US1823558A - Purification of tar acid-bearing oils - Google Patents

Description

Patented Sept. 15, 1931 vireo STATES PATENT OFFICE STEPHEN P. BURKE, OF NEW YORK, N. Y., ASSIGNOB TO OOMBUSTION-UTILITIES CORPORATION, OF NEW YORK, N. Y., A CORPORATION'OF MAINE PURIFICATION OF TAR ACID-BEARING OILS No Drawing.

7 The present invention relates to the purification of tar acid-bearing oils, and more particularly to a process for eliminating colorproducing compounds from tar acid-bearing 5 oils containing them. I I

Some tar acid-bearing oils (such as low temperature tars, blast furnacetars, vertical retort tars, shale oils and other liquid 'condensates resulting from the distillation of bituminous material under carbonizing conditions mild enoughto preserve the liquid by-products in a substantially primary and undecomposed form) contain certain impurities which render them unsatisfactory or make them undesirable for certain uses. One form in which these impurities manifest themselves is in the production of colored compounds when such oils are "used for the manufacture of disinfectants, animal dips, saponified cresol or tar acid'solutions and related products; After exhaustive and thorough investigation of the chemical compositions and properties of these colored compounds their origin has been traced to certain strongly reducing ortho-dihydrictar acids, similar to but not including catechol. Thus one of these bodies has been isolated and identified as a new homologue of catechol comprising 3, 4- or 3, G-dimethyl catechol.

The primary object of the present invention is to provide a process for removing color producing compounds of the type referred to from tar acid-bearing oils containing them. Heretofore in preparing and refining tar acid-bearing oils of the class described for use in the manufacture of disinfectants, animal dipsand similar products, the oils have been subjected to washing treatments with aqueous sodium carbonate solution. This treatment, however, failsto give even approximately complete removal of the color forming matter except with oils which contain unusually small amounts of such colorproducing bodies. In treating other tar acid-bearing oils, washing with dilute caustic soda solution has been employed, but this treatment involves a very considerable loss of the desirable tar acids of-high germicidal.

value, which areextracted together with the color-forming materials. by the caustic soda Application filed September 22, 1926. Serial No. 137,174.

treatment. Another method has been recent lyproposed for removing these color producing compounds from coal tar distillates and the like, which comprises washing theoils with aqueous solutions of weakly alkaline buffer agents such as calcium hydroxide and ammonium hydroxide. While this latter method of treatingthe'oils has proved to be much more satisfactory than methods now in use in the trade,- it has been found that the action of the alkaline buffer agents is often incomplete in the case of taracid-bearing oils containing appreciably large quantities of color-producing matter. Fractionation of the oilswith rejection of the portion boiling above-230 C. has alsobeen advocated, but since this excludes the larger'portion of the oil, including most of the high boiling tar acids which are the most valuable germicides present in the oils, the method is not commercially feasible.

Another objectof the present invention is to provide a process by which the color-producing bodies present in such tar acid-bearing oils can be cheaply and completely extracted without also removing valuable tar acids.

With these and other objects and features in view the invention consists in the process for purifying tar acid-containing oils hereinafter described and particularly defined in the claims. a

Essentially the. process for purifying tar acid-bearing oils forming the subject of the present invention, in its preferred form, consists in precipitating the color-producing bodies from the oil by means of a water-solublenon-acidic salt of aheavy metal, parblack, fullers earth, activatedcarbon or the tar acids from a tar acid-bearing oil. No favorable catalysis of secondary reactions with the color-producing compounds appears to takeoplace, and practically none of the desirable and valuable monohydroxy tar acids of high germicidal value are precipitated from theoil.

The following procedure isset forth as an example of a satisfactory method of treating tar acid-bearingoilshaving a relatively bid owing-tothe presence of gelatinous lead salts of color-producing impurities original- 1y present in the oil, was mixed with 1% of its weight of a filter-aid (for example bone like) and filtered with suction. The resulting oil filtrate was clear, and a disinfectant prepared from it by means of. rosin soap gave an emuls1on with water which was practically free of red color. The oil may be distilled either before or after treatment if desired, although such distillation is not necessary for the'removal of the color-producing bodies. Without the use of some filter aid such as bone black, fullers earth or the like, experiments have shown that it is extremely difficult to get a complete, separation of the insoluble lead salts of the color-producing-bodies from the oil in which they are suspended. Filtration or centrifuging of the oil has been tried, butin many cases the oil obtained by either of these treatments is not entirely freed ofv the insoluble salts of the color-producing bodies. It has been found desirable to heat the oil during the period of agitation with thetreating agent, forthe reason that since the reaction leading to'the formation of insoluble metal salts takes place in the aqueous phase,the heat increases the solubility of thecolor-forming material in the aqueous phaseand thereby hastens the completion of the reaction and insures the completeness of interaction between the reagent and the color-producing impurities. Once formed, the insoluble metal salts leave the aqueous phase and pass into the oil, where'they remain in suspension. If an excess of the precipitating agent is present in the aqueous solution, the latter may be drawn off and used again for treating another batch of oil, and this process reagent remains in the aqueous solution.

It is not intended by the above description to limit the scope of the present invention to the treatment of oils containing definite compounds, nor to the use of definite proportions of the precipitating agent, nor to the employment of particular temperatures or particular time limitations of agitation, nor to the use of any particular metal salt as a precipitating agent or particular methods of separating the oil and insoluble material@ Any metal salt which gives an insoluble compound on interaction with orthodihydric tar acids of the class referred to may be employed. The process is applicable not only to the treatment of the tars themselves, but also to the treatment of a tar acid fraction alone (unadmixed with hydrocarbon oil), The volume 'of the precipitating agent used is preferably limited to a. slight excess above that required for removing the color-producing impurities.

By employing the process forming the subject matter of the present invention for the purification of tar acid-bearing oil, disinfectant emulsions can be prepared from a soap base blend of the oil which will not turn pink, and the purification of the oil can be completed at relatively small expense without materially lowering the value of the disinfectants and the germicidal agents prepared therefrom.

' The term tar acid-bearing oil is used in the description and claims to include all tar acid containing oils or liquid condensates obtained in the distillation of coal or oil shale. The tar acid content of most of such oils, and particularly those obtained by the low temperature distillation of coal, often consists almost entirely of compounds, which, while they resemble the, phenols or tar acids of coke oven tar in some of their properties, do not come within the generally accepted definition of a phenol, but are rather hydroxyl derivatives of cyclic hydrocarbons which are nonaromatic in character, having hydrogen and alkvl side chains attached to the aromatic nucleus.

The preferred form of the invention having been thus described, what is claimed as new 1s: I

1; The method of removing color-produc- Iing compounds from an oil containing mono- 7 producing bodies thereby precipitated from peatedas long as suiiicientprecipitating the residual purified oil. 3. The method of removing color-producmg compounds, including ortho-dihydric tar acids, from an oil containing the same together with other tar acids without substantial removal of the latter from the oil which comprises agitating a mixture of the oil and a non-acidic salt ofa metal which forms insoluble compounds with ortho-dihydric tar acids, and subsequently separating the purified oil and the, insoluble compounds thus formed.

4. The method of removing color-producing compounds, including ortho-dihydric tar acids, from an oil containing the same together with other tar acids without substantial removal of the latter from the oil which comprises agitating a mixture of the oil and an aqueous solution of a non-acidic salt of a metal which forms insoluble compounds with ortho-dihydric tar acids, and separating the insoluble compounds thus formed from the residual oil.

5. The method of removing color-producing compounds from an oil containing monohvdric tar acids while conserving the content of the latter, which comprises agitating the oil for about thirtv minutes at a temperature of about C. with about an equal volume of a 10% aqueous solution of normal lead acetate, separating the aqueous layer from the treated oil. mixing with the latter a small percentage of a filter aid material, and filtering to separate the insoluble metal salt precipitates of the color-producing bodies from the oil filtrate.

6. The method of removing color-producing compounds from an oil containing monohvdric tar acids while conserving the content of the latter, which comprises agitating the oils with an aqueous solution of normal lead acetate.

7. The method of removing color-producing compounds from an oil containing monohvdric tar acids while conserving the content of the latter, which comprises agitating the oil with an aqueous solution of a non-acidic salt of a heavy metal, separating the aqueous solution of excess treating agent from the treated oil, and employing the solution thus separated in purifying another batch of oils containing tar acid.

8. The method of removing color-producing compounds from an oil containing monohvdric tar acids while conserving the content of the latter, which comprises agitating the oils with an aqueous solution of a non-acidic salt of a heavy metal, separating the aqueous layer from the treated oil, mixing with the oil layer a small percentage of a filter aid and filtering to separate the insoluble metal salt precipitates from the oil filtrate.

In testimony whereof I aflix mv signature.

STEPHEN P. BURKE.