US2026213A

US2026213A - Process for treating mineral oils

Info

Publication number: US2026213A
Application number: US664118A
Authority: US
Inventors: Carney Bernard Richard; Crosby Ralph Hoagland
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1933-04-03
Filing date: 1933-04-03
Publication date: 1935-12-31
Anticipated expiration: 1952-12-31

Description

Dec. 31,1935. B. R, CARNEY Er AL 2,026,213

PROCESS FOR TREATING MINERAL OILS Filed April 5, 1955 Patented Dec. 31V, 1935 UNITED `s'rrrls PATENT OFFICE signors to Shell Development Company, San Francisco, Calif., a corporation of Delaware- Application April 3, 1933, Serial No. 664,118

9 Claims.

This invention relates to the methods of relining mineral oils and is more particularly concerned with refining residual oils obtained in the course of producing light refined distillates such as obtained, for example, by cracking of petroleum or its products. It is a widely practiced method of rening the relatively light petroleum oil distillates by subjecting them to the action of a` mineral acid, such as sulfuric, hydrochloric,

10 phosphoric, etc., followed by neutralization with an alkali (dry or in solution), or other basic substance, and then redistilling such treated distillates in order to separate the refined fractions.' of desired volatility from the heavier components, which either were present in the original distillate, or were formed as a result of the chemical treatment. These heavier components of the acid treated and neutralized distillates, when separated by distillation from the lighter components, form the residual oils, which unless rened, present certain diilculties when put to further uses. As the examples of such uses, cracking of these residual oils and burning them as fuels can be mentioned. The character of the difficulties encountered in connection with the utilization of the residual oils of this type depends, of course, upon the particular use that is made of them. It is not an infrequent occurrance, for example, that clogging of the burners and screens is experienced when such residual oils are used as fuel; on the other hand, undesirable deposits of coke-like material with high mineral matter content are often rapidly built up in the heating coils of the cracking furnaces, 'in which these oils are subjected to destructive distillation or cracking.

It is the object of this invention to provide a process for treating the residual or other oils containing reaction products o-f mineral acid and 40 neutralization treatments in such amanner that their tendency to form coke-like materials Vunder cracking conditions, or sludge-like deposits at the normal or elevated temperatures, is'materially reduced o-r practically eliminated.

Another object of this invention is to provide the particular conditions for carrying out the process above referred to to the best advantage.

WhileY the method of this invention has been found Very effective for improving qualities of Various oils containing reaction pro-ducts of acid treated mineral oil distillate with an alkaline substance, such as acid treated and neutralized gasolines, kerosenes, stove oils, etc., or the residues from their distillation, it was found particularlyusefulfor refining the distillation bottoms of the cracked sulfuric acid treated neutralized distillates. The composition of these residual oils is quite complex, involving organic, mineral, and organo-mineral substances, some of which are present in a colloidal or otherwise nely dis- 5 persed form not readily separable from the oil by prolonged settling. These substances (which among other compounds include alkali soaps) form sludges which clog burners, or screens in` the fuel lines, when the oil is used for fuel, or l0 cause so called coking of apparatus, if the oil is again subjected to heating. Generally, the detrimental effect of the acid` and alkali treatments followed by redistillation upon the distillation residues increases with the intensity of acid l5 treatment, and also with the degree of the unsaturation of the raw distillates; thus it has been found that the residual oils, containing reaction products after treatment with sulfuric acid of over 90% strength, and/or produced from cracked 20 distillates which contained 40% by volume o-r more unsaturates (98% H2804 absorption method), usually contain relatively large amounts of screen clogging and/or other objectionable material, but respond very readily to the treatment 25 of this invention with great reduction or elimination of screen clogging tendency or coke formation on heating. While the mechanism of the refining action is not entirely clear, it is believed that removal of the objectionable oil components, 30 aswell as their chemical transformations, are involved in this treating process.

According to the present invention, the oils containing undesirable substances, which apparently are'the reaction products referred to above, are 35 intimately contacted with a brine containing a substantial quantity of NaCl and/ or other suitable mineral salts such as CaC12 whereafter the oilbrine mixture is allowed to settle and the refined oil is separated from the aqueous layer.

The details of the treatment will be further understood from the following description which is set forth by way of example only, without being intended to limit the scope of the invention. The iiow of the various liquids used in the process is 45 diagrammatically shown in Fig. 1 of the drawing.

A cracked distillate with a gasoline content of about boiling up to about 560 F. and containing about 50% unsaturates, is drawn from a tank I and subjected to a treatment in an agi- 50 tator 2 with about 3 lbs. of 93% H2SO4 from tank 3 per barrel of the distillate. The sludge is Withdrawn by means of a line 4 and the treated oil is thoroughly water washed in a tank 5 and neutralized in a treater 6 with a caustic solution from 55 a tank 7. The resulting treated distillate is redistilled, for example, in a fractionating column 8 to eliminate low boiling fractions, which are removed by means of pipe 9, and the residue (an oil of about 26 A. P. I. gravity) is drawn through line I0, and is subjected to a treatment to remove the screen clogging material and other objectionable components. Prior to this treatment it may be ascertained that the residual oil is substantially neutral, i. e., has an acid indication with phenolphthalein and an alkaline reaction with methyl orange indicators. This neutral residual oil is then treated with about 20% of its volume of a 50% saturated aqueous NaCl solution in an agitator or agitators, such as I I, I2 and I3, the temperature being maintained at about 150 F. The mixture is then conducted to a settling tank I4 and allowed to settle therein while at about the same temperature. An interphase layer of sludge like material is formed upon settling. Next, the brine, the sludge and the refined oil layers are separated, the latter being conducted to storage or to some other destination such as a cracking still or a furnace.

An improved process may consist in passing countercurrent streams of the oil being treated and of the treating brine through a series of mixing and separating devices, so that, for example, the raw oil is rst contacted with a substantially spent salt solution in agitator II, is partly refined thereby, separated, and then contacted again in a series of similar steps with progressively more effective or fresher salt solutions until, finally, the practically completely rened oil is contacted with fresh brine from tank I5 in agitator I3, separated therefrom, and conducted to the settling tank I4.

The efficiency of the process may be considerably increased by using centrifugal mixers and separators, wherein the unrefined oil and the brine are quickly and effectively contacted, the rened oil being then separated from the spent brine. Such an operation considerably increases the throughput of a plant and permits a continuous operation. It has been demonstrated that the quality of the oil is greatly improved by this brine treatment.

The particular method for evaluating the tendency of a fuel oil to clog burners and screens involved the use of an apparatus which consisted of an oil container (about 1 gallon capacity) connected through a bottom outlet to a long vertical tube provided at its lower end with a small opening over which was placed a screen of 60 mesh. The oil was passed by gravity from the container through this small opening in 500 cc. portions, and the time required for passing each portion was noted. After withdrawal of each portion an equal quantity of unscreened oil was added to the container and the rate of ow for the next 500 cc. portion was then determined. A substantially constant oil temperature within the range 'l0-80 F. was maintained during the tests. From these determinations a chart shown on Fig. 2 of the drawing was constructed wherein the gradually decreasing rates of flow (due to clogging of the screen), expressed in terms (percent) of the initial rate of flow (100%), were plotted against the amount of the oil discharged through the graphically represented on the accompanying diagram. It is observed that the residual oil, as taken from the still, clogged the screen after 3200 cc. of it was discharged, while the oil'"treated according to this invention flowed freely even after a Very large quantity of it was passed through.

Referring now to certain particulars concerning practicing the invention, it should be noted that while it is possible to employ in this process brines containing less than 50% of salt saturation, it is preferable to use more concentrated solutions, containing over 50% salt saturation; such conu) centrated solutions have much less tendency to form emulsions with the oils than more dilute ones.

It is quite important for an efficient operation of the treatment to subject to agitation the oil- 15 brine mixture which has neutral reaction, 1. e., acid to phenolphthalein and'alkaline to methyl orange; it is preferable that this be brought about by making both the oil and the brine to react neutral before mixing them together. The inten- 20 sity of agitation and the time of contact of the oil with the brine should be regulated so as to effect bringing together of substantially every particle of the oil being treated with a body of brine,whereby the refining action of the brine 25 is assured.

. The temperature of treatment has a considerable bearing upon the eifectiveness of the rening. In general, it is preferable to contact and separate the oil and the brine at slightly elevated l temperatures; it has been discovered, that the temperatures within the range 1Z0-200 F., and especially 14C-170 F., are particularly favorable for quickly breaking and settling the mixtures produced by stirring the reacting materials. 35

Having fully described the process of our in- Vention, we claim as new and useful:

'1. A process of refining a mineral oil which has been treated with a mineral acid and neutralized with an alkali, comprising, contacting the oil with the concentrated aqueous solution of a salt selected from the following group: sodium chloride and calcium chloride, and then separating the oil from said solution.

2. The process as in claim l, wherein the acid 45,

treated oil has been produced by treating an oil with sulfuric acid.

3. The process as in claim 1, wherein the acid treated oil has been produced by treating an oil with sulfuric acid of not less than concen- 50 tration.

4. The process as in claim 1, wherein the oil to be refined contains reaction products resulting from neutralization of an oil treated with sulfuric acid by means of sodium hydroxide.

5. A process of refining a mineral oil which comprises, contacting the oil with a mineral acid, thereby separating acid soluble oil components into a sludge and producing an acid treated oil, separating the latter from the sludge, neutraliz- 60 ing the acid treated oil, and then treating the neutral oil with the concentrated aqueous solution of a salt selected from the following group:

sodium chloride and calcium chloride.

6. The process as in claim 5, wherein treat- 65 trating said products in the oil by distilling oif a. 75.

portion of the neutralized oil, and then freeing the remaining portion of the oil from said objectionable reaction products by treating said portions with the aqueous solution of a salt selected from the following group: sodium chloride and calcium chloride. Y

8. Continuous process for rening a cracked oil containing reaction products of acid and alkali treatments, which comprises, maintaining continuous countercurrent streams of the oil and the concentrated aqueous solution of a salt selected fro-m the following group: sodium chloride and calcium chloride, and repeatedly contacting and separating said oil and solution in a series of steps in such a manner that unrened oil is contacted with a substantially exhausted salt solution, the resulting partly purifled oil is contacted with a partly exhausted salt solution, and the resulting substantially purified oil is contacted with a fresh salt solution.

9. A process of rening a mineral oil, which has been treated with a mineral acid and neutralized with an alkali, comprising contacting the oil with the aqueous solution of a salt selected from the following group: sodium chloride and calcium chloride, said solution being of at least 50%'saturation, and then separating the refined oil from the aqueous solution.

BERNARD RICHARD CARNEY. RALPH HOAGLAND CROSBY.