Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
132~39~
The present invention relates to petroleum oils, and more
particularly to crude oils, vacuum ~as oils and residual oils,
possessing improved flow properties.
The Prior art
The low temperature beha~ior of petroleums and petroleum
products is decisively influenced by the paraffins which they con-
tair.. On cooling, the parafins crystallize out. The fluidity of
the oils is thus reduced or inhibited altogether. On being heated,
the paraffins generally again go into solution in the oil matrix.
To improve their low temperature flow properties, the oils can be
~dewaxed. Moreover, additives known as pour point depressants have
been.developed which effectively lower the pour point, that is, the
lowest temperature at which the oil will flow (DIN 51,597), even in
concentrations of from 0.05 to 1 weight pe~rcent. With regard to
their mode of action, it has been hypothesized that paraffinlike
`~ compounds~are being incorporated into the growing paraffin crystal
aces and so prevent the f~urther growth o the crystals and the for-
mation of extensive interlocklng networks of crystals. From an
empirical point of view, the mode of action of suoh pour point
improvers appears to be tied to the presence of certain structural
elements, namely, alkyl groups of sufficient chain Iength to be
incorporated into the growing paraffin crystals from nucleation,
, .
and to the presence of side~~chains or side groups spaced ~ar enough
apart to interfere with crystal growth. (see Ullmanns ~nzyklopadie
~; der technischen Chemie, 4th ed., vol. 20, p. 548 ff., Verlag Chemie,
' 1981.) -~
132~396 -:
Apart from ethylene/vinyl acetate (EVA) copolymers and
long chain polyalkyl fumarates, it has been maLnly polyalkyl acry-
lates with C18-C24 alkyl groups which have found practical use as -
crude oil flow improvers. Their development was probably based on
the teaching of German patent 17 70 695 from the year 1959, which
proposed the use of long chain (C>12) polyalkyl acrylates and meth- -
acrylates as flow improvers for crude oils.
he ~roblem and the solution
Dwindling resources are making it necessary to exploit
increasingly oil deposits whose processing gives rise to more
serious technological problems than had to be contended with even a
few years or a few decades ago. To some extent, these prQblems stem
from the paraffin content of the various crude oils, which over~ll
is higher but differs according to the source. It has thus become
stRadi~y ~ore difficult to make available additives that will in-
fluence the propertles of crude oils as desired at least in the case
of a majority of the deposits. ~t should preferably be possible to -
~anufacture these additives at low cost and to use them by conven-
tional technigues.
The present invention thus has as its object to provide
flow improvers for crude oils in the broadest sense, for vacuum gas
oils,or for residual oils,which can be depended on to meet the
requirements on flow improvers for these oils on the basis of spe-
c~fic characteristics. one such characteristic is the temperature-
dependent onset of paraffin crystallization in the oils. (With
~egard to methods for its determination, see A. Ecker in "Erdol und
Kohle", vol. 38 (,6), 281 (1985); A. Ecker, Erd~l, Erdgas 101, 154
~1985); C. S. Moynihan et al., Thermochimica Acta 52, 131 ()1982);
and R. L. Blaine, NGLI Spokesman, June 1976.)
s
-- 2 --
1325396
On cooling, the paraffins contained in the oils crystallize
out with liberation of heat. The heat liberated can be detected as a
peak exotherm by means of differential thermal analysis (DTA) or,
preferably, of differential scanning calorimetry (DSC), and the onset
of paraffin crystallization can thus be determined satisfactorily,
whereas the determination of the wax appearance point or of the
cloud point, which is based on visual observation, generally is not
effective in the case of dark colored products and of residues.
It has now been found that petroleum oils from the group
of crude oils, vacuum gas oils,and residual oils, where the onset of
paraffin crystallization occurs at or below 30 C, and which contain
from 1 to 10,000 ppm of at least one polymer P, selected from the
group of polyalkyl acrylates and methacrylates or of polydialkyl
fumarates, wherein the onset of crystallization, determined as the
cloud point of a 0.1 weight percent solution of the polyalkyl acry-
late or methacrylate or of the polydialkyl fumarate in isooctane in
conformity with DIN 51,5g7 or ASTM D 97-66, occurs at a temperature
below 15 C, possess improved properties, and in particular improved -
flow properties, which as a rule meet practical requirements.
The determination of the onset of paraffin crystallization
is best performed, in connection with the present invention, by means
of differential scanning calorimetry. (See above.) -
The standard condition adopted, under which the onset of
paraffin crystallization was fixed at S 30 C, ls a cooling rate of
the oil sample of 10 K/min.
The determination of the onset of crystallization of the -
polyalkyl acryla~es and methacrylates P-I or polydialkyl fumarates
P-II is based by definition on the determination of the cloud point
of a 0.1 weight percent solution of the polymer in isooctane in con-
formity with DIN Sl,597.
132~396
The ~olyalkyl acrylates and methacrYIates P-I or Pol~dialkYl fuma-
rates P-II
The polyalkyl acrylates and methacrylates P-I differ on the
basis of the definition adopted from the commonly used polyalkyl~
acrylates of the prior art (see above) with C18-C24 alkyl groups,
whose association temperature (onset of crystallization) is about
20 C. The polyalkyl acrylates and methacrylates to be used in
accordance with the invention, which have an association temperature -
of less than 15 C, are polymers of esters of acrylic or methacrylic
acid with longer chained alkanols (rom C8 and up to c40)l in other
words, including those with C16-C24 alkyl groups, which, however,
should be selected so that said association-temperature reguirement
ls met. The following criteria may be employed in their selection:
- Polymerization or copolymerization of esters of acrylic
; acid with alkyl groups having 18 or fewer carbon atoms, and more
particularly from 12 to 18 carbon atoms.
- Polymerization or copolymerization of esters of meth-
acrylic acid instead of acrylio ac~d, particularly those with C12-C40
alkyl groups~
- Copolymerization with mcnomers which are not capable of
side-chain crystallization, and particularly with alkyl groups having
fewer than 10 carbon atoms, or with branched alky} groups having from
3 to 40 carbon atoms.
- Examples of polymer types which satisfy that condition are:
Polytallow acrylate (C16-C18 alkyl acrylate) = P-I-l.
Polybehenyl me~hacrylate (C18-C24 alkyl methacrylate) = P-I-2.
Copolymer of behenyl acrylate (C18-C24 alkyl acrylate) and isodecyl
acrylate = P-I-3.
The molecular weights of the polymers P-I and P-II usually
range from 5,000 to 1,000,000, and preferably from 10,000 to 500,000.
The molecular weight is maintained within this range by the use of
:.
-- 4 --
132~39~
conventional chain transfer agents of the organosulfur type, or ex-
ample. (See Th. Volker and H. Rauch-Puntigam, Acryl- und Methacryl-
verbindungen, Springer-Verlag, 1967.) Particularly well suited are
mercaptans such as dodecyl mercaptan, used in amounts of from 0.01
to 2 weight percent based on the monomers. The molecular weights
are determined by gel permeation chromatography (GPC) using poly-
methyl methacrylate as calibrating substance. (See Kirk-Othmer,
Encyclopedia of Chemical Technology, 3rd ed., vol. 18 , pp. 209 and
749, John Wiley ~ Sons, 1982.)
The polydialkyl fumarates P-II, which in accordance with -
the invention are also to be used, correspond with respect to their
preparation and to their molecular weight to those used in the prior
art. (See T. Otsu et al., Mem. Fac. Eng., Osa~a City Univ. 23, 79-91
(1982); Y. Murata et al., Chem. Econ., Eng. Rev. 17 ~10), 18-22 (1985).
The alkyI groups correspond to those commonly used with
acrylic or methacrylic esters, in other words, al~yl groups having up
to 40 carbon atoms, and more particularly from 8 to 40 carbon atoms, ~
and preferably from 18 t~ 4,0. carbon atoms. ~-
:- ; .
~ he starting monomers are known per se or can be prepared
conventianally, for example by transesterificatlon of lower acry-
lates or methacrylates; such as ~he methyl or ethyl ester with higher
alcohols. The preparation of the polymers may be based on the prior
art free radical polymerization methods.~ (See Th. Volker and H.
Rauch-Puntigam, Acryl- ùnd Methacrylverbindungen,~Springer-Verlag,
Berlin 1967.) An inert medium, preferably of the type of the petro-
leum oils themselves, for example, 100 N oil, should be used as poly-
merization medium.
Suitable reaction vessels are those comm~only used, which -
are preferably eguipped with a stirrer, heating means, a thermo-
meter, a reflux condenser and a feed inlet. The polymeriza, ~ ~
tion is preferably carried out under an inert gas such as carbon -- -
5 _ . . -
132~39~
dioxide. Moreover, the usual free radical initiators, preferably
peresters, peroxides or azo compounds, for example, tert-butyl per-
oxybenzoate or tert-butyl peroxypivalate, should be employed in the
usual concentrations, for example, from 0.1 to 5 weight percent, and
preferably from 0.3 to 1 weight percent, based on the total amount
of the monomers. As a rule, the process is started at an elevated
temperature, preferably above 60O C, and more particularly at 70
i 5 C. Initiator is then added~ and the temperature will reach a
peak that may be above 80 C, for example 140 + 10 C. By heating
and/or the addition of initiator, a temperature range may optionally
be reached which is suitable for further polymerization. Polymeriza-
tion is usually completed within approximately five hours.
The petroleum oils
By definition, the petroleum oils or petroleum oil products
whose properties, and particularly the temperature dependant flow
properties, are improved by the present invention are those where the
onset of paraffin crystallLzation occurs at or beIow 30 C. Within
the meaning of the present invention, the petroleum oils suitable for
use include: ~
- Crude petroleums. ~ -
- Vacuum gas oils with a boiling range of from 320 to 500 C at
normal pressure. (True boiling point.)
- Residual oils (distillation residues that would distill at above
350 C). ~ -
(See Winnac~er-KUchler, Chemische Technologie, vol. 5, 4th ed., Carl
Hanser Verlag, Munich 1981.) Not included are, therefore, petroleum
oils or petroleum products where paraffin crystallization sets in at
a temperature above 30 C. The onset of paraffin crystallization
(cloud point) as a function of temperature is an important charac- -
teristic of petroleum oils from the various sources and of the re-
spective petroleum products and is routinely determined by those
132~39~
skilled in the art. As pointed out earlier, the preferred method of
its determination is differential scanning calorimetry (DSC~.
By definition, the petroleum oils should contain from 1 to
10,000 ppm, and preferably from 50 to 2,000 ppm, of the polymers P,
depending on the source of the oils whose flow properties are to be
improved.
Practice of the invention
After polymerizatlon, the polymers P are advantageously
diluted with an appropriate compatible solvent, for example, a hydro-
carbon such as xylene, toluene, kerosene,or Shellsol~. The solution
so obtained may then be used in the preparation of the petroleum
oil blends. In special cases, this solution can be added to the
crude oil directly at the casinghead or in the pipeline.
The polymers P, preferably in the form of said solutions,
are admixed with the petroleum oils, such as crude oils, vacuum gas
oils or residual oils, appropriately~at elevated temperature, for -
example at from 40 to about 80 C.
The flow improving additives will retain their activity
over the period of time normally reguired. As a rule, there will
be no need for adding flow improvers other than the polymers of the
invention.
':
Advanta~es
As already mentloned, it is important during the present
difficult raw material situation to have the proper additive avail-
able for a petroleum from a given source or for a given petroleum -
product. -
The idea that there was nothing to be done except to find
a suitable additive for petroleum oils from every source by trial
and error was rather discouraging. The present invention, which
establishes criteria for the suitability of specific additives and
132~39~
for the characterization o such suitable additives, must therefore
be regarded as a most welcome development. Even if the polymers to
be used in accordance with the invention were only as effective as
those of the prior art, they would still represent a significant
improvement because of the substantially better raw material basis
or the decidedly more favorable cost situation compared with the
C18-C24 polyacrylates, for example.
Actually, the inventive polymers can be shown to have
improved activity in at least a number of crude oils investigated
that meet the established criteria. This enhanced effec~iveness is -
all the more surprising as the inventive polymers produce little
effect, if any, in crude oils where the onset of paraffin crystal-
lization occurs at temperatures above 30~ C.
A better understanding of the present invention and
.~ ,~ . . .
~ of its many advantages will be had from the following Examples, -
. -~ . ..
given by way of illustration.
In ehe Examples, certain properties of the improved
=~ petroleum oil products and of its components were determined
according to following techniques (A) - (D)~
' ' ' `
~'
- 8 -
132~39~
(A) Determination of onse~ of crvstallization of the Pol~mers P
(cloud P~int; .visual)
The determination is performed on the basis of DIN 51,597
or AS~M D 97-66 as follows:
A 0.1 wt. ~ solutlon of the polyalkyl acrylate or meth-
acrylate or of the polydialkyl fumarate in isooctane is prepared --
at 80 C and transferred to a sample flask in a ~acketed vessel.
The solution is cooled by being placed ln a temperature controlled
cooling bath. At intervals of 1 C, the solution is inspected for
a cloudy appearance. The very first clouding indicates the onset~ --
of crystallization of the polymer.
, . A ~ .
(3) Determination of onset of cr~stallization in the Petroleum ~-~
oils (DSC) (See DIN 51,005)
The measurements commence at 80 to 100 C. The cooling
rate is 10 K/min.~ The onset of crystallization is the temperature
at which the peak exotherm sets in, which~is the so called onset ~ -
temperature.
tC) Determinati n of freezinq Point of the inventive Petroleum oil ~-
blends (based on DIN 51,597 or ASTM D 97-66)
. .
~ As a departure from the DIN standard, the sample was taken
-~; from the oooling bath at intervals of 1 C and tested for fluidity.
The freezing points, in other words the temperatures at whiah the `-
oil will no longer flow, are given. The automatic measuring in- -
strument made by Herzog, Lauda (Federal Republic of Germanyl, is
advantageously used for the determination.
(D) PreParation of the PolYmers P
~, .....
By "100 N oil" is meant a base oil with a viscosity of ~
4 mm2/sec at 100 C, which is the accepted meaning in the industry. ;-
132~39~
The determination of the reduced viscosity is performed
in chloroorm at 20 C in con~ormity with DIN 1342 or DIN 51,562.
The determination of the cloud point tCP) is outlined
above.
ExamPle 1
Pre~aration of Polvtallow acrvlate P~
To a 150-liter kettle, 85 kg of tallow acrylate (C16-C18
acrylate), 15 kg of 100 N oil,and 0.425 kg of dodecyl mercaptan were
charged. The mixture was degassed by the addition of dry ice (CO2)
and then heated to 70 c. Then 0.425 kg of tert-butyl peroxy-
pivalate was added. The temperature then rose to 148 C. One and
two hours, respectively, after peak temperature had been reached,
0.17 kg of dodecyl mercaptan and 0.085 kg of tert-butyl peroxy-
benzoate were added at 130 C. Polymerization was complPted after
5 hours.
Mw (GPC, calibration with PMMA): 118,000 g/mol
Reduced viscosity (ChC13, 20 C): 21 ml/g
CP (0.1% in isooctane): +10 C
ExamPle 2
Pre~aration of PolYbehen~l methacrvlate P-I-2
. .
To a 100-liter stirred kettle, 30 kg of behenyl meth- ?
acrylate (C18-C24 methacrylate~, 30 kg of 100 N oil,and 0.60 kg of
dodecyl mercaptan were charged. After the mixture had been degassed
with dry ice (CO2), it was heated to 70 C and 0.60 kg of tert-butyl
peroxyplvalate was added. Two hours after the peak temperature of
96.5 C had been reached, the mixture was heated to 130 C and 0.03
kg of dodecyl mercaptan and 0.06 kg of tert-butyl peroxybenzoate
were added. Polymerization was completed after 5 hours.
-- 10 --
132~3~
Mw ~GPC, calibration with PMMA): 24,300 g/mol
Reduced viscosity tCHC13, 20 C): 11 ml/g
CP (0.1% in isooctane): -2 C
ExamPle 3 ~-
PreParation of a coPolYmer P-I-3 of behenYl acrYlate and isodecyl
acrvlate
To a 100-liter stirred kettle, 30 kg of 100 N oil, 20 kg of
behenyl acrylate (C18-C24 acrylate), and 9 kg isodecyl acrylate were -
charged. After the addition of 0.60 kg of dodecyl mercaptan, the
mixture was degassed with dry ice (Co2) and then heated to 70 C.~ -
Polymerization was initiated by the addition of 0.12 kg of tert-
butyl peroxypivalate. After the peak temperature of 83 C had been ~ -
reached, the mixture was heated to 130 C and further polymerized by
the addition of 0.03 kg;of dodecyl mercaptan and 0.06 kg of tert-
butyl peroxybenzoate. The further polymerization was completed
af,t~r 3 hours.
Mw (GPC, calibration with PMMA): 24,900 g/mol
Reduced viscosity ~CHC13, 20 C): 10.1 ml/g
CP (0.1% in isooctane): ~1.5 C
Exam le 4 (Com~arison) ~ -
Pre~aration of PolvbehenYl acrvlate V-I-l
To a 100-liter stirred kettle, Sl kg of behenyl acrylate
(C18-C24 acrylate3, 9 kg of 100 N oil,and 0.051 kg of dodecyl mer-
captan wère charged, degassed with dry ice (CO2), and heated to 70 C.
Polymerization was initiated by the additio~ of 0.191 kg af tert-
butyl peroxypivalate and 0.115 kg of tert-butyl peroxybenzoate. One
hour after the peak temperature of 134 C had been reached, the --
charge was mixed with 0.077 kg of dodecyl mercaptan and 0.051 kg of
ter~-butyl peroxybenzoate and further polymerized at 130 C for 3
hours. - ~-
'.
- 11 -
132~39~
Mw (GPC, calibration with PMMA): 560,000 g/mol
Reduced viscosity (CHC13, 20 c): 48 ml/g
CP (0.1~ isooctane): 19.5 C
ExamPle S
PreParatlon of Polvbehenvl acrYlate V-I-2
To a 150-liter stirred kettle, 45 ~g of behenyl acrylate,
45 kg of 100 N oil,and 0.675 kg of dodecyl mercaptan were charged
and then degassed with dry ice (CO2). After heating to 70 C, 0.18 kg
of tert-butyl peroxypivalate was added. After the peak temperature of
120 c had been reached, the charge was heated to 130 C, and 0.045 kg
of dodecyl mercaptan and 0.09 kg of tert-butyl peroxyoctoate were
added. Polymerization was completed after 5 hours.
Mw (GPC, calibration with PMMA): 23,200 q/mol
Reduced viscosity (CHC13, 20 C): 11 ml/g
CP (0.1% ln isooctane): 20.5O C
(EI Examples lllustratinq effectiveness
ExamPles 6 to ll
The polymers P-I-l to P-1-4 and V-I-l to V-I-2 were added
to the crude oils as 10% stock solutions in xylene at~80 C. All
guantlties are based on the polymer. The freezing points were deter-
~ ~ .
~ mined on the basis of DIN 51,597 with an automatic measuring in-
, ~
strument made by Herzog in~Lauda. The onset of paraffin crystalli-
zation ~CP) in the crude oils was determined by DSC at a coolinq
rate of 10 Kjmin.
- 12 -
. .
132~39~
Exa~le 6
Australian crude oil, 43.8~ n-a1Jcane oonterlt; cloud polnt, 25 C.
Freezlng point
C
W~thou~ add~ ~lve ~ 21 .
~, 000 ppm P~I-l .~ 11 .
1, 0~0 pprn P-~-2 + 12
1,000 ppm P-~3 + 13
1, 000 ppm V~ 15
1, 000 ppm V-I 2 ~ 16
Example 7
:
Pakistani crude oil, 34.396 n-a1kane contentl oloud point, 22 C.
~reezlng po~nt
' ' ~ :''
~uantlty o~ addltlvo100 ppm SOO, ppm
P~ 2 ~ 7
P~ 9 ~ 7
P-I-3 +fl . + 6
V-I-2 +18 + 16
Without addl~lve + 21 ..
~'~ . ~'''''.
' '
~ .
- 13 - :~
132~3~`~
Exam~le 8 -
South German crude oil, 22.7% n-alkane content; cloud point, 29 C.
Freezing point
C
Quantity.:added 100 200 5001000 ppm
P-I-l + 13 + 9 + 6+ 4
P-I-2 + 7+ 4
P-I-3 + 9 + 7
V-I-2 + 15 ~ 11 + 8+ 5
Without additive + 21
',
ExamPle 9
Paklstani crude oil, 25.3% n-alkane content; cloud point, 24 C
~ ~ .
~:~5 Freezing point
~ . . C
Without additive ~ + 2I
:: lO0 ppm P-I-l + 7
100 ppm P-I-2 ~ 3
100 ppm P-I-3 + 4
100 ppm V-I-l + 12 -
100 ppm V-I-2 +:12
Example 10 ~Com~arison)
~ .
~:~ In contrast to Examples 6 to 9, North Sea crude oil, with .
-
~ an n-alkane content of 14.7%j has a cloud point of 47 C, in other
: words, above 30 C.
; . .. :.
- 14 -
132~3~ :
.,:
Freezing po~nt
C . .
.
Without additive + 27
With 1000 ppm P-I-l + 26
1000 ppm P-I-2 + 27 -.
1000 ppm P-I-3 + 27
With 1000 ppm V-I-2 + 0
.
ExamPle 11 (comParison)
. ~ombay high crude, 22..6% n-alkane c,ontent; cloud poLnt, 38 C, in
:~ other words, again above 30 C.
Freezing point .
C
Without additlve + 30 .
With lS0 ppm P-I-l :+ 30
150 ppm P-I-2 + 30
: .
150 ppm P-I-3 + 30
. :With lS0 ppm V-I-l + 9 : :- :
.
`~ ~ 150 ppm V-I-2 + 11 ~
~ ~ .
Exam~le 12 ~ComParison)
African crude oil, 10.6% ~-alkane content; cloud point,. 35 C.
Freezing point :
:~: C .
~ ,
: Without additive ~ + 24
~; With 250 ppm P-I-l + 20
250 ppm P-I-2 : + 21
~:: : - . ,
~ .
~ : With 250 ppm V-I-l + 10
,
:~ - 15 -
,~
132~
Example 13
North Gcrman vacuum gas oi.l, 2.2% n-alkane cont~nt; cloud point, 12C
Freezing point
. .
Without ad~t~ve ~ l9
Wil:h 1,000 ppm P~ 2
wlth 1, 000 ppm P X-2 - 5
With },000 ppm P-I-3 - 5
With l, 000 ppm P-I-l + ~ 2 ~ l ; l ) - 2
Wi~h 1, 000 ppm P-I-l + P-I-3 ( 1 ; 1 ) - 3
With l, 000 ppm P-I-l + P-I-3 ~ - 5
. ._ , .
Wi.th l,OOO ppm V-l-1 + ~
Wi.t:h l,OOO ppm V-1-2 + S
The flow improvers as used in vacU~n ga6 oil and in crude oil( see aboYe)
also proved eff~ctive in residual oil of variable oriqin.
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gOl-02-19
