US2190007A - Refining light hydrocarbon distillates - Google Patents

Description

Patented Feb. 13, 1940 umr REFINING LIGHT HYDROOARBON DISTILLATES Howard B. Batchelder and Bernard H.Shoemaker, Hammond, Ind., assignors to Standard Oil Company, Chicago, 111., a corporation of Indiana N Drawing. Application Septemberl, 1937,

Serial No. 161,962 g 10 Claims. (Cl. 196-33) This invention relates to a process of refining hydrocarbons and particularly refining motor fuels such as gasoline and motor benzol. Other hydrocarbon fuels such as the petroleum naphthas and kerosene may also be refined by our process.

The principal object of our invention is, to remove corrosive sulfur from motor fuels. Another object of our invention is to refine corrosive motor fuels and render them satisfactory when subjected to the most rigorous corrosion tests. Still another object of our invention is to improve the prior process of treating corrosive gasoline and naphtha so that a more complete removalof corresive constituents is obtained in a shorter time. It is well known that gasoline and petroleum naphthas frequently are contaminated with corrosive sulfur and sulfur compounds which are not removed by the ordinary refining processes 20 such as treatment with sulfuric acid, doctor, etc. In order to remove corrosive sulfur it has been previously proposed in U. S. Patent 1,668,225, May 1, 1928, to add to the gasoline a small amount of mercaptan and then treat the gasoline with 25 sodium plumbite in the presence of which the mercaptan reacts with the sulfur and plumbite to form insoluble lead'sulfide. Mercaptans employed were the lower mercaptans of ten car- 40 to treat the oil with this reagent. We have also found that the use of the heavier mercaptans, for example butyl, amyl, hexyl and octyl mercaptans, requires great care in avoiding an excess which will render the stock sour. At the same time, 45 if insufficient mercaptan is employed the oil will remain corrosive and fail to pass the more stringent corrosion specifications, particularly the specification for aviation gasoline wherein a sample of the gasoline is evaporated on the steam 50 bath in a polished copper dish and any corrosive constituents which it may contain are concentrated during the evaporation, producing a discoloration of the copper. In order to satisfactorily pass this test a gasoline must produce sub- 55 stantially no discoloration of the copper.

According to our process wehave provided a method of overcoming these difiiculties in the'following manner. The corrosive naphtha or gasoline is first treated by dissolving therein an amount of a heavier mercaptan'insuificient to 5" effect complete refining to a corrosion-free stock. For this purpose we prefer to employ butyl mercaptan, either normal, tertiary or isobutyl mercaptan. However, we may employ any of the still heavier'mercapta'ns, such as amyl, hexyl or 10 rapidly and after a few minutes of agitation'the oil is substantially free of corrosive agents. In order to complete the reaction, however, we next add a small amount of alighter mercaptan, for example ethyl mercaptan, and agitate further. Although theamount of ethyl mercaptan found necessary for this method is very small, we prefer to add an excess rather than attempt to determine the exact quantity required for complete refining.

After agitating the stock with the ethyl mercaptan in the presence of a plumbite solution air is introduced into the mixture to remove excess mercaptan which occurs principallyby oxidation, although some of the low boiling mercaptan may be directly evaporated. We have discovered that the lighter mercaptans, such as methyl and ethyl mercaptans particularly, are readily oxidized by atmospheric oxygen to produce unobjectionable compounds in the presence of sodium plumbite solution. Furthermore, any minute traces of the light mercaptan which may be left in the stock disappear on standing, apparently due to oxidation reactions occurring in the presence of air or dissolved oxygen.

We have discovered that although we employ heavy mercaptans for removing the major portion of the corrosive materials in gasoline and naphthas, the amount of these mercaptans is less than would be required were lighter mercaptans used. The reason for this improved efficiency of the heavier mercaptans is quite obscure inasmuch as itwould be expected that, because of their greater molecular weight, a larger amount would be required. Perhaps the heavy mercaptans form complex polysulfides on reaction with elemental sulfur and thus remove a larger amount of sulfur than can be accounted for by the commonly accepted reaction, according to which the mercaptan is converted to a disulfide only. This phenomenon is well illustrated by the following example: a naphtha solution containing 10 mg. of sulfur per 100 cc. was treated in one case with butyl mercaptan and in the other case with ethyl mercaptan and then agitated with doctor solution. Varying amounts of the mercaptans were employed and after the treatment the samples were tested for corrosion with the following results:

Mercaptan used Mg./l cc. Corrosion test Ethyl mercaptan Positive. Slight. Negative. Positive. Negative.

It will be observed from these results that the heavier mercaptan is more than twice as effective as the lighter mercaptan.

In this specification we employ the term higher molecular weight mercaptan to mean butyl mercaptan and mercaptans with hydrocarbon radicals having more than four carbon atoms and by the term lower molecular weight mercaptans 2. The presence of claim 1 wherein the higher molecular weight mercaptan is butyl mercaptan.

3. The process of claim 1 wherein the lower molecular weight mercaptan is ethyl mercaptan.

4. The process of claim 1 wherein the higher molecular weight mercaptan is tertiary butyl mercaptan.

5. The process of claim 1 wherein the higher molecular weight mercaptan is isobutyl mercaptan.

6. The process of completely eliminating corrosive sulfur from gasoline and light hydrocarbon distillates which comprises subjecting said distillates to the action of a sodium plumbite solution in the presence of added higher molecular weight mercaptan, the amount of which has been determined to be insufficient for complete removal of sulfur effecting a chemical reaction between the said mercaptan and the sulfur in said gasoline whereby said added mercaptan is consumed adding a lower molecular weight mercaptan in an amount in excess of that required for completely removing the sulfur, agitating with sodium plumbite solution and finally removing excess lower molecular weight mercaptan by oxidation with gaseous oxygen and separating said hydrocarbon distillate from said solution.

7. The process of claim 6 wherein the higher molecular weight mercaptan is butyl mercaptan.

8. The process of claim 6 wherein the lower molecular weight mercaptan is ethyl mercaptan.

9. The process of claim 6 wherein the higher molecular weight mercaptan is tertiary butyl mercaptan.

10. The process of claim 6 wherein the higher molecular weight mercaptan is isobutyl mercaptan.

HOWARD R. BATCHELDER. BERNARD H. SHOEMAKER.

CERTIFICATE OF CORRECTION.

Patent No. 2,190,007. February '15,.l9h0- HOWARD R. BATCHELDER, ET AL.

It is hereby certified that error appears inthe printed specification of the above numbered patent requiring correction as follows: Page 2., second column, line 1, claim 2, for the word "presence" read process; and that the said Letters. Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 19th day of March, A. D. l9LLO.

Henry Van Arsdale, (Seal) 2 Acting Commissioner of Patents.