US2357252A - Process for the recovery of phenols - Google Patents

Description

. by caustic treatment Patented Aug. 29, 1944 UNITED STATES PATENT orrlce 2,357,252 PROCESS FOR THE RECOVERY OF PHENQLS Henry G. Berger,

8. Angel, Woodbury,

' Vacuum Oil Company,

Edwin M. Nyraard, and Henry N. 3., assignors to Soconylneorporated, New York,

,N. Y., a corporation or New York No Drawing.

Application January 3, 1942, Serial No. 425,518

4 Claimsr (Cl. 260-627) substantially pure phenols are recovered from the aforesaid liquors. v

The process contemplated by the present invention comprises the following sequence of operations. The caustic liquor obtained from a caustic treated petroleum fraction and which contains phenolates, naphthenates and mercaptides is acidified with a mineral acid, such as acidification of caustic liquors from caustictreated petroleum fractions.

As is well known to. those familiar with the art, crude petroleum oils and distillate fractions obtained therefrom contain constituents other than compounds consisting only of carbon and hydrogen. Among these are compounds containing sulphur, nitrogen, oxygen, etc. Generally,

such oxygen compounds are represented by phenols, naphthenic acids, etc., and such sulphur compounds by mercaptans, thiophenes, disulfldes,

etc. Various methods are employed to extract these compounds from the petroleum fractions and methods have been proposed for recovery of the phenols so removed from the mixture in which they are extracted. Usually, phenols, naphthenic acids and mercaptans are removed from petroleum fractions containing these compounds by treatment with strong aqueous or alcoholic caustic solution. Such treatment converts phenols to phenolates, naphthenic' acids to naphthenates, and mercaptans to mercaptides. Then, the caustic solution containing phenolates, naphthenates and mercaptides is separated from the oil. The caustic solution is then oxidized with H202, C12, 02, etc., to convert mercaptides to disulfldes, which are insoluble in the caustic solution and separate as an oil, which is withdrawn from the mixture. This procedure is unsatisfactory, however, for part of the phenols are destroyed by degradational oxidation; the undestroyed phenols remain in solution as alkali metal phenolates in combination with the alkali metal salts of the naphthenic acids; and some disulfides remain occluded in the caustic solution. Thus the processes proposed in the prior art do not provide for the complete removal of sulphur compounds, and do not provide for the production of substantially pure phenols.

The primary object of this invention is the recovery of substantially pure phenols from liquors obtained by caustic treatment of petroleum fractions. We have discovered a process which inmercaptans.

HCI, H2804, etc., thereby converting said phenolates, naphthenates and mercaptides to the corresponding phenols, naphthenic acids and mercaptans. Upon acidification two phases, an oil phase and an aqueous phase, are formed. A separation is eflected of the oil phase containing phenols, naphthenic acids and mercaptans, and the aqueous phase containing inorganic salts and small quantities of phenols, naphthenic acids and This aqueous phase may be discarded; or, may be extracted with a small quanvolves a novel sequence of operations by which tity of a water-immiscible organic solvent whereupon the organic solvent layer containing the small quantities of phenols, naphthenic acids and mercaptans, and the aqueous layer are separated,

and the organic solvent-extract combined with the oil phase containing the main body of the phenols, naphthenic acids and mercaptans. The oil phase, with or without the organic solventextract, which'is hereinafter referred to as acidified caustic liquor, is then distilled with steam or vacuum, and the distillate extracted with a water-inuniscible organic solvent. This solvent extract is then admixed with an alkalicarbonate in aqueous solution in an amount suificient to convert said naphthenic acids to the alkali naphthenates. A separation is efiected of the resulting layers, the aqueous alkali carbonate layer containing the naphthenates and the organic solvent layer containing the phenols and mercaptans. To the organic solvent layer are added an aqueous alkali hydroxide solution and elementary sulphur in amounts sufflcient to convert the mercaptans to disulfides and the phenols to phenolates. This mixture is agitated, and then allowed to settle whereupon two layers, an alkali hydroxide layer and an organic'solvent layer, are formed. The alkali hydroxide layer containing the phenolates and the organic solvent layer containing the disulfides are separated. The aqueous alkali hydroxide layer is acidified to liberate the phenols. The liberated phenols may be separated from the acidified aqueous solution and purified by distilling with steam. Or the liberated phenols may be extracted from the acidified aqueous solution with a water-immiscible organic solvent in which the phenols dissolve.

In this latter case the acidified aqueous layer and the organic solvent layer containing the phenols are separated and the organic solvent evaporated from the latter phase to obtain the purified phenols.

Considered in another way, the present invention also contemplates the recovery of substantially pure phenols from acidified caustic liquids containing phenols, naphthenic acids, and mercaptans obtained by acidification of caustic liquors from caustic-treated petroleum fractions. For example, in view of the space required to transport the caustic liquors and difilculties encountered during such, it has been found more convenient to transport the acidified caustic liquor rather than the untreated caustic liquor. The acidification of the caustic liquor as in the procedure described above is .followed by a separation of the oil phase from the aqueous phase; and it is the oil phase thus obtained, to which may or may not have been added an organic solvent-extract as described above, which is subjected to further treatment. This oil phase or "acidified caustic liquor" is first distilled with either steam or vacuum, and the distillate treated as given above.

Petroleum fractions the treatment of which yields caustic liquors suitable for the purposes of the present invention, are those containing phenols, naphthenic acids and mercaptans. Broadly, thermally or catalytically cracked petroleum distillates are suitabl for the process described herein.

Caustic liquors, as described herein, are those liquors obtained by caustic treatment or caustic washing of petroleum fractions Alkali hydroxides such as sodium hydroxide, potassium hydroxide, etc., are useful for this purpose, and sodium hydroxide is preferred in view of its lower cost.

Organic solvents having the property of immiscibility with water serve the purposes of this invention. Preferred solvents of this type are benzene, ether, chloroform, carbon tetrachloride, etc., and low boiling petroleum distillates, such as, for example, petroleum ether.

The following illustrative example is given order to demonstrate the invention:

EXAMPIE An acidified spent caustic wash liquor containing a crude mixture of phenols, naphthenic acids and sulphur compounds, and represented by the data given in Tables I and II, was treated as described below:

306 grams of the crude material were distilled at atmospheric pressure to a vapor temperature of 101 C. The undistilled residue was now vacuum distilled to a vapor temperature 01' 140 C. The undistilled residue was discarded.

The combined distillates were dissolved in benzene and extracted with several hundred c. c. of

strong sodium carbonate solution. Enough water was added to dissolve the voluminous white precipitate. The extraction with sodium carbonate. was repeated until there was no further evolution of carbon dioxide. The aqueous sodium carbonate layer containing the naphthenates was separated from the benzene layer containing the phenols and mercaptans. The sodium carbonate extracts were acidified with hydrochloric acid. The liberated naphthenic acids were extracted with petroleum ether and the petroleum ether evaporated. The residue represents naphthenic acids.

To the material left unextracted by the sodium carbonate treatment containing phenols and sulphur compounds in benzene solution were added 348 c. c. of 10% sodium hydroxide solution and sufficient sulphur dissolved in benzene to convert the sodium mercaptides to disulfides. After agitation of this mixture the layers were separated. Evaporation of benzene from the benzene extract left the disulfides as a residue.

The aqueous caustic layer was acidified with hydrochloric acid and the liberated phenols extracted with'diethyl ether. The acidified aqueous layer was separated from the diethyl ether layer containing the liberated phenols. The ether was evaporated from the phenol-containing ether layer, and the phenols remained as a residue.

Results of this illustrative example are summarized in Table III given below:

TABLE III Summary of data on products obtained after processing Original material Grams Percent of Percent Percent Product total isolated total sulphur sulphur Sulphur compounds neutral oil. 48. 5 16. 0 4. 5 0. 72 Naphthenic acid 78. 0 25. 5 0. 7 0. l8 henol 86. 0 28. 0 0. 6 0. l7 Residue 25. 0 8.2 11. 9 0. 95 I Represented by Loss Hi0 content..- 22.0 7. 2 By manipulation... 46. 5 15. 3

From the above data, it is apparent that substantially pure phenols can be recovered from the caustic wash liquors of petroleum fractions by employing the hereinbefore described process. As given in Table I, the sulphur content 01' the original material is 2.72, and in Table III, the

sulphur content of the purified phenols is onlyand naphthenic acids separated from an aqueous phase after acidification of an aqueous caustic solution containing mercaptides, phenolates, and naphthenates which comprises, distilling the oil phase; dissolving the distillate in a water-immiscible organic solvent and admixing the solution with an alkali carbonate in aqueous solution in an amount just suflicient to convert said naphthenic acids to the alkali naphthenates; separating the aqueous alkali carbonate layer containing the naphthenates from the organic solvent layer containing the phenols and'mercaptans, adding to the organic solvent layer an aqueous alkali hydroxide solution and elementary sulphur in amounts sufiicient to convert the v mercaptans to disulphides and the phenols to phenolates in separat phases; agitating'the mixture; separating the alkali hydroxide layer containing the phenolates from the organic solvent layer containing the disulphides; acidifying the aqueous alkali hydroxide layer to liberate the phenols; and separating the liberated phenols from the acidified aqueous solution.

'2. A process as claimed in claim 1 in which the separation of the liberated phenols from the acidified aqueous solution comprises extracting the acidified aqueous solution with a water-irnmiscible organic solvent to dissolve the phenols;

- separating the aqueous layer from the organic solvent layer containing the phenols and removing the organic solvent to obtain the purified phenols.

K 3. A process as claimed in claim 1 in which the liberated phenols are purified by distillation with steam. r a 4 4. A process for the recovery of phenols from an oil phase containing phenols, mercaptans, and

naphthenic acids separated from an aqueous phase after acidification of an aqueous caustic solution containing mercaptides, phenolates, and naphthenates which comprises, distilling said acidified caustic liquor with vacuum; dissolving the distillate with benzene and admixing the benzene solution with sodium carbonate in aqueous'solution in. an amount suificient to convert said naphthenic acids to the sodium naphthenates; separating the aqueoussodium carbonate layer containing the naphthenates from the benzene layer containing the phenols and mercaptans; adding to the benzene layer an aqueous sodium hydroxide solution and elementary sulphur in amounts s'umcient to convert the mercaptansto disulphides and the phenols to phenolates;