FI96913C - Method for inhibiting aerobic mold growth in water-contaminated hydrocarbons - Google Patents

Description

96913

Method for inhibiting aerobic mold growth in water-contaminated hydrocarbons

The present invention relates to a process for inhibiting the growth of aerobic molds in aqueous hydrocarbons, for example semi-distilled fuels, by adding to them a material having biostatic activity and aqueous hydrocarbon compositions containing material having such biostatic activity.

In the presence of water and oxygen, at least some hydrocarbons containing, for example, semi-distilled fuels are readily present in aerobic molds, typically ubiquitous Cladosporium resinae. attack-15 as its target. These molds can cause the following problems: (i) Form a tightly braided mycelial mat on the oil / water interface, resulting in the accumulation of mixed mold and bacterial rib pulp on the interface. The detachment of these mats 20 tends to clog the filters.

(ii) This mixed population produces soluble organic compounds, which are often effective emulsifiers. As a result, the fuel / water separation deteriorates. Acid metabolites and biopolymers are also produced.

25 (iii) Dead biomass accumulating at the bottom of the tank allows the growth of anaerobic, sulfate-reducing bacteria.

With reference to (iii) above, once aerobic molds have initiated events that lead to the formation of an anaerobic acid-free oxygen-free environment, sulfate-reducing bacteria can begin to develop. Bacteria obtain the energy needed for their metabolism by reducing sulfate ions to sulfide, e.g., H2S, and in doing so cause a bad odor in the fuel, but worse than this, they have been shown to cause rapid progressive cavitation in the metals with which they are in contact, e.g. in fuel tanks.

The problems caused by the presence of aerobic molds 5 in fuels, for example, are now well known on a practical level. Thus, clogging growth in storage tanks of domestic or industrial heating systems can produce acidic by-products or SRB activity that damages metal surfaces and if this corrosion is not controlled, it can eat its way through the tank walls eventually leading to tank replacement. In addition, slimy growth can clog tank floats, block flow in fuel lines, clog filters, and prevent fuel oil from burning. Corrosion of the legs of the drilling rig, where diesel fuel is sometimes stolen-15, is also a significant problem.

Since molds that start the problem only grow at or near the oil / water interface, it would be clearly wise to avoid any accumulation of old water in the fuel system, but this is not always practical. As the severity of decomposition increases, the concentration of aromatic substances in all fuels increases, leading to increased water solubility and susceptibility to emulsion formation. Although several additives are known to be used to clean the system, all. 25 are not entirely satisfactory. There is a need for a simple additive material that (i) is not deactivated by any enzyme system that can be produced by microbes, (ii) does not contaminate drinking water, namely it must be added to and remain in the fuel and have low toxicity to the animal, (iii) is effective for use at sufficiently low levels of treatment as a package to be added a total of a few hundred ppm and (iv) which need not necessarily have a biocidal (lethal) effect, the biostatic (growth inhibitory) effect should be 35.

li 96913 3

Compositions have now been found consisting of a hydrocarbyl-substituted succinic strip in which the hydrocarbyl substituent is large enough to allow the hydrocarbon to dissolve and boron gives at least some of the above properties.

the use of an oil-soluble borated acylated nitrogen compound in combination with gasoline fuel is known. Accordingly, U.S. Pat. No. 4,092,127 discloses an anti-diesel composition of a fuel added in an amount sufficient to provide 80 to 10,400 parts per million by weight of boron, comprising: (a) 1 part by weight of an oil-soluble acyl nitrogen compound having: the structure is characterized by the presence of a substantially saturated hydrocarbon-substituted polar group selected from the group consisting of acyl, acylimidoyl, and acyloxy radicals, the substantially saturated hydrocarbon substituent containing at least about 16 to 180 aliphatic carbon atoms, and nitrogen the fact that the nitrogen atom 20 is attached directly to said polar material, and (b) from about 2 to about 40 parts by weight of a solvent oil which is oxidatively stable and has a viscosity ranging from 8 to 20 and 99 ° C.

US-A-4 184 851 discloses a fuel composition comprising for the most part, namely more than 50% by weight, a distilled petroleum fraction, preferably having a boiling point in the atmosphere of between about 120 ° C and 400 ° C, and about 0.001-1.0 % by weight of borated oil-soluble succinic acid or a derivative thereof having the following formula:

R - CH- COX

ch2 to COX1 4 96913 wherein R is a straight chain aliphatic hydrocarbon group having 0 to 1 sites unsaturated (alkyl or alkenyl) attached to the secondary carbon atom of the succinyl group and having a length of at least 8 carbon atoms, generally between 14 and 40 carbon atoms and more generally between 15 and 30 carbon atoms carbon atoms; one of X and X1 is hydroxyl and the other is -NYY1 where N is normal, nitrogen and Y and Y1 are aliphatic hydrocarbyl groups having a length of 8 to 40 carbon atoms, more usually 14 to 30 carbon atoms having a total of about 30 to 52 carbon atoms, more usually 32 to 48 carbon atoms, optimally 32 to 40 carbon atoms, said one of X and X 1 being preferably of the formula: OH (NHY 2 Y 3) n 20 wherein n ranges from 0 to 1, Y 2 and Y 3 belong to the category containing hydrogen, 1 to 30 carbon atoms an aliphatic hydrocarbon containing 3 to 30 carbon atoms and an oxyaliphatic hydrocarbon, and Y 2 and Y 3 may be combined with the nitrogen to which they are attached to form a heterocyclic ring having 5 to 7 ring members.

Neither US-A-4 092 127 nor US-A-4 184 851 shows a mold growth problem in water-contaminated hydrocarbon fuels.

The invention is characterized in that (i) the hydrocarbon is selected from the group consisting of diesel fuels, heavy marine fuels and fuel oils, (ii) the hydrocarbon is stored, (iii) the additive contains boric acid or a salt thereof and a hydrocarbyl-substituted succinimide containing a hydrocarbyl substituent. from about 40 to about 150 carbon atoms, and

II

5 969 η (iv) the additive is used in an amount sufficient to provide up to 500 ppm by weight of hydrocarbon.

The invention also relates to a fuel composition comprising a water-contaminated hydrocarbon and an anti-mold amount additive, characterized in that (i) the hydrocarbon is selected from diesel fuels, heavy marine fuels and fuel oils, (ii) the hydrocarbon is stored, (iii) the additive contains boric acid a salt and a hydrocarbyl-substituted succinimide wherein the hydrocarbyl substituent contains from about 40 to about 150 carbon atoms, and (iv) the additive is used in an amount sufficient to provide up to 500 ppm by weight of the hydrocarbon.

Hydrocarbyl-substituted succinimides are known as highly dispersing additives in lubricating oils, see for example GB-A-922 831; GB-A-1 565 627 and EP-A-0 031 236, which are representative of the extensive patent literature in this field. Both mono- and bis-succinimides can be used. The hydrocarbyl substituent may suitably be a substantially saturated hydrocarbyl group containing from about 20 to about 300 carbon atoms, preferably from about 40 to 150 carbon atoms. The substantially saturated hydrocarbyl group is preferably derived from a polyolefin, even more preferably polyisobutylene.

»25 Boron may be present in the additive either in the form of a physical mixture or chemically bound to a hydrocarbyl-substituted succinimide.

In the form of a physical mixture, boron may suitably be present as a boron compound, preferably in its particulate dispersion form, suitably also containing a carrier for the boron compound. The boron compound may suitably be present as boric acid or boron salt. The boron compound is preferably in the form of an ammonium salt of boric acid. The carrier may suitably be a hydrocarbon compatible high boiling point material. Suitable carrier materials 6 96913 include mineral oils, which may be solvent-refined synthetic lubricating oils, for example ester type, liquid polyolefins, for example low molecular weight polyisobutenes, or oxidized or aminated derivatives thereof, copolymers of olefinic derivatives and polyolegins. The carrier may also contain a hydrocarbyl succinimide moiety. The average particle size of the particulate dispersion may suitably be less than 1 micro-10 meters, preferably less than 0.5 micrometers.

A suitable dispersion of a boron compound can be prepared in whole or in part by mixing a solvent-carrier emulsion of a boron compound solution in the presence or absence of hydrocarbyl-substituted succinimide, preferably in its presence. Suitable solvents for the boron compound include relatively low boiling hydrocarbons and substituted hydrocarbons and water, with water being preferred.

The preparation of a particulate dispersion of a boron compound is described more fully in the co-pending EP 0 288 296 (BP Case No. 6651/6756), the contents of which are incorporated herein by reference.

There is an extensive patent literature describing boronized succinimides and their preparation. Representatives of the patent literature include US-A-3 344 069; US-A-3,322,670; US-A-3,338,832; US-A-3,282,955; US-A-3 254 025 and US-A-3 087 936. The borated succinimides described in any of the above patents can be used. The boron content of borated succinimide may range from about 0.1% to about 20% by weight.

A hydrocarbon can be any hydrocarbon that is prone to mold growth in the presence of water and oxygen. Thus, the hydrocarbon may be crude oil or a distilled fraction of crude oil. Suitable hydrocarbon fractions include diesel fuel, heavy marine fuels and fuel oils, including both domestic and industrial heating oils. Any hydrocarbon is contaminated with water, which may be present in amounts as small as 0.1% w / w or less.

5 The amount of additive suitably used can be readily determined by the amount of boron added to the fuel. The amount of additive suitably used is sufficient to form up to 500, more often 200, ppm by weight of hydrocarbon.

The additive may be suitably combined with other additives commonly used in fuel assemblies, for example in the case of a diesel fuel assembly, the additive package may further comprise at least one anti-corrosion agent, antifoam agent, antioxidant and emulsifier. The additives of the present invention have the advantage that, in addition to their biostatic activity, they also give dispersant properties, namely they act as multifunctional additives.

The invention will now be further described with reference to the following 20 examples.

Most of the examples use commercially available polyisobutylene monosuccinimide as the starting material, hereinafter referred to as PMS, which is polyisobutylene (molecular weight about 1,000) substituted with succinic anhydride added 1: 1 tetraethylpentamine (ΤΕΡΑ). In one example, polyisobutylene-bis-succinimide was used, hereinafter referred to as PBS, which is polyisobutylene (molecular weight about 1,000) substituted succinic anhydride added at 2: 1 ΤΕΡΑ.

Preparative Methods' (I) An aqueous solution of boric acid was added at about 40 ° C to a mixture of carrier (alkaline oil) and either PMS or PBS for 30 minutes in a Manton Gaul grinder and homogenized for 2-3 hours, during which time 35 a lot of water evaporated. The resulting solution was removed from the homogenizer and used without further treatment.

(II) One mole of either PMS or PBS was heated to 175 ° C at atmospheric pressure. 5 Boric acid (2 moles) was added slowly and the mixture was allowed to react for one hour. A vacuum was then formed and maintained for one hour. The vacuum was then removed and the hot mixture was decanted and filtered.

The analysis of additives is shown in Table 1.

10

Table 1 (a) (b) (c) (d)

Nitrogen (% by weight) 0.72 0.78 2.68 1.8

Boron (% by weight) 1.1 1.2 0.96 0.42 15

Additives (a) to (d) were combined into a multifunctional diesel fuel additive package that was tested with diesel fuel. In addition to the biostatic additive (borated succinimide (a) to (d)), the kit contained 20 anti-rust agents, antifoams, an emulsifier and an antioxidant.

In the following tests A to H, borated succinimides and boron fuel levels are shown in Table 2.

* · 25 Table 2

Ash-free Tested Preparative Borated Boron additive combustible method material fuels level (ppm by weight) 30 (a) AI PMS 0.31 B PMS 3.08 (b) CI PMS 0.33 D PMS 3.33 (C) E II PBS 0.16 35 F PBS 1.66 (d) G II PMS 0.12 H PMS 1.18

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9 96913

additive Testing

Test fuels A to H were tested for 4 mold strains using the method described by Smith and Crook (The germination and Growth of Cladosporium 5 resinae in fuel oil, "Biodeterioration. The Proceedings of the Fourth International Biodeterioration Symposium, Berlin" (TA Oxley, G. Becker and D. Allsopp, eds.) Pitman, London, pp. 29-36, 1980). In this method, a sterile aqueous medium is inoculated in test tubes with a home-10 spore suspension and then fueled with known levels of additives to be tested. The tubes are incubated for approximately 28 days and periodically inspected for mold developed on the oil / water interface.

In addition, test fuel (I) was tested, which did not contain any additives. Finally, a commercially available additive (Biobor JF, US Borax) was tested on test fuels X and Y (270 ppm level).

Microbiological Methods 20 (a) Mold Cultures Four cultures were used:

Aspergillus niger,

Cephalosporium sp,

Cladosporium sp ja; 25 Penicillium avellaneum.

(b) Preparation of conidial suspension Mold cultures were initially grown on Sabouraud Dextrose Agar slants (5 slopes from each culture) for 10 days at 27 ° C. Sterile quarter-strength Ringers' solution (5 ml) was added to each oblique surface and shaken to obtain a conidial (spore) suspension. The suspensions were then run in a Sorvali Superspeed type SS3 centrifuge at 5,000 rpm for 15 minutes. The conidia pellet was washed once with sterile 35 quarter strength Ringers solution and the suspension was adjusted to a final concentration of 10 ** conidia per ml.

(c) Screening of the test tube program

Tap water enriched in 10% Bushnell 5 and Haas medium (a mineral salt medium for the cultivation of hydrocarbon molds containing NH 3 NOg (1 g), KH 2 PO 4 (1 g), K 2 HPO 4 (1 g), MgSO 4 (0, 2 g), FeCl 2 (0.01 g), CaCl 2 (0.02 g), distilled water (1 liter), pH

7.0 ± 0.3, autoclaved at 121 ° C for 15 minutes (Bushnell, 10 LD and Haas, HF, J. Bact., 41, 653-673, 1941)) and 0.5% (w / w) yeast extract was dispensed 2.5 ml aliquots into 20 ml Bellco screw-capped glass test tubes and then sterilized by autoclaving at 121 ° C for 15 minutes. A series of tubes were then inoculated with one drop of conidial suspension 15 using a sterile Pasteur pipette. A 2.5 ml aliquot of the test fuel was then placed on an aqueous medium. An uninoculated aqueous medium on which the test fuel had been placed was used as a control. Five replicates of each fuel-20 nasal sample were used. The method was repeated for all four species tested.

Control fuels, namely diesel fuel minus additives and diesel fuel containing jet engine fuel biocide, Biobor JF (Borax .. Holdings Limited), at a concentration of 270 ppm (20 ppm boron), were placed on an inoculated and non-inoculated medium as above.

All tubes were then incubated at 25 ° C for 32 days. The tubes were inspected after 7, 14, 21 and 32 days 30. The amount of growth in the fuel / water interface and in the water layer was recorded.

Scoring of Results The depth of interfacial contamination was roughly measured and reported numerically as POINT A. The level of development of mold colony 35 in water was assessed as zero (0), weak (+),

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11,96913 good (++) or very good (+++) and this was converted to numerical points O, 1, 2 or 3 (POINT B).

Score

The mean scores for the five replicates in each of the 5 treatments are given in Table 3. The scores for low boron levels and higher boron levels for each mold strain were then combined and depicted in Figures 1-4 with the corresponding results for fuel containing Biobor JF and untreated fuel. Error bars indicate the distribution of results for low and higher levels of boron additive.

For inhibition of mold development at the fuel / water interface (point A results), there appeared to be little differences between the four different additives, namely A / B, C / D, E / F, and 15 G / H. Those with low levels of boron additive showed indications of early decline in interfacial development in Aspergillus and Cephalosporium species. Higher boron levels inhibited mold growth in the interface for 21 days with Caldosporium species and were effective until 14 days with 20 Penicillium species. At the end of the 32-day test period, fuels containing higher levels of boron additive were much less contaminated at the interface than other fuels.

Biobor JF was ineffective in interfacial protection, 25 except in the case of the Cladosporlum strain.

In the aqueous layer, Biobor JF was slightly more inhibitory for mold development, but by no means were any of the additives particularly effective (point B results).

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Claims (9)

A process for preventing aerobic mold growth in water-contaminated cow water by adding to it an additive, characterized in that (i) the hydrocarbon is selected from the group of diesel fuels, heavy marine fuels and fuel oils, (ii) the hydrocarbon is stored; (iii) the additive contains boric acid or a site thereof and hydrocarbyl substituted succinimide wherein the hydrocarbyl substituent contains about 40 to about 150 carbon atoms, and (iv) the additive is used in an amount sufficient to make up to 500 ppm by weight of the hydrocarbon . 15 2. A process according to claim 1, characterized in that the hydrocarbyl substituent of the succinimide is polyisobutene, which contains about 40 to about 150 carbon atoms. 3. A process according to claim 1 or 2, characterized in that boric acid or a site thereof is present in the additive in the form of a physical mixture with the hydrocarbyl-substituted succinimide. 4. A process according to claim 1 or 2, characterized in that boric acid or a site thereof is present in the additive chemically bonded to the hydrocarbyl-substituted succinimide. Process according to Claim 1 or 2, characterized in that boric acid or a site thereof is present in the form of a particulate dispersion. 30 6. A process according to claim 5, characterized in that boric acid or the salt thereof is the ammonium salt of the boric acid. Process according to claim 5 or 6, characterized in that the particulate dispersion contains a carrier for boric acid or a site thereof, the carrier being a hydrocarbon compatible material with a high boiling point. Process according to any of the preceding claims, characterized in that the amount of additive used is sufficient to constitute up to 200 ppm of the weight of the hydrocarbon. 9. Fuel composition containing a deliberately contaminated hydrocarbon and a mold growth inhibitory amount of additive, characterized in that (i) the hydrocarbon is selected from the group of diesel fuels, heavy maize fuels and fuel oils, (ii) the hydrocarbon is stored, (iii) contains boric acid or a site thereof and hydrocarbyl-substituted suckinimide wherein the hydrocarbyl substituent contains about 40 to about 150 carbon atoms, and (iv) the additive is used in an amount sufficient to make up to 500 ppm by weight of the hydrocarbon.