Note: Descriptions are shown in the official language in which they were submitted.
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Clariant GmbH 1997 DE 403 Dr. KM/sch
Description
Fuel oils based on middle distillates and copolymers of ethylene and
unsaturated
carboxylic esters
The present invention relates to fuel oils which contain middle distillates
and
copolymers of ethylene and esters of unsaturated carboxylic acids and which
exhibit
improved cold flow behavior.
Crude oils and middle distillates such as gas oil, diesel oil or heating oil,
obtained by
distillation of crude oils, contain, depending on the origin of the crude
oils, different
amounts of n-paraffins, which crystallize out as lamellar crystals when the
temperature is lowered and in some cases agglomerate with inclusion of oil.
This
results in a deterioration in the flow properties of these oils or
distillates, giving rise
to problems, for example in the recovery, transport, storage and/or use of the
mineral oils and mineral oil distillates. In the case of mineral oils, this
crystallization
phenomenon can lead to deposits on the pipe walls during transport through
pipelines, especially in the winter, and in individual cases, for example when
the
pipeline is shut down, even to complete blockage thereof. The precipitation of
paraffins can also cause difficulties in storage and further processing of the
mineral
oils. Thus, it may be necessary in winter to store the mineral oils in heated
tanks. In
the case of mineral oil distillates, blockage of the filters in diesel engines
and
furnaces may occur owing to the crystallization, with the result that reliable
metering
of the fuels is prevented and complete interruption of the fuel or heating
medium
feed may occur.
In addition to the traditional methods for eliminating the paraffins which
have
crystallized out (thermally, mechanically or by means of solvents), which
relate only
to the removal of the precipitates already formed, recent years have seen the
development of chemical additives (so-called flow improvers or paraffin
inhibitors)
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which physically interact with the precipitating paraffin crystals and thus
modify their
shape, size and adhesion properties. The additives act as additional crystal
seeds
and partially crystallize out with the paraffins, resulting in a larger number
of smaller
paraffin crystals with modified crystal shapes. A part of the action of the
additives is
also explained by dispersing of the paraffin crystals. Modified paraffin
crystals have
less tendency to agglomerate, so that the oils into which additives have been
introduced can be pumped or processed even at temperatures which are often
more
than 200 lower than in the case of oils not containing additives.
The flow and low-temperature behavior of mineral oils and mineral oil
distillates is
described by stating the pour point (determined according to ISO 3016) and the
cold
filter plugging point (CFPP; determined according to EN 116). Both
characteristics
are measured in C.
Typical flow improvers for crude oil and middle oil distillates are copolymers
of
ethylene with carboxylic esters of vinyl alcohol. Thus, according to DE-A-11
47 799,
oil-soluble copolymers of ethylene and vinyl acetate having a molecular weight
between about 1,000 and 3,000 are added to mineral oil distillate fuels having
a
boiling point between about 120 and 400 C. Copolymers which contain from about
60 to 99% by weight of ethylene and from about 1 to 40% by weight of vinyl
acetate
are preferred. They are particularly effective if they were prepared by free
radical
polymerization in an inert solvent at temperatures of from about 70 to 130 C
and
pressures of from 35 to 2,100 atm (gage pressure) (DE-A-19 14 756).
Other polymers used as flow improvers contain, in addition to ethylene and
vinyl
acetate, for example 1-hexene (cf. EP-A-0 184 083), diisobutylene (cf.
EP-A-0 203 554) or an isoolefin of the formula
CH3
R CH2 C CHR'
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in which R and R' are identical or different and are hydrogen or C,-C4-alkyl
radicals
(EP-A-0 099 646). Copolymers of ethylene, alkenecarboxylic esters andlor vinyl
esters and vinyl ketone are also used as pour point depressants and for
improving
the flow behavior of crude oils and middle distillates of crude oils (EP-A-0
111 888).
In addition, copolymers based on a,13-unsaturated compounds and maleic
anhydride
are also used as flow improvers. DE-196 45 603 describes copolymers of from 60
to
99 mol% of structural units derived from ethylene and from 1 to 40 mol% of
structural units which are derived from maleic acid, its anhydride or its
imides.
DE-1 162 630 discloses copolymers of ethylene and vinyl esters of straight-
chain
fatty acids having 4 to 18 carbon atoms as a pour point-depressing additive
for
distillate fuels having a medium boiling point, such as heating oil or diesel
oil.
EP-A-0 217 602 discloses ethylene copolymers with vinyl esters carrying C,- to
C18-
alkyl radicals as flow improvers for mineral oil distillates having boiling
ranges
(90 - 20 %) of less than 100 C.
EP-A-0 493 769 discloses terpolymers which are prepared from ethylene, vinyl
acetate and vinyl neononanoate or neodecanoate, and their use as additives for
mineral oil distillates.
EP-A-0 746 598 discloses copolymers of ethylene and dialkyl fumarates as a
mixture with mineral oils which a cloud point of less than -10 C.
The efficacy of the known additives for improving the properties of mineral
oil
fractions is dependent, inter alia, on the origin of the mineral oil from
which they
were obtained and hence in particular on its composition. Additives which are
very
suitable for establishing specific properties of fractions of a crude oil can
therefore
lead to completely unsatisfactory results in the case of distillates of crude
oils of
different origin.
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Against the background of the increased environmental consciousness, fuels
which
give rise to less environmental pollution during their combustion have
recently been
produced. Appropriate diesel fuels are distinguished by a very low sulfur
content of
less than 500 ppm and in particular less than 100 ppm, a low aromatics content
and
a low density of less than 0.86, in particular less than 0.84, g/mI. They
cannot be
treated with conventional flow improvers or can be treated therewith only to
an
inadequate extent. In particular the winter grades of diesel fuels produced
for use
under arctic conditions and having extreme low-temperature properties, such
as, for
example, a cloud point of less than -8 C and in particular less than -15 C,
very
narrow distillation cuts with boiling ranges of 20 to 90% by volume below 120
C, in
particular below 100 C and in some cases also below 80 C, and a distillation
volume
of 95% by volume at temperatures below 360 C, in particular below 350 C and
especially below 330 C, present problems. The low-temperature properties of
such
distillates can be satisfactorily improved at present only by adding low-
boiling, low-
paraffin components, such as, for example, kerosene.
The composition caused by narrow distillation cuts and low final boiling
points
presents problems with regard to the response behavior of flow improvers in
these
oils: These oils have a paraffin distribution with a maximum at about C12 to
C14 and
contain only insignificant amounts of the n-paraffins crystallizing out of
conventional
grades and having hydrocarbon chains longer than C18. The cloud points and
CFPP
values are so low, especially in the case of winter grades, that conventional
flow
improvers do not respond and the low-temperature properties must be
established
by dilution with kerosine.
It was therefore the object to develop new fuel oils having an improved low-
temperature flowability compared with the prior art.
Surprisingly, it has been found that main chain polymers of ethylene which
carry side
chains having more than 5 carbon atoms are suitable for lowering the CFPP also
in
the middle distillates described above. Ethylene/vinyl acetate copolymers
having
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29374-297
corresponding comonomer contents are on the other hand
virtually insoluble in hydrocarbons.
The invention relates to fuel oils containing
A) a mineral oil having a cloud point of less than
5-8 C, a boiling range (90-20%) of less than 120 C and a
difference between CFPP and PP of less than 10 C and
B) one or more copolymers containing bivalent
structural units of the formula
Bi) -CH2-CHZ- (1)
and one or more of the bivalent structural units B2)
B2) -CHZ-CR1R2- (2)
in which R' is hydrogen or methyl and R2 is C00R3, OR3 or
OCOR3, R3 being an alkyl radical having at least 4 and at
most 30 carbon atoms, or wherein component B2) is a bivalent
structural unit of formula (2a)
-HC-CH-
O-~ >=O
N (2a)
1 3
R
derived from maleic acid.
According to one aspect of the present invention,
there is provided a fuel oil containing cold flow improvers,
comprising A) a mineral oil having a sulfur content of less
than 500 ppm, a low aromatics content and a density of less
than 0.86 g/ml, a cloud point of less than -8 C, a boiling
range of 20 to 90% by volume below 120 C and a difference
between CFPP and PP of less than 10 C, and as the cold flow
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5a
improvers B) one or more copolymers containing bivalent
structural unit of formula (1)
-CH2-CH2- (1)
and one or more bivalent structural units selected from
bivalent structural units of formulae (2) and (2a) wherein
the bivalent structural unit of formula (2) is:
-CH2-CR1R2- (2)
wherein R' is hydrogen or methyl, R 2 is COOR3, OR3 or OCOR3,
and R3 is a neoalkyl radical having 7 to 11 carbon atoms, and
the bivalent structural unit of formula (2a) is:
-HC-
p~
(2a)
3
R
which is derived from maleic acid, wherein R3 is an alkyl
radical having at least 4 and at most 30 carbon atoms.
The sulfur content of the mineral oils stated
under A) is preferably less than 500, particularly less than
300 ppm, especially less than 100 ppm. Their cloud point is
preferably less than -15 C. The boiling ranges (90-20%) of
the distillation cuts are preferably less than 100 C, in
particular less than 80 C. The use of mineral oils
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having a 95% distillation point of less than 360 C, in particular less than
350 C,
especially less than 330 C, is preferred.
R' is preferably hydrogen. R3 is preferably a linear or branched CS-C24-alkyl
radical,
particularly preferably a linear or branched C$-C1e-alkyl radical. In a
further,
particularly preferred embodiment of the invention, R is a neoalkyl radical
having 7 to
11 carbon atoms, in particular a neoalkyl radical having 8, 9 or 10 carbon
atoms.
The neoalkanoic acids from which the abovementioned neoalkyl radicals can be
derived are described by the formula (3):
R" R'
(3)
COOH
R' and R" are linear alkyl radicals having together preferably 5 to 9, in
particular 6, 7
or 8, carbon atoms. The vinyl ester used for the copolymerization accordingly
has
the formula (4):
R "* R '
(4)
COO-'-
Further suitable comonomers are those which can be derived from acrylic acid:
:~ ~/O\R 3
~~ (5)
O
Preferred radicals R3 are, for example, butyl, tert-butyl, pentyl, neopentyl,
octyl,
2-ethylhexyl, decyl, dodecyl, tetradecyl, hexadecyl, octadecyl and behenyl.
The fuel oil compositions according to the invention preferably contain
copolymers in
which the comonomers 131) are contained in an amount of from 85 to 97 mol% and
the comonomers B2) in an amount of from 3 to 15 mol%. From 4 to 10 mol% of B2)
and from 90 to 96 mol% of 131) are particularly preferred.
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The copolymers stated under B) can be prepared by the conventional
copolymerization methods, such as, for example, suspension polymerization,
solution polymerization, gas-phase polymerization or high-pressure mass
polymerization. The high-pressure mass polymerization at pressures of,
preferably,
from 50 to 400, in particular from 100 to 300, MPa and temperatures of,
preferably,
from 50 to 300 C, in particular from 100 to 250 C, is preferred. The reaction
of the
monomers is initiated by initiators forming free radicals (free radical chain
initiators).
This class of substances includes, for example, oxygen, hydroperoxides,
peroxides
and azo compounds, such as cumyl hydroperoxide, tert-butyl hydroperoxide,
dilauroyl peroxide, dibenzoyl peroxide, bis(2-ethylhexyl)peroxocarbonate, tert-
butyl
perpivalate, tert-butyl permaleate, tert-butyl perbenzoate, dicumyl peroxide,
tert-butyl
cumyl peroxide, di-(tert-butyl) peroxide, 2,2'-azobis(2-methylpropanonitrile)
and
2,2'-azobis(2-methylbutyronitrile). The initiators are used individually or as
a mixture
comprising two or more substances in amounts of from 0.001 to 20% by weight,
preferably from 0.01 to 10% by weight, based on the monomer mixture.
Preferably, the copolymers stated under B) have melt viscosities at 140 C of
from
to 10,000 mPas, in particular from 30 to 5000 mPas, especially from 50 to 2000
mPas. The desired melt viscosity of these copolymers is established for a
given
20 composition of the monomer mixture by varying the reaction parameters
pressure
and temperature and, if required, by adding moderators. Hydrogen, saturated or
unsaturated hydrocarbon, e.g. propane, aidehydes, e.g. propionaldehyde,
n-butyraidehyde or isobutyraidehyde, ketones, e.g. acetone, methyl ethyl
ketone,
methyl isobutyl ketone or cyclohexanone, or alcohols, e.g. butanol, have
proven
useful as moderators. Depending on the intended viscosity, the moderators are
used
in amounts of up to 20% by weight, preferably from 0.05 to 10% by weight,
based on
the monomer mixture.
The copolymers stated under B) may contain up to 4% by weight of vinyl acetate
or
up to 5% by weight of further comonomers. Such comonomers may be, for example,
vinyl esters, vinyl ethers, alkyl acrylates, alkyl methacrylates or higher
olefins having
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at least 5 carbon atoms. Preferred higher olefins are hexene, 4-methylpentene,
octene or diisobutylene.
In order to obtain the copolymers stated under B), monomer mixtures which
contain,
in addition to ethylene and, if required, a moderator, from 1 to 50% by
weight,
preferably from 3 to 40% by weight, of comonomers are used. The different
polymerization rates of the monomers are taken to account by virtue of the
fact that
the composition of the monomer mixture differs from the composition of the
copolymer. The polymers are obtained as colorless melts which solidify to waxy
solids at room temperature.
The high-pressure mass polymerization is carried out batchwise or continuously
in
known high-pressure reactors, for example autoclaves or tube reactors; tube
reactors have proven particularly useful. Solvents, such as aliphatic and/or
aromatic
hydrocarbons or hydrocarbon mixtures, benzene or toluene, may be contained in
the
reaction mixture. The solvent-free procedure is preferred. In a preferred
embodiment
of the polymerization, the mixture comprising the monomers, the initiator and,
if
used, the moderator is fed to a tube reactor via the reactor inlet and via one
or more
side branches. The monomer streams may have different compositions here
(EP-A-O 271 738).
The copolymers stated under B) are added to the mineral oils or mineral oil
distillates stated under A) in the form of solutions or dispersions. These
solutions or
dispersions contain preferably from 1 to 90, in particular from 10 to 80, % by
weight
of the copolymers. Suitable solvents or dispersants are aliphatic and/or
aromatic
hydrocarbons or hydrocarbon mixtures, for example gasoline fractions,
kerosine,
decane, pentadecane, toluene, xylene, ethylbenzene or commercial solvent
mixtures, such as Solvent Naphtha, Shellsol AB, Solvesso 150, Solvesso 200,
Exxsol, ISOPAR and Shellsol D types. The fuel oils according to the
invention
contain preferably from 0.001 to 2, in particular from 0.005 to 0.5, % by
weight of
copoiymer, based on the distillate.
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The fuel oils according to the invention may contain further oil-soluble co-
additives
which by themselves improve the cold flow properties of crude oils,
lubricating oils or
fuel oils. Examples of such coadditives are vinyl acetate-containing
copolymers or
terpolymers of ethylene, polar compounds which disperse paraffins (paraffin
dispersants) and comb-like polymers.
Oil-soluble polar compounds having ionic or polar groups, for example amine
salts
and/or amides, which are obtained by reacting aliphatic or aromatic amines,
preferably long-chain aliphatic amines, with aliphatic or aromatic mono-, di-,
tri- or
tetracarboxylic acids or anhydrides thereof have proven useful as paraffin
dispersants (cf. US-4 211 534). Other paraffin dispersants are copolymers of
maleic
anhydride and a,(3-unsaturated compounds, which, if required, can be reacted
with
primary monoalkylamines and/or aliphatic alcohols (cf. EP-A-0 154 177), the
reaction products of alkenylspirobislactones with amines (cf. EP-A-0 413 279)
and,
according to EP-A-0 606 055, reaction products of terpolymers based on
a,R-unsaturated dicarboxylic anhydrides, a,R-unsaturated compounds and
polyoxyalkenyl ethers of lower unsaturated alcohols.
Comb-like polymers are polymers in which carbon radicals having at least 8, in
particular at least 10, carbon atoms are bonded to a polymer skeleton. They
are
preferably homopolymers whose alkyl side chains contain at least 8 and in
particular
at least 10 carbon atoms. In the case of copolymers, at least 20%, preferably
at
least 30%, of the monomers have side chains (cf. Comb-like Polymers -
Structure
and Properties; N.A. Plate and V.P. Shibaev, J. Polym. Sci. Macromolecular
Revs.
1974, 8, 117 et seq.). Examples of suitable comb-like polymers are
fumarate/vinyl
acetate copolymers (cf. EP-A- 0 153 176), copolymers of a C6-C24-a-olefin and
an
N-C6- to C22-alkylmaleimide (cf. EP-A-O 320 766) and furthermore esterified
olefin/maleic anhydride copolymers, polymers and copolymers of a-olefins and
esterified copolymers of styrene and maleic anhydride.
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The novel fuel oils may contain other additives, for example dewaxing
assistants,
corrosion inhibitors, antioxidants, lubricity additives and sludge inhibitors.
Examples
5
The following additives Al to A5 were prepared:
A1: Ethylene-MA copolymer imidated with coconut fatty alkylamine and
containing
30% by weight (8 mol%) of MA.
A2: Ethylene-VeoVa copolymer containing 7 mol% of VeoVa 10 and having a V140
of 200 mPas.
A3: Ethylene-VeoVa copolymer containing 14 mol% of VeoVa 10 and having a
V140 of 270 mPas.
A4: Ethylene-VeoVa copolymer containing 7 mol% of VeoVa 11 and having a V140
of 84 mPas.
A5: Copolymer of ethylene and 8 mol% of stearyl acrylate, having a V140 of 65
mPas.
MA = maleic anhydride
VeoVa 10/11 = vinyl neodecanoate/neoundecanoate
V140 = melt viscosity of the copolymer, determined according to
ISO 3219 using the plate-and-cone measuring system at
140 C
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Efficiency of the additive
Table 3 shows the efficiency of the additives as flow improvers for mineral
oil
distillates on the basis of the CFPP test (Cold Filter Plugging Test according
to EN
116) in different distillates from Scandinavian refineries. The additives are
used as
50% strength solutions in Solvent Naphtha. As a comparison, the efficiency of
a
commercial ethylene-vinyl acetate copolymer (EVA copolymer) containing 13.3
mol% of vinyl acetate and having a melt viscosity V140 of 125 mPas (V1) and
that of
a commercial ethylene-vinyl acetate-vinyl neodecanoate terpolymer containing
16
mol% of vinyl acetate and 1.2 mol% of vinyl neodecanoate and having a melt
viscosity V140 of 140 mPas (V2) are shown.
Table 2: Characterization of the test oils:
Test oil 1 Test oil 3 Test oil 4 Test oil 5 Test oil 6
Initial boiling 195 C 127 C 190 C 192 C 183 C
point
% 226 C 193 C 219 C 218 C 226 C
90 % 280 C 318 C 291 C 288 C 330 C
20 95 % 300 C 330 C 311 C 306 C 347 C
Cloud Point -30 C -23 C -24 C -27 C -9 C
CFPP -31 C -23 C -29 C . -34 C -12 C
Pour Point -30 C -42 C -27 C -27 C -21 C
CFPP-PP -1 C 19 C -2 C -7 C 9 C
Density (15 ) 0.821 0.822 0.817 0.819 0.835
The CFPP is determined according to EN116 and the PP according to ISO 3016
TM
using an automatic apparatus (Herzog MC 852).
12
Table 3: CFPP efficiency
Test oil 1 Test oil 3 Test oil 4 Test oil 5 Test oil 6
100 200 400 1000 100 200 400 100 250 500 50 100 250 50 100 200
ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm ppm
Al -38 -40 <- <-40 -36 -36 -40 -39 -39 <-
40 40
A2 -38 -39 -40 <-40 -28 <- <- -36 -38 -39 -18 -20 -23
VI
40 40
A3 -33 -35 -38 -40 <- <- <- -16 -17 -19
40 40 40
A4 -36 -38 -39 <-40
A5 -39 <- <- <-40
40 40
V1 -37 -35 -35 -34 -26 -38 <- -35 -34 -34 -39 -36 -35 -17 -20 -22
V2 -33 -35 -35 -33 -26 -35 -39 -35 -34 -33 -11 -15 -22
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List of the tradenames used
Solvent Naphtha aromatic solvent mixtures having a boiling Shellsol AB
range from 180 to 210 C
Solvesso 150
Solvesso 200 aromatic solvent mixture having a boiling range
from 230 to 287 C
Exxsol dearomatized solvent having various boiling ranges, for
example Exxsol D60: 187 to 215 C
ISOPAR (Exxon) isoparaffinic solvent mixture having various boiling
ranges, for example ISOPAR L: 190 to 210 C
Shellsol D mainly aliphatic solvent mixtures having various boiling
ranges
