ADDITIVES FOR IMPROVING THE RESISTANCE TO WEAR AND
LACQUERING OF VEHICLE FUELS OF THE GAS OIL OR BIO GAS OIL TYPE
A subject of the present invention is additives making it possible to limit the
formation of soaps and/or varnishes in the internal parts of the injection systems 5 of
engines for (bio)gas oil type vehicle fuels, i.e. in particular to increase their
resistance to lacquering.
Gas oil or diesel is a vehicle fuel for diesel engines (compression engines)
comprising middle distillates with a boiling point comprised between 100 and
10 500°C.
A gas oil can be constituted by a mixture of middle distillates of fossil origin
and biofuels.
By biofuel, is meant the vehicle fuels obtained from organic matter
(biomass), as opposed to the vehicle fuels originating from fossil resources. There
15 can be mentioned, as examples of known biofuels, the bio gas oils (or also called
biodiesel) and the alcohols.
Biodiesel or bio gas oil is an alternative to standard vehicle fuel for diesel
engines. This biofuel is obtained from vegetable or animal oil (including used
cooking oils) converted by a chemical process called transesterification causing
20 this oil to react with an alcohol in order to obtain fatty acid esters. With methanol
and ethanol, fatty acid methyl esters (FAMEs) and fatty acid ethyl esters (FAEEs)
are obtained respectively.
Mixtures of middle distillates of fossil origin and bio gas oil are denoted by
the letter "B" followed by a number indicating the percentage of bio gas oil
25 contained in the gas oil. Thus, a B99 contains 99% bio gas oil and 1% middle
distillates of fossil origin, and B20 contains 20% bio gas oil and 80% middle
distillates of fossil origin etc.
Gas oil vehicle fuels of the B0 type, which do not contain oxygencontaining
compounds are therefore distinguished from bio gas oil vehicle fuels of
30 the Bx type which contain x% (v/v) vegetable oil esters or fatty acid esters, most
3
often methyl esters (FAME or VOME). When the bio gas oil is used alone in the
engines, the vehicle fuel is denoted by the term B100.
In the remainder of the present application, the term (bio) gas oil is used to
identify the B0 or Bx type vehicle fuels for diesel engines (compression engines).
In many countries the sulphur content of (bio) gas oil vehicle fuels ha5 s
been subject to a very significant reduction for environmental reasons, in particular
in order to reduce the SO2 emissions. For example in Europe, the maximum
sulphur content of road gas oil type vehicle fuels is currently 10 ppm by mass.
As well as reducing the sulphur content, the methods of preparation of low10
sulphur gas oil or diesel vehicle fuel bases, for example hydrotreatment methods,
also reduce the polycyclic aromatic compounds and polar compounds contained in
these gas oil vehicle fuel bases for diesel engines. It is known that gas oil or diesel
vehicle fuels having a low (less than 100 ppm) or even very low sulphur content
have a reduced ability to lubricate the engine fuel injection system, which results
15 for example in early failure of the engine fuel injection pump during the lifetime of
the engine, failure occurring for example in high-pressure vehicle fuel injection
systems, such as high-pressure rotary distributors, in-line pumps and combined
pump-injector units.
In order to compensate for the loss of compounds ensuring the lubricating
20 character of these vehicle fuels, numerous lubricity and/or anti-wear and/or friction
modifying additives have been introduced into the fuels on the market. Their
characteristics are broadly described in the patents EP 915944, EP 839174 and
EP680506.
It is known that the diesel vehicle fuels on the market must meet national
25 or supranational specifications (for example standard EN 590 for diesel vehicle
fuels in the EU). For commercial vehicle fuels, there is no legal obligation regarding
the incorporation of so-called performance additives (chemical compounds
incorporated in fuels to improve their properties, for example detergent additives,
friction-reducing additives, anti-corrosion additives, anti-foaming additives and
30 additives for improving low temperature performance); the oil companies and the
distributors are free to add or not add additives to their vehicle fuels. From a
4
commercial standpoint, in the field of distribution of fuels, a distinction is made
between the "standard or entry-level" fuels, with little or no additives, and highergrade
fuels, in which one or more additives are incorporated to improve their
performance (above the regulation performance).
Within the meaning of the present invention, by higher-grade vehicle fuel 5 l of
the gas oil or bio gas oil type is meant any gas oil or bio gas oil vehicle fuel to
which at least 50 ppm by mass of deposit reducing and/or detergent and/or
dispersant additives have been added.
10 FIGURES
- Figure 1 is a photograph of a diesel engine injector with high-pressure direct
injection
- Figure 2 is a photograph of a needle of a diesel engine injector with direct
injection, fouled with soap and/or varnish type deposits (“lacquering”)
15 - Figure 3 is a photograph of a nozzle of a diesel engine injector with indirect
injection, fouled with coking type deposits
- Figure 4 is a photograph of a needle of a diesel engine injector with direct
injection, fouled with soap and/or varnish type deposits (“lacquering”)
20 As shown in Figures 1 and 2, it has been found that during the use of
certain higher-grade (bio) gas oil vehicle fuels, deposits 1 appear on the needles 2
of the injector 3 of the injection systems of diesel engines, in particular those of
Euro 3 to Euro 6 type. Thus, the use of anti-wear and/ or friction modifying and/ or
anti-coking type deposit additives have sometimes exhibited unsatisfactory, or
25 even very unsatisfactory, resistance to lacquering. This results in the formation of
deposit 1 generally covered by the term “lacquering”, which will be used hereinafter,
or the acronym IDID (internal diesel injector deposits).
Within the meaning of the present invention, the lacquering phenomenon
does not relate to the deposits which are present on the outside of the injection
30 system 5 or 5’ (Figure 1 and 3) and which are associated with coking which gives
5
rise to fouling and partial or total blocking of the injection nozzles 4 or 4’ (nozzle
“coking” or “fouling”).
Lacquering and coking are two phenomena clearly distinguished by:
- the causes of these deposits,
- the conditions for the appearance of these deposits and5 ,
- the site where these deposits are produced.
Coking is a phenomenon which appears only downstream of a diesel
injection system.
As shown in Figure 3, the deposits 5’ formed are characterized in that they
10 are constituted by pyrolysis of the hydrocarbons entering the combustion chamber
and have the appearance of carbonaceous deposits. In the case of high-pressure
direct injection diesel engines, it has been found that the coking tendency is much
less marked. This coking is simulated in the CEC F098-08 DW10B standard
engine test, in particular when the vehicle fuel tested is contaminated with metallic
15 zinc.
In the case of indirect injection engines, the injection of the vehicle fuel is
not carried out directly in the combustion chamber as in the case of direct injection
engines. As described for example in the document US4604102, there is a
prechamber before the combustion chamber into which the fuel is injected. The
20 pressure and the temperature in a prechamber are below those of a combustion
chamber of direct injection engines.
Under these conditions, the pyrolysis of the vehicle fuel produces
carbonaceous particles which are deposited on the surface of the nozzles 4’ of the
injectors (“throttling diesel nozzle”) and block the apertures 6 of the nozzles 4’
25 (Figure 3). Only the surfaces of the nozzle 4’ exposed to the combustion gases are
at risk of carbon deposits (coking). In terms of performance, the phenomenon of
coking causes a loss of engine power.
Lacquering is a phenomenon that appears only in direct injection diesel
engines and only occurs upstream of the combustion chamber i.e. in the injection
30 system.
6
As shown in Figures 1 and 2, the injectors 3 of direct injection diesel engines
comprise a needle 2 the lift of which allows precise control of the quantity of fuel
injected at high pressure directly into the combustion chamber.
The lacquering causes the appearance of deposits 1 which appear
specifically at the level of the needles 2 of the injectors 3 (Figures 1 and 2). 5 The
lacquering phenomenon is linked to the formation of soap and/or varnish in the
internal parts of the injection systems of engines for (bio) gas oil type fuels. The
lacquering deposit 1 can be located on the end 4 of the needles 2 of the injectors
3, both on the head and on the body of the needles 2 of the vehicle fuel injection
10 system but also throughout the entire needle lift control system (valves not shown)
of the injection system. This phenomenon is particularly marked in the case of
engines using higher-grade (bio) gas oil vehicle fuels. When these deposits are
present in large quantities, the mobility of the needle 2 of the injector 3 fouled with
these deposits 1 is compromised. This lacquering phenomenon can eventually
15 generate a loss of flow rate of vehicle fuel injected and therefore a loss of engine
power.
Moreover, unlike coking, lacquering can also cause an increase in engine
noise and sometimes starting problems. Indeed, the parts of the needles 2 fouled
by the deposits of soap and/or varnish 1 can adhere to the internal walls of the
20 injector 3. The needles 2 are then blocked and the fuel can no longer pass through.
Generally a distinction is made between 2 types of deposits of the
lacquering type:
1. deposits that are rather whitish and powdery; on analysis, it is found
that these deposits consist essentially of soaps of sodium (sodium carboxylates,
25 for example) and/or calcium (type 1 deposits);
2. organic deposits resembling coloured varnishes localized on the
needle body (type 2 deposits).
Regarding the type 1 deposits, there are many possible sources of sodium
in bio gas oil vehicle fuels of the Bx type:
30  catalysts for transesterification of vegetable oils for producing esters
of the fatty acid (m)ethyl ester type such as sodium formate;
7
 another possible source of sodium can be from the corrosion
inhibitors used when petroleum products are conveyed in certain pipes, such as
sodium nitrite;
 finally, accidental exogenous pollution, via water or air for example,
can contribute to the introduction of sodium into vehicle fuels (sodium being a ve5 ry
widely occurring element).
There are many possible sources of acids in vehicle fuels of the Bx type,
for example:
o residual acids in biofuels (see standard EN14214 which fixes a
10 maximum permitted level of acids)
o corrosion inhibitors used in the conveyance of petroleum products in
certain pipes such as DDSA (dodecenylsuccinic anhydride) or HDSA
(hexadecenylsuccinic anhydride) or some of their functional derivatives such as
acids.
15 With regard to type 2 organic deposits, some publications state that they
may in particular result from reactions between deposit reducers/dispersants used
to prevent coking (for example PIBSI type detergents which are derivatives of
polyamines) and acids (which would be present inter alia as fatty acid ester
impurities in bio gas oil).
20 In the publication SAE 880493, Reduced Injection Needle Mobility Caused
by Lacquer Deposits from Sunflower Oil, the authors M Ziejewski and HJ Goettler
describe the lacquering phenomenon and its harmful consequences for the
operation of engines operating with sunflower oils as vehicle fuel.
In the publication SAE 2008-01-0926, Investigation into the Formation and
25 Prevention of Internal Diesel Injector Deposits, the authors J Ullmann, M Geduldig,
H Stutzenberger (Robert Bosch GmbH) and R Caprotti, G Balfour (Infineum) also
describe the reactions between acids and deposit reducers/dispersants to explain
the type 2 deposits.
Moreover, in the publication SAE International, 2010-01-2242, Internal
30 Injector Deposits in High-Pressure Common Rail Diesel Engines, the authors S.
Schwab, J. Bennett, S. Dell, J. Galante-Fox, A. Kulinowski and Keith T. Miller
8
explain that the internal parts of the injectors are generally covered with a slightly
coloured deposit which is visible to the naked eye. Their analyses made it possible
to determine that it mainly comprised sodium salts of alkenyl (hexadecenyl or
dodecenyl) succinic acids; the sodium originating from dehydrating agents, from
caustic solutions used in the refinery, from tank bottom water or from seawate5 r,
and the succinic diacids being used as corrosion inhibitors or present in
multifunctional additive packages. Once formed, these salts are insoluble in lowsulphur
diesel fuels, and as they are in the form of fine particles they pass through
gas oil filters and are deposited inside the injectors. In this publication, the
10 development of an engine test is described, making it possible to reproduce the
deposits. This publication emphasizes that only the diacids generate deposits, in
contrast to monocarboxylic acids or the neutral esters of organic acids.
In the publication SAE International, 2010-01-2250, Deposit Control in
Modern Diesel Fuel Injection System, the authors, R. Caprotti, N. Bhatti and G.
15 Balfour, also investigate the same type of internal deposits in the injectors and
assert that the appearance of deposits is not linked specifically to one type of
vehicle fuel (B0 or containing FAME(Bx)) nor to vehicles of one type (light vehicles
or heavy goods vehicles) equipped with modern motorizations (common rail). They
demonstrate the performance of a new deposit reducer/dispersant, effective on all
20 types of deposits (coking and lacquering).
The present invention proposes additives with preventive and curative effects,
making it possible to limit the soap and/or varnish deposits in the internal parts of
the injection systems, i.e. to improve resistance to the phenomenon of lacquering
25 in engines using higher-grade (bio) gas oil and/or (bio) diesel type vehicle fuels, the
sulphur content of which is less than or equal to 500 ppm by mass, and which
comprise at least 50 ppm by mass of deposit reducer(s) and/or detergents and/or
dispersant(s). These additives therefore prevent these deposits to form
(preventive), and allow when they are formed, to be removed by render the
30 injectors cleaner (curative).
9
These problems of the resistance to lacquering of (bio) gas oil type vehicle
fuels are solved by the use of at least one additive which comprises at least 50%
by mass of partial polyol ester(s), said polyol esters comprising x ester units, y
hydroxylated units and z ether units, x, y and z being integers such that x varies
from 1 to 10, y varies from 1 to 10, and z varies from 0 to 6, preferably x var5 ies
from 1 to 10, y varies from 3 to 10, and z varies from 0 to 6.
The synthesis of partial polyol esters is known per se; they can for example
be prepared by esterification of fatty acid(s) and linear and/or branched polyols
optionally comprising (hetero)cycles of 5 to 6 atoms bearing hydroxyl functions.
10 The product(s) originating from this esterification reaction comprise(s) a distribution
of ester units, hydroxylated units and ether units such that x varies from 1 to 4, y
varies from 1 to 7 and z varies from 1 to 3. Generally this type of synthesis leads to
a mixture of mono-, di- , tri- and optionally tetra-esters as well as small quantities of
fatty acid(s) and polyols which have not reacted.
15 According to an embodiment, the polyol esters are obtained by
esterification of fatty acid(s) and of linear and/or branched polyols optionally
comprising heterocycles of 4 to 5 carbon atoms and an oxygen atom, bearing
hydroxyl functions.
Within the framework of the present invention, the polyols will be chosen
20 from the linear polyols comprising more than three hydroxyl functions and the
polyols comprising at least one (hetero)cycle of 5 or 6 atoms, preferably
heterocycles of 4 to 5 carbon atoms and an oxygen atom, optionally substituted by
hydroxyl groups, these polyols being able to be used alone or in a mixture.
In the remainder of the present discussion, these polyols are referenced R
25 in the formulations mentioned below.
Among the polyols R, the polyols with linear or branched hydrocarbon
chains comprise at least four units represented in formula (I) below:
H - (OCH2)p-(CHOH)q-(CH2OH) (I)
With p and q being integers, p being equal to or greater than 0, q is greater
30 than 2, these numbers not being able to exceed 10.
10
Among the polyols R, the polyols with linear or branched hydrocarbon
chains comprise at least four units represented in formula (II) below:
H-(OCH2)p-(CR1R2)q-(CH2OH) (II)
With p and q being integers, p being equal to or greater than 0, q is greater
than 1, these numbers not being able to exceed 5, R1 and R2 are identical 5 or
different and represent either the hydrogen atom, or a -CH3 or –C2H5 group or
a -CH2-OH group
Among the polyols R, some comprise at least one (hetero)cycle of 4 or 5
carbon atoms and an oxygen atom, optionally substituted by hydroxyl groups and
10 correspond to general formula (III) below:
O
/ HO-CH2-(CHOH)s-[HC-(CHOH)t] (III)
with s and t being integers, and when s is equal to 1, t is equal to 3 and
15 when s is zero, t is equal to 4.
Among the polyols R, some comprise at least two heterocycles of 4 or 5
carbon atoms and one oxygen atom connected by the formation of an acetal bond
between a hydroxyl function of each ring, those heterocycles being optionally
substituted by hydroxyl groups.
20
Preferably, the polyols are chosen from the group comprising erythritol,
xylitol, D-arabitol, L-arabitol, ribitol, sorbitol, malitol, isomalitol, lactitol, sorbitan,
volemitol, mannitol, pentaerythritol, 2-hydroxymethyl-1,3-propanediol, 1,1,1-
tri(hydroxymethyl)ethane, trimethylolpropane and carbohydrates such as sucrose,
25 fructose, maltose, glucose and saccharose, preferably sorbitan.
According to a preferred variant, the partial polyol esters are chosen from
the partial sorbitan esters, preferably sorbitan monooleate, used alone or in a
mixture.
The fatty acids from which the esters according to the invention originate
30 can be chosen from the fatty acids the chain length of which varies from 10 to 24
carbon atoms and/or at least one diacid substituted by at least one polymer, for
example poly(iso)butene comprising from 8 to 100 carbon atoms. They are
11
preferably chosen, in the case of the mono acids, from the stearic, isostearic,
linolenic, oleic, linoleic, behenic, arachidonic, ricinoleic, palmitic, myristic, lauric and
capric acids, and mixtures thereof and, in the case of the diacids from the alkyl- or
alkenylsuccinic, alkyl-or alkenylmaleic acids.
The fatty acids can originate from the transesterification or th5 e
saponification of vegetable oils and/or animal fats. The preferred vegetable oils
and/or animal fats are chosen according to their oleic acid concentration.
Reference may be made for example to Table 6.21 of Chapter 6 of the publication
Carburants & Moteurs by J.C. Guibet and E. Faure, 2007 edition in which the
10 compositions of several vegetable oils and animal fats are given.
The fatty acids can also originate from tall oil fatty acids which comprise a
majority of fatty acids, typically greater than or equal to 90% by mass as well as
resin acids and unsaponifiables in a minority, i.e. in quantities generally less than
10%.
15
Preferred additives according to the invention capable of improving the
lacquering resistance of higher-grade (bio)diesel vehicle fuels comprise partial
sorbitan esters.
Other preferred additives comprise at least 50% by mass of mono- and/or
20 diester(s) of isobutylenesuccinic acid and polyols according to one of formulae I to
III.
Other preferred additives comprise at least 50% by mass of mono- and/or
diester(s) of monocarboxylic acids with 12 to 24 carbon atoms and polyols
according to one of formulae I to III.
25 The invention also relates to an additive package for (bio) gas oil vehicle
fuels containing at least one lacquering resistance additive as defined previously
and at least one or more other functional additives, such as deposit
reducers/dispersants, anti-oxidants, combustion improvers, corrosion inhibitors,
low temperature performance additives (improving the cloud point, sedimentation
30 rate, filterability and/or low temperature flow), colorants, emulsion breakers, metal
deactivators, anti-foaming agents, agents improving the cetane number,
12
compatibilizing agents, lubricity additives, anti-wear agents and/or friction
modifiers, and one or more solvents or co-solvents.
The use of the additives according to the invention makes it possible to
improve the lacquering resistance at the level of the fuel injectors, and thus limit
the formation (the deposit) of soap and/or varnish in the presence of the additive5 s
such as the deposit reducers and/or detergent and/or dispersants. The use of
these additives in (bio) gas oil vehicle fuels makes it possible to reduce the
blockage rate and deterioration in the fuel admission or injection system, in
particular on the injection pump.
10 The bio gas oil vehicle fuels (liquid fuels for compression engines) can
comprise middle distillates having a boiling point comprised between 100 and
500°C; their incipient crystallization temperature ICT is often above or equal to -
20°C, in general comprised between -15°C and +10°C. These distillates are
mixtures of bases that can be selected for example from the distillates obtained by
15 direct distillation of gasoline or crude hydrocarbons, vacuum distillates,
hydrotreated distillates, distillates originating from the catalytic cracking and/or
hydrocracking of vacuum distillates, the distillates resulting from ARDS
(atmospheric residue desulphurization) type conversion processes and/or
visbreaking.
20 The (bio) gas oil vehicle fuels can also contain light cuts such as the
gasolines originating from distillation, catalytic or thermal cracking units, alkylation,
isomerization, desulphurization units and steam cracking units.
Moreover, the (bio) gas oil vehicle fuels can contain novel sources of
distillates, among which there can be mentioned in particular:
25 - heavier cuts originating from the cracking and visbreaking processes
concentrated in heavy paraffins, comprising more than 18 carbon atoms,
- synthetic distillates originating from gas conversion such as those
originating from the Fischer Tropsch process,
- synthetic distillates resulting from the treatment of biomass of vegetable
30 and/or animal origin, such as in particular NexBTL, alone or in a mixture,
- coker gas oils,
13
- alcohols, such as methanol, ethanol, butanols, ethers, (MTBE, ETBE, etc)
in general used in a mixture with the gasoline vehicle fuels, but sometimes with
heavier vehicle fuels of the gas oil type,
- vegetable and/or animal oils and/or their esters, such as vegetable oil or
fatty acid methyl or ethyl esters (VOME, FAME, VOEE, FAEE5 ),
- hydrotreated and/or hydrocracked and/or hydrodeoxygenated (HDO)
vegetable and/or animal oils,
These novel vehicle fuel and fuel bases can be used alone or in a mixture
with conventional petroleum middle distillates as vehicle fuel base(s); they
10 generally comprise paraffin long chains greater than or equal to 10 carbon atoms,
preferably from C14 to C30.
Within the framework of the present invention, the (bio) gas oil vehicle fuels
have a sulphur content less than or equal to 500 ppm by mass, advantageously
15 less than or equal to 100 ppm by mass, and capable of being reduced to a content
less than or equal to 50 ppm by mass, or even less than or equal to 10 ppm by
mass (this is the case of diesel fuels for current vehicles for which the sulphur
content according to European standard EN 590 currently in force must be less
than or equal to 10 ppm by mass).
20 The additives providing resistance to lacquering, i.e. to the formation of
soap and/or varnish in the internal parts of the injection systems of engines for (bio)
gas oil vehicle fuels according to the invention can be incorporated in the vehicle
fuels up to a value of 10% by mass. Advantageously the concentration of partial
esters according to the invention in the final vehicle fuel is comprised between 20
25 and 1000 ppm by mass and advantageously between 30 and 200 ppm by mass, i.e.
ppm by mass relative to the total mass of the vehicle fuel with additives.
According to an embodiment, the higher-grade (bio) gas oil compositions
contain at least 20 ppm by mass of at least one additive according to the invention
and optionally at least one or more other functional additives. Preferably, the
30 concentration of additives according to the invention in the composition, i.e. the
14
concentration of partial ester can vary from 20 to 1000 ppm by mass, and more
particularly from 30 to 200 ppm by mass m/m.
Among the other functional additives, the lacquering resistance additives of
the present invention can be used alone or in a mixture with deposit reducers
and/or detergents and/or dispersants, anti-oxidants, combustion improvers5 ,
corrosion inhibitors, low temperature performance additives (improving the cloud
point, sedimentation rate, filterability and/or low temperature flow), colorants,
emulsion breakers, metal deactivators, anti-foaming agents, agents improving the
cetane number, anti-wear and lubricity additives and/or friction modifiers, co10
solvents, compatibilizing agents etc.
The other functional additive(s) can be chosen non-limitatively from:
 combustion-improving additives; for vehicle fuels of the gas oil type,
there can be mentioned cetane booster additives, in particular (but non-limitatively
15 chosen from alkyl nitrates, preferably 2-ethyl hexyl nitrate, aryl peroxides,
preferably benzyl peroxide, and alkyl peroxides, preferably di tert-butyl peroxide;
for vehicle fuels of the gasoline type, there can be mentioned octane number
improver additives; for fuel such as domestic heating oil, heavy fuel oil, marine
diesel oil, there can be mentioned methyl cyclopentadienyl manganese tricarbonyl
20 (MMT);
 anti-oxidant additives, such as aliphatic, aromatic amines, hindered
phenols, such as BHT, BHQ;
 emulsion breakers or demulsifiers;
 anti-static or conductivity improver additives;
25  colorants;
 anti-foaming additives, in particular (but non-limitatively) chosen for
example from polysiloxanes, oxyalkylated polysiloxanes, and fatty acid amides
originating from vegetable or animal oils; examples of such additives are given in
EP 861 182, EP 663 000, EP 736 590;
30  the detergent or dispersant additives, in particular (but nonlimitatively)
chosen from the group constituted by the amines, succinimides,
15
succinamides, alkenylsuccinimides, polyalkylamines, polyalkyl polyamines,
polyetheramines, Mannich bases; examples of such additives are given in EP 938
535;
 anti-corrosion additives such as ammonium salts of carboxylic acids;
 chelating agents and/or metal sequestering agents, such as triazole5 s,
disalicylidene alkylene diamines, and in particular N,N’ bis (salicylidene) 1,3-
propane diamine;
 low temperature performance additives and in particular additives for
improving the cloud point, in particular, (but non-limitatively) chosen from the group
10 constituted by the long-chain olefin/(meth)acrylic ester/maleimide terpolymers, and
the polymers of fumaric/maleic acid esters. Examples of such additives are given in
EP 71 513, EP 100 248, FR 2 528 051, FR 2 528 423, EP1 12 195, EP 1 727 58,
EP 271 385, EP 291367; anti-sedimentation and/or dispersant additives for
paraffins in particular (but non-limitatively) chosen from the group constituted by
15 the (meth)acrylic acid/alkyl (meth)acrylate copolymers amidified by a polyamine,
alkenylsuccinimides derived from polyamine, phthalamic acid and double-chain
fatty acid derivatives; alkyl phenol/aldehyde resins; examples of such additives are
given in EP 261 959, EP 593 331, EP 674 689, EP 327 423, EP 512 889, EP 832
172; US 2005/0223631; US 5 998 530; WO 93/14178; multi-functional low
20 temperature operability additives chosen in particular from the group constituted by
olefin- and alkenyl nitrate-based polymers such as those described in EP 573 490;
 other additives improving the low temperature performance and the
filterability (CFI), such as EVA and/or EVP copolymers;
 metal passivators, such as triazoles, alkylated benzotriazoles;
25  acidity neutralizers such as cyclic alkylamines;
 markers, in particular the markers mandated by regulations, for
example the colorants specific to each type of vehicle fuel or fuel.
 fragrancing agents or agents for masking odours, such as those
described in EP 1 591 514;
30  lubricity additives, anti-wear agents and/or friction modifiers other
than those described above, in particular (but non-limitatively) chosen from the
16
group constituted by fatty acids and their ester or amide derivatives, in particular
glycerol monooleate, and derivatives of mono- and polycyclic carboxylic acids;
examples of such additives are given in the following documents: EP 680 506, EP
860 494, WO 98/04656, EP 915 944, FR2 772 783, FR 2 772 784.
The optional other additives are generally incorporated in quantitie5 s
varying from 50 to 1500 ppm m/m, i.e. ppm by mass relative to the total mass of
the vehicle fuel with additives.
These additives can be incorporated into the fuels following any known
method; by way of example, the additive or the mixture of additives can be
10 incorporated in concentrate form comprising the additive(s) and a solvent,
compatible with the (bio) diesel fuel, the additive being dispersed or dissolved in
the solvent. Such concentrates in general contain from 20 to 95% by mass of
solvents.
A person skilled in the art will easily adapt the concentration of additives
15 according to the invention as a function of any dilution of the additive in a solvent,
the possible presence of other components originating for example from the
esterification reaction and/or other functional additives incorporated in the final
vehicle fuel.
The solvents are organic solvents that generally contain hydrocarbon
20 solvents. By way of example of solvents, there can be mentioned petroleum
fractions, such as naphtha, kerosene, heating oil; aliphatic and/or aromatic
hydrocarbons such as hexane, pentane, decane, pentadecane, toluene, xylene,
and/or ethylbenzene and alkoxyalkanols such as 2-butoxyethanol and/or mixtures
of hydrocarbons such as mixtures of commercial solvents such as for example
25 Solvarex 10, Solvarex LN, Solvent Naphtha, Shellsol AB, Shellsol D, Solvesso 150,
Solvesso 150 ND, Solvesso 200, Exxsol, ISOPAR and optionally co-solvents or
combatibilizing agents, such as 2-ethylhexanol, decanol, isodecanol and/or
isotridecanol.
The invention relates to the use of at least one additive composition
30 according to the invention incorporated in a vehicle fuel of the higher-grade (bio)
gas oil type for improving the resistance to lacquering, i.e. fouling on the head
17
and/or on the body of the needles of the fuel injection system but also in the whole
needle lift control system (valves) of the injection system, in particular for engines
provided with high-pressure direct fuel injection systems, with which most vehicles
complying with the Euro 3 and more recent regulations are equipped.
According to a particular embodiment, the subject of the present inventio5 n
also relates to the use of a composition of (bio) gas oil vehicle fuel as described
above, in order to limit the soap and/or varnish deposits in the internal parts of the
injection systems of the engines using said composition, preferably direct injection
engines, in particular high-pressure direct injection engines.
10 The subject of the present invention also relates to a process for limiting
the soap and/or varnish deposits in internal parts of the injection system of an
engine for (bio) gas oil vehicle fuels (diesel engines) having a sulphur content less
than or equal to 500 ppm by mass, said process comprising the combustion in said
engine of a (bio) gas oil vehicle fuel composition as defined above. Preferably, the
15 process applies to direct injection engines, in particular high-pressure direct
injection engines.
Thus, the process according to the invention avoids and prevents the
formation of deposits of soap and/or varnish in the internal parts of the injection
system of the engine, in order to keep said engine clean.
20 Advantageously, the process according to the present invention removes the soap
and/or varnish deposited in the internal parts of the injection system of the engine,
for a curative action, cleaning up the engine.
EXAMPLES
25 In order to test the performances of these additives according to the
invention, the inventors have also developed a novel method that is reliable and
robust for evaluating the sensitivity of (bio) gas oil vehicle fuels, in particular those
of higher grade, to lacquering. This method, unlike the methods described in the
publications cited above, is not a laboratory method but is based on engine tests
30 and is therefore of industrial interest and makes it possible to quantify the
18
effectiveness of the additives or of the additive compositions against lacquering.
The method for measuring lacquering developed by the inventors is detailed below:
- The engine used is a four-cylinder, 16-valve, high-pressure injection
common rail diesel engine with a cylinder capacity of 1500 cm3 and a power of 80
hp: regulation of the fuel injection pressure takes place in the high-pressure part 5 rt of
the pump.
- The power point is used over a period of 40 h at 4000 rpm; the position of
the injector in the chamber has been lowered by 1 mm relative to its nominal
position, which on the one hand promotes the release of thermal energy from
10 combustion, and on the other hand brings the injector closer to the combustion
chamber.
- The flow rate of vehicle fuel injected is adjusted so as to obtain an
exhaust temperature of 750°C at the start of the test.
- The injection advance was increased by 1.5° crankshaft relative to the
15 nominal setting (changing from + 12.5° to + 14° crankshaft) still with the aim of
increasing thermal stresses to which the injector nozzle is subjected.
- Finally, to increase the stresses to which the vehicle fuel is subjected, the
injection pressure was increased by 10 MPa relative to the nominal pressure (i.e.
changing from 140 MPa to 150 MPa) and the temperature is set at 65°C at the inlet
20 of the high-pressure pump.
The technology used for the injectors requires a high fuel return, which
promotes degradation of the vehicle fuel since it can be subjected to several cycles
in the high-pressure pump and the high-pressure chamber before being injected
into the combustion chamber.
25 A variant of the method for testing the clean-up effect (i.e. cleaning of type
1 and/or type 2 deposits) has also been developed. It is based on the preceding
method but is separated into two 20 hour periods:
 For the first 20 hours a higher-grade gas oil B7 is used (containing
detergent of the PIBSI type and an acid product) known for its tendency to cause
30 lacquering. After 20 hours, two of the four injectors are dismantled and assessed in
19
order to verify the quantity of deposits present and then replaced by two new
injectors.
 For the last 20 hours of the test, the product to be assessed is used.
At the end of the test (40 hours in total), the injectors are dismantled and assessed.
At the end of the test, three sets of two injectors are availab5 le:
 Set 1: 2 injectors having undergone 20 hours of higher-grade vehicle
fuel known for its tendency to cause lacquering.
 Set 2: 2 injectors having undergone 20 hours of higher-grade vehicle
fuel known for its tendency to cause lacquering + 20 hours of product to be
10 assessed.
 Set 3: 2 injectors having undergone 20 hours of product to be
assessed.
Expression of the results:
15 In order to ensure the validity of the result, various parameters are
monitored during the test: power, torque and fuel consumption indicate whether the
injector is fouled or whether its operation has deteriorated through formation of
deposits, since the operating point is the same throughout the test.
The characteristic temperatures of the various fluids (cooling liquid, vehicle
20 fuel, oil) allow the validity of the tests to be monitored. The vehicle fuel is adjusted
to 65°C at the pump inlet, and the cooling liquid is adjusted to 90°C at the engine
outlet.
The smoke values allow the combustion timing to be monitored at the start
of the test (target value 3FSN) and ensure that it is properly repeatable from one
25 test to the next.
The injectors are dismantled at the end of the test in order to inspect and
assess the deposits formed along the needles. The procedure adopted for
assessing the needles is as follows:
The scale of scores varies from -2.5 (for a heavy deposit) to 10 (for a new
30 needle without any deposit). The final score is a weighted average of the scores
20
over all the assessed surfaces of the needle i.e. the conical part and the body or
cylindrical part of the needle.
Thus the cylindrical zone (directly following the conical part) represents
68% of the overall assessment of the needle and the conical zone represents 32%
of the overall assessment of the needle; In order to facilitate the assessment, eac5 h
of these two zones is divided into 4. In Figure 4, the percentages shown
correspond to one quarter of the surface area of the needles: the overall surface
area weighting is therefore 17 x 4 = 68%.
A product performance threshold was determined with respect to this
10 assessment procedure: Result < 4 = Unsatisfactory, result > 4 = Satisfactory.
The following examples illustrate the invention without limiting it.
Example 1- measurements of lacquering resistance
According to the procedure for measuring the lacquering resistance
15 described above, the performance is assessed of several packets of additives
introduced into a gas oil matrix representative of the French market (B7 = gas oil
produced in France containing 7% FAME (fatty acid methyl ester) and complying
with EN 590). Details of each vehicle fuel composition tested, as well as the results
obtained, are shown in Table 1.
20 The quantities shown in Table 1 are quantities by mass (m/m).
21
Table 1
These tests clearly demonstrate the effectiveness of the products of th5 e
invention in preventing and limiting the formation of varnish or soap type deposits
(keep-clean action), since the needle assessments results at the end of the tests
are much better than the assessment result obtained when the vehicle fuel
contains only a PIBSI capable of forming soaps on the injector needles .
10
Example 2- measurements of lacquering resistance
According to the procedure for measuring the lacquering resistance in its
clean-up version described above, the performance is assessed of several packets
of additives introduced into a gas oil matrix representative of the French market
15 (B7 = gas oil produced in France containing 7% FAME (fatty acid methyl ester) and
complying with EN 590). Details of each vehicle fuel composition tested, as well as
Test No. A B C D E F
Vehicle fuel B7 B7 B7 B7 B7 B7
PIBSI type diesel detergent ---
330
ppm
170
ppm
170
ppm
170
ppm
330
ppm
Fatty acid mixture, mainly
oleic acid with an acid
number of 180 mg of KOH/g
---
200
ppm
--- --- --- ---
Sorbitan monooleate --- ---
200
ppm
--- ---
100
ppm
Pentaerythritol mono- + dioleate
--- --- ---
200
ppm
--- ---
Type 1 deposits score 8.7 -1 7.2 4.1 7.2 5.2
Type 2 deposits score 7.1 -1 6.9 6.7 6.0 6.2
Overall score 8.2 -1 7.0 5.0 6.4 5.9
22
the results obtained, are shown in Table 2. Note tests G, G’ and G’’ correspond to
the same test, with G corresponding to the result for the set of injectors 1, G’
corresponding to the result for the set of injectors 2 and G’’ corresponding to the
result for the set of injectors 3.
The quantities shown in Table 2 are quantities by mass (m/m5 )
Table 2
Test No. G G’ G’’
Vehicle fuel B7 B7 B7
PIBSI type diesel detergent 330 ppm 330 then 170 ppm 170 ppm
Fatty acid mixture, mainly oleic acid
with an acid number of 180 mg of
KOH/g
200 ppm 200 then 0 ppm ---
Sorbitan monooleate --- 0 then 200 ppm 200 ppm
Type 1 deposits score 2.6 3.7 6.2
Type 2 deposits score 1.4 3.7 6.5
Overall score 1.8 3.7 6.4
These tests demonstrate the curative effectiveness (clean-up action) of the
products of the invention i.e. in removing the varnish or soap type deposits already
10 formed on the needles since the assessment of the set of injectors G’ is better than
that of the set of injectors G (significant cleaning of the needle has been started),
and also confirms their preventive effectiveness (keep-clean action) since the
assessment of the set of injectors G’’ is much higher.
15
23
We Claim:
1. Additives for limiting the soap and/or varnish deposits in the internal parts of
the injection systems of engines for (bio) gas oil type vehicle fuels, having 5 a
sulphur content less than or equal to 500 ppm by mass, comprising at least 50% by
mass of partial polyol ester(s), said polyol esters comprising x ester units, y
hydroxylated units and z ether units, x, y and z being integers such that x varies
from 1 to 10, y varies from 1 to 10, and z varies from 0 to 6.
10
2. Additives according to claim 1 characterized in that the polyol esters are
obtained by esterification of fatty acid(s) and linear and/or branched polyols
optionally comprising (hetero)cycles of 5 to 6 atoms, preferably heterocycles of 4 to
5 carbon atoms and an oxygen atom, bearing hydroxyl functions.
15
3. Additives according to one of claims 1 and 2 characterized in that in said
polyol esters, the ester unit, hydroxylated unit and ether unit distribution is such
that x varies from 1 to 4, y varies from 1 to 7 and z varies from 1 to 3.
20 4. Additives according to any one of claims 1 to 3, characterized in that the
polyols R are chosen from the linear polyols comprising more than three hydroxyl
functions and the polyols comprising at least one heterocycle of 5 or 6 atoms,
preferably heterocycles of 4 to 5 carbon atoms and an oxygen atom, optionally
substituted by hydroxyl groups, these polyols being able to be used alone or in a
25 mixture.
5. Additives according to any one of claims 1 to 4 characterized in that R is a
polyol comprising at least four units presented in formula (I) below;
H -(OCH2)p-(CHOH)q-(CH2OH) (I)
30 with p and q being integers, p being equal to or greater than 0, q is greater than 2,
these numbers not being able to exceed 10.
24
6. Additives according to any one of claims 1 to 4 characterized in that R is a
polyol comprising at least four units presented in general formula (II) below:
H - (OCH2)p-(CR1R2)q-(CH2OH) (II)
with p and q being integers, p being equal to or greater than 0, q is greater than 5 1,
these numbers not being able to exceed 5, R1 and R2 are identical or different and
represent either the hydrogen atom, or a -CH3 or –C2H5 group, or a -CH2OH
group.
10 7. Additives according to any one of claims 1 to 4 characterized in that R is a
polyol comprising at least two heterocycles of 4 or 5 carbon atoms and an oxygen
atom, connected by the formation of an acetal bond between a hydroxyl function of
each ring, those heterocycles being optionally substituted by hydroxyl groups.
15 8. Additives according to any one of claims 1 to 4, characterized in that the
partial polyol esters are chosen from the partial sorbitan esters, preferably sorbitan
monooleate, used alone or in a mixture.
9. Additives according to any one of claims 1 to 8, characterized in that the
20 polyols R are chosen from the group comprising erythritol, xylitol, arabitol, ribitol,
sorbitol, malitol, isomalitol, lactitol, sorbitan, volemitol, mannitol, pentaerythritol, 2-
hydroxymethyl-1,3-propanediol, 1,1,1-tri(hydroxymethyl)ethane, trimethylolpropane
and carbohydrates such as sucrose, fructose, maltose, glucose and saccharose,
preferably sorbitan.
25
10. Additives according to any one of claims 1 to 9 characterized in that the
partial polyol esters are obtained by reaction of the polyols with at least one fatty
acid with a chain length varying from 10 to 24 carbon atoms and/or at least one
diacid substituted by at least one polymer, for example poly(iso)butene comprising
30 from 8 to 100 carbon atoms.
25
11. Additives according to claim 10, characterized in that the partial polyol
esters are chosen from the group constituted by monoesters or diesters obtained
from mono acids chosen from the stearic, isostearic, linolenic, oleic, linoleic,
behenic, arachidonic, ricinoleic, palmitic, myristic, lauric, capric acids, and mixtures
thereof and/or diacids chosen from the alkyl- or alkenylsuccinic, alkyl- 5 or
alkenylmaleic acids.
12. Use of an additive as defined in any one of claims 1 to 11 for limiting the
soap and/or varnish deposits in the internal parts of the injection systems of
10 engines for (bio) gas oil vehicle fuels, having a sulphur content less than or equal
to 500 ppm by mass.
13. Use according to claim 12, characterized in that said additive is intended to
be incorporated in a (bio) gas oil vehicle fuel for said engine, preferably at a
15 concentration of at least 20 ppm by mass.
14. Use according to one of claims 12 to 13, characterized in that the engines
are direct injection engines:
20 15. Compositions of (bio) gas oil vehicle fuel having a sulphur content less than
or equal to 500 ppm by mass, containing at least one additive as defined in any
one of claims 1 to 11, and optionally at least one or more other functional additives,
such as deposit reducers and/or detergents and/or dispersants, anti-oxidants,
combustion improvers, corrosion inhibitors, low temperature performance additives,
25 colorants, emulsion breakers, metal deactivators, anti-foaming agents, agents
improving the cetane number, lubricity additives, anti-wear agents and/or friction
modifiers, and co-solvents and combatibilizing agents.
16. Compositions of (bio) gas oil vehicle fuel according to claim 15 containing
30 up to 10% by mass of one or more additives as defined in any one of claims 1 to
11.
26
17. Compositions of higher-grade (bio) gas oil vehicle fuel containing at least 50
ppm by mass of deposit reducers/detergents/dispersants, and containing at least
20 ppm by mass of an additive as defined in any one of claims 1 to 11 and
optionally at least one or more other functional additives such as anti-oxidan5 ts,
combustion improvers, corrosion inhibitors, low temperature performance additives,
colorants, emulsion breakers, metal deactivators, anti-foaming agents, agents
improving the cetane number, lubricity additives, anti-wear agents and/or friction
modifiers, and co-solvents and combatibilizing agents.
10
18. Compositions of (bio) gas oil vehicle fuel according to any one of claims 15
to 17 having a mono- and di-ester concentration varying from 20 to 1000 ppm by
mass, and preferably between 30 and 200 ppm by mass m/m.
15 19. Use of a composition as defined according to any one of claims 15 to 18, for
limiting the soap and/or varnish deposits in the internal parts of the injection
systems of engines using said composition.
20. Use according to claim 19, characterized in that the engines are direct
20 injection engines.
21. Process for limiting the soap and/or varnish deposits in the internal parts of
the injection system of an engine for (bio) gas oil vehicle fuel (diesel engine) having
a sulphur content less than or equal to 500 ppm by mass, said process comprising
25 the combustion in said engine of a composition as defined according to any one of
claims 15 to 18.
22. Process according to claim 21, characterized in that the engine is a direct
injection engine.
30
27
23. Process according to one of claims 21 and 22, characterized in that the
formation of soap and/or varnish deposits in the internal parts of the injection
system of the engine is avoided and prevented, in order to keep said engine clean.
24. Process according to any one of claims 21 to 23, in which the soap and/5 /or
varnish deposits in the internal parts of the injection system of the engine are
removed, for a curative action of cleaning up the engine.