# Patent

## Title
Additive mixture for the bactericidal and anticorrosive additization of fuels

## Abstract

An additive mixture for fuels including a) at least one N-formal, b) at least one antioxidant and c) at least one corrosion inhibitor. The additive mixture ensures that the additized fuels and lubricants have biocidal and corrosion-inhibiting additization, especially when they include proportions of renewable raw materials, such as biodiesel, and when they are in contact with copper-containing surfaces.

## Background
The invention relates to an additive mixture for the bactericidal and anticorrosive additization of fuels. The additive can be formulated as a liquid concentrate or as a semiconcentrate. The invention further relates to the use of the additive mixture for bactericidal and anticorrosive additization of fuels, and to correspondingly additized fuels. The invention also relates to a method for operating a system with a fuel which comprises the components of the inventive additive mixture.
In systems which come into contact with fuels (such as heating oil) (storage tanks, conduits, valves, filters, probes, measuring instruments, burners, etc.), different materials are used, for example plastics, metals and alloys, especially copper-containing materials. Owing to the interaction of long storage times, different compositions of the fuel and external influences such as formation of water of condensation, and oxidative and/or microbial degradation processes, the composition of the fuel can change and lead to undesired consequent phenomena. These consequent phenomena include corrosion, turbidity up to and including precipitation (formation of “sludge”), blockage of filters and material wear. This can lead to failure of the system and to the necessity of expensive repairs. Similar problems arise in fuel-processing systems such as stationary and mobile diesel engines and the corresponding injection systems.
The prior art discloses biocidal compositions for fuels. For example, DE 103 40 830 A1 describes compositions based on formaldehyde depot compounds and antioxidants, and the use thereof for preserving industrial products, for example fuels. An illustrative formaldehyde depot compound is N,N′-methylenebis(5-methyloxazolidine), which is sold by Schülke & Mayr GmbH (Norderstedt, Federal Republic of Germany) as Grotan® OX (Grotamar® 71, Mar° 71). The compositions have very good storability as concentrates and have a constantly low level of deformation of the plastic vessel containing the concentrate (“neck-in effect”).
DE 199 61 621 A1 relates to compositions which comprise a bactericidal N-formal, a fungicide and a stabilizer, for use, for example, in fuel additives. The compositions are storage-stable and have good meterability.
In the systems mentioned, as well as fossil fuels such as mineral oil, biofuels (such as biodiesel) are increasingly being used, which comprise fatty acid alkyl esters such as fatty acid methyl esters (FAME), for example rapeseed oil methyl ester (RME). This is both because of legal stipulations and financial support and because of the insight that, in the generation of energy from renewable raw materials, the release of CO2 is climate-neutral. Since the use of biofuels, however, there has been a significant increase in material compatibility problems. It is assumed that biodiesel, for example, leaches copper ions out of copper-containing constituents of the systems. The increased copper ion content in turn accelerates the decomposition of the biodiesel and ultimately leads to the problems mentioned above.
WO2009/060057 A2 relates to the use of water-soluble biocides in biodiesel. An example of a biocide is 3,3′-methylenebis(5-methyloxazolidine). To improve the efficacy of the biocides, ethers are proposed. The ethers according to WO2009/060057 A2 are needed in a certain amount to dissolve the biocides in the biodiesel. However, ethers readily form peroxides which can convert constituents in biodiesel, inactivate antioxidants and wear away material. The biocidal activity of ethers, moreover, is not comparable to that of formaldehyde depot compounds, and therefore (also as boosters) have to be used at a higher concentration and are therefore uneconomic. Moreover, ethers have a comparatively low flashpoint and can lead to less favorable labelling of products.
For this reason, it is desirable to add to the fuel improved additives which suppress these troublesome influences (decomposition of the biodiesel, formation of sludge) or do not allow them to arise at all, without necessarily needing to use ethers. More particularly, it was an object of the present invention to provide additive mixtures which are suitable for biocidal and anticorrosive additization of those fuels which comprise proportions of renewable raw materials, for example biodiesel. The additive mixtures should also be stable as concentrates and be easy to dose.
It has now been found that, surprisingly, these objects are achieved by an additive mixture which comprises

    
    
        a) at least one N-formal,
        b) at least one antioxidant and
        c) at least one corrosion inhibitor.
    
    


Inventive additives protect fuels to which they are added from infestation by bacteria, yeasts and moulds, and at the same time provide them with the necessary corrosion protection. The advantages of the additive mixtures are found more particularly in the case of addition to fuels which comprise components composed of renewable raw materials, for example biodiesel.
a) N-Formal
Inventive additive mixtures comprise at least one N-formal. The advantages of these active microbicidal ingredients are disclosed in DE 103 40 830 A1. Particularly suitable N-formals are reaction products of formaldehyde and amines (preferably alkanolamines) with a molar formaldehyde excess.
Examples of N-formals are condensation products of paraformaldehyde and isopropanolamine in a molar ratio of 3:2, condensation products of paraformaldehyde and isopropanolamine in a molar ratio of 3:2 and urea, and condensation products of paraformaldehyde and isopropanolamine in a molar ratio of 3:2 and urea and ethylene glycol.
N-Formals which are used with preference in accordance with the invention are N,N′-methylenebis(5-methyloxazolidine), α,α′,α′′-trimethyl-1,3,5-triazine-1,3,5-(2H,4H,6H)triethanol, 4,4-dimethyloxazolidine, dimethylolurea, 5-ethyl-3,7-dioxa-1-azabicyclo[3.3.0]octane, 2-(hydroxymethylamino)ethanol, methylenebistetrahydro-1,3-bisoxazine, 5-methylolchloro-acetamide, bis(hydroxymethyl)-5,5-dimethylhydantoin, diazolidinylurea, sodium hydroxymethylglycinate and 3,4,4-trimethyloxazolidine, 2,2′,2′′-(hexahydro-1,3,5-triazine-1,3,5-triyl)triethanol (Grotan® BK), tetrahydro-1,3,4,6-tetrakis(hydroxylmethyl)imidazo[4,5-d]imidazole-2,5-(1H,3H)dione (TMAD) and tetramethylolglycoluril.
Preference is given to low-water formaldehyde depot compounds.
Particular preferred formaldehyde depot compounds are 3,3′-methylenebis(5-methyloxazolidine), 2,2′,2′′-(hexahydro-1,3,5-triazine-1,3,5-triyl)-triethanol, α,α′,α′′-trimethyl-1,3,5-triazine-(2H,4H,6H)triethano 1, tetrahydro-1,3,4,6-tetrakis(hydroxymethyl)imidazo[4,5-d]imidazole-2,5(1H,3H)-dione, dimethylurea and the products Grotan OF (methylenebis(5-methyloxazolidine)+urea) and Grotan OK (methylenebis(5-methyloxazolidine)+urea+ethylene glycol).
A very particularly preferred formaldehyde depot compound is 3,3′-methylenebis(5-methyloxazolidine).
b) Antioxidant
The inventive additive mixture comprises at least one antioxidant. Preferred antioxidants are liquid or are sufficiently soluble in the formaldehyde depot compound at room temperature. Examples of antioxidants are selected from sterically hindered phenols, amines, vitamin E and derivatives thereof, and alkyl gallates, preferably 3-tert-butyl-4-hydroxyanisole (BHA), 2,6-di-tert-butyl-p-cresol (BHT), 2,6-di-tert-butylphenol, lauryl gallate and vitamin E.
Especially preferred as antioxidants are 2,6-di-tert-butylphenol and BHT.
c) Corrosion Inhibitor
The inventive additive mixture comprises, as a further obligatory component c), at least one corrosion inhibitor. Preferred corrosion inhibitors are liquid or are sufficiently soluble in the formaldehyde depot compound at room temperature. Particularly preferred corrosion inhibitors are triazole derivatives, for example benzotriazole, tolyltriazole or N,N-bis(2-ethylhexyl)((1,2,4-triazol-1-yl)methyl)amine.
Particular preference is given to using N,N-bis(2-ethylhexyl)((1,2,4-triazol-1-yl)methyl)amine, which is supplied by BASF SE (Ludwigshafen, Federal Republic of Germany) as Irgamet® 30.
Amounts of Components a), b) and c)
In additive mixtures preferred in accordance with the invention, the weight ratio of component b) to component c) is typically 20:1 to 1:20, preferably 1:10 to 10:1, especially 1:4 to 4:1, for example 1:1.
As explained hereinafter, inventive additives are typically formulated as liquid concentrates or semiconcentrates.
Liquid Concentrate
In inventive additive mixtures formulated as liquid concentrates, the proportion of component a) is preferably at least 60% by weight, preferably at least 80% by weight, especially at least 90% by weight, for instance 92% by weight. The proportions of components b) and c) are typically each at least 0.5% by weight, preferably at least 1% by weight, especially at least 2 by weight, for instance 4% by weight. Particular preference is given to liquid concentrates which consist of components a), b) and c), i.e. comprise no further constituents.
A particularly preferred liquid concentrate consists of:

    
    
        a) 92% by weight of 3,3′-methylenebis(5-methyloxazolidine),
        b) 4% by weight of 2,6-di-tert-butylphenol and
        c) 4% by weight of Irgamet 30.
    
    


The liquid concentrate is prepared by initially charging component a) (for example 3,3′-methylenebis(5-methyloxazolidine)) and then dissolving component b) (such as 2,6-di-tert-butylphenol or BHT) and component c) (such as Irgamet 30) while stirring. The product is clear and colourless to pale yellow.
Inventive liquid concentrates are used prophylactically in fuels which are yet to be microbially infested in concentrations of 20 to 100 mg/l (ppm), and in fuels which have already been contaminated in amounts of 200 to 1000 ppm.
Semiconcentrate
In inventive additive mixtures which have been formulated as a semiconcentrate, the proportion of component a) is typically at least 5% by weight, preferably at least, preferably at least 10% by weight, especially at least 15% by weight, for instance 20% by weight. Components b) and c) are typically present in an amount of in each case at least 0.1% by weight, preferably at least 0.25% by weight, especially at least 0.5% by weight, for instance 0.9% by weight.
Semiconcentrates comprise, as well as the inventive components a), b) and c), a carrier. Examples of carriers are selected from diesel oil, biodiesel oil, fatty acid methyl esters, mineral oil (e.g. Shellsol A 150), aliphatic or aromatic hydrocarbons (such as toluene), alkylbenzenes, for example Marlican (RG), and mixtures thereof. The amount of the carrier in the concentrate is preferably at least 50% by weight, more preferably at least 60% by weight, especially at least 70% by weight, for instance 78% by weight.
A particularly preferred semiconcentrate comprises:

    
    
        a) 20% by weight of 3,3′-methylenebis(5-methyloxazolidine),
        b) 0.9% by weight of 2,6-di-tert-butylphenol
        c) 0.9% by weight of Irgamet 30
    
    


and, as the remainder, a hydrocarbon as a carrier which is soluble in FAME-containing hydrocarbons, for example diesel fuel. For example, the carriers used are, for example, ShellSol A 150 or alkylbenzene (Marlican).
To prepare the semiconcentrate, the carrier is initially charged and component a) (such as 3,3′-methylenebis(5-methyloxazolidine)), component b) (such as 2,6-di-tert-butylphenol or BHT) and component c) (such as Irgamet 30) are dissolved while stirring. The product is clear and colourless to pale yellow.
Inventive semiconcentrates are used prophylactically in fuels which are yet to be microbially infested in concentrations of 100 to 500 ppm, and in fuels which have already been contaminated in amounts of 1000 to 5000 ppm.
The invention further relates to the use of the inventive additive mixture for biocidal and anticorrosive additization of fuels, and to the protection thereof from oxidative degradation.
According to the invention, the corrosion of copper in particular as a constituent of the materials of systems through which the fuel flows or in which it is stored. As mentioned above, the corrosion of copper presented a problem especially when the fuel comprises proportions of renewable raw materials, for example FAME. The proportion of renewable raw materials (such as FAME) which is typically present in the fuel is up to 100% by volume, preferably up to 20% by volume, especially up to 10% by volume, such as 5 to 7% by volume.
According to the invention, components a), b) and c) are used in the fuel in an amount which ensures effective protection from microbial attack and from oxidative and corrosive influences. In the fuel, the proportion of component a) should be at least 5 ppm, more preferably at least 100 ppm and especially preferably at least 200 ppm, for example 500 ppm. The proportions of components b) and c) should each be at least 0.25 ppm, preferably at least 5 pmm and more preferably at least 10 ppm, for example 25 ppm.
The invention further relates to the use of the inventive liquid concentrate for producing a semiconcentrate.
Components a), b) and c) are used—in combination—in fuels, preferably in the form of the inventive liquid concentrates or semiconcentrates. They are used in accordance with the invention in lubricants, cooling lubricant concentrates and emulsions, transformer oils, fuels, biofuels, biodiesels, diesel fuels, kerosenes, heavy oils, heating oils, mineral oils, all of which are referred to here as fuels. They are preferably used in fuels with proportion of material composed of renewable raw materials, especially biodiesel.
The inventive formulations can be combined with further active biocidal ingredients, functional additives and auxiliaries, as disclosed, for example, in WO2009/060057 A2, DE 10 2006 035013 A1 or DE 103 40 830 A1.
The combination of components a), b) and c) is used in fuels preferably by adding a liquid concentrate or a semiconcentrate. Alternatively, it is possible to add components a), b) and c) individually, but this alternative is not preferred.
The invention further relates to a method for operating a system with a fuel, in which the additive mixture described is added to the fuel, or in which the components are added individually.
The invention also relates to a fuel which comprises components a), b) and c) in such an amount that the concentration (based in each case on the fuel)

    
    
        of component a) is at least 5 ppm, preferably at least 100 ppm and especially at least 200 ppm, for instance 500 ppm;
        of component b) is at least 0.25 ppm, preferably at least 5 ppm and especially at least 10 ppm, for instance 25 ppm; and
        of component c) is at least 0.25 ppm, preferably at least 5 pmm and especially at least 10 ppm, for instance 25 ppm.
    
    


The inventive liquid concentrates or semiconcentrates have the following advantages:

    
    
        they are clear, homogeneous, fluid, low-viscosity, free-flowing, low-odour, readily distributable, readily incorporable, possess good stability (cold stability, storage stability, sufficient thermal stability) and are easy to handle;
        they have a broad profile of action: they are bactericidally, fungicidally and algicidally active, protect from oxidative degradation, give a good coating on the surfaces to be treated, protect from corrosion, especially in the case of nonferrous metals;
        they protect systems and materials which come into contact with fuels, especially biofuels;
        they effectively prevent sludge formation in fuel systems and vessels;
        they improve the shelf life of the treated products;
        they improve the lubricant properties of the treated products;
        they possess good compatibility with a multitude of materials;
        they have good solubility in different bases, such as oils;
        they possess good dissolution capacity for further/additional additives;
        no additional solvents are required and
        they enhance the calorific value of heating oil.
    
    


The advantages of the invention are evident more particularly from the examples which follow.


EXAMPLES
Unless stated otherwise, all percentages are based on weight.
Example 1
Materials used:

    
    
        3,3′-methylenebis(5-methyloxazolidine)
        brass 63 (100×20×1 mm), Cat. No.: 16-24 from Riegger Industriehandel, Reinbek, Federal Republic of Germany
        E-copper ((100×20×1 mm), Cat. No.: 15-54 from Riegger
        diesel fuel to EN 590, with 5% (V/V) fatty acid methyl ester
    
    


Procedure: The solutions and the metal sheet were each introduced into a 500 ml wide-neck bottle. Solutions 1A-1C were not stirred; solutions 1D-1G were stirred with a magnetic stirrer. The appearance of the solutions was assessed visually.














Sample
Experiment
Start
After 4 weeks
After 6 weeks







1A
Cu sheet in diesel; without stirring
clear yellow solution
clear yellow solution
clear yellow solution


1B
Cu sheet in diesel + 500 ppm
clear yellow solution
clear yellow solution
slightly turbid yellow 



of 3,3′-methylenebis(5-methyl-


solution



oxazolidine); without stirring





1C
Cu sheet in diesel + 50 ppm
clear yellow solution
clear yellow solution
turbid yellow solution



of 3,3′-methylenebis(5-methyl-






oxazolidine); without stirring





1D
Cu sheet in diesel; with stirring
clear yellow solution
clear yellow solution
clear yellow solution


1E
Cu sheet in diesel + 500 ppm 
clear yellow solution
clear yellow solution
highly turbid solution, 



of 3,3′-methylenebis(5-methyl-


some dark coating on 



oxazolidine); with stirring


the sheet and at the






base of the bottle


1F
Cu sheet in diesel + 50 ppm
clear yellow solution
clear yellow solution
clear yellow solution, 



of 3,3′-methylenebis(5-methyl-


fluff in the solution



oxazolidine); with stirring





1G
Brass sheet in diesel + 500 ppm 
clear yellow solution
clear yellow solution
turbid yellow solution, 



of 3,3′-methylenebis(5-methyl-


some dark coating 



oxazolidine); with stirring


on the sheet and at 






the base of the bottle









Example 2
Materials used:

    
    
        3,3′-methylenebis(5-methyloxazolidine)
        semiconcentrate 2: 20% 3,3′-methylenebis(5-methyloxazolidine), 0.9% di-tert-butylphenol, 0.9% Irgamet 30; dissolved in ShellSol A 150
        E-copper (100×20×1 mm), Cat. No.: 15-54 from Riegger
        diesel fuel to EN 590, with 5% (V/V) fatty acid methyl ester content
    
    


Procedure: The solutions and the metal sheet were each introduced into a 500 ml wide-neck bottle and stirred at room temperature with a magnetic stirrer.













Sample






2A
Diesel, stirred


2B
Diesel + copper sheet, stirred


2C
Diesel + 500 ppm of 3,3′-methylenebis (5-methyloxazolidine); stirred


2D
Diesel + copper sheet + 500 ppm 3,3′-methylenebis (5-methyloxazolidine)


2E
Diesel + 2500 ppm of semiconcentrate 2, stirred


2F
Diesel + copper sheet + 2500 ppm of semiconcentrate 2, stirred















Copper content 







mg/l (ppm)
2 days
1 week
2 weeks
3 weeks
6 weeks





2A
0.1
0.1
0.2
not determined
0.1


2B
1.3
1.5
1.8
1.6
2.3


2C
0.1
0.1
0.1
0.1
0.2


2D
0.6
0.6
0.8
1.0
1.0


2E
0.1
<0.1
<0.1
<0.1
0.2


2F
not determined
0.5
not determined
0.7
0.7
















Appearance
2A
2B
2C
2D
2E
2F





Start
clear yellow
clear yellow
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution
solution
solution


after 1 week
clear yellow
clear yellow
clear yellow
clear yellow 
clear yellow
clear yellow



solution
solution
solution
solution
solution
solution


after 2 weeks
clear yellow 
clear yellow
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution
solution
solution


after 3 weeks
clear yellow 
clear yellow
clear yellow
clear yellow 
clear yellow
clear yellow



solution
solution
solution
solution
solution
solution


after 5 weeks
clear yellow 
clear yellow
clear yellow
turbid yellow
clear yellow
clear yellow



solution
solution
liquid
solution
solution
solution


after 10 weeks 
clear yellow 
turbid yellow 
clear yellow
red sludge at
clear yellow
clear yellow



solution
liquid
solution
the base of a
solution
solution






turbid yellow








liquid




after 11 weeks
clear yellow 
red sludge at 
clear yellow 
red sludge at 
clear yellow
clear yellow



solution
the base of a
solution
the base of a
solution
solution




turbid yellow

turbid yellow






liquid

liquid




after 12 weeks 
clear yellow
red sludge at
clear yellow 
red sludge at 
clear yellow
clear yellow



solution
the base of a
solution
the bottom of
solution
solution




turbid yellow

a turbid






liquid

yellow liquid




after 13 weeks
clear yellow
red sludge at
turbid
red sludge at
somewhat 
somewhat 



solution
the base of a

the base of a
more intense
more intense




turbid yellow

turbid yellow
yellow
yellow




liquid

liquid




after 14 weeks
clear yellow
red sludge at
turbid, a
red sludge at
somewhat 
somewhat 



solution
the base of a
little brown
the base of a
more intense
more intense




turbid yellow
sludge at the
turbid yellow
yellow
yellow, brown




liquid
base
liquid

crumbs in the








solution


after 15 weeks
clear yellow
red sludge at
turbid, a
red sludge at
somewhat 
somewhat 



solution
the base of a
little brown
the base of a
more intense
more intense




turbid yellow
sludge at the
turbid yellow
yellow
yellow, brown




liquid
base
liquid

crumbs in the








solution


after 20 weeks
clear yellow
red sludge at
turbid, a
red sludge at
slightly
slightly



solution
the base of a
little brown
the base of a
turbid,
turbid,




turbid yellow
sludge at the
turbid yellow
somewhat 
somewhat 




liquid
base
liquid
more intense
more intense







yellow
yellow, brown








crumbs/fluff








in the








solution









Example 3
Materials used:

    
    
        Concentrate X: 92% 3,3′-methylenebis(5-methyloxazolidine)+4% BHT+4% benzotriazole
        Concentrate Y: 92% 3,3′-methylenebis(5-methyloxazolidine)+4% 2,6-di-tert-butylphenol+4% Irgamet 30
        E-copper (100×20×1 mm), Cat. No.: 15-54 from Riegger
        diesel fuel to EN 590, with 5% (V/V) fatty acid methyl ester content
    
    


Procedure: The solutions and the metal sheet were each introduced into a 500 ml bottle and stirred with a magnetic stirrer.













Sample






3A
Diesel + 500 ppm of concentrate X, stirred


3B
Diesel + 500 ppm of concentrate X + copper sheet, stirred


3C
Diesel + 500 ppm of concentrate Y, stirred


3D
Diesel + copper sheet + 500 ppm of concentrate Y; stirred













Copper content





mg/l (ppm)
Blank value
3 weeks
6 weeks





3A
0.2
0.2
0.16


3B
0.2
1.4
2.1


3C
0.2
0.2
0.25


3D
0.2
0.7
0.67














Appearance
3A
3B
3C
3D





Start
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution


after 3 weeks
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution


after 6 weeks
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution


after 7 weeks
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution


after 8 weeks
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution


after 9 weeks
clear yellow
clear yellow
clear yellow
clear yellow



solution
solution
solution
solution


after 10 weeks 
clear yellow
slightly
clear yellow
clear yellow



solution
turbid, 
solution
solution




brown fluff




after 11 weeks
clear yellow
turbid, brown
clear yellow
clear, intensely



solution
sludge at the
solution
yellow solution




base




after 12 weeks
clear yellow
turbid, brown
clear yellow
clear, intensely



solution
sludge at the
solution
yellow solution




base




after 17 weeks
slightly turbid,
turbid, brown 
very slightly
turbid, fluff/



yellow
sludge at the
turbid,
crumbs in the




base
yellow
solution









Example 4
Materials used:

    
    
        3,3′-Methylenebis(5-methyloxazolidine)
        Semiconcentrate 4: 20% 3,3′-methylenebis(5-methyloxazolidine), 0.9% di-tert-butylphenol, 0.9% Irgamet 30; dissolved in ShellSol A 150
        Diesel fuel to EN 590, with 5% (V/V) fatty acid methyl ester content
        Copper naphthenate (copper content: 7.97%; stock solution: 12.55 g of copper naphthenate are dissolved/100 g of toluene, corresponding to 1% copper)
    
    













Sample
Test setup







4A
Diesel


4B
Diesel + 500 ppm of 3,3′-methylenebis(5-methyloxazolidine)


4C
Diesel + 2500 ppm of semiconcentrate 4


4D
Diesel + 1 ppm of copper + 500 ppm of 3,3′-methylenebis(5-



methyloxazolidine)


4E
Diesel + 5 ppm of copper + 500 ppm of 3,3′-methylenebis(5-



methyloxazolidine)


4F
Diesel + 1 ppm of copper + 2500 ppm of semiconcentrate 4


4G
Diesel + 5 ppm of copper + 2500 ppm of semiconcentrate 4


4H
Diesel + 1 ppm of copper (after 2 weeks)


4I
Diesel + 5 ppm of copper (after 2 weeks)









All samples are stirred in a 250 ml screwtop bottle with a magnetic stirrer at room temperature. The appearance changed as follows:



















Appearance
4A
4B
4C
4D
4E
4F
4G
4H
4I







Start
clear yellow
clear
clear
clear 
clear
clear
clear





solution
yellow
yellow
yellow
yellow
yellow
yellow






solution
solution
solution
solution
solution
solution




after 2
clear yellow
clear
clear
turbid
turbid
clear
clear
clear
clear


weeks
solution
yellow
yellow
yellow
yellow
yellow
yellow
yellow
yellow




solution
solution
liquid
liquid 
solution
solution
solution 
solution


after 3
clear yellow
clear
clear
turbid
dark
clear
clear
clear
turbid


weeks
solution
yellow
yellow
yellow
sludge
yellow
yellow
yellow
yellow




solution
solution
liquid
in
solution
solution
solution
liquid







turbid











yellow











liquid






after 4
clear yellow
clear
clear
dark sludge
dark
clear
clear
dark
dark


weeks
solution
yellow
yellow
in turbid
sludge
yellow
yellow
sludge
sludge in




solution
solution
yellow
in
solution
solution
in
turbid






liquid
turbid


turbid
yellow







yellow


yellow
liquid







liquid


liquid



after 5
clear yellow
clear
clear
dark sludge
dark
clear 
turbid,
dark
dark


weeks
solution
yellow
yellow
in turbid
sludge
yellow
flocs
sludge
sludge in




solution
solution
yellow
in
solution

in
turbid






liquid
turbid


turbid
yellow







yellow


yellow
liquid







liquid


liquid



after 6
clear yellow
clear
clear
dark sludge
dark
clear 
turbid,
dark
dark


weeks
solution
yellow
yellow
in turbid
sludge
yellow
flocs
sludge
sludge in




solution
solution
yellow
in
solution

in
turbid






liquid
turbid


turbid
yellow







yellow


yellow
liquid







liquid


liquid



after 7
clear yellow
clear
clear
dark sludge
dark
turbid,
turbid,
dark
dark


weeks
solution
yellow
yellow
in turbid
sludge 
yellow,
flocs
sludge 
sludge in




solution 
solution
yellow
in
flocs

in
turbid






liquid
turbid


turbid
yellow







yellow


yellow
liquid







liquid


liquid



after 12
clear yellow 
clear
clear
dark sludge
dark
turbid, 
turbid,
dark
dark


weeks
solution
yellow
yellow
in turbid
sludge 
yellow,
flocs
sludge 
sludge in




solution 
solution
yellow
in
flocs

in
turbid






liquid
turbid


turbid
yellow







yellow


yellow
liquid







liquid


liquid









Example 5
Materials used:

    
    
        EL heating oil, low-sulfur (purely mineral, no fatty acid methyl esters)
        Fatty acid methyl esters
        3,3′-Methylenebis(5-methyloxazolidine)
        Semiconcentrate X: 20% 3,3-methylenebis(5-methyloxazolidine), 0.9% di-tert-butylphenol, 0.9% Irgamet 30; dissolved in ShellSol A 150
        E-copper (100×20×1 mm) Cat. No.: 15-4 from Riegger
    
    















Diesel 



sample
Composition (% by vol.)





5A
100% heating oil + 0% biodiesel


5B
 90% heating oil + 10% biodiesel


5C
 80% heating oil + 20% biodiesel


5D
 70% heating oil + 30% biodiesel





Sample
Experiment





5A1
5A + Cu


5A2
5A + 500 ppm of 3,3-methylenebis(5-methyloxazolidine)


5A3
5A + 500 ppm of 3,3-methylenebis(5-methyloxazolidine) + Cu


5A4
5A + 2500 ppm of semiconcentrate X


5A5
5A + 2500 ppm of semiconcentrate X + Cu


5B1
5B + Cu


5B2
5B + 500 ppm of 3,3-methylenebis(5-methyloxazolidine)


5B3
5B + 500 ppm of 3,3-methylenebis(5-methyloxazolidine) + Cu


5B4
5B + 2500 ppm of semiconcentrate X


5B5
5B + 2500 ppm of semiconcentrate X + Cu


5C1
5C + Cu


5C2
5C + 500 ppm of 3,3-methylenebis(5-methyloxazolidine)


5C3
5C + 500 ppm of 3,3-methylenebis(5-methyloxazolidine) + Cu


5C4
5C + 2500 ppm of semiconcentrate X


5C5
5C + 2500 ppm of semiconcentrate X + Cu


5D1
5D + Cu


5D2
5D + 500 ppm of 3,3-methylenebis(5-methyloxazolidine)


5D3
5D + 500 ppm of 3,3-methylenebis(5-methyloxazolidine) + Cu


5D4
5D + 2500 ppm of semiconcentrate X


5D5
5D + 2500 ppm of semiconcentrate X + Cu









The appearance of the individual sample changed as follows:




















After 1
After 2
After 3
After 4
After 5
After 6
After 11



Start
week
weeks
weeks
weeks
weeks
weeks
weeks







5A1
clear red
clear red
clear red
clear red
clear red
clear red
clear red
clear red



solution
solution
solution
solution
solution
solution
solution
solution


5A2
clear red
clear red
clear red
clear red
clear red
clear red
clear red
clear, red,



solution
solution
solution
solution
solution
solution
solution
sediment on










the metal










and at the










base


5A3
clear red
clear red
clear red
clear red
clear red
clear red
clear red
Slightly



solution
solution
solution
solution
solution
solution
solution
turbid,










sediment at










the base


5A4
clear red
clear red
clear red
clear red
clear red
clear red
clear red
clear red



solution
solution
solution
solution
solution
solution
solution
solution


5A5
clear red
clear red
clear red
clear red
clear red
clear red
clear red
clear red



solution
solution
solution
solution
solution
solution, a
solution,
solution, a








little fluff
a little
little









fluff
fluff


5B1
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution, a
turbid,
turbid,








little fluff
crumbs
crumbs


5B2
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment at









at the
the base









base



5B3
clear red
turbid red
dark sludge
dark sludge
dark sludge
dark sludge
dark
dark sludge



solution
liquid
in turbid
in turbid
in turbid
in turbid
sludge in
in turbid





red liquid
red liquid
red liquid
red liquid
turbid red
red liquid









liquid



5B4
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment at









at the
the base









base



5B5
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment at









at the
the base









base



5C1
clear red
clear red
clear red
clear red
clear red
turbid
turbid
turbid, has



solution
solution
solution
solution
solution


become










lighter


5C2
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment a









at the
the base









base



5C3
clear red
turbid red
dark sludge
dark sludge
dark sludge
dark sludge
dark
dark sludge



solution
liquid
in turbid
in turbid
in turbid
in turbid
sludge in
in turbid





red liquid
red liquid
red liquid
red liquid
turbid red
red liquid









liquid



5C4
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment at









at the
the base









base



5C5
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment at









at the
the base









base



5D1
clear red
clear red
clear red
clear red
clear red
turbid
turbid
decolorized



solution
solution
solution
solution
solution


to orange,










turbid and










sediment


5D2
clear red
clear red
clear red
clear red
clear red
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid, a
turbid, a









little
little









sediment
sediment a









at the
the base









base



5D3
clear red
turbid red
dark sludge
dark sludge
dark sludge
dark sludge
dark
dark sludge



solution
liquid
in turbid
in turbid
in turbid
in turbid
sludge in
in turbid





red liquid
red liquid
red liquid
red liquid
turbid red
red liquid









liquid



5D4
clear red
clear red 
clear red 
clear red 
clear red 
clear red
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid
turbid


5D5
clear red
clear red
clear red 
clear red
clear red 
clear red 
slightly
slightly



solution
solution
solution
solution
solution
solution
turbid
turbid









Evaluation of the Examples
Example 1 shows that 3,3′-methylenebis(5-methyloxazolidine) is incompatible as an additive to diesel oil (with 5% FAME) with a time delay and in a concentration-dependent manner and more particularly in turbulent flow, when it comes into contact with copper or nonferrous metal. 3,3-Methylenebis(5-methyloxazolidine) is thus, as an additive to diesel/biodiesel, associated with disadvantages when there is contact with nonferrous metal. The biocide, which in principle has good suitability, is thus not very suitable owing to its incompatibility.
Example 2 shows that diesel fuel with 5% FAME can leach considerable amounts of copper salt out of copper sheet (2B). In the case of addition of 3,3′-methylenebis(5-methyloxazolidine), the copper wear is lower (2D), and in the case of addition of inventive semiconcentrate with ShellSol A 150 significantly lower (2F). The formation of sludge in the solution correlates with the amount of copper salt released. Even in the absence of copper sheet, the performance of the inventive semiconcentrate is somewhat better than that of 3,3′-methylenebis(5-methyloxazolidine) (see 2E compared to 2C).
Example 3 shows that diesel fuel with 5% FAME in contact with copper sheet is protected better by addition of a concentrate composed of 92% 3,3′-methylenebis(5-methyloxazolidine), 4% 2,6-di-tert-butylphenol and 4% Irgamet 30 than by addition of a likewise inventive concentrate composed of 92% 3,3′-methylenebis(5-methyloxazolidine), 4% BHT and 4% benzotriazole.
In Example 4, a defined amount of copper salt (copper naphthenate, dissolved in toluene) is added to diesel fuel with 5% FAME (4D to 4I). WHEN 3,3′-methylenebis(5-methyloxazolidine) is added, there is incompatibility depending on the copper concentration (4D, 4E). An addition of inventive semiconcentrate significantly improves the stability of the diesel fuel (4F, 4G). Diesel fuel with 5% FAME leads, after addition of copper salt, to the formation of sludge (see 4H, 4I). Diesel fuel with 5% FAME without addition of copper salt is stable (4A), and likewise in the case of addition of 3,3′-methylenebis(5-methyloxazolidine) (4B) or inventive semiconcentrate (4C). This demonstrates that inventive semiconcentrates are also suitable for products which do not have a proportion of material composed of renewable raw materials.
Example 5 shows the unfavourable influence of FAME (10 to 30% by volume) on diesel fuel when the latter is in contact with Cu. An addition of 3,3′-methylenebis(5-methyloxazolidine) worsens the compatibility further (e.g. 5C3 compared to 5C1); only an addition of inventive semiconcentrate gives a stable liquid in the presence of copper sheet (e.g. 5C5).
This shows that an N-formal such as 3,3′-methylenebis(5-methyloxazolidine) is incapable of protecting FAME-containing liquids which are in contact with nonferrous metals against microbial degradation. Only the combination with sufficient amounts of antioxidant and corrosion inhibitor leads to a product which protects FAME-containing liquids which are in contact with nonferrous metals from microbial degradation. FAME-containing liquids are then storage-stable and do not form undesired precipitates.

## Claims

1. An additive mixture for fuels as a liquid concentrate, consisting of:
a) 92% by weight of N,N′-methylenebis (5-methyloxazolidine);
b) 4% by weight of 2,6-di-tert-butylphenol as an antioxidant; and
c) 4% by weight of N,N-bis(2-ethylhexyl) (1,2,4-triazol-1-ylmethyl)amine as a corrosion inhibitor.

2. A method for producing a semiconcentrate comprising dissolving the additive mixture as a liquid concentrate according to claim 1 in a carrier, said dissolved liquid concentrate in said carrier being a semiconcentrate.

3. The method according to claim 2, wherein said carrier is selected from the group consisting of diesel oil, biodiesel oil, fatty acid methyl esters, mineral oil, aliphatic or aromatic hydrocarbons and mixtures thereof, and said carrier is at least 50% by weight of said semiconcentrate.

4. A method for operating a system with fuel, in which the additive mixture as a liquid concentrate according to claim 1 is added to the fuel.

5. A semiconcentrate consisting of:
a carrier is selected from the group consisting of diesel oil, biodiesel oil, fatty acid methyl esters, mineral oil, aliphatic or aromatic hydrocarbons and mixtures thereof; and
the additive mixture as a liquid concentrate according to claim 1 dissolved in said carrier.

6. The semiconcentrate according to claim 5, wherein said carrier is at least 50% by weight of said semiconcentrate.

7. The semiconcentrate according to claim 5, wherein,
said N,N′-methylenebis (5-methyloxazolidine) is 20% by weight of said concentrate,
said 2,6-di-tert-butylphenol is 0.9% by weight of said concentrate; and
said N,N-bis(2-ethylhexyl)(1,2,4-triazol-1-ylmethyl) amine is 0.9% by weight of said concentrate.

8. A method for biocidal and corrosion-inhibiting additization of a fuel that flows through or is stored in a system comprising copper-containing material in contact with said fuel, comprising:
adding to said fuel a liquid concentrate consisting of:
a) N,N′-methylenebis (5-methyloxazolidine);
b) an antioxidant selected from the group consisting of sterically hindered phenols, amines, vitamin E and derivatives thereof, alkyl gallates and mixtures thereof; and
c) a corrosion inhibitor selected from the group consisting of benzotriazole, tolyltriazole, N,N-bis(2-ethylhexyl)(1,2,4-triazol-1-ylmethyl) amine and mixtures thereof,

said antioxidant and said corrosion inhibitor being present in a weight ratio of 1:10 to 10:1, and for 100% of said concentrate, said antioxidant and said corrosion inhibitor are each at least 2% by weight,
wherein corrosion of copper in a system through which the fuel flows or in which the fuel is stored is inhibited.

9. The method according to claim 8, wherein the fuel comprises proportions of fatty acid methyl esters.

10. The method according to claim 9, wherein the proportion of the fatty acid methyl esters is up to 100% by volume.

11. The method according to claim 8, wherein the liquid concentrate is used in an amount of 20 to 1000 ppm.

12. A fuel comprising at least 5 ppm of N,N′-methylenebis(5-methyloxazolidine);
at least 0.25 ppm of an antioxidant comprising 2,6-di-tert-butylphenol and BHT
at least 5 ppm a corrosion inhibitor selected from the group consisting of benzotriazole, tolyltriazole, N,N-bis(2-ethylhexyl) (1,2,4-triazol-1-ylmethyl)amine and mixtures thereof, and
fatty acid methyl esters
wherein said antioxidant and said corrosion inhibitor are present in a weight ratio of 1:10 to 10:1,
wherein said fuel is selected from the group consisting of biofuels, biodiesels, diesel fuels, kerosenes, heavy oils, heating oils, and mineral oils.

13. The fuel according to claim 12, wherein said N,N′-methylenebis(5-methyloxazolidine), said antioxidant, and said corrosion inhibitor are present together in said fuel in an amount of 20 to 1000 ppm.