US2683108A - Removal of phenolic substances from petroleum fractions - Google Patents

Description

Patented July 6, 1954 REMOVAL OF PHENIOLIO SUBSTANCES FROM PETROLEUM FRACTIONS William K. T. Gleim, Orland Park, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application January 2, 1952, Serial No. 264,687

6 Claims.

This invention relates ,to a process for the separation of phenols, including phenol itself, the alkyl phenols and thiophenols from petroleum fractions as a means of improving the petroleum products for use in motor fuels, burners, etc. More specifically, the invention concerns an extraction procedure more commonly referred to as treating for the removal of phenols and/or thiophenols particularly from liquid petroleum distillate fractions utilizing an extractant or treating agent comprising an aqueous solution of a Water-soluble alkaline earth metal carbohydrate complex.

The effect of sulfur-containing compounds and phenols normally present in petroleum distillates and the conversion products of petroleum on the combustion properties and storage stability of such petroleum-derived products is well known and generally recognized as undesirable. known, for example, that the phenolic and sulfurcontaining compounds present in petroleum fractions are the major cause of the corrosion of refinery equipment in which the petroleum distillatcs are processed; they are generally of disagreeable odor and. their presence in the gasoline produced therefrom causes undesirable gum formation in internal combustion engines and reduces substantially the susceptibility of such gasoline products to the addition of tetraethyl lead anti-knock agent thereto. In the case of fuel oil and diesel fuel distillates of petroleum, the phenolic and sulfur-containing components, generally present in such distillates, if not previously removed therefrom are believed to be the cause of the formation of gum precipitates which subsequently clog fuel lines and burner tips in which the fuels are carried or consumed. Thus, it be,- comes a matter of considerable importance in the preparation of fuels and other hydrocarbon petroleum-derived fractions for domestic and commercial use that such phenolic and sulfur-containing contaminants be removed therefrom prior to their use, and preferably by suitable treatment at the refinery. V

In response to the long recognized need for such refined petroleum products, a large number of processes have been proposed to accomplish the desulfurization and removal of phenolic coma pounds from petroleum products, these processes, in general, depending for their efiectiveness on the well recognized acidic nature of the sulfurcontaining and phenolic compounds. The processes heretofore developed for the above purposes generally depend upon an extraction or washing procedure utilizing a hydrocarbon-immiscible sol- It is vent which in itself is alkaline or which contains dissolved therein an alkaline substance which is relatively basic in comparison with such acidic sulfur-containing and phenolic contaminants. Thus, aqueous alkali metal hydroxides such as an aqueous caustic solution, have been found to be effective for this purpose, not only for treating liquid petroleum distillates, but gaseous hydrogen and hydrocarbon fractions as Well. Certain difliculties, however, are encountered in widespread use of such reagents for the treatment of hydrocarbon fractions on a commercial scale, including their initial relatively high cost and the stability of the resulting caustic phenolates and the compounds formed by reaction of the caustic treating agent with the acidic sulfur compounds, the latter necessitating the use of additional auxiliary equipment and the relatively large consumption of utilities, such as heating and cooling facilities, to effect regeneration of the caustic solution before recycling the reagent to the treating or extracting stage of the process in the adaptation of the method to commercial refining operations. A further difliculty encountered in the use of reagents containing alkali metal hydroxides is their highly caustic properties which involves hazards to refinery personnel, corrosion of equipment, etc. The present invention provides an extractant, solvent, or treating agent for the removal of phenolic contaminants, including the phenols and thiophenols from hydrocarbon fractions Without the substantial disadvantages accompanying the use of strongly caustic treating agents.

In one of its embodiments the present invention concerns a process for separating phenolic compounds selected from the group consisting of phenols and thiophenols from a hydrocarbon contaminated with said phenolic compounds which comprises contacting the contaminated hydrocarbon with an aqueous solution of an alkaline earth metal carbohydrate complex, said carbohydrate being selected from the group consisting of the monoand disaccharide ketoses and aldoses containing from five to six carbon atoms per saccharide unit.

A more specific embodiment of the invention relates to a process for removing a thiophenol from a normally liquid hydrocarbon fraction which comprises mixing said fraction with a saturated aqueous solution of calcium glucosate in an extraction zone therefor, separating the resulting aqueous extract phase from the hydrocarbon raffinate phase, contacting said extract with carbon dioxide, separating the resulting liberated thiophenol from the resulting aqueous phase,

mixing the aqueous phase with calcium oxide at reaction conditions suificient to form calcium glucosate, and recycling the aqueous glucosate solution to said extraction zone.

The present treating process is particularly applicable to the treatment of normally liquid hydrocarbon fractions such as the normally liquid hydrocarbon distillates of petroleum, including the gasoline, kerosene, diesel oil, gas oil, and fuel oil fractions. Thus, the invention may be utilized for the removal of phenols and thiophenols from gasolines, particularly straight-run gasolines. The process may also be employed for the removal of thiophenols from benzene and from cleaners naphtha and for the removal of such phenolic contaminants from gas oil as a means of pretreating the latter prior to subjecting the same to catalytic cracking. Although primarily useful for treating normally liquid petroleum fractions contaminated with sulfur-containing compounds, the present treating agent may also be contacted with such fractions in their gaseous state or with normally gaseous hydrocarbon fractions containing phenolic contaminants.

The sulfur compounds which are selectively removed by means of the present treating process are the generally acidic thiophenols present in the petroleum fraction, although under modified conditions of operation other mercaptans, may

be removed from liquid hydrocarbon fractions subjected to the present treating process.

The treating agent utilized in the present extraction or treating process is herein characterized as an alkaline earth metal complex of a monoor di-saccharide carbohydrate selected from the aldoses and ketoses containing from five to six carbon atoms per saccharide unit. Typical carbohydrates utilizable in the preparation of the alkaline earth metal complexes thereof are such mono-saccharides as glucose, mannose, galactose, fructose, xylose, etc. and such disaccharides as sucrose, maltose, lactose, etc., which although all operable in the process, are not necessarily equivalent in producing treating agents of the same degree of effectiveness. In general, glucose represents the least expensive and the most effective carbohydrate utilizable in the preparation of the treating agent. For certain types of hydrocarbon mixtures to be treated requiring aqueous treating solutions of specific properties, a carbohydrate other than glucose may be preferred. The treating agent is prepared by reacting an aqueous solution of the carbohydrate, preferably containing at least up to about 25% of the carbohydrate dissolved therein with a basic alkaline earth metal compound, such as the oxide or hydroxide which is preferably suspended in Water and reacted with the carbohydrate in a ballmill at room temperature. After suflicient trituration, the excess of alkaline earth compound is filtered from the aqueous solution of carbohydrate complex. One of the preferred alkaline earth metal compounds with which the carbohydrate may be reacted to form the present treating agent is a basic compound of calcium, such as calcium oxide, or calcium hydroxide, although the basic compounds of other members of the alkaline earth metal group, that is, strontium and barium may be employed for the preparation of the carbohydrate complex treating agent for specific purposes. The treating agent is prepared by mixing an aqueous solution of the desired carbohydrate containing from one to about by weight of the carbohydrate dissolved therein with the alkaline earth metal oxide or hydroxide, the latter preferably being in a powdered or finely divided condition, at temperatures of from about 0 to about 100 (3., preferablt at room temperature or slightly above. The resulting aqueous solution of mono-, and/or di-alkaline earth metal complex of the carbohydrate is filtered to remove unreacted or excess alkaline earth metal compound when present in the reaction mixture and thereby clarify the aqueous solution for use as treating agent. The mixing of the aqueous carbohydrate solution with the alkaline earth metal basic compound may best be efiected in a ballmill at tempera tures not over 100 C.

A hydrocarbon fraction containing phenolic compounds as contaminants thereof may be subjected to the action of the treating agent, usually at a temperature below about 100 C. and under sufiicient pressure to maintain the hydrocarbons and aqueous treating agent in substantially liquid phase. The process may be effected in any suitable manner whereby contact between the hydrocarbon charging stock with the aqueous treating agent may be effected and whereby provision is made for separating and recovering the desired products, usually by a suitable decantetion of the aqueous phase from the treated hydrocarbon phase.

The treatment may be effected by either a batch-type operation or continuously. In a typical batch-type operation, for xaniple, the

, contacted hydrocarbons and treating agent are introduced into a mixing chamber, the two phases entirely mixed therein and thereafter allowed to settle in the same or a different chad her. The upper hydrocarbon layer will contain a lower concentration of phenolic compounds therein, particularly of thiophenols and may be withdrawn to storage or may be further treated to accomplish removal of additional impurities therefrom. The lower layer will comprise an aqueous solution of the alkaline earth metal carbohydrate complex in which the phenolic contaminant of the initial hydrocarbon feed stock is dissolved.

The treating process may be operated continuously by countercurrent contact between the hydrocarbon charged stock and the treating agent in a countercurrent extraction zone wherein the two phases are maintained at the above specified reaction temperatures and at pressure sufficient to maintain substantially liquid phase. The aqueous treating agent being generally the phase of greatest density in the extraction zone is preferably introduced into the top of the extraction column and allowed to flow downwardly against a rising stream of the hydrocarbon feet stock. The extraction zone may be of any suitable design customarily employed for extraction operations, such as a bubble plate column, a column packed with contacting materials such as quartz chips, beryl saddles etc. or it may simply comprise a vertical tubular column containing an arrangement of baffles Within the column to obtain mixing between the hydrocarbon and aqueous phases. The treated hydrocarbon phase removed from the top of the extraction column will contain a lower percentage of phenolic contaminants while the aqueous treating agent removed from the bottom of the column will contain a major proportion of the contaminants present in the feed stock dissolved therein. In many instances the aqueous extracting agent realso the extractant for recycling purposes.

moved from a particular operation is not completely saturated with respect to extracted phenolic contaminants and may be capable of further use as the extracting agent in a subsequent extraction operation, for example in a column placed in series with the preceding extraction column.

The spent or used extraction agent containing the phenolic contaminants dissolved therein, whether formed in either batch or continuous types of operation may be regenerated for recycling in the process by suitable removal of the contaminating phenolic substances from the extracting agent, One means for regeneration of the alkaline earth metal carbohydrate complex solution whereby the phenolic materials recovered from the hydrocarbon feed stock may be recovered if desired, comprises subjecting the spent treating agent to steam distillation, collecting the distillate which comprises phenols and thiophenols contained in the initial hydrocarbon feed stock and extracted therefrom. by the present treating agent. Another suitable method for regeneration of the treating agent comprises carbonating the spent treating-agent, preferably at room temperature or below, and preferably at a superatmospheric pressure of carbon dioxide. In the latter operation, the aqueous treating agent absorbs carbon dioxide to form carbonic acid which is relatively more acidic than the phenolic components dissolved in the treating agent, re- Suiting in the displacement of the phenolic compounds ironi the aqueous solution and precipitation of the alkaline earth metal carbonate from the treating solution. The phenolic compounds thereby released from the treating agent may be recovered by extraction with a relatively waterimmiscible solvent for the phenolic compounds, such as liquid butane, pentane, hexane, and other hydrocarbon solvents, ethers such as di-ethyl ether, di-propyl ether etc. or other suitable waterimmiscible extractant for the phenols. A preferred solvent for this purpose is one which boils at a temperature either above or below the boiling point of the phenolic compounds, such that separation of the solvent from the recovered phenols may be effected by distillation, thereby enabling recovery not only of the phenolic compounds but The alkaline earth metal carbonate formed during the treatment of the spent treating agent with carbon dioxide may be filtered from the aqueous solution.

of regenerated carbohydrate, dried and heated to form the alkaline earth metal oxide which may again be utilized to form the alkaline earth metal carbohydrate complex, if desired.

Still another method of regenerating the spent treating agent comprises adding thereto an acid which is stronger than carbonic acid, such as sulfuric acid which releases the phenolic compound from its combination with the alkaline earth metal carbohydrate and reacts with the alkaline earth metal to form a salt of the latter with the particular acid utilized to release the phenolic compound from the aqueous treating solution. The free phenolic compounds may be separated by extraction from the resulting aqueous solution in the manner hereinabove described to recover the phenolic compounds from the resulting aqueous alkaline earth salt phase. The free carbohydrate dissolved in the aqueous solution may thereafter be reacted with additional alkaline earth metal oxide or hydroxide to form an aqueous solution of the alkaline earth metal carbo- 6. hydrate for recycling as the regenerated treating agent.

The present process is further illustrated with respect to certain specific embodiments thereof in the following examples, which however, are not intended to limit the generally broad scope of the invention in strict accordance therewith.

Example I Mono-calcium glucosate was prepared by triturating one mole of calcium oxide with one mole of glucose. ml. of water was added to the mixture of glucose and calcium oxide, causing an orange-colored mass to develop, which solidified on further standing. The solid mass was broken up into particles and steam thereafter passed over the particles until a clear, viscous liquid was formed. The resulting solution was diluted with an additional quantity of water in an amount suflicient to form a 10% solution of calcium glucosate which was utilized as the treating agent for the removal of phenolic compounds from a gasoline fraction, as hereinafter described.

A thermally cracked gasoline fraction containing 0.005% phenol and 0.001% thiophenol was washed with 10 volume per cent of the above 10% aqueous solution of mono-calcium glucosate at a temperature of 25 C. by placing the gasoline fraction and aqueous treating agent in a kettle,

Example II A thermally cracked gasoline fraction containing 0.041 phenol and a second fraction containing 0.056% thiophenol were each separately treated with ten volume per cent of 10% calcium glucosate solution at 25 C. in the method described in Example I above, Analysis of the recovered hydrocarbon fractions from the treating operation indicated that the gasoline fraction containing 0.041% phenol after washing with the treating agent contained 0.017% phenol, representing a removal of approximately 59% of the phenol from the initial gasoline fraction. The gasoline feed stock containing initially 0.056% thiophenol after washing with the treating agent contained less than 0.001 thiophenol, representing approximately 100% removal of the thiophenol originally contained in the gasoline feed stock.

Example III A calcium sucrate solution was prepared by grinding one mole of calcium hydroxide with one mole of sucrose in a ballmill with sufiicient water to form a 10 aqueous solution of calcium sucrate which is utilized as the treating agent in the following example to remove phenolic compounds from a thermally cracked gasoline fraction. Ten volume per cent of the calcium sucrate solution is shaken with the thermally cracked gasoline fraction containing 0.048% phenol and 0.035% thiophenol at a temperature of 25 C. The aqueous layer is allowed to separate from an upper hydrocarbon layer and the latter recovered by decantation from the aqueous phase. The washed hydrocarbon fraction contains 0.005% phenol representing approximately 90% removal of the original phenol content o i 'the cracked gasoline fraction and 0.001% thiophenol, representing approximately 97% removal of the latter thiophenol contaminant of the original gasoline fraction.

I claim as my invention:

1. A process for separating phenolic compounds selected from the group consisting of phenols and thiophenols from a hydrocarbon containinated with said phenolic compounds which comprises contacting the contaminated hydrocarbon with an aqueous solution of a Water soluble alkaline earth metal carbohydrate complex, said carbohydrate being selected from the group consisting of the monoand di-saccharide ketoses and aldoses containing from 5 to 6 carbon atoms per saccharide unit.

2. The process of claim 1 further characterized in that said aqueous solution contains from about 1 to about 25% by Weight of said alkaline earth metal carbohydrate complex.

3.v The process of claim 1 further characterized in that said contaminated hydrocarbon and said aqueous solution are contacted at a temperature of from about 0 to about 100 C. and at a pressure sufiicient to maintain the resulting mixture in substantially liquid phase.

4. The process of claim 1 further characterized in that said alkaline earth metal carbohydrate complex is' calcium mono-glucosate.

5'. The process of claim 1 further characterized in that said alkaline earth metal carbohydrate complex is mono-calcium sucrate.

6. The process of claim 1 further characterized inv that said alkaline earth metal carbohydrate complex is a mono-calcium xylosate.

References Cited in the file of this patent UNITED STATES PATENTS- Number Name Date 1,654,154 Ackerman Dec. 27, 1927 1,654,155 Ackerman Dec. 27, 1927 1,742,020 Ackerman Dec. 31, 1929 1,742,021 Ackerman Dec. 31, 1929

Claims (1)

1. A PROCESS FOR SEPARATING PHENOLIC COMPOUNDS SELECTED FROM THE GROUP CONSISTING OF PHENOLS AND THIOPHENOLS FROM A HYDROCARBON CONTAMINATED WITH SAID PHENOLIC COMPOUNDS WHICH COMPRISES CONTACTING THE CONTAMINATED HYDROCARBON WITH AN AQUEOUS SOLUTION OF A WATER SOLUBLE ALKALINE EARTH METAL CARBOHYDRATE COMPLEX, SAID CARBOHYDRATE BEING SELECTED FROM THE GROUP CONSISTING OF THE MONO- AND DI-SACCHARIDE KETOSES AND ALDOSES CONTAINING FROM 5 TO 6 CARBON ATOMS PER SACCHARIDE UNIT.