder to the first inlet thereby at an angle of 135°-225° degrees.

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