Metallocene complexes with vinylene bridge for alpha-olefin polymerization

Abstract

The disclosure provides transition metal-based metallocene complexes, catalyst compositions including such complexes, and processes for preparing poly-alpha olefins (PAO) using such catalyst compositions.

Description

METALLOCENE COMPLEXES WITH VINYLENE BRIDGE FOR ALPHA-OLEFIN POLYMERIZATIONTECHNICAL FIELD

[0001] The present disclosure generally relates to transition metal-based metallocene complexes, catalyst compositions including such complexes, and to a process for preparing polyalpha olefins (PAO) using such catalyst compositions.BACKGROUND

[0002] Poly-a-olefins (PAOs; poly-alpha olefins) comprise a class of hydrocarbons prepared by the catalytic oligomerization of linear alpha-olefins (LAOs), such as 1 -hexene, 1 -octene, 1- decene, and the like as feedstock, either as LAOs or mixtures of two or more LAOs. Such PAOs may serve as synthetic base oils in a variety of applications. The oligomerization can be achieved via either Friedel-Crafts initiators or via so-called metallocene catalysts. The properties of metallocene based poly-alpha-olefins (mPAOs) differ from poly-alpha-olefins prepared by the conventional Friedel-Crafts process. The cause for these property differences is that metallocene catalysts typically display a regular 1,2-enchainment of the monomeric units, whereas the Friedel- Crafts initiators result in PAOs with irregular enchainment. As a result, mPAOs can outperform conventional PAOs, for instance in Viscosity Index (VI; i.e., the temperature sensitivity of the viscosity) and Pour Point (PP; where a lower PP indicates that the PAO can be used at lower temperature). Promising metallocene catalysts for the synthesis of PAOs have previously been reported. However, the catalyst activity (i.e., the amount of PAO produced per amount of metallocene) of such metallocene catalysts needs improvement to be useful in commercially viable, cost-effective processes for production of mPAO's. Further, it is desirable in the art to develop metallocene catalysts that can produce a wide range of molecular weights of mPAO's for different applications that require different viscosities of the lubricant.SUMMARY

[0003] The present technology is generally directed to transition metal-based metallocene complexes, a process to produce poly-alpha olefin (PAO) polymers by polymerizing one or more alpha-olefin monomers in the presence of a catalyst composition comprising the transition metal-based metallocene complex, and to PAOs prepared according to the disclosed process. Advantageously, the catalyst compositions exhibit high catalytic activity and produce PAOs with desirable molecular weights.

[0004] The present disclosure includes, without limitation, the following embodiments.Embodiment 1 : A metallocene complex having a structure according to Formula I or Formula II:wherein:M is titanium, zirconium, or hafnium;Xi and X2 are each independently selected from halogen and Ci to C10 alkyl;Ri and R2 are each H; orRi and R2, together with the carbon atoms to which they are bound, form a 6-membered optionally substituted aromatic ring;R3 is optionally substituted Ce-Cio aryl, preferably optionally substituted Ce aryl;R4is H; or R3 and R4, together with the carbon atoms to which they are bound, form a 6- membered optionally substituted aromatic ring;Rs is H or optionally substituted Ci to Ce alkyl; andR, R', R", and R'" each represent one or more substituents, each independently selected for each instance from the group consisting of H, halogen, optionally substituted Ci to C10 alkyl, and optionally substituted Ce-Cio aryl, preferably, wherein each substituent is H.

[0005] Embodiment 2: The metallocene complex of embodiment 1, wherein M is zirconium.

[0006] Embodiment 3: The metallocene complex of embodiment 1 or 2, wherein Xi and X2 are each Cl.

[0007] Embodiment 4: The metallocene complex of embodiment 1 or 2, wherein Xi and X2 are each CEE.

[0008] Embodiment 5: The metallocene complex of any one of embodiments 1-4, wherein:Ri and R2 are H;R3 and R4 form a 6-membered optionally substituted aromatic ring; andRs is H.

[0009] Embodiment 6: The metallocene complex of any one of embodiments 1-4, wherein: Ri and R2 form a 6-membered optionally substituted aromatic ring;R3 is optionally substituted phenyl;R4 is H; andRs is H or Ci to Ce alkyl.

[0010] Embodiment 7: The metallocene complex of any one of embodiments 1-4, wherein: Ri and R2 form a 6-membered optionally substituted aromatic ring; andR3 and R4 form a 6-membered optionally substituted aromatic ring.

[0011] Embodiment 8: The metallocene complex of embodiment 1, having a structure selected

[0012] Embodiment 8: The metallocene complex of embodiment 1, having a structure

[0013] Embodiment 9: A process for the preparation of poly-alpha-olefins comprising polymerizing one or more alpha-olefin monomers having from 4 to 30 carbon atoms, in the presence of a catalyst composition comprising a co-catalyst and the metallocene complex of any one of embodiments 1-8.

[0014] Embodiment 10: A process for the preparation of poly-alpha-olefins comprising polymerizing one or more alpha-olefin monomers having from 4 to 30 carbon atoms, in the presence of a catalyst composition comprising a metallocene complex and a co-catalyst, the metallocene complex having a structure according to Formula III:wherein:M is titanium, zirconium, or hafnium, preferably, wherein M is zirconium;Xi and X2 are each independently selected from halogen and Ci to C10 alkyl;Re and R7 are each H, optionally substituted Ci to C10 alkyl, or optionally substituted Ce-Cio aryl; andR, R', R", and R'" each represent one or more substituents, each independently selected for each instance from the group consisting of H, halogen, optionally substituted Ci to C10 alkyl, and optionally substituted Ce-Cio aryl, preferably, wherein each substituent is H.

[0015] Embodiment 12: The process of embodiment 11, Re and R7 are each CH3 or are eachPh.

[0016] Embodiment 13: The process of any one of embodiments 9-12, wherein the one or more alpha-olefin monomers are selected from the group consisting of 1 -hexene, 1 -octene, 1- decene, 1 -dodecene, and combinations thereof.

[0017] Embodiment 14: A poly-alpha-olefin prepared by the process of any one of embodiments 9 to 13.

[0018] Embodiment 15: The poly-alpha-olefin of embodiment 14, having a kinematic viscosity at a temperature of 100 °C (KvlOO) in a range from about 2 to about 1000 centi-stokes (cSt), such as from about 1 to about 30, or from about 30 to about 500 cSt, and / or having a weight averaged molecular mass (Mw) of about 5,000 daltons or less, such as about 100 daltons to about 2,000 daltons.

[0019] These and other features, aspects, and advantages of the present disclosure will be apparent from a reading of the following detailed description together with the accompanying figures, which are briefly described below. The present disclosure includes any combination of two, three, four or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined or otherwise recited in a specific example implementation described herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosure, in any of its aspects and example implementations, should be viewed as combinable, unless the context of the disclosure clearly dictates otherwise.

[0020] Other objects, features and advantages of the disclosure will become apparent from the following detailed description and examples. It should be understood, however, that the detailed description and examples, while indicating specific embodiments of the disclosure, are given by way of illustration only and are not meant to be limiting. Additionally, it is contemplated that changes and modifications within the spirit and scope of the disclosure will become apparent to those skilled in the art from this detailed description. In further embodiments, features from specific embodiments may be combined with features from other embodiments. For example, features from one embodiment may be combined with features from any of the other embodiments. In further embodiments, additional features may be added to the specific embodiments described herein.DETAILED DESCRIPTION

[0021] The present disclosure will now be described more fully hereinafter with reference to example embodiments thereof. These example embodiments are described so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Indeed, the disclosure may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.

[0022] Although specific terms are employed, the terms are used in a descriptive sense only and not for purposes of limitation. Embodiments of systems and methods have been described in considerable detail with specific reference to the illustrated embodiments. However, it will be apparent that various modifications and changes can be made within the spirit and scope of the embodiments of systems and methods as described in the foregoing specification, and such modifications and changes are to be considered equivalents and part of this disclosure.

[0023] The following includes definitions of various terms and phrases used throughout this specification.

[0024] The use of the words "a" or "an" when used in conjunction with the term "comprising," "including," "containing," or "having" in the claims or the specification may mean "one," but it is also consistent with the meaning of "one or more," "at least one," and "one or more than one."

[0025] The words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "includes" and "include") or "containing" (and any form of containing, such as "contains" and "contain") are inclusive or open-ended and do not exclude additional, unrecited elements or method steps. The process of the present disclosure can "comprise," "consist essentially of," or "consist of' particular ingredients, components, compositions, etc., disclosed throughout the specification.

[0026] The terms "about" or "approximately" are defined as being close to as understood by one of ordinary skill in the art. In one non-limiting embodiment the terms are defined to be within 10%, such as within 5%, or within 1%, or within 0.5%.

[0027] The terms "wt%," "vol%," or "mol%" refer to a weight, volume, or molar percentage of a component, respectively, based on the total weight, the total volume, or the total moles of material that includes the component. In a non-limiting example, 10 moles of component in 100 moles of the material is 10 mol% of component.

[0028] The term "substantially" and its variations are defined to include ranges within 10%, within 5%, within 1%, or within 0.5%.

[0029] The term "poly-alpha-olefin" as used herein refers to polymers or oligomers prepared by the polymerization of alpha-olefin monomers. For the avoidance of doubt, poly-alpha-olefins are distinct from polyolefins (e.g., polyethylene, polypropylene). Specifically, poly-alpha-olefins have a much lower number of repeating monomeric units as compared to polyolefins andconsequently exhibit much lower molecular weights. For example, poly-alpha-olefins of the present disclosure typically have a weight average molecular weight (Mw) in a range of 200 to 32,000 daltons, such as 300 to 25,000, or 400 to 18,000. In contrast, the polyolefin polyethylene typically has a molecular weight of hundreds of thousands of daltons.

[0030] Suitable alpha-olefin monomers generally include from 4 to about 30 carbon atoms and may be represented by the formula CH2=CHR, where R is a pendant hydrocarbyl group, such as alkyl, aryl, or aralkyl. Relative to the polymer backbone chain, the pendant hydrocarbyl groups may be arranged in different stereochemical configurations which are denominated as atactic, isotactic, or syndiotactic pendant group configuration. The degree and type of tacticity of a polyolefin molecule is a determinant of the physical properties which such molecules will exhibit. Example alpha-olefin monomers include 1 -hexene, 1 -octene, and 1 -decene.

[0031] The term "metallocene" as used herein refers to organometallic compounds that contain a transition metal atom (e.g., Zr, Ti, Hf, etc.) "sandwiched" between two cyclopentadienyl (Cp) ring systems, which may be substituted.

[0032] The present disclosure is directed to metallocene complexes, catalyst compositions comprising such metallocene complexes, and processes for the preparation of poly-alpha-olefins comprising polymerizing (i.e., oligomerizing) one or more alpha-olefin monomers in the presence of such catalyst compositions. Each of the components of the complexes, compositions and processes are further described herein below.Metallocene Complex

[0033] In one aspect is provided a metallocene complex having a structure according to Formula I or Formula II:wherein:M is titanium, zirconium, or hafnium;Xi and X2 are each independently selected from halogen and Ci to C10 alkyl;Ri and R2 are each H; orRi and R2, together with the carbon atoms to which they are bound, form a 6-membered optionally substituted aromatic ring;R3 is optionally substituted Ce-Cio aryl, preferably optionally substituted Ce aryl;R4is H; or R3 and R4, together with the carbon atoms to which they are bound, form a 6- membered optionally substituted aromatic ring;Rs is H or optionally substituted Ci to Ce alkyl; andR, R', R", and R'" each represent one or more substituents, each independently selected for each instance from the group consisting of H, halogen, optionally substituted Ci to C10 alkyl, and optionally substituted Ce-Cio aryl, preferably, wherein each substituent is H.

[0034] In some embodiments, M is zirconium.

[0035] In some embodiments, Xi and X2 are each Cl.

[0036] In some embodiments, Xi and X2 are CH3.

[0037] In some embodiments, Ri and R2 are each H; R3 and R4form a 6-membered optionally substituted aromatic ring; and Rs is H.

[0038] In some embodiments, Ri and R2 form a 6-membered optionally substituted aromatic ring; R3 is optionally substituted phenyl; R4is H; and Rs is H or Ci to Ce alkyl.

[0039] In some embodiments, Ri and R2 form a 6-membered optionally substituted aromatic ring; and R3 and R4form a 6-membered optionally substituted aromatic ring.

[0040] In some embodiments, the metallocene complex has a structure selected from the group consisting of:

[0041] In some embodiments, the metallocene complex has a structure

[0042] The metallocene complexes as described herein may be prepared according to synthetic transformations known in the art and, for example, as disclosed herein in Examples 1-7. The preparation of certain complexes is also described in International Patent Application Publication No. WO2014 / 139949, incorporated herein by reference in its entirety. Alternatively, complexes of the disclosure may be obtained according to equation 1 or equation 2:

[0043] In some embodiments, the metallocene complex is immobilized on a support. In some embodiments, the entire catalyst composition as described herein below (i.e., further comprising one or more co-catalysts, activators, co-activators, scavengers, and the like) are immobilized on a support. In some embodiments, the support is inert, such as a porous inert material, which may be organic or inorganic. Examples of porous organic support materials include cross-linked or functionalized polystyrene, polyvinyl chloride (PVC), and cross-linked polyethylene. Examples of porous inert support materials include, but are not limited to, talc, clay inorganic chlorides, zeolites, and inorganic oxides. In some embodiments, the support is an inorganic oxide. Suitable inorganic oxides include metal and metalloid oxides such as silica, alumina, and mixtures thereof. Other inorganic oxides that may be employed either alone or in combination with silica or alumina include, but are not limited to, magnesia, titania, zirconia, and the like. In some embodiments, the support comprises or is silica.

[0044] In some embodiments, the support has a particle size in a range from about 1 to about 120 micrometers, such as from about 20 to about 80 micrometers. In some embodiments, the support has an average particle size from about 40 to about 50 micrometers.

[0045] In some embodiments, the support is silica having a surface area from about 200 to about 900 m2 / g and a pore volume from about 0.5 to about 4 milliliters per gram. Surface area can be determined, for example, using the Brunauer, Emmet, and Teller (BET) method with nitrogen gas used as the absorbate. Pore volume determinations are described in, for example, Lowell, S. et al. "Characterization of Porous Solids and Powders: Surface Area, Pore Size and Density" 1st ed. (2004), Dordrecht, The Netherlands: Springer, incorporated by reference herein.Catalyst compositionCo-catalyst

[0046] In another aspect is provided a catalyst composition comprising a metallocene complex as disclosed herein and a co-catalyst. Such catalysts are useful in, for example, polymerization of alpha-olefin monomers to form PAOs as described herein. In such catalyst compositions, generally,the co-catalyst is a compound capable of reacting with the metallocene complex to form a non- or weakly coordinating anionic species. Such co-catalysts may also be referred to as "catalyst activators." Suitable co-catalysts include any compound capable of activating the metallocene complex so that it is capable of polymerizing (i.e., oligomerizing) an alpha-olefin monomer. Co-catalysts are typically Lewis acids or an ionic species. Suitable co-catalysts include aluminum-, zinc-, and / or b or on-containing compounds. For avoidance of doubt, reference to a cocatalyst is intended to define the nature of the co-catalyst prior to reaction with the metallocene complex, and accordingly does not reflect the actual catalyst composition specie(s) formed following such reaction.

[0047] In some embodiments, the catalyst composition comprises an organoaluminum co- catalyst. Examples of aluminum-containing co-catalysts include, but are not limited to, aluminoxanes, alkyl aluminum compounds, and aluminum-alkyl-chlorides. Suitable aluminoxanes are known and typically comprise an oligomeric linear, cyclic alkyl aluminoxane represented by the formula R-(A1R6-O)n-A1R62, an oligomeric, cyclic aluminoxane represented by the formula - (A1R6-O)m-, or a combination thereof, where n is an integer from 1 to 40, such as from 10 to 30; m is an integer from 3 to 40, such as from 3 to 30, and R6is a Ci to Cs alkyl group. In some embodiments, R6is a methyl group. In some embodiments, R6is an isobutyl group. In some embodiments, R6is a combination of isobutyl groups and methyl groups. In some embodiments, the co-catalyst is methylaluminoxane (MAO),

[0048] Other suitable organoaluminum co-catalysts include trimethylaluminum, triethylaluminium, tri-isopropylaluminum, tri-n-propylaluminum, tri-isobutylaluminum, tri-n- butylaluminum, triamylaluminium, dimethylaluminum ethoxide, diethylaluminum ethoxide, diisopropylaluminum ethoxide, di-n-propylaluminum ethoxide, di-isobutylaluminum ethoxide, di-n- butylaluminum ethoxide, dimethylaluminum hydride, diethylaluminum hydride, diisopropylaluminium hydride, di-n-propylaluminum hydride, di-isobutylaluminum hydride, di-n- butylaluminum hydride, ethylaluminium di-chloride, di-ethylaluminiumchloride, ethylaluminium- sesqui-chloride, dimethylanilinium tetrakisperfluorophenyl aluminate, and mixtures thereof.

[0049] In some embodiments, the catalyst composition comprises a boron-containing co- catalyst. Examples of boron-containing co-catalysts include, but are not limited to, trialkylboranes, triarylboranes, perfluoroarylboranes, and perfluoroarylborates. In some embodiments, the boron- containing co-catalyst is a trialkylborane. In some embodiments, the trialkylborane istrimethylborane or tri ethylborane. In some embodiments, the co-catalyst is a triphenylborane. In some embodiments, the boron-containing co-catalyst is a perfluoroarylborane, such as tris- perfluorophenylboron, tetrakisperfluorophenylborate, triphenylcarboniumtetrakis- perfluorophenylborate, dimethylanilinium tetrakisperfluorophenylborate, triphenyl carb oniumtetrakis perfluorophenylborate, and combinations thereof. In some embodiments, the co-catalyst comprises both an organoaluminum and an organoboron compound.

[0050] In some embodiments, the catalyst composition comprises a zinc-containing co- catalyst. Examples of suitable zinc-containing co-catalysts include, but are not limited to, dialkyl zinc compounds, such as diethyl zinc.

[0051] The quantity of co-catalyst present in the catalyst composition may vary. In some embodiments, the co-catalyst is present in an amount from about 10 to about 100,000 molar equivalents relative to the metallocene complex, such as from about 10 to about 10,000 mol per mol of the metallocene complex. In some embodiments, the co-catalyst is an organoborane or organoborate, and the organoborane or organoborate is present in an amount from about 0.1 to about 100 molar equivalents relative to the metallocene complex, such as from about 0.5 to about 100 mol per mol of the metallocene complex.Co-Activators and Scavengers

[0052] In some embodiments, the catalyst composition further comprises a co-activator, a scavenger, or a combination thereof. A co-activator is a compound capable of alkylating an intermediate catalyst complex, in combination with a co-catalyst, to from an active catalyst. Coactivators include alumoxanes such as methylalumoxane, modified alumoxanes such as modified methylalumoxane, and aluminum alkyls such trimethylaluminum, triisobutylaluminum, triethylaluminum, tri-isopropylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, tri-n- decylaluminum, and tri-n-dodecylaluminum. Co-activators are typically used in combination with Lewis acid activators and ionic activators when the catalyst is not a dihydrocarbyl or dihydride complex. In various embodiments, co-activators may also be used as scavengers to deactivate impurities in feed or reactors. U.S. Pat. No. 9,409,834 provides a detailed description of coactivators that may be used in catalyst compositions of the present disclosure. The disclosure of this patent is incorporated herein by reference with respect to activators, scavengers, and co- activators.

[0053] A scavenger is a compound added to facilitate oligomerization or polymerization by scavenging impurities. Some scavengers may also act as activators and accordingly may alternatively be referred to as co-activators. To the extent scavengers facilitate the metallocene complex in performing the intended catalytic function, scavengers, if used, are sometimes considered as a part of the catalyst composition. Suitable scavengers are disclosed in, for example, U.S. Pat. No. 9,409,834, previously incorporated by reference. In some cases, it can be advantageous to modify the scavenger as described in, for example, International PatentApplication Publication No. WO2021 / 213836, incorporated by reference herein in its entirety.Process for preparation of poly-alpha-olefins

[0054] In another aspect is provided a process for the preparation of poly-alpha-olefins (PAOs). The process generally comprises polymerizing (i.e., oligomerizing) one or more alphaolefin monomers in the presence of a catalyst composition as described herein.

[0055] In some embodiments, the catalyst composition comprises a metallocene complex having a structure according to Formula II:wherein:M is titanium, zirconium, or hafnium;Xi and X2 are each independently selected from halogen and Ci to C10 alkyl;Re and R7 are each H, optionally substituted Ci to C10 alkyl, or optionally substituted Ce- C10 aryl; andR, R', R", and R'" each represent one or more substituents, each independently selected for each instance from the group consisting of H, halogen, optionally substituted Ci to C10 alkyl, and optionally substituted Ce-Cio aryl, preferably, wherein each substituent is H.

[0056] In some embodiments, Re and R7 are each CH3 or are each Ph.

[0057] In some embodiments, the catalyst composition comprises a metallocene complex as described above, and further comprises a co-catalyst, activator, co-activator, scavenger, or combinations thereof, each as described herein above. In some embodiments, one or more of the components of the catalyst composition are immobilized on a support as described herein above.

[0058] In some embodiments, the metallocene complex is allowed to react with the co-catalyst and optionally any additional components (e.g., activators, co-activators, scavengers) to form the catalyst composition in the same vessel in which the PAOs are produced. In some embodiments, the catalyst composition is formed in a separate vessel and subsequently fed to the reaction vessel in which the PAOs are produced. During the reaction to form the catalyst composition, an inert solvent can be used. Suitable solvents are described below and are generally the same as those suitable for use in the olefin polymerization reaction.Alpha-olefin monomer

[0059] The process generally comprises contacting the catalyst composition with an alphaolefin monomer. Suitable alpha-olefin monomers may have an even number or an odd number of carbon atoms. In some embodiments, the alpha-olefin monomer has an even number of carbon atoms. The total number of carbon atoms may vary. In some embodiments, the alpha-olefin monomer has from 4 to about 30 carbon atoms, such as from about 6 to 18 carbon atoms, or from about 6 to 12 carbon atoms. In some embodiments, the alpha-olefin monomer has from 6 to 10 carbon atoms, such as 6, 8, or 10 carbon atoms. In some embodiments, the alpha-olefin monomer is 1 -butene, 1 -pentene, 1 -hexene, 1 -heptene, 1 -octene, 1 -nonene, 1 -decene, 1 -undecene, 1- dodecene, 1 -tridecene, 1 -tetradecene, 1 -hexadecene, 1 -octadecene, 1-eicosene, 4-m ethyl- 1- pentene, 5-methyl-l-nonene, 3 -methyl- 1 -pentene, 3,5,5-trimethyl-l-hexene, vinylcyclohexene, or a combination thereof. In some embodiments, the alpha-olefin monomer is a single monomer. In some embodiments, the alpha-olefin monomer is a combination of two or more alpha-olefin monomers. In some embodiments, the alpha-olefin monomer is selected from the group consisting of 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene, and combinations thereof.

[0060] In some embodiments, the alpha-olefin monomer may be characterized by a low content of non-terminal unsaturation, such as below 30% by weight, such as below 10%, or even below 5% of non-terminal unsaturation.

[0061] In some embodiments, the alpha-olefin monomer may be characterized as substantially free of ethylene and propylene, or completely free of ethylene and propylene, such as includingless than about 0.1% by weight, or less than about 0.01% by weight, or even 0% by weight of ethylene and propylene.Polymerization of alpha-Olefin Monomers

[0062] The polymerization (i.e., oligomerization) of the alpha-olefin monomer may be performed under a variety of conditions, and by various processes. For example, the polymerization may be performed by contacting the catalyst composition with the alpha-olefin monomer in a slurry or a solution, process. Further, the polymerization conditions for example temperature, time, pressure, monomer concentration, and catalyst composition concentration may be selected from numerous ranges, and the polymerization may be carried out in batch, semi-batch or continuous processes, in either a single reactor or in multi-stage reactors. Generally, the reaction conditions are controlled so as to cause effective conversion of the alpha-olefin monomer to the desired poly-alpha-olefin product.

[0063] In some embodiments, the polymerization of the alpha-olefin monomer is performed using a solution or slurry of the catalyst composition in a suitable solvent or diluent, respectively. In slurry reactors, the solvent, generally a low boiling hydrocarbon solvent, is employed as a continuous medium, and monomer, catalyst etc. is added to this continuous phase. Suitable solvents include, but are not limited to, benzene, toluene, xylene, propane, butane, pentane, hexane, heptane, cyclohexane, methylene chloride, and combinations thereof. The choice of solvent is dependent upon the particular monomer, catalyst composition, desired reaction temperature, and the like. The PAO formed is insoluble in the reaction medium, producing a slurry of PAO and catalyst composition. Slurry reactors may be divided into loop reactors and continuous stirred tank reactors (CSTR). In case of a CSTR, heat can at least partially be removed by the heat of vaporization of solvent, which is later condensed and returned to the reactor. PAO is removed as slurry from the reactor and flashed to remove solvent, which is recycled. Slurry loop reactors may be horizontally or vertically oriented. Water flowing through the reactor- wall serves to remove heat and maintain a relatively constant temperature. Slurry flow is achieved by pumps which maintain the polymer slurry at relatively high velocity. Product PAO is removed either continuously or discontinuously from a "settling leg."

[0064] Typically, the polymerization of the alpha-olefin monomer with the catalyst composition of the disclosure is polymerization via a solution-based process. In a solution process, the PAO product is formed as a solution in a suitable solvent. The solvent may be the non-convertedolefin monomer or may be an inert hydrocarbon solvent. When the non-converted monomer is used as the solvent, the process might also be referred to as a bulk process. Suitable solvents include, but are not limited to, benzene, toluene, xylene, propane, butane, pentane, hexane, heptane, cyclohexane, methylene chloride, and combinations thereof. Suitable reactors may be loop reactors, which may be equipped with static mixer elements, or may be tank reactors. The removal of the heat of polymerization may be done either through external cooling using a suitable coolant flowing through the reactor-wall, or via an external cooler or via cooling of the feedstream. Combinations thereof are also possible.

[0065] The temperature at which the polymerization of the alpha-olefin monomer is performed may vary. In some embodiments, the temperature is in a range from about -100 °C to about 300 °C, such as from about 0 °C to about 200 °C, or about 50 °C to about 200 °C. In some embodiments, the temperature is in a range from about 25 °C to about 150 °C, or from about 50 °C to about 135 °C.

[0066] The polymerization time may vary, and is generally in a range from about 10 seconds to about 20 hours, such as from about 1 minute to about 10 hours, or from about 5 minutes to about 5 hours.

[0067] In some embodiments, the polymerization of the alpha-olefin monomer is performed in a sequential series of two or more reactors, such as two reactors or three reactors. In some embodiments, the residence time in the first reactor is from about 0.2 to about 3 hours, and if a second reactor is utilized, from about 0.2 to about 1.5 hours in said second reactor. The residence time in a third reactor, if used, would typically be from about 10 minutes to about 1 hour.

[0068] In some embodiments, the metallocene complex, co-catalyst, and optionally other components (e.g., scavenger, activators, and the like) are contacted in a first reactor to form the catalyst composition, and the catalyst composition is co-fed with the olefin monomer to a second reactor.

[0069] In some embodiments, a mixture of catalyst composition and alpha-olefin monomer is fed into a first reactor, where it is partially reacted, and the reaction mixture is fed into a second reactor, where the reaction may be allowed to continue to completion, or optionally, the mixture may be fed to a third reactor.

[0070] Generally, each of the one or more reactors is equipped with a mixing or stirring means for mixing the feed and catalyst composition to provide intimate contact. In some embodiments,CSTRs are used in series. The operation of CSTRs is known in the art. In some embodiments, no recycling of unconverted monomer is used. In some embodiments, the process comprises recycling of unconverted monomer.

[0071] The polymerization reaction of the alpha-olefin monomer is not particularly pressure dependent, and it is most economical to operate the reactors at a low pressure. In some embodiments, the alpha-olefin monomer is polymerized at a reactor pressure ranging from standard atmospheric pressure to about 5 bar. In some embodiments, the alpha-olefin monomer is polymerized at a reactor pressure ranging from 1 to 3500 bar, such as from 1 to 2500 bar, from 1 to 1000 bar, from 1 to 500 bar, or from 1 to 100 bar.

[0072] The polymerization of the alpha-olefin monomer may be conducted by a batch process, a semi-continuous process or a continuous process and may also be conducted in two or more steps of different polymerization conditions. The PAO produced is separated from the solvent and unreacted monomer and further purified by methods known to a person skilled in the art.

[0073] In some embodiments, the molecular weight of the PAO produced according to the disclosed process is controlled by various means, including time, temperature, concentration of components, and the like. In some embodiments, the molecular weight of the PAO can be controlled by use of hydrogen in the polymerization. In some embodiments, a chain terminating agent is utilized in the process. Examples of such chain terminating agents include, but are not limited to, metal alkyls, for example, alkyl zinc compounds such as diethyl zinc. Accordingly, in some embodiments, the process further comprises introducing a suitable amount of hydrogen or dialkyl zinc into the reactor in order to moderate the properties of the PAO so obtained. In some embodiments, the process further comprises adding hydrogen to the polymerization reactor(s).

[0074] In some embodiments, the as-synthesized PAO has some degree of unsaturation, such as in the form of terminal vinylidene groups. In some embodiments, the as-synthesized PAO exhibits sites of unsaturation, and the process further comprises hydrogenation of the synthesized PAO to produce a saturated PAO. In some embodiments, the PAO may be hydrogenated by reaction with hydrogen gas in the presence of a catalytic amount (e.g., 0.1 to 5 wt. %) of a hydrogenation catalyst. Examples of suitable hydrogenation catalysts include metals of Group VIII of the Periodic Table, such as iron, cobalt, nickel, rhodium, palladium, and platinum. These catalytic metals may be deposited on alumina, silica gel, or activated carbon supports. In some embodiments, the catalyst is palladium or nickel, such as palladium on activated carbon or nickelon kieselguhr. The hydrogenation can be carried out in the presence or absence of solvents, which serve to increase the volume of the reaction. Examples of suitable solvents are hydrocarbons such as pentane, hexane, heptane, octane, decane, cyclohexane, methylcyclohexane, and cyclooctane; and aromatic hydrocarbons such as toluene, xylene, and benzene. The temperature of the hydrogenation reaction may range, for example, from about 150 °C to about 500 °C, such as from about 250 °C to about 350 °C. The hydrogenation reaction pressure may be, for example, in the range of 15-75 bar. The hydrogenated PAO product is then recovered by conventional procedures. In the hydrogenated product, the double bonds formed in the oligomerization step have been hydrogenated so that the PAO is a separate product. Details pertaining to hydrogenation are described in, for example, WO2021 / 086926A1, incorporated herein by reference.Poly-alpha-olefins

[0075] In another aspect is provided a poly-alpha-olefin (PAO) prepared by the process disclosed herein. Properties of the PAO may vary based on the monomer used, the catalyst composition, and the reaction conditions.

[0076] In some embodiments, the PAO produced from the process of the present disclosure may be used for preparing lubricant oil. For example, low viscosity crankcase lubricants typically consist of a mixture of C30 to Ceo hydrocarbons with a weight average molecular weight (Mw) between 400-850. High viscosity lubricants have a higher Mw, such as up to 32 kilodaltons. In some embodiments, the metallocene complexes of the present disclosure produce PAOs well- suited for lubricant oil applications in terms of at least one or more of oxidative stability, molecular weight range, viscosity (e.g., Viscosity Index), and Pour Point in comparison to PAO prepared by other known catalysts.

[0077]

[0078] In some embodiments, the PAO has a weight-averaged molecular weight (Mw) or a number averaged molecular mass (Mn) in a range from about 200 to about 65,000 daltons, such as from about 3000 to about 32,000 daltons as measured by high-performance liquid chromatography (HPLC), gel permeation chromatography, or gas chromatography (GC). It has been found that the method according to some embodiments is particularly suitable in providing relatively low molecular weight PAOs (e.g., dimers to pentamers). Accordingly, in some embodiments, the PAO has a Mw or Mn of less than about 5,000 daltons, such as about 100 toabout 2,000 daltons or about 150 to about 1,000 daltons. In some embodiments, the PAO has a Mw from about 168 to about 420 daltons.

[0079]

[0080] The molecular weight distribution (expressed as Mw / Mn) of the PAO may vary. In some embodiments, the distribution is in a range from about 1.5 to about 5, such as from 2.1 to 4, or from 2.5 to 3.5.

[0081] The viscosity of the PAO may vary. The viscosity of a PAO can be determined as the kinematic viscosity measured at a temperature of 100 °C (KvlOO) or measured at 40 °C (Kv40), typically expressed in units of centi-Stokes (cSt). The viscosity depends on the degree of oligomerization (Pn), which in turn directly correlates to the averaged molecular mass of the oligomer, expressed as the number averaged molecular mass (Mn) or the weight averaged molecular mass (Mw). Such correlations between Pn and kinematic viscosity at a temperature of 100 °C (KvlOO) can be found for instance in US Patent Nos. 7,989,670 and 9,365,663, incorporated herein by reference. Additional references for such correlations can be found in Molecular Systems Design & Engineering 2021, 6, pages 722-729.

[0082] In some embodiments, the PAO has a KvlOO in a range from about 1 to about 1000 cSt, such as from about 1 to about 30, or from about 30 to about 500 cSt. For example, in some embodiments, medium to high viscosity PAO’s display a KvlOO in the range of 30 - 500 cSt, depending on the specific grade and application. In some embodiments, low viscosity PAO’s are of commercial interest, which display a lower KvlOO, such as below 30 cSt or even below 10 cSt. In case such low viscosities are required, the degree of polymerization should be relatively low, for instance as low as an average degree of polymerization of 2, 3, 4, or 5, corresponding to dimers, trimers, tetramers or pentamers respectively. PAOs having such a low degree of polymerization may be also referred to as oligomers, and the terms polymer and oligomer, as well as the corresponding process terms (polymerization and oligomerization, respectively) are used interchangeably herein.EXPERIMENTALExample 1. Preparation of metallocene complex 1

[0083] Metallocene complex 1 was prepared as described in WO2014 / 139949, incorporated herein by reference in its entirety.Example 2. Preparation of metallocene complex 2

[0084] Metallocene complex 2 was prepared as described in WO2014 / 139949, incorporated herein by reference in its entirety.Example 3. Preparation of metallocene complex 3

[0085] Metallocene complex 3 was prepared as described in WO2014 / 139949, incorporated herein by reference in its entirety.Example 4. Preparation of metallocene complex 4Scheme 1

[0086] Metallocene complex 4 was prepared by a multi-step route as illustrated in Scheme 1, using reactions known to one of skill in the art.Example 5. Preparation of metallocene complex 5Scheme 2

[0087] Metallocene complex 5 was prepared by a multi-step route as illustrated in Scheme 2, using reactions known to one of skill in the art. Example 6. Preparation of metallocene complex 6

[0088] Metallocene complex 6 was prepared by a multi-step route comparable to Example 5, but replacing the lithiated indenyl with cyclopentadienyl lithium.Example 7. Preparation of metallocene complex 7

[0089] Metallocene complex 7 was prepared by a multi-step route comparable to Example 5, but replacing the di-lithiated biphenyl with di-lithiated 4,4’-di-Zbutyl-biphenyl.Example 8. General procedure for polymerization of alpha-olefin monomers and characterization of polymers

[0090] Polymerizations were performed in a Parallel Pressure Reactor (PPR48) containing 48 reactors mounted in a triple glovebox (Freeslate; California / USA). A typical polymerization run was carried out as follows. Prior to polymerization, the PPR48 underwent a '‘bake-and-purge1cycle overnight (8 h at 85 °C with intermittent dry N2 flow) to remove any contaminants and left-overs from previous experiments. After cooling to glove-box temperature, the stir tops were taken off, the 48 cells fitted with disposable 10 mL glass inserts (pre-weighed in a Bohdan Balance Automator) and titanium stir paddles, after which the stir tops were put back in place. Next, the modules were heated at 45 °C, and proper volumes of toluene, scavenger (Methylaluminoxane (MAO), a mixture of organoaluminum compounds with the approximate formula (Al(CH3)O)n, 250 mM solution, 50 pmol; or tri-isobutylaluminum (TIB A), 100 mM solution, 10 pmol), and monomer (1-octene, 4.1 mL), for a total volume of 4.2 mL, were loaded into each reaction cell. The modules were then pressurized with nitrogen (50 psi) to seal the rubber septa of the reaction cells, and heated to the desired reaction temperature (60, 80, or 100 °C) under stirring at 400 rpm. Once thermal equilibrium was reached, proper volumes of toluene solutions of metallocene complex (typically 0.02 mM) and activator (MAO, 25 mM or dimethylanilinium-tetrakis- pentafluorophenylborate (AB), 1 mg mL1) were injected into each cell. After the desired time (5- 120 min), the reactions were quenched with an overpressure of dry air. After all cells were quenched, the modules were cooled down and vented, the stir-tops removed, and the glass inserts containing the reaction phase were taken out and transferred to a centrifugal evaporator (Genevac EZ2-Plus), where all volatiles were removed and the oligomers thoroughly dried overnight (75 °C,5 mbar). Monomer conversion was measured by robotically weighing the dry oligomers while still in the reaction vials, subtracting the pre-recorded tare.

[0091] HPLC chromatograms of all oligomer samples were recorded using an Agilent 1260 Infinity II setup, equipped with a refractive index (RI) detector. Depending on the target MW, two different set of columns were employed: (i) Agilent PL-GEL-MIXED-D 5 pm columns with a linear MW operating range of 1 - 300 kDa; or (ii) Agilent InfinityLab Oligopore 6 pm columns with a linear MW operating range of 0.1 - 3.3 kDa. In particular, the samples produced at 60 °C were characterized using the former, while the samples produced at 80 °C and 100 °C were analyzed using the latter. The samples (approximately 3 mg) were dissolved at RT in proper volumes of THF containing BHT as stabilizer, so as to obtain solutions at a concentration of 1.0 mg mL’1. After complete dissolution, the samples were sequentially injected into the column line at 35°C and a flow rate of 1.0 mL min'1. Calibration was carried out with the universal method using two different set of 10 monodisperse polystyrene samples.

[0092] Sample were also characterized by proton NMR.JH NMR spectra (400 MHz) of selected samples were recorded on a Bruker Advance III 400 spectrometer equipped with a 5 mm high temperature cry oprobe and a robotic sample changer with pre-heated carousel (24 positions). The samples (~25 mg) were dissolved at 120 °C in tetrachloroethane- l,2-d2 (0.7 mL) containing BHT as a stabilizer and loaded in the carousel maintained at the same temperature. The spectra were taken sequentially with automated tuning, matching and shimming. Operating conditions were: 90° pulse; acquisition time, 2.0 s; relaxation delay, 10.0 s; 16 transients. Numb er- Average degrees of oligomerization (Pn) were estimated from the mole fraction of unsaturated terminal chain ends, measured as the ratio between the total proton and vinylidene proton integrals in quantitative spectra.Example 8A. Polymerization of 1-octene-single temperature

[0093] The monomer 1 -octene was polymerized according to the general procedure of Example 8, at a fixed temperature of 60 °C and a reaction time of 1 hour. Two reference metallocene complexes were used ((bis(n-butylcyclopentadienyl)zirconium dichloride ((nBuCp)2ZrCh) and bis(l,3-n-butylmethylcyclopentadienyl)zirconium dichloride (BuMeCp)2ZrCh)), along with the inventive metallocene complexes of Examples 1-7. The scavenger was MAO. Results of the polymerization study are provided in Table 1.

[0094] As shown in Table 1, the inventive complexes of Examples 1-7 generally produced significantly higher PAO weight average molecular weights, in a range particularly well-suited for high viscosity lubricants, relative to the two reference complexes. Additionally, the inventive complexes of Examples 1-7 generally exhibited higher activity than the reference complexes at one or both of the complex concentrations tested. In particular, the complexes of Examples 5 and 7 afforded high activity.Table 1. Conditions and characterization of PAOsExample 12B. Polymerization of 1-octene-various temperatures

[0095] The monomer 1 -octene was polymerized according to the general procedure ofExample 12, at fixed temperatures of 60 °C, 80 °C, and 100 °C, and a reaction time of 30 minutes or 1 hour. One reference metallocene complex was used ((nBuCp^ZrCh), along with the inventive metallocene complexes of Examples 2, 4, 5, and 9. The scavenger was MAO. Results of the polymerization study are provided in Table 2.

[0096] The data in Table 2 confirms that the complexes of Examples 4, 5, and 7 generally produce higher molecular weight PAO than the reference complexes and afford high activity.Table 2. Conditions and characterization of PAOsExample 12C. Polymerization of 1-octene-different ratios of activator to zirconium

[0097] The monomer 1 -octene was polymerized according to the general procedure of Example 12, at a fixed temperature of 100 °C, and a reaction time of 30 minutes or 1 hour, using the inventive metallocene complexes of Examples 1-3 and different ratios of activator to zirconium. Methylaluminoxane (MAO), and dimethylanilinium-tetrakis-pentafluorophenylborate (AB) were used as co-catalysts. When using the latter, tri-isobutyl-aluminum (TiBA) was used as a scavenger and alkylating agent. In all cases, 50 nanomoles of complex was used. Results of the polymerization study are provided in Table 3.Table 3, Conditions and characterization of PAOs

Claims

CLAIMSWhat is claimed is:

1. A metallocene complex having a structure according to Formula I or Formula II:wherein:M is titanium, zirconium, or hafnium;Xi and X2 are each independently selected from halogen and Ci to C10 alkyl;Ri and R2 are each H; orRi and R2, together with the carbon atoms to which they are bound, form a 6-membered optionally substituted aromatic ring;R3 is optionally substituted Ce-Cio aryl, preferably optionally substituted Ce aryl;R4is H; or R3 and R4, together with the carbon atoms to which they are bound, form a 6- membered optionally substituted aromatic ring;Rs is H or optionally substituted Ci to Ce alkyl; andR, R', R", and R'" each represent one or more substituents, each independently selected for each instance from the group consisting of H, halogen, optionally substituted Ci to C10 alkyl, and optionally substituted Ce-Cio aryl, preferably, wherein each substituent is H.

2. The metallocene complex of claim 1, wherein M is zirconium.

3. The metallocene complex of claim 1 or 2, wherein Xi and X2 are both Cl.

4. The metallocene complex of claim 1 or 2, wherein Xi and X2 are both CH3.

5. The metallocene complex of any one of claims 1-4, wherein:Ri and R2 are H;R3 and R4 form a 6-membered optionally substituted aromatic ring; and Rs is H.

6. The metallocene complex of any one of claims 1-4, wherein:Ri and R2 form a 6-membered optionally substituted aromatic ring;R3 is optionally substituted phenyl;R4 is H; andRs is H or Ci to Ce alkyl.

7. The metallocene complex of any one of claims 1-4, wherein:Ri and R2 form a 6-membered optionally substituted aromatic ring; and R3 and R4 form a 6-membered optionally substituted aromatic ring.

8. The metallocene complex of claim 1, selected from the group consisting of9. The metallocene complex of claim 1, having a structure10. A process for the preparation of poly-alpha-olefins comprising polymerizing one or more alpha-olefin monomers having from 4 to 30 carbon atoms, in the presence of a catalyst composition comprising a co-catalyst and the metallocene complex of any one of claims 1-9.

11. A process for the preparation of poly-alpha-olefins comprising polymerizing one or more alpha-olefin monomers having from 4 to 30 carbon atoms, in the presence of a catalyst composition comprising a metallocene complex and a co-catalyst, the metallocene complex having a structure according to Formula III:wherein:M is titanium, zirconium, or hafnium;Xi and X2 are each independently selected from halogen and Ci to C10 alkyl;Re and R7 are each H, optionally substituted Ci to C10 alkyl, or optionally substituted Ce-Cio aryl; andR, R', R", and R'" each represent one or more substituents, each independently selected for each instance from the group consisting of H, halogen, optionally substitutedCi to C10 alkyl, and optionally substituted Ce-Cio aryl, preferably, wherein each substituent is H.

12. The process of claim 11, wherein Re and R7 are each CH3 or are each Ph.

13. The process of any one of claims 10 to 12, wherein the one or more alpha-olefin monomers are selected from the group consisting of 1 -hexene, 1 -octene, 1 -decene, 1 -dodecene, and combinations thereof.

14. A poly-alpha-olefin prepared by the process of any one of claims 10 to 13.

15. The poly-alpha-olefin of claim 14, having a kinematic viscosity at a temperature of 100 °C (KvlOO) in a range from about 2 to about 1000 centi-stokes (cSt), such as from about 1 to about 30, or from about 30 to about 500 cSt, and / or having a weight averaged molecular mass (Mw) of about 5,000 daltons or less, such as about 100 daltons to about 2,000 daltons.

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