LIGANDS FOR PRODUCTION OF 1-OCTENE IN CHROMIUM ASSISTED ETHYLENE OLIGOMERIZATION PROCESS

Abstract

Processes to produce tunable mixtures of 1-hexene and 1-octene are described. The process includes contacting a mixture of a 1-hexene catalyst and a 1-octene catalyst with ethylene under conditions sufficient to produce a composition that includes a desired amount 1-hexene and 1-octene are described.

Claims

1. A catalyst composition for the production of 1-hexene and 1-octene, the catalyst composition comprising a 1-hexene catalyst and a 1-octene catalyst, wherein the 1-hexene catalyst, the 1-octene catalyst, or both comprise a nitrogen, phosphorous, nitrogen, phosphorous, nitrogen (NPNPN) ligand.

2. The catalyst composition of claim 1, wherein catalyst composition further comprises: a chromium (III) species, preferably chromium (III) acetylacetonate, Cr(2,2,6,6,-tetramethyl-3,5-heptadionate)3, chromium(III)2-ethylhexanoate, chromium trichloride tris-tetrahydrofuran; (benzene)tricarbonyl chromium; chromium (III) octanoate; chromium hexacarbonyl; or chromium (III) naphthenate; and an activator or co-catalyst, preferably, methylaluminoxane compound, more preferably methyl iso-butyl aluminum oxide compound.

3. The catalyst composition of any one of claims 1 to 2, wherein the 1-octene catalyst comprises a ligand having a structure of: ##STR00022## where Ar.sup.1 and Ar.sup.2 are each independently an aromatic group or a substituted aromatic group, n is 0 or 1 and m=n+3.

4. The catalyst composition of claim 3, wherein the Ar.sup.1 and Ar.sup.2 are each independently a phenyl group or an alkyl substituted phenyl group, preferably Ar.sup.1 and Ar.sup.2 are phenyl.

5. The catalyst composition of claim 4, wherein n is 0, and the ligand has the structure of: ##STR00023##

6. The catalyst composition of claim 5, wherein n is 1 and the ligand has the structure of: ##STR00024##

7. The catalyst composition of claim 1, wherein the 1-hexene catalyst comprises a ligand having a structure of: ##STR00025## where R.sup.1 and R.sup.2 are the same or different and are selected from the group consisting of (i) C.sub.3 to C.sub.4 non-cyclic aliphatic groups, (ii) C.sub.5 to C.sub.10 aliphatic groups which may be cyclic or non-cyclic, linear or branched, substituted or unsubstituted, and (iii) any combination thereof, and wherein n is 0 or 1, and m=n+3.

8. The catalyst composition of claim 7, wherein R.sup.1 and R.sup.2 are each independently a cyclic hydrocarbon group, a substituted cyclic hydrocarbon group, a linear hydrocarbon group or a branched hydrocarbon group having 5 to 10 carbon atoms, preferably R.sup.1 and R.sup.2 are each a cyclohexyl group.

9. The catalyst composition of claim 8, wherein n is 0, and the 1-hexene ligand has the structure of: ##STR00026##

10. The catalyst composition of claim 9, wherein n is 1 and the 1-hexene ligand has a structure of: ##STR00027##

11. The catalyst composition of claim 1, wherein the 1-octene catalyst comprises a ligand having the structure of: ##STR00028## and the 1-hexene catalyst comprises ligand having the structure of: ##STR00029##

12. A process to produce a composition comprising 1-hexene and 1-octene from olefins, the process comprising contacting a reactant stream comprising ethylene with a solution comprising the catalyst composition of any one of claims 1 to 11 under conditions sufficient to oligomerize the ethylene and produce an oligomer composition comprising the 1-hexene and 1-octene.

13. The process of claim 12, wherein a weight ratio of the 1-hexene catalyst to 1-octene catalyst is from 10:1 to 1:10.

14. The process of claim 12, wherein the weight ratio of 1-hexene to 1-octene in the oligomer composition is greater than 0.5:1.

15. The process of claim 12, wherein the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:1, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is at least 2.5:1

16. The process of claim 12, wherein the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:2.3, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is at least 1.5:1.17.

17. The process of claim 12, wherein the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:4, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is 1:1 or greater; or the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:8, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is greater than 1:1.3.

18. The process of claim 13, wherein the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:1, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is at least 2.5:1

19. The process of claim 13, wherein the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:2.3, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is at least 1.5:1.17.

20. The process of claim 13, wherein the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:4, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is 1:1 or greater; or the weight ratio of 1-hexene catalyst to 1-octene catalyst is about 1:8, and the weight ratio of 1-hexene to 1-octene in the oligomer composition is greater than 1:1.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Advantages of the present invention may become apparent to those skilled in the art with the benefit of the following detailed description and upon reference to the accompanying drawings.

[0038] FIG. 1 is an illustration of a schematic of a system to produce a composition that include 1-hexene and 1-octene from the oligomerization of ethylene.

[0039] FIG. 2 is graphical illustration of the activity and product distribution from composition that includes various ratios of the 1-hexene and 1-octene catalysts.

[0040] While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings. The drawings may not be to scale.

DETAILED DESCRIPTION OF THE INVENTION

[0041] A discovery has been made that provides a way to produce tunable amounts of 1-hexene and 1-octene in acceptable yields, in high selectivity, and without making significant amounts of solvent insoluble material from the oligomerization of ethylene. The discovery is premised on using a mixture of a 1-hexene catalyst and a 1-octene catalyst with both catalysts having a NPNPN ligand systems specific for production of 1-hexene or 1-octene. Notably, and as illustrated in a non-limiting manner in the examples, the amounts of 1-hexene and 1-octene can be tuned based on the amount of specific catalyst used. By way of example, 1 50 wt. % of each catalyst produces a mixture that includes 65 to 70 wt. % 1-hexene and 30 wt. % to 35 wt. % to 1-octene while a 90:10 weight ratio of 1-octene catalyst to 1-hexene catalyst produces a mixture that includes 40 to 45 wt. % 1-hexene and 55 to 60 wt. % of 1-octene. In all cases. Further, less than 2 wt. % polymeric material is produced. Notably, the process can use the same solvent, chromium source and optional co-activators. This combination of catalyst provides an elegant and simple tunable process for the production of 1-hexene and 1-octene in high purity

[0042] These and other non-limiting aspects of the present invention are discussed in further detail in the following sections.

A. Catalyst Compositions

[0043] The catalyst compositions can include the ligands of the present invention, a chromium (III) species, and an activator or co-catalyst. The ligands of the present invention can be prepared as described throughout the specification and in the Examples. The catalyst composition can be provided as a solution in an aliphatic or aromatic hydrocarbon solvent. Aliphatic hydrocarbon solvents can include hexane, methylcyclohexane, cyclohexane, n-heptane, toluene, and the like.

[0044] The chromium species can be an organic salt, an inorganic salt, a coordination complex, or an organometallic complex of Cr(III). In an embodiment, the chromium species is an organometallic Cr(III) species. Non-limiting examples of the chromium species include Cr(III)acetylacetonate, Cr(III)octanoate, CrCl.sub.3(tetrahydrofuran).sub.3, Cr(III)-2-ethylhexanoate, Cr(III)chloride, or any combination thereof. The molar ligand/Cr ratio for each catalyst can be from about 0.5 to 50, about 0.5 to 5, about 0.8 to about 2.0, about 1.0 to 5.0, or preferably from about 1.0 to about 1.5.

[0045] The activator (also known in the art as a co-catalyst) can be an aluminum compound. Non-limiting examples of aluminum compounds include trimethylaluminum, triethylaluminum, triisopropylaluminum, triisobutylaluminum, diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, methylaluminoxane, or a mixture thereof. In some embodiments, the activator can be a modified methylaluminoxane, more preferably MMAO-3A (CAS No. 146905-79-5), which is a modified methylaluminoxane, type 3A, available from Akzo Nobel in toluene solution containing 7% aluminum, which corresponds to an MMAO-3A concentration of about 18%. The molar Al/Cr ratio can be from about 1 to about 1000, about 10 to about 1000, about 1 to 500, about 10 to 500, about 10 to about 300, about 20 to about 300, or preferably from 50 to about 300.

[0046] The catalyst composition can further include a solvent. The solvent can be the same or different than the solvent used in the oligomerization process with the proviso that the solvents are miscible. Non-limiting examples of solvents are straight-chain and cyclic aliphatic hydrocarbons, straight-chain olefins, ethers, aromatic hydrocarbons, and the like. A combination comprising at least one of the foregoing solvents can be used. Preferably, the solvent is n-heptane, toluene, or methylcyclohexane or any mixture thereof.

[0047] The concentration of the chromium compound in the catalyst solvent vary depending on the particular compound used and the desired reaction rate. In some embodiments, the concentration of the chromium compound is from about 0.01 to about 100 millimole per liter (mmol/L), about 0.01 to about 10 mmol/L, about 0.01 to about 1 mmol/L, about 0.1 to about 100 mmol/L, about 0.1 to about 10 mmol/L, about 0.1 to about 1 0 mmol/L, about 1 to about 10 mmol/L, and about 1 to about 100 mmol/L. Preferably, the concentration of the chromium compound is from about 0.1 to about 1.0 mmol/L.

[0048] 1. 1-Hexene Catalyst Ligands

[0049] The ligands of the 1-hexene catalyst of the present invention can be represented by the following formula:

##STR00015##

where R.sup.1 and R.sup.2 selected from the group consisting of (i) C.sub.3 to C.sub.4 non-cyclic aliphatic groups, (ii) C.sub.5 to C.sub.10 aliphatic groups which may be each be cyclic or non-cyclic, linear or branched, substituted or unsubstituted, and (iii) any combination thereof, and wherein n is 0 or 1, and m=n+3. The C.sub.5 to C.sub.10 aliphatic groups can include cyclic or non-cyclic, linear or branched, substituted or unsubstituted. Non-limiting examples of C.sub.5 to C.sub.10 aliphatic groups include pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl, cyclononyl, decyl, cyclodecyl, which can include substituents that make the compounds substituted or branched. In a preferred instance, R.sup.1 and R.sup.2 are cyclohexyl. The C.sub.3 to C.sub.4 non-cyclic aliphatic groups can be iso-propyl and tert-butyl. The ligands can be (CH.sub.3)(n-C.sub.4H.sub.9)NP(R.sup.1)N(CH.sub.3)NP(R.sup.2)N(CH.sub.3)(n-C.sub.4H.sub.9) and (CH.sub.3CH.sub.2)(n-C.sub.5H.sub.11)NP(R.sup.1)N(CH.sub.3)NP(R.sup.2)N(CH.sub.2CH.sub.3)(n-C.sub.5H.sub.11) (CH.sub.3)(n-C.sub.4H.sub.9)NP(C.sub.6H.sub.11)N(CH.sub.3)NP(C.sub.6H.sub.11)N(CH.sub.3)(n-C.sub.4H.sub.9) and (CH.sub.3CH.sub.2)(n-C.sub.5H.sub.11)NP(C.sub.6H.sub.11)N(CH.sub.3)NP(C.sub.6H.sub.11)N(CH.sub.2CH.sub.3)(n-C.sub.5H.sub.11). Non-limiting structures of the ligands are as follows:

##STR00016##

##STR00017##

where R.sup.3 and R.sup.4 represent alkyl groups on any carbon atom. Non-limiting examples of R.sup.3 and R.sup.4 include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, and pentyl, and the like.

[0050] The NPNPN ligand system can be made by synthetic approaches known to those skilled in the art. In some embodiments, ligand (1) is accessible by reaction pathways as shown in Scheme I.

##STR00018##

where R.sup.1 and R.sup.2 are defined above, and R.sup.5 is methyl or ethyl, and R.sup.6 is butyl when R.sup.5 is methyl and R.sup.6 is pentyl when R.sup.5 is ethyl.

[0051] In some embodiments, the catalyst composition includes Cr(III)acetylacetonate as the chromium compound, Et(n-pentyl)N—P(cyclohexyl)-N(Me)-P(cyclohexyl)-N(n-pentyl)Et as the NPNPN ligand, and MMAO-3A as the activator. In another embodiment, the catalyst composition includes Cr(III)acetylacetonate as the chromium compound, Me(n-butyl)N—P(cyclohexyl)-N(Me)-P(cyclohexyl)-N(n-butyl)Me as the NPNPN ligand, and MMAO-3A as the activator.

[0052] 2. 1-Octene Catalyst Ligands

[0053] The critical parameters of the 1-octene catalyst include the choice of phosphorous substituents and nitrogen substituents. The phosphorous substituents include an aromatic group or an alkyl substituted aromatic group, the middle nitrogen substituent includes a methyl substituent, and the terminal nitrogen substituents include different linear alkyl hydrocarbons groups that differ in the number of carbon atoms by 3. The ligands of the 1-octene catalyst present invention can be represented by the following formula:

##STR00019##

where Ar.sup.1 and Ar.sup.2 can each be independently an aromatic group or a substituted aromatic group, n is 0 or 1 and m=n+3. Aromatic groups or substituted aromatic groups include phenyl (Ph), C.sub.6-C.sub.11 aryl or C.sub.6-C.sub.20 substituted aryl. Non-limiting examples of C.sub.6-C.sub.11 aryl groups include methylbenzyl, dimethylbenzyl (ortho, meta, and para substituted), ethylbenzyl, propylbenzyl, and the like. Non-limiting examples of substituents for substituted C.sub.6-C.sub.20 aryl groups include alkyl, substituted alkyl groups, linear or branched alkyl groups, linear or branched unsaturated hydrocarbons, halogen, hydroxyl, alkoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, amine, nitro, amide, nitrile, acyl, alkyl silane, thiol and thioether substituents. Non-limiting examples of alkyl groups include linear and branched C.sub.1 to C.sub.5 hydrocarbons. Non-limiting examples of unsaturated hydrocarbons include C.sub.2 to C.sub.5 hydrocarbons containing at least one double bond (e.g., vinyl). The aryl or alkyl group can be substituted with the halogen, hydroxyl, alkoxy, haloalkyl, haloalkoxy, carboxylic acid, ester, ether, amine, nitro (—NO.sub.2), amide, nitrile (—CN), acyl, alkyl silane, thiol and thioether substituents. Non-limiting examples of halogens include chloro (—Cl), bromo (—Br), or fluoro (—F) substituents. Non-limiting examples of haloalkyl substituents include —CX.sub.3, —CH.sub.2X, —CH.sub.2CH.sub.2X, —CHXCH.sub.2X, —CX.sub.2CHX.sub.2, —CX.sub.2CX.sub.2 where X is F, Cl, Br or combinations thereof. Non-limiting examples, of amine substituents include —NH.sub.2, —CH.sub.2NH.sub.2, —CHCH.sub.2NH.sub.2, —C(NH.sub.2)CH.sub.3. Non-limiting examples of alkoxy include —OCH.sub.3, —OCH.sub.2CH.sub.3, and the like. Non-limiting examples, of alkyl silane substituents include —Si(CH.sub.3).sub.3, —Si(CH.sub.2CH.sub.3).sub.3, and the like. Non-limiting examples of polycyclic groups include fused aromatic rings and substituted fused aromatic rings such as —C.sub.10H.sub.7 and substituted ten carbon fused aromatic ring systems. In some embodiments, the C.sub.6-C.sub.20 aryl groups are chlorobenzene, bromobenzene, trifluorotoluene, phenylamine, nitrobenzene, dichlorotoluene, benzonitrile, trimethylbenzylsilane, benzylmethyl ether, or a fused aromatic ring (C.sub.10H.sub.7). The ligands can be (CH.sub.3)(n-C.sub.4H.sub.9)NP(Ar.sup.1)N(CH.sub.3)NP(Ar.sup.2)N(CH.sub.3)(n-C.sub.4H.sub.9) and (CH.sub.3CH.sub.2)(n-C.sub.5H.sub.11)NP(Ar.sup.1)N(CH.sub.3)NP(Ar.sup.2)N(CH.sub.2CH.sub.3)(n-C.sub.5H.sub.11) (CH.sub.3)(n-C.sub.4H.sub.9)NP(C.sub.6H.sub.5)N(CH.sub.3)NP(C.sub.6H.sub.5)N(CH.sub.3)(n-C.sub.4H.sub.9) and (CH.sub.3CH.sub.2)(n-C.sub.5H.sub.11)NP(C.sub.6H.sub.5)N(CH.sub.3)NP(C.sub.6H.sub.5)N(CH.sub.2CH.sub.3)(n-C.sub.5H.sub.11). The structure of the ligands can be illustrated as follows:

##STR00020##

where R.sup.7 and R.sup.8 represent alkyl groups substituted on the aromatic ring. Non-limiting examples of such alkyl groups include methyl, ethyl, propyl, isopropyl, butyl, tert-butyl, and pentyl, and the like.

[0054] The NPNPN ligand system can be made by synthetic approaches known to those skilled in the art. In some embodiments, ligand (1) is accessible by reaction pathways as shown in Scheme I

##STR00021##

where Ar.sup.1 and Ar.sup.2 are defined above, and R.sup.5 is methyl or ethyl, and R.sup.6 is butyl when R.sup.5 is methyl and pentyl when R.sup.6 is ethyl.

[0055] Non-limiting examples of a 1-hexene catalyst system in the mixture includes Cr(III)acetylacetonate as the chromium compound, Et(n-pentyl)N—P(Ph)-N(Me)-P(Ph)-N(n-pentyl)Et as the NPNPN ligand, and MMAO-3A as the activator. In another embodiment, the catalyst system includes Cr(III)acetylacetonate as the chromium compound, Me(n-butyl)N—P(Ph)-N(Me)-P(Ph)-N(n-butyl)Me as the NPNPN ligand, and MMAO-3A as the activator.

B. System for Oligomerization of Ethylene to 1-Hexane and 1-Octene

[0056] The mixture of the above-described catalyst compositions of the present invention can be used in a process for the tunable oligomerization of ethylene to produce a composition that includes a desired ratio of 1-hexene and 1-octene. In an embodiment, the process encompasses contacting ethylene with the catalyst composition under ethylene oligomerization conditions effective to produce mixtures of 1-hexene and 1-octene. Those skilled in the art will understand that oligomerization of ethylene to produce 1-hexene and 1-octene can be by trimerization and tetramerization of ethylene, respectively. The weight ratio of 1-hexene catalyst to 1-octene catalyst can be 10:1 to 1:10, or 10:1, 9:1, 8:1, 7:1, 6:1, 5:1, 4:1, 3:1, 2:1, 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10. The weight ratio of 1-hexene to 1-octene in the composition can be greater than 0.5:1, or 0.5:1, 1.0:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1, or 5:1 when the weight ratio of 1-hexene catalyst to 1-octene catalyst is from 1:1 to 10:1. The weight ratio of 1-hexene to 1-octene in the composition can be greater than 0.5:1, or 0.5:1, 1:1, 1:1.5, 1:2, 1:2.5, 1:1, 1:3.5, 1:4, or 1:5 when the weight ratio of 1-hexene catalyst to 1-octene catalyst is from 1:1 to 1:10.

[0057] The oligomerization solvent can include any solvent the catalyst system is soluble in. By way of example a saturated hydrocarbon, more preferably, n-hexane, n-heptane, methylcyclohexane, or a mixture thereof can be used. Reaction conditions can be include temperature and pressure. The reaction temperature can be 15° C. to 100° C., or at least any one of, equal to any one of, or between any two of 15° C., 20° C., 25° C., 30° C., 35° C., 40° C., 45° C., 50° C., 55° C., 60° C., 65° C., 70° C., 75° C., 80° C., 85° C., 90° C., 95° C. and 100° C. In some instances, the reaction temperature can range from 40° C. to 70° C. Reaction pressures can include at least any one of, equal to any one of, or between any two of 2 MPa, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 and 20 MPa. In some embodiments, the reaction pressure is 2 to 20 MPa. By way of example, a reaction temperature can be 40° C. to 70° C. at a pressure of 2 to 7 MPa.

[0058] FIG. 1 depicts a schematic for a system to produce a tunable mixture of 1-hexene and 1-octene. System 100 can include inlet 102 for a reactant feed that includes ethylene, reaction zone 104 that is configured to be in fluid communication with the inlet, and outlet 106 configured to be in fluid communication with reaction zone 104 and configured to remove a product stream that includes a mixture of 1-hexene and 1-octene from the reaction zone. Reactant zone 104 can include the catalyst mixture of the present invention. The ethylene reactant feed can enter reaction zone 104 via the inlet 102. In some embodiments, the ethylene reactant feed can be used to maintain a pressure in reaction zone 104. In some embodiments, the reactant feed stream includes inert gas (e.g., nitrogen or argon). After a sufficient amount of time, the product stream having the desired amount of 1-hexene and 1-octene can be removed from the reaction zone 104 via product outlet 106. The product stream can be sent to other processing units, stored, and/or transported. In some embodiments, product stream 106 is sent to a separation unit, which separates the mixture into streams of 1-hexene and 1-octene.

[0059] System 100 can include one or more heating and/or cooling devices (e.g., insulation, electrical heaters, jacketed heat exchangers in the wall) or controllers (e.g., computers, flow valves, automated values, etc.) that can be used control the reaction temperature and pressure of the reaction mixture. While only one reactor is shown, it should be understood that multiple reactors can be housed in one unit or a plurality of reactors housed in one heat transfer unit.

[0060] As discussed above, the process and catalyst composition of the present invention allows for the production of 1-octene and 1-hexene with high selectivity with the LAO product distribution being limited to 1-hexene and 1-octene. Tunable selectivity for 1-octene and 1-hexene is an advantageous feature inasmuch as it leads to higher product purity, thereby circumventing the need for additional purification steps in the separation train. Further advantageous features of the catalyst selection and process include suppression of ethylene polymerization leading to undesirable polymer formation, milder reaction conditions and, as a result, lower capital costs for equipment as well as operational and energy costs. Additionally, a relatively simple, straight-forward process design is possible. The purity for 1-octene can be at least about 99%, or 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9%. A purity of at least 99.1% is preferred. The purity for 1-hexene can be at least about 99%, or 99.1%, 99.2%, 99.3%, 99.4%, 99.5%, 99.6%, 99.7%, 99.8%, or 99.9%. A purity of at least 99.1% is preferred. In an embodiment, when 1-octene is produced, the weight ratio of 1-octene to 1-hexene can be less than 03, or 0 to 0.3, or 0.1, 0.15, 0.2, 0.25 or 0.3 or any range or value there between.

EXAMPLES

[0061] The present invention will be described in greater detail by way of specific examples. The following examples are offered for illustrative purposes only, and are not intended to limit the invention in any manner. Those of skill in the art will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially the same results.

Example 1

Synthesis of Ligand 2

[0062] Route A, General Procedure (See, Scheme I). All manipulations were carried out under inert atmosphere. Bis(chlorophosphino)amine C.sub.6H.sub.11P(Cl)N(CH.sub.3)P(Cl)C.sub.6H.sub.11 (4.60 g, 14 mmol) was dissolved in 20 mL of anhydrous toluene. Appropriate secondary amine (29.4 mmol of butylamine) and NEt.sub.3 (35 mmol) was mixed with 30 mL of anhydrous toluene and cooled down to −10° C. Toluene solution of bis(chlorophosphino)amine was added dropwise to the reaction mixture under inert atmosphere with vigorous stirring. Addition of the reagent resulted in precipitation of white gel-like material. With continuous stirring, solution was left to warm up to 25° C. for 3 hours, then heated to 75° C. and stirred at that temperature for additional 12 hrs. After evaporation of all volatile compounds under vacuum, the residue was taken up in anhydrous hot n-heptane and insoluble material was separated by filtration. Evaporation of the solvent led to pale yellow oil. Purity of the product was verified using .sup.1H, .sup.13C and .sup.31P NMR. If desired, the products can be recrystallized from n-hexane, cyclohexane, n-heptane or n-pentane to increase the purity.

[0063] Route B, General Procedure (See, Scheme I). All manipulations were carried out under inert atmosphere. The appropriate secondary amine (10 mmol) was dissolved in 20 mL of anhydrous n-heptane, cooled down to −10° C. and treated with 5% mol. excess of n-BuLi in n-hexane. The solution was then stirred for 3 hrs letting the temperature raise to 25° C., forming white precipitate. Solid was separated from solution, washed with n-hexane and transferred to the flask with 30 mL of anhydrous Et.sub.2O. Resulted suspension was cooled down to −10° C. and solution of bis(chlorophosphino) amine C.sub.6H.sub.11P(Cl)N(CH.sub.3)P(Cl)C.sub.6H.sub.11 (1.61 g, 4.9 mmol) in 30 mL of anhydrous Et.sub.2O was added dropwise to the reaction mixture with vigorous stirring. After the addition, reaction mixture was continuously stirred for 12 hours letting it warm up to 25° C. During the course of the reaction, white solid was formed. Insoluble material was separated by filtration, washed with Et.sub.2O and discarded. Solution and washing liquids were combined and solvent was removed in vacuum, producing pale yellow viscous oil. Purity of the product was verified using .sup.1H, .sup.13C and .sup.31P NMR. If desired, the products can be recrystallized from n-hexane, cyclohexane, n-heptane or n-pentane to increase the purity.

[0064] Precursor (C.sub.6H.sub.11)P(Cl)N(Me)P(Cl)(C.sub.6H.sub.11) was prepared using the procedure of Jefferson et al. (J. Chem. Soc. Dalton Trans. 1973, 1414-1419).

Example 1

Synthesis of Ligand 7

[0065] Two methodologies can be used to prepare ligands have structures (2) and (3) above. The comparative ligand had the structure below where the amino functionality included a methyl group and ethyl group (i.e., n is less than 3).

[0066] Route A, General Procedure (See, Scheme 1). All manipulations were carried out under inert atmosphere. Bis(chlorophosphino)amine (PhP(Cl)N(CH.sub.3)P(Cl)Ph, 4.42 g, 14 mmol) was dissolved in 20 mL of anhydrous toluene. An appropriate secondary amine (29.4 mmol) and NEt.sub.3 (35 mmol) was mixed with 30 mL of anhydrous toluene and cooled down to −10° C. Toluene solution of bis(chlorophosphino)amine was added dropwise to the reaction mixture under inert atmosphere with vigorous stirring. Addition of the reagent resulted in precipitation of white gel-like material. With continuous stirring, solution was left to warm up to 25° C. for 3 hours, then heated to 75° C. and stirred at that temperature for additional 12 hrs. After evaporation of all volatile compounds under vacuum, the residue was taken up in anhydrous hot n-heptane and insoluble material was separated by filtration. Evaporation of the solvent led to a white oil. Purity of the product was verified using .sup.1H, .sup.13C and .sup.31P NMR. If desired, the products can be recrystallized from n-hexane, cyclohexane, n-heptane or n-pentane to increase the purity.

[0067] Route B, General Procedure (See, Scheme 1). All manipulations were carried out under inert atmosphere. The appropriate secondary amine (10 mmol) was dissolved in 20 mL of anhydrous n-heptane, cooled down to −10° C. and treated with 5% molar excess of n-BuLi in n-hexane. The solution was then stirred for 3 hrs letting the temperature raise to 25° C., forming a white precipitate. The solid was separated from solution, washed with n-hexane and transferred to the flask with 30 mL of anhydrous ether. The resulted suspension was cooled down to −10° C. and solution of bis(chlorophosphino) amine (PhP(Cl)N(CH.sub.3)P(Cl)Ph, 1.55 g, 4.9 mmol) in 30 mL of anhydrous ether was added dropwise to the reaction mixture with vigorous stirring. After the addition reaction mixture was continuously stirred for 12 hours letting it warm up to 25° C. During the course of the reaction, a white solid was formed. The insoluble material was separated by filtration, washed with ether and discarded. Solution and washing liquids were combined, and the solvent was removed in vacuum, producing a white viscous oil. Purity of the product was verified using .sup.1H, .sup.13C and .sup.31P NMR. If desired, the products can be recrystallized from n-hexane, cyclohexane, n-heptane or n-pentane to increase the purity.

[0068] Precursor PhP(Cl)N(Me)P(Cl)Ph was prepared using the procedure of Jefferson et al. (J. Chem. Soc. Dalton Trans. 1973, 1414-1419).

Example 2

Catalyst Composition Preparation and Oligomerization of Ethylene

[0069] The reactor, equipped with dip tube, thermowell, mechanical paddle stirrer, cooling coil, control units for temperature, pressure and stirrer speed (all hooked up to a data acquisition system) was then inertized heating to 130° C. in under vacuum and cooled down by venting with dry nitrogen stream to 30° C. An isobaric ethylene supply was maintained by gas dosing control unit connected to data acquisition system. Ethylene consumption was monitored via pressure loss in the feeding cylinder over time by means of a computerized data acquisition system.

[0070] Suitable amounts of the stock toluene solutions of the ligands (ligand (2) of the present invention or the comparative ligand) and Cr(III)acetylacetonate as chromium precursor, at a ligand to Cr ratio of 1.20, were measured and charged to a Schlenk tube under inert atmosphere. A volume of 30 mL anhydrous n-heptane was added introduced in stainless steel pressure reactor and warmed up to the reaction temperature. After temperature of the reactor become stable, reactor was pressurized to 30 bar with ethylene and left for 0.5 hour with continuous mechanical stirring. After that time, pressure was reduced to 0.2 bar (0.02 MPa) and appropriate amount of 0.3 M stock solution of MMAO-3A in anhydrous n-heptane was introduced in the reactor through the charging port, providing Al to Cr ratio of 300. Stirring was continued for 10 min. Following that, mixture of Cr and ligand solutions was introduced into the reactor through the charging port.

[0071] Immediately after introduction of the catalyst in the reactor, pressure was increased to 30 bar (3 MPa). Standard reaction conditions are: pressure of ethylene of 30 bar (3 MPa), T of 45° C., stirrer speed of 450 RPM. After 1 hour catalytic run, ethylene supply was cut and reactor temperature lowered to 5° C. Ethylene from the reactor was vented to the pressure of 0.2 bar (0.02 MPa). The reaction was stopped by quenching with 0.3 M HCl/iso-propanol mixture. Liquid products were analyzed using gas chromatography with a known amount of toluene internal standard. Any insoluble by-products, i.e., waxes, polyethylene, were filtered, dried, and weighed. A consecutive catalyst experiment was performed without cleaning the reactor was performed using the same ingredients and amounts described above. Table 1 shows the results of ligand having structures 2 and 7 and the mixtures thereof.

TABLE-US-00001 TABLE 1 Solvent Insol- Activity % wt. C6 % wt. C8 ubles Catalyst (kg/g.sub.Cr * h) (1-hexene, %) (1-octene, %) % wt. 1-Hexene Catalyst 99.0 24.1(77.67) 72.6(99.52) 1.46 1-Octene Catalyst 170.5 87.2(99.92) 5.7(99.99) 0.89 TANDEM 93.5 68.6(96.98) 26.56(99.51) 0.96 1-Octene catalyst 50% wt. 1-Hexene catalyst 50% wt. TANDEM 97.9 61.2(95.60) 35.3(99.57) 0.90 1-Octene catalyst 70% wt. 1-Hexene catalyst 30% wt. TANDEM 46.9 47.7(91.85) 49.3(99.81) 1.53 1-Octene catalyst 80% wt. 1-Hexene catalyst 20% wt. TANDEM 46.4 41.2(87.6) 56.8(99.53) 1.43 1-Octene catalyst 90% wt. 1-Hexene catalyst 10% wt.

[0072] Table 1 summarizes the results of ethylene oligomerization experimental runs performed under these standard conditions and using catalyst systems prepared with the mixtures of 1-hexene and 1-octene catalyst and the individual catalysts. The Table shows the respective selectivities for hexene (C6), octene (C8), and solvent insolubles in wt. % in the liquid phase. Numbers in parentheses denote the selectivities of the respective linear alpha-olefin in the overall C6/C8 fraction. These LAO purities were generally advantageously high. FIG. 2 is a graphical representation of the Table 1 results for the catalyst mixtures. As can be seen from the results, mixing of the catalysts led to selectivity in the final mixture composition without detrimental effects on purity of terminal alkenes and catalytic activity.

[0073] Although embodiments of the present application and their advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the embodiments as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the above disclosure, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein can be utilized. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.