US1684159A - Process of refining oils - Google Patents

Description

' which, when mixed with the oil in the form Patented Sept. 11,1928.

UNITED STATES 1,684,159 PATENT oFF1c SIJ'ZBREN TIJ'LISTRA, OF MADISON COUNTY, ILLINOIS, ASSIGNOR TO ROXANA PETRO- LEUM CORPORATION, A CORPORATION 01? VIRGINIA.

PROCESS OF REFINING OILS.

Ho Drawing.

This invention relates to a process of refining oils, and consists in the novel procedure hereinafter disclosed.

As is knowng many of the cracked hydrocarbon oils have a high sulphur content. It has been the practice to apply to these oils the so-called doctor treatment, which consists in treating such oils with a solution of lead oxide dissolved in a caustic soda solution under agitation, and then adding free sulphur to precipitate out the lead sulphide. The disadvantage of such a treatment is that it is extremely diificult to add only the required amount of free sulphur to carry out the reaction, and, at the same time, prevent the solution of sulphur in the hydrocarbon oil..

The disadvantage of a high sulphur content in the final product is fully recognized, inasmuch as it causes corrosion of the metal containers and passages with which it essentially comes in contact when used as a motor fluid. It is the purpose of the present invention to control the sulphur content of the finished product in order to avoid an excess of free sulphur, or sulphur dissolved in the oils, by providing a method of precipitation of the lead compounds produced by the action of the doctor treatment of oil.

Another advantage of the present process is the provision of a method of treatment which may be conducted as a continuous process, resulting in the removal of the products of the doctor treatment and, at the same time, produciug a doctor sweet final product. The process, briefly stated, consists in the usual step of treatin the oil with a solution formed from a solution of lead oxide and a solution of caustic soda. This treatment removes certain of the sulphur compounds in the oil and also converts certain other of'the sulphur compounds present to a form in which they are unobj ectionable and not detrimental to the final product.

The product is then allowed to settle and the excess of the doctor solution is drained OE and the product given a water wash.

It is then treated with a polysulphide, such, for instance, as a polysulphide of sodium of a water solution of suitable concentration, releases a suflicient amount of free sulphur only to carry out the necessary chemical reaction to precipitate from the oil the lead comunds resulting from the doctor treatment 1n the form of lead sulphide and, at the same Application filed December 6, 192a. Serial No. 153,044. A

time, to prevent an excess of free sulphur resulting in the oil and thereby imparting to the product a corrosive efl'ect.

The reason that the polysul hides of the alkaline earth metals contemp ated for use in the present process release only a sufficient amount of sulphur to complete the precipitating action of the lead sulphide is that the sulphur atoms contained in the polysulphide compounds are loosely bound. Therefore, these polypsulphides easily decompose into elementary sulphur and a sulphide or polysulphides with a lower sulphur content.

For example, and by way of illustration of the chemical action involved, the following reversible reactions occur in relation to the polysulphides of sodium, namely:

Na S Na,S +S Na S 1:1: Na s +8 It therefore follows that,- when the polysulphides of the type contemplated, when mixed with a'doctor treated oil in a water solution, the sulphur is freed in the form of a water solution which reacts with the lead compounds dissolved in the oil, producing the same chemical reaction to precipitate the lead compounds from the oil.

When the sulphur is freed in this manner from the water solution of the polysulphide, only a small amount of sulphur is released, due to the decomposition of the polysulphide. The amount of sulphur that is released is dependent upon the amounts .1 of polysulphides and of sulphide present in the water solution for the reason that, in every reversible reaction, there is a definite relation between the concentrations in the solution of the products of the reaction. Furthermore, inasmuch, as sulphur is soluble in oil, some of the free sulphur present in the water solution will dissolve in' the oil. But the amount that is dissolved will be determined by the definite relationship between the concentration of the sulphur 1n the water polysulphide solution and the concentration of free sulphur in the oil, so that the amount remaining in the final product can be easily controlled and reduced to an amount that will not be detrimental by imparting a corrosive action to the finished product.

By selecting the proper degree of concentration of polysulphides in the water solution and of the proper composition of the polysulphide, it is possible to maintain a very low content of free sulphur in the oil. That is to say, the sulphur content entering into the solution with the oil can be held to a point where it is only sufiicient to cause the desired precipitation of the lead compounds dissolved in the oil as the result of the doctor treatment and, at the same time, sufliciently low so that the finished oil is noncorrosive. Likewise, if there is an excessive amount of sulphur in oil, the addition of a water solution of sodium sulphide or of a water solution of a polysulphide having a low sulphur content, the sulphur may be removed from the oil to an extent suflicient to make it non-corrosive by the conversion of the sulphide or polysulphide to a polysulphide having a higher sulphur content. This essentially follows from the fact that the reactions exemplified above are reversible and that the free sulphur in excess readily enters into chemical combination with the sulphide or the lower content sulphur poly- I sulphide. This reaction is facilitated by using a higher temperature, preferably about 200 degrees Fahrenheit.

As an example of the practice of the process, the following procedure may be had:

The oil stock is first treated with the doctor solution, that is to say, lead oxide dissolved in caustic soda solution. The doctor treated oil is then allowedto settle and the excess of the doctor solution is drawn off. This is then followed by a water wash. The product is then treated with a polysulphide solution, the solution for this purpose comprising preferably sodium disulphide or trisulphide. The polysulphide solution may be added in excess, as the excess of the solution has no detrimental effect uponthe product. It may be added, therefore, by a continuous feed. This step of the treatment is preferably carried out at a temperature from 80 to 90 degrees Fahrenheit andv the polysulphide solution is preferably approximately 21. five percent degree of concentration; The product is then allowed to settle and the treated oil is decanted off. It is then washedwith water and is ready to be It follows, therefore, that the process greatly improves the method of treatment of doctor treated oils, as the operation is facilitated by permitting continuous feed of the polysulphide solution and the resulting product is greatly improved by reason of the fact that excess sulphur in solution in the oil is avoided. It will be understood that the specific mention of the polysulphides of sodium is merely by way of example, and that any of the polysulphides capable of decomposing into free sulphur and a sulphide of lower content is contemplated.

It will also be understood that the specific mode of procedure outlined is not essential,

but what I claim and desire to secure by Letters Patent is 2- I 1. The process of treating oils which consists in adding thereto a doctor solution and then adding to said treated oil a water solution of a polysulphide capable of releasing free sulphur for precipitating the lead compounds from the oil. I

2. The process of treating hydrocarbon oils which consists in subjecting the oil to a treatment with an alkali metal plumbite in a water solution, then extracting the plumbite solution from the oil, then treating the oil with an alkali metal polysulphide, and then removing the .polysulphide solution fromthe oil.

3. The step in the treatment of hydrocarbon oils containing lead compounds which consists .in addingthereto a polysulphide salt in a Water solution, which salt is capable of releasing only sufiicient sulphur to precipitate the lead compounds and to prevent an excess amount of sulphur entering into solution in the oil. SIJBREN TIJMSTRA.-