[0001] This invention relates to olefin polymerization processes; more particularly, this
invention relates to olefin polymerization processes with product viscosity and pour
point control.
[0002] At present, there is a trend to more severe service ratings for IC lubricants; for
example, the SAE service ratings of SD and SF are obsolescent because more engine
manufacturers specify an SF rating and it is expected that even more severe ratings
will need to be met in the future as engine core temperatures increase in the movement
toward greater engine efficiency. This progressive increase in service severity dictates
a need to develop better lubricants; for example, lubricants with improved resistance
to oxidation at high temperatures and higher VI requirements to ensure that the lubricants
will have adequate viscosity at high temperatures without excessive viscosity when
the engine is cold. In part, improved performance may be obtained by improved additive
technology, but significant advances are needed in basestock performance to accommodate
more severe service requirements.
[0003] It is known from US 3149178 and 3382291 to utilize BF₃ and AlCl₃, as catalyst, to
polymerize olefins useful for producing synthetic lubricants.
[0004] The use of aluminium alkyl halide compounds is described in U.S. 4,041,098 and 4,469,910.
The alkyl aluminium halide catalyzed process presents environmental problems and disposal
problems considering the catalyst being utilized. Furthermore, the process is complicated.
[0005] The use of peroxide treatment for modifying the viscosity of various lubestocks including
distillates and hydrocracked resids has been described in U.S. 3,128,246 and 3,594,320.
Other peroxide treatment processes are described in U.S. 4,594,172 and 4,618,737.
Peroxide treatment has not, however, previously been proposed for use with light neutral
viscosity range decene oligomers from a BF₃ polymerization process.
[0006] The invention seeks to provide a process which eliminates the need for such alkyl
aluminum chloride or esters thereof while providing a significant advance in the art
by further reduction in pour point and increase in viscosity without significant change
in viscosity index.
[0007] The present invention provides a process for producing a high viscosity index, low
pour point synthetic lubricant from a 1-olefin feed, which process comprises:
(i) feeding to a reaction zone a stream (1) of a 1-olefin, having from 5 to 20 carbon
atoms, saturated with BF₃ and a stream (2) of BF₃ complexed, in a 1:1 molar ratio,
with a promoter, the BF₃ and the BF₃ complexed with a promotor being the sole catalyst
system;
(ii) commingling streams (1) and (2) in a reaction zone under polymerization reaction
conditions;
(iii) controlling the relative rate of addition of streams (1) and (2) to charge from
0.006 mole to 0.01 mole promotor per l00 g of 1-olefin;
(iv) recovering an oily liquid polymer; and
(v) subjecting the polymer to treatment with an organic peroxide compound to increase
the viscosity and lower the pour point of the oily liquid polymer.
Figure 1 shows a schematic depiction of an alkylaluminum chloride process; and
Figure 2 shows a schematic depiction of a BF₃ catalyzed process.
[0008] The improved synthetic lubricants of the present invention are suitably produced
from 1-decene, or from a mixture of 1-olefins, having between about 6 and about 12
carbon atoms, having a mean value of the olefin chain length of about 10 carbon atoms,
although the 1-olefin charge can be any normally liquid 1-olefin having between about
5 and about 20 carbon atoms or mixtures of such 1-olefins. Examples of the 1-olefin
charge are 1-pentene; 3-methyl-1-butene; 1-hexene; 3,3-dimethyl-1-butene; 2,3-dimethyl-1-butene;
1-heptene; 1-octene; 2,3,3-trimethyl-1-pentene; 2-ethyl-1-hexene; 1-decene; 1-undecene;
1-dodecene; 1-tetradecene; 1-hexadecene; 1-octadecene; and 1-eicosene, with 1-decene
being preferred.
[0009] In accordance with this process, a 1-olefin charge is saturated with BF₃, suitably
at room temperature, before it is charged to the reaction zone. The second stream
that is charged to the reactor is a 1:1 molar complex of BF₃ and a promotor compound.
This complex, upon contacting the first stream in the reactor, effects the polymerization
reaction.
[0010] The promoter compound used to form BF₃-promoter catalyst complexes include, by way
of example, water; alcohols, such as octanol and 1-decanol; acids, such as acetic
acid, propionic acid, and butyric acid; ethers, such as diethyl ether; acid anhydrides
such as acetic acid anhydride and succinic anhydride; esters, such as ethyl acetate
and methyl propionate; ketones, such as acetone; and aldehydes, such as benzaldehyde.
The rate of addition of stream (2) is conveniently expressed in terms of moles of
promoter per weight unit of olefin. This rate will be between 0.006 mole promoter
and 0.01 mole promoter per 100 g. of 1-olefin charge.
[0011] The reaction temperature employed is generally below 60°C and preferably between
0°C and 35°C. The reaction can be carried out at atmospheric pressure, but moderate
pressures from about 1 psig up to about 500 psig are preferred.
[0012] The present process is suitably used with neutral lube feeds, that is, a vacuum stripped
bottoms fraction of the oily liquid polymer, ranging from light neutrals, that is,
from 100 SUS at 100°F to heavy neutrals, that is, 700 SUS at 100°F. Typical light
to medium neutral stocks may have an IBP below 650°F (about 345°C) (ASTM D-2887) and
the end point may be below 1000°F (about 540°C). Heavier neutrals will generally boil
in the range 650°F to 1050°F (about 345°C to 565°C, ASTM D-1160, 10 mm Hg), typically
from 750°F to 1050°F (about 400°C to 565°C, ASTM D-1160).
[0013] Figure 2 schematically depicts the process of the invention. The first step is the
BF₃ polymerization process. The oligomers formed (oily liquid polymer) includes the
light neutral viscosity range oligomers. This synthetic lubrication product can be
washed as shown, using conventional techniques.
[0014] Figure 2 further shows a stripping step used to separate the light neutral viscosity
range oligomer. It can occur in an autoclave under vacuum. The peroxide treatment
can precede or follow the distillation step. Treatment before stripping is preferred.
[0015] Depending upon the quantity of residual unsaturation in the distillate product, it
may be desirable to carry out a final hydrotreatment to remove at least some of these
unsaturates and to stabilize the product.
[0016] Conventional hydrotreating catalysts and conditions are suitably used. Catalysts
typically comprise a base metal hydrogenation component such as nickel, tungsten,
cobalt, nickel-tungsten, nickel-molybdenum or cobalt-molybdenum, on a inorganic oxide
support of low acidity such as silica, alumina or silica-alumina, generally of a large
pore, amorphous character. Typical hydrotreating conditions use moderate temperatures
and pressures, e.g. 100°-400°C (about 212°-750°F), typically 150°-300°C (about 300°-570°F),
up to 20,000 kPa (about 3000 psig), typically about 2125-14000 kPa (about 300-2000
psig) hydrogen pressure. Space velocities of about 0.3-2.0, typically 1 LHSV, with
hydrogen circulation rates typically about 600-1000 n.l.l.⁻¹ (about 107 to 5617 SCF/Bbl)
usually about 700 n.l.l.⁻¹ (about 3930 SCF/Bbl).
[0017] As shown in Figure 2, the catalyst can be filtered after hydrogenation is complete.
[0018] The oily liquid polymer product is subjected to treatment with an organic peroxide
compound at elevated temperature to affect a coupling between the polymer components
to increase the viscosity of the lubricant. The treatment preferably occurs before
stripping but can occur afterwards. The treatment can be repeated.
[0019] The preferred class of organic peroxides are ditertiary alkyl peroxides represented
by the formula ROOR¹ where R and R¹, which may be the same or different, each represent
tertiary alkyl groups, preferably lower (C₄ to C₆) tertiary alkyl groups. Suitable
peroxides of this kind include ditertiary butyl peroxide, ditertiary amyl peroxide
and tertiary butyl, tertiary amyl peroxide. Other organic peroxides may also be used
including dialkyl peroxides with one to ten carbon atoms such as dimethyl peroxide,
diethyl peroxide, dipropyl peroxide, di-n-butyl peroxide, dihexyl peroxide and acetylperoxides
such as dibenzoylperoxide.
[0020] The amount of peroxy compound used in the process is determined by the increase in
viscosity which is desired in the treatment. In general, the increase in viscosity
is related to the amount of peroxide used with greater increases resulting from greater
amounts of peroxide. As a general guide, the amount of peroxide catalyst used will
be from 1 to 50, preferably from 4 to 30 weight percent of oil. There is an essentially
exponential relationship between the proportion of peroxide used and the viscosity
increase, both with batch and continuous reaction. The presence of hydrogen may decrease
peroxide utilization slightly, but significant increases in viscosity may still be
obtained without other lube properties being significantly affected. The exception
to this statement is that pour point is reduced.
[0021] It is practicable to cascade the effluent from a catalytic hydrotreating unit directly
to a peroxide treatment reactor, permitting the hydrogen to remain in the stream.
The coupling of components out of the lube boiling range would, in this case, increase
lube yield and for this reason may represent a preferred process configuration.
[0022] The reaction between the lubricant component and the peroxide is carried out at elevated
temperature, suitably at temperatures from 50°C to 300°C and in most cases from 100°C
to 200°C. The treatment duration will normally be from 1 hour to 6 hours. There is
no fixed duration because various starting materials will vary in their reactivity
and amenability to coupling by this method. The pressure used depends upon the temperature
and upon the reactants and, in most cases, needs to be sufficient only to maintain
the reactants in the liquid phase during the reaction. Space velocity in continuous
operation will normally be from 0.25 to 5.0 LHSV (hr⁻¹).
[0023] The peroxide is converted during the reaction primarily to an alcohol whose boiling
point will depend upon the identity of the selected peroxide. This alcohol by-product
may be removed during the course of the reaction by simple choice of temperature and
pressure. Accordingly, temperature and pressure may be selected together to ensure
removal of this product. The alcohol may be converted back to the peroxide in an external
regeneration step and recycled for further use. If ditertiary butyl peroxide is used,
the tertiary butyl alcohol formed may be used directly as a gasoline octane improver.
Alternatively, it may be readily converted back to the original ditertiary butyl peroxide
by reaction with butyl hydroperoxide in the presence of a mineral acid, as described
in U.S. 2,862,973, with the butyl hydroperoxide being obtained by the direct oxidation
of isobutane, as described in U.S. 2,862,973.
[0024] The reaction may be carried out batchwise or continuously. In either case, it is
preferable to inject the peroxide compound incrementally to avoid exotherms and production
of lower quality products associated with high reaction temperatures. If the reaction
is carried out in a continuous tubular reactor, it is preferred to inject the peroxide
compound at a number of points along the reactor to achieve the desired incremental
addition.
[0025] The effect of the peroxide treatment is principally to increase the viscosity of
the lubricant and reduce pour point without affecting a significant reduction in viscosity
index or significant increase in cloud point. The increase in viscosity implies an
increase in molecular weight. It is thought that the action of the peroxide is by
the removal of hydrogen atoms to form free radicals in non-terminal positions which
then combine with each other to form branched chain dimers which are capable of reacting
even more rapidly than the monomer. Thus, the viscosity of the treated material increases
rapidly in the presence of additional amounts of peroxide which generate new free
radicals. The greater reactivity perceived with the initial dimer may be attributed
to reactive tertiary hydrogens which are present in the dimers and higher reaction
products but not on the paraffins present in the starting material. The greater reactivity
of the dimers indicates that the incremental addition of successively smaller amounts
of peroxide, particularly in continuous tubular reactor synthesis, will produce relatively
greater progressive increases in viscosity. The reactivity also ensures that the range
of molecular weights in the product will be narrower and that product quality will
be more consistent.
[0026] The products of the present process are characterized by a high viscosity index coupled
with a low pour point. Viscosity indices of at least 130, for example, 140 or 150
are characteristic of the products but with low pour points indicating a significant
quantity of iso-paraffinic components. Pour points below 10°F for the base stock (that
is, without pour point improvers or other additives) and in most cases below 5°F are
readily obtained, for example, 0°F with correspondingly low Brookfield viscosities,
for example, less than 2500b at -20°F. Use of the present viscosity and pour point
modification process enables product viscosity to be increased from that of a light
neutral to that of a heavy neutral or a bright stock with little or no adverse effect
on viscosity index. Concurrently, pour point is reduced to generally less than -65°F
and in general, less than -85°F. Thus, the present lubricant base stocks have an extremely
good combination of properties making them highly suitable synthetic lubricants.
[0027] The following Examples illustrate the invention.
Comparative Example 1
[0028] A light neutral viscosity range lube is made from 1-decene as described in U.S. 3,382,291.
Properties before and after hydrogenation are as follows:
|
After Hydrogenation |
Before Hydrogenation |
Gravity, API |
39.9 |
38.0 |
Specific |
0.8256 |
0.8348 |
Pour Point, °F |
less than -65 |
less than -65 |
K.V. 40°C, cs |
28.54 |
27.98 |
K.V. 100°C, cs |
5.55 |
5.47 |
K.V. 100°F, cs |
31.1 |
30.5 |
K.V. 210°F, cs |
5.67 |
5.58 |
SUS 100°F |
147 |
144 |
SUS 210°F |
44.8 |
44.5 |
Viscosity Index |
135.9 |
135.1 |
Example 2
[0029] 100 g. of hydrogenated stock from Example 1 is placed in a 500 ml round bottom flask
equipped with a stirrer, thermometer, water condenser, condenser liquid take-off and
dropping burette. The flask is heated to 150°C, and 20 g DTBP is added dropwise from
the burette over a one hour period. The temperature is held at 150°C for an additional
three hours, then raised to 185°C in the next two hours. The contents are then cooled
to room temperature and topped first at atmospheric pressure to a pot temperature
of 300°C, then under a vacuum of 0.1 mm pressure to a pot temperature of 190°C to
remove any DTBP decomposition products not condensed in the take-off during the reaction
period.
[0030] The 99.6 g of lube product had the following properties:
Gravity, °API |
37.2 |
Specific |
0.8388 |
Pour Point, °F |
less than -65 |
KV at 40°C, cs |
68.8 |
KV at 100°C, cs |
10.55 |
KV at 100°F, cs |
75.9 |
KV at 210°F, cs |
10.86 |
SUS at 100°F |
352 |
SUS 210°F |
62.1 |
Viscosity Index |
141.1 |
Example 3
[0031] 100 g of stock from Example 1, which is not hydrogenated, is reacted with 20 DTBP
in the same manner as described in Example 2. The 98.8 g of lube product had the following
properties:
Gravity, °API |
35.0 |
Specific |
0.8499 |
Pour Point, °F |
-65 |
KV at 40°C, cs |
98.8 |
KV at 100°C, cs |
13.6 |
KV at 100°F, cs |
110.0 |
KV at 210°F, cs |
14.0 |
SUS at 100°F |
508 |
SUS at 210°F |
74.0 |
Viscosity Index |
138.5 |
[0032] The viscosity of this product charging the unhydrogenated oligomer is higher than
that of Example 2, 508 vs. 352 SUS at 100°F.
Example 4
[0033] 50 g of the lube product from Example 3 is reacted with 10 g DTBP in the same manner
as described in Example 2. The 49.8 g of lube product had the following properties:
Gravity, °API |
32.2 |
Specific |
0.8639 |
Pour Point, °F |
-40 |
KV at 40°C, cs |
385.5 |
KV at 100°C, cs |
38.5 |
KV at 100°F, cs |
435 |
KV at 210°F, cs |
39.7 |
SUS at 100°F |
2012 |
SUS at 210°F |
187 |
Viscosity Index |
147.7 |
Example 5
[0034] The experiment in this example is carried out in a two gallon autoclave. 4934 g of
stock (unhydrogenated oligomers as in Example 3) and 1233 g. of DTBP are added together
to the autoclave. After purging with nitrogen, the autoclave is sealed with nitrogen
at room pressure and gradually heated up to 150°C while stirring at 200 RPM. After
heating at 150°C for three hours, the total liquid product is flashed at 150°C for
0.5 hour followed by nitrogen purging at 125°C for two hours to remove all by-products
(alcohol and acetone). The lube product is then cooled to room temperature and discharged.
The lube product had the following properties:
Specific Gravity |
0.854 |
Pour Point, °F |
-55 |
KV at 40°C, cs |
210.4 |
KV at 100°C, cs |
24.09 |
KV at 100°F, cs |
235 |
KV at 210°F, cs |
24.8 |
SUS at 100°F |
1091 |
SUS at 210°F |
119 |
Viscosity Index |
142.5 |
[0035] The autoclave experiment shows much higher viscosity compared to the glassware experiment
in Example 3 (1091 vs 508 SUS at 100°F and 143 vs 138.5 VI) although the DTBP dosage
used is only slightly higher (20 wt% vs 16.7 wt% DTBP). Thus, the peroxide utilization
is improved with the closed autoclave experiment because of better contact and the
elimination of peroxide loss due to evaporation.
Example 6
[0036] An alkyl aluminum chloride polymerization process is used to make the following high
viscosity lube stocks from 1-decene. This process is described in U.S. Patent Nos.
4,041,098 and 4,469,910. A schematic presentation appears in Fig. 1.
Pour Point, °F |
-50 |
-30 |
KV at 40°C, cs |
80.4 |
390.7 |
KV at 100°C, cs |
11.7 |
38.8 |
KV at 100°F, cs |
89 |
440 |
KV at 210°F, cs |
12 |
40 |
SUS at 100°F |
42.5 |
2038.1 |
SUS at 210°F |
66.4 |
188.0 |
Viscosity Index |
138.0 |
147.3 |
[0037] These properties compare with those with about the same viscosity from the combination
BF₃-DTBP process as follows:
|
Alkyl |
Alkyl |
Process |
Aluminum Chloride |
BF₃-DTBP |
Aluminum Chloride |
BF₃-DTBP |
Example |
6 |
3 |
6 |
4 |
KV at 40°C, cs |
80.4 |
98.8 |
390.7 |
385.5 |
KV at 100°C, cs |
11.7 |
13.6 |
38.8 |
38.5 |
Viscosity Index |
138.0 |
138.5 |
147.3 |
147.3 |
Pour Point, °F |
-50 |
-65 |
-30 |
-40 |
[0038] The results show that in all comparisons the combination BF₃-DTBP process gives a
lower pour point and the same or higher viscosity index.
[0039] The combination of BF₃-DTBP process eliminates the need for alkyl aluminum chloride
to make higher viscosity polyalpha olefin lubricants which cannot be made with BF₃
alone. Additionally, because the need for alkyl aluminum chlorides is avoided, the
process of the present invention avoids environmental and disposal problems incurred
in the use of the alkyl aluminum chloride process. Thus, environmental problems in
disposing of the alkyl aluminum chloride heel are avoided. Moreover, corrosion of
vessels and lines and a complicated process utilizing extensive washing necessary
with the alkyl aluminum chloride process are avoided.
[0040] The DTBP step can be integrated into the BF₃ process preferably before the vacuum
stripping step. Product yield for the combined BF₃-DTBP process will still be 99%
compared to 90 to 93% for the alkyl aluminum chloride process.
1. A process for producing a high viscosity index, low pour point synthetic lubricant
from a 1-olefin feed, which process comprises:
(i) feeding to a reaction zone a stream (1) of a 1-olefin, having from 5 to 20 carbon
atoms, saturated with BF₃ and a stream (2) of BF₃ complexed, in a 1:1 molar ratio,
with a promoter, the BF₃ and the BF₃ complexed with a promotor being the sole catalyst
system;
(ii) commingling streams (1) and (2) in a reaction zone under polymerization reaction
conditions;
(iii) controlling the relative rate of addition of streams (1) and (2) to charge from
0.006 mole to 0.01 mole promotor per 100 g of 1-olefin;
(iv) recovering an oily liquid polymer; and
(v) subjecting the polymer to treatment with an organic peroxide compound to increase
the viscosity and lower the pour point of the oily liquid polymer.
2. A process according to Claim 1, wherein the peroxide comprises a ditertiary alkyl
peroxide.
3. A process according to Claim 2, wherein the peroxide comprises ditertiary butyl
peroxide.
4. A process according to any preceding claim, wherein the polymer is treated with
the peroxide at a temperature from 100° to 300°C.
5. A process according to any preceding claim, wherein the amount of peroxide used
to treat the polymer is from 1 to 50 weight percent of the polymer.
6. A process according to any preceding claim which further comprises washing the
polymer prior to treatment with the peroxide compound.
7. A process according to any preceding claim which further comprises stripping the
polymer prior to treatment with the peroxide compound to recover a light neutral viscosity
range oligomer.
8. A process according to any preceding claim which further comprises stripping the
polymer, after treatment with the peroxide compound, to recover a light neutral viscosity
range oligomer.
9. A process according to Claim 7 or 8 which further comprises hydrogenating the light
neutral viscosity range oligomer.
10. A process according to any preceding claim, wherein the 1-olefin comprises 1-decene.
11. A process according to any preceding claim which further comprises repeating the
organic peroxide compound treatment.
12. A process according to any preceding claim, wherein the polymer is treated with
organic peroxide compound in an autoclave under vacuum.