US2220507A - Method for refining organic acids obtained from oxidized hydrocarbons - Google Patents

Description

or uncombined hydrocarbons.

Patented Nov. 5, 1940 PATENT OFFICE METHOD FOR REFINING oacamo some OBTAINED mom oxmrznn mznnoosn- BONS' Arthur L. 'Blount, Pains Verdes Estates, Calif, as-

signor to Union Oil Company of California, Los Angeles, Calif., a corporation of California No Drawing. Application January 4, 1937, Serial N0. 1191"") 9 Claims.

The present invention relates to the oxidation of hydrocarbons andmore particularly pertains to the production of'new and useful, products resulting from the liquid phase oxidation of petroleum hydrocarbons with oxygen or oxygencontaining gases, such as air.

It is well known that the liquid phase oxidation of hydrocarbons gives rise to a wide variety of products embracing unsubstituted carboxylic acids, hydroxy acids, keto acids, aldehyde acids,

alcohols, ethers, esters, ketones, resinous or resinforming materials, and a number of other more or less oxygenated products, as well as unreacted I It is also known that the liquid phase oxidation of naphthenic or asphalt base petroleum fractions or distillates results in the formation of most of the aforementioned and other more or less oxygenated types of products. It is therefore the main object of the present invention to provide a method for treating said products of oxidation tov isolate one or more new and valuable products or fractions having distinctive characteristics and utilities. A I

' further object of the invention is to treat the 25 products of the liquid phase oxidation of naphthenic or asphalt base petroleum fractions to produce and/or isolate therefrom the aforementioned new and useful products.

As previously stated, the oxidation of a naphthenic or asphaltic petroleum distillate produces a mixture containing some unreacted hydrocarbons and a mixture of products which are oxidized to a greater or less extent. These products vary in their solubility in the hydrocarbon fraction and in each other to such an extent that two phases are formed when the oxidation is sufil- 1 ciently prolonged. In general, the more highly oxidized products are the least soluble, and their gradual formation during the progress of'the oxidation is accompanied by the appearance and growth of the heavier second phase comprising them.. This heavy phase which contains only minor amounts of unreacted hydrocarbons is hereinafter referred to as the "oil-insoluble fraction. Therefore, it is a still further objector the present invention to treat the oil-insoluble fraction obtained in the above liquid phase oxidation to isolate therefrom certain types of new and useful products having certain distinctive characteristics and utilities which will be more fully described hereinbelow.

It has now been discovered that the above and other objects may be obtained by the use of oer-- tain steps described herelnbelow, some of these steps being. old per se, others being in the form of substitutions for known steps of operation, while still othersconstitute or comprise additional steps to be incorporated into the known methods of oxidation and treatment of petroleum fractions and particularly of fractions or distillates derived from naphthenic or asphalt base crude oils. These various steps will be pointed out hereinbelow with a typical description of a preferred form ofrealiration of the treating operations constituting one of the objects of the present invention. 4

As stated above, the oxidation of a petroleum fraction, and particularly of one containing naphthenic constituents, gives rise to an oil-in- .soluble phase which is heavier than the conjugate phase comprising. the unreacted hydrocarbons and products solubletherein. The oil-insoluble phase may be recovered by settling and decantation or by other obvious means, which process constitutes the first .ste'p in the treatment. By

means of this step the oil-insoluble phase is recluded or emulsified portions of the conjugate phase. If desired, the oil-insoluble phase may then be further subjected to a dehydrating step, such as to evaporative heating or refluxing with toluene with a trapped return, in order to remove any associated or dissolved water.

The oil-insoluble phase obtained as a result of the first step of phase separation with or without the additional steps of naphtha washing and/or dehydration, is a mass having a fluid to highly viscous consistency, and E of a brown to black color. This mass is substantially soluble in caustic alkaline solutions and substantially insoluble in light paraiilnic hydrocarbons and heavier paraflln or naphthenic hydrocarbons, such as the stock from which it was produced, even when the solvent power of such hydrocarbons is enhanced by the presence of soluble oxidation products. It is distinguished from the oxidation product in toto by the absence of the more soluble or less oxidized oxidation products and also by the substantial absence of unreacted hydrocarbons. Chemically it is preponderantly acidic in character and may be roughly classed as ccnslsting'predominantly of oxy-aclds such saponiflcation values, and oxygen contents. al-

' plex mixture.

sulfuric or phosphoric acids are eifective solvents.

or reagents in resolving the oil-insoluble phase into constituent fractions thereof, especially when used in conjunction with organic diluents or solvents in a manner which will be more fully described hereinbelow. It is therefore still a further object of the present invention to provide a process whereby the complex oil-insoluble phase obtained as a product of liquid phase oxidation of hydrocarbons may be treated with oxygencontaining dior tri-basic inorganic acids to produce and/or. isolate therefrom simpler fractions of a more homogeneous or purer character and of consequently greater utility. For purposes of exposition, the invention will be more fully described in conjunction with a typical example, the various phases of the invention being discussed at greater length in connection therewith. I

Approximately 38,000 grams of an untreated topped light gas-oil fraction obtained from naph thenic or asphalt base crude oil, and having a boiling point range of from 393 to 612 F. and a gravity of about 33 A. P. I. were oxidized by agitating with air for a period of seven hours at a pressure of 100 lbs. gauge and at an average temperature of 300 F. in the presence of approximately 210 grams of a magnesium oxide catalyst. By separation of the soluble and insoluble phases,

an oil-insoluble phase was obtained which weighed 9580 grams or 25.2% on the basis of the original charge. In order to treat the oil-insoluble phase with sulfuric acid or the like in the most advantageous manner, it has been found essential to form a fluid and more or less-dilute solution of said oil-insoluble phase. This is produced with the aid of a solventwhich is relatively substantially inert to the sulfuric acid. It is, however, not necessary to choose a powerful solvent, such as chloroform or carbon disulfide, which is capable of dissolving the entire oilinsoluble fraction. In most instances preference is given to a moderately powerful solvent, such as benzene' or toluene or mixtures of naphtha and chloroform, etc., which will dissolve andextract a relatively more liquid fraction and leave as a residue a highly viscous or even solid fraction which may subsequently be worked up or treated along different lines, which do not constitute any part of the present invention. By thus extracting the oil-insoluble phase with a selective solvent, an extract is obtained which is more amenable to treatment with sulfuric acid'than when the entire oil-insoluble fraction isthus. treated. Furthermore the products resulting from the subsequent acid treatment of this extract encompass a smaller variety of constituents, which is in line with the objects of the invention. The selective solvent used need not be indifferent to the sulfuric acid, and may comprise such materials as acetone or ethyl alcohol, provided that such solvent is supplanted by an indifferent solvent before treating the sulfuric acid.

In the present instance, about 7500 grams ofa substantially oil-free oil-insoluble phase was extracted with benzene to yield, after evaporation of the benzene, about 4000 grams of a benzenesoluble fraction. This extract fraction was redissolved in nine parts of benzene and the solution treated twice with one volume per cent portions of 60% sulfuric acid, the treatments being carried out at room temperature. The acid sludges were combined and set aside. ed benzene solution was then extracted with dilute caustic to remove the free organic acids, and the aqueous soap solution thus obtained was decomposed with requisite quantities of a mineral acid to yield or liberate about 1350 grams of organic acids hereinafter referred to as the refined benzene-soluble acids. The caustic washed benzene solution was then evaporated to yield approximately 1200 grams of material hereinafter referred to as benzene-soluble neutrals. By hydrolyzing the acid sludge, as by strong dilution with water, or by the addition of aqueous alkali up to incipient neutralization, a still further oily water-insoluble fraction was obtained with a yield of 1000 grams, which fraction is hereinafter referred to as sludge acids. Finally, the two aqueous phases representing the wastes from the above caustic extraction and the sludge hydrolysis were worked up to yield, respectively, 330 and 30 grams of water soluble acids, this treatment being realized by extracting the aqueous phases with ethyl ether, or by salting out, by evaporation, etc.

Thus the oil-insoluble phase, apart from the initial formation of a benzene-insoluble fraction, has been resolved into four fractions, namely the refined benzene-soluble acids, the benzene-soluble neutrals, the sludge acids, and the water soluble acids, all of which, as will be shown subsequently, are substantially distinct in their chemical and physical properties.

-indeed they were transparent and red when viewed in thin layers. These refined acids had 7 an acid number of 208, a saponification numberof 234, an iodine number of 33.3, and an acetyl value of 198. These figures indicate the presence of 0.35 double bonds and 1.1 hydroxyl groups per acid equivalent. It is thus seen that the The treat-- number of double bonds and hydroxyl groups were decreased substantially by 50% when compared to the number thereof in the crude benzene-soluble acids. Many uses suggest themselves for refined acids of this character, particularly in view of their solubility characteristics. In addition, they possess the unusual property of forming excellent resins when heated by themselves or with an equivalent quantity of glycerin.

This property of re'sinification is also displayed to some extent by the crude benzene-soluble fraction, but the resins obtained from this latter material are less satisfactory from the viewpoint of color and consistency.

The sludge acids were approximately of the same consistency as that of the refined acids, and had an acid number of 71, a saponification number of 98, an iodine number of 105, and an acetyl value of 112. On the basis of these figures, 326 double bonds and 1.7 hydroxyl groups are indicated per acid equivalent. Such relatively high unsaturation and hydroxylation make this acidic fraction of interest for many uses, in addition to which it displays resinifying properties approaching, but not equalling, those of the refined benzene-soluble acids.

The benzene-soluble neutral fraction is a fluid material with a terpene-like odor, having an acid number of 6, a saponification number of 119, an iodine number of 35.4, and an acetyl value of 112.

It can thus be characterized as consistinglargely of esters and similar saponifiable materials, which apparently bear free hydroxyl groups. The characteristics of this fraction adapt themselves well for use in the manufacture of solvents, plasticizers, resins, etc.

The water-soluble acids are of syrupy consistency, and have an acid number of 372, a saponification value of 383, an iodine number of 12.2, and an acetyl value of 200. These figures indicate the presence of 0.07 double bonds and 0.7

hydroxyl groups per acid equivalent. This fraction thus represents a cheaply produced mixture of water-soluble hydroxy acids, and as such tration of the inorganic acid depends on the character of the material treated, its degree of dilution in an inert diluent, the type of inorganic acid employed, as well as the degree of purification desired. Sulfuric acid has been found,

to be effective in concentrations ranging from 40 to 95%, and even higher, the most economic concentrations being in the neighborhood of 60 to 80%. However. to realize the same degree of purification or treatment with phosphoric acid as the treating agent, it has been generally found that a slightly higher range of concentration is generally necessary. Obviously the quantity of inorganic acid used must vary according to the character of the acid employed and the degreeof refining desired. The most practical results have been obtained by the use of from 1 to 5 volume percent of the inorganic acid as calculated on the basis of the volume of the solution treated. Generally speaking sharper separation and more effective treatment is realized by increasing the degree of dilution of the organic acids with the inert solvent. Obviously, such dilution must .be maintained within limits since excessive dilution will necessitate the handling of a large bulk of solute, and the use of unnecessarily large quantities of inorganic .acid. Such procedure would thus become cumbersome and probably uneconomical. The optimum dilution, from a practical and economical standpoint, has been found to fall within the range of the use of from 5 to 15 volumes of diluent-solvent to one volume of the organic acids to be treated. This range, however,.varies to some extent with the character of the solvent and of the material treated.

but is also applicable, without essential modifications, to the treatment of other acidic fractions arising from the oxidation of petroleum oils, their fractions or distillates. Thus, the above process may be used to refine or purify the oilinsoluble phase, the oil-soluble phase, or any and all fractions or cuts thereof. In case of acid treatment of the oil-soluble phase, the unreacted the solvent which may be dissolved in or emulsifled with the soap phase (during the alkali extraction which follows the acid treating step) may then be readily removed for example by evaporation or distillation. The use of such solvents having a diflerent boiling point range from that of the organic acids dissolved therein, is however not essential if the presence of smalltraoes of such solvents in the refined organic acids is not objectionable. Furthermore, it is tobe noted that the presence of the diluent-solvent tends to suppress the aforementioned emulsification during the saponiflcation step.

In case it is not deemed advantageous or desirable to separate the neutral oils as a separate fraction, the solvent may be removed from the treated acidic material by a simple evaporation or distillation. Obviously, such a procedure necessitates the initial use of a solvent which has a different and preferably a lower boiling point range from that of th organic acidic fraction treated.

The acid numbers and saponification values presented hereinabove refer to the milligrams of potassium hydroxide necessary to neutralize or saponify respectivelm. one gram of the acidic material. It is obvious that the acid numbers, saponification values, iodine numbers and acetyl values, as wellas the, number of double bonds and hydroxyl groups per acid equivalent, are

.only specific to the particular fraction when obtained from the given original stock by the various steps of operation described hereinabove. These specific characteristics will naturally vary to a certain degree with a change in the original stock and the degree and character of oxidation and subsequent treatment. It has however been found that the general physicaland/or chemical features of these various fractions will remain substantially constant, or at least similar to those described hereinabove.

It is to be understood that it is desired to comprehend within this invention such modifications and changes as may adapt it to varying conditions and uses, the various phases of theinvencarbon insoluble fraction with a selective solvent selected from the class consisting of benzene, toluene, ethyl alcohol, acetone and mixtures thereof. with naphtha and chloroform, and treating the fraction soluble in said selective solvent with an inorganic acid selected from the class consisting of the oxygen-containing diand-tribasic acids.

2. In a process according to claim 1 wherein the acid treatment is realized in the presence of the selective solvent employed for the abovementioned extraction of the hydrocarbon insoluble fraction.

3. A process for treating products of liquid phase oxidation of naphthenic petroleum- 011s which comprises-separating said products-ot-oxidation into a phase soluble in the unreacted oils and a phase insolublethere'in, commingling said oil-insoluble fraction with a selective'solvent selected from'the'class consisting of benzene, toluene, ethyl alcohol, acetone, and mixtures thereof with naphtha and chloroform, separating the phase insoluble in said selective solvent'irom the phase soluble therein and treating the hase soluble in said solvent with an inorganic acid selected from= the class c'onsisting iof the oxygencontaining diandtri-basic inorganic acids.

4. In a 'process according to claim 3 wherein the acid treating step is realized in the presence of a solvent ilne'rt tmthe action of the inorganic and a phase insoluble therein, commingling said oil-insoluble fraction with benzene to cause phase separation between the fractions solublein said solvent and a fraction insoluble thereinyand treating said benzene-soluble phase with an inorganic acid selected rrom the class consisting of the' oxygen-containing diand tri-basic inorganic'acids.

6. In a process according to claim 5 wherein sulfuric acid is employed in the acid treating step.

7. In a process according to claim 5 wherein sulfuric acidin concentrations ranging from approximately 40. to 95% is employed in the acid treating step.

' 8. A process for treating products or liquid. phase oxidation of naphthenic petroleum oils which comprises separating said products of oxioil-insoluble phase with benzene to separate therefrom the benzene soluble phase, commingling said benzene soluble phase in solution in said benzene with sulfuric acid of a concentration ranging from about 45 to 90% and in quantities ranging irom about 1 to 5 volume percent as calculated on the basis of the volume of the solution treated, separating th sludge acids thus produced, and"further treating the acid treated treated solution, separation of the soap :solution thus produced from the unsaponifled materials, and the liberation oi the resin-forming acids from said solution by addition of necessary quantities of an inorganic acid.

ARTHUR L. BLOUNT