Note: Descriptions are shown in the official language in which they were submitted.
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Case 8711(2)
LUBRICATlNG OILS
This invention relates to a process for the production of lubricating oils
from a mixed feedstock comprising 1 -olefins having 5 to 18 carbon atoms.
It is well known to oligomerize 1-olefins to hydrocarbons of higher
molecular weight and then to hydrogenate or isomerise the oligomer so formed to
produce lubricating oils (See eg) US-A-3763244. In most ofthese cases, the 1-
olefins are derived initially frorn ethylene (by the so called "ethylene chain growth
and displ~c.em~nt" method) which is a relatively expensive source for such 1-
olefins. Moreover, lubricating oils have been produced by oligomerization of
relatively pure 1-olefins (see US-A-3780128 and EP-A-0 468 109). This last
document also discloses that once the oligomers have been produced, the
oligomers of various 1-olefins can be blended either before or after the
hydrogenation or isomerization steps in order to produce the lubricating oils of the
desired properties such as viscosity index and pour point. For instance, a
feedstock co~ g substantially pure olefin such as eg 1-decene gives rise to a
lubricant having a relatively high viscosity index but these products comprise
exclusively of units which are multiples of 10 as would be expected of oligomers of
decene and predominate in discrete units having 30, 40, 50? 60 and 70 carbon
atoms. Such a blendl whilst suitable for some purposes, is not an ideal synthetic
lubricant since it is desirable for the molecular weight distribution of the
components in a synthetic lubricant blend to sim~ te those of a mineral oil in their
dispersity index7 ie a standard deviation curve so that there is continuity and
gradual blending of the components in the mixture of products. The molecular
weight distribution ofthe products from discrete multiples of 10 described abovedo not resemble a standard deviation curve and would therefore lack the
2 5 consistency of properties due to absence of a continuity and gradual blending of
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closely related oligomers. That is? the blend lacks consistency of properties due to
the absence of a continuity and gradual blending of closely related/m~tclled
oligomers. Furthermore, the use of a relatively pure single olefin is relativelyexpensive. It is also known to oligomerize the olefinic products from a Fischer
s Tropsch synthesis followed by hydrogenation or isomerization of the o!i~omer to
form lubricating oils (see eg Monoolefins? Chemistry & Technology, by F Asinger,pp 900 and 1089 (1968) and published by Pergamon Press). However, these
publications relating to use of the Fischer Tropsch products as the source material
for the oligomel i~lion step do not indicate the product mix required to achieve the
10 desired oligomer or the catalyst suitable for the oligo,lleli,~lion step. In our prior
published EP-A-0583072 we have claimed and described a process for the
catalytically oligomerising an olefinic feedstock comprising a mixture of C5 to C18
olefins but having at least 6% w/w of l-hexene and at least 2.6% w/w of 1-deceneto lubricating oils.
It is therefore the object of the present invention to look at feedstock which
would firstly meet the criteria of forming a product with the right blend of
components but would also be producible from a relatively inexpensive and
commercially available raw material. One such feedstock is the mixture of olefins
from a Fischer Tropsch synthesis which is readily available. However, the choice20 ofthe feedstock alone is insufficient to achieve this objective since it is also
necessary to identify a catalyst system and the oligomerisation conditions whichwould give rise to the right blend of oligomers.
It has now been found, for instance, that a mixture of 1-olefins which is
commercially available eg from conventional Fischer Tropsch processes is a very
2 5 desirable feed for the oligomerization step and the oligomers thus formed can be
converted to lubricating oils by using specific catalysts.
Accordingly, the present invention is a process for the production of
lubricating oils having a viscosity index of at least 120 and a pour point of -45~C or
less, said process comprising oligomerizing a feedstock comprising one or more C5
30 - C18 1-olefins in the presence of an oligomerization catalyst comprising an ionic
liquid to form a lubricating oil.
The 1-olefin feedstock comprises one or more olefins having 5-18 carbon
atoms, preferably from 6-12 carbon atoms. A particularly plere-led example of
such a feedstock is the olefin stream formed by the Fischer Tropsch synthesis.
35 Such an olefin feedstock is preferably a mixture of olefins.
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Normally in a Fischer Tropsch synthesis (hereafter "FTS"), a mixture of
carbon monoxide and hydrogen is passed over or through a heated catalyst bed to
form a wide variety of hydrocarbons. When the hydrogen content of the reactant
mixture is high, the reaction products predo~llinanlly contain palarrlllic
hydrocarbons. However, if the proportion of hydrogen in the reaction mixture is
low, the reaction products predom;l1al-lly contain olefinic hydrocarbons.
It is, however, important that even in the case where the reaction products
of the FTS are predo-.linalllly olefins, the reaction conditions of the FTS have to be
controlled to obtain the desired mixture of 1-olefins. For instance, Gasol derived
by FTS and described in "Mono-olefins Chemistry & Technology", by F Asinger,
page 1089 (1968), published by Pergamon Press, contains about 50% but-2-ene
and is said to give poor lubricating materials on polymerization with alllmini~lm
chloride. Thus, any unspecified product mix of an unspecified FTS is unlikely tobe suitable as feedstock for the process of the present invention. If the products of
an FTS are used as feedstock, the FTS can be operated in such a manner that the
olefin products of the synthesis contain predominantly a mixture of C7-C10 1-
olefins. One such FTS product contains at least 2.6% w/w of 1-decene, preferablyat least 7% w/w, and at least 6% w/w of 1-hexene, preferably at least 13% w/w.
Such a product mix can be obtained by the conventional FTS processes in which
the conditions of operation should be so controlled that the product has a Schulz-
Flory alpha value from 0.6 - 0.9, preferably from 0.7 - 0.8. The Schulz-Flory alpha
value is a well recognised concept and is defined eg by P J Flory in "J Am Chem
Soc", 58, 1877 (1950)1 and by G V Schulz in "Z Phys Chem", B43, 25 (1935).
This value can be defined by the followi~g equation:
log[Wn/n] = nloga + [(1-a)2/a]
where Wn is the weight fraction, n is the carbon number and a the probability ofchain growth.
In this context the choice of the oligomerization catalyst used is very
important. Whilst any of the conventional cationic polymerization catalysts can be
used for oligomerization in general, it is essential that an ionic liquid catalyst is
used if a lubricating oil of higher viscosity than that achievable by conventional
catalysts is desired.
Ionic liquids are primarily mixtures of salts which melt below room
temperature. Such salt mixtures include (a) aluminium or gallium compound in
combination with one or more of (b) imidazolium halides, pyridinium halides or
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phosphonium halides and the latter may be further substituted by alkyl groups.
Thus, the ionic liquid catalyst used may comprise (a) an aluminium or gallium
compound which is suitably a tri-halide, such as aluminium trichloride or gallium
trichloride, or, an alkyl aluminium/gallium dihalide such as an alkyl
s ~ minil~m/gallium dichloride or a dialkyl aluminium/gallium halide and is
p,el~-~bly ethyl aluminium/gallium dichloride. The component (b) in the ionic
liquid is suitably a hydrocarbyl substituted imidazolium halide, a hydrocarbyl
substituted pyridinium halide, an alkylene substituted pyridinium dihalide and/or a
hydrocarbyl substituted phosphonium halide. Specific examples of component (b)
include 1-methyl-3-ethyl imidazolium chloride, 1-ethyl-3-butyl imidazolium
chloride, 1-methyl-3-butyl imidazolium chloride or bromide, 1-methyl-3-propyl
imidazolium chloride, ethyl pyridinium-chloride or bromide7 ethylene pyridinium
dichloride or dibromide, butyl pyridinium chloride, benzyl pyridinium bromide and
the like. Methods of pl epal alion of these and other higher alkyl substituted
imidazolium halides are described in our prior published EP-A-0 558 187 and WO
95/21871. Furthermore, ionic liquids which are ternary melts and comprise in
addition ammonium salts such as those described in our prior published WO
95/21872 can also be used. The ionic liquids described in these prior publications
are incorporated herein by reference.
The relative ratios ofthe two components (a) and (b) in the ionic liquid
should be such that they are capable of ~ e-llaining in the liquid state under the
reaction conditions. Typically, the relative mole ratio of aluminium/gallium
compound to the component (b) in the ionic liquid is suitably in the range from 1:
2 to 3: 1, preferably from 1.5: 1 to 2: 1. Within this range, the amount of
component (a) is preferably greater than 50 mole % of the total ionic liquid.
It is also important to control the ratio of the catalytic components to the 1-
olefin in the feed. For instance, if the 1 -olefin feed in the mixture comprises a
blend of C6-C10 1-olefins, the mole ratios of olefin to the aluminium and/or
gallium halide in the ionic liquid may suitably vary in the range from 1: 1 to 300: 1
, preferably from 10: 1 to 200 :1.
The precise concentration of the two catalytic components chosen would
depend upon the specific property desired in the final lubricating oil such as eg the
viscosity.
The oligomerization is suitably carried out at ambient temperature, eg
temperatures at or below 30~C, preferably around -20 to +20~C. The reaction
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pressures can be ambient or elevated.
The oligomerization is suitably carried out in the presence of a solvent inert
under the reaction conditions, preferably a pa~ a~ liC hydrocarbon eg n-hexane.
- It is preferable to add the ionic liquid catalyst to the l-olefin fee-lstor~ and
s is preferably added dropwise with continuous stirring. After the addition of the
catalyst, the reaction mixture is allowed to stand for a duration to effect
oligomerisation and the reaction mixture can thereafter be neutralised eg by
bubbling ammonia therethrough, then diluted by addition of water. This step of
neutralisation and dilution with water may be avoided since the ionic liquid forms a
separate phase from the reaction mixture when allowed to stand and can be
separated by simple dec~nt~tion. This is a further advantage over the process
using conventional catalysts such as tertiary butyl chloride and alkyl alllmini~.m
halides which are soluble in the reaction mixture. The organic products can thenbe rendered free of the inert solvent by eg rotary evaporation. The above steps
can be, if desired7 carried out in continuous operation.
The resultant residue is an oligomer. This oligomer is a lubricating oil with
important and desirable prope, lies but may contain a small proportion of olefinic
groups.
The oligomerisation products of the present invention are excellent
lubricants and can be used as such or for blending with other additives in a
lubricating oil. The products of the present process can have pour points of up to -
60~C and viscosity index values above 155, eg 198. These viscosity index values
are superior to those achievable by using conventional catalysts.
The present invention is further illustrated with reference to the following
2 5 Examples:
EXAMPLES:
The ionic liquid used was prepared by adding aliquots of aluminium
chloride solid with stirring to l-ethyl-3-methyl imidazolium chloride solid in a mole
ratio of
2: l respectively with cooling to 8~C. The mixture was then heated to 60~C with
stirring. The resultant ionic liquid was cooled and stored in a glove box.
The 1-olefin feedstocks used for these Examples were either single olefins
or mixtures eg ~ffin~te II was mixed with l-decene in various ratios as shown inthe Tables below.
The catalysts were tested in a glass autoclave cooled to -5~C. A heptane
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diluent was used to reduce reaction exotherms, typically 350 g of heptane were
used. In the Examples, 450g of the olefinic feedstock was used (typically
comprising 225 g each of R~ffin~te II and 1-decene). The feedstock was added to
the heptane with stirring (at 1000 rpm). Molecular sieves (about 10 g) were added
5 to dry the reaction mixture prior to the addition of the catalyst.
When using the ionic liquid catalyst according to the invention, 5 ml of this
catalyst was added to the reaction mixture with stirring.
When using a tertiary butyl chloride/ethyl alllminillm dichloride catalyst
(co~ .al~ti~/e test, not according to the invention), 13 g oftertiary butyl chloride
10 was added rapidly to the reaction mixture followed by dropwise addition of 15 ml
of a 1 molar hexane solution of ethyl aluminium dichloride with stirring.
Following the reaction, the catalyst was neutralised by bubbling ammonia
through the reaction mixture for 1-2 minutes, followed by addition of 100 ml of
water. [This step was used for both the catalyst systems to compare like with like
15 although when using an ionic liquid this step can be elimin~ted since ionic liquids
form a separate phase from the reaction mixture and hence can be readily separated
by dec~nt~tion unlike the tertiary butyl chloride/ethyl al~lmini~lm dichloride catalyst
which is soluble in the reaction mixture].
After washing, the solvent and light polymers were removed by rotary
20 evaporation at 100~C under vacuum. The resultant products were analysed and the
following results were obtained:
Table 1 - Using Ionic Liquid Catalyst:
Ex. 1-Decene R~ffin~te II KV (40) KV(100) VI Pour Point Yield %
No (g) (~) cSt cSt (~C)
0 475 47.95 6.75 92 -51 76
2 113 338 35.15 6.39 135 <-50 74
3 225 225 45.2 8.21 159 <-53 90
4 338 113 17.22 4.57 198 <-49 nd
2 5 nd - not determined
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Table 2 - Using TertiaN, Butyl Chloride/Ethyl Aluminium Dichloride Catalyst:
CT 1-Decene R~ffin~te II KV (40) KV(100) VI Pour Point Yield
No (~ ) cSt cSt (~C)
0 450 22.5 4.1 65 <-52 82
2 113 338 33.5 5.92 121 -51 56
3 225 224 55.1 8.76 136 -57 84
4 338 113 58.9 9.69 149 <-51 90
450 0 62.1 11.04 172 -57 97
CT - Comparative Tests, Not according to the invention.
s
The above data clearly show by using an olefinic feedstock comprising 1-
decene with or without Raffinate II, ionic liquid catalysts produce a synthetic
lubricant of a higher viscosity index than that achievable using a conventional
tertiaN butyl chloride/ethyl aluminium dichloride catalyst. Moreover, in the case of
10 E~ffin~te II/1-decene mixed feed, the ionic liquid catalyst can produce a synthetic
lubricant having a VI > 120 for as little as approximately 20% w/w ofthe 1-decene
comonomer.
Examl~le 5
A solution of mixed C6 10 olefins was prepared as follows:
204g (2.429 moles) I-hexene
158 g (1.411 moles) 1-octene
113 g (0.807 moles) 1 -decene
The solution of 460 g mixed olefin (4.647 moles olefin) was added to 213 g
heptane solvent with stirring (1000 rpm) and cooling to -5~C.
Ionic liquid preparation was as follows: 130.0 g of solid aluminium chloride
were added slowly with stirring to 71.5 g of 1-ethyl-3-methyl-imidazolium chloride
solid with cooling to 8~C. The mixture was then heated to 60~C for 1 h, then
transfered to a glove box. The resultant ionic liquid consisted of 66 mol% AIC13.
5ml of ionic liquid catalyst (7.0 g = 0.0509 moles) was added dropwise to the
25 reaction mix. Thus, feed:catalyst ratio was 91.3. An exotherm of+7~C was
obseNed upon catalyst addition. The reaction was allowed to proceed for 3h.
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Following reaction, catalyst neutralisation was effected by bubbling with
ammonia for 1-2 mins? followed by addition of 100 ml water as previously. After
washing, solvent and light polymer were removed by rotary evaporation at 100~C
under vacuum.
5 Table 3 - Using Ionic Liquid Catalyst:
Ex No. KV(40) KV(100) VI PP Yield
cSt cSt ~C %
5 151.3 19.85 152 -45 88
The data clearly show that the ionic liquid catalyst can produce synlube having a
viscosity index above 150 cSt and a pour point of-45~C from a mixed 1-olefin feed
o in which each of the olefins have more than five carbon atoms.
