US1957840A - Process of refining hydrocarbons - Google Patents

Description

Patented May 8, 1934 PROCESS OF REFINING HYDROCARBONS Robert I. Lewis, Wilmington, Calif., assignor to Shell Development Company, San Francisco, Calif., a corporation of Delaware No Drawing. Application July 15, 1929, Serial No. 378,572

Claims.

My invention relates to a process for the refining of hydrocarbons, especially petroleum, and refers especially to a process for treating petroleum oils for the manufacture of gasoline or mo- 1 tor fuels.

The sulphur content of those petroleum oils utilized as motor fuels is specified, in this country, as not being over 0.1 of 1%. Since the motor fuels secured as a result of both straight run and cracking processes normally contain sulphur in excess of this value, they must be treated to reduce the sulphur content.

The treating processes usually involve the contacting of the oil with a reagent whereby a portion of the bodies containing the sulphur are removed. Usually a sludge is formed when the reagent and oil are contacted. This sludge contains the sulphur bodies removed from the oil together with a portion of the oil with which the reagent has reacted to form heavier constituents. It is of course readily apparent that the ideal treatment, from the standpoint of economy, would be the one in which only the sulphur bodies are removed, the oil being otherwise unchanged. The desirability of such a process is further enhanced by the fact that those portions of the oil with which the reagent reacts are, in many instances, those which assure the best performance and highest efiiciency of the engine in which they are utilized.

Various processes have recently been proposed for the treatment of petroleum wherein the treating loss is said to be materially reduced. In one of these it has been proposed to treat with sulphuric acid at a temperature below 38 F. I have found that such a cold treatment has a marked disadvantage, as is set forth in the copending application Ser. No. 308,583, filed September 26, 1928, in that upon the distillation of the treated distillate a portion of the sulphur compounds distills over with the gasoline. This, as is readily apparent, is extremely undesirable for it obviates entirely the effect of a goodly portion of the treatment to remove the sulphur bodies.

It is therefore an object of my invention to provide a process for removing the sulphur bodies from a hydrocarbon oil which can be carried out in such a manner that the hydrocarbon oil produced contains the desired minimum sulphur content.

A further object of my invention is to provide a process by which a gasoline or motor fuel may be produced having the desired quality characteristics.

55 Further objects of my invention will appear in the following specification in which I have set forth the preferred process of my invention. It is to be understood that the invention, as defined by the appended claims, is to be accorded a range of equivalents consistent with the state of the prior art.

My invention may be briefly characterized as comprising the treatment of a hydrocarbon with a relatively weak reagent at a normal or room temperature and of about F., treating the hydrocarbon with a relatively strong reagent at a substantially lower temperature, and further treating the hydrocarbon with a relatively strong reagent at a normal temperature.

In the following I will describe the invention in connection with pressure distillate, the name usually applied to the gasoline fraction secured as a result of the cracking of a heavier oil. However, it is to be understood, that my invention is applicable to other hydrocarbons and other petroleum fractions. Further I will describe my invention in connection with the use of sulphuric acid as the treating reagent. Other materials as well as sulphuric acid may be used for the treating of hydrocarbon oils and, accordingly, I do not wish to limit my invention to the use of only sulphuric acid since such other materials as hydrochloric acid and nitric acid can be utilized.

One process which I have preferably utilized in treating pressure distillate was conducted in the following mannerz-To the pressure distillate at normal atmospheric temperature 27 B. sulphuric acid (containing 31% H2SO4) amount to 5% by volume of the pressure distillate (25.8 pounds per barrel) was added in one dump. The mixture was agitated for about 30 minutes after which it was allowed to settle. The spent acid was drained off and the distillate chilled to about 20 F. One dump of four pounds per barrel of 100% I-I2S04 as 97.4% acid was then added. With the temperature maintained substantially between 15 and 20 F. the mixture was agitated and allowed to settle. The sludge was drained off and another dump of 5 pounds per barrel of the same acid was added. With the low temperature similarly maintained the mixture was agitated, settled and drained. Subsequently the distillate was brought up to normal atmospheric temperature and four pounds per barrel of 100% H2804 as 97.4% acid was added in two equal dumps. After agitation, settling and removal of the sludge the distillate was subjected to the regular neutralization. It was then distilled with Ell " continuous manner.

' mal temperature.

steam and fractionated and the gasoline recovered in the usual manner.

The original pressure distillate contained. 0.8 of 1% of sulphur and the doctor and other quality tests indicated that a high percentage of very objectionable sulphur bodies were present. After treatment according to the above process, the sulphur content had been reduced below the required minimum and the quality tests were all highly satisfactory. Samples of the distillate were subjected to sunlight continuously for a week at the end of which time the Saybolt color had only dropped from to 26. During this period there was no indication of gum formation. This indicates a high degree of stability under very severe test conditions.

The same pressure distillate, when treated in the manner practiced before the process of my invention was known, did not result in a gasoline having as low a sulphur content, did not give as excellent results in the sulphur corrosion tests, nor the highly desirable color stability.

By the employment of apparatus well known in the art the process is readily conducted in a It is of course to be understood that the sulphuric acid employed during the cold treat must be one whose freezing point is not above the temperature employed. If this precaution is not observed the freezing of lines,

pump and agitators may occur if the temperature is carried too low.

The acid added to the chilled distillate has, I believe, a solvent action upon part of the sulphur compounds to a greater extent than acid of nor- The remaining sulphur compounds do not undergo, apparently, a raise in boiling point probably because of less polymerization. Consequently, upon redistillation these do not remain in the still bottoms but vaporize and come over with the gasoline. The subsequent treatment of the cold treated distillate with acid at normal temperature finishes the treating of the distillate, apparently by polymerization of the sulphur bodies which have not been removed by the cold treatment, in such a manner that they do not distill over subsequently with the distillate.

I have also found it desirable in treating distillates to add the same amount of reagent, in certain instances, in smaller quantities for each operation than I have here set forth, thus making for a greater number of treating operations. This generally results in a reduced sulphur content of the distillate for the same amount of reagent. I am now or the opinion that this is w due to the fact that when the reagent is added in one large dump a portion of it is utilized to polymerize the undissolved sulphur bodies which uses up the reagent. When the reagent is added in smaller amounts a greater relative percentage is effective in dissolving the sulphur bodies while only a small portion is lost in the polymerizing or" the remaining bodies.

While the processes herein described are well adapted to accomplish the purposes of this invention, it is to be appreciated that various modifications may be made Without departing from the spirit of the invention. Thus, depending upon the hydrocarbon being treated, it may be desirable to utilize sulphuric acid of different strengths from that which I have set forth in the sample given. The temperatures and the order of the steps outlined may also be varied to secure a more eflicient treatment. Hydrocarbon mixtures, such as petroleum, vary so in character that the most eihcient manner of treatment for each cannot be specified but must be determined by a certain amount of experimentation.

I claim:

1. The process of treating a hydrocarbon oil which comprises contacting the oil with sulphuric acid of relatively low concentration at a normal temperature of about ER, separating the spent acid from the oil, chilling the oil to at least 38 contacting the chilled oil with concentrated sulphuric acid whereby additional sludge is formed, separating the additional sludge from the oil, raising the temperature of the oil, contacting the oil with concentrated sulphuric acid at a normal temperature of about 70 F. whereby a further sludge is formed, and separating the further sludge from the oil.

2. The process of treating a hydrocarbon oil which comprises contacting the oil with sulphuric acid of relatively low concentration at a normal temperature of about 70 separating the spent acid from the oil, chilling the oil to at least 38 F., contacting the chilled oil with concentrated sulphuric acid whereby additional sludge is formed while maintaining the oil chilled, separating the additional oil sludge from the oil, raising the temperature of the oil, contacting the oil with concentrated sulphuric acid at a normal temperature of about 70 F. whereby a further sludge is formed, and separating the further sludge from the oil.

3. The process of treating a hydrocarbon oil substantially as set forth in claim 1, but in which the volume of sulfuric acid of at least one concentration used in the process is divided into a number of fractions for treating oil in the corresponding number of successive operations.

i. The process of treating a hydrocarbon oil which comprises treating the oil with sulphuric acid of a relatively low concentration and at a normal atmospheric temperature of about 70 F., separating spent acid from the oil, then chilling said oil substantially to a temperature lower than 38 F., treating said chilled oil with separate volumes of a concentrated sulphuric acid in a series of at least two steps whereby sludge. is formed, and separating sludge from the oil after each step, then raising the temperature of the oil, treating said oil with concentrated sulphuric acid at a normal atmospheric temperature of about 70 F. whereby further sludge is formed, and separating said further sludge from said oil.

5. In the process of treating a hydrocarbon oil the steps which comprise treating the oil with sul-.- furic acid of about 27 B. at a normal temperature of about 70 F., separating the treated oil 135 from the spent acid, chilling the oil to about 20 F., treating the chilled oil with sulfuric acid of about 100% concentration whereby sludge is formed, separating the oil from the sludge, raising the temperature of the oil, treating the oil with 140 concentrated sulfuric acid at a normal temperature of about 70 F. whereby a further sludge is formed, and separating this sludge from the oil.

ROBERT I. LEWIS.