EP0422019A1 - Olefinic oligomers having lubricating properties and process of making such oligomers. - Google Patents

Abstract

New lubricant compositions comprising polyalpha-olefins have a high viscosity index and a reduced pour point. These compositions are characterized by having a uniform molecular structure with a low rate of branching. A liquid lubricant composition comprises C30-C1300 hydrocarbons and a branching rate of less than 0.19, a weighted average molecular weight of between 300 and 45,000, a numerical mean molecular weight of between 300 and 18,000, a molecular weight distribution of between 1 and 5 and a pour point below -15 ° C. The invention relates to a trimeric 1-decene comprising 9-methyl, 11-octylheneneicosan and 11-octyldocosan. These lubricant compositions are produced by bringing the alpha olefin into contact with a reduced solid catalyst supporting the VIB group (for example chromium) under oligomerization conditions at a temperature of between 40 and 250 ° C. in order to produce a liquid lubricating hydrocarbon. The hydrogenated hydrocarbon product in the lubricant class has a viscosity index between about 130 and 280 and a viscosity which can be up to 750 mm2 / s (cs). This process is particularly useful when the basic alpha olefin essentially comprises an olefinic hydrocarbon having between 8 and 14 carbon atoms or mixtures thereof, when the conditions for carrying out the process include a reaction temperature of between 100 and about 180 ° C, and when the support catalyst comprises inert porous silica.

Description

OLEFINIC OLIGOMERS HAVING LUBRICATING PROPERTIES AND PROCESS OF MAKING SUCH OLIGOMERS

This invention relates to novel lubricant compos itions and more particularly , to novel synthetic lubricant compositions prepared from alpha-olefins , or 1-alkenes . The invention ^* specifically relates to novel synthetic lubricant compositions from 1-alkenes exhibiting superior viscosity indices and other improved characteristics essential to useful lubricating oils. This invention further relates to a process for manufacturing such lubricant compositions .

Efforts to improve upon the performance of natural mineral oil based lubricants by the synthes is of oligomeri c hydrocarbon fluids have been the subject of important research and development in the petroleum industry for at least fifty years and have led to the relatively recent market introduction of a number of superior polyalpha-olefin (PAO) syntheti c lubricants, primarily based on the oligomerization of alpha-olefins or 1-alkenes . In terms of lubri cant property improvement , the thrust of the industrial research effort on synthetic lubricants has been toward fluids exhibiting useful viscosities over a wide range of temperature, i .e. , improved viscos ity index (VI ) , while also showing lubricity, thermal and oxidative stabili ty and pour point equal to or better than mineral oil . These new syntheti c lubricants lower friction and hence increase mechanical effi ciency across the full spectrum of mechanical loads from worm gears to traction drives and do so over a wider range of operating conditions than mineral oil lubricants . The chemical focus of the research effort in synthetic lubricants has been on the polymerization of 1-alkenes. Well known structure/property relationships for high polymers as contained in the various discipl ines of polymer chemistry have pointed the way to 1-alkenes as a fruitful field of investigation for the synthes is of oligomers with the structure thought to be needed to confer improved lubricant properties thereon. Due largely to studies on the polymerization of propene and vinyl monomers, the mechanism of the polymerization of 1-alkene and the effect of that mechanism on polymer structure is reasonably well understood, providing a strong resource for targeting on potentially useful oligomerization methods and oligomer structures. Building on that resource, in the prior art oligomers of 1-alkenes from C to C_2Q have been prepared with commercially useful synthetic lubricants from 1-decene oligomerization yielding a distinctly superior lubricant product via either cationic or Ziegler catalyzed polymerization.

Theoretically, the oligomerization of 1-decene, for example, to lubricant oligomers in the C,Q and C.Q range can result in a very large number of structural isomers. Henze and

12 Blair,J.A.C.S. 54,1538, calculate over 60 xlO isomers for C -C._Q. Discovering exactly those isomers, and the associated oligomerization process, that produce a preferred and superior synthetic lubricant meeting the specification requirements of wide-temperature fluidity while maintaining low pour point represents a prodigious challenge to the workers in the field. Brennan, Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, 2-6, cites 1-decene trimer as an example of a structure compatible with structures associated with superior low temperature fluidity wherein the concentration of atoms is very close to the center of a chain of carbon atoms. Also described therein is the apparent dependency of properties of the oligomer on the oligomerization process, i.e., cationic polymerization or Ziegler-type catalyst, known and practiced in the art.

One characteristic of the molecular structure of 1-alkene oligomers that has been found to correlate very well with improved lubricant properties in commercial synthetic lubricants is the ratio of methyl to methylene groups in the oligomer. The ratio is called the branch ratio and is calculated from infra red data as discussed in "Standard Hydrocarbons of High Molecular Weight", Analytical Che istrv, Vol.25 , no. 10, p. 1466 (1953) . Viscosity index has been found to increase with lower branch ratio. Heretofore , oligomeric liquid lubricants exhibiting very low branch ratios have not been synthes ized from 1-alkenes . For instance , oligomers prepared from 1-decene by either cationic polymerization or Ziegler catalyst polymerization have branch ratios of greater than 0.20. Shubkin, Ind. Eng .Chem. Prod. Res. Dev . 1980 , 19 , 15-19, provides an explanation for the apparently limiting value for branch ratio based on a cationic polymerization reaction mechanism involving rearrangement to produce branching . Other explanations suggest isomerization of the olefinic group in the one position to produce an internal oiefin as the cause for branching . Whether by rearrangement , isomerization or a yet to be elucidated mechanism it is clear that in the art of 1-alkene oligomerization to produce synthetic lubricants as practiced to -date excessive branching occurs and constrains the l imits of achievable lubricant properties , parti cularly with respect to viscosity index . Obviously , increased branching increases the number of isomers in the ol igomer mixture , orienting the composition away from the structure which would be preferred from a cons ideration of the theoreti cal concepts discussed above.

U.S. Patent 4 , 282 , 392 to Cupples et al . discloses an alpha-olefin oligomer synthetic lubri cant having an improved viscos ity-volatil ity relationship and containing a high proportion of tetramer and pentamer via a hydrogenation process that effects skeletal rearrangement and isomeric compos ition . The compos ition claimed is a trimer to tetramer ratio no higher than one to one. The branch ratio is not disclosed .

A process us ing coordination catalysts to prepare high polymers from 1-alkenes , especially chromium catalyst on a s ilica support , is described by Weiss et al . in Jour. Catalysis J38 , 424 -430 (1984) and in Offen . DE 3,427,319. The process and products therefrom are discussed in more detail hereinafter in comparison with the process and products of the instant invention . It is well known that Lewis acids such as promoted BF_j and/ or metal halides can catalyze Friedel-Crafts type reactions.

However, oiefin oligomers and more particularly PAO oligomers have been produced by methods in whic double bond isomerization of the starting 1-olefin occurrs easily. As a result, the oiefin oligomers have more short side branches. These side branches degrade their lubricating properties .

Liquid hydrocarbon lubricant compos itions have been obtained from Cg-C^_Q 1-alkene oligomerization that exhibit surprisingly high viscos ity index (VT) while, equally surprisingly, exhibit very low pour points. The compositions comprise

^C30~^1300 • d^rocarb°^ns > the compos itions having a branch ratio of less than 0.19 ; weight average molecular weight between 300 and 45 ,000; number average molecular weight between 300 and 18 ,000 ; molecular weight distribution between 1 and 5 and pour point below

- 15°C.

Further, a novel composition has been discovered compris ing 11-octyldocosane having the structure

H

The foregoing compos ition has been found to exhibit superior lubricant properties either alone or in a mixture with 9-methyl,ll-octylhenei cosane. Surprisingly, the mixture has a viscosity index of greater than 130, preferably from 130 to 280, while maintaining a pour point less than -15°C. These compos itions are representative of the instant invention comprising C,QH₆₂ alkanes having a branch ratio, or CH,/CH₂ ratio, of less than 0.19, preferably 0.10 to 0.16. These low branch ratios and pour points characterize the compositions of the invention, ref erred to herein as polyalpha -oiefin or HVI-PAO, conferring upon the compos itions especially high viscos ity indices in comparison to commercially available polyalpha-olefin (PAO) synthetic lubricants . Unique lubricant oligomers of the instant invention an also be made in a wide range of molecular weights and viscosities comprising C,_Q to C _{I QQQ} -hydrocarbons having a branch ratio of less than 0.19 and molecular weight distribution of about 1.05 to 2.5. The oligomers can be mixed wi th conventional mineral oils or greases of other properties to provide compos itions also possessing outstanding lubricant properties .

Compos itions of the present invention can be prepared by the oligomerization of alpha-olefins such as 1-decene under oligomerization conditions in contact with a supported and reduced valence state metal oxide catalyst from Group VIB of the IUPAC Periodic Table. Chromium oxide is the preferred metal oxide .

The present invention provides a process for producing liquid oligomers of olefins , such as 1-decene, with branch ratios below 0. 19 and having higher viscosity indi ces than oligomers with higher branch ratios . These ol igomers with low branch ratios can be used as basestocks for many lubri cants or greases with an improved viscos ity-temperature relationship, oxidative stabil ity , volatil ity , etc. They can also be used to improve viscosities and viscosity indices of lower quality oils . The olefins can, for example , be oligomerized over a supported and reduced metal oxide catalyst from Group VIB of the Periodic Table to give oligomers suitable for lubricant application. More particularly, the instant application is directed to a process for the oligomerization of olefinic hydrocarbons containing 6 to 20 carbon atoms which comprises oligomerizing said hydrocarbon under oligomerization conditions , wherein the reaction product cons ists essentially of substantially non-iso erized olefins . For example, alpha olefins such as 1-decene, and wherein a major proporti on of the double bonds of the olefins or olefinic hydrocarbons are not isomerized , in the presence of a suitable catalyst , e.g. , a supported and reduced metal oxide catalyst from Group VIB of the Periodic Table.

The use of reduced Group VIB chromium-containing metal oxide on an inert support oligomerizes liquid olefins which are suitable for use as good quality lube oils is a novel technique.

Figure 1 is a comparison of PAO and HVI-PAO syntheses . Figure 2 compares VI for PAO and HVI-PAO Figure 3 shows pour points for PAO and HVI-PAO Figure 4 shows C-13 NMR spectra for HVI-PAO from 1-hexene. Figure 5 shows C- 13 NMR spectra of 5cs HVI-PAO from

1-decene.

Figure 6 shows C- 13 NMR spectra of 50cs HVI-PAO from 1-decene.

Figure 7 shows C-13 NMR spectra of 145cs HVI-PAO from 1-decene.

Figure 8 shows the gas chro atograph of HVI-PAO 1-decene t rimer.

Figure 9 shows C- 13 NMR of HVI-PAO trimer of 1-decene. Figure 10 shows C-13 NMR calculated vs. observed chemical shifts for HVI-PAO 1-decene trimer components.

In the following description, unless otherwise stated, all references to HVI-PAO oligomers or lubricants refer to hydrogenated oligomers and lubricants in keeping with the practice well known to those skilled in the art of lubricant production. As oligomerized, HVI-PAO oligomers are mixtures of dialkyl vinyledenic and 1, 2 dialkyl or trialkyl mono-olef ins . Lower molecular weight unsaturated oligomers are preferably hydrogenated to produce thermally and oxidatively stable, useful lubricants. Higher molecular weight unsaturated HVI-PAO oligomers are sufficiently thermally stable to be utilized without hydrogenation and, optionally, may be so employed. Both unsaturated and hydrogenated HVI-PAO of lower or higher molecular exhibit viscosity indices of at least 130, preferably from 130 to 280 , and pour point below -15 °C, preferably -45 °C. — 1-

Referring to Figure 1 , the novel oligomers of the invention, or high viscos ity index polyalphaolefins (HVI-PAO) are described in an illustration comparing them with conventional polyalphaolefins (PAO) from 1-decene. Polymerization with the novel reduced chromium catalyst described hereinafter leads to an oligomer substantially free of double bond isomerization . Conventional PAO, on the other hand , promoted by BF, or A1C13 forms a carbonium ion which, in turn, promotes isomerization of the olefini c bond and the formation of multiple isomers. The HVI-PAO produced in the present invention has a structure with a CH-./CHH.- ratio< 0.19 compared to a ratio of > 0.20 for PAO.

Figure 2 compares the viscos ity index versus viscosity relationship for HVI -PAO and PAO lubricants , showing that HVI-PAO is distinctly superior to PAO at all viscos ities tested. Remarkably , despite the more regular structure of the HVI-PAO oligomers as shown by branch ratio that results in improved viscosity index (VI) , they show pour points superior to PAO. Conceivably, oligomers of regular structure containing fewer isomers would be expected to have higher sol idification temperatures and higher pour points , reducing their util ity as lubricants . But , surprisingly , such is not the case for HVI-PAO of the present invention . Figure 2 and 3 illustrate superiori ty of HVI-PAO in terms of both pour point and VI.

It has been found that the process described herein to produce the novel HVI-PAO oligomers can be controlled to yield oligomers having weight average molecular weight between 300 and 45 ,000 and number average molecular weight between 300 and 18 ,000.

Measured in carbon numbers, molecular weights range from C- to C, ,QQ and viscosity up to 750 mm 2 /s(cs ) at 100°C, with a preferred range of C,_Q to C-_fi00 and a viscos ity of up to 500 mm /s(cs) at 100°C, preferably between 3 and 750 mm /s .

Molecular weight distributions (MWD) , defined as the ratio of weight average molecular weight to number average molecular weight , range from 1.00 to 5 , with a preferred range of 1.01 to 3 and a more preferred MWD of about 1.05 to 2.5. Compared to conventional PAO derived from BF, or A1C1, catalyzed polymerization of 1-alkene, HVI-PAO of the present invention has been found to have a higher proportion of higher molecular weight polymer molecules in the product.

Viscosities of the novel HVI-PAO oligomers measured at

2 2

100 °C range from 3 mm s(cs) to 5000 mm /s(cs). The viscosity index for the new polyalpha-olef ins is approximately described by the following equation: ₀ VI =129.8 + 4.58 x ( v^~ ₁₀₀ ^oC)^{0 , 5} , where V_10Q C is kinematic viscosity in centistokes measured at 100°C.

The novel oligomer compos itions disclosed herein have been examined to define their unique structure beyond the important characteristics of branch ratio and molecular weight already noted.

■_[5 Dimer and trimer fractions have been separated by distillation and components thereof further separated by gas chromatography. These lower oligomers and components along with complete reaction mixtures of HVI-PAO oligomers have been studied using infra-red spectroscopy and C-13 NMR. The studies have confirmed the highly uniform

2o structural composition of the products of the invention , particularly when compared to conventional polyalphaolefins produced by BF.. , A1C1, or Ziegler-type catalysis . The unique capability of C -13 NMR to identify structural isomers has led to the identification of distinctive compounds in lower oligomeric

25 fractions and served to confirm the more uniform isomeric mix present in higher molecular weight oligomers compatible with the finding of low branch ratios and superior viscosity indices.

1-hexene HVI-PAO oligomers of the present invention have been shown to have a very uniform linear C . branch and contain

₃₀ regular head-to-tail connections. In addition to the structures from the regular head-to -tail connections , the backbone structures have some head-to-head connection, indicative of the following structure as confirmed by NMR: ._<_.-

H(-CH-CH i₇.-) x -(-CH₇ _-CH-) y H

(CH₂)₃ (CH₂)₃

CH₃ CH₃

The NMR poly(l-hexene) spectra are shown in Figure 4. The oligomerization of 1-decene by reduced valence state, supported chromium also yields a HVI-PAO with a structure analogous to that of 1-hexene oligomer. The lubricant products after distillation to remove light fractions and hydrogenation have characteristic C-13 NMR spectra. Figures 5, 6 and 7 are the C-13 NMR spectra of typical HVI-PAO lube products with viscosities of 5

2 ^'η 2 mm /s(cs), 50 mm"/s(cs) and 145 mm /s(cs) at 100°C.

In the following tables, Table A presents the NMR data for

Figure 5, Table B presents the NMR data for Figure 6 and Table C presents the NMR data for Figure 7.

Table A (Fig. 5)

Point Shift(ppm) Intensity Width(Hz)

1 79.096 138841. 2.74

2 74.855 130653. 4.52

3 42.394 148620. 6.68

4 40.639 133441. 37.6

5 40.298 163678. 32.4

6 40.054 176339. 31. 2

7 39.420 154904. 37.4

8 37.714 445452. 7.38

9 37.373 227254. 157

10 37.081 145467. 186

11 36.788 153096. 184

12 36.593 145681. 186

13 36.447 132292. 189

14 36.057 152778. 184

15 35.619 206141. 184

16 35.082 505413. 26.8

17 34.351 741424. 14.3

18 34.059 1265077. 7.65

19 32.207 5351568. 1.48

20 30.403 3563751. 4.34

21 29.965 8294773. 2.56

22 29.623 4714955. 3.67

23 28.356 369728. 10.4

24 28.161 305878. 13.2

25 26.991 1481260. 4.88

26 22.897 4548162. 1.76

27 20.265 227694. 1.99

28 14.221 4592991. 1.62 Table B(Fig. 6)

No. Freq(Hz) PPM Int%

1 1198.98 79.147 1856

2 1157.95 77.004 1040

3 1126.46 74.910 1025

4 559.57 37.211 491

5 526.61 35.019 805

6 514.89 34.240 1298

509.76 33.899 1140

8 491.45 32.681 897

9 482.66 32.097 9279

10 456.29 30.344 4972

11 488.24 29.808 9711

12 444.58 29.564 7463

13 426.26 28.347 1025

14 401.36 26.691 1690

15 342.77 22.794 9782

16 212.40 14.124 8634

17 0.00 0.000 315

Table C ( Fig .7)

Point Shift(ppm) Intensity Width (Hz)

1 76.903 627426. 2.92

2 40.811 901505. 22.8

3 40.568 865686. 23.1

4 40.324 823178. 19.5

5 37.158 677621. 183.

6 36.915 705894. 181.

7 36.720 669037. 183.

8 36.428 691870. 183.

9 36.233 696323. 181.

10 35.259 1315574. 155 .

11 35.015 1471226. 152.

12 34.333 1901096. 121.

13 32.726 1990364. 120.

14 32. 141 20319110. 2.81

15 31.362 1661594. 148.

16 30.388 9516199. 19.6

17 29.901 17778892. 9.64

18 29.609 18706236. 9.17

19 28.391 1869681. 122.

20 27.514 1117864. 173.

21 26.735 2954012. 14.0

22 22.839 20895526. 2.17

23 14.169 16670130. 2.06

In general, the novel oligomers have the following regular head-to-tail structure where n can be 3 to 17 : -CGH₂-(H)_χ-

I

(CH₂)_n CH₃ with some head-to-head connections.

The trimer of 1-decene HVI-PAO oligomer is separated from

2 the oligomerization mixture by distillation from a 20 mm /s(cs) as -synthes ized HVI-PAO in a short -path apparatus in the range of 165-210°C at 13.3-26.6 Pa (0.1-0.2 torr) . The unhydrogenated trimer exhibited the following viscometric properties :

V <a 40 °C = 14.88 mm²/s(cs ) ; V § 100 °C =3.67 mm²/s(cs) ; VI = 1 The trimer is hydrogenated at 235 °C and 4200 kPa H₂ with

Ni on kieselguhr hydrogenation catalyst to give a hydrogenated HVI-PAO trimer with the following properties :

V @ = 40 °C = 16.66 mm²/s(cs ) ; V § 100°C = 3.91 mm²/s(cs) VI =

Pour Point = less than -45 °C; Gas chromatographic analysis of the trimer reveals that it is composed of essentially two components having retention times of 1810 seconds and 1878 seconds under the following conditions :

Gas chroma tograph (g .c. ) column-60 me ter capillary column, 0.32 mmid (mm ins ide diameter) , coated with stationary phase SPB-1 with film thickness 0.25mm , available from Supelco chromatography supplies , catalog no. 2-4046. Separation Conditions - Varian Gas chroma to raph, model no.

3700 , equipped with a flame ionizati on detector and capillary injector port with split ratio of about 50. ₂ carrier gas flow rate is 2.5 ml/minute. Injector port temperature 300°C ; detector port temperature 330 °C, column temperature is set initially at 45°C for 6 minutes, programmed heating at 15 °C/minute to 300°C final temperature and holding at final temperature for 60 minutes . Sample injection size is 1 microliter. Under these conditions , the retention time of a g .c . standard , n-dodecane, is 968 seconds. A typical chroma tograph is shown in Figure 8. The C- 13 NMR spectra, (Figure 9) , of the distilled C30 product confirm the chemical structures. Table D lists C- 13 NMR data for Fi gure 9. Table D ( Fig . ( 9)

Point Shift (ppm) Intensity Width(Hz)

1 55.987 11080. 2.30

2 42.632 13367. 140.

3 42.388 16612. 263.

4 37.807 40273. 5.90

5 37.319 12257. 16.2

6 36.539 11374. 12.1

7 35.418 11631. 35.5

8 35.126 33099. 3.14

9 34.638 39277. 14.6

10 34.054 110899. 3.52

11 33.615 12544. 34.9

12 33.469 13698. 34. 2

13 32.981 11278. 5.69

14 32.835 13785. 57.4

15 32.201 256181. 1.41

16 31.811 17867 . 24.6

17 31.470 13327. 57.4

18 30.398 261859. 3.56

19 29.959 543993. 1.89

20 29.618 317314. 1.19

21 28.838 11325. 15.1

22 28.351 24926. 12.4

23 28.156 29663. 6.17

24 27.230 44024. 11.7

25 26.986 125437. -0.261

26 22.892 271278. 1.15

27 . 20.260 17578. -22.1

28 14.167 201979. 2.01 The individual peak assignment of the C-13 spectra are shown in Figure 9. Based on these structures , the calculated chemical shifts , as shown in Figure 10 , matched closely with the observed chemical shifts . The calculation of chemical shifts of hydrocarbons is carried out as described is "Carbon- 13 NMR for

Organic Chemists" by G. C. Levy and G. L. Nelson, 1972 , by John Wiley $ Sons, Inc. , Chapter 3, p 38-41. The components were identified as 9-methyl , ll-octylhenei cosane and 11-octyldocosane by infra-red and C- 13 NMR analys is and were found to be present in a ratio between 1 :10 and 10 : 1 henei cosane to docosane. The hydrogenated 1-decene trimer produced by the process of this invention has an index of refraction at 60°C of 1.4396.

The process of the present invention produces a surpris ingly simpler and useful dimer compared to the dimer produced by 1-alkene oligomerization with BF, or A1C1, as commercially practi ced. Typically , in the present invention i t has been found that a significant proportion of unhydrogenated dimerized 1-alkene has a vinylidenyl structure as follows :

where R, and R-, are alkyl groups representing the residue from the head-to-tail addition of 1-alkene molecules . For example, 1-decene dimer of the invention has been found to contain only three major components, as determined by GC. Based on C NMR analysis , the unhydrogenated components were found . to be 8-eicosene, 9-eicosene, 2 -octyldodecene and 9-methyl-8 or 9-methyl-9-nonadecene.

The hydrogenated dimer components were found to be n-ei cosane and 9-methylnonacosane .

Olefins suitable for use as starting material in the inventi on include those olefins containing from 2 to about 20 carbon atoms such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene,

1-octene , 1-decene , 1-dodecene and 1-tetradecene and branched chain isomers such as 4-methyl-l-pentene. Also suitable for use are olef in-containing refinery feedstocks or effluents . However , the olefins used in this invention are preferably alpha olefinic as for example 1-heptene to 1-hexadecene and more preferably 1-octene to 1-tetradecene, or mixtures of such olefins.

Oligomers of alpha-olefins in accordance with the invention have a low branch ratio of less than 0.19 and superior lubricating properties compared to the alpha-olefin oligomers with a high branch ratio, as produced in all known commercial methods.

This new class of alpha-olefin oligomers are prepared by oligomerization reactions in which a major proportion of the double bonds of the alphaolefins are not isomerized. These reactions include alpha-olefin oligomerization by supported metal oxide catalysts , such as Cr compounds on silica or other supported IUPAC Periodic Table Group VIB compounds. The catalyst most preferred is a lower valence Group VIB metal oxide on an inert support. Preferred supports include silica, alumina, titania, silica alumina, magnesia and the like. The support material binds the metal oxide catalyst.

Those porous substrates having a pore opening of at least 40 x

-4 10 _ju-.m are preferred.

The support material usually has high surface area and large pore volumes with average pore size of 40 to 350 x .

The high surface area are beneficial for supporting large amount of highly dispersive , active chromium metal centers and to give maximum efficiency of metal usage, resulting in very high activity catalyst. The support should have large average pore openings of at

-4 least 40 x 10 ^m, with an average pore opening of >60 to 300 x ^β4 10 ytΛ. m being preferred. This large pore opening will not impose any diffusional restriction of the reactant and product to and away from the active catalytic metal centers, thus further optimizing the catalyst productivity. Also, for this catalyst to be used in fixed bed or slurry reactor and to be recycled and regenerated many times , a silica support with good physical strength is preferred to prevent catalyst particle attrition or dis integration during handling or reaction. The supported metal oxide catalysts are preferably prepared by impregnating metal salts in water or organic solvents onto the support. Any suitable organic solvent known to the art may be used, for example, ethanol, methanol, or acetic acid . The solid catalyst precursor is then dried and calcined at 200 to 900°C by air or other oxygen- containing gas . Thereafter the catalyst is reduced by any of several various and well known reducing agents such as, for example, CO , H₂ , NH-, , H₂S, CS₇ , CH-.SCH-, , CH,SSCH, , metal alkyl containing compounds such as R₃A1 , R,B,R₂Mg , RLi , R_,Zn, where R is alkyl , alkoxy, aryl and the like. Preferred are CO or H₂ or metal alkyl containing compounds . Alternatively, the Group VIB metal may be applied to the substrate in reduced form, such as CrI I compounds. The resultant catalyst is very active for oligomerizing olefins at a temperature range from below room temperature to about 250°C, preferably

90 °-250°C, most preferably 100 °- 180 °C, at a pressure of 10 .1 kPa ( 0.1 atmosphere ) to 34500 kPa ( 5000 psi ) . Contact time of both the oiefin and the catalyst can vary from one second to 24 hours. The weight hourly space velocity (WHSV) is 0.1 to 10 , based on total catalyst weight . The catalyst can be used in a batch type reactor or in a fixed bed , continuous -flow reactor.

In general the support material may be added to a solution of the metal compounds , e.g. , acetates or nitrates, etc. , and the mixture is then mixed and dried at room temperature. The dry solid gel is purged at successively higher temperatures to 600°C for a period of 16 to 20 hours. Thereafter the catalyst is cooled down under an inert atmosphere to a temperature of 250 to 450°C and a stream of pure reducing agent is contacted therewith for a period when enough CO has passed through to reduce the catalyst as indicated by a distinct color change from bright orange to pale blue. Typically , the catalyst is treated with an amount of CO equivalent to a two-fold stoichiometric excess to reduce the catalyst to a lower valence CrII state. Finally the catalyst is cooled down to room temperature and is ready for use. The product oligomers have a very wide range of viscosities with high viscos ity indices suitable for high performance lubrication use. The product oligomers also have atactic molecular structure of mostly uniform head-to -tail connections with some head-to-head type connections in the structure. These low branch ratio oligomers have high viscosity indices at least 15 to 20 units and typically 30-40 units higher than equivalent viscosity prior art oligomers, which regularly have higher branch ratios and correspondingly lower viscosity indices. These low branch oligomers 0 maintain better or comparable pour points .

The branch ratios defined as the ratios of CH, groups to CH₂ groups in the lube oil are calculated from the weight fractions of methyl groups obtained by infrared methods, published in Analytical Chemistry-, Vol. 25, No. 10, p. 1466 (1953) . 5

Branch ratio = wt fraction of methyl group

l- (wt fraction of methyl group) As referenced hereinbefore , supported Cr metal oxide in different oxidation states is known to polymerize alpha olefins from ⁰ C₃ to C (De 3427319 to H. L. Krauss and Journal of Catalysis

88 , 424-430 , 1984) using a catalyst prepared by CrO, on silica.

The referenced disclosures teach that polymerization takes place at low temperature, usually less than 100 °C, to give adhesive polymers and that at high temperature, the catalyst promotes

--' isomerization, cracking and hydrogen transfer reactions. The present inventions produce low molecular weight oligomeric products under reaction conditions and using catalysts which minimize side reactions such as 1-olefin isomerization, cracking, hydrogen transfer and aromati∑ation. To produce the novel low molecular

³⁰ weight products suitable for use as lube basestock or as blending stock with other lube stock , the reaction of the present invention is carried out at a temperature higher (90-250 oC) than the temperature suitable to produce high molecular weight polyalpha-olef ins . The catalysts used in the present invention do not cause a significant amount of side reactions even at high temperature when oligomeric, low molecular weight fluids are produced.

The catalysts for this invention thus minimize all side reactions but oligomerize alpha olefins to give low molecular weight polymers with high efficiency. It is well known in the prior art that chromium oxides , especially chromia with average +3 oxidation states , either pure or supported , catalyze double bond isomerization, dehydrogenation, cracking , etc. Although the exact nature of the supported Cr oxide is difficult to determine, it is thought that the catalyst of the present invention is rich in Cr(I I) supported on silica, which is more active to catalyze alpha-olefin oligomerization at high reaction temperature without caus ing significant amounts of isomerization , cracking or hydrogenation reacti ons , etc . However , catalysts as prepared in the ci ted references can be richer in Cr (I II) . They catalyze alpha-olefin polymerization at low reaction temperature to produce high molecular weight polymers . However, as the references teach, undes irable isomerization, cracking and hydrogenation reaction takes place at higher temperatures . In contrast , high temperatures are needed in this invention to produce lubricant products. The prior art also teaches that supported Cr catalysts rich in Cr(III). or higher

₃ oxidation states catalyze 1-butene isomerization with 10 higher activity than polymerization of 1-butene. The quality of the catalyst , method of preparation, treatments and reaction conditions are critical to the catalyst performance and compos ition of the product produced and distinguish the present invention over the prior art.

In the instant invention very low catalyst concentrations based on feed, from 10 wtl to 0.01 wt% , are used to produce oligomers; whereas, in the cited references catalyst ratios based on feed of 1 :1 are used to prepare high polymer. Resorting to lower catalyst concentrations in the present invention to produce lower molecular weight material runs counter to conventional polymerization theory, compared to the results in the cited references.

The oligomers of 1-olefins prepared in this invention usually have much lower molecular weights than the polymers produced in cited reference which are semi-solids , with very high molecular weights. These high polymers are not suitable as lubricant basestocks and usually have no detectable amount of dimer or trimmer

(CI Q-C,Q) components from synthesis. Such high polymers also have very low uns a tu rations . However, products in this invention are free-flowing liquids at room temperature, suitable for lube basestock, containing significant amount of dimer or trimer and have high unsaturations.

The following examples of the instant invention are presented merely for illustration purposes and are not intended to limit the scope of the present invention.

Example 1 Catalyst Preparation and Activation Procedure

1.9 grams of chromium (II) acetate

(Cr₂ (0COCH_j)^2H₂O) (5.58 mmole) (commercially obtained) is dissolved in 50 ml of hot acetic acid. Then 50 grams of a silica

2 gel of 8-12 mesh size, a surface area of 300 m /g , and a pore volume of 1 ml/g, also is added. Most of the solution is absorbed by the silica gel. The final mixture is mixed for half an hour on a rotavap at room temperature and dried in an open-dish at room temperature. First , the dry solid ( 20 g) is purged with N₂ at 250°C in a tube furnace. The furnace temperature is then raised to 400°C for 2 hours . The temperature is then set at 600°C with dry air purging for 16 hours. At this time the catalyst is cooled down under N₂ to a temperature of 300 °C. Then a stream of pure CO (99.99% from Matheson) is introduced for one hour. Finally, the catalyst is cooled down to room temperature under N₂ and ready for use.

Example 2

The catalyst prepared in Example 1 (3.2 g ) is packed in a 3/8" stainless steel tubular reactor inside an N₂ blanketed dry box. The reactor under N₂ atmosphere is then heated to 150°C by a single-zone Lindberg furnace. Pre-purified 1-hexene is pumped into the reactor at 965 kPa ( 140 psi ) and 20 ml/hr. The liquid effluent is collected and stripped of the unreacted starting material and the low boiling material at 6.7 kPa ( 0.05 mm Hg) . The residual clear, colorless liquid has viscos ities and VI ' s suitable as a lubricant base stock.

Sample Pre run

T. O.S. , hr. 2 3.5 5 .5 21.5

Lube Yield, wtl 10 41 74 31

Viscosity , mm- s

(cs) , at

40 °C 208.5 123.5 104.4 166.2

100°C 26.1 17.1 14.5 20.4

VI 159 151 142 143

Example 3

Similar to Example 2, a fresh catalyst sample is charged into the reactor and 1-hexene is pumped to the reactor at 101 kPa (1 atm) and 10 ml per hour. As shown below, a lube of high viscosities and high VI ' s is obtained. These runs show that at different reaction conditions, a lube product of high viscosities can be obtained. Sample B

T.O.S. , hrs. 20 44

Temp., °C 100 50

Lube Yield, 1 8.2 8.0

Viscosities, mm /s

(cs) at

40°C 13170 19011

100°C 620 1048

VI 217 263

Example 4

A commercial chrome/silica catalyst which contains 1% Cr on a large-pore volume synthetic silica gel is used. The catalyst is first calcined with air at 800°C for 16 hours and reduced with CO at 300 °C for 1.5 hours. Then 3.5 g of the catalyst is packed into a tubular reactor and heated to 100°C under the N₂ atmosphere. 1-Hexene is pumped through at 28 ml per hour at 101 kPa (1 atmosphere). The products are collected and analyzed as follows :

Sample C E F

T.O.S. , hrs > 3.5 4.5 6.5 22.5

Lube Yield, % 73 64 59 21

Viscosity, mm /s

(cs), at

40°C 2548 2429 3315 9031

100°C 102 151 197 437

VI 108 164 174 199

These runs show that different Cr on a silica catalyst are also effective for oligomerizing olefins to lube products . Example 5 As in Example 4, purified 1-decene is pumped through the reactor at 1830 kPa to 2310 kPa ( 250 to 320 psi) . The product is collected periodically and stripped of light products boiling points below 343°C ( 650°F ) . High quality lubes with high VI are obtained (see following table ).

Reaction WHSV Lube Product Properties

Temp . °C g/g/hr V at 40°C V at 100°C VI

120 2.5 1555.4cs 157.6cs 217

135 0.6 389.4 53.0 202

150 1.2 266.8 36.2 185

166 0.6 67.7 12.3 181

197 0.5 21.6 5. 1 172

Example 6

Similar catalyst is used in testing 1-hexene oligomerization at different temperature. 1-Hexene is fed at 28 ml/hr and at 101 kPa (1 atmosphere) .

Sample G H

Temperature, °C 110 200

Lube Yield, wt . l 46 3

Viscosities , mm 2 //s

(cs) at

40 °C 3512 3760

100°C 206 47

VI 174 185 Example 7

1.5 grams of a similar catalyst as prepared in Example 4 was added to a two-neck flask under N₂ atmosphere. Then 25 g of

1-hexene was added. The slurry was heated to 55 °C under N₂ atmosphere for 2 hours. Then some heptane solvent was added and the catalyst was removed by filtration. The solvent and unreacted starting material was stripped off to give a viscous liquid with a

61% yield. This viscous liquid had viscosities of 1536 and 51821

2 πm /2 (cs) at 100°C and 40°C, respectively. This example demonstrated that the reaction can be carried out in a batch operation.

The 1-decene oligomers as described below were synthesized by reacting purified 1-decene with an activated chromium on silica catalyst . The activated catalyst was prepared by calcining chromium acetate (1 or 3% Cr) on silica gel at 500-800°C for 16 hours, followed by treating the catalyst with CO at 300 -350 ^CC for 1 hour.

1-Decene was mixed with the activated catalyst and heated to reaction temperature for 16-21 hours. The catalyst was then removed and the viscous product was distilled to remove low boiling components at 200°C/13.3 kPa(0.1 mmHg) .

Reaction conditions and results for the lube synthesis of

HVI-PAO are summarized below:

Table 1

1-decene/

Example Cr on Calcinatii an Treatment Catalyst Lube

NO. Silica Temp. Temp. Ratio Yld

8 3wt% 700 °C 350°C 40 90

9 3 700 350 40 90

10 1 500 350 45 86

11 1 600 350 16 92 Branch Ratios and Lube Properties of Examples 8-11 Alpha Oiefin Oligomers

Table 2

Example Branch CH_j V40°C V100°C VI

No. Ratios CH^

8 0.14 150.5 22.8 181

9 0.15 301.4 40. 1 186

10 0. 16 1205 .9 128.5 212

11 0. 15 5238.0 485.1 271

Branch Ratios and Lubricating Properties of Alpha Oiefin

Oligomers Prepared in the Prior-Art

Table 5

Example Branch CH-, V40°C V100°C VI

No. Ratios CH₇

12 0.24 28.9 5 .21 156

13 0.19 424.6 41.5 148

14 0.19 1250 100 168

15 0.19 1247.4 98.8 166

These samples are obtained from the commercial market. They have higher branch ratios than samples in Table 2. Also, they have lower VI ' s than the previous samples .

Comparison of these two sets of lubricants clearly demonstrates that oligomers of alpha-olefins , as 1-decene, with branch ratios lower than 0.19, preferably from 0.13 to 0.18, have higher VI and are better lubricants . The examples prepared in accordance with this invention have branch ratios of 0.14 to 0.16, providing lube oils of excellent quality which have a wide range of viscosities from 3 to 483.1 cs at 100°C with viscosity indices of 130 to 280.

Example 16

A commercial Cr on silica catalyst which contains 1% Cr on a large pore volume synthetic silica gel is used. The catalyst is first calcined with air at 700 °C for 16 hours and reduced with CO at

350°C for one to two hours. 1.0 part by weight of the activated catalyst is added to 1-decene of 200 parts by weight in a suitable reactor and heated to 185 °C. 1-Decene is continuously fed to the reactor at 2-3.5 parts/minute and 0.5 parts by weight of catalyst is added for every 100 parts of 1-decene feed. After 1200 parts of

1-decene and 6 parts of catalyst are charged, the slurry is stirred for 8 hours. The catalyst is filtered and light product boiled below 150°C § 0.1mm Hg is stripped. The residual product is hydrogenated with a Ni on Kieselguhr catalyst at 200°C. The

2 finished product has a viscosity at 100°C of 18.5 mm /s(cs) , VI of

165 and pour point of -55 °C.

Example 17

Similar as in Example 16, except reaction temperature is

125°C. The finished product has a viscosity at 100 °C of 145 2 ran /s(cs), VI of 214, pour point of -40°C.

Example 18

Example 16 is repeated except reaction temperature is

100°C. The finished product has a viscosity at 100°C of 298 cs, VI of 246 and pour point of -32°C. The final lube products in Example 16 to 18 contain the following amounts of dimer and trimer and isomeric distribution

(distr.). —27—

Example 16 11 11

V @100°C, mm²/s 18.5 145 298

VI 165 214 246

Pour Point , °C -55 °C -40 °C -32 wt% dimer 0.01 0.01 0.027 wt% isomeric distr. dimer n-ei cosane 51% 28% 73 %

9-meth lnonacosane 49% 72% 27% wt% trimer 5.53 0.79 0.27 wt% isomeric distr. trimer

11-octyldocosane 55 48 44

9-methyl, 11-octyl- henei cosane 35 49 40 others 10 13 16

These three examples demonstrate that the new HVI-PAO of wide viscosities contain the dimer and trimer of unique structures in various proportions .

The molecular weights and molecular weight distributions are analyzed by a high pressure liquid chromatography, composed of a Constametric II high pressure , dual piston pump from Milton Roy Co. and a Tracor 945 LC detector. During analys is, the system pressure is 4600 kPa (650 psi) and THF solvent (HPLC grade) deliver rate is 1 ml per minute. The detector block temperature is set at 145 C. ml of sample, prepared by dissolving 1 gram PAO sample in ml THF solvent , is injected into the chroma tograph. The sample is eluted over the following columns in series, all from Waters Associates : Utrastyragel 10⁵ A, P/N 10574 , Utrastyragel 10⁴ A, P/N 10573 , Utrastyragel 10³ A, P/N 10572 , Utrastyragel 500 A, P/N 10571. The molecular weights are calibrated against commercially available PAO from Mobil Chemical Co, Mobil SHF-61 and SHF-81 and SHF-401.

The following table summarizes the molecular weights and distributions of Examples 16 to 18 . —28—

Examples tf 17 18

V §100 °C,mm²/s(cs) 18.5 145 298

VI 165 214 246

number-averaged molecular weights, MW_n 1670 2062 5990 weight-averaged molecular weights, MW_w 2420 4411 13290 molecular weight distribution, MWD 1.45 2.14 2. 22

Under similar conditions, HVT-PAO product with viscosity as low as 3 mm 2 /s (cs) and as high as 500 mm 2 /s (cs) , with VI between 130 and 280 , can be produced.

Ethene can be employed as a starting material for conversion to higher C₆-C_2Q alpha olefins by conventional catalytic procedure, for instance by contacting ethene with a Ni catalyst at 80-120°C and about 7000 kPa (1000 psi) using commercial synthesis methods described in Chem System Process

Evaluation/Research Planning Report - Alpha- Olefins, report number

82-4. The intermediate product alpha oiefin has a wide distribution range from Cg to C_2Q carbons. The complete range of alpha olefins from growth reaction, or partial range such as C₆ to

C₁₄, can be used to produce a lube of high yields and high viscosity indices . The oligomers after hydrogenation have low pour points.

Example 19 An alpha oiefin growth reaction mixture, as described above, containing ^C6~^C8~^cιo"^ci2"^C14~^C16~^C18"^C20 ^of equal molar concentration is reacted with 2 wt. % activated Cr/Si0₂ catalyst at 130°C and under nitrogen atmosphere. After 225 minutes reaction time, the catalyst is filtered and the reaction mixture distilled to remove light fraction which boils below 120°C/0.1 mm-Iig. The residual lube yield is 95% and has V-_IQO_OQ 67.07 cS and VI 195.

Example 20 An equimolar C,. -C-_>Q alpha oiefin mixture as described above is fed continuously over activated Cr/Si0₂ catalyst packed in a tubular reactor. The results are summarized below.

Table 20

Starting

SAMPLES Material A B C D

Temp, °C 125 150 190 200

Pres . , psig 310 500 250 280 HSV, g/g/hr 1.2 1.2 1.2 1.2

Product Dist ribution, wt . ■ .

1-C₆= 4.7 0.3 0.5 0.5 1. 1

1-C₈- 12.8 0 0.5 1. 1 2. 5

1-Cχo^" 22.0 1.8 1.8 2.5 4.6

1-C₁₂- 19.4 0.3 0.5 1. 4 5. 4

1-C₁₄= 16 .0 0.9 0.9 1.9 4.8 ι-c₁₆- 11.0 0.6 0.4 1.9 4.5

1-Ci8^~ 7.7 0.8 1. 5 2.7 6.0

1-C₂₀ ^" 6.5 0.5 1.8 5. 1 6.9

^C20^{" C}30 ° 4. 4 2.6 7.8 18.7

Lube 90.5 90.1 78.5 47.5

Lube properties

^V100°C ^cS 75.11 51. 24 12.12 14.84 VI 190 184 168 164

Example 21

Equimolar oief in mixture of ^6"^8"⁽-ιo~^i2~^14 ^s reacted over Cr/Si0₂ catalyst s imilar to Example 2. The results are summarized in Table 21. —30-

Table 21

Starting

SAMPLES Material A B C D

Temp, °C 120 150 190 204 Pres . , psig 250 210 200 200 WffiV, g/g/hr 2.5 2.5 2.5 2.5

Product Distri .bution, wt. . )

^c20"^c30 0 0.0 5.1 23.8 18.7 Lube 0 93.0 88.4 65.8 42.7

Lube properties

^V100°C» ^cS 101.99 46.31 17.97 7.31

VI 187 165 168 157 pour points after H₂ ,°C -33 -43 -50 -41

A range of alpha olefins from ethylene growth reactions and metathesis processes can be used to produce high quality lube by the present process, thus rendering the process cheaper and the feedstock flexible than using pure single monomer.

Example 22 The standard 1-decene oligomerization synthesis procedure employed above is repeated at 125°C using different Group VIB metal species, tungsten or molydenum. The W/Mo treated porous substrate is reduced with CO at 460°C to provide 1 wt. % metal in reduced oxide state. Molybdenum catalyst gives a 1% yield of a viscous liquid. Tungsten gives C₂₀ dimer only. The use of supported Group VIB oxides as a catalyst to oligomerize olefins to produce low branch ratio lube products with low pour points was heretofore unknown. Catalytic production of oligcmers with structures having a low branch ratio which does not use a corrosive co-catalyst and produces a lube with a wide range of viscosities and good V. I . 's was also heretofore unknown and more specifically the preparation of lube oils having a branch ratio of less than about 0.19 was also unknown heretofore.

Although the present invention has been described with preferred embodiments, it is to be understood that modifications and variations may be resorted to, without departing from the spiri t and scope of this invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims.

Claims

CLAIMS:

1. A liquid lubricant composition comprising ^C30~(_1300 hydrocarbons, said composition having a branch ratio of less than 0.19 , weight average molecular weight between 300 and 45 ,000, number average molecular weight between 300 and 18 ,000, molecular weight distribution between 1 and 5 and pour point below -15°C.

2. The composition of claim 1 wherein said hydrocarbons comprise C,_Q-C,_Q0Q hydrocarbons and molecular weight distribution of about 2.5.

3. The composition of claim 1 wherein said hydrocarbons comprise alkanes or alkenes.

4. The composition of claim 1 having a viscosity index greater than 130 and viscosity at 100°C between 3 mm /s and 750 mm /s..

5. The compos ition of claim 1 having a C-,_Q fraction with a branch ratio below 0.19, viscosity index greater than 130 and pour point below -45 °C

6. The composition of claim 1 wherein the composition comprises the polymeric residue of 1-alkenes taken from linear Cg - C₂₀ 1-alkenes.

7. The composition of claim 6 wherein said 1-alkenes comprise Cg-C,, alkenes.

8. The composition of claim 6 wherein said polymeric residue comprises hydrogenated polymeric residue of said 1-alkenes .

9. The composition of claim 6 wherein said polymeric residue comprises poly 1-decene.

10. The compos it ion of claim 9 wherein the polymeric residue of 1-decene has a molecular weight of about 422.

11. The composition of claim 10 having a viscosity index of about 134 and a pour point less than -45 °C.

12. A liquid lubricant hydrocarbon compos ition having the recurring polymeric structure •55-

[-CH--CH-] 2 x

^n CH₃

where n is 3 to 17 and x is 5 to 500.

13. The composition of claim 12 vihere n is seven and average x is at least fifteen.

14. The composition of claim 12 having a viscosity index greater than 130 and a pour point less than -15°C.

15. A hydrocarbon composition useful as a lubricant comprising a mixture of C-,_Q alkanes consisting essentially of 9-methyl,ll-octylhenei cosane and 11-octyldocosane.

16. The composition of claim 15 wherein the mole ratio of 9-methyl,ll-octylhenei cosane to 11-octyl do cosane is between about 1:10 and 10:1.

17. The composition of claim 16 wherein said mole ratiois preferably about 1:2 to 2:1.

18. A hydrocarbon composition useful as a lubricant comprising alkanes having a branch ratio less than 0.19 and pour point below -15°C.

19. The composition of claim 18 wherein said alkanes have a viscosity between 3cs and 4cs at 100°C, viscosity index greater than 150 and pour point below -45 °C.

20. A composition of matter comprising 11-octyldocosane having the structure,

H CH₃(CH2)₁₀C(CH2)9CH₃ (CH₂)₇ CH₃ .

21. A lubricant composition comprising the

11-octyl do cosane of claim 20.

22. A process for the preparation of liquid hydrocarbons suitable as lubricant basestocks from alpha olefins containing 6 to 20 carbon atoms, or mixtures of such olefins, comprising: contacting said olefins under oligomerization conditions , at reaction temperature of about 90 to 250°C with a chromium catalyst on a porous support, which catalyst has been treated by oxidation at a temperature of 200°C to 900°C in the presence of an oxidizing gas and then by treatment with a reducing agent at a temperature and for a time sufficient to reduce said catalyst to a lower valence state; to obtain an oligomeric liquid lubricant compos ition comprising C,Q-C, ,QQ hydrocarbons, said composition having a branch ratio of less than 0.19 , weight average molecular weight between 420 and

45 ,000, number average molecular weight between 420 and 18 ,000, molecular weight distribution between 1 and 5 and a pour point below - 15°C.

23. The process of claim 22 wherein said reducing agent comprises CO , the oligomerization temperature is about 100-180°C, and the yield of C,Q oligomer is at least 85 wt% for product having a viscosity of at least 15cS at 100 °C.

24. The process of claim 23 wherein the support comprises porous s ilica.

25. The process of claim 23 wherein the oiefin consists essentially of 1-octene, 1-decene, 1-dodecene, 1-tetradecene or mixtures thereof .

26. The process of claim 22 wherein said catalyst is not subjected to a further oxidation step after said reduction.

27. The process of claim 22 wherein said oiefin comprises 1-decene, and the oligomer has a VI of 181 or greater and a branch ratio of from about 0.14 to 0.16.

28. A process for oligomerizing alpha oiefin to produce lubricant range hydrocarbon stock including the step of contacting said alpha oiefin with a supported solid reduced metal oxide catalyst under oligomerization conditions at a temperature of about 90 to 250 °C; said metal oxide_^ comprising a lower valance form of- at least one Group VIB metal, whereby the lubricant range hydrocarbon product has a branch ratio from about 0.10 to about 0.16 and a viscosity index of at least about 130.

29. The process of claim 28 wherein said alpha oiefin comprises olefinic hydrocarbon having 8 to 14 carbon atoms or mixtures thereof; wherein the process conditions include reaction temperature of about 100 to 180° ; and wherein said support catalyst includes a porous inert support having a pore opening of at least 40

Angstroms.

30. The process of claim 29 wherein the process conditions are controlled to oligomerize alpha oiefin without isomerizing double bonds therein.

31. The process of claim 29 wherein said catalyst comprises chromium oxide prepared by treating an oxidized chromium oxide with a reducing agent for a time sufficient to reduce said chromium oxide.

32. A process for oligomerizing alpha oiefin to produce lubricant range hydrocarbon including the step of contacting C₆~C_2Q alpha oiefin with a supported solid reduced metal oxide catalyst under oligomerization conditions at a temperature of about 90 to 250°C ; said metal oxide comprising a lower valance form of at least one Group VIB metal to produce lubricant range hydrocarbon product having a branch ratio from about 0.10 to about 0.16 and a viscosity index of at least about 130.

33. A process for oligomerizing alpha oiefin to produce lubricant range hydrocarbon stock including the step of contacting said alpha oiefin with a supported solid reduced chromium catalyst under oligomerization conditions at a temperature of about 90 to 250°C to produce liquid lubricant hydrocarbon comprising the polymeric residue of 1-alkenes consisting essentially of linear r - C₂₀ 1-alkenes, said composition having a branch ratio of less than 0.19 , weight average molecular weight between 420 and 45 ,000 , number average molecular weight between 420 and 18 ,000, molecular weight distribution between 1 and 5 and pour point below -15°C; and wherein the lubricant range hydrocarbon product has a viscosity index of about 130 to 280 and a viscosity up to about 750

2 mm /s(cs) .

34. The process of claim 33 wherein said alpha oiefin consists essentially of hydrocarbon having 8 to 14 carbon atoms or mixtures thereof ; wherein the process conditions include reaction temperature of about 100 to 180°C; and wherein said support catalyst includes a porous inert support.

35. The process of claim 35 wherein the oligomerization conditions comprise reaction temperature of about 90°-250°C and feedstock to catalyst weight ratio between 10 : 1 and 30 :1; said catalyst comprises CO reduced CrO, and said support comprises silica having a pore size of at least 40 Angstroms .