Note: Descriptions are shown in the official language in which they were submitted.
3 l ii~
D# 80,963-F
RRS
PROCESS FOR OLIGOMERIZING OLEFINS USING
HETEROPOLY ACIDS ON INERT SUPPORTS
(D# 80, ~63 -F)
Backqround of the Invention
Field of the Invention
The invention relates to the preparation of synthetic
lubricant base stocks, and more particularly to synthetic lubricant
base stocks made by oligomerizing long-chain linear olefins.
Descri~tion of Related Methods
Synthetic lubricants are prepared from man-made basa
stocks having uniform molecular structures and, therefore, well-
defined properties that can be tailored to specific applications.
Mineral oil base stocks, o~ the other hand, are prepared from crude
oil and consist of complex mixtures of naturally occurring
hydrocarbons. The higher degree of uniformity found in synthetic
lubricants generally results in superior performance properties.
For example, synthetic lubricants are characterized by excellent
thermal stability. As automobile engines are reduced in size to
save weight and fuel, they run at higher temperatures, therefore
requiring a mor~ thermally stable oil. Because lubricants made
from synthetic base stocks have such properties as excellent
oxidative/thermal stability, very low volatility, and good
viscosity indices over a wide range of temperatures, they offer
better lubrication and permit longer drain intervals, with less oil
vaporization loss between oil changes.
Synthetic base stocks may be prepared hy oligomerizing
internal and alpha-olefin monomers to form a mixture of dimers,
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1,'
`' : -' , ' 'i, , , : - ~:
~ 3~
trimers, tetramers, and pentamers, with minimal amounts of higher
oligomers. The unsaturated oligomer products are then hydrogenated
to improve their oxidative stability. The resulting synthetic base
stocks have uniform isoparaffinic hydrocarbon structures similar to
high quality paraffinic mineral base stocks, but have the superior
properties mentioned due to their higher deqree of uniformity.
Synthetic base stocks are produced in a broad range of
viscosity grades~ It is common practice to classify the base
stocks by their viscosities, measured in centistokes (cSt) at
100C. Those base stocks with viscosities less than or equal to
about 4 cSt are commonly referred to as "low viscosity" base
stocks, whereas base stocks having a viscosity in the range of
around 40 to 100 cSt are commonly referred to as "high viscosity"
base stocks. Base stocks having a viscosity of about 4 to about 8
cSt are referred to as "medium viscosity" base stocks. The low
viscosity base stocks generally are recommended for low temperature
applications. Higher temperature applications, such as motor oils,
automatic transmission fluids, turbine lubricants, and other
industrial lubricants, generally require higher viscosities, such
as those provided by medium viscosity base stocks (i.e. 4 to 8 cSt
grades). High viscosity base stocks are used in gear oils and as
blending stocks.
The viscosity of the base stocks is determined by the
length of the oligomer molecules formed during the oligomerization
reaction. The degree of oligomerization is affected by the
catalyst and reaction conditions employed during the
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: :
oligomerization reaction. The length of the carbon chain o~ the
monomer starting material also has a direct influence on the
properties of the oligomer products. Fluids prepared ~rom short-
chain monomers tend to have low pour points and moderately low
viscosity indices, whereas fluids prepared from long-chain monomers
tend to have moderately low pour points and higher viscosity
indices. Oligomers prepared from long-chain monomers generally
are more suitable than those prepared from shorter-chain monomers
for use as medium viscosity synthetic lubricant base stocks.
one known approach to ollgomerlzing long-chain ole~lns to
prepare synthetic lubricant base stocks is to contact the olefin
with boron trifluoride together with a promotor at a reaction
temperature sufficient to e~fect oliyomerization of the olefin.
See, for example, co-assigned U.S. Patent Nos. 4,400,565;
4,420,646; 4,420,647; and 4,434,308. However, boron trifluoride
gas (BF3) is a pulmonary irritant, and breathing the gas or fumes
formed by hydration of the gas with atmospheric moisture poses
ha2ard-~ preferably avoided. Thus, a method for oligomerizing long-
chain olefins using a less hazardous catalyst would be an
improvement in the art.
Applicants have discovered, surprisingly, that a high
conversion of long-chain olefin to oligomer may be obtained by
contacting the olefin with a catalyst comprising a heteropoly acid
on an inert support. In addition to being excellent catalysts,
these heteropoly acids on inert supports are less hazardous and
more easily handled than boron triflouride.
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; , ,.~ . . ~ , : .
Summary of the Invantion
The invention relates to a process for the preparation of
oligomers, comprising contacting a linear olefin containing from 10
to 24 carbon atoms with a heteropoly acid on an inert support.
Description of the Preferred Embodiments
The olefin monomer feed stocks used in the present
invention may be selected from compounds comprising (1) alpha-
olefins having the formula R"CH=CH2, where R" is an alkyl radical
of 8 to 22 carbon atoms, and ~2) internal olefins having the
formula RCH=CHR', where R and Rl are the same or different alkyl
radicals of 1 to 21 carbon atoms, provided that the total number of
carbon atoms in any one olefin shall be within the ranye of 10 to
24, inclusive. A preferred range for the total number of carbon
atoms in any one olefin molecule is 12 to 18, inclusive, with an
especially preferred range being 14 to 16, inclusive. Mixtures of
internal and alpha-olefins may be used, as well as mixtures of
olefins having different numbers of carbon atoms, provided that the
total number of carbon atoms in any one olefin shall be within the
range of 10 to 24, inclusive. The alpha and internal-olefins to be
oligomerized in this invention may be obtained by processes well-
known to those skilled in the art and are commercially available.
The oligomerization reaction may be represented by the
following general equation:
catalyst
nCmH2m ----~ ~~~~~~> CmnH2w~
;
~, ~3 A ~ ~ i''1 ,J
where n represents moles of monomer and m represents the number of
carbon atoms in the monomer. Thus, the ol1gomerization of l-decene
may be represented as follows:
catalyst
nC10H20 ----~ ~~~~~~> ClOnH20n
The reaction occurs sequentially. Initially, ole~in monomer reacts
with olefin monomer to form dimer~. The ~imers that are formed
then react with additional olefin monomer to form trimers, and so
on. This results in an oligomer product distribution that varies
with reaction time. As the reaction time increases, the olefin
monomer conversion increases, and the selectivities for the heavier
oligomers increase. Generally, each resulting oligomer contains
one double bond.
The heteropoly acid component of the catalysts used in
the subject reaction may be selected from a class of acids formed
by the condensation of two or more inorganic oxyacids. For
example, phosphate and tungstate ions, when reacted in an acidic
medium, are condensed to form 12-tungstophosphor$c acid, a typical
heteropoly acid ~HPA), as demonstrated in the following equation:
Po43 ~ 12 W042 ~ 27 H ---- > H3PW12040 ~ 12 H20
The central atom of the HPA anion, also called the heteroatom (P in
the equation above), may be selected from a wide variety of
elements ranging from Group I to Group VIII. The nature of the
heteroatom is a factor which determines both the condensation
structure and the physical properties of the HPA. Atoms
coordinated to the heteroatom via oxygen atoms are called polyatoms
(W in the equation above), and in most cases are any one of such
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species as molybdenum, tungsten, niobium and vanadium. The nature
of the heteroatoms, condensation ratios and chemical formulas for
typical heteropoly acids are exempli~ied ~y the heteromolybdate
anions described in Table I, below~
TABLe I
Heleromolybdate Anions
Condens~tion R~tios Heten:)atoms (X) Chem;cal Fo~mulas
1:12 K~Rgin slructure p~t As~+. Si4~, Gc~ [X Mol20
Sih~ on stmcture ceJ~, Th~ tX:~ Mol~O,~
1:11 Ke~gin structure P~, As5~, Si~+, Ge4~ lxn~Mollo39] ~12. ~)
(decomposition)
2:18 Dn~son slructure Ps~ MolaO
1:9 Waugh structure Mn~, Ni~ IX~M~
1:6 t~ndelson stNcture
pe) Te~, 171' 1Xn~Mo~sO2~1-(12n)
(~ Iype) Co~' A13~ C~ XI~M~02~H6~ s' )
~:12 As5~ 54M01~~21'~'
2:5 p5~ IP2Mo~ul
-
Anions containing the Keggin structure have a condensation ratio of
1:12. The synthesis of these HPA's is well documented in the
literature (see, for example, U.S. Pat. No. 3,947,332 (1976),
incorporated herein by reference).
To oligomerize 10 to 24 carbon atom olefins, suitable
heteropoly acid catalysts may contain polyatoms selected from the
group molybdenum, tungsten, niobium and vanadium, while tha
heteroatom may be selected from phosphorus, silicon, germanium, and
arsenic. Preferably, the polyatoms are tungsten or molybdenum and
the heteroatom is phosphorus or silicon. These heteropoly acids
would likely have the Xeggin structure H8ntXM12040], were X = P or
Si, M = Mo or W, and n is an i~teger of 4 or 5.
The preferred heteropoly acids for the practice of this
invention include 12-molybdophosphoric acid (H3PMol2040),
12-tungstophosphoric acid (H3Pwl2o4o)~ molybdosilicic acid
. : :
,
(H4SiMo12040), and tungstosilicic acid (H3SiW12o4o). It is especially
preferred that the heteropoly acid be 12-tungstophosphoric acid.
Preferably, the heteropoly acids are bound to an lnert
support. Compounds which may be employed are those containing an
element of Groups III or IV of the periodic table. Suitable
compounds include the oxides of Al, Si, Ti and Zr, e.g. alumina,
silica (silicon dioxide), titania (titanium dioxide) and zirconia,
as well as combinations thereof. Also suitable are carbon, ion-
exchange resins, and carbon-containing supports. It is preferred
that the inert support be sioz or Tio2.
The inert support may be in the form of powders, pellets,
spheres, shapes, and extrudates, and may have a surface area of
from about lo to about looo m2/g. As demonstrated in the examples,
the supports preferably are of high purity and high surface area.
Applicants have discovered that a greater conversion of olefin to
oligomer is achieved where the support has a high surface area.
Preferably, the surface area of the support is greater than about
30 m2/g. Where the support is a silica support, it is more
preferred that the surface area of the support be greater than
about 100 m2/g, and especially preferred that the surface area of
the support be about 300 m2/g or greater. Where the support is a
titania support, it is especially preferred that the surface area
of the support be from about 50 to about 60 m2/g. An extrudate
which works well is an HSA titania carrier extrudate fro~ Norton
Company: 1/8" extrudate with a sur~ace area o~ 51 m2/g. Another
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useful titania extrudate is Norton Company's 1/8" extrudate with a
surface area of 60 m2/g.
The weight percent of heteropoly acid to inert support
should be such that the concentration of the polyatom (Mo, W, Nb or
V) in the formulated catalyst preferably is in the range of about
0.1 to about 30 wt.%. However, one skilled in the art may find
other weight percentages to be useful in the practice of this
invention. Where the heteropoly acid is, for example,
12-molybdophosphoric acid, supported on titania, a suitable
quantity of molybdenum is about 1 to about 10 wt.%~ In the
preparation of a tungstophosphoric acid-on-titania catalyst, on the
other hand, the tungsten content may be from about 1 to about 30
wt.~.
The oligomerization reaction may be carried out in either
a stirred slurry reactor or in a fixed bed continuous flow reactor.
The catalyst concentration should be sufficient to provida the
desired catalytic effect. The temperatures at which the
oligomerization may be performed are between about 50 and 300C,
with the preferred range being about 150 to 180C. The reaction
may be run at pressures of from 0 to 1000 psig.
Following the oligomerization reaction, the unsaturated
oligomers may be hydrogenated to improve their thermal stability
and to guard against oxidiative degradation during their use as
lubricants. The hydrogenation reaction for l-decene oligomers may
be represented as follows:
catalyst
onH20n + ~2 ~~~~~~~~~~~ Clon~20~2
? ~ '' J~
( ~ , -~,. .. ..
where n represents moles of monomer used to form the oligomer.
Hydrogenation processes Xnown to those skilled in the art may be
used to hydxogenate the oligomers. A number of metal catalysts
are suitable for promoting the hydrogenation reaction, including
nickel, plati~um, palladium, copper, and Raney nickel. These
metals may be supported on a variety of porous materials such as
kieselguhr, alumina, or charcoal, or they may be formulated into a
bulk metal catalyst. A particularly preferred catalyst for this
hydrogenation is a nickel-copper-chromia catalyst described in U.S.
Patent No. 3,152,998, incorporated by reference herein. Other U.S.
patents disclosing known hydrogenation procedures include U.S.
Patent Nos. 4,045,508; 4,013,736; 3,997,622; and 3,g97,621.
Unreacted monomer may be removed either prior to or after
the hydrogenation step. Optionally, unreacted monomer may be
stripped from the oligomers prior to hydrogenation and recycled to
the catalyst bed for oligomerization. The removal or recycle of
unreacted monomer or, if after hydrogenation, the removal of non-
oligomerized alkane, should be conducted under mild conditions
using vacuum distillation procedures known to those skilled in the
art. Distillation at temperatures exceeding 250 C may cause the
oligomers to break down in some ~ashion and come off as volatiles.
Preferably, therefore, the reboiler or pot temperature should be
kept at or under about 225 C when stripping out the monomer.
Procedures known by those skilled in the art to be alternatives to
vacuum distillation also may be employed to separate unreacted
components from the oligomer.
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While it is known to include a distillation step after
the hydrogenation procedure to obtain products of various 100C
viscosities, it is preferred in the method of the present invention
that no further distillation (beyond monomer flashing) be
conducted. In other words, the monomer-s~ripped, hydrogenated
bottoms are the desired synthetic lubricant components. Thus, the
method of this invention does not reqUire the c03tly, customary
distillation step, yet, sUrprisingly, produces a synthetic
lubricant component that has excellent properties and that performs
in a superior fashion. However, in some contexts, one skilled in
the art may find subsequent distillation useful in the practice of
this invention.
The invention will be further illustrated by the
following examples, which are given by way o~ illustration and not
as limitations on the scope of this invention. The entire text of
every patent, patent application or other reference mentioned above
is hereby incorporated herein by reference.
EXAMPLES
In the examples detailed below, the following procedures
were used:
Preparation of 12-Tungstophosphoric Acid~on Titania
To a flask containing 250 cc of titania 1/8" diameter
extrudates (from The Norton Company) was added a solution of 12-
tungstophosphoric acid (80 g) dissolved in 300 ml of distilled
water. The mixture was stirred for 1-2 hours, the exc~ss liquid
was removed by rotary evaporation under vacuum, and the solids were
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calcined at 150 C for 1 hour, and then 350 'C for 2 hours in a
stream of nitrogen.
The recovered extrudates were found to contain:
% Tungsten - 9.5
- % Phosphorus - 0.27
PreParation of a 12-Tunqstophosphoric Acid on Silica
To a flask containing 125 cc of silica gel (from MC/B
Man~facturing) was added a solution of 12-tungstophosphoric acid
(40 g) dissolved in 150 ml of distilled water. The mixture was
stirred for 1-2 hours, the excess liquid was recovered by rotary
evaporation under vacuum, and the solids were calcined at 150 ~C
for 1 hours, then 350 C for 2 hours in a stream of nitrogen.
The recovered powder was ~ound to contain:
% Phosphorus - 0.5
Oligomerization of Olefins
Olefin and finely ground catalyst were charged to a
three-necked flask equipped with an overhead stirrer, thermom~ter,
heatinq mantle, and a water-cooled condenser tN2 purge). The
mixture was vigorously stirred and heated to the desired
temperature for the desired time. ~he mixture was then cooled to
ambient tamperature and filtered wlth suction. The liquid was
analyzed by liquid chromatography. The results are detailed in the
table that ~ollows.
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OLEFIN OLIGOMERIZATION USlrlG HETEROPOLY ACIDS ON INERT SUPPORTS
r ~ =
Ex. ¦ fint~) C~ly,t (g3 Tim~/Temp Con. (Ib) Resull~ from Liquid Chrom~togr~phy
No. I ~Dy c~rbon (Hr)1(C) M(%) D~%)T+(%) D/T+
numbcr) _ Rd(jo
¦ C-14A TPA on TiO2 10 5.0/160 8S.614.4 63.4 22.2 2.86
l _ .
2 ¦ C-14A TPA on SiO2 10 5.0/160 86.613.4 49.6 37.1 1.34
_ .
3 ¦ C-14A TPA on TiO2 10 5.0/160 _o ~ 100 -- --
_ lW=4.11
4 C-14A TPA on TiO2 10 5.0/140 69.730.3 55.0 13.7 3.74
C-14A TPA on TiO2 10 5.0/160 83.816.2 61.t 22.7 2.69
6 ¦ C-14A TPA on TiO2 10 4.0/180 76.523.5 58.4 18.1 3.23
_
7 ¦ C-14A TPA on Al2O~ 10 5.0/160 68.9 31.1 S3.4 14.9 3.63
l lW = 25,31
8 ¦ C-14A TPA on TiO2 10 5.01160 791 20.9 61 .4 17.6 3.49
l lW- 17,01
9 I C-14A TPA on S1O2 10 5.0/160 62.437.6 50.0 12.3 4.07
.. . . .
¦ C-14A TPA on TiO~ 10 5.0/160 62.4 37.6 51.8 8.48 6.11
l lW = 3 01
1 l l C-14A TPA on TiO2 10 5.0/160 32.0 68.1 25.8 1.38 4.ao
IW=6.01 -
12 C-14A TPA on SiO2 5.0 5.0/160 84.8 15.2 55.5 28.7 1.93
1~ ¦ C-12A TPA on SiO2 10 5.0/160 89.1 10.9 48.6 39.5 1.23
_ _
14 C-131,141 TPA on SiO2 10 5.0/160 86.4 13.6 51.0 35.3 1.44
C-16A TPA on SiO2 10 5.0/160 81.9 18.1 54.4 27.4 1.98
I _
16 1 C-1$1,181 TP.~ on SiO2 10 5.0/160 74.3 25.7 52.1 22.2 2.35
_
17 ¦ C-14A TPA on TiO2 10 5.0/160 84.4 15.6 60.1 23.8 2.53
, .
18 C-16A TPA on TiO2 10 5.0/160 76.0 24.0 62.0 14.0 4.43
11
19 C-151,181 TPA on r~O2 10 5.0/160 61.338.7 52.7 8.62 6.11
¦ C-12A TPA on TiO2 10 5.0/160 85.2 14.8 59.4 25.8 2.3
_ ... ___ , .. _ - . .__. _
21 C-12A TPA on TiO2 10 5.0/140 83.1 16.9 60.7 22.4 2.71
22 ¦ C-12A TPA on TiO2 10 4.0/180 85.1 14.4 60.0 25.0 2.40
- . . __ ___ . . __ _ . . .
23 1 C-14A TSA on SiO2 9.7 5.0/160 --0 ~ 100 _ _
_ ....
24 C-14A TSA on SiO2 10 5.0/160 18.7 81.3 17.6 -O
C~ISA TSA on rlo2 10 5.0/160 15.2 83.8 12.1 1.41 8.01
26 C-14A TSA on rlo2 10 5.0/160 49.1 50~9 __ 40.9 8.21 4.98
_ _ .
27 C-14A MPA on TiO2 10 5.0/160 ~3 ~97 ~3
28 C-14A MPA on rl2 10 5.0/160 ~6 ~94 ~6 -- --_
29 ¦ C-14A TPA on Low 10 5.0/160 19.3 80.7 16.7 2.68 6.23
_ S/Area SiO2_ _ ~ _
¦ C-14A TPA on High 10 5.0/160 80.6 19.4 55.8 24.8 2.25
S/Are~ SiO2 _ _
31 ¦ C-14A Anunonium 10 5.0/160 ~o ~ 100 -- --
Tung~tale on
I TiO2
Con.--:onvenion; h --Moromer; D = Dimer-, T = Trimer + Tetr~n :r ~ elc.; A - Alphn; I--Lnl~ n~l; TPA a Tungsto,ohosp lorlc ~cid;
TS~ ~ Tung-to~i1icic llc;d; MPA ~ Molybdopho~phoric ~cid; S/Are~ a Surr~ce Are~.
12
a ~x
~ _ - _ _
¦ Ex. Olefin(~) Cat~l~nt ~g) Time/T~mp Con. (%) M(%) D(%) T-~(%) DIT+
o. (by c~rbon (Hr)l( C) R~tio
number)
_
32 C-14A MPA on TiO2 10 4.0/180 28.6 71.4_ 23.6 2.5 9.44
33 C-14A MPA on TiO2 10 5.0/160 14.2 85.8 11.4 ~o
Con. = Conv~r~ion; M = Monomer; t~ = Dimer; T+ ~= ~rTncr + T~tr~m~r + ~ic.~ A ~ I Alph~ I = ,nt~n~l,
MPA = Molybdopho}pho-ic ~cid.
The SiO2 used as the catalyst support in examples 2,
12, 13~ 14, 15, and 16 had a surface area greater than 100 m2/g.
The sio2 used as the catalyst support in examples 23 and 24 had a
surface area o~ >50 m2/g. The low surface area SiO2 used in
example 29 had a surface area of 30 mZ/g. The high surface area
sio2 used in example 30 had a surface area of 300 m2/g.
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