CA1167477A - Olefin dimerization - Google Patents

Abstract

Abstract of the Disclosure Internal olefins such as those obtained from a disproportionstion of l-olefins like l-decene are dimerized over a promoted boron trifluoride catalyst to yield oils useful as lubricant basestock.

Description

Th,is invention relates to the production of an oil from a specific oleEin. In another aspect, this invention rela-tes to the synthesis of an oil having a low pour point and being useful in lubrication. Still another aspect of this invention is a new dimerization reaction.
Background of the Invention Hydrocarbon conversions and particularly the reactions of olefins con~titute a very important section of the organic chemistry.
The l-olefins can be polymerized to high polymers, they can be alkylated to high octane fuels and they can be oligomerized to oils.
~ ubricating oils have been refined in recent years to match the increasing demands concerning their performance. Not only many addi-tives have been developed for lubricating oils, but also entirely synthetic oils have been produced wh-ich exhibit special properties not found in oils produced from crude petroleum alone.
One of the key features in many chemical reactions is the desired purity of the end product. This feature is particularly difficuIt to achieve in hydrocarbon conversion reactions. The larger the hydrocarbon molecules are, the more difficult it becomes to perform a reaction with only one or two reaction products resulting therefrom.
Particularly, producing a hydrocarbon oil with a well defined molecular weight and structure is a continuing goal in the petrochemical industry.
Such pure oils can then be used as such or blended into other mixtures with reproducible and reliable properties.

' Among the known hydrocarbon conversion reactions, dimeri~ation is of particular interest here. ~urthermore, the disproportionation (metathesis) reactions are important for this invention.
O]efin oligomerization and particularly dimerization reactions are well known in the art. These reactions start from 1 olefins, i.e.
hydrocarbons having a double bond at the end of a hydrocarbon chain. The dimerization reaction is normally carried out by contacting the l-olefin with a dimerization catalyst. One known procedure u~ilizes for instance l-decene and subjects it to an oligomerization in which dimers~ trimers, and tetramers are produced with respectively 20, 3~ and 40 carbon atoms in the molecule. One problem in this process is that a significant portion of each of these oligomers is produced and that the products there-Eore have a fairly wide spread of molecular weight.
Statement of the Invention It is an object of this invention to provide a new process for dimerizing a hydrocarbon with good selectivity.
Another object of this invention is to provide a process for combining 4 olefin molecules with high selectivity into a desired oil compound. Yet another objec~ of this invention is to provide a process for producing a hydrocarbon oil useful in lubrication from l-olefins.
Other objects, advantages, details, features and embodiments of this invention will become apparent to those skilled in the art from the following detailed description of the invention and the appended claims.
In accordance with a first embodiment of this invention a new hydrocarbon is provided which can be characterized as tetra-n-alkyl-ethylene having 28 to 44 carbon atoms per molecule with the proviso that the n-alkyl radicals have 4 - 13 carbon atoms. The new composition of matter can also be characterized by the structural formula Rl \ /R3 C = C
R2 / \ R4 wherein Rl, R~, R3 and R4 are n-alkyl radicals of 4 to 13 carbon atoms.
These new substituted ethylenes are oils -that prior to and particularly after hydrogenation are useful as lubricating oils. In addition these A '~ 7 substituted ethylenes are valuable in-termediates for the production of other organic chemicals.
The hydrogenated compounds are also believed to be novel composition and constitute another embodiment of this invention. These 1,1,2,2-tetra-n-alkyl-ethanes having 28 to 44 carbon atoms per molecule can be characterized by the formula Rl - C - R2 H

wherein the radicals R1 - R4 have the meaning defined above. The new compositions are as such useful as lubricating oils or can be blended with other ingredients to form lubricating oils. The preferred tetra-substituted ethylenes and ethanes are those in which the n-alkyl radicals R1 - R4 have 6 - g carbon atoms.
In accordance with a further embodiment of this invention it has been found that specific internal olefins can be converted into hydrocarbon oils with good selectivity to the desired oil by contacting these internal olefins with a promoted boron -~rifluoride catalyst under dimerization conditions. The present invention utilizes as the starting material for the dimerization process an internal olefin having the formula R-CH-CH-R' (1) In this form~la, R and R' can be the same or different and represent alkyl radicals having 4 to 12 carbon atoms.
Another embodiment of this invention resides in a process to produce a mixture containing a hydrocarbon oil useful in lubrication from a 1-olefin. This process comprises essentially the following three steps:
a) contacting at least one 1 olefin having the formula R"-CH=CH2 (2) wherein R" has the same meani.ng as R and R' above, with a disproportionation catalys-t under disproportionation conditions.
b) The unreacted 1-oleEins and -the lnternal olefin of the Eormula (1) above are then separated.
c) The internal olefin of the formula (1) above thus separated and being essentially free of unreacted l-olefins is then contacted with a dimerization catalyst under dimerization conditions to form a mix-ture containing the desired hydrocarbon oil.
Ideally the process of this invention can be illustrated by the formulae:
Metathesis:
R - CH = CH2 - Ra _ CH = CH - Rb ~ C2H4 Rb _ CH = CH2 Rc _ CH = CH2 c ~ CH = CH - Rd + C2H4 Rd _ CH = CH2 Dimerization:
Ra _ CH = CH - Rb Rl - C - R2 - ll Rc _ CH = CH - Rd R3 - C - R4 with two of the radicals Rl, R2, R3, R4, selected from Ra, Rb, RC, Rd, and the.other two of the radicals Rl - R4 selected from -CH2-Ra,.-CH2-Rb, -CH2-RC, -CH2-Rd. The number of carbon atoms in all four radicals Ra, Rb, Rc, Rd together being equal to the number of carbon atoms in all radicals of Rl, R2, R3, and R4 -together minus 2.
Metathesis Step In the disproportionation or metathesis step of the combined process of this invention alpha olefins can be used that have 6 to 14 carbon atoms. Examples of such olefins are he~ene-l, heptene-l, octene-l, nonene-l, decene-l, undecene-l, and dodecene-l. The octene, nonene, and decene homologs are particularly preferred. The normal isomers of these olefins are preferred, although small concentrations of branched isomers can be present. Branched alpha olefins reduce the viscosity index of the oil produced and hence are less desirable components of the starting material.
The initial step of the combined process is the metathesis or disproportionation of alpha olefins to produce a larger internal olefin as follows:

CH2=CHR ~ CH2=CHR~ C2H4 ~ RCN=C~

where R and R' are alkyl radicals, preferably n~alkyl radicals, having 4 to 12 carbon atoms. The preferred olefin feedstock is one in which R and R' are the same. In this reaction i-t is very desirable to prevent or minimize isomerization of the double bond in the olefin product. If a small de&ree of isomerization in the metathesis should occur, it is contemplated that this will not shift the double bond by more than two carbon atoms. In other words, R' in the i.nternal olefin may have one or two carbon atoms more (less) than R' of the starting l-olefin, and correspondingly R in such an internal olefin will then have one or two carbon atoms less (more) than R of the starting l-olefin, without leaving the scope of this invention.
Consequently the metathesis reaction is preferably effected at a mild temperature, and with a catalyst useful under mild disproportionation conditions, such as one comprising an oxide of rhenium. U.S. patent 3,676,520 discloses such a catalyst. The presently preferred disproportionation catalyst is Re207 on alumina.
The temperature for the metathesis reaction can be from about 0-50C; preferably it will be between 20-30C.
The pressure for the metathesis reaction can be from about 0.01 to 2 atmospheres absolute (l x 103 to 2 x 105 Pa). For convenience atmospheric pressure is preferred. These relatively low pressures permit continuous or frequent removal of the ethylene produced in the reaction.
Without its removal the internal olefin can be cleaved to regenerate the alpha olefins via the reverse metathesis reaction.
Olefln metathesis can be effected continuously or batchwise;
~5 for this process the batchwise mode is preferred. Using a catalyst as ~ lB~7~ 77 disclosed in the aboYe identified paten~, the weight ratio of alpha olefin to catalyst can range from l:l to 100:1. The preferred ratio is about 10:1 to 50:1. It is generally impractical to convert all the alpha olefins because of reaction rates. However, contact time between catalyst and olefin for batchwise reaction can range between about 1-1000 hours; preferably the contact time is 10-500 hours.
If continuous metathesis is to be effected, catalyst and conditions disclosed in U.S. patents 3,658,927 and 3,5~6,731 can be used.
The former teaches catalysts supported on alumina and the latter teaches catalysts supported on silica. These catalysts are treated with alkaline materials that reduce or destroy catalyst acidity that causes double bond isomerization as described in detail in U.S. patent 3,586,731. Use of the lower temperatures cited in these patents will help to minimize the undesirable isomerization.
The metathesis catalyst is separated from the hydrocarbon product in a rnanner that is well known in the art. Such a separation is, for instance, described in the U.S. patent 3,558,518, col. 9. Other possibilities for separating the disproportiona-tion catalyst from the hydrocarbons produced would be filtration or centrifu~ation where applicable.
Olefin Separation Step Following alpha olefin metathesis, unreacted alpha olefins are separated from the internal olefin product of that reaction.
Dis~illation provides a convenient way to make the separation and, unless ~5 the alpha olefins selected for the metathesis reaction contained too large a range of molecular weights, there will be a large break between the boiling point of the highest boiling alpha olefin and the lowest boiling internal olefin product.
This separation o the alpha olefins from the internal olefins for the preferred embodiment of this invention utilizing olefins with ~
to 10 carbon atoms is thus carried out by distillation in which the end point for alpha olefins at atmospheric pressure is not above about 175C
and the initial boiling point of the internal olefin is not below about 235C. The alpha olefin thus separated is preferably recycled to the metathesis step.

~ lB'7~7 Dimeri2ation Step The separated product of the metathesis reaction (which is essentially free of alpha olefins~ is converted by dimerization to compounds that are useful as lubricating oil basestock. The catalysts that can be used to effect dimerization, are promoted boron trifluoride catalysts. The alcohol-promoted boron trifluoride catalysts are preferred. Preparation and use of such catalysts as are disclosed in U.S. patent 3~780,12g, Col. 2, line 48 to Col. 5, line 15. The oligomerization of less reactive internal olefins in the invention is carried out at preferably higher temperatures than those disclosed in this patent. Although temperatures in the range -10 to 150C can be used for dimerization, the preferred range is about 40-80C. The other details concerning the catalyst composition and concentration~ method of effecting the reaction, time and pressure of reaction, removal of catalyst, and hydrogenation of the resulting hydrocarbon to produce a synthetic lubricant base stock from U.S. patent 3,780,128 is applicable to this step of the invention process also, and is herewith incorporated by reference.
The hydrocarbon oil produced as well as any unreacted internal olefin are then removed from -the dimerization catalyst. This separation is done by conventional techniques such as those described in U.S. patent 3,763,244. Other methods to separate the hydrocarbons from the catalyst are filtering or centrifuging.
Recover and Purification of the Oil Product Y
To obtain the desired physical properties in the synthetic lubricant it is frequently desirable to distill the mixture remaining after the dimerization step. The concentra~ion o~ unreacted internal olefin is generally small but, after removal of the alcohol-promoted boron trifluoride catalyst, it can be removed by distillation and returned to the dimerization process.
In the pxeferred embodiment of this invention this distillation step is done by heating the hydrocarbon mixture to a temperature usually in the range of 350C to 400C. The tempera~ure is between the boiling point of the highest boiling internal olefin and the boiling point of the lowest boiling dimer of the internal olefins.
Product having unacceptably high molecular weight preferably is removed by vacuum distillation. The hydrocarbon oil in ~his process is ~ 1 6 ~

removed as the distillate whereas the ~mdesirably high molecular weight product is remQved as the bottom product from a distillation column. The vacuum distillation is usually carried out under a pressure of 0.01 torr to 100 torr preferably 1-5 torr, and by heating the product ~o obtain a product that has a correc-~ed boiling point less than about 525C. The thus purified and evaporated oil is recondensed and recovered.
Prior to or af~er the vacuum distillation the oil produced is generally catalytically hydrogenated. This hydrogenation is done in a conventional procedure such as the one described in U.S. patent

2,270,303. Typical hydrogenation catalysts that can be used are Ni on alumina, cobalt molybdate on alumina, Pd, Pt, or Ru on alumina or carbon, but not acidic supports. The contacting of the oil produced with hydrogen and the hydrogenation catalyst is preferably carried out while the hydrocarbon oil is in the vapor phase as the distillate coming from the vacuum distillation for removing the hi8h molecular weight product described above.
Without undue limitation, the following examples describe further preferred details of this invention.
Example 1 Metathesis of five different alpha olefin compositions was made. All runs started with l-octene and/or l-decene which were contacted with 9 wt. % Re207 on alu~ina catalyst. The quantities of the ingredients as well as the reaction conditions are shown in the following table. Before each run the catalyst was activated by heating in flowing air at 450C for three hours, then flushed with nitrogen at that temperature for 20 minutes, and cooled. It was placed in an oven~dried oxygen-free flask which was then closed with a rubber serum closure.
Measured quantities of alpha olefin were added to the flask and it was allowed to stand at ambient temperature (about 25C). ~uring reaction the flask was vented via a hypodermic needle through the serum cap to permit ethylene produced in the metathesis reaction to escape. The product was separated from the catalyst by filtration. Table I
summarizes the five runs, including the composition of the product as determined by gas-liquid chromatography (G~C) at th~ times indicated.

~ 1~ 7 ~ 7 Table I
Run _I II III* IV* V VI
Feed composition, moles 51 Octene 2.6 - 3.0 0.51 0.50 1.0 0 1-Decene O - l.O 0.54 0.50 3.0 2.1 Wt. catalyst, g 44 - 50 32 50 50 44 Reaction time, hr66 90 90 20 40 90 92 116 Product analysis, wt. %
C - - tr 0.4 0.1 0.3 C8 33 0 32.524.7 17.6 8.8 6.8 Cg 0.3 0.9 0.5 0.2 tr tr C10 0.3 0.6 g.4 25.7 11.3 28.2 35.4 31.9 15 ~11 1.8 2.0 1.3 0.~ 0.8 0.4 0.8 0.8 C12 0.2 0.2 0.1 0.2 0.4 ~.8 0.7 C13 0.2 1.0 0 5 1.3 1.2 1.8 1.8 C14 ~4.3 61.934.1 10.4 15.1 2.9 0.5 0.4 C15 3 0.2 tr 0.3 0.8 1.2 2.0 2.4 20 C16 1.624.7 27.9 40.3 22.7 0.6 0.4 17 tr - tr 0.1 0.2 0.2 C18 4.1 16.5 21.3 35.7 57.4 61.0 C19+ - - - tr tr 0.1 0.5 0.4 1~01efin 25conversion, % 67.0 67.565.9 56.7 79.9 65.0 64.6 68.1 *Runs III and IV were made with a partial vacuum (~104 Pa) on the reaction flask to facilitate removal of ethylene. Abou~ 8 wt. ~ of C8~ 30 was also lost to the vacu~m during the reaction period.
The products anticipated from metathesis of these alpha olefins were produced with good selectivity at these conditions, namely, C14 from C from 1-decene, and C14, C16, and ~18 1-octene and 1-decene. The concentration of olefins having odd carbon numbers, which result from undesirable double bond isomerization, is low.
In runs I and VI the reaction mixture was analyzed at two different times. The results show that the reaction is not fast, but maintains its selectivity. Rlms III and IV were made at reduced pressure; run IV showed the highest alpha olefin conversion of all runs, at the relatively short reaction time of 40 hours.
Reac~ion mixtures from metathesis of l-octene and/or l-decene were subjected to distillation to separate the heavier metathesis product from the reactants. Table II summarizes ~he composition of the mixture after the ClO-fraction had been removed.

Tabel II
Run V VIII IX X XI_ Metathesis feed, mole %
l-Octene 100 75 50 25 0 l-Decene 0 25 50 75 100 Cll~ fraction, wt. %
C10 G.3 Cl1 1.2 0.6 ~12 0.4 0.6 Gl3 1.6 0.8 1.7 1.9 C14 94.~ 43.7 18.6 4.6 C15 0.5 0.6 1.0 1.8 2.1 C16 1.5 46.7 ~8.5 34.2 0.S
C17 0.2 0.2 0.4 0.6 C18 _ 8.0 28.5 56.1 95.8 Cl9* - _ 0.2 0-4 -~
Th~ Cl~t fractions from runs ~ XI above were dimerized with n~propanol-boron trifluoride catalyst. The dimeriæation reactions were made in a glass flask as follows. To the ~lask that had been swep-t with nitrogen measured amounts of the olefin mi~ture plus ligh-t paraffinic hydrocarbon diluent and n-propanol were added. The flask stood in a water bath on a hot plate, was fitted with a high speed stirrer, and was vented through a mercury manostat that permitted operation at about five cm. mercury above atmospheric pressure. Boron trifluoride was added as required to maintain the reaction pressure. Reaction was initiated by warming gently to about 40C, and was maintained at or near that temperature during the run. At the end of the run the ca-talyst was separa~ed in a separatory funnel from the hydrocarbon phase, and the ~ ~ ~7~

latter was washed with about 200 ml of an aqueous solu-tion oE a base, e.g., 1.3 normal sodium hydroxide or preferably 5 normal ammonium hydroxide, to remove dissolved boron trifluoride. The hydrocarbon was dried over activated 3A molecular sieve, filtered, then distilled (in vacuum) to separate a <410C fraction and a lube oil (410-510C) fraction. The lubricating oil fraction of the distillate was hydrogenated, after dilution with 100 ml of n-hexane, in an autoclave at 160C for two hours at 2.g x 106 Pa hydrogen pressure over 0.25g of 10~
palladium on caroon catalyst. After hydrogenation the hexane diluent was removed by distillation and the resulting lubricating oil was inspected by standard me-thods for pertinent physical properties. Table III
summarizes dimeriæation runs made with five different olefin mixtures and the propertiPs of the products that were obtained.

~ ~7~77 Table IIX
Run XII XIII XIV XV XVI
_ _ _ _ _ Metathesis product from run VII VIII IX X XI
Charge to dimerization reactor, g Olefin mixture 107.6 77.6 78.3 78.7 121.0 n-Hexane (diluent) 110.6 138.8 102.0 n-Heptane (diluent) 136.7 135.4 n-Propanol 2.3 2.4 3.2 3.2 2.3 Boron trifluoride ~2.7 ~~.8 ~3.7 ~3.7 ~2.7 Dimerization conditions Time, hr. o 7 7 ~ 7 Temp., C 40 24-46 24-47 20-43 40 Conversion of reac-tant oleEins, wt. % 80 7~ 77 70 76 Selectivity to, ~t. %:
~ights (IBP~410C) 7 5.5 5.4 2.5 2 Lube oil (410-510C) 81 84.8 82.3'; B0 77 Xeavies (>510C) 12 9.7 12.3 17.5 21 Properties of hydrogenated lube oil Viscosity, SUS at 100~ 101.7 101.7 125.0 116.4 133.2 Viscosi~y, SUS at 210F 39.7 4D.6 42.3 41.7 43.6 Viscosity Index 105 115 120 124 134 Pour point, C <-54 -54 -48 -37 -34 *415-520C

Example 2 Two dimerization runs were also made using an 85% phosphoric acid-boron trifluoride catalyst. One used an olefin feed having a composition resembling that from run IX in Table II. The other contained, in addition, heavier olefins from thP <410C fraction that had been isolated by distillation from a previous run. Table IV summarizes the ôlefin feed composition, dimerization conditions and results, and pertinent physical properties of the lubricating oil. In these runs a preformed catalyst was used, i.e., boron trifluoride was not addPd through the reaction period.

7~77 Table IV
Ru_ XVII XVIII
Composition of metathesis product used, wt. %
Cll 0.3 0.3 C12 0.4 0.3 cl3 1 . g 1 . 1 C14 21.~ 11.6 C 2.1 43.2 C1~ 48.1 43.2 C17 0.7 1.8 C18 25.2 32.1 6.9 C28+ 2.7 Charge to dimerization reactor, g n Hexane (diluent 107 141 Olefin mixture 208.5 247.3 52.5 wt. % BF3 in 85% H3P04 118.0 107.2 Dimerization conditions Time, hr. 6 8 Temp., C 30-43 30-60 Conversion of reactant olefins, wt. /O 82.4 44 Selectivity to, wt. %
Lights IBP~410C) 22.5 4.7 Lube oil (410-510C) 58.1 84.4 Heavies (~510C) lg.4 10.9 Property of hydrogenated lube oil Viscosity, SUS at 100F 109.6 130.g Vsicosity, SUS at 210F 41.2 42.7 Viscosity index 125 121 30 Pour Point, C -37 -32 *>520C

Properties of the lubricating oil obtained from using ~he phosphoric acid-boron trifluoride dimerization catalyst are very similar to those of the oil prepared from the n-propanol-boron trifluoride catalyst. However selectivity to lubricating oil from the phosphoric acid catalyst was lower than with the n-propanol catalyst.
These results from the use of phosphoric acid-boron trifluoride catalyst, which has for a long time been known to be active or olefin dimerization and polymerization show that the results when using an alcohol-boron trifluoride catalyst are unexpectedly superior to those using the phosphoric acid promoted boron trifluoride catalyst for making a lubricating oil.
Reasonable variations and modifications which will become apparent to those skilled in the art can be made fro~ this invention without departing from the spirit and scope thereof~

Claims (13)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A process for producing a hydrocarbon oil comprising contacting an internal olefin having the formula R-CH=CH-R' wherein R and R' which can be the same or different each represent an alkyl radical of 4-12 carbon atoms, under dimerization conditions with alcohol promoted boron halide as a dimerization catalyst to produce a mixture comprising said hydrocarbon oil which is a tetra-n-alkyl ethylene having 28 to 44 carbon atoms.

2. A process in accordance with claim 1 wherein a) at least one alpha olefin having the formula R"-CH=CH2 wherein R" has the same meaning as R and R', is contacted under disproportionation conditions with a disproportionatlon catalyst to produce a first product comprising unreacted alpha olefins and said internal olefin, b) said internal olefin and said unreacted alpha olefin are separated to form a second product comprising said internal olefin but being essentially free of unreacted alpha olefin, c) said second product is contacted with said dimerization catalyst.

3. A process in accordance with claim 2 wherein said disproportionation catalyst is an oxide of rhenium catalyst.

4. A process in accordance with claim 2 wherein said alpha olefin is one having 8, 9 or 10 carbon atoms.

5. A process in accordance with claim 2 wherein step b) is carried out by heating said first product in a heating zone to a temperature between the boiling point of said alpha olefin and the boiling point of said internal olefin to evaporate said unreacted alpha olefin and by withdrawing a stream containing alpha olefin vapors from said heating zone, both boiling points referring to that temperature at which the specified hydrocarbon boils at the operating pressure.

6. A process in accordance with claim 5 wherein at least a portion of said alpha olefin vapors is recycled to said disproportionation reaction in step a).

7. A process in accordance with claim 1 comprising a) removing said dimerization catalyst from said mixture to produce a hydrocarbon fluid, b) subjecting said hydrocarbon fluid to a distillation to remove unreacted internal olefin from said hydrocarbon fluid leaving a hydrocarbon liquid, c) subjecting said hydrocarbon liquid to a distilation at a temperature above the boiling point of the dimer of said internal olefin under the given pressure of the vacuum distillation to produce a purified hydrocarbon oil.

8. A process in accordance with claim 7 where said hydrocarbon oil prior to or after said vacuum distillation step c) is contacted under hydrogenation conditions with molecular hydrogen and a hydrogenation catalyst such as to remove essentially all of the olefinic unsaturation from the hydrocarbon oil.

9. A process in accordance with claim 2 wherein ethylene formed during the reaction of step a) is continuously removed from a reaction zone in which the disproportionation reaction of step a) is carried out.

10. A process in accordance with claim 1 wherein said dimerization catalyst is promoted boron trifluoride.

11. Tetra-n-alkylethylene having 28-44 carbon atoms per molecule the n-alkyl radicals being the same or different and having 4 to 13 carbon atoms.

12, 1,1,2,2-Tetra-n-alkylethane having 28 to 44 carbon atoms per molecule the n-alkyl radicals being the same or different and having 4 to 13 carbon atoms.

13. A composition of matter in accordance with claims 11 or 12 characterized in that two of the four n-alkyl radicals have the same number of carbon atoms and the other two each have one more carbon atom.