US2186249A - Process of recovering organic acids - Google Patents

Description

Patented Jan-9,1940 Y i 1 7 UNITED s'rA'rssfrnTEuT om s Arthur Lazar, Berkeley, and Lionel Samuel Gal staun. SanFranoisco, Calif.., minors to Tide Water Associated Oil Company, San'l ranoiloo," Oalif., a corporation of'Delaware No Drawing. Application January 17, 1939. Serial No. 251,444 f v 14 Claim (Ci. zed-4 2) The principal object of this invention is the either frequent replacement of ordinary apparaseparation of naphthenic and other organic acids W5 the use PDM'EW eomtl'llcwd from hydrocarbon materials, such as petroleum p s ve B Y D s. glass. or the like, or any fraction thereof, in such a manner that Third. in the use of cau'stic alkalies", all'types of the reagents used in said separation mayeconomacidic compounds'are extracted from the oil along Ii I ically be recovered and reused in subsequent sepawith the desired naphthe'nicror fatty acids,"e.g., rations. phenolic compounds oi the type 8-'-OH are fex- Another object is the separation of naphthenic tracted to e h r wi h th ir d acids Ofthe acids, or fattyacids, from petroleum or-any or its tyne R-COO a d u ue processing is necfractions in such a mannerthat such separated essary to separate thesetwotypes of bodies. acids are substantially free from phenolic com- Q Naphthenicacids, and particularly soaps of" pounds and other weakly acidic compounds pres- 'naphthenic acids, havev found extensive use in a ent in the petroleum. 1 number of arts. For example, naphthenic acid Other objects will become apparent from the soaps are used as detergentsin the textile indusc following description. r c t try, as blendingagents forspecial lubricants, and

I There are a number of more or less wellesas catalytic drying ingredients of paints and vartablished methods for the recovery of organic ni he 'Depending'on the use tobe made of the acids present in hydrocarbonmixtures such as naphthenic acids. or ofthe: soaps made therepetroleum distillates and 'the like. In general, irom, it isgenerally desirable, and in some cases these methods consist in treating theoils with'an essential, that the 'naphthenic acids be free rom 9 aqueous solution of a caustic alkali, such as. socertain impurities, especially phenols and other dium or potassium hydroxide, or with an aqueous weakly acidic bodies. Freedom from phenols in solution of sodium carbonate in. whlchthegor v particular is an essential requirement for'acids ganic acids combine with the alkali to form water used in the preparation of naphthenlc' soaps for u soluble soaps which enter the aqueous phase. the manufacture of paints and specialized lubril5 Stratiilcationinto two layers is then induced cants. This istruenotonly because metal napheither by settling alone, or else. in case emulsions thenates which are free from phenolates are more form, by heating or adding emulsion breakers. ,compatible'with hydrocarbon materials, but also The aqueous phase is separated and acidified, because the presence of phenolatesproduces unwhereupon-the soaps are decomposed and the free desirable chemical ireactlo'ns. For example, in 80 acids separate out as a distinct layer which may paints; the presence of phenolic bodies tends to then be dried; This layer constitutes as such, resist the normal oxidation-"anddrying of the I crude organic acids. These operations may be paint. Also, in lubricants, phenolic bodies excarried out oncrude petroleum. raw distillates of hlblt a thermal instability detrimental to the use any volatility or viscosity. or distillates that have of the-lubricant at elevated temperatures. been subjected to the usual treating processes, Certain processes are known for removing either with sulfuric acid or with selective solvents, phenols from napthenic acids. but these operate w Such extraction methods with caustic alkalles without the economic recovery ofthe' treating or alkali carbonates have several inherent disagent. This invention overcomes the drawbacks 40 advantages, each of which isobvlated in the pracof conventional processesby the use of a novel, 0

tice oi' this invention. 1 economical and efilcientprocess for removing and First, in order to set free the organic acids from recovering the naphthenic acids in substantially the water soluble soap solution, a sufllcient quanpure form. ,Theproducts oi'this process are subtity of'mineral acid, ordinarily sulfuric acid, is stantially free from phenols, and moreover, can I employed to decompose the soap and, in addition, be prepared very economically because the treat- 45 to neutralize the excess alkali present. Neither ing reagent is recoverable. I the alkali used for extracting the soaps, nor the In general, application of the invention comacid used in their decomposition, are economicprises the treatment of hydrocarbon, or other oily ally recoverable, but on the contrary, are conmaterial, containing acidic material to be re- I vcrtvd into useless salt solutions the disposal of covered with ammonia or an amino compound, or 'which is sometimes burdensome. other basic compound, by the use of which the Second, the presence of any excess sulfuric acid, soaps formed inthe reaction are susceptible to a K which may have been added during the dccomporelatively, simple decomposition yielding the comsition of the soaps causes corrosion of the metals poncnt acidic and basic materials. Coupled. with i do ordinarily used in plant apparatus and resultsin this broad principle;is,thc selective removal of I i of the RP-OH type is contacted with an aqueous solution of ammonia. The desired acids combine with the ammonia to form watersoluble soaps which dissolve in the aqueous phase; the phenols,-

' however, because of their weaker acidic character,

do not undergo this reaction and remain as free phenols in the oil phase. The two phases are separated and the aqueous phase is subjected to distillation. Under the influence of the temperature attained during distillation the ammonium soaps are decomposed, yielding free ammonia and simultaneously releasing the organic acids. The

ammonia ,is recovered by absorption in water in any suitable absorber, such as a packedtower, and may thus be reused repeatedly. The distillation may be discontinued, if desired, when the. ammonia has been substantially removed, and the acids remaining; in the still may then be separated from the remaining waterand driedif desired. Optionally the distillation may be carried to a degree where the water and ammonia are. both removed, leaving the acids in a dry condition. At this point the acids are ordinary'dark colored liquids, the appearance of i which can be greatly enhanced by continuing the distillation, using vaccum with or without steam if desired, after the water and ammonia are removed, thereby'recovering the acids as a separate overhead cut or fraction. Obviously, the distillation of the acids may be performed in the same still as that, used for ammonia distillation or, preferably, such distillation may be performed in a second still or series of stills.

Crude petroleum from anysource, or any of its fractions, whether or not previou ly treated with acid or solvents, maybe used as a source of the desired organic acids. Likewise,- liquid hydrocarbon materialof any nature, containing fatty acids. may be subjected to the process of the invention to extract the fatty acids therefrom. Fractions obtained from California ,crude petroleum, being relativelyrich in organic acidity,

comprise excellent material for the recovery of Although the organic acids from desired acids. all petroleum fractions are valuable products and are amenable to recovery by this process, the lower viscosity fractions, such as gas-oil fractions. comprise apref'erred material to be treated. 'T'h s pre erence is due to the fact that low viscosity oils separate more rapidly from the ammoniacal soap solutions and are more easily treated with the ammonia solution. In treating heavier lubricating oil fractions it is necessary to allow for longer settling times or to accelerate separation bv centrifuging. but it should be understood that the scope of the invention is not limited to the treatment of any particular mation saturated with ammonia under superatmos pheric pressure, and the quantity of ammonia solution used may vary from that containingjust the organic acids.

sumcient ammonia to neutralize the desired acids up to large excesses of ammonia. It is preferable however, to treat the petroleum, or fraction, with a solution containing from 4% to 30% by weight of ammonia, in quantities corresponding up to 1000% excess. The use of such a large excess is advisable for two reasons. First, it provides suflicient aqueous phase for proper separation. Second, it insures complete extraction of In general, the use of solutions more dilute than 4% ammonia usually results in excessive emulsification.

If desired, an emulsion breaker, such as methyl or ethyl alcohol, acetone, or a saturated solution of a salt such as sodium chloride, may be incorporated in the ammonia solution or added to the mixture of oil and ammonia solution before or after agitation, or even after partial settling. Such an emulsion breaker may be desirable to reduce the time necessary for complete separation or to obtain the recovered organic acids less contaminated with hydrocarbons. Although ammonia solutions have been described above as the treating agent of our process, the process also contemplates the use of volatile amines, such as the lower alkyl amines, ethyl or methyl amines, or ethylene diamine, which have the necessary alkalinity, to combine with the naphthenic or separated by distillation. Alkylol amines, such as monoethanolamine, di'ethanolamine, triethanolamine, propanolamine, iso-propanolamine and similarcompounds may be used. DiethanoL amine and triethanolamine are less desirable due to their high boiling points and tendency to form emulsions.

)The following examples illustrate practice of I the invention in a pilot plant and are given merely as illustrations. EXAMPLE 1 a 25 gallons of gas oil were contacted with 1 gallon of 10% ammonia in aqueous solution at atmospheric temperature. The mixture was allowed to settle over night whereupon the contents of the agitator were found to be stratifledinto essentially two layers, with a very small intersorber and the condensate contained the recovered aqueous ammonia. The residue from this distillation consisted substantially of organic acidsresulting from the decomposition of the water soluble soap solution. The organic acids recovered were. freeof phenols which remained in the upper oil layer.

The gas oil used in. the above example was obtained from a Central California crude oil,

commonly knownto the trade as Coalinga Crude, and had the following properties:

Table 1 Gravity; 26.0 A. P. I. 1 Viscosity 4'7 sec. S. U. 100 F. A. S. T. M. distillation:

' I. B. P 469 F.

% ll l 556 F.

E. P 730 F.

Front the above treatment of this gas oil the iollowing yield of organic acids was obtained.

Table 2 Yield of crude aclds 0.8% of'the acid oil Analysis of crude acids: v

Hydrocarbons 38.0% Acidic substance"--- 62.0% Analysis of acidic substances: Naphthenic acids 100.0% Phenolic compounds- 0.0% Equivalent weight of naphthenic acids 277 (by titration) Yield of naphthenic acids. 0.5% of acid 011 EXAMPLE 2 The treatment in Example 1 was repeated with the exception that the extracting agent used was 1 gallon of alcoholic-aqueous ammonia having the following compositions: Ammonia 10%. Water 68% Ethyl alcohol 22% In this case the separation of the soap layer occurred rapidly, and was complete without the interphase emulsion noted in Example 1.

The alcohol was found to be substantially in the aqueous phase and was recovered with the By this treatment theamount'of' ammonia. hydrocarbon contamination of the naphthenic acids was reduced, as seen from the following:

Table 3 Yield ofcrude acids 0.8% of acid oil Analysis of crude acids:

Hydrocarbons Acidic substances Analysis of acidic substances:

Naphthenic acids 100% Phenolic compounds 0% Equivalent weight of naphthenic acids 270 Yield ofnaphthenlc acids 0.58%

To test the efllciency of the extraction of the organic acids by the use oi. this process, as com+ pared to the conventional use of sodium 'hydroxide, 25 gallons of the gas oil were agitated with 1 gallon of 0.3% sodium hydroxidesolution; After settling ldhours, the alkaline soap layer was separated and acidified with an excess of sulfuric acid. The yield of naphthenic acids as follows:

I Table 4 Yield of crude acids Analysis of crude acidst Hydrocarbons 28% Acidic substances 72% Analysis of acidic substances:

Naphthenic acids 96% Phenolic compounds 4% Equivalent wt. ofnaphthen acids 277 Yield pure naphthenic acids 0.62%

From the above examples it is evident that by the practice of our invention it is possible to selectively obtain naphthenic acids substantially free from phenolic compounds by a simple extraction.

If it is desired to obtain naphthenic acids free from the entrained hydrocarbons, use may be' made of their difference in volatility. For example, a laboratory fractionation conducted in a obtained'was 0.88% p of acid 011 mea still, using ilask with a three inch length of V4" by i 500 ml. "Pyrex" distilling v prym ring packing in the neck, yielded the fol- 1 lowing figures; for the hydrocarbon content of successive 10% cuts.

Charging stock: 200- ml. of c'rude acids substantially free from phenolic compounds and containing 28% hydrocarbon matter.

. Table 5 Percent Percent "1 Percent Fraction hydro Fraction hydro- Fraction hydrocarbon carbon I carbon 0-10 9e 21 6o-7o 0 10-20 75 40-60i'- 10 70-80"... 0 20-30. 40 50-60..." 4 -93"..- 0

7 With the highly efficient fractionation possible in industrial scale equipment, a sharper separation is'easily. obtainable.

ExAm'Lr: 3. As a further-example of similarly treating a gas oilcontaining naphthenlc acids of average molecular weight about 290, the oil was treated with 4% by volume of ammonia of varying concentrations, and also with 4% ethylene diamine.

The-results are as'follows:

Similarly, .a treatment with 6% of a 100% monoethanol amine yielded 55% of crude acids giving a yield of 0,48%."naphthenic acids and no phenolic compounds in the said acids.

At the lower percentage treating rates of about 4%, due to thelow concentration oi. basic material, complete recovery of the acids is not pos- 'sible and a certain percentage of the acids will,

remain in theoil either as free acids, or scans. or both, from which the soaps maybe recovered by further washing, or repeated washing with basic material, purify the oil- Howevenit is generally more desirable to use i 'a percentage of basic material'and a concentration thereof sufficient to recover a high percent,- age of acids, irrespective of whether the object organic acids.

if the object is to completely.

is to purify the oil-or simply to selectively recover Any hydrocarbons contained in the crude acids recovered may .eas'ily be removed by well known methods.

.While the above descriptions refer to a'batch process, the method is readilycapable of execution in a continuous system. For this purpose satisfactory types of continuous extractors and stills will be readily apparent to one skilled in' the art.

With heavier streams, emulsion difiiculties may be encountered and under such cases the extraction is successfully carried out under conditions of high temperature in a closed system, under elevated pressure. With the more viscous streams, many systems for using ipacked towers .in countercurrent continuous treatment are available to insure proper contact between the acid oil and the aqueous the time of contact.

When the treatment is carried on at elevated temperatures for the purpose of reducing emulsion difliculties, care should be taken to maintain the lowest temperature which will bring about the desired reduction in viscosity of the oil. At eleammcnia and to prolong vated temperatures, particularly above C.,

ammonia has a tendency to react with organic acids to form acid amides. These acid amides, if present, would not be decomposed during the subsequent distillation of the process but'would remain dissolved in the extracted acids. .When thus contaminated, the extracted acids require treatment with mineral acid to decompose the acid amides according to the following equation:

for the reaction and, consequentlyit isat times-- prefereable to dilute viscous oils with non-viscous solvents, such asfor example naptha or, gas oil, than to use high temperatures to reduce the viscosity. However, in other cases, treatment at temperatures as high as 60 to 80 C. may prove advantageous.

In the foregoing description and examples it has been shown how ammonia or its derivatives maybe'used to selectively extract the stronger organic acids free from weakly acidic phenolic compounds. The invention contemplates, moreover, the separation of stronger acids, readily reactive with weak volatile bases, from all types of weakly acidic substances, of whichthere are a great number present in petroleum. For ex-. ample, naphthenic acids can be successfully separated from a petroleum fraction containing undesired mercaptans using ammonia as an extractant. I

The invention also contemplates the puriflation of organic acids which are contaminated with organic matter such as hydrocarbons, phe- I "nols, and the like.

By first diluting the organic acids with a suitable solvent, for example, with a light oil, organic acids in substantially pure form may be obtained by the process. 7

This application is a continuation-in-part of our copending application Serial Number 155,562, filed July 24, 1937.

We claim:

1. The process of separating organic acids from oily material containing the same, which comprises: treating said oily material containing organic acids with a basic reagent of higher volatility than said acids whereby soaps are formed and at a temperature below that at which amides tend to be formed, separating said soaps from said oily material, then dissociating said soaps by distillation to separately recover the organic acids and basic reagent.

2. The process according to claim 1 in which the basic reagent is ammonia.

4. The process according to claim 1 in which the basic reagent is alkylamine.

5. The process according to claim 1 in which the basic reagent is an alkylolamine.

6. The process according to claim 1 in which the basic reagent is ammonia in aqueous solution between about 4% and 30% by volume of the oily material.

'7. The process of separating organic acids from oily material containing the same, which comprises treating a petroleum distillate containing naphthenic acids with a basic reagent of higher volatility than said acids whereby soaps are formed and at a temperature below that at which amides tend to be formed. separating said soaps from said. oily material, then dissociating said soaps by distillation to separately recover the organic acids and basic reagent.

8. The process of separating organic acids from oily material containing the same, which comprises: treating said oily material containing I organic acids with a basic reagent of higher volatility than said acids together with sufilcient alcohol to prevent substantial emulsiflcation whereby soaps are formed and at a temperature below that at which amides tend to be formed, separating said soaps from said oily material,

then dissociating said soaps, .by distillation to separately recover the organic acids and basic reagent.

3. The process according to claim 1 in which 9. The process of selectively recovering organic acids from petroleum hydrocarbons which comprises: treating petroleum hydrocarbons containing organic acids of the R-COOI-I type and R-OH type with from about 4% to 30% by volume of a basic amino reagent of higher volatility than said acids whereby said R-COOH type acids alone are saponifled, removing said saponified product from said hydrocarbons, then distilling said product to separately recover said basic reagent and said acids.

10. The process of recovering organic acids from petroleum hydrocarbons which comprises: treating petroleum hydrocarbons containing naphthenic acids and phenols with from about 4% to 30% by volume of aqueous ammonia to selectively saponify said naphthenic acids, separating the soaps formed as an aqueous solution, then fractionally distilling said solution to separately recover an aqueous solution of ammonia and said naphthenic acids.

11. The process of selectively recovering organic acids from oily material containing the same, which comprises: treating a petroleum distillate containing relatively strong organic acids and relatively weakly acidic organic compounds with a basic reagent of higher volatility than said stronger acids whereby soaps are formed, separating said soaps from said distillate, then dissociating said soaps by distillation to separately recover said stronger acids and said basic reagent.

12. The process according to claim 1 in which the basic reagent is an aqueous solution of a soap =forming derivative of ammonia.

13. The process according to claim 1 in which the basic reagent is an aqueous solution of an alkylamine.

14. The process according to claim 1 in which the basic reagent is an aqueous solution of an alkylolamine.

ARTHUR LAZAR. LIONEL SAMUEL GALSTAUN.

' CERTIFICATE OF CORRECTION. Patent No. 2,186,2u9. J y 9, 9

ARTHUR LAZAR, ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, second eolumr' 'line 7, for "'8OH" read R-OH; page2, first'column, line 5h, for the word "ordinary" read ordinarily; line 57, forv "vaccum" read vacuum; page 5, first column; line 18, after "treatment" insert given; and that the said Letters Patent should be-read with this correction therein 'that the same ma'yconform to the record of the case in the Patent Office. I

Signed and sealed this 5th dayof March, A. 1). 19m.

v Henry Van Arsdale,

(Seal) Acting Commissioner of Patents.