US2844446A

US2844446A - Stabilization of hydrocarbon distillates

Info

Publication number: US2844446A
Application number: US562939A
Authority: US
Inventors: Henry A Cyba; Ralph B Thompson
Original assignee: Universal Oil Products Co
Current assignee: Universal Oil Products Co
Priority date: 1956-02-02
Filing date: 1956-02-02
Publication date: 1958-07-22
Anticipated expiration: 1975-07-22

Description

drums, tanks, etc.

United States Patent 2,844,44 Patented July 22, 1958 STABILIZATION or HYDROCARBON. f

No Drawing. Application February 2,1956 Serial No. 562,939

' sclaims. "(CL 44-63 This application is a continuation-impart of our co pending application Serial No. 478,488, filed December 29, 1954, now abandoned, and relates to a novel process for the stabilization of-hydrocarbon distillates.

' As will be shown by the examples appended to the present specifications, the novel process of the present invention serves to improve hydrocarbon distillates in a number of important ways. For example, in fuel oil, burner'oil, range oil, diesel oil, marine oil, turbine oil, cutting oil, rolling oil, drawing oil, slushing oil, lubricating oil, etc., the oil is improved in one or more ways including retarding and/ or preventing sediment formation, dispersion of sediment when formed, preventing and/or retarding discoloration, oxidation inhibitor, rust or corro sion preventative, detergent properties, etc. In lubricating type oils, in addition to some of the other properties hereinbefore setforth, the additive may function as a pour point depressant, viscosity index improver, antifoaming agent, extreme pressure additive, oilness additive, etc. In gasoline, naphtha, aromatic solvents, kerosene, jet fuels, etc., 'the additive serves as a corrosion inhibitor, along grees.

The hydrocarbon distillate may be cracked, straight run or mixtures thereof. Many fuel oils and particularly blends of straight run and cracked fuel oils undergo deterioration in storage resulting in the formation of sediment, discoloration, etc. The formation of sediment is objectionable because the sediment tends to plug burner tips, injectors, etc. In diesel fuel, the deterioration tends,

to: form varnish and sludge in the diesel engine. Dis coloration of fuel oils is objectionable for various reasons, including customers preference for light colored oils.

In the handling of hydrocarbon distillates, it is often.

necessary to transport and/or store such materials in metal containers, as in steel or other metal pipe lines, Since these. materials often contain varying amounts of water in solution or in suspension which may separate, due to temperature changes, internal 5 corrosion of the container by separating water almost invariably occurs to a greater or'lesser degree. The water thus separated forms as a film or'in minute droplets in the pipe line or on the container walls or even in small pools at the bottom of the container. This brings about ideal conditions for corrosion and consequent damage to the metal surfaces of the container, as well as the serious I contamination of the hydrocarbon oil contained therein'by the corrosion products.

Corrosion problems also occur, for example, in the lubrication of internal combustion engines or steam en- 'gines, including turbines and other similar machinery, in

which quantities of Water are often observed as a separate phase within the lubricating system as a result of the condensation of water from the atmosphere or, in the case of internal combustion engines, as the result of dispersion or absorption in lubricating oil of Water formed as a product of fuel combustion. Water in such instances corrodes the various metal parts of the machinery with with the other functions mentioned above to various de-,

the reaction temperature and slow the reaction,

which it comes into contact, the corrosion products cans ing further mechanical damage to bearing surfaces and the like due to their abrasive nature and catalytically promoting the chemical degradation of the lubricant.

In one embodiment the present invention relates to 'a process for stabilizing a hydrocarbon distillate which comprises incorporating therein a stabilizing concentration of a bis-tetrahydropyrimidine joined at the 2-position through a divalent hydrocarbon radical.

In a specific embodiment the present invention relates to a process for stabilizing fuel oil which comprises incorporating therein a stabilizing concentration of a bistetrahydropy-rimidine joined at the 2-position through a divalent hydrocarbon radical. e

The bis-tetrahydropyrirnidines for use in accordance with the present invention may be illustrated by the fol lowing general formula.

where R is a hydrocarbon radical containing at least 2 carbon atoms and R is hydrogen, a hydrocarbon or a substituted hydrocarbon radical. It will be noted that the bis-tetrahydropyrimidines for use in the present invention are joined together through thel2-position. p i

.The specific composition of the R radical will depend upon the particular polycarboxylic acid utilized in preparing the. bis-tetrahydropyrimidine as hereinafterwill be described in. detail. Similarly, the specific composition of the'R' radicals will depend upon the particular alkylene polyamine utilized in preparing the compound, as well as the furtherreaction thereof, both of which will be further described in detail herein.

The bis-tetrahydropyrimidines for use in the present invention are prepared by the condensation, with the formation of 4 molecules'of water, of 2 mols of an alkylene polyamine having at least 1 primary amino group separated from another primary or secondary amino group by 3 carbon atoms, withl mol of a dicarboxylic acid. This reaction generally is effected at a temperature above about F., and preferably at a higher temperature which usually will not exceed about 350, to 400 F. As hereinbefore mentioned, Water is formed during the reaction and, to facilitate the removal thereof and to effect more complete reaction, a hydrocarbon solvent, preferablyone 'whichformsan azeotropic mix ture with water, may be utilized. Preferred solvents comprise aromatic hydrocarbons including benzene, toluene, xylene, cumene, naphtha, etc. Any suitable amount of solvent may be employed and preferably should not comprise a large excess because this will tend to lower In another embodiment, removal of the water may be facilitated by operating under a reduced pressure. In still another embodiment, the water of reaction maybe removed by distillation of the reaction product at elevated tem-.

perature.

As hereinbefore set forth, the specific compositions 3 of R and R in the above general formula will depend upon the particular reactants utilized. For example, the condensation of 2 mols of 3,3-imino-bis-propylamine with 1 mol of succinic acid, with the formation of 4 molecules of water, produces a bis-tetrahydropyrimidine of the following formula:

The above reaction and product are typical illustrations of the additive compounds for use in the present invention and the method of preparation thereof. The same general reaction is elfected utilizing other alkylene polyamines having at least 1 primary amino group separated from another primary or secondary amino group by 3 carbon atoms.

The following are mentioned as representative of suitable alkylene polyamines for use in preparing the additive: 1,3-propylene diamine,- dipropylene triamine, 1,3- diaminobutane, 2,4-diaminopentane, N-ethyl-trimethylene diamine, N-aminoethyl-trimethylene diamine, aminopropyl-stearylamine, tripropylene-tetramine, tetrapropylene-pentamine, 3,3-imino-bis-propylamine, higher boiling polyamines prepared by the condensation of 1,3-propylene dichloride with ammonia, other polyamines in which at least 1 primary amino group is separated from another primary or secondary amino group by 3 carbon atoms, and mixtures of alkylene polyamines.

For the purpose to be hereinafter set forth in detail, 3,3-imino-bis-propylamine is a preferred alkylene polyamine for use in the preparation of the bis-tertahydropyrimidines. However, for economic reasons, in some cases, it may be desirable to utilize certain substituted propylene polyamines which are recovered, usualy as a mixture of compounds, as a by-product in the manufacture of certain pure compounds or which may be prepared from a mixture of reactants available at a lower cost. In many cases, the final products formed from the mixture will be satisfactory for the desired use and, therefore, can be prepared at a much lower cost. It is understood that the bis-tetrahydro-pyrimidine so produced may comprise a mixture of bis-terta-hydropyrimidines and also that the product may contain other components. Examples of such a mixture available commercially are alkyl propylene diamines in which the alkyl group is derived from tallow, lauric acid, cotton seed and soya, these being available under the trade names of Duomeen-T. Duomeen-IZ, Duomeen-C, and Duomeen- S, respectively. Duomeen-T is particularly preferred and is believed to contain from about 12 to about 20 carbon atoms per alkyl group, mostly 16 to 18 carbon atoms, and has a theoretical molecular weight of 320 and a combining molecular weight (based on 80% active ingredient) of about 400. It is a soft paste and has a melting range of from 111 to 118 F.

Any suitable polycarboxylic acid may be utilized in preparing the bistetrahydropyrimidines. Polycarboxylic acids include oxalic, malonic, succinic, glutaric, itaconic, mesaconic, citraconic, adipic, pimelic, suberic, a'zelaic, sebacic, phthalic, aconitic, citric, hemimellitic, trimellitic,

trimesic, prehnitic, mellophanic, pyromellitic, mellitic, etc., higher polybasic carboxylic acids, and mixtures thereof.

Here again, for economic reasons, it may be preferred to use a dicarboxylic acid product available commercialy at lower cost and preferably containing from about 10 to about 50 carbon atoms per molecule. An example of such an acid is available as dimer acid (dilinoleic acid), which is liquid at 77 F., and is said to have an acid number of l80192, an iodine number of 80-95 and a dimer content of about Another example of a byproduct acid is one being marketed commercially under the trade name of VR-l Acid. This acid is a liquid at 77 F., and is stated to have an acid number of about 150, an iodine number of about 36 and average molecular weight of about 1000. It is believed that this acid contains about 30 to 40 carbon atoms per molecule. When such an acid is used in preparing the bis-tetrahydropyrimidines, it is understood that the reaction product will contain a mixture thereof.

As hereinbefore set forth, the reaction of the alkylene polyamine with the polycarboxylic. acid generally is effected at a temperature within the range of about to about 400 F., although higher or lower temperatures may be employed under certain conditions. The exact temperature will depend upon whether a solvent is used and, when employed, on the particular solvent. For example, with benzene as the solvent, the temperature will be of the order of 176 F., with toluene the temperature in the. order of 248 F. and with xylene the temperature in the order of 297 F. When no solvent is employed, the temperature will be sufiicient to remove the water formed in the reaction. The reaction may be continued until it goes to completion, which may be determined by measuring the amount of water evolved which, as hereinbefore set forth, will comprise 4 molecules of water per mol of dicarboxylic acid. However, for many purposes, as will be hereinafter described, the reaction need not go to completion. In any event, at least a substantial portion of the reactionproduct will comprise a bis-tetrahydropyrimidine having the configuration hereinbefore set forth. The water formed in the reaction may be removed in the manner hereinbefore described and the resultant product is recovered as a viscous liquid in most cases. In some cases, the bis-tetrahydropyrimidine will be utilized as a solution in a solvent. Conveniently, this solvent comprises the same solvent utilized in preparing the bistetrahydropyrimidine and advantageously is recovered in admixture with at least a portion of the solvent, thereby avoiding the necessity of removing all of the solvent and subsequently adding it back. When a more dilute solutionis desired than is recovered in the manner hereinbefore set forth, it is understood that the same or different solvent may be commingled with the mixture to form a solution of the desired concentration.

It is understood that the bis-tetrahydropyrimidines for use in the present invention may contain substituents replacing one or all of the hydrogen atoms attached to the carbon atoms in the 4, 5, 6, 4', 5' and 6' positions, as well as replacing hydrogens attached to the carbon atoms in the side chains. The substituents may be hydrocarbon or substituted hydrocarbon groups, the latter including those containing oxygen, nitrogen, phosphorus, sulfur, halogen, etc. These substituents may inherently be present clue to the specific reactants employed in preparing the bistetrahydropyrimidine or they may be added by a subsequent condensation reaction.

In another embodiment of the invention, the additive comprises an amide formed by reacting the bis-tetrahydropyrimidine having a side chain containing a primary or secondary amino group with a carboxylic acid, with the evolution of 2 molecules of water. For example, the his tetrahydropyrimidine formed by the condensation of 2 mols of 3,3'-imino-bis-propylamine with 1 mol of sucetc.

The above reaction and product are typical illustrations of one additive for use in the present invention. The formation of the amide is effected under substantially the same conditions as hereinbefore set forth for the preparation of the bis-tetrahydropyrimidines. However, when the side chain contains more than one primary and/or secondary amino groups, it is desirable to use a lower temperature, preferably below about 215 F., in order to avoid forming additional pyrimidine or otherrings.

Any suitable monocarboxylic acid may be utilized in preparing the amide. The monocarboxylic acid preferably is selected with reference to the particular bistetrahydropyrimidine and the purpose for which the final compound is to be used. For example, where increased solubility. in a particular hydrocarbon distillate is desired, it generally is preferred to utilize a comparatively long chain monocarboxylic acid. Particularly preferred monocarboxylic acids for use in the preparation of an amide, which in turn is to be utilized as an additive to hydrocarbon distillates, include fatty acids and particularly oleic acid, linoleic acid, palmitic acid, stearic acid, etc. Other monocarboxylic acids include formic, acetic, propionic, butyric, valeric, trimethylacetic, caproic, theptylic, caprylic, pelargonic capric, lauric, myristic, arachidic, behenic, lignoceric, cerotic, etc., decylenic, dodecylenic, palrnitoleic, ricinoleic, petroselinic, vaccenic, linolenic, eleostearic, licanic, parinaric, gadoleic,

arachidonic, cetoleic, erucic, selacholeic, etc., and mixtures thereof. 1

In some cases, the monocarboxylic acid may contain hydroxy substituents as, for example, in acids as glycolic, lactic, hydroxybutyric, etc. In other cases, the monocarboxylic acid may contain other substituents attached thereto, which sub'stituents may be hydrocarbon or substituted hydrocarbon groups, the latter including those containing oxygen, nitrogen, phosphorus, sulfur, halogen,

In another embodiment, a mixture of monocarboxylic acids may be employed. As hereinbefore set forth, the above acids are recited merely for illustrative purposes and are not intended to be limiting. The particular acid will be selected on the basis of the particular hydrocarbon distillate in which the additive is to be incorpo-- rated. It is understood that the various amides formed in the manner hereinbefore set forth will not necessarily be equivalent.

. As an example of a modification of the amide comprised within the scope of the present invention, a histetrahydropyrimidine having a primary amino group in the side chain may be reacted with an aldehyde or ketone in the presence of hydrogen, and the resultant secondary. amino groups utilized to form the amide by reaction with the monocarboxylic acid.

' While the amide formed from the monocarboxylic acid generallyis preferred, it is understood that amide formed in accordance with the present invention. 'The polycarfrom polycarboxylic acids may be prepared and utilized I boxylic acid may be selected from those hereinbefo're set forth in connectionwith the preparation of the bis-tetrahydropyrimidine. I

In still another embodiment, the additive for use in the present invention comprises a carboxylic acid salt of the bis-tetrahydropyrimidine or of the amide thereof. The salt may be an acid, basic or neutral salt, depending upon the amount of carboxylic acid utilized in preparing the salt. The neutral salt is prepared by utilizing stoichiometric amounts of the acid and amino groups. Each of the pyrimidine rings has a basicity equivalnt to one amino group. Therefore, the amino groups, which are computed in determining the amount of carboxylic acid, will be 2 aminogroups for the'bis-tetrahydropyrimidine and 1 each for the primary and'secondary amino groups in the side chains. In preparing the neutral salt, the concentration of carboxylic acid and amine groups will be selected so that there will be an equivalent number of carboxylic acid groups and amino groups. Thus, the specific concentrations will depend upon whether the acid is monobasic, dibasic, tribasic or higher polybasic acid, and on the number of amino groups as hereinbefore set forth. In another embodimennthe salt may be a basic, salt, which is prepared by utilizing a deficiency of carboxylic acid groups in relation to the amino groups as, for example, by utiliing' 1 equivalent of carboxylic acid per 2 equivalents of amino groups.

pared by using an excess of acid with relation to the amino group as, for example, 2 equivalents of acid per 1 equivalent of amino group. -It is understood that these different salts are not necessarily equivalent.

When-a monocarboxylic acid is utilized in preparing the salt, it may be selectedfrom the monocarboxylic acids specifically set forth hereinbefore. Similarly, when a polycarboxylic acid is utilized in forming the salt, it may be selected from those hereinbefore set forth in connection with the preparation of the tetrahydropyrimidine. Advantageously, the dicarboxylic acid utilized in preparing the bis tetrahydropyrimidine may be employed in preparing the salt. In another preferred embodiment, the monocarboxylic acid utilized in forming the amide is advantageously utilized in preparing the salt. It is understood that the-amide and/ or salt may be prepared simultaneously with the preparation of thebis-tetrahydropyrimidine or the salt prepared simultaneously with the preparation of the amide. This may be accomplished by utilizing a sufficient excess of the carboxylic acid in order to form the desired product. Inaddition to the formation of the amide'and/ or salt, in some cases there is evidence of the formation of a complex between the amine and acid, which complex as yet has not been completely identified. It is understood that the novelcomposition of bis-tetrahydropyrimidine, amide and/or salt also may I contain the complex.

The salt may be prepared in any suitable manner. It

In still another embodiment, an acid salt may be employed, which may be pre-- vigorous stirring. The salt is prepared readily at room temperature, although slightly elevated temperatures which generally will not exceed about 200 F. may be employed when desired. Excessive temperatures should be avoided in order not to form amides or additional rings When not desired. In some cases, it may be desirable to utilize a solvent during the formation of the salt and, as hereinbefore set forth, the solvent advantageously is the same as that utilized in forming the final solution of the product.

It is understood that the various additives which may be prepared and used in accordance with the present invention are not necessarily equivalent in the same or different hydrocarbon distillates. As an example, a bistetrahydropyrimidine, amide or salt may be more effective in one fuel oil, while another bis-tetrahydropyrirnidine, amide or salt may be more effective in a ditferent fuel oil. Furthermore, the particular bis-tetrahydropyrimidine, amide or salt to be used will depend upon the specific benefits desired in the particular hydrocarbon distillate being treated.

As hereinbefore set forth, the particular additive will be selected on the basis of the purpose which it is to serve and also on the specific hydrocarbon distillate in which it is to be used. In the case where increased solubility is desired in the hydrocarbon distillate, an additive containing a higher number of carbon atoms is generally preferred, the larger number of carbon atoms may be obtained by a judicious selection of the amine and/or acid utilized in preparing the bis-tetrahydropyrimidine, in the selection of a long chain monocarboxylic acid in forming the amide, and/or in the use of a salt prepared from a long chain carboxylic acid. Where increased corrosion prevention is desired, it generally is preferred to use an acid salt of the bis-tetrahydropyrimidine or amide. The concentration of additive to be used likewise will depend upon the particular hydrocarbon distillate and the particular benefits desired. In general, the additive is used in a concentration of from about 0.0000l% to about by weight or more and generally in a concentration of from about 0.000l% to about 1% by weight of the hydrocarbon distillate. The additive may be used along with other additives which are incorporated in a hydrocarbon distillate for specific purposes including, for example, metal deactivators, antioxidant, synergists, dyes, fuel irnprovers, etc.

The additive is incorporated in the hydrocarbon distillate in any suitable manner. As hereinbefore set forth, the additive conveniently is utilized as a solution in a suitable solvent including hydrocarbons and particular aromatic hydrocarbons as benzene, toluene, xylene, cumene, etc. The additive is readily incorporated in the hydrocarbon distillate by adding it in the desired amount to the distillate and suitable agitating or otherwise mixing in order to obtain intimate admixing of the additive and the distillate. When the additive is to be utilized as a corrosion inhibitor in plant equipment, it may be intro duced into a fractionator, vapor line or at any other suitable point in order to prevent corrosion of the plant equipment. In this embodiment, the additive carries over into the product of the process and also serves therein as a beneficient. It is understood that a portion of the additive may be introduced into the plant equipment and an additional portion of the additive added to the effluent product when so desired.

The following examples are introduced to illustrate further the novelty and utility of the present invention but not with the intention of unduly limiting the same.

EXAMPLE I In this example the additive was utilized in a catalytically cracked cycle stock which is marketed as a fuel oil. The beneficial efiects obtained by the use of the additive are determined by means of a number of different methods. In one method a sample of the fuel oil it Without additive is stored at F. for 6 months or longer, and the amount of sediment formed during such storage, as well as thecolor of the oil, is determined. At the same time, another sample of the same oil containing an additive is stored under the same conditions and the sediment and color also are determined.

In another method of analysis, after storage at about 100 F. the different samples of the oil are passed through a 400 mesh wire screen and the time in seconds for successive 300 cc. portions of the oil to pass through the screen is recorded. This method analyzes the different samples as regards the property thereof to clog burner screen in actual service. As hereinbefore mentioned, clogging of burner screens is objectionable because it prevents satisfactory use of the fuel oil.

The colors of the different samples were determined in a Lumetron, Model 402,E spectrophotometer. Distilled water is rated as 100. A very dark oil would be rated as 0 in this analysis.

The additive used in this example is a bis-tetrahydropyrimidine and was prepared by reacting 2 mols of Duomeen-T with 1 mol of Dimer acid. The properties of Duomeen-T are set forth hereinbefore. The Dimer acid is dilinoleic acid and the properties thereof likewise are set forth hereinbefore. The Duorneen-T and Dimer acid were commingled with xylene as the solvent, and the mixture was refluxed at a temperature of about 300 F. for a period of about 6 hours. 4 molecules of water were evolved per mol of acid. The product is a viscous medium brown liquid having an index of refraction of 1.4907. Infrared spectrum showed a C=N band. It cannot be distilled without decomposition.

0.005% by Weight of the bis-tetrahydropyrimidine prepared in the above manner was incorporated in a sample of the catalytic fuel oil, and the properties thereof after storage in the manner hereinbefore set forth are reported below. Similar properties of another sample of the fuel oil not containing the additive also are reported in the table.

Before storage in the manner hereinbefore set forth, the sample of oil was free from sediment and had a color of 94. It will be noted that the additive served to benefit the oil in reducing the sediment after about 200 days of storage from 14 to 3.8 mg./l00 ml. and to have a final color of 35 as compared to 20 for the control sample. Also, in the screen test, the sample without additive required over 200 seconds to pass through the screen, thus indicating plugging of the screen, whereas the sample containing the additive passed through the screen in 10-14 seconds.

EXAMPLE II 3,3'-imino-bis-propylamine was reductively alkylated with ethylamyl ketone to form N-octyl-3,3'-imino-bispropylamine. The N-octyl-3,3'-imino-bis-propylamine, dilinoleic acid and xylene were refluxed at 300-3l0 F. for about 6 hours, with the evolution of 4 molecules of water per mol of acid. The product was a light brown viscous liquid having an index of refraction of 1.4970. The product could not be distilled without decomposition. The calculated mol combining weight is 281.5. Actual combining weight was 298.

0.01% of the bis-tetrahydropyrimidine was incorporated in a catalytically cracked fuel oil and exposed to air 9 at 212 F. for 20 hrs. The oil after this exposure had a color of 73.3. A control sample of the oil not containing additive had a color of about 11 after similar exposure.

EXAMPLE III A bis-amide of bis-tetrahydropyrimidine was prepared as follows: 3,3-imino-bis-propylamine, sebacic acid and xylene were refluxed at 300-310 F. for about 6 hours. Subsequently, 2 mols of oleic acid per mol of bis-tetrahydropyrimidine and xylene were added, and the mixture refluxed at 300-310 F. for about 7 hours, with the separation of 2 molecules of water per mol of bis-tetrahydropyrimidine. The bis-amide was converted to the oleic acid salt with an index of refraction of 1.4907. It could not be distilled without decomposition. The bis-amide as prepared in the above manner in incorporated in a commercial fuel oil in a concentration of 0.01% to reduce sediment formation therein and to improve the color of the oil during storage.

EXAMPLE IV tion of 1.4838. Calculated mol combining weight is 878.5. Actual was 853.

When incorporated in another sample of the catalytically cracked fuel oil and exposed as described in Example III, the fuel oil had a color of 81.3 as compared to about 11 for the control sample.

EXAMPLE V pounds per 1000 pounds of oil of the acid salt of VR-1 Acid and the bis-tetrahydropyrimidine prepared from N-octyl-3,3'-imino-bis-propylamine and VR-l Acid are injected into the vapor line of fractionating column in a cracking plant. This will serve to keep the I in storage containing a bis-tetrahydropyrimidine joined at the 2-position through a divalent hydrocarbon radical, said compound having the property of and being present in sufficient amount to retard said sediment formation.

3. Fuel oil normally susceptible to sediment formation in storage containing an amide of a bis-tetrahydropyrimidine joined at the 2-position through a divalent hydrocarbon radical, said compound having the property of and being present in suflicient amount to retard said sediment formation.

4. Fuel oil normally susceptible to sediment formation in storage containing a salt of a bis-tetrahydropyrimidine joined at the 2-position-through a divalent hydrocarbon radical, said compound having the property of and being present in sufiicient amount to retard said sediment formation.

5. Fuel oil normally susceptible to sediment formation in storage containing an acid salt of a bis-tetrahydropyrimidine joined .at the 2-position through a divalent'hydrocarbon radical, said compound having the property of and being present in sufficient amount to retard said sediment formation.

References Cited in the file of this patent UNITED STATES PATENTS 2,194,419 Chwala Mar. 19, 1940 2,622,018 White et al. Dec. 16, 1952 2,640,029 Blair et al. May 26, 1953 2,646,399 Hughes July 21, 1953

Claims

1. FUEL OIL NORMALLY SUSCEPTIBLE TO SEDIMENT FORMATION IN STORAGE CONTAINING A COMPOUND SELECTED FROM THE GROUP CONSISTING OF A BIS-TETRAHYDROPYRIMIDINE JOINED AT THE 2-POSITION THROUGH A DIVALENT HYDROCARBON RADICAL AND THE AMIDES, SALTS AND ACID SALTS OF SAID BIS-TETRAHYDROPYRIMIDINE, SAID COMPOUND HAVING THE PROPERTY OF AND BEING PRESENT IN SUFFICIENT AMOUNT TO RETARD SAID SEDIMENT FORMATION.