US2163312A - Process for treating hydrocarbon oil - Google Patents

Description

?atented June 20, l$3$ 2,163,312 4 PROCESS FOR TfiEd'lfillNG HYDRO(JAlitllfwON Walter A. Schulze, Bartlesville, Okla", assjgnor to Phillips Petroleum Company, a corporation of Delaware No Drawing.

6 Claims.

(1) 4RSH+2CuCl2- Mercap- Cupric v tan chloride RSSR+2RS-Cu+4I-IC1 Disulfide Cuprous Hydromercaptide chloric acid (2) 2RSCu+2CuClz- Cuprous Cupric mercaptide chloride RS--SR+4CLIC1 Disulfide Cuprous chloride It is noted that in the first stage of the reaction one-half of the mercaptans are converted to disulfides and the other half to cuprous mercaptide. Then in the second stage of the reaction the cuprous mercaptide is oxidized to the disulfide' form. Thereiore, when the reaction is 100 per cent completed all of the mercaptans will have been converted in disulfides and there will be no cuprous mercaptide left dissolved in the gasoline. Such a condition, however, isseldom attained in commercial plant-operation. In such operation the sour gasoline is intimately contacted with' the copper solution in a centrifugal pump or by some means for an extremely short period of time-longer contacting with aqueous solutions, would be economically impractical. The treated gasoline will be negative to the so-called doctor test and for all practical purposes-is sweet, but

nevertheless it will contain in solution a small amount of the intermediate reaction product, cuprous mercaptide. v The amount of the cuprous mercaptides left dissolved in the gasoline will depend on many factors, such as the type of gasoline, the oxidation potential of the solution, the intimacy of contact of the copper solution with the gasoline, the .presence or absence of particularly refractory mercaptans, etc. In general, however, the soluble copper compounds left in the gasoline sweetened by plant methods will be present to the extent of 0.001 to 0.00001 per cent copper. While these quantities are extremely low, they are more than sufiicient as deleterious oxidation catalysts. In the presence of dissolved copper mercaptides or other copper-containing compounds, which are potent oxidation catalysts, many gasolines have a tendency to be unstable with respect to formation of color and gum, or if they are not subject Application May 11, 1937, Serial No. 142,018

to instability in themselves, they may produce these effects when blended with other gasolines which are more susceptible to oxidation. For example, a straight-run gasoline consisting principally of saturated hydrocarbons may be entirely stable even though it contains appreciable quantitles of copper-containing impurities, but will cause instability in the resulting blend when mixed with a copper-free and relatively stable crackedgasoline. 3

Since most motor fuels are marketed as a blend of two or more base gasolines, it is desir-. able that each component be free of copper, re-

' gardless of whether or not it is stable by itself.

As an adjunct to the copper sweetening process it is, therefore, necessary tofollow the sweetening step with a secondary treatment designed to 'removeany traces of copper compounds which are present in the treated on.

As stated above, it should be understood that the concentration of these impurities is so minute that they cannot usually be detected by ordinary analytical means, and it may be days or weeks before their presence is detected by effect. Special analytical tests have had to be devised for the quantitative determinations mentioned herein. A deleterious concentration of copper mercapatide may be present even when the oil displays the characteristic negative concentration to the standard, doctor test, and this test therefore cannot be depended'on as a criterion of the presence or absence of mercaptides. Relatively large amounts of mercaptides, however,- will generally give a delayed positive reaction to the doctor test, 1. e., the positive reaction is discernible only after 'a period of from several minutes to several' hours after the sample has been; contacted with the doctor test'solutionand sulfur, the period of delay depending mainly on the concentration of mercaptide present.

I have found that a more sensitive and reliable test involves acceleration of color formation in the presence of copper by addition of benzoyl peroxide to the sample, or if the sample is a relatively stable oil to a mixture of the sample and an oil known to be susceptible to oxidation and free of copper. One way of making this test consists in adding 10 mg. of benzoyl peroxide,

dissolved in 1 ml. of benzene, to (a) 100 ml. of the sample, and (b) a second 100 ml. of the sample after washing it with a sodium sulfide solution to remove any traces of copper-present. Discoloration of ,portion (0.) in comparison to the blank (11) after the two have stood in the dark for from one to four hours indicates the presence. of copper. A copper concentration as low as 0.00001 per cent in gasoline maybe easily detected.

It is an object ofthe present invention to stabilize petroleum oil which has been treated with a copper sweetening reagent.

It is a further object of this invention to stabilize petroleum oil which has been treated by a copper reagent against catalytic deterioration.

A still further and more specific object of this present invention is the removal of relatively small amounts of copper-containing reaction products from petroleum oils which have been treated previously with copper sweetening reagents.

Other objects and advantages of the present invention will be apparent from the following detailed description of the invention.

Applicant has now found that the aforementioned copper mercaptides which are left in oil that has been treated with copper solutions may be rapidly and completely removed by subjecting the oil to a secondary treatment with a concentrated solution containing cupric and choride ions adsorbed on a solid adsorbent carrier material. The reaction appears to be as follows:

2CuSR+CuCh- 2CuCl+RSS-R Cuprous Cupric Cuprous Disulflde mercaptide chloride chloride The reagent for the secondary treatment may be prepared by impregnating such solid adsorbent materials as fullers earth (preferred), charcoal, silica gel, alumina, etc., with concentrated aqueous solutions of copper chloride, or of copper sulfate or other copper salts, and sodium chloride or other alkali chlorides. To securev even distribution of the solution on the adsorbent, relatively dilute solutions may be applied to the adsorbent and subsequently concentrated as desired by removal of a portion of the water of solution.

This secondary or stabilizing treatment of the oil with the above described reagent consists in contacting it in liquid phase in a manner similar to filtration, at flow rates preferably within the range of from 1 to 10 volumes of oil per hour per volume of reagent, at substantially atmospheric temperatures, preferably 60,to 100 F., and nominal pressures.

As one example of the operation of this invention, a straight run gasoline from West Texas crude was sweetened with a copper solution containing approximately 15 per cent CuSO4-5H2O and 15 per cent NaCl, having an oxidation potential within the range of 380 to 440 millivolts and pH 2.8. After this treatment it contained copper mercantides varying within the range of 0.0002 to 0.0001 per cent copper, and always showed strongly positive on the benzoyl peroxide test. This gasoline Wasfiltered through a stabilizing reagent pre ared by impregnating, 15-30 mesh fullers cart with a solution .of. copper sulfate and sodium chloride. The stabilizing reagent contained approximately 3 per cent copper, 5 per cent chloride, and 15 percent water. The sweetened oil was filtered throughthe reagent at rates or 2 to 5 volumes per hour. Noair' was added to the gasoline during either the sweetening or the stabilizingstep. Over an extended period of operation during which more than 2000 volumes of sweetened oil were treated, the finished gasoline was completely free of copper as evidenced by the extremely sensitive benzoyl peroxide test described above. Furthermore, there was no noticeable depreciation in the activity of the stabilizing reagent after the treatment of 2000 volumes of gasoline and its life is undoubtedlyvery long.

When using fullers earth without the adsorbed copper and chloride solution, it was noted that the copper mercaptides were extracted from the first several volumes of gasoline by adsorption on the earth but that the earth quickly became saturated with the mercaptides and became inactive. As explained above, the copper solution adsorbed on the fullers earth (as a carrier body) oxidizes the cuprous mercaptides to disul fides and thereby makes the sweetening reaction 100 per cent complete. Fullers earth alone cannot do this.

It is evident from the foregoing that applicant has discovered and disclosed a new method of stabilizing copper reagent treated oils which constitutes an important technical step forward in the art.

Having thus described the present invention, what is claimed is:

1. In the process of sweeteningoils with solutions of copper salts in which the copper salt solution is intimately admixed with the oil, the step ofv removing copper mercaptides from the sweetened oil by contacting said oil in the absence of air with a solid adsorbent material impregnated with a solution of cupric and chloride ions.

2. The method of stabilizing petroleum oil which has been treated with a solution of a copper sweetening reagent, which comprises passing said treated oil in liquid phase in the absence of .air through a filter bed of treating agent consisting of adsorbent carrier material impregnated with an aqueous solution yielding cupric and chloride ions, whereby the oil is freed of coppercontaining compounds and stabilized against catalytic deterioration, and separating the stabilized oil from the treating agent.

3. The method of stabilizing petroleum oil which has been sweetened with copper solution which comprises passing the sweetened oil in the absence of air through a filter bed of solid ad sorbent material impregnated with a concentrated aqueous solution of copper sulfate and an excess of sodium chloride.

4. In the process of sweetening petroleum oil with copper solutions, the step of subjecting the sweetened oil in the absence of air to the action of a solid adsorbent material impregnated with a solution containing cupric ions and chloride ions, whereby copper-containing impurities are removed.

'1y contacting said' oil with an aqueous solution containing cupric ions and chloride ions to sweeten the hydrocarbon oil, and subsequently passing said sweetened. oil in the absence of added free oxygen-containing gas over atreating agent consisting of adsorbent carrier material impregnated with an aqueous solution yielding cupric and chloride ions, whereby the oil is freed of coppercontaining compounds resulting from the first mentioned treatment and stabilized against catalytic deterioration, and separating the stabilized oil from the treating agent.

WALTER A. SCHULZE.