US1967172A - Process of refining cracked distillates - Google Patents

Description

Patented July 17, 1934 PROCESS OF 'REFINING CRACKED DISTILLATES Jacque C. Morrell, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a corporation of South Dakota No Drawing. Application June 19, 1931, Serial No. 545,481

5 Claims. (01. 196-40 alkali and alkaline earth metals, being extremely stable. While hydrobromic and hydriodlc acids are in general less reactive than the two preceding, they react readily with certain types of organic compounds, for example, the oleflns, and in this respect are specially adaptable for use in the present invention.

The effects produced in the refining of petroleum distillate with sulphuric acid and halogen acids according to the process of the present invention, while generally similar, will also vary to a degree somewhat dependent upon the nature of the This invention relates to the treatment of hydrocarbon oils, and refers particularly to the treatment of the lower boiling distillates from crude petroleums or from-the cracking of the heavier portions thereof.

More specifically the invention has reference to the treatment of such distillates by chemical reagents adapted to bring them to a degree of refinement demanded by commercial specifications for motor fuels, etc.

Refining of petroleum distillates, particularly cracked distillates, is necessitated by the fact that they contain material amounts of unsaturated hydrocarbons which tend to polymerize and deposit gums and also by the fact that they contain larger percentages of sulphur than are usually allowable. Of the various methods of treating for the removal of the necessary amounts of these undesirable impurities the use of sulphuric acid is most common, treatment being conducted principally on the oils in the liquid phase. It is with improvements in the methods of refining these distillates that the present invention is concerned, a clear description of the process of the invention being given in the following specification from which the aims and objects thereof will more fully appear.

In one specific embodiment the invention comprises treating hydrocarbon oils simultaneously with sulphuric acid and a halogen acid. Sulphuric acid of varying concentration from a relatively dilute aqueous solution up to and including acids containing free sulphur trioxide may be used and any one of the halogen acids, which group includes hydrofluoric acid, hydrochloric acid, hydrobromic acid and hydriodic acid.

The properties of the halogen acids in general vary progressively in the order given above. For example, the reactivity of the acids decreases from hydrofluoric to hydriodic in practically all chemical reactions in which they are involved. Hydrofluoric acid, for example, as the most active member of the series, reacts with extreme vigor with metals to form fluorides, decomposes silicates with the production of metal fluorides and liberation of silicon as silicon tetra fluoride and in general presents great difliculties in handling. Hydrochloric acid, while less reactive than hydrofluoric, still exhibits a high degree of activity, the chlorides of many metals, for example, of the halogen acid OFFICE as well as upon the strength and amount of sulphuric acid employed and other conditions of treatment. It has been found that efliciency of the treatment is increased so that smaller quantities of the reagents are needed with resultant economy in cost of treatment.

The halogen acids may be introduced into the sphere of reaction either as such from outside sources or may be generated in situ from halogen compounds with which the sulphuric acid interacts to liberate the halogen acid. For example, an effective treatment may be conducted upon petroleum oils by suspending finely divided fluorspar, or calcium fluoride in the oil to be treated and then adding the necessary amounts of sulphuric acid to produce the desired treating effects, the sulphuric acid reacting with the fluorspar to form sponding equivalent of calcium sulphate.

free hydrofluoric acid and a corre- Similarly, other metallic halides' may be used which liberate the brought into corresponding halogen acid when contact with sulphuric acid. For

example, to generate hydrochloric acid sodium chloride or common salt may be employed and to generate hydrobromic or hydriodic acid sodium bromide or s tively.

odium iodide may be used respec- The use of hydriodic acid has been found to possess special advantages in that there is a liberation of free iodine due to the oxidizing efiect of the sulphuric acid, the liberated iodine being particularly active in inducing polymerization and catalyzing the treating reactions.

The process of the invention may be employed as a single treatment in some instances, but it is preferably used in conjunction with other refining treatments. As an example of a series of treatments which may be used the following may be mentioned which has been found to produce good results in the treatment of cracked distillates:

1. Treatment with caustic soda to remove hydrogen sulphide;

2. Treatment with sulfuric acid and a halogen acid according to the process of the present invention;

3. Treatment with strong caustic soda;

4. Redistillation to produce an end point gasoline;

5. Treatment with dilute caustic and water wash.

While the process of the invention may be con-= ducted in many types and arrangements of equipment and is not limited to any particular type of equipment, a few forms of apparatus may be mentioned, the most common being the batch agitator generally employed in petroleum refineries. In such an agitator, which is essentially a vertical cylindrical tank with a cone bottom, the reagents may be added while the oil is being circulated by an outside pump irom the bottom of the cone back into the top of the agitator, circulation being continued until the reagents are spent or until the desired treating efiect is obtained, such a treatment being followed by a period for subsidence of reaction products which are then drawn from the cone.

Another type of treating apparatus that may be employed is the so-called continuous treating plant commonly comprising a series of mixers followed by settling drums with the necessary refining and washing agents added to the oil stream as it passes through the mixing devices. In still other cases reagents may be added to the stream of oil entering a heating element in which case treatments may be efiected at superatmospheric temperatures and pressures, the treated products being discharged directly into a suitable fractionating column from whence refined end point vapors are taken, condensed and collected.

Examples of results obtainable by treating cracked distillates with mixtures of sulphuric and halogen acids might be multiplied considerably,

but a few typical cases will be suficent to indi' cate the good results obtainable.

As one example of a treatment comprised within the scope of the invention and results obtainable therefrom, the treatment of a California cracked distillate may be mentioned. Such a distillate as originally condensed from the cracking unit may have an end point of 500 F. and yield upon subsequent distillation without chemical treatment other than caustic soda solutions 75% of a 410 F. end point gasoline which has a color of only 15 on the Saybolt scale, a gum content by the copper dish method of I00 rugs. and a sulphur content of 0.25%. According to one modification of the process of the invention the raw distillate may be treated after washing with caustic soda to remove hydrogen sulphide and minor amounts of mercaptans, with five pounds per barrel of 66 B. sulphuric acid at normal temperatures, there being suspended in the 011 undergoing treatment finely divided fluorspar at the rate of 1.5 pounds per barrel of distillate treated. After this treatment followed by suitable neutralization and sweetening steps and redistilling for end point gasoline, the finished product may have the following properties:

Gums by the copper dish method- 30 mgs. Sulphur 0.1% Color +30 Saybolt Color after 4 hours exposure to sunlight 26 invention a pressure distillate resulting from the f? cracking of a Mid-continent gas oil may be treated in the liquid phase at ordinary temperatures with six pounds per barrel of 66 Be. sulphuric acid and one pound per barrel of hydrochloric acid, the latter being injected as a substantially anhydrous gas during the sulphuric acid treatment which, is conveniently conducted by cir culating the acid from the cone back into top of a batch agitator. The raw or untreated distillate may have a 480 F. end point and yield upon distillation approximately of a gasoline of 410 end point which, however, is unsuited for use as motor fuel due to its having a gum content of 400 rngs. by the copper dish method,

a color of i l on the Saybolt scale and a sulphur content of 0.5%. -Redistillation of the pressure distillate after treatment in the manner described followed by neutralizing and sweetening may result in a distinct improvement in the gasoline fraction as compared with the gasoline pro duced from the raw material, the properties 02 the treated gasoline being as follows:

Gums 20 mgs. Color +30 Saybolt Color after 4 hours exposure to sunlight 2d Sulphur 0 .15

Treatments on an experimental scale using hydrobromic or hydriodic acid in conjunction with sulphuric acid treatments also have shown effects of a higher order than those obtainable by the use of sulphuric acid alone, but as the present cost of these reagents is prohibitive from a commercial standpoint their use is apparently not practical in the immediate iuture and is merely mentioned to indicate that they may be used advantageously if economic conditions should result in a lowering of their cost.

The preceding specification and citations 05.

examples of results obtainable by the use of the present invention will indicate in a sufficiently clear manner that a process has been disclosed which possesses manifest advantages. However, many other applications are possible than the ones specifically described and they are not to be construed in a limiting sense upon the broad scope of the invention.

I claim as myinvention:

1. A process of refining cracked hydrocarbon distillate, which comprises subjecting the distil- 4. A process for refining cracked hydrocarbon distillate which comprises subjecting the distillate to the action of sulphuric acid containing a halogen acid selected from the group consisting of hydrofluoric acid, hydrobromic acid and hydriodic acid.

5. A process for refining cracked hydrocarbon distillate which comprises subjecting the distillate to the action of sulphuric acid containing hydrobromic acid.

JACQUE C. MORRELL.

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