DE1264139B - Jet fuels - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Cl .:

ClOl

German class: 46a6-7

Number: 1 264 139

File number: B 76944IV d / 46 a6

Filing date: May 27, 1964

Open date: March 21, 1968

It often happens in practice that commercial hydrocarbon distillate fuels are a Suffer peroxidation, which gives rise to various types of operational problems. These Peroxidation of commercial fuels, mainly motor and aviation fuels, has variously caused difficulties in terms of odor, gum formation, deterioration of the Octane number and attack on rubber parts in the fuel system. Peroxidation of fuel is due to physical factors, e.g. B. by exposure to oxygen, light, storage time and Temperature, presence of catalytic metal, etc. Their occurrence also depends on certain Properties of the fuel, e.g. B. the molecular weight, the type composition and the absence of peroxidation inhibitors (natural or other).

Problems of this type have occurred in the past with motor gasoline, particularly with types of fuel which contain a substantial proportion of cracked products and for a long time at a high level Have been stored at ambient temperature. Bad smell, resinification of fuel systems and attack on rubber parts, e.g. B. pump diaphragms, are typical symptoms of peroxidized Fuel. One of the methods that have been used to solve the problem is to turn it off of cracked components, addition of common antioxidants in massive doses and of course the development of peroxide-resistant rubbers. The one is still known Addition of disulphide to motor gasoline to stabilize resin formation to reach.

More recently, the problem has arisen with fuels for aircraft turbines where noted that destruction of fuel hoses made of nitrile rubber on the high Peroxide content of the fuel were due. Fuel for aircraft turbines (kerosene or high-cut gasoline) are in accordance with the strict requirements of the applicable official Specification (D Eng RD 2482, 2486, 2488 and 2494) which specify the amount of olefinic material, severely limit that can be included. These fuels are usually straight-run distillate blends, the larger amounts of kerosene components in the boiling range from 150 to 250 C. contained and subjected to various forms of refining operations in order to achieve them the specifications for color, odor, jet fuel

Applicant:

The British Petroleum Company Limited,

London

Representative:

Dr.-Ing. A. v. Kreisler, Dr.-Ing. K. Schönwald,
Dr.-Ing. Th. Meyer

and Dipl.-Chem. Dr. JF Fues, patent attorneys,
5000 Cologne 1, Deichmannhaus

Named as inventor:

Peter Jonathan Maile,

Ronald Alfred Dean,

Sunbury on Thames, Middlesex (Great Britain)

Claimed priority:

Great Britain May 28, 1963 (21251)

Sulfur content, stability, etc. Standard refining procedures include treatment with copper chloride, plumbite, sulfuric acid, hypochlorite, hydrogen, solvent extraction and treatment with adsorbents, not only removing unwanted trace components but often also a useful reduction in the total sulfur content of the fuel is effected (maximum according to specification 0.2 to 0.4 percent by weight depending on the type of fuel).

The total sulfur content of a fuel specified in this description is the value which has been determined by the British Institute of Petroleum's standard method IP 107.

Studies have now shown that the susceptibility to peroxidation in straight-run fuels is related to the very low sulfur content, and it has been confirmed that this Susceptibility to an almost complete removal of such organic sulfur compounds which normally act as natural peroxidation inhibitors.

A test program has been carried out to determine the propensity of propellants for aircraft turbines,

809 519/529

which are produced by different refining processes and have different total sulfur contents have to determine peroxide formation. In the work described below, samples were used of commercial kerosene for aircraft turbines that meet the requirements of the specification D Eng RD 2494, subjected to conditions selected so that the potential tendency to peroxide formation fuel was favored in a relatively short time. These short-term exams were carried out under the following conditions:

1. 2 liters of the sample were ^{heated to 100 °} C. for 8 hours a day.

2. The sample was continuously exposed to light.

3. Air was continuously passed through the sample.

The results of these tests (Table 1) showed that the tendency to peroxidation was in fact a function of the total sulfur content and at values below about 0.01 weight percent sulfur was extremely strong.

The peroxide content of the fuel samples was determined according to the test method BP 378/63 T, at which shaken a known amount of fuel with a solution of ferrothiocyanate and the red colored one Ferrothiocyanate is titrated with a standard titanium (III) solution until the color has disappeared.

Table 1

Total sulfur Peroxide content in milliequivalents / liter after after content of the flight 50hours
treatment 100 hours longer
treatment kerosene sample,
Weight percent to try
beginning 0.030 0.015 0.146 0.005 0.085 0.020 0.109 0.004 0.040 0.015 0.080 0.005 0.022 0.010 0.017 0.010 22.1 184.0 0.005 0.085 26.5 255.0 0.001 0.010

30th

35

40

45

Although these short-term tests were carried out at high temperature and under the influence of daylight Experiments have confirmed that peroxidation also occurs in the dark and at ambient temperatures (albeit at a slower rate), as it occurs in practice, takes place.

One would normally have expected that by using common antioxidants (as allowed by the specification) suppresses peroxidation in sensitive fuels will, however, tests have shown that these additives are not full for this purpose are effective. However, it has been shown that the tendency of these fuels to peroxide formation by adding a small amount of certain organic. Effectively prevents sulfur compounds can be.

The invention accordingly relates to jet fuels which are characterized in that they refined to a total sulfur content below about 0.01 percent by weight and subsequently with an or several organic sulfur compounds of the type commonly found in such fuels the refining are present, have been mixed in such an amount that the total sulfur content of the refined jet fuels is at least about 0.01 weight percent.

Cyclic compounds of the type are preferably added as sulfur compounds usually found in straight-run kerosene. An overview of such connections, which were identified in a kerosene made from a Middle Eastern crude oil, is mentioned in the later Reference included. Particularly suitable of the cyclic sulfur compounds of the normally however, the types present in straight-run distillates are, for example, thiocyclopentane and thiocyclohexane and their mono-, di- and tri-alkyl substituted homologues.

The amount of sulfur compounds added should preferably not exceed 1.0 percent by weight. This amount increases the total sulfur content of the fuel in general brought about 0.2 percent by weight. Of course, a lower limit may be prescribed by the specification that the respective fuel must meet. A maximum of 0.2 percent by weight is the usual limit in specifications for aviation kerosene.

The sulfur compounds can be added as such (for example, thiocyclopentane is commercially available as a means for improving odor), but it has been shown that easily and inexpensively available materials containing them can be just as effective. For example it is possible to switch off the tendency to peroxidation to the desired extent and still the Meet the requirements of the specification for the finished fuel by adding an accurately sized Amount of raw (straight-run) kerosene is added to the refined fuel.

However, it has been found that tar oil fractions extracted from the kerosene, in particular fractions of this type from a Middle Eastern crude oil, are a particularly suitable form of the sulfur compounds for the addition. These materials can be made by treating crude petroleum distillate in the light petroleum boiling area with concentrated sulfuric acid, separating the acid tar so formed, washing this tar with water to remove sulfuric acid, and allowing the tar oil to settle. The tar oil consists mainly of cyclic sulfur compounds, which ^{boil in the range from 130 to 250 0} C (see "Sulfur Compounds in Kerosine Boiling Range of Middle East Crudes", SF Birch et al., Ind. Eng. Chem., 1955, 47, p. 240). The amount of this tar oil required will vary depending on the sulfur content of the oil (usually about 10 to 30 percent by weight) and the sulfur content of the refined luminescent petroleum. However, it must be so high that the sulfur content of the treated fuel is brought to at least 0.1 percent by weight. The amount added must of course not be so high that the fuel no longer meets the applicable specification.

As an example, accelerated peroxidation tests carried out in the manner described with a low-sulfur aviation kerosene obtained by hydrogen treatment had been received. The same

Product contained different amounts of an inhibitor according to the invention. The results approved oxidation inhibitor (2,4-dimethyl- these tests are in Tables 2 and 3 on-6-tert-butylphenol) as well as various oxidation guides.

Table 2

Influence of oxidation inhibitors on peroxide formation in low-sulfur kerosene

for aircraft turbines

Composition of the mixture Antioxidant Type at Peroxide content in Milliequivalent / liter 24 50 100 VJ I / O ul 111
sulfur- Attempt 4.83 26.5 25-5.0 salary, lot beginning - 11.10 125.0 Weight Base fuel Weight - 8.21 118.0 percent percent 2,4-dimethyl Treatment duration in hours 0.211 3.84 113.0 6-tert-butyl Q 0.001 Low sulfur 0.0007 phenol 0.010 0.346 0.12 0.29 0.117 0.001 Kerosene for flight 0.0014 from Leuchtpetro - 16 (0.021 after 0.001 power turbines 0.0029 *) extract leum - 1.13 200 hours 0.001 (with hydrogen tar oil 0.136 - the) treated) 0.89 - 0.159 **) (0.75 Vo 0.09 0.192 lumpro cent) 0.103

*) 0.003 percent by weight is the upper limit for antioxidants that is permissible according to the above-mentioned D Eng RD specifications. **) 0.2 percent by weight is the upper limit for the total sulfur content in the above specification D Eng RD 2494.

Table 3

Influence of oxidation inhibitors on peroxide formation in low-sulfur kerosene

for aircraft turbines

Composition of the mixture Oxy
lot dation inhibitor Peroxide content in milliequivalents / liter Treatment duration in hours 8th 16 24 50 100 total Base fuel Volume Type at
Attempt 0.108 0.208 0.270 0.67 0.88 sulfur
salary,
Weight percent beginning percent 0.05 from Leuchtpetro Low sulfur leum extracted 0.010 0.068 0.131 0.231 0.368 0.168 0.01 Kerosene for flight Tar oil generation turbines (with 0.10 from Leuchtpetro Hydrogen treated leum extracted 0.010 0.55 0.63 0.76 1.32 1.41 0.02 delt) Tar oil 1.07 1.47 1.07 0.52 0.22 0.0275 Thiocyclopentane 0.17 0.28 0.47 4.0 3.4 5.0 raw aviation kerosene 0.010 0.12 0.0437 2,3,4,5-tetra 0.016 0.38 1.1 1.6 8.0 0.6 0.01 methylthiophene 0.058 0.012 0.0458 Di-n-butyl mono- 0.46 1.5 2.2 5.5 0.5 sulfide 0.021 0.011 0.0632 Di-n-hexyl mono- 0.347 0.584 0.91 2.58 3.34 sulfide 0.066 0.51 1.07 1.60 1.53 0.75 0.011 0.0275 Thiocyclopentane 5.0 raw aviation kerosene 0.133 0.012 *) 0.016 0.01 *)

*) These results were obtained from tests on a sample that was not treated with air.

From the values in Tables 2 and 3 fuel (Siedeanfang 140 ⁰ C, final boiling point of 250 ⁰ C) is

it can be seen that the commercially available oxidation 6o with 0.4 percent by volume 98% sulfuric acid

inhibitor the propellant's tendency to Perqxyd- rend a conventional refining treatment of the

formation was not suppressed very effectively while tractor fuel was being obtained

that according to the invention in the jet fuels then with the same volume of water

contained inhibitors were very effective. mixed to remove traces of sulfuric acid,

The 65 obtained as an extract from kerosene and 8 hours before the separation of the tar oil and allowed to settle in the experiments described above. After removing the highly used Tar oil was prepared as follows: boiling residue (above 254 ° C) and An acid tar that was produced by treating tractors- the aromatic hydrocarbons

obtained hydrocarbon-free tar oil, which had a total sulfur content of 18.9 weight percent, and essentially consisted of cyclic sulfides in the boiling range of about 130 to 250 ⁰ C.

Claims (3)

Patent claims: 1. Jet fuels, characterized in that that they are refined to a total sulfur content below about 0.01 weight percent and thereafter with one or more organic sulfur compounds of the type commonly used present in such fuels prior to refining has been blended in such amount are that the total sulfur content of the refined jet fuels is at least about 0.01 weight percent amounts to. 2. Jet propellants according to claim 1, characterized in that these are the organic Sulfur compounds via a sulfur-containing straight-run kerosene or an off Luminous petroleum extracted tar oil have been added. 3. Jet propellants according to Claims 1 and 2, characterized in that they are added as organic sulfur compounds cyclic compounds and especially thiocyclopentane, Thiocyclohexane, their mono-, di- and trialkyl-substituted homologues or mixtures of these Connections included. Considered publications:
Chemisches-Zentralblatt, 1951, I., p. 546. 809 519/529 3.68 © Bundesdruckerei Berlin