Note: Descriptions are shown in the official language in which they were submitted.
~ ~7tj~?~
BACKGROUND OF THE INVENTIO~
FIELD OF THE INVENTIO~
This invention relates to a method of increasing
the flow of hydrocarbon liquids through conduits. More
particularly, it relates to a method of increasing the flow
rate of hydrocarbon liquids such as crude oil in conduits
such a pipelines by reducing the frictional resistance of
the hydrocarbon liquid flowing in the conduit.
PRIOR ART
When fluids are pumped through a condui-t, such
as a pipeline, friction resulting from the movement of the
fluid over the inside surface of the conduit causes a pres-
sure drop in the fluid which increases as the downstream
distance from the pump increases. Because of the loss in
pressure, it is usually necessary to install additional
pumps at selected points along the pipeline to keep the
1uid moving at the desired rate in the conduit. Sometimes
it is desirable to increase the throughpu-t of fluids
through conduits but this cannot always be sa-tisfactorily
accomplished by installiny additional booster pumps. The
flow rate of the fluid through the conduit can also be
increased by reducing the friction of the fluid in the
conduit. Accordingly, it would be desirable to find an
efficient technique for reducing the pressure loss due to
friction, commonly referred to as "friction loss" or "drag."
One method of reducing friction loss in fluids
moving through conduits is to inject into the -fluid a sub-
stance which is capable of reducing the friction loss oE
the fluid moving through the conduit. Such substances mus-t
not only reduce the friction loss of the fluid, but must be
L~.~
S,! ~'
--2--
~ 1 7'71~
compatible with the fluid and must not interere with the
intended use of the fluid.
Recent shortages in imported crude oil have made
it necessary to increase the flow of crude oil moving
through existing pipelines from domestic oil fields to
refineries. Studies have been undertaken to find substances
which meet the requirements stated above. It has been
discovered that certain oil-compatible polymeric substance~
have been used with some success in reducing friction loss
in crude oil through pipelines. U. S. Patent No. 3,692,676
discloses the reduction of friction loss in hydrocarbon
liquids flowing through pipelines by adding to such liquids
small amounts of homopolymers or copolymers of alpha-olefins
having from 6 to 20 carbon atoms. Even though such addit-
ives may effect drag reduction in hydrocarbon liquids
flowing through conduits they are costly to use since the
described polymers are prepared from monomers which are
expensive and not readily available in large quantities.
Oil-compatible drag reducing agents have been
prepared from less costly rnonomers but these generally have
not been completely satisfactory, often for such reasons as
their inability to sufficiently reduce the friction loss of
the flowing liquid or their propensity to undergo excessive
shear degradation under actual field conditions. In this
category are drag reducing agents disclosed in U. S. Patent
3,215,154, which teaches the use of polyisobutylene as a
hydrocarbon liquid friction loss reducing agent; U.S. Patent
3,434,485, which discloses the use of low molecular weight
polybutene to reduce friction loss in a crude oil pipeline;
U. S. Patents 3,351,079; 3,493,000; 3,559,66~ and 3,682,187,
~ ~ ~7~t~
which disclose the addition of copolymers of ethylene and
propylene or other low molecular weight alpha-monoolefin to
to hydrocarbon fluids as fluid flow friction loss reducing
additives; and U.S. Patent 3,454,379, which describes the
addition of low molecular weight polyethylene to distillate
hydrocarbon fuel oil to improve the pumpability of the fuel
oil.
An efficient method of reducing the friction loss
of hydrocarbon liquids flowing in conduits using inexpensive
chemical additives which do not undergo significant shear
degradation has now been discovered. Accordingly, it is an
object of the invention to present an improved method oE
reducing friction loss in hydrocarbon fluids flowing through
conduits. It is another object of the invention to present
an inexpensive and efficient method of reducing friction
loss in hydrocarbon fluids flowing through conduits. It is
ano-ther object of the invention to present novel polymeric
composi-tions having unexpected hydrocarbon pipeline friction
reducing properties. It is another object of the invention
to present a method of reducing friction loss in a hydro-
carbon fluid flowing through a conduit by means of a poly-
meric additive which does not undergo significant shear
degradation under actual field conditions. It is another
object of the invention to presen~ an inexpensive and
efficient method of reducing the friction loss in crude oil
flowing through pipelines. These and other objects of the
invention are supported in the following description and
examples.
SUMMARY OF THE INVENTION
New compositions have been discovered which
~'7'~
signi~icantly attenuate friction resistance in hydrocarbon
pipelines. According to the invention the friction loss of
hydrocarbon fluids flowing in conduits is reduced by injec-
ting into the hydrocarbon fluids small amounts o~ high
molecular weight copolymer compositions prepared from
butene-l and one or more other alpha-monoolefins having 5
to 20 carbon atoms. The copolymers of the invention
desirably have an average molecular weight of 100,000 or
more and their average molecular weights are usually in the
range of about 100,000 to 20 million. The copolymer in the
compositions of the invention generally comprises about 10
to 90 mole percent of C4 hydrocarbon units and about 90 to
10 mole percent of units derived from the other alpha-
monoolefin component. The copolymer composition is added
to the hydrocarbon fluid at a concentration which is effec-
tive to produce the desired friction loss reductionD In
preferred embodiments of the inven-tion the alpha-monoolefin
component which is copolymerized with the butene-l has 6
to 14 carbon atoms, the copolymer in the composition
contains 25 to 75 mole percent C4 hydrocarbon units, the
copolymer composition is added to -the hydrocarbon fluid at
a polymer concentration of about 2 to 500 ppm and the
copolymer has an average molecular weight in the range of
about 500,000 to 10 million. Preferred copolymers for use
in the invention are those prepared with butene-l and one
or more of hexene-l, octene-l, decene-l, dodecene-l and
tetradecene-l.
DETAILED DESCRIPTION OF THE INVENTION
The copolymers useful in the invention may be
prepared by copolymeriziny butene-l with at least one other
alpha-monoolefin having 5 to 20 or more carbon atoms.
Alpha-monoole~ins having more than 20 carbon atoms may be
used in preparing compositions of the invention, however,
they are not as desirable as the lower molecular weight
monomers because of their high costs and their lower poly-
merization reactivities. The preferred alpha-monoolefins
are those having 6 to 14 carbon atoms. Particularly useful
alpha-monoolefins are hexene-l, octene-l, decene-l,
dodecene-l and tetradecene-l.
The method of copolymerization of the monomers is
not a part of the invention. In general, any of the several
well known methods for polymerizing alpha-monooleins can
be employed. A particularly suitable method is the Ziegler
process using catalyst systems comprising combinations of
a compound of a metal of Groups IV-B, V-B, VI-B or VIII of
the Periodic Chart of the Elements found on pages 392-393
of the Handbook of Chemistry and Physics, 37th Edition with
an organometal compound of a rare earth or metal from Groups
I-A, II-A, III-B of the Periodic Chart of the Elements.
Particularly suitable catalyst systems are those comprising
titanium halides and organoaluminum compounds. A typical
polymerization procedure is to contact the monomeric
mixture with the catalyst in a suitable inert hydrocarbon
solvent for the monomers and the catalyst in a closed
reaction vessel at reduced temperatures and autogenous
pressure and in a nitrogen atmosphere. Further details of
the ziegler process are set forth in U.S. Patent 3,692,676.
The total C4 hydrocarbon concentration in the
copolymers of the drag reducing compositions of the inven-
tion desirably varies from about 90 mole percent to about
-
10 mole percent. The factor limitiny the upper concentra-
tion of butene-l in the copolymers of the invention is
solubility. As the butene-l concentration in the copolymers
increases, the crystallinity increases and the solubility of
the copolymers in hydrocarbons decreases. Decreasing
solubility has an adverse effect on the drag reducing
effectiveness of the copolymers. The solubility limits of
copolymers varies, of course, with different copolymer
systems. In general, the practical upper butene-l content
limit for useful drag reducing copolymers is about 90 mole
percent. Copolymer compositions having C4 concentrations
exceeding about 90 mole percent have relatively poor drag
reducing properties and shear degradation resistance. On
the other hand the economic advantage of using the less
expensive butene-l in the preparation of the copolymer
compositions is lost if the C4 hydrocarbon incorporation in
the polymer drops below about 10 mole percent. In preferred
embodiments of the invention the total C~ hydrocarbon
concentration is about 25 to 75 mole percent and the total
concentration of alpha-monoolefin having 5 to 20 carbon
atoms is about 75 to 25 mole percent. Those skilled in the
art will appreciate the fact that small amoun-ts oE the
butene-l may incorporate into the copolymer composition as
homopolymer and that the abovestated C4 hydrocarbon concen-
trations refer to the total C4 hydrocarbon content of the
copolymer compositions and includes butene-l homopolymer
and butene-l present in copolymer form. On a weight basis
copolymers coming within the scope of the invention are
those having about 10 to 90 weight percent butene-l and
preferably about 25 -to 75 weight percent butene-l. The
-- 7 --
optimium butene-l concentrations will, of course, vary
depending on which monomer or monomers are used as the
other alpha-monoolefirl component.
As noted above, high molecular weight copolymers
are used in the compositions of the invention. The only
limitation on molecular weight is that it must be high
enough to produce ef-fective drag reduc-tion. In general,
the effectiveness of the drag reducing compositions
increases as the molecular weight increases. On the upper
end of the scale the molecular weight of polymers useahle
in the invention is limited only by the practicability of
of making the copolymers. The average molecular weight of
desirable copolymers is usually over 100,000 and is
generally in the range of about 100,000 to about 20 million.
The average molecular weight of copolymers used in the
invention is preferably in the range of about 500,000 to 10
million and most preferably in the range of about l to 5
million. The molecular weight of polymers can be determirled
by any one of several methods~ some of which provide a
weight average molecular weight and others of which provide
a number average molecular weight. For the sake of unifor-
mity the term "average molecular weight" as used herein
shall mean the weight average molecular weight. The weight
average molecular weight can be conveniently determined by
any of the well known methods. In the examples described
below, the weight average molecular weights were determined
by gel permeation chromatography at 135C using narrow
molecular weight range polystyrene samples as calibration
standards and using orthodichlorobenzene as solvent.
Number average molecular weights and polydispersities are
~ 3~,~
also listed in the examples. The weight average molecular
weight (Mw) and the number average molecular weight (Mn)
relate to each other according to the equation
Mw = ~n x Polydispersity
The amount of polymer required in the hydrocarbon
fluid, expressed as ppm (parts by weigh-t of copolymer per
million parts by weight of hydrocarbon fluid), to produce
the desired result will vary depending upon the physical
properties and composition of the hydrocarbon fluid. In
some hydrocarbon fluids the desired result may be obtained
by the addition of 2 ppm or less of the polymer to the
hydrocarbon fluid. On the other hand some hydrocarbon
fluids may require as much as l000 ppm or more of polymer
additions to produce the desired result. It has been found
that the desired result is usually obtained by the use of
l000 ppm or less, and its often preferred to add the copoly-
mer to the hydrocarbon fluid in amounts of about 2 to 500
ppm and most preferably in amounts of about 5 to 200 ppm.
It should be understood that the above concentra-
tions are based on the total weight of polymeric components
in the composition. The weight of additives, such as
diluents, is no-t included in the measurements. Since the
copolymer is a solid at the stated molecular weight it is
usually pre-ferred to dissolve it in a suitable solvent or
suspend it in a suitable diluent prior to use since it is
easier to add to the hydrocarbon fluid in the form of a
solution or a slurry. Suitable solvents and diluents
include kerosene, naptha and other petroleum distillates
and inert hydrocarbons, such as heptane, octane, etc.
Other additives which can be included in the
~ ~ ~ 7~
polymeric compositions of the invention are dyes, rust
inhibitors, antistatic agents, etc.
The copolymer compositions can be conveniently
added to the hydrocarbon ~luid by continuous injection into
the conduit carrying the hydrocarbon fluid by means of
proportionating pumps situated at desired locations along
the conduit. The copolymer compositions are ideally suited
for increasing the flow rate o~ crude oil in pipelines.
The following examples illustrate specific embodi-
ments of the invention. Unless otherwise stated parts and
percentages are on a weight basis. The amount of polymer
formed is measured by carbon 13 nuclear magnetic resonance
analysis and the weight average molecular weight and the
number average molecular weigh-t of the polymeric products
is determined by gel permea-tion chromatographic analysis,
as described aboveO
Example I
Into a two liter stainless steel reactor which
- has been purged with nitrogen and which is equlpped with a
ther-mocouple, an agitator and a cooling ~acket is charged
225 gms of kerosene which has been previously purified by
passage through a bed of molecular sieve, 0~67 mole of
dodecene-l, 13.7 mls of 25 weight percent solution of
diethyl aluminum chloride in heptane and 1.5 gms of
aluminum-activated titanium trichloride. Under a nitrogen
blanket 0.67 mole of purified butene-l is charged to the
reactor. The reactor is sealed and the reactor pressure is
adjusted to 20+ 5 psig with nitrogen and the reactor temp-
erature is reduced to 10C. The reaction begins immediately
upon addition of the reactants and catalyst. During the
J ~ r ~
course of the reaction the temperature is maintaine~ ak 10t
1C, the pressure is autogenous and the reactor contents
are agitated sufficiently to ensure a uniform temperature
throughout the reaction mixture. One hour after the reac-
tion begins/ 154 gms of purified kerosene is added to the
reactor to reduce the viscosity of the reac-tion mixture
which increases as polymeric product is formed. After the
kerosene addition the reaction is permitted to proceed for
an additional four hours during which time no further
viscosity reduction is necessary. The reaction is then
terminated by the addition of sufficient alcoholic sodium
hydroxide to completely inactivate the catalyst. The
reaction product is stabilized by the addition of 200 ppm
of a phenolic type antioxidant.
The conversion of monomer to polymer is 24~. The
polymeric product contains 51 mole percent C4 hydrocarbon
units and 49 mole percent C12 hydrocarbon units. The poly-
meric product has a number average molecular weight of 1.14
million, a polydispersity of 4.5, and a weight average
molecular weight of 5.13 million.
Example II
The procedure of Example I is repeated except
that the reaction is conducted in the temperature range of
-3 to -6C for a period of twenty hours.
The conversion of monomer to polymer is 35~. The
polymer in the product contains 52 mole percent of butene
units and 48 mole percent of dodecene units and has a number
average molecular weight 1.44 million, a polydispersity of
3.8. and a weight average molecular weight of 5.47 million.
-- 11 --
Example III
The procedure of Example II is repea-ted except
that the monomer charge comprises 0.89 mole of hexene-l and
1.34 moles of butene-l, the amount of diethyl aluminum
chloride is 9.1 mls of 25 weight percent solution and the
reaction is carried out for eight hours.
The conversion of monomer to polymer is 15%. The
polymer in the product contains 56 mole percent C4 hydro-
carbon units and 44 mole percent C6 hydrocarbon units and
will have a number average molecular weight above 1 million.
Example IV
The drag reducing efficiency of the polymer
compositions prepared in Examples I to III is determined by
comparing the pressure drop which occurs when a sample of
crude oil containing a test drag reducing agent (DRA) is
pumped through a test loop with the pressure drop which
occurs when the same crude oil, but containing no DRA, is
pumped through the test loop. The crude oil is from the
Sadlerochit formation, Prudoe Bay, Alaska, and has an API
gravity of 27. The test loop is one hundred feet long and
is constructed of one inch nominal pipe. The polymer
compositions are added to the crude oil as 5 weight percent
solutions in kerosene. Test samples are prepared by blend-
ing 45.4 gms of the 5 weight percent polymer solution with
500 pound batches of the crude oil for two hoursO The
resulting mixture contained 10 ppm polyrner. The blended
mixture is forced through the test loop using wa-ter as the
pumped displacing fluid. The percentage pressure drop loss
(percentage drag reduction) for each test run is calculated
from the following formula:
- 12 -
~ ~'77~
% Drag Reduction = ~Pco ~P x 100
wherein Pco is the measured drop which occurs when the
crude oil without drag reducing agent is pumped through -the
test loop and Ps is the measured pressure drop which
occurs when a DR~containing crude oil sample is pumped
through the test loop.
The tests were carried out at a number of differ-
ent linear flow velocities in order to evaluate the effic-
iency of the DRA's at various flow rates. The test results
are tabulated in the following table. During the tests the
liquid being pumped is maintained at 140 ~ 3F. Each
control run and test run lasted 2 to 3 minutes. The
reported pressure drops are the average pressure drops
measured during the -test period.
TABLE
Linear Vel, ~P,Drag
RunDRA -Ft/Sec. _ pslRed., %
none 7.4 14.6 ~-
2 a 7.4 10.031.5
3 b 7.4 8.48 41.9
4 c 7.4 8.55 41.
5 none 5.6 8.90 --
6 a 5.6 6.13 30.6
7 b 5.6 5.20 41.5
8 c 5.6 5.30 40.
9 none 4.5 5-97 --
a 4.5 4.30 28.0
11 b 4.5 3.55 40.5
12 c 4.5 3.75 37.2
.
-- 13 --
1. The letters a, b and c designate DRA's prepared
in ~xamples I, II and ~II, respectively.
The results tabulated in the table show that very
significant drag reductions are obtained when small amounts
of very high molecular weight copolymers of butene-l and
either hexene-l or dodecene-l are added to crude oil being
pumped through a test pipeline. The results listed also
show that significant drag reduction is obtained over a
range of linear velocities.
Although the invention is described by certain
examples, it is not limited to the specific details of
these examples. Other embodiments which are within the
spiri-t of the invention are included. For example, the
polymeric drag reduction agent may be prepared from more
than two olefinic monomers and the agents of the inven-tion
may be used to reduce drag in hydrocarbon liquids other
than crude oil. The scope of the invention is limited only
by the breadth of the appended claims.
- 14 -
