US3068084A - Stabilized middle distillate fuels - Google Patents

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3,063,034 STABHLEZED MmDlLE DESTHLLATE FUELS John V. Clarke, 3n, @ranford, and Stephen 3. Metro, Elizabeth, NJL, and John 8. Smith, in, Swampscott, Mass, assignors to Ease Research and Engineering Company, a corporation of Delaware No Drawing. Filed Nov. 8, 1957, Ser. No. 695,221 8 flairns. (Ci. 44-72) The present invention relates to improved hydrocarbon oils and more particularly relates to improved petroleum distillate fuels stabilized against deterioration during storage by the incorporation therein of small amounts of certain tetraalkyl ammonium salts of phosphosulfurized hydrocarbons.

The unstable characteristic of petroleum distillate fuels such as heating oils, diesel fuels, jet engine fuels and similar fuel products boiling in the range between about 300 F. and about 900 F. often give rise to serious difliculties. Such fuels generally contain small amounts of unsaturated hydrocarbons and other relatively unstable constituents. During storage of the fuels these unstable materials tend to oxidize, polymerize or otherwise react to form sludge and sediment. When the fuels are subse quently introduced into engines and burner systems, sludge and sediment thus formed is frequently responsible for the plugging and clogging of fuel lines, filter-s, orifices and the like.

The use of additive agents to overcome or at least arneliorate these difliculties is Well known and has been widely practiced. The additives found most effective and most widely used in the past have been metallic compounds such as metal naphthenates, metal sulfonates, metal salts of alkyl metal sulfides and similar materials which leave a residue when burned. It is known that the use of such additives leads to a build-up of carbonmetallic deposits in combustion chambers and on burner nozzles. Various ashless compounds have been proposed for use as stabilizing agents in such fuels in order to avoid the formation of deposits of this type but in general such materials have not been highly effective.

The present invention provides a class of improved additive materials for use in petroleum distillate fuels which, when added thereto in small amounts, effectively stabilize such fuels against deterioration and permit their storage for extended periods under adverse conditions. In accordance with the invention it has been found that certain tetraalkyl ammonium salts of phosphosulfurized hydrocarbons can advantageously be employed as stabilizing additives for petroleum distillate fuels boiling in the range between about 300 F. and about 900 F. and that such salts have advantages not possessed by additive materials employed in the past.

The tetraalkyl ammonium salts of the phosphosulfurized hydrocarbons employed as stabilizing additives in accordance with the present invention are prepared by first reacting a hydrocarbon with a sulfide of phosphorus to form an acidic product and then reacting the product obtained with a tetraalkyl ammonium hydroxide having alkyl groups containing from 1 to about 4 carbon atoms. It is believed that the active ingredient of the material thus formed is an alkyl dithiophosphonic acid salt having the following structural formula:

where R is-a hydrocarbon radical and R is an alkyl group containing from 1 to about 4 carbon atoms. These compounds are ashless and have the added advantage of being ionic materials. This latter characteristic is of particular importance in that ionic compounds added to such fuels assist in dissipating static electricity built up in the fuels as they are pumped through pipelines and into storage vessels. Numerous explosions have occurred recently as a result of static build-up in distillate fuels. Ionic additives alleviate the danger of such explosions.

A wide variety of hydrocarbon materials including parafiins such as those obtained by dewaxing lubricating oils; olefins such as isobutylene, decylene, dodecylene, octadecylene and the like; polymers of low molecular weight olefins; and petroleum fractions such as lubricating oils and bright stocks may be used in preparing the phosphosulfurized hydrocarbons from which the additive materials of the invention are made. Olefinic polymers having molecular weigh-ts ranging from about 800 to about 20,000 and petroleum bright stock fractions are preferred hydrocarbon materials for the purpose of the invention.

The olefinic polymers from which the phosphosulfurized hydrocarbons used in preparing the additive agents of the invention are produced are prepared by the polymerization of low molecular'weight olefins such as ethylene, propylene, butylene, isobu-tylene or combinations of such olefins. One method of carrying out such polym erization reactions is to employ a Friedel-Crafts catalyst such as boron trifluoride or aluminum trichloride at low temperatures in the range of from about 0 F. to about .40 F. Other methods familiar to those skilled in the art may also be used. Polybutene having a molecular weight between about 800 and about 10,000 is particularly preferred olefinic polymer for use in accordance with the invention. In the petroleum industry polybutene is conventionally understoodto mean polyisobutylene and is so used here. p p

The bright stocks which may be used in preparing the phosphosulfurized hydrocarbons are conventional products of petroleum refining. They are refined petroleum fractions which are high viscosity lubricating oils. Such stocks are conventionally prepared by first deasphalting the reduced crude oil and then dewaxing it, following this with phenol extraction and sulfuric acid treating, and finally clay filtering the oil as a finishing step. Such bright stocks generally have viscosities in the range of from about 145 to about 155 Saybolt Universal seconds at 210 F. The A.P.I. gravity of such stocks may range from about 25 to about 28. Their color may vary from about 3 to about 4 /2 on the Robinson scale.

The sulfide of phosphorus which is employed in preparing the phosphosulfurized hydrocarbon may be P 8 P 5 P 8 P 8 or a similar phosphorus sulfide. Phosphorus pentasulfide, P 8 is preferred as a phosphosulfurizing agent.

The phosphosulfurization reaction may be effected by treating the hydrocarbon with from about 5% to about 20% of the phosphorus sulfide by weight, based on the oil. It is usually preferred to add the phosphorus sulfide to the oil in powdered form at a temperature in the range of from about 200 F. to about 250 F. and then heat the mixture to the reaction temperature, about 300 to about 550 F. Agitation should be provided during the addition of the phosphorus sulfide to insure complete mixing. The

mixture is held at the reaction temperature for a period of from about 2 to about 10 hours and at the end of that time is filtered to obtainthe phosphosulfurized hydrocarbon product. 7 v

The tetraalkyl ammonium hydroxide which is reacted with the phosphosulfurized. hydrocarbon prepared as described above may be one having alkyl groups containing from 1 to about 4carbon atoms. Tetraethyl ammonium hydroxide is particularly preferred for purposes of the invention.

3 The reaction of the tetraalkyl ammonium hydroxide with the phosphosulfurized hydrocarbon to obtain the additive materials of the invention may be carried out by reacting equimolar quantities of the two materials in the presence of a suitable solvent such as benzene. It is preferred to employ the tetraalkyl ammonium hydroxide in the form of an aqueous solution of from about to concentration. The reaction may be carried out in a side arm refluxing apparatus for ease of water removal. The mixture containing the reactants is refluxed at a temperature between about 150 F. and about 200 F. for a period of from about 2 to about 6 hours. The water initially present and water formed during the reaction is driven off as the mixture is refluxed. The benzene added as a solvent is then removed by vacuum distillation and the tetraalkyl ammonium salt of the phosphosulfurized hydrocarbon is recovered.

The petroleum distillate fuels in which the additive materials of the invention are employed are those which boil in the range between about 300 F. and about 900 F. Typical of such fuels are heating oils falling within grades 1 and 2 of ASTM Specification D-396-48T, diesel fuels meeting the requirements for grades 1D, 2D, and 4D fuels as set forth in ASTM Specification D-975-53T and jet engine fuels such as those defined by U.S. Military Specifications MIL-iF-5624C and MIL-F-5616. The additive materials of the invention may be incorporated into such fuels in concentrations ranging from about 0.001% to about 5% by weight, preferably 0.001 to 2% by weight.

Concentrations of from about 0.005% to about 0.05% are generally satisfactory for most purposes. The additives may be added directly to the fuels or may be incorporated into a suitable hydrocarbon solvent which is then added to the fuels.

The effectiveness of the additive materials of the invention may be readily seen from the following examples.

EXAMPLE I Polybutene having a molecular weight averaging about 1100 by the Staudinger method was treated with 10% by weight of P 8 at a temperature of 425 F. for a period of about 8 hours. The resulting phosphosulfurized polybutene contained 3.32 weight percent sulfur and 1.84 weight percent of phosphorus. One hundred grams of this material was then mixed with 87.4 grams of an aqueous solution containing 10 weight percent of tctraethyl ammonium hydroxide. One hundred and fifty cc. of benzene were added to the reaction mixture and the mixture was then refluxed at a temperature of about 175 F. for 4 hours during which time the water was removed by azeotropic distillation. Benzene was removed by vacuum distillation. The resultant product had a clear amber color. Analysis showed it to be the tetraethyl ammonium salt of the phosphosulfurized polybutene.

The tetraethyl ammonium salt of a P S -treated bright stock was prepared in a similar manner, utilizing a bright stock which had a viscosity of 150 Saybolt Universal seconds at 210 F. This oil was phosphosulfurized by treating with 10% by weight of P 8 and the product was reacted with an equimolar quantity of tetraethyl ammonium hydroxide.

The tetra-n-propyl ammonium salt of phosphosulfurized polybutene was prepared in the same manner used to prepare the tetraethyl ammonium above except that tetran-propyl ammonium hydroxide was utilized in place of tetraethyl ammonium hydroxide.

The trimethylphenyl ammonium salt of phosphosulfurized polybutene was prepared in a similar manner by treating the phosphosulfurized butene with trimethylphenyl ammonium hydroxide.

EXAMPLE II The materials prepared in the previous example were incorporated into samples of a middle distillate heating oil additive;

in concentrations of 0.01 weight percent. Typical properties of such a heating oil are as follows:

Gravity, API 32 Color, Tag Robinson 13 Flash, "F 150 Sulfur, percent 0.8 Aniline point, F 137 Distillation, F.

IBP 330 FBP 645 The samples thus prepared, together with a sample of the oil containing no additive, were then subjected to an accelerated storage stability test which comprised heating the samples for a period of 16 hours at a temperature of 210 F. At the end of this period, the samples were filtered through sintered glass filters and the weight of sediment collected from each sample was determined. The data obtained in this test are shown in the following table:

Table I ACCELERATED STORAGE STABILITY TEST From the above table it can be seen that the tetraalkyl ammonium salts of phosphosulfurized hydrocarbons are excellent stabilizing additives for middle distillate fuels.

-The data also show that a similar material wherein a phenyl group was substituted for one of the alkyl groups in the ammonium radical did not possess stabilizing qualities and instead resulted in the formation of considerably more sediment than was formed in the oil containing no EXAMPLE III I In order to further demonstrate the invention, an amine salt of a phosphosulfurized polybutene was prepared by treating a portion of the polybutene used in preparing the materials of Example I with P 8 in the manner described and then reacting the product with an equimolar quantity 'of tertiary butyl amine. This was then subjected to an accelerated storage stability test as described in Example II. The results are shown in Table II below:

7 Table II ACCELERATED STORAGE STABILITY TEST Fuel: Sediment, mgms./ 600 gms. Base heating oil 17.9 Base heating oil+0.05 wt. percent of tertiary butyl amine salt of P 8 treated polybutene; 23.8

The'above data indicate that the stabilizing properties previously demonstrated are peculiar to the tetraalkyl ammonium salts of the phosphosulfurized hydrocarbons and that amine derivatives of phosphosulfurized hydrocarbons and that amine derivatives of phosphosulfurized hydrocarbons do not possesses such stabilizing properties.

EXAMPLE IV The eifect of the additive materials of the invention upon potential sediment in middle distillate fuels can be i seen from the data obtained in the potential sediment test. A sample of a heating oil similar to those employed in Examples 11 and III and a sample of the same oil to which had been added 0.01 wt. percent of the tetraethyl ammonium salt of the P 5 treated polybutene were heated in glass bombs at a temperature of 100 F. for 24 hours. The sediment which formed in each sample was then measured. The data obtained are as follows:

Table III POTENTIAL SEDIMENT TEST From the above it can be seen that the tetraalkyl ammonium salt of the phosphosulfurized hydrocarbon significantly reduced the potential sediment in the oil.

It will be understood that the additive materials of the present invention may be incorporated into petroleum distillate fuels in conjunction with other additive materials intended to overcome other fuel deficiencies such as rusting, corrosion and the like.

What is claimed is:

1. An improved petroleum distillate fuel boiling in the range between about 300 F. and about 900 F. to which has been added from about 0.001% to about 5% by weight of a tetraalkyl ammonium salt of a phosphosulfurized hydrocarbon, the alkyl groups in the ammonium radical of said salt each containing from 1 to about 4 carbon atoms.

2. A fuel as defined by claim 1 wherein said salt is i0! present in a concentration between about 0.001 and about 2% by weight.

3. A fuel as defined by claim 1 wherein said salt is a tetraalkyl ammonium salt of a phosphosulfurized petroleum bright stock.

4. A fuel as defined by claim I wherein said salt is a tetraethyl ammonium salt.

5. An improved petroleum distillate fuel boiling between about 300 F. and about 900 F. having incorporated therein from about 0.001% to about 5% by weight of a tetraalkyl ammonium salt of a phosphosulfurized polyolefin having a molecular weight between about 800 and about 20,000, the alkyl groups in the ammonium radical of said salt each containing from 1 to about 4 carbon atoms.

6. A fuel as defined by claim 5 wherein said salt is present in a concentration between about 0.005 and about 0.05% by weight.

7. A fuel as defined by claim 5 wherein said polyolefin is a polyisobutylene.

8. A petroleum distillate fuel boiling between about 300 F. and about 900F. stabilized by the addition thereto of from 0.005 to 0.05 wt. percent of a tetraethyl ammonium salt of a P S -treated polyisobutylene having a molecular weight of from about 800 to about 10,000.

References Cited in the file of this patent UNITED STATES PATENTS 2,534,217 Bartleson Dec. 19, 1950 2,636,858 Jones et a1 Apr. 28, 1953 2,688,612 Watson Sept. 7, 1954 2,712,528 Hill et al. July 5, 1955 2,768,999 Hill Oct. 30, 1956

Claims (1)

1.AN IMPROVED PETROLEUM DISTILLATE FUEL BOILING IN THE RANGE BETWEEN ABOUT 300*F. AND ABOUT 900*F. TO WHICH HAS BEEN ADDED FROM ABOUT 0.001% TO ABOUT 5% BY WEIGHT OF A TETRAALKYL AMMONIUM SALT OF A PHOSPHOSULFURIZED HYDROCARBON, THE ALKYL GROUPS IN THE AMMONIUM RADICAL OF SAID SALT EACH CONTAINING FROM 1 TO ABOUT 4 CARBON ATOMS.