EP1967568A1 - Polyisobutyl succinic acid anhydride derivatives as corrosion inhibitors in fuels - Google Patents

Abstract

A method for preventing corrosion in storage tanks, pipelines and fuel supply systems in motor vehicles which are in contact with fuel, involves adding to the fuel small amounts of derivative(s) of polyisobutylsuccinic anhydride (I) with at least one prim. or sec. amino group, imino group and/or hydroxyl group.

Description

The present invention relates to an improved method of protecting storage containers, conduits and fuel supply devices in internal combustion engines in contact with fuel from corrosion. Furthermore, the present invention relates to the use of certain polyisobutylsuccinic anhydride derivatives as corrosion inhibitors in fuels.

In storage containers and lines for liquid fuels, which are essentially hydrocarbon mixtures, due to traces of moisture or localized water separation, corrosion phenomena often occur in the case of the devices mentioned, which are usually made of iron or steel. Similar undesirable corrosion phenomena can also be found in the fuel delivery devices in internal combustion engines that run on these fuels.

From the EP-A 0 167 358 (1) It is known that fuels such as gasolines, diesel fuels or aviation gasoline containing corrosion inhibitors of monoalkenylsuccinic acids having 8 to 18 carbon atoms in the alkenyl group such as dodecenylsuccinic and aliphatic and cycloaliphatic secondary or tertiary amines having 2 to 12 carbon atoms such as N, N-dimethylcyclohexylamine, triethanolamine or morpholine , Storage tanks, piping and fuel supply devices in internal combustion engines in contact with this fuel provide some protection against corrosion. However, the corrosion-inhibiting effect is still in need of improvement.

In the EP-A 0 839 840 (2) describes the use of alkyl or alkenyl succinimides in lubricating oils for diesel engines to protect against corrosion or wear of engine parts due to the corrosive action of sulfur oxides produced by combustion. Such alkenylsuccinimides may be formed, for example, from polyisobutylsuccinic anhydride having a number average molecular weight of 1000 for the polyisobutyl radical and tetraethylenepentamine or pentaethylenehexamine.

The object of the present invention was to provide improved corrosion protection for storage tanks, pipes and fuel supply devices in internal combustion engines in contact with fuel. In particular, the amount of corrosion inhibitor needed should be kept small.

Accordingly, a method for protecting storage containers, pipes and fuel supply devices in internal combustion engines in contact with fuel has been found from corrosion, which is characterized in that the fuel small amounts of at least one derivative of a polyisobutylsuccinic anhydride having at least one primary or secondary amino group, an imino group and / or a hydroxyl group added.

For the purposes of the present invention, storage containers are to be understood as meaning, in particular, the fuel storage tanks in the refineries, at the filling stations and in the fuel-operated vehicles or machines, and the fuel containers on trucks and railway vehicles. Lines are primarily the supply lines to the dispensers in the gas stations, the dispensers and dispensers in the gas stations themselves and supply lines to the fuel-powered internal combustion engines. Fuel supply devices in internal combustion engines are, for example, carburetor devices and injection pumps, which are operated well below the temperatures of the combustion zone of the fuel in the engine. The devices and units mentioned are usually constructed of corrosion-sensitive metals such as iron or steel alloys.

The polyisobutylsuccinic anhydride derivatives are generally added to the fuel in an amount of from 5 to 5000 ppm by weight, preferably from 7 to 2500 ppm by weight, in particular from 10 to 1000 ppm by weight, especially from 20 to 500 ppm by weight. very particularly preferably 25 to 300 ppm by weight, added, wherein these dosage data relate to the total amount of all added Polyisobutylbernsteinsäureanhydrid derivatives. For some grades of fuel and batches or some specific polyisobutylsuccinic anhydride derivatives, the threshold at which the desired corrosion-inhibiting effect may only be discernible may be relatively high, for example greater than 50 ppm by weight, greater than 100 ppm by weight or greater than 150 Ppm by weight.

The determination of the corrosion properties of a fuel with respect to the exposure to certain metals at low temperatures is usually carried out in accordance with standard specification ASTM D 665 A or B. In this case, the fuel with distilled water (variant ASTM D 655 A) or with synthetic seawater (variant ASTM D 655 B) stirred at elevated temperature for a certain time and the corrosive effect (rusting) is determined on a steel finger immersed in this mixture.

For the preparation of the polyisobutylsuccinic anhydride derivatives used according to the invention, these are normally produced from corresponding polyisobutylsuccinic anhydrides; the latter in turn are preferably obtained by thermal reaction of maleic acid or maleic anhydride with polyisobutenes, which in particular highly reactive polyisobutenes - ie those having a high content of terminal vinylidene double bonds, in particular with at least 65 mol%, especially with at least 75 mol% of terminal vinylidene double bonds - are suitable.

For this purpose, the polyisobutenes are reacted in a manner known per se with the maleic acid or the maleic anhydride. The molar ratio of polyisobutenes to maleic acid or maleic anhydride is, for example, 1: 3 to 1: 0.95, preferably 1: 2 to 1: 0.98, in particular 1: 1.3 to 1: 0.99, especially 1: 1.1 to 1: 1, ie there is usually a clear or slight excess of maleic acid or maleic anhydride in the reaction medium. If necessary, excess unreacted maleic acid or excess unreacted maleic anhydride can be removed from the reaction mixture by extraction or by distillation after completion of the reaction, for example by stripping with inert gas at elevated temperature and / or under reduced pressure. Ideally, the reaction is carried out in equimolar or approximately equimolar ratio of both reactants due to the almost complete reaction.

The thermal reaction of the polyisobutenes with the maleic acid or maleic anhydride is usually at a reaction temperature in the range of 100 to 300 ° C, preferably in the range of 130 to 270 ° C, in particular in the range of 150 to 250 ° C, especially in the range of 160 to 220 ° C, performed. The reaction time is usually 50 minutes to 20 hours, and preferably 1 to 6 hours.

The thermal reaction of the polyisobutenes with the maleic acid or maleic anhydride is usually carried out in the absence of oxygen and moisture in order to avoid undesirable side reactions. However, the degree of conversion in the presence of atmospheric oxygen or a few ppm halogen such as bromine may be higher than under inert conditions. Preferably, however, the reaction is carried out with appropriately purified starting materials in an inert gas atmosphere, e.g. under dried nitrogen, since it is then possible to do without a subsequent filtration step due to the lower formation of by-products.

If desired, the thermal reaction of the polyisobutenes with the maleic acid or the maleic anhydride can be carried out in a solvent which is inert under the reaction conditions, for example to adjust a suitable viscosity of the reaction medium or to avoid crystallization of maleic acid or maleic anhydride at colder sites of the reactor. Examples of suitable solvents are aliphatic hydrocarbons and mixtures thereof, for example naphtha, petroleum or paraffins having a boiling point above the reaction temperature, furthermore aromatic hydrocarbons and halogenated hydrocarbons, for example toluene, xylenes, isopropylbenzene, chlorobenzene or dichlorobenzenes, ethers, such as dimethyldiglycol or diethyldiglycol and mixtures of the aforementioned solvents. The process products themselves are also suitable as solvents. In principle, however, the reaction can also be carried out in the absence of solvents.

If desired, the thermal reaction of the polyisobutenes with the maleic acid or the maleic anhydride can be carried out in the presence of at least one carboxylic acid as catalyst. Suitable carboxylic acids are, in particular, aliphatic dicarboxylic acids having 2 to 6 carbon atoms, e.g. Oxalic acid, fumaric acid, maleic acid (in the case of the sole use of maleic anhydride as starting material) or adipic acid. The dicarboxylic acids mentioned can be added directly to the reaction mixture; in the case of maleic acid, this can also be formed by adding appropriate amounts of water from maleic anhydride under the reaction conditions. The amounts of catalyst are in this case usually 1 to 10 mol%, in particular 3 to 8 mol%, in each case based on the polyisobutene used.

The highly reactive polyisobutenes and maleic acid or maleic anhydride can be mixed before the reaction and reacted by heating to the reaction temperature. In a further embodiment, only a part of the maleic acid or maleic anhydride can be initially charged and the remaining part of the reaction mixture added at the reaction temperature so that there is always a homogeneous phase in the reactor. After completion of the reaction, the process product is worked up in a conventional manner, in general all volatile constituents are distilled off and the distillation residue is isolated. The polyisobutylsuccinic anhydrides prepared by the process according to the invention fall tar-free or largely tarry, which generally allows further processing of these products without further purification measures.

The process according to the invention makes it possible to prepare polyisobutylsuccinic anhydrides, in particular from highly reactive polyisobutenes having a number average molecular weight M _n of about 450 to more than 10,000. Such highly reactive polyisobutenes usually have a relatively narrow molecular weight distribution, ie a low polydispersity (PDI = M _w / M _n ) usually in the range of 1.0 to 3.0.

Highly reactive polyisobutenes as starting materials are composed entirely or predominantly of isobutene units. If they consist of 98 to 100 mol% of isobutene units, isobutene homopolymers are present. However, it is also possible for up to 20 mol% of 1-butene units to be incorporated into the polymer strand without this significantly changing the properties of the highly reactive polyisobutene. Furthermore, up to 5 mol% of further olefinically unsaturated C ₄ monomers such as 2-butenes or butadienes may be incorporated as units without fundamentally changing the properties of the highly reactive polyisobutene.

The polyisobutyl radical on the succinic acid skeleton for the present invention preferably has a number-average molecular weight M _n of 500 to 2300, in particular of 550 to 1500. In a particularly preferred embodiment, the polyisobutyl radical has a number average molecular weight M _n of 800 to 1300, in particular from 900 to 1100, on. In a particularly preferred alternative embodiment, the polyisobutyl radical here has a number average molecular weight M _n of 550 to 800, in particular from 650 to 750, on.

It is very particularly preferred to use the fuel 5 to 400 ppm by weight, in particular 10 to 300 ppm by weight, especially 20 to 200 ppm by weight, very particularly preferably 25 to 150 ppm by weight, of at least one such polyisobutylsuccinic anhydride Derivatives in which the polyisobutyl radical has a number average molecular weight M _n of 550 to 800, in particular from 650 to 750, having.

Polyisobutylsuccinic anhydrides can be converted in a manner known per se by reaction with amines, alcohols or aminoalcohols usually with elimination of water into the said polyisobutylsuccinic anhydride derivatives which have at least one primary or secondary amino group, an imino group and / or a hydroxyl group. These derivatives are usually hemiamides, amides, imides, esters or mixed amide esters of polyisobutylsuccinic acids. Imides are of particular interest here. When using amines or amino alcohols, the second non-amidated or esterified carboxyl group in the derivatives may also be in the form of the corresponding ammonium carboxylates.

Amines as reaction partners are preferably compounds which are in principle capable of imide formation, ie, in addition to ammonia, compounds with one or more primary or secondary amino groups. It is possible to use mono- or dialiphatic amines, cycloaliphatic amines or aromatic amines. Of particular interest are polyamines, especially aliphatic polyamines having 2 to 10, especially 2 to 6 nitrogen atoms, with at least one primary or secondary amino group. These aliphatic polyamines carry alkylene groups such as ethylene, 1,2-propylene or 2,2-dimethylpropylene.

Particularly good results are achieved in the present invention when the at least one polyisobutylsuccinic anhydride derivative used is a reaction product of the polyisobutylsuccinic anhydride with an aliphatic polyamine containing 2 to 10, especially 2 to 6 nitrogen atoms, at least one of which is a primary amino group. Examples of such compounds are ethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, dipropylenetriamine, tripropylenetetramine and N, N-dimethylpropylene-1,3-diamine. The reaction products of the polyisobutylsuccinic anhydride with said aliphatic polyamines having 2 to 10 nitrogen atoms, at least one of which is a constituent of a primary amino group, generally have imide structures.

Further polyamines suitable for reaction with the polyisobutylsuccinic anhydrides are, for example, N-amino-C ₁ -C ₆ -alkyl-piperazines, such as 4- (2-aminoethyl) -piperazine.

Amines also suitable for reaction with the polyisobutylsuccinic anhydrides are, for example, monoalkylamines and alkylene-amines in which the alkyl or alkylene radicals are interrupted by one or more non-adjacent oxygen atoms which may optionally also have hydroxyl groups and / or further amino groups, e.g. 4,7-Dioxadecane-1,10-diamine, 2- (2-aminoethoxy) ethanol or N- (2-aminoethyl) ethanolamine.

Suitable alcohols for reaction with the polyisobutylsuccinic anhydrides are, for example, di- or polyols having preferably 2 to 5 hydroxyl groups, e.g. Ethylene glycol, glycerol, diglycerol, triglycerol, trimethylolpropane, pentaerythritol and ethoxylated and / or propoxylated derivatives of these diols or polyols.

Suitable amino alcohols for reaction with the polyisobutylsuccinic anhydrides are, for example, alkanolamines such as ethanolamine and 3-aminopropanol.

Also suitable for reaction with the polyisobutylsuccinic anhydrides are ethoxylated and / or propoxylated derivatives of the abovementioned amines and aminoalcohols.

The molar ratio of polyisobutene succinic anhydride to said amines, alcohols or amino alcohols in the reaction is usually in the range of 0.4: 1 to 4: 1, preferably 0.5: 1 to 3: 1. For compounds with only one primary or Secondary amino group is often used at least equimolar amounts of amine.

When primary amines are used, amide and / or imide structures can be formed by reaction with the maleic anhydride moiety, the reaction conditions preferably being selected to form imide structures, since the products obtained thereby are preferred on account of their better performance properties are.

Amines with two amino groups, preferably with two primary amino groups, are also capable of forming corresponding bisamides or bisimides. Preferably, for the production of the bisimides, the amine will be used in approximately the necessary stoichiometry. Usually, these diamines are used here in an amount of less than 1 mol, in particular in an amount of from 0.3 to 0.95 mol, especially in an amount of from 0.4 to 0.9 mol per mol of the polyisobutylsuccinic anhydride.

Depending on the reactivity of the selected reactants, the reaction of the polyisobutene succinic anhydride with the stated amines, alcohols or aminoalcohols is usually carried out at a temperature in the range from 25 to 300 ° C., in particular in the range from 50 to 200 ° C., in particular in the range from 70 to 170 ° C, optionally using a conventional amidation catalyst performed. If desired, excess amine or excess alcohol or aminoalcohol can be removed from the reaction mixture by extraction or by distillation after completion of the reaction, for example by stripping with inert gas at elevated temperature and / or under reduced pressure. Preferably, the reaction is carried out to a conversion of the components of at least 90, in particular 95% (in each case based on the component used in deficit), wherein the progress of the reaction can be monitored by means of water formation by conventional analytical methods, for example on the acid number. The formation of compounds with imide structure from those with amide structure can be monitored by infrared spectroscopy.

The described polyisobutylsuccinic anhydride derivatives can be used in their function as corrosion inhibitors in the context of the present invention in all customary liquid fuels. In particular, they are suitable for use in this respect in gasoline fuels and especially in middle distillate fuels.

As gasoline fuels are all commercially available gasoline fuel compositions into consideration. A typical representative here is the market-standard basic fuel of Eurosuper according to EN 228. Furthermore, petrol fuel compositions of the specification are also according to WO 00/47698 Possible fields of use for the present invention.

As middle distillate fuels are all commercial diesel fuel and heating oil compositions into consideration. Diesel fuels are usually petroleum raffinates, which generally have a boiling range of 100 to 400 ° C. These are mostly distillates with a 95% point up to 360 ° C or even beyond. However, these may also be so-called "ultra low sulfur diesel" or "city diesel", characterized by a 95% point of, for example, a maximum of 345 ° C and a maximum sulfur content of 0.005 wt .-% or by a 95% point of, for example 285 ° C and a maximum sulfur content of 0.001 wt .-%. In addition to the Refined diesel fuels whose major constituents are longer-chain paraffins are those obtainable by coal gasification or gas-to-liquid (GTL) fuels. Also suitable are mixtures of the abovementioned diesel fuels with regenerative fuels such as biodiesel or bioethanol. Of particular interest currently are low sulfur diesel fuels, that is having a sulfur content of less than 0.05% by weight, preferably less than 0.02% by weight, more preferably less than 0.005% by weight, and especially of less than 0.001% by weight of sulfur. Diesel fuels can also contain water, for example in an amount of up to 20% by weight, for example in the form of diesel-water microemulsions or as so-called "white diesel".

Fuel oils are, for example, low-sulfur or high-sulfur petroleum refines or stone or lignite distillates, which usually have a boiling range of 150 to 400 ° C. Fuel oils may be standard heating oil in accordance with DIN 51603-1, which has a sulfur content of 0.005 to 0.2% by weight, or are low-sulfur heating oils with a sulfur content of 0 to 0.005% by weight. As examples of heating oil is especially called heating oil for domestic oil firing systems or fuel oil EL.

The described corrosion-inhibiting polyisobutylsuccinic anhydride derivatives may either be added to the respective base fuel, in particular the gasoline or diesel fuel, alone or preferably as part of fuel additive packages, e.g. the so-called gasoline or diesel performance packages. Such additive packages are added to the fuel before delivery to the end user. Packages of this type constitute fuel additive concentrates and contain customary fuel additives in customary amounts for this purpose. In addition to solvents, these are usually a number of other components as co-additives, such as detergent additives, carrier oils, cold flow improvers, other corrosion inhibitors, demulsifiers, dehazers, defoamers, Cetanzahlverbesserer, combustion improvers, antioxidants or stabilizers, antistatic agents, metallocenes, metal deactivators, solubilizers, markers and / or dyes in the customary amounts. The polyisobutylsuccinic anhydride derivatives described generally themselves have a detergent effect; of course, they may be used in the fuel compositions together with other detergent-effecting additives, in which case the proportion of the described polyisobutylsuccinic anhydride derivatives in the total amount of detergent-effecting additives is generally at least 30% by weight, especially at least 60% by weight. is.

The present invention also provides the use of polyisobutylsuccinic anhydride derivatives which contain at least one primary or secondary Amino group, an imino group and / or a hydroxyl group, as corrosion inhibitors in fuels for the protection of storage containers, lines and fuel supply devices in internal combustion engines, which are in contact with fuel, from corrosion.

With the present inventive method, more effective corrosion protection for storage vessels, conduits and fuel delivery devices in internal combustion engines in contact with fuel can be achieved than with the known prior art means. In order to achieve the level of corrosion protection required by the industry, it is generally necessary to use significantly lower amounts of the polyisobutylsuccinic anhydride derivatives described than in the case of the corrosion inhibitors customarily used.

The following examples are intended to illustrate the present invention without limiting it.

Examples

Corrosion tests were carried out analogously to the standard specification ASTM D 665 B. For this purpose, in each case 300 ml of a commercial diesel fuel (lot designation: RF-93-T-95), which contained no other additives except the below specified amount of polyisobutylsuccinic anhydride derivative ("PIBSI"), mixed with 30 ml of synthetic seawater and at 60 ° C stirred for 24 hours. A cylindrical steel finger dipped completely into the mixture. At the end of the test, the degree of rusting of the steel finger was evaluated by the "NACE" classification according to the above mentioned standard. The following table shows the results: Experiment No. PIBSIs Concentration on PIBSI
[Ppm] Rating (NACE level) blind test - 0 e 1 A 145 e 2 A 190 C 3 A 280 B 4 B 145 B

The "NACE" ratings indicate the percentage of the rusted area and are determined visually: A rusted area: 0% B ++ rusted area: 0.1% or less B + rusted area: 0.1 to 5% B rusted area: 5 to 25% C rusted area: 25 to 50% D rusted area: 50 to 75% e rusted area: 75 to 100%

PIBSI "A" is a polyisobutyl succinic anhydride whose polyisobutyl moiety has an M _n of 1000, and tetraethylenepentamine polyisobutyl succinimide.

PIBSI "B" is a polyisobutylsuccinic anhydride made from polyisobutylsuccinic anhydride whose polyisobutyl moiety has an M _n of 700 and tetraethylenepentamine prepared polyisobutylsuccinic acid imide.

It can be seen from the results of experiments 3 and 4 that a polyisobutylsuccinic anhydride derivative having a polyisobutyl radical having a M _n of 700, in significantly lower concentration, the same corrosion-inhibiting effect unfolds as a corresponding polyisobutylsuccinic anhydride derivative with a polyisobutyl radical which has a M _n of 1000.

Claims (8)

Method for protecting storage containers, lines and fuel supply devices in internal combustion engines in contact with fuel against corrosion, characterized in that small amounts of at least one derivative of a polyisobutylsuccinic anhydride containing at least one primary or secondary amino group, an imino group and / or has a hydroxyl group added. A method according to claim 1, characterized in that the fuel is added 5 to 5000 ppm by weight of the polyisobutylsuccinic anhydride derivatives. A method according to claim 1 or 2, characterized in that the polyisobutyl radical has a number average molecular weight M _n of 500 to 2,300. A process according to claims 1 to 3, characterized in that the fuel is added 5 to 400 ppm by weight of at least one such polyisobutylsuccinic anhydride derivatives in which the polyisobutyl radical has a number average molecular weight M _n of 550 to 800. Process according to claims 1 to 4, characterized in that the at least one polyisobutylsuccinic anhydride derivative is a reaction product of the polyisobutylsuccinic anhydride with an aliphatic polyamine having 2 to 10 nitrogen atoms, at least one of which is a constituent of a primary amino group. A process according to claims 1 to 5, characterized in that the corrosion-inhibiting polyisobutylsuccinic anhydride derivatives are constituents of an additive package added to the fuel before delivery to the end user, which contains the fuel additives customary for this purpose in the amounts customary in this case. Process according to claims 1 to 6, characterized in that the fuel is a middle distillate fuel. Use of polyisobutylsuccinic anhydride derivatives having at least one primary or secondary amino group, an imino group and / or a hydroxyl group as corrosion inhibitors in fuels for protecting storage tanks, pipes and fuel supply devices in internal combustion engines in contact with fuel from corrosion.