US2163227A

US2163227A - Process for desulphurizing alkyl phenols

Info

Publication number: US2163227A
Application number: US175876A
Authority: US
Inventors: Walter J Hund; Thomas Samuel Benson; Jr Daniel B Luten
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1937-11-22
Filing date: 1937-11-22
Publication date: 1939-06-20
Anticipated expiration: 1956-06-20

Description

Patented June 20, 1939 UNITED STATES PATENT OFFICE PROCESS FOR DESULPHURIZING ALKYL PHENOLS pany, San Francisco, Calii'., a

Delaware corporation of No Drawing. Application November 22, 1937,

- Serial No. 175,876

11 Claims.

This is a continuation-in-part of our copending application Serial No. 144,658, filed May 25,

1937, and relates to an improvement in the methd of purifying alkyl phenols containing aromatic mercaptans i. e., thiophenols and other organic non-mercaptan sulphur compounds. More particularly it deals with an improved method for desulphurizing alkyl phenols recovered from petroleum oils by highly efllcient extraction means.

In the above mentioned co-pending application Serial No. 144,658, we have shown that in a order to recover the largest portion of alkyl phenols from petroleum oils, methods of extraction must be employed which yield extracts containing besides the alkyl phenols high percentages of impurities, notably neutral oils, carboxylic acids, and sulphur and nitrogen com pounds. Some of these impurities are removed from the alkyl phenols with extreme diillculty only, and the expenses due to consumption of chemicals and losses of alkyl phenols are often excessive.

We have further shown that by a process in which a series of individually known steps is carried out and combined in a certain manner, good yields of commercially pure alkyl phenols, i. e., which are sufliciently pure to meet commercial requirements, are obtained at a much lower cost than has been possible heretofore. This process consists essentially of the following steps:

(1) Extracting a petroleum oil containing alkyl phenols, while in the liquid state, with an aqueous alkali metal hydroxide solution of an original concentration of 35-50% under conditions to form two layers and separating the layers:

(2) subjecting the aqueous layer to a prolonged steaming with substantially saturated steam to drive off certain impurities and to precipitate a sludge which is separated, and continuing to steam until no further sludge precipitates;

(3) carbonating the steamed clear liquid aqueous layer with carbon dioxide to liberate alkyl phenols, thereby forming two layers, and separating the layers;

(4) rapidly distilling the liberated alkyl phenols under vacuum;

(5) if desired, further purifying the distilled alkyl phenols by oxidation, preferably with air at a temperature between about 140-150 C. followed by redistillation, and the redistilled product may further be blown at about room temperature to remove possible foul odors.

The distillates resulting from Step 4 contain as their main impurities sulphur compounds, largely in the form of aromatic mercaptans, i. e., thiophenols, and the object of the subsequent oxidation step is mainly to eliminate these thiophenols.

It is a purpose of the present invention to improve the above process, particularly the oxidation step, so that commercially pure alkyl phenols of even lower contents of thiophenols and other sulphur compounds can be had, if possible, at no increased cost. In some instances where an exceptionally low sulphur content is required, consumption of treating chemicals may, however, have to be raised.

One of the difliculties of our former procedure consisted of the necessity of having to carry out the oxidation with air at relatively high temperatures, because at lower temperatures the rate of oxidation of thiophenols to disulphides is too slow in, most cases. With increasing tem peratures the rate increases; however, at the same time undesirable side reactions set in, some of which consume alkyl phenols and lead to the formation of dehydrogenated products of unknown composition.

Furthermore it is sometimes diflicult, if not impossible, to remove by distillation at least a portion of the disulphides from alkyl phenol mixtures, particularly if the latter has a long boiling range, because relatively low boiling thiophenols may form disulphides boiling within a boiling range of the higher boiling alkyl phenols. Moreover at the relatively high temperatures of distillation, even when distilling under high vacuum, aromatic disulphides may be reconverted to thiophenols.

Now we have discovered that the oxidation of thiophenols in the alkaline state proceeds satisfactorily at about room temperature. At this temperature undesirable reactions do not take place to a material extent. With increasing temperature the rate of oxidation of thiophenols to disulphides increases, but at the same time a reversal of this reaction, namely reduction of disulphides to thiophenols at the expense of alkyl phenols also accelerates. Therefore, temperatures substantially above room temperature not only fail to give better conversions of thiophenols to disulphides, but may result in material losses of alkyl phenols.

We have found that at temperatures above about to C. the reversed reaction proceeds at such a rapid rate that for practical purposes no oxidation of thiophenols to disulphides takes place, and alkyl phenols only are attacked. Similarly, if an alkali alkyl phenolate solution containing disulphides is heated to about 90 C, or higher, thiophenols are reformed rapidly and alkyl phenols are oxidized even in the absence of air. For these reasons we maintain during the oxidation and afterwards as long as disulphides are present temperatures below about to C. and preferably below about 50 C. At 50 C. or lower the reformation of thiophenols from disulphides is sufliciently slow so that oxidation of thiophenols to disulphides and sepa ration of the latter from the alkali alkyl phenolate solution can be achieved without appreciable loss of alkyl phenols.

In addition to enabling satisfactory oxidation with air without undue interference from side reactions, when operating in the alkaline state at about room temperature, this method has the further advantage of making possible easy separation of the disulphides from the alkali alkyl phenolate solution as will be described later.

Accordingly the present invention comprises the steps of effecting the oxidation of sulphur compounds and in particular thiophenols, conpending application. By so doing no chemicals 7 in excess of those used in our older process are required, and yet after carbonation and vacuum distillation of the liberated alkyl phenols a product is obtained which has a sulphur content considerably lower than that obtainable by air blowing the free alkyl phenols in the acid state after completed vacuum distillation as was formerly done.

An alternative method which may have to be resorted to, where sulphur requirements are exceedingly low, consists of redissolving the liberated vacuum distilled alkyl phenol in a suitable alkaline liquid medium to produce a phenolate solution, air blowing the latter at about room temperature, separating disulphides, and reacidifying the blown solution to liberate the alkyl phenols.

If desired, both modifications may be combined, i. e., the alkyl phenolate extract after being steamed and separated from precipitated sludge is air blown, disulphides are separated, and the blown solution is carbonated to liberate the alkyl phenols. The alkyl phenols are vacuum distilled, redissolved in a suitable alkaline medium and the resulting solution is again blown with air. Disulphides are separated, the blown solution is acidified and liberated phenols may be redistilled.

The entire extraction and treating process is as follows:

A petroleum .oil containing alkyl phenols, such as a cracked distillate boiling between about to 300 C. is extracted with an aqueous solution of an alkali metal hydroxide.

The step of extracting the petroleum oil consists essentially of treating the liquid oil with an amount of an aqueous. alkali metal hydroxide solution, preferably sodium or potassium hydroxide, of an original concentration of 35-50%, which amount contains a quantity of free hydroxide only slightly in excess of that required to convert caustic alkali solution of about 35-50% concentration a precipitation of phenolates takes place, and upon further addition of a certain minimum critical amount of alkyl phenols, which amount is less than that required to consume all of the free alkali metal hydroxide, the precipitated phenolates are redissolved in the aqueous phase. Thus by adding to an alkali metal hydroxide solution of the above strength the minimum critical amount of alkyl phenols required to form a single aqueous phase of phenolates, a solution is obtained which contains besides the phenolates considerable quantities of free alkali metal hydroxide. This critical amount varies considerably with the concentration of the hydroxide and the type of alkyl phenols added. For instance, when using a mixture of alkyl phenols of an average molecular weight'of xylenols, the critical amount required to produce a single phase would be as follows for aqueous sodium hydroxide solutions of various concentrations:

Critical amount of alkyl phenols percent by weight of solution Original concentration of NaOH in caustic solution Per cent 35 cats.

The resulting phenolate solution containing free alkali metalhydroxide is the most effective extractant for alkyl phenols from hydrocarbon oils, if contacted with the oil in the proper proportion. The amount of alkaline alkyl phenolate solution used to treat a given amount of oil containing alkyl phenols should be such that the amount of alkyl phenols in the oil is sumcient to convert a portion only of the free alkali hydroxide to alkali phenolates, and the enriched phenolate solution thus produced should preferably contain phenols after this extraction. A portion of the phenolate solution is then withdrawn from circulation to be treated as will be described hereinafter. The remainder of the alkyl phenolate solution is mixed with'an amount of fresh caustic alkali solution of 35-50% concentration sufficient to replace the amount of alkali metal withdrawn before, and the resulting mixture containing free alkali is again contacted with fresh oil as described above.

While by this method of extraction substantially complete removal of alkyl phenols from petroleum oil is accomplished, the alkyl phenols so extracted are highly contaminated with impurities. Besides alkyl phenols, other substances are dissolved in the aqueous phenolate solution, notably naphthenic and other carboxylic acids,

neutral hydrocarbons, sulphur compounds, n11 V trogen bases,' r'esinous bodies, etc.,-and in addition the-aqueous'solution may contain varying- "amounts of emulsifiedheavy tarry material, part,

of which may settle out, upon prolonged s'tanding Alkyl phenolsliberated.from-the'untreated phenolate solution by' acidification -may contain lfl ormore .per cent of'neutral oil, sulphur in" excess ..of 1%, andinit'rogen bases as high as 6 -to a prolonged.steamingpreferably at substantially normal pressures and with substantially saturated; steam. The use of highly; superheated almostimpossible to obtain by any subsequent treatment, or combination .of simple treatments, except by double use of alkali metal hydroxide extraction {and acidification as forinstance described-by Merrill in U. S. Patent 2,000,244, alkyl phenols of sufficient stability and purity vto meet even the most liberal commercial requirements. I

During the early stages of the steaming perio'd,

neutral oils; nitrogen bases, sulphur compounds and a small portion, amounting'to less than l of the alkyl phenols of relatively -l ow uacidities are vaporized .and removed overhead. Steaming, however, must be continued for some timeafter the removal of the volatilizable compounds has is recognized when the exhaust steam, upon con- 1 densation, no, longer turns turbid. While steaming proceeds, sludge is being formed and precipitated,-.and when the phenolate solution is al-, lowed to rest, two-separate layers form, an aqueouslayer and a heaviersludge layer. fUpon continued steaming the amount of sludge formed eventually "reaches a maximum, so that when i the sludge is separated andjthe desludged aquepouslayer is further steamed, no additional sludge is formed; The time of steamingrequired to reach this point of maximum sludge formation normally varies between about 4 and 16 hours, alkyl phenolates derived from relatively lowboiling distillateslnormally requiring shorter time for-complete steaming than'alkylphenolates obtain'ed 'from heavier oils. a

: It, is absolutely essentialjthat steamingbecartion; I While thereactions responsiblefor 'the'for, ination disludgeiarenot quite understood, it ap-1 ofrre'moving neutral oils which act as disp'ersers for actual slud 'er i. e.-, sludge-which' 'ispresent which take place during the steaming after re-.

The, phenolate solution containing 2 neutral, basic "and; sulphurousimpurities is now subjected process. 'Unless it is carried far enough it isbeen substantially completed. This latter point j 'ried out to the-maximum; point of; sludge forma- I v commercially pure alkyl phenols in +pe'ars -that its production is. due to a combination from, the beginning; and condensation'freactions the phenolate solution.

solution contains emulsified organic matter other than sludge, which refuses to separate: at this point; In such a case diluting the phenolate somovaljrof neutral oils-and lead to the formation of;-additional-sludg e, for convenience called herein gpotential" sludge f Apparently nitrogen" :bases' take actiYefpartQJin {these condensation'-- reactions iforr'nirig, high-"boiling 'compounds,- and although; a considerable portion of; the-nitrogenous. condenv sationproducts mayremain in the: alkalinesolu i ftio'n- -after steaming, th'e'y 'la-ter. form partof the 'ftarryiresldue'produced'in the subsequent vacuuinulsnnauon of the liberated alkyl phenols.

'It" appears that considerable time is required to condense the nitrogen bases, and if. steaming is the unreacted portion thereof will go overhead in -the subsequent vacuum distillation jointlywith I .the alkyl phenols. 'Slnce nitrogen bases, -to-.- gether with sulphur compounds arethe most harmful and obnoxious. impurities .in commercial alkyl phenols, it is readily seen how importantv it is to conduct the steaming to the point of maximum sludge formation.

-' We'are aware that alkyl phenols have been pro'duc'edby extracting coal tars with aqueous caust-ic alkali solution, blowing the extract with 'steam,,liberating the phenols and distilling and 'blowing'same with air. However, in contrast to the above, phenolate solutions obtained from coal tar distillates wlth'alkali metal hydroxide solutions of customary concentrations, which are generally much lower than those hereinbefore described, do not produce sludge upon steaming, perhaps because phenolate solutions obtained with relatively weak .alkali hydroxide solutions are comparatively little contaminated with im- 1 phenols in petroleum oils is usually below 5% and. more often about ..1% or below. Obviously more effective means of extraction must-be applied to petroleum oils than to coal-tar distillates, and thegreater .efficlency of extraction is at least partly responsible for the greater dimculties experienced in the subsequent refining of the alkyl phenols, impurities which are normally associated with petroleum being extracted as well.

Aside from the relative amounts of the respective impurities, it also appears that there are considerable diiferences regarding their nature. As pointed out before, in petroleum alkyl phenols a class of little known nitrogen bases constitutes the most harmful impurities, which nitrogen compounds seem to be almost completely absent from coal tar phenols. For this reason theextent of the steaming just sufficient to remove neutral oils has proven adequate in the purification of coal tar phenols, but in the case of purification of petroleum phenols has met with failure; and

longed .to. give time for the condensation reactions'described above it was impossible'to obtain the simple manner proposed by us.

, When the steaming has progressed-so that up .on further steaming no additional-"sludge is formed; the precipitated sludge is separated from Usually the 'desludged lution with at least an equal volume ofwater willr eadily break the emulsion. We have found it very convenient as a rule to dilute the solution gto about.10%. If this doesnot produce a com plete. break of the'emu'lsion, resort may be-had fto centrifugation or filtration'through a suitable too short. condensation remains incomplete and before our discovery that steaming must be pro- I 4 amass? medium which is preferentially wetted by the organic matter.

The phenolate solution is now perfectly clear and of much lighter color than before steaming, since neutral oils capable of dissolving sludge have been removed substantially quantitatively as well as most sludge-forming compounds and a portion of the sulphur compounds. This clear phenolate solution may now be blown with air at temperatures between about and 90 C. and preferably below 50 C., for instance at about normal room temperatures. Attemperatures below 0 C. the rate of conversion of thiophenols to disulphides is too low to be practical, and at temperatures above about 90 C. the reversion of disulphides to thiophenols proceeds at such a rate as to prevent accumulation of disulphides, and results'in losses of alkyl phenols, as has been described hereinbefore.

The time required for blowing in the absence of catalysts may be of the order of to 60 hours depending upon the exact temperature of blowing, the sulphur content of the alkyl phenols, the desired degree of desulphurization, etc. Oxidation catalysts may be added to accelerate the rate of formation of disulphides. Suitable catalysts are, for instance the metals, oxides and sulphides of copper, lead, manganese and ferrous metals,

or mixtures thereof, in particular the nickel and lead sulphides. However, other known oxidation catalysts may also be used.

The disulphides formed in the oxidation are largely insoluble in the phenolate solution. They are compounds of high wetting powers for silicates, metals and many other solids and consequently tend to adhere to them. They may be separated from the phenolate solution by conventional method such as settling, centrifuging, flltering through a filter bed of solids; or washing with a hydrocarbon solvent such as naphtha, benzene, or other suitable organic liquid which is immiscible with the phenolate solution and which does not extract phenols from phenolate solutions to an appreciable extent, or by a combination of these methods. Frequently the disulphides appear as a finely dispersed suspension, in which case settling and centrifuging are insuillcient and extremely vigorous agitation with a solvent or filtration through a bed of sand or the like may be necessary.

The separation of the disulphides is preferably carried out without substantially raising the temperature, because upon heating even in the acid state, but more so in the alkaline state, the aromatic disulphides tend to revert to their respective mercaptans. In this respect aromatic disulphides differ considerably from aliphatic di- I sulphides which normally can be distilled without material decomposition. Therefore phenolate solutions containing separated and/or dissolved aromatic disulphides should not be heated above about 90 C., and atemperature below about 50 C. is preferably maintained before and during the removal of the latter.

The desulphurizedphenolate solution is now carbonated by introducing into it carbon dioxide or a gas containing carbon dioxide such as flue gas, or lime kiln gas, etc. in an amount so that preferably the resulting aqueous solution contains about an equi-molar mixture of carbonate and bicarbonate. Since phenols are acids weaker than carbon dioxide, they are liberated while the stronger carboxylic acids as well as hydrogen sulphide, if present, remain in the aqueous solution as alkali metal salts. Together with the alkyl phenols, organic hydrosulphides such as thio phenols and mercaptans not removed by steaming, are liberated. The liberated alkyl phenols form a separate layer and are removed from the resulting aqueous carbonate solution in which the carboxylic acids are retained. The alkyl phenols may be water washed, such a wash often lowering the sulphur content by about .2 to 3%. If desired, the carboxylic acids may be liberated and recovered from the carbonated solution, for instance by treating same with a relatively strong acid, such as sulphuric, sulphurous, hydrochloric, phosphoric acid, etc.

The separated alkyl phenols which usually conv tain a relatively small amount of sulphur com- Pounds and more or less of dark colored resinous or tarry matter, are now subjected to a quick distillation, preferably a flash distillation under a reduced pressure, e. g., below about 25 mm. mercury. Since the resinous or tarry compounds associated with the crude alkyl phenols are thermally unstable and crack very readily, thereby forming both neutral oils and tar, distillation must proceed at the lowest practical temperature, preferably below 180 C. and at the highest rate possible. The resulting distillates are mixtures of alkyl phenols of light colors, good color stabilities and very low sulphur contents.

As has been indicated hereinbefore instead of proceeding as described, the steps of blowing with air and separating disulphides may be carried out after completed vacuum distillation. In this case the alkyl phenols which may or may not have had an air blowing treatment or redissolved in an alkaline liquid medium to form aliquld solution. We prefer to use an aqueous alkali metal hydroxide in which to dissolve the phenols, although other suitable bases such as various amino bases for instance aqueous ammonia, alkyl amines, alkanol amines, alkylenediamines, aniline, aqueous quaternary ammonium bases may be used instead. The resulting phenolate solution is then blown for several hours with air at a temperature preferably below about 50 C. such as room temperature, and disulfldes are then separated by one of the methods described before which may be applicable. The blown and desulphurized phenol- ,ate solution is carbonated to liberate the alkyl phenols and if desired the latter may be redistilled.

The reductions in the sulphur content which can be had by our improved process are well illustrated in the following examples:

A mixture of alkyl phenol which was produced in accordance with the method of our co-pending application Serial No. 114,658, had a mercaptan sulphur content of 1.5 prior to blowing with air at 140 to 150 C. After blowing for 10 hours at 145 C. and redistilling, under vacuum the mercaptan sulphur content was 0.5%.

When, however, producing alkylphenols from the same source by the method of this invention, according to which the alkyl phenolate extract was blown following completed steaming and sludge separation, the mercaptan sulphur content was reduced to .05%. If instead of air blowing the aqueous phenolate extract, the vacuum distillated phenols containing 1.5% of mercaptan sulphur were redissolved in a 10% aqueous caustic soda and the resulting phenolate solution was blown at room temperature for 10 hours, the mercaptan sulphur content after separation of disulfldes was of the order of .001 to .005%;' and if air blowing in alkaline solution was employed twice,- namely before and after vacuum distillation contents of mercaptan sulphur were well below .001%.

We claim as our invention:-

1. In the process of refining alkyl phenols containing aromatic mercaptans, the steps comprising blowing the alkyl phenols with air at a temperature between and 90 C. while in solution of an alkaline-reacting liquid medium stable under the conditions of the treatment, for a time sufllcient to convert mercaptides to disulphides which are largely insoluble in said solutions and form a separate phase, and removing the separated disulphides from the solution while maintaining a temperature below about 90 C.

2. In the process of refining alkyl phenols containing aromatic mercaptans, the steps comprising blowing the alkyl phenols with air at a temperature between 0 and 50 C. while in solution of an alkaline-reacting liquid medium stable under the conditions of the treatment, for a time sufllcient to convert mercaptides to disulphides which are largely insoluble in said solutions and form a separate phase, and removing the separated disulphides from the solution while maintaining a temperature below about 50 C.

3. In the process of refining alkyl phenols containing aromatic mercaptans, the steps comprising oxidizing the alkyl phenols while in solution of a liquid aqueous alkali metal hydroxide, by blowing same with air at a temperature between 0 and 90 C., for a time sufilcient to convert mercaptides to disulphides which are largely insoluble in said solutions and form a separate phase, and removing the separated disulphides from the solution while maintaining a temperature below about 90 C.

4. Theprocess of claim 3 in which the oxidation is carried out in the presence of an oxidation catalyst capable of accelerating the oxidation of mercaptans to disulphides.

5. In the process of refining alkyl phenols containing aromatic mercaptans, the steps comprising blowing the alkyl phenols with air at a temperature between 0 and 90 C. while in solution of an alkaline-reacting liquid medium stable under the conditions of the treatment, for a time suflicient to convert mercaptides to disulphides which are largely insoluble in said solutions and form a separate phase, and filtering the solution while maintaining a temperature below about 90 C.

6. In the process of producing commercially pure alkyl phenols from a petroleum distillate containing same and aromatic mercaptans, comprising extracting the distillate with a quantity of an aqueous alkali metal hydroxide solution 'of 35 to 50% concentration to form an alkali metal alkyl phenolate solution containing aromatic mercaptides, free alkali metal hydroxide and a suflicient amount of alkyl phenols to prevent precipitation of the alkyl phenolates, steaming the resulting aqueous alkaline solution for a time sufficient to expel volatile impurities and to precipitate actual and potential sludges, separating the sludges from the solution of alkyl phenolates and mercaptides, carbonating the desludged solution with an amount of carbon dioxide suflicient to liberate alkyl phenols and mercaptans, thereby forming two layers, an alkyl phenol layer containing aromatic mercaptans and an aqueous layer, separating the layers, distilling the alkyl phenols and mercaptans under conditions to prevent substantial cracking, and

subjecting the alkyl phenols to an oxidation treatment to convert mercaptans to disulphides, the

improvement comprising effecting the oxidation by blowing the alkyl phenols containing mercaptans with air at a temperature between 0 and 90 C. while in solution of an alkaline-reacting liquid medium stable under the conditions of the treatment, for a time sufficient to convert mercaptans to disulphides which are largely insoluble in said solutions and form a separate phase, and removing the separated disulphides from the alkaline solution while maintaining a temperature below about 90 C.

7. In the process of producing commercially pure alkyl phenols from a petroleum distillate containing same and aromatic mercaptans, comprising extracting the distillate with a quantity of an aqueous alkali metal hydroxide solution of 35 to 50% concentration to form an alkali metal alkyl phenolate solution containing aromatic mercaptides, free alkali metal hydroxide and a suflicient amount of alkyl phenols to prevent precipitation of the alkyl phenolates, steaming the resulting aqueous alkaline solution for a time suflicient to expel volatile impurities and to precipitate actual and potential sludges, separating the sludges from the solution of alkyl phenolates and mercaptides, carbonating the desludged solution with an amount of carbon dioxide sufficient to liberate alkyl phenols and mercaptans, thereby forming two layers, an alkyl phenol layer containing aromatic mercaptans and an aqueous layer, separating the layers, distilling the alkyl phenols and mercaptans under conditions to prevent substantial cracking, and subjecting the distilled mixture to an oxidation treatment to convert mercaptans to disulphides, the improvement comprising redissolving the distilled mixture in a liquid alkali reacting medium stable under the conditions of the treatment, to produce an alkyl phenolate and mercaptide solution, blowing the solution with air at a temperature between 0 and 90 0., for a time sumcient to convert mercaptides to disulphides which are largely insoluble in said solutions and form a separate phase, and removing the separated disulphides from the alkaline solution while maintaining a temperature below about 90 C.

8. In the process of refining alkyl phenols containing aromatic mercaptans, the steps comprising blowing the alkyl phenols with air at a temperature between 0 and 90 C. while'in solution of an alkaline-reacting liquid medium stable under the conditions of the treatment, for a time sufiicient to convert mercaptides to disulphides which are largely insoluble in said solution and form a separate phase, and extracting the resulting mixture with an organic preferential solvent for disulphides which is immiscible with the solution to remove disulphides, while maintaining a temperature below about 90 C.

9. In the process of refining alkyl phenols containing aromatic mercaptans, the step comprising blowing the alkyl phenols with air at a temperature between 0 and 90 C. while in-solution of an alkaline-reacting liquid medium stable under the conditions of the treatment, for atime sufiicient to convert mercaptides to disulphides which are largely insoluble in said solution and form a separate phase, and extracting the resulting mixture with a hydrocarbon solvent to remove disulphides, while maintaining a temperature below about 90 C.

10. In the process of refining alkyl phenols containing aromatic mercaptans, the step comprising blowing the alkyl phenols with air at a teml perature between 0 and 90 C. while in solution an alkali metal phenolate solution containing mercaptides and volatile impurities, steaming said phenolate solution to expel said volatile impurities, contacting the steamed solution with air at a temperature between 0 and 90 C. for a time sufllcient to convert at least a portion of said mercaptides to disulphides which are largely insoluble in said phenolate solution and form a separate phase, and removing the separated disulphides from the phenolate solution while maintaining a temperature below about 90 C.

WALTER J. HUND.

SAMUEL BENSON THOMAS. DANIEL B LUTEN, JR.