CA1284512C

CA1284512C - PROCESS FOR DIMERIZING .alpha.-OLEFINS

Info

Publication number: CA1284512C
Application number: CA000544409A
Authority: CA
Inventors: Lynn Henry Slaugh; Galeon Wayne Schoenthal
Original assignee: Shell Canada Ltd
Current assignee: Shell Canada Ltd
Priority date: 1986-08-15
Filing date: 1987-08-13
Publication date: 1991-05-28
Anticipated expiration: 2008-05-28
Also published as: JPH07116065B2; AU7683987A; AU604252B2; DE3766191D1; US4658078A; JPS6351340A; EP0257696A1; EP0257696B1

Abstract

A B S T RA C T
PROCESS FOR DIMERIZING ALPHA-OLEFINS

Process for preparing .alpha.-olefins CH2=C(R)CH2CH2R, R being C1-30-alkyl, cycloalkyl or cycloalkenyl, by dimerizing .alpha.-olefins CH2=C(R)H, at -60 to +280 °C, with a catalyst comprising a) a metallocene (cyclopentadienyl)2MY2, M being Zr or Hf and Y being H, halogen, C1-5-alkyl or C6-20-aryl, and b) an alumoxane, using an atom ratio Al to M from 1 to 100.

Description

P~D OESS POR DIMERIZING ALPHA--OLEFINS

The inventiQn relates to a process for the preparation of alpha-olefins hav mg the general formula I
H R H ~
H-C=C-C-C~R (I) H H
wherein R represents an aIkyl, cycloalkyl or cycloalkenyl grcup having in the range of from 1 to 30 carbon atcms by dimerization of an alpha-olefin having the general formula II
H R
H-C=C-H (II) wherein R has the same meanin~ as in the general formula I.
Products of the general formula I are useful as intermediates in preparing, for example, specialty detergents or lubricant additives.
10Metallocene/alumoKane catalysts are known in the art for producmg polymers from alpha-olefins. Kaminsky, in Chemical and Engineer News, July 4, 1983, pp 29-30 and in M~Xramol Chem., Rapid Ccmmun. 4, 417-421 (1983) discloses ziroonium and titanium metallo-cenes in ccmbination with alumaxanes as catalysts for the polymeri-15zation of olefins. U.S. patent specification 4,404,344 deals with the use of zirconium metallocenes in combination with alum~xanes as catalysts for the polymerization of ethylene and propylene or oopolymerization of ethylene with other alpha-olefins, respecti-vely, with which a controlled molecular weight distribution is obtaLned. This known process is carried out using an atom ratio aluminium to zirconium between 10:1 and 10~:1; in the sole example on polymerization of pr~ylene this atom ratio was 1.5x108:1.
European patent specification No. 128,045 deals with the use of at least tWD metallocenes in combination with alumDxane for polymerization of ethylene to products with a br~ad mDlecular weight distribution. Metallocenes disclosed are titanocenes, zircono-cenes, hafnocenes and vanadocenes.
A process of the type described in the beginning has now been found which surprisingly yields dimers with a very high selectivi-ty, little or no polymers being formed. The "selectivity to acertain compound" is defined herein as 100 a:b in which "a" is the amount of starting alpha-olefin of the general formula II that has been converted into that certain compound and "b" is the total amount of starting ocmpound of the general form~la II that has been converted.
Accordingly, the invention provides a process for the prepara-tion of alpha-olefins hav m g the general formula I
H R H H
H-C=C-C-C-R (I) H H
wherein R represents an alkyl, cycloaIkyl or cycloalkenyl group having in the range of from 1 to 30 carbon atcms by dimerization of an alpha-olefin having the general formula II
H R
H-C-C-H (II) wherein R has the same meaning as in the general form~la I, which process comprises contacting an alpha-olefin having the general form~la II at a temperature in the range of from -60 C to 280 C
with a catalyst ccmprising:-a) a metallocene having the general formula III
(cyclopentadienyl)2MY2 (III) wherein M represents a zirconium or hafnium atom and each Y
individually represents a hydrogen atom, a halogen atom, an aIkyl group having in the range of from 1 to 5 carbon atoms or an aryl group having in the range of from 6 to 20 carbon atcms, and b~ an alumoxane, the catalyst having an atom ratio of aluminium to M in the range of from 1 to 100.

In general, R can not be to~ bulky or dimerization rates areinhibited. The group R is too bulky if the carbon atcm with the free valence is a quaternary carbon atom. It is a routine matter to test a particular olefin with the catalysts use~ in the instant invention. Mixtures of alpha-olefins can be used as st~rting materials, resulting in various cross dimerization products.
Examples of starting olefins that have been utilized in the instant process are propylene, 1-butene, 1-hexene, 1-octene, 1-eicosene and 4-vinyl-1-cyclohexane. 3,3-Dimethyl-1-butene (neohexRne) was found to be unreactive alone but would cross dimerize with 1-octene.
Styrene, internal olefins and di-olefins were substantially unreactive in the instant process. Di-olefins, particularly conjugated di-olefins adversely affect the dimerization process.
The al~muroKanes (or alumoxanes) are well kncwn in the art and are polymeric alumunium compcunds which can be represented by the general formula (R-Al-O)n which is a cyclic compound and R(R-Al-O)n ~ , which is a linear ocmpound. In the general formLla, R represents an alkyl group having in the range of fro~ 1 to 5 carbon atoms such as, for example, methyl, ethyl, propyl, butyl and pentyl and n is an integer from 1 to about 20. Most preferably, R
represents a methyl group. Generaily, in the preparation of alumino-xanes from, for example, trimethylalummium and water, a mixture of the linear and cyclic compc~ni~ are obtained.
me alumincxanes can be prepared in various ways. Preferably, they are prepared by contacting water with a solution of a trialkyl-aluminium, such as, for example, trimethylaluminium, in a suitable organic solvent such as benzene or an aliphatic hydrccarbon. me solvents that can be used are well-kncwn and include the saturated aliphatic co~pounds such as butane, pentane, hexane, heptane, octane, isooctane and purified kerosenes; cycloaliphatics such as cyclobutane, cyclapentane, cyclohexane, cycloheptane, methylcycloheptane and the dimethylcyclopentanes; alkenes, such as prapylene, butene and l-octene; aramatic solvents such as benzene, toluene and the xylenes. The major requirements in the selection of a solvent are that it be liquid at reaction temperatures, that it L~
~ 63293-2~33 does not react with water or the aluminoxanes or interfere ~ith the desired dimerization reaction. The solvent must be oxygen-free. Hydroxy, ether, carboxyl, keto, and the like groups adversely affect aluminoxane production. A particularly suitable solvent is the olefin to be dimerized. For example, the alkylaluminium is treated with water in the form of a moist solvent or the alkylaluminium such as trimethylaluminium can be desirably contacted with a hydrated salt such as hydrated copper sulphat2 or aluminium sulphate.
The aluminoxane can be prepared in the presence of a hydrated copper sulphate. This method comprises treating a dilute solution of trimethylaluminium in, for example, toluene, with copper sulphate represented by the formula CuS04.5H20. The ratio of copper sulphate to trimethylaluminium is desirably about 1 mol of copper sulphate for 5 mol of trimethylaluminium. The reaction is evidenced by the evolution of methane.
In general, the molar ratio of alkylaluminium to water will be about 1:1 although variations of this ratio can occur without adversely affecting the aluminoxane product; i.e., the Al/water molar ratio can vary between 0.66:1 to about 2:1, preferably between about 0.75:1 to about 1.25-1. A continuous method for producing aluminoxanes is given in U.S. patent specification 3,300,458. Another suitable method involves the use of hydrated aluminium salts as given in U.S. patent specification 4,544,762. Another suitable method is to use water which has been ultrasonically dispersed in a solvent as described in Canadian patent application Serial No. 543,358, filed on July 30, 1987, or water which has been dispersed using high speed shearing as b.~

4a 63293-2833 descrihed in Canadian patent application Serial No. 543,355, filed on July 30, 1987.
Preferably each Y in the general formula III
individually repres0nts a hydrogen or chlorine atom or a methyl group. It is understood that the two Ys may be the same or different. ~is-~cyclopentadienyl~ zirconium dichloride is the preferred metallocene.

For the purposes of this invention, included with the definition of the above cyclopentadienyl mDiety is the lower alkyl(Cl-C5)-substituted, preferably the methyl-substituted cyclcpentadienyl moiety. Other metallocenes such as those containing titanium, S vanadium and niobium have been found not to w~rk adequately in the instant process.
In general terms, the catalyst is prepared by adding the alu~Qnoxane dissolved in an organic solvent, preferably the solvent utilized to prepare the alumlnoxane, to a well-stirred suspension of the metallocene ~n an orga m c solvent, which can be mert with respect to the catalyst system or, preferably can be the olefin which ccmprises the feed. When the stirred solution to which the aluminoxane has been added becomes homDgeneous, the catalyst has been formed, and if the feed olefin has ~een used as solvent, the dimerization reaction ccmmences.
Critical to the production of dimers rather than polymers is the selection of the particular metallocene and the particular atom ratio of Al to Zr in the catalyst. The atom ratio of Al to 2r ranges from l:l to l00:l preferably from l:l to 50:l. m e atom ratio of Al to Zr in the catalyst effects the selectivity and conversion in opposite ways AS the Al/Zr at~m ratio increases, the conversion and rate of reaction increases, but the selectivity to the dimer falls off. Also, as the number of carbon atoms per molecule of the alpha-olefin of the general formula II is increased, the Al/Zr atom ratio also must increase to provide equivalent results. Thus, a given Al/Zr atom ratio may be optimum for a given olefin feed, but not for a different olefin feed.
The dimerization reactlon is carried out in a conventional fashion. It may be carried out continuously in a stirred tank reactor wherein olefin and catalyst are added continuously to a stirred tank and reactant, product and catalyst are removed from the stirred tank with the product separated and the catalyst and used reactant recycled back to the stirred tank. Alternatively, the reaction may be carried out in a batch reactor, whereLn the catalyst, or the catalyst precursors, and reactant olefin are ~ ~,r~ S ~

charged to an autoclave, and after being reacted for an appropriate time, product is separated from the reaction mixture by conventio-nal means, such as distillation. The dimerization is preferably carried out at a temçerature in the range of 0 C to 150 C.
Pressures are not critical and can range from about 1 to about 506 bar or higher.
The following Examples further illustrate the invention.
Example 1 A typical catalyst was prepared in a dry box by adding 4.6 g of a solution of 25% by weight of trimethylalumdnium (16 mmol) in toluene to a magnetically stirred bottle containing 1.0 g ccpper sulphate pentahydrate (contaming 16 mmDl water) in 20 ml toluene.
After 15 min the gas evolution slcwed and slow stirring was star-ted. ~t 1.5 h the material was heated to 60 C and cooled. me liquid was withdrawn and added to a 100 ml autoclave cont~ning 0.29 g (1 mmol) bis(cyclopentadienyl)zirconium dichloride(Cp2ZrC12). Propylene (25 g, 0.6 mol) was charged to the autoclave, and the vessel heated at 40-46 C for 3 h. The pressure rose to a of 13.8 bar and drapped to a final pressure of 3.8 bar. The reactian product was removed and analyzed.
Conversion of the prcpylene was greater than 95%.
The selectivities to C6-olefins and to Cg-olefins were 95.8 and 4.2%, respectively.
NMR analysis of the C6-hydrocarbons shcwed the following oomposition:

Compcund ~ bv weight 2-methyl-1-pentene 95.8 2,3-dimethyl-1-butene 1.8 2-methylpentane 2.3 2,3-dimethylbutane 0.1 It can be seen that the C6-hydracarbons had a very high content of 2-methyl-1-pentene, being an olefin of the general foLmula I.

Example 2 A catalyst was prepared as described in example 1 except that the quantities were cut in half. The catalyst was added to l-octene (200 ml, 1.23 mol) in a 500 ml round bot~omed flask fitted with a magnetic stirrer, a thermometer and a nitrogen purged stopcock for sa~ple withdrawal. The flask was heated to about 33-40 C. After 24 h the conversion of 1-octene was 94.8%, with a selectivity to dimer of 92.6% and to trlmer of 3.0%. NMR shcwed the C16 consisted of more than 96% by weight of 2-hexyl-1-decene.
Exan~les 3-7 and Ccmpo~ ve Experiments A-C
Catalysts were prepared sImilar to Example 1 with varying Al:Zr ratios. mese catalysts were prepared from met~ylaluminoxane (from trimethylaluminium) and bis(cyclcpentadienyl)zirconium dichloride and were used to dimeriz~ propylene. me dImerization was carried out in a 100 ml autoclave, using 21-23 g propylene, a reaction temperature of 20-33 C and autogenous pressure. A
reaction time of 1 h was used. The results presented in Table I
hereinafter show that only at an atom ratio Al to Zr below 100 a high selectivity to dimers (C6) is cbtained.

~U~
o~ u~
o`p u~ ~ ~
c~
~ o ~ l-~ ~ ~ a~ o u~
o o o o ~
~p -~ ~ a~ o ~ co ~ u -l ~
t~
~ rr~ ~ ~ ~ O ~D
/
t~
~D a~D er ~ ~ ~ U~
~~ ~ ~ G~ O a~ o ~ 1-- 1` X C3 ~ ~ o In ~ In U~

o ~
N n~ ~ ~D ~r N ~r 0~ ~D O
~ D ~ ~ O

~1~
_I U ~ t-- U7 a ~ u~ ~ O O
~ ~ ~ 1 0 0 0 0 ~3 '~ ~
~ ~ ~ m u ~ _, Examples 8 and 9 and ~mparative ~erime_t D
These exFeriments show the effects of the atom ratio Al:Zr on the dimerization of propylene. Example 3 was repeated with a run time of 2 h inste~d of 1 h using toluene t20 ml), prcpylene (25-27 g), (cyclopentadiene)2 ZrC12 and methylalum moxane, a temperature of 35-47 C and autogenous pressure. The iso~er composition of ~he dimers was detenmined. The results observed after a reaction time of 2h and presented in Table II show that only at an atom ratio Al to Zr below 100 a high selectivity to dimers is obtained.

~ ~r~
~ ~ 0~ ~

~ ~ ,~
~ N I
~1 1~
U~ ~ ~ O
8 ~
.
rl N C~
dP
coc~ r-~ ~ uim ~D `

dP dP r~
~i ~ ~ U~
rl ~1 t~
~3 ~ O O ~ iP N
~, cn a~ 1- o o ~ O ~ ~ ~
dP a~
O
.~ U~ U~ U~
CO ~D O
C _I ~ I~ ~ O

.8.88 ~ ~I h a~ .~
~ ~ O ~ ~
~ ,_ ~

Examples 10-13 Catalysts were prepared similar to Example 1 with varying Al:Zr atom ratios. The catalysts were preparel frcm methylaluminoxane (from tri~ethylal D ium) and bis(cyclGpentadienyl)zirco m um dichloride and were used to dimerize l-octene. The results are shcwn Ln Table III.

T ,,~ .J

1~ o ~
~ ~ Il-) o a~ ~ ~ ~ N

~ ~D~O~
.........
~3 ~ .

.~ r~ o~
,~ o o o ~57 co oo a~ ~

ao 1` ~D O t~ N ,~ ~q o dP y 1~

H ~ ~ ~ CO ~ ~~ 0 0 0 , 9 0 ~ 4 ~ o i` o U~

~rC ~ ~
~ ~ ~ r x ~ ~
~.~
c) D ~ o b ~ ~ o l o~ O ~ o o o N ~ 0 ~
.~3 h ~o 4ol 0 0 z ~ 8 ~
~Ro ~ O ~
~ ~ U ~ ~

Examples 14-17 Catalysts were prepared similar to Example 1, from methylalu~lnoxane (from 4 mmol of trimethylaluminium and 5 mmDl of water) and bis(cyclopentadienyl)zirconium dichloride (various s amounts) and were used to dimerize l-hexene (400 mmol). Toluene (30 ml) was used as a solvent and the temperatNre was 40 C. The results are presented in Table IV.

; ~l s~

~ ~DS~

O ~rl 00 ~ N i-- O
~ ~ ~ ~ In ~r ~
.~

~ S~ u7 ~D ~ ~ ~ ~
.,1 a~

$ ~ ~ 1-- ~ CO ~ S`J
O ~r ~ ~1 ~ ~ ~ ,~ o u ~ Ir~ ~ N ~r 1~

O d~
o si~

v~-l u~ ~
~ ~3 o o o o ~ ~ ~

a~

iL ~ 1,3_,1~

Ex~n~les 18-20 and Comparative Rxperiment E
These experiments illustrate the differences in reactivities as the number of carbon atcms per molecule of the feed increases.
m e catalysts were prepared from methylalumLnoKane ~from trimethyl-aluminium) and bis(cyclopentadienyl)zirconium dichloride and had anatom ratio Al bo zr of 16:1. m e feeds were propylene, butene, 3-methyl-1-butene and 3,3-dimethyl-1-butene. TDluene (10 ml) was used as a solvent and a reaction temperature of 28-35 C was used.
m e results observed after a reaction time of 1.0 h are presented in Table V. m ey show that 3-methyl-1-butene can be dimerized, the vinyl grcup thereof being bound to a tertiary carbon atom. 3,3-Di-methyl-l-bute~e can not be dimerized, the vinyl group thereof being bound to a qu2ternary carbon atom and the tertiary butyl grGUp to which this vinyl g m up is bcund being too bulky.

TA~LE V

Conparative Example No. Experiment Feed Mmol Conversion, %

18 Propylene 476 49.4 19 l-butene 475 41.9 3-Methyl-1-butene 484 23 E3,3-Dimethyl-l-butene 480 0 Examples 21-23 Catalysts were prepared similar to Example 1 with differing alumQnoxane precursors and bis(cycloFentadienyl)zirconium dichlori-de at a Al:Zr ratio of 16:1. The experiments were carried out in a 100 ml autoclave, using 21-25 g prcpylene, 16 l of R3Al and 20 mmol of water from CuS04.5H20, 1.0 mm~l of (cyclopentadiene)2ZrCl2, a reaction te~perature of 35-45 C and autogenous pressure. m e results presented in Table Vl show ~hat the highest conversion is obtained with trimethylaluminium.

i~ Y~ 'L~

o ~
3 ~ ~ o lo I
~ Io .~

~ oo ~ ~r X
O d~
s~ o ~ a~
~ o æ

Z ~ ~.p Example 24 Bis(cycloFentadienyl)zirconium dimethyl (0.5 mmol), alumLno-xane (4 mmol) and 1-octene (50 ml) were heated in the stirred round bottcmed flask at 40 C for 1 h. Anal~sis of the reaction product shoNed a 19.1% conversion of l-octene, with a selectivity to octene dimer of 72.2% and bo octene trimer of 19.7%.

Example 25 Bis(cyclopentadi~nyl~zirconium hydrogen chloride (1 D 1), alun~noKane (3 mmol) and l-butene (0.47 mol) were heated in an ]0 autcclave at 70 C for 1 h. Analysis of the reaction product shcwed a 20% ccnversion of 1-butene, with a selectivity to dimer of 96%
and to trimer of 4%.

Example 26 ~ is(cyclopentadienyl)zirconium hydrcgen chloride (1 mmDl), alu=:ncxare (4 D 1) and l-octene (50 ml) were heabed in an auto-clave at 40 C for 1 h. Analysis of the reaction product shcwed an 8% conversion of the l-octene, with a selectivity to the dimer of 72% and to the trimer of 1.5%.

Examples 27-33 In these experiments various amounts of water were used to prepare the alumincNa=e and the results on the dimerization cata-lysts were measured.
The catalysts were prep~red as follows: 20 ml of dry toluene were placed in a bottle fitted with a nitrogen purge system and the bottle was placed in an ultrasonic bath (Branson). Ihe ultrasonic was started and the designated amount of water was added through a hypodermic syringe. After a five min period of sonification, 4 D 1 of trimethylaluminium (as a 25% by weight solution in toluene) was added. After the reaction was co~pleted (as evidenced by termina-tion of gas evolution~, 50 ml of 1-octene and 0.5 mmol of bis-(cyclopentadienyl)zirconium dichloride was added and the mixtures were heated to 40 C. After 30 min samples were removed for analysis. m e results sl~ecified in Table VIII show that the highest conversions of l-cctene are obtained at an Al:water m~lar ratio between 0.75:1 and abou~ 1.25:1.

IABLE VIII

Example Waber, Al~Water Cbnversion No. mm~lmolar ratio _ _ of l-octene, %

27 3.0 0.75 37 28 3.2 0.8 57 29 3.6 0.9 72 3.9 0.975 67 31 4.0 1.0 49 32 4.2 1.05 29 33 4.7 1.175 12

Claims

1. A process for the preparation of alpha-olefins having the general formula I

(I) wherein R represents an alkyl, cycloalkyl or cycloalkenyl group having in the range of from 1 to 30 carbon atoms by dimerization of an alpha-olefin having the general formula II
(II) wherein R has the same meaning as in the general formula I, which process comprises contacting an alpha-olefin having the general formula II at a temperature in the range of from -60 °C to 280 °C
with a catalyst comprising:-a) a metallocene having the general formula III
(cyclopentadienyl)2MY2 (III) wherein M represents a zirconium or hafnium atom and each Y
individually represents a hydrogen atom, a halogen atom, an alkyl group having in the range of from 1 to 5 carbon atoms or an aryl group having in the range of from 6 to 20 carbon atoms, and b) an alumoxane, the catalyst having an atom ratio of aluminium to M in the range of from 1 to 100.

2. A process as claimed in claim 1 wherein each Y in the general formula III individually represents a hydrogen or chlorine atom or a methyl group.

3. A process as claimed in claim 1 wherein M in the general formula III represents a zirconium atom.

4. A process as claimed in claim 3 wherein the metallocene of the general formula III is bis(cyclopentadienyl) zirconium dichloride.

5. A process as claimed in claim 1, 2 or 3 wherein the atom ratio of aluminium to M is in the range of from 1 to 50.

6. A process as claimed in claim 1, 2 or 3 which is carried out at a temperature in the range of from 0°C to 150°C.