US2311593A - Method of treating hydrocarbons - Google Patents

Description

Patented Feb. 1 6, 1 943 IVIETHOD' OF TREATING HYDROCARBONS Vladimir A. Kalichevsky, Eugene T. Scare, and 1 Kenne th F. Hayden, Woodbury, N. J., assignors to Socuny-Vacuum Oil Company, Incorporated, New York, N. Y., a corporation of New York No Drawing. Application December 6, 1940, Serial No. 368,932

3 Claims.

This invention has to do with the removal of mercaptans and hydrogen sulphide from petroleum hydrocarbon fractions. These compounds are objectionable, as such, and must be removed or converted to innocuous compounds. The customary process has been conversion to unobjectionable disulphides, but, in gasoline to be leaded, these reduce the efliciency of the antiknock agent. Increasing attention has been drawn to processes which remove rather than convert mercaptans. Attention has been given processes using solid alkalies, without as yet any particularly acceptable commercial process having been developed.

This invention has for its object the provision of an efficient and economical method for the removal of sulphur compounds from hydrocarbon oil fractions by the use of solid alkali.

Anhydrous sodium hydroxide is capable of removing quantitatively mercaptans from petroleum oils provided sufiicient time is allowed for completing the reaction. With some gasolines plant operation, the surface area of sodium hydroxide required to sweeten the above sample of gasoline should be by interpolation approximately 200 sq. cm. The theoretical quantity of sodium hydroxide required to sweeten the above sample of gasoline is 0.0113 per cent weight on the gasoline. The specific gravity of this gasoline was 0.751 at 60 F. while the specific gravity of sodium hydroxide is 2.13. Therefore, the depth of penetration of mercaptides into the sodium hydroxide during the 30 minute contact period was 0.000024 cm. Considering particles of spherical type the maximum diameter of such particles should not be over 0.000048 cm. if the gasoline must besweetened in 30 minutes or less.

- The above figure is an approximation of the be somewhat greater or less than that shown containing higher mercaptans from two to twenty-four hours of continuous agitation may be necessary to sweeten the gasoline, depending on the state of subdivision of the reagent. In addition, the surface of the sodium hydroxide particles is quickly coated with the adsorbed layer of mercaptides, thus preventing further reaction. For this reason, the quantity of sodium hydroxide required to sweeten the gasoline is much greater than theoretical. We have found that .both the time of the reaction and the quantity of sodium hydroxide required for sweetening gasoline depends primarily on the surface of sodium hydroxide exposed to gasoline rather than on the total quantity of sodium hydroxide resent. This may be visualized from the following experimental data.

Relation of surface area of sodium hydroxide particles to the time required to completely sweeten a 120 cc. sample of cracked gasoline Mixing Surface area, Sqtime Minutes sweetening of the above sample of gasoline was accompanied with a reduction of its mercaptan sulfur content from 0.0092 to 0.0002 per cent by weight. Considering that minutes time of contact is within practical limits for above.

1. Colloidal mills.

2. Electric are.

3. Deposition of thin layers of solid anhydrous alkali on inert materials possessing high surface areasu 4. Spraying molten anhydrous alkali into gasoline.

Gasoline containing mercaptans is brought in contact with the finely divided particles of anhydrous sodium hydroxide by agitating or filtering, depending whether the reagent is in a finely divided form or deposited in thin layers.

The treated gasoline is freed from suspended particles of mercaptides by washing it with water or by bringing it in contact with adsor tive substances, such as clay. The use of water for removing the mercaptides is possible because the rate of hydrolysis is slow. However, excessive contact time of gasoline containing the mercaptides and water should be avoided.

Similar methodsare also applicable for treating gasoline with anhydrous potassium hydroxide which is best suited for the removal of elementary sulfur, i. e. for treating corrosive gasolines.

These methods have the advantage or presenting the reagent to the reaction in the form of a surface so extended that the reaction products do not mask of! any useful portion of the reagent, which feature has nullified the results of previous attempts to use solid anhydrous alkalies in larger states of subdivision such as 20-100 mesh. They also avoid a common failing of another proposed alternative method of utilizing solid alkalies, viz., that of utilizing a common solvent such as alcohol, wherein a solution of alkali in alcohol would be added to the hydrocarbon resulting in the precipitation therein of alkali particles of sub-colloidal or molecular dimension, but also obscuring and obstructing the reaction by the presence of the mutual solvent and'necessitating the later removal of that mutual solvent.

The named methods of securing dispersions of solids in liquids by mechanical means are known and require no explanation.

Any solid anhydrous alkali of properly reactive characteristics may be used, the usual and pre- {gr-red ones being sodium and potassium hydrox- We claim:

1. That method of removing sulphur constituents such as elemental sulphur. hydrogen sulphide and mercaptans from hydrocarbon oil fractions comprising contacting said oil with solid anhydrous alkali particles oi colloidal sizes.

2. That method of removing sulphur constituents such as elemental sulphur, hydrogen sulphide and mercaptans from hydrocarbon oils comprising the steps of mechanically dispersing solid anhydrous alkali to particles oi. colloidal dimensions in said oil and separating the resulting reaction products from the oil.

3. "first method of removing sulphur constituents such as elemental sulphur, hydrogen sulphide and mercaptans from hydrocarbon oils comprising the steps of mechanically dispersing solid anhydrous alkali to particles of colloidal dimension, ranging from about 0.0000001 cm. to about 0.00001 cm. in diameter, in said oil and stgparatin'g the resulting reaction products from e oil.

VLADIMIR A, KALICHEVSKY.

EUGENE T. BCAFE.

mum F. HAYDEN.