US3027246A - Liquid hydrocarbon distillate fuels containing hydrocarbon-soluble betaines as antistatic agents - Google Patents

Description

United States Patent ()filice 3,027,246 Patented Mar. 27, 1962 3,027,246 LIQUID HYDROCARBON DISTILLATE FUELS CQNTAllNlNG HYDROCARBON S DLUBLE BETATNE AS ANTESTATEC AGENTS Philip Lee Bartlett, Wilmington, Del., assignor to E. I. du Pont de Nernours and Company, Wilmington, Del, a corporation of Delaware No Drawing. Filed Nov. 3, 1958, Ser. No. 771,215 9 Claims. (Cl. 44-66) This invention is directed to the treatment of hydrocarbons, such as the distillate fuels, which tend to accumulate potentially hazardous electrostatic charges in service. Acording to the present invention, the addition of a hydrocarbon-soluble betaine to a static-prone hydrocarbon substrate minimizes the accumulation of static electricity in such substrate.

The accumulation of electrical charges in the handling of hydrocarbons is widely recognized as a serious hazard. A number of explosions and fires that have occurred in recent years during the bulk handling of distillate fuels and solvents have been attributed to the accumulation (and subsequent discharge) of static electricity in the systems involve-d. Some handling conditions that contribute to the rapid generation of dangerous charge levels are rapid flow of fuel through pipelines and hoses, splash filling of receiving vessels (storage tanks and seagoing tankers), and, mixing of the fuel with water.

The problem of static formation in the distillate fuels is of considerable concern to the military as well as to the petroleum industry, and much searching has been and is being done to find a solution thereto. The results of a number of investigations indicate that most distillate fuels would be expected to produce substantial amounts of static electricity under service conditions, and practically all produce sufiicient static electricity to ignite vapor-air mixtures, providing there is present a mechanism for collecting and discharging the electricity. The production of static electricity in such fuels is associated with the presence of colloidal impurities which are ionic or which are capable of becoming ionized in the hydrocarbon environment. These impurities are believed to be either naturally occurring or represent fuel degradation and oxidation products or residues from treating operations. As a result of preferential adsorption of positively or negatively charged ions from the impurities on thec ontainer (e.g. wall or hose lining), the fuel will acquire a charge of the opposite sign. The rate of production of static electricity in liquid hydrocarbons increases with the flow rate and is accelerated by the presence of small amounts of water, air and dispersed solids. Since leakage of the charge from the body of the hydrocarbon is normally a very slow process, a potential may soon be established during the normal handling of the fuel to ignite fuel-air mixtures or to cause submerged explosions within the fuel when the electricity finally discharges. The problem is particularly acute with jet fuels.

As discussed in Electrostatics in the Petroleum Industry, edits/.1 by A. Klingenberg and J. L. van der Nenne, Elsevier, 1958, expedients such as grounding the apparatus, blanketing of the fuel with inert gases, and mechanical modifications in the handling procedures are helpful but not entirely satisfactory safeguards. The most promising approach appears to be the use of additives. To be practical, particularly for use in jet fuels where stringent specifications have to be met, an antistatic additive should (1) be effective, in technically feasible small concentrations, in fuels of both charge types i.e. in positive prone and negative prone fuels; (2) have no adverse effect on water-tolerance characteristics of the fuel (3) have no adverse effect on jet fuel thermal stability; (4) have no adverse effect on fuel storage stability;

and, (5) be non-metallic since metals in general adversely affect fuel stability and contribute to the formation of combustion deposits, and, tend to embrittle alloys used for turbine engines.

Deficient in at least one of the above requirements are the polar compounds suggested heretofore; compounds such as metal or ammonium (including quaternary ammonium) salts of inorganic and organic acids (including acids of phosphorus, sulfur and carboxylic acids) are representative of such polar compounds. For example, Rogers, McDermott and Munday, Static Electricity in Petroleum Products, Oil and Gas J. 55, 166-95 (1957), disclose that all the additives studied so far are polar compounds which are surface active and promote the formation of emulsions when the blends are mixed with water. Thus, they fail to meet the water tolerance specifications of jet fuels and in adition are rather easily extracted on contact of the fuel with water.

it is an object of the present invention to provide novel antistatic agents which are significantly effective, in liquid hydrocarbons, in minimizing the accumulation of static electricity in both types of charge-prone liquid hydrocarbons. It is a further object of this invention to provide novel liquid hydrocarbon compositions containing antistatic agents which antistatic agents do not adversely af fect other fuel properties such as water tolerance characteristics. It is still another object of the present invention to provide novel liquid hydrocarbon compositions containing antistatic agents, said liquid hydrocarbon being a jet fuel and said antistatic agent, in addition to minimizing the accumulation of static electricity, minimizing the adverse effects of thermal stress on jet fuels, which adverse effects are normally encountered.

These and other objects will be apparent in the fol- I lowing specification and claims.

More specifically, the objects of the present invention are achieved by employing a hydrocarbon-soluble betaine, as hereinafter described and claimed, as the antistatic agent in small quantity sufiicient to minimize the tendency of the hydrocarbon to accumulate electrostatic charge. Such quantity will usually be in the range of from about 0.1 to 30 lbs. per 1000 barrels (0.000033 to 0.01% by weight) of the static-prone liquid hydrocarbon. It is preferred to use an antistatic quantity of at least 0.5 lb. and not more than 15 lbs. per 1000 barrels.

Betaines which may be used according to this invention are hydrocarbon-soluble members of the class of dipolar ions represented by Formula I which follows:

where R, is a divalent hydrocarbon radical, such as an alkylene or alkylidene radical, R and R are aliphatic hydrocarbyl radicals, such as the loWer-alkyl radicals, and R is an uncharged aliphatic radical such as hydrocarbyl and hydrocarbyl substituted by ether (-O), hydroxyl (OH) and carbonyl (C=O) groups. R, is primarily a solubilizing group and should be free of substituents that promote the emulsification of the fuel with water. To have sufiicient hydrocarbon-solubility the betaine should contain at least about 11 carbon atoms and preferably at least about 16 carbon atoms in the molecule. Ordinarily the betaine will contain no more than about 35 carbon atoms, and usually up to about 30 carbon atoms.

Preferably, R will be an alkylene radical, particularly methylene, or an alkylidene radical having up to 17 carbon atoms, such as ethylidene, propylidene, undecylidene, tridecylidene and heptadecylidene.

R and R may be the same or different C -C alkyl radicals, e.g. methyl, ethyl propyl, butyl and amyl, preferably C -C Preferably, R is an aliphatic hydrocarbyl radical containing up to 20 carbon atoms and may be saturated. or unsaturated, straight chain or branched chain. Representative examples of R are methyl, butyl, hexyl, decyl, dodecyl, tridecyl, octadecyl, octadecenyl, octadecadienyl, and 3,7-dimethyl-2,6-octadienyl. Also, R may be an hydroxy-alkoxy-alkyl radical, such as a 2-hydroxy-3- alkoxypropyl radical.

where R is an aliphatic hydrocarbyl radical as defined for R above, that is, it may be for example an alkyl, alkenyl, or alkadienyl radical having up to 20 carbon atoms, preferably one having 10 or more carbons.

Also, R may be a hydrocarbon radical containing a carbonyl group, as in where R is as defined above. The preferred betaines may be represented generically by Formula II which follows:

where x= or 1 andR R R and R are as preferentially defined above. The R groups and x may be varied in accordance with the above definition so that the hydrocarbon content of the dipolar ion is sufiicient for solubilization of a substantial quantity of the compound in the hydrocarbon to be treated; that is, the compound should contain from about 11 to about 35 carbon atoms.

The following are representative betaines of the present invention in which R; of Formula I is an aliphatic hydrocarbyl radical attached to nitrogen of a dialkyl glycine radical: N-lauryl betaine (i.e. N-lauryl-N,N-dimethyl glycine), N-hexadecyl betaine, N-octadecyl betaine, N-octaclecenyl betaine, N-lauryl-N,N-dipropyl glycine, C-decyl betaine (i.e., 2-trimethylammonio-dodecanoate), C-dodecyl betaine, C-tetradecyl betaine; and, N-lauryl-C-methyl betaine. The above betaines are described and may be prepared by methods disclosed by Downing and Johnson in U.S. Patent 2,129,264.

Other betaines which may beused according to this invention are those in which R, is an aliphatic substituted hydrocarbyl radical, e.g. ROCH CHOHCH of Formula II, attached to nitrogen of an N,N-dialkyl glycine. Representative examples are N-(2-hydroxy-3-butyloxypropyl)betaine, N-(2-hydroxy-3-decy l oxypropyl)betaine, N-(2-hydroxy-3-lauryloxypropyl)betaine, N-[2-hydroxy-3 (3,7 dimethyl 2,6 octadienyl)oxypropyl]betaine, N-(2-hydroxy-3-tridecyloxypropyl)betaine, N-(2- hydroxy-3 octadecenyloxypropyl) N,N diethyl glycine and the correspondingly substituted -N,N-dipropyl glycine.

The above N-(2-hydroxy-3-alkoxypropyl)-N,N-dialkyl glycines may be prepared by known methods, for example by condensing an'alcohol with epichlorhydrin and reacting the intermediate condensation product thus obtained with an alkali metal salt of an N,N-dialkyl glycine. Preferably, the alcohol will contain from 10 to 20 carbon atoms. Available alcohols of this type are the Lorol fatty alcohol mixtures, e.g. Lorol 5 which contains alcohols having from to 18 carbon atoms with lauryl alcohol predominating; Ocenol fatty alcohols, e.g. Ocenol P which is principally oleyl alcohol; geraniol (3,7-dimethyl-2,6-octadienol); oxo-alc'ohols, which are mixtures of branched chain primary alkanols, e.g. oxo tridecanol.

As illustrated above, R, R R R and x will be chosensosthat the dipolar ion will be soluble in hydrocarbon media to the extent of at least about 0.1 lb., preferably at least 0.5 lb., per 1000 barrels (bbls.) of the hydrocarbon. The quantity of the antistatic agent needed to minimize the accumulation of static electricity in the hydrocarbon substrate will vary with the particular betaine and the particular liquid hydrocarbon product, and, will depend, in general, on how prone such hydrocarbon is to accumulate static electricity. Normally, from about 0.5 to 15 lbs. of additive, and preferably 1 to 15 per 1000 bbl. of substrate will be employed. Larger quantities, e.g. 30 lbs/1000 bbl. are operable for antistatic effects, but are usually unnecessary, also such unduly large quantities tend to promote the water emulsification of distillate fuels. While smaller quantites, e.g. 0.1 lb./l000 bbls., may also beoperable, they do not always provide thedesireddegree. of protection.

It should be understood that the presence of the antistatic agent in the hydrocarbon substrate does not do away with the need for adequate grounding of the equipment for containing and handling the hydrocarbon product. The antistat apparently functions to minimize the accumulation of static electricity in the hydrocarbonprodnot by conducting the charge (as it tendsto buildup in the hydrocarbon) from the hydrocarbon to the grounding means.

The use of the betaine antistatic. agents of the present invention is applicable to any liquid hydrocarbon that boils in the distillate fuel range and is prone to accumu-v late static electricity in service. These include hydrocarbon solvents -and distillate fuels, representative examples of which are the solvent naphthas, Varsols and Stoddard solvent, isooctane, both raw and refined kerosines, gasoline (both automotive and aviation), jet fuels (JP-4, JP-S and LIP-6), diesel fuel and heating oil. The problem appears to be particularly acute with the jet fuels; accordingly, the preferred embodiment of the invention is the use of the instantly described and claimed antistatic additives in jet fuels.

For convenience in handling, the betaine antistatic agents may be added to the hydrocarbon substrateas a concentrate in a suitable carrier, which is preferably a liquid hydrocarbon. For example, a 20 to 60%, usually about 50%, by weight of N-lauryl betaine in xylene or kerosene is a preferred form of the antistatic additive.

The antistatic additives may be used in the presence of other additives that the hydrocarbon product may normally contain, such as the approved oxidation and rust inhibitors for the jet fuels.

The betaines of this invention are effective antistatic agents in practical use concentrations. They are ashless (i.e. being non-metallic they leave no. harmful residues in the combustion of fuels containing them) and in general do not promote the tendency of the fuel blends containing them to emulsify when mixed with water. This is particularly surprising and important since betaines in general are regarded as surface active agents and it is known that polar additives that are surface active, when used in concentrations required for antistatic activity, have the major disadvantage of failing to meet the water tolerance specifications of fuels such as the jet fuels.

As shown in the examples, jet fuel containing N-lauryl betaine as an antistat not only passes the standard water tolerance test, but shows no tendency to accumulate electrostatic charge even after the blended fuel has been shaken with as much as 5 vol. percentof water. Further, as shown in the examples, N-lauryl betaine, in antistat concentration, is very elfective to minimize the deterioration of jet fuel when the blended jet fuel is subjected to the thermal stresses of the CFR Coker Test.

The following representative examples illustrate the present invention.

EXAMPLES Testing of the betaine antistatic agents was conducted by the procedure described by Rogers et al.', Oil and Gas Journal, 55, 166-95 (1957.). The equipment employed was essentially a duplicate of that described in the above reference and was enclosed in a constant humidity chamber.

The tests involve recirculating a sample of the liquid hydrocarbon (with or without additive) at a flow rate of 1450 rah/minute through a column packed with Pyrex glass wool (Filtering Fiber Cat. No. 800). The glass wool acts as a charge separator. A tungsten wire electrode inserted into the packed column leads to an external spark gap, which provides the means for discharging the accumulating static electricity. The humidity of the atmosphere contained in the Lucite enclosure for the whole apparatus was maintained at 15% or less, to minimize the eifect of moisture on the conductivity of the air through which the spark gap fires. In the present runs the fuel was circulated (and recirculated) through the glass wool packed column for a minute warmup period, and then a 20 minute run was made during which time the number of discharges were counted across the spark gap which had been calibrated to fire at 2000 volts (2 kv.). The number of 2 kv. discharges in 20 minutes is a measure of the tendency of the fuel to accumulate static electricity and thus is a measure of the efiectiveness of the antistatic additive.

In addition, each fuel (with and without additives) was subjected to the water tolerance test in accord with Method 3251 of Federal Specification VVL79lc. The test consists of shaking 80 ml. of the fuel and 20 ml. of water (containing a pH 7 phosphate buffer) in a 100 ml. stoppered graduate cylinder for 2 minutes, and allowing it to stand for 5 minutes. To pass the test, the water and oil phases must break cleanly within the 5 minute standing period. Any emulsion or lace in the oil, or preciiptate at the interface leads to a fail rating.

Example 1 A 50 weight percent xylene solution of N-(Z-hydroxy- 3-octadeceny1"oxypropyl) betaine was blended by stirring into a liquid hydrocarbon product as designated below, to provide the concentration of the active ingredient also given below. The results obtained in the circulating static electricity test on the treated and untreated hydrocarbons follow:

A leaded automotive-type gasoline containing 3 ml. of tetraethyl lead per gallon.

All the above compositions passed the water tolerance test.

The results of the electrostatic test show that the betaine effectively minimizes the accumulation of static electricity (being completely eiiective at the lb./1000 bbl. level) in liquid hydrocarbon products, irrespective of the charge sign the hydrocarbon may acquire.

The N(2-hydroxy-3-octadecenyl-oxypropyl) betaine of this example was prepared by reacting Ocenol P fatty alcohol with epichlorhyclrin in the presence of sulfuric acid catalyst, followed by reacting the thus-produced octadecenyl glyceryl ether chloride with sodium N,N-dimethylglycinate in the presence of KI catalyst.

Employing the corresponding N(2-hydroxy-3-octadecenyloxypropyl)-N,N-diisopropyl glycine, at a concentration of 15 lbs./ 1000 bbl. in Fuels A and B above, gave identical results in the electrostatic and water tolerance tests.

Substantially similar results are obtained on employing other betaines of this type, as indicated in the following example.

Example 2 By the procedure of Example 1, Fuels A and B described above were treated to contain N(2-hydroxy-3- octadecyloxypropyl) betaine in the concentrations given below, and the resulting blends tested to yield the following results:

2-kv. Discharges in 20 Minutes Additive Cone, lbs/1,000 bbl.

Fuel A Fuel B None (Control) 720 5. 30 94 7.5 0 31 15 0 0 30. 0 0

All the fuel blends passed the water tolerance test.

Exacple 3 A 50 weight percent solution in xylene of a betaine of the formula:

R 1Ti(c1nn R.-ooiwas blended by stirring into liquid hydrocarbon products B and C described in Example 1. R and R of the beta- 1ne, the concentrations of betaine employed, and the results of the electrostatic test are as described below:

All the hydrocarbon blends passed the water tolerance test.

Example 4 The procedure of Example 3 was repeated, employing:

at a concentration corresponding to 15 lbs/i000 bbl. (This betaine was prepared by reacting n-dodecyl alphachloroacetate with the sodium salt of N,N-dimethyl glycine.) The results ot the antistatic test in hydrocarbons l3 and D were as follows:

The number of 2-kv. discharges in 20 minutes was reduced from 720 to in positive'prone Fuel B, and from 459 to 19 in negative-prone Fuel D. Both compositions (containing the betaine) passed the water tolerance test.

Example 5 A refined kerosine, with and without Nlauryl betaine at a concentration corresponding to 1 lb./ 1000 bbl., was vigorously shaken with 0.1 and 5 volume percent of water for about 5 minutes and the mixtures allowed to 7 settle for 16 hours. The electrostatic test results on the thus-treated products follow:

obtained at room temperature using a platinum ring coated with polythene.

The results show that fuel containing N-lauryl betaine (1 lb./ 1000 bbl.) resists accumulating static electricity even after being contacted with water.

Example 6 This example shows the beneficial effect of N-lauryl betaine on jet fuel filterability and pre-heater tube deposits as determined in the CPR Coker Test, in accordance with CRC Manual No. 3, Instructions for Operation and Maintenance of CPR Fuel Coker, March 1957, of the Coordinating Research Council, Inc. (The fuel coker is a laboratory apparatus designed to measure the fuels high temperature stability. In principle, it subjects the test fuel to the same level of temperature stress and in a manner similar to that occurring in jet engines.)

The results obtained with two LIP-4 jet fuels-one relatively stable (Fuel F) the other relatively unstable (Fuel G)-are tabulated below. The following code was used to rate each inch of the preheater tubcs 13 inches of length:

No visible deposits 1Visible haze or dulling, but no color 2Barely visible discoloration 3-Light tan to peacock stain 4-Heavier than 3 CFR FUEL COKER DATA FOR N-LAURYL BETAINE 1 The additive passed the Water tolerance test in both fuels.

9 Total time for the test was 300 minutes; where a pressure drop of 25 inches of mercury occurred before 300 minutes had elapsed, the run eas stopped to remove the filter and then continued to 300 minutes.

The pressure drop across the filter and the condition of the preheater tube after 300 minutes with respect to tube deposits are a measure of the fuels high temperature stabiltiy. The betaine reduced the preheater tube deposits formed with both fuels. It improved the filterability of the less stable fuel (G) and did not significantly depreciate the filterability of the more stable fuel (F).

As stated, none of the betaine additives, in any of the hydrocarbon compositions described above, promoted the emulsification of hydrocarbon with water, as determined by the water tolerance test.

The non-emulsifying effect of the subject betaines is also shown in the following example.

Example 7 The data below show the eifect of N-lauryl betaine on the interfaeial tension between jet fuels B and G (JP- and iP-4) and water. The measurements were N-Lauryl Inter-facial Fuel betaine, Tension,

lbs. /l,000 dynes/cm.

bbls.

None 40. 7 7. 5 36. 7 15. 31. 5 None 35. 6 7. 5 31. 6 15. 26. 4

It is currently believed that an additive cannot reduce the interfacial tension between fuel and Water below 15 dynes/em. without interfering with the operation of fuelwater separators. Thus, the above results indicate N- lauryl betaine, at concentrations that are effective for antistatic use, should not cause difiiculty in the separation of fuel from water.

It will be apparent that many widely different embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

I claim:

1. A liquid hydrocarbon boiling in the distillate fuel range containing an antistatic quantity, of from 0.1 to 30 pounds per 1000 barrels of said hydrocarbon, of a hydrocarbon-soluble betaine of the formula wherein R is a saturated divalent hydrocarbon radical, R and R are saturated aliphatic hydrocarbon radicals, and R is an uncharged aliphatic radical taken from the group consisting of hydrocarbon radicals and ether oxygen-, hydroxyl-, and carbonyl-substituted hydrocarbon radicals, R being free of substituents that promote the emulsification of said liquid hydrocarbon with water, said betaine containing from about 11 to about 35 carbon atoms.

2. The composition of claim 1 containing an antistatic quantity of from 0.5 to 15.0 lbs. of said betaine per 1000 barrels of said liquid hydrocarbon.

3. A liquid hydrocarbon boiling in the distillate fuel range containing an antistatic quantity of from 0.1 to 30.0 pounds per 1000 barrels of said liquid hydrocarbon of a hydrocarbon-soluble betaine of the formula wherein x is an integer within the range of 0 to 1, R is an aliphatic hydrocarbon radical, R is a saturated divalent hydrocarbon radical, and R and R are saturated aliphatic hydrocarbon radicals, said betaine containing from about 11 to about 35 carbon atoms.

4. The composition of claim 3 wherein the liquid hydrocarbon contains from 0.5 to 15.0 lbs. of said betaine per 1000 barrels of said liquid hydrocarbon.

5. A jet fuel liquid hydrocarbon boiling in the distillate fuel range containing from 0.1 to 30.0 lbs. per 1000 barrels of said jet fuel of N-lauryl-N,N-dimcthyl glycine.

6. The composition of claim 5 containing an antistatic quantity of from 0.5 to 15.0 lbs. of said betaine per 1000 barrels of said liquid hydrocarbon.

7. As an antistatic additive for liquid hydrocarbons boiling in the distillate fuel range, (1) a liquid hydro- 10 carbon carrier and (2) from 20-60% by weight of said betaine containing from about 11 to about 35 carbon carrier of a hydrocarbon-soluble betaine of the formula atoms.

R2 8. The additive of claim 7 wherein the liquid hydro- R I carbon carrier is xylene.

I 5 9. The additive of claim 7 wherein the liquid hydrocara bon carrier is kerosene. wherein R is a saturated divalent hydrocarbon radical, References Cited in the file of this patent R and R are saturated aliphatic hydrocarbon radicals, and R is an uncharged aliphatic radical taken from the UNITED STATES PATENTS group consisting of hydrocarbon radicals and ether oxy- 10 2,129,264 Downing et a1. Sept. 6, 1938 gen-, hydroxyl-, and carbonyl-substituted hydrocarbon 2,697,656 Stayner et a1. Dec. 2 1, 1954 radicals, R being free of substituents that promote the 2,886,423 Vitaiis May 12, 1959 emulsification of said liquid hydrocarbon with Water, said 2,951,751 McDermott Sept. 6, 1960

Claims (1)

1. A LIQUID HYDROCARBON BOILING IN THE DISTILLATE FUEL RANGE CONTAINING AN ANTISTATIC QUANTITY, OF FROM 0.1 TO 30 POUNDS PER 1000 BARRELS OF SAID HYDROCARBON, OF A HYDROCARBON-SOLUBLE BETAINE OF THE FORMULA