US2301281A - Refining mineral oil - Google Patents

Description

Nov. 10, 1942. i HUGGETT 2,3015281 REFINING MINERAL OIL Filed Jan. 16, 1940 CoNnENJER scaly/w A 0 3 l 65:22: /0 g .8 1

TREATING UNIT FEED has? STILL 0/1. OUTLET effect further sulfur reduction.

Patented Nov. 10, 1942 OFFICE REFINING MINERAL OIL Jack L. Huggett, Dartmouth, Nova Scotia, Canada, assignor to Standard Oil Development Company,

a corporation of Delaware Application January 16, 1940, Serial No. 314,031

Claims.

The present invention relates to the refining of mineral oils. The invention is more particularly concerned with an improved process for treating petroleum oils boiling in the range below about 420 F. which comprises segregating said petroleum oils into relatively higher and into relatively lower boiling range fractions and treating the respective fractions in a manner best adapted for the preservation of naturally occurring inhibitors and for the production of higher quality products. In accordance with the present process, petroleum oils boiling in the range from below about 420 F. are segregated into fractions boiling in the range from about 100 F. to 225 F. and into fractions boiling in the range from about 225 F. to 420 F. The relatively lower boiling fractionsare treated with an alkali metal hydroxide solution preferably with a sodium hydroxide solution, While the relatively higher boiling fractions are treated with an alkali metal carbonate solution preferably with a sodium carbonate solution.

It is well known in the art to refine petroleum oils by various processes in order to-produce high quality motor fuels. For example, it is known to segregate petroleum oils boiling in the range below about 420 F. into various fractions and to optimally treat the respective fractions. This procedure is usually followed in the processing of relatively high sulfur stocks in which the relatively higher boiling fraction is segregated from the relatively lower boiling fraction and treated in a manner to reduce the sulfur concentration usually by contacting with sulfuric acid. The relatively lower boiling fraction by-passes the sulfuric acid treat and is combined with the acid treated relatively higher boiling fraction and the entire blend then further refined as for example soda washed to remove acidic materials and to However, with respect to petroleum oils having relatively low sulfur concentrations, as for example, those oils having sulfur concentrations in the range of less than about 0.1%, it has not been necessary to refine the same for the reductionof sulfur. The common practice has been to; handle and refine these oils without segregating particular boiling range fractions. These oils are generally refined by treating the same with a strong caustic solution, as for example, by treatment with an aqueous solution of sodium hydroxide in order to remove undesirable relatively low boiling mercaptan compounds.

I have found that the process is undesirable due to the fact that the strong caustic solution also removes valuable phenolic type inhibitors.

By removing these natural inhibitors, the oil is rendered more susceptible to decomposition necessitating the addition of larger quantities of added inhibitors. I have now discovered a proc:- ess by which it is possible to treat petroleum naphthas, particularly petroleum naphthas having a relatively low sulfur concentration in a manner by which it is possible to preserve the naturally occurring inhibitors and to produce a higher quality product in a more economical manner. In accordance with my invention, petroleum oils boiling in the motor fuel boiling range are segregated into relatively low and into relatively high boiling range fractions. The relatively low boiling range fraction having an end point in the range from about 200 F. to 225 F. is washed with a sufficient amount of caustic while the relatively high boiling range fraction having an initial point in the range fromabout 200 F. to 225 F. is treated with a sodium carbonate or equivalent solution.

The process of my invention may be readily understood by reference to the attached drawing illustrating one modification of the same. For the purpose of illustration, it is assumed that the feed oil is a cracked petroleum naphtha boiling in the range below about 420 F. and secured from a low sulfur crude, as for example, a cracked petroleum naphtha from an East Texas crude. The feed oil is introduced into still I by means of feed line 2. Temperature and. pressure conditions are maintained on still I adapted to remove overhead a relatively lower boiling range fraction having a final boiling point in the range from about 200 F. to 225 F. The relatively higher boiling fraction having an initial boiling point in the range from about 200 F. to 225 F. and a final boiling point of about 420 F. is removed from still I by means of line 3 and introduced into sodium carbonate treating unit 4. Sodium carbonate, having a concentration of about 15 B., is introduced into unit 4 by means of line 5. The spent carbonate solution is withdrawn from treating unit 4 by means of line 6, while the treated relatively higher boiling range petroleum oil fraction is withdrawn by means of line 7. The relatively lower boiling oil fraction removed overhead from still I by means of line 8 is condensed in condenser 9, passed into treating unit I 0 in which it is contacted With a 25 B. solution of sodium hydroxide. The sodium hydroxide solution is introduced into unit It] by means of line II and withdrawn by means of line I2. The sodium hydroxide treated oil is withdrawn from contacting unit ID by means of line I3, combined with the sodium carbonate treated oil and passed to finished motor fuel storage by means of line H.

The process of the present invention may be widely varied. Although the invention may be applied in the treatment of any petroleum oil for the reduction of sulfur compounds and for the preservation of naturally occurring inhibitors, the invention is particularly applicable in the treatment of petroleum oils boiling in the motor fuel boiling range. Especially desirable results are secured by the process of the present invention in the refining of oils boiling in the motor fuel boiling range and having a relatively low sulfur concentration. Oils of this character are not normally treated with sulfuric acid for the removal of sulfur compounds, but are usually contacted with sodium hydroxide or an equiv alent solution for the removal of undesirable mercaptan compounds.

The particular fractions into which the petroleum oil is segregated likewise may vary considerably. I have, however, discovered that the desirable naturally occurring inhibitors are of a phenolic structure and have a boiling point in the range from about 225 F. to 420 F. It is therefore desirable that the final boiling point of the fraction subjected to caustic treatment should have a final boiling point in the range not above about 250 F., preferably in the range below about 225 F.

The concentration and amount of sodium hydroxide solution used in contacting the relatively lower boiling fraction may vary considerably and will depend upon the particular characteristics of the petroleum oil being treated and the concentration and character of undesirable sulfur compounds present. In general, when employing sodium hydroxide, it is preferred to contact the relatively lower boiling fraction with from to 1 volume of sodium hydroxide solution of a concentration in the range from about 20 B. to 30 Be. Although sodium hydroxide is preferred, other caustic solution, as for example, potassium hydroxide and the like may also be employed.

The amount and concentration of the carbonate solution used for treating the relatively higher boiling fraction likewise may vary considerably and will also depend upon-the character of the feed oil and upon the concentration and character of the sulfur compounds present. In general, when utilizing a sodium carbonate solution, it is preferred to use from to 1 volume of sodium carbonate solution having a concentration in the range from Be. to B. per volume of oil being treated. Although sodium carbonate is preferred, other salts, as for example, potassium carbonate, sodium sulfide and the like may also be employed.

In order to further illustrate the invention, the following examples are given which should not be construed as limiting the invention in any manner whatsoever.

EXAMPLE 1 length in time required for the pressure to drop this amount was taken as the breakdowntime-in minutes. i

the individual fractions were determined by and injecting oxygen up to Table l Breakdown time minutesaverage Distillate boiling range to 325 F 325 to 400 F Greaterthan400R it is apparent that the From the above data naturally occurring inhibitors have a boiling point in the range above 325 F.

EXAMPLE 2 Table II Breakdown Distillate Treated with time,

minutes m A Sodiumhydroxide. 60 B Sodium carbonate.

EXAMPLE 3 A heavy naphtha boiling in the range from about 225 F. to 400 F. was treated with sodium carbonate in one operation and sodium hydroxide in another operation. The results of these operations were as follows:

Table III Breakdown Mercaptan Copper dish time, minutes number gum A Sodiumcarbonate 100 7 49. 8 Sodium hydroxide 45 5 126. 8

*Mercaptan number determined by agitating a 50 cc. sample of oil with a standard copper solution, each cc. of which is equivalent to 1 mg. of mercaptan sulfur, in 1 cc. portions until the blue of the copper solution is no longer discharged. The cc.s of copper soluas the mercaptan number.

Copper dish gum determined by evaporating a portion of the sample and weighing the amount of gum From the above data it is apparent that the petroleum oil contacted with sodium carbonate is materially higher in quality. The stability is well over 100% increased and the gum is like wise materially improved.

The process of the present invention is not to be limited by any theory or mode of operation but only in and by the following claims in which it is desired to claim all novelty in so far as the prior art permits.

I claim:

1. Process for the production of high quality motor fuels of increased stability from petroleum oil fractions boiling in the range below about 420 F., said petroleum oil fractions having a relatively low sulfur content and being of the character that they would not be subjected to treatment with sulfuric acid for the reduction of sulfur comprising segregating said petroleum oil into a relatively high boiling fraction and into a relatively low boiling fraction, subjecting said relatively high boiling fraction to treatment with sodium carbonate solution and subjecting said low boiling fraction to treatment with a stronger solution of sodium hydroxide, separating the treated oils from the respective treating agents and blending the same for the production of said high quality motor fuel.

2. Process in accordance with claim 1 in which the sulfur content of said feed oil is in the range below about 0.1

3. Process for the production of high quality motor fuels of increased stability from petroleum oils boiling in the range below about 420 F. and containing naturally occurring inhibitors, comprising segregating said petroleum oils into a fraction boiling in the range from about 100 F. to 225 F. and into a fraction boiling in the range from about 225 F. to 420 F., treating said relatively low boiling fraction with an alkali metal hydroxide solution under conditions to remove objectionable mercaptan compounds, treating said relatively high boiling fraction with a weaker solution of an alkali metal carbonate under conditions to remove objectionable sulfur compounds without materially afiecting said naturally occurring inhibitors, combining the treated fractions whereby a motor fuel of relatively low sulfur content and increased stability is secured.

4. Process in accordance with claim 3 in which said alkali metal is sodium.

5. A process for producing stable hydrocarbon

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