US2220506A - Method for refining oxy-acids obtained from oxidized hydrocarbons - Google Patents

Description

Patented Nov. '5,

' Arthur L. Blount, Palos Verdes, Estates, Calif, as-

signor to Union Oil Company of California, Los Angeles, Calif., a corporation of California NoDrawing. Application Januaryd, 1937, Serial No. 118,999

6 Claims (o1. 260-452) The present invention'relates to the oxidation of. hydrocarbons, and more particularly pertains to the production of new and useful products resulting-from liquid phase oxidation of petroleum hydrocarbons. More specifically stated, the

invention covers a treatment of products resulting from the liquid phase oxidation of petroleum .hydrocarbonswith oxygen or an oxygen-containing gas, said treatment causing the. separation=or 10 isolation .ofcertainoxygenated productshaving distinctand valuable characteristics and utilities:

It -is well known that the liquid phase oxida-' tion of hydrocarbons gives rise to, a wide varietyof 7 products embracing "unsubstituted carboxylic acids, ,hydroxy acids-,keto acids, aldehyde acids, alcohols, esters, ethers, ketones, lactones, resinous and resin-forming materials and a number of other more .or less oxygenated products. Also, unless the liquid phase oxidation iscarried'out for excessively long: periods of time and under excessive operating conditions, a certain quantity of hydrocarbons is usually left in" 'an unreacted or uncombined condition. It is also known that the'liquid phase oxidation of petroleum fractionsandparticularly, of those which are obtained from naphthenic orflasphaltfbase crudes results in the formation ofa heterogeneous mixture containing most if not all of'the above types of-more or less oxygenated hydrocarbon products. It is therefore the main object of the present invention to provide a method for treating said products of oxidation to recover or isolate therefrom new and valuableproducts or fractionshaving distinct characteristics and utilities. A furtherobject of the invention is to treat the products resulting from theiiquid phase oxidation-with air 01" a naphthenic 'petroleumoil, its fractions and/or distillates, to produce and/or isolate therefromithe'; aforementioned new and useful 40 pIOdllQt-S.

As previously stated," the oxidation lot a petroleum fraction, particularly' of one containing naphthenic constituents,,.produces a ,mi'xiaue comprising some unreacted or unoxidized hydrocarbons and a number of products which" are oxidized to a greater." or lessextent. The seproducts'vary in. their solubility in the hydrocarbon fraction and in e'aehother to such an extent that two phases are formed when the oxidation is sirmciently prolonged In general, the more highly oxidized products such as keto and hydroxy acids, are the least soluble while most of the unsubstituted, some'of-the substituted carboxylic'acids, and certain ethers, esters, lactones, etc, are found to'be relatively more soluble in each other andin the unreacted hydrocarbons.

I It .is therefore obvious that the heterogeneous mass produced by the liquid phase oxidation of petroleum and particularly naphthenic hydrocarbons. may be easily separated into two frac- 6 tions by allowing the mass to stand. One of the phases thus produced, as mentioned above, contains the unconverted or .uncombined hydrocarbons and the products of oxidation soluble therein, while the insoluble phase which deposits 10 out upon standing contains most of the highly oxidized products as well as certain oxygenated substances nowbelieved to comprise polyhydric alcohols. These phases may be easily separated from each other as we simple decantation. For 15 purposes of simplicity, the first mentioned fraction or phase will be hereinafter referred to as the oil-soluble phase or fraction, and the acids therein will be termed as the oil-soluble acids.

0n the other hand, the fraction generally insolgo 1 uble in the oil-soluble phasewill be hereinafter termed as the oil-insoluble? fraction or phase. The present invention primarily deals with the oil-soluble fraction and the oil-soluble acids contained therein. Therefore, it is a still fur- E25 ther object of the present invention to treat the oil-soluble fraction obtained during the above I describedliquid phase oxidation to isolate there-' fromcertain types of new and useful acids having certain distinctive characteristics and utili- 3o ties which will be described more fully hereinbelow. i

It has recently been discovered that the oilsoluble phase obtained by the liquid phase. oxidation of' a predominantly naphthenic petroleum 35 fraction may be fractionated to isolate therefrom certain of its constituent fractions, said separation or isolation being realized by a series of steps which will be described and pointed out hereinbelow in connection with the typical description 1 of a preferred form of realization. Thus, the free carboxylic acids and easily saponiflable lactones; etc. contained in the oil-soluble phase may be removed therefrom by treating said oil-soluble phase with .an alkali to-convert the aforementioned substances into their soaps or salts, while leaving the unconverted petroleum hydrocarbons,

as well as certain of the oxygenated products, such as ethers and alcohols, in an unchanged form. The aqueous soap solution produced by. this saponification may then be separated from the unreacted fraction as by decantation, the acids thus saponified being then liberated as by the addition of inorganic acids of the type of sulf ric acid or the hire. These oil-soluble acids,

obtained aslthe result of the first steps of sepa they are roughly-classed as consisting predominantly of unsubstituted :and substituted carboxration, "are'fiuid and of. dark color. Chemically,

is far from conclusive as .tothejexact character fofsuch a complex mixture; Ithas'gbeen found,

" however, that these oil-soluble acids contain rmtions which'var'y greatly in their chemical-and physical properties and that for some uses the" action of one fraction is antagonistic to that of another, so that the full utility of the product is available only upon the resolution of said oilsolubie acids into simpler and more coherent fractions. 7

The oil-soluble acids may be segregated or separated into two fractionsby extraction with a petroleum ether or a similar light hydrocarbon 'diluent or solvent.

This extraction causes phase separation in that certain of the acids and particularly the relatively more highly substituted acids are found to be insoluble in said diluent or solvent. In what will follow hereinbelow these insoluble acids will be referred to as the petroleum ether-insoluble acids." Generally speaking, these crude petroleum ether-insoluble acids are insoluble in propane, but completely miscible with kerosene, benzene, alcohol, acetone and carbon tetrachloride.

It has now been discovered that these petroleum ether-insoluble acids may be effectively resolved into still further constituent fractions when said organic acids are treated with oxygencontaining dior tri-basic inorganic acids, such as sulfuric acid or phosphoric acid. It has been further discovered that these oxygen-containing inorganic acids are effective solvents or'reagents in said resolution of the crude petroleum etherinsoluble acids when said inorganic acids are used in conjunction with organic diluents or so]- vents in a manner more fully described hereinbelow. It is therefore a still further object of the present invention to provide a process whereby the relatively complex petroleum ether-insoluble acids, obtained as one of the fractions derived from the treatment of products of liquid phase oxidation of petroleum hydrocarbons, may be treated with oxygen-containing dior tribasic inorganic, acids to produce or isolate from said petroleum ether-insoluble acids simpler fractions of a more homogeneous-character and consequently of greater utility.

For the purpose 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 naphthenic or asphalt base crude oil, havinga boiling point range of 393-612 F;, a gravity of about 33 A. P. I. and containing approximately 79% of naphthenes and paraffins, about 19% of aromatics and about 2% of unsaturates, was oxidized'by agitating with air for a period of about seven hours at a pressure of approximately 100 lb. gauge and at an average temperature of 300 F. This oxidation was realized in the presence of a catalyst consisting of approximately 210 grams of magnesium oxide. By separation of the soluble and insoluble phases, an oil soluble and comprised 74.73% of the original charging stock. The acid number of this oil-soluble phase was 21' KOH/g., .whiie the saponiflcation value was equal to 47. 7 Since someof the acids contained in said oil-soluble phasewere known to be water-soluble, the wholeoil-soluble phase was washed with water. The'water-soluble acids extracted by this washing weighed about 175 grams, had anacid number of 378 and a saponiflcation value of, 427. These acids were slightly soluble in benzene, alcohol and acetone, were somewhat soluble in kerosene but insoluble in propane,

petroleum ether, and carbon tetrachloride. In

oxygenated products was realized by a mere decantation and separation of thephases thus phase wasobtained weighed 28,425

produced. The oil-soluble acids saponified by the above described-treatment with cold sodium hydroxide were then liberated by the addition to the soap solution of requisite quantities of an inorganic acid, such as sulfuric acid. As in the previous treatment, the acidification again caused the formation of two phases,'the oily phase consisting of the gas oil-soluble acids, and the aqueous phase consisting of the salt water. After separating the salt water, the oil-soluble acids were found to weigh 1,838 grams or 4.8%

KOH/g., while the saponification number was 206. In order to further simplify the composition of the acids present in the oil-soluble acid phase, this mixture of acids was treated or extracted with petroleum ether or a like solvent, such as low boiling naphtha, gasoline, etc. Although the optimum quantity of petroleum ether used for this extraction depends on the type and character of the original material oxidized, and therefore of themixture of acids comprising the oil-soluble acid phase, it has been found that quantities ranging from equal volumes of petroleum ether and of the oil-soluble acids to 10 volumes of the former to 1 volume of the latter, produces the best results. The optimum results, however, were found to be produced by the dilution of the acids in two volumes of petroleum ether. This extraction causes the precipitation of a mixture of acids which are herein termed petroleum ether-insoluble acids and which have generally the characteristics described more fully hereinabove. In the example described herein the petroleum ether-insoluble acids weighed 519 grams, comprised 1.36% of the original charge, hadan acid number of I48 and a saponification value of 208.

In order to treat "the petroleum ether-insoluble acids with sulfuric acid in the most advantageous manner it was found necessary first to bring these acids into a more or less dilute solution in a solvent which is relatively inert to the inorganic acid. In most instances preference is given to solvents such as benzene, toluene, or mixtures of naphtha and chloroform. In the present instance the petroleum ether-insoluble acids were dissolved in benzene in the proportion of 1 part of the acids to 9 parts of benzene, the solution being then treatedtwice with 1 volume percent portions of '70,% 'sulfuricacid at roomtemperature. The acid sludges being separated. the treated benzene solution was then extracted with dilute caustic to remove the free organic acids.

therefrom, and the aqueous soap solution thus obtained was decomposed-with a mineral acid to yield approximately 340 grams of organic acids hereinafter referred to as the refined petroleum ether-insoluble acids. The caustic washed benzene solution was then evaporated to yield 65 grams of a material hereinafter referred to as the petroleuimether-insolubleneutrals." By hydrolizing the acid'sludge, asby 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 70 grams, saidfraction being referred 'to-as the sludge acids. Finally, the two aqueous phases representing the wastes from the caustic extraction and the sludge hydrolysis were extracted with ethyl ether or treated by salting out, evapo-- ration, etc., to yield respectively 35 grams and 10 grams of water-soluble acids. Thus, according to the process constituting the objects of the present invention, the petroleum ether-insoluble acid phase has been resolved into four fractions, namely, the acid treated petroleum ether-insoluble acids, the petroleum ether-insoluble neutrals, the sludge acids, and the water-insoluble acids.

substantially distinct in their ical properties.

As stated above, the crude petroleum ether! insoluble acids were comparatively dark and had a high viscosity. Th ese acids had an acid number of about 148, a saponification number of 208, and iodine number of 16.2 and'an acetyl value of chemical and phys- 163. These figures indicate the presence of 0.24

double bond and 1.23 hydroxyl groups per acid equivalent. On the other hand the acid treated or refined petroleum ether-insoluble acids represented a material of a tacky consistency with a dark reddish brown color, the substance being transparent and practically bright red when viewed in thin layers. These acid treated acids had an acid number of 191, a saponification number of 224, an iodine number of 15.4 and an acetyl value of 96. The figures indicate the presence of 0.19 double bond and 0.56 hydroxyl group per acid equivalent. These acid treated petroleum ether-insoluble acids were found to possess the unusual property of forming excellent resins when heated by themselves or with an equivalent quantity of glycerine. This property of resinification is also displayed to some extent by the crude petroleum ether-insoluble acids, but the resins obtained from this latter material have been found to be less satisfactory from the viewpoint of color and consistency. I

The sludge acids had an acid number of 147 and a saponification number of 198. They were found to be highly unsaturated and possessed of a high degree of hydroxylation, which makes this acidic fraction of interest for many uses. Additionally these sludge acids were found to display resinifying properties which, however, do not equal those of the aforementioned acid treated petroleum ether-insoluble acids. As the neutral fraction derived as described above, this was a fluid material with a terpene-like odor having an acid number of 33, a saponillcation value number of around 250 and a saponification value of 361. This fraction thus represents a mixture of water-soluble hydroxy acids-having obvious uses in the various technical and chemical arts. Inthe example described above the oil-soluble phase was washed with water'prior to extraction with alkali. This step isnot necessary and may a be" omitted, in which case it may be desirable to work up the water from the alkali extraction, af-

ter the oil-soluble acids are recoveredtherefrom by acidification, to recover the water-soluble acids present therein. A

That treatment of the petroleum ether-insoluble acids with dior tri-basic oxygen containing inorganic acids may be realized under various conditions. The optimum concentration of the inorganic acid depends on the character of the material treated and its degree of dilution with an inert solvent. Sulfuric acid has been found effective in concentrations ranging from 40 to 95%,, and higher, the most economic concentrations being in the neighborhood of 70-80%. To realize the same degree of treatment with phosphoricacid a slightly higherirange of concentra tion is usually required. The quantity of inor-- In general, sharper separation and more effective treatment is realized by increasing the degree of All of these, as will be shown subsequently are it dilution of the organic acid with the ine solvent, but the optimum dilution from a practical and economic standpoint is from 5 to 15 fold, this rangevarying somewhat with the character of the solvent and of the material to be treated.

It has also been found that the process of treating with inorganic acids in the presence of a solvent as described above with regard to petroleum ether-insolubleacids is alsoapplicable withoutessential modificationto the treatment of other acidic fractions arising in the oxidation of petroleum, e.g.the petroleum-soluble acids, the oilinsoluble phaseand constituents thereof, or the oil-soluble phase in-toto, in which case the unreacted stock may form a portion or all of the diluent-solvent. It is obvious that in these diverse applications the diluent-solvent must be so chosen that it is capable of dissolving the material to be treated. In general it is advantageous to use a solvent with a boiling range difiering from that of the material treated, in order that such solvent as is subsequently dissolved or emulsified in the' v tends to suppress the degree of such emulsification.

rate the neutrals as a separate fraction, the solvent may be removed from the treated material by evaporation or distillation, in which case it is essential that the solvent be of a different boiling range from that of thematerial treated. The acid numbers and saponification values presented herein refer to the milligrams of potassium hydroxide necessary to neutralize or saponify, respectively, one gram of the material in issue.

While the invention is set forth in detail specifically in the examples given hereinabove, it is to be understood that the process is compre- Where it is not deemed advantageous to sepation insoluble in petroleum ether, commingling said acidic fraction with petroleum ether thereby separating an acidic fraction insoluble in said petroleum ether, dissolving said petroleum 'lected from' the class-consisting of benzene, toluene and mixtures thereof with naphtha and chloroform, and reacting said 'solution with an inorganic'acid.

2. A. process for treating products of liquid phase oxidation of naphthenic petroleum oils which comprises separating said products ot oxidation into a phase soluble in the unreacted oils and a phase insoluble therein, commingling said oil soluble phase with an aqueous *alkalisolution to saponiiy the carboxylic acids and the easily saponiflable lactones produced by the oxidation step, separating the aqueous soap solution 'irom th unsaponifled mixture. liberating the acids from said soap solution, separating' the acidic traction thus produced from the aqueous'phase, extracting said acidic fraction with petroleum ether to reject an acidic traction insoluble therein, and treating said petroleum ether insoluble acidic -fraction with an inorganic acid selected from the class consisting of the oxygen-containing diand tri-bas'ic inorganic acids.

3. In a process according to claim 2 wherein the acid treating step is followed by the'removal ether insoluble acldiciractlon in a solvent se-- 4.;A process tortreating products of liquid phase oxidation of naphthenic petroleum oils.

which comprises separating said products "of oxidation into a phaaesoluble' in'the unreactedblls anda phase insoluble therein, :commingling'said oil soluble Phase with aqueous "alkalisolutionto saponiiy; the -carbo'xylle acids and the easily sapon'iflable' lactones produced by the oxidation step, separating the aqueous'soap solution from the unsaponifled mixture, liberating "the acids irom. said soap solution, separating the acidic ether to reject an acidic iraction' insoluble therein, commingling said petroleum ether insoluble acid fraction with a solvent hYWhlch-llld i'raction is soluble, and treating 'said'solution with optimum quantities ofi-suliuric =acidtoiorm an acid sludge and a refined-acid traction having resin-forming characteristics.

s. In a process according to clairn'i-wherein the petroleum ether insoluble acids are dissolved in benzene and wherein the concentration ofv the sulfuric acid employed for the '-'acid treatment ranges mm about '40 to approximately'95%.

6. In a process according to'clai'm 4, wherein the petroleum ether insoluble acids are dissolved in benzene in a quantity or one part of the acids to approximately 9 partsoi benzene and the solution thus'produ'ced is then reacted with sulfuric acid employed in quantities ranging from about 1 to 5 volume percent as calculated "on the basis 01' the volume of the solution treated.

L. BLOUNT.

"traction thus produced iron the aqueous phase, extracting said acidic traction"with petroleum