WO2002042313A2

WO2002042313A2 - Process for the preparation of an aluminium alkyl growth product and its use in the oligomerisation of olefins

Info

Publication number: WO2002042313A2
Application number: PCT/US2001/044248
Authority: WO
Inventors: Harold W. Boone; Michael J. Mullins; Peter N. Nickias; Vernon Snelgrove
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 2000-11-27
Filing date: 2001-11-13
Publication date: 2002-05-30
Anticipated expiration: 2003-05-27
Also published as: WO2002042313A3; AU2002219867A1

Abstract

A process for the preparation of an aluminum alkyl chain growth product by the chain growth reaction of an alpha -olefin on an aluminum alkyl, optionally followed by displacement and recovery of the oligomeric alpha-olefin employing as a catalyst for the chain growth reaction a compositon comprising a Group 6 metal trisazacycloalkane complex and an activating cocatalyst.

Description

CATALYSTS FOR OLIGOMERIZATION OF ETHYLENE This invention relates generally to the preparation of aluminum alkyls by the chain growth reaction of a lower olefm, especially ethylene, with a lower molecular weight alkyl aluminum and more specifically to an improved chain growth process catalyzed by derivatives of certain metal complexes.

Stepwise ethylene chain growth on aluminum alkyls was discovered in the 1950's by K. Ziegler et al. The reaction proceeds thermally at temperatures in the range of 100° to 200°C under high ethylene pressure, typically 2000 to 4000 psi (14 to 28 MPa). At higher temperatures, a displacement reaction or cracking step competes with chain growth, producing α-olefins and regenerating aluminum alkyl compounds. For a review see, "Comprehensive Organometallic Chemistry:, 1982, Pergammon Press, Vol. 7, Section 46. The process may be advanced by catalysts, both for the step-wise growth of the aluminum alkyl and the catalyzed displacement of α-olefins therefrom. Ziegler-Natta catalysts such as those discovered by Kaminsky et al. (Angew. Chem. Int. Ed. Engl., 1976, Vol. 15, pages 630 to 632) may be used to catalyze the growth process. This process is thought to involve active transition metal catalysts which rapidly insert olefins to the aluminum alkyl chains. Chain growth is terminated in the displacement or cracking step, principally by β-hydrogen or β-alkyl elimination to give a vinylic end group or by hydrogenolysis to give a paraffinic end group, thereby regenerating a catalytically active transition metal hydride or alkyl and an aluminum hydride or alkyl.

If an aluminum hydride is formed it may be regenerated by reaction with the same or a different olefin, and reused in the oligomerization. 1-butene is especially desired for this application. See. Developments in α-olefm Production Technology, Chem. Systems Inc., Jan. 1999. The manufacture of α-olefins using the foregoing step addition to aluminum alkyls is commercially practiced in large volume. Suitable processes operating at lower temperatures and pressures than those employed by early artisans are disclosed in US-A-5, 276,220 (using actinide metal metallocene based complexes, which unfortunately are radioactive, as catalysts) and in US-A-5,210,338 (using metallocene based complexes of zirconium and hafnium). A desired result of the foregoing processes is the production of aluminum alkyls and the resulting α-olefin products having a narrow molecular weight distribution (Poisson distribution). In many such processes, the products are undesirably broad, and best described by the Schulz-Flory statistical distribution. These statistical distributions are commonly known and defined by the equations: Poisson: X_p =(χ^p-e"^x)/ρ!, and Schulz-Flory: X_p=β(l+β)^~p, where X_p is the mole fraction with p added ethylenes, x is the Poisson distribution coefficient equal to the average number of ethylene molecules added per Al-C bond, and β is the Schulz- Flory distribution coefficient. A Poisson distribution is a normal distribution curve approximately centered about the number average degree of polymerization. It is more desired than a Shulz-Flory distribution, which describes a product that contains the greatest molar amount of the smallest oligomers and includes a broader range of products, but lower quantities of any individual oligomer. The formation of low molecular weight polyethylenes (paraffins) or branched by-products by the foregoing processes is also undesired.

Despite the advance in the art encompassed by the foregoing known processes, a process that operates at milder temperatures and pressures to produce purer α-olefm products and provide a Poisson type chain length distribution while limiting polyethylene or branched co-products is still desired. Moreover, avoiding the use of radioactive catalyst is also highly desirable. The α-olefin products of the foregoing process are useful industrial chemicals employed to prepare plastics, including high molecular weight polyethylene, or solvents such as linear, primary alcohols. In accordance with this invention there is provided an improved process for the preparation of an aluminum alkyl chain growth product by the chain growth reaction of an α- olefin on an aluminum alkyl, optionally followed by displacement and recovery of the oligomeric alpha-olefm from the aluminum alkyl chain growth product, said process comprising catalyzing the chain growth reaction with a catalyst composition comprising a Group 6 metal trisazacycloalkane complex and an activating cocatalyst.

Also provided is an improved process for the preparation of oligomeric alpha-olefins by the chain growth reaction of an α-olefin on an aluminum alkyl followed by olefin displacement of the oligomeric alpha-olefm, comprising catalyzing the chain growth reaction with a catalyst composition comprising a Group 6 metal trisazacycloalkane complex and an activating cocatalyst.

Also provided is an improved process for the preparation of primary alcohols by the chain growth reaction of α-olefins on an aluminum alkyl followed by oxidation of the aluminum alkyl chain growth product to form alkoxides and acid hydrolysis of the alkoxides to produce linear primary alcohols, comprising catalyzing the chain growth reaction with a catalyst composition comprising a Group 6 metal trisazacycloalkane complex and an activating cocatalyst.

Oligomeric products and derivatives prepared by the present invention have a uniform distribution closely approximating a Poisson distribution, and reduced by-product content. Figure 1 is the product distribution obtained from the oligomerization of Example 5 compared with a Schulz-Flory distribution having a Schulz-Flory constant of 0.85. All references to the Periodic Table of the Elements herein shall refer to the Periodic Table of the Elements, published and copyrighted by CRC Press, Inc., 1997. Also, any references to a Group or Groups shall be to the Groups or Groups reflected in this Periodic Table of the Elements using the IJJPAC system for numbering groups. For purposes of United States patent practice, the contents of any patent, patent application or publication referenced herein are hereby incorporated by reference in their entirety, especially with respect to the disclosure of synthetic techniques and general knowledge in the art.

Examples of α-olefins suitable for chain growth herein include, but are not limited, to C₂ to C₆ straight chain α-olefms, with ethylene being the preferred olefin. Suitable Group 6 metal triazocycloalkanes for use as the catalyst component of the present invention correspond to the following formula:

wherein M is a Group 6 metal, especially chromium;

R¹ independently in each occurrence is a Cι„₂₀ hydrocarbylene group, especially ethylene;

R² independently in each occurrence is an anionic ligand of up to 20 atoms not counting hydrogen, preferably a C^o hydrocarbyl group, most preferably, methyl; and

X is an anionic ligand of up to 20 atoms not counting hydrogen, preferably hydride, halide, or a hydrocarbyl-, silyl-, hydrocarbyloxy- or siloxy- group of up to 10 atoms; most preferably chloride or methyl.

Preferred Group 6 metal triazocycloalkane compounds are l,4,7-trimethyl-l,4,7- triazacyclononane chromium dichloride and l,4,7-trimethyl-l,4,7-triazacyclononane chromium dimethyl.

Suitable aluminum alkyl compounds for use herein include trialkyl aluminums, dialkyl aluminum hydrides, dialkyl aluminum halides, and mixtures thereof, containing from 2 to 20 carbons in each alkyl group. Specific non-limiting examples of suitable aluminum alkyl compounds include triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, tri-n- hexylaluminum, and diethylaluminurn hydride. A preferred aluminum alkyl compound is triethylaluminum (TEA) or tri-n-butylaluminum (TNBA). In the presence of the aluminum alkyl compound, it is believed that alkylation of a non-alkylated Group 6 metal compound results, thereby producing a catalyst composition capable of forming a cationic complex by removal of a leaving group upon exposure to the cocatalyst. Furthermore, it is believed that activation of the metal complex herein results in generation of a cationic species as the active catalyst composition. It is to be understood that ^• such expressed beliefs as to the theory of operation of the present invention are not binding on the inventors, it being sufficient that the present disclosure of the invention and of the method to make and use the same is adequately set forth herein.

The foregoing Group 6 metal complexes are activated to form the actual catalyst composition by combination with a cocatalyst, preferably an aluminoxane, a cation forming cocatalyst, or a combination thereof. Additional additives, such as a chain transfer agent, for example, hydrogen, used to control chain length, may be present in the reaction as well. The lengths of the product alkyl chains and thus the resulting olefϊn products essentially follow the Poisson statistical distribution, and the process is characterized by low temperatures and pressures. Moreover, low molecular weight polyethylene coproducts are virtually eliminated. Suitable alumoxanes for use herein include polymeric or oligomeric alumoxanes, especially methylalumoxane, triisobutyl aluminum modified methylalumoxane, or isobutylalumoxane; neutral Lewis acid modified polymeric or oligomeric alumoxanes, such as the foregoing alkylalumoxanes modified by addition of a Cι_₃₀ hydrocarbyl substituted Group 13 compound, especially a tri(hydrocarbyl)aluminum- or tri(hydrocarbyl)boron compound, or a halogenated (including perhalogenated) derivative thereof, having from 1 to 10 carbons in each hydrocarbyl or halogenated hydrocarbyl group, more especially a perfluorinated tri(aryl)boron compound or a perfluorinated tri(aryl)aluminum compound.

The Group 6 metal complexes may also be rendered catalytically active by combination with a cation forming cocatalyst, such as those previously known in the art for use with Group 4 metal olefin polymerization complexes. Suitable cation forming cocatalysts for use herein include neutral Lewis acids, such as Cι_₃₀ hydrocarbyl substituted Group 13 compounds, especially tri(hydrocarbyl)aluminum- or tri(hydrocarbyl)boron compounds and halogenated (including perhalogenated) derivatives thereof, having from 1 to 10 carbons in each hydrocarbyl or halogenated hydrocarbyl group, more especially perfluorinated tri(aryl)boron compounds, and most especially tris(pentafluoro-phenyl)borane; nonpolymeric, compatible, noncoordinating, ion forming compounds (including the use of such compounds under oxidizing conditions), especially the use of ammonium-, phosphonium-, oxonium-, carbonium-, silylium- or sulfonium- salts of compatible, noncoordinating anions, or ferrocenium-, lead- or silver salts of compatible, noncoordinating anions; and combinations of the foregoing cation forming cocatalysts and techniques. The foregoing activating cocatalysts and activating techniques have been previously taught with respect to different metal complexes for olefin polymerizations in the following references: EP-A-277,003, US-A- 5,153,157, US-A-5,064,802, US-A-5,321,106, US-A-5,721,185, US-A-5,350,723, US-A- 5,425,872, US-A-5,625,087, US-A-5,883,204, US-A-5,919,983, US-A-5,783,512, WO 99/15534, and W099/42467, (equivalent to USSN 09/251,664, filed February 17, 1999).

Examples of cation forming cocatalysts include compounds comprising a cation that is a Brønsted acid capable of donating a proton, and a compatible, noncoordinating anion, A". As used herein, the term "noncoordinating" means an anion or substance which either does not coordinate to the metal complex or the catalytic derivative derived therefrom, or which is only weakly coordinated to such complexes thereby remaining sufficiently labile to be displaced by a neutral Lewis base. A noncoordinating anion specifically refers to an anion which when functioning as a charge balancing anion in a cationic metal complex does not transfer an anionic substituent or fragment thereof to said cation thereby forming neutral complexes. "Compatible anions" are anions which are not degraded to neutrality in operation and are noninterfering with desired subsequent oligomerization process.

Preferred anions are those containing a single coordination complex comprising a charge-bearing metal or metalloid core which anion is capable of balancing the charge of the active catalyst species (the metal cation) which may be formed when the two components are combined. Also, said anion should be sufficiently labile to be displaced by olefinic, diolefmic and acetylenically unsaturated compounds or other neutral Lewis bases such as ethers or nitriles. Suitable metals include, but are not limited to, aluminum, gold and platinum. Suitable metalloids include, but are not limited to, boron, phosphorus, and silicon.

Compounds containing anions which comprise coordination complexes containing a single metal or metalloid atom are, of course, well known and many, particularly such compounds containing a single boron atom in the anion portion, are available commercially.

Preferably such cocatalysts may be represented by the following general formula: (L*-H)_d ⁺ (A)^d", wherein:

L* is a neutral Lewis base;

(L*-H)⁺ is a conjugate Brønsted acid of L*;

A^d" is a noncoordinating, compatible anion having a charge of d-, and d is an integer from 1 to 3. More preferably, A^d" corresponds to the formula: [M'Q₄] "; wherein:

M' is boron or aluminum in the +3 formal oxidation state; and Q independently each occurrence is selected from hydride, dialkylamido, halide, hydrocarbyl, hydrocarbyloxide, halo-substituted hydrocarbyl, halo-substituted hydrocarbyloxy, and halo- substituted silylhydrocarbyl radicals (including perhalogenated hydrocarbyl- perhalogenated hydrocarbyloxy- and perhalogenated silylhydrocarbyl radicals), said Q having up to 20 carbons with the proviso that in not more than one occurrence is Q halide. Examples of suitable hydrocarbyloxide Q groups are disclosed in US-A-5,296,433.

In a more preferred embodiment, d is one, that is, the counter ion has a single negative charge and is A^". Activating cocatalysts comprising boron which are particularly useful in the preparation of catalysts of this invention may be represented by the following general formula:

(L*-H)⁺(BQ₄)-; wherein:

L* is as previously defined; B is boron in a formal oxidation state of 3; and Q is a hydrocarbyl-, hydrocarbyloxy-, fluorohydrocarbyl-, fluorohydrocarbyl-oxy-, hydroxyfluorohydrocarbyl-, dihydrocarbylaluminumoxyfluorohydrocarbyl-, or fluorinated silylhydrocarbyl- group of up to 20 nonhydrogen atoms, with the proviso that in not more than one occasion is Q hydrocarbyl.

Preferred Lewis base salts are ammonium salts, more preferably trialkylammonium salts containing one or more C₁ . ₀ alkyl groups. Most preferably, Q is each occurrence a fluorinated aryl group, especially, a pentafluorophenyl group.

Illustrative, but not limiting, examples of boron containing cation forming cocatalysts are tri-substituted ammonium salts such as: trimethylammonium tetrakis(pentafluorophenyl) borate, triethylarnmonium tetrakis(pentafluorophenyl) borate, tripropylammonium tetrakis(pentafluorophenyl) borate, tri(n-butyl)ammonium tetrakis(pentafluorophenyl) borate, tri(sec-butyl)ammonium tetrakis(pentafluorophenyl) borate,

N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate, N,N-dimethylanilimum n-butyltris(pentafluorophenyl) borate,

N,N-dimethylanilinium benzyltris(pentafluorophenyl) borate,

N,N-dimethylanilinium tetrakis(4-(t-butyldimethylsilyl)-2, 3, 5, 6-tetrafluorophenyl) borate,

N,N-dimethylanilinium tetrakis(4-(triisopropylsilyl)-2, 3, 5, 6-tetrafluorophenyl) borate,

N,N-dimethylanilinium pentafluorophenoxytris(pentafluorophenyl) borate, N,N-diethylanilinium tetrakis(pentafluorophenyl) borate,

N,N-dimethyl-2,4,6-trimethylanilinium tetrakis(pentafluorophenyl) borate, dimethyltetradecylammonium tetrakis(pentafluorophenyl) borate, dimethylhexadecylammonium tetrakis(pentafluorophenyl) borate, dimethyloctadecylammonium tetrakis(pentafluorophenyl) borate, methylditetradecylammonium tetrakis(pentafluorophenyl) borate,

N,N-ditetradecyl(2,4,6-tiimethylphenyl)ammonium tetrakis(pentafluorophenyl) borate, methylditetradecylammonium (diethylaluminoxyphenyl)tris(pentafluorophenyl) borate, methyldihexadecylammonium tetrakis(ρentafluorophenyl) borate, N,N-dihexadecyl(2,4,6-trimethylphenyl)ammonium tetrakis(pentafluorophenyl) borate, methyldihexadecylammonium (diethylaluminoxyphenyl)tris(pentafluorophenyl) borate, methyldioctadecylammonium tetrakis(pentafluorophenyl) borate,

N,N-dioctadecyl(2,4,6-trimethylphenyl)ammonium tetrakis(pentafluorophenyl) borate, methyldioctadecylammonium (diethylaluminoxyphenyl)tris(pentafluorophenyl) borate, and mixtures thereof.

Another suitable ion forming, activating cocatalyst comprises a salt of a cationic oxidizing agent and a noncoordinating, compatible anion represented by the formula:

(Ox^e+)_d(A^d-)_e. wherein:

Ox^e+ is a cationic oxidizing agent having a charge of e+; e is an integer from 1 to 3; and A " and d are as previously defined.

Examples of cationic oxidizing agents include: ferrocenium, hydrocarbyl-substituted ferrocenium, Ag⁺' or Pb⁺². Preferred embodiments of A^d" are those anions previously defined with respect to the Bronsted acid containing activating cocatalysts, especially tetrakis(pentafluorophenyl)borate. The use of the above salts as activating cocatalysts for addition polymerization catalysts is known in the art, having been disclosed in U.S. Patent No. 5,321,106.

Another suitable ion forming, activating cocatalyst comprises a compound which is a salt of a carbenium ion and a noncoordinating, compatible anion represented by the formula: ©⁺ wherein:

©⁺ is a Cι_₂₀ carbenium ion; and

A^" is as previously defined. A preferred carbenium ion is the trityl cation, that is triphenylmethylium. The use of the above carbenium salts as activating cocatalysts for addition polymerization catalysts is known in the art, having been disclosed in U.S. Patent No. 5,350,723.

A further suitable ion forming, activating cocatalyst comprises a compound which is a salt of a silylium ion and a noncoordinating, compatible anion represented by the formula: R³ ₃Si(X')_q ⁺A" wherein: R³ is C_LIO hydrocarbyl, and X', q and A^" are as previously defined. Preferred silylium salt activating cocatalysts are trimethylsilylium tetrakispentafluorophenylborate, triethylsilylium tetrakispentafluorophenylborate and ether substituted adducts thereof- The use of the above silylium salts as activating cocatalysts for addition polymerization catalysts is known in the art, having been disclosed in U.S. Patent No. 5,625,087.

Certain complexes of alcohols, mercaptans, silanols, and oximes with tris(pentafluorophenyl)borane are also effective catalyst activators and may be used according to the present invention. Such cocatalysts are disclosed in U.S. Patent No. 5,296,433.

Another class of suitable catalyst activators are expanded anionic compounds corresponding to the formula: (A^1+a ) ₎ ^l(^¹]¹)^~c^d¹> wherein:

A¹ is a cation of charge ÷a¹,

Z¹ is an anion group of from 1 to 50, preferably 1 to 30 atoms, not counting hydrogen atoms, further containing two or more Lewis base sites;

J¹ independently each occurrence is a Lewis acid coordinated to at least one Lewis base site of Z¹, and optionally two or more such J¹ groups may be joined together in a moiety having multiple Lewis acidic functionality, j¹ is a number from 2 to 12 and a¹, b¹, c¹, and d¹ are integers from 1 to 3, with the proviso that a¹ x b¹ is equal to c¹ x d¹.

The foregoing cocatalysts (illustrated by those having imidazolide, substituted imidazolide, imidazolinide, substituted imidazolmide, benzimidazolide, or substituted benzimidazolide anions) may be depicted schematically as follows:

wherein:

A¹⁺ is a monovalent cation as previously defined, and preferably is a trihydrocarbyl ammonium cation, containing one or two ^o alkyl groups, especially the methylbis(tetradecyl)ammonium- or methylbis(octadecyl)ammonium- cation, R⁸, independently each occurrence, is hydrogen or a halo, hydrocarbyl, halocarbyl, halohydrocarbyl, silylhydrocarbyl, or silyl, (including mono-, di- and tri(hydrocarbyl)silyl) group of up to 30 atoms not counting hydrogen, preferably Cι„₂₀ alkyl, and

J¹ is tris(pentafluorophenyl)borane or tris(pentafluorophenyl)aluminane. Examples of these catalyst activators include the trihydrocarbylammonium-, especially, methylbis(tetradecyl)ammonium- or methylbis(octadecyl)ammonium- salts of: bis(tris(pentafluorophenyl)borane)imidazolide, bis(tris(pentafluorophenyl)borane)-2-undecylimidazolide, bis(tris(pentafluorophenyl)borane)- 2-heptadecylimidazolide, bis(tris(pentafluorophenyl)borane)-4,5-bis(undecyl)imidazolide, bis(tris(pentafluorophenyl)borane)-4,5-bis(heptadecyl)imidazolide, bis(tris(pentafluorophenyl)borane)imidazolinide, bis(tris(pentafluorophenyl)borane)-2-undecylimidazolinide, bis(tris(pentafluorophenyl)borane)-2-heptadecylimidazolinide, bis(tris(pentafluorophenyl)borane)-4,5-bis(undecyl)imidazolinide, bis(tris(pentafluorophenyl)borane)-4,5 -bis(heptadecyl)imidazolinide, bis(tris(pentafluorophenyl)borane)-5,6-dimethylbenzimidazolide, bis(tris(pentafluorophenyl)borane)-5,6-bis(undecyl)benzimidazolide, bis(tris(pentafluorophenyl)alumane)imidazolide, bis(tris(pentafluorophenyl)alumane)-2-undecylimidazolide, bis(tris(pentafluorophenyl)alumane)-2-heptadecylimidazolide, bis(tris(pentafluorophenyl)alumane)-4,5-bis(undecyl)imidazolide, bis(tris(pentafluorophenyl)alumane)-4,5-bis(heptadecyl)imidazolide, bis(tris(pentafluorophenyl)alumane)imidazolinide, bis(tris(pentafluorophenyl)alumane)-2-undecylimidazolinide, bis(tris(pentafluorophenyl)alumane)-2-heptadecylimidazolmide, bis(tris(pentafluorophenyl)alumane)-4,5-bis(undecyl)imidazolinide, bis(tris(pentafluorophenyl)alumane)-4,5-bis(heptadecyl)imidazolmide, bis(tris(pentafluorophenyl)alumane)-5,6-dimethylbenzimidazolide, and bis(tris(pentafluorophenyl)alumane)-5,6-bis(undecyl)benzimidazolide. A further class of suitable activating cocatalysts include cationic Group 13 salts corresponding to the formula: rM"Q¹ ₂L'ι.]⁺(Ar^f ₃M'Q²)- wherein:

M" is aluminum, gallium, or indium; M' is boron or aluminum; Q¹ is Cι.₂₀ hydrocarbyl, optionally substituted with one or more groups which independently each occurrence are hydrocarbyloxy, hydrocarbylsiloxy, hydrocarbylsilylamino, di(hydrocarbylsilyl)amino, hydrocarbylamino, di(hydrocarbyl)amino, di(hydrocarbyl)phosphino, or hydrocarbylsulfido groups having from 1 to 20 atoms other than hydrogen, or, optionally, two or more Q¹ groups may be covalentiy linked with each other to form one or more fused rings or ring systems;

Q² is an alkyl group, optionally substituted with one or more cycloalkyl or aryl groups, said Q² having from 1 to 30 carbons;

L' is a monodentate or polydentate Lewis base, preferably L' is reversibly coordinated to the metal complex such that it may be displaced by an olefin monomer, more preferably L' is a monodentate Lewis base;

1' is a number greater than zero indicating the number of Lewis base moieties, L', and

Ar f independently each occurrence is an anionic ligand group; preferably Ar f is selected from the group consisting of halide, C^o halohydrocarbyl, and Q ligand groups, more preferably Ar is a fluorinated hydrocarbyl moiety of from 1 to 30 carbon atoms, most preferably Ar is a fluorinated aromatic hydrocarbyl moiety of from 6 to 30 carbon atoms, and most highly preferably Ar is a perfluorinated aromatic hydrocarbyl moiety of from 6 to 30 carbon atoms.

Examples of the foregoing Group 13 metal salts are alumicinium tris(fluoroaryl)borates or gallicinium tris(fluoroaryl)borates corresponding to the formula:

[M"Q¹ ₂L'i>]⁺(Ar^f ₃BQ²)-, wherein M" is aluminum or gallium; Q¹ is Cι.₂₀ hydrocarbyl, preferably Cι.₈ alkyl; Ar^f is perfluoroaryl, preferably pentafluorophenyl; and Q² is Cι.₈ alkyl, preferably Cι_g alkyl. More preferably, Q¹ and Q² are identical Cχ._s alkyl groups, most preferably, methyl, ethyl or octyl. Reaction temperatures for the oligomerization process may vary from 20° to 150°C, preferably from 30°C to 120°C, with higher temperatures tending to increase branched impurities and broaden molecular weight distribution. Pressures of ethylene may be varied from 15 to 1000 psig (100 kPa to 7 MPa), preferably from 50 to 500 psig (350 kPa to 3.4 MPa). The mole ratio of catalyst composition (based on amount of Group 6 metal) to aluminum alkyl may be varied from lxlO^"7 to

1 9 .

1x10^" , preferably from 1x10^" to 1x10^" , and more preferably is in the range from 2x10^" to

_₃ 5x10^" . The ratio of aluminum alkyl to olefin has been found to affect the distribution of olefin products. Preferably, to obtain a narrow α-olefin product distribution, preferably a Poisson distribution, the molar ratio of aluminum alkyl compound to olefin reactant should be greater than 5, preferably greater than 10. Where used, the mole ratio of aluminoxane to Group 6 metal complex, expressed as moles of total aluminum in the aluminoxane, may range from 5/1 at high catalyst concentrations to 50,000/1 at low catalyst concentrations. The catalyst composition, cocatalyst or both may be added entirely at the initiation of the process, in portions throughout the reaction, or continuously, such as by means of a pump, through out the reaction.

Intermittent or continuous addition of cocatalyst prolongs catalyst lifetimes and increases the value of x. The mole ratio of cation forming cocatalyst to Group 6 metal complex may range from 0.5/1 at high catalyst concentrations to 10/1 at low catalyst concentrations. With the cation forming cocatalysts, no aluminoxane cocatalyst is required, although aluminoxane can be useful in extending the catalyst lifetimes, especially at higher temperatures. When a mixture of cation forming cocatalysts and aluminoxane is employed, the molar ratio thereof is desirably from 1:1 to 100.

It may be helpful under some operating conditions to pre-activate the catalyst in order to avoid an induction period. In one method, the catalyst is heated to 60-120°C in the presence of the aluminum alkyl and olefin prior to addition of the cocatalyst. A suitable period for such pretreatment is from 1 to 10 minutes. In another method, the catalyst is incubated in a solution of the cocatalyst, suitably at a temperature from 20 to 50°C prior to addition of the aluminum alkyl and olefin. In this method a suitable incubation period is from one minute to 20 minutes. According to either method, uptake of olefin occurs rapidly upon contacting with the active catalyst composition.

A solvent may be used in the process if desired. Preferred solvents include aliphatic or aromatic hydrocarbons, especially toluene, C₅.₈ alkanes and C₂.g olefins, especially the olefin used as the addition monomer.

The oligomeric α-olefin product can be recovered by cracking the alkylaluminum chain growth products or by use of thermal or catalytic displacement by known procedures such as, for example, using ethylene and/or butene as the displacing olefin as described in US- A-4,935,569. Alternatively, the chain growth products can be oxidized and hydrolyzed using known procedures to produce primary alcohols.

EXAMPLES

The skilled artisan will appreciate that the invention disclosed herein may be practiced in the absence of any component which has not been specifically disclosed. The following examples are provided as further illustration of the invention and are not to be construed as limiting. Unless stated to the contrary all parts and percentages are expressed on a weight basis. The term "overnight", if used, refers to a time of approximately 16 to 18 hours, the term "room temperature", refers to a temperature of 20 to 25 °C, and the term "mixed alkanes" refers to a commercially obtained mixture of C₆.₉ aliphatic hydrocarbons available under the trade designation Isopar E^®, from Exxon Chemicals Inc. In the event the name of a compound herein does not conform to the structural representation thereof, the structural representation shall control. The synthesis of all metal complexes and the preparation of all screening experiments were carried out in a dry nitrogen atmosphere using dry box techniques. All solvents used were HPLC grade (Aldrich) and were dried before their use. Ethylene (Aeriform) was instrument grade and was passed through an oxygen scrubber prior to use. All alumoxanes were obtained from Akzo Nobel. All other reagents were purchased from Strem and Aldrich Chemical Co. Gas chromatography (GC) data, if reported, were obtained from a HP-5890 Series 11 gas chromatograph equipped with 30m by 0.25mm OD by 0.25 μm film thickness DB-1 capillary column with FID detector. The temperature program used: initial temperature 40°C (hold for 5 min), ramp from 40°C to 300°C at 10°C / min, total temperature 300°C (hold for 10 min).

Example 1 Synthesis of CrCl? ^• lA7-frimethyl-1.4.7-triazacvclononane

To a stirred ethanol (25 mL) solution of l,4,7-trimethyl-l,4,7-triazacyclononane (0.067g, 0,390 mmol) was added chromium (II) chloride (0.054g, 0.440 mmol). The mixture was stirred overnight at 50°C via a heating mantle with attached condenser. The reaction mixture was then filtered and washed with 5mL of both ethanol and diethylether. The isolated dark green solid was dried under vacuum. Yield was 0.035g, 31 percent.

Example 2 Synthesis of CrCL ^• l,4.7-trimethyl-l,4,7-triazacyclononane (repeat)

To a stirred THF (15mL) solution of l,4,7-xrimethyl-l,4,7-triazacyclononane (0.064g, 0.53 mmol) was added chromium (II) chloride (0.087g, 0.53 mmol). The mixture was stirred overnight at 50°C via a heating mantle with attached condenser. The reaction mixture was then filtered and washed with 5mL of tetrahydrofuran (THF). The isolated pale green solid was dried in vacuo. Yield was 0.146 g, 96 percent.

Example 3 Synthesis of CrMe? ^• lA7-trimethyl-1.4.7-triazacyclononane

To a stirred slurry of CrCl₂ ^• l,4,7-trimethyl-l,4,7-triazacyclononane (0.1 OOg, 0.342 mmol) in THF (25 mL) was added methyl lithium (0.017g, 0.800 mmol). The mixture was stirred for one day at room temperature. The THF was then removed in vacuo to dryness and the remaining solids were extracted with CH₂C1₂ (3 mL). A white residue was left behind and the brown solution was dried in vacuo. A brown solid was isolated after removal of CH₂C1₂.

Yield was 0.024g, 27 percent. Example 4: Ethylene oligomerization with CrCl? ^• 1.4.7-trimethyl- 1.4.7 -triazacyclononane in the presence of EtτA.1

To a 45 mL Parr reactor equipped with a pressure transducer and thermocouple was ^• added 5 mL of toluene, catalyst from Example 1 (2 mg, 7 μmole), 50 μL of triisobutyl aluminum modified methylalumoxane (MMAO, toluene solution, 6.5 percent Al, 0.12 mmol), and triethylaluminum (200 μL of a 1M in hexane, 0.20 mmol). Ethylene was introduced into the reactor using a manifold until the pressure equilibrated at 150 psig (1.03 MPa, 0.4 g total ethylene weight, 14.3 mmol). The heating block was then shaken and the internal reactor pressure was recorded with a computer. After 60 minutes the pressure had dropped to 50 psig (345 KPa). The reaction was quenched by venting excess ethylene, opening the Parr reactor, and adding dropwise 5-10 mL of 1.0M aqueous HC1. The aqueous layer was then removed and discarded. Analysis of the organic layer was performed using gas chromatography to identify oligomeric linear alkanes present and their distributions. The resulting product had a number average degree of polymerization of 8.

Example 5: Ethylene oligomerization with CrCl? ^• l,4,7-trimethyl-1.4.7-triazacyclononane in the presence of Me^Al

The reaction conditions of example 4 were substantially repeated using trimethylaluminum (100 μL 2M solution in toluene, 0.20 mmol) instead of triethylaluminum. After 60 minutes the pressure had dropped to 20 psig (138 KPa). The reactor was vented and worked up using the procedure described in example 4. The resulting product had a number average degree of polymerization of 11. The product distribution obtained from the oligomerization along with a comparison Schulz-Flory distribution having a Schulz-Flory constant of 0.85 is depicted in Figure 1.

Example 6: Ethylene oligomerization with CrCl? ^• 1 A7-trimethyl-l,4.7-triazacyclononane in the absence of trialkylaluminum

The reaction conditions of Example 4 were substantially repeated, except that no trialkylaluminum was added, and the ethylene pressure was maintained between 100 (690 KPa) and 140 psig (960 KPa). The resulting product had a number average degree of polymerization of 7.5.

Example 7: Ethylene oligomerization with CrMe? ^• 1.4.7-trimethyl-1.4.7-triazacvclononane in the presence of trimethylaluminum The reaction conditions of Example 4 were substantially repeated using CrMe₂ ^• l,4,7-trimethyl-l,4,7-triazacyclononane, Example 3 (2 mg, 7 μmol), methylalumoxane (PMAO-IP, available from Akzo Nobel Inc., 100 μL of a toluene solution containing 6.45 weight percent Al, 0.24 mmol), trimethylaluminum (100 μL of a 2M toluene solution, 0.20 mmol), and N,N-dimethylanilinium tetrakis(pentafluorophenyl) borate (0.5 mL of a 0.0794M solution in toluene, 79 μmol). After 35 minutes the reactor pressure had dropped to 25 psig (173 KPa) and the reaction was quenched according to the same procedure described in Example 4. The resulting product had a number average degree of polymerization of 12.

Claims

1. A process for the preparation of an aluminum alkyl chain growth product by ^• the chain growth reaction of an α-olefin on an aluminum alkyl, optionally followed by displacement and recovery of the oligomeric alpha-olefm from the aluminum alkyl chain growth product, said process comprising catalyzing the chain growth reaction with a catalyst composition comprising a Group 6 metal trisazacycloalkane complex and an activating cocatalyst.

2. The process of claim 1 wherein the Group 6 metal corresponds to the formula:

wherein M is a Group 6 metal, especially chromium;

R¹ independently in each occurrence is a Cι.₂o hydrocarbylene group, especially ethylene;

R² independently in each occurrence is an anionic ligand of up to 20 atoms not counting hydrogen, preferably a Cι_₂₀ hydrocarbyl group, most preferably, methyl; and X is an anionic ligand of up to 20 atoms not counting hydrogen, preferably hydride, halide, or a hydrocarbyl-, silyl-, hydrocarbyloxy- or siloxy- group of up to 10 atoms; most preferably chloride or methyl.

3. A process according to claim 1 or 2 wherein the cocatalyst is an aluminoxane, a cation forming cocatalyst, or a combination thereof.

4. A process according to claim 3 wherein the aluminum alkyl compound is a trialkyl aluminum, a dialkyl aluminum hydride, a dialkyl aluminum halide, or a mixture thereof, containing from 2 to 20 carbons in each alkyl group, preferably triethylaluminum, tri- n-propylaluminum, tri-n-butylaluminum, tri-n-hexylaluminum, diethylaluminum hydride, or a mixture thereof.